Semiconductor module with temperature detecting element

The present invention relates to a semiconductor module and more particularly to a semiconductor module including a temperature detecting element for detecting the temperature of a semiconductor device.

PTD 1 discloses a power conversion device including first and second semiconductor modules. Each of the first and second semiconductor modules includes a switching element first and second external terminals, and a diode connected between the first and second external terminals for detecting the temperature of the switching element. The switching elements of the first and second semiconductor modules are connected in parallel with each other.

The first external terminal of the first semiconductor module receives constant current from a constant current source the second external terminal of the first semiconductor module is connected to the first external terminal of the second semiconductor module through a wiring pattern, and the second external terminal of the second semiconductor module receives a ground potential. The voltage between the first external terminal of the first semiconductor module and the second external terminal of the second semiconductor module changes according to the average temperature of the switching elements of the first and second semiconductor modules. When the average temperature exceeds a threshold temperature, current flowing through the switching elements is reduced, and overheat of the switching elements is prevented.

Patent Document

PTD 1 Japanese Patent Laying-Open No. 2013-250175

Technical Problem

Unfortunately, in PTD 1 since four external terminals are provided for two diodes, the number of external terminals is large, resulting in a large size of the power conversion device.

A main object of the present invention is therefore to provide a semiconductor module capable or achieving size reduction or the device.

Solution to Problem

A semiconductor module according to the present invention includes first to N-th semiconductor chips, and first and second external terminals. N is an integer equal to or greater than two. Each of the first to N-th semiconductor chips includes a switching element, first and second internal terminals, and a temperature detecting element connected between the first and second internal terminals and having a resistance value changing according to temperature of the switching element. The first internal terminal of the first semiconductor chip is connected to the first external terminal. The second internal terminal of the N-th semiconductor chip is connected to the second external terminal. Given that n is an integer equal to or greater than one and equal to or smaller than (N−1), one of the first and second internal terminals of the n-th semiconductor chip and one of the first and second internal terminals of the (n−1)th semiconductor chip are connected with each other.

Advantageous Effects of Invention

In the semiconductor module according to the present invention, since the first or second internal terminal of the n-th semiconductor chip and the first or second internal terminal or the (n−1)th semiconductor chip are connected with each other, the number of external terminals can be set to any one of 2 to (N−1). Therefore, compared with a conventional example in which 2N external terminals are provided for N temperature detecting elements, the number of external terminals can be reduced, thereby achieving size reduction of the device.

FIG. 1 is a circuit diagram showing a configuration of a semiconductor module according to a first embodiment of the present invention.

FIG. 2 is a block diagram illustrating how the semiconductor module shown in FIG. 1 is used.

FIG. 3 is a circuit block diagram showing a configuration of a part related to detection of temperature of transistors in a control circuit shown in FIG. 2 .

FIG. 4 is a diagram showing a layout of the semiconductor module shown in FIG. 1 .

FIG. 5 is a cross-sectional view showing the main part of the semiconductor module shown in FIG. 4 .

FIG. 6 is a circuit diagram shoving a configuration of a semiconductor module according to a second embodiment of the present invention.

FIG. 7 is a circuit block diagram showing a configuration of a part related to detection of temperature of transistors in a control circuit controlling the semiconductor module shown in FIG. 6 .

FIG. 8 is a diagram showing a layout of the semiconductor module shown in FIG. 6 .

FIG. 9 is a circuit diagram showing a configuration of a semiconductor module according to a third embodiment of the present invention.

FIG. 10 is a circuit block diagram showing a configuration of a part related to detection of temperature of transistors in a control circuit controlling the semiconductor module shown in FIG. 9 .

FIG. 11 is a diagram showing a layout of the semiconductor module shown in FIG. 9 .

FIG. 12 is a circuit diagram showing a configuration of a semiconductor module according to a fourth embodiment of the present invention.

FIG. 13 is a circuit block diagram showing a configuration of a part related to detection of temperature of transistors in a control circuit controlling the semiconductor module shown in FIG. 12 .

FIG. 14 is a diagram showing a layout of the semiconductor module shown in FIG. 12 .

First Embodiment

FIG. 1 is a circuit diagram showing a configuration of a semiconductor module 1 according to a first embodiment of the present invention. Two or three semiconductor modules 1 shown in FIG. 1 are connected in parallel to form an inverter that converts direct-current (DC) power into alternating-current (AC) power.

Semiconductor module 1 includes four switching semiconductor chips C 1 to C 4 and four rectifying semiconductor chips C 11 to C 14 . Each of semiconductor chips C 1 to C 4 includes a transistor 2 (switching element) and a diode 3 for detecting the temperature of transistor 2 . Transistor 2 is, for example, an IGBT (Insulated Gate Bipolar Transistor) and includes a collector, a gate, an emitter, and a sense emitter, Minute current having a value corresponding to the collector current flows through the sense emitter. Each of semiconductor chips C 11 to C 14 includes a freewheel diode 4 .

This semiconductor module 1 further includes, as external terminals, DC terminals Tp and Tn, an AC terminal Tac, control terminals T 1 g , T 1 a , T 1 se , and T 1 e provided corresponding to semiconductor chip C 1 control terminals T 2 g , T 2 k , T 2 se , and T 2 e provided corresponding to semiconductor chip C 2 , control terminals T 3 g , T 3 a , T 3 se , and T 3 e provided corresponding to semiconductor chip C 3 , control terminals T 4 g , T 4 k , T 4 se , and T 4 e provided corresponding to semiconductor chip C 4 , a control terminal T 1 ak shared by semiconductor chips C 1 and C 2 , and a control terminal T 2 ak shared by semiconductor chips C 3 and C 4 .

The collectors of transistors 2 of semiconductor chips C 1 and C 2 are both connected to DC terminal Tp, and the emitters thereof are both connected to AC terminal Tac. The collectors of transistors 2 of semiconductor chips C 3 and C 4 are both connected to AC terminal Tac, and the emitters thereof are both connected to DC terminal Tn.

Transistors 2 of semiconductor chips C 1 to C 4 have their gates connected to control terminals T 1 g to T 4 g , respectively, their emitters connected to control terminals T 1 e to T 4 e , respectively, and their sense emitters connected to control terminals T 1 se to T 4 se , respectively.

Temperature-detecting diodes 3 of semiconductor chips C 1 and C 3 have their anodes connected to control terminals T 1 a and T 3 a , respectively, and their cathodes connected to control terminals T 1 ak and T 2 ak , respectively. Temperature-detecting diodes 3 of semiconductor chips C 2 and C 4 have their anodes connected to control terminals T 1 ak and T 2 ak , respectively, and their cathodes connected to control terminals T 2 k and T 4 k , respectively.

Freewheel diodes 4 of semiconductor chips C 11 to C 14 have their anodes connected to the emitters of transistors 2 of semiconductor chips C 1 to C 4 , respectively, and their cathodes connected to the collectors of transistors 2 of semiconductor chips C 1 to C 4 , respectively. That is, freewheel diodes 4 are connected in anti-parallel with the corresponding transistors 2 .

FIG. 2 is a block diagram illustrating how semiconductor module 1 is used. In FIG. 2 , DC terminals Tp and Tn are connected to a positive-side output terminal 10 a and a negative-side output terminal 10 b , respectively, of a DC power supply 10 . DC power supply 10 may be a battery or may be a converter that converts AC voltage into DC voltage. AC terminal Tac is connected to a load 11 (for example, motor) driven with AC voltage supplied from semiconductor module 1 . The block of the semiconductor module shown in FIG. 2 may include a plurality of semiconductor modules.

Control terminals T 1 g to T 4 g , T 1 se to T 4 se , T 1 e to T 4 e , T 1 a , T 3 a , T 1 ak , T 2 ak , T 2 k , and T 4 k are connected to a control circuit 12 for controlling semiconductor module 1 .

Control circuit 12 applies a first control signal between control terminals T 1 g and T 1 e for turning on and off transistor 2 of semiconductor chip C 1 . Control circuit 12 applies a second control signal between control terminals T 2 g , and T 2 e for turning, on and off transistor 2 of semiconductor chip C 2 . Control circuit 12 applies a third control signal between control terminals T 3 g and T 3 e for turning on and off transistor 2 of semiconductor chip C 3 . Control circuit 12 applies a fourth control signal between control terminals and T 4 g and T 4 e for turning on and off transistor 2 of semiconductor chip C 4 .

When the first to fourth control signals are set to “H” level, the transistors 2 of semiconductor chips C 1 to C 4 turn on, and when the first to fourth control signals are set to “L” level, the transistors 2 of semiconductor chips C 1 to C 4 turn off. Transistors 2 of semiconductor chips C 1 and C 2 are simultaneously turned on, and transistors 2 of semiconductor chips C 3 and C 4 are simultaneously turned on. Transistors 2 of semiconductor chips C 1 and C 2 are connected in parallel, and transistors 2 of semiconductor chips C 3 and C 4 are connected in parallel whereby load current larger than rating current of a single transistor 2 can be supplied. Transistors 2 of semiconductor chips C 1 and C 2 are not turned on simultaneously with transistors 2 of semiconductor chips C 3 and C 4 .

When transistors 2 of semiconductor chips C 1 and C 2 are turned on, current flows from DC terminal Tp to AC terminal Tac through transistors 2 of semiconductor chips C 1 and C 2 . When transistors 2 of semiconductor chips C 3 and C 4 are turned on, current flows from AC terminal Tac to DC terminal Tn through transistors 2 of semiconductor chips C 3 and C 4 . Therefore, for example, transistors 2 of semiconductor chips C 1 and C 2 and transistors 2 of semiconductor chips C 3 and C 4 are turned on alternately to allow AC power to be output to AC terminal Tac.

Furthermore, three semiconductor modules 1 may be provided to perform PWM (Pulse Width Modulation) control with three semiconductor modules 1 phase-shined by 120 degrees, so that three phase AC voltages can be output from three AC terminals Tac.

Furthermore, control circuit 12 detects collector currents of transistors 2 of semiconductor chips C 1 to C 4 , based on minute currents flowing out of control terminals T 1 se to T 4 se . When the detected value of collector current of any of transistors 2 of semiconductor chips C 1 to C 4 exceeds a predetermined upper limit value, that is, when overcurrent flows through any of transistors 2 of semiconductor chips C 1 to C 4 , control circuit 12 sets the first and second, or the third and fourth, or the first to fourth control signals to “L” level to turn off all the transistors 2 . At this point of time, DC power supply 10 may be electrically cut off from semiconductor module 1 , or semiconductor module 1 may be electrically cut off from load 11 .

Furthermore, control circuit 12 detects temperatures T 1 to T 4 of transistors 2 of semiconductor chips C 1 to C 4 , based on forward voltages VF 1 to VF 4 of temperature-detecting diodes 3 of semiconductor chips C 1 to C 4 . Control circuit 12 adjusts, for example, the on time (that is, current) and the on and off frequencies of the transistors of semiconductor chips C 1 to C 4 such that temperatures T 1 to T 4 of transistors 2 of semiconductor chips C 1 to C 4 do not exceed a predetermined upper limit temperature.

FIG. 3 is a circuit block diagram showing a part related to detection of temperature of transistors 2 in control circuit 12 . In FIG. 3 , control circuit 12 includes constant current sources 13 and 14 and a temperature detector 15 . Control terminals T 1 a , T 1 ak , T 2 k , T 3 a , T 2 ak , and T 4 k are all connected to temperature detector 15 . Constant current source 13 is connected between the line of power supply voltage VCC and control terminal T 1 a . Constant current source 14 is connected between the line of power supply voltage VCC and control terminal T 3 a . Control terminals T 2 k and T 4 k are both connected to the line of ground voltage VSS. Although control terminals T 2 k and T 4 k are connected to the lines of the same voltage here, they may be connected to lines of different voltages.

Constant current is thus fed to each of diodes 3 of semiconductor chips C 1 to C 4 , and Forward voltages VF 1 to VF 4 are produced in diodes 3 of semiconductor chips C 1 to C 4 , respectively. When transistors 2 of semiconductor chips C 1 to C 4 are turned and off, a loss occurs in each transistor 2 (switching loss, conduction loss), and this loss generates heat to increase the temperature of transistor 2 .

When temperatures T 1 to T 4 of transistors 2 of semiconductor chips C 1 to C 4 rise, electric resistance values R 1 to R 4 of diodes 3 of semiconductor chips C 1 to C 4 decrease accordingly, and forward voltages VF 1 to VF 4 of diodes 3 of semiconductor chips C 1 to C 4 decrease. Temperature detector 15 obtains temperatures T 1 to T 4 of transistors 2 of semiconductor chips C 1 to C 4 based on forward voltages VF 1 to VF 4 and outputs signals φT 1 to φT 4 indicating the obtained temperatures T 1 to T 4 . Control circuit 12 adjusts, for example, the on time (that is, current) and the on and off frequencies of transistors 2 of semiconductor chips C 1 to C 4 such that temperatures T 1 to T 4 indicated by signals φT 1 to φT 4 do not exceed a predetermined upper limit temperature.

FIG. 4 is a diagram showing a layout of semiconductor module 1 . In FIG. 4 , semiconductor module 1 includes two substrates 21 A and 21 B disposed vertically in the figure. Each of substrates 21 B and 21 B is formed of an insulator in a rectangular shape. The short side of each of substrates 21 A and 21 B extends in the X direction (horizontal direction) in the figure, and the long side of each substrate 21 A and 21 B extends in the Y direction (vertical direction) in the figure. Conductor layers 224 and 22 B are formed on the front surfaces of substrates 21 A and 21 B, respectively. In the center region of the front surface of conductor layer 224 , semiconductor chips C 2 and C 1 are disposed n the left and the right in the figure.

In an upper end portion in the figure of the front surface of semiconductor chip C 1 , control pads (internal terminals) P 1 se , P 1 k , P 1 a , and P 1 g are sequentially disposed in the X direction. An emitter electrode EL 1 is formed in a region of the front surface of semiconductor chip C 1 , excluding control pads P 1 se , P 1 k , P 1 a , and P 1 g . Control pad P 1 se , control pad P 1 g , and emitter electrode EL 1 are respectively connected to the sense emitter, the gate, and the emitter of transistor 2 of semiconductor chip C 1 .

Control pads P 1 k and P 1 a are disposed adjacent to each other and respectively connected to the cathode and the anode of temperature-detecting diode 3 of semiconductor chip C 1 . Control pad P 1 a receiving temperature detecting current and control pad P 1 k receiving temperature detecting current are disposed adjacent to each other to cancel a magnetic field produced by the temperature detecting current and eliminate or reduce the effect of the magnetic field produced by current flowing through the main circuit while reducing noise by the magnetic field. On the back side of semiconductor chip C 1 , a collector electrode (not shown) connected to the collector of transistor 2 is formed, and the collector electrode is connected to conductor layer 22 A.

In an upper end portion in the figure of the front surface of semiconductor chip C 2 , control pads P 2 se , P 2 k , P 2 a , and P 2 g are sequentially disposed in the X direction. An emitter electrode EL 2 is formed in a region of the front surface of semiconductor chip C 2 , excluding control pads P 2 se , P 2 k , P 2 a , and P 2 g . Control pad P 2 se , control pad P 2 g , and emitter electrode EL 2 are respectively connected to the sense emitter, the gate, and the emitter of transistor 2 of semiconductor chip C 2 .

Control pads P 2 k and P 2 a are disposed adjacent to each other and respectively connected to the cathode and the anode of temperature-detecting diode 3 of semiconductor chip C 2 . Control pad P 2 a receiving temperature detecting current and control pad P 2 k receiving temperature detecting current are disposed adjacent to each other to cancel a magnetic field produced by the temperature detecting current and reduce noise by the magnetic field. On the back surface of semiconductor chip C 2 , a collector electrode (not shown) connected to the collector of transistor 2 is formed, and the collector electrode is connected to conductor layer 22 A.

In an upper region in the figure of the front surface of conductor layer 22 A, control terminals T 2 se , T 2 k , T 1 ak , T 2 e , T 2 g , T 1 se , T 1 a , T 1 e , and T 1 g are sequentially disposed in the X direction. Control terminals T 2 se , T 2 k , T 1 ak , T 2 g , T 1 se , T 1 a , and T 1 g are respectively disposed in the Y direction of control pads P 2 se , P 2 k , P 2 a , P 2 g , P 1 se , P 1 a , and P 1 g.

Control terminal T 2 e is disposed between control terminals T 1 ak and T 2 g . Control terminal T 1 e is disposed between control terminals T 1 a and T 1 g . Each of control terminals T 2 se , T 2 k , T 1 ak , T 2 e , T 2 g , T 1 se , T 1 a , T 1 e , and T 1 g is formed in an L shape as viewed in the X direction and insulated from conductor layer 22 A.

At the front surface of conductor layer 22 A, a strip-like wiring portion 23 A is formed in a region between semiconductor chips C 2 , C 1 and control terminals T 2 se , T 2 k , T 1 ak , T 2 e , T 1 se , T 1 a , T 1 e , T 1 g . The distance from control terminals T 2 se , T 2 k , T 1 ak , T 2 e , T 2 g , T 1 se , T 1 a , T 1 c , and T 1 g to semiconductor chips C 2 and C 1 is larger than the distance from wiring portion 23 A to semiconductor chips C 2 and C 1 . Wiring portion 23 A extends in the X direction and is insulated from conductor layer 22 A.

One end portion of wiring portion 23 A is connected to control pad P 2 a through metal wire W and connected to the front surface of the lower end portion of control terminal T 1 ak through metal wire W. The other end portion of wiring portion 23 A is connected to control pad P 1 k through metal wire W. Thus, the cathode of temperature-detecting diode 3 of semiconductor chip C 1 and the anode of temperature-detecting diode 3 of semiconductor chip C 2 are connected to control terminal T 1 ak.

Control pad P 1 a of semiconductor chip C 1 is connected to the front surface of the lower end portion of control terminal T 1 a through metal wire W, and control pad P 2 k of semiconductor chip C 2 is connected to the Front surface of the lower end portion of control terminal T 2 k through metal wire W. Thus, the anode of temperature-detecting diode 3 of semiconductor chip C 1 is connected to control terminal T 1 a , and the cathode or temperature-detecting diode 3 of semiconductor chip C 2 is connected to control terminal T 2 k.

Control pad P 1 se of semiconductor chip C 1 is connected to the front surface of the lower end portion of control terminal T 1 se through metal wire W, emitter electrode EL 1 is connected to the front surface of the lower end portion of control terminal T 1 e through metal wire W, and control pad P 1 g is connected to the front surface of the lower end portion of control terminal T 1 g through metal wire W. Thus, the sense emitter, the emitter, and the gate of transistor 2 of semiconductor chip C 1 are respectively connected to control terminals T 1 se , T 1 e , and T 1 g.

Control pad P 2 se of semiconductor chip C 2 is connected to the front surface of the lower end portion of control terminal T 2 se through metal wire W, emitter electrode EL 2 is connected to the front surface of the lower end portion of control terminal T 2 e through metal wire W, and control pad P 2 g is connected to the front surface of the lower end portion of control terminal T 2 g through metal wire W. Thus, the sense emitter, the emitter, and the gate of transistor 2 of semiconductor chip C 2 are respectively connected to control terminals T 2 se , T 2 e , and T 2 g.

In the lower region in the figure of the front surface of conductor layer 22 A, semiconductor chips C 12 and C 11 are disposed on the left and the right. An anode electrode EL 11 is formed on the front surface of semiconductor chip C 11 . Anode electrode EL 11 is connected to the anode of diode 4 of semiconductor chip C 11 . A cathode electrode (not shown) is formed on the back surface of semiconductor chip C 11 , and the cathode electrode is connected to the cathode of diode 4 of semiconductor chip C 11 and connected to conductor layer 22 A.

An anode electrode EL 12 is formed on the front surface of semiconductor chip C 12 . Anode electrode EL 12 is connected to the anode of diode 4 of semiconductor chip C 12 . A cathode electrode (not shown) is formed on the hack surface of semiconductor chip C 12 , and the cathode electrode is connected to the cathode of diode 4 of semiconductor chip C 12 and connected to conductor layer 22 A.

DC terminal Tp is formed at the upper end center portion in the figure of the front surface of conductor layer 22 A. DC terminal Tp is connected to conductor layer 22 A. Thus, the collectors of transistors 2 of semiconductor chips C 1 and C 2 and the cathodes of diodes 4 of semiconductor chips C 11 and C 12 are connected to DC terminal Tp.

A lead frame 24 A is provided on semiconductor chips C 1 , C 2 , C 11 , and C 12 . Lead frame 24 A is connected to emitter electrode EL 1 of semiconductor chip C 1 , emitter electrode EL 2 of semiconductor chip C 2 , anode electrode EL 11 of semiconductor chip C 11 , anode electrode EL 12 of semiconductor chip C 12 , and the upper end center portion in the figure of conductor layer 22 B. Part of lead frame 24 A extends in the X direction, and its front end portion is used as AC terminal Tac. Thus, the emitters of transistors 2 of semiconductor chips C 1 and C 2 and the anodes of diodes 4 of semiconductor chips C 11 and C 12 are connected to AC terminal Tac.

In the center region of the front surface of conductor layer 22 B, semiconductor chips C 3 and C 4 are disposed on the left and the right in the figure. In the lower end portion in the figure of the front surface of semiconductor chip C 3 , control pads P 3 g , P 3 a , P 3 k , and P 3 se are sequentially disposed in the X direction. An emitter electrode EL 3 is formed in a region of the front surface of semiconductor chip C 3 , excluding control pads P 3 g , P 3 a , P 3 k , and P 3 se . Control pad P 3 g , control pad P 3 se , and emitter electrode EL 3 are respectively connected to the gate, the sense emitter, and the emitter of transistor 2 of semiconductor chip C 3 .

Control pads P 3 a and P 3 k are disposed adjacent to each other and respectively connected to the anode and the cathode of temperature-detecting diode 3 of conductor chip C 3 . Control pad P 3 a receiving temperature detecting current and control pad P 3 k receiving temperature detecting current are disposed adjacent to each other to cancel a magnetic field produced by the temperature detecting current and reduce noise by the magnetic field. A collector electrode (not shown) connected to the collector of transistor 2 is Conned on the back surface of semiconductor chip C 13 , and the collector electrode is connected to conductor layer 22 B.

In the lower end portion in the figure of the front surface of semiconductor chip C 4 , control pads P 4 g , P 4 a , P 4 k , and P 4 se are sequentially disposed in the X direction. An emitter electrode EL 4 is formed in a region of the front surface of semiconductor chip C 4 , excluding control pads P 4 g , P 4 a , P 4 k , and P 4 se . Control pad P 4 g , control pad P 4 se , and emitter electrode EL 4 are respectively connected to the gate, the sense emitter, and the emitter of transistor 2 of semiconductor chip C 4 .

Control pads P 4 a and P 4 k are disposed adjacent to each other and respectively connected to the anode and the cathode of diode 3 of semiconductor chip C 4 . Control pad P 4 a receiving temperature detecting current and control pad P 4 k receiving temperature detecting current are disposed adjacent to each other to cancel a magnetic field produced by the temperature detecting current and eliminate or reduce the effect of the magnetic field produced by current flowing through the main circuit while reducing noise by the magnetic field. A collector electrode (not shown) connected to the collector of transistor 2 is formed on the back surface of semiconductor chip C 4 , and the collector electrode is connected to conductor layer 22 B.

In the lower region in the figure of the front surface of conductor layer 22 B control terminals T 3 g , T 3 e , T 3 a , T 3 se , T 4 g , T 4 e , T 2 ak , T 4 k , and T 4 se are sequentially arranged in the X direction. Control terminals T 3 g , T 3 a , T 3 se , T 4 g , T 2 ak , T 4 k , and T 4 se are disposed in the Y direction of control pads P 3 g , P 3 a , P 3 se , P 4 g , P 2 ak , P 4 k , and P 4 se , respectively.

Control terminal T 3 e is disposed between control terminals T 3 g and T 3 a . Control terminal T 4 e is disposed between control terminals T 4 g and T 2 ak . Each of control terminals T 3 g , T 3 e , T 3 a , T 3 se , T 4 g , T 4 e , 1 ′ 2 ak , T 4 k , and T 4 se is formed in an L shape as viewed in the X direction and insulated from conductor layer 22 B.

At the front surface of conductor layer 22 B, a strip-like wiring portion 23 B is formed in a region between semiconductor chips C 3 , C 4 and control terminals T 3 g , T 3 e , T 3 a , T 3 se , T 4 g , T 4 e , T 2 ak , T 4 k , T 4 se . The distance from control terminals T 3 g , T 3 e , T 3 a , T 3 se , T 4 g , T 4 e , T 2 ak , T 4 k , and T 4 se to semiconductor chips C 3 and C 4 is larger than the distance from wiring portion 23 B to semiconductor chips C 3 and C 4 . Wiring portion 23 B extends in file X direction and is insulated from conductor layer 22 B.

One end portion of wiring portion 23 B is connected to control pad P 3 k through metal wire W. The other end portion of wiring portion 23 B is connected to control pad P 4 a through metal wire W and connected to the front surface of the lower end portion of control terminal T 2 ak through metal wire W. Thus, the cathode of temperature-detecting diode 3 of semiconductor chip C 3 and the anode of temperature-detecting diode 3 of semiconductor chip C 4 are connected to control terminal T 2 ak.

Control pad P 3 a of semiconductor chip C 3 is connected to the front surface of the lower end portion of control terminal T 3 a through metal wire W, and control pad P 4 k of semiconductor chip C 4 is connected to the front surface of the lower end portion of control terminal T 4 k through metal wire W. Thus, the anode of temperature-detecting diode 3 of semiconductor chip C 3 is connected to control terminal T 3 a , and the cathode of temperature-detecting diode 3 of semiconductor chip C 4 is connected to control terminal T 4 k.

Control pad P 3 g of semiconductor chip C 3 is connected to the front surface of the lower end portion of control terminal T 3 g through metal wire W, control pad P 3 se is connected to the front surface of the lower end portion of control terminal T 3 se through metal wire W, and emitter electrode EL 3 is connected to the front surface of the lower end portion of control terminal T 3 e through metal wire W. Thus, the gate, the sense emitter, and the emitter of transistor 2 of semiconductor chip C 3 are respectively connected to control terminals T 3 g , T 3 se , and T 3 e.

Control pad P 4 g of semiconductor chip C 4 is connected to the front surface of the lower end portion of control terminal T 4 g through metal wire W, control pad P 4 se is connected to the front surface of the lower end portion of control terminal T 4 se through metal wire W, and emitter electrode EL 4 is connected to the front surface of the lower end portion of control terminal T 4 e through metal wire W. Thus, the gate, the sense emitter, and the emitter of transistor 2 of semiconductor chip C 4 are respectively connected to control terminals T 4 g , T 4 se , and T 4 e.

In the upper region in the figure of the front surface of conductor layer 22 B, semiconductor chips C 13 and C 14 are disposed on the left and the right. An anode electrode EL 13 is formed on the front surface of semiconductor chip C 13 . Anode electrode EL 13 is connected to the anode of diode 4 of semiconductor chip C 13 . A cathode electrode (not shown) is formed on the back surface of semiconductor chip C 13 , and the cathode electrode is connected to the cathode of diode 4 of semiconductor chip C 13 and connected to conductor layer 22 B.

An anode electrode EL 14 is formed on the front surface of semiconductor chip C 14 . Anode electrode EL 14 is connected to the anode of diode 4 of semiconductor chip C 14 . A cathode electrode (not shown) is formed on the back surface of semiconductor chip C 14 , and the cathode electrode is connected to the cathode of diode 4 of semiconductor chip C 14 and connected to conductor layer 22 B. Thus, the collectors of transistors 2 of semiconductor chips C 3 and C 4 and the cathodes of diodes 4 of semiconductor chips C 13 and C 14 are connected to AC terminal Tac.

A lead frame 24 B is provided on semiconductor chips C 3 , C 4 , C 13 , and C 14 . Lead frame 24 B is connected to emitter electrode EL 3 of semiconductor chip C 3 , emitter electrode EL 4 of semiconductor chip C 4 , anode electrode EL 13 of semiconductor chip C 13 , and anode electrode EL 14 of semiconductor chip C 14 . Part of lead frame 24 B extends downward in the figure and its front end portion is used as DC terminal Tn. Thus, the emitters of transistors 2 of semiconductor chips C 3 and C 4 and the anodes of diodes 4 of semiconductor chips C 13 and C 14 are connected to DC terminal Tn.

FIG. 5 is a cross-sectional view showing a main part of semiconductor module 1 shown in FIG. 4 . In FIG. 5 , a conductor layer 204 is formed on the back surface of substrate 214 . Conductor layer 20 A is affixed to a cooler (not shown) for cooling semiconductor module 1 . Heat generated in transistor 2 is transmitted to the cooler and dissipated from the fin of the cooler into refrigerant.

Conductor layer 22 A is formed on the front surface of substrate 21 A. Semiconductor chips C 2 and C 12 are provided in the front surface or conductor layer 22 A, and lead frame 24 A is provided on semiconductor chips C 2 and C 12 . The collector electrode on the lower surface of semiconductor chip C 2 is bonded t the front surface of conductor layer 224 through a conductive bonding member 31 , and emitter electrode EL 2 on the upper surface of semiconductor chip C 2 is bonded to the lower surface oaf lead frame 24 A through a conductive bonding member 32 . The cathode electrode on the lower surface of semiconductor chip C 12 is bonded to the front surface of conductor layer 224 through a conductive bonding member 33 , and anode electrode EL 12 on the upper surface of semiconductor chip C 12 is bonded to the lower surface of lead frame 244 through a conductive bonding member 34 .

Lead frame 244 may be formed of metal such as copper or may be formed of a clad member having an alloy called invar sandwiched between copper. Bonding members 31 to 34 are formed of solder, silver, or the like. When lead frame 24 A is bonded using solder, lead frames 244 and 24 B in semiconductor module 1 may be bonded collectively.

A cushioning member for alleviating stress may be added between lead frame 24 A and semiconductor chips C 2 and C 12 . Instead of lead frame 244 , a wire formed of metal such as aluminum, copper, and gold may be used.

Wiring portion 23 A and L-shaped control terminal T 1 ak are further provided on the front surface of conductor layer 22 A. An insulator layer 35 is provided between wiring portion 23 A and conductor layer 22 A. An insulator layer 36 is provided between control terminal T 1 ak and conductor layer 22 A. Insulator layer 36 may be formed by an insert molding process or may be Formed by a molding process using epoxy resin. Insulator layer 36 may be affixed to the surface of conductor layer 224 using adhesive.

Wiring portion 234 is connected to control pad P 2 a (the anode of diode 3 ) of semiconductor chip C 2 through metal wire W and connected to the front surface of the lower end portion of control terminal T 1 ak through metal wire W. Metal wire W is formed of metal such as aluminum, copper, and gold.

A tubular housing 37 is provided on the outer periphery of the front surface of conductor layer 22 A. The inside of housing 37 is sealed by an insulating member 38 , except for the upper end portion of the control terminal. The upper end portion of control terminal T 1 ak is exposed in the air. Insulating member 38 is gel, epoxy resin, or the like. The insulation distance can be reduced in the inside of insulating member 38 compared with in the air.

The opening on the upper side of housing 37 is closed by a control substrate 39 . Control circuit 12 for controlling semiconductor module 1 is mounted on control substrate 39 . The upper end portion of control terminal T 1 ak passes through control substrate 39 and is connected to control circuit 12 . A cover for covering control substrate 39 may be further provided.

In semiconductor module 1 shown in FIG. 4 , all the parts mounted on the front surface of conductor layers 224 and 22 B are scaled by insulating member 38 , except for the upper end portions of control terminals T 1 g , . . . , T 4 se . The insulation distance is reduced by sealing control pads P 1 g , . . . , P 4 se of semiconductor chips C 1 to C 4 , the portions of control terminals T 1 g , . . . , T 4 se excluding the upper end portions, wiring portions 23 A and 23 B, and metal wires W by insulating member 38 . The upper ends of control terminals T 1 g , . . . , T 4 se and the portions (DC terminals Tp and Tn and AC terminal Tac) outside the front surfaces of conductor layers 22 A and 22 B are exposed in the air.

As described above, in the present first embodiment, common control terminal T 1 ak is provided for two semiconductor chips C 1 and C 2 , and common control terminal T 2 ak is provided for two semiconductor chips C 3 and C 4 , thereby reducing the number of control terminals, compared with conventional examples. That is, if control terminals as many as the control pads and the emitter electrode of semiconductor chips C 1 to C 4 are provided, five control terminals are necessary for each of semiconductor chips C 1 to C 4 . Since the upper end portions of the control terminals are not sealed by insulating member 38 and are exposed in the air, the control terminals need to be spaced apart from each other by a distance allowing for insulation.

If the number of semiconductor chips connected in parallel increases and the number of control terminals increases accordingly, the length of the control terminal row increases accordingly, which increases the size of the semiconductor module. In a semiconductor module including four switching semiconductor chips, if five control terminals are provided for each semiconductor chip, in total, 20 control terminals are necessary. By contrast, the present first embodiment requires, in total, 18 control terminals. Therefore, the present first embodiment can reduce the number of control terminals and achieve size reduction of the device.

In the present first embodiment, the distance from semiconductor chips C 1 and C 2 (or C 3 and C 4 ) to wiring portion 23 A (or 23 B) is shorter than the distance from semiconductor chips C 1 and C 2 (or C 3 and C 4 ) and control terminals T 1 g , . . . (or T 3 g , . . . ). This can reduce the length of the current path compared with when diodes 3 of semiconductor chips C 1 and C 2 (or C 3 and C 4 ) are connected on control substrate 39 . This can reduce a voltage drop due to parasitic resistance and improve the accuracy of signal detection.

In the present first embodiment, since in each of semiconductor chips C 1 to C 4 , the control pad (for example, P 1 a ) for the anode of diode 3 and the control pad (for example, P 1 k ) for the cathode are disposed adjacent to each other, the effect of electromagnetic interference can be reduced, and the accuracy of detecting forward voltage (for example, VF 1 ) of diode 3 can be improved.

In the present first embodiment, IGBTs are used as transistors 2 of switching semiconductor chips C 1 to C 4 . However, the embodiments are not limited thereto, and a MOSFET (metal-oxide-semiconductor field-effect transistor) may be used as transistor 2 . In this case, a parasitic diode present in the MOSFET can be used as freewheel diode 4 , without using rectifying semiconductor chips C 11 to C 14 .

In the present first embodiment, temperature detecting elements (diodes 3 ) and overcurrent detecting cells (sense emitters) are provided only in switching semiconductor chips C 1 to C 4 . However, temperature detecting elements and overcurrent detecting cells may be also provided in rectifying semiconductor chips C 11 to C 14 .

In the present first embodiment, two sets of switching semiconductor chip C 1 , C 2 (or C 3 , C 4 ) and rectifying semiconductor chip C 11 , C 12 (or C 13 , C 14 ) are connected in parallel. However, N sets of a switching semiconductor chip and a rectifying semiconductor chip may be connected in parallel. N is an integer equal to or greater than two. In the present first embodiment, N=2.

When the first to N-th switching semiconductor chips are connected in parallel, N temperature-detecting diodes 3 are connected in series. Given that n is an integer equal to or greater than one and equal to or smaller than (N−1), the cathode of temperature-detecting diode 3 or the n-th semiconductor chip is connected to the anode of temperature-detecting diode 3 of the (n)th semiconductor chip.

A control terminal is connected to each or the anode of temperature-detecting diode 3 of the first semiconductor chip and the cathodes of temperature-detecting diodes 3 of the first to N-th semiconductor chips, and, in total, (N−1) temperature-detecting control terminals are provided. If a control terminal is connected to each of the anode and the cathode of temperature-detecting diode 3 of each of the first to N-th semiconductor chips, in total, 2N temperature-detecting control terminals are necessary. Therefore, the present first embodiment can reduce the number of temperature-detecting control terminals.

Furthermore, the number of switching semiconductor chips may not be equal to the number of rectifying semiconductor chips, and two switching semiconductor chips and one rectifying semiconductor chip may be connected in parallel.

In the present first embodiment, transistor 2 with an overcurrent detecting cell (sense emitter) is used. However, a transistor not having an overcurrent detecting cell (sense emitter) may be used.

In order to reduce the number of control terminals, control terminals T 1 g and T 2 g (or T 3 g and T 4 g ) of switching semiconductor chips C 1 and C 2 (or C 3 and C 4 ) connected in parallel may be connected with each other, and control terminals T 1 e and T 2 e (or T 1 e and T 4 e ) may be connected with each other.

Furthermore, instead using temperature-detecting diode 3 as a temperature detecting element, a thermistor with an electrical resistance value changing with temperature may be used. In this case, the thermistor is preferably disposed as close as possible to the semiconductor chip.

Furthermore, in a case where semiconductor chips formed of a wide-bandgap semiconductor such as SiC (Silicon Carbide) are used, inexpensive and compact semiconductor chips may be used, and a large number of semiconductor chips may be connected in parallel. The present first embodiment is also effective for reducing the site of the device in such a case.

Second Embodiment

FIG. 6 is a circuit diagram showing a configuration of a semiconductor module 41 according to a second embodiment of the present invention, in comparison with FIG. 1 . Referring to FIG. 6 , semiconductor module 41 differs from semiconductor module 1 in FIG. 1 in that control terminals T 1 ak and T 2 ak are removed. Temperature-detecting diodes 3 of semiconductor chips C 1 and C 2 are connected in series between control terminals T 1 a and T 2 k . Temperature-detecting diodes 3 of semiconductor chips C 3 and C 4 are connected in series between control terminals T 3 a and T 4 k.

FIG. 7 is a circuit block diagram showing a configuration of a part related to detection of temperature of transistors 2 in control circuit 12 controlling semiconductor module 41 , in comparison with FIG. 3 . Referring to FIG. 7 , this circuit part differs from the circuit part of FIG. 3 in that temperature detector 15 is replaced by a temperature detector 42 .

Control terminals T 1 a , T 2 k , T 3 a , and T 4 k are all connected to temperature detector 42 . Constant current source 13 is connected between the line of power supply voltage VCC and control terminal T 1 a . Constant current source 14 is connected between the line of power supply voltage VCC and control terminal T 3 a . Control terminals T 2 k and T 4 k are both connected to the line of ground voltage VSS. Although control terminals T 2 k and T 4 k are connected to the lines of the same voltage here, they may be connected to lines of different voltages.

Thus, constant current flows through each of temperature-detecting diodes 3 of semiconductor chips C 1 to C 4 , and forward voltages VF 1 to VF 4 are generated in diodes 3 of semiconductor chips C 1 to C 4 , respectively. When transistors 2 of semiconductor chips C 1 to C 4 are turned on and off a loss occurs in each transistor 2 , and this loss generates heat, which increases the temperature of transistor 2 .

When temperatures T 1 to T 4 of transistors 2 of semiconductor chips C 1 to C 4 rise, forward voltages VF 1 to VF 4 of temperature-detecting diodes 3 of semiconductor chips C 1 to C 4 decrease accordingly. Temperature detector 42 obtains the average temperature of transistors 2 of semiconductor chips C 1 and C 2 : T 12 (T 1 +T 2 )/2, based on the average value (VF 1 +VF 2 )/2 of forward voltages VF 1 and VF 2 , and outputs a signal φT 12 indicating the obtained average temperature T 12 .

Furthermore, temperature detector 42 obtains the average temperature of transistors 2 of semiconductor chips C 3 and C 4 : T 34 =(T 3 +T 4 )/2, based on the average value (VF 3 +VF 4 )/2 of forward voltages VF 3 and VF 4 , and outputs a signal φT 34 indicating the obtained average temperature T 34 . Control circuit 12 adjusts, for example, the on time (that is, current) and the on and off frequencies of transistors 2 of semiconductor chips C 1 to C 4 such that average temperatures T 12 and T 34 indicated by signals φT 12 and φT 34 do not exceed a predetermined upper limit temperature.

FIG. 8 is a diagram showing a layout of semiconductor module 41 , in comparison with FIG. 4 . Referring to FIG. 8 , semiconductor module 41 differs from semiconductor module 1 in that control terminals T 1 ak and T 2 ak are removed. Metal wire W connecting control terminal T 1 ak to wiring portion 23 A and metal wire W connecting control terminal T 2 ak to wiring portion 23 B are removed. Thus, temperature-detecting diodes 3 of semiconductor chips C 1 and C 2 are connected in series between control terminals T 1 a and T 2 k . Temperature-detecting diodes 3 of semiconductor chips C 3 and C 4 are connected in series between control terminals T 3 a and T 4 k.

In this second embodiment, since control terminals T 1 ak and T 2 ak are removed, the number of control terminals can be reduced, compared with the first embodiment, thereby achieving size reduction of the device.

In the present second embodiment, two sets of switching semiconductor chip C 1 , C 2 (or C 3 , C 4 ) and rectifying semiconductor chip C 11 , C 12 (or C 13 , C 14 ) are connected in parallel. However, N sets of a switching semiconductor chip and a rectifying semiconductor chip may be connected in parallel. N is an integer equal to or greater than two. In the present second embodiment, N=2.

When the first to N-th switching semiconductor chips are connected in parallel, N temperature-detecting diodes 3 are connected in series. Given that n is an integer equal to or greater than one and equal to or smaller than (N−1), the cathode of temperature-detecting diode 3 or the n-th semiconductor chip is connected to the anode of temperature-detecting diode 3 of the (n·1)th semiconductor chip.

A control terminal is connected to each or the anode of temperature-detecting diode 3 of the first semiconductor chip, the cathode of temperature-detecting diode 3 of the N-th semiconductor chip, and, in total, two temperature-detecting control terminals are provided. If a control terminal is connected to each of the anode and the cathode of temperature-detecting diode 3 of each of the first to N-th semiconductor chips, in total, 2N temperature-detecting control terminals are necessary. Therefore, the present second embodiment can reduce the number of temperature-detecting control terminals.

Third Embodiment

FIG. 9 is a circuit diagram showing a configuration of a semiconductor module 51 according to a third embodiment of the present invention, in comparison with FIG. 1 . Referring t FIG. 9 , semiconductor module 51 differs from semiconductor module 1 in FIG. 1 in that control terminals T 1 ak , T 2 ak , T 2 k , and T 4 k are removed and control terminals T 1 k , T 3 k , T 2 a , and T 4 a are added.

The cathodes of temperature-detecting diodes 3 of semiconductor chips C 1 and C 2 are both connected to control terminal T 1 k , and the anode of temperature-detecting diode 3 of semiconductor chip C 2 is connected to control terminal T 2 a . The cathodes of temperature-detecting diodes 3 of semiconductor chips C 3 and C 4 are both connected to control terminal T 3 k , and the anode of temperature-detecting diode 3 of semiconductor chip C 4 is connected to control terminal T 4 a.

FIG. 10 is a circuit block diagram showing a configuration of a part related to detection of temperature of transistors 2 in control circuit 12 controlling semiconductor module 51 , in comparison with FIG. 3 . In FIG. 10 , control circuit 12 includes constant current sources 52 to 55 and a temperature detector 56 . Control terminals T 1 a , T 2 a , T 1 k , T 3 a , T 4 a , and T 3 k are all connected to temperature detector 56 .

Constant current source 52 is connected between the line of power supply voltage VCC and control terminal T 1 a . Constant current source 53 is connected between the line of power supply voltage VCC and control terminal T 2 a . Constant current source 54 is connected between the line of power supply voltage VCC and control terminal T 3 a . Constant current source 55 is connected between the line of power supply voltage VCC and control terminal T 4 a . Control terminals T 1 k and T 3 k are both connected to the line of ground voltage VSS. Although control terminals T 1 k and T 3 k are connected to the lines of the same voltage here, they may be connected to lines of different voltages.

Thus, constant current flows through each of temperature-detecting diodes 3 of semiconductor chips C 1 to C 4 , and forward voltages VF 1 to VF 4 are generated in temperature-detecting diodes 3 of semiconductor chips C 1 to C 4 , respectively. When transistors 2 of semiconductor chips C 1 to C 4 are turned on and off, a loss occurs in each transistor 2 , and the loss generates heat, which increases the temperature of transistor 2 .

When temperatures T 1 to T 4 of transistors 2 of semiconductor chips C 1 to C 4 rise, forward voltages VF 1 to VF 4 of temperature-detecting diodes 3 of semiconductor chips C 1 to C 4 decrease accordingly. Temperature detector 56 obtains temperatures T 1 to T 4 of transistors 2 of semiconductor chips C 1 to C 4 based on forward voltages VF 1 to VF 4 and outputs signals φT 1 to φT 4 indicating the obtained temperatures T 1 to T 4 . Control circuit 12 adjusts, for example, the on time (that is, current) and the on and off frequencies of transistors 2 of semiconductor chips C 1 to C 4 such that temperatures T 1 to T 4 indicated by signals φ 1 to φ 4 do not exceed a predetermined upper limit temperature.

FIG. 11 is a diagram showing a layout of semiconductor module 51 , in comparison with FIG. 4 . Referring to FIG. 11 semiconductor module 51 differs from semiconductor module 1 in that control terminals T 1 ak and T 2 ak are respectively replaced by control terminals T 2 a and T 4 a , control terminals T 2 k and T 4 k are removed, control terminals T 1 k and T 3 k are added, and wiring portions 23 A and 23 B are respectively replaced by wiring portions 25 A and 25 B.

Control pad P 2 a of semiconductor chip C 2 is connected to control terminal T 2 a through metal wire W. Control pad P 2 k of semiconductor chip C 2 is connected to one end portion of wiring portion 25 A through metal wire W. Control pad P 1 k of semiconductor chip C 1 is connected to the other end portion of wiring portion 25 A through metal wire W. Control terminal T 1 k is disposed adjacent to control terminal T 1 a in the Y direction of control pad P 1 k . Control terminal T 1 k is connected to the other end portion of wiring portion 25 A through metal wire W. Thus, the anode of temperature-detecting diode 3 of semiconductor chip C 2 is connected to control terminal T 2 a , and the cathodes of temperature-detecting diodes 3 of semiconductor chips C 1 and C 2 are both connected to control terminal T 1 k.

Control pad P 4 a of semiconductor chip C 4 is connected to control terminal T 4 a through metal wire W. Control pad P 3 k of semiconductor chip C 3 is connected to one end portion of wiring portion 25 B through metal wire W. Control terminal T 3 k is disposed adjacent t control terminal T 3 a in the Y direction of control pad P 3 k . Control terminal T 3 k is connected to one end portion of wiring portion 25 B through metal wire W. Control pad P 4 k of semiconductor chip C 4 is connected to the other end portion of wiring portion 25 B through metal wire W. Thus, the anode of temperature-detecting diode 3 of semiconductor chip C 4 is connected to control terminal T 4 a , and the cathodes of temperature-detecting diodes 3 of semiconductor chips C 3 and C 4 are both connected to control terminal T 3 k.

In this third embodiment, common control terminal T 1 k is provided for two semiconductor chips C 1 and C 2 , and common control terminal T 3 k is provided for two semiconductor chips C 3 and C 4 , thereby reducing the number of control terminals, compared with conventional examples. That is, if control terminals as many as the control pads and the emitter electrode of semiconductor chips C 1 to C 4 are provided, five control terminals are necessary for each of semiconductor chips C 1 to C 4 . Since the upper end portions of the control terminals are not sealed by insulating member 38 and are exposed in the air, the control terminals need to be spaced apart from each other by a distance allowing for insulation. If the number of semiconductor chips connected in parallel increases and the number of control terminals increases accordingly, the length of the control terminal row increases accordingly, which increases the size of the semiconductor module. In a semiconductor module including four switching semiconductor chips, if five control terminals are provided for each semiconductor chip, in total, 20 control terminals are necessary. By contrast, the present third embodiment requires, in total, 18 control terminals. Therefore, the present third embodiment can reduce the number of control terminals and achieve size reduction of the device.

In the present third embodiment, wiring portion 25 A (or 25 B) is disposed between semiconductor chips C 1 , C 2 (or C 3 , C 4 ) and control terminals T 12 , . . . (or T 3 g , . . . ). In other words, the distance from semiconductor chips C 1 and C 2 (or C 3 and C 4 ) to wiring portion 25 A (or 25 B) is shorter than the distance from semiconductor chips C 1 and C 2 (or C 3 and C 4 ) to control terminals T 1 g , . . . (or T 3 g , . . . ). Therefore, the length of the current path can be reduced, compared with when temperature-detecting diodes 3 of semiconductor chips C 1 , C 2 (or C 3 , C 4 ) are connected on control substrate 39 . This can reduce a voltage drop due to parasitic resistance and improve the accuracy of signal detection.

In the present third embodiment, two sets of switching semiconductor chip C 1 , C 2 (or C 3 , C 4 ) and rectifying semiconductor chip C 11 , C 12 (or C 13 , C 14 ) are connected in parallel. However, N sets of a switching semiconductor chip and a rectifying semiconductor chip may be connected in parallel. N is an integer equal to or greater than two. In the present second embodiment, N 2.

When the first t N-th switching semiconductor chips are connected in parallel, the cathodes of N temperature-detecting diodes 3 are connected with each other. Given that n is an integer equal t or greater than one and equal to or smaller than (N−1), the cathode of temperature-detecting diode 3 of the n-th semiconductor chip is connected to the cathode of temperature-detecting diode 3 of the (n−1)th semiconductor chip.

A control terminal is connected to each of the anodes of temperature-detecting diodes 3 of the first to N-th semiconductor chips, a common control terminal is connected to the cathodes of temperature-detecting diodes 3 of the first to N-th semiconductor chips, and, in total, (N+1) temperature-detecting control terminals are provided. If a control terminal is connected to each of the anode and the cathode of each of temperature-detecting diodes 3 of the first to N-th semiconductor chips, in total, 2N temperature-detecting control terminals are necessary. Therefore, the present third embodiment can reduce the number of temperature-detecting control terminals.

Fourth Embodiment

FIG. 12 is a circuit diagram showing a configuration of a semiconductor module 61 according to a fourth embodiment of the present invention, in comparison with FIG. 9 . Referring to FIG. 12 , semiconductor module 61 differs from semiconductor module 51 in FIG. 9 in that control terminals T 2 a and T 4 a are removed. The anodes of temperature-detecting diodes 3 of semiconductor chips C 1 and C 2 are both connected to control terminal T 1 a . Temperature-detecting diodes 3 of semiconductor chips C 1 and C 2 are connected in parallel between control terminals T 1 a and T 1 k . The anodes of temperature-detecting diodes 3 of semiconductor chips C 3 and C 4 are both connected to control terminal T 3 a . Temperature-detecting diodes 3 of semiconductor chips C 3 and C 4 are connected in parallel between control terminals T 3 a and T 3 k.

FIG. 13 is a circuit block diagram showing a configuration of a part related to detection of temperature of transistors 2 in control circuit 12 controlling semiconductor module 61 , in comparison with FIG. 10 . In FIG. 13 , control circuit 12 includes constant current sources 62 and 63 and a temperature detector 64 . Control terminals T 1 a , T 3 a , T 1 k , and T 3 k are all connected to temperature detector 64 .

Constant current source 62 is connected between the line of power supply voltage VCC and control terminal T 1 a . Constant current source 53 is connected between the line of power supply voltage VCC and control terminal 13 a . Control terminals T 1 k and 13 k are both connected to the line of ground voltage VSS. Although control terminals T 1 k and T 3 k are connected to the lines of the same voltage here, they may be connected to lines of different voltages.

Current from constant current source 62 is divided into temperature-detecting diodes 3 of semiconductor chips C 1 and C 2 such that forward voltages VF 1 and VF 2 of temperature-detecting diodes 3 of semiconductor chips C 1 and C 2 have the same value. Electric resistance values R 1 and R 2 in the forward direction of diodes 3 of semiconductor chips C 1 and C 2 change according to temperatures T 1 and T 2 of transistors 2 of semiconductor chips C 1 and C 2 , respectively. The ratio 11 / 12 between currents 11 and 12 flowing through temperature-detecting diodes 3 of semiconductor chips C 1 and C 2 is the inverse ratio R 2 /R 1 between electric resistance values R 1 and R 2 of transistors 2 of semiconductor chips C 1 and C 2 .

Temperature detector 64 estimates average temperature T 12 of transistors 2 of semiconductor chips C 1 and C 2 , based on the current value obtained by dividing the current value of constant current source 62 by the parallel number (in this case, two) of temperature-detecting diodes 3 , and the output voltage VF 1 =VF 2 , and outputs a signal φT 12 indicating the estimated average temperature T 12 .

Similarly, temperature detector 64 estimates average temperature T 34 of transistors 2 of semiconductor chips C 3 and C 4 , based on the current value obtained by dividing the current value of constant current source 63 by the parallel number (in this case, two) of temperature-detecting diodes 3 , and the output voltage VF 3 =VF 4 , and outputs a signal φT 34 indicating the estimated average temperature T 34 . Control circuit 12 adjusts, for example, the on time (that is, current) and the on and off frequencies of transistors 2 of semiconductor chips C 1 to C 4 such that average temperatures T 12 and T 34 indicated by signals φT 12 and φT 34 do not exceed a predetermined upper limit temperature.

FIG. 14 is a diagram showing a layout of semiconductor module 61 , in comparison with FIG. 11 . Referring to FIG. 14 , semiconductor module 61 differs from semiconductor module 51 in that control terminals T 2 a and T 4 a are removed and wiring portions 26 A and 26 B are added.

At the front surface of conductor layer 22 A, a strip-like wiring portion 26 A is formed in a region between semiconductor chips C 2 , C 1 and wiring portion 25 A. The distance from control terminals T 2 se , T 2 e , T 2 g , T 1 se , T 1 k , T 1 a , T 1 e , and T 1 g to semiconductor chips C 2 and C 1 is larger than the distance From wiring portion 26 A to semiconductor chips C 2 and C 1 . Wiring portion 26 A extends in the X direction and is insulated from conductor layer 22 A.

One end portion of wiring portion 26 A is connected to control pad P 2 a through metal wire W. The other end portion of wiring, portion 26 A is connected to control pad P 1 k through metal wire W and connected to control terminal T 1 a through metal wire W. Thus, the cathode of temperature-detecting diode 3 of semiconductor chip C 1 and the anode of temperature-detecting diode 3 of semiconductor chip C 2 are connected to control terminal T 1 a . Temperature-detecting diodes 3 of semiconductor chips C 1 and C 2 are connected in parallel between control terminals T 1 a and T 1 k.

At the front surface of conductor layer 22 B, a strip-like wiring portion 26 B is formed in a region between semiconductor chips C 3 , C 4 and wiring portion 25 B. The distance from control terminals T 3 g , T 3 e , T 3 a , T 3 k , T 3 se , T 4 g , T 4 e , and T 4 se to semiconductor chips C 3 and C 4 is larger than the distance From wiring portion 26 B to semiconductor chips C 3 and C 4 . Wiring portion 26 B extends in the X direction and is insulated from conductor layer 22 B.

One end portion of wiring portion 26 B is connected to control pad P 3 a through metal wire W and connected to control terminal T 3 a through metal wire. The other end portion of wiring portion 26 B is connected to control pad P 4 a through metal wire W. Thus, the anode of temperature-detecting diode 3 of semiconductor chip C 3 and the anode of temperature-detecting diode 3 of semiconductor chip C 4 are connected to control terminal T 3 a . Temperature-detecting diodes 3 of semiconductor chips C 3 and C 4 are connected in parallel between control terminals T 3 a and T 3 k.

In this fourth embodiment, since control terminals T 2 a and T 4 a are removed, the number of control terminals can be reduced compared with the third embodiment, thereby achieving size reduction of the device.

The number of control terminals is the same as in the second embodiment. The voltage VF 1 =VF 2 (or VF 3 =VF 4 ) applied to temperature detector 64 is ½ of the voltage VF 1 +VF 2 (or VF 3 +VF 4 ) applied to temperature detector 42 in the second embodiment. On the contrary, the current value of constant current sources 62 and 63 is twice the current value of constant current sources 13 and 14 in the second embodiment.

In the present fourth embodiment, two sets of switching semiconductor chip C 1 , C 2 (or C 3 , C 4 ) and rectifying semiconductor chip C 11 , C 12 (or C 13 , C 14 ) are connected in parallel. However, N sets of a switching semiconductor chip and a rectifying semiconductor chip may be connected in parallel. N is an integer equal to or greater than two. In the present fourth embodiment, N=2.

When the first to N-th switching semiconductor chips are connected in parallel, the anodes of N temperature-detecting diodes 3 are connected with each other, and the cathodes of N temperature-detecting diodes 3 are connected with each other. Given that n is an integer equal to or greater than one and equal to or smaller than (N−1), the anode of temperature-detecting diode 3 of the n-th semiconductor chip is connected to the anode of temperature-detecting diode 3 of the (n+1)th semiconductor chip. The cathode of temperature-detecting diode 3 of the n-th semiconductor chip is connected to the cathode of temperature-detecting diode 3 of the (n+1)th semiconductor chip.

A common control terminal is connected to the anodes of temperature-detecting diodes 3 of the first to N-th semiconductor chips, a common control terminal is connected to the cathodes of temperature-detecting diodes 3 of the first to N-th semiconductor chips, and, in total, two temperature-detecting control terminals are provided. If a control terminal is connected to each of the anode and the cathode of temperature-detecting diode 3 or each of the first to N-th semiconductor chips, in total, 2N temperature-detecting control terminals are necessary. Therefore, the present fourth embodiment can reduce the number of temperature-detecting control terminals.

It is needless to say that the first to fourth embodiments and modifications thereof can be combined as appropriate.

The embodiment disclosed here should be understood as being illustrative rather than being limitative in all respects. The scope of the present invention is shown not in the foregoing description but in the claims, and it is intended that all modifications that come within the meaning and range of equivalence to the claims are embraced here.

1 , 41 , 51 , 61 semiconductor module, Tp, Tn DC terminal, Tac AC terminal, T 1 g to T 4 g , T 1 se to T 4 se , T 1 e to T 4 e , T 1 a to T 4 a , T 1 ak , T 2 ak , T 1 k to T 4 k control terminal, C 1 to C 4 , C 11 to C 14 semiconductor chip, 2 transistor, 3 diode, 4 freewheel diode, 10 DC power supply, 11 load, 12 control circuit, 13 , 14 , 52 to 55 , 62 , 63 constant current source, 15 , 42 , 56 , 64 temperature detector, 21 A, 21 B substrate, 20 A, 20 B, 22 A, 22 B conductor layer, P 1 se to P 4 se , P 1 k to P 4 k , P 1 a to P 4 a , P 1 g to P 4 g control pad, EL 1 to EL 4 emitter electrode, EL 11 to EL 14 anode electrode 23 A, 23 B, 25 A, 25 B, 26 A, 26 B wiring portion, W metal wire, 24 A, 24 B lead frame, 31 to 34 bonding member, 35 , 36 insulator layer, 37 housing, 38 insulating member 39 control substrate.