Full bridge inverter with push/pull control chip

1. Field of the Invention

The present invention relates to a full bridge inverter with a push/pull control chip, and more specifically relates to a push/pull control chip controlling the full bridge switch assembly for driving the load.

2. Description of the Related Art

The primary power supply of the cold cathode fluorescent lamp (CCFL) of the TFT LCD is used with the inverter circuit. The prior art inverter circuit converts DC power into AC power, and is discriminated into half bridge inverter, full bridge inverter and push/pull inverter, for example, by the topology of the different circuits.

Referring to FIG. 1 , the transformer T 1 divides the whole circuit into a front circuit 101 and a back circuit 102 , and there is a push/pull control chip 103 connected between the front circuit 101 and the back circuit 102 . The front circuit 101 comprises a DC power, a first switch Q 1 , a second switch Q 2 etc. and the back circuit 102 comprises at least a capacitor (C 1 , C 2 , C 3 ), a load, at least a diode (D 1 , D 2 ) etc.

Referring to FIG. 2 , the push/pull control chip 103 transmits a first control signal a and a second control signal b to the first switch Q 1 and the second switch Q 2 , respectively, for switching the two switches. Power is thus supplied to the load through the transformer T 1 according to the DC power. The voltage wave c of the secondary of the transformer T 1 is the wave of the ac voltage at point C in FIG. 2 .

In the above description, the push/pull control chip 103 is chip LX1686 and the series LX1686, LX1688, LX1691 of the LINFINITY (MICROSEMI) Corp., the series of the chip O2-9RR of the O2 Micro International Limited Corp., and the series of the chip BIT3105, BIT3494 of the Beyond Innovation Technology Corp.

As shown in FIG. 3 , the transformer T 2 divides the whole circuit into a front circuit 201 and a back circuit 202 . The front circuit 201 comprises four electronic switches (P 1 , P 2 , N 1 , N 2 ), a full bridge control chip 203 and a capacitor C 1 . Moreover the back circuit 202 comprises a load. Referring to FIG. 4 , the full bridge control chip 203 transmits four control signals (POUT 1 , POUT 2 , NOUT 1 , NOUT 2 ) to the four electronic switches (P 1 , P 2 , N 1 , N 2 ), respectively; by switching those switches, power is supplied to the load through the transformer T 2 according to the DC power. The full bridge control chip 203 is the BIT3105 of the Beyond Innovation Technology Corp.

In the above description, driving the full bridge switch assembly requires the full bridge control chip 203 and driving the push/pull inverter requires the push/pull control chip 103 , thus lacking practical flexibility. Furthermore, the control chip of the inverter circuit is limited in use so as to be hard to purchase together.

The primary object of the present invention uses two similar drivers to connect between the output terminal of the push/pull control chip and the control terminal of the full bridge switch assembly, and the push/pull control chip controls the full bridge switch assembly for switching.

The present invention is connected between the four electronic switches (P 1 , P 2 , N 1 , N 2 ) of the full bridge switch assembly of the prior art and the push/pull control chip with the two similar drivers. Moreover, the push/pull control chip controls switching of the four electronic switches (P 1 , P 2 , N 1 , N 2 ) of the full bridge switch assembly through two similar drivers.

In the above description, the driver comprises a first accelerated diode connected to the output terminal of the push/pull control chip with a negative pole terminal and connected to the control terminal of the electronic switch with a positive pole terminal for speedily cutting off the N-MOSFET, a first resistor parallel to the first accelerated diode for restraining the current via the control terminal of the N-MOSFET, a link capacitor connected to the negative pole terminal of the first accelerated diode and the positive pole terminal of a second accelerated diode and thereby the second accelerated diode connected to the control terminal of the P-MOSFET with a negative pole terminal for speedily cutting off the P-MOSFET, a second resistor parallel to the second accelerated diode for restraining the current via the control terminal of the P-MOSFET, a Zener diode connected to a positive pole terminal of the second accelerated diode with a positive pole terminal and connected to the DC power with a negative pole terminal for preventing excessive voltage. A third resistor is parallel to the Zener diode for producing a Zener voltage.

In the above description, the present invention receives the control signals transmitted from the push/pull control chip with two similar drivers for controlling the four electronic switches (P 1 , P 2 , N 1 , N 2 ) of the full bridge switch assembly for switching.

Then the present invention uses two similar drivers to connect to the prior art full bridge switch assembly, and the prior art full bridge switch assembly controlled by the push/pull control chip. The present invention also can use the push/pull control chip to control the push/pull inverter and control the full bridge switch assembly through the two drivers so as to increase the flexibility and the practical worth thereof.

The various objects and advantages of the present invention will be more readily understood from the following detailed description when read in conjunction with the appended drawing, in which:

FIG. 1 is a circuit schematic diagram of a prior art push/pull inverter driving the load;

FIG. 2 is a wave schematic diagram of control signals of the push/pull control chip and the voltage of the load.

FIG. 3 is a circuit schematic diagram of a prior art full bridge inverter driving the load;

FIG. 4 is a wave schematic diagram of control signals of a prior art full bridge inverter;

FIG. 5 is a circuit schematic diagram of the push/pull control chip controlling the full bridge switch assembly of the present invention; and

FIG. 6 is a wave schematic diagram of control signals of the push/pull control chip and the voltage of the AC power.

Referring to FIG. 5 , the present invention connects to the primary winding of a transformer T 2 through a full bridge switch assembly 302 for converting DC power VCC into AC power, and supplies power to the load through the transformer T 2 . In the above description, the peak to peak of the AC power is a voltage of 2VCC.

Referring to FIG. 5 , the present invention comprises a push/pull control chip 103 , two drivers 304 and a full bridge switch assembly 302 . The push/pull control chip 103 transmits two control signals through two output terminals A and B. The input terminals of the two drivers 304 are connected to the two output terminals A and B of the push/pull control chip 103 , respectively, and are controlled by the push/pull control chip 103 . The full bridge switch assembly includes four electronic switches (P 1 , P 2 , N 1 , N 2 ), and connects to the output terminal of the two drivers 304 with control terminal G of each electronic switch. Moreover, the present invention converts DC power into AC power with the two drivers 304 , and transmits the AC power to the primary winding of the transformer T 2 . In the above description, the electronic switches P 1 , P 2 are P-MOSFET switches and the electronic switches N 1 , N 2 are N-MOSFET switches.

Referring to FIG. 5 , the sources of the electronic switch P 1 , P 2 are connected to the DC power, and the sources of the electronic switch N 1 , N 2 are connected to a reference terminal. The drains of the electronic switches P 1 , N 1 are connected to one terminal of the primary winding of the transformer T 2 , and the drains of the electronic switches P 2 , N 2 are connected to other terminals of the primary winding of the transformer T 2 . Moreover, the control terminal of the electronic switches P 1 , P 2 , N 1 , N 2 are connected to the output terminal of the driver 304 , respectively. In the above description, the electronic switch P 1 , P 2 , N 1 , N 2 constitute the full bridge switch assembly, and the electronic switch P 1 , N 2 constitute a positive half cycle driver, while the electronic switches N 1 and P 2 constitute a negative half cycle driver so as to form the AC power.

Referring to FIG. 5 , a driver 304 comprises a first accelerated diode D 3 connected to a output terminal A of the push/pull control chip 103 with a negative pole terminal and connected to the control terminal G of the electronic switch N 1 with a positive pole terminal, while a first resistor R 3 is connected in parallel with the first accelerated diode D 3 . A second accelerated diode D 2 is connected to the control terminal G of the electronic switch P 1 with a negative pole terminal and is connected to the output terminal A of the push/pull control chip 103 through a link capacitor C 2 with a positive pole terminal; a second resistor R 2 is connected in parallel with the second accelerated diode D 2 . Moreover, a Zener diode D 1 is connected to a positive pole terminal of the second accelerated diode D 2 with a positive pole terminal and connected to the DC power with a negative pole terminal, and a third resistor R 1 is connected in parallel with the Zener diode D 1 . The driver 304 mentioned above is used to drive the electronic switch P 1 and electronic switch N 1 .

Referring to FIG. 5 , in the above description, the other driver 304 comprises a first accelerated diode D 6 connected to an output terminal B of the push/pull control chip 103 with a negative pole terminal and connected to the control terminal G of the electronic switch N 2 with a positive pole terminal; a first resistor R 6 is connected in parallel with the first accelerated diode D 6 . A second accelerated diode D 5 is connected to the control terminal G of the electronic switch P 2 with a negative pole terminal and connected to the output terminal B of the push/pull control chip 103 through a link capacitor C 3 with a positive pole terminal; a second resistor R 5 is connected in parallel with the second accelerated diode D 5 . Moreover, a Zener diode D 4 is connected to a positive pole terminal of the second accelerated diode D 5 with a positive pole terminal and connected to the DC power with a negative pole terminal; a third resistor R 4 is connected in parallel with the Zener diode D 4 . The driver 304 mentioned above is used to drive the electronic switch P 2 and electronic switch N 2 .

In the above description, the two drivers 304 are controlled by the push/pull control chip 103 for driving the four electronic switches (N 1 , N 2 , P 1 , P 2 ) of the full bridge switch assembly 302 so as to convert the DC power into the AC power, and the AC power is transmitted to the primary winding of the transformer T 2 . A capacitor C 1 is connected to the primary winding of the transformer T 2 and the full bridge switch assembly 302 for disconnecting the DC component in the AC power.

Referring also to FIG. 5 , in FIG. 6 , the push/pull control chip 103 is the chip LX1686 and the series LX1686, LX1688, LX1691 of the LINFINITY (MICROSEMI) Corp., and the series of the chip O2-9RR of the O2 Micro International Limited Corp., and the series of the chip BIT3105, BIT3494 of the Beyond Innovation Technology Corp.

A first control signal a is output via the output terminal A of the push/pull control chip 103 , and a second control signal b is output via the output terminal B of the push/pull control chip 103 . Moreover, a voltage wave ac of the AC power is in the terminal T 21 of the primary winding of the transformer T 2 , and the peak to peak of the AC power is 2 DC power.

Referring to FIG. 5 , as well as FIG. 6 , at time t 1 -t 2 , the potential of the first control signal a is high and the second control signal b is the low potential. The first control signal a is transmitted to the control terminal G of the electronic switch N 1 through the first resistor R 3 to turn on the electronic switch N 1 , and transmitted to the control terminal G of the electronic switch P 1 through the link capacitor C 2 , the second accelerated diode D 2 and the second resistor R 2 to turn off electronic switch P 1 . Moreover, the second accelerated diode D 2 accelerates turning off the electronic switch P 1 . The second control signal b is transmitted to the control terminal G of the electronic switch N 2 through the first accelerated diode D 6 to turn off the electronic switch N 2 , and transmitted to the control terminal G of the electronic switch P 2 through link capacitor C 3 and the second resistor R 5 to turn off the electronic switch P 2 .

At this time, the electronic switches N 1 and P 2 are on and the electronic switches N 2 , P 1 are off. DC power is then transmitted to the primary winding of the transformer T 2 by turning on the electronic switch N 1 , P 2 , and the AC power measured at the terminal T 21 of the transformer T 2 is the negative of the DC power.

Referring also to FIG. 5 , as well as FIG. 6 , at time t 2 -t 3 , the potential of the first control signal a is reduced to low from high and the second control signal b still at the low potential. At this time, the first accelerated diode D 3 accelerates turning the electronic switch N 1 . The first control signal a is transmitted to the control terminal G of the electronic switch P 1 through the link capacitor C 2 and the second resistor R 2 to turn on the electronic switch P 1 . Because the second control signal b is still at the low potential, the electronic switch P 2 is still on and the electronic switch N 2 is still off.

It is understood that, in the above description, when time is t 2 -t 3 , the electronic switches P 1 , P 2 are on and the electronic switches N 1 , N 2 are off. At this time, the energy stored in the transformer T 2 leaks according to the short of the primary winding of the transformer T 2 . The AC power measured at the terminal T 21 of the transformer T 2 is then at the zero potential.

Referring also to FIG. 5 , as well as FIG. 6 , at time t 3 -t 4 , the first control signal a still at the low potential and the potential of the second control signal b is reduced to low level from high level. The second control signal b is transmitted to the control terminal G of the electronic switch N 2 through the first resistor R 6 to turn on the electronic switch N 2 , and transmitted to the control terminal G of the electronic switch P 2 through the link capacitor C 3 , the second accelerated diode D 5 and the second resistor R 5 to turn off the electronic switch P 2 . Moreover, the second accelerated diode D 5 accelerates turning off the electronic switch P 2 . Because the first control signal a is still at a low potential, the electronic switch P 1 is still on and the electronic switch N 1 is still off.

At this time, the electronic switches N 2 , P 1 is on and the electronic switches N 1 , P 2 is off. The DC power is then transmitted to the primary winding of the transformer T 2 by turning on the electronic switches N 2 , P 1 , and the AC power measured at the terminal T 21 of the transformer T 2 is the positive of the DC power.

Referring also to FIG. 5 , as well as FIG. 6 , at time t 4 -t 5 , the first control signal a is still at the low potential and the potential of the second control signal b is increased to high level from low level. At this time, the first accelerated diode D 6 accelerates turning off the electronic switch N 2 . The second control signal b is transmitted to the control terminal G of the electronic switch P 2 through the link capacitor C 3 and the second resistor R 5 to turn on the electronic switch P 2 . Because the first control signal a is still at the low potential, the electronic switch P 1 is still on and the electronic switch N 1 is still off.

It is understood that, in the above description, when time is t 4 -t 5 , the electronic switches P 1 , P 2 are on and the electronic switches N 1 , N 2 are off. At this time, the energy stored in the transformer T 2 leaks according to the short of the primary winding of the transformer T 2 . The AC power measured at the terminal T 21 of the transformer T 2 is then at the zero potential.

Referring also to FIG. 5 , as well as FIG. 6 , the action of the present invention circuit and the voltage wave ac of the terminal T 21 of the transformer T 2 at time t 5 -t 6 are the same at time t 1 -t 2 . The rest may be deduced by analogy from the above description. The peak to peak of the AC power is double DC power, and converted to the secondary winding of the transformer T 2 for supplying the load with power.

Reference is made to FIG. 5 , in which the Zener diodes D 1 and D 4 protect the electronic switches P 1 , P 2 for preventing the over-voltage. Moreover, the third resistors R 3 , R 4 are in parallel with the Zener diodes D 1 , D 4 , respectively, to provide a Zener voltage.

In the above description, the present invention uses two similar drivers to connect to the prior art full bridge switch assembly, and the prior art full bridge switch assembly is controlled by the push/pull control chip. The present invention uses the push/pull control chip to control the push/pull inverter and control the full bridge switch assembly through the two drivers so as to increase the flexibility and the practical value thereof.

Although the present invention has been described with reference to the preferred embodiment thereof, it will be understood that the invention is not limited to the details thereof. Various substitutions and modifications have been suggested in the foregoing description, and other will occur to those of ordinary skill in the art. Therefore, all such substitutions and modifications are embraced within the scope of the invention as defined in the appended claims.