Modularized inverter control circuit

The power supply for a backlight source of a TFT LCD panel makes use of an inverter circuit to accomplish energy conversion and drive a cold cathode fluorescent lamp (CCFL) to be on. Conventional inverter circuits can be divided into half-bridge type, full-bridge type and push-pull type according to different circuit topologies. An inverter circuit is a circuit for converting a DC power into an AC power.

As shown in FIG. 1 , a transformer T 1 divides the circuit into a front-end circuit at the primary side 101 and a rear-end circuit at the secondary side 102 . The front-end circuit at the primary side 101 comprises a DC voltage source Vcc, a first switch Q 1 , and a second switch Q 2 . The rear-end circuit at the secondary side 102 comprises at least a capacitor (C 1 , C 2 , C 3 ), a load, and at least a diode (D 1 , D 2 ). A push-pull type control chip 103 is connected between the front-end circuit at the primary side 101 and the rear-end circuit at the secondary side 102 . Please also refer to FIG. 2 . The push-pull type control chip 103 outputs a first control signal a and a second control signal b for controlling switching actions of the two switches Q 1 and Q 2 at the primary side 101 , respectively. The DC power source Vcc is used to provide energy, and the transformer T 1 raises and converts the voltage of the DC power Vcc to the rear-end circuit 102 for driving the load. The output voltage waveform c at the secondary side of the transformer T 1 is the voltage waveform at point C. As shown in FIG. 2 , the output voltage waveform c at the secondary side is an AC voltage waveform.

In the above description, the push-pull type control chip 103 is produced by Linfinity (Microsemi) Corporation with type of LX1686.

As shown in FIG. 3 , a transformer T 2 divides the circuit into a front-end circuit at the primary side 201 and a rear-end circuit at the secondary side 202 . The front-end circuit at the primary side 201 comprises four electronic switches (P 1 , P 2 , N 1 , and N 2 ), a full-bridge type control chip 203 , and a capacitor C 1 . The rear-end circuit at the secondary side 202 comprises a load. Please also refer to FIG. 4 . The full-bridge type control chip 203 outputs four control signals POUT 1 , POUT 2 , NOUT 1 , and NOUT 2 for controlling switching actions of the four electronic switches P 1 , P 2 , N 1 , and N 2 , respectively. The DC power source Vcc is used to provide energy, and the transformer T 2 raises and converts the voltage of the DC power Vcc to the rear-end circuit 202 for driving the load. The full-bridge type control chip 203 is produced by Beyond Innovation Technology with the type of BIT3105.

As shown in FIG. 5 , a transformer T 3 divides the circuit into a front-end circuit at the primary side 301 and a rear-end circuit at the secondary side 302 .

The front-end circuit at the primary side 301 comprises a DC voltage source Vcc, two electronic switches (Q 1 , Q 2 ), a half-bridge type control chip TL494, two capacitors (C 1 , C 2 ) and an isolation transformer Tr. The rear-end circuit at the secondary side 302 comprises a load. Please also refer to FIG. 6 . The half-bridge control chip TL494 outputs control signals D 1 –D 2 via two output terminals D 1 and D 2 . The control signals D 1 –D 2 control switching actions of the two electronic switches Q 1 and Q 2 via the isolation transformer Tr, respectively. The two electronic switches Q 1 and Q 2 are n-channel FETs or p-channel FETs. Through switching actions of the two electronic switches Q 1 and Q 2 , electric energy stored in the capacitors C 1 and C 2 can be transferred to a primary side terminal T 31 of the transformer T 3 via a coupling capacitor C 3 to form an AC power source ac. The voltage of the capacitors C 1 and C 2 is a half (Vcc/2) of the DC voltage Vcc. The AC power source ac is used to provide energy for the transformer T 3 , which boosts and converts the ac power source to the secondary side 302 for driving the load.

Please refer to FIG. 7 . An inverter circuit 40 and a control chip 42 are connected and disposed on the same printed circuit board. If the used inverter circuit 40 is of the full-bridge type, a full-bridge type control chip 42 needs to be matched for normal operations, if the used inverter circuit is of the half-bridge type, a half-bridge type control chip needs to be matched for normal operations, and if the used inverter circuit is of the push-pull type, a push-pull type control chip needs to be matched for normal operations. Therefore, there is less flexibility and commonality in practical use. Moreover, use of the inverter circuit 40 is usually limited by the control chip 40 to cause malfunction of the inverter circuit 40 .

1. Field of the Invention

The present invention relates to a modularized inverter control circuit and, more particularly, to a control circuit making use of a push-pull type control IC to connect other accessory circuit units and packaged and disposed on a printed circuit board to accomplish modularization for driving and control of various inverter circuits.

2. Description of Related Art

Accordingly, one object of the present invention is to provide a modularized inverter control circuit, which makes use of a push-pull type control IC to connect other accessory circuit units and is packaged and disposed on a printed circuit board to accomplish modularization for driving and control of various inverter circuits.

In the modularized inverter control circuit of the present invention, a control circuit conventionally disposed on the same printed circuit board is separated and disposed on another printed circuit board. The control circuit is used to connect and control an inverter circuit for driving several lamps. The modularized inverter control circuit comprises a control IC used to output two control signals via two output signal pins NOUT 1 and NOUT 2 , a lamp current feedback unit connected to the control IC and at least a lamp and used to get working currents of the lamps and convert them into voltage forms sent to the control IC, a turn-on voltage limit unit connected to the control IC and the lamps and used to get working voltages of the lamps and send them to the control IC, a lamp protection unit connected to the control IC and the lamps and used for open-circuit and short-circuit protection of the lamps, a power source control unit connected to the control IC and used to provide the required electric power for the control IC, and a reference unit connected to the control IC and composed of several resistors and capacitors and used to provide the required reference values for operation of the control IC.

The modularized inverter control circuit of the present invention can thus be flexibly matched with various inverter circuits. The primary advantages are as follows.

1. Standardization and formularization can be accomplished to enhance the quality and reliability of product.

2. The development time of product like the time spent on debug and layout can be shortened.

3. Market requirements can be met

4. Mass production can be accomplished to lower the cost.

5. Inverter circuits of different topologies like externally excited push-pull type, half-bridge type, and full-bridge type can be matched.

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 diagram showing how a conventional push-pull type inverter circuit drives a load;

FIG. 2 is a waveform diagram of control signals outputted by a conventional push-pull type control chip and an output voltage at the load end;

FIG. 3 is a circuit diagram showing how a conventional full-bridge type inverter circuit drives a load;

FIG. 4 is a waveform diagram of control signals outputted by a conventional full-bridge type control chip;

FIG. 5 is a circuit diagram showing how a conventional half-bridge type inverter circuit drives a load;

FIG. 6 is a waveform diagram of control signals outputted by a conventional half-bridge type control chip and an AC power source voltage;

FIG. 7 is a control architecture diagram of a conventional inverter circuit;

FIG. 8 is a diagram of a modularized inverter control circuit of the present invention;

FIG. 9 is a simple architecture diagram showing how the present invention controls various inverter circuits;

FIG. 10 is a circuit diagram of a push-pull type inverter circuit;

FIG. 11 is a circuit diagram of a full-bridge type inverter circuit;

FIG. 12 is a circuit diagram of a half-bridge type inverter circuit;

FIG. 13 is a circuit diagram of another half-bridge type inverter circuit;

FIG. 14 is a circuit diagram of yet another half-bridge type inverter circuit; and

FIG. 15 is a circuit diagram of still yet another half-bridge type inverter circuit.

As shown in FIG. 8 , a modularized inverter control circuit 50 of the present invention is packaged and arranged on a printed circuit board (not shown) and used to connect and control an inverter circuit (not shown) for driving of several lamps (not shown). The modularized inverter control circuit 50 comprises a control IC 500 used to output two control signals via two output signal pins NOUT 1 and NOUT 2 , a lamp current feedback unit 502 connected to the control IC 500 and at least the lamps and used to get working currents of the lamps and convert them into voltage forms sent to the control IC 500 , a turn-on voltage limit unit 504 connected to the control IC 500 and the lamps and used to get working voltages of the lamps and send them to the control IC 500 , a brightness adjustment unit 505 connected to the control IC 500 and the lamps, a lamp protection unit 506 connected to the control IC 500 and the lamps and used for open-circuit and short-circuit protection of the lamps, a power source control unit 508 connected to the control IC 500 and used to provide the required electric power for the control IC 500 , and a reference unit 509 connected to the control IC 500 and composed of several capacitors (C 1 , C 2 , C 3 ) and a resistor (R 1 ) and used to provide the required reference values for operation of the control IC 500 .

Please refer to FIG. 8 again. The control IC 500 is a push-pull type control IC. The lamp current feedback unit 502 is composed of a resistor R 2 and a capacitor C 5 , and gets the working currents of the lamps via a feedback pin (F/B) and converts them into voltage forms sent to the control IC 500 . The turn-on voltage limit unit 504 is composed of resistors (R 4 , R 5 ) and capacitors (C 8 , C 9 ), and gets the working voltages of the lamps via a voltage acquisition pin (CLAMP) and sends them to the control IC 500 . The brightness adjustment unit 505 is composed of a resistor R 3 and capacitors (C 6 , C 7 ), and is used to adjust the brightness of the lamps. The lamp protection unit 506 is composed of resistors (R 6 , R 7 ), a capacitor C 10 , and a diode (D 1 ), and gets open-circuit and short-circuit signals of the lamps via a protection pin (PORT), and send them to the control IC 500 . The power source control unit 508 is composed of resistors (R 8 ˜R 14 ), capacitors (C 10 , C 11 ), a diode D 3 , and transistors (Q 1 , Q 2 , Q 3 ), and gets the required electric power of the control IC 500 via a power source pin VCC and gets a switch selection signal via a switch pin (ON/OFF).

FIG. 9 is a simple architecture diagram showing how the present invention controls various inverter circuits. Users can more flexibly connect the modularized inverter control circuit of the present invention to inverter circuits of different topologies like a push-pull type inverter circuit 52 , a full-bridge type inverter circuit 54 , and a half-bridge type inverter circuit 56 to control these inverter circuits for driving the lamps to be on.

Please refer to FIG. 10 as well as FIG. 8 . In FIG. 10 , the push-pull type inverter circuit 52 makes use of control terminals of a power switch Q 5 and a power switch Q 6 connect the two output signal pins (NOUT 1 , NOUT 2 ) of the control IC 500 in FIG. 8 via a resistor R 15 and a resistor R 16 , respectively, and receives two control signals outputted by the two output signal pins (NOUT 1 , NOUT 2 ). Moreover, the terminals F/B, CLAMP, and PORT shown in FIG. 10 are correspondingly connected to the feedback pin (F/B), the voltage acquisition pin (CLAMP), and the protection pin (PORT) of the control IC 500 .

In the above illustration, the modularized inverter control circuit of the present invention can be connected to the push-pull type inverter circuit 52 and use the two control signals to control switching actions of the power switches Q 5 and Q 6 of the push-pull type inverter circuit 52 for driving the lamps CCFL to be on.

Please refer to FIG. 11 as well as FIG. 8 . In FIG. 11 , the full-bridge type inverter circuit 54 is connected to the two output signal pins (NOUT 1 , NOUT 2 ) of the control IC 500 in FIG. 8 via a conversion circuit 540 , and receives two control signals outputted by the two output signal pins (NOUT 1 , NOUT 2 ). Moreover, the terminals F/B, CLAMP, and PORT shown in FIG. 11 are correspondingly connected to the feedback pin (F/B), the voltage acquisition pin (CLAMP), and the protection pin (PORT) of the control IC 500 .

In the above illustration, the modularized inverter control circuit of the present invention can be connected to the full-bridge type inverter circuit 54 , send the two control signals to the conversion circuit 540 of the full-bridge type inverter circuit 54 , and use the conversion circuit 540 to control switching actions of a power switch set Q 7 and a power switch set Q 8 for driving the lamps CCFL to be on.

Please refer to FIG. 12 as well as FIG. 8 . In FIG. 12 , the half-bridge type inverter circuit 56 is a dual-NMOS half-bridge type inverter circuit, and is connected to the two output signal pins (NOUT 1 , NOUT 2 ) of the control IC 500 in FIG. 8 via a conversion circuit 560 , and receives two control signals outputted by the two output signal pins (NOUT 1 , NOUT 2 ). Moreover, the terminals F/B, CLAMP, and PORT shown in FIG. 12 are correspondingly connected to the feedback pin (F/B), the voltage acquisition pin (CLAMP), and the protection pin (PORT) of the control IC 500 .

In the above illustrations, the modularized inverter control circuit of the present invention can be connected to the half-bridge type inverter circuit 56 , send the two control signals to the conversion circuit 560 of the full-bridge type inverter circuit 56 , and use the conversion circuit 560 to control switching actions of a power switch set Q 9 and a power switch set Q 10 for driving the lamps CCFL to be on.

Please refer to FIG. 13 as well as FIG. 8 . In FIG. 12 , the half-bridge type inverter circuit 56 is a 1N1P-MOS half-bridge type inverter circuit, and is connected to the two output signal pins (NOUT 1 , NOUT 2 ) of the control IC 500 in FIG. 8 via a conversion circuit 660 , and receives two control signals outputted by the two output signal pins (NOUT 1 , NOUT 2 ).

Please refer to FIG. 14 as well as FIG. 8 . In FIG. 14 , the half-bridge type inverter circuit 56 is a 1N1P-MOS half-bridge type inverter circuit, and is connected to the two output signal pins (NOUT 1 , NOUT 2 ) of the control IC 500 in FIG. 8 via a conversion circuit 760 , and receives two control signals outputted by the two output signal pins (NOUT 1 , NOUT 2 ).

Please refer to FIG. 15 as well as FIG. 8 . In FIG. 15 , the half-bridge type inverter circuit 56 is a 1N1P-MOS half-bridge type inverter circuit, and is connected to the two output signal pins (NOUT 1 , NOUT 2 ) of the control IC 500 in FIG. 8 via a conversion circuit 860 , and receives two control signals outputted by the two output signal pins (NOUT 1 , NOUT 2 ).

To sum up, the present invention mainly applies to control of an inverter circuit of a display backlight panel. The modularized inverter control circuit of the present invention can be flexibly matched with various inverter circuits of different topologies. The primary advantages are as follows.

1. Standardization and formularization can be accomplished to enhance the quality and reliability of product.

2. The development time of product like the time spent on debug and layout can be shortened.

3. The requirements of market can be met

4. Mass production can be accomplished to lower the cost.

5. Inverter circuits of different topologies like externally excited push-pull type, half-bridge type, and full-bridge type can be matched.

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 intended to be embraced within the scope of the invention as defined in the appended claims.