TWI409740B - Inverter circuit - Google Patents

Abstract

An inverter circuit is used for driving a light source module. An input signal circuit is used for providing a power signal. A power stage circuit is used for converting the power signal to a square-wave electrical signal. A transformer circuit is used for converting the square-wave electrical signal to an electrical signal to drive the light source module. A voltage detecting circuit is used for detecting voltage added to the light source module, and outputting a voltage detected signal. A feedback circuit is used for feeding back current flowing through the light source module, and outputting a current feedback signal. A protection circuit is used for outputting a latch signal according to the detected voltage signal and the feedback current signal. A PWM control circuit is connected to the power stage circuit and the protection circuit, for cutting the output thereof according to the latch signal. The DC signal or the switching signal is an external power signal to maintain the protection circuit to work normally.

Description

Inverter circuit

The present invention relates to an inverter circuit, and more particularly to an inverter circuit having a protection function.

At present, the panel of a liquid crystal display (LCD) mainly uses a discharge lamp (Discharge Lamp) as a backlight, and such a lamp requires a high driving voltage to illuminate. In order to ensure the normal operation of the discharge lamp, it will not be burnt out when the circuit is abnormal. It is usually necessary to detect the voltage applied across the lamp and the current flowing through the lamp to judge the working state of the discharge lamp. Protect the lamp.

FIG. 1 is a schematic diagram of a conventional inverter circuit function module for driving a light source module 14 including an input signal circuit 10, a power conversion circuit 11, a transformer circuit 12, a voltage sensing circuit 13, and a feedback circuit. 15 and PWM control circuit 16. The PWM control circuit 16 includes a PWM controller and a driving circuit 161 and a latch signal generator 162. The input signal circuit 10 is used to provide a DC signal to the power conversion circuit 11 and the PWM controller and the drive circuit 161. The power conversion circuit 11 is configured to convert the DC signal into a square wave signal. The transformer circuit 12 is used to convert the square wave signal into a sine wave signal required by the light source module 14. The voltage sensing circuit 13 is for sensing a voltage applied across the light source module 14. The feedback circuit 15 is used The current flowing through the light source module 14 is fed back to the PWM controller and the driving circuit 161 and the latch signal generator 162. Under normal circumstances, the PWM controller and the driving circuit 161 controls the output of the power conversion circuit 11 according to the feedback signal of the feedback circuit 15, thereby adjusting the current flowing through the light source module 14. In an abnormal situation, that is, when the voltage applied to the light source module 14 or the current flowing therethrough exceeds the allowable range, the latch signal generator 162 outputs a latch signal according to the output of the voltage sensing circuit 13 or the feedback circuit 15. . At the same time, the PWM controller and the driving circuit 161 output the off control signal to the power conversion circuit 11 according to the latch signal, thereby cutting off the light source module 14.

In the conventional converter circuit, the PWM controller and drive circuit 161 and the latch signal generator 162 are usually integrated in the PWM control circuit 16, that is, the functions are performed by one IC. For different converter circuits, the protection function needs to design the detection circuit according to the actually selected PWM control circuit 16. Moreover, the operation level parameter of the PWM control circuit 16 is a fixed value and cannot be modified. Also, the overall line error is also considered and the range in which the PWM control circuit 16 is applicable is reduced.

In view of this, it is desirable to provide an inverter circuit that separates the detection protection circuit from the PWM control circuit without having to design the circuit each time; and at the same time, expands the range in which the PWM control circuit can be applied.

An inverter circuit for driving a light source module, the converter circuit comprising an input signal circuit, a power conversion circuit, a transformer circuit, a voltage sensing circuit, a feedback circuit, a protection circuit, and a PWM control circuit. Input signal circuit for Provide power signal. The power conversion circuit is connected to the input signal circuit for converting the power signal into a square wave signal. The transformer circuit is connected between the power conversion circuit and the light source module, and is used for converting the square wave signal into a driving signal capable of driving the light source module. The voltage sensing circuit is connected to the transformer for sensing the voltage applied across the light source module and outputting a voltage sensing signal. The feedback circuit is connected to the light source module for feeding back the current flowing through the light source module and outputting a current feedback signal. The protection circuit is connected to the voltage sensing circuit, the feedback circuit, and the input signal circuit for outputting the latch signal according to the voltage sensing signal or the current feedback signal. The PWM control circuit is connected to the power conversion circuit and the protection circuit for turning off its output to the power conversion circuit according to the latch signal. The power signal is used as an external power signal of the protection circuit. When the protection circuit does not have the power signal input, the latch signal is reset.

An inverter circuit for driving a light source module, the converter circuit comprising an input signal circuit, a power conversion circuit, a complex transformer circuit, a complex voltage sensing circuit, a feedback circuit, a protection circuit, and a PWM control circuit. The input signal circuit is used to provide a power signal. The power conversion circuit is connected to the input signal circuit for converting the power signal into a square wave signal. The transformer circuit is connected between the power conversion circuit and the light source module, and is used for converting the square wave signal into a driving signal capable of driving the light source module. The voltage sensing circuits are connected to the transformers for sensing voltages applied across the light source module and outputting voltage sensing signals. The feedback circuit is connected to the light source module for feeding back the current flowing through the light source module and outputting a current feedback signal. The protection circuit is connected to the voltage sensing circuit, the feedback circuit, and the input signal circuit for Voltage sensing signal or current feedback signal, output latch signal. The PWM control circuit is connected to the power conversion circuit and the protection circuit for turning off its output to the power conversion circuit according to the latch signal. The power signal is an external power signal of the protection circuit. When the protection circuit does not have the power signal input, the latch signal is reset.

In the inverter circuit of the present invention, the protection circuit is designed independently of the PWM control circuit, so that it can be applied to different PWM control circuits in different converter circuits, and the design of the protection detection circuit is not required every time.

20, 40‧‧‧ input signal circuit

21, 41‧‧‧ power conversion circuit

22, 42n‧‧‧ transformer circuit

23, 43n‧‧‧ voltage sensing circuit

24, 44n‧‧‧ light source module

25, 45‧‧‧Responsive circuit

26, 46‧‧‧Protection circuit

27, 47‧‧‧ PWM control circuit

T, Tn‧‧‧ transformer

C, Cn, C1, C2‧‧‧ capacitor

261‧‧‧Exception Signal Generator

262‧‧‧Latch signal generator

R1, R2, R3, R4, R5, R6, R7‧‧‧ resistance

Q1, Q2, Q3‧‧‧ transistor

P1‧‧‧ Abnormal signal sensing end

Figure 1 is a functional block diagram of a conventional inverter circuit.

2 is a functional block diagram of an inverter circuit according to a first embodiment of the present invention.

Figure 3 is a diagram showing the internal structure of the protection circuit of the present invention.

4 is a detailed circuit diagram of a latching signal generator of the protection circuit of the present invention.

Fig. 5 is a functional block diagram of an inverter circuit according to a second embodiment of the present invention.

2 is a functional block diagram of a converter circuit according to a first embodiment of the present invention, which is used to drive a light source module 24, and the converter circuit includes an input signal circuit 20, a power conversion circuit 21, and a transformer circuit 22. The voltage sensing circuit 23, the feedback circuit 25, the protection circuit 26, and the PWM control circuit 27.

The input signal circuit 20 is used to provide a power signal. In this embodiment, the power signal includes a DC signal or a switching signal. The power conversion circuit 21 is connected to the input circuit 20 for converting the received DC power signal into a square wave signal. The transformer circuit 22 is connected to the power conversion circuit 21 for converting the square wave signal into a driving signal required by the light source module 24. In this embodiment, the driving signal is a sine wave signal. The transformer circuit 22 includes a transformer T and a capacitor C. The primary side of the transformer T is connected to the power conversion circuit 21, and the secondary side high voltage end thereof is connected to the light source module 24 through the capacitor C. The voltage sensing circuit 23 is simultaneously connected to the high voltage end and the low voltage end of the secondary side of the transformer for sensing the voltage applied to the two ends of the light source module 24 and outputting the voltage sensing signal V _IN1 . Wherein, when any of the lamps in the light source module 24 is not connected, or when the peripheral circuit of the transformer T is defective, or when the lamp is touched by humans, an overvoltage is generated in the transformer T, if the abnormal voltage is loaded In the circuit, not only the lamp is burned out but also other circuit components are damaged, so it is necessary to detect the abnormal voltage.

The feedback circuit 25 is connected between the light source module 24 and the PWM control circuit 27 for feeding back the current flowing through the light source module 24. The protection circuit 26 is connected to the input signal circuit 20, the voltage sensing circuit 23, the feedback circuit 25, and the PWM control circuit 27 for outputting the latch signal V _OUT according to an abnormal voltage signal or an abnormal current signal. In the present embodiment, the feedback circuit 25 inputs the current flowing through the light source module 24 to the protection circuit 26 and the PWM control circuit 27, respectively.

Specifically, in the normal case, the PWM control circuit 27 controls the output of the current in the power conversion circuit 21 based on the current feedback signal of the feedback circuit 25. In an abnormal situation, when the voltage sensed by the voltage sensing circuit 23 or the current fed back by the feedback circuit 25 exceeds the allowable range, the protection circuit 26 inputs according to the voltage signal V _IN1 or the feedback circuit 25 input by the voltage sensing circuit 23 . The current signal V _IN2 outputs a latch signal V _OUT to the PWM control circuit 27. At the same time, the PWM control circuit 27 is also connected to the input signal circuit 20 and the power conversion circuit 21 for turning off the output of the PWM signal to the power conversion circuit 21 according to the output of the latch signal V _OUT . In this embodiment, the power signal outputted by the input signal circuit 20 is an external power signal of the protection circuit 26.

Referring also to Figure 3, there is shown an internal architecture of the protection circuit 26 of the present invention. The protection circuit 26 includes an abnormal signal generator 261 and a latch signal generator 262, both connected to the input signal circuit 20 for receiving the power signal as its external power signal. The abnormal signal generator 261 is configured to compare the received voltage sensing signal V _IN1 or the current feedback signal V _IN2 with an internal abnormal voltage preset value or an abnormal current preset value, when the voltage sensing signal V is _{When the IN1} or the current feedback signal V _IN2 exceeds its corresponding preset value, the abnormal signal is output to the abnormal signal sensing terminal P1 of the latch signal generator 262. At this time, the latch signal generator 262 outputs the latch signal V _OUT according to the abnormal signal.

In the present embodiment, when the inverter circuit is abnormal, the protection circuit 26 outputs the latch signal V _OUT , such as a high level, and the PWM control circuit 27 turns off its output to the power conversion circuit 21, and the entire circuit cannot operate. Since the power signal acts as an external power signal for the protection circuit 26, the latch signal V _OUT will always exist as long as it is not turned off. In other words, the protection circuit 26 resets the latch signal V _OUT only when the output of the input signal circuit 20 is turned off.

Specifically, when an abnormality occurs in the inverter circuit, the protection circuit 26 generates the latch signal V _OUT , and the PWM control circuit 27 turns off its output, so that the entire circuit stops operating. At this time, the user will cut off the output of the input signal circuit 20, and the protection circuit 25 will release the latch signal V _OUT and reset it so that the inverter circuit can resume operation when the power is turned on again.

4 is a specific circuit diagram of the latch signal generator 262 of FIG. 3, which includes a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, a fifth resistor R5, and a sixth resistor R6. a seventh resistor R7; a first capacitor C1, a second capacitor C2; a first transistor Q1, a second transistor Q2, and a third transistor Q3. Among them, the transistors Q1 and Q3 are NPN transistors, and the transistors Q2 are PNP transistors.

The base of the transistor Q1 is connected to the abnormal signal sensing terminal P1, and the emitter is grounded. The base of the transistor Q2 is connected to the drain of the transistor Q1, and the emitter receives the power signal output from the input signal circuit 20, and its drain is connected to the base of the transistor Q1. The base of the transistor Q3 also receives the power signal output from the input signal circuit 20, and its drain is used as the output terminal of the protection circuit 26 for outputting the latch signal V _OUT , and its emitter is grounded.

The resistor R1 is connected in series between the abnormal signal input terminal P1 and the base of the transistor Q1, and the capacitor C1 is connected between the base of the transistor Q1 and the ground. In this embodiment, the resistor R1 and the capacitor C1 form a delay circuit, and delay the abnormal signal input by the abnormal signal input terminal P1 to determine whether the abnormal input signal belongs to a true abnormal signal.

The resistor R2 is connected in parallel with the capacitor C1, which forms a discharge loop with the capacitor C1. When the inverter circuit is restarted, the electrical energy in the capacitor C1 is discharged through the resistor R2. At the same time, when the transistor Q2 is turned on, the resistor R2 can also prevent the current flowing through it from being excessive.

The resistor R3 is connected between the drain of the transistor Q1 and the base of the transistor Q2 for A bias voltage is supplied to the transistor Q2.

One end of the resistor R4 is connected to the input signal circuit 10 for receiving the power signal, and the other end is connected to the drain of the transistor Q1. The resistor R5 is connected between the drain of the transistor Q1 and the base of the transistor Q3, and the resistor R6 is connected between the base of the transistor Q3 and the ground. Capacitor C2 is connected in parallel with resistor R6. Similarly, the resistor R5 and the capacitor C2 form a delay circuit, and the resistor R6 and the capacitor C2 form a discharge loop.

The resistor R7 is connected in series between the input signal circuit 20 and the drain of the transistor Q3 for preventing the current flowing through the transistor Q3 from being excessive.

In this embodiment, when the protection circuit 26 has no abnormal voltage V _IN1 or abnormal current signal V _IN2 input, that is, when the abnormal signal sensing terminal P1 of the latch signal generator 262 has no abnormal signal input, the transistors Q1 and Q2 At the end, the transistor Q3 is turned on. Therefore, the drain output latch signal V _OUT of the transistor Q3 is at a low level. When the protection circuit 26 has an abnormal voltage V _IN1 or an abnormal current signal V _IN2 input, that is, when the abnormal signal sensing terminal P1 of the latch signal generator 262 has an abnormal signal input, the transistors Q1 and Q2 are turned on, and the transistor Q3 is turned on. cutoff. Therefore, the drain output latch signal V _OUT of the transistor Q3 is at a high level.

Fig. 5 is a functional block diagram of an inverter circuit according to a second embodiment of the present invention. The converter circuit is substantially the same as the converter circuit shown in FIG. 2, except that the converter circuit is configured to drive a complex light source module 44n (n=1, 2, 3, . . . , n), which includes a plurality Transformer circuit 42n (n = 1, 2, 3, ..., n), complex voltage sensing circuit 43n (n = 1, 2, 3, ..., n). The internal architecture of the transformer circuits 42n (n = 1, 2, 3, ..., n) is the same as the internal architecture of the transformer circuit 42 of Figure 2, The connection relationship between the complex transformer circuit 42n (n=1, 2, 3, ..., n) and the light source modules 44n (n = 1, 2, 3, ..., n) and the transformer circuit 22 and the light source mode in Fig. 2 The connection relationship of the group 24 is the same, and the connection relationship of the complex voltage sensing circuits 43n (n = 1, 2, 3, ..., n) is the same as the connection relationship of the voltage sensing circuit 23 in Fig. 3. Therefore, it will not be described here.

In the inverter circuit of the present invention, the protection circuit 26 is designed independently of the PWM control circuit 27, so that it can be applied to different PWM control circuits 16 in different inverter circuits, and it is not necessary to perform the protection detection circuit every time. The design.

In summary, the present invention is disclosed above in the context of the Luojia embodiment, and is not intended to limit the invention. However, any person skilled in the art will be able to make changes and refinements without departing from the spirit and scope of the invention, and the scope of the invention is defined by the scope of the appended claims.

20‧‧‧Input signal circuit

21‧‧‧Power conversion circuit

22‧‧‧Transformer circuit

23‧‧‧Voltage sensing circuit

24‧‧‧Light source module

25‧‧‧Return circuit

26‧‧‧Protection circuit

27‧‧‧PWM control circuit

T‧‧‧Transformer

C‧‧‧ capacitor

Claims (18)

An inverter circuit for driving a light source module, the converter circuit comprising: an input signal circuit for providing a power signal; and a power conversion circuit connected to the input signal circuit for converting the power signal into a square a transformer circuit connected between the power conversion circuit and the light source module for converting the square wave signal into a driving signal capable of driving the light source module; and a voltage sensing circuit connected to the transformer circuit The method is configured to sense a voltage applied to the two ends of the light source module, and output a voltage sensing signal; the feedback circuit is connected to the light source module, and is configured to feedback current flowing through the light source module, and output a current feedback signal a protection circuit coupled to the voltage sensing circuit, the feedback circuit, and the input signal circuit for outputting a latch signal according to the voltage sensing signal or the current feedback signal; and a PWM control circuit, and the power conversion The circuit is connected to the protection circuit for turning off the output of the power conversion circuit according to the latch signal; wherein the power signal is external to the protection circuit Signal source, the protective circuit when the power signal is no input, the latch signal is reset. The inverter circuit of claim 1, wherein the power signal comprises a direct current signal or a switching signal. The inverter circuit of claim 1, wherein the PWM control circuit is further connected to the feedback circuit for controlling the power according to the current feedback signal The output of the source conversion circuit. The inverter circuit of claim 1, wherein the transformer circuit comprises: a transformer, a primary side of which is connected to the power conversion circuit, a secondary side of which is connected to the light source module; and a capacitor connected to the capacitor The high voltage end of the secondary side of the transformer is between the light source module. The inverter circuit of claim 4, wherein the voltage sensing circuit is simultaneously connected to the high voltage end and the low voltage end of the secondary side of the transformer. The inverter circuit of claim 1, wherein the protection circuit comprises: an abnormal signal generator, configured to compare the voltage sensing signal or the current feedback signal with a preset value thereof to generate An abnormal current signal or an abnormal voltage signal; and a latch signal generator connected to the abnormal signal generator for outputting the latch signal according to the abnormal voltage signal or the abnormal current signal; wherein the abnormal signal generator and the The latch signal generators are all connected to the input signal circuit. The inverter circuit of claim 6, wherein the latch signal generator comprises: a first transistor having a base connected to the abnormal signal generator and an emitter grounded; the second transistor; The base is connected to the drain of the first transistor, the emitter is connected to the input signal circuit, and the drain is connected to the base of the first transistor; a third transistor having a base connected to the power conversion circuit, and a drain as an output end of the latch signal, connected to the PWM control circuit, and an emitter grounded; wherein the first transistor and the second When the crystal is turned off, the third transistor is turned on, and the latch signal is outputted to a low level; when the first transistor and the second transistor are turned on, the third transistor is turned off, and the latch signal is output. Is high. The inverter circuit of claim 7, wherein the first transistor and the third transistor system are NPN transistors, and the second transistor system is a PNP transistor. The inverter circuit of claim 1, wherein the driving signal is a sine wave signal. An inverter circuit for driving a plurality of light source modules, the converter circuit comprising: an input signal circuit for providing a power signal; and a power conversion circuit coupled to the input signal circuit for converting the power signal into a square wave signal; a complex transformer circuit correspondingly connected between the power conversion circuit and the light source modules for converting the square wave signal into a driving signal capable of driving the light source modules; a plurality of voltage sensing circuits, Corresponding to the transformers, for sensing voltages applied across the light source modules, and outputting a voltage sensing signal; a feedback circuit connected to the light source module for feedback flowing through the light source module Group current, and output current feedback signal; protection circuit, and the voltage sensing circuit, the feedback circuit, and the input signal The circuit is connected to output a latch signal according to the voltage sensing signals or the current feedback signals; and a PWM control circuit is connected to the power conversion circuit and the protection circuit for closing according to the latch signal Disconnecting the output to the power conversion circuit; wherein the power signal is an external power signal of the protection circuit, and the latch signal is reset when the protection circuit has no power signal input. The inverter circuit of claim 10, wherein the power signal comprises a direct current signal or a switching signal. The inverter circuit of claim 10, wherein the PWM control circuit is further connected to the feedback circuit for controlling an output of the power conversion circuit according to the current feedback signal. The inverter circuit of claim 10, wherein the transformer circuit comprises: a transformer, the primary side of which is connected to the power conversion circuit, the secondary side of which is connected to the light source module; and the capacitor and the connection The high voltage end of the secondary side of the transformer is between the light source module. The inverter circuit of claim 13, wherein the voltage sensing circuit is simultaneously connected to the high voltage end and the low voltage end of the secondary side of the corresponding transformer. The inverter circuit of claim 10, wherein the protection circuit comprises: an abnormal signal generator, configured to compare the voltage sensing signal or the current feedback signal with a preset value thereof to generate An abnormal current signal or an abnormal voltage signal; and a latch signal generator connected to the abnormal signal generator for using the different The normal voltage signal or the abnormal current signal outputs the latch signal; wherein the abnormal signal generator and the latch signal generator are both connected to the input signal circuit. The inverter circuit of claim 15, wherein the latch signal generator comprises: a first transistor having a base connected to the abnormal signal generator and an emitter grounded; and a second transistor; a base thereof is connected to the drain of the first transistor, an emitter is connected to the input signal circuit, a drain is connected to a base of the first transistor, and a third transistor, a base thereof and the power source a switching circuit is connected, the drain is connected to the PWM control circuit, and the emitter is connected to the PWM control circuit. The third transistor is turned on when the first transistor and the second crystal are turned off. Then, the latch signal outputted is low level; when the first transistor and the second crystal are turned on, the third transistor is turned off, and the latch signal outputted is high level. The inverter circuit of claim 16, wherein the first transistor and the third transistor system are NPN transistors, and the second transistor system is a PNP transistor. The inverter circuit of claim 10, wherein the driving signal is a sine wave signal.