TWI410165B - Light-emitting diode backlight module power supply circuit - Google Patents

Abstract

Disclosed is a power supply circuit of an LED backlight module. The power supply circuit comprises a transformer whose secondary side includes at least a system electricity winding and an ignition electricity winding. The system electricity winding induces system electricity. The ignition electricity winding induces inducted electricity and further connects to a power switch unit and a control circuit. The control circuit drives the power switch unit to modulate the power of the inducted electricity passing through the power switch unit. Furthermore, the ignition electricity winding connects to a plurality of parallel-connected balancing capacitors and an ignition circuit at the rear end of each balancing capacitor. Since the plural parallel-connected capacitors influence each other, the currents passing through the plurality of balancing capacitors are made equal. The ignition circuits of the rear ends modulate the inducted electricity passing through the balancing capacitors to thereby turn the inducted electricity into the ignition electricity, and each ignition circuit respectively drives an LED lamp set.

Description

Power circuit of LED backlight module

A power supply circuit for a light-emitting diode backlight module, in particular to a system that simultaneously supplies system power and lighting power to supply a liquid crystal control circuit and illuminate a plurality of light-emitting diode lamps.

Due to the driving technology of the light-emitting diode and the continuous breakthrough in the field of use, liquid crystal displays using a discharge bulb (such as a cold cathode tube) as a backlight have also begun to use a light-emitting diode as a light source. Since the light-emitting diode is driven by direct current, the brightness of the light-emitting depends on the current, and the more common way is to use the constant current mode to drive, so that the industry needs to specially design a power supply matching the liquid crystal display and the light-emitting diode. The basic structure of the power supply for matching the liquid crystal display and the light-emitting diode can be referred to FIG. 1. The power supply has a main transformer 91 that receives input power from a front-stage modulation circuit 100. The main transformer 91 includes at least one primary side. The winding 911 and a secondary winding 912, the input power flows through the primary winding 911, and an induced power is generated in the secondary winding 912. The first use of the inductive power is to separate a system power 913 for operation of the control system of the liquid crystal display. On the other hand, the secondary winding 912 is connected to the plurality of lighting circuit groups 92, and the plurality of lighting circuit groups 92. The inductive power is obtained and each of the light-emitting diode lamps 93 is lit. Each of the lamp circuit groups 92 includes a DC power converter 921 connected to the LED lamp set 93, a power switch 94, and a control circuit 922. The control circuit 922 drives the DC power converter 921 to sense the power. The LED light is turned on to illuminate the LED array 93, and the control circuit 922 also drives the power switch 94 to adjust the current through the LED sub-lamp 93. The control circuit 922 detects the current passing through the LED group 93, thereby controlling the operation of the DC power converter 921.

Although the above-mentioned conventional power supply architecture can match the needs of the liquid crystal display and the light-emitting diode, each set of the light-emitting diode lamp group 93 is matched with a light-emitting circuit 92, and each lighting circuit 92 has a DC power converter 921 and control. The circuit 922 has a high cost and a large volume. If it is used on a liquid crystal display having a relatively large area, the cost is too high, the volume is too large, and it is not competitive. In addition, when the DC power converter 921 is omitted, if the lighting circuit 92 and the control system of the liquid crystal display share the induction power of the same secondary winding 912, if the system power 913 is used for voltage stabilization control, The induced power obtained by the lighting circuit 92 is caused to fluctuate together, causing a work load on the lighting circuit 92, and even causing fluctuations in the lighting power, which is a problem caused by the cross regulation. In addition, since the plurality of light-emitting diode lamp sets 93 are applied to the same liquid crystal display panel, in addition to the above technical problems, a control method in which the light-emitting diodes are all bright is required. Therefore, in order to enable the light-emitting diode to be applied to a liquid crystal display at a lower cost, it is required to provide a superior circuit structure to provide a power supply for matching the liquid crystal display and the light-emitting diode.

In view of the above-mentioned technical problems, the purpose of the present invention is to provide a power source that matches the working requirements of the liquid crystal display and the light-emitting diode, and achieves the goal of more precise and stable power control and lower cost.

The present invention is a power supply circuit of a light-emitting diode backlight module. The power circuit has a transformer, and the secondary side of the transformer includes at least one system power winding and a one-light power winding. The system power winding senses a system of power that is required to supply a liquid crystal control circuit for operation. The lighting power winding senses an inductive power, and the lighting power winding is coupled to a power switching unit and a control circuit that drives the power switching unit to regulate the inductive power through the power switching unit. Moreover, the lighting power winding is further connected with a plurality of parallel and mutually balanced balance capacitors of the induced power voltages of the parallel terminals, and a lighting circuit connected to the rear end of each of the balancing capacitors. Since the plurality of parallel balanced capacitors are mutually restrained, the currents passing through the plurality of balanced capacitors are equal, so that the lighting circuit at the rear end is modulated and converted into a lamp power by the inductive power of the balancing capacitor, and each lighting circuit drives a light-emitting diode. Polar body light set.

The first feature of the above structure is that the secondary side of the transformer is divided into a system power winding that supplies the liquid crystal control circuit, and a lighting power winding that supplies the backlight module, so that the system power and the lighting power can be adjusted separately. Interference improves the problem of conventional cross regulation. The second feature is that the rear end of the lighting power winding is regulated by a control circuit and a power switching unit to output power to the back end. Before the inductive power is transmitted to the lighting circuit, the current is balanced by a plurality of parallel balancing capacitors, and the current passing through the balancing capacitors is substantially equalized by the mutual voltage of the balancing capacitors to achieve a current balancing effect. Through the above circuit characteristics, the advantages of omitting the DC converter, using only one control unit, and current balancing are achieved; the circuit components are further reduced, the power supply volume is reduced, and the production cost is reduced.

The present invention is a power supply circuit for a light-emitting diode backlight module, and is applied to a liquid crystal display using a light-emitting diode as a backlight. The circuit structure of the present invention will be described below with reference to the drawings. Referring to FIG. 2 , the power circuit has a transformer 1 , a primary winding 11 of the transformer 1 , and the primary winding 11 is electrically connected to a pre-modulation circuit 100 to obtain an input power. The pre-stage modulation circuit 100 provides the input power to the transformer 1 by initially adjusting the commercial power. The present embodiment does not limit the form of the pre-stage modulation circuit 100, and the pre-stage modulation circuit 100 It will be familiar to those of ordinary skill in the art, and will not be described again. The secondary side of the transformer 1 includes at least one system power winding 12 and a one-light power winding 13, the system power winding 12 senses a system power supply to a liquid crystal control circuit 2, and the lighting power winding 13 senses an induced power . The lighting power winding 13 is connected to a power switching unit 4, and a control circuit 3 is provided to generate a duty cycle signal, and the duty cycle signal drives the power switching unit 4 to regulate the power through the power switching unit 4 by turning on or off. power. The rear end of the lighting power winding 13 is further connected with a plurality of parallel capacitors and mutually restraining the balancing capacitor 5 of the inductive power voltage of the parallel terminal. The inductive power after the regulated power passes through the balancing capacitor 5, and the voltage between the balancing capacitors 5 is mutually restrained. The induced current current passing through the balancing capacitor 5 is substantially equal. Each of the parallel connected balance capacitors 5 is connected to a light-emitting circuit 6 at the rear end. The lighting circuit 6 modulates the induced power passing through the balanced capacitor 5, and converts the induced power into a little lamp power to drive a light-emitting diode. The body lamp group 7, the multi-array light-emitting diode lamp group 7 becomes the backlight module light source of the liquid crystal display. The first feature of the above circuit architecture is that the secondary side of the transformer 1 is divided into a system power winding 12 for supplying the liquid crystal control circuit 2, and a lighting power winding 13 for lighting the plurality of light-emitting diode lamps 7, and The lighting power can be independently adjusted by the control circuit 3 and the power switching unit 4, so that the system power and the lighting power can be separately adjusted without interfering, improving the problem of the conventional cross regulation. The second feature is that the rear end of the lighting power winding 13 is regulated by the control circuit 3 and the power switching unit 4 to output power to the rear end. Before the inductive power is transmitted to the lighting circuit 6, the voltage across each of the balanced capacitors 5 is substantially equalized by the mutual balancing of the voltages across the balancing capacitors 5 through the plurality of parallel balancing capacitors 5, thereby achieving current balance. Effect. In addition, in order to match the lighting frequency of the light-emitting diode lamp set 7 with the operation of the liquid crystal display panel, the control circuit 3 sets a detection point (p) from the system power winding 12 to detect the system power, and determines the The frequency and phase of the system power, and the duty cycle signal is modulated, so that the induced power regulated by the power switching unit 4 has the same frequency and phase as the system power. Furthermore, the plurality of lighting circuits 6 can be connected in series with a resistor 8. The current flowing through the balancing capacitor 5 and the lighting circuit 6 can pass through the resistor 8 at a plurality of feedback points (n ₁ , n ₂ ... n _m ). A plurality of DC voltages are formed, and the control circuit 3 modulates the duty cycle signal according to the DC voltages to further control the power sent to the lighting circuit 6.

Referring to FIG. 3 , FIG. 3 shows an embodiment of the lighting circuit 6 and the control unit 3 , wherein the lighting circuit 6 includes a rectifying unit 61 that obtains induced power from the balancing capacitor 5 and is connected across the rectifying unit. The back-end energy storage capacitor 62, since the power of the induced power has been adjusted by the control unit 3 and the power switch unit 4, and through the current sharing function of the balance capacitors 5, the lighting circuit 6 only needs to pass the rectification The unit 61 converts the induced power into a direct current, and the lighting power is generated by the storage capacitor 62 to drive the light-emitting diode group 7. The control circuit 3 includes a synchronization detecting unit 31, a waveform generating unit 32, a feedback and protection unit 33, and a comparing unit 34. The synchronization detecting unit 31 detects from the detecting point (p). The system generates power, and the synchronization detecting unit 31 generates a synchronization signal according to the system power, and the waveform generating unit 32 generates a sawtooth wave signal according to the variation of the synchronization signal. The feedback and protection unit 33 transmits the DC voltage indirectly through the conversion of the resistor 8 to detect the current flowing through the plurality of lighting circuits 6, thereby generating a feedback signal. Furthermore, the feedback and protection unit 33 may also set an upper limit value to determine whether the obtained DC voltage exceeds the upper limit value, and when the DC voltage exceeds the upper limit value, a preset protection mode may be performed. The protection mechanism is This technical field is well known to those of ordinary skill and will not be described again. The comparing unit 34 compares the sawtooth wave signal with the size of the feedback signal to generate the duty cycle signal. Through the design of the control circuit 3 described above, the power level of the lighting power can be controlled, and the synchronization relationship between the lighting power and the system power is also considered.

Compared with the conventional circuit, the above technical features of the present invention change the operation of the complex DC converter to drive the plurality of lamp groups, and use the complex balancing capacitor 5 to achieve the purpose of current sharing, and only one of the rear ends of the lighting power winding 13 is used. The control unit 3 enables the present invention to further reduce circuit components, reduce power supply volume, and reduce production costs.

Although the present invention has been disclosed in the above preferred embodiments, it is not intended to limit the invention, and any modifications and refinements made by those skilled in the art without departing from the spirit and scope of the invention are intended to be covered by the present invention. Therefore, the scope of protection of the present invention is defined by the scope of the appended claims.

In summary, the present invention enhances the above-mentioned effects in comparison with the conventional creations, and should fully comply with the novelty and progressive statutory innovation patent requirements, and submit an application according to law, and invites you to approve the invention patent application to encourage creation. Feeling the virtues.

100‧‧‧Pre-stage modulation circuit

1‧‧‧Transformer

11‧‧‧ primary winding

12‧‧‧System Power Winding

13‧‧‧Lighting power winding

2‧‧‧LCD control circuit

3‧‧‧Control circuit

31‧‧‧Synchronous detection unit

32‧‧‧ Waveform generating unit

33‧‧‧Return and protection unit

34‧‧‧Comparative unit

4‧‧‧Power switch unit

5‧‧‧Balance capacitance

6‧‧‧Lighting circuit

61‧‧‧Rectifier unit

62‧‧‧ storage capacitor

7‧‧‧Lighting diodes

8‧‧‧resistance

91‧‧‧Transformer

911‧‧‧ primary winding

912‧‧‧secondary winding

913‧‧‧System Power

92‧‧‧Lighting circuit group

921‧‧‧DC power converter

922‧‧‧Control circuit

93‧‧‧Lighting diodes

94‧‧‧Power switch

Figure 1 is a block diagram of a conventional circuit.

Figure 2 is a block diagram of the circuit of the present invention.

Figure 3 is a schematic diagram of the implementation of the circuit of the present invention.

100‧‧‧Pre-stage modulation circuit

1‧‧‧Transformer

11‧‧‧ primary winding

12‧‧‧System Power Winding

13‧‧‧Lighting power winding

2‧‧‧LCD control circuit

3‧‧‧Control circuit

4‧‧‧Power switch unit

5‧‧‧Balance capacitance

6‧‧‧Lighting circuit

7‧‧‧Lighting diodes

8‧‧‧resistance

Claims (4)

A power supply circuit for a light-emitting diode backlight module, wherein the power supply circuit has a transformer, the secondary side of the transformer includes at least one system power winding and a light power winding, and the system power winding senses a system power supply to a liquid crystal control circuit The lighting power winding senses an inductive power, and the lighting power winding is connected:
a power switch unit;
a control circuit for generating a duty cycle signal, the duty cycle signal driving the power switch unit to regulate an induced power power through the power switch unit:
a plurality of balanced capacitors in parallel with each other to reject the induced power voltage of the parallel terminal;
A plurality of lighting circuits are connected to the rear end of each of the balancing capacitors, and the lighting circuits are modulated to convert a sensing power of the balancing capacitor into a lamp power to drive a light-emitting diode lamp group. The power supply circuit of the light-emitting diode backlight module of claim 1, wherein the lighting circuit comprises a rectifying unit that obtains induced power from the balancing capacitor and crosses the rear end of the rectifying unit to form the point. A storage capacitor for lamp power. The power supply circuit of the light-emitting diode backlight module of claim 1, wherein the control circuit detects the power of the system, and the duty cycle signal is modulated to adjust the induced power of the power switch unit. The system power has the same frequency and phase. The power supply circuit of the LED backlight module of claim 3, wherein the control circuit comprises a synchronization detecting unit for detecting power of the system, a waveform generating unit, a feedback and protection unit, and a comparison unit, wherein the synchronization detection unit generates a synchronization signal according to the power of the system, and the waveform generation unit generates a sawtooth wave signal according to the change of the synchronization signal, and the feedback and protection unit detects the flow of the plurality of lights The current of the circuit generates a feedback signal, and the comparing unit compares the sawtooth wave signal with the size of the feedback signal to generate the duty cycle signal.