CN216647824U

CN216647824U - Power supply circuit and display device

Info

Publication number: CN216647824U
Application number: CN202122617338.XU
Authority: CN
Inventors: 王灵松
Original assignee: Guangzhou Shikun Electronic Technology Co Ltd
Current assignee: Guangzhou Shikun Electronic Technology Co Ltd
Priority date: 2021-10-28
Filing date: 2021-10-28
Publication date: 2022-05-31
Anticipated expiration: 2031-10-28

Abstract

The disclosure relates to the field of display devices, and discloses a power supply circuit and a display device, wherein the power supply circuit comprises a conversion circuit, a backlight driving circuit and a feedback protection circuit; the first end of the conversion circuit is connected with a mains supply, the second end of the conversion circuit is connected with the first end of the backlight driving circuit, the second end of the backlight driving circuit is connected with the lamp strip, the third end of the conversion circuit is connected with the first end of the feedback protection circuit, the fourth end of the conversion circuit is connected with the second end of the feedback protection circuit, and the third end of the backlight driving circuit is connected with the third end of the feedback protection circuit. Through the power supply circuit that this disclosure provided, can protect the lamp strip when the drive circuit that is shaded is invalid.

Description

Power supply circuit and display device

Technical Field

The present disclosure relates to the field of display devices, and in particular, to a power supply circuit and a display device.

Background

With the popularization of intelligent household appliances, the market demand of household appliances such as televisions, displays and intelligent lamps is huge, and most of the household appliances use LED light bar luminous sources as backlight of the displays or illumination of the lamps; an LED (Light-Emitting Diode) Light bar needs to work under a DC constant Current condition, so that a combination of power supply topologies such as AC (Alternating Current) -DC (Direct Current) and DC-DC is needed to convert an AC mains supply into an output in a constant DC mode for supplying to the LED Light bar;

the flyback circuit and the Buck voltage reduction circuit are combined, so that a scheme that an LED lamp bar is commonly used by intelligent equipment on the market is provided, a constant voltage can be output by utilizing the multi-path output of the flyback circuit to supply power to a CPU control part, another constant voltage can be output by the other path to be supplied to the Buck voltage reduction circuit, and the constant voltage is converted into a constant current output by the voltage reduction circuit to drive the LED lamp bar; when a consumer uses the LED lamp, the Buck circuit switching tube is short-circuited and fails due to the service life problem of the device or the external severe environment (high temperature and high humidity, dust, small animal foreign matters and the like), so that the voltage reduction effect cannot be achieved, the constant voltage is equivalent to the constant voltage for directly supplying power to the LED lamp bar, the current flowing through the LED lamp bar can be continuously increased under the condition of constant voltage power supply due to the characteristics of the LED lamp, and the voltage and the current of the lamp bar reach dynamic balance according to the volt-ampere characteristics of the LED lamp bar, and finally reach constant current; when the equipment demands that the overpower protection point of the AC-DC circuit is higher, the current of the LED lamp strip is abnormally increased and cannot trigger the overpower protection of the AC-DC circuit within a certain range, and the current flowing through the LED lamp strip is far beyond the rated current specification of the LED lamp strip to continuously work at the moment, so that the overload work of the LED lamp strip generates high temperature, and dangers of roasting and melting the rear shell of the equipment, firing, explosion of lamp beads and the like can exist, and the life and property safety of consumers is endangered.

SUMMERY OF THE UTILITY MODEL

The main purpose of this disclosure is to provide a power supply circuit and display device, can realize carrying out the technological effect protected to LED lamp strip.

The present disclosure provides a power circuit, which includes a conversion circuit, a backlight driving circuit, and a feedback protection circuit;

the first end of the conversion circuit is connected with a mains supply, the second end of the conversion circuit is connected with the first end of the backlight driving circuit, the second end of the backlight driving circuit is connected with the lamp strip, the third end of the conversion circuit is connected with the first end of the feedback protection circuit, the fourth end of the conversion circuit is connected with the second end of the feedback protection circuit, and the third end of the backlight driving circuit is connected with the third end of the feedback protection circuit.

The present disclosure further provides a display device, which includes a light bar and further includes the power circuit described in any one of the above.

The power supply circuit and the display device provided by the disclosure have the advantages that the feedback protection circuit is arranged, so that when the backlight driving circuit fails, the feedback protection circuit protects the backlight driving circuit, the voltage before the backlight driving circuit is subjected to voltage reduction is reduced to the voltage incapable of enabling the lamp strip to work, the lamp strip is protected, the protection locking state can be realized, the system cannot be repeatedly restarted, the large current is interrupted, and the risk is further reduced.

Drawings

FIG. 1 is a schematic diagram of a power circuit according to an embodiment of the present disclosure;

wherein: 1. a conversion circuit; 2. a backlight driving circuit; 3. a feedback protection circuit.

The objects, features, and advantages of the present disclosure will be further explained with reference to the accompanying drawings.

Detailed Description

The technical solution of the present invention will be further described in detail with reference to the accompanying drawings.

Referring to fig. 1, an embodiment of the present disclosure provides a power supply circuit including: the backlight protection circuit comprises a conversion circuit 1, a backlight driving circuit 2 and a feedback protection circuit 3;

the first end of the conversion circuit 1 is connected with a mains supply, the second end of the conversion circuit 1 is connected with the first end of the backlight driving circuit 2, the second end of the backlight driving circuit 2 is connected with the lamp strip, the third end of the conversion circuit 1 is connected with the first end of the feedback protection circuit 3, the fourth end of the conversion circuit 1 is connected with the second end of the feedback protection circuit 3, and the third end of the backlight driving circuit 2 is connected with the third end of the feedback protection circuit 3

In this embodiment, the conversion circuit 1 is connected to the commercial power, and is configured to convert 220V ac power of the commercial power into two paths of dc power, where one path of the dc power Vo2 is processed by the backlight driving circuit 2, and then converted into a light bar voltage with a lower voltage amplitude, and transmitted to the light bar, so that the light bar operates; the other direct current Vo1 is used as the sampling voltage of the feedback signal of the constant output voltage, and when the feedback protection circuit 3 detects that the backlight driving circuit 2 is failed, the circuit can enter a protection state by adjusting Vo 1. Components and parts among the drive circuit 2 that is shaded can lead to the switch tube short circuit of Buck circuit to become invalid because of reasons such as life-span problem or outside adverse circumstances (high temperature and high humidity, dust, little animal foreign matter etc.), and when the drive circuit 2 that is shaded inefficacy back, the higher voltage of voltage amplitude can directly load the lamp strip, and the current of loading on the lamp strip can continuously increase until reaching dynamic balance, but the lamp strip can be burnt out under dynamic balance's current. This embodiment, through setting up feedback protection circuit 3 for when being shaded drive circuit 2 and inefficacy, feedback protection circuit 3 protects, and the voltage that makes the voltage reduction of drive circuit 2 in a poor light before to make is shaded and reduces to the voltage that can't make lamp strip work, makes the lamp strip obtain the protection, can realize protection lock-out state simultaneously, can not make the system restart repeatedly make the heavy current be interrupted and strike the lamp strip, further reduces danger.

In an embodiment, the feedback protection circuit 3 includes an optical coupler, a first three-terminal adjustable shunt reference source UB1, a second three-terminal adjustable shunt reference source UB2, a first diode D1, a transistor Q1, a first comparator U1A, a second comparator U2A, a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, a fifth resistor R5, a sixth resistor R6, a seventh resistor R7, and an eighth resistor R8;

a first end of the optical coupler is connected with a third end of the conversion circuit 1, a second end of the optical coupler is connected with one end of a first resistor R1, a third end of the optical coupler is connected with a cathode of a first three-end adjustable shunt reference source UB1, an anode of a first three-end adjustable shunt reference source UB1 is connected with one end of a second resistor R2 and an emitter of the triode Q1, a reference electrode of the first three-end adjustable shunt reference source UB1, the other end of the second resistor R2, one end of a third resistor R3 and one end of a fourth resistor R4 are connected, the other ends of the first resistor R1 and the fourth resistor R4 are connected with a fourth end of the conversion circuit 1, the other end of the third resistor R3 is connected with a collector of the triode Q1, and a base of the triode Q1 is connected with one end of the fifth resistor and one end of the sixth resistor R6, the other end of the fifth resistor is grounded, the other end of the sixth resistor R6 is connected to the output end of the first comparator U1A, the negative input end of the first comparator U1A is connected to one end of the eighth resistor R8, the positive input end of the first comparator U1A, the cathode of the second three-terminal adjustable shunt reference source UB2, the reference electrode of the second three-terminal adjustable shunt reference source UB2, one end of the seventh resistor R7, and the negative input end of the second comparator U2A are connected, the output electrode of the second comparator U2A is connected to the anode of the first diode D1, the cathode of the first diode D1 is connected to the positive input end of the second comparator U2A, the other end of the seventh resistor R7, the first power supply pin of the first comparator U1A, the first power supply pin of the second comparator U2A, and the positive input end of the second comparator U2R 2A are connected to the positive input end of the eighth resistor R8, the other end of the eighth resistor R8 is connected to the third end of the backlight driving circuit 2.

In this embodiment, after the plug CN1 is connected to the commercial power 220Vac, the plug enters a power-up process, and is converted into 2-way dc voltage outputs Vo1 and Vo2 by the conversion circuit 1, in the power-up process, the backlight driving circuit 2 does not work yet and cannot supply power to the first comparator U1A, so that the first comparator U1A also does not work yet, and the triode Q1 is in an open-circuit state, so that the amplitude of the output voltage of the Vo1 is determined by voltage division of the second resistor R2 and the fourth resistor R4, the voltage sampling signal Vo1 is divided by the second resistor R2 and the fourth resistor R4 and then input to a reference electrode of a first three-terminal adjustable shunt reference source UB1 (usually a TL431 chip), and a feedback signal is transmitted to the conversion circuit 1 by combining with an optical coupler, so as to output a constant voltage Vo 1; because the two voltages output by the conversion circuit 1 pass through the two output windings N1 and N2, and the two output windings N1 and N2 have a coupling relationship, the constant output voltages Vo2 and Vo1 have a proportional relationship, Vo2 ═ Vo1 (N2/N1), for example, N1 is 4 turns, N2 is 20 turns, the specifications of the output Vo2 and Vo1 can be Vo1 ═ 12V, Vo2 ═ 60V, 300mA of current and 50V of voltage are required when the LED light bar operates in a steady state, and after a switching MOS transistor in the backlight driving circuit 2 is short-circuited and fails, when the current input to the LED light bar is greater than 1000mA, the feedback protection circuit 3 triggers protection.

The first resistor R1 and the seventh resistor R7 are current-limiting resistors, and limit the magnitude of current flowing through the first three-terminal adjustable shunt reference source UB1 and the second three-terminal adjustable shunt reference source UB2, so as to achieve a protection effect. Therefore, during power-up, Vo1 is 2.5V × (R4+ R2/R2) is 2.5 × (7.5+18/7.5) is 8.5V, and since there is a coupling relationship between the two output windings N1 and N2 (i.e., the fourth winding and the third winding), Vo2 is Vo1 × (N2/N1) is 8.5 × (20/4) is 42.5V, and at this time, the voltage of Vo2 cannot turn on the LED light bar.

When the first comparator U1A starts to work, the input voltage at the positive input terminal of the first comparator U1A is 2.5V (the regulated voltage output of the voltage regulator circuit consisting of the seventh resistor R7 and the first three-terminal adjustable shunt reference source UB1, and the UB1 and UB2 are usually TL431 precision voltage regulators); the lower voltage in the backlight driving circuit 2 is input to the negative input terminal of the first comparator U1A through the eighth resistor R8; since the voltage of the positive input end is greater than that of the negative input end, the first comparator U1A outputs high level to drive the triode Q1 to be in saturation conduction, so that the second resistor R2 and the third resistor R3 form a parallel connection state, and then the amplitude of the voltage output by the Vo1 is only formed by the fourth resistors R4 and R4_{And are}(i.e., the parallel resistance of the second resistor R2 and the third resistor R3) is determined by dividing the voltage, i.e.:

Vo1＝2.5V×(R4+R_{and are})/R_{And are}＝2.5×[18+(7.5//13)]/(7.5//13)＝12V

The voltage Vo1 rises; due to the coupling relation of the output windings N1 and N2 of the conversion circuit 1, the voltage Vo2 is synchronously increased to 60V to reach a higher voltage amplitude, and after the system runs and works, the backlight driving circuit 2 is controlled to carry out voltage reduction work, so that the voltage Vo2 is reduced to 50V through the backlight driving circuit 2, and the light bar is driven to work. Meanwhile, the voltage passing through the eighth resistor R8 is transmitted to the positive input terminal of the second comparator U2A, and under the normal operation condition, the voltages of the positive input terminals of the second comparator U2A are all smaller than the voltage of the negative input terminal, so the outputs of the second comparator U2A are all low level, but due to the reverse bias cut-off characteristic of the first diode D1, the low level output by the second comparator U2A does not affect the operations of other circuits.

When the short circuit failure of the switching MOS transistor in the backlight driving circuit 2 is caused by the lifetime problem of the device itself or the external harsh environment (high temperature, high humidity, dust, foreign matter from small animals, etc.), the higher voltage Vo2 is directly applied to the light bar, the current on the light bar will continuously increase until the dynamic balance is reached, and when the current increases to more than 1000 mA; at this time, the current of the backlight driving circuit 2 increases, the voltage flowing through the ninth resistor R9 increases, the corresponding voltage input to the comparator through the eighth resistor R8 also increases, when the voltage is greater than 2.5V, the first comparator U1A outputs a low level, the transistor Q1 is not turned on, the second resistor R2 and the third resistor R3 are disconnected from a parallel state, the output voltage Vo1 is determined by the voltage division of the first resistor R1 and the fourth resistor R4, Vo1 is maintained at 8.5V, and Vo2 synchronously decreases proportionally and is maintained at 42.5V, at this time, the voltage amplitude of Vo2 decreases to a lower voltage which cannot enable the light bar to operate.

Meanwhile, when the current of the light bar is larger than a rated value, the voltage of the positive input end of the second comparator U2A is larger than that of the negative input end, the output end of the second comparator U2A outputs a high level (approximately equal to Vo1), the high level is loaded on the positive input end through the forward conduction action of the first diode D1, and meanwhile, the high level cannot be pulled down to GND to become a low level due to the existence of the eighth resistor R8, so that the second comparator U2A realizes high-level output self-locking; the output voltage of this auto-lock loads on the negative pole input end of first comparator U1A simultaneously, make first comparator U1A also auto-lock output low level, make triode Q1 continuously break off, second resistance R2 and third resistance R3 continuously remove parallel state, can make Vo2 voltage amplitude continuously stabilize at a lower, can't make the voltage of lamp strip work, and continuously lock the protection under the condition that display device does not break off the electric wire netting, reach the effect of protection lamp strip. Meanwhile, a resistor, a capacitor, a small-signal switch diode, a triode Q1, a comparator and the like which are commonly used in the industry are used, the purchasing difficulty is small, and the cost advantage is obvious.

In an embodiment, the backlight driving circuit 2 includes a ninth resistor R9, a second diode D2, a first MOS transistor QB1, an inductor L1, a first capacitor C1, and a first control chip;

the one end of ninth resistance R9, the second end of converting circuit 1, the GND pin of first control chip is connected, the other end of ninth resistance R9, the source of first MOS pipe QB1, the current detection pin of first control chip is connected, the grid of first MOS pipe QB1 with the PWM drive pin of first control chip is connected, the drain electrode of first MOS pipe QB1 with the anode of second diode D2 is connected, the anode of second diode D2 with the negative pole of first electric capacity C1 passes through inductance L1 connects, and with the lamp strip is connected, the cathode of second diode D2, the positive pole of first electric capacity C1 with the lamp strip is connected.

In this embodiment, the inductor L1 is an energy storage filter inductor L1, which is used to limit a large current from passing through, and convert the current flowing through the inductor L1 into magnetic energy for energy storage. Meanwhile, the capacitor can convert part of current into charge to be stored, and the second diode D2 mainly plays a role of freewheeling. The EN pin and the DIM pin of the first control chip are respectively connected with the CPU, and the CPU transmits a control switch backlight signal to the EN pin to achieve the function of controlling the light bar switch.

In an embodiment, the converter circuit 1 includes a flyback power supply circuit or a resonant converter circuit.

In this embodiment, different AC-DC voltage topologies can be flexibly combined to form a protection system, for example, a flyback power circuit, a resonant converter circuit, etc. are combined, and a power scheme that 1 transformer outputs multiple outputs is used in combination.

In an embodiment, the flyback power supply circuit includes a rectifier bridge, a second MOS transistor QB2, a first winding, a second winding, a third winding, a fourth winding, a flyback control chip, a third diode D3, a fourth diode D4, a second capacitor C2, a third capacitor C3, a fourth capacitor C4, and a tenth resistor R10;

the first end of the rectifier bridge, the input end of the first winding, the positive pole of the second capacitor C2 are connected, the second end of the rectifier bridge is connected with the zero line of the commercial power, the third end of the rectifier bridge is connected with the live wire of the commercial power, the fourth end of the rectifier bridge, the negative pole of the second capacitor C2 are grounded, one end of the tenth resistor R10 is connected with the negative pole of the second capacitor C2, the other end of the tenth resistor R10 is connected with the source of the second MOS transistor QB2, the drain of the second MOS transistor QB2 is connected with the output end of the first winding, the gate of the second MOS transistor QB2 is connected with the PWM driving pin of the flyback control chip, the other end of the tenth resistor R10 is connected with the current detection pin of the flyback control chip, the input end of the second winding is connected with the VCC power supply pin of the flyback control chip, and the output end of the second winding is grounded, the flyback control chip is connected with the first end of the feedback protection circuit 3, the input end of the third winding is connected with the anode of the third diode D3, the cathode of the third diode D3, the anode of the third capacitor C3 and the first end of the backlight driving circuit 2 are connected, the cathode of the third capacitor C3 and the output end of the third winding are grounded, the input end of the fourth winding is connected with the anode of the fourth diode D4, the cathode of the fourth diode D4, the anode of the fourth capacitor C4 and the second end of the backlight driving circuit 2 are connected, and the cathode of the fourth capacitor C4 and the output end of the fourth winding are grounded.

In this embodiment, the flyback power supply circuit uses a flyback high-frequency transformer to isolate the switching power supply of the input/output circuit. When the switching tube is on, the inductor L1 connected in series in the backlight driving circuit 2 is in a discharging state in contrast to when the input is high, and when the switching tube is off, the inductor L1 connected in series in the backlight driving circuit 2 is in a charging state in response to the input being high. The polarity of the first winding and the polarity of the third winding of the transformer are opposite, when the switching tube is switched on, the current of the primary inductor L1 of the transformer starts to rise, at the moment, due to the relation of the second dotted terminal, the third diode D3 is cut off, the transformer stores energy, and the light bar is powered by the capacitor. When the switch tube is cut off, the voltage induced by the primary inductor L1 of the transformer is reversed, the third diode D3 is turned on, the energy in the transformer supplies power to the lamp strip through the third diode D3, and the capacitor is charged to supplement the energy just lost.

An embodiment of the present disclosure further provides a display device, which includes a light bar and further includes the power circuit as described in any one of the above.

In this embodiment, by adding the power supply circuit into the display device, the light bar is protected from being overloaded and generating high temperature after the backlight driving circuit 2 is disabled, and from being baked and melted on the rear shell of the display device, catching fire, exploding the lamp bead and the like, thereby protecting the personal and property safety of consumers.

In summary, an embodiment of the present disclosure provides a power circuit and a display device, where the power circuit includes a conversion circuit 1, a backlight driving circuit 2, and a feedback protection circuit 3; the first end of the conversion circuit 1 is connected with a mains supply, the second end of the conversion circuit 1 is connected with the first end of the backlight driving circuit 2, the second end of the backlight driving circuit 2 is connected with the lamp strip, the third end of the conversion circuit 1 is connected with the first end of the feedback protection circuit 3, the fourth end of the conversion circuit 1 is connected with the second end of the feedback protection circuit 3, and the third end of the backlight driving circuit 2 is connected with the third end of the feedback protection circuit 3. Through setting up feedback protection circuit 3, realize the protection to the lamp strip, the protection lamp strip is unlikely to after being out of efficacy at drive circuit 2 in a poor light, and lamp strip overload work produces high temperature to and take place to roast danger such as melting display device's backshell, catching fire, lamp pearl explosion, protection consumer's personal, property safety.

It should be noted that, in this document, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, apparatus, article, or method that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, apparatus, article, or method. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other like elements in a process, apparatus, article, or method that includes the element.

The above description is only a preferred embodiment of the present disclosure, and not intended to limit the scope of the present disclosure, and all modifications of equivalent structures and equivalent processes, which are made by using the contents of the present disclosure and the accompanying drawings, or directly or indirectly applied to other related technical fields, are also included in the scope of the present disclosure.

Claims

1. A power supply circuit comprises a conversion circuit, a backlight driving circuit and a feedback protection circuit;

2. The power supply circuit of claim 1, wherein the feedback protection circuit comprises an optocoupler, a first three-terminal adjustable shunt reference source, a second three-terminal adjustable shunt reference source, a first diode, a triode, a first comparator, a second comparator, a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, a seventh resistor, and an eighth resistor;

the first end of the optical coupler is connected with the third end of the conversion circuit, the second end of the optical coupler is connected with one end of the first resistor, the third end of the optical coupler is connected with the cathode of the first three-end adjustable shunt reference source, the anode of the first three-end adjustable shunt reference source is connected with one end of the second resistor and the emitter of the triode, the reference electrode of the first three-end adjustable shunt reference source, the other end of the second resistor, one end of the third resistor and one end of the fourth resistor are connected, the other ends of the first resistor and the fourth resistor are connected with the fourth end of the conversion circuit, the other end of the third resistor is connected with the collector of the triode, the base of the triode is connected with one end of the fifth resistor and one end of the sixth resistor, and the other end of the fifth resistor is grounded, the other end of the sixth resistor is connected with the output end of the first comparator, the negative electrode input end of the first comparator is connected with one end of the eighth resistor, the anode input end of the first comparator, the cathode of the second three-terminal adjustable shunt reference source, the reference electrode of the second three-terminal adjustable shunt reference source, one end of the seventh resistor and the cathode input end of the second comparator are connected, the output electrode of the second comparator is connected with the anode of the first diode, the cathode of the first diode is connected with the positive input end of the second comparator, the other end of the seventh resistor, a first power supply pin of the first comparator and a first power supply pin of the second comparator are connected, and the positive electrode input end of the second comparator is connected with one end of the eighth resistor, and the other end of the eighth resistor is connected with the third end of the backlight driving circuit.

3. The power supply circuit according to claim 1, wherein the backlight driving circuit comprises a ninth resistor, a second diode, a first MOS transistor, an inductor, a first capacitor, and a first control chip;

one end of the ninth resistor, the second end of the conversion circuit and the GND pin of the first control chip are connected, the other end of the ninth resistor, the source electrode of the first MOS tube and the current detection pin of the first control chip are connected, the grid electrode of the first MOS tube is connected with the PWM driving pin of the first control chip, the drain electrode of the first MOS tube is connected with the anode of the second diode, the anode of the second diode is connected with the cathode of the first capacitor through the inductor and is connected with the lamp bar, and the cathode of the second diode, the anode of the first capacitor and the lamp bar are connected.

4. The power supply circuit of claim 1, wherein the conversion circuit comprises a flyback power supply circuit or an LLC power supply circuit.

5. The power supply circuit of claim 4, wherein the flyback power supply circuit comprises a rectifier bridge, a second MOS transistor, a first winding, a second winding, a third winding, a fourth winding, a flyback control chip, a third diode, a fourth diode, a second capacitor, a third capacitor, a fourth capacitor and a tenth resistor;

the first end of the rectifier bridge, the input end of the first winding and the anode of the second capacitor are connected, the second end of the rectifier bridge is connected with the zero line of the commercial power, the third end of the rectifier bridge is connected with the live wire of the commercial power, the fourth end of the rectifier bridge and the cathode of the second capacitor are grounded, one end of the tenth resistor is connected with the cathode of the second capacitor, the other end of the tenth resistor is connected with the source electrode of the second MOS tube, the drain electrode of the second MOS tube is connected with the output end of the first winding, the grid electrode of the second MOS tube is connected with the PWM driving pin of the flyback control chip, the other end of the tenth resistor is connected with the current detection pin of the flyback control chip, the input end of the second winding is connected with the VCC power supply pin of the flyback control chip, and the output end of the second winding is grounded, the flyback control chip is connected with the first end of the feedback protection circuit, the input end of the third winding is connected with the anode of the third diode, the cathode of the third diode, the anode of the third capacitor and the first end of the backlight driving circuit are connected, the cathode of the third capacitor and the output end of the third winding are grounded, the input end of the fourth winding is connected with the anode of the fourth diode, the cathode of the fourth diode, the anode of the fourth capacitor and the second end of the backlight driving circuit are connected, and the cathode of the fourth capacitor and the output end of the fourth winding are grounded.

6. A display device comprising a light bar, and further comprising the power circuit of any one of claims 1-5.