CN202495873U - Power supply circuit and television - Google Patents

Abstract

The utility model provides a power supply circuit and a TV set using the power supply circuit, wherein the power supply circuit solves the problem in the prior art that the output voltage is too high when the power factor correction circuit works abnormally, causing damage to the subsequent stage circuit. It includes an AC rectification filter circuit, a power factor correction boost circuit, a large electrolytic capacitor filter circuit, a standby DC/DC power supply circuit and a main power DC/DC power supply circuit, and the power supply circuit also includes an overvoltage protection circuit. The utility model also protects a TV set. The power supply circuit provided by the utility model can effectively prevent serious consequences such as bursting of electrolytic capacitors when the power factor correction circuit works abnormally, and at the same time, it also plays a certain role in protecting the subsequent circuit. Since the components used in the overvoltage protection circuit are relatively low-cost resistors, capacitors, triodes, etc., the cost will not increase a lot, which provides a new idea and method for the application and development of power supply technology.

Description

A kind of power supply circuit and TV set

technical field

The utility model relates to a power supply circuit and a television set. the

Background technique

As shown in Figure 1, in the existing flat-panel LCD TV power supply, the 100HZ filter electrolytic capacitor of the rectifier bridge rear stage circuit is a very critical device, because it not only plays the role of filtering the 100HZ AC ripple, but also when the AC power grid is not When it is clean (distorted AC, superimposed clutter, surge), large electrolytic capacitors can also effectively suppress it. It is this function of the large electrolytic capacitor that can ensure the orderly and safe operation of the subsequent DC/DC circuit. Among the TV products repaired in the market, the large electrolytic capacitors have the largest damage ratio due to overvoltage damage, especially the power supply with power factor correction circuit accounts for more than 80%. This is because the power factor correction circuits we use today are basically boost (BOOST) circuits. When individual components in the circuit are defective or the production process is not well controlled, causing a certain component to be soldered or connected, it is easy to cause power factor correction. When the output voltage of the large electrolytic capacitor rises, when it exceeds the breakthrough voltage of 550VDC (for a capacitor with a nominal withstand voltage of 450V), the large electrolytic capacitor will easily burst and be damaged. Some capacitors with poor quality may even catch fire, igniting the back of the TV. This is also a form commonly known as "burning machine", which will not only damage the equipment, but also endanger the personal safety of consumers. the

Therefore, how to set up an overvoltage protection circuit to provide effective protection for the subsequent circuit when the output voltage is too high due to an abnormality in the circuit has become an important problem that must be solved at present. the

Utility model content

The purpose of the utility model is to provide a power supply circuit, aiming to solve the problem in the prior art that the output voltage is too high when the power factor correction circuit works abnormally, causing damage to the subsequent circuit. In order to solve the above-mentioned technical problems, the utility model adopts the following schemes to be realized. the

The utility model provides a power supply circuit, comprising an AC rectification filter circuit, a power factor correction boost circuit, a large electrolytic capacitor filter circuit, a standby DC/DC power supply circuit and a main power DC/DC power supply circuit. The first input end of the voltage circuit is connected to the AC rectification filter circuit, the second input end of the power factor correction boost circuit is connected to the first output end of the standby DC/DC power supply circuit, and the large electrolytic capacitor The input end of the filter circuit is connected to the power factor correction boost circuit, the first output end of the large electrolytic capacitor filter circuit is connected to the input end of the standby DC/DC power supply circuit, and the input end of the large electrolytic capacitor filter circuit The second output end is connected to the first input end of the main power DC/DC power supply circuit, and the second output end of the standby DC/DC power supply circuit is connected to the second input end of the main power DC/DC power supply circuit ;

The power supply circuit also includes an overvoltage protection circuit, the input end of the overvoltage protection circuit is connected to the large electrolytic capacitor filter circuit, and the output end of the overvoltage protection circuit is connected to the standby DC/DC power supply circuit.

The standby DC/DC power supply circuit includes a standby chip, the input terminal of the standby chip is connected to the power supply voltage of the chip, and the feedback pin of the standby chip is connected to the second voltage. the

The overvoltage protection circuit includes a first transient suppression diode, a second transient suppression diode, a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a capacitor, and a triode;

The cathode of the first transient suppression diode is connected to the first voltage, and the anode is connected to the cathode of the second transient suppression diode, and the anode of the second transient suppression diode passes through the first resistor, the second resistor, and the second resistor in sequence. The three resistors are connected to the first end of the fourth resistor, the two ends of the capacitor are respectively connected to the two ends of the fourth resistor, the triode is an NPN type triode, and the emitter of the triode is connected to the fourth The second end of the resistor is connected to the ground, and the collector of the triode is connected to the feedback end of the standby chip through the fifth resistor.

Another object of the present utility model is to provide a TV set, including the above-mentioned power supply circuit. the

The power supply circuit provided by the utility model can effectively prevent serious consequences such as bursting of electrolytic capacitors when the power factor correction circuit works abnormally, and at the same time, it also has a certain protective effect on the subsequent stage circuit. Since the components used in the overvoltage protection circuit are relatively low-cost resistors, capacitors, triodes, etc., the cost will not increase a lot, which provides a new idea and method for the application and development of power supply technology. the

Description of drawings

Fig. 1 is the schematic diagram of existing power supply circuit;

Fig. 2 is the schematic diagram of the power supply circuit provided by the utility model;

Fig. 3 is a detailed circuit diagram of the overvoltage protection circuit in the power circuit provided by the utility model.

Detailed ways

In order to make the purpose, technical solutions and advantages of the present utility model clearer, the utility model will be further described in detail below in conjunction with the accompanying drawings and embodiments; it should be understood that the specific embodiments described here are only used to explain the utility model, It is not used to limit the utility model. the

As shown in Figure 2, the utility model provides a power supply circuit, including an AC rectification filter circuit 11, a power factor correction boost circuit 12, a large electrolytic capacitor filter circuit 13, a standby DC/DC power supply circuit 14 and a main power DC/DC DC power supply circuit 15, the first input end of the power factor correction boost circuit 12 is connected to the AC rectification filter circuit 11, the second input end of the power factor correction boost circuit 12 is connected to the standby DC/DC The first output end of the power circuit 14 is connected, the input end of the large electrolytic capacitor filter circuit 13 is connected to the power factor correction boost circuit 12, the first output end of the large electrolytic capacitor filter circuit 13 is connected to the standby The input terminal of the DC/DC power supply circuit 14 is connected, the second output terminal of the large electrolytic capacitor filter circuit 13 is connected with the first input terminal of the main power DC/DC power supply circuit 15, and the standby DC/DC power supply circuit The second output end of 14 is connected with the second input end of the main power DC/DC power supply circuit 15;

The power supply circuit also includes an overvoltage protection circuit 21, the input end of the overvoltage protection circuit 21 is connected to the large electrolytic capacitor filter circuit 13, and the output end of the overvoltage protection circuit 21 is connected to the standby DC/DC The power supply circuit 14 is connected.

The standby DC/DC power supply circuit 14 includes a standby chip 141, the input terminal of the standby chip 141 is connected to the chip power supply voltage VDD, and the feedback pin FB of the standby chip 141 is connected to the second voltage V2. the

The overvoltage protection circuit 21 includes a first transient suppression diode T1, a second transient suppression diode T2, a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, a fifth resistor R5, a capacitor C. Transistor Q;

The cathode of the first transient suppression diode T1 is connected to the first voltage V1, and the anode is connected to the cathode of the second transient suppression diode T2, and the anode of the second transient suppression diode T2 passes through the first resistor R1, The second resistor R2 and the third resistor R3 are connected to the first end of the fourth resistor R4, the two ends of the capacitor C are respectively connected to the two ends of the fourth resistor R4, the transistor Q is an NPN transistor, The emitter of the transistor Q is connected to the second end of the fourth resistor R4 and grounded, and the collector of the transistor Q is connected to the feedback terminal FB of the standby chip 141 through the fifth resistor R5.

Another object of the present utility model is to provide a TV set, including the above-mentioned power supply circuit. the

The working principle is explained as follows:

The power supply circuit shown in Figure 1 is a block diagram of the power supply structure of the LCD universal power supply above 32 inches. The alternating current is sent to the power factor correction boosting circuit 12 after being passed through the rectifying and filtering circuit 11, and then the large electrolytic capacitor filtering circuit 13 is used to smooth the waveform, and the smoothed direct current is provided to the standby DC/DC power supply circuit 14 (providing 5V) all the way, and the other One path is provided to the main power DC/DC power supply circuit 15 (providing 24V and 12V). After the DC/DC power supply circuit 14 works normally, the power factor correction boost circuit 12 and the main power DC/DC power supply circuit 15 start to work normally.

The power supply circuit shown in Figure 2 is a circuit block diagram with an overvoltage protection circuit 21 added. The overvoltage protection circuit 21 samples the DC voltage on the large electrolytic capacitor. The DC/DC power supply circuit 14 provides a shutdown signal to cut off the power supply of the power factor correction boost circuit 12, thereby suppressing the voltage rise on the electrolytic capacitor. the

As shown in Figure 3, when the power supply circuit is in a normal working state, the first voltage V1 is within the normal voltage range, and the voltage drop is 0V, the transistor Q is not conducting, which has no effect on the feedback terminal FB of the standby chip 141, and the standby chip 141 works normally. the

When the first voltage V1 output by the power factor correction booster circuit 12 rises abnormally, the voltage is still at a high level through the clamping action of the first TVS diode T1 and the second TVS diode T2. After the resistor R1, the second resistor R2, the third resistor R3, the fourth resistor R4, and the capacitor C divide and filter the voltage, the base of the transistor Q is at a high level, the transistor Q is turned on, and the feedback terminal of the standby chip 141 FB is grounded through the fifth resistor R5, the feedback terminal FB drops to a low level, the standby chip 141 stops working, and the standby DC/DC power supply circuit 14 stops supplying power to the power factor correction booster circuit 12, thus avoiding the power factor correction circuit Serious consequences such as electrolytic capacitor burst occur when the work is abnormal. the

The power supply circuit provided by the utility model can effectively prevent serious consequences such as bursting of electrolytic capacitors when the power factor correction circuit works abnormally, and at the same time, it also has a certain protective effect on the subsequent stage circuit. Since the components used in the overvoltage protection circuit are relatively low-cost resistors, capacitors, triodes, etc., the cost will not increase a lot, which provides a new idea and method for the application and development of power supply technology. the

The above descriptions are only preferred embodiments of the present utility model, and are not intended to limit the present utility model. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present utility model shall be included in this utility model. within the scope of protection of utility models. the

Claims (4)

1. A power supply circuit, comprising an AC rectification filter circuit, a power factor correction boost circuit, a large electrolytic capacitor filter circuit, a standby DC/DC power supply circuit and a main power DC/DC power supply circuit, the power factor correction boost circuit The first input terminal is connected to the AC rectification filter circuit, the second input terminal of the power factor correction boost circuit is connected to the first output terminal of the standby DC/DC power supply circuit, and the large electrolytic capacitor filter circuit is connected to the first input terminal. The input end is connected to the power factor correction boost circuit, the first output end of the large electrolytic capacitor filter circuit is connected to the input end of the standby DC/DC power supply circuit, and the second output of the large electrolytic capacitor filter circuit terminal is connected to the first input terminal of the main power DC/DC power supply circuit, and the second output terminal of the standby DC/DC power supply circuit is connected to the second input terminal of the main power DC/DC power supply circuit; It is characterized in that the power supply circuit also includes an overvoltage protection circuit, the input end of the overvoltage protection circuit is connected to the filter circuit of the large electrolytic capacitor, and the output end of the overvoltage protection circuit is connected to the standby DC/DC Power circuit connection. 2. The power supply circuit according to claim 1, wherein the standby DC/DC power supply circuit comprises a standby chip, the input terminal of the standby chip is connected to the chip power supply voltage, and the feedback pin of the standby chip is connected to the second voltage . 3. The power supply circuit according to claim 2, wherein the overvoltage protection circuit comprises a first TVS diode, a second TVS diode, a first resistor, a second resistor, a third resistor, a first TVS diode, and a second TVS diode. Four resistors, fifth resistor, capacitor, triode; The cathode of the first transient suppression diode is connected to the first voltage, and the anode is connected to the cathode of the second transient suppression diode, and the anode of the second transient suppression diode passes through the first resistor, the second resistor, and the second resistor in sequence. The three resistors are connected to the first end of the fourth resistor, the two ends of the capacitor are respectively connected to the two ends of the fourth resistor, the triode is an NPN type triode, and the emitter of the triode is connected to the fourth The second end of the resistor is connected to the ground, and the collector of the triode is connected to the feedback end of the standby chip through the fifth resistor. 4. A television set, comprising the power supply circuit according to any one of claims 1-3.

Images