CN205545180U - Short -circuit protection circuit and power supply device - Google Patents

Abstract

The utility model discloses a short circuit protection circuit and a power supply device. The short circuit protection circuit comprises a switch unit, a protection unit and a filter unit. The switch unit is connected to a protection unit and a filter unit, and the filter unit is connected to a back-end device. The switch unit performs on-off switching according to the control signal to control the output state of the supply voltage. The filtering unit filters the power supply voltage and outputs it to supply power to the back-end equipment. When the protection unit detects the short circuit of the back-end equipment, it controls the switch unit to turn off and stops outputting the power supply voltage; and controls the switch unit to turn on again after the short circuit disappears, so as to restore the output of the power supply voltage. It solves the problem of continuous on-off heating of the switch unit during hiccup protection, causing the built-in MOS tube to fall off or even an open flame; it reduces safety hazards and protects the MOS tube, making the hardware circuit part of the TV product more safe and reliable; its circuit structure Very simple, low cost, suitable for vigorous promotion.

Description

A short circuit protection circuit and power supply device

technical field

The utility model relates to the technical field of television, in particular to a short circuit protection circuit and a power supply device.

Background technique

As a popular household appliance, the safety and reliability of TV products have attracted much attention. In the signal board circuit design of the TV, in order to better control the standby power consumption, some MOS circuits must be used for power supply control. As shown in Figure 1 and Figure 2, the existing TV is powered by 12V, the input voltage (12V) is stepped down to 5V by the synchronous step-down DC-DC chip N1 (model SY8113), and the power is output from the output port 5Vstb circuit (as shown in Figure 2). In the power supply circuit, the power supply port 5VA is connected to the back-end equipment; the control signal PM_PWR_ON provided by the main chip controls the on-off state of the transistor Q1. When the TV is in the standby state, the control signal PM_PWR_ON is at low level, and the MOS transistor Q2 is in the off state, thereby disconnecting the power supply to the back-end equipment. When the control signal PM_PWR_ON is at a high level, the MOS transistor Q2 is in the conduction state, and the 5V voltage output supplies power to the back-end equipment.

However, when the MOS transistor Q2 is in the conduction state, if the back-end device is short-circuited, the power supply port 5VA is short-circuited, and the output port 5Vstb is short-circuited and pulled down. Then the front-end DC-DC chip N1 will be in the short-circuit protection state, so as to perform hiccup protection, and further make the MOS transistor Q2 in the continuous switching state of on and off, until the short circuit disappears before returning to normal. The continuous on-off of the MOS tube Q2 will greatly increase its temperature rise, causing the solder to melt and cause the MOS tube Q2 to fall off; in severe cases, an open flame will be generated, which poses a major safety hazard.

Therefore it is necessary to improve the prior art.

Utility model content

In view of the shortcomings of the above-mentioned prior art, the purpose of this utility model is to provide a short circuit protection circuit and a power supply device to solve the problem that in the existing TV set, the MOS tube continues to be turned on and off under the short circuit protection state to heat up and cause the MOS tube to fall off. There are even problems with open flames.

In order to achieve the above object, the utility model has taken the following technical solutions:

A short-circuit protection circuit, connected to the main chip and back-end equipment, which includes:

A switch unit for on-off switching according to the control signal output by the main chip to control the output state of the power supply voltage;

A filter unit used to filter the power supply voltage and output it to the back-end equipment for power supply;

It is used to control the switching unit to disconnect when the back-end equipment is short-circuited, and stop outputting the power supply voltage; and the protection unit that controls the switching unit to be turned on after the short circuit disappears;

The switch unit is connected to the protection unit and the filter unit, the filter unit is connected to the back-end equipment, and the main chip is connected to the switch unit and the protection unit.

In the short-circuit protection circuit, the switch unit includes a first resistor, a second resistor, a MOS tube and a triode; the source of the MOS tube is connected to one end of the first resistor and the input terminal of the short-circuit protection circuit, and the MOS tube The gate is connected to one end of the second resistor, and the other end of the second resistor is connected to the other end of the first resistor and the collector of the triode; the drain of the MOS tube is connected to the protection unit, the control terminal of the short circuit protection circuit and the filter unit, and the base of the triode The pole is connected to the protection unit, and the emitter of the triode is grounded.

In the short-circuit protection circuit, the protection unit includes a first diode, the anode of the first diode is connected to the base of the triode and the control terminal of the short-circuit protection circuit, and the cathode of the first diode is connected to the MOS Tube drain and filter unit.

In the short-circuit protection circuit, the filtering unit includes a capacitor, one end of the capacitor is connected to the cathode of the first diode and the output end of the short-circuit protection circuit, and the other end of the capacitor is grounded.

In the short-circuit protection circuit, the MOS transistor is a PMOS transistor, and the transistor is an NPN transistor.

In the short circuit protection circuit, the model of the first diode is 2CZ20100.

In the short-circuit protection circuit, the protection unit further includes a third resistor, one end of the third resistor is connected to the anode of the first diode and the base of the triode, and the other end of the third resistor is connected to the short-circuit protection circuit. Control terminal.

A power supply device, which is connected with the main chip and the back-end equipment, includes a step-down circuit for stepping down the input voltage and outputting the power supply voltage, and also includes the short-circuit protection circuit, and the short-circuit protection circuit is output according to the The control signal and the short-circuit state of the back-end equipment control the output state of the power supply voltage; the step-down circuit is connected to the input end of the short-circuit protection circuit, the main chip is connected to the control end of the short-circuit protection circuit, and the output end of the short-circuit protection circuit is connected to the back-end equipment.

Compared with the prior art, the utility model provides a short-circuit protection circuit and a power supply device. The short-circuit protection circuit includes a switch unit, a protection unit and a filter unit. The switch unit is connected to a protection unit and a filter unit, and the filter unit is connected to a back-end device. The switch unit performs on-off switching according to the control signal to control the output state of the supply voltage. The filter unit filters the power supply voltage and outputs it to supply power to the back-end equipment. When the protection unit detects the short circuit of the back-end equipment, it controls the switching unit to turn off and stops outputting the power supply voltage; and controls the switching unit to resume conduction after the short circuit disappears, so as to restore the output of the power supply voltage. It solves the problem of continuous on-off heating of the switch unit during hiccup protection, causing the built-in MOS tube to fall off or even an open flame; it reduces safety hazards and protects the MOS tube, making the hardware circuit part of the TV product more safe and reliable; its circuit structure Very simple, low cost, suitable for vigorous promotion.

Description of drawings

FIG. 1 is a circuit diagram of a step-down circuit in an existing television.

Fig. 2 is a circuit diagram of a power supply circuit in an existing television.

Fig. 3 is a structural diagram of the power supply device provided by the embodiment of the present invention.

FIG. 4 is a circuit diagram of a short circuit protection circuit provided by an embodiment of the present invention.

detailed description

The utility model provides a short-circuit protection circuit and a power supply device. In order to make the purpose, technical solution and effect of the utility model clearer and clearer, the utility model will be further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described here are only used to explain the utility model, and are not intended to limit the utility model.

The utility model provides a power supply device of a TV set, which is connected with a main chip and back-end equipment. As shown in FIG. 3 , the power supply device includes a step-down circuit 100 and a short circuit protection circuit 200 . The step-down circuit 100 is connected to the input terminal 5Vstb of the short-circuit protection circuit 200, the main chip is connected to the control terminal CL of the short-circuit protection circuit 200, and the output terminal 5VA of the short-circuit protection circuit 200 is connected to the back-end equipment. The step-down circuit 100 steps down the input voltage (12V) to output a supply voltage (5V). The short-circuit protection circuit 200 controls the output state of the power supply voltage according to the control signal PM_PWR_ON output by the main chip and the short-circuit state of the back-end equipment, specifically: when the control signal PM_PWR_ON is at a low level, the short-circuit protection circuit 200 is turned off, and the power supply voltage stops output, the back-end equipment is powered off. When the control signal PM_PWR_ON is at a high level, the short-circuit protection circuit 200 is turned on, and the power supply voltage is output to supply power to back-end devices. If the back-end equipment is short-circuited during the power supply process, the short-circuit protection circuit 200 is turned off to stop outputting the supply voltage, and the back-end equipment is temporarily powered off. When the short-circuit situation disappears, the short-circuit protection circuit 200 is turned on again to restore the output of the supply voltage.

It should be understood that this embodiment mainly improves the circuit structure of the short circuit protection circuit 200 . Step-down circuit 100 is prior art, circuit structure as shown in Figure 1; Main chip is the TV chip commonly used in the TV, model is such as mstar 6a918, mstar 6a828, mstar 6a638 etc., here prior art does not do detailed description .

Please also refer to FIG. 4 , the short circuit protection circuit 200 includes a switch unit 210 , a protection unit 220 and a filter unit 230 . The switch unit 210 is connected to the protection unit 220 and the filter unit 230 , the filter unit 230 is connected to the back-end equipment, and the main chip is connected to the switch unit 210 and the protection unit 220 . The switch unit 210 performs on-off switching according to the control signal to control the output state of the supply voltage. The filtering unit 230 filters the power supply voltage and outputs it to the back-end equipment for power supply. The protection unit 220 controls the switch unit 210 to turn off when detecting a short circuit of the back-end equipment, and stops outputting the supply voltage; and controls the switch unit 210 to turn on after the short circuit disappears, thereby restoring the output of the supply voltage.

The switch unit 210 includes a first resistor R1, a second resistor R2, a MOS transistor V1, and a triode V2; the source of the MOS transistor V1 is connected to one end of the first resistor R1 and the input terminal 5Vstb of the short circuit protection circuit 200, and the MOS transistor V1 The gate of V1 is connected to one end of the second resistor R2, the other end of the second resistor R2 is connected to the other end of the first resistor R1 and the collector of the triode V2, and the drain of the MOS transistor V1 is connected to the protection unit 220 and the short circuit protection circuit 200. The control terminal CL and the filtering unit 230, the base of the transistor V2 is connected to the protection unit 220, and the emitter of the transistor V2 is grounded.

The protection unit 220 includes a first diode D1, the anode of the first diode D1 is connected to the base of the transistor V2 and the control terminal CL of the short-circuit protection circuit 200, and the cathode of the first diode D1 is connected to the MOS transistor Drain of V1 and filtering unit 230 .

The filtering unit 230 includes a capacitor C1, one end of the capacitor C1 is connected to the cathode of the first diode D1 and the output end 5VA of the short circuit protection circuit 200, and the other end of the capacitor C1 is grounded.

Wherein, the MOS transistor V1 is a PMOS transistor, and the transistor V2 is an NPN transistor. The type of the first diode D1 is 2CZ20100, and its voltage drop is 0.3V.

This embodiment utilizes the reverberation cutoff characteristic of the increased first diode D1, when the control signal PM_PWR_ON input by the main chip is at a low level, the triode V2 is cut off, and the gate voltage of the MOS transistor V1 is controlled by the first resistor R1 and the second resistor R2 The pull-up is high level, the MOS transistor V1 is in the off state, the power supply voltage stops outputting, and the back-end equipment is powered off, which is consistent with the existing low-level input working conditions.

When the control signal PM_PWR_ON is at a high level, the transistor V2 is turned on and the gate of the MOS transistor V1 is pulled down, and the MOS transistor V1 is turned on to supply power to the back-end equipment. At this time, if the back-end device is short-circuited, the potential of the output terminal (ie 5VA) of the filter unit 230 is 0. At this time, the cathode voltage of the first diode D1 is 0, and the anode voltage is 0.3V (voltage drop). The anode voltage is too small to turn on the triode V2, and the MOS transistor V1 is correspondingly turned off. In this way, as long as the short circuit does not disappear, the MOS transistor V1 will remain in the disconnected state. No matter how the hiccup protection is performed in the step-down circuit 100, the MOS transistor V1 will not be in a continuous switching state of on and off, thereby avoiding a large temperature rise. Solder melting caused by the increase causes the MOS transistor V1 to fall off, thereby protecting the MOS transistor V1.

When the short circuit disappears, the cathode of the first diode D1 is no longer forcibly pulled low, and the high-level control signal PM_PWR_ON turns on the transistor V2 and the MOS transistor V1, thereby restoring the power supply to the back-end equipment.

Some TV sets have power-on delay requirements when powering on. In order not to affect the power-on sequence, a resistor can also be added to the protection unit 220 to form an RC delay circuit with the capacitor in the filter unit 230 during specific implementation. . That is, the protection unit 220 also includes a third resistor R3, one end of the third resistor R3 is connected to the anode of the first diode D1 and the base of the triode V2, and the other end of the third resistor R3 is connected to the short circuit protection circuit 200. Control terminal CL. By setting the resistance value of the third resistor R3, the delay time of the power-on sequence can be adjusted. In this embodiment, the resistance of the third resistor R3 is 0 ohms.

In a specific implementation, the switching unit 210 also includes a capacitor, as shown in FIG. 4, which is connected between the source and the gate of the MOS transistor V1, and is used to adjust the turn-on and turn-off time of the MOS transistor V1 so as to to slow start.

In order to increase the filtering effect, the filtering unit 230 may further include two capacitors, which are connected in parallel with the capacitor C1 to achieve a better filtering effect.

To sum up, the short-circuit protection circuit and power supply device provided by the utility model can directly turn off the MOS tube (that is, the MOS tube V1) in the short-circuit protection by adding a diode, which solves the problem of continuous on-off of the MOS tube caused by the hiccup protection of the step-down circuit The problem of heating up, causing the MOS tube to fall off or even creating an open flame. The potential safety hazard is reduced and the MOS tube is protected, so that the hardware circuit part of the TV product has higher safety and reliability; the circuit structure is very simple, the cost is very low, and it is suitable for vigorous promotion.

It can be understood that those skilled in the art can make equivalent replacements or changes according to the technical solution of the utility model and its utility model concept, and all these changes or replacements should belong to the appended claims of the utility model protected range.

Claims (8)

1. A short circuit protection circuit is connected with main chip and back-end equipment, it is characterized in that, comprising: A switch unit for on-off switching according to the control signal output by the main chip to control the output state of the power supply voltage; A filter unit used to filter the power supply voltage and output it to the back-end equipment for power supply; It is used to control the switching unit to disconnect when the back-end equipment is short-circuited, and stop outputting the power supply voltage; and the protection unit that controls the switching unit to be turned on after the short circuit disappears; The switch unit is connected to the protection unit and the filter unit, the filter unit is connected to the back-end equipment, and the main chip is connected to the switch unit and the protection unit. 2. The short-circuit protection circuit according to claim 1, wherein the switch unit comprises a first resistor, a second resistor, a MOS transistor and a triode; the source of the MOS transistor is connected to one end of the first resistor and the short circuit The input terminal of the protection circuit, the gate of the MOS transistor is connected to one end of the second resistor, and the other end of the second resistor is connected to the other end of the first resistor and the collector of the triode; the drain of the MOS transistor is connected to the protection unit and the short circuit protection circuit. The control terminal and the filtering unit, the base of the triode are connected to the protection unit, and the emitter of the triode is grounded. 3. The short circuit protection circuit according to claim 2, wherein the protection unit comprises a first diode, the anode of the first diode is connected to the base of the triode and the control terminal of the short circuit protection circuit, The cathode of the first diode is connected to the drain of the MOS transistor and the filtering unit. 4. The short-circuit protection circuit according to claim 3, wherein the filtering unit includes a capacitor, one end of the capacitor is connected to the negative pole of the first diode and the output end of the short-circuit protection circuit, and the other end of the capacitor is grounded . 5. The short-circuit protection circuit according to claim 2, wherein the MOS transistor is a PMOS transistor, and the transistor is an NPN transistor. 6. The short circuit protection circuit according to claim 3, characterized in that the model of the first diode is 2CZ20100. 7. The short-circuit protection circuit according to claim 3, wherein the protection unit further comprises a third resistor, one end of the third resistor is connected to the anode of the first diode and the base of the triode, and the third resistor The other end of the resistor is connected to the control end of the short circuit protection circuit. 8. A power supply device, connected to the main chip and back-end equipment, including a step-down circuit for stepping down the input voltage and outputting the power supply voltage, characterized in that it also includes a short circuit as claimed in any one of claims 1-7 protection circuit, the short-circuit protection circuit controls the output state of the supply voltage according to the control signal output by the main chip and the short-circuit state of the back-end equipment; the step-down circuit is connected to the input end of the short-circuit protection circuit, and the main chip is connected to the control circuit of the short-circuit protection circuit The output end of the short-circuit protection circuit is connected to the back-end equipment.