Switching power supply over-temperature protection control circuit

Abstract

The utility model discloses an over-temperature protection control circuit of a switching power supply, which mainly solves the problem of poor protection effect of the existing over-temperature protection control circuit. The over-temperature protection control circuit comprises a temperature detection circuit connected with an output pin of an optocoupler isolation module in the switching power supply, an amplification circuit connected with the temperature detection circuit, a first bias circuit and a second bias circuit which are connected with the amplification circuit, and a charging and discharging switching circuit connected with the first bias circuit, and the output negative feedback circuit is connected with the charging and discharging switch circuit. Through the above design, in the whole over-temperature protection process, the high induction of the temperature near the switching power supply can be realized, the condition of false triggering is avoided, and stable and accurate over-temperature protection is provided for the switching power supply. Therefore, the method is suitable for popularization.

Description

Technical Field

[0001] The utility model belongs to the technical field of switching power supplies, and in particular relates to an over-temperature protection control circuit of a switching power supply. Background Art

[0002] A switching power supply is an energy converter. As a power device, it works in a switching state. It is characterized by high frequency, low power consumption, high working efficiency, small size, and wide input range. It is regulated by a closed-loop system to keep the output voltage stable. A switching power supply is generally composed of a pulse width modulation (PWM) control IC and a MOSFET. With the development and innovation of power electronics technology, switching power supply technology is also constantly innovating. At present, switching power supplies are widely used in almost all electronic devices due to their small size, light weight, and high efficiency. They are an indispensable power supply method for the rapid development of today's electronic information industry.

[0003] The switching power supply continuously generates heat energy during normal operation. Traditional switching power supplies generally achieve high temperature protection in the following ways: one solution is to connect a fuse in series in the circuit. Once the temperature is too high, the fuse will automatically blow to disconnect the circuit. This over-temperature protection method is relatively extreme. When the temperature recovers, the components need to be replaced to restore the normal operation of the circuit; another solution is to connect a thermistor in series in the protection circuit, and detect the temperature by connecting the thermistor in series with an ordinary resistor voltage divider. When the temperature rises, the resistance of the thermistor decreases, the sampling voltage increases, and the transistor in the protection circuit switches to the on state to pull down the control port of the control chip, so that the switching power supply is turned off. However, this method has the defects of unstable temperature maintenance characteristics and low over-temperature protection accuracy. Utility Model Content

[0004] The utility model aims to provide a switching power supply over-temperature protection control circuit, mainly to solve the problem that the existing over-temperature protection control circuit has a poor protection effect.

[0005] In order to achieve the above purpose, the technical solution adopted by the utility model is as follows:

[0006] A switching power supply over-temperature protection control circuit comprises a temperature detection circuit connected to an output pin of an optocoupler isolation module in the switching power supply, an amplifier circuit connected to the temperature detection circuit, a first bias circuit and a second bias circuit connected to the amplifier circuit, a charge and discharge switch circuit connected to the first bias circuit, and an output negative feedback circuit connected to the charge and discharge switch circuit.

[0007] Furthermore, in the utility model, the temperature detection circuit includes a thermistor RTC connected to the output pin of the optocoupler isolation module, a resistor R1 connected to the other end of the thermistor RTC, and a capacitor C1 connected to the other end of the resistor R1 and grounded; wherein the other end of the resistor R1 is connected to the amplifier circuit.

[0008] Furthermore, in the utility model, the amplifier circuit includes a resistor R2 connected to the other end of the resistor R1, a resistor R3, a capacitor C2, and a capacitor C3 all connected to the other end of the resistor R2, a resistor R4 having one end connected to the other end of the capacitor C2 and the other end grounded, an operational amplifier OP1 having a non-inverting input end connected to the common end of the capacitor C2 and the resistor R4, and resistors R5 and R6 both connected to the inverting input end of the operational amplifier OP1; wherein the other end of the capacitor C3 is grounded, the other ends of the resistors R6 and R3 are connected to the output end of the operational amplifier OP1, and the output end of the operational amplifier OP1 is connected to the first bias circuit; and the other end of the resistor R5 is connected to the second bias circuit.

[0009] Further, in the utility model, the first bias circuit includes a capacitor C4 connected to the output end of the operational amplifier OP1, a transistor VT1 whose collector is connected to the other end of the capacitor C4, a resistor R8 whose one end is connected to the emitter of the transistor VT1 and the other end is grounded, a resistor R7 whose one end is connected to the base of the transistor VT1 and the other end is connected to the switching circuit, and a capacitor C5 and an inductor L1 whose one end is connected in parallel to the base of the transistor VT1 and the other end is grounded; wherein the common end of the capacitor C4 and the transistor VT1 is connected to the charge and discharge switch circuit as a bias signal output end.

[0010] Further, in the utility model, the second bias circuit includes a resistor R9 connected to the other end of the resistor R5, a transistor VT2 whose collector is connected to the other end of the resistor R9, a capacitor C6 whose one end is connected to the emitter of the transistor VT2 and whose other end is grounded, a resistor R10 whose one end is connected to the base of the transistor VT2 and whose other end is connected to the other end of the resistor R5, and a capacitor C7 and an inductor L2 whose one end is connected in parallel to the base of the transistor VT2 and whose other end is grounded; wherein the common end of the resistor R9 and the transistor VT2 is connected to the charge and discharge switch circuit as a bias signal output end.

[0011] Furthermore, in the utility model, the charge and discharge switch circuit includes a chip U2 and a chip U3 connected by a plurality of pins, a capacitor C12 having one end connected to the 15th pin of the chip U2 and the other end connected to the 14th pin of the chip U3, a capacitor C8 having one end connected to the 14th pin of the chip U2 and the other end connected to the 14th pin of the chip U3, a single-pole double-throw switch S1 having a fixed end connected to the 14th pin of the chip U2, a diode D1 having a positive electrode connected to the Q4 pin of the chip U2 and a negative electrode connected to the 15th pin of the chip U2, a resistor R8 having one end connected to the negative electrode of the diode D1 and the other end connected to ground, and a resistor R8 having one end connected to the 14th pin of the chip U2 and the other end connected to ground. A resistor R9 with one end grounded, a capacitor C9 with one end connected to the 3rd pin of chip U2 and the 13th pin of chip U3, a capacitor C10 with one end connected to the 2nd pin of chip U2 and the 5th pin of chip U3, a capacitor C11 with one end connected to the 4th pin of chip U2 and the 6th pin of chip U3, and a resistor R10 with one end connected to the free ends of capacitors C9, C10, and C11 and the other end grounded; wherein, the 1st, 3rd, 8th, and 10th pins of chip U3 are connected to the collector of transistor VT1 as input ends, the active end of switch S1 is respectively connected to the collectors of transistors VT1 and VT2, and the output end OUT of the charge and discharge switch circuit is connected to the output negative feedback circuit.

[0012] Furthermore, in the utility model, the output negative feedback circuit includes a resistor R13 having one end connected to the output end OUT of the charge and discharge switch circuit, an operational amplifier OP2 having two input ends respectively connected to both ends of the resistor R13, a resistor R14 connected between the output end and the inverting input end of the operational amplifier OP2, a resistor R15 having one end connected to the inverting input end of the operational amplifier OP2 and the other end grounded, and a resistor R16 having one end connected to the output end of the operational amplifier OP2 and the other end grounded; wherein the other end of the resistor R16 is externally connected to the main control MCU of the switching power supply.

[0013] Compared with the prior art, the utility model has the following beneficial effects:

[0014] The utility model detects the temperature in the switching power supply through a thermistor, and after amplifying the relevant temperature signal through an amplifier circuit, the voltage at the output end of the operational amplifier in the amplifier circuit is pulled down, and then a bias signal is generated through a first bias circuit and a second bias circuit to make the charge and discharge switch circuit enter a corresponding working mode, thereby controlling the charge and discharge mode of the entire switching power supply, and making the switching power supply enter over-temperature protection. During the whole process, a high degree of sensing of the temperature near the switching power supply can be achieved, and false triggering will not occur, thereby providing stable and accurate over-temperature protection for the switching power supply. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1It is the overall structural principle block diagram of the utility model.

[0016] Figure 2 This is a schematic diagram of a charge and discharge switch circuit in an embodiment of the present utility model. DETAILED DESCRIPTION

[0017] The present invention is further described below in conjunction with the accompanying drawings and embodiments. The present invention includes but is not limited to the following embodiments.

[0018] like Figure 1 , 2 As shown, the utility model discloses a switching power supply over-temperature protection control circuit, including a temperature detection circuit connected to the output pin of the optocoupler isolation module in the switching power supply, an amplifier circuit connected to the temperature detection circuit, a first bias circuit and a second bias circuit connected to the amplifier circuit, a charge-discharge switch circuit connected to the first bias circuit, and an output negative feedback circuit connected to the charge-discharge switch circuit. The circuit detects the temperature of the switching power supply during operation through the temperature detection circuit, and amplifies the relevant temperature signal through the amplifier circuit, so that the voltage at the output end of the operational amplifier in the amplifier circuit is pulled down, and then the bias signal is generated through the first bias circuit and the second bias circuit to make the charge-discharge switch circuit enter the corresponding working mode, thereby controlling the charge-discharge mode of the entire switching power supply, and making the switching power supply enter over-temperature protection.

[0019] In this embodiment, the temperature detection circuit includes a thermistor RTC connected to the output pin of the optocoupler isolation module, a resistor R1 connected to the other end of the thermistor RTC, and a capacitor C1 connected to the other end of the resistor R1 and grounded; wherein the other end of the resistor R1 is connected to the amplifier circuit. When the thermistor RTC detects that the ambient temperature gradually rises to a preset temperature value, the resistance value of the negative temperature coefficient thermistor RTC also drops to a certain value, and the temperature detection circuit outputs a signal to the amplifier circuit.

[0020] In this embodiment, the amplifier circuit includes a resistor R2 connected to the other end of the resistor R1, a resistor R3 connected to the other end of the resistor R2, a capacitor C2, and a capacitor C3, a resistor R4 connected to the other end of the capacitor C2 at one end and grounded at the other end, an operational amplifier OP1 connected to the common end of the capacitor C2 and the resistor R4 at the non-inverting input end, and resistors R5 and R6 connected to the inverting input end of the operational amplifier OP1; wherein the other end of the capacitor C3 is grounded, the other ends of the resistors R6 and R3 are connected to the output end of the operational amplifier OP1, and the output end of the operational amplifier OP1 is connected to the first bias circuit; the other end of the resistor R5 is connected to the second bias circuit. The circuit mainly amplifies and transmits the signal through the action of the operational amplifier OP1.

[0021] In this embodiment, the first bias circuit includes a capacitor C4 connected to the output end of the operational amplifier OP1, a transistor VT1 whose collector is connected to the other end of the capacitor C4, a resistor R8 whose one end is connected to the emitter of the transistor VT1 and whose other end is grounded, a resistor R7 whose one end is connected to the base of the transistor VT1 and whose other end is connected to the switching circuit, and a capacitor C5 and an inductor L1 whose one end is connected in parallel to the base of the transistor VT1 and whose other end is grounded; wherein the common end of the capacitor C4 and the transistor VT1 is connected to the charge and discharge switch circuit as a bias signal output end. The second bias circuit includes a resistor R9 connected to the other end of the resistor R5, a transistor VT2 whose collector is connected to the other end of the resistor R9, a capacitor C6 whose one end is connected to the emitter of the transistor VT2 and whose other end is grounded, a resistor R10 whose one end is connected to the base of the transistor VT2 and whose other end is connected to the other end of the resistor R5, and a capacitor C7 and an inductor L2 whose one end is connected in parallel to the base of the transistor VT2 and whose other end is grounded; wherein the common end of the resistor R9 and the transistor VT2 is connected to the charge and discharge switch circuit as a bias signal output end.

[0022] In this embodiment, the charge and discharge switch circuit includes a chip U2 and a chip U3 connected by multiple pins, a capacitor C12 having one end connected to the 15th pin of the chip U2 and the other end connected to the 14th pin of the chip U3, a capacitor C8 having one end connected to the 14th pin of the chip U2 and the other end connected to the 14th pin of the chip U3, a single-pole double-throw switch S1 having a fixed end connected to the 14th pin of the chip U2, a diode D1 having a positive electrode connected to the Q4 pin of the chip U2 and a negative electrode connected to the 15th pin of the chip U2, a resistor R8 having one end connected to the negative electrode of the diode D1 and the other end connected to ground, and a resistor R8 having one end connected to the 14th pin of the chip U2 and the other end connected to ground. The resistor R9 is connected to the 3rd pin of the chip U2 and the 13th pin of the chip U3, the capacitor C9 is connected to the 2nd pin of the chip U2 and the 5th pin of the chip U3, the capacitor C10 is connected to the 4th pin of the chip U2 and the 6th pin of the chip U3, and the resistor R10 is connected to the free ends of the capacitors C9, C10 and C11 and the other end is grounded; wherein the 1st, 3rd, 8th and 10th pins of the chip U3 are connected to the collector of the transistor VT1 as input ends, the active end of the switch S1 is connected to the collectors of the transistors VT1 and VT2 respectively, and the output end OUT of the charge and discharge switch circuit is connected to the output negative feedback circuit. Among them, the chip U2 and the chip U3 both use the voltage stabilizing chip model H6103.

[0023] In this embodiment, the output negative feedback circuit includes a resistor R13 connected to the output end OUT of the charge and discharge switch circuit at one end, an operational amplifier OP2 whose two input ends are respectively connected to both ends of the resistor R13, a resistor R14 connected between the output end and the inverting input end of the operational amplifier OP2, a resistor R15 connected to the inverting input end of the operational amplifier OP2 at one end and grounded at the other end, and a resistor R16 connected to the output end of the operational amplifier OP2 at one end and grounded at the other end; wherein the other end of the resistor R16 is externally connected to the main control MCU of the switching power supply. The circuit is mainly used to feedback the entire over-temperature protection result to the main control MCU of the switching power supply.

[0024] When the thermistor RTC detects that the ambient temperature gradually rises to the preset temperature value, the resistance of the negative temperature coefficient thermistor RTC decreases. At this time, the total resistance of the second bias circuit is lower than the total resistance of the first bias circuit, and the voltage at the positive input terminal of the operational amplifier OP1 is less than the voltage value at the negative input terminal. The output terminal of the operational amplifier outputs a low level. After the level is pulled low, the switch S1 is turned on, and the voltage of the optocoupler is pulled down, so that the duty cycle of the output terminal of the optocoupler changes, and the charge and discharge of the AC power is adjusted through the charge and discharge switch circuit, thereby controlling the switching power supply to enter over-temperature protection.

[0025] Through the above design, the over-temperature protection of the utility model can achieve a high degree of sensitivity to the temperature near the switching power supply during the whole process, and will not cause false triggering, thereby providing stable and accurate over-temperature protection for the switching power supply. Therefore, it is suitable for promotion and application.

[0026] According to the above embodiments, the present utility model can be implemented well.

Claims

1. A switching power supply over-temperature protection control circuit, characterized in that: The invention comprises a temperature detection circuit connected to an output pin of an optocoupler isolation module in a switching power supply, an amplifier circuit connected to the temperature detection circuit, a first bias circuit and a second bias circuit connected to the amplifier circuit, a charge and discharge switch circuit connected to the first bias circuit, and an output negative feedback circuit connected to the charge and discharge switch circuit; the temperature detection circuit comprises a thermistor RTC connected to the output pin of the optocoupler isolation module, a resistor R1 connected to the other end of the thermistor RTC, and a capacitor C1 connected to the other end of the resistor R1 and grounded; wherein the other end of the resistor R1 is connected to the amplifier circuit.

2. A switching power supply over-temperature protection control circuit according to claim 1, characterized in that: The amplifier circuit includes a resistor R2 connected to the other end of the resistor R1, a resistor R3, a capacitor C2, and a capacitor C3 all connected to the other end of the resistor R2, a resistor R4 having one end connected to the other end of the capacitor C2 and the other end grounded, an operational amplifier OP1 having a non-inverting input end connected to the common end of the capacitor C2 and the resistor R4, and resistors R5 and R6 both connected to the inverting input end of the operational amplifier OP1; wherein the other end of the capacitor C3 is grounded, the other ends of the resistor R6 and the resistor R3 are connected to the output end of the operational amplifier OP1, and the output end of the operational amplifier OP1 is connected to a first bias circuit; and the other end of the resistor R5 is connected to a second bias circuit.

3. A switching power supply over-temperature protection control circuit according to claim 2, characterized in that: The first bias circuit includes a capacitor C4 connected to the output end of the operational amplifier OP1, a transistor VT1 whose collector is connected to the other end of the capacitor C4, a resistor R8 whose one end is connected to the emitter of the transistor VT1 and whose other end is grounded, a resistor R7 whose one end is connected to the base of the transistor VT1 and whose other end is connected to the switching circuit, and a capacitor C5 and an inductor L1 whose one end is connected in parallel to the base of the transistor VT1 and whose other end is grounded; wherein the common end of the capacitor C4 and the transistor VT1 is connected to the charge and discharge switch circuit as a bias signal output end.

4. A switching power supply over-temperature protection control circuit according to claim 3, characterized in that: The second bias circuit includes a resistor R9 connected to the other end of the resistor R5, a transistor VT2 whose collector is connected to the other end of the resistor R9, a capacitor C6 whose one end is connected to the emitter of the transistor VT2 and whose other end is grounded, a resistor R10 whose one end is connected to the base of the transistor VT2 and whose other end is connected to the other end of the resistor R5, and a capacitor C7 and an inductor L2 whose one end is connected in parallel to the base of the transistor VT2 and whose other end is grounded; wherein the common end of the resistor R9 and the transistor VT2 is connected to the charge and discharge switch circuit as a bias signal output end.

5. A switching power supply over-temperature protection control circuit according to claim 4, characterized in that: The charge and discharge switch circuit includes a chip U2 and a chip U3 connected by a plurality of pins, a capacitor C12 having one end connected to the 15th pin of the chip U2 and the other end connected to the 14th pin of the chip U3, a capacitor C8 having one end connected to the 14th pin of the chip U2 and the other end connected to the 14th pin of the chip U3, a single-pole double-throw switch S1 having a fixed end connected to the 14th pin of the chip U2, a diode D1 having a positive electrode connected to the Q4 pin of the chip U2 and a negative electrode connected to the 15th pin of the chip U2, a resistor R8 having one end connected to the negative electrode of the diode D1 and the other end connected to ground, and a resistor R1 connected to the 14th pin of the chip U2 and the other end connected to ground. 9, a capacitor C9 having one end connected to the 3rd pin of chip U2 and the 13th pin of chip U3, a capacitor C10 having one end connected to the 2nd pin of chip U2 and the 5th pin of chip U3, a capacitor C11 having one end connected to the 4th pin of chip U2 and the 6th pin of chip U3, a resistor R10 having one end connected to the free ends of capacitors C9, C10 and C11 and the other end grounded; wherein, pins 1, 3, 8 and 10 of chip U3 are connected to the collector of transistor VT1 as input ends, the active end of switch S1 is respectively connected to the collectors of transistors VT1 and VT2, and the output end OUT of the charge and discharge switch circuit is connected to the output negative feedback circuit.

6. A switching power supply over-temperature protection control circuit according to claim 5, characterized in that: The output negative feedback circuit includes a resistor R13 having one end connected to the output end OUT of the charge and discharge switch circuit, an operational amplifier OP2 having two input ends respectively connected to both ends of the resistor R13, a resistor R14 connected between the output end and the inverting input end of the operational amplifier OP2, a resistor R15 having one end connected to the inverting input end of the operational amplifier OP2 and the other end grounded, and a resistor R16 having one end connected to the output end of the operational amplifier OP2 and the other end grounded; wherein the other end of the resistor R16 is externally connected to the main control MCU of the switching power supply.

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