Protection device of high-power power switch

Abstract

The utility model relates to the technical field of power switches, in particular to a protection device of a high-power power switch, which comprises a protection circuit, the protection circuit comprises a current protection circuit and a no-load protection circuit, a triode Q1 and a triode Q2 are arranged on the current protection circuit, and an operational amplifier A2 is arranged on the no-load protection circuit. A pin 7 of the operational amplifier A2 is electrically connected with a triode VT through a resistor R18, and the triode VT is provided with a load RL2 and a resistor R20 in parallel. When the load current is too large or the output is short-circuited, the triode Q1 is in a saturated state, the two ends of the triode Q1 are saturated and voltage is reduced, the emitter and the collector of the triode are connected with the source and the grid of the triode Q2 in parallel, the grid-source voltage of the triode Q2 is clamped to a certain voltage, the triode Q2 is closed, and the post-stage output is cut off. And a load and a post-stage circuit can be effectively protected.

Description

Technical Field

[0001] The utility model relates to a protection device, in particular to a protection device for a high-power power switch, belonging to the technical field of power switches. Background Art

[0002] Protection devices for high-power power switches are widely used in various applications requiring stable and reliable power supply, such as communications equipment, industrial equipment, medical equipment, and other fields. In these fields, the stability and reliability of the power supply are crucial to the normal operation of the equipment. Therefore, the use of power switches with comprehensive protection functions is an important means to ensure the stable operation of the equipment.

[0003] For high-power loads, there is a situation where the load is short-circuited. When the current or short circuit occurs, the normal operation of the load is affected and even the load is damaged, thus causing unnecessary losses.

[0004] Therefore, there is an urgent need to improve the protection device of the high-power power switch to solve the above-mentioned problems. Utility Model Content

[0005] The purpose of the utility model is to provide a protection device for a high-power power switch. When the load current is too large or the output is short-circuited, the transistor Q1 is in a saturated state. At this time, the two ends of the transistor Q1 are saturated and the voltage is reduced. The emitter and collector of the transistor are connected in parallel with the source and gate of the transistor Q2. At this time, the gate-source voltage of the transistor Q2 is clamped to a certain voltage, the transistor Q2 is turned off, and the subsequent stage output is cut off, which can effectively protect the load and the subsequent stage circuit.

[0006] In order to achieve the above-mentioned purpose, the main technical solutions adopted by this utility model include:

[0007] A protection device for a high-power power switch, comprising a protection circuit, wherein the protection circuit comprises a current protection circuit and a no-load protection circuit;

[0008] The current protection circuit is provided with a transistor Q1 and a transistor Q2, and resistors R1 and R2 are provided in parallel on pins 2 and 3 of the transistor Q1. Pin 3 of the transistor Q1 is electrically connected to pin 1 of the transistor Q2 via a resistor R4. A capacitor C1 is provided in parallel with the resistor R1, and pins 1 and 2 of the transistor Q2 are electrically connected to a Zener diode D1;

[0009] The no-load protection circuit is provided with an operational amplifier A2, and pin 7 of the operational amplifier A2 is electrically connected to a transistor VT via a resistor R18. A load RL2 and a resistor R20 are provided in parallel with the transistor VT. The load RL2 and the resistor R20 are electrically connected to pin 6 of the operational amplifier A2 via a resistor R16.

[0010] Preferably, resistors R22 and R3 are arranged in parallel between the transistor Q1 and the transistor Q2, pins 2 and 3 of the transistor Q2 are electrically connected to a resistor R5 and a capacitor C2 arranged in series, and pin 3 of the transistor Q2 is connected to a load RL1.

[0011] Preferably, the pin 5 of the operational amplifier A2 is electrically connected to a resistor R14 and a resistor R15, and a diode VD1 is provided in parallel with the resistor R14 and the resistor R15.

[0012] Preferably, the transistor VT is electrically connected to a resistor R19 , and the resistor R19 is electrically connected to the resistor R14 through the resistor R13 .

[0013] Preferably, the protection circuit includes an overheating protection circuit, an operational amplifier A1 is provided on the overheating protection circuit, a thermistor NTC is electrically connected to pin 5 of the operational amplifier A1, and pin 7 of the operational amplifier A1 is electrically connected to pin 5 of the operational amplifier A1 through a resistor R9.

[0014] Preferably, a resistor R7 and a resistor R8 are provided in parallel on the pin 6 of the operational amplifier A1, a voltage regulator tube VS1 is provided in parallel on the resistors R7 and R8, and a resistor R6 is electrically connected to the voltage regulator tube VS1.

[0015] Preferably, the protection circuit includes a voltage protection circuit, and the voltage protection circuit is provided with a thyristor V and a photocoupler U1 , and the thyristor V is electrically connected to a resistor R12 and a resistor R11 via a voltage regulator tube VS2 .

[0016] Preferably, a resistor R13 and a capacitor C3 are electrically connected between the thyristor V and the voltage regulator tube VS2.

[0017] The utility model has at least the following beneficial effects:

[0018] 1. When the load current is too large or the output is short-circuited, the transistor Q1 is in a saturated state. At this time, the two ends of the transistor Q1 are saturated and the voltage is reduced. The emitter and collector of the transistor are connected in parallel with the source and gate of the transistor Q2. At this time, the gate-source voltage of the transistor Q2 is clamped to a certain voltage, and the transistor Q2 is turned off, cutting off the subsequent stage output, which can effectively protect the load and the subsequent stage circuit.

[0019] 2. To prevent the voltage on the transformer winding from being too high and to make the load effect of the power supply from no-load to full-load smaller, the output terminal of the switching regulated power supply is not allowed to be open-circuited. Resistors R14 and R15 provide a fixed voltage U+ to the non-inverting input terminal of the operational amplifier. Resistor R20 is a shunt resistor for sampling the load current. When the external circuit is not connected to the load RL2, there is no current on resistor R20, and the voltage U at the inverting input terminal of the operational amplifier is 0 V. Therefore, U+ > U−, and the output voltage of the operational amplifier is relatively high, causing the triode VT to be saturated and conducting, automatically connecting the dummy load resistor R19 inside the power supply. When the power supply is connected to the load RL2, the voltage drop on resistor R20 makes U− > U+, the output voltage of the operational amplifier is zero, and the triode VT is cut off, disconnecting resistor R19.

[0020] 3. The thermistor NTC is a negative temperature coefficient thermistor for measuring the temperature of the transformer. A hysteresis comparator is formed by the thermistor NTC, resistor R7, and operational amplifier A1. During normal operation, the temperature of the transformer is normal, the resistance value of the thermistor NTC is relatively large, and the voltages U+ < U− at the two input terminals of the operational amplifier A1, and the output is zero. When the transformer is abnormal and the temperature rises to the set value, the operational amplifier A1 outputs a high level and sends it to the PWM control chip to turn off the output pulse. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The drawings described herein are used to provide a further understanding of the present application and form a part of the present application. The schematic embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation to the present application. In the drawings:

[0022] Figure 1 is the schematic diagram of the present utility model;

[0023] Figure 2 is the current protection circuit diagram of the present utility model;

[0024] Figure 3 is the no-load protection circuit diagram of the present utility model;

[0025] Figure 4 is the overheat protection circuit diagram of the present utility model;

[0026] Figure 5 is the voltage protection circuit diagram of the present utility model.

[0027] In the figures, 1. Protection circuit; 101. Current protection circuit; 102. No-load protection circuit; 103. Overheat protection circuit; 104. Voltage protection circuit. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0028] The following will describe the implementation methods of the present application in detail with reference to the accompanying drawings and examples, so that the implementation process of how the present application applies technical means to solve technical problems and achieve technical effects can be fully understood and implemented accordingly.

[0029] like Figure 1-Figure 5 As shown, the protection device for a high-power power switch provided in this embodiment includes a protection circuit 1, which includes a current protection circuit 101 and a no-load protection circuit 102;

[0030] The current protection circuit 101 is provided with a transistor Q1 and a transistor Q2. Resistors R1 and R2 are connected in parallel to pins 2 and 3 of transistor Q1. Pin 3 of transistor Q1 is electrically connected to pin 1 of transistor Q2 via resistor R4. Capacitor C1 is connected in parallel to resistor R1. A voltage zener diode D1 is electrically connected to pins 1 and 2 of transistor Q2. When the load current is too large or the output is short-circuited, assuming the current is 1A, the voltage drop across the current-sense resistor is 0.7V, and transistor Q1 is in a saturated state. At this time, the saturation voltage drop across transistor Q1 is approximately 0.3V. The emitter and collector of the transistor are connected in parallel with the source and gate of transistor Q2. In other words, the gate-source voltage of transistor Q2 is clamped at 0.3V, transistor Q2 is turned off, and the downstream output is cut off, which can effectively protect the load and downstream circuits.

[0031] Resistors R22 and R3 are connected in parallel between transistors Q1 and Q2. Resistors R5 and C2 are electrically connected in series to pins 2 and 3 of transistor Q2. A load RL1 is connected to pin 3 of transistor Q2. Resistors R1 and R2 divide the voltage. The upper end of resistor R2 has a voltage of approximately 12V. Ignoring the voltage drop across resistor R4, the gate voltage of transistor Q2 is 12V and the source voltage is close to 24V. At this point, Vgs ≈ -12V, transistor Q2 is turned on, and the circuit operates normally.

[0032] Capacitor C1 has two functions: one is to filter out high-frequency noise signals; the other is to increase the parasitic capacitance between the gate and source GS of transistor Q2. When two capacitors are connected in parallel, the capacitance Cgs between the gate and source will increase, the charging time will be longer, and the MOSFET will turn on smoothly.

[0033] Transistor Q1 is in the amplification state. Since resistors R1 and R2 are very small, the Ic current of transistor Q1 is also very small at this time.

[0034] Resistors R3 and R22 are current-sense resistors. The two resistors are connected in parallel and have a resistance of 0.7 ohms. When the load current exceeds 1A or the output is short-circuited, the voltage drop across resistors R3 and R22 exceeds 0.7V. During normal operation, the voltage drop is less than 0.7V.

[0035] Resistor R4: Since there is parasitic capacitance between the gate and source of transistor Q2 and parasitic inductance in the circuit, LC easily causes oscillation during charging and discharging. Adding resistor R4 can effectively suppress oscillation. However, this resistance should not be too large, otherwise it will cause the charging time to be too long and the transistor Q2 to open slowly. This value is usually below 100 ohms.

[0036] During normal operation, the voltage regulator diode D1 is closed. When Vgs exceeds -12V due to some reasons, such as excessive power supply voltage or short circuit of resistor R2, the voltage regulator diode can clamp the voltage of Vsg at 12V. Generally, the maximum withstand voltage of Vsg of this transistor Q2 is about 20V.

[0037] The no-load protection circuit 102 is provided with an operational amplifier A2. Pin 7 of the operational amplifier A2 is electrically connected to a transistor VT via a resistor R18. A load RL2 and a resistor R20 are provided in parallel with the transistor VT. A resistor R16 is provided between the load RL2 and the resistor R20. It is electrically connected to pin 6 of the operational amplifier A2. Resistors R14 and R15 are electrically connected to pin 5 of the operational amplifier A2. A diode VD1 is provided in parallel with resistors R14 and R15. Resistors R19 are electrically connected to transistor VT. Resistors R19 are electrically connected to resistor R14 through resistor R13. In order to prevent the voltage on the transformer winding from being too high and to reduce the load effect of the power supply from no-load to full load, the output end of the switching regulated power supply is not allowed to be open-circuited. Resistors R14 and R15 provide a fixed voltage U+ to the non-inverting input end of the operational amplifier. Resistors R20 are shunts for sampling the load current. When the external circuit is not connected to the load RL2, there is no current in resistor R20, and the voltage U=0 at the inverting input end of the operational amplifier. V, so U+>U-, the output voltage of the operational amplifier is higher, making the transistor VT saturated and turned on, and automatically connecting the dummy load resistor R19 inside the power supply. When the power supply is connected to the load RL2, the voltage drop on the resistor R20 makes U->U+, the output voltage of the operational amplifier is zero, the transistor VT is cut off, and the resistor R19 is disconnected.

[0038] Further, such as Figure 4As shown in the figure, the protection circuit 1 includes an overheat protection circuit 103. An operational amplifier A1 is provided on the overheat protection circuit 103. A thermistor NTC is electrically connected to pin 5 of the operational amplifier A1. Pin 7 of the operational amplifier A1 is electrically connected to pin 5 of the operational amplifier A1 through a resistor R9. A resistor R7 and a resistor R8 are connected in parallel on pin 6 of the operational amplifier A1. A voltage stabilizing diode VS1 is connected in parallel on the resistor R7 and the resistor R8. A resistor R6 is electrically connected to the voltage stabilizing diode VS1. The thermistor NTC is a negative temperature coefficient thermistor for measuring the temperature of the transformer. The thermistor NTC, the resistor R7, and the operational amplifier A1 form a hysteresis comparator. During normal operation, the transformer temperature is normal, the resistance value of the thermistor NTC is large, the voltages at the two input terminals of the operational amplifier A1 are U+ < U−, and the output is zero;

[0039] When the transformer is abnormal and the temperature rises to the set value, the operational amplifier A1 outputs a high level and sends it to the PWM control chip to turn off the output pulse.

[0040] Furthermore, as Figure 5 shown in the figure, the protection circuit 1 includes a voltage protection circuit 104. A thyristor V and an optocoupler U1 are provided on the voltage protection circuit 104. The thyristor V is electrically connected to a resistor R12 and a resistor R11 through a voltage stabilizing diode VS2. A resistor R13 and a capacitor C3 are electrically connected between the thyristor V and the voltage stabilizing diode VS2. The breakdown voltage of the voltage stabilizing diode VS2 is slightly greater than the rated output voltage. When the output is normal, the voltage stabilizing diode VS2 is not conducting, the gate voltage of the thyristor V is zero, and it is not conducting. When the output is overvoltage, the voltage stabilizing diode VS2 breaks down, the thyristor V is triggered to conduct, the output triode current of the optocoupler increases, and the switching tube is turned off through the UC3842.

[0041] As Figure 1-Figure 5 shown in the figure, the principle of the protection device for the high-power power switch provided in this embodiment is as follows: When the load current is too large or the output is short-circuited, assuming the current is 1 A, the voltage drop across the current detection resistor is 0.7 V at this time, and the triode Q1 is in the saturation state. At this time, the saturation voltage drop across the triode Q1 is about 0.3 V. The emitter and collector of the triode are connected in parallel with the source and gate of the triode Q2. In other words, at this time, the gate-source voltage of the triode Q2 is clamped at 0.3 V, and the triode Q2 is turned off, cutting off the subsequent stage output, which can effectively protect the load and the subsequent stage circuit;

[0042] Resistors R22 and R3 are connected in parallel between transistors Q1 and Q2. Pins 2 and 3 of transistor Q2 are electrically connected to resistor R5 and capacitor C2 in series. Pin 3 of transistor Q2 is connected to load RL1. Resistors R1 and R2 divide the voltage. The upper end of resistor R2 is approximately 12V. Ignoring the voltage drop on resistor R4, the gate voltage of transistor Q2 is 12V and the source voltage is close to 24V. At this time, Vgs≈-12V, transistor Q2 is turned on, and the circuit operates normally.

[0043] For example, certain words are used in the specification and claims to refer to specific components. Those skilled in the art should understand that hardware manufacturers may use different terms to refer to the same component. This specification and claims do not use differences in names as a way to distinguish components, but use differences in the functions of the components as the criteria for distinction. For example, "including" mentioned throughout the specification and claims is an open term, so it should be interpreted as "including but not limited to". "Approximately" means that within an acceptable error range, those skilled in the art can solve technical problems within a certain error range and basically achieve technical effects.

[0044] It should be noted that the terms "include," "comprises," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a product or system comprising a series of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such product or system. In the absence of further limitations, an element defined by the phrase "comprising a..." does not exclude the presence of other identical elements in the product or system comprising the element.

[0045] The above description shows and describes several preferred embodiments of the present invention. However, as previously mentioned, it should be understood that the present invention is not limited to the form disclosed herein and should not be construed as excluding other embodiments. Instead, the present invention can be used in various other combinations, modifications, and environments and can be modified within the scope of the present invention as taught herein or through the techniques or knowledge in the relevant field. Modifications and variations made by those skilled in the art that do not depart from the spirit and scope of the present invention are intended to be protected by the claims appended hereto.

Claims

1. A protection device for a high-power power switch, comprising a protection circuit (1), characterized in that: The protection circuit (1) comprises a current protection circuit (101) and a no-load protection circuit (102); The current protection circuit (101) is provided with a transistor Q1 and a transistor Q2, and resistors R1 and R2 are provided in parallel on pins 2 and 3 of the transistor Q1, and pin 3 of the transistor Q1 is electrically connected to pin 1 of the transistor Q2 via a resistor R4, and a capacitor C1 is provided in parallel with the resistor R1, and a voltage stabilizing diode D1 is electrically connected to pins 1 and 2 of the transistor Q2; The no-load protection circuit (102) is provided with an operational amplifier A2, and a transistor VT is electrically connected to a pin 7 of the operational amplifier A2 via a resistor R18. A load RL2 and a resistor R20 are provided in parallel on the transistor VT, and the load RL2 and the resistor R20 are electrically connected to a pin 6 of the operational amplifier A2 via a resistor R16.

2. The protection device for a high-power power switch according to claim 1, characterized in that: Resistors R22 and R3 are connected in parallel between the transistors Q1 and Q2. Pins 2 and 3 of the transistor Q2 are electrically connected to a resistor R5 and a capacitor C2 connected in series. Pin 3 of the transistor Q2 is connected to a load RL1.

3. The protection device for a high-power power switch according to claim 1, characterized in that: Pin 5 of the operational amplifier A2 is electrically connected to a resistor R14 and a resistor R15 , and a diode VD1 is connected in parallel to the resistor R14 and the resistor R15 .

4. The protection device for a high-power power switch according to claim 3, characterized in that: The transistor VT is electrically connected to a resistor R19 , and the resistor R19 is electrically connected to the resistor R14 through the resistor R13 .

5. The protection device for a high-power power switch according to claim 1, characterized in that: The protection circuit (1) includes an overheat protection circuit (103), an operational amplifier A1 is provided on the overheat protection circuit (103), a thermistor NTC is electrically connected to pin 5 of the operational amplifier A1, and a pin 7 of the operational amplifier A1 is electrically connected to pin 5 of the operational amplifier A1 via a resistor R9.

6. The protection device for a high-power power switch according to claim 5, characterized in that: A resistor R7 and a resistor R8 are connected in parallel to the pin 6 of the operational amplifier A1 . A voltage regulator tube VS1 is connected in parallel to the resistors R7 and R8 . The voltage regulator tube VS1 is electrically connected to the resistor R6 .

7. The protection device for a high-power power switch according to claim 1, characterized in that: The protection circuit (1) comprises a voltage protection circuit (104), wherein a thyristor V and a photoelectric coupler U1 are provided on the voltage protection circuit (104), and the thyristor V is electrically connected to a resistor R12 and a resistor R11 via a voltage regulator tube VS2.

8. The protection device for a high-power power switch according to claim 7, characterized in that: A resistor R13 and a capacitor C3 are electrically connected between the thyristor V and the voltage regulator tube VS2.

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