Passive adjustable voltage clamping circuit with temperature protection function

Abstract

The utility model discloses a passive adjustable voltage clamping circuit with a temperature protection function, which comprises an input positive end IN +, an input negative end IN-, a diode D1, a diode D2, a diode D3, a triode Q1, a field effect transistor Q2, a triode Q3, a controllable precise voltage stabilizing source N1, a temperature sensor RT1, a resistor R1, a resistor R2, a resistor R3, a resistor R4, a resistor R5, a resistor R6, a resistor R7 and a slide rheostat R8, the input positive end IN + and the input negative end IN-serve as input power sources, the clamping circuit works passively and can bear very high power, and the bearing power depends on the peak power of the field efficiency tube; the clamping voltage is adjustable, the voltage precision is high, the error is controlled below 1%, the field effect transistor Q2 has an over-temperature protection function, the circuit is prevented from being damaged due to thermal breakdown when external high voltage lasts for a long time, the circuit is simple, the circuit is composed of discrete components, the cost is low, implementation is easy, and the cost performance is high.

Description

Technical Field

[0001] This utility model relates to a passive adjustable voltage clamping circuit with temperature protection function. Background Technology

[0002] In power supply products or battery charging equipment, the most commonly used circuit is the switching power supply. Switching power supplies convert energy using magnetic components (typically transformers or inductors). During each energy conversion cycle, energy is stored in the magnetic component (such as the transformer). However, if the load at the output of the switching power supply abruptly changes from a high current to a low current or zero current, the energy in the magnetic component cannot be released instantaneously, resulting in a very high voltage that is transmitted to the output. This causes the output voltage to spike, potentially damaging the connected load. Therefore, the industry typically adds a Zener diode or TVS diode to the output circuit for voltage clamping to suppress the instantaneous high voltage during load changes.

[0003] Battery charging equipment uses diodes or TVS diodes for output voltage clamping, with a fixed and high clamping voltage. When the battery pack triggers overvoltage protection during charging, the equipment continues to output a high voltage (e.g., 80V clamping voltage), causing the power transistors in the battery pack's BMS (e.g., MOSFETs in mobile phone batteries have a withstand voltage of only 12V) to break down due to overvoltage. The clamping voltage range is wide, making precise voltage clamping impossible. The diodes used in the clamping circuit have low power, making them prone to breakdown and failure under large power surges. High input voltage leading to continuous temperature increases in the clamping circuit can cause thermal breakdown. Low clamping accuracy means that when the voltage is close to but not reached, the circuit's current consumption can reach the mA level, increasing losses and potentially affecting testing. Utility Model Content

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a passive adjustable voltage clamping circuit with temperature protection function.

[0005] To achieve the above objectives, this utility model is implemented through the following technical solution:

[0006] A passive adjustable voltage clamping circuit with temperature protection includes an input positive terminal IN+, an input negative terminal IN-, diodes D1, D2, and D3, transistors Q1, Q2, and Q3, a controllable precision voltage regulator N1, a temperature sensor RT1, resistors R1, R2, R3, R4, R5, R6, and R7, and a variable resistor R8. The input positive terminal IN+ and the input negative terminal IN- serve as the input power supply. The input positive terminal IN+ is connected to the drain of MOSFET Q2 through diode D3. The source of MOSFET Q2 is connected to the input negative terminal IN-. The input positive terminal IN+ is connected to the emitter of transistor Q1. The collector of transistor Q1 is connected to the gate of MOSFET Q2 through resistor R1. The gate of MOSFET Q2 is connected to resistor R8. R2 is connected to the negative input terminal IN-. The positive input terminal IN+ is connected to the base of transistor Q1 through resistor R3. The base of transistor Q1 is connected to the cathode of controllable precision voltage regulator N1 through resistor R4. The anode of controllable precision voltage regulator N1 is connected to the negative input terminal IN-. The reference terminal of controllable precision voltage regulator N1 is connected to the negative input terminal IN- through sliding rheostat R8. The collector of transistor Q1 is connected to the anode of diode D1 through resistor R6. The cathode of diode D1 is connected to the negative input terminal IN- through diode D2. The gate of MOSFET Q2 is connected to the collector of transistor Q3. The emitter of transistor Q3 is connected to the negative input terminal IN-. The base of transistor Q3 is connected to the negative input terminal IN- through resistor R7. The temperature sensor RT1 is connected between the anode of diode D1 and the base of transistor Q3.

[0007] Preferably, the temperature sensor RT1 is a thermistor.

[0008] Preferably, transistor Q1 is a PNP transistor and transistor Q3 is a PNP transistor.

[0009] Preferably, the field-effect transistor Q2 is an N-channel field-effect transistor.

[0010] As a preferred option, the controllable precision voltage regulator N1 is model AZ431.

[0011] Preferably, resistor R1 is 3K, resistor R2 is 100K, resistor R3 is 2K, resistor R4 is 10K, resistor R5 is 200K, resistor R6 is 3K, and resistor R7 is 3.9K.

[0012] Preferably, the resistance value of the sliding rheostat R8 is in the range of 0-100K.

[0013] The beneficial effects of this utility model are as follows:

[0014] 1. The clamping circuit of this utility model operates passively and can withstand very high power, the power of which depends on the peak power of the field efficiency transistor; the clamping voltage is adjustable; the high-power transistor used for clamping has high temperature protection and reverse polarity input protection.

[0015] 2. The clamping voltage is controlled by a controllable precision voltage regulator N1, which has high voltage accuracy and the error is controlled below 1%.

[0016] 3. The field-effect transistor Q2 has an over-temperature protection function to prevent the circuit from being damaged by thermal breakdown when the external high voltage is maintained for a long time;

[0017] 4. When the input voltage is lower than the clamping voltage, the current consumption is very small, only in the μA range, which does not affect normal use. The clamping voltage is the reference voltage of the AZ431 controllable precision voltage regulator N1, which is 2.5V.

[0018] 5. The circuit is simple, composed of discrete components, has low cost, is easy to implement, and has a high cost-performance ratio. Attached Figure Description

[0019] Figure 1 This is the circuit schematic. Detailed Implementation

[0020] The technical solution of this utility model will be further described below with reference to the accompanying drawings:

[0021] like Figure 1As shown, a passive adjustable voltage clamping circuit with temperature protection includes an input positive terminal IN+, an input negative terminal IN-, diodes D1, D2, and D3, transistor Q1, field-effect transistor Q2, transistor Q3, a controllable precision voltage regulator N1, a temperature sensor RT1, resistors R1, R2, R3, R4, R5, R6, and R7, and a sliding rheostat R8. The input positive terminal IN+ and the input negative terminal IN- serve as the input power supply. The input positive terminal IN+ is connected to the drain of field-effect transistor Q2 through diode D3. The source of field-effect transistor Q2 is connected to the input negative terminal IN-. The input positive terminal IN+ is connected to the emitter of transistor Q1. The collector of transistor Q1 is connected to the gate of field-effect transistor Q2 through resistor R1. The gate of field-effect transistor Q2 is connected to... Resistor R2 is connected to the negative input terminal IN-. The positive input terminal IN+ is connected to the base of transistor Q1 via resistor R3. The base of transistor Q1 is connected to the cathode of controllable precision voltage regulator N1 via resistor R4. The anode of controllable precision voltage regulator N1 is connected to the negative input terminal IN-. The reference terminal of controllable precision voltage regulator N1 is connected to the negative input terminal IN- via sliding rheostat R8. The collector of transistor Q1 is connected to the anode of diode D1 via resistor R6. The cathode of diode D1 is connected to the negative input terminal IN- via diode D2. The gate of field-effect transistor Q2 is connected to the collector of transistor Q3. The emitter of transistor Q3 is connected to the negative input terminal IN-. The base of transistor Q3 is connected to the negative input terminal IN- via resistor R7. A temperature sensor RT1 is connected between the anode of diode D1 and the base of transistor Q3. The temperature sensor RT1 is a thermistor.

[0022] like Figure 1 As shown, transistor Q1 is a PNP transistor, transistor Q3 is a PNP transistor, field-effect transistor Q2 is an N-channel field-effect transistor, the controllable precision voltage regulator N1 is model AZ431, resistor R1 is 3K, resistor R2 is 100K, resistor R3 is 2K, resistor R4 is 10K, resistor R5 is 200K, resistor R6 is 3K, resistor R7 is 3.9K, and the resistance range of the sliding rheostat R8 is 0-100K.

[0023] The sliding rheostat R8 is used to adjust the clamping voltage; the field-effect transistor Q2 is used for power absorption; the controllable precision voltage regulator N1 is used to precisely control the clamping voltage; the temperature sensor RT1 is fixed to the housing of the field-effect transistor Q2 with thermally conductive adhesive for high-temperature protection of the field-effect transistor; the forward voltage drop of the two diodes connected in series is used to generate the supply voltage for the NTC thermistor RT1.

[0024] The circuit operates as follows:

[0025] like Figure 1 As shown,

[0026] 1. Clamping circuit not activated: When the input power supply voltage is reversed, the entire circuit does not work due to the unidirectional conductivity of D3, thus providing input reverse polarity protection. When the input power supply polarity is normal, and the voltage division value after the input voltage passes through R5 and R8 in series is less than the reference voltage of the AZ431 controllable precision voltage regulator N1 (2.5V), that is, when the input voltage is lower than the preset clamping voltage value, the controllable precision voltage regulator N1 is in a high-resistance cutoff state. At this time, there is no current at the base of Q1, Q1 is in the off state, and Q2 is also in the off state. The circuit does not work, and the current consumption is very small, in the μA range.

[0027] 2. Clamping Circuit Operation: When the voltage drop across the input power supply after passing through R5 and R8 in series exceeds the reference voltage of the AZ431 controllable precision voltage regulator N1 (2.5V), i.e., when the input voltage exceeds the preset clamping voltage, the AZ431 controllable precision voltage regulator N1 is turned on. At this time, current is generated at the base of Q1, and Q1 is turned on. Q1, R6, D1, and D2 form a small current loop, clamping the positive terminal of D1 at 1.4V, thus providing a stable 1.4V voltage to the NTC thermistor. If Q2 is at a low temperature, the resistance of the NTC thermistor RT1 is high, the base voltage of Q3 is low, and Q3 is also in the off state, then the positive terminal voltage drives Q2 to conduct through Q1 and R1. The current from the input power supply will be diverted through D3 and the conducting Q2. When the current value is large enough that the voltage division value of the input power supply after R5 and R8 are equal to the reference voltage of 2.5V of the AZ431 controllable precision voltage regulator N1, the input power supply voltage is clamped and no longer rises.

[0028] 3. High-temperature protection operation of power transistor during clamping: When the user mistakenly sets the clamping voltage to be lower than the normal output voltage of the power supply, the clamping circuit will always be in a voltage clamping state with large current absorption. At this time, the temperature of the field-effect transistor Q2 will gradually rise. As the temperature of Q2 increases, the resistance of NTC will decrease. When Q2 reaches the preset temperature (e.g., 50 degrees Celsius), the voltage value after the voltage division of NTC resistor RT1 and R7 will cause the base voltage of Q3 to reach more than 0.7V, which will drive Q3 to conduct, thereby pulling down the gate voltage of Q2 and turning off Q2, thus preventing the field-effect transistor Q2 from being damaged by thermal breakdown due to excessive temperature.

[0029] The input voltage of the clamping circuit is divided by a fixed resistor and an adjustable resistor and then connected to the voltage reference terminal of the AZ431 controllable precision voltage regulator N1. The AZ431 controllable precision voltage regulator N1 drives the transistor, and the transistor controls the MOSFET. A diode is connected in series with the MOSFET. The circuit uses an NTC thermistor and a resistor to divide the voltage and drive the transistor, which in turn controls the gate of the MOSFET.

[0030] Transistors Q1 and Q3 can be replaced with corresponding field-effect transistors.

[0031] 1. The clamping circuit of this utility model operates passively and can withstand very high power, the power of which depends on the peak power of the field efficiency transistor; the clamping voltage is adjustable; the high-power transistor used for clamping has high temperature protection and reverse polarity input protection.

[0032] 2. The clamping voltage is controlled by a controllable precision voltage regulator N1, which has high voltage accuracy and the error is controlled below 1%.

[0033] 3. The field-effect transistor Q2 has an over-temperature protection function to prevent the circuit from being damaged by thermal breakdown when the external high voltage is maintained for a long time;

[0034] 4. When the input voltage is lower than the clamping voltage, the current consumption is very small, only in the μA range, which does not affect normal use. The clamping voltage is the reference voltage of the AZ431 controllable precision voltage regulator N1, which is 2.5V.

[0035] 5. The circuit is simple, composed of discrete components, has low cost, is easy to implement, and has a high cost-performance ratio.

[0036] It should be noted that the above examples are only one specific embodiment of this utility model. Obviously, this utility model is not limited to the above embodiments and can have many variations. In short, all variations that can be directly derived or conceived by those skilled in the art from the content disclosed in this utility model should be considered within the protection scope of this utility model.

Claims

1. A passive adjustable voltage clamping circuit with temperature protection function, characterized in that, The system includes an input positive terminal IN+, an input negative terminal IN-, diodes D1, D2, and D3, transistor Q1, field-effect transistor Q2, transistor Q3, a controllable precision voltage regulator N1, a temperature sensor RT1, resistors R1, R2, R3, R4, R5, R6, and R7, and a variable resistor R8. The input positive terminal IN+ and the input negative terminal IN- serve as the input power supply. The input positive terminal IN+ is connected to the drain of field-effect transistor Q2 through diode D3. The source of field-effect transistor Q2 is connected to the input negative terminal IN-. The input positive terminal IN+ is connected to the emitter of transistor Q1. The collector of transistor Q1 is connected to the gate of field-effect transistor Q2 through resistor R1. The gate of field-effect transistor Q2 is connected to the input negative terminal IN- through resistor R2. The positive input terminal IN+ is connected to the base of transistor Q1 through resistor R3. The base of transistor Q1 is connected to the cathode of controllable precision voltage regulator N1 through resistor R4. The anode of controllable precision voltage regulator N1 is connected to the negative input terminal IN-. The reference terminal of controllable precision voltage regulator N1 is connected to the negative input terminal IN- through sliding rheostat R8. The collector of transistor Q1 is connected to the anode of diode D1 through resistor R6. The cathode of diode D1 is connected to the negative input terminal IN- through diode D2. The gate of field-effect transistor Q2 is connected to the collector of transistor Q3. The emitter of transistor Q3 is connected to the negative input terminal IN-. The base of transistor Q3 is connected to the negative input terminal IN- through resistor R7. A temperature sensor RT1 is connected between the anode of diode D1 and the base of transistor Q3.

2. The passive adjustable voltage clamping circuit with temperature protection function according to claim 1, characterized in that, The temperature sensor RT1 is a thermistor.

3. The passive adjustable voltage clamping circuit with temperature protection function according to claim 1, characterized in that, Transistor Q1 is a PNP transistor, and transistor Q3 is a PNP transistor.

4. The passive adjustable voltage clamping circuit with temperature protection function according to claim 1, characterized in that, The field-effect transistor Q2 is an N-channel field-effect transistor.

5. The passive adjustable voltage clamping circuit with temperature protection function according to claim 1, characterized in that, The controllable precision voltage regulator N1 is model AZ431.

6. The passive adjustable voltage clamping circuit with temperature protection function according to claim 1, characterized in that, The resistor R1 is 3K, the resistor R2 is 100K, the resistor R3 is 2K, the resistor R4 is 10K, the resistor R5 is 200K, the resistor R6 is 3K, and the resistor R7 is 3.9K.

7. The passive adjustable voltage clamping circuit with temperature protection function according to claim 1, characterized in that, The resistance range of the sliding rheostat R8 is 0-100K.

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