An isolated control circuit with overvoltage protection

Abstract

The utility model discloses an isolation control circuit of output overvoltage protection, including overvoltage detection circuit, signal transmission circuit and signal output circuit, overvoltage detection circuit includes resistance R2, capacitor C1 and stabilivolt diode Z1, signal transmission circuit includes photoelectric coupler, signal output circuit includes resistance R1, resistance R3, diode D1, resistance R2 one end, capacitor C1 one end connect stabilivolt diode Z1 anode, resistance R2, capacitor C1 other end connect switching power supply system output ground, stabilivolt diode Z1 cathode connects photoelectric coupler 2 feet, photoelectric coupler 1 foot connects switching power supply system output voltage, and photoelectric coupler 3 feet and diode D1 anode one end, resistance R3 one end are connected in common, and photoelectric coupler 4 feet connect resistance R1 one end, and resistance R1 other end connect external auxiliary power, and resistance R3 other end connect switching power supply system input ground, and diode D1 cathode connects switching power's PWM control chip, the utility model discloses can effectively block circuit interference, and prevent output overvoltage damage module device.

Description

Technical Field

[0001] This utility model belongs to the technical field of isolated switching power supply circuit design, specifically relating to an isolated control circuit for output overvoltage protection. Background Technology

[0002] With the widespread application of electronic devices in automobiles, industrial control, and consumer electronics, their safety and reliability have become core concerns for industry development. Especially in automotive electronic systems, the complex operating environment can easily lead to device damage or failure due to overvoltage, causing system malfunctions or even safety accidents. Although traditional protection circuits can achieve basic protection, they have problems such as response delay, false triggering, or fixed protection thresholds, and often rely on a single threshold trigger. Summary of the Invention

[0003] The purpose of this invention is to provide an isolation control circuit for output overvoltage protection, so as to solve the problem in the prior art that output overvoltage damages the module itself and downstream devices.

[0004] To solve the above technical problems, the following technical solution is adopted: An isolation control circuit for output overvoltage protection includes an overvoltage detection circuit, a signal transmission circuit, and a signal output circuit. The overvoltage detection circuit includes a resistor R2, a capacitor C1, and a Zener diode Z1. The signal transmission circuit includes an optocoupler IC1. The signal output circuit includes a resistor R1, a resistor R3, and a diode D1. One end of resistor R2 and one end of capacitor C1 are connected to the anode of Zener diode Z1, and the other ends of resistor R2 and capacitor C1 are connected to the output ground SCND of the switching power supply system. The cathode of Zener diode Z1 is connected to pin 2 of optocoupler IC1. Pin 1 of optocoupler IC1 is connected to the output voltage +Vo of the switching power supply system. Pin 3 of optocoupler IC1 is connected to one anode of diode D1 and one end of resistor R3. Pin 4 of optocoupler IC1 is connected to one end of resistor R1. The other end of resistor R1 is connected to an external auxiliary power supply VCF1, the other end of resistor R3 is connected to the input ground PGND of the switching power supply system, and the cathode of diode D1 is connected to the CS pin of the PWM control chip of the switching power supply.

[0005] Furthermore, the Zener diode Z1 is model BZX584C5V1.

[0006] Furthermore, the optocoupler IC1 is model number OR-3H7C2-TP-G-(CG).

[0007] Furthermore, the diode D1 is model number 1N4148WT.

[0008] Furthermore, the capacitor C1 has a parameter of 100pF; the resistor R1 has a parameter of 4.7K, the resistor R2 has a parameter of 2.2K, and the resistor R3 has a parameter of 5.1K.

[0009] Compared with the prior art, the beneficial effects of this utility model are as follows: (1) Optocouplers are used to achieve signal isolation between the input and output ends and rapid signal transmission after output overvoltage. The core advantage of optocouplers lies in their excellent electrical isolation performance. They achieve complete electrical isolation between the input and output ends through optical signals, effectively blocking circuit interference and signal crosstalk, and ensuring high safety.

[0010] (2) A Zener diode is used to achieve the voltage regulation protection function. The Zener diode can maintain the voltage across its terminals basically unchanged after reverse breakdown. Even if the load current or power supply voltage fluctuates, its output voltage can still remain stable, preventing overvoltage damage to the module itself and downstream devices, and protecting the system from damage. At the same time, the Zener diode has a voltage regulation range, which can ensure that the system works normally within the normal output voltage accuracy, avoid the system being falsely triggered, and the protection threshold is also a fluctuating range, which will not affect the normal operation of the system.

[0011] (3) This utility model can be used with different PWM control chips. It can also achieve this function by raising the voltage of the reset pin of some PWM control chips. This function is highly versatile, small in size, low in cost, safe and stable, and has broad application prospects.

[0012] (4) All components used in this utility model are general-purpose domestic components with a high degree of self-control and stable and reliable delivery time, meeting the requirements of special equipment for 100% domestic components and having a wide range of applications.

[0013] In summary, this utility model aims to break through the performance bottleneck of traditional protection circuits, provide highly reliable, fast-response, and low-power integrated solutions for automotive electronics, new energy equipment, and industrial control systems, and fill the technical gap in multi-parameter collaborative protection. Attached Figure Description

[0014] Figure 1 This is the circuit schematic diagram of this utility model. Detailed Implementation

[0015] The following are specific embodiments of the present invention. It should be noted that the present invention is not limited to the following specific embodiments. All equivalent modifications made based on the technical solutions of this application fall within the protection scope of the present invention.

[0016] The present invention will now be described in further detail with reference to the accompanying drawings: like Figure 1As shown, the isolation control circuit for output overvoltage protection provided by this utility model includes an overvoltage detection circuit, a signal transmission circuit, and a signal output circuit. The overvoltage detection circuit includes a resistor R2, a capacitor C1, and a Zener diode Z1. The signal transmission circuit includes an optocoupler IC1. The signal output circuit includes a resistor R1, a resistor R3, and a diode D1. One end of the resistor R2 and one end of the capacitor C1 are connected to the anode of the Zener diode Z1. The other ends of the resistor R2 and the capacitor C1 are connected to the output ground SCND of the switching power supply system. The cathode of the Zener diode Z1 is connected to pin 2 of the optocoupler IC1. Pin 1 of the optocoupler IC1 is connected to the output voltage +Vo of the switching power supply system. Pin 3 of the optocoupler IC1 is connected to one anode of the diode D1 and one end of the resistor R3. Pin 4 of the optocoupler IC1 is connected to one end of the resistor R1. The other end of the resistor R1 is connected to the external auxiliary power supply VCF1, and the other end of the resistor R3 is connected to the input ground PGND of the switching power supply system. The cathode of the diode D1 is connected to the CS pin of the PWM control chip.

[0017] The output overvoltage protection isolation control circuit of this invention enables precise monitoring of the output voltage. Once the safety threshold is exceeded, the acquired signal is safely and losslessly transmitted to the primary side via optocoupler IC1, guiding the PWM chip to perform a protection action to ensure the safe and stable operation of the system. The working principle of this invention is as follows: By selecting Zener diodes of different specifications, the regulated voltage is set. However, the actual regulated voltage will be higher than the selected Zener diode voltage due to the influence of other circuits on the secondary side. By consulting the datasheets for the optocoupler and Zener diode, the resistance value of R2 is set appropriately to ensure that the optocoupler IC1 operates at a suitable current transfer ratio, allowing the Zener diode Z1 to reach its operating current range. If the output voltage +Vo is +5V, and the Zener diode Z1 is a BZX584C5V1 model, then the protection threshold for this circuit is approximately 5.1V + 1.2V (the voltage drop across the internal LED of the optocoupler). During normal operation, +Vo is less than the protection threshold, the Zener diode Z1 is in the off state, almost no current flows through it, and no current flows through the LED inside the optocoupler IC1. The phototransistor inside the optocoupler IC1 is not conducting, and the anode of diode D1 is essentially open, with no voltage. This does not affect the CS pin voltage, and the PWM controller can operate normally. When +Vo reaches the output overvoltage protection threshold, the PN junction of Zener diode Z1 breaks down in reverse, causing a sudden increase in the current flowing through it. However, due to its voltage regulation characteristics, +Vo is stabilized within a certain range, preventing system damage. Simultaneously, the current in the LED inside optocoupler IC1 also increases, turning on the phototransistor. The anode voltage of diode D1 is divided by resistors R1 and R3, providing sufficient voltage. After passing through diode D1, this voltage exceeds the CS pin voltage of the PWM controller, thus shutting down the PWM controller and stopping the system, achieving the protection function. When the output voltage +Vo decreases, the current flowing through Zener diode Z1 decreases, causing it to stop working. No current flows through Zener diode Z1, and no current flows through the LED inside the optocoupler. The phototransistor inside the optocoupler does not conduct, and there is no voltage at the anode of diode D1, which does not affect the CS pin voltage. The PWM controller then operates normally, and the system returns to normal operation.

[0018] In this embodiment, if +Vo is 5V and the auxiliary power supply VCF1 is 10V, the device specifications and model selections in this utility model are as follows: Zener diode Z1 is model BZX584C5V1, optocoupler IC1 is model OR-3H7C2-TP-G-(CG), diode D1 is model 1N4148WT; capacitor C1 has a parameter of 100pF; resistor R1 has a parameter of 4.7K, resistor R2 has a parameter of 2.2K, and resistor R3 has a parameter of 5.1K.

[0019] The switching power supply enable control circuit provided by this utility model can be used with different PWM control chips, and can control different pins of the PWM chip. It has strong versatility, small size, low cost, safety and stability, and has broad application prospects.

[0020] The above description is only a preferred embodiment of the present utility model, but the protection scope of the present utility model is not limited thereto. Any changes or substitutions that can be conceived by those skilled in the art within the technical scope disclosed in the present utility model without creative effort should be included within the protection scope of the present utility model.

Claims

1. An isolation control circuit for output overvoltage protection, characterized in that, The system includes an overvoltage detection circuit, a signal transmission circuit, and a signal output circuit. The overvoltage detection circuit includes a resistor R2, a capacitor C1, and a Zener diode Z1. The signal transmission circuit includes an optocoupler IC1. The signal output circuit includes resistors R1 and R3, and a diode D1. One end of resistor R2 and one end of capacitor C1 are connected to the anode of Zener diode Z1. The other ends of resistor R2 and capacitor C1 are connected to the output ground SCND of the switching power supply system. The cathode of Zener diode Z1 is connected to pin 2 of optocoupler IC1. Pin 1 of optocoupler IC1 is connected to the output voltage +Vo of the switching power supply system. Pin 3 of optocoupler IC1 is connected to one anode of diode D1 and one end of resistor R3. Pin 4 of optocoupler IC1 is connected to one end of resistor R1. The other end of resistor R1 is connected to the external auxiliary power supply VCF1. The other end of resistor R3 is connected to the input ground PGND of the switching power supply system. The cathode of diode D1 is connected to the CS pin of the PWM control chip of the switching power supply.

2. The isolation control circuit for output overvoltage protection as described in claim 1, characterized in that, The Zener diode Z1 is model BZX584C5V1.

3. The isolation control circuit for output overvoltage protection as described in claim 1, characterized in that, The optocoupler IC1 is model OR-3H7C2-TP-G-(CG).

4. The isolation control circuit for output overvoltage protection as described in claim 1, characterized in that, The diode D1 is model 1N4148WT.

5. The isolation control circuit for output overvoltage protection as described in claim 1, characterized in that, The capacitor C1 has a value of 100pF; the resistor R1 has a value of 4.7K, the resistor R2 has a value of 2.2K, and the resistor R3 has a value of 5.1K.

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