CN203911741U - Protection circuit of module power supply - Google Patents

Abstract

A protection circuit for a module power supply, the protection function is not affected by the input voltage and capacitive load, and the protection delay of the adjustment circuit can be set freely, so as to adjust the capacity of the power supply with capacitive load, which not only improves the protection of the full input voltage range With capacitive load capacity, it also has the characteristics of low power consumption when the load is short-circuited for a long time. The utility model has a simple structure, low cost, and is easy to debug. The short-circuit protection circuit cooperates with the current-type PWM control chip application circuit, which effectively solves the problem of module power supply The problem of long-term short-circuit protection of loads under different input voltages is especially suitable for low-voltage isolated module power supplies.

Description

A protection circuit for a module power supply

technical field

The utility model relates to the technical field of a module power supply, in particular to a protection circuit of a module power supply.

Background technique

Short-circuit protection is an important factor in measuring the reliability of a module's power supply. With the wide application of modular power supplies in various industries, users have higher requirements for their reliability. This requires the module power supply to be able to protect itself and the safety of the equipment under various abnormal conditions. Among the various protections of the module power supply, the short circuit protection is particularly important. When the module power supply is short-circuited, a large current will flow through each power device, and some power devices will generate a lot of heat and even damage the power device, resulting in the paralysis of the entire module power supply. Therefore, designing a circuit that can protect itself and the equipment in the event of a short circuit is the key to solving this problem.

The current module power supply generally adopts PWM (Pulse Width Modulation) control technology, among which UCC2800 is a popular current-mode PWM control chip, which has the advantages of high precision, stable operation, simple peripheral circuit, etc., and is widely used in module power supply. The over-current and short-circuit protection function of the 2800 chip is to use a resistor or a current transformer to detect the current on the primary side of the transformer, and send the obtained current sampling signal to pin 3 of the 2800. When the power supply is over-current or short-circuited, the current on the primary side of the transformer increases to make 3 When the pin current sampling signal voltage is higher than 1.5V, the chip over-current protection action will reduce the duty cycle of the 6-pin output, thereby reducing the conduction time of the power MOS tube, reducing the output voltage, reducing power consumption, and realizing protection. Although this protection method has a fast response and can realize cycle-by-cycle protection, the average power consumption is still large during long-term overcurrent or short-circuit conditions, especially in module power supplies with a wide input voltage range. In the case of long-term overload or short-circuit, it is still easy to damage the power device of the module, and the long-term load short-circuit protection cannot be realized.

Contents of the invention

In order to overcome the deficiencies of the prior art above, the purpose of this utility model is to provide a protection circuit for a module power supply. The short-circuit protection circuit cooperates with the application circuit of the current-type PWM control chip to effectively solve the problem of the module power supply being loaded for a long time under different input voltages. The problem of short-circuit protection is especially suitable for low-voltage isolated module power supplies.

In order to achieve the above object, the technical scheme that the utility model takes is:

A protection circuit for a module power supply, including an operational amplifier U3, where pin 1 of the operational amplifier U3 is connected to one end of a resistor R8 and a resistor R9, and pin 2 of the operational amplifier U3 is connected to one end of a resistor R10, a capacitor C8, and a capacitor C9 and is directly grounded , pin 3 of op amp U3 is connected to the other end of capacitor C8 and resistor R10, pin 4 of op amp U3 is connected to the cathode of diode D4 and diode D6, pin 5 and pin 6 of op amp U3 are connected to pin 8 of PWM control chip U1 Connection; the anode of diode D4 is connected to pin 1 of op amp U3, the cathode of diode D5 is connected to one end of resistor R10, the anode of diode D6 is connected to pin 1 of PWM control chip U1; one end of capacitor C9 is connected to pin 5 of op amp U3 One end of the resistor R11 is connected to the anode of the diode D5, and the other end is connected to the anode of the diode D6; the other end of the resistor R8 is connected to the pin 8 of the PWM control chip U1; the other end of the resistor R9 is directly connected to the ground.

The PWM control chip U1 adopts the control chip 2800 or 2803 .

The operational amplifier U3 adopts TLV341.

The diode D4, the diode D5 and the diode D6 are Schottky diodes.

The short-circuit protection circuit provided by the utility model has simple structure, low cost, and is convenient for debugging. The protection function is not affected by the input voltage and capacitive load. , so as to adjust the capacitive load capacity of the power supply, which not only improves the capacitive load capacity of the full input voltage range, but also has the characteristics of low power consumption when the load is short-circuited for a long time.

Description of drawings

Accompanying drawing is the circuit diagram of the utility model.

Detailed ways

Below in conjunction with accompanying drawing, the utility model is described in further detail.

A short-circuit protection circuit provided by the utility model is mainly designed for the module power supply using the current-type PWM control chip 2800 series. Operational amplifier U3, pin 1 of operational amplifier U3 is connected to one end of resistor R8 and resistor R9, pin 2 of operational amplifier U3 is connected to one end of resistor R10, capacitor C8, and capacitor C9 and directly grounded, and pin 3 of operational amplifier U3 is connected to capacitor C8, the other end of the resistor R10 is connected, the 4 pins of the op amp U3 are connected to the cathodes of the diode D4 and diode D6, the 5 and 6 pins of the op amp U3 are connected to the 8 pins of the PWM control chip U1; the anode of the diode D4 is connected to the op amp Connect pin 1 of U3, the cathode of diode D5 is connected to one end of resistor R10, the anode of diode D6 is connected to pin 1 of PWM control chip U1; one end of capacitor C9 is connected to pin 5 of operational amplifier U3, and the other end is directly grounded; resistor R11 One end of the resistor R8 is connected to the anode of the diode D5, and the other end is connected to the anode of the diode D6; the other end of the resistor R8 is connected to the pin 8 of the PWM control chip U1; the other end of the resistor R9 is directly grounded.

The PWM control chip U1 adopts the control chip 2800 or 2803 .

The operational amplifier U3 adopts TLV341.

The diode D4, the diode D5 and the diode D6 are Schottky diodes.

The working principle of the utility model is:

When the load is over-current or short-circuited, the current of the primary side of the feedback optocoupler isolator decreases, and the current of the secondary side also decreases, so that the voltage of pin 1 of the PWM control chip rises. When it rises to a certain level, the operational amplifier U3 Action, pin 4 of op amp U3 outputs low potential (about 0.2V), diode D4 and diode D6 conduct, pin 1 potential of op amp U3 is clamped at about 0.5V by diode D4, pin 1 of PWM control chip U1 The potential is clamped at about 0.5V by the diode D6, so that the pin 6 of the PWM control chip U1 quickly reduces the output of the duty cycle, thereby reducing the output voltage and realizing protection. Because of the existence of capacitor C8, the voltage of pin 3 of op amp U3 drops more slowly than the voltage of pin 1 of op amp U3, so that pin 4 of op amp U3 can continue to be at a low potential for a period of time, so that diode D6 also continues to conduct For a period of time, the potential of pin 1 of the PWM control chip U1 is continuously pulled down. When the energy stored in capacitor C8 is released to a certain extent, when the potential of pin 3 of op amp U3 is lower than that of pin 1 of op amp U3, the output high potential of pin 4 of op amp U3 is close to 5V, and diode D4 and diode D6 are cut off. The potential of pin 1 of PWM control chip U1 rises, the duty cycle of pin 6 of PWM control chip U1 becomes larger, and the module resumes output. If the over-current and short-circuit state is not released at this time, the voltage of pin 1 of PWM control chip U1 rises again, diode D6 conducts again, and the potential of pin 1 of PWM control chip U1 is pulled down to ground potential again, reducing the duty cycle output, reduce the output voltage, and achieve protection again; after the overcurrent and short circuit conditions are released, the output voltage is established because the current of the primary side and secondary side of the optocoupler isolator in the feedback circuit increases, so that the potential of pin 1 of the PWM control chip U1 is controlled. Pull it low, so that the operational amplifier U3 does not operate, the diode D6 is cut off, and the pin 6 of the PWM control chip U1 returns to the normal duty ratio output, so that the module resumes normal operation.

The utility model is not only applicable to the module power supply adopting 2800, but also applicable to adopting other similar current-type PWM control chips such as 2803 and the like.

The above is only a specific embodiment of the utility model, but the scope of protection of the utility model is not limited thereto, and any person familiar with the art can think of it without creative work within the technical scope disclosed in the utility model. Labor or replacement should be covered within the protection scope of the present utility model.

Claims (4)

1. A protection circuit for a module power supply, comprising an operational amplifier U3, characterized in that: pin 1 of the operational amplifier U3 is connected to one end of resistor R8 and resistor R9, and pin 2 of the operational amplifier U3 is connected to resistor R10, capacitor C8, and capacitor C9 One end of the op amp U3 is connected to the other end of the capacitor C8 and the resistor R10, and the other end of the resistor R10 is connected to the 3 pins of the op amp U3. The 4 pins of the op amp U3 are connected to the cathodes of the diode D4 and the diode D6. The 8-pin connection of the control chip U1; the anode of the diode D4 is connected to the 1-pin of the operational amplifier U3, the cathode of the diode D5 is connected to one end of the resistor R10, the anode of the diode D6 is connected to the 1-pin of the PWM control chip U1; one end of the capacitor C9 is connected to The 5-pin of the operational amplifier U3 is connected, and the other end is directly grounded; one end of the resistor R11 is connected to the anode of the diode D5, and the other end is connected to the anode of the diode D6; the other end of the resistor R8 is connected to the 8-pin of the PWM control chip U1; the other end of the resistor R9 directly to ground. 2. A protection circuit for a module power supply according to claim 1, wherein the PWM control chip U1 is a control chip 2800 or 2803. 3. A protection circuit for a module power supply according to claim 1, wherein the operational amplifier U3 adopts TLV341. 4. A protection circuit for a module power supply according to claim 1, wherein said diode D4, diode D5, and diode D6 are Schottky diodes.