WO2019061824A1

WO2019061824A1 - Optical coupling overvoltage protection circuit and related electrical appliance

Info

Publication number: WO2019061824A1
Application number: PCT/CN2017/114754
Authority: WO
Inventors: 李屹
Original assignee: 深圳光峰科技股份有限公司
Priority date: 2017-09-27
Filing date: 2017-12-06
Publication date: 2019-04-04
Also published as: CN109560537A

Abstract

An optical coupling overvoltage protection circuit, relating to the technical field of circuit safety protection and comprising: a fuse (F2), a power supply chip (U6), a transient diode (D11), and an optocoupler (U5); the fuse (F2), the power supply chip (U6) and the optocoupler (U5) are connected in turn. The cathode of the transient diode (D11) is connected with one end of the power supply chip (U6) and a pin (3) of the output end of the optocoupler (U5), and the anode of the transient diode (D11) is grounded together with the pin (4) of the output end of the optocoupler (U5).The transient diode (D11) is configured to protect the optocoupler (U5) at an instant high voltage, and perform by using the fuse (F2) circuit protection on a large current generated by the transient diode (D11) at the same time, thereby enhancing the safety protection and reliability of the circuit. Further provided is an electric appliance comprising the optical coupling overvoltage protection circuit.

Description

Optical coupling overvoltage protection circuit and related electrical appliances

Technical field

The present invention relates to the field of circuit safety protection technologies, and in particular, to an optocoupler overvoltage protection circuit.

Background technique

At present, the overvoltage protection between the primary and secondary of the switching power supply often uses optocoupler as the feedback device, and the output voltage is adjusted by the conduction of the optocoupler to achieve the purpose of constant output, so the optocoupler is the most critical device in the voltage feedback circuit. Its stability and safety directly affect the entire switching power supply.

technical problem

When an overvoltage or short-circuit fault occurs in the switching power supply, a large voltage or a large current directly acts on the optocoupler, so that the potential difference exceeds the voltage that the optocoupler can withstand, causing it to be broken down and burying the circuit. A safety hazard.

Technical solution

The main object of the present invention is to provide an optocoupler overvoltage protection circuit. The transient diode is used for the protection of the optocoupler when the voltage is large at a moment, and the fuse is used for the protection of the optocoupler when the current is used at a large current, thereby enhancing the safety protection and reliability of the circuit. .

To achieve the above object, an optocoupler overvoltage protection circuit includes: a fuse, a power chip, a transient diode, and an optocoupler, wherein the fuse, the power chip, and the optocoupler are sequentially connected, wherein the transient diode The negative electrode is connected to one end of the power chip and the pin 3 of the photocoupler output terminal, and the positive electrode of the transient diode is grounded together with the pin 4 of the photocoupler output terminal.

In one embodiment, the fuse is a self-recovering fuse, one end of the self-recovering fuse is connected to a circuit voltage input end, and the other end of the self-recovering fuse is connected to the other end of the power chip.

In one embodiment, a voltage dividing circuit of the circuit voltage output terminal is further included, and the input end of the optocoupler is connected.

In one embodiment, the voltage dividing circuit includes: a Zener diode, a first resistor, a second resistor, and a third resistor, wherein the pin 3 of the Zener diode is grounded together with one end of the third resistor, and the Zener diode The pin 2 is connected to the other end of the third resistor and one end of the second resistor. The pin 1 of the Zener diode is connected to the pin 2 of the optocoupler input end, and the other end of the second resistor is connected to the first resistor. One end is connected, and the other end of the first resistor is connected to the pin 1 of the optocoupler input terminal as a circuit voltage output terminal.

In one embodiment, the Zener diode is an adjustable precision Zener diode.

In one embodiment, when the voltage received by the pin 4 of the optocoupler output is greater than a predetermined voltage value, the transient diode conducts before the optocoupler and discharges to ground to protect the optocoupler.

In one embodiment, when a short circuit fault occurs across the power chip, the power source is directly input to the optocoupler and the transient diode, and the transient diode is turned on before the optocoupler to form a large current, causing the fuse to blow to protect the optocoupler.

In one embodiment, the optocoupler comprises: a light emitting diode and a phototransistor.

In one embodiment, the power chip is a flyback power chip.

The present invention also protects an electrical appliance comprising a power supply system comprising the optocoupler overvoltage protection circuit of any of the above.

Beneficial effect

The optocoupler overvoltage protection circuit of the invention sequentially connects the fuse, the power chip and the optocoupler output end, so that the negative pole of the transient diode is connected with one end of the power chip and the pin 3 of the optocoupler output end, so that the transient diode The positive pole is grounded together with the pin 4 of the optocoupler output terminal, so that the transient diode and the optocoupler output end are connected in parallel, so that the rapid conduction of the transient diode is avoided when an instantaneous large voltage occurs at both ends of the optocoupler output terminal element. A large current flows through the optocoupler output terminal, and the fuse is used to avoid large current damage to the circuit, thereby enhancing the safety protection and reliability of the circuit.

DRAWINGS

FIG. 1 is a circuit diagram of an optocoupler overvoltage protection circuit according to an embodiment of the present invention.

The implementation, functional features, and advantages of the present invention will be further described in conjunction with the embodiments.

Embodiments of the invention

It is understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. The words "left" and "right" in the text are merely for convenience of description with reference to the accompanying drawings, and do not constitute a limitation of the embodiments.

As shown in FIG. 1 , in the embodiment, an optocoupler overvoltage protection circuit includes: a fuse F2, a power chip U6, a transient diode D11, an optocoupler U5, and a voltage dividing circuit, the fuse F2, and a power chip. U6 and the output end of the optocoupler U5 are sequentially connected, and the input end of the optocoupler U5 is connected to the voltage dividing circuit. Wherein, the cathode of the transient diode D11 is connected to one end of the power chip U6 and the pin 3 of the output end of the optocoupler U5, and the anode of the transient diode D11 is grounded together with the pin 4 of the output end of the optocoupler U5; The coupling U5 is used to detect the change of the output voltage of the circuit through the current change at the input end thereof, and feed back the change result to the power supply chip U6 for adjusting the output voltage.

The power chip can be a flyback switching power supply chip.

In this embodiment, the transient diode D11 rapidly short-circuits when an instantaneous large voltage occurs at the output end of the optocoupler U5, thereby forming a large current on the branch, avoiding a large current flowing through the output end of the optocoupler U5, thereby illuminating the light. The output of the U5 is coupled for protection, and the fuse F2 is used for fusing at a large current, thereby enhancing the safety protection and reliability of the circuit.

In this embodiment, the Transient Voltage Suppressor (TVS) is a high-performance protection device in the form of a diode. When the two poles of a TVS diode are subjected to a reverse transient high-energy shock, it can change the high impedance between the two poles to a low impedance at a speed of the order of 10 minus 12 powers, absorbing up to several kilowatts of surge power. The voltage between the two poles is clamped to a predetermined value, effectively protecting the precision components in the electronic circuit from various surge pulses.

In this embodiment, the optocoupler U5 overvoltage protection circuit prevents the circuit input voltage U-IN and the like from being short-circuited, causing the output terminal (pin 4) of the optocoupler U5 to have a high voltage, thereby causing the photocoupler U5 to fail.

In this embodiment, the fuse F2 is a self-recovering fuse, one end of the self-recovering fuse is connected to the circuit voltage input terminal U-IN, and the other end of the self-recovering fuse is connected to one end of the power chip U6.

In this embodiment, the voltage dividing circuit includes: a Zener diode U2, a first resistor R1, a second resistor R2, and a third resistor R3, wherein the pin 3 of the Zener diode U2 and one end of the third resistor R3 Grounded together, the pin 2 of the Zener diode U2 is connected to the other end of the third resistor R3 and one end of the second resistor R2, and the pin 1 of the Zener diode U2 is connected to the pin 2 of the input end of the optocoupler U5. The other end of the second resistor R2 is connected to one end of the first resistor R1, and the other end of the first resistor R1 is connected to the pin 1 of the input end of the optocoupler U5 as a circuit voltage output terminal.

In this embodiment, the Zener diode is an adjustable precision Zener diode, the type is TL431; the first resistor R1, the second resistor R2, and the third resistor R3 are parallel voltage dividing resistors, and the first resistor R1 and the second resistor The resistor R2 and the third resistor R3 serially divide the power supply output voltage, U2 detects and stabilizes the divided voltage on the third resistor R3, and turns on the right diode of the U5 according to the magnitude of the voltage on the third resistor R3, and causes the light to be changed. U5 left transistor conductance and conduction, so that the output voltage change is fed back to the power chip U6 for output voltage regulation. When the pin 4 of U5 receives a large voltage, the TVS tube is quickly turned on to discharge to the ground to protect the optocoupler U5; in addition, when a fault occurs, causing a short circuit between point A and point B as shown in FIG. 1, the U-IN is directly input. To the TVS tube and the optocoupler U5, the TVS will be turned on quickly before the optocoupler U5, forming a large current, causing the fuse F2 to be blown, thereby protecting the optocoupler U5.

It can be understood that the input end of the optocoupler U5 is not limited to the voltage dividing circuit, and may be other circuits known in the art capable of providing an electrical signal.

In this embodiment, when the voltage received by the pin 4 of the photocoupler U5 is greater than the preset voltage value, the transient diode D11 is turned on before the photocoupler U5 and discharged to the ground to protect the optocoupler U5.

In this embodiment, when a short circuit fault occurs at both ends of the power chip U6, the power source U-IN is directly input to the optocoupler U5 and the transient diode D11, and the transient diode D11 is turned on before the photocoupler U5 to form a large current, causing a large current. Fuse F2 is blown to protect optocoupler U5.

In this embodiment, the photocoupler U5 includes a light emitting diode U5-B and a phototransistor U5-A.

In this embodiment, the output end of the photocoupler U5 is a phototransistor, wherein the pin 4 is the emitter of the phototransistor, and the pin 3 is the collector of the phototransistor. In other embodiments of the present invention, in order to enhance the output signal of the optocoupler, another one or more transistors and a phototransistor may be cascaded as an output of the optocoupler, and the pin 4 may be the emitter of the cascade circuit. The pin 3 can be the collector of the cascade circuit.

The invention also claims an electrical appliance comprising a power supply system comprising the optocoupler overvoltage protection circuit described above. The electric appliance can be, for example, a television, a projector, or the like.

It is to be understood that the term "comprises", "comprising", or any other variants thereof, is intended to encompass a non-exclusive inclusion, such that a process, method, article, or device comprising a series of elements includes those elements. It also includes other elements that are not explicitly listed, or elements that are inherent to such a process, method, article, or device. An element that is defined by the phrase "comprising a ..." does not exclude the presence of additional equivalent elements in the process, method, item, or device that comprises the element.

The serial numbers of the embodiments of the present invention are merely for the description, and do not represent the advantages and disadvantages of the embodiments.

The above are only the preferred embodiments of the present invention, and are not intended to limit the scope of the invention, and the equivalent structure or equivalent process transformations made by the description of the present invention and the drawings are directly or indirectly applied to other related technical fields. The same is included in the scope of patent protection of the present invention.

Claims

An optocoupler overvoltage protection circuit, comprising: a fuse, a power chip, a transient diode, and an optocoupler, wherein the fuse, the power chip, and the optocoupler are sequentially connected, wherein the negative electrode and the power source of the transient diode One end of the chip and the pin 3 of the optocoupler output are connected together, and the anode of the transient diode is grounded together with the pin 4 of the optocoupler output.

2. The optocoupler overvoltage protection circuit according to claim 1, wherein the fuse is a self-recovering fuse, one end of the self-recovering fuse is connected to a circuit voltage input end, and the other end of the self-recovering fuse is connected. The other end of the power chip.

3. The optocoupler overvoltage protection circuit according to claim 1, further comprising a voltage dividing circuit of the circuit voltage output terminal, connected to the input end of the optocoupler.

The optocoupler overvoltage protection circuit according to claim 3, wherein the voltage dividing circuit comprises: a Zener diode, a first resistor, a second resistor, and a third resistor, wherein the Zener diode tube The pin 3 is grounded together with one end of the third resistor, and the pin 2 of the Zener diode is connected to the other end of the third resistor and one end of the second resistor, and the pin 1 of the Zener diode and the tube of the optocoupler input end The foot 2 is connected, the other end of the second resistor is connected to one end of the first resistor, and the other end of the first resistor is connected to the pin 1 of the optocoupler input terminal as a circuit voltage output terminal.

5. The optocoupler overvoltage protection circuit according to claim 3, wherein the Zener diode is an adjustable precision Zener diode.

The optocoupler overvoltage protection circuit according to claim 3, wherein when the voltage received by the pin 4 of the optocoupler output terminal is greater than a preset voltage value, the transient diode is turned on before the optocoupler, and Discharge to the ground.

7. The optocoupler overvoltage protection circuit according to claim 3, wherein when a short circuit fault occurs at both ends of the power chip, the power source is directly input to the optocoupler and the transient diode, and the transient diode is turned on before the optocoupler , a large current is formed, causing the fuse to blow to protect the optocoupler.

8. The optocoupler overvoltage protection circuit of claim 3, wherein the optocoupler comprises: a light emitting diode and a phototransistor.

9. The optocoupler overvoltage protection circuit according to claim 1, wherein the power chip is a flyback power chip.

10. An electrical appliance comprising a power supply system comprising the optocoupler overvoltage protection circuit of any one of claims 1-9.