Input under-voltage protection circuit

Abstract

The utility model provides an input under-voltage protection circuit, which relates to the technical field of electronic circuits and comprises a rectifying unit, a voltage dividing unit and a feedback unit. The rectifying unit comprises a rectifying bridge, the input end of the rectifying bridge is connected with an input power supply, and the output end of the rectifying bridge is connected with the voltage dividing unit; the voltage dividing unit comprises a capacitor module and a voltage dividing resistor module which are connected in series, the output end of the voltage dividing unit is connected with an adjustable reference voltage chip, and the adjustable reference voltage chip is connected with a Ctrl pin through an MOSFET (Metal-Oxide-Semiconductor Field Effect Transistor); and the Ctrl pin is externally connected with a PWM (Pulse Width Modulation) chip and is used for outputting a control voltage to the PWM chip. According to the utility model, voltage detection is carried out through the common capacitor and the voltage-sharing resistor, the types and the number of devices required by the detection circuit are reduced, and the structure of the detection circuit is greatly simplified and the detection cost is reduced on the basis of meeting the input voltage under-voltage protection requirement.

Description

TECHNICAL FIELD

[0001] The utility model relates to electronic circuit technical field especially, relates to an input under -voltage protection circuit. BACKGROUND

[0002] At present, driving power is widely applied in each field, and is used for power supply of electric equipment in each field, namely load, to make the electric equipment work normally. However, in the process of normal work of electric equipment and driving power, under -voltage problem can be caused due to various reasons, thereby causing great influence on the operation of electric equipment, for example, in the field of industrial control, motor protection, etc., when under -voltage, namely when the real -time working voltage of electric equipment is lower than the preset working voltage of electric equipment, short -circuit spontaneous combustion and other problems can occur, leading to damage of electric equipment. SUMMARY

[0003] The utility model discloses the purpose is: to solve the problem that the current power supply circuit is easy to cause element damage when under -voltage, the utility model provides an input under -voltage protection circuit.

[0004] The technical scheme of the embodiment of the application is as follows:

[0005] The embodiment of the application provides an input under -voltage protection circuit, which comprises a rectifier unit, a voltage dividing unit and a feedback unit;The rectifier unit comprises a rectifier bridge, the input end of the rectifier bridge is connected with an input power supply, and the output end of the rectifier bridge is connected with the voltage dividing unit;The voltage dividing unit comprises a capacitor module and a voltage dividing resistor module connected in series, the output end of the voltage dividing unit is connected with an adjustable reference voltage chip, and the adjustable reference voltage chip is connected with a Ctrl pin through a MOSFET effect tube;The Ctrl pin is externally connected with a PWM chip, and is used for outputting control voltage to the PWM chip.

[0006] Optionally, the capacitor module comprises a first capacitor C1 and a second capacitor C2;The first capacitor C1 and the second capacitor C2 are connected in series.

[0007] Optionally, the voltage dividing resistor module comprises a first resistor R1, a second resistor R2 and a third resistor R3;The voltage dividing resistor module is connected with the reference pin of the adjustable reference voltage chip.

[0008] Optionally, when the voltage at both ends is lower than 2.5V, the adjustable reference voltage chip is cut off, the MOSFET effect tube is turned on, the control voltage output by the Ctrl pin is reduced, the PWM chip stops working, and the input power supply is turned off.

[0009] Optionally, in the case that the voltage at both ends is not less than 2.5V, the adjustable reference voltage chip is turned on, the MOSFET effect tube is turned off, the control voltage output by the Ctrl pin returns to normal, the PWM chip starts to work, and the input power supply resumes output.

[0010] Optionally, a second capacitor C3 is further connected in parallel with the third resistor R3; one end of the second capacitor C3 is connected with the anode pin of the adjustable reference voltage chip, and the other end is connected with the reference pin of the adjustable reference voltage chip.

[0011] Optionally, a fourth resistor R4 is further connected; one end of the fourth resistor R4 is connected with the cathode pin of the adjustable reference voltage chip, and the other end is connected with the Ctrl pin.

[0012] Optionally, a fifth resistor R5 is further connected; one end of the fifth resistor R5 is connected with the anode pin of the adjustable reference voltage chip, and the other end is connected with the MOSFET effect tube.

[0013] Optionally, a sixth resistor R6 is further connected; one end of the sixth resistor R6 is connected with the MOSFET effect tube, and the other end is connected with the Ctrl pin.

[0014] Optionally, a voltage stabilizing diode U1 is further connected; the input end of the voltage stabilizing diode is connected with the voltage dividing resistor module, and the output end of the voltage stabilizing diode is connected with the Ctrl pin.

[0015] Compared with the prior art, the technical scheme provided by the application has the beneficial effects that:

[0016] The utility model provides an input under -voltage protection circuit, including rectifier unit, voltage dividing unit and feedback unit, rectifier unit includes rectifier bridge, and the input end of rectifier bridge is connected with input power supply, and the output end of rectifier bridge is connected with voltage dividing unit, voltage dividing unit includes series connection's capacitor module and series connection's voltage dividing resistor module, and the output end of voltage dividing unit is connected with adjustable reference voltage chip, and adjustable reference voltage chip is connected with Ctrl pin through MOSFET effect tube, and the PWM chip is connected outside Ctrl pin, and is used for outputting control voltage to PWM chip. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 It is a structure schematic view of input under -voltage protection circuit provided by the utility model embodiment. DETAILED DESCRIPTION

[0018] Embodiments of the present application will be described herein below with reference to drawings. It should be understood, however, that the description is merely exemplary and is not intended to limit the scope of the present application. In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the embodiments of the present application. However, it will be apparent to one skilled in the art that one or more embodiments can be practiced without these specific details. In other instances, well-known structures and

[0019] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present application. As used herein, the term "includes" and tautological expressions thereof, such as "including," "includes," "include," "contains," "containing," and so forth, mean the term "comprises."

[0020] All terms used herein (including technical and scientific terms) have the meanings commonly understood by one of ordinary skill in the art, unless otherwise defined. It should be noted that the terms used herein are to be interpreted as having a meaning that is consistent with the understanding of a person of ordinary skill in the art, and should not be interpreted in an idealized or overly formal manner.

[0021] Some of the blocks and / or flowcharts in the drawings represent computer program instructions. It should be understood that these computer program instructions can be implemented by a processor of a general-purpose computer, a special-purpose computer, or other programmable data processing apparatus. These instructions can create means for implementing the functions / operations specified in the block diagrams and / or flowcharts when the instructions are executed by the processor.

[0022] In some embodiments, please refer to Figure 1 , Figure 1 A flowchart of an input undervoltage protection circuit provided by embodiments of the present application is shown. The input undervoltage protection circuit provided by embodiments of the present application includes a rectification unit, a voltage division unit, and a feedback unit. The rectification unit includes a rectification bridge, an input end of the rectification bridge is connected with an input power supply, and an output end of the rectification bridge is connected with the voltage division unit. The voltage division unit includes a capacitor module and a voltage division resistor module connected in series, an output end of the voltage division unit is connected with an adjustable reference voltage chip, and the adjustable reference voltage chip is connected with a Ctrl pin through a MOSFET effect tube. The Ctrl pin is externally connected with a PWM chip, and is used to output a control voltage to the PWM chip.

[0023] In some embodiments, the capacitor module includes a first capacitor C1 and a second capacitor C2, and the first capacitor C1 and the second capacitor C2 are connected in series.

[0024] In some embodiments, the voltage dividing resistor module includes a first resistor R1, a second resistor R2 and a third resistor R3; the voltage dividing resistor module is connected with the reference pin of the adjustable reference voltage chip.

[0025] In some embodiments, when the voltage across the two ends is lower than 2.5V, the adjustable reference voltage chip is turned off, the MOSFET effect tube is turned on, the control voltage output by the Ctrl pin is reduced, the PWM chip stops working, and the input power supply is turned off.

[0026] In some embodiments, when the voltage across the two ends is not lower than 2.5V, the adjustable reference voltage chip is turned on, the MOSFET effect tube is turned off, the control voltage output by the Ctrl pin returns to normal, the PWM chip starts working, and the input power supply restores output.

[0027] In the embodiment, the input power supply is input through L and N, rectified by the rectifier bridge BD1, and connected with the first capacitor C1 and the second capacitor C2. Since the input voltage is very high, the capacitors are connected in series to increase the withstand voltage of the capacitors. Considering that the capacitors connected in series will have the problem of uneven voltage division, therefore, in the circuit, the first resistor R1, the second resistor R2 and the third resistor R3 will play a role in voltage equalization, and the voltage dividing resistor module composed of R1, R2 and R3 is connected with the reference pin of the adjustable reference voltage chip U1. Here, the adjustable reference voltage chip can be TL431, which plays a role in detecting voltage UD. When the input voltage changes, UD will also change with the input voltage. When the input voltage decreases, UD will also decrease, and the voltage dividing resistor module composed of R1, R2 and R3 will make the voltage of the reference pin of U1 decrease, and when the voltage is lower than 2.5V, U1 is turned off, the voltage between the gate and the source of the MOSFET effect tube Q1 rises, Q1 is turned on, the voltage of the Ctrl pin decreases, and after being fed back to the PWM chip, the PWM chip stops working, and the power supply is turned off. When the input voltage increases, UD will also increase, and the voltage dividing resistor module composed of R1, R2 and R3 will make the voltage of the reference pin of U1 increase, and when the voltage increases to about 2.5V, U1 is turned on, the voltage between the gate and the source of the MOSFET effect tube Q1 decreases, Q1 is turned off, the voltage of the Ctrl pin returns to normal due to the turn-off of Q1, and after being fed back to the PWM chip, the PWM chip restarts, works normally, and the power supply restores output.

[0028] In some embodiments, a second capacitor C3 is further connected in parallel with the third resistor R3; one end of the second capacitor C3 is connected with the anode pin of the adjustable reference voltage chip, and the other end is connected with the reference pin of the adjustable reference voltage chip.

[0029] In some embodiments, a fourth resistor R4 is further included, one end of the fourth resistor R4 is connected with the cathode pin of the adjustable reference voltage chip, and the other end is connected with the Ctrl pin.

[0030] In some embodiments, a fifth resistor R5 is further included, one end of the fifth resistor R5 is connected with the anode pin of the adjustable reference voltage chip, and the other end is connected with the MOSFET effect tube.

[0031] In some embodiments, a sixth resistor R6 is further included, one end of the sixth resistor R6 is connected with the MOSFET effect tube, and the other end is connected with the Ctrl pin.

[0032] It should be noted that the fourth resistor R4, the fifth resistor R5 and the sixth resistor R6 serve as protection resistors in the circuit, can play a role in current limiting, avoid the damage of components caused by excessive current in the circuit. The specific resistance value can be set according to the upper and lower limit threshold of the working parameters of the adjustable reference voltage chip and the MOSFET effect tube, which is not limited here.

[0033] In some embodiments, a zener diode U1 is further included, the input end of the zener diode is connected with the voltage dividing resistor module, and the output end of the zener diode is connected with the Ctrl pin.

[0034] The utility model discloses a voltage dividing sets a reference voltage, when detecting that input voltage is below a threshold, U1 is cut off, Q1 is conducted, on the feedback to PWM chip, make product close output, reach the purpose of input under voltage protection, can effectively solve the drawback that switch power supply input under voltage brings, in addition, reduce the device type and device quantity required by detection circuit, on the basis of satisfying input under voltage protection requirement, greatly simplify the structure of detection circuit, reduce the detection cost, with low cost, reliability and so on.

[0035] Those skilled in the art can understand that the features described in various embodiments and / or claims of the present application can be combined and / or combined, even if such combinations or combinations are not explicitly described in the present application. In particular, the features described in various embodiments and / or claims of the present application can be combined and / or combined without departing from the spirit and teachings of the present application. All these combinations and / or combinations fall within the scope of the present application. Therefore, the scope of the present application should not be limited to the above embodiments, but should be determined not only by the appended claims, but also by the appended claims.

Claims

1. An input under-voltage protection circuit, characterized by, Comprise: The rectifier unit, the voltage dividing unit and the feedback unit; the rectifier unit comprises a rectifier bridge, the input end of the rectifier bridge is connected with the input power supply, and the output end of the rectifier bridge is connected with the voltage dividing unit; the voltage dividing unit comprises a capacitor module in series and a voltage dividing resistor module in series, the capacitor module comprises a first capacitor C1 and a second capacitor C2 in series, the voltage dividing resistor module comprises a first resistor R1, a second resistor R2 and a third resistor R3, the output end of the voltage dividing unit is connected with an adjustable reference voltage chip, and the adjustable reference voltage chip is connected with a Ctrl pin through a MOSFET effect tube; the Ctrl pin is externally connected with a PWM chip, and is used for outputting a control voltage to the PWM chip.

2. The input undervoltage protection circuit of claim 1, wherein, In the case that the voltage at both ends is lower than 2.5V, the adjustable reference voltage chip is cut off, the MOSFET effect tube is turned on, the control voltage output by the Ctrl pin is reduced, the PWM chip stops working, and the input power supply stops outputting.

3. The input undervoltage protection circuit of claim 1, wherein, In the case that the voltage at both ends is not lower than 2.5V, the adjustable reference voltage chip is turned on, the MOSFET effect tube is cut off, the control voltage output by the Ctrl pin returns to normal, the PWM chip starts working, and the input power supply resumes outputting.

4. The input undervoltage protection circuit of claim 3, wherein, Further comprising a second capacitor C3 connected with the third resistor R3 in parallel; one end of the second capacitor C3 is connected with the anode pin of the adjustable reference voltage chip, and the other end is connected with the reference pin of the adjustable reference voltage chip.

5. The input undervoltage protection circuit of claim 1, wherein, Further comprising a fourth resistor R4, one end of the fourth resistor R4 is connected with the cathode pin of the adjustable reference voltage chip, and the other end is connected with the Ctrl pin.

6. The input undervoltage protection circuit of claim 1, wherein, Further comprising a fifth resistor R5, one end of the fifth resistor R5 is connected with the anode pin of the adjustable reference voltage chip, and the other end is connected with the MOSFET effect tube.

7. The input undervoltage protection circuit of claim 1, wherein, Further comprising a sixth resistor R6, one end of the sixth resistor R6 is connected with the MOSFET effect tube, and the other end is connected with the Ctrl pin.

8. The input undervoltage protection circuit of claim 1, wherein, Further comprising a voltage stabilizing diode U1, the input end of the voltage stabilizing diode is connected with the voltage dividing resistor module, and the output end of the voltage stabilizing diode is connected with the Ctrl pin.

Images