A DC input self-powered input undervoltage protection circuit

Abstract

This utility model belongs to the field of switching power supply technology and discloses a DC input self-powered input undervoltage protection circuit. The +VDC port is connected to one end of resistor R4. The other end of resistor R4 is connected to one end of resistor R3 and pin 2 of switching transistor Q2. The other end of resistor R3 is connected to pin 1 of switching transistor Q2 and the cathode of Zener diode Z1. Pin 3 of switching transistor Q2 is connected to one end of capacitor C19, pin 8 of operational amplifier U5, and port VDD. The anode of Zener diode Z1 is connected to the other end of capacitor C19, pin 4 of operational amplifier U5, and port GND. The advantages of this utility model are: it is implemented using pure hardware circuitry, requires fewer external circuit components, has high accuracy, low cost, high versatility, and can connect to different models of main control chips.

Description

Technical Field

[0001] This utility model relates to the field of switching power supply technology, and in particular to a DC input self-powered input undervoltage protection circuit. Background Technology

[0002] As power supply equipment for electronic products, switching power supplies, in addition to meeting the basic performance requirements of the products, must also have their own protection measures, such as undervoltage, overcurrent, and overtemperature protection. When the input voltage of a switching power supply is too low, the power conversion efficiency decreases, leading to increased heat generation, reduced reliability, and even damage to the power supply. Therefore, it is necessary to introduce input voltage undervoltage protection into switching power supplies to protect them in time when the input voltage is too low. Although some main control chips in existing technology have input undervoltage protection functions, these chips are expensive, increasing production costs.

[0003] Therefore, it is necessary to provide a DC input self-powered input undervoltage protection circuit, which can realize undervoltage protection for switching power supplies when the main control chip does not have undervoltage protection function. Utility Model Content

[0004] This utility model discloses a DC input self-powered input undervoltage protection circuit, which can effectively solve the technical problems involved in the background art.

[0005] To achieve the above objectives, the technical solution of this utility model is as follows:

[0006] A DC input self-powered input undervoltage protection circuit includes a port +VDC, which is connected to one end of a resistor R4. The other end of the resistor R4 is connected to one end of a resistor R3 and pin 2 of a switching transistor Q2. The other end of the resistor R3 is connected to pin 1 of the switching transistor Q2 and the cathode of a Zener diode Z1. Pin 3 of the switching transistor Q2 is connected to one end of a capacitor C19, pin 8 of an operational amplifier U5, and port VDD. The anode of the Zener diode Z1 is connected to the other end of the capacitor C19, pin 4 of the operational amplifier U5, and port GND.

[0007] The port VDD is connected to one end of resistor R14, and the other end of resistor R14 is connected to pin 3 of voltage regulator U6, pin 1 of voltage regulator U6, one end of capacitor C23 and port VREF. Pin 2 of voltage regulator U6 is connected to the other end of capacitor C23 and port GND.

[0008] The +VDC port is connected to one end of resistor R15. The other end of resistor R15 is connected to one end of resistor R16 and one end of resistor R18. The other end of resistor R18 is connected to pin 2 of operational amplifier U5. Pin 3 of operational amplifier U5 is connected to one end of resistor R17 and one end of resistor R19. The other end of resistor R17 is connected to port VREF. The other end of resistor R19 is connected to pin 1 of operational amplifier U5 and the positive terminal of diode D2. The negative terminal of diode D2 is connected to one end of resistor R20. The other end of resistor R20 is connected to one end of resistor R26 and pin 1 of switching transistor Q4. Pin 2 of switching transistor Q4 is connected to the cathode of optocoupler OT1. The anode of optocoupler OT1 is connected to one end of resistor R1. The other end of resistor R1 is connected to port VDD. The other end of resistor R16 is connected to the other end of resistor R26, pin 3 of switching transistor Q4, the emitter of optocoupler OT1, and port GND. The collector of optocoupler OT1 is connected to the output terminal.

[0009] A DC input self-powered input undervoltage protection circuit is disclosed, comprising a DC power input sampling circuit, a reference voltage circuit, a comparator circuit, a power supply circuit, a first switching circuit, and a second switching circuit. The DC power input sampling circuit is connected to the negative input terminal of the comparator circuit, the output terminal of the reference voltage circuit is connected to the positive input terminal of the comparator circuit, the control terminal of the first switching circuit is connected to the output terminal of the comparator circuit, and the second switching circuit is connected between the voltage sampling pin of the main control chip and ground. The power supply circuit supplies power to the reference voltage circuit, the comparator circuit, and the first switching circuit respectively. This circuit can effectively achieve input undervoltage protection even when the main control chip does not have undervoltage protection functionality.

[0010] As a preferred improvement of this utility model: the switching transistor Q2 is a triode, wherein pin 1 is the base, pin 2 is the collector, and pin 3 is the emitter.

[0011] As a preferred improvement of this utility model: the switching transistor Q4 is a triode, wherein pin 1 is the base, pin 2 is the collector, and pin 3 is the emitter.

[0012] As a preferred improvement of this utility model: the port +VDC is connected to the DC circuit to be protected, and the output terminal is connected to the controller U2. The controller U2 is used for undervoltage protection of the DC circuit to be protected.

[0013] As a preferred improvement of this utility model: the controller U2 is OB2276, and the output terminal is connected to pin 4 of the controller U2.

[0014] As a preferred improvement of this utility model: the operational amplifier U5 is model LM2904DGKR.

[0015] As a preferred improvement of this utility model: the voltage regulator U6 is a controllable precision voltage regulator TL431, wherein pin 1 is the reference stage, pin 2 is the anode, and pin 3 is the cathode.

[0016] As a preferred improvement of this utility model, the port GND is grounded.

[0017] The beneficial effects of this utility model are as follows:

[0018] The DC input self-powered input undervoltage protection circuit is implemented using pure hardware circuitry. It requires fewer external circuit components, has high accuracy, low cost, and high versatility. It can be connected to different models of main control chips. As long as a certain pin of the main control chip is at a low level, the protection can be triggered. This self-powered input undervoltage protection can protect electronic products and prevent some accidents from happening. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of this utility model, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort, wherein:

[0020] Figure 1 This is a sub-circuit of a DC input self-powered input undervoltage protection circuit according to this utility model. Figure 1 ;

[0021] Figure 2 This is a sub-circuit of a DC input self-powered input undervoltage protection circuit according to this utility model. Figure 2 ;

[0022] Figure 3 This is a sub-circuit of a DC input self-powered input undervoltage protection circuit according to this utility model. Figure 3 . Detailed Implementation

[0023] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0024] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present invention are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indication will also change accordingly.

[0025] Furthermore, in this invention, descriptions involving "first," "second," etc., are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0026] In this invention, unless otherwise explicitly specified and limited, the terms "connection," "fixed," etc., should be interpreted broadly. For example, "fixed" can mean a fixed connection, a detachable connection, or an integral part; it can mean a mechanical connection or an electrical connection; it can mean a direct connection or an indirect connection through an intermediate medium; it can mean the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0027] Furthermore, the technical solutions of the various embodiments of the present invention can be combined with each other, but only if they are feasible for those skilled in the art. If the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0028] Please see Figure 1 As shown, this utility model provides a DC input self-powered input undervoltage protection circuit, including a port +VDC. The port +VDC is connected to one end of resistor R4. The other end of resistor R4 is connected to one end of resistor R3 and pin 2 of switching transistor Q2. The other end of resistor R3 is connected to pin 1 of switching transistor Q2 and the cathode of Zener diode Z1. Pin 3 of switching transistor Q2 is connected to one end of capacitor C19, pin 8 of operational amplifier U5, and port VDD. The anode of Zener diode Z1 is connected to the other end of capacitor C19, pin 4 of operational amplifier U5, and port GND. Port GND is grounded. The port +VDC is connected to the DC circuit to be protected and is converted into a supply current through DC input. The switching transistor Q2 is a transistor, where pin 1 is the base, pin 2 is the collector, and pin 3 is the emitter. In this embodiment, the operational amplifier U5 is an LM2904DGKR.

[0029] Please see Figure 2 As shown, the port VDD is connected to one end of resistor R14. The other end of resistor R14 is connected to pin 3 of voltage regulator U6, pin 1 of voltage regulator U6, one end of capacitor C23, and port VREF. Pin 2 of voltage regulator U6 is connected to the other end of capacitor C23 and port GND. VDD serves as the power supply terminal, generating the standard voltage VREF. In this embodiment, voltage regulator U6 is a controllable precision voltage regulator TL431, where pin 1 is the reference stage, pin 2 is the anode, and pin 3 is the cathode.

[0030] Please see Figure 3 As shown, the +VDC port is connected to one end of resistor R15. The other end of resistor R15 is connected to one end of resistor R16 and one end of resistor R18. The other end of resistor R18 is connected to pin 2 of operational amplifier U5. Pin 3 of operational amplifier U5 is connected to one end of resistor R17 and one end of resistor R19. The other end of resistor R17 is connected to port VREF. The other end of resistor R19 is connected to pin 1 of operational amplifier U5 and the positive terminal of diode D2. The negative terminal of diode D2 is connected to one end of resistor R20. The other end of resistor R20 is connected to one end of resistor R26 and pin 1 of switching transistor Q4. Pin 2 of switching transistor Q4 is connected to the cathode of optocoupler OT1. The anode of optocoupler OT1 is connected to one end of resistor R1. The other end of resistor R1 is connected to port VDD. The other end of resistor R16 is connected to the other end of resistor R26, pin 3 of switching transistor Q4, the emitter of optocoupler OT1, and port GND. The collector of optocoupler OT1 is connected to the output terminal. The switching transistor Q4 is a bipolar transistor, with pin 1 being the base, pin 2 the collector, and pin 3 the emitter. The output terminal is connected to controller U2, which provides undervoltage protection for the DC circuit to be protected. Controller U2 is an OB2276, and its output terminal is connected to pin 4.

[0031] Specifically, it includes a DC power input sampling circuit, a reference voltage circuit, a comparator circuit, a power supply circuit, a first switching circuit, and a second switching circuit. The DC power input sampling circuit is connected to the negative input terminal of the comparator circuit, the output terminal of the reference voltage circuit is connected to the positive input terminal of the comparator circuit, the control terminal of the first switching circuit is connected to the output terminal of the comparator circuit, and the second switching circuit is connected between the voltage sampling pin of the main control chip and ground. The power supply circuit supplies power to the reference voltage circuit, the comparator circuit, and the first switching circuit.

[0032] The DC power input sampling circuit includes a first resistor (R15), a second resistor (R16), and a third resistor (R18); the reference voltage circuit includes a controllable precision voltage regulator, a fourth resistor (R14), a fifth resistor (R17), and a first capacitor (C23); the first end of the first resistor is connected to the DC power input terminal, the second end is connected to the first ends of the second and third resistors, the second end of the second resistor is grounded, and the second end of the third resistor is connected to the negative terminal of pin 2 of the operational amplifier; the first end of the fourth resistor is connected to the DC power input terminal, the second end is connected to the cathode of the controllable precision voltage regulator, the anode of the controllable precision voltage regulator and the first end of the first capacitor are grounded, the reference terminal of the controllable precision voltage regulator is connected to the second end of the first capacitor and the first end of the fifth resistor, and the second end of the fifth resistor is connected to the positive terminal of pin 3 of the operational amplifier.

[0033] The comparator circuit includes an operational amplifier, a diode, R19, a sixth resistor (R20), and a seventh resistor (R26). The first terminal of R19 is connected to the positive terminal of pin 3 of the operational amplifier. The output terminal of pin 1 of the amplifier is connected to the second terminal of R19 and the anode of the diode. The cathode of the diode is connected to the first terminal of the sixth resistor, and the second terminal is connected to the first terminal of the seventh resistor. The second terminal is grounded.

[0034] The power supply circuit includes an eighth resistor (R4), a ninth resistor (R3), a first NPN transistor (Q2), a Zener diode (Z1), a second capacitor (C19), and an operational amplifier. The first end of the eighth resistor is connected to the DC power input terminal, and the second end is connected to the first end of the ninth resistor and the collector of the first NPN transistor. The second end of the ninth resistor is connected to the base of the first NPN transistor and the cathode of the Zener diode. The emitter of the first NPN transistor and one end of the second capacitor are connected to the power input terminal of pin 8 of the operational amplifier. The anode of the Zener diode, the other end of the second capacitor, and pin 4 of the operational amplifier are grounded together.

[0035] The first switching circuit includes a tenth resistor (R1), a phototransistor (OT1), and a second NPN transistor (Q4). The first end of the tenth resistor is connected to the emitter of the first NPN transistor, and the second end is connected to the anode of the photodiode. The collector of the second NPN transistor is connected to the cathode of the photodiode. The base of the second NPN transistor is connected to the common terminal of the sixth and seventh resistors. The emitter of the second NPN transistor is grounded.

[0036] The second switching circuit includes a light-emitting diode (LED), which is connected between the voltage sampling pin of the main control chip and ground. Even when the main control chip lacks overvoltage protection, it can still effectively provide undervoltage protection for the input. It should be further noted that any other components used to achieve the above effects should fall within the inventive concept of this utility model and should be protected within its scope.

[0037] Working principle:

[0038] The DC power input sampling circuit connects resistors R15 and R16 in series. The first terminal of resistor R15 is connected to the DC input, and the second terminal passes through resistor R16. The sampling circuit detects the DC input voltage and generates a low voltage, which is then sampled from pin 2 of operational amplifier U5-A via resistor R18. Resistors R15 and R16 are 2KΩ, R16 is 2KΩ, and R18 is 1KΩ. The operational amplifier U5 is an LM2904DGKR.

[0039] The reference voltage circuit includes resistor R14, a controllable precision voltage regulator U6, capacitor C23, and resistor R17. The VDD voltage supplies power to the controllable precision voltage regulator U6 through resistor R14. After the controllable precision voltage regulator is working, it provides a reference voltage of 2.5V, which is sampled by pin 3 of operational amplifier U5-A through resistor R17. The resistance of resistor R14 is 10K, the resistance of R17 is 1K, and the capacitance of capacitor C23 is 100Pf.

[0040] The comparator circuit includes operational amplifier U5-A, resistor R19, diode D2, resistor R20, and resistor R26. Resistor R19 is connected to pins 3 and 1 of operational amplifier U5-A. After comparison, pin 1 outputs a high level, which conducts transistor Q4 through the voltage divider of diode D2 and resistors R20 and R26.

[0041] The power supply circuit includes resistors R4 and R3, an NPN transistor Q2, a Zener diode Z1, and a capacitor C19. The DC input voltage is connected to the collector of transistor Q2 through resistor R4, and to the base of transistor Q2 and the cathode of Zener diode Z1 through resistors R4 and R3. The anode is grounded. Transistor Q2 outputs a voltage through its emitter, which is stored in capacitor C19 to power operational amplifier U5-C and controllable precision voltage regulator U6. The resistance values ​​of resistors R4 and R3 are 4.7KΩ, the Zener diode Z1 is 20V, and the capacitance value of capacitor C19 is 2.2µF.

[0042] The first switching circuit includes a resistor R1, a phototransistor OT1-B, and an NPN transistor Q4. The VDD voltage is connected through the resistor R1 and the anode of the phototransistor OT1-B, and the cathode is connected to the collector of the transistor Q4. The emitter of the transistor Q4 is grounded. The operational amplifier U5-A outputs a high level to drive the base of the transistor, and the photodiode OT1-B is turned on. The resistance of the resistor R1 is 10K.

[0043] The second switching circuit includes a light-emitting diode OT1-A, which is connected between the voltage sampling pin of the main control chip U2 and ground. When the photodiode OT1-B is turned on, the light-emitting diode OT1-A is also turned on, and the main control chip (i.e., controller U2) is pulled to ground, thus playing a protective role.

[0044] The aforementioned DC input self-powered undervoltage protection circuit is implemented entirely in hardware, requiring fewer external circuit components, offering high accuracy, low cost, and high versatility. It can be connected to different models of main control chips, as long as a low-level pin on the main control chip triggers the protection. This self-powered input undervoltage protection can protect electronic products and prevent some accidents.

[0045] Although the embodiments of this utility model have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for this utility model. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, this utility model is not limited to the specific details and the illustrations shown and described herein.

Claims

1. A DC input self-powered input undervoltage protection circuit, characterized in that: The circuit includes a port +VDC, which is connected to one end of resistor R4. The other end of resistor R4 is connected to one end of resistor R3 and pin 2 of switching transistor Q2. The other end of resistor R3 is connected to pin 1 of switching transistor Q2 and the cathode of Zener diode Z1. Pin 3 of switching transistor Q2 is connected to one end of capacitor C19, pin 8 of operational amplifier U5, and port VDD. The anode of Zener diode Z1 is connected to the other end of capacitor C19, pin 4 of operational amplifier U5, and port GND. The port VDD is connected to one end of resistor R14, and the other end of resistor R14 is connected to pin 3 of voltage regulator U6, pin 1 of voltage regulator U6, one end of capacitor C23 and port VREF. Pin 2 of voltage regulator U6 is connected to the other end of capacitor C23 and port GND. The +VDC port is connected to one end of resistor R15. The other end of resistor R15 is connected to one end of resistor R16 and one end of resistor R18. The other end of resistor R18 is connected to pin 2 of operational amplifier U5. Pin 3 of operational amplifier U5 is connected to one end of resistor R17 and one end of resistor R19. The other end of resistor R17 is connected to port VREF. The other end of resistor R19 is connected to pin 1 of operational amplifier U5 and the positive terminal of diode D2. The negative terminal of diode D2 is connected to one end of resistor R20. The other end of resistor R20 is connected to one end of resistor R26 and pin 1 of switching transistor Q4. Pin 2 of switching transistor Q4 is connected to the cathode of optocoupler OT1. The anode of optocoupler OT1 is connected to one end of resistor R1. The other end of resistor R1 is connected to port VDD. The other end of resistor R16 is connected to the other end of resistor R26, pin 3 of switching transistor Q4, the emitter of optocoupler OT1, and port GND. The collector of optocoupler OT1 is connected to the output terminal.

2. The DC input self-powered input undervoltage protection circuit according to claim 1, characterized in that: The switching transistor Q2 is a bipolar transistor, wherein pin 1 is the base, pin 2 is the collector, and pin 3 is the emitter.

3. The DC input self-powered input undervoltage protection circuit according to claim 1, characterized in that: The switching transistor Q4 is a bipolar transistor, wherein pin 1 is the base, pin 2 is the collector, and pin 3 is the emitter.

4. The DC input self-powered input undervoltage protection circuit according to claim 1, characterized in that: The +VDC port is connected to the DC circuit to be protected, and the output terminal is connected to the controller U2. The controller U2 is used for undervoltage protection of the DC circuit to be protected.

5. A DC input self-powered input undervoltage protection circuit according to claim 4, characterized in that: The controller U2 is OB2276, and the output terminal is connected to pin 4 of the controller U2.

6. The DC input self-powered input undervoltage protection circuit according to claim 1, characterized in that: The operational amplifier U5 is model LM2904DGKR.

7. The DC input self-powered input undervoltage protection circuit according to claim 1, characterized in that: The voltage regulator U6 is a controllable precision voltage regulator TL431, wherein pin 1 is the reference stage, pin 2 is the anode, and pin 3 is the cathode.

8. The DC input self-powered input undervoltage protection circuit according to claim 1, characterized in that: The port is grounded (GND).

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