CN116937496A - Passive input protection circuit - Google Patents

Passive input protection circuit Download PDF

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Publication number
CN116937496A
CN116937496A CN202310892787.6A CN202310892787A CN116937496A CN 116937496 A CN116937496 A CN 116937496A CN 202310892787 A CN202310892787 A CN 202310892787A CN 116937496 A CN116937496 A CN 116937496A
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CN
China
Prior art keywords
resistor
power supply
return difference
module
input
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Pending
Application number
CN202310892787.6A
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Chinese (zh)
Inventor
成伟宏
何勇志
熊起锐
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Shenzhen Huayuan Power Technology Co ltd
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Shenzhen Huayuan Power Technology Co ltd
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Priority to CN202310892787.6A priority Critical patent/CN116937496A/en
Publication of CN116937496A publication Critical patent/CN116937496A/en
Pending legal-status Critical Current

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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
    • H02H3/20—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to excess voltage
    • H02H3/202—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to excess voltage for DC systems
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
    • H02H3/24—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to undervoltage or no-voltage
    • H02H3/243—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to undervoltage or no-voltage for DC systems
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of AC power input into DC power output; Conversion of DC power input into AC power output
    • H02M7/02—Conversion of AC power input into DC power output without possibility of reversal
    • H02M7/04—Conversion of AC power input into DC power output without possibility of reversal by static converters
    • H02M7/06—Conversion of AC power input into DC power output without possibility of reversal by static converters using discharge tubes without control electrode or semiconductor devices without control electrode

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Protection Of Static Devices (AREA)

Abstract

The passive input protection circuit provided by the invention comprises the rectification circuit, the first return difference module, the overvoltage protection module, the second return difference module, the undervoltage protection module and the switching power supply control chip, so that the passive input overvoltage and undervoltage protection circuit is formed, auxiliary power supply is not needed, the pin function of the power supply management chip is fully utilized to be combined with the overvoltage protection module and the undervoltage protection module to play the role of overvoltage and undervoltage protection, the realization cost is low, the overvoltage protection module and the undervoltage protection module cannot be influenced by slight disturbance of voltage in the working process by arranging the first return difference module and the second return difference module, the circuit anti-interference capability is improved, the input overvoltage and undervoltage protection circuit with return difference is formed under the condition that no additional auxiliary power supply is used for supplying power, and the anti-interference capability of the switching power supply is improved while the switching power supply is improved.

Description

Passive input protection circuit
Technical Field
The invention relates to the technical field of switching power supplies, in particular to a passive input protection circuit.
Background
Switching power supplies are important devices for daily electricity, and are often used for converting commercial power into the type of power required by electric equipment. Because of the instability of the power grid, switching power supplies are typically provided with overvoltage and undervoltage protection circuits. The publication number is as follows in the prior art: the CN209787038U discloses a passive overvoltage and undervoltage protection circuit for a switching power supply, which can provide accurate and reliable overvoltage and undervoltage protection functions under the condition of no independent power supply, and has the advantages of low cost, convenient adjustment and flexible application.
However, the sampling point in the circuit is located behind the rectifier bridge, which causes the protection circuit to be commonly grounded with the primary of the DC-DC (direct current-direct current) converter, and the protection may be delayed and damage to the switching tube is easy to cause. Meanwhile, no return difference is arranged in the circuit, and when the input voltage has tiny fluctuation near the protection point, the problem of repeated switching on and switching off exists. Therefore, it is difficult to perform effective over-voltage and under-voltage protection in practical applications.
Disclosure of Invention
The technical problems to be solved by the invention are as follows: the passive input protection circuit improves the anti-interference capability of the switching power supply while improving the protection of the switching power supply.
In order to solve the technical problems, the invention adopts the following technical scheme:
a passive input protection circuit comprises a rectification circuit, a first return difference module, an overvoltage protection module, a second return difference module, an undervoltage protection module and a switching power supply control chip; the output end of the rectifying circuit is respectively connected with the power input end of the first return difference module and the power input end of the second return difference module; the input end of the rectifying circuit is used for being connected with an external power supply; the sampling end of the first return difference module is connected with the input end of the overvoltage protection module, and the control input end of the first return difference module is connected with the output end of the switching power supply control chip; the output end of the overvoltage protection module is connected with the input end of the switching power supply control chip; the sampling end of the second return difference module is connected with the input end of the under-voltage protection module, and the control input end of the second return difference module is connected with the output end of the switching power supply control chip; and the output end of the undervoltage protection module is connected with the input end of the switching power supply control chip.
The invention has the beneficial effects that: the passive input overvoltage and undervoltage protection circuit is formed by the rectifier circuit, the first return difference module, the overvoltage protection module, the second return difference module, the undervoltage protection module and the switching power supply control chip, auxiliary power supply is not needed, the pin function of the power supply management chip is fully utilized to be combined with the overvoltage protection module and the undervoltage protection module to play the role of overvoltage and undervoltage protection, the realization cost is low, the influence of slight disturbance of voltage can not be received by the overvoltage protection module and the undervoltage protection module in the working process through the arrangement of the first return difference module and the second return difference module, the circuit interference resistance is high, the input overvoltage and undervoltage protection circuit with return difference is formed under the condition that no additional auxiliary power supply is provided, and the anti-interference capability of the switching power supply is improved when the switching power supply is protected.
Drawings
FIG. 1 is a schematic diagram of a passive input protection circuit according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of a circuit connection of a passive input protection circuit according to an embodiment of the present invention;
description of the reference numerals:
1. a rectifying circuit; 2. a first return difference module; 3. an overvoltage protection module; 4. a second return difference module; 5. an undervoltage protection module; 6. a switching power supply control chip;
r1, a first resistor; r2, a second resistor; r3, a third resistor; r4, a fourth resistor; r5, a fifth resistor; r15, sixth resistance; r14, seventh resistance; r11, eighth resistor; r13, ninth resistor;
c1, a first capacitor; c2, a second capacitor; c5, a third capacitor;
d3, a first diode; d6, a second diode; d9, a third diode;
q1, a first transistor; q2, a first MOS tube; q4, a second MOS tube; q5, the first triode.
Detailed Description
In order to describe the technical contents, the achieved objects and effects of the present invention in detail, the following description will be made with reference to the embodiments in conjunction with the accompanying drawings.
Referring to fig. 1, a passive input protection circuit includes a rectifying circuit, a first return difference module, an overvoltage protection module, a second return difference module, an undervoltage protection module, and a switching power supply control chip; the output end of the rectifying circuit is respectively connected with the power input end of the first return difference module and the power input end of the second return difference module; the input end of the rectifying circuit is used for being connected with an external power supply; the sampling end of the first return difference module is connected with the input end of the overvoltage protection module, and the control input end of the first return difference module is connected with the output end of the switching power supply control chip; the output end of the overvoltage protection module is connected with the input end of the switching power supply control chip; the sampling end of the second return difference module is connected with the input end of the under-voltage protection module, and the control input end of the second return difference module is connected with the output end of the switching power supply control chip; and the output end of the undervoltage protection module is connected with the input end of the switching power supply control chip.
From the above description, the beneficial effects of the invention are as follows: the passive input overvoltage and undervoltage protection circuit is formed by the rectifier circuit, the first return difference module, the overvoltage protection module, the second return difference module, the undervoltage protection module and the switching power supply control chip, auxiliary power supply is not needed, the pin function of the power supply management chip is fully utilized to be combined with the overvoltage protection module and the undervoltage protection module to play the role of overvoltage and undervoltage protection, the realization cost is low, the influence of slight disturbance of voltage can not be received by the overvoltage protection module and the undervoltage protection module in the working process through the arrangement of the first return difference module and the second return difference module, the circuit interference resistance is high, the input overvoltage and undervoltage protection circuit with return difference is formed under the condition that no additional auxiliary power supply is provided, and the anti-interference capability of the switching power supply is improved when the switching power supply is protected.
Further, the first return difference module comprises a first resistor, a second resistor, a third resistor and a first transistor; one end of the first resistor is connected with the output end of the rectifying circuit, and the other end of the first resistor is respectively connected with one end of the second resistor, one end of the third resistor and the input end of the overvoltage protection module; the control input end of the first transistor is connected with the output end of the switching power supply control chip, the power supply output end of the first transistor is connected with the other end of the second resistor, and the power supply input end of the first transistor is connected with the other end of the third resistor.
As can be seen from the above description, the return difference module is formed by using discrete components such as a resistor and a transistor, and the on or off state of the first transistor is controlled by matching the first transistor with the output end of the switching power supply control chip, so that when the first transistor is turned on, the second resistor is connected in parallel with the third resistor to pull down the sampling voltage, and when the first transistor is turned on or off, the second resistor is used for separately dividing the voltage to pull up the sampling voltage, thereby realizing the return difference control, and compared with the integrated components such as a comparator, the circuit is easier to debug.
Further, the first return difference module further comprises a first capacitor; one end of the first capacitor is connected with one end of the second resistor, and the other end of the first capacitor is connected with the other end of the second resistor and the power output end of the first transistor respectively.
As can be seen from the above description, by setting the first capacitor and setting the first capacitor at the front end of the sampling end in the first return difference module, filtering of the sampling voltage is achieved through the first capacitor, and protection accuracy of the circuit is improved.
Further, the second return difference module has the same circuit structure as the first return difference module.
As can be seen from the above description, by using the same circuit for the second return difference module and the first return difference module, the high-voltage return difference and the low-voltage return difference can be formed with the overvoltage protection module and the low-voltage return difference respectively by changing the type of the transistor and the parameters of the discrete device, so as to realize the input overvoltage and undervoltage protection circuit with the return difference.
Further, the first return difference module further comprises a fourth resistor and a second capacitor; one end of the fourth resistor is connected with the output end of the switching power supply control chip, and the other end of the fourth resistor is respectively connected with one end of the second capacitor and the control input end of the first transistor; the other end of the second capacitor is connected with the power output end of the first transistor.
As can be seen from the above description, the fourth resistor is provided to form the current limiting resistor, and the second capacitor is provided to filter out high-frequency interference, so as to improve the control effect of the switching power supply control chip on the first transistor, thereby improving the control effects of the overvoltage return difference and the undervoltage return difference.
Further, the overvoltage protection module comprises a first diode and a first MOS tube; the negative electrode of the first diode is connected with the sampling end of the first return difference module, and the positive electrode of the first diode is connected with the grid electrode of the first MOS tube; the drain electrode of the first MOS tube is connected with the input end of the switching power supply control chip; and the source electrode of the first MOS tube is grounded.
According to the above description, the overvoltage protection module is formed by the first diode and the first MOS tube, so that after the input voltage breaks down the first diode, the first MOS tube is controlled to be conducted, the first MOS tube pulls the input end of the switching power supply control chip to a low level and cannot be started, and overvoltage protection is further achieved.
Further, the overvoltage protection module further comprises a fifth resistor; one end of the fifth resistor is connected with the grid electrode of the first MOS tube; the other end of the fifth resistor is connected with the source electrode of the first MOS tube.
As can be seen from the above description, by setting the fifth resistor, the fifth resistor is set between the gate and the source of the first MOS transistor, so as to ensure that the gate potential of the first MOS transistor is low, and prevent the first MOS transistor from being misled.
Further, the undervoltage protection module comprises a second diode, a second MOS tube, a sixth resistor, a seventh resistor and a first triode; the negative electrode of the second diode is respectively connected with the sampling end of the second return difference module and one end of the sixth resistor, and the positive electrode of the second diode is connected with the grid electrode of the second MOS tube; the drain electrode of the second MOS tube is respectively connected with the other end of the sixth resistor and one end of the seventh resistor, and the source electrode of the second MOS tube is grounded; the base of the first triode is connected with the other end of the seventh resistor, the collector of the first triode is connected with the input end of the switching power supply control chip, and the emitter of the first triode is grounded.
According to the above description, the second diode, the second MOS tube, the sixth resistor, the seventh resistor and the first triode are arranged to form the overvoltage protection module, so that when the input voltage is reduced to a value that the second diode cannot be broken down, the second MOS tube is controlled to be cut off, the base potential of the first triode is enabled to be high through the actions of the sixth resistor and the seventh resistor, the input end of the switching power supply control chip is pulled to be low level to be unable to be started after the first triode is conducted, and the undervoltage protection is further achieved.
Further, the undervoltage protection module further comprises an eighth resistor and a third diode; one end of the eighth resistor is connected with the anode of the second diode and the cathode of the third diode respectively, and the other end of the eighth resistor is connected with the anode of the third diode and the source electrode of the second MOS tube respectively.
As can be seen from the above description, by providing the eighth resistor to prevent the second MOS transistor from being turned on by mistake, and by providing the third diode as a protection clamp diode, breakdown of the gate and the source of the MOS transistor when the input voltage is too high can be prevented from causing damage to the MOS transistor.
Further, the undervoltage protection module further comprises a ninth resistor and a third capacitor; one end of the ninth resistor is connected with one end of the third capacitor and the base electrode of the first triode respectively, and the other end of the ninth resistor is connected with the other end of the third capacitor and the emitter electrode of the first triode respectively.
As is apparent from the above description, by arranging the ninth resistor and the third capacitor in parallel between the base and the emitter of the first transistor, a potential difference is formed between the base and the emitter of the first transistor, and the control effect on the first transistor is improved.
The passive input overvoltage and undervoltage protection circuit can be suitable for application scenes of various switching power supplies, achieves passive input overvoltage and undervoltage protection with return difference, improves the protection and anti-interference capability of the switching power supplies, and is described by specific embodiments below:
example 1
Referring to fig. 1, a passive input protection circuit includes a rectifying circuit 1, a first return difference module 2, an overvoltage protection module 3, a second return difference module 4, an undervoltage protection module 5, and a switching power supply control chip 6; the output end of the rectifying circuit 1 is respectively connected with the power input end of the first return difference module 2 and the power input end of the second return difference module 4; the input end of the rectifying circuit 1 is used for being connected with an external power supply; the sampling end of the first return difference module 2 is connected with the input end of the overvoltage protection module 3, and the control input end of the first return difference module 2 is connected with the output end of the switching power supply control chip 6; the output end of the overvoltage protection module 3 is connected with the input end of the switching power supply control chip 6; the sampling end of the second return difference module 4 is connected with the input end of the under-voltage protection module 5, and the control input end of the second return difference module 4 is connected with the output end of the switching power supply control chip 6; the output end of the undervoltage protection module 5 is connected with the input end of the switching power supply control chip 6, and specifically:
referring to fig. 2, L, N is a single-phase ac power source, including a mains supply; after passing through the rectifying circuit 1 composed of the diode D1 and the diode D2, the external power supply is input into the first return difference module 2 and the second return difference module 4; the output end of the switch power supply control chip 6 is VREF and is a reference voltage pin for controlling the switch power supply control chip 6; the input end of the switch power supply control chip 6 comprises a COMP pin and a VCC pin, wherein COMP is a compensation pin for controlling the feedback pin of the switch power supply control chip 6, VCC is a power supply pin for controlling the switch power supply control chip 6, and GND is the ground of the switch power supply;
the first return difference module 2 comprises a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, a first transistor Q1, a first capacitor C1 and a second capacitor C2; wherein, the first transistor Q1 may be a MOS transistor or a triode; as shown in fig. 2, the first transistor Q1 is an NPN transistor, and is turned off when the base potential thereof is not at a high level; one end of the first resistor R1 is connected with the output end of the rectifying circuit 1, namely, the output ends of the diode D1 and the diode D2; the other end of the first resistor R1 is respectively connected with one end of the second resistor R2, one end of the third resistor R3, one end of the first capacitor C1 and the negative electrode (the sampling point of the input overvoltage protection circuit) of the first diode D3; the base electrode of the first transistor Q1 is connected to the other end of the fourth resistor R4 and one end of the second capacitor C2, and one end of the fourth resistor R4 is connected to the output end (VREF) of the switching power supply control chip 6; the emitter of the first transistor Q1 is connected to the other end of the second resistor R2, the other end of the second capacitor C2, and the other end of the first capacitor C1, respectively; the collector of the first transistor Q1 is connected to the other end of the third resistor R3.
In an alternative embodiment, the second return difference module 4 has the same circuit structure as the first return difference module 2; as shown in fig. 2, the second return difference module 4 has the same circuit structure as the circuit of the first return difference module 2, wherein the transistor Q3 in the second return difference module 4 is a PNP-type triode, and when the base potential is low level, the triode is turned on;
the overvoltage protection module 3 comprises a first diode D3, a first MOS transistor Q2 and a fifth resistor R5, wherein the first diode D3 is a zener diode; the negative electrode of the first diode D3 is connected with the sampling end of the first return difference module 2 (i.e., the end of the third resistor R3 far away from the first transistor Q1), and the positive electrode of the first diode D3 is connected with the gate of the first MOS transistor Q2; the drain electrode of the first MOS transistor Q2 is connected with the input end (namely, a COMP pin and a VCC pin) of the switching power supply control chip 6; the source electrode of the first MOS tube Q2 is grounded; one end of the fifth resistor R5 is connected with the grid electrode of the first MOS tube Q2; the other end of the fifth resistor R5 is connected with the source electrode of the first MOS tube Q2.
The under-voltage protection module 5 comprises a second diode D6, a second MOS transistor Q4, a sixth resistor R15, a seventh resistor R14, a first triode Q5, an eighth resistor R11, a third diode D9, a ninth resistor R13 and a third capacitor C5; the negative electrode of the second diode D6 is respectively connected with the sampling end of the second return difference module 4 and one end of the sixth resistor R15, and the positive electrode of the second diode D6 is connected with the grid electrode of the second MOS tube Q4; the drain electrode of the second MOS tube Q4 is respectively connected with the other end of the sixth resistor R15 and one end of the seventh resistor R14, and the source electrode of the second MOS tube Q4 is grounded; the base electrode of the first triode Q5 is connected with the other end of the seventh resistor R14, the collector electrode of the first triode Q5 is connected with the input end of the switching power supply control chip 6, and the emitter electrode of the first triode Q5 is grounded; one end of the eighth resistor R11 is connected to the anode of the second diode D6 and the cathode of the third diode D9, and the other end of the eighth resistor R11 is connected to the anode of the third diode D9 and the source of the second MOS transistor Q4; one end of the ninth resistor R13 is connected to one end of the third capacitor C5 and the base of the first triode Q5, and the other end of the ninth resistor R13 is connected to the other end of the third capacitor C5 and the emitter of the first triode Q5.
The working principle of the passive input protection circuit is as follows:
when the switching power supply enters a steady state:
at the moment, the power chip works normally to generate a reference voltage VREF; the first transistor Q1 in the first return difference module 2 is conducted, and the second resistor R2 is connected with the third resistor R3 in parallel; the input sine alternating current is divided by the first resistor R1, the second resistor R2 and the third resistor R3, and a direct current voltage with low ripple is generated and output to the next stage; when the input voltage is in the normal input voltage range, the first diode D3 is not broken down, and at this time, the gate potential of the first MOS transistor Q2 is low, that is, the first MOS transistor Q2 is turned off, the COMP pin and the VCC pin of the switching power supply control chip 6 are not affected, and the overvoltage protection module 3 maintains a stable state.
Meanwhile, when the switching power supply enters a steady state, the triode in the second return difference module 4 is cut off; the voltage of the sampling point of the input undervoltage protection is divided by a resistor R8 and a resistor R7, and after filtering through a large capacitor C3, the DC voltage with low ripple is generated and output to the next stage; when the input voltage is in the normal input voltage range, the second diode D6 is broken down, the gate potential of the second MOS transistor Q4 is high, that is, the second MOS transistor Q4 is turned on, the voltage at the connection point of the sixth resistor R15 and the seventh resistor R14 is pulled down to a low level, so that the base voltage of the first triode Q5 is low, that is, the first triode Q5 is turned off, the COMP pin and the VCC pin of the switching power supply control chip 6 are not affected, and the under-voltage protection module 5 maintains a stable state.
Overvoltage protection:
when the input voltage gradually rises until the first diode D3 breaks down, the gate potential of the first MOS transistor Q2 is high, that is, the first MOS transistor Q2 is turned on, so that the COMP pin potential of the switching power supply control chip 6 is pulled to a low level, and therefore the duty ratio of the switching power supply control chip 6 cannot be expanded, and the output of the post-stage circuit is terminated; the VCC pin of the switch power supply control chip 6 is limited by a resistor R6 to pull down the voltage, so that the starting voltage of the chip cannot be reached, and the switch power supply control chip 6 is prevented from being damaged due to repeated restarting.
After the protection is finished, the switching power supply control chip 6 is powered down and cannot be started; at this time, the VREF pin of the switching power supply control chip 6 has no output, i.e., the base level potential of the first transistor Q1 is not high level, and the first transistor Q1 is turned off; the voltage dividing circuit is converted from the parallel connection of the second resistor R2 and the third resistor R3 to the independent voltage division of the second resistor R2; therefore, at this time, the voltage sampled by the sampling point increases under the same input voltage, and the first diode D3 is deepened by the degree of breakdown. Therefore, if the normal operation needs to be restored, the input voltage needs to be adjusted to be lower than the voltage during protection, namely, the return difference of the input overvoltage protection circuit is realized. Meanwhile, parameters of components can be adjusted according to return difference requirements, so that the return difference voltage is controlled to be 10-20V.
When the input voltage is regulated down to a set recovery point, the first diode D3 is cut off, the first MOS transistor Q2 is cut off, the VCC pin of the switching power supply control chip 6 is not affected, the built voltage starts to be started normally, and the output voltage is recovered to be normal; therefore, the overvoltage protection circuit is an input overvoltage protection circuit which can be recovered without re-electrifying; meanwhile, the VCC pin and the COMP pin of the switching power supply control chip 6 are further provided with a diode D4 and a diode D5, which are protection diodes for preventing the voltage of the VCC pin and the COMP pin from flowing backward.
Under-voltage protection:
when the input voltage is gradually reduced until the voltage of the sampling point cannot break down the zener diode D6, the gate potential of the second MOS transistor Q4 is low, and the second MOS transistor Q4 is cut off; because one end of the sixth resistor R15 is connected to the input under-voltage sampling point and the second MOS transistor Q4 is turned off, the base potential of the first triode Q5 is high, namely the first triode Q5 is turned on; at this time, the COMP pin potential of the switching power supply control chip 6 is pulled to a low level, the duty ratio of the switching power supply control chip 6 cannot be expanded, and the output of the post-stage circuit is terminated. Meanwhile, the VCC pin of the switch power supply control chip 6 is limited by a resistor R12 to pull down the voltage, and the starting voltage which cannot be reached is prevented from being damaged due to repeated restarting of the switch power supply control chip 6.
After the protection is finished, the switching power supply control chip 6 is powered down and cannot be started; at this time, the VREF pin of the switching power supply control chip 6 does not output, and the base potential of the triode Q3 is low level, namely the triode Q3 is conducted; the voltage division of the dividing circuit is converted into parallel voltage division of the resistor R7 and the resistor R9 by the resistor R7; thus, at the same input voltage, the voltage sampled by the sampling point decreases, and the second diode D6 is more separated from the breakdown voltage point by a voltage difference. Therefore, if the normal operation needs to be restored, the input voltage needs to be adjusted to be higher than the voltage during protection, namely the return difference of the input under-voltage protection circuit is realized. Meanwhile, parameters of components can be adjusted according to return difference requirements, so that the return difference voltage is controlled to be 10-20V.
When the input voltage is adjusted to a set recovery point, the second diode D6 is turned on, the second MOS transistor Q4 is turned on, the voltage at the connection point of the sixth resistor R15 and the seventh resistor R14 is pulled down, that is, the base-level voltage of the first triode Q5 is pulled down, the first triode Q5 is turned off, the VCC pin of the switching power supply control chip 6 is not affected, the set-up voltage starts to be started normally, and the power supply output is recovered to be normal. Therefore, the under-voltage protection circuit is an input under-voltage protection circuit which can be recovered without being electrified again. Meanwhile, the VCC pin and the COMP pin of the switching power supply control chip 6 are further provided with a diode D7 and a diode D8, which are protection diodes for preventing the VCC pin and the COMP pin from voltage backflow.
In summary, the passive input protection circuit provided by the invention comprises the rectifying circuit, the first return difference module, the overvoltage protection module, the second return difference module, the undervoltage protection module and the switching power supply control chip to form the passive input overvoltage and undervoltage protection circuit, auxiliary power supply is not needed, the input overvoltage and undervoltage protection circuit is combined with each pin of the switching power supply control chip, the realization cost is low, the overvoltage protection module and the undervoltage protection module are not influenced by slight disturbance of voltage in the working process by arranging the first return difference module and the second return difference module, the circuit interference resistance is high, the input overvoltage and undervoltage protection circuit with return difference is formed under the condition that no additional auxiliary power supply is provided, and the switching power supply protection is improved, and meanwhile, the interference resistance of the switching power supply is improved; meanwhile, a circuit module is formed by adopting a discrete device mode, and when the demand is changed, parameters and functions are easy to debug.
The foregoing description is only illustrative of the present invention and is not intended to limit the scope of the invention, and all equivalent changes made by the specification and drawings of the present invention, or direct or indirect application in the relevant art, are included in the scope of the present invention.

Claims (10)

1. The passive input protection circuit is characterized by comprising a rectification circuit, a first return difference module, an overvoltage protection module, a second return difference module, an undervoltage protection module and a switching power supply control chip;
the output end of the rectifying circuit is respectively connected with the power input end of the first return difference module and the power input end of the second return difference module; the input end of the rectifying circuit is used for being connected with an external power supply;
the sampling end of the first return difference module is connected with the input end of the overvoltage protection module, and the control input end of the first return difference module is connected with the output end of the switching power supply control chip; the output end of the overvoltage protection module is connected with the input end of the switching power supply control chip;
the sampling end of the second return difference module is connected with the input end of the under-voltage protection module, and the control input end of the second return difference module is connected with the output end of the switching power supply control chip; and the output end of the undervoltage protection module is connected with the input end of the switching power supply control chip.
2. The passive input protection circuit of claim 1, wherein the first return difference module comprises a first resistor, a second resistor, a third resistor, and a first transistor;
one end of the first resistor is connected with the output end of the rectifying circuit, and the other end of the first resistor is respectively connected with one end of the second resistor, one end of the third resistor and the input end of the overvoltage protection module;
the control input end of the first transistor is connected with the output end of the switching power supply control chip, the power supply output end of the first transistor is connected with the other end of the second resistor, and the power supply input end of the first transistor is connected with the other end of the third resistor.
3. The passive input protection circuit of claim 2, wherein the first return difference module further comprises a first capacitor;
one end of the first capacitor is connected with one end of the second resistor, and the other end of the first capacitor is connected with the other end of the second resistor and the power output end of the first transistor respectively.
4. A passive input protection circuit as claimed in any one of claims 1, 2 or 3, wherein the second return difference module is of the same circuit configuration as the first return difference module.
5. A passive input protection circuit as claimed in claim 2 or 3, wherein said first return difference module further comprises a fourth resistor and a second capacitor;
one end of the fourth resistor is connected with the output end of the switching power supply control chip, and the other end of the fourth resistor is respectively connected with one end of the second capacitor and the control input end of the first transistor;
the other end of the second capacitor is connected with the power output end of the first transistor.
6. The passive input protection circuit of claim 1, wherein the overvoltage protection module comprises a first diode and a first MOS transistor;
the negative electrode of the first diode is connected with the sampling end of the first return difference module, and the positive electrode of the first diode is connected with the grid electrode of the first MOS tube;
the drain electrode of the first MOS tube is connected with the input end of the switching power supply control chip;
and the source electrode of the first MOS tube is grounded.
7. A passive input protection circuit as defined in claim 6, wherein the overvoltage protection module further comprises a fifth resistor;
one end of the fifth resistor is connected with the grid electrode of the first MOS tube;
the other end of the fifth resistor is connected with the source electrode of the first MOS tube.
8. The passive input protection circuit of claim 1, wherein the undervoltage protection module comprises a second diode, a second MOS transistor, a sixth resistor, a seventh resistor, and a first triode;
the negative electrode of the second diode is respectively connected with the sampling end of the second return difference module and one end of the sixth resistor, and the positive electrode of the second diode is connected with the grid electrode of the second MOS tube;
the drain electrode of the second MOS tube is respectively connected with the other end of the sixth resistor and one end of the seventh resistor, and the source electrode of the second MOS tube is grounded;
the base of the first triode is connected with the other end of the seventh resistor, the collector of the first triode is connected with the input end of the switching power supply control chip, and the emitter of the first triode is grounded.
9. The passive input protection circuit of claim 8, wherein the undervoltage protection module further comprises an eighth resistor and a third diode;
one end of the eighth resistor is connected with the anode of the second diode and the cathode of the third diode respectively, and the other end of the eighth resistor is connected with the anode of the third diode and the source electrode of the second MOS tube respectively.
10. The passive input protection circuit of claim 8, wherein the undervoltage protection module further comprises a ninth resistor and a third capacitor;
one end of the ninth resistor is connected with one end of the third capacitor and the base electrode of the first triode respectively, and the other end of the ninth resistor is connected with the other end of the third capacitor and the emitter electrode of the first triode respectively.
CN202310892787.6A 2023-07-20 2023-07-20 Passive input protection circuit Pending CN116937496A (en)

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Application Number Priority Date Filing Date Title
CN202310892787.6A CN116937496A (en) 2023-07-20 2023-07-20 Passive input protection circuit

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN202310892787.6A CN116937496A (en) 2023-07-20 2023-07-20 Passive input protection circuit

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CN116937496A true CN116937496A (en) 2023-10-24

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN119070617A (en) * 2024-11-06 2024-12-03 成都华普电器有限公司 A switching power supply with power supply interference resistance

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN119070617A (en) * 2024-11-06 2024-12-03 成都华普电器有限公司 A switching power supply with power supply interference resistance

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