Direct-current power supply protection circuit

Abstract

The invention discloses a direct-current power supply protection circuit, and the circuit comprises an anti-reverse connection backward flow unit which is used for controlling a reverse connection response switch to disconnect a power supply loop from a direct-current power supply to a load when the positive electrode and the negative electrode of the power supply are reversely connected, and controlling a backward flow response switch to conduct a discharge loop between the load and a grounding end when the direct-current power supply is instantaneously powered down; the power-on overcurrent protection delay unit is used for responding to the power-on of the direct-current power supply and enabling the protection function of the overcurrent and overvoltage protection unit after delaying a set time; and the overcurrent and overvoltage protection unit is used for switching on the power supply loop in response to the power-on of the direct-current power supply, and controlling the protection execution switch to switch off the power supply loop through the protection driving circuit in response to the fact that the output voltage or the output current of the direct-current power supply exceeds a preset safety value in an enabling state. The direct-current power supply protection circuit has the functions of reverse connection prevention, current backflow prevention and overvoltage and overcurrent protection at the same time, and can reduce the power consumption of the circuit while improving the safety of the circuit.

Description

Technical Field

[0001] The present invention relates to the technical field of power supply protection, and in particular to a direct current power supply protection circuit. Background Art

[0002] With the widespread application of DC power supplies in aerospace power supplies, new energy vehicles, medical electronic equipment, industrial control systems, and other fields, circuit protection technology faces severe challenges. In practical applications, there are potential fault hazards such as incorrect (reverse) power polarity connection, transient overvoltage shocks, and abnormal load overcurrent. Existing protection solutions often use discrete devices (such as diodes and fuses) or circuits to implement a single protection function. Furthermore, some traditional solutions, such as using diodes for reverse polarity protection, produce high voltage drops and power consumption issues, while using fuses for overcurrent protection is irreversible, seriously affecting the reliability of continuous operation of the equipment. For example:

[0003] Patent CN222915684U discloses a protection circuit that receives a supply voltage from an external power source by providing an anti-reverse polarity circuit, and outputs the supply voltage to a boost circuit, which ultimately outputs it to an external device. This patented protection circuit only has an anti-reverse polarity function, and in the design of the anti-reverse polarity circuit, the diode and the body diode in the MOS tube function identically, resulting in design redundancy. Whether Q1 tube can function properly depends on the output of the subsequent boost chip U1. Abnormal output from U1 may cause circuit problems.

[0004] Patent CN215120128U discloses a reverse polarity overvoltage protection circuit, including a reverse polarity protection circuit and an overvoltage cutoff protection circuit, for implementing reverse polarity protection and overvoltage protection for the load. The reverse polarity current protection scheme of this patent does not consider the current backflow problem caused by inductive loads. The overvoltage protection part can achieve shutdown protection when the voltage is too high, but does not have the protection function for excessive current.

[0005] Patent CN222381338U discloses a reverse polarity overvoltage protection circuit, including a reverse polarity protection circuit, an overcurrent limiting circuit, an overvoltage protection circuit, and an operating indicator light circuit. This patent's reverse polarity protection also fails to account for current backflow. The overcurrent limiting circuit connects transistors in series in the main circuit, resulting in high drive power consumption, a high saturation voltage drop, and significant conduction losses. Summary of the Invention

[0006] The purpose of the present invention is to provide a DC power supply protection circuit, which has the functions of preventing reverse connection, current backflow, and overvoltage and overcurrent protection, thereby improving circuit safety while having lower power consumption.

[0007] The technical solution adopted by the present invention is: a DC power supply protection circuit, comprising a reverse connection protection unit, a power-on overcurrent protection delay unit, and an overcurrent and overvoltage protection unit, which are sequentially arranged on the power supply circuit between the DC power supply output terminal and the load;

[0008] The reverse connection and backflow prevention unit includes a reverse connection response switch and a backflow response switch. The reverse connection and backflow prevention unit is used to: control the reverse connection response switch to disconnect the power supply circuit of the DC power supply to the load when the positive and negative poles of the power supply are reversed, and control the backflow response switch to connect the discharge circuit between the load and the ground terminal when the DC power supply is instantly powered off;

[0009] The power-on overcurrent protection delay unit is used to enable the protection function of the overcurrent and overvoltage protection unit after a set delay time in response to the DC power supply being powered on;

[0010] The overcurrent and overvoltage protection unit includes a protection drive circuit and a protection execution switch connected to the power supply circuit; the overcurrent and overvoltage protection unit is used to: turn on the power supply circuit in response to the DC power supply being powered on; in the enabled state, in response to the DC power supply output voltage or output current exceeding a preset safety value, control the protection execution switch through the protection drive circuit to disconnect the power supply circuit.

[0011] Optionally, the power-on overcurrent protection delay unit is provided with a reset switch; the power-on overcurrent protection delay unit is also used to, after the DC power supply is powered on, when the protection execution switch is in the disconnected state, in response to the reset switch being pressed and released, control the protection execution switch through the protection drive circuit to turn on the power supply circuit.

[0012] Optionally, in the reverse connection and backflow prevention unit, the reverse connection response switch is a PMOS tube Q2 whose source and drain are connected to the positive line of the power input terminal, and the gate of Q2 is connected to the ground terminal via a resistor;

[0013] The backflow response switch is a PNP transistor Q3 whose emitter and collector are connected between the source of Q2 and the ground terminal, and the base of Q3 is connected to the ground terminal via a resistor;

[0014] The anti-reverse connection and backflow prevention unit further includes a second reverse connection response switch for cooperating with Q2 to control Q3 to be disconnected when the DC power supply is not reverse connected.

[0015] In one embodiment, the second reverse connection response switch is a PNP transistor Q1 whose emitter and collector are connected between the positive electrode of the power input terminal and the ground terminal, and Q1 is connected to the base of Q3.

[0016] Optionally, the power-on overcurrent protection delay unit includes a charging capacitor C1 and a resistor R3 connected in series between the positive and negative lines of the output end of the anti-reverse backflow unit, and a controllable switch Q4 for disabling the protection function of the overcurrent and overvoltage protection unit, wherein the control end of Q4 is connected between C1 and R4, and the output end thereof is connected to the protection drive circuit of the overcurrent and overvoltage protection unit. After the DC power supply is powered on, the voltage across the charging capacitor gradually increases so that the voltage at the connection point between the resistor R1 and C4 drops to 0, then Q4 is disconnected, and the overcurrent and overvoltage protection circuit resumes its protection function.

[0017] Furthermore, to enable the aforementioned power-on overcurrent protection delay unit to reset the protection execution switch in the overcurrent and overvoltage protection unit, in one embodiment, a reset switch SW1 is connected in parallel across charging capacitor C1 in the power-on overcurrent protection delay unit. When the reset switch is pressed, the charging capacitor discharges, turning Q4 on. When the reset switch is released, Q4 switches from the on state to the off state after a delay, thereby switching the protection execution switch in the overcurrent and overvoltage protection unit from the off state to the on state, and restoring the overvoltage and overcurrent protection functions.

[0018] As an embodiment, in the present invention, Q4 disables the protection drive circuit of the overcurrent and overvoltage protection unit from controlling the shutdown of the protection execution switch by outputting a high-level signal. Specifically:

[0019] In the overvoltage and overcurrent protection unit, the protection execution switch is a PMOS transistor Q7 whose source and drain are connected to the positive connection terminal of the load power supply, and whose gate is connected to the ground terminal via a resistor; the protection drive circuit includes an overcurrent response switch Q5, a direct control switch Q6, and a reference source circuit;

[0020] The reference source circuit includes a resistor divider circuit and a reference source U1 connected to the power output terminal of the power-on overcurrent protection delay unit; the cathode of the reference source U1 is connected to the positive electrode of the power output terminal of the power-on overcurrent protection delay unit via resistors R9 and R10, and is connected to the voltage dividing point of the resistor divider circuit via a diode D1, and the anode of D1 is connected to the cathode of U1; the anode of the reference source U1 is connected to the ground terminal, the comparison voltage input terminal is connected to the control output terminal of Q4, and is connected to the voltage dividing point of the resistor divider circuit via a resistor R7;

[0021] The direct control switch Q6 is a PNP transistor, the base of which is connected between the resistor R9 and the resistor R10, the emitter of which is connected to the positive terminal of the power output of the power-on overcurrent protection delay unit, and the collector of which is connected to the gate of the protection execution switch Q7;

[0022] The overcurrent response switch Q5 is a PNP transistor, whose collector is connected to the voltage dividing point of the resistor voltage divider circuit, the collector is connected to the positive power output terminal of the power-on overcurrent protection delay unit, the base is connected to the source of the protection execution switch Q7, and a resistor R8 is connected in series on the DC power supply positive electrode line between the base and emitter of Q5.

[0023] Optionally, a diode D2 is connected between the comparison voltage input terminal of the reference source U1 and the ground terminal, with its cathode connected to the connection point between the comparison voltage input terminal of the reference source U1 and the resistor R7. When the voltage difference between the comparison input terminal and the anode of the reference source U1 is greater than the regulated voltage value, D2 is turned on to protect the reference source U1 from damage caused by the excessive voltage difference.

[0024] Beneficial effects

[0025] Compared with the prior art, the present invention has the following advantages and improvements:

[0026] The DC power supply circuit of the present invention integrates functions such as anti-reverse connection, anti-backflow, and overcurrent and overvoltage delay protection. The anti-reverse connection and backflow circuit can prevent the damage to the subsequent circuit caused by the reverse connection of the DC power supply, and prevent the current generated by the inductive load from flowing back into the power supply during a sudden voltage drop and affecting the DC power supply; the overvoltage and overcurrent protection function is delayed by the power-on overcurrent protection delay unit, which can avoid the instantaneous surge current at power-on triggering the overvoltage and overcurrent protection to cut off the power supply circuit; the overcurrent and overvoltage protection circuit can provide overcurrent and overvoltage protection for the subsequent circuit when the subsequent circuit is abnormal or the DC power supply is abnormal, thereby ensuring the safety of the entire circuit.

[0027] The circuit of the present invention has more perfect functions and, through the mutual coordination of the connection relationship between the functional circuits of each part, the circuit has a higher integration level, is relatively simple, and has lower power consumption.

[0028] In addition, in the case where the power supply circuit is cut off after the overcurrent and overvoltage protection is triggered, the DC power supply protection circuit of the present invention can exit the abnormal protection state through a one-button reset function. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 FIG2 is a schematic diagram showing the structure and principle of a DC power supply protection circuit according to an embodiment of the present invention;

[0030] Figure 2 FIG. 1 is a schematic diagram showing the principle of a DC power supply protection circuit in an embodiment of the present invention. DETAILED DESCRIPTION

[0031] The following is a further description with reference to the accompanying drawings and specific embodiments.

[0032] Example 1

[0033] This embodiment introduces a DC power supply protection circuit with anti-reverse connection, anti-current backflow and overvoltage and overcurrent protection functions. Figure 1 As shown, it includes an anti-reverse connection and backflow protection unit, a power-on overcurrent protection delay unit, and an overcurrent and overvoltage protection unit, which are sequentially arranged on the power supply circuit between the DC power supply output terminal and the load;

[0034] The reverse connection and backflow prevention unit includes a reverse connection response switch and a backflow response switch. The reverse connection and backflow prevention unit is used to: control the reverse connection response switch to disconnect the power supply circuit of the DC power supply to the load when the positive and negative poles of the power supply are reversed, and control the backflow response switch to connect the discharge circuit between the load and the ground terminal when the DC power supply is instantly powered off;

[0035] The power-on overcurrent protection delay unit is used to enable the protection function of the overcurrent and overvoltage protection unit after a set delay time in response to the DC power supply being powered on;

[0036] The overcurrent and overvoltage protection unit includes a protection drive circuit and a protection execution switch connected to the power supply circuit; the overcurrent and overvoltage protection unit is used to: turn on the power supply circuit in response to the DC power supply being powered on; in the enabled state, in response to the DC power supply output voltage or output current exceeding a preset safety value, control the protection execution switch through the protection drive circuit to disconnect the power supply circuit.

[0037] Example 2

[0038] Based on the same inventive concept as that of Example 1, this embodiment introduces a specific implementation of a DC power supply protection circuit on the basis of Example 1.

[0039] refer to Figure 2 As shown, in the anti-reverse polarity backflow unit, transistors Q1, Q3, MOS transistor Q2, and resistors R1 and R2 constitute an anti-reverse polarity backflow circuit, and the PMOS transistor Q2 is the reverse polarity response switch, whose source and drain are connected to the positive line of the power input terminal, and the gate is grounded via a resistor. The PNP transistor Q3 is the reverse polarity response switch, whose emitter and collector are connected between the source of Q2 and the ground terminal, and the base is grounded via a resistor. The PNP transistor Q1 is the second reverse polarity response switch, whose emitter and collector are connected between the positive pole of the power input terminal and the ground terminal, and the base is connected to the base of Q3, and is used to cooperate with Q2 to control the disconnection of Q3 when the DC power supply is not reversed.

[0040] When the DC power supply is connected normally, transistor Q1 is on, Q3 is off, and MOS transistor Q2 is on. When the DC power supply is connected in the reverse direction, transistors Q1, Q3, and MOS transistor Q2 are all off, providing reverse connection protection. If the DC power supply experiences a momentary power loss, the equivalent capacitor C2 in the load circuit discharges, generating reverse current. At this point, transistor Q3 turns on, discharging the current to the negative terminal, providing reverse current protection.

[0041] In the power-on overcurrent protection delay unit, transistor Q4, resistors R3 and R4, and capacitor C1 form the power-on overcurrent protection delay circuit. Charging capacitor C1 and resistor R3 are connected in series between the positive and negative output terminals of the reverse polarity protection unit. Controllable switch Q4 is a PNP transistor used to disable the overcurrent and overvoltage protection unit's protection functions for a short period after power-on. Q4's control terminal is connected between C1 and R4, and its output terminal is connected to the overcurrent and overvoltage protection unit's protection drive circuit.

[0042] When the circuit is powered on, due to the presence of capacitor C2 in the load, an inrush current (overcurrent phenomenon) will be generated. If the overcurrent and overvoltage protection unit operates normally at this time, the overvoltage and overcurrent protection function will be triggered, causing the circuit to shut down. Therefore, this embodiment uses a power-on overcurrent protection delay unit to delay the overcurrent protection triggered at power-on. After power-on, capacitor C2 is gradually charged so that the base voltage of Q4 drops from VCC to 0, and then Q4 gradually changes from the on state at power-on to the off state. In its on state, the protection drive circuit of the overvoltage and overcurrent protection unit cannot perform the protection action, that is, the overvoltage and overcurrent protection function is disabled, avoiding the circuit shutdown caused by the power-on inrush current (overcurrent). After the DC power supply is powered on for a period of time, the voltage across the charging capacitor gradually increases, causing the voltage at the connection point between resistor R1 and C4 to drop to 0, then Q4 is disconnected, and the overcurrent and overvoltage protection circuit resumes its protection function.

[0043] In this embodiment, Q4 disables the protection drive circuit of the overcurrent and overvoltage protection unit from controlling the shutdown of the protection execution switch by outputting a high-level signal, thereby achieving the purpose of delaying the overvoltage and overcurrent protection function.

[0044] In the overcurrent and overvoltage protection unit, a programmable reference source U1, transistors Q5 and Q6, a PMOS transistor Q7, a diode D1, a Zener diode D2, and resistors R5, R6, R8, R7, R9, R10, and R11 form the overvoltage and overcurrent protection circuit. PMOS transistor Q7 serves as the protection execution switch, with its source and drain connected to the positive terminal of the load power supply and its gate connected to ground via resistor R11.

[0045] The protection drive circuit includes an overcurrent response switch Q5, a direct control switch Q6 and a reference source circuit; the reference source circuit includes a resistor divider circuit and a reference source U1 connected to the power output end of the power-on overcurrent protection delay unit; the resistor divider circuit is composed of resistors R5 and R6 connected in series, the cathode of the programmable reference source U1 is connected to the positive pole of the power output end of the power-on overcurrent protection delay unit through resistors R9 and R10, and is connected to the voltage dividing point of the resistor divider circuit through a diode D1, and the anode of D1 is connected to the cathode of U1; the anode of the reference source U1 is grounded, the comparison voltage input end is connected to the control output end of the transistor Q4, and is connected to the voltage dividing point of the resistor divider circuit through a resistor R7.

[0046] The PNP transistor Q6 is the direct control switch, whose base is connected between the resistor R9 and the resistor R10, the emitter is connected to the positive power output terminal of the power-on overcurrent protection delay unit, and the collector is connected to the gate of the protection execution switch Q7.

[0047] The PNP transistor Q5 is the overcurrent response switch, whose collector is connected to the voltage dividing point of the resistor voltage divider circuit, the collector is connected to the positive power output terminal of the power-on overcurrent protection delay unit, the base is connected to the source of the protection execution switch Q7, and a resistor R8 is connected in series on the DC power supply positive electrode line between the base and emitter of Q5.

[0048] When the voltage and current are normal, transistors Q5 and Q6 are turned off, MOS transistor Q7 is turned on, and the circuit is powered on normally. When an overvoltage occurs, the programmable reference source U1 is turned on, transistor Q6 is turned on, causing MOS transistor Q7 to turn off, generating an overvoltage protection function.

[0049] When an overcurrent occurs, transistor Q5 is turned on, causing the programmable reference source U1 to be turned on, and transistor Q6 to be turned on, causing MOS tube Q7 to be turned off, generating an overcurrent protection function.

[0050] Example 3

[0051] On the basis of Example 2, this embodiment further implements circuit design, and realizes the reset function of the protection execution switch in the overcurrent and overvoltage protection unit through the power-on overcurrent protection delay unit.

[0052] Still refer to Figure 2 As shown, the power-on overcurrent protection delay unit is also provided with a reset switch; the power-on overcurrent protection delay unit is also used to, after the DC power supply is powered on, when the protection execution switch is in the disconnected state, in response to the reset switch being pressed and released, control the protection execution switch through the protection drive circuit to resume conducting the power supply circuit.

[0053] Specifically, in the power-on overcurrent protection delay unit, a reset switch SW1 is connected across charging capacitor C1. When the reset switch is pressed, the charging capacitor discharges, turning Q4 on and Q7 back on. When the reset switch is released, Q4 switches from on to off after a delay, and the overvoltage and overcurrent protection unit resumes its overvoltage and overcurrent protection function.

[0054] Furthermore, within the overvoltage and overcurrent protection unit, a diode D2 is connected between the reference source U1's comparison voltage input and ground, with its cathode connected to the junction between the reference source U1's comparison voltage input and resistor R7. When the voltage difference between the reference source U1's comparison input and anode exceeds the regulated voltage value, D2 conducts, protecting the reference source U1 from damage caused by the excessive voltage difference.

[0055] The working principles of the above-mentioned embodiment 1 and embodiment 2 are as follows:

[0056] DC power supply positive connection:

[0057] The DC power supply outputs a forward voltage and current signal. The emitter of transistor Q1 is connected to the DC power supply's positive terminal, VCC. The base of Q1 is connected to the DC power supply's negative terminal, GND, through resistor R1. The voltage difference between the emitter and base is VCC, turning transistor Q1 on. When transistor Q1 is on, the base voltage of transistor Q1 is VCC minus the voltage drop between the emitter and base of transistor Q1. This typical value is 0.6V, so the base voltage of transistor Q1 is VCC-0.6V.

[0058] The drain of MOS transistor Q2 is connected to VCC, and the gate is connected to GND through resistor R2. MOS transistor Q2 is first turned on by the body diode of the device itself, so that the source voltage is VCC minus the body diode voltage drop, which is generally 1.2V. At this time, the voltage difference between the source and gate of Q2 is VCC-1.2V, which is greater than the Q2 turn-on voltage. , Q2 is turned on.

[0059] The emitter of transistor Q3 is connected to the source of MOS transistor Q2. When MOS transistor Q2 is turned on, the source voltage is almost VCC, so the emitter of transistor Q3 is VCC. The base of Q3 is connected to the base of transistor Q1, and the voltage is VCC-0.6V. Because the voltage difference between the emitter and base of Q3 is no more than 0.6V, Q3 is turned off.

[0060] Reverse connection of DC power supply:

[0061] The DC power supply outputs reverse voltage and current signals. If there is no voltage drop between the gate and source of the MOS transistor Q2, the MOS transistor Q2 cannot be turned on, and the power supply circuit between the DC power supply and the load is cut off, thus realizing the reverse connection protection function to prevent the DC power supply 10 from damaging the subsequent circuits due to reverse connection.

[0062] Instantaneous DC power failure:

[0063] When the DC power supply experiences a momentary power loss, the voltage across the capacitor remains constant due to the presence of equivalent capacitor C2 in load 50. C2 discharges, generating a reverse voltage differential with DC power supply 10 and outputting a reverse voltage and current signal. At this point, the emitter voltage of transistor Q3 is VCC minus the voltage drop across the body diode of MOS transistor Q7, which equals VCC-1.2V. Q3's base is connected to the negative electrode GND via resistor R1, resulting in a voltage difference between the emitter and base of Q3 equal to VCC-1.2V. Q3 conducts, transferring the reverse voltage and current signal to the negative electrode through resistors R1 and R3. At this point, the voltage difference between the gate and source of MOS transistor Q2 equals the voltage drop during saturation conduction of transistor Q3, which is less than Q2's turn-on voltage. Therefore, Q2 turns off, providing protection against reverse voltage and current flow to DC power supply 10.

[0064] Power-on overcurrent protection delay:

[0065] When Q2 in the reverse polarity protection unit 20 is in the on state, the power-on overcurrent protection delay unit 30 receives a power signal, and capacitor C1 and resistor R1 form an RC charging circuit, causing the voltage at the top of resistor R3 to slowly drop from VCC to 0V. The collector of transistor Q4 is connected to pin 2 of the programmable reference source U1, the base is connected to the top of resistor R3 through resistor R4, and the emitter is connected to the negative electrode GND. The voltage difference between the base and emitter of transistor Q4 slowly drops from VCC to 0V. After a delay, transistor Q4 automatically switches from the on state to the off state, forcing pin 2 of the programmable reference source U1 to be pulled down to 0V and then automatically switches to being affected by the voltage at the top of resistor R6 after a delay. By controlling pin 2 of the reference source U1 to 0V, transistor Q6 is controlled to be turned off, so that MOS tube Q7 is not turned off. When the DC power supply 10 is powered on, the instantaneous surge current (overcurrent phenomenon) caused by the equivalent capacitor C2 in the simulated inductive load 50 is prevented from triggering the overcurrent protection of the overvoltage and overcurrent protection circuit 40 and causing the protection execution switch Q7 to be turned off.

[0066] As the voltage at the top of resistor R3 slowly drops from VCC to 0V, transistor Q4 turns on. When the voltage at the top of resistor R3 drops to 0V, transistor Q4 automatically turns off, enabling the overvoltage and overcurrent protection function of the overvoltage and overcurrent protection unit.

[0067] Overvoltage and overcurrent protection recovery:

[0068] The power-on overcurrent protection delay unit 30 automatically turns off transistor Q4 after a period of time. If an overcurrent or overvoltage condition occurs during operation in the DC power supply circuit, triggering the shutdown of Q7, pressing button SW1 discharges capacitor C1, turning Q4 on. Releasing SW1 causes Q4 to automatically switch from the on state to the off state after a delay. During this process, the protection execution switch Q7 in the overvoltage and overcurrent protection unit 40 switches from the off state to the on state, implementing the recovery function of the power-on overcurrent protection delay unit 30.

[0069] Overcurrent and overvoltage protection

[0070] Under normal operating conditions, the output voltage and current of the DC power supply 10 are both less than the preset safety values. Since the conduction reference voltage threshold of pin 2 of the programmable reference source U1, i.e., the reference voltage input terminal, is 2.5V, the voltage safety value of the overvoltage and overcurrent protection unit 40 is {2.5×(1+R5 / R6)}V, and the current safety value is (0.6 / R8)A. When the voltage and current of the conduction signal are both less than the preset safety values, the voltage difference between the emitter and base of transistor Q5 is less than 0.6V, transistor Q5 is not conducting, the voltage at the top of R6 is less than 2.5V, pin 2 of the programmable reference source U1 is connected to the top of R6, and the reference voltage threshold of pin 2 is less than 2.5V.

[0071] Pin 1, the cathode, and pin 3, the anode, of programmable reference source U1 are not conducting. The emitter of transistor Q6 is connected to the source of MOS transistor Q2. When Q2 is on, the emitter of transistor Q6 is VCC. When pins 1 and 3 of programmable reference source U1 are not conducting, the base of transistor Q6 is pulled up to VCC through resistor R9, turning off transistor Q6. The source of MOS transistor Q7 is connected to resistor R8. When Q2 is on, the source of Q7 is VCC. When transistor Q6 is off, the gate of Q7 is connected to the negative electrode (GND) through pull-down resistor R11. The voltage difference between the source and gate of MOS transistor Q7 is VCC, Q7 is conducting, and DC power supply 10 can supply power to the load.

[0072] When DC power supply 10 or the simulated inductive load 50 is abnormal, the output voltage or current of DC power supply 10 exceeds a preset safety value. When the output voltage of DC power supply 10 exceeds the preset safety value, the voltage at the upper end of resistor R6 exceeds 2.5V, pin 2 of programmable reference source U1 is connected to the upper end of resistor R6 via current-limiting resistor R7, the reference voltage threshold of pin 2 exceeds 2.5V, and pins 1 and 3 of programmable reference source U1 are conductive. Diode D1 is used to unidirectionally conduct the current in the path between resistor R10 and pin 1 of programmable reference source U1 to resistor R6, keeping programmable reference source U1 continuously conductive. Zener diode D2 is connected between pins 2 and 3 of programmable reference source U1. When the voltage difference between pins 2 and 3 of programmable reference source U1 exceeds the regulated voltage value, D2 conducts. D2 protects programmable reference source U1 from damage caused by the excessive voltage difference between pins 2 and 3. The emitter of transistor Q6 is connected to the source of MOS transistor Q2. When Q2 is on, the emitter of transistor Q6 is connected to VCC. When pins 1 and 3 of programmable reference source U1 are conducting, the base-emitter voltage difference of transistor Q6 is VCC × (R9 / R9 + R10), which is greater than 0.6V, turning transistor Q6 on. The source of MOS transistor Q7 is connected to resistor R8. When Q2 is on, the source of Q7 is connected to VCC. When transistor Q6 is on, the gate of Q7 is connected to VCC through Q6. The source-gate voltage difference of MOS transistor Q7 is the voltage drop of transistor Q6 during saturation conduction, which is less than the turn-on voltage. Therefore, Q7 is turned off, and the DC power supply cannot supply power to the load, thus achieving the overvoltage protection function of overvoltage and overcurrent protection circuit 40.

[0073] When the output current of DC power supply 10 exceeds a preset safety value, the emitter of transistor Q5 is connected to the left end of resistor R8, and the base is connected to the right end of resistor R8. The voltage difference between the base and emitter of transistor Q5 exceeds 0.6V, transistor Q5 turns on, and the upper end of resistor R6 is connected to the collector of transistor Q6. When transistor Q6 turns on, the voltage across resistor R6 exceeds 2.5V. Pin 2 of programmable reference source U1 is connected to the upper end of R6 via current-limiting resistor R7. The reference voltage threshold of pin 2 exceeds 2.5V, and pins 1 and 3 of programmable reference source U1 conduct. Diode D1 is used to unidirectionally conduct the current in the path between resistor R10 and pin 1 of programmable reference source U1 to resistor R6, keeping programmable reference source U1 continuously conducting. When the voltage difference between pins 2 and 3 of programmable reference source U1 exceeds the regulated voltage value, diode D2 turns on. The emitter of transistor Q6 is connected to the source of MOS transistor Q2. When Q2 is on, the emitter of transistor Q6 is connected to VCC. When pins 1 and 3 of programmable reference source U1 are conducting, the base-emitter voltage difference of transistor Q6 is VCC × (R9 / R9 + R10), which is greater than 0.6V, turning transistor Q6 on. The source of MOS transistor Q7 is connected to resistor R8. When Q2 is on, the source of Q7 is connected to VCC. When transistor Q6 is on, the gate of Q7 is connected to VCC through Q6. The source-gate voltage difference of MOS transistor Q7 is the voltage drop of transistor Q6 during saturation conduction, which is less than the turn-on voltage. Therefore, Q7 is turned off, and the DC power supply cannot supply power to the load, thus realizing the overcurrent protection function of overvoltage and overcurrent protection unit 40.

[0074] The embodiments of the present invention are described above in conjunction with the accompanying drawings, but the present invention is not limited to the above-mentioned specific implementation methods. The above-mentioned specific implementation methods are merely illustrative and not restrictive. Under the guidance of the present invention, ordinary technicians in this field can also make many forms without departing from the scope of protection of the purpose of the present invention and the claims, which are all protected by the present invention.

Claims

1. A DC power supply protection circuit, characterized in that: It includes an anti-reverse connection and backflow protection unit, a power-on overcurrent protection delay unit, and an overcurrent and overvoltage protection unit, which are sequentially arranged on the power supply circuit between the DC power supply output terminal and the load; The reverse connection and backflow prevention unit includes a reverse connection response switch and a backflow response switch. The reverse connection and backflow prevention unit is used to: control the reverse connection response switch to disconnect the power supply circuit of the DC power supply to the load when the positive and negative poles of the power supply are reversed, and control the backflow response switch to connect the discharge circuit between the load and the ground terminal when the DC power supply is instantly powered off; The power-on overcurrent protection delay unit is used to enable the protection function of the overcurrent and overvoltage protection unit after a set delay time in response to the DC power supply being powered on; The overcurrent and overvoltage protection unit includes a protection drive circuit and a protection execution switch connected to the power supply circuit; the overcurrent and overvoltage protection unit is used to: turn on the power supply circuit in response to the DC power supply being powered on; in the enabled state, in response to the DC power supply output voltage or output current exceeding a preset safety value, control the protection execution switch through the protection drive circuit to disconnect the power supply circuit.

2. The DC power supply protection circuit according to claim 1, wherein: The power-on overcurrent protection delay unit is provided with a reset switch; the power-on overcurrent protection delay unit is also used to, after the DC power supply is powered on, when the protection execution switch is in the disconnected state, in response to the reset switch being pressed and then released, control the protection execution switch through the protection drive circuit to turn on the power supply circuit.

3. The DC power supply protection circuit according to claim 1, wherein: In the reverse connection and backflow prevention unit, the reverse connection response switch is a PMOS tube Q2 whose source and drain are connected to the positive line of the power input terminal, and the gate of Q2 is connected to the ground terminal via a resistor; The backflow response switch is a PNP transistor Q3 whose emitter and collector are connected between the source of Q2 and the ground terminal, and the base of Q3 is connected to the ground terminal via a resistor; The anti-reverse connection and backflow prevention unit further includes a second reverse connection response switch for cooperating with Q2 to control Q3 to be disconnected when the DC power supply is not reverse connected.

4. The DC power supply protection circuit according to claim 3, wherein: The second reverse connection response switch is a PNP transistor Q1 whose emitter and collector are connected between the positive electrode of the power input terminal and the ground terminal, and Q1 is connected to the base of Q3.

5. The DC power supply protection circuit according to claim 4, wherein: The power-on overcurrent protection delay unit includes a charging capacitor C1 and a resistor R3 connected in series between the positive and negative lines of the output end of the anti-reverse backflow unit, and a controllable switch Q4 for disabling the protection function of the overcurrent and overvoltage protection unit. The control end of Q4 is connected between C1 and R4, and its output end is connected to the protection drive circuit of the overcurrent and overvoltage protection unit.

6. The DC power supply protection circuit according to claim 5, wherein: In the power-on overcurrent protection delay unit, both ends of the charging capacitor C1 are connected in parallel with a reset switch SW1 .

7. The DC power supply protection circuit according to claim 6, characterized in that the controllable The switch Q4 disables the protection drive circuit of the overcurrent and overvoltage protection unit to control the shutdown of the protection execution switch by outputting a high-level signal. In the overvoltage and overcurrent protection unit, the protection execution switch is a PMOS transistor Q7 whose source and drain are connected to the positive connection terminal of the load power supply, and whose gate is connected to the ground terminal via a resistor; the protection drive circuit includes an overcurrent response switch Q5, a direct control switch Q6, and a reference source circuit; The reference source circuit includes a resistor divider circuit and a reference source U1 connected to the power output terminal of the power-on overcurrent protection delay unit; the cathode of the reference source U1 is connected to the positive electrode of the power output terminal of the power-on overcurrent protection delay unit via resistors R9 and R10, and is connected to the voltage dividing point of the resistor divider circuit via a diode D1, and the anode of D1 is connected to the cathode of U1; the anode of the reference source U1 is connected to the ground terminal, the comparison voltage input terminal is connected to the control output terminal of Q4, and is connected to the voltage dividing point of the resistor divider circuit via a resistor R7; The direct control switch Q6 is a PNP transistor, the base of which is connected between the resistor R9 and the resistor R10, the emitter of which is connected to the positive terminal of the power output of the power-on overcurrent protection delay unit, and the collector of which is connected to the gate of the protection execution switch Q7; The overcurrent response switch Q5 is a PNP transistor, whose collector is connected to the voltage dividing point of the resistor voltage divider circuit, the collector is connected to the positive power output terminal of the power-on overcurrent protection delay unit, the base is connected to the source of the protection execution switch Q7, and a resistor R8 is connected in series on the DC power supply positive electrode line between the base and emitter of Q5.

8. The DC power supply protection circuit according to claim 7, wherein: A diode D2 is further connected between the comparison voltage input terminal of the reference source U1 and the ground terminal, and the cathode of the diode D2 is connected to the connection point between the comparison voltage input terminal of the reference source U1 and the resistor R7.

Images