An output voltage protection control circuit for a direct current power supply

Abstract

This invention relates to an output voltage protection control circuit for a DC power supply, belonging to the field of power electronics technology. It solves the problems of existing output voltage protection circuits being unable to accurately control the maximum rise slope and unable to continuously control the maximum rise slope after power-on. The circuit includes a delayed voltage protection circuit for receiving the output voltage of the main power circuit and comparing it with a preset delayed overvoltage protection value, outputting a delayed protection voltage signal based on the comparison result; an output voltage maximum rise slope control circuit for receiving the output voltage and converting the output voltage rise slope into a slope voltage signal, sampling and amplifying the slope voltage signal before outputting it; an execution circuit for comparing the delayed protection voltage signal and the amplified slope voltage signal with a control threshold, outputting a control signal based on the comparison result; and a control chip for outputting a drive control signal based on the control signal to perform power control of the main power circuit.

Description

Technical Field

[0001] This invention relates to the field of power electronics technology, and in particular to an output voltage protection control circuit for a DC power supply. Background Technology

[0002] Currently, the commonly used method to suppress the output voltage rise slope and starting inrush current during the startup of a DC power supply is to adopt an output soft-start control method. That is, during the startup process, the duty cycle of the drive signal is controlled to gradually increase from the minimum duty cycle, and the corresponding output voltage will slowly build up, thereby achieving the purpose of limiting the output voltage rise slope.

[0003] The existing soft-start control circuit is shown in the attached figure. Figure 1 As shown, its working principle is as follows: Using the control chip A1 of the DC power supply, an external soft-start capacitor C1 is connected. When the power supply starts, the voltage of the soft-start capacitor C1 is 0V. Through diode D1, the voltage at the inverting input of the sawtooth wave comparator N2 inside the control chip is pulled low, causing N2 to output a low level, thus achieving a 0% duty cycle for the drive signal and limiting the output voltage of the DC power supply. During startup, the constant current source CL inside the control chip charges the external soft-start capacitor C1, causing the voltage of C1 to gradually rise from 0V. Since the output feedback voltage of the voltage regulator controller is very low at this time, it does not reach the voltage value set by the voltage regulation loop. The operational amplifier N1 saturates and outputs a high level, and its voltage... When the voltage across the soft-start capacitor C1 is greater than the voltage across the capacitor, diode D1 conducts, and the inverting input voltage of comparator N2 is clamped by the voltage across capacitor C1, thus enabling the inverting input voltage of N2 to gradually increase from 0V. The duty cycle of the output control signal of comparator N2 gradually increases from 0V. Since the output voltage of the DC power supply is proportional to the duty cycle of the drive control signal, the output of the DC power supply gradually increases from 0V, thereby realizing the soft-start function of the DC power supply. When the voltage across C1 rises to a level greater than the output voltage of operational amplifier N1, diode D1 is reverse-biased and cut off. The voltage regulator formed by N1 adjusts the output of comparator N2, realizing closed-loop control and ending the soft-start process.

[0004] However, existing DC power supply output voltage protection circuits cannot accurately control the maximum rise rate of the output voltage. At the same time, after the power supply completes startup, the soft-start circuit will lose its function and cannot control the maximum voltage rise rate during the dynamic process of the output voltage. Summary of the Invention

[0005] Based on the above analysis, the present invention aims to provide an output voltage protection control circuit for a DC power supply, in order to solve the problems that existing output voltage protection circuits cannot accurately control the maximum rise rate and cannot continuously control the maximum rise rate after the power supply has finished starting.

[0006] This invention provides an output voltage protection control circuit for a DC power supply, including a delayed voltage protection circuit, an output voltage maximum rise slope control circuit, an execution circuit, a control chip, and a main power circuit.

[0007] The delayed voltage protection circuit is used to receive the output voltage of the main power circuit, compare it with the preset delayed overvoltage protection value, and output a delayed protection voltage signal according to the comparison result.

[0008] The maximum rise slope control circuit for the output voltage is used to receive the output voltage of the main power circuit, convert the rise slope of the output voltage into a slope voltage signal, sample and amplify the slope voltage signal, and then output it.

[0009] The execution circuit is used to compare the delay protection voltage signal and the amplified slope voltage signal with the set control threshold, and output a control signal according to the comparison result.

[0010] The control chip is used to output a drive control signal to the main power circuit according to the received control signal, so as to perform power control of the main power circuit.

[0011] Furthermore, the delay voltage protection circuit outputs the delay protection voltage signal in the following manner:

[0012] If the output voltage is greater than the preset overvoltage protection value and the duration is greater than the preset delay time, the output delay protection voltage signal is a high-level signal and is maintained until the control circuit is powered off, reset, and restarted; otherwise, the output delay protection voltage signal is a low-level signal; wherein, the high-level signal voltage value is greater than the control threshold and the low-level signal voltage value is less than the control threshold.

[0013] Furthermore, it also includes a transient voltage protection circuit;

[0014] The instantaneous voltage protection circuit is used to receive the output voltage of the main power circuit, compare it with the preset instantaneous overvoltage protection value, and output an instantaneous protection voltage signal according to the comparison result;

[0015] The execution circuit is also used to compare the instantaneous protection voltage signal with the set control threshold and output a control signal based on the comparison result.

[0016] Furthermore, the instantaneous voltage protection circuit outputs the instantaneous protection voltage signal in the following manner:

[0017] If the output voltage is greater than the preset instantaneous overvoltage protection value, the output instantaneous protection voltage signal is a threshold signal; otherwise, the output instantaneous protection voltage signal is a low-level signal; wherein, the threshold signal is equal to the set control threshold.

[0018] Furthermore, the execution circuit is equipped with an output voltage sampling circuit for sampling the output voltage of the main power circuit to obtain an output voltage sampling signal; the execution circuit outputs control signals in the following manner:

[0019] When the value of any one of the delayed protection voltage signal, instantaneous protection voltage signal, or amplified slope voltage signal is greater than or equal to the control threshold, the output control signal is a high-level signal. At this time, the control chip shuts off the output drive control signal, and the main power circuit stops working.

[0020] Otherwise, the output control signal is the output voltage sampling signal. In this case, the control chip outputs a drive control signal based on the received output voltage sampling signal, and the main power circuit works normally.

[0021] Furthermore, the delay voltage protection circuit includes an operational amplifier P1, diodes D1, D2 and D6, resistors R1 and R2, capacitor C2 and a reference voltage circuit.

[0022] The non-inverting input of operational amplifier P1 is connected to the cathode of diode D1, the anode of diode D6, one end of capacitor C2, one end of resistor R1, and one end of resistor R2; the other end of capacitor C2 is connected to the other end of resistor R2 and then grounded; the cathode of diode D6 is connected to the other end of resistor R1 and serves as the input of the delay voltage protection circuit, used to receive the output voltage of the main power circuit; the anode of diode D1 is connected to the output of operational amplifier P1.

[0023] The inverting input terminal of the operational amplifier P1 is connected to the reference voltage circuit to receive the reference voltage output by the reference voltage circuit.

[0024] The output terminal of the operational amplifier P1 is also connected to the positive terminal of the diode D2, and the negative terminal of the diode serves as the output terminal of the delay voltage protection circuit, used to output the delay protection voltage signal.

[0025] Furthermore, the maximum rise slope control circuit for the output voltage includes a current sensor CT1, a capacitor C1, resistors R7 to R11, and operational amplifiers P2 and P3.

[0026] The same-name terminal of the primary winding of the current sensor CT1 is connected to one end of the capacitor C1, and the opposite-name terminal is grounded; the other end of the capacitor C1 serves as the input terminal of the maximum rise slope control circuit of the output voltage, and is used to receive the output voltage of the main power circuit.

[0027] The same-name terminal of the secondary winding of the current sensor CT1 is connected to one end of resistor R7 and one end of resistor R8; the other end of resistor R8 is connected to one end of resistor R9 and the non-inverting input terminal of operational amplifier P2; the other end of resistor R9 is grounded; the opposite-name terminal of the secondary winding of the current sensor CT1 is connected to the other end of resistor R7 and one end of resistor R10; the other end of resistor R10 is connected to one end of resistor R11 and the inverting input terminal of operational amplifier P2; the other end of resistor R11 is connected to the output terminal of operational amplifier P2.

[0028] The output terminal of the operational amplifier P2 is also connected to the non-inverting input terminal of the operational amplifier P3;

[0029] The inverting input terminal and the output terminal of the operational amplifier P3 are shorted together and used as the output terminal of the maximum rise slope control circuit of the output voltage, which is used to output the amplified slope voltage signal.

[0030] Furthermore, the execution circuit includes MOSFETs Q1 and Q2, Zener diode VZ2, resistors R12 to R14, diodes D4 and D5, and an output voltage sampling circuit.

[0031] The gate of the MOSFET Q1 is connected to the negative terminal of the Zener diode VZ2 and one end of the resistor R12; the other end of the resistor R12 serves as the first input terminal of the execution circuit, used to receive the delay protection voltage signal, the instantaneous protection voltage signal, and the amplified slope voltage signal; the drain of the MOSFET Q1 is connected to the positive terminal of the Zener diode VZ2 and then grounded; the source of the MOSFET Q1 is connected to the drain of the MOSFET Q2 via resistors R14 and R13 in series, and the drain of the MOSFET Q2 is also connected to a voltage source;

[0032] The gate of the MOSFET Q2 is connected to the common terminal of the resistors R14 and R13; the source of the MOSFET Q2 is connected to the positive terminal of the diode D4, and the negative terminal of the diode D4 serves as the output terminal of the execution circuit for outputting control signals.

[0033] The input terminal of the output voltage sampling circuit serves as the second input terminal of the execution circuit, used to receive the output voltage of the main power circuit; the output terminal of the output voltage sampling circuit is connected to the positive terminal of diode D5, and the negative terminal of diode D5 is connected to the negative terminal of diode D4.

[0034] Furthermore, the instantaneous voltage protection circuit includes a Zener diode VZ1, a resistor R3, and a diode D3;

[0035] The negative terminal of the Zener diode VZ1 serves as the input terminal of the instantaneous voltage protection circuit, used to receive the output voltage of the main power circuit; the positive terminal of the Zener diode VZ1 is connected to one end of the resistor R3 and the positive terminal of the diode D3 respectively; the other end of the resistor R3 is grounded; the negative terminal of the diode D3 serves as the output terminal of the instantaneous voltage protection circuit, used to output the instantaneous protection voltage signal.

[0036] Furthermore, the reference voltage circuit includes a voltage reference chip Z1, a capacitor C3, and resistors R4 to R6;

[0037] The cathode of the voltage reference chip Z1 serves as the output terminal of the reference voltage circuit, used to output a reference voltage to the delay voltage protection circuit.

[0038] The reference terminal of the voltage reference chip Z1 is connected to one end of resistor R4 and one end of resistor R5; the other end of resistor R4 is connected to the cathode of the voltage reference chip Z1, one end of resistor R6, and one end of capacitor C3.

[0039] The other end of resistor R5 is connected to the anode of voltage reference chip Z1 and the other end of capacitor C3 and then grounded; the other end of resistor R6 is connected to a voltage source.

[0040] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0041] This invention provides an output voltage protection control circuit for a DC power supply.

[0042] 1. By setting the maximum rise slope control circuit of the output voltage, precise control of the maximum rise slope of the output voltage is achieved. After the power supply is started, the maximum rise slope of the output voltage can be continuously monitored and corresponding control is performed to ensure that the output voltage slope of the power supply meets the requirements of the electrical equipment, resulting in better control effect and wider range.

[0043] 2. By setting a delayed voltage protection circuit, the delayed overvoltage protection function of the power supply output voltage can be realized. This can avoid false overvoltage protection caused by output voltage interference signals. Once the delayed overvoltage protection is triggered, the voltage protection signal is locked to prevent damage to electrical equipment caused by long-term overvoltage and improve the reliability of protection.

[0044] 3. By setting a transient voltage protection circuit, the transient overvoltage protection function of the power supply output voltage can be realized. It can quickly realize the overvoltage protection of the output voltage, effectively suppress transient voltage overshoot, and after the output voltage returns to normal, the transient overvoltage protection signal is canceled, and the power supply can continue to work normally, effectively improving the rapid protection function of the output voltage.

[0045] 4. The threshold of the maximum rise slope of the output voltage, as well as the delay overvoltage protection value, delay time, and instantaneous overvoltage protection value of the delay protection circuit can be flexibly set to meet the usage requirements of various power supplies. It can be applied to the control circuits of various power supply devices, making it more versatile.

[0046] In this invention, the above-described technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of this invention will be set forth in the following description, and some advantages may become apparent from the description or be learned by practicing the invention. The objects and other advantages of this invention can be realized and obtained from what is particularly pointed out in the description and drawings. Attached Figure Description

[0047] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0048] Figure 1 It is a traditional power supply output voltage protection and control circuit;

[0049] Figure 2 A schematic block diagram of an output voltage protection control circuit for a DC power supply provided in an embodiment of the present invention;

[0050] Figure 3 The circuit connection diagram for the output voltage protection control circuit of a DC power supply provided in the embodiment of the present invention is shown. Detailed Implementation

[0051] Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which form part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention.

[0052] One specific embodiment of the present invention discloses an output voltage protection control circuit for a DC power supply, such as... Figure 2 As shown, it includes a delay voltage protection circuit, an output voltage maximum rise slope control circuit, an execution circuit, a control chip, and a main power circuit.

[0053] The delayed voltage protection circuit is used to receive the output voltage of the main power circuit, compare it with the preset delayed overvoltage protection value, and output a delayed protection voltage signal according to the comparison result.

[0054] The maximum rise slope control circuit for the output voltage is used to receive the output voltage of the main power circuit, convert the rise slope of the output voltage into a slope voltage signal, sample and amplify the slope voltage signal, and then output it.

[0055] The execution circuit is used to compare the delay protection voltage signal and the amplified slope voltage signal with the set control threshold, and output a control signal according to the comparison result.

[0056] The control chip is used to output a drive control signal to the main power circuit according to the received control signal, so as to perform power control of the main power circuit.

[0057] During implementation, the control chip is selected according to the control requirements of the power supply. Specifically, the appropriate duty cycle control method or frequency modulation control method control chip is selected according to the power supply's fixed frequency duty cycle or frequency modulation control method. The control chip has a GND terminal, an output voltage feedback comparison terminal FB, and an output terminal OUT. The internal reference voltage of the control chip is 5V or 2.5V.

[0058] In implementation, the delay voltage protection circuit outputs the delay protection voltage signal in the following manner:

[0059] If the output voltage is greater than the preset overvoltage protection value and the duration is greater than the preset delay time, the output delay protection voltage signal is a high-level signal and is maintained until the control circuit is powered off, reset, and restarted; otherwise, the output delay protection voltage signal is a low-level signal; wherein, the high-level signal voltage value is greater than the control threshold and the low-level signal voltage value is less than the control threshold.

[0060] Preferably, it further includes a transient voltage protection circuit; the transient voltage protection circuit is used to receive the output voltage of the main power circuit, compare it with a preset transient overvoltage protection value, and output a transient protection voltage signal according to the comparison result;

[0061] The execution circuit is also used to compare the instantaneous protection voltage signal with the set control threshold and output a control signal based on the comparison result.

[0062] Specifically, the instantaneous voltage protection circuit outputs the instantaneous protection voltage signal in the following manner:

[0063] If the output voltage is greater than the preset instantaneous overvoltage protection value, the output instantaneous protection voltage signal is a threshold signal; otherwise, the output instantaneous protection voltage signal is a low-level signal; wherein, the threshold signal is equal to the set control threshold.

[0064] In implementation, the execution circuit is equipped with an output voltage sampling circuit for sampling the output voltage of the main power circuit to obtain an output voltage sampling signal; the execution circuit outputs control signals in the following manner:

[0065] When the value of any one of the delayed protection voltage signal, instantaneous protection voltage signal, or amplified slope voltage signal is greater than or equal to the control threshold, the output control signal is a high-level signal. At this time, the control chip shuts off the output drive control signal, and the main power circuit stops working.

[0066] Otherwise, the output control signal is the output voltage sampling signal. In this case, the control chip outputs a drive control signal based on the received output voltage sampling signal, and the main power circuit works normally.

[0067] In specific implementation, such as Figure 3 As shown, the delay voltage protection circuit includes an operational amplifier P1, diodes D1, D2, and D6, resistors R1 and R2, capacitor C2, and a reference voltage circuit. The non-inverting input of the operational amplifier P1 is connected to the cathode of diode D1, the anode of diode D6, one end of capacitor C2, one end of resistor R1, and one end of resistor R2. The other end of capacitor C2 is connected to the other end of resistor R2 and then grounded. The cathode of diode D6 is connected to the other end of resistor R1 and serves as the input of the delay voltage protection circuit, used to receive the output voltage of the main power circuit. The anode of diode D1 is connected to the output of operational amplifier P1. The inverting input of operational amplifier P1 is connected to the reference voltage circuit and used to receive the reference voltage output by the reference voltage circuit. The output of operational amplifier P1 is also connected to the anode of diode D2, and the cathode of diode D2 serves as the output of the delay voltage protection circuit, used to output a delay protection voltage signal.

[0068] Specifically, the reference voltage circuit includes a voltage reference chip Z1, a capacitor C3, and resistors R4 to R6; the cathode of the voltage reference chip Z1 serves as the output terminal of the reference voltage circuit, used to output a reference voltage to the delay voltage protection circuit; the reference terminal of the voltage reference chip Z1 is connected to one end of resistor R4 and one end of resistor R5; the other end of resistor R4 is connected to the cathode of the voltage reference chip Z1, one end of resistor R6, and one end of capacitor C3; the other end of resistor R5 is connected to the anode of the voltage reference chip Z1 and the other end of capacitor C3, and then grounded; the other end of resistor R6 is connected to a voltage source.

[0069] More specifically, the voltage source voltage is 15V, and the reference voltage is 5V; the reverse voltage rating of diode D1 is greater than the voltage source voltage of 15V, and the reverse voltage ratings of diodes D2 and D6 are greater than the maximum output voltage of the main power circuit. The voltage reference chip Z1 is a TL431, and the operational amplifier P1 is a rail-to-rail output operational amplifier; the capacitance of capacitor C3 is 0.1uF, the resistances of resistors R4 and R5 are 10kΩ, and the resistance of resistor R6 is 5.1kΩ. Together with the voltage reference chip Z1, they transform the 15V voltage source voltage into a stable 5V reference voltage.

[0070] More specifically, the resistance value of resistor R1 is determined according to the following formula:

[0071]

[0072] In the formula, V P2 It is the preset overvoltage protection value of the power supply output voltage, which can be selected according to the power consumption and protection requirements of the electrical equipment; the resistance value of R2 is between 10kΩ and 100kΩ, preferably 20kΩ.

[0073] The capacitance value of capacitor C2 is selected according to the following formula:

[0074]

[0075] In the formula, T S It is the set delay time of the delay voltage protection circuit.

[0076] The working principle is as follows:

[0077] When the power is turned on, the inverting input of operational amplifier P1 receives the reference voltage, and the non-inverting input receives the voltage divider signal obtained by the voltage divider of resistors R1 and R2. When the output voltage exceeds the preset overvoltage protection value, capacitor C2 is charged through resistor R1. After the preset delay time, the charging voltage of capacitor C2 reaches the reference voltage. At this time, the output of operational amplifier P1 outputs a high-level signal. This signal clamps the voltage at the non-inverting input of operational amplifier P1 to the clamping voltage (i.e., the voltage value of the high-level signal minus the voltage drop of diode D1, which is approximately equal to the high-level signal voltage value). Even if the output voltage drops below the overvoltage protection value, the output of operational amplifier P1 will still output a high-level signal, thereby locking the overvoltage protection output of operational amplifier P1. At this time, the control chip is controlled by the execution circuit to turn off the output, and the main power circuit is turned off. In other words, since the operational amplifier P1 is locked to the output, the protection has the function of locking the output to shut down. After the protection occurs, the output voltage drops and is less than the delayed overvoltage protection value, the circuit will still control the power supply to shut down the output. It has the function of overvoltage lockout protection, which can avoid false overvoltage protection caused by output voltage interference signals. Once the delayed overvoltage protection is triggered, the voltage protection signal is locked to prevent damage to electrical equipment caused by long-term overvoltage and improve the reliability of protection.

[0078] Meanwhile, when the control circuit is powered off, capacitor C2 discharges rapidly to 0V through diode D6. When the system is powered on again and the power supply output voltage returns to normal, the voltage at the non-inverting input of operational amplifier P1 is less than the reference voltage at the inverting input, and operational amplifier P1 outputs a low-level signal, thus enabling the execution circuit to control the control chip to output normally.

[0079] It is understandable that the time-delay voltage protection circuit is designed to protect against overvoltage phenomena that have a certain duration. It will only activate the protection action and shut down the power output when an overvoltage phenomenon occurs and lasts for a certain duration. It also has a self-locking function. After the fault disappears, a power-off restart is required to clear the protection.

[0080] In specific implementation, such as Figure 3 As shown, the maximum rise slope control circuit of the output voltage includes a current sensor CT1, a capacitor C1, resistors R7 to R11, and operational amplifiers P2 and P3.

[0081] The same-name terminal of the primary winding of the current sensor CT1 is connected to one end of the capacitor C1, and the opposite-name terminal is grounded; the other end of the capacitor C1 serves as the input terminal of the maximum rise slope control circuit of the output voltage, and is used to receive the output voltage of the main power circuit.

[0082] The same-name terminal of the secondary winding of the current sensor CT1 is connected to one end of resistor R7 and one end of resistor R8; the other end of resistor R8 is connected to one end of resistor R9 and the non-inverting input terminal of operational amplifier P2; the other end of resistor R9 is grounded; the opposite-name terminal of the secondary winding of the current sensor CT1 is connected to the other end of resistor R7 and one end of resistor R10; the other end of resistor R10 is connected to one end of resistor R11 and the inverting input terminal of operational amplifier P2; the other end of resistor R11 is connected to the output terminal of operational amplifier P2.

[0083] The output terminal of the operational amplifier P2 is also connected to the non-inverting input terminal of the operational amplifier P3; the inverting input terminal of the operational amplifier P3 is shorted to the output terminal and serves as the output terminal of the maximum rise slope control circuit of the output voltage, used to output the amplified slope voltage signal.

[0084] Specifically, operational amplifiers P2 and P3 are rail-to-rail output operational amplifiers.

[0085] Specifically, resistors R8 and R10 have the same resistance value of 10kΩ; resistors R9 and R11 have the same resistance value; resistors R7, R9, and R11 are determined using the following formula:

[0086]

[0087]

[0088] I C1 ×N×R7≤50mV

[0089] In the formula, V th The voltage value is the control threshold voltage value of the execution circuit; N is the current transformation ratio of the current sensor CT1, preferably N = 10; I C1 Smax is the current flowing through capacitor C1 and current sensor CT1; Smax is the maximum rise slope of the output voltage, which can be selected according to the power consumption and protection requirements of the electrical equipment; the capacitance value of capacitor C1 is between 10nF and 100nF, preferably 22nF.

[0090] The working principle is as follows:

[0091] When the power supply is turned on, the current flowing through the current sensor CT1 is proportional to the rising slope of the output voltage. The current is sampled and amplified by the voltage sensor CT1 and resistor R7 and converted into a slope voltage signal. Then, the slope voltage signal is further amplified by resistors R8, R9, R10, R11 and operational amplifiers P2 and P3 to obtain the amplified slope voltage signal. When the amplified slope voltage signal output by operational amplifier P3 is greater than or equal to the control threshold of the execution circuit, the execution circuit controls the control chip to turn off the output. At this time, the main power circuit does not output voltage, and its output voltage slope will decrease, thereby achieving the purpose of limiting the maximum rising slope of the output voltage.

[0092] When the amplified slope voltage signal output by operational amplifier P3 is less than the control threshold of the execution circuit, the execution circuit controls the control chip to output normally.

[0093] It should be noted that the control threshold is related to the maximum rise slope of the output voltage of the control circuit. Based on the maximum rise slope and the control threshold, the circuit structure with corresponding parameters can be obtained.

[0094] Understandably, when the slope of the power supply output voltage is less than its maximum rising slope, that is, when the amplified slope voltage signal is greater than or equal to the control threshold of the execution circuit, the maximum rising slope control circuit of the output voltage does not intervene in the output voltage control. The power supply achieves a stable output voltage through the closed-loop control of its control chip. The control circuit only intervenes in the control when the slope of the output voltage is greater than or equal to its maximum rising slope, that is, when the amplified slope voltage signal is less than the control threshold of the execution circuit.

[0095] In specific implementation, such as Figure 3 As shown, the instantaneous voltage protection circuit includes a Zener diode VZ1, a resistor R3, and a diode D3;

[0096] The negative terminal of the Zener diode VZ1 serves as the input terminal of the instantaneous voltage protection circuit, used to receive the output voltage of the main power circuit; the positive terminal of the Zener diode VZ1 is connected to one end of the resistor R3 and the positive terminal of the diode D3 respectively; the other end of the resistor R3 is grounded; the negative terminal of the diode D3 serves as the output terminal of the instantaneous voltage protection circuit, used to output the instantaneous protection voltage signal.

[0097] Specifically, the reverse voltage rating of diode D3 is greater than the voltage source voltage of 15V.

[0098] Specifically, the voltage regulation value V of the Zener diode VZ1 is... z1 Determined according to the following formula:

[0099] V z1 =V p1 -V D3 -V th

[0100] In the formula, V p1 The transient overvoltage protection value for the power output can be selected according to the power consumption and protection requirements of the electrical equipment. V D3 This is the forward voltage drop of diode D3.

[0101] The resistance value of resistor R3 is determined according to the following formula:

[0102]

[0103] In the formula, I Z1 Zener diode V z1 The rated steady-state operating current.

[0104] The working principle is as follows:

[0105] When the power supply is turned on, when the output voltage reaches its transient overvoltage protection value, the Zener diode VZ1 breaks down, the diode D3 conducts, and the output threshold signal is output. This signal then shuts off the output of the control chip through the execution circuit, thus achieving transient overvoltage protection. It is understandable that since no capacitor is used for delay in the transient voltage protection circuit, the output is immediately shut off when the output voltage exceeds the transient overvoltage protection value, thus achieving transient overvoltage protection.

[0106] When the output voltage returns to normal and drops below the transient overvoltage protection value, a low-level signal is output, and the execution circuit controls the control chip to output normally. The transient overvoltage protection circuit will not lock the protection state, and the output can work normally after the output voltage is lower than the transient overvoltage protection value.

[0107] Understandably, transient voltage protection circuits provide rapid overvoltage protection against short-term output overvoltage phenomena. When an output overvoltage occurs, the power supply output is immediately shut off, and the protection is automatically removed after the fault disappears. It can quickly achieve overvoltage protection of the output voltage, effectively suppress transient voltage overshoot, and after the output voltage returns to normal, the transient overvoltage protection signal is removed, and the power supply can continue to work normally, effectively improving the rapid protection function of the output voltage.

[0108] In specific implementation, such as Figure 3 As shown, the execution circuit includes MOSFETs Q1 and Q2, Zener diode VZ2, resistors R12 to R14, diodes D4 and D5, and an output voltage sampling circuit.

[0109] The gate of the MOSFET Q1 is connected to the negative terminal of the Zener diode VZ2 and one end of the resistor R12; the other end of the resistor R12 serves as the first input terminal of the execution circuit, used to receive the delay protection voltage signal, the instantaneous protection voltage signal, and the amplified slope voltage signal; the drain of the MOSFET Q1 is connected to the positive terminal of the Zener diode VZ2 and then grounded; the source of the MOSFET Q1 is connected to the drain of the MOSFET Q2 via resistors R14 and R13 in series, and the drain of the MOSFET Q2 is also connected to a voltage source;

[0110] The gate of the MOSFET Q2 is connected to the common terminal of the resistors R14 and R13; the source of the MOSFET Q2 is connected to the positive terminal of the diode D4, and the negative terminal of the diode D4 serves as the output terminal of the execution circuit for outputting control signals.

[0111] The input terminal of the output voltage sampling circuit serves as the second input terminal of the execution circuit, used to receive the output voltage of the main power circuit; the output terminal of the output voltage sampling circuit is connected to the positive terminal of diode D5, and the negative terminal of diode D5 is connected to the negative terminal of diode D4.

[0112] Among them, the gate saturation conduction drive voltage of MOSFET Q1 is equal to the control threshold.

[0113] Specifically, MOSFET Q1 is an N-channel enhancement-mode MOSFET, and MOSFET Q2 is a P-channel enhancement-mode MOSFET. The source-drain breakdown voltage of MOSFETs Q1 and Q2 is greater than the voltage source voltage by 15V; the reverse breakdown voltage of diodes D4 and D5 is greater than the voltage source voltage by 15V.

[0114] Specifically, resistor R12 has a resistance of 10Ω and is used to suppress the oscillation of the gate drive voltage of MOSFET Q1. Zener diode VZ2 is used to provide overvoltage protection for the gate of MOSFET Q1. The Zener voltage regulation value of Zener diode VZ2 is V. z2 Determined by the formula below

[0115]

[0116] In the formula, V Q1-GS(th) V is the gate saturation drive voltage for MOSFET Q1. Q1-GS(max) It is the maximum voltage that the gate of MOSFET Q1 can withstand.

[0117] The resistance of resistor R14 is 10kΩ, and the resistance of resistor R13 is determined according to the following formula:

[0118]

[0119] In the formula, V Q2-GS(th) This is the gate saturation drive voltage for MOSFET Q2.

[0120] The working principle is as follows:

[0121] When the delayed overvoltage protection signal is high, or the instantaneous overvoltage protection value is a threshold signal, or the amplified slope voltage signal is greater than or equal to the control threshold, the received signal is greater than or equal to the gate saturation drive voltage of MOSFET Q1, and Q1 is saturated and turned on. Consequently, resistor R14 is connected to the source terminal of MOSFET Q1 at the same level as ground. Then, through the voltage divider network formed by resistors R14 and R13, the gate voltage of MOSFET Q2 is pulled low, causing the gate-source voltage of MOSFET Q2 to reach its gate saturation drive voltage, and MOSFET Q2 is saturated and turned on. The voltage is output through the drain of MOSFET Q2 and diode D4 to the output voltage feedback comparison terminal FB of control chip U1. This voltage is higher than the sampling voltage of the output voltage sampling circuit (which is 5V or 2.5V in steady state), and diode D5 is reverse-biased and cut off. Since the reference voltage of the comparator inside control chip U1 is 5V or 2.5V, the voltage at the output voltage feedback comparison terminal FB of control chip U1 is greater than the reference voltage inside the control chip. Control chip U1 will turn off the output drive control signal, thereby turning off the switching transistor inside the main power circuit and cutting off the power output.

[0122] When the delayed overvoltage protection signal is low, or the instantaneous overvoltage protection value is low, or the amplified slope voltage signal is less than the control threshold, the received signal is less than the gate saturation drive voltage of MOSFET Q1. MOSFETs Q1 and Q2 are both turned off. After the output voltage is processed by the output voltage sampling circuit, the output voltage sampling signal is sent to the output voltage feedback comparison terminal FB of the control chip U1 via diode D5, thereby realizing closed-loop control of the output voltage.

[0123] Compared with existing technologies, this embodiment provides an output voltage protection control circuit for DC power supplies. By setting a maximum output voltage rise rate control circuit, it achieves precise control of the maximum output voltage rise rate. After the power supply starts up, it can continuously monitor the maximum output voltage rise rate and perform corresponding control to ensure that the output voltage rise rate of the power supply meets the requirements of the electrical equipment. The control effect is better and the range is wider. Furthermore, the threshold of the maximum output voltage rise rate, as well as the delay overvoltage protection value, delay time, and instantaneous overvoltage protection value of the delay protection circuit can be flexibly set, thereby meeting the usage requirements of various power supplies. It can be applied to the control circuits of various power supply devices, making it more applicable.

[0124] Those skilled in the art will understand that all or part of the processes of the methods described in the above embodiments can be implemented by a computer program instructing related hardware, and the program can be stored in a computer-readable storage medium. The computer-readable storage medium may be a disk, optical disk, read-only memory, or random access memory, etc.

[0125] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. An output voltage protection control circuit for a direct current power supply, characterized by, It includes a delay voltage protection circuit, an output voltage maximum rise slope control circuit, an execution circuit, a control chip, and a main power circuit; The delayed voltage protection circuit is used to receive the output voltage of the main power circuit, compare it with the preset delayed overvoltage protection value, and output a delayed protection voltage signal according to the comparison result. The maximum rise slope control circuit for the output voltage is used to receive the output voltage of the main power circuit, convert the rise slope of the output voltage into a slope voltage signal, sample and amplify the slope voltage signal, and then output it. The execution circuit is used to compare the delay protection voltage signal and the amplified slope voltage signal with the set control threshold, and output a control signal according to the comparison result. The control chip is used to output a drive control signal to the main power circuit according to the received control signal, so as to perform power control of the main power circuit. The maximum rise slope control circuit for the output voltage includes a current sensor CT1, a capacitor C1, resistors R7~R11, and operational amplifiers P2 and P3. The same-name terminal of the primary winding of the current sensor CT1 is connected to one end of the capacitor C1, and the opposite-name terminal is grounded; the other end of the capacitor C1 serves as the input terminal of the maximum rise slope control circuit of the output voltage, and is used to receive the output voltage of the main power circuit. The same-name terminal of the secondary winding of the current sensor CT1 is connected to one end of resistor R7 and one end of resistor R8; the other end of resistor R8 is connected to one end of resistor R9 and the non-inverting input terminal of operational amplifier P2; the other end of resistor R9 is grounded; the opposite-name terminal of the secondary winding of the current sensor CT1 is connected to the other end of resistor R7 and one end of resistor R10; the other end of resistor R10 is connected to one end of resistor R11 and the inverting input terminal of operational amplifier P2; the other end of resistor R11 is connected to the output terminal of operational amplifier P2. The output terminal of the operational amplifier P2 is also connected to the non-inverting input terminal of the operational amplifier P3; The inverting input terminal and the output terminal of the operational amplifier P3 are shorted together and used as the output terminal of the maximum rise slope control circuit of the output voltage, which is used to output the amplified slope voltage signal.

2. The output voltage protection control circuit for a DC power supply according to claim 1, characterized by, The delayed voltage protection circuit outputs the delayed protection voltage signal in the following manner: If the output voltage is greater than the preset overvoltage protection value and the duration is greater than the preset delay time, the output delay protection voltage signal is a high-level signal and is maintained until the control circuit is powered off, reset, and restarted; otherwise, the output delay protection voltage signal is a low-level signal; wherein, the high-level signal voltage value is greater than the control threshold and the low-level signal voltage value is less than the control threshold.

3. The output voltage protection control circuit for a DC power supply according to claim 2, characterized in that, It also includes a transient voltage protection circuit; The instantaneous voltage protection circuit is used to receive the output voltage of the main power circuit, compare it with the preset instantaneous overvoltage protection value, and output an instantaneous protection voltage signal according to the comparison result; The execution circuit is also used to compare the instantaneous protection voltage signal with the set control threshold and output a control signal based on the comparison result.

4. The output voltage protection control circuit for a DC power supply according to claim 3, characterized in that, The instantaneous voltage protection circuit outputs the instantaneous protection voltage signal in the following manner: If the output voltage is greater than the preset instantaneous overvoltage protection value, the output instantaneous protection voltage signal is a threshold signal; otherwise, the output instantaneous protection voltage signal is a low-level signal; wherein, the threshold signal is equal to the set control threshold.

5. The output voltage protection control circuit for a DC power supply according to claim 4, characterized in that, The execution circuit is equipped with an output voltage sampling circuit for sampling the output voltage of the main power circuit to obtain an output voltage sampling signal; the execution circuit outputs control signals in the following manner: When the value of any one of the delayed protection voltage signal, instantaneous protection voltage signal, or amplified slope voltage signal is greater than or equal to the control threshold, the output control signal is a high-level signal. At this time, the control chip shuts off the output drive control signal, and the main power circuit stops working. Otherwise, the output control signal is the output voltage sampling signal. In this case, the control chip outputs a drive control signal based on the received output voltage sampling signal, and the main power circuit works normally.

6. The output voltage protection control circuit for a DC power supply according to claim 2, characterized in that, The delay voltage protection circuit includes an operational amplifier P1, diodes D1, D2 and D6, resistors R1 and R2, capacitor C2 and a reference voltage circuit. The non-inverting input of operational amplifier P1 is connected to the cathode of diode D1, the anode of diode D6, one end of capacitor C2, one end of resistor R1, and one end of resistor R2; the other end of capacitor C2 is connected to the other end of resistor R2 and then grounded; the cathode of diode D6 is connected to the other end of resistor R1 and serves as the input of the delay voltage protection circuit, used to receive the output voltage of the main power circuit; the anode of diode D1 is connected to the output of operational amplifier P1. The inverting input terminal of the operational amplifier P1 is connected to the reference voltage circuit to receive the reference voltage output by the reference voltage circuit. The output terminal of the operational amplifier P1 is also connected to the positive terminal of the diode D2, and the negative terminal of the diode serves as the output terminal of the delay voltage protection circuit, used to output the delay protection voltage signal.

7. The output voltage protection control circuit for a DC power supply according to claim 3, characterized in that, The execution circuit includes MOSFETs Q1 and Q2, Zener diode VZ2, resistors R12 to R14, diodes D4 and D5, and an output voltage sampling circuit. The gate of the MOSFET Q1 is connected to the negative terminal of the Zener diode VZ2 and one end of the resistor R12; the other end of the resistor R12 serves as the first input terminal of the execution circuit, used to receive the delay protection voltage signal, the instantaneous protection voltage signal, and the amplified slope voltage signal; the drain of the MOSFET Q1 is connected to the positive terminal of the Zener diode VZ2 and then grounded; the source of the MOSFET Q1 is connected to the drain of the MOSFET Q2 via resistors R14 and R13 in series, and the drain of the MOSFET Q2 is also connected to a voltage source; The gate of the MOSFET Q2 is connected to the common terminal of the resistors R14 and R13; the source of the MOSFET Q2 is connected to the positive terminal of the diode D4, and the negative terminal of the diode D4 serves as the output terminal of the execution circuit for outputting control signals. The input terminal of the output voltage sampling circuit serves as the second input terminal of the execution circuit, used to receive the output voltage of the main power circuit; the output terminal of the output voltage sampling circuit is connected to the positive terminal of diode D5, and the negative terminal of diode D5 is connected to the negative terminal of diode D4.

8. The output voltage protection control circuit for a DC power supply according to claim 3, characterized in that, The instantaneous voltage protection circuit includes a Zener diode VZ1, a resistor R3, and a diode D3; The negative terminal of the Zener diode VZ1 serves as the input terminal of the instantaneous voltage protection circuit, used to receive the output voltage of the main power circuit; the positive terminal of the Zener diode VZ1 is connected to one end of the resistor R3 and the positive terminal of the diode D3 respectively; the other end of the resistor R3 is grounded; the negative terminal of the diode D3 serves as the output terminal of the instantaneous voltage protection circuit, used to output the instantaneous protection voltage signal.

9. The output voltage protection control circuit for a DC power supply according to claim 6, characterized in that, The reference voltage circuit includes a voltage reference chip Z1, a capacitor C3, and resistors R4~R6; The cathode of the voltage reference chip Z1 serves as the output terminal of the reference voltage circuit, used to output a reference voltage to the delay voltage protection circuit. The reference terminal of the voltage reference chip Z1 is connected to one end of resistor R4 and one end of resistor R5; the other end of resistor R4 is connected to the cathode of the voltage reference chip Z1, one end of resistor R6, and one end of capacitor C3. The other end of resistor R5 is connected to the anode of voltage reference chip Z1 and the other end of capacitor C3 and then grounded; the other end of resistor R6 is connected to a voltage source.

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