Input power failure maintaining circuit with shutdown oscillation preventing function

Abstract

The invention relates to an input power-down holding circuit with a shutdown oscillation preventing function. The input power-down holding circuit comprises an input voltage sampling and comparing circuit, an energy storage circuit voltage sampling and comparing circuit, a switching circuit and an energy storage circuit. The input voltage sampling circuit samples an input voltage and compares the input voltage with a reference voltage, and if the input voltage is not greater than a set value, the switching circuit and the energy storage circuit are controlled to be turned on to supply power to the input so as to ensure the stability of the output voltage of the main circuit; the energy storage circuit voltage sampling circuit samples voltage on the energy storage circuit and compares the voltage with reference voltage, and if the voltage of the energy storage circuit is not larger than a set value, the switching circuit is controlled to be switched off so as to prevent the energy storage circuit from being switched off when the voltage on the energy storage circuit is lower than an undervoltage point. Output oscillation is caused by repeated restart of a main circuit due to voltage rebound caused by the characteristics of an energy storage circuit. When the power supply system is powered off, the standby energy storage circuit can supply power in time, and stability of output voltage is guaranteed; when the system is normally shut down, the output voltage can be normally and stably powered off.

Description

Technical Field

[0001] The invention relates to the technical field of power supply, and in particular to an input power-off maintenance circuit with a function of preventing shutdown oscillation. Background Art

[0002] As a DC / DC converter of the secondary power supply of the system, the power supply component is widely used in electronic systems such as aerospace, aviation, ships, weapons, electronics, railways, communications, medical electronics, and industrial automation equipment. Especially in the field of aviation, when the power supply system is undervoltage for a short time or even the power supply is interrupted, if the power supply component can output normally, it is required that the power supply component has an internal integrated circuit with low-voltage surge resistance and power-off maintenance. The power-off maintenance circuit must ensure that the backup energy storage circuit can be powered on in time when the power supply system is powered off, and that the output voltage can be powered off normally and smoothly when the power is shut down normally, so the design of the power-off maintenance circuit becomes critical.

[0003] Although the existing input power-off maintenance circuit has shown certain effects in some applications, it still has some shortcomings in actual use. These shortcomings are mainly reflected in the following aspects:

[0004] (1) Slow response

[0005] The power-off maintenance circuit in the prior art usually relies on digital controllers or complex feedback mechanisms to detect power supply anomalies and respond. This design may cause delays in the detection and switching process, especially in application scenarios that require fast response (such as avionics), where any delay may affect the normal operation of the system.

[0006] (2) High complexity

[0007] Many existing solutions introduce a large number of components and complex control logic to achieve multiple functions (such as overvoltage protection, undervoltage lockout, etc.). Due to the complex circuit structure, once a problem occurs, it becomes difficult to troubleshoot and repair, which increases maintenance costs and time. This not only increases costs, but also increases the probability of failure, reducing system reliability and maintenance convenience.

[0008] (3) Limitations in specific application scenarios

[0009] Some existing technologies are only suitable for systems of a certain type or power level, and are difficult to be widely used in different fields (such as aerospace, communication base stations, medical instruments, etc.). In addition, there is insufficient support for the demand for multifunctional components, which cannot flexibly adapt to a variety of working conditions.

[0010] In summary, the existing input power-off maintenance circuit has many shortcomings in terms of reaction speed, complexity, scope of application and maintenance convenience. These problems not only affect the reliability of the system, but also increase the cost of development and maintenance. Therefore, it is necessary to develop a simpler, more efficient, faster-responding and more stable power-off maintenance circuit to meet a wider range of application needs. Summary of the invention

[0011] The purpose of the present invention is to provide an input power-off maintenance circuit with the function of preventing shutdown oscillation. The circuit can solve the shortcomings of the prior art. When the power supply system has a short-term undervoltage or even power outage, the power supply component can output normally, and when the power is shut down normally, the power supply component can be powered off normally and smoothly.

[0012] To achieve the above object, the present invention adopts the following technical solutions:

[0013] An input power-off maintenance circuit with a function of preventing shutdown oscillation comprises a main circuit, an input voltage sampling and comparison circuit, a switch circuit, an energy storage circuit voltage sampling and comparison circuit and an energy storage circuit.

[0014] The external input power supply is used to power the main circuit, and the main circuit forms the voltage output required by the system through internal power conversion; the external input power supply also charges the energy storage circuit. After the energy storage circuit is fully charged, the energy storage circuit is automatically disconnected from the external input power supply, and the energy storage circuit is in a standby state. The input voltage sampling and comparison circuit collects the input voltage of the external input power supply, compares it with the internal reference voltage VREF1, and determines the on-off of the switch circuit. The energy storage circuit voltage sampling and comparison circuit collects the voltage on the energy storage circuit, compares it with the internal reference voltage VREF2, and determines the on-off of the switch circuit. The switch circuit is used to connect the energy storage circuit and the main circuit, receive the output signals of the input voltage sampling and comparison circuit and the energy storage circuit voltage sampling and comparison circuit, and determine the on-off of the connection between the energy storage circuit and the main circuit according to the two output signals.

[0015] As a further improvement of the above technical solution, the input voltage sampling and comparison circuit includes a comparator N1, a diode V1, a resistor R1, a resistor R2, a resistor R3, a resistor R4 and a filter capacitor C1; the first end of the resistor R1 is connected to an external input power supply, the second end is connected to the first end of the resistor R2, and the second end of the resistor R2 is grounded; the first end of the resistor R2 is connected to the in-phase input end of the comparator N1; the filter capacitor C1 is connected in parallel to the two ends of the resistor R2; the resistor R1 and the resistor R2 are connected in series to divide the voltage, and the connection node between the two is connected to the comparator N1 The inverting input terminal of the comparator N1 is connected to the reference voltage VREF1, the first end of the resistor R3 is connected to the inverting input terminal of the comparator N1, and the second end of the resistor R3 is connected to the output terminal of the comparator N1; the first end of the resistor R4 is connected to the output terminal of the comparator N1, and the second end of the resistor R4 is connected to the power supply VCC; the anode of the diode V1 is connected to the output terminal of the comparator N1 and the second end of the resistor R3, and the cathode of the diode V1 is connected to the input terminal of the switch circuit as the output terminal of the input voltage sampling and comparison circuit.

[0016] As a further improvement of the above technical solution, the resistor R1 and the resistor R2 sample the input voltage of the external input power supply, and compare the input voltage with the reference voltage VREF1 through the comparator N1; when the input voltage drops to the set value, the comparator N1 outputs a low level.

[0017] As a further improvement of the above technical solution, the switch circuit includes a MOS tube V3, a triode V4, a diode V5, a PMOS tube V6, a diode V7, a resistor R5, a resistor R10, a resistor R11, a resistor R12 and a resistor R13; the base of the MOS tube V3 serves as the input end of the switch circuit, the collector of the MOS tube V3 is connected to the first end of the resistor R10, the second end of the resistor R10 is connected to the first end of the resistor R11, and the second end of the resistor R11 is connected to the output end of the energy storage circuit; the first end of the resistor R5 is connected to the base of the MOS tube V3, and the second end of the resistor R5 is grounded; the emitter of the MOS tube V3 is grounded; the base of the triode V4 is connected to the node between the resistor R10 and the resistor R11, and the emitter of the triode V4 is connected to the output end of the energy storage circuit 5. , the collector of the transistor V4 is connected to the first end of the resistor R13, and the second end of the resistor R13 is grounded; the first end of the resistor R13 is connected to the first end of the resistor R12, and the second end of the resistor R12 is connected to the output end of the energy storage circuit 5; the anode of the diode V5 is connected to the collector of the transistor V4, and the cathode of the diode V5 is connected to the output end of the energy storage circuit 5; the collector of the transistor V4 is connected to the gate of the PMOS tube V6, and the emitter of the transistor V4 is connected to the source of the PMOS tube V6; the cathode of the diode V5 is connected to the source of the PMOS tube V6, and the anode of the diode V5 is connected to the gate of the PMOS tube V6; the source of the PMOS tube V6 is connected to the output end of the energy storage circuit 5; the drain of the PMOS tube V6 is connected to the anode of the diode V7, and the cathode of the diode V7 is connected to the external power supply input end.

[0018] As a further improvement of the above technical solution, when the MOS tube V3 is turned on, the resistors R11 and R10 form a voltage divider for the energy storage voltage output by the energy storage circuit, so that the transistor V4 is turned on, thereby pulling the gate-source voltage Vgs of the PMOS tube V6 to 0V, the PMOS tube V6 is turned off, and the energy storage circuit stops supplying power to the main circuit; when the MOS tube V3 is turned off, the transistor V4 is turned off due to the lack of driving current, the resistors R12 and R13 form a voltage divider for the energy storage voltage output by the energy storage circuit, the PMOS tube V6 is turned on, and the energy storage circuit starts to supply power to the main circuit 1.

[0019] As a further improvement of the above technical solution, the resistor R10 is a voltage-dividing resistor; the MOS tube V3 is an N-type MOS tube; the transistor V4 is a PNP-type transistor; the diode V7 is a Schottky diode; the resistor R12 and the resistor R13 are voltage-dividing resistors.

[0020] As a further improvement of the above technical solution, the energy storage circuit voltage sampling and comparison circuit includes a comparator N2, a diode V2, a resistor R6, a resistor R7, a resistor R8, a resistor R9 and a filter capacitor C2; the first end of the resistor R6 is connected to the output end of the energy storage circuit, the second end of the resistor R6 is connected to the first end of the resistor R7, and the second end of the resistor R7 is grounded; the capacitor C2 is connected in parallel to the two ends of the resistor R7; the non-inverting input end of the comparator N2 is connected to the reference voltage VREF2, and the inverting input end of the comparator N2 is connected between the resistor R6 and the resistor R7; the resistor R6 and the resistor R7 are connected in series for voltage division; the first end of the resistor R8 is connected to the in-phase input end of the comparator N2, and the second end of the resistor R8 is connected to the output end of the comparator N2; the anode of the diode V2 is connected to the output end of the comparator N2, and the cathode of the diode V2 is connected to the input end of the switch circuit as the output end of the energy storage voltage sampling and comparison circuit; the first end of the resistor R9 is connected to the node between the output end of the comparator N2 and the diode V2, and the second end of the resistor R9 is connected to the power supply VCC.

[0021] As a further improvement of the above technical solution, the resistor R6 and the resistor R7 collect the energy storage voltage of the energy storage circuit and compare it with the reference voltage VREF2; when the energy storage voltage drops to a set value, the comparator N2 outputs a high level, and the high level signal causes the energy storage circuit to stop supplying power to the main circuit through the switch circuit.

[0022] Compared with the prior art, the advantages of the present invention are:

[0023] The input power-off maintenance circuit with the function of preventing shutdown oscillation described in the present invention can supply power to the backup energy storage circuit in time when the power supply system loses power, thereby ensuring the stability of the output voltage; when the system shuts down normally, the output voltage can be powered off normally and smoothly. The circuit has a simple structure, few components, and is a pure analog device with a fast response speed, providing a good design solution for multifunctional components with such needs. The present invention solves the problem that the backup power supply cannot be quickly enabled when the power supply system suddenly loses power and the main circuit oscillates when the power is normally cut off. The switching speed between the power supply and the backup power supply is fast, and the power can be turned off smoothly. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a circuit block diagram of an input power-off maintenance circuit with a shutdown oscillation prevention function in the present invention;

[0025] Figure 2 It is a circuit principle diagram of an input power-off maintenance circuit with a shutdown oscillation prevention function in the present invention;

[0026] Figure 3The waveform of the output voltage waveform and the intermediate bus voltage waveform of the input power-off maintenance circuit with the function of preventing shutdown oscillation described in the present invention Figure 1 ;

[0027] Figure 4 The waveform of the output voltage waveform and the intermediate bus voltage waveform of the input power-off maintenance circuit with the function of preventing shutdown oscillation described in the present invention Figure 2 .

[0028] in:

[0029] 1. Main circuit, 2. Input voltage sampling and comparison circuit, 3. Switching circuit, 4. Energy storage circuit voltage sampling and comparison circuit, 5. Energy storage circuit. DETAILED DESCRIPTION

[0030] The present invention will be further described below in conjunction with the accompanying drawings:

[0031] like Figure 1 An input power-off maintenance circuit with a shutdown oscillation prevention function is shown, and the input power-off maintenance circuit includes a main circuit 1, an input voltage sampling and comparison circuit 2, a switch circuit 3, a tank circuit voltage sampling and comparison circuit 4, and a tank circuit 5. The input power-off maintenance circuit reduces the number of components and wiring through an integrated design, reduces the failure rate of the circuit, and reduces the volume and weight.

[0032] The external input power supply is used to power the main circuit 1, and the main circuit 1 forms the voltage output required by the system through internal power conversion. The external input power supply also charges the energy storage circuit 5. After being fully charged, the energy storage circuit 5 is automatically disconnected from the external input power supply to prevent the energy storage circuit from backflowing back to the external input power supply. After that, the energy storage circuit 5 is in a standby state. The input voltage sampling and comparison circuit 2 samples the input voltage through a sampling resistor and compares it with the internal reference voltage VREF1, thereby determining the on and off of the switch circuit 3. The energy storage circuit voltage sampling and comparison circuit 4 samples the voltage on the energy storage circuit through a sampling resistor and compares it with the internal reference voltage VREF2, thereby determining the on and off of the switch circuit 3. The switch circuit 3 is used to connect the energy storage circuit 5 and the main circuit 1, receive the output signals of the input voltage sampling and comparison circuit 2 and the energy storage circuit voltage sampling and comparison circuit 4, and determine whether to open or close the connection between the energy storage circuit and the main circuit according to the two output signals. The main circuit 1 is not limited to a specific circuit form, and can be a power source or a power supply after isolation.

[0033] like Figure 2As shown, the input voltage sampling and comparison circuit 2 includes a comparator N1, a diode V1, a resistor R1, a resistor R2, a resistor R3, a resistor R4 and a filter capacitor C1. The first end of the resistor R1 is connected to an external input power supply, the second end is connected to the first end of the resistor R2, and the second end of the resistor R2 is grounded; the first end of the resistor R2 is connected to the non-inverting input end of the comparator N1. The filter capacitor C1 is connected in parallel to both ends of the resistor R2. The resistor R1 and the resistor R2 are connected in series to divide the voltage, and the connection node of the two is connected to the non-inverting input end of the comparator N1. The inverting input end of the comparator N1 is connected to the reference voltage VREF1, the first end of the resistor R3 is connected to the non-inverting input end of the comparator N1, and the second end of the resistor R3 is connected to the output end of the comparator N1. The first end of the resistor R4 is connected to the output end of the comparator N1, and the second end of the resistor R4 is connected to the power supply VCC. The anode of the diode V1 is connected to the output end of the comparator N1 and the second end of the resistor R3 , and the cathode of the diode V1 is used as the output end of the input voltage sampling and comparison circuit 2 and is connected to the input end of the switch circuit 3 .

[0034] The working principle of the input voltage sampling and comparison circuit 2 is:

[0035] The input voltage of the external input power supply is sampled by resistor R1 and resistor R2, and the input voltage is compared with the reference voltage VREF1 through comparator N1. When the input voltage drops to the set value, comparator N1 outputs a low level. Resistor R3 and comparator N1 form a hysteresis comparator to increase the anti-shake function of the input voltage.

[0036] like Figure 2As shown, the switch circuit 3 includes a MOS transistor V3, a triode V4, a diode V5, a PMOS transistor V6, a diode V7, a resistor R5, a resistor R10, a resistor R11, a resistor R12 and a resistor R13. The base of the MOS transistor V3 serves as the input end of the switch circuit 3, the collector is connected to the first end of the resistor R10, the second end of the resistor R10 is connected to the first end of the resistor R11, and the second end of the resistor R11 is connected to the output end of the energy storage circuit 5. The first end of the resistor R5 is connected to the base of the MOS transistor V3, and the second end of the resistor R5 is grounded. The emitter of the MOS transistor V3 is grounded. The base of the triode V4 is connected to the node between the resistor R10 and the resistor R11, the emitter is connected to the output end of the energy storage circuit 5, the collector is connected to the first end of the resistor R13, and the second end of the resistor R13 is grounded. The first end of the resistor R13 is connected to the first end of the resistor R12, and the second end of the resistor R12 is connected to the output end of the energy storage circuit 5. The anode of the diode V5 is connected to the collector of the transistor V4, and the cathode is connected to the output end of the energy storage circuit 5. The collector of the transistor V4 is connected to the gate of the PMOS tube V6, and the emitter of the transistor V4 is connected to the source of the PMOS tube V6. The cathode of the diode V5 is connected to the source of the PMOS tube V6, and the anode of the diode V5 is connected to the gate of the PMOS tube V6. The source of the PMOS tube V6 is connected to the output end of the energy storage circuit 5. The drain of the PMOS tube V6 is connected to the anode of the diode V7, and the cathode of the diode V7 is connected to the external power supply input end.

[0037] As a further improvement of the above technical solution, the resistor R10 is a voltage dividing resistor.

[0038] As a further improvement of the above technical solution, the MOS tube V3 is an N-type MOS tube.

[0039] As a further improvement of the above technical solution, the transistor V4 is a PNP transistor.

[0040] As a further improvement of the above technical solution, the diode V7 is a Schottky diode.

[0041] As a further improvement of the above technical solution, the resistor R12 and the resistor R13 are voltage-dividing resistors.

[0042] The working principle of the switch circuit 3 is:

[0043] When the MOS tube V3 is turned on, the resistors R11 and R10 divide the energy storage voltage output by the energy storage circuit 5, so that the PNP transistor V4 is turned on, thereby pulling the gate-source voltage Vgs of the PMOS tube V6 to about 0V, the PMOS tube V6 is turned off, and the energy storage circuit 5 stops supplying power to the main circuit 1. Conversely, when the MOS tube V3 is turned off, the PNP transistor V4 is turned off due to the lack of driving current, and the resistors R12 and R13 divide the energy storage voltage output by the energy storage circuit 5. By setting the ratio of the resistor R12 to the resistor R13, the energy storage voltage range is taken into account, the PMOS tube V6 is turned on, and the energy storage circuit 5 starts to supply power to the main circuit 1. The Schottky diode V7 is used to prevent the voltage of the main circuit 1 from affecting the energy storage circuit 5 through the parasitic diode of the PMOS tube V6. In the design of the switch circuit 3, a combination of MOS tube V3, triode V4 and PMOS tube V6, as well as matching resistors, is used to achieve precise control of the connection between the energy storage circuit and the main circuit. This design not only improves the response speed of the circuit, but also simplifies the circuit design by reducing the number of components. The energy storage circuit 5 allows rapid switching to the energy storage circuit power supply when the external input power supply is interrupted, ensuring the stability of the output voltage of the main circuit. This design effectively solves the shutdown oscillation problem caused by input power failure and improves the high stability and high reliability of the circuit.

[0044] like Figure 2 As shown, the energy storage circuit voltage sampling and comparison circuit 4 includes a comparator N2, a diode V2, a resistor R6, a resistor R7, a resistor R8, a resistor R9 and a filter capacitor C2.

[0045] The first end of the resistor R6 is connected to the output end of the energy storage circuit 5, the second end of the resistor R6 is connected to the first end of the resistor R7, and the second end of the resistor R7 is grounded. The capacitor C2 is connected in parallel to the two ends of the resistor R7. The non-inverting input end of the comparator N2 is connected to the reference voltage VREF2, and the inverting input end of the comparator N2 is connected to the node between the resistor R6 and the resistor R7. The resistor R6 and the resistor R7 are connected in series for voltage division. The first end of the resistor R8 is connected to the non-inverting input end of the comparator N2, and the second end of the resistor R8 is connected to the output end of the comparator N2. The anode of the diode V2 is connected to the output end of the comparator N2, and the cathode of the diode V2 is connected to the input end of the switch circuit 3 as the output end of the energy storage voltage sampling and comparison circuit 4. The first end of the resistor R9 is connected to the node between the output end of the comparator N2 and the diode V2, and the second end of the resistor R9 is connected to the power supply VCC.

[0046] The working principle of the energy storage circuit voltage sampling and comparison circuit 4 is:

[0047] The resistor R6 and the resistor R7 sample the energy storage voltage of the energy storage circuit 5 and compare it with the reference voltage VREF2. When the energy storage voltage drops to the set value, the comparator N2 outputs a high level, and the high level signal causes the energy storage circuit 5 to stop supplying power to the main circuit through the switch circuit 3. This design can prevent the main circuit from repeatedly restarting and causing output oscillation due to the voltage rebound caused by the characteristics of the energy storage circuit itself after the energy storage circuit is shut down when the voltage on the energy storage circuit is lower than the undervoltage point.

[0048] The input voltage sampling and comparison circuit 2 and the energy storage circuit voltage sampling and comparison circuit 4 realize accurate sampling and comparison of the input voltage and the energy storage circuit voltage by using comparators N1 and N2 and the corresponding resistors and capacitors, thereby effectively controlling the on and off of the switch circuit. This design improves the accuracy of voltage sampling and reduces the circuit instability problem caused by voltage fluctuations.

[0049] The working principle of the input power-off maintenance circuit with the function of preventing shutdown oscillation described in the present invention is:

[0050] After the external input power supply is powered on, one path is connected to the main circuit 1, and after the power conversion inside the main circuit 1, the required voltage output is formed. The other path of the external input power supply supplies power to the energy storage circuit 5, which can be an energy storage capacitor or an independent converter (the energy storage capacitor is used as an example in this embodiment). The energy storage circuit 5 converts the supply voltage of the external input power supply to a higher voltage, and then charges the energy storage capacitor. Because the energy stored in the energy storage capacitor in the energy storage circuit 1 is equal to 1 / 2CU2, when the capacity is constant, the higher the voltage, the more energy is stored. After the energy storage capacitor is fully charged, it is in a standby state.

[0051] When the power supply system experiences an undervoltage surge or even a power outage, the comparator N1 in the input voltage sampling and comparison circuit 2 is reversed, and the voltage at the in-phase input terminal of the comparator N1 is less than the voltage at the inverting input terminal, and the comparator N1 outputs a low level. At this time, the voltage of the energy storage circuit 5 in the standby state is relatively high, and the voltage at the inverting input terminal of the comparator N2 is also higher than its in-phase input terminal, so the comparator N2 also outputs a low level. After the low level passes through the diode V1 and the diode V2 "OR", the low level is output, the MOS tube V3 is turned off, and the PNP transistor V4 is turned off due to the lack of base current. After the energy storage voltage is divided by the resistor R12 and the resistor R13, the source voltage of the PMOS tube V6 is lower than the gate voltage, and when the PMOS tube reaches the opening threshold, the PMOS tube V6 is turned on, thereby connecting the energy storage circuit 5 and the main circuit 1, so that the main circuit 1 will not lose power due to input undervoltage or input interruption.

[0052] The interruption maintenance time of main circuit 1 is given by the formula It is calculated, where C is the capacity of the energy storage capacitor in the energy storage circuit 5, U1 is the voltage of the energy storage capacitor before discharge, U2 is the voltage of the energy storage capacitor after discharge, and P is the input power of the main power circuit, that is, the input power of the main circuit.

[0053] When the power supply system is shut down normally, the input voltage sampling and comparison circuit 2 will also sample the input power failure, and the energy storage circuit 5 will be turned on to supply power to the main circuit 1, so that the main circuit 1 will be turned off after a delay. As the charging progresses, the voltage of the energy storage circuit 5 becomes lower and lower. When the voltage on the energy storage circuit 5 is lower than the undervoltage point and is turned off, the voltage rebounds due to the characteristics of the energy storage circuit 5 itself, causing the main circuit 1 to restart repeatedly when shutting down, resulting in output oscillation. The energy storage circuit voltage sampling and comparison circuit 4 samples the voltage on the energy storage circuit 5 through the sampling resistors R6 and R7, and compares it with the internal reference voltage VREF2. When the voltage of the energy storage circuit 5 reaches the set value, the voltage at the in-phase input terminal of the comparator N2 is higher than the voltage at the inverting input terminal, and the comparator N2 outputs a high level, thereby turning on the MOS tube V3, and the PNP transistor V4 is also turned on due to the base current, and the gate-source voltage of the PMOS tube V6 is clamped to about 0V, and the PMOS tube V6 is turned off, and the energy storage circuit stops supplying power to the main circuit, and the main circuit is also shut down normally due to no power supply.

[0054] Taking an input voltage of 10-40V, a main circuit output of 24V, and a storage circuit voltage of 36V as an example, the performance of the input power-off maintenance circuit with a shutdown oscillation prevention function of the present invention is described.

[0055] When the input power is off, the output voltage waveform and the intermediate bus voltage waveform are as follows Figure 3 As shown, the green line represents the 28V input voltage, the yellow line represents the 24V output of the main circuit, and the blue line represents the midpoint bus voltage waveform. When the input voltage represented by the green line suddenly loses power, the intermediate bus voltage represented by the blue line follows the input voltage to lose power, the input voltage sampling and comparison circuit detects the input power failure, opens the control switch to allow the energy storage circuit to work, and the intermediate bus voltage rises rapidly to 36V. As the power supply continues, the energy storage capacitor voltage decreases linearly until the input voltage returns to normal, the input voltage sampling and comparison circuit closes the control switch to close the energy storage circuit, and the bus voltage returns to the 28V input voltage.

[0056] like Figure 4 As shown, the input voltage sampling and comparison circuit reacts very quickly. The power-off falling edge of the input voltage of the green line is 200uS, and the energy storage circuit can enter the power supply state within a few uS (the blue line is the intermediate bus voltage from 28V-36V).

[0057] In summary, the input power-off maintenance circuit with the function of preventing shutdown oscillation described in the present invention is suitable for power supply components that are maintained by undervoltage surges or input power supply interruptions. This circuit can quickly respond to input power failures to ensure the stability of the output voltage of the main circuit, while effectively solving the shutdown output voltage oscillation, ensuring the high stability and high reliability of the circuit. The circuit uses fewer devices and occupies less space, which is more conducive to the miniaturization design of multifunctional power supply components. The circuit design is independent of the main control unit and does not require the participation of additional programming devices. It realizes automatic detection of power-off signals and switches circuits to delay shutdown. This design is not only low-cost, but also improves the safety and reliability of the circuit due to its independence and simplicity.

[0058] The above-described embodiments are merely descriptions of preferred implementations of the present invention and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the scope of protection determined by the claims of the present invention.

Claims

1. An input power-off maintenance circuit with a function of preventing shutdown oscillation, characterized in that: The input power-off maintenance circuit comprises a main circuit (1), an input voltage sampling and comparison circuit (2), a switch circuit (3), an energy storage circuit voltage sampling and comparison circuit (4) and an energy storage circuit (5); The external input power supply supplies power to the main circuit (1), and the main circuit (1) forms a voltage output required by the system through internal power conversion; the external input power supply also charges the energy storage circuit (5), and after the energy storage circuit (5) is fully charged, the energy storage circuit (5) is automatically disconnected from the external input power supply, and the energy storage circuit (5) is in a standby state; The input voltage sampling and comparison circuit (2) collects the input voltage of the external input power supply, compares it with the internal reference voltage VREF1, and determines whether the switch circuit (3) is on or off; The energy storage circuit voltage sampling and comparison circuit (4) collects the voltage on the energy storage circuit (5), compares it with the internal reference voltage VREF2, and determines whether the switch circuit (3) is on or off; The switch circuit (3) is used to connect the energy storage circuit (5) and the main circuit (1), receive the output signals of the input voltage sampling and comparison circuit (2) and the energy storage circuit voltage sampling and comparison circuit (4), and determine the on / off of the connection between the energy storage circuit and the main circuit based on the two output signals.

2. The input power-off maintenance circuit with the function of preventing shutdown oscillation according to claim 1, characterized in that: The input voltage sampling and comparison circuit (2) comprises a comparator N1, a diode V1, a resistor R1, a resistor R2, a resistor R3, a resistor R4 and a filter capacitor C1; the first end of the resistor R1 is connected to an external input power supply, the second end is connected to the first end of the resistor R2, and the second end of the resistor R2 is grounded; the first end of the resistor R2 is connected to the in-phase input end of the comparator N1; the filter capacitor C1 is connected in parallel to both ends of the resistor R2; the resistor R1 and the resistor R2 are connected in series to divide the voltage, and the connection node of the two is connected to the in-phase input end of the comparator N1; The inverting input terminal of the comparator N1 is connected to a reference voltage VREF1; the first end of the resistor R3 is connected to the non-inverting input terminal of the comparator N1, and the second end of the resistor R3 is connected to the output terminal of the comparator N1; the first end of the resistor R4 is connected to the output terminal of the comparator N1, and the second end of the resistor R4 is connected to a power supply VCC; the anode of the diode V1 is connected to the output terminal of the comparator N1 and the second end of the resistor R3; the cathode of the diode V1 is used as the output terminal of the input voltage sampling and comparison circuit (2), and is connected to the input terminal of the switch circuit (3).

3. The input power-off maintenance circuit with the function of preventing shutdown oscillation according to claim 2, characterized in that: The resistor R1 and the resistor R2 sample the input voltage of the external input power supply, and compare the input voltage with the reference voltage VREF1 through the comparator N1; when the input voltage drops to a set value, the comparator N1 outputs a low level.

4. The input power-off maintenance circuit with shutdown oscillation prevention function according to claim 1, characterized in that: The switch circuit (3) comprises a MOS tube V3, a triode V4, a diode V5, a PMOS tube V6, a diode V7, a resistor R5, a resistor R10, a resistor R11, a resistor R12 and a resistor R13; the base of the MOS tube V3 serves as the input end of the switch circuit (3); the collector of the MOS tube V3 is connected to the first end of the resistor R10; the second end of the resistor R10 is connected to the first end of the resistor R11; the second end of the resistor R11 is connected to the output end of the energy storage circuit (5); the first end of the resistor R5 is connected to the base of the MOS tube V3; the second end of the resistor R5 is grounded; the emitter of the MOS tube V3 is grounded; the base of the triode V4 is connected to the node between the resistor R10 and the resistor R11; the emitter of the triode V4 is connected to the output end of the energy storage circuit 5; The collector of transistor V4 is connected to the first end of the resistor R13, and the second end of the resistor R13 is grounded; the first end of the resistor R13 is connected to the first end of the resistor R12, and the second end of the resistor R12 is connected to the output end of the energy storage circuit 5; the anode of the diode V5 is connected to the collector of the triode V4, and the cathode of the diode V5 is connected to the output end of the energy storage circuit 5; the collector of the triode V4 is connected to the gate of the PMOS tube V6, and the emitter of the triode V4 is connected to the source of the PMOS tube V6; the cathode of the diode V5 is connected to the source of the PMOS tube V6, and the anode of the diode V5 is connected to the gate of the PMOS tube V6; the source of the PMOS tube V6 is connected to the output end of the energy storage circuit 5; the drain of the PMOS tube V6 is connected to the anode of the diode V7, and the cathode of the diode V7 is connected to the external power supply input end.

5. The input power-off maintenance circuit with shutdown oscillation prevention function according to claim 4, characterized in that: When the MOS tube V3 is turned on, the resistors R11 and R10 form a voltage divider for the energy storage voltage output by the energy storage circuit (5), so that the triode V4 is turned on, thereby pulling the gate-source voltage Vgs of the PMOS tube V6 to 0V, the PMOS tube V6 is turned off, and the energy storage circuit (5) stops supplying power to the main circuit (1); when the MOS tube V3 is turned off, the triode V4 is turned off due to the lack of driving current, the resistors R12 and R13 form a voltage divider for the energy storage voltage output by the energy storage circuit (5), the PMOS tube V6 is turned on, and the energy storage circuit (5) starts supplying power to the main circuit 1.

6. The input power-off maintenance circuit with shutdown oscillation prevention function according to claim 4, characterized in that: The resistor R10 is a voltage-dividing resistor; the MOS tube V3 is an N-type MOS tube; the transistor V4 is a PNP-type transistor; the diode V7 is a Schottky diode; the resistor R12 and the resistor R13 are voltage-dividing resistors.

7. The input power-off maintenance circuit with the function of preventing shutdown oscillation according to claim 1, characterized in that: The energy storage circuit voltage sampling and comparison circuit (4) comprises a comparator N2, a diode V2, a resistor R6, a resistor R7, a resistor R8, a resistor R9 and a filter capacitor C2; The first end of the resistor R6 is connected to the output end of the energy storage circuit (5), the second end of the resistor R6 is connected to the first end of the resistor R7, and the second end of the resistor R7 is grounded; the capacitor C2 is connected in parallel to the two ends of the resistor R7; the non-inverting input end of the comparator N2 is connected to the reference voltage VREF2, and the inverting input end of the comparator N2 is connected to the node between the resistor R6 and the resistor R7; the resistor R6 and the resistor R7 are connected in series for voltage division; the first end of the resistor R8 is connected to the non-inverting input end of the comparator N2, and the second end of the resistor R8 is connected to the output end of the comparator N2; the anode of the diode V2 is connected to the output end of the comparator N2, and the cathode of the diode V2 is used as the output end of the energy storage voltage sampling and comparison circuit (4) and is connected to the input end of the switch circuit (3); the first end of the resistor R9 is connected to the node between the output end of the comparator N2 and the diode V2, and the second end of the resistor R9 is connected to the power supply VCC.

8. The input power-off maintenance circuit with shutdown oscillation prevention function according to claim 7, characterized in that: The resistor R6 and the resistor R7 collect the energy storage voltage of the energy storage circuit (5) and compare it with the reference voltage VREF2; when the energy storage voltage drops to a set value, the comparator N2 outputs a high level signal, and the high level signal causes the energy storage circuit (5) to stop supplying power to the main circuit (1) through the switch circuit (3).

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