Closed-loop voltage stabilizing circuit based on self-excited oscillation and design method

Abstract

This invention relates to a self-oscillating closed-loop voltage regulator circuit, comprising a self-oscillating circuit, a primary power supply undervoltage indicator circuit, a secondary power supply undervoltage indicator circuit, a key valid indicator circuit, a power amplifier circuit, and a boost control circuit. The self-oscillating circuit outputs a fixed-frequency reference square wave signal. Undervoltage, overvoltage, and key valid indicator signals are passed through an AND gate to output a variable-frequency square wave signal. This variable-frequency square wave signal is then passed through a complementary pull-up circuit to increase the driving capability. The complementary output variable-frequency square wave controls the boost circuit. When the battery is low or the secondary power supply is undervoltage, the output frequency of the self-oscillating circuit controls the switching of the boost circuit to achieve rapid voltage boost. When the battery and secondary power supply voltages are normal, the boost control circuit is shut down. This effectively ensures stable operation under normal control conditions and is particularly suitable for the automotive electronics industry.

Description

Technical Field

[0001] This invention belongs to the field of vehicle engine power management technology, and particularly relates to a closed-loop voltage regulator circuit and its design method based on self-excited oscillation. Background Technology

[0002] In the power management system of the vehicle engine electronic controller, the normal output of the secondary power supply during primary power undervoltage and fluctuations is a crucial performance indicator for the product's proper functioning. Ensuring the normal operation of the electronic controller is of great significance to the safety of the entire vehicle.

[0003] Existing methods, such as "A BOOT Boost IC Circuit with Precise Output Voltage Control," describe a method based on a BOOST boost chip and output voltage control circuit. However, since it only outputs a precise voltage through the IC without acquiring the output voltage to participate in the control of the boost circuit, it cannot achieve closed-loop control. Another method is "A Feedback Control Circuit and Power Management Module." The main components of this design include a sampling and analysis circuit, a comparator circuit, a switch control circuit, and the sampling and analysis circuit connected to a power management chip. This circuit cannot achieve simultaneous control of the duty cycle of multiple switching transistors, and the power management chip used is expensive and has low reliability.

[0004] In view of this, the present invention is hereby proposed. Summary of the Invention

[0005] The purpose of this invention is to provide a closed-loop voltage regulator circuit based on self-excited oscillation, which achieves reverse polarity protection and ensures normal operation of the product through power management, while also possessing strong anti-interference capabilities. The technical solution of this invention has many beneficial effects, as described below:

[0006] A closed-loop voltage regulator circuit based on self-excited oscillation includes a closed-loop voltage regulator circuit, a self-excited oscillation circuit, a boost control circuit, and a battery. The closed-loop voltage regulator circuit includes a primary power supply undervoltage indicator circuit, a secondary power supply undervoltage indicator circuit, a key enable indicator circuit, and a power amplifier circuit connected in sequence. The output of the closed-loop voltage regulator circuit is connected to the power amplifier circuit, and the output of the boost control circuit is also connected to the power amplifier circuit. The self-excited oscillation circuit includes an RC circuit and a Schmitt trigger, and the primary power supply undervoltage indicator circuit includes a comparator.

[0007] The self-excited oscillation circuit is connected to an RC circuit via a Schmitt trigger, and can output a square wave signal with a fixed period.

[0008] The primary power supply undervoltage indication circuit is used to collect the primary power supply voltage of the battery, and when the battery is depleted, causing the battery voltage to be lower than the normal operating voltage of the product, the comparator outputs a high level.

[0009] The secondary power supply undervoltage indicator circuit is used to collect the internal secondary power supply voltage of the product, suppress the instantaneous current of the secondary power supply voltage to the load, and avoid significant voltage fluctuations. When the voltage is lower than the normal operating voltage, the comparator outputs a high level.

[0010] The key enable indicator circuit is used to collect the key power supply voltage. When the power supply voltage of the key enable indicator circuit and the battery voltage are higher than the normal operating voltage, the comparator outputs a high level.

[0011] The boost control circuit is used to operate when the supply voltage of the primary power supply, the secondary power supply, and the key are not in the enabled state, causing the product to not meet the normal operating voltage. The boost control circuit stops operating when the supply voltage of the secondary power supply meets the requirements.

[0012] Compared with the prior art, the technical solution provided by the present invention has the following beneficial effects:

[0013] This invention relates to a self-oscillating closed-loop voltage regulator circuit designed to ensure the controller can operate normally under conditions where the battery is depleted or the primary power output is unstable during the vehicle engine startup process. This circuit guarantees the normal output of the controller's secondary power supply under these conditions, ensuring the controller's normal operation. Its design is simple, easy to implement, and can be widely applied in the field of power control for automotive electronic controllers. Attached Figure Description

[0014] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0015] Figure 1 This is a block diagram of a closed-loop voltage regulator circuit based on self-excited oscillation.

[0016] Figure 2 This is a circuit diagram for a closed-loop voltage regulator based on self-excited oscillation.

[0017] Figure 3 This is a circuit diagram of a self-excited oscillation circuit.

[0018] Figure 4 This is a circuit diagram for a primary power supply undervoltage indicator.

[0019] Figure 5 This is a circuit diagram for a secondary power supply undervoltage indicator.

[0020] Figure 6 Circuit diagram for key validity indicator;

[0021] Figure 7 Diagram of complementary power drive enable circuit;

[0022] Figure 8 This is a diagram of the boost control circuit. Detailed Implementation

[0023] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that, in the absence of conflict, the following embodiments and features in the embodiments can be combined with each other. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0024] It should be noted that various aspects of embodiments within the scope of the appended claims are described below. It will be apparent that the aspects described herein can be embodied in a wide variety of forms, and any particular structure and / or function described herein is merely illustrative. Based on this invention, those skilled in the art will understand that one aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, any number of aspects set forth herein can be used to implement the device and / or practice the method. Additionally, this device and / or method can be implemented using structures and / or functionalities other than one or more of the aspects set forth herein.

[0025] It should also be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. The drawings only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0026] Furthermore, specific details are provided in the following description to facilitate a thorough understanding of the examples. However, those skilled in the art will understand that aspects can be practiced without these specific details. To enable those skilled in the art to better understand the invention, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined as "first" and "second" may explicitly or implicitly include one or more of that feature. In the description of the invention, unless otherwise stated, "a plurality of" means two or more.

[0027] See Figures 1 to 8 The self-oscillating closed-loop voltage regulator circuit shown is suitable for the drive control of power amplifier circuits. It includes a closed-loop voltage regulator circuit, a self-oscillating circuit, a boost control circuit, and a battery. The closed-loop voltage regulator circuit includes a primary power supply undervoltage indicator circuit, a secondary power supply undervoltage indicator circuit, a key enable indicator circuit, and a power amplifier circuit connected in sequence. The output of the closed-loop voltage regulator circuit is connected to the power amplifier circuit, and the output of the boost control circuit is also connected to the power amplifier circuit. The self-oscillating circuit includes an RC circuit and a Schmitt trigger, and the primary power supply undervoltage indicator circuit includes a comparator.

[0028] The self-excited oscillation circuit is connected to a single RC circuit through a Schmitt trigger and is used as an oscillation circuit. It can output a square wave signal with a fixed period and participate in boost control.

[0029] The primary power supply undervoltage indicator circuit is used to collect the power supply voltage of the primary battery. When the battery is depleted and its voltage is lower than the normal operating voltage of the product, the comparator outputs a high level and participates in the boost control.

[0030] The secondary power supply undervoltage indication circuit is used to acquire the internal secondary power supply voltage of the product, suppress the instantaneous current supplied by the secondary power supply voltage to the load, and avoid significant voltage fluctuations. When the voltage is lower than the normal operating voltage, the comparator outputs a high level; it also participates in the boost control.

[0031] The key enable indicator circuit is used to collect the key power supply voltage. Since the key signal is connected to the battery through a switch, when the key signal is turned on, and when the power supply voltage of the key enable indicator circuit and the battery voltage are higher than the normal operating voltage, the comparator outputs a high level.

[0032] like Figure 2As shown, the boost control circuit operates when the primary and secondary power supply voltages, as well as the key, are not at the enable state, causing the product to fail to meet the normal operating voltage. The boost control circuit stops operating once the secondary power supply voltage meets the requirements. A self-excited oscillation circuit outputs a fixed-frequency reference square wave signal. Undervoltage, overvoltage, and key validity indicators are passed through an AND gate to output a variable-frequency square wave signal. This variable-frequency square wave signal is then passed through a complementary pull-up circuit to increase the driving capability. The complementary variable-frequency square wave output controls the boost circuit. When the battery is low or the secondary power supply is undervoltage, the output frequency of the self-excited oscillation circuit controls the switching of the boost circuit to achieve rapid voltage boost. When the battery and secondary power supply voltages are normal, the boost control circuit shuts down.

[0033] The optional or preferred implementations of each of the circuits described above are as follows:

[0034] The self-excited oscillation circuit is a closed-loop voltage-regulated circuit, such as... Figure 3 As shown, it includes resistor R1, capacitor C1, Schmitt trigger U5, Schmitt trigger U6, and Schmitt trigger U7, wherein:

[0035] One end of capacitor C1 is connected to the input pin of Schmitt trigger U5, and the other end is grounded;

[0036] One end of resistor R1 is connected to the input pin of Schmitt trigger U5, and the other end is connected to the output pin of Schmitt trigger U5. The output pin of Schmitt trigger U5 is connected to the input pin of Schmitt trigger U6, and the output pin of Schmitt trigger U6 is connected to the input pin of Schmitt trigger U7. The output signal of Schmitt trigger U7 is oscillated by the RC circuit to become a square wave signal of a fixed frequency. For example, by configuring R and C, it can output a square wave signal of 200kHz.

[0037] like Figure 4 The following is a primary power supply undervoltage indication circuit:

[0038] The components include transistor V2, capacitor C2, resistors R6, R7, R8, R9, R10, hysteresis resistor R11, resistor R12, comparator U1, and pull-up resistor R12, where:

[0039] The +24V MOS input of the primary power supply is connected to the emitter of transistor V2. The collector of transistor V2 is connected to resistors R6 and R8 in parallel, with one end of resistor R6 grounded. Resistor R8 is connected in parallel with resistor R7 and capacitor C2. One end of resistor R7 and capacitor C2 is grounded, and the other end serves as the inverting input of comparator U1. One end of resistor R9 supplies +5V, and the other end is connected in parallel with resistor R10 and hysteresis resistor R11. One end of resistor R10 is grounded, and one end of hysteresis resistor R11 is connected across the positive input of comparator U1. The other end is connected in series with pull-up resistor R12, with one end of resistor R12 providing +5V. The output of comparator U1 is connected to the output of pull-up resistor R12 to output an indication signal of the primary power supply undervoltage status.

[0040] Furthermore, the emitter of transistor V2 is connected to a +24V MOSFET, a resistor R5 is connected in parallel between the base and emitter of transistor V2, a resistor R4 is connected to the base of transistor V2, one end of resistor R4 is connected to the collector of NPN transistor V1, the emitter is grounded, a resistor R3 is connected in parallel between the base and emitter, and a resistor R2 is connected to the base. The output signal of resistor R2 is CPU-C1.

[0041] The primary power supply undervoltage indication circuit outputs a high level when the voltage is 10V below the normal operating voltage, and a low level when the voltage is 10V below the normal operating voltage. When the key valid signal outputs a high level, the primary power supply voltage is connected to the comparator. The +24V MOS voltage from the primary power supply is divided and enters the negative terminal of the comparator; the voltage divided by the selected 5V comparator voltage enters the positive terminal of the comparator. When the key signal is below 5V and the primary power supply is below 10V, the comparator outputs a low level; when the key signal is above 5V and the primary power supply is below 10V, the comparator outputs a low level; when the key signal is above 5V and the primary power supply is above 10V, the comparator outputs a high level.

[0042] Secondary power supply undervoltage indicator circuit

[0043] like Figure 5 As shown, it includes comparator U2, resistors 13, 14, 15, 16, and 17, capacitors C3 and C4, wherein:

[0044] The positive input of comparator U2 is connected to one end of resistor 15, and the other end of resistor 15 is connected to a +5V voltage. Resistor 15 is connected in parallel with resistor 16, capacitor C4, and resistor 17, with one end of resistor 16 and capacitor C4 sharing a common ground. One end of resistor 17 is connected to the positive input of comparator U2, and the other end is connected to the output of comparator U2. The output of comparator U2 is connected to pull-up resistor R18, and the input of pull-up resistor R18 is a +5V voltage. Using a secondary power supply, the undervoltage indication circuit outputs a high level when the voltage is below the normal operating voltage of 25V, and a low level when the voltage is below 25V. The secondary power supply (+24V_POST) is divided and enters the negative terminal of the comparator; a 5V reference voltage is divided and enters the positive terminal of the comparator. When the secondary power supply voltage is above 25V, the comparator outputs a low level; when the secondary power supply voltage is below 25V, the comparator outputs a high level.

[0045] Key enable indicator circuit

[0046] like Figure 6 As shown, it includes: comparator U3, resistor R21, resistor R19, resistor R23, and resistor R24, wherein:

[0047] The positive input of comparator U3 is connected to resistor R21. Resistor R22 and capacitor C5 are connected in parallel with resistor R21, and one end of resistor R22 and capacitor C5 are grounded. The key signal KEY is input to the input of resistor R21. Resistor R23 is set between the positive input and output of comparator U3, and resistor R24 ​​is connected to the output of comparator U3. The input of resistor R24 ​​is connected to +5V. The output of comparator U3 is pulled up to +5V by R25, and outputs a key valid indication signal.

[0048] Comparator U3's forward and reverse inputs are connected to resistor R19. Resistor R19's input is supplied with +5V. Resistor R20 and capacitor C6 are connected in parallel to R19's input, with one end of R20 and capacitor C6 sharing a common ground. A key-enabled indicator circuit is used; when the voltage is higher than 5V, the output is high after passing through the voltage comparator circuit; when the voltage is lower than 5V, the output is low after passing through the voltage comparator circuit.

[0049] As a specific implementation method provided in this case, it also includes logic circuits, such as... Figure 7As shown, the outputs of the self-excited oscillation circuit, the primary power supply undervoltage indicator circuit, the key enable indicator circuit, and the secondary power supply undervoltage indicator circuit are connected to the logic circuit to generate a variable frequency square wave. Using the key signal enable indicator circuit, when the key signal KEY is divided, it enters the positive terminal of the comparator; the reference voltage is 5V, divided, and then enters the positive terminal of the comparator; when the key supply voltage is higher than 5V, the comparator outputs a high level; when the key supply voltage is lower than 25V, the comparator outputs a low level.

[0050] Furthermore, the power amplifier circuit is used to increase the drive output current of the boost control circuit, including: resistor R26, PNP transistor V3 and NPN transistor V4. The emitters of transistor V3 and V4 are complementary, and the bases of transistor V3 and V4 are connected. Resistors R27 and R28 are respectively provided to pull the NPN transistor up to the power supply and the PNP transistor down to ground, thereby increasing the output drive current.

[0051] The collector of transistor V3 is supplied with a +5V DC power supply, and the collector of transistor V4 is grounded.

[0052] The output of the logic circuit is connected to the input of resistor R26, and the output of resistor R26 is connected to the output of resistor R27 and the input of resistor R28.

[0053] A square wave of fixed frequency, a primary power supply undervoltage indication signal, a secondary power supply undervoltage indication signal, and a key valid indication signal are input into the logic circuit. The output is a square wave of variable frequency. After being conditioned by a push-pull circuit composed of transistors V3 and V4, complementary output is achieved.

[0054] The square wave signal output by the self-excited oscillation, the undervoltage status indicator signal, the overvoltage status indicator signal, and the key valid indicator signal are output as variable frequency square wave signals through a 4-channel AND gate circuit. After passing through complementary pull-down and pull-up transistors to form a complementary output circuit, the drive current is increased to enable and disable the boost control circuit. When the self-excited oscillation square wave signal is high and the key signal is greater than 5V, the primary power supply is lower than 10V and the secondary power supply is lower than 25V, the boost control circuit is enabled; in other states, the boost state is disabled.

[0055] Furthermore, such as Figure 8 As shown, the boost control circuit includes an N-channel enhancement-mode MOSFET U4, capacitor C5, and capacitor C6, wherein:

[0056] The source of MOSFET U4 is grounded, its gate is connected to the signal conditioned by the push-pull circuit, and its drain is connected to the output of inductor L1 and the anode of power diode V5, respectively. The input of inductor L1 is the +24V MOSFET of the primary power supply, and it has a capacitor C5 grounded at one end. The cathode of power diode V5 receives the +24V POS signal, and it also has a capacitor C6 grounded at one end. The +24V MOSFET is connected in series with inductor L1, power diode V5, and the boosted +24V POS output, which is then connected to ground via C8. The gate of U4 receives the complementary output signal, serving as the control signal for the boost circuit.

[0057] When using the boost control circuit, when the primary power supply indicator circuit outputs a high level and the secondary power supply undervoltage indicator circuit outputs a high level, they, together with the self-excited oscillation circuit and logic, control the enable control signal of the boost circuit.

[0058] When either the primary power supply indicator circuit or the secondary power supply undervoltage indicator circuit outputs a low level, the boost circuit is disabled. The boost circuit controls the charging and discharging of the inductor through the enable control circuit to achieve voltage boost.

[0059] Secondly, a design method for a self-oscillating closed-loop voltage regulator circuit is provided. Using the self-oscillating closed-loop voltage regulator circuit described above, the design method includes:

[0060] Step 1: When the Schmitt trigger is configured with RC, a self-excited oscillation circuit is formed, which outputs a square wave signal with a fixed frequency. This parameter can be used to control the switching frequency of the boost circuit.

[0061] Step 2: Compare the primary power supply with the threshold value. If it is higher than the threshold value, output a low level to disable boost control. If it is lower than the threshold value, OR the secondary power supply, key power-on indicator signal and self-excited oscillation signal to enable boost control.

[0062] Step 3: The secondary power supply is compared with the threshold value. If it is higher than the threshold value, the output is low and boost control is disabled. If it is lower than the threshold value, the output is ORed with the primary power supply, the key power-on indicator signal and the self-excited oscillation signal to enable boost control.

[0063] Step 4: The key voltage is compared with the threshold value. When it is lower than the threshold value, a high level is output. This high level is then ORed with the primary power supply, secondary power supply indicator signals, and self-excited oscillation signal to enable boost control. When it is lower than the threshold value, a low level is output to disable boost control.

[0064] Step 5: The output of the self-excited oscillation circuit, the primary power supply undervoltage indicator, the secondary power supply undervoltage indicator, and the key valid indicator signal work together to control the boost circuit.

[0065] Step 6: When boost control is enabled via the boost circuit, boost output can be achieved by charging and discharging the inductor; when boost control is disabled, charging and discharging of the power supply is disabled.

[0066] For example

[0067] in Figure 3 The self-excited oscillation circuit is implemented as follows: a Schmitt trigger is used, and an external RC circuit is formed by connecting a resistor R1 across the input and output terminals of the Schmitt trigger and a pull-down capacitor C1 at the input terminal. The circuit outputs a square wave signal with a fixed frequency. R1 is selected as a 50kΩ resistor, C1 as a 100pF resistor, and the oscillation frequency is 200Hz.

[0068] in Figure 4 Using a primary power supply undervoltage indicator circuit, when the key valid signal outputs a high level, V1 and V2 are turned on. The +24V MOS of the primary power supply is divided by R8 (60kΩ) and R7 (20kΩ) and then fed to the negative terminal of comparator U1. The voltage is also divided by R9 (20kΩ) and R10 (20kΩ) and then fed to the positive terminal of comparator U1. When the key signal is below 5V and the primary power supply is below 10V, comparator U1 outputs a low level; when the key signal is above 5V and the primary power supply is below 10V, comparator U1 outputs a low level; when the key signal is above 5V and the primary power supply is above 10V, comparator U1 outputs a high level.

[0069] in Figure 5 The secondary power supply undervoltage indication circuit uses a secondary power supply. When the secondary power supply +24V_POST is used, it is divided by resistors R13 (90kΩ) and R14 (100kΩ) and then enters the negative terminal of comparator U2. When the secondary power supply voltage is used, it is divided by resistors R9 (20kΩ) and R10 (20kΩ) and then enters the positive terminal of comparator U1. When the secondary power supply voltage is higher than 25V, comparator U2 outputs a low level; when the secondary power supply voltage is lower than 25V, comparator U2 outputs a high level.

[0070] in Figure 6 The enable indicator circuit using the key signal works as follows: when the key signal KEY is divided by resistors R21 and R22 (20kΩ each), it enters the positive terminal of comparator U3; when the key supply voltage is 5V, it enters the positive terminal of comparator U3 by resistors R19 and R20 (20kΩ each). When the key supply voltage is higher than 5V, comparator U3 outputs a high level; when the key supply voltage is lower than 25V, comparator U2 outputs a low level.

[0071] in Figure 7The complementary power drive enable circuit diagram shows that the square wave signal output from the self-excited oscillation, the undervoltage state indicator signal, the overvoltage state indicator signal, and the key valid indicator signal are output as variable frequency square wave signals through a 4-channel AND gate circuit. After passing through the complementary pull-down transistor V4 and the pull-up transistor V3 to form a complementary output circuit, the drive current is increased to enable and disable the boost control circuit. When the self-excited oscillation square wave signal is high and the key signal is greater than 5V, and the primary power supply is lower than 10V and the secondary power supply is lower than 25V, the boost control circuit is enabled; in other states, the boost state is disabled.

[0072] in Figure 8 The boost control circuit diagram uses the NMOS transistor U4 as a switch. When the switch is on, inductor L1 is grounded, diode V5 is off, and the +24V_MOS charges inductor L1. When the switch is off, inductor L1 has completed charging and current flows through it. Since current cannot change abruptly, a voltage will be induced, diode V4 will conduct, and voltage will be supplied to the secondary power input.

[0073] This circuit is a self-excited oscillating closed-loop voltage regulator designed to ensure the controller can function normally under conditions such as battery depletion or unstable primary power output during engine startup. It ensures the controller's secondary power supply can output normally under these conditions, guaranteeing the controller's normal operation.

[0074] The product provided by this invention has been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the embodiments above are merely for the purpose of helping to understand the core ideas of this invention. It should be noted that those skilled in the art can make various improvements and modifications to the invention without departing from the principles of the invention, and these improvements and modifications also fall within the protection scope of the invention claims.

Claims

1. A closed-loop voltage regulator circuit based on self-excited oscillation, suitable for drive control of power amplifier circuits, characterized in that, The system includes a closed-loop voltage regulator circuit, a self-oscillating circuit, a boost control circuit, and a battery. The closed-loop voltage regulator circuit comprises a primary power supply undervoltage indicator circuit, a secondary power supply undervoltage indicator circuit, a key enable indicator circuit, and a power amplifier circuit, which are connected in sequence. The output of the closed-loop voltage regulator circuit is connected to the power amplifier circuit, and the output of the boost control circuit is also connected to the power amplifier circuit. The self-oscillating circuit includes an RC circuit and a Schmitt trigger. The primary power supply undervoltage indicator circuit includes a comparator. The self-excited oscillation circuit is connected to an RC circuit via a Schmitt trigger, and can output a square wave signal with a fixed period. The primary power supply undervoltage indication circuit is used to collect the primary power supply voltage of the battery, and when the battery is depleted, causing the battery voltage to be lower than the normal operating voltage of the product, the comparator outputs a high level. The secondary power supply undervoltage indicator circuit is used to collect the internal secondary power supply voltage of the product, suppress the instantaneous current of the secondary power supply voltage to the load, and avoid significant voltage fluctuations. When the voltage is lower than the normal operating voltage, the comparator outputs a high level. The key enable indicator circuit is used to collect the key power supply voltage. When the power supply voltage of the key enable indicator circuit and the battery voltage are higher than the normal operating voltage, the comparator outputs a high level. The boost control circuit is used to operate when the supply voltage of the primary power supply, the secondary power supply, and the key are not enabled, causing the product to not meet the normal operating voltage. The boost control circuit stops operating when the supply voltage of the secondary power supply meets the requirements. The self-excited oscillation circuit is a closed-loop voltage-regulated circuit, including resistor R1, capacitor C1, Schmitt trigger U5, Schmitt trigger U6, and Schmitt trigger U7, wherein: One end of the capacitor C1 is connected to the input pin of the Schmitt trigger U5, and the other end is grounded; One end of the resistor R1 is connected to the input pin of the Schmitt trigger U5, and the other end is connected to the output pin of the Schmitt trigger U5. The output pin of the Schmitt trigger U5 is connected to the input pin of the Schmitt trigger U6, and the output pin of the Schmitt trigger U6 is connected to the input pin of the Schmitt trigger U7. The output signal of the Schmitt trigger U7 is a square wave signal with a fixed frequency after being oscillated by the RC circuit.

2. The closed-loop voltage regulator circuit based on self-excited oscillation according to claim 1, characterized in that, The primary power supply undervoltage indication circuit includes transistor V2, capacitor C2, resistors R6, R7, R8, R9, and R10, hysteresis resistor R11, resistor R12, comparator U1, and pull-up resistor R12, wherein: The +24V MOS input of the primary power supply is connected to the emitter of transistor V2. The collector of transistor V2 is connected to resistors R6 and R8 in parallel, with one end of resistor R6 grounded. Resistor R8 is connected in parallel with resistor R7 and capacitor C2. One end of resistor R7 and capacitor C2 is grounded, and the other end serves as the inverting input of comparator U1. One end of resistor R9 supplies +5V, and the other end is connected in parallel with resistor R10 and hysteresis resistor R11. One end of resistor R10 is grounded, and one end of hysteresis resistor R11 is connected across the positive input of comparator U1. The other end is connected in series with pull-up resistor R12, with one end of resistor R12 providing +5V. The output of comparator U1 is connected to the output of pull-up resistor R12 to output an indication signal of the primary power supply undervoltage status.

3. The closed-loop voltage regulator circuit based on self-excited oscillation according to claim 2, characterized in that, The secondary power supply undervoltage indication circuit includes comparator U2, resistors 13, 14, 15, 16, and 17, capacitors C3 and C4, wherein: The positive input terminal of comparator U2 is connected to one end of resistor 15, and the other end of resistor 15 is connected to a +5V voltage. Resistor 15 is connected in parallel with resistor 16, capacitor C4 and resistor 17 respectively. One end of resistor 16 and capacitor C4 are grounded together. One end of resistor 17 is connected to the positive input terminal of comparator U2, and the other end is connected to the output terminal of comparator U2. The output terminal of comparator U2 is connected to pull-up resistor R18, and the input terminal of pull-up resistor R18 is connected to a +5V voltage.

4. The closed-loop voltage regulator circuit based on self-excited oscillation according to claim 3, characterized in that, The key enable indicator circuit includes comparator U3, resistor R21, resistor R19, resistor R23, and resistor R24, wherein: The positive input terminal of comparator U3 is connected to resistor R21. Resistor R22 and capacitor C5 are connected in parallel with resistor R21, and one end of resistor R22 and capacitor C5 are grounded. The key signal KEY is input to the input terminal of resistor R21. Resistor R23 is provided between the positive input terminal and the output terminal of comparator U3, and resistor R24 ​​is connected to the output terminal of comparator U3. The input terminal of resistor R24 ​​is connected to a +5V voltage. The positive and negative input terminals of comparator U3 are connected to resistor R19. The input terminal of resistor R19 is supplied with a +5V voltage. Resistor R20 and capacitor C6 are connected in parallel with resistor R19, and one end of R20 and capacitor C6 are grounded.

5. The closed-loop voltage regulator circuit based on self-excited oscillation according to claim 4, characterized in that, It also includes logic circuits, wherein: The outputs of the self-excited oscillation circuit, the primary power supply undervoltage indicator circuit, the key enable indicator circuit, and the secondary power supply undervoltage indicator circuit are connected to the AND logic circuit, which generates a variable frequency square wave.

6. The closed-loop voltage regulator circuit based on self-excited oscillation according to claim 5, characterized in that, The power amplifier circuit is used to increase the drive output current of the boost control circuit. It includes a resistor R26, a PNP transistor V3, and an NPN transistor V4. The emitters of transistor V3 and V4 are complementary, and the bases of transistor V3 and V4 are connected. Resistors R27 and R28 are also provided. The collector of transistor V3 is supplied with a +5V DC power supply, and the collector of transistor V4 is grounded. The output terminal of the logic circuit is connected to the input terminal of resistor R26, and the output terminal of resistor R26 is connected to the output terminal of resistor R27 and the input terminal of R28. A square wave of fixed frequency, a primary power supply undervoltage indication signal, a secondary power supply undervoltage indication signal, and a key valid indication signal are input into the logic circuit. The output is a square wave of variable frequency. After being conditioned by a push-pull circuit composed of transistors V3 and V4, complementary output is achieved.

7. The closed-loop voltage regulator circuit based on self-excited oscillation according to claim 6, characterized in that, The boost control circuit includes an N-channel enhancement-mode MOSFET U4, capacitor C5, and capacitor C6, wherein: The source of MOSFET U4 is grounded, the gate input is the signal conditioned by the push-pull circuit, and the drain is connected to the output of inductor L1 and the anode of power diode V5, respectively. The input of inductor L1 is a +24V MOSFET with a primary power input and a capacitor C5 with one end grounded. The cathode of power diode V5 receives a +24V POS signal and a capacitor C6 with one end grounded is also provided at the cathode of power diode V5.

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