A low dropout linear voltage regulator circuit

Abstract

The application discloses a low-dropout linear voltage stabilizing circuit, which comprises an input filter circuit, a current-limiting circuit, a switching machine circuit, a low-dropout voltage stabilizing circuit, an output voltage regulating circuit, a current-sharing circuit and an output filter circuit. The low-dropout linear voltage stabilizing circuit is used in parallel with two low-dropout voltage stabilizing circuits, the current-sharing circuit and the switching machine circuit are added, the device thermal stress problem of the low-dropout voltage stabilizing circuit under low voltage and large current is solved, the large current application occasion of the low-dropout voltage stabilizing chip is realized, the low voltage, large current and high stability voltage output is realized to a certain extent, and the high heat consumption problem of the low-dropout linear voltage stabilizing chip caused by the large current can be greatly reduced.

Description

Technical Field

[0001] This invention relates to a low-dropout linear voltage regulator circuit, belonging to the field of secondary power supply technology design. Background Technology

[0002] As satellite payloads become increasingly diverse, the demand for space power supplies is also growing, requiring power supplies to provide lower operating voltages, higher operating currents, and the ability to shut down immediately in case of failure.

[0003] Currently, satellite payload power supplies can be integrated into a single multi-output, power-distributable power supply unit by combining brick-type power supplies with different output channels, according to actual load requirements, to meet the needs of downstream payloads. Each brick-type power supply has closed-loop negative feedback regulation for its main output, while the auxiliary voltage is not controlled. For applications requiring lower output voltage and higher accuracy, the auxiliary circuit uses a low-dropout voltage regulator chip to ensure output voltage stability. Furthermore, low-dropout voltage regulator chips offer advantages such as simple structure, low cost, and high reliability.

[0004] However, the maximum output current of the low-dropout voltage regulator chips commonly used in aerospace is 5A, which is not suitable for higher power levels. Secondly, current low-dropout voltage regulator circuits are all in an immediate start-up state upon power-on. When a downstream circuit fails and the power supply needs to be shut down, the only way is to shut down the entire brick power supply or send a shutdown command to the power supply unit. This affects the normal power supply to the main load of the brick power supply or other loads within the unit.

[0005] A search of relevant domestic and international literature revealed no information regarding the low-dropout linear voltage regulator circuit of this invention. Summary of the Invention

[0006] The technical problem solved by this invention is: in view of the lack of low dropout linear voltage regulator circuit design technology in the current technology that can not affect the power supply of other loads in a single machine, a low dropout linear voltage regulator circuit is proposed.

[0007] The present invention solves the above-mentioned technical problem through the following technical solution:

[0008] A low-dropout linear voltage regulator circuit includes an input filter circuit, a current limiting circuit, a power-on / off circuit, a low-dropout voltage regulator circuit, an output voltage regulation circuit, a current sharing circuit, and an output filter circuit, wherein:

[0009] The input filter circuit filters the external input voltage to provide power to the low-dropout linear regulator circuit; the power-on / off circuit receives external commands and controls the power-on and power-off of the low-dropout linear regulator circuit; the current-limiting circuit provides voltage to the power-on / off circuit, limits the current, and then sends it to the low-dropout linear regulator circuit; the output voltage regulation circuit provides the regulation voltage and sends it to the output filter circuit; the current sharing circuit collects the output current of each low-dropout regulator circuit and feeds it back to the low-dropout linear regulator circuit for current sharing regulation; the output filter circuit receives the voltage generated by the output voltage regulation circuit, filters it, and outputs it for use by the external load.

[0010] The low-dropout linear regulator circuit includes a main low-dropout linear regulator circuit and an auxiliary low-dropout linear regulator circuit. The output voltage regulation circuit includes a main output voltage regulation circuit and an auxiliary output voltage regulation circuit, wherein:

[0011] The main low-dropout linear regulator circuit and the main output voltage regulation circuit, the auxiliary low-dropout linear regulator circuit and the auxiliary output voltage regulation circuit are connected in series, and then connected in parallel. After being connected in series, one end of each circuit is connected to a current limiting circuit, and the other end is connected to a current sharing circuit.

[0012] The input filter circuit includes capacitors C1 and C2, which are connected in parallel to achieve the filtering function; the output filter circuit includes capacitors C4 and C5, which are connected in parallel to achieve the filtering function; the input filter circuit and the output filter circuit provide stable output voltage for the low dropout voltage regulator circuit and the external load, respectively; the current limiting circuit includes resistors R1 and R4, which are connected in series, with one end connected to the input bus and the other end connected to the power-on / off circuit, providing current to the low dropout voltage regulator circuit.

[0013] The main output voltage regulation circuit includes resistor R2, resistor R3, and capacitor C3. One end of resistor R2 is connected to the circuit output terminal, and the other end is connected to one end of resistor R3. The other end of resistor R3 is grounded, and capacitor C3 is connected across resistor R2.

[0014] The auxiliary output voltage regulation circuit includes resistors R7, R8, and R9, and capacitor C7. Resistors R7, R8, and R9 are connected in series, and capacitor C7 is connected to both ends of the series connection of resistors R7 and R8, with the connection position between resistors R8 and R9.

[0015] Both the main output voltage regulation circuit and the auxiliary output voltage regulation circuit are equipped with low dropout voltage regulator chips, which are located between the current limiting circuit and the input terminals of the main output voltage regulation circuit and the auxiliary output voltage regulation circuit.

[0016] The main output voltage regulation circuit adjusts the output voltage by setting the resistance values ​​of resistors R2 and R3, and the auxiliary output voltage regulation circuit adjusts the output voltage by setting the resistance values ​​of resistors R7, R8, and R9. The output voltage of the auxiliary output voltage regulation circuit is lower than that of the main output voltage regulation circuit. The main output voltage regulation circuit and the auxiliary output voltage regulation circuit adjust the parameters of the auxiliary output voltage regulation circuit so that the output voltage is clamped by the output voltage of the main output voltage regulation circuit.

[0017] The power-on / off circuit includes resistor R5, resistor R6, capacitor C6, and transistor Q1. One end of resistor R5 is connected to the external input, and the other end is connected to the base of transistor Q1. Resistor R6 and capacitor C6 are respectively connected between the base and emitter of the transistor. One end of the collector of transistor Q1 is connected to the current limiting circuit, and the other end is connected to the input ground.

[0018] When the external command is TTL high level, the voltage is divided by resistors R5 and R6 to provide the working voltage to the base of transistor Q1, transistor Q1 is turned on, the enable terminal EN of the low dropout voltage regulator circuit is pulled low, and the low dropout voltage regulator chip is turned off; when the external command is floating, transistor Q1 is turned off, the voltage of the low dropout voltage regulator chip is the input bus voltage, and the low dropout voltage regulator chip works normally.

[0019] The current sharing circuit includes resistors R10 to R13, capacitor C8, transistors Q2 and Q3. One end of resistor R10 is connected to the current detection terminal of the main low-dropout regulator circuit, and the other end is connected to the collector of transistor Q3. The emitter of transistor Q3 is connected to one end of resistor R12, and the other end of resistor R12 is connected to the output ground. The collector of transistor Q2 is connected to the current detection terminal of the auxiliary low-dropout regulator circuit, and the emitter is connected to one end of resistor R11, and the other end of resistor R11 is connected to the output ground. Transistors Q2 and Q3 are mirror images of each other, with their bases connected together and connected to the collector of transistor Q3. They are also connected to the current detection terminal of the auxiliary low-dropout regulator circuit through capacitor C8 and resistor R13.

[0020] In the current sharing circuit, transistor Q3 compensates for the temperature of transistor Q2. The emitters of transistors Q2 and Q3 are grounded through resistors R11 and R12, respectively. Current sharing is achieved by obtaining different proportions of collector current through resistance changes.

[0021] The current sharing circuit also includes a compensation resistor R13 and a compensation capacitor C8, which are located at the output terminal of the low-dropout voltage regulator chip in the auxiliary output voltage regulation circuit and connected to the collectors of transistors Q3 and Q2, in order to change the frequency characteristics of the current sharing circuit and improve its stability.

[0022] The main output voltage regulation circuit uses a low-dropout voltage regulator chip as the main chip, and the auxiliary output voltage regulation circuit uses a low-dropout voltage regulator chip as the auxiliary chip. Through master-slave control, the current at the current detection terminal of the auxiliary low-dropout voltage regulator circuit is forced to be the same as the current at the current detection terminal of the main low-dropout voltage regulator circuit. After internal adjustment of the low-dropout voltage regulator chip, the current sharing of the output current when the main output voltage regulation circuit and the auxiliary output voltage regulation circuit are connected in parallel is forced to improve the output load capacity of the low-dropout voltage regulator chip.

[0023] The advantages of this invention compared to the prior art are:

[0024] (1) The low dropout linear voltage regulator circuit provided by the present invention adopts a main and auxiliary output voltage regulation circuit and a current sharing circuit, which realizes the parallel operation of the low dropout voltage regulator chip, can provide a larger load operating current, and realizes the flexible control of the low dropout voltage regulator chip through the power-on circuit adopted by the expansion design. By utilizing the simple form of the parallel circuit, the expansion capability is improved, the output power capability of the system is increased, and it is suitable for larger power applications.

[0025] (2) By adding an auxiliary low-dropout voltage regulator circuit, an auxiliary output voltage regulation circuit, and a current sharing circuit, the present invention achieves output power expansion, realizes low-voltage, high-current, and high-stability voltage output to a certain extent, and can significantly reduce the high heat dissipation problem of low-dropout linear regulator chips caused by high current. Attached Figure Description

[0026] Figure 1 A schematic diagram of a low-dropout linear voltage regulator circuit provided for the invention;

[0027] Figure 2 Schematic diagram of a low-dropout linear voltage regulator circuit provided for the invention;

[0028] Figure 3 The schematic diagram of the expanded low-dropout linear voltage regulator circuit provided for the invention;

[0029] Figure 4 A schematic diagram of the expanded current sharing circuit provided for the invention; Detailed Implementation

[0030] A low-dropout linear regulator circuit includes an input filter circuit, a current limiting circuit, a power-on / off circuit, a low-dropout regulator circuit, an output voltage regulation circuit, a current sharing circuit, and an output filter circuit. By using two low-dropout regulator circuits in parallel and adding a current sharing circuit and a power-on / off circuit, the thermal stress problem of the low-dropout regulator circuit under low voltage and high current is solved. This enables the low-dropout regulator chip to be used in high-current applications, and to a certain extent, achieves a low-voltage, high-current, and highly stable voltage output. It can also significantly reduce the high heat dissipation problem of the low-dropout linear regulator chip caused by high current.

[0031] In a low-dropout linear regulator circuit, the input filter circuit filters the external input voltage to provide the power supply voltage for the low-dropout linear regulator circuit; the power-on / off circuit receives external commands to control the power-on and power-off of the low-dropout linear regulator circuit; the current-limiting circuit provides voltage to the power-on / off circuit, limits the current, and then sends it to the low-dropout linear regulator circuit; the output voltage regulation circuit provides the regulation voltage and sends it to the output filter circuit; the current sharing circuit collects the output current of each low-dropout regulator circuit and feeds it back to the low-dropout linear regulator circuit for current sharing regulation; the output filter circuit receives the voltage generated by the output voltage regulation circuit, filters it, and outputs it for use by the external load.

[0032] Specifically, the low-dropout linear regulator circuit includes a main low-dropout linear regulator circuit and an auxiliary low-dropout linear regulator circuit, and the output voltage regulation circuit includes a main output voltage regulation circuit and an auxiliary output voltage regulation circuit, wherein:

[0033] The main low-dropout linear regulator circuit and the main output voltage regulation circuit, the auxiliary low-dropout linear regulator circuit and the auxiliary output voltage regulation circuit are connected in series, and then connected in parallel. After being connected in series, one end of each circuit is connected to a current limiting circuit, and the other end is connected to a current sharing circuit.

[0034] The input filter circuit includes capacitors C1 and C2, which are connected in parallel to achieve the filtering function; the output filter circuit includes capacitors C4 and C5, which are connected in parallel to achieve the filtering function; the input filter circuit and the output filter circuit provide stable output voltage for the low dropout voltage regulator circuit and the external load, respectively; the current limiting circuit includes resistors R1 and R4, which are connected in series, with one end connected to the input bus and the other end connected to the power-on / off circuit, providing current to the low dropout voltage regulator circuit.

[0035] The main output voltage regulation circuit includes resistors R2 and R3, and capacitor C3. One end of resistor R2 is connected to the circuit output terminal, and the other end is connected to one end of resistor R3. The other end of resistor R3 is grounded, and capacitor C3 is connected across resistor R2.

[0036] The auxiliary output voltage regulation circuit includes resistors R7, R8, and R9, and capacitor C7. Resistors R7, R8, and R9 are connected in series, and capacitor C7 is connected to both ends of the series connection of resistors R7 and R8, with the connection position between resistors R8 and R9.

[0037] Both the main output voltage regulation circuit and the auxiliary output voltage regulation circuit are equipped with low dropout voltage regulator chips, which are located between the current limiting circuit and the input terminals of the main output voltage regulation circuit and the auxiliary output voltage regulation circuit.

[0038] The main output voltage regulation circuit adjusts the output voltage by setting the resistance values ​​of resistors R2 and R3, while the auxiliary output voltage regulation circuit adjusts the output voltage by setting the resistance values ​​of resistors R7, R8, and R9. The output voltage of the auxiliary output voltage regulation circuit is lower than that of the main output voltage regulation circuit. The main output voltage regulation circuit and the auxiliary output voltage regulation circuit switch to clamp the output voltage of the main output voltage regulation circuit by adjusting the parameters of the auxiliary output voltage regulation circuit.

[0039] The power-on / off circuit includes resistor R5, resistor R6, capacitor C6, and transistor Q1. One end of resistor R5 is connected to the external input, and the other end is connected to the base of transistor Q1. Resistor R6 and capacitor C6 are connected between the base and emitter of the transistor, respectively. One end of the collector of transistor Q1 is connected to the current limiting circuit, and the other end is connected to the input ground.

[0040] When the external command is TTL high level, the voltage is divided by resistors R5 and R6 to provide the working voltage to the base of transistor Q1, transistor Q1 is turned on, the enable pin EN of the low dropout voltage regulator circuit is pulled low, and the low dropout voltage regulator chip is turned off; when the external command is floating, transistor Q1 is turned off, the voltage of the low dropout voltage regulator chip is the input bus voltage, and the low dropout voltage regulator chip works normally.

[0041] The current sharing circuit includes resistors R10 to R13, capacitor C8, transistors Q2 and Q3. One end of resistor R10 is connected to the current detection terminal of the main low-dropout regulator circuit, and the other end is connected to the collector of transistor Q3. The emitter of transistor Q3 is connected to one end of resistor R12, and the other end of resistor R12 is connected to the output ground. The collector of transistor Q2 is connected to the current detection terminal of the auxiliary low-dropout regulator circuit, and the emitter is connected to one end of resistor R11. The other end of resistor R11 is connected to the output ground. Transistors Q2 and Q3 are mirror images of each other, with their bases connected together and connected to the collector of transistor Q3. They are also connected to the current detection terminal of the auxiliary low-dropout regulator circuit through capacitor C8 and resistor R13.

[0042] In the current sharing circuit, transistor Q3 compensates for the temperature of transistor Q2. The emitters of transistors Q2 and Q3 are grounded through resistors R11 and R12, respectively. The current sharing is achieved by obtaining different proportions of collector current through the resistance changes.

[0043] The current sharing circuit also includes a compensation resistor R13 and a compensation capacitor C8, which are located at the output terminal of the low dropout voltage regulator chip in the auxiliary output voltage regulation circuit and connected to the collectors of transistors Q3 and Q2. These components are used to change the frequency characteristics of the current sharing circuit and improve its stability.

[0044] The main output voltage regulator circuit uses a low-dropout voltage regulator chip as the main chip, while the auxiliary output voltage regulator circuit uses a low-dropout voltage regulator chip as the auxiliary chip. Through master-slave control, the current at the current detection terminal of the auxiliary low-dropout voltage regulator circuit is forced to be the same as the current at the current detection terminal of the main low-dropout voltage regulator circuit. Through internal adjustment of the low-dropout voltage regulator chip, the current sharing of the output current when the main output voltage regulator circuit and the auxiliary output voltage regulator circuit are connected in parallel is forced to improve the output load capacity of the low-dropout voltage regulator chip.

[0045] The following description, in conjunction with the accompanying drawings and preferred embodiments, provides further details:

[0046] In the current embodiment, a schematic diagram of the low-dropout linear regulator circuit is shown below. Figure 1 As shown, the specific schematic diagram of the low dropout linear regulator circuit is as follows: Figure 2 As shown, the schematic diagram of the expanded low-dropout linear regulator circuit is as follows: Figure 3 As shown, the schematic diagram of the current sharing circuit is as follows: Figure 4 As shown, where:

[0047] The input filter circuit consists of capacitors C1 and C2 connected in parallel to provide a stable input voltage for the low dropout voltage regulator chip.

[0048] The output filter circuit consists of capacitors C4 and C5 connected in parallel to provide a stable output voltage for the subsequent load.

[0049] The current limiting circuit consists of R1 and R4, with one end connected to the input bus and the other end connected to the power-on / off circuit, providing pull-up current to the enable terminal of the low dropout voltage regulator chip.

[0050] The main output voltage regulation circuit includes resistors R2 and R3, and capacitor C3. One end of resistor R2 is connected to the positive output line, and the other end is connected to R3. The other end of R3 is connected to the output ground. C3 is connected across R2. The auxiliary output voltage regulation circuit includes resistors R7, R8, and R9, and capacitor C7. The positive output line passes through R7, R8, and R9 sequentially to the ground line. One end of C7 is connected to the positive output line, and the other end is connected to the junction of R8 and R9. In the circuit implementation, the main output voltage regulation circuit provides the required voltage by selecting appropriate values ​​for resistors R2 and R3; the auxiliary output voltage regulation circuit, by selecting appropriate values ​​for resistors R7, R8, and R9, ensures that the output voltage of the auxiliary low-dropout regulator is lower than that of the main low-dropout regulator. When the main and auxiliary circuits are connected in parallel, setting appropriate auxiliary output voltage parameters makes the auxiliary output voltage lower than the main output voltage. Thus, the auxiliary output voltage is clamped by the main output voltage, allowing the parallel system to provide the required output voltage to the load.

[0051] The power-on / off circuit includes resistors R5 and R6, capacitor C6, and transistor Q1. One end of resistor R5 is connected to the external command, and the other end is connected to the base of transistor Q1. Resistor R6 and capacitor C6 are connected between the base and emitter of the transistor, respectively. One end of the collector of transistor Q1 is connected to the current-limiting circuit, and the other end is connected to the input ground. When the external command is a TTL high level, the voltage is divided by resistors R5 and R6 to provide the operating voltage to the base of transistor Q1, turning on transistor Q1. This pulls down the enable pin (EN) of the low-dropout voltage regulator circuit, turning off the low-dropout voltage regulator chip. When the external command is floating, transistor Q1 is cut off, and the voltage of the low-dropout voltage regulator chip is provided by the input bus voltage, ensuring the normal operation of the low-dropout voltage regulator chip.

[0052] The current sharing circuit includes resistors R10, R11, R12, and R13, capacitor C8, and transistors Q2 and Q3. One end of resistor R10 is connected to the current sensing terminal of the main low-dropout regulator circuit, and the other end is connected to the collector of transistor Q3. The emitter of transistor Q3 is connected to one end of resistor R12, and the other end of resistor R12 is connected to the output ground. The collector of transistor Q2 is connected to the current sensing terminal of the auxiliary low-dropout regulator circuit, and its emitter is connected to one end of resistor R11, and the other end of resistor R11 is connected to the output ground. Transistors Q2 and Q3 are mirror images of each other, with their bases connected together and connected to the collector of transistor Q3. They are also connected to the current sensing terminal of the auxiliary low-dropout regulator circuit through capacitor C8 and resistor R13.

[0053] In the current sharing circuit, transistor Q3 provides temperature compensation for transistor Q2, resulting in better temperature stability of the collector current of transistor Q2 in the auxiliary low-dropout regulator circuit. Adding resistors R11 and R12 to the emitters of transistors Q2 and Q3 allows for different collector current ratios by varying the emitter resistor values, thus further achieving varying current sharing effects. In practical applications, to ensure similar heat dissipation across different low-dropout regulator chips, resistors R11 and R12 are often set to the same value. Simultaneously, to eliminate system self-oscillation and ensure overall system stability, a frequency compensation network (compensation resistor R13 and compensation capacitor C8) is added between the base and collector of the auxiliary transistor in the current mirror current sharing circuit. By altering the circuit's frequency characteristics, the amplitude-frequency response decays rapidly at the high end of the bandwidth, improving system stability. In practical applications, the parameters of compensation resistor R13 and compensation capacitor C8 need to be determined through tuning to achieve stable system operation with a wide bandwidth.

[0054] This circuit employs master-slave control, using one low-dropout voltage regulator chip as the master chip and the others as auxiliary chips. The current sharing circuit uses a mirrored current source circuit to force the current at the current sensing terminal of the auxiliary low-dropout voltage regulator circuit to be the same as the current at the current sensing terminal of the master low-dropout voltage regulator circuit. Through internal adjustment of the low-dropout voltage regulator chip, forced current sharing is achieved when the auxiliary and master circuits are connected in parallel, improving the output load capacity of the low-dropout voltage regulator chip and reducing the thermal stress problem caused by uneven current distribution.

[0055] This circuit also features output power expansion capabilities. By adding an auxiliary low-dropout regulator circuit, an auxiliary output voltage regulation circuit, and a current sharing circuit, the output power can be expanded. Compared with existing technologies, it achieves a certain degree of low-voltage, high-current, and highly stable voltage output, and significantly reduces the high heat dissipation problem of low-dropout linear regulator chips caused by high current.

[0056] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make possible changes and modifications to the technical solutions of the present invention by utilizing the methods and techniques disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solutions of the present invention shall fall within the protection scope of the technical solutions of the present invention.

[0057] The contents not described in detail in this specification are common knowledge to those skilled in the art.

Claims

1. A low-dropout linear voltage regulator circuit, characterized in that: It includes an input filter circuit, a current limiting circuit, a power-on / off circuit, a low-dropout voltage regulator circuit, an output voltage regulation circuit, a current sharing circuit, and an output filter circuit, wherein: The input filter circuit filters the external input voltage to provide power to the low-dropout linear regulator circuit; the power-on / off circuit receives external commands and controls the power-on and power-off of the low-dropout linear regulator circuit; the current-limiting circuit provides voltage to the power-on / off circuit, limits the current, and then sends it to the low-dropout linear regulator circuit; the output voltage regulation circuit provides the regulation voltage and sends it to the output filter circuit; the current sharing circuit collects the output current of each low-dropout regulator circuit and feeds it back to the low-dropout linear regulator circuit for current sharing regulation; the output filter circuit receives the voltage generated by the output voltage regulation circuit, filters it, and outputs it for use by the external load. The low-dropout linear regulator circuit includes a main low-dropout linear regulator circuit and an auxiliary low-dropout linear regulator circuit. The output voltage regulation circuit includes a main output voltage regulation circuit and an auxiliary output voltage regulation circuit, wherein: The main low-dropout linear regulator circuit and the main output voltage regulation circuit, the auxiliary low-dropout linear regulator circuit and the auxiliary output voltage regulation circuit are connected in series, and then connected in parallel. After being connected in series, one end of each circuit is connected to a current limiting circuit, and the other end is connected to a current sharing circuit.

2. The low-dropout linear voltage regulator circuit according to claim 1, characterized in that: The input filter circuit includes capacitors C1 and C2, which are connected in parallel to achieve the filtering function; the output filter circuit includes capacitors C4 and C5, which are connected in parallel to achieve the filtering function; the input filter circuit and the output filter circuit provide stable output voltage for the low dropout voltage regulator circuit and the external load, respectively; the current limiting circuit includes resistors R1 and R4, which are connected in series, with one end connected to the input bus and the other end connected to the power-on / off circuit, providing current to the low dropout voltage regulator circuit.

3. The low-dropout linear voltage regulator circuit according to claim 2, characterized in that: The main output voltage regulation circuit includes resistor R2, resistor R3, and capacitor C3. One end of resistor R2 is connected to the circuit output terminal, and the other end is connected to one end of resistor R3. The other end of resistor R3 is grounded, and capacitor C3 is connected across resistor R2. The auxiliary output voltage regulation circuit includes resistors R7, R8, and R9, and capacitor C7. Resistors R7, R8, and R9 are connected in series, and capacitor C7 is connected to both ends of the series connection of resistors R7 and R8, with the connection position between resistors R8 and R9. Both the main output voltage regulation circuit and the auxiliary output voltage regulation circuit are equipped with low dropout voltage regulator chips, which are located between the current limiting circuit and the input terminals of the main output voltage regulation circuit and the auxiliary output voltage regulation circuit.

4. The low-dropout linear voltage regulator circuit according to claim 3, characterized in that: The main output voltage regulation circuit adjusts the output voltage by setting the resistance values ​​of resistors R2 and R3, and the auxiliary output voltage regulation circuit adjusts the output voltage by setting the resistance values ​​of resistors R7, R8, and R9. The output voltage of the auxiliary output voltage regulation circuit is lower than that of the main output voltage regulation circuit. The main output voltage regulation circuit and the auxiliary output voltage regulation circuit adjust the parameters of the auxiliary output voltage regulation circuit so that the output voltage is clamped by the output voltage of the main output voltage regulation circuit.

5. The low-dropout linear voltage regulator circuit according to claim 4, characterized in that: The power-on / off circuit includes resistor R5, resistor R6, capacitor C6, and transistor Q1. One end of resistor R5 is connected to the external input, and the other end is connected to the base of transistor Q1. Resistor R6 and capacitor C6 are respectively connected between the base and emitter of the transistor. One end of the collector of transistor Q1 is connected to the current limiting circuit, and the other end is connected to the input ground. When the external command is TTL high level, the voltage is divided by resistors R5 and R6 to provide the working voltage to the base of transistor Q1, transistor Q1 is turned on, the enable terminal EN of the low dropout voltage regulator circuit is pulled low, and the low dropout voltage regulator chip is turned off; when the external command is floating, transistor Q1 is turned off, the voltage of the low dropout voltage regulator chip is the input bus voltage, and the low dropout voltage regulator chip works normally.

6. The low-dropout linear voltage regulator circuit according to claim 5, characterized in that: The current sharing circuit includes resistors R10~R13, capacitor C8, transistors Q2 and Q3. One end of resistor R10 is connected to the current detection terminal of the main low-dropout regulator circuit, and the other end is connected to the collector of transistor Q3. The emitter of transistor Q3 is connected to one end of resistor R12, and the other end of resistor R12 is connected to the output ground. The collector of transistor Q2 is connected to the current detection terminal of the auxiliary low-dropout regulator circuit, and the emitter is connected to one end of resistor R11. The other end of resistor R11 is connected to the output ground. Transistors Q2 and Q3 are mirror images of each other, with their bases connected together and connected to the collector of transistor Q3. They are also connected to the current detection terminal of the auxiliary low-dropout regulator circuit through capacitor C8 and resistor R13.

7. A low-dropout linear voltage regulator circuit according to claim 6, characterized in that: In the current sharing circuit, transistor Q3 compensates for the temperature of transistor Q2. The emitters of transistors Q2 and Q3 are grounded through resistors R11 and R12, respectively. Current sharing is achieved by obtaining different proportions of collector current through resistance changes.

8. A low-dropout linear voltage regulator circuit according to claim 7, characterized in that: The current sharing circuit also includes a compensation resistor R13 and a compensation capacitor C8, which are located at the output terminal of the low-dropout voltage regulator chip in the auxiliary output voltage regulation circuit and connected to the collectors of transistors Q3 and Q2, in order to change the frequency characteristics of the current sharing circuit and improve its stability.

9. A low-dropout linear voltage regulator circuit according to claim 8, characterized in that: The main output voltage regulation circuit uses a low-dropout voltage regulator chip as the main chip, and the auxiliary output voltage regulation circuit uses a low-dropout voltage regulator chip as the auxiliary chip. Through master-slave control, the current at the current detection terminal of the auxiliary low-dropout voltage regulator circuit is forced to be the same as the current at the current detection terminal of the main low-dropout voltage regulator circuit. After internal adjustment of the low-dropout voltage regulator chip, the current sharing of the output current when the main output voltage regulation circuit and the auxiliary output voltage regulation circuit are connected in parallel is forced to improve the output load capacity of the low-dropout voltage regulator chip.

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