Load power distribution pre-charging circuit and control method thereof

Abstract

The invention relates to a load power distribution pre-charging circuit and a control method thereof. The load power distribution pre-charging circuit comprises a pre-charging switch circuit, a current limiting circuit, a voltage sampling circuit, an MCU and a power switch. The current limiting circuit comprises a first resistor, a second resistor, a third resistor and a PNP triode; the pre-charging switch circuit comprises a fourth resistor, a P-MOSFET switch and a driving circuit. The voltage sampling circuit is used for collecting a voltage signal of a power input end of a load; when the voltage signal is smaller than a preset voltage threshold value, the MCU outputs a PWM signal to the driving circuit to drive the P-MOSFET switch to be turned on for load pre-charging; and when the voltage signal is equal to the preset voltage threshold value, the MCU outputs a control signal to control the power switch to be closed to normally supply power to the load, and outputs a low-level signal to the driving circuit to drive the P-MOSFET switch to be closed to end pre-charging of the load, so that the instantaneous power of the current-limiting resistor is reduced on the premise of short charging time.

Description

Technical Field

[0001] The present application relates to the technical field of load power distribution, and in particular to a load power distribution pre-charging circuit and a control method thereof. Background Art

[0002] In high-power battery-powered systems, such as automobiles and robots, power distribution control is required for various functional loads at the initial startup. Some loads have large input filter capacitors due to their special functions, such as inverters, power amplifiers and other loads. For such loads with large input filter capacitors, when the distribution unit controller controls switches such as relays, MOSFETs or IGBTs to power them on, the capacitor can be regarded as a short circuit to the ground at the moment of power on, and a large surge current will be generated in the distribution unit and busbar. This large surge current may cause overheating and damage to switch components (relays, MOSFETs or IGBTs), wiring harnesses or connector terminals, and may also cause undervoltage abnormalities in the distribution system due to the large current pulling down the power supply voltage of the distribution unit.

[0003] Soft start or pre-charge is usually used to solve the problems of equipment overheating and damage and distribution system undervoltage abnormality caused by large surge current. Soft start is mainly to control the power-on current of the subsequent load by gradually increasing the switching duty cycle of the distribution switch MOSFET or controlling the MOSFET gate voltage rise rate. Pre-charge is to provide a small charging current to the input filter capacitor of the load through the pre-charge circuit. When the input filter capacitor voltage of the load gradually rises to close to the battery voltage, the power switch is turned on to supply power to ensure that the charging current is within the control range.

[0004] like Figure 1 The figure shows a common pre-charging circuit, which mainly adds a current limiting resistor R in the pre-charging circuit. The battery BT1 charges the input filter capacitor CL of the load through the current limiting resistor R. R limits the maximum charging current, and the voltage of the input filter capacitor CL will slowly increase over time. The charging time depends on the current limiting resistor R, the input filter capacitor CL and the equivalent parallel resistance RL of the load. If the current limiting resistor R is small, the charging current is large, and the charging speed is correspondingly fast, but the instantaneous power of the current limiting resistor R is large, and a high-power current limiting resistor is required. Therefore, the current limiting resistor has the defects of large size and high cost; if the current limiting resistor R is large, the charging current is small, and the instantaneous power of the current limiting resistor R can be reduced, but the charging speed will be correspondingly slow, and the voltage of the input filter capacitor CL may not be increased to close to the battery voltage due to the power consumption of the equivalent parallel resistance RL of the load. Summary of the invention

[0005] The purpose of this application is to propose a load distribution pre-charging circuit and a control method thereof, so as to reduce the instantaneous power of the current limiting resistor under the premise of a shorter charging time.

[0006] To achieve the above-mentioned purpose, according to the first aspect of the present application, a load power distribution pre-charging circuit is provided, comprising a pre-charging switch circuit, a current limiting circuit, a voltage sampling circuit, an MCU and a power switch; the current limiting circuit comprises a first resistor, a second resistor, a third resistor and a PNP transistor; the pre-charging switch circuit comprises a fourth resistor, a P-MOSFET switch and a driving circuit;

[0007] One end of the power switch is connected to the input power supply, and the other end is connected to the power input end of the load; the load is provided with an input filter capacitor;

[0008] One end of the voltage sampling circuit is connected to the voltage output end of the power switch, and the other end is connected to the MCU;

[0009] One end of the first resistor is connected to the voltage input terminal of the power switch, and the other end is connected to the source of the P-MOSFET switch; one end of the second resistor is connected to the source of the P-MOSFET switch, and the other end is connected to the base of the PNP transistor; one end of the third resistor is connected to the base of the PNP transistor, and the other end is connected to the emitter of the PNP transistor;

[0010] The drain of the P-MOSFET switch is connected to the voltage output terminal of the power switch; one end of the fourth resistor is connected to the gate of the P-MOSFET switch, and the other end is connected to the source of the P-MOSFET switch; one end of the drive circuit is connected to the gate of the P-MOSFET switch, and the other end is connected to the MCU;

[0011] The voltage sampling circuit is used to collect the voltage signal of the power input terminal of the load;

[0012] The MCU is used to receive the voltage signal, and when the voltage signal is less than a preset voltage threshold, generate a PWM signal according to the voltage signal, and output the PWM signal to the drive circuit to control the drive circuit to drive the P-MOSFET switch to turn on for load pre-charging; when the voltage signal is equal to the preset voltage threshold, output a control signal to the power switch to control the power switch to close for normal load power supply, and output a low-level signal to the drive circuit to control the drive circuit to drive the P-MOSFET switch to turn off to end load pre-charging.

[0013] According to a second aspect of the present application, a control method for a load power distribution pre-charging circuit as described in the first aspect is provided, comprising:

[0014] The voltage sampling circuit collects a voltage signal from the power input terminal of the load and sends the voltage signal to the MCU;

[0015] When the voltage signal is less than a preset voltage threshold, the MCU generates a PWM signal according to the voltage signal, and outputs the PWM signal to the drive circuit to control the drive circuit to drive the P-MOSFET switch to turn on for load precharging;

[0016] When the voltage signal is equal to a preset voltage threshold, the MCU outputs a control signal to the power switch to control the power switch to close for normal power supply to the load, and outputs a low-level signal to the drive circuit to control the drive circuit to drive the P-MOSFET switch to close to end load pre-charging.

[0017] The present application provides a load distribution pre-charging circuit and a control method thereof, which have the following beneficial effects:

[0018] When the MCU outputs a high-level signal to the drive circuit, the drive circuit provides a voltage to the gate of the P-MOSFET switch. The P-MOSFET begins to conduct under the action of the gate voltage, allowing current to flow to the load capacitor CL and starting the charging process. As charging proceeds, the charging current gradually increases from 0. When the current is small, the PNP transistor is in a cut-off state and will not affect the gate voltage of the P-MOSFET switch. When the charging current increases to the preset current limiting current I (limit), the PNP transistor begins to conduct. The conduction of the PNP transistor causes the current between its collector and emitter (CE) to flow, which raises the gate voltage of the P-MOSFET switch. As the gate voltage of the P-MOSFET switch increases, the P-MOSFET switch begins to work in the amplification region, and its internal resistance increases. The increased internal resistance limits the charging current flowing through the first resistor (current limiting resistor), so that the current no longer increases and is maintained at a constant value. In this way, a constant current charging state is achieved, and the charging current is stabilized at I (limit), thereby reducing the power of the current limiting resistor and the P-MOSFET switch.

[0019] The MCU generates a corresponding PWM signal based on the voltage signal at the power input end of the load collected by the voltage sampling circuit, which is used to control the P-MOSFET switch and control the dissipated power of the P-MOSFET switch within the maximum dissipated power range allowed by the P-MOSFET switch. As the voltage at the power input end of the load increases, the duty cycle of the PWM signal is adjusted synchronously, so that the charging speed will not slow down due to the increase in the voltage at the power input end of the load, shortening the overall pre-charging time. At the same time, even if the load is abnormally short-circuited, the P-MOSFET switch will not be burned out, and it has the function of abnormal load short-circuit protection. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0021] Figure 1 This is the circuit diagram of a common pre-charging circuit.

[0022] Figure 2 This is a circuit diagram of a load power distribution pre-charging circuit in an embodiment of the present application.

[0023] Figure 3 is a circuit diagram of a driving circuit in an embodiment of the present application.

[0024] Figure 4 is a circuit diagram of a voltage sampling circuit in an embodiment of the present application.

[0025] Figure 5 This is a flow chart of a method for controlling a load power distribution pre-charging circuit in an embodiment of the present application.

[0026] Figure 6 This is a specific flow chart of a control method for a load power distribution pre-charging circuit in an embodiment of the present application.

[0027] exist Figure 2-4 middle:

[0028] R1 is the first resistor; R2 is the first resistor; R3 is the first resistor; R4 is the first resistor; R5 is the first resistor; R6 is the first resistor; R7 is the first resistor; R8 is the first resistor; R9 is the first resistor; Q2 is a PNP transistor; Q3 is an NPN transistor; Q1 is a P-MOSFET; C1 is a first capacitor. DETAILED DESCRIPTION

[0029] The detailed description of the drawings is intended as an illustration of the current embodiment of the present application, and is not intended to represent the only form in which the present application can be implemented. It should be understood that the same or equivalent functions can be accomplished by different embodiments intended to be included in the spirit and scope of the present application.

[0030] See also Figure 2 , one embodiment of the present application provides a load power distribution pre-charging circuit, including a pre-charging switch circuit, a current limiting circuit, a voltage sampling circuit, an MCU and a power switch; the current limiting circuit includes a first resistor, a second resistor, a third resistor and a PNP transistor; the pre-charging switch circuit includes a fourth resistor, a P-MOSFET switch and a driving circuit;

[0031] One end of the power switch is connected to the input power supply, and the other end is connected to the power input end of the load; the load is provided with an input filter capacitor;

[0032] One end of the voltage sampling circuit is connected to the voltage output end of the power switch, and the other end is connected to the MCU;

[0033] One end of the first resistor is connected to the voltage input terminal of the power switch, and the other end is connected to the source of the P-MOSFET switch; one end of the second resistor is connected to the source of the P-MOSFET switch, and the other end is connected to the base of the PNP transistor; one end of the third resistor is connected to the base of the PNP transistor, and the other end is connected to the emitter of the PNP transistor;

[0034] The drain of the P-MOSFET switch is connected to the voltage output terminal of the power switch; one end of the fourth resistor is connected to the gate of the P-MOSFET switch, and the other end is connected to the source of the P-MOSFET switch; one end of the drive circuit is connected to the gate of the P-MOSFET switch, and the other end is connected to the MCU;

[0035] The voltage sampling circuit is used to collect the voltage signal of the power input terminal of the load;

[0036] The MCU is used to receive the voltage signal, and when the voltage signal is less than a preset voltage threshold, generate a PWM signal according to the voltage signal, and output the PWM signal to the drive circuit to control the drive circuit to drive the P-MOSFET switch to turn on for load pre-charging; when the voltage signal is equal to the preset voltage threshold, output a control signal to the power switch to control the power switch to close for normal load power supply, and output a low-level signal to the drive circuit to control the drive circuit to drive the P-MOSFET switch to turn off to end load pre-charging.

[0037] Specifically, the MCU is provided with an ADC signal port, a PWM signal port and an IO signal port; the ADC signal port is connected to the voltage sampling circuit, and is used to receive the voltage signal of the power input end of the load collected by the voltage sampling circuit; the PWM signal port is connected to the drive circuit, and is used to output the PWM signal to the drive circuit; the IO signal port is connected to the power switch, and is used to output the control signal to the power switch.

[0038] The working principle of the load power distribution pre-charging circuit of this embodiment is as follows:

[0039] like Figure 2As shown, the load is simplified as a parallel structure of an input filter capacitor CL and an equivalent parallel resistor RL. The load power distribution pre-charging circuit of this embodiment forms two loops, the first loop is formed by the input power supply (Vin), the power switch and the load, and the second loop is formed by the input power supply (Vin), the pre-charging switch circuit, the current limiting circuit and the load. The MCU acts as a control unit to control the power switch and the P-MOSFET switch in the pre-charging switch circuit to turn on or off according to the sampling result of the voltage sampling circuit, so as to close or disconnect the first loop to supply normal power to the load, or close or disconnect the second loop to pre-charge the load.

[0040] When the MCU outputs a high-level signal to the drive circuit, the drive circuit provides a voltage to the gate of the P-MOSFET switch. The P-MOSFET begins to conduct under the action of the gate voltage, allowing current to flow to the load capacitor CL and starting the charging process. As charging proceeds, the charging current gradually increases from 0. When the current is small, the PNP transistor is in a cut-off state and will not affect the gate voltage of the P-MOSFET switch. When the charging current increases to the preset current limiting current I (limit), the PNP transistor begins to conduct. The conduction of the PNP transistor causes the current between its collector and emitter (CE) to flow, which raises the gate voltage of the P-MOSFET switch. As the gate voltage of the P-MOSFET switch increases, the P-MOSFET switch begins to work in the amplification region, and its internal resistance increases. The increased internal resistance limits the charging current flowing through the first resistor (current limiting resistor), so that the current no longer increases and is maintained at a constant value. In this way, a constant current charging state is achieved, and the charging current is stabilized at I (limit), thereby reducing the power of the current limiting resistor and the P-MOSFET switch.

[0041] The MCU generates a corresponding PWM signal based on the voltage signal at the power input terminal of the load collected by the voltage sampling circuit, which is used to control the P-MOSFET switch and control the dissipated power of the P-MOSFET switch within the maximum dissipated power range allowed by the P-MOSFET switch. As the voltage (Vout) at the power input terminal of the load increases, the duty cycle of the PWM signal is adjusted synchronously, so that the charging speed will not slow down due to the increase in the voltage (Vout) at the power input terminal of the load, thereby shortening the overall pre-charging time. At the same time, even if the load is abnormally short-circuited, the P-MOSFET switch will not be burned out, and it has the function of abnormal load short-circuit protection.

[0042] Specifically, the current limiting current I(limit) is calculated as shown in the following formula (1), which is determined by the first resistor, the second resistor, the third resistor, and the BE voltage Vbe of the PNP transistor, where the second resistor and the third resistor are much larger than the first resistor, and Vbe is approximately -0.7V at room temperature. The peak power P of the first resistor is R1 The calculation is shown in the following formula (2), and the power resistor with the appropriate peak value can be selected according to the resistor power;

[0043] I(limit)≈(-Vbe) / R3*(R2+R3) / R1(1)

[0044] P R1 =I(limit)*I(limit)*R1 (2)

[0045] In this embodiment, the instantaneous power of the first resistor (current limiting resistor) is reduced under the premise of a shorter charging time. Therefore, the first resistor can be selected, for example, a chip power resistor, which occupies a small space and is simple to produce and process, while improving the power utilization of the pre-charging rear-stage power resistor.

[0046] See also Figure 3 , in some embodiments, the driving circuit includes an NPN transistor, a fifth resistor, a sixth resistor and a seventh resistor;

[0047] One end of the fifth resistor is connected to the gate of the P-MOSFET switch, and the other end is connected to the collector of the NPN transistor; one end of the sixth resistor is connected to the PWM signal port of the MCU, and the other end is connected to the base of the NPN transistor; one end of the seventh resistor is connected to the base of the NPN transistor, and the other end is grounded; the emitter of the NPN transistor is grounded.

[0048] Specifically, the working principle of the driving circuit is as follows:

[0049] When the PWM signal port of the MCU outputs a high level, the current will flow to the base of the NPN transistor through the sixth resistor, causing the NPN transistor to turn on; when the NPN transistor is turned on, the resistance between its collector and emitter decreases, allowing current to flow to the gate of the P-MOSFET through the fifth resistor, thereby turning on the P-MOSFET; when the PWM signal port of the MCU outputs a low level, the base current of the NPN transistor is cut off, and the NPN transistor is turned off, thereby cutting off the current path of the gate of the P-MOSFET, causing the P-MOSFET to turn off; in this way, the PWM signal of the MCU can effectively control the conduction and cutoff of the P-MOSFET, thereby controlling the pre-charging process.

[0050] See also Figure 4In some embodiments, the voltage sampling circuit includes an eighth resistor, a ninth resistor and a first capacitor; one end of the eighth resistor is connected to the drain of the P-MOSFET switch, and the other end is connected to one end of the ninth resistor; one end of the ninth resistor is connected to the ADC signal port of the MCU, and the other end is grounded; the first capacitor is connected in parallel with the ninth resistor.

[0051] Specifically, the working principle of the voltage sampling circuit is as follows:

[0052] When the P-MOSFET switch is turned on, the drain voltage will form a voltage divider through the eighth resistor and the ninth resistor; the divided voltage signal can be transmitted to the ADC signal port of the MCU through the ninth resistor, and the MCU can read this voltage value to monitor the working status of the P-MOSFET; the first capacitor is connected in parallel to the ninth resistor, which can help smooth the voltage signal and reduce voltage fluctuations caused by other switching actions in the circuit or external interference; the voltage sampling circuit allows the MCU to monitor the drain voltage of the P-MOSFET in real time, which is very important for closed-loop control. For example, the MCU can adjust the duty cycle of the PWM signal according to the change of the drain voltage to maintain a constant charging current or achieve other control goals.

[0053] In some embodiments, the duty cycle of the PWM signal increases as the voltage signal at the power input terminal of the load increases.

[0054] Specifically, the duty cycle of the PWM signal in this embodiment is adjusted according to the change of the voltage signal (Vout) at the power input terminal of the load. In the early stage of pre-charging, the voltage difference between the voltage (Vin) of the input power supply and the voltage (Vout) of the power input terminal of the load is large, that is, (Vin-Vout)>(I(limit)*R1). When the PWM signal of the MCU is at a high level, the P-MOSFET switch is turned on, allowing current to flow to the load capacitor for charging. In the stage of (Vin-Vout)>(I(limit)*R1), the charging current is limited to the maximum current I(limit). As the charging process proceeds, the voltage of Vout gradually increases, and the voltage difference (Vin-Vout) gradually decreases. In order to maintain a constant maximum charging current I(limit), the MCU will gradually increase the duty cycle of the PWM signal, that is, in the PWM cycle, the proportion of the high level time increases, and the proportion of the low level time decreases. By increasing the duty cycle, the charging current can be maintained at I(limit) even if Vout increases. In this way, the charging speed will not slow down due to the increase in Vout, and the overall pre-charging time can be effectively shortened because it ensures that the charging current is maintained at the maximum value I(limit) as much as possible during the entire pre-charging process.

[0055] In some embodiments, the MCU is also used to detect whether the load pre-charging has timed out. If so, the load is determined to be abnormal, and a low-level signal is output to the drive circuit to control the drive circuit to drive the P-MOSFET switch to turn off to end the load pre-charging, and record the load abnormality information.

[0056] Specifically, the MCU has a built-in timer or clock to monitor the time of the pre-charging process. When the pre-charging process starts, the MCU starts timing. If the pre-charging process lasts longer than the preset time threshold (i.e., timeout), the MCU will determine that this may be due to an abnormality in the load. The abnormality may include a load short circuit, an open circuit, or other faults, which may cause the load to be unable to complete pre-charging within the normal time. Once the pre-charging timeout is detected and the load is determined to be abnormal, the MCU will output a low-level signal to the drive circuit. The function of this low-level signal is to turn off the P-MOSFET switch, thereby stopping the pre-charging of the load. This can prevent further current flow and avoid possible damage to the circuit or battery. After turning off the P-MOSFET switch, the MCU will also record the information of the load abnormality, such as the time, duration, and type of abnormality. Recording this information is very important for fault diagnosis and system maintenance. It can help engineers or technicians understand the working status of the system, analyze the cause of the abnormality, and take corresponding maintenance or improvement measures.

[0057] See also Figure 5 Another embodiment of the present application further provides a method for controlling the load power distribution pre-charging circuit as described above, comprising the following steps:

[0058] Step S10, the voltage sampling circuit collects a voltage signal from the power input terminal of the load, and sends the voltage signal to the MCU;

[0059] Step S20, when the voltage signal is less than a preset voltage threshold, the MCU generates a PWM signal according to the voltage signal, and outputs the PWM signal to the drive circuit to control the drive circuit to drive the P-MOSFET switch to turn on for load precharging;

[0060] Step S30, when the voltage signal is equal to the preset voltage threshold, the MCU outputs a control signal to the power switch to control the power switch to close for normal power supply to the load, and outputs a low-level signal to the drive circuit to control the drive circuit to drive the P-MOSFET switch to close to end load pre-charging.

[0061] In some embodiments, the duty cycle of the PWM signal increases as the voltage signal at the power input terminal of the load increases.

[0062] In some embodiments, the MCU generates a PWM signal according to the voltage signal, further comprising:

[0063] The duty cycle of the PWM signal is calculated according to the following formula:

[0064] Vds=-(Vin-I(limit)*R1-Vout) (3)

[0065] P Q1 =-Vds*I(limit) (4)

[0066] DUTY=P Q1 / P max (5)

[0067] Wherein, Vds is the voltage value between the drain d and the source s of the P-MOSFET switch, Vin is the voltage value of the input power supply, Vout is the voltage value of the voltage signal at the power input end of the load, I(limit) is the current value of the current limiting current, R1 is the resistance value of the first resistor, P Q1 is the peak power of the P-MOSFET switch, DUTY is the duty cycle of the PWM signal, P max is the maximum power dissipation of the P-MOSFET switch.

[0068] In some embodiments, the current value of the current limiting current is calculated according to the following formula:

[0069] I(limit)=(-Vbe) / R3*(R2+R3) / R1

[0070] Wherein, Vbe is the voltage value of the voltage between the base b and the emitter e of the PNP transistor, R2 is the resistance value of the second resistor, and R3 is the resistance value of the third resistor.

[0071] In some embodiments, the step S20 further includes:

[0072] During the load pre-charging process, when the charging current increases to the current limiting current, the PNP transistor starts to conduct, and the current between the base and the emitter of the PNP transistor will raise the gate voltage of the P-MOSFET switch, causing the P-MOSFET switch to operate in the amplification area. The internal resistance of the P-MOSFET switch increases, thereby limiting the charging current flowing through the first resistor from increasing.

[0073] In some embodiments, Figure 6 As shown, the step S20 further includes:

[0074] During the load pre-charging process, the MCU detects whether the load pre-charging has timed out. If not, it continues to generate a corresponding PWM signal to control the P-MOSFET switch according to the voltage Vout at the power input terminal of the load. If it times out, it determines that the load is abnormal, and outputs a low-level signal to the drive circuit to control the drive circuit to drive the P-MOSFET switch to turn off to end the load pre-charging, and record the load abnormality information.

[0075] It should be noted that the control method of this embodiment is implemented based on the load power distribution pre-charging circuit of the above-mentioned embodiment. The working principle of the control method of this embodiment has been described in detail in the load power distribution pre-charging circuit of the above-mentioned embodiment. Therefore, the contents not described in detail in the control method of this embodiment can be obtained by referring to the contents of the load power distribution pre-charging circuit of the above-mentioned embodiment, and will not be repeated in this embodiment.

[0076] The embodiments of the present application have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and changes will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The selection of terms used herein is intended to best explain the principles of the embodiments, practical applications, or technical improvements in the market, or to enable other persons of ordinary skill in the art to understand the embodiments disclosed herein.

Claims

1. A load power distribution precharging circuit, characterized in that: It includes a pre-charging switch circuit, a current limiting circuit, a voltage sampling circuit, an MCU and a power switch; the current limiting circuit includes a first resistor, a second resistor, a third resistor and a PNP transistor; the pre-charging switch circuit includes a fourth resistor, a P-MOSFET switch and a driving circuit; One end of the power switch is connected to the input power supply, and the other end is connected to the power input end of the load; the load is provided with an input filter capacitor; One end of the voltage sampling circuit is connected to the voltage output end of the power switch, and the other end is connected to the MCU; One end of the first resistor is connected to the voltage input terminal of the power switch, and the other end is connected to the source of the P-MOSFET switch; one end of the second resistor is connected to the source of the P-MOSFET switch, and the other end is connected to the base of the PNP transistor; one end of the third resistor is connected to the base of the PNP transistor, and the other end is connected to the emitter of the PNP transistor; The drain of the P-MOSFET switch is connected to the voltage output terminal of the power switch; one end of the fourth resistor is connected to the gate of the P-MOSFET switch, and the other end is connected to the source of the P-MOSFET switch; one end of the drive circuit is connected to the gate of the P-MOSFET switch, and the other end is connected to the MCU; The voltage sampling circuit is used to collect the voltage signal of the power input terminal of the load; The MCU is used to receive the voltage signal, and when the voltage signal is less than a preset voltage threshold, generate a PWM signal according to the voltage signal, and output the PWM signal to the drive circuit to control the drive circuit to drive the P-MOSFET switch to turn on for load pre-charging; when the voltage signal is equal to the preset voltage threshold, output a control signal to the power switch to control the power switch to close for normal load power supply, and output a low-level signal to the drive circuit to control the drive circuit to drive the P-MOSFET switch to turn off to end load pre-charging.

2. The load power distribution precharge circuit according to claim 1, wherein The driving circuit includes an NPN transistor, a fifth resistor, a sixth resistor and a seventh resistor; One end of the fifth resistor is connected to the gate of the P-MOSFET switch, and the other end is connected to the collector of the NPN transistor; one end of the sixth resistor is connected to the PWM signal port of the MCU, and the other end is connected to the base of the NPN transistor; one end of the seventh resistor is connected to the base of the NPN transistor, and the other end is grounded; the emitter of the NPN transistor is grounded.

3. The load power distribution pre-charging circuit according to claim 1, wherein The voltage sampling circuit includes an eighth resistor, a ninth resistor and a first capacitor; one end of the eighth resistor is connected to the drain of the P-MOSFET switch, and the other end is connected to one end of the ninth resistor; one end of the ninth resistor is connected to the ADC signal port of the MCU, and the other end is grounded; the first capacitor is connected in parallel with the ninth resistor.

4. The load power distribution precharge circuit according to claim 1, wherein The duty cycle of the PWM signal increases as the voltage signal at the power input terminal of the load increases.

5. The load power distribution pre-charging circuit according to any one of claims 1 to 4, characterized in that: The MCU is also used to detect whether the load pre-charging has timed out. If so, it is determined that the load is abnormal, and a low-level signal is output to the drive circuit to control the drive circuit to drive the P-MOSFET switch to turn off to end the load pre-charging, and record the load abnormality information.

6. A control method for a load power distribution pre-charging circuit as claimed in claim 1, characterized in that: include: The voltage sampling circuit collects a voltage signal from the power input terminal of the load and sends the voltage signal to the MCU; When the voltage signal is less than a preset voltage threshold, the MCU generates a PWM signal according to the voltage signal, and outputs the PWM signal to the drive circuit to control the drive circuit to drive the P-MOSFET switch to turn on for load precharging; When the voltage signal is equal to a preset voltage threshold, the MCU outputs a control signal to the power switch to control the power switch to close for normal power supply to the load, and outputs a low-level signal to the drive circuit to control the drive circuit to drive the P-MOSFET switch to close to end load pre-charging.

7. The control method according to claim 6, characterized in that: The duty cycle of the PWM signal increases as the voltage signal at the power input terminal of the load increases.

8. The control method according to claim 7, characterized in that: The MCU generates a PWM signal according to the voltage signal, further comprising: The duty cycle of the PWM signal is calculated according to the following formula: Vds=-(Vin-I(limit)*R1-Vout) P Q1 =-Vds*I(limit) DUTY=P Q1 / P max Wherein, Vds is the voltage value of the voltage between the drain and source of the P-MOSFET switch, Vin is the voltage value of the input power supply, Vout is the voltage value of the voltage signal at the power input end of the load, I(limit) is the current value of the current limiting current, R1 is the resistance value of the first resistor, P Q1 is the peak power of the P-MOSFET switch, DUTY is the duty cycle of the PWM signal, P max is the maximum power dissipation of the P-MOSFET switch.

9. The control method according to claim 8, characterized in that: The current value of the current limiting current is calculated according to the following formula: I(limit)=(-Vbe) / R3*(R2+R3) / R1 Wherein, Vbe is the voltage value of the voltage between the base and the emitter of the PNP transistor, R2 is the resistance value of the second resistor, and R3 is the resistance value of the third resistor.

10. The control method according to claim 9, characterized in that: The method further comprises: During the load pre-charging process, when the charging current increases to the current limiting current, the PNP transistor starts to conduct, and the current between the base and the emitter of the PNP transistor will raise the gate voltage of the P-MOSFET switch, causing the P-MOSFET switch to operate in the amplification area. The internal resistance of the P-MOSFET switch increases, thereby limiting the charging current flowing through the first resistor from increasing.

11. The control method according to any one of claims 6 to 10, characterized in that: The method further comprises: During the load pre-charging process, the MCU detects whether the load pre-charging has timed out. If so, it determines that the load is abnormal, and outputs a low-level signal to the drive circuit to control the drive circuit to drive the P-MOSFET switch to turn off to end the load pre-charging, and record the load abnormality information.

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