Control method capable of adjusting voltage soft start time

Abstract

The invention belongs to the field of chips, and provides a control method capable of adjusting voltage soft start time, which is characterized in that the method is applied to an ascending soft start circuit or a descending soft start circuit, and each of the ascending soft start circuit and the descending soft start circuit comprises a current mirror, a current source, a controllable charging unit and a fixed voltage source. In the rising soft start circuit and the falling soft start circuit, a fixed voltage source supplies power to an MSO tube in a current mirror, a current source is connected to the input side of the current mirror, and a controllable charging unit is arranged on the output side of the current mirror, and the method comprises the steps that when starting voltage needs to be increased, the starting voltage is slowly increased based on the rising soft start circuit; when the starting voltage needs to be reduced, the starting voltage is slowly reduced based on the descending soft starting circuit; the problem that in the prior art, when a soft start function is performed to enable voltage to rise or fall slowly, limitation exists when capacitor charging is adopted can be solved.

Description

Technical Field

[0001] The present invention relates to the field of chips, and in particular to a control method capable of adjusting voltage soft start time. Background Art

[0002] In general chip applications, if you want to perform a soft start function to make the voltage rise or fall slowly, you will use a constant current charging capacitor to achieve the function of slow voltage rise and fall. Although it is easy to implement, if you want to extend the voltage rise time, you must reduce the current or increase the capacitance. There is a process limit to reducing the current. When the current is too small, the current variation caused by the process will become larger, resulting in inaccurate voltage rise or fall time. Increasing the capacitance will increase the circuit area and increase the chip cost. In addition, the voltage of the existing technology can only rise or fall at a fixed slope, and the slope cannot be adjusted. Summary of the invention

[0003] In view of the above technical problems, the present invention provides a control method capable of adjusting the voltage soft start time, so as to solve the problem in the prior art that when the soft start function is performed to allow the voltage to rise or fall slowly, there are limitations in using capacitor charging.

[0004] Other features and advantages of the present disclosure will become apparent from the following detailed description, or may be learned in part by the practice of the present disclosure.

[0005] The present invention discloses a control method capable of adjusting voltage soft start time. The method is applied to a rising soft start circuit or a falling soft start circuit. The rising soft start circuit and the falling soft start circuit both include a current mirror, a current source, a controllable charging unit, and a fixed voltage source. In the rising soft start circuit and the falling soft start circuit, the fixed voltage source supplies power to an MSO tube in the current mirror, the current source is connected to the input side of the current mirror, and the controllable charging unit is arranged at the output side of the current mirror. The method includes:

[0006] When the starting voltage needs to rise, the starting voltage is slowly raised based on the rising soft start circuit. In the rising soft start circuit, the current source is not in common with the fixed voltage source, the controllable charging unit is not in common with the fixed voltage source, and the starting voltage is located between the output end of the controllable charging unit and the current mirror. Initially, the controllable charging unit is short-circuited so that the starting voltage is discharged. When it needs to rise, the controllable charging unit is connected, and the current generated by the current source flows to the controllable charging unit through the current mirror, so that the starting voltage is gradually raised after the controllable charging unit is charged.

[0007] When the starting voltage needs to be decreased, the starting voltage is slowly decreased based on the decreasing soft start circuit. In the decreasing soft start circuit, the current source and the fixed voltage source have a common terminal, and the controllable charging unit and the fixed voltage source have a common terminal. The starting voltage is located between the output terminal of the controllable charging unit and the current mirror. Initially, the controllable charging unit is short-circuited so that the starting voltage is charged by the fixed voltage source. When decreasing, the controllable charging unit is passed through. The current generated by the current source passes through the current mirror and discharges the controllable charging unit in the reverse direction. When the controllable charging unit is discharged, the starting voltage is pulled down.

[0008] Furthermore, a first switch is provided in both the rising soft start circuit and the falling soft start circuit, and the first switch is located between the output end of the current mirror and the controllable charging unit. When the controllable charging unit is charged or discharged, the conduction time of the first switch is controlled so that the charging time or discharging time of the controllable charging unit is changed.

[0009] Furthermore, the current source is fixed.

[0010] Furthermore, the current source is variable, and includes an operational amplifier, an MN tube, and a first resistor. The positive input terminal of the operational amplifier is connected to a variable reference voltage, and the output terminal thereof is connected to the gate of the MN tube and its own negative input terminal, wherein:

[0011] In the rising soft start circuit, the drain of the MN tube is connected to the input side of the current mirror, the source thereof is connected to one end of the first resistor, and the other end of the first resistor is grounded;

[0012] In the falling soft start circuit, the source of the MN tube is connected to the input side of the current mirror, the drain is connected to one end of the first resistor, and the other end of the first resistor is connected to the fixed voltage source;

[0013] When the rising soft start circuit needs to charge the controllable charging unit and the falling soft start circuit needs to discharge the controllable charging unit, the variable reference voltage is adjusted so that the charging time or the discharging time of the controllable charging unit is changed.

[0014] Furthermore, a first switch is provided in both the rising soft start circuit and the falling soft start circuit, and the first switch is located between the output end of the current mirror and the controllable charging unit. When the rising soft start circuit needs to charge the controllable charging unit and the falling soft start circuit needs to discharge the controllable charging unit, the variable reference voltage and the conduction time of the first switch are regulated so that the charging time or discharging time of the controllable charging unit is changed.

[0015] Furthermore, the controllable charging unit includes a capacitor and a second switch connected in parallel with the capacitor. When the controllable charging unit is short-circuited, the second switch is closed, and when the controllable charging unit is connected, the second switch is opened.

[0016] Furthermore, the controllable charging unit includes a calculation unit and a variable resistance digital unit, wherein:

[0017] The computing unit comprises n flip-flops connected in series, the clock input terminal of the first flip-flop is connected to the clock signal, the clock input terminal of the (I+1)th flip-flop is connected to the non-Q terminal of the (I)th flip-flop, the reset terminals of all the flip-flops are connected to the same reset signal, and the D terminals of all the flip-flops are connected to the non-Q terminals thereof;

[0018] The variable resistor digital unit includes n second resistors connected in series, and n third switches connected in parallel to each of the second resistors, and the first third switch is controlled by the Q end of the first trigger.

[0019] The technical solution disclosed in this disclosure has the following beneficial effects:

[0020] By setting the current mirror in the rising soft start circuit or the falling soft start circuit, whether the starting voltage needs to be increased or decreased, charging or discharging can be achieved by changing the conduction state of the controllable charging unit, thereby achieving a slow change of the starting voltage, which can effectively reduce the chip cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is a flow chart of a control method for adjusting voltage soft start time in an embodiment of this specification;

[0022] Figure 2 This is a schematic diagram of the rising soft start circuit in Embodiment 1 of this specification;

[0023] Figure 3 This is a schematic diagram of the falling soft start circuit in Embodiment 1 of this specification;

[0024] Figure 4 This is a schematic diagram of the rising soft start circuit in Embodiment 2 of this specification;

[0025] Figure 5 A schematic diagram of the rise of the starting voltage of the rising soft start circuit in the second embodiment of this specification;

[0026] Figure 6 This is a schematic diagram of the falling soft start circuit in Embodiment 2 of this specification;

[0027] Figure 7This is a schematic diagram of the rising soft start circuit in Embodiment 3 of this specification;

[0028] Figure 8 This is a schematic diagram of the soft start circuit for going down the well in the third embodiment of this specification;

[0029] Fig. 9 This is a schematic diagram of the rising soft start circuit in the fourth embodiment of this specification;

[0030] Fig.10 This is a schematic diagram of the soft start circuit for going down the well in the fourth embodiment of this specification;

[0031] Fig.11 This is a schematic diagram of the rising soft start circuit in Embodiment 5 of this specification;

[0032] Fig.12 This is a circuit schematic diagram of a calculation unit in Embodiment 5 of this specification;

[0033] Fig.13 is a schematic diagram of a signal cycle of a calculation unit in Embodiment 5 of this specification;

[0034] Fig.14 This is a circuit diagram of a variable resistor digital unit in Embodiment 5 of this specification;

[0035] Fig.15 This is a graph showing the rise of the starting voltage in Embodiment 5 of this specification;

[0036] Fig.16 This is a schematic diagram of the falling soft start circuit in the fifth embodiment of this specification. DETAILED DESCRIPTION

[0037] Example embodiments will now be described more fully with reference to the accompanying drawings. However, example embodiments can be implemented in a variety of forms and should not be construed as being limited to the examples set forth herein; on the contrary, these embodiments are provided so that the present disclosure will be more comprehensive and complete, and the concepts of the example embodiments are fully conveyed to those skilled in the art. The described features, structures, or characteristics may be combined in one or more embodiments in any suitable manner. In the following description, many specific details are provided to provide a full understanding of the embodiments of the present disclosure. However, those skilled in the art will appreciate that the technical solutions of the present disclosure may be practiced while omitting one or more of the specific details, or other methods, components, devices, steps, etc. may be adopted. In other cases, known technical solutions are not shown or described in detail to avoid obscuring various aspects of the present disclosure.

[0038] In the first embodiment, Figure 1-3As shown, the embodiment of this specification provides a control method for adjusting the voltage soft start time, the method is applied to a rising soft start circuit or a falling soft start circuit, the rising soft start circuit and the falling soft start circuit both include a current mirror 1, a current source 2, a controllable charging unit 3, and a fixed voltage source VIN, in the rising soft start circuit and the falling soft start circuit, the fixed voltage source is respectively used to power the MSO tube in the current mirror, the current source is connected to the input side of the current mirror, and the controllable charging unit is arranged at the output side of the current mirror, the method includes steps S101-102:

[0039] In step S101, when the starting voltage needs to rise, the starting voltage is slowly raised based on the rising soft start circuit. In the rising soft start circuit, the current source is not in common with the fixed voltage source, the controllable charging unit is not in common with the fixed voltage source, and the starting voltage is located between the output end of the controllable charging unit and the current mirror. Initially, the controllable charging unit is short-circuited so that the starting voltage is discharged. When the starting voltage needs to rise, the controllable charging unit is connected, and the current generated by the current source flows to the controllable charging unit through the current mirror, so that the starting voltage is gradually raised after the controllable charging unit is charged.

[0040] In step S102, when the starting voltage needs to be decreased, the starting voltage is slowly decreased based on the decreasing soft start circuit. In the decreasing soft start circuit, the current source and the fixed voltage source have a common terminal, and the controllable charging unit and the fixed voltage source have a common terminal. The starting voltage is located between the output terminal of the controllable charging unit and the current mirror. Initially, the controllable charging unit is short-circuited so that the starting voltage is charged by the fixed voltage source. When decreasing, the controllable charging unit is connected. The current generated by the current source passes through the current mirror and discharges the controllable charging unit in the reverse direction. When the controllable charging unit is discharged, the starting voltage is pulled down.

[0041] The controllable charging unit includes a capacitor and a second switch connected in parallel with the capacitor. When the controllable charging unit is short-circuited, the second switch is closed, and when the controllable charging unit is connected, the second switch is opened.

[0042] Among them, the rising soft start circuit is as follows Figure 2As shown, S0 is the second switch used to reset VO when the power is turned on. When the power is turned on, S0 will be short-circuited to discharge VO to 0V. VO is the starting voltage. When the VO voltage starts to rise, S0 will be disconnected. After S0 is disconnected, the current source generates a current I, which is converted into a current multiple through the current mirror MOS tube MP1 and MOS tube MP2 to obtain a current NxI. This current is then used to charge the capacitor C below, so that a slowly rising voltage VO can be obtained. Using the capacitor charge formula CV=IT, it can be obtained that the rising slope of VO is: ΔVO / ΔT=NxI / C.

[0043] Similarly, if you want to get a slowly decreasing voltage, Figure 3 As shown, S0 is the second switch used to reset VO when the power is turned on. When the power is turned on, S0 will be short-circuited to charge VO to VIN. When the VO voltage starts to drop, S0 will be disconnected. After S0 is disconnected, a constant current source I is used to convert the current multiples using current mirrors MN1 and MN2 to obtain a current NxI. This current is then used to discharge the upper capacitor C, so that a slowly rising voltage VO can be obtained. The VO drop slope is: ΔVO / ΔT=NxI / C.

[0044] In the second embodiment, Figure 4-6 As shown, different from the above embodiment, the rising soft start circuit and the falling soft start circuit are both provided with a first switch S1, and the first switch S1 is located between the output end of the current mirror 1 and the controllable charging unit 3. When the controllable charging unit 3 is charged or discharged, the conduction time of the first switch S1 is controlled so that the charging time or discharging time of the controllable charging unit 3 is changed. Among them, the current source 2 is fixed and generates a constant current.

[0045] Among them, S0 is the second switch used to reset VO when the power is turned on. When the power is turned on, S0 will be short-circuited to charge VO to VIN. When the VO voltage starts to drop, S0 will be disconnected. After S0 is disconnected, the switch S1 is used to control the time for the MOS tube MP2 current to flow through the lower capacitor C. When S1 is short-circuited, the MP2 current charges the lower capacitor. When S1 is disconnected, the MP2 current stops charging the lower capacitor. Figure 5 The schematic diagram of VO voltage rise is shown below. Assuming that S1 is short-circuited for only d time per cycle T, the VO rise slope is: ΔVO / ΔT=NxI / Cx(d / T). In this way, the VO rise time is T / d times of the original circuit. For example, if S1 is only connected for 1 / 10 of the time per cycle, the VO rise time can be extended by 10 times. The VO rise speed can be adjusted by simply changing the S1 on time (d).

[0046] Similarly, if you want to slowly reduce the voltage, you can use Figure 6 Circuit implementation: Assuming that S1 is only turned on for d time per cycle T, the VO falling slope is: ΔVO / ΔT=NxI / Cx(d / T).

[0047] In the third embodiment, Figure 7-8 As shown, the current source 2 is variable, and the current source 2 specifically includes an operational amplifier OP, a MN tube MN1, and a first resistor R. The positive phase input terminal of the operational amplifier OP is connected to a variable reference voltage VREF, and the output terminal thereof is connected to the gate of the MN tube MN1 and its own negative phase input terminal, wherein: in the rising soft start circuit, the drain of the MN tube MN1 is connected to the input side of the current mirror, the source thereof is connected to one end of the first resistor R, and the other end of the first resistor is grounded; in the falling soft start circuit, the source of the MN tube MN1 is connected to the input side of the current mirror, the drain thereof is connected to one end of the first resistor R, and the other end of the first resistor R is connected to the fixed voltage source; when the rising soft start circuit needs to charge the controllable charging unit and the falling soft start circuit needs to discharge the controllable charging unit, the variable reference voltage VREF is regulated so that the charging time or the discharging time of the controllable charging unit is changed.

[0048] Among them, Figure 7 As shown, the current source 2 under the MOS tube MP1 on the input side of the current mirror is changed into three devices: operational amplifier OP, MN tube MN1 and the first resistor R. Through the action of the operational amplifier OP, the voltages at the + and - ends of the operational amplifier OP can be made consistent, that is, VFB = VREF, so I = VREF / R can be obtained. It can be concluded that the rising slope of VO is: ΔVO / ΔT = NxI / C = NxVREF / (RxC). As long as the variable reference voltage VREF is changed, the rising speed of VO can be adjusted. Similarly, if you want the voltage to drop slowly, you can use Figure 8 The circuit is implemented, and the VO falling slope is: ΔVO / ΔT=Nx(VIN-VREF) / (RxC).

[0049] In the fourth embodiment, Figure 9-10 As shown, the rising soft start circuit and the falling soft start circuit are both provided with a first switch S1, and the first switch S1 is located between the output end of the current mirror 1 and the controllable charging unit 3. When the rising soft start circuit needs to charge the controllable charging unit 3 and the falling soft start circuit needs to discharge the controllable charging unit 3, the variable reference voltage VREF and the conduction time of the first switch S1 are regulated so that the charging time or the discharging time of the controllable charging unit 3 is changed.

[0050] Specifically, the fourth embodiment is combined with the second and third embodiments proposed above, that is, assuming that the first switch S1 is short-circuited for only d time per cycle T, the VO rising slope can be expressed as:

[0051] ΔVO / ΔT=NxI / Cx(d / T)=Nx(d / T)xVREF / (RxC);

[0052] The rising speed of VO can be adjusted by changing the variable reference voltage VREF or the short-circuit time (d) of the first switch S1. Similarly, if you want the voltage to drop slowly, you can use Fig.10 The circuit implementation of VO, the falling slope is:

[0053] ΔVO / ΔT=Nx(d / T)x(VIN–VREF) / (RxC);

[0054] In Example 5, Figure 11-16 As shown, the controllable charging unit includes a calculation unit 4 and a variable resistance digital unit 5, wherein:

[0055] The calculation unit 4 comprises n flip-flops connected in series, the clock input terminal of the first flip-flop is connected to the clock signal, the clock input terminal of the (I+1)th flip-flop is connected to the non-Q terminal of the (I)th flip-flop, the reset terminals of all the flip-flops are connected to the same reset signal, and the D terminals of all the flip-flops are connected to the non-Q terminals thereof;

[0056] The variable resistor digital unit 5 includes n second resistors connected in series, and n third switches connected in parallel to each of the second resistors, and the first third switch is controlled by the Q terminal of the first trigger.

[0057] Specifically, the control method is similar to that of the second embodiment, but the capacitor C in the lower right corner is replaced by the calculation unit 4 and the variable resistor digital unit 5. Figure 12-13 The circuit diagram and operation principle of the calculation unit are as follows:

[0058] Whenever the CK signal is high, CNT[n:0]+1, and when the RST signal is high, CNT[n:0] will return to 0, and when CNT[n:1]=2n-1, if the CK high level is encountered again, CNT[n:1] will also return to 0.

[0059] Fig.14 The circuit diagram of the variable resistor digital unit 5 is shown in FIG. Fig.15In the example, there are n second resistors, each of which is matched with a third switch. The switch of the R0 resistor is controlled by CNT[0]. When CNT[0]=1, the switch is disconnected, and when CNT[0]=0, the switch is short-circuited. Similarly, the switch of the Rn resistor is controlled by CNT[n]. When CNT[n]=1, the switch is disconnected, and when CNT[n]=0, the switch is short-circuited. When all bits of CNT[n:0] are 1, all switches are disconnected, and the equivalent resistance of the variable resistor digital unit is RDAC=R0+R1+…+Rn, at which time the resistance is maximum. If all bits of CNT[n:0] are 0, all switches are short-circuited, and the equivalent resistance of the variable resistor digital unit is 0, at which time the resistance is minimum. Therefore, by matching the calculation unit and the variable resistor digital unit, a variable resistor whose resistance value changes with the calculation number can be formed. If the calculation unit accumulates 1 from 0 to 1 at a speed of period T, the VO voltage rise slope can be expressed as follows:

[0060] ΔVO / ΔT=NxIxRDAC / T=NxVREF / RxRDAC / T;

[0061] Fig.15 FIG. 4 is a schematic diagram of VO variation, where RDAC is composed of R0, R1…Rn, and the calculation unit stops when it counts from 0 to 2n-1.

[0062] The control method of the fifth embodiment is relatively complex, but it reduces the capacitance variation, and the first resistor R and the second resistor in the variable resistor digital unit 5 are inversely related in the VO rising slope. The layout technique can be used inside the chip to match R and RDAC, so that the first resistor R and the second resistor in the variable resistor digital unit 5 can change synchronously, and the two are in a reciprocal relationship, so the resistance variation can offset each other. Because there is less capacitance and resistance variation, the climbing time of VO is more accurate, and the voltage height at which VO stops climbing can be set by the counting of the calculation unit. For example, if the calculation unit stops at 4, VO will stop at VO = NxVREF / RxR2. As long as the calculation unit does not move, VO will not rise any further. In addition, the climbing speed of VO can be adjusted by the height of the controllable variable reference voltage VREF and the counting cycle of the calculation unit. Similarly, if you want the voltage to drop slowly, you can use Fig.16 Circuit implementation, VO voltage drop slope can be expressed as follows:

[0063] ΔVO / ΔT=NxIxRDAC / T=NxVREF / RxRDAC / T;

[0064] In summary, this case proposes five methods to change the voltage climbing speed:

[0065] 1. Embodiment 2 proposes a method of changing the switch-on time to adjust the voltage climbing speed, rather than using a method of increasing the capacitor area and reducing the current to adjust, which can effectively reduce chip costs and reduce current variation problems.

[0066] 2. Embodiment 3 proposes a method of changing the reference voltage value and adjusting the voltage climbing speed instead of increasing the capacitor area and reducing the current, which can effectively reduce chip costs and reduce current variation problems.

[0067] 3. Embodiment 4 proposes a method for adjusting the voltage climbing speed by combining the reference voltage and the switch opening time. More diversified adjustment methods can provide more flexibility in selecting chip design solutions.

[0068] 4. Embodiment 5 proposes a method of determining the voltage climbing speed and height by calculating the frequency and the termination number of the unit, thereby avoiding the variation caused by the capacitor and the resistor and improving the accuracy of the voltage climbing time.

[0069] Beneficial effects:

[0070] By setting the current mirror in the rising soft start circuit or the falling soft start circuit, whether the starting voltage needs to be increased or decreased, charging or discharging can be achieved by changing the conduction state of the controllable charging unit, thereby achieving a slow change of the starting voltage, which can effectively reduce the chip cost.

[0071] Those skilled in the art will readily appreciate other embodiments of the present disclosure after considering the specification and practicing the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of the present disclosure that follow the general principles of the present disclosure and include common knowledge or customary technical means in the art that are not disclosed in the present disclosure. The specification and embodiments are to be considered exemplary only, and the true scope and spirit of the present disclosure are indicated by the claims.

Claims

1. A control method capable of adjusting voltage soft start time, characterized in that: The method is applied to a rising soft start circuit or a falling soft start circuit, wherein the rising soft start circuit and the falling soft start circuit both include a current mirror, a current source, a controllable charging unit, and a fixed voltage source. In the rising soft start circuit and the falling soft start circuit, the fixed voltage source respectively supplies power to the MSO tube in the current mirror, the current source is connected to the input side of the current mirror, and the controllable charging unit is arranged at the output side of the current mirror. The method includes: When the starting voltage needs to rise, the starting voltage is slowly raised based on the rising soft start circuit. In the rising soft start circuit, the current source is not in common with the fixed voltage source, the controllable charging unit is not in common with the fixed voltage source, and the starting voltage is located between the output end of the controllable charging unit and the current mirror. Initially, the controllable charging unit is short-circuited so that the starting voltage is discharged. When it needs to rise, the controllable charging unit is connected, and the current generated by the current source flows to the controllable charging unit through the current mirror, so that the starting voltage is gradually raised after the controllable charging unit is charged. When the starting voltage needs to be decreased, the starting voltage is slowly decreased based on the decreasing soft start circuit. In the decreasing soft start circuit, the current source and the fixed voltage source have a common terminal, and the controllable charging unit and the fixed voltage source have a common terminal. The starting voltage is located between the output terminal of the controllable charging unit and the current mirror. Initially, the controllable charging unit is short-circuited so that the starting voltage is charged by the fixed voltage source. When decreasing, the controllable charging unit is passed through. The current generated by the current source passes through the current mirror and discharges the controllable charging unit in the reverse direction. When the controllable charging unit is discharged, the starting voltage is pulled down.

2. The control method for adjusting the voltage soft start time according to claim 1, characterized in that: A first switch is provided in both the rising soft start circuit and the falling soft start circuit. The first switch is located between the output end of the current mirror and the controllable charging unit. When the controllable charging unit is charged or discharged, the conduction time of the first switch is controlled so that the charging time or discharging time of the controllable charging unit is changed.

3. The control method for adjusting the voltage soft start time according to claim 1, characterized in that: The current source is fixed.

4. The control method for adjusting the voltage soft start time according to claim 1, characterized in that: The current source is variable and includes an operational amplifier, an MN tube, and a first resistor. The positive input terminal of the operational amplifier is connected to a variable reference voltage, and the output terminal is connected to the gate of the MN tube and its own negative input terminal, wherein: In the rising soft start circuit, the drain of the MN tube is connected to the input side of the current mirror, the source thereof is connected to one end of the first resistor, and the other end of the first resistor is grounded; In the falling soft start circuit, the source of the MN tube is connected to the input side of the current mirror, the drain is connected to one end of the first resistor, and the other end of the first resistor is connected to the fixed voltage source; When the rising soft start circuit needs to charge the controllable charging unit and the falling soft start circuit needs to discharge the controllable charging unit, the variable reference voltage is adjusted so that the charging time or the discharging time of the controllable charging unit is changed.

5. The control method for adjusting the voltage soft start time according to claim 4, characterized in that: The rising soft start circuit and the falling soft start circuit are both provided with a first switch, and the first switch is located between the output end of the current mirror and the controllable charging unit. When the rising soft start circuit needs to charge the controllable charging unit and the falling soft start circuit needs to discharge the controllable charging unit, the variable reference voltage and the conduction time of the first switch are regulated so that the charging time or the discharging time of the controllable charging unit is changed.

6. The control method for adjusting the voltage soft start time according to claim 1, characterized in that: The controllable charging unit includes a capacitor and a second switch connected in parallel with the capacitor. When the controllable charging unit is short-circuited, the second switch is closed, and when the controllable charging unit is connected, the second switch is opened.

7. The control method for adjusting the voltage soft start time according to claim 1, characterized in that: The controllable charging unit includes a calculation unit and a variable resistance digital unit, wherein: The computing unit comprises n flip-flops connected in series, the clock input terminal of the first flip-flop is connected to the clock signal, the clock input terminal of the (I+1)th flip-flop is connected to the non-Q terminal of the (I)th flip-flop, the reset terminals of all the flip-flops are connected to the same reset signal, and the D terminals of all the flip-flops are connected to the non-Q terminals thereof; The variable resistor digital unit includes n second resistors connected in series, and n third switches connected in parallel to each of the second resistors, and the first third switch is controlled by the Q end of the first trigger.

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