CN110350774B - Soft start circuit and method - Google Patents
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- CN110350774B CN110350774B CN201910594735.4A CN201910594735A CN110350774B CN 110350774 B CN110350774 B CN 110350774B CN 201910594735 A CN201910594735 A CN 201910594735A CN 110350774 B CN110350774 B CN 110350774B
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
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Abstract
The invention discloses a soft start circuit and a method, the circuit comprises a voltage dividing circuit, an integrating circuit, a voltage modulation selection circuit, a voltage following circuit and a subtracting circuit, the soft start circuit monitors a controlled voltage signal in real time in the power-on start stage, dynamically adjusts the feedback gain coefficient of the controlled voltage signal according to the value of the controlled voltage signal, when the controlled voltage signal is smaller, the soft start is carried out by adopting a larger voltage feedback gain coefficient, then the feedback gain coefficient is exponentially attenuated, after the controlled voltage signal reaches a first voltage target value, the voltage modulation selection circuit adjusts the feedback gain coefficient to be 1, and the soft start process is ended. The soft start circuit adopted by the invention is independent of a closed loop control circuit of the converter, the parameter setting is not limited by the loop characteristic of the converter, and the soft start circuit realizes the soft start function of the converter by flexibly controlling the feedback gain coefficient of the controlled parameter.
Description
Technical Field
The invention belongs to the field of power converter control, and particularly relates to a soft start circuit and a soft start method.
Background
In recent decades, with the rapid development of power electronic technology, power electronic devices have been widely used in various fields such as industry, agriculture, military affairs, and life. When the switching power supply converter is started, the problem of overhigh voltage stress of components can occur in the occasions of applying high direct-current voltage to an electric automobile charger, an uninterruptible power supply, an electrostatic generator, an electric tractor and the like, for example, the voltage stress of an output electrolytic capacitor, a switching tube, a diode and the like exceeds the standard, so that the components are damaged. Therefore, a soft start circuit is required to be added into the switching power supply converter to inhibit voltage and current impact in the power-on process and ensure the normal work of the converter.
Currently, there are several categories of commonly used soft starts: the first type is to convert a voltage error signal into a current signal, and charge a resistance-capacitance network through the current signal so as to prevent the switching power supply from generating a limit duty ratio in a starting stage. However, in this method, the soft start circuit is coupled to the closed loop control loop of the converter, and the parameter setting affects the loop characteristics of the converter. And the second type is that a constant current mode is adopted to charge a capacitor, a soft start signal which slowly climbs at a certain speed is obtained to replace a reference, so that the output is controlled to slowly climb, when the soft start signal is higher than the reference signal, the control function of the soft start signal disappears, and the reference voltage is used for finely adjusting the output voltage. However, this method needs a large capacitor to implement, and in practical application, a resistor and a capacitor need to be connected to the outside of the chip, which increases the complexity of the circuit.
Disclosure of Invention
The invention aims to provide a soft start circuit and a method.
The technical solution for realizing the purpose of the invention is as follows: a soft start circuit comprises a voltage division circuit, an integral circuit, a voltage modulation selection circuit, a voltage follower circuit and a subtraction circuit, wherein the input end of the voltage division circuit is connected with the output voltage of a switching power supply converter, the output end of the voltage division circuit is connected with the input end of the voltage follower circuit and the input end of the voltage modulation selection circuit, the output end of the voltage follower circuit is connected with the input end of the integral circuit and the positive input end of the subtraction circuit, the first output end of the voltage modulation selection circuit is connected with the first control end of the integral circuit, the second output end of the voltage modulation selection circuit is connected with the second control end of the integral circuit, the output end of the integral circuit is connected with the negative input end of the subtraction circuit, and the subtraction.
A soft start method comprises the following control steps:
step 1, when the power-on is started, the output voltage v of the switching power supply converteroutOutputting a first feedback signal v via a voltage divider circuit1Wherein
In the formula, R1And R2The first resistor and the second resistor of the voltage division circuit are respectively arranged;
step 2, first feedback signal v1Outputting a voltage signal v via a voltage follower circuit2Wherein
Step 3, first feedback signal v1And a reference voltage VrefWhen the first feedback signal v passes through the voltage modulation selection circuit1Less than reference voltage VrefAt the moment, the first output end and the second output end of the voltage modulation selection circuit both output high levels;
step 4, the first output end and the second output end of the voltage modulation selection circuit output high levels to the first control end and the second control end of the integrating circuit, and the triode Q is controlled to be conducted;
step 5, voltage signal v2Outputting a second feedback signal v via an integrating circuit3Wherein
Namely, it is
In the formula, R3And C1A third resistor and a capacitor of the integrating circuit respectively;
step 6, voltage signal v2And a second feedback signal v3The feedback voltage signal v is output through a subtraction circuitFBWherein
Namely, it is
In the formula, R6、R7、R8And a sixth resistor, a seventh resistor, an eighth resistor and a ninth resistor of the subtraction circuit, respectively;
step 7, when the output voltage v isoutReaches the first voltage target value Vt1Then, the second output end of the voltage modulation selection circuit outputs low level to control the disconnection of a triode Q in the integrating circuit, at the moment, the integrating circuit is bypassed, and a second feedback signal v3Is equal to the voltage signal v2；
Step 8, voltage signal v2And a second feedback signal v3Outputting a feedback voltage signal v via the subtraction circuitFBAt this time
Namely, it is
Step 9, the soft start process is finished, and the voltage feedback signal is finally equal to the reference voltage signal Vref。
Compared with the prior art, the invention has the following remarkable advantages: the invention avoids the occurrence of limit duty ratio at the power-on starting stage of the converter by flexibly controlling the feedback gain coefficient of the controlled parameter, realizes the soft starting function of the converter, and simultaneously, the adopted soft starting circuit is independent of a closed loop control circuit of the converter, and the parameter setting is not limited by the loop characteristic of the converter.
Drawings
FIG. 1 is a schematic diagram of a soft start circuit according to the present invention.
Fig. 2 is a schematic diagram of a control circuit of the TI-Boost PFC converter according to an embodiment of the present invention.
Detailed Description
The scheme of the invention is further explained by combining the attached drawings and the specific embodiment.
The invention provides a soft start circuit aiming at switching power converters such as PFC converters, DC-DC converters and the like, the specific circuit structure is shown in figure 1, the soft start circuit comprises a voltage division circuit, an integration circuit, a voltage modulation selection circuit, a voltage follower circuit and a subtraction circuit, the input end of the voltage division circuit is connected with the output voltage of the switching power converter, the output end of the voltage division circuit is connected with the input end of the voltage follower circuit and the input end of the voltage modulation selection circuit, the output end of the voltage follower circuit is connected with the input end of the integration circuit and the positive input end of the subtraction circuit, the first output end of the voltage modulation selection circuit is connected with the first control end of the integration circuit, the second output end of the voltage modulation selection circuit is connected with the second control end of the integration circuit, the output end of the integration circuit is connected, controlling the switching power converter. The invention can realize the purpose of soft start of the output voltage of the switching power supply converter by adjusting the feedback gain coefficient of the controlled signal.
The voltage division circuit comprises a first resistor R1And a second resistor R2The first resistor R1One end of the voltage divider circuit is connected with the output voltage v of the switching power supply converteroutThe first resistor R1The other end is connected with a second resistor R2Said second resistance R2The other end is connected with the ground end, and the first resistor R1And a second resistor R2The connecting end of the voltage divider circuit is the output end of the voltage divider circuit.
The voltage follower circuit comprises a first operational amplifier U1Said first operational amplifier U1The positive phase input end is the input end of the voltage follower circuit and is connected with the output end of the voltage division circuit, and the first operational amplifier U1The inverting input end is connected with a first operational amplifier U1Output terminal, the first operational amplifier U1The output end is the output end of the voltage follower circuit.
The voltage modulation selection circuit comprises a second comparator U2Diode D1A fourth resistor R4And a fifth resistor R5Said second comparator U2The inverting terminal is the input terminal of the voltage modulation selection circuit and is connected with the output terminal of the voltage division circuit, and the second ratioComparator U2The positive phase terminal is connected with a reference voltage signal VrefAnd a diode D1Anode of the diode D1The cathode is connected with a fourth resistor R4Said fourth resistor R4The other end is a first output end of a voltage modulation selection circuit, and the second comparator U2The output end is connected with a fifth resistor R5Said fifth resistor R5The other end is a second output end of the voltage modulation selection circuit.
The integration circuit comprises a third resistor R3Triode Q and capacitor C1Said third resistance R3One end of the third resistor is an input end of the integrating circuit and is connected with the output end of the voltage follower circuit, and the other end of the third resistor is a third resistor R3The other end of the triode Q collector is connected with a triode Q collector which is a first control end of an integrating circuit and is connected with a first output end of a voltage modulation selection circuit, the base electrode of the triode Q is a second control end of the integrating circuit and is connected with a second output end of the voltage modulation selection circuit, and the emitter electrode of the triode Q is connected with a capacitor C1Said capacitor C1The other end is connected with the ground end, and the third resistor R3And the connection end of the triode Q collector is the output end of the integrating circuit.
The subtraction circuit comprises a third operational amplifier U3The fourth operational amplifier U4A sixth resistor R6A seventh resistor R7An eighth resistor R8And a ninth resistor R9Said sixth resistance R6One end of the sixth resistor R is a positive input end of the subtraction circuit and is connected with the output end of the voltage follower circuit6The other end is connected with a seventh resistor R7 and a fourth operational amplifier U4A positive input terminal, the seventh resistor R7The other end is connected with the ground end, and the third operational amplifier U3The positive phase input end is the negative input end of the subtraction circuit and is connected with the output end of the integrating circuit, and the third operational amplifier U3The inverting input end is connected with a third operational amplifier U3Output terminal, the third operational amplifier U3The output end is connected with an eighth resistor R8Said eighth resistor R8The other end is connected with a ninth resistor R9And a fourth operational amplifier U4Reverse phase transmissionInput terminal, the ninth resistor R9The other end is connected with a fourth operational amplifier U4Output terminal, the fourth operational amplifier U4The output end is the output end of the subtraction circuit and outputs a voltage feedback signal.
The soft start method of the circuit comprises the following control steps:
step 1, when the power-on is started, the output voltage v of the switching power supply converteroutOutputting a first feedback signal v via a voltage divider circuit1Wherein
Step 2, first feedback signal v1Outputting a voltage signal v via a voltage follower circuit2Wherein
Step 3, first feedback signal v1And a reference voltage VrefWhen the first feedback signal v passes through the voltage modulation selection circuit1Less than reference voltage VrefAt the moment, the first output end and the second output end of the voltage modulation selection circuit both output high levels;
step 4, the first output end and the second output end of the voltage modulation selection circuit output high levels to the first control end and the second control end of the integrating circuit, and the triode Q is controlled to be conducted;
step 5, voltage signal v2Outputting a second feedback signal v via an integrating circuit3Wherein
Namely, it is
Step 6, voltage signal v2And a second feedback signal v3The feedback voltage signal v is output through a subtraction circuitFBWherein
Namely, it is
Step 7, when the output voltage v isoutReaches the first voltage target value Vt1Then, the second output end of the voltage modulation selection circuit outputs low level to control the disconnection of a triode Q in the integrating circuit, at the moment, the integrating circuit is bypassed, and a second feedback signal v3Is equal to the voltage signal v2；
Step 8, voltage signal v2And a second feedback signal v3Outputting a feedback voltage signal v via the subtraction circuitFBAt this time
Namely, it is
Step 9, the soft start process is finished, and the voltage feedback signal is finally equal to the reference voltage signal Vref。
The first voltage target value Vt1Can be freely set when the controlled voltage signal is lower than the first voltage target value Vt1When the voltage signal is greater than the first voltage target value V, the converter enters soft startt1And when the soft start process is finished, the controlled voltage signal is finally equal to the control target signal. First output voltage target value Vt1Specifically composed ofVoltage circuit and reference voltage signal VrefDetermining a first output voltage target value Vt1The expression is as follows:
because the soft start circuit provides a larger voltage feedback gain coefficient, the limit duty ratio in the start stage of the circuit is avoided, and meanwhile, the feedback gain coefficient is exponentially attenuated, and when the controlled voltage signal reaches the first voltage target value Vt1Then, the voltage modulation selection circuit adjusts the feedback gain coefficient to 1.
The whole soft start time tau is measured by a third resistor R in the integral circuit3And a capacitor C1Determining, a third resistance R3And a capacitor C1Are all proportional to the soft start time, i.e.
τ＝R3C1。
Examples
In order to verify the validity of the scheme of the invention, TI-Boo is usedsthe t PFC converter is a control object and details the control steps of the scheme of the invention.
Assume that the output voltage value V of the TI-Boost PFC converter shown in FIG. 2out800V, reference voltage value Vref5V and a first output voltage target value Vt1＝400V；
According to the first output voltage target value Vt1And a reference voltage value VrefDetermining resistance R in voltage divider circuit1And a resistance R2The proportion relation of (a) is specifically as follows:
determining the resistance R in the subtraction circuit according to the controlled voltage signal being equal to the control target signal6Resistance R7Resistance R8And a resistance R9The relationship (c) is specifically as follows:
namely, it is
R7＝R8＝2R6＝2R9
Determining resistance R in an integrating circuit based on soft start time3And a capacitor C1Resistance R3And a capacitor C1The charging time constant τ of (d) is:
τ＝R3C1
the soft start method comprises the following control steps:
step 1, outputting voltage v during power-on startingoutOutputting a first feedback signal v through the voltage divider circuit1Wherein:
step 2, first feedback signal v1Outputting a voltage signal v via the voltage follower circuit2Wherein:
step 3, first feedback signal v1Less than reference voltage VrefAt the moment, the first output end and the second output end of the voltage modulation selection circuit both output high levels;
step 4, the first output end and the second output end of the voltage modulation selection circuit output high levels to the first control end and the second control end of the integrating circuit, and the triode Q is controlled to be conducted;
step 5, voltage signal v2Outputting a second feedback signal v via an integrating circuit3Wherein:
namely:
step 6, voltage signal v2And a second feedback signal v3Output feedback voltage signal vF through subtraction circuitBWherein:
namely:
at this time, the soft start circuit provides a feedback gain factor
The limit duty ratio in the starting process is avoided, and meanwhile, the feedback gain coefficient is exponentially attenuated;
step 7, when the output voltage v isoutReaches the first voltage target value Vt1Then, the second output end of the voltage modulation selection circuit outputs low level, a triode Q in the integrating circuit is disconnected, the integrating circuit is bypassed at the moment, and a second feedback signal v3Is equal to the voltage signal v2；
Step 8, voltage signal v2And a second feedback signal v3Outputting a feedback voltage signal v via the subtraction circuitFBAt this time:
namely:
step 9, the soft start process is finished, and the voltage feedback signal is finally equal to the reference voltage signal Vref。
The soft start circuit adopted by the invention is independent of a closed loop control circuit of the converter, the parameter setting is not limited by the loop characteristic of the converter, the provided soft start circuit avoids the occurrence of limit duty ratio at the power-on start stage of the converter by flexibly controlling the feedback gain coefficient of the controlled parameter, and the soft start function of the converter is realized, thus being a new soft start circuit solution.
Claims (9)
1. A soft start circuit is characterized by comprising a voltage division circuit, an integrating circuit, a voltage modulation selection circuit, a voltage follower circuit and a subtraction circuit, wherein the input end of the voltage division circuit is connected with the output voltage of a switching power supply converter, the output end of the voltage division circuit is connected with the input end of the voltage follower circuit and the input end of the voltage modulation selection circuit, the output end of the voltage follower circuit is connected with the input end of the integrating circuit and the positive input end of the subtraction circuit, the first output end of the voltage modulation selection circuit is connected with the first control end of the integrating circuit, the second output end of the voltage modulation selection circuit is connected with the second control end of the integrating circuit, the output end of the integrating circuit is connected with the negative input end of the subtraction circuit, and the subtraction circuit.
2. A soft-start circuit according to claim 1, characterized in that the voltage dividing circuit comprises a first resistor (R)1) And a second resistance (R)2) The first resistance (R)1) One end of the voltage divider circuit is connected with the output voltage v of the switching power supply converteroutThe first resistance (R)1) The other end is connected with a second resistor (R)2) Said second resistance (R)2) The other end is connected with the ground end, and the first resistor (R)1) And a second resistance (R)2) The connecting end of the voltage divider circuit is the output end of the voltage divider circuit.
3. The method of claim 1Soft start circuit, characterized in that the voltage follower circuit comprises a first operational amplifier (U)1) Said first operational amplifier (U)1) The positive phase input end is the input end of the voltage follower circuit and is connected with the output end of the voltage division circuit, and the first operational amplifier (U)1) The inverting input terminal is connected with a first operational amplifier (U)1) An output terminal, the first operational amplifier (U)1) The output end is the output end of the voltage follower circuit.
4. A soft-start circuit according to claim 1, characterized in that the voltage modulation selection circuit comprises a second comparator (U)2) Diode (D)1) A fourth resistor (R)4) And a fifth resistance (R)5) Said second comparator (U)2) The inverting terminal is the input terminal of the voltage modulation selection circuit and is connected with the output terminal of the voltage division circuit, and the second comparator (U)2) The positive phase terminal is connected with a reference voltage signal VrefAnd a diode (D)1) Anode, said diode (D)1) The cathode is connected with a fourth resistor (R)4) Said fourth resistance (R)4) The other end is a first output end of the voltage modulation selection circuit, and the second comparator (U)2) The output end is connected with a fifth resistor (R)5) The fifth resistance (R)5) The other end is a second output end of the voltage modulation selection circuit.
5. A soft-start circuit according to claim 1, characterized in that the integrating circuit comprises a third resistor (R)3) Triode (Q) and capacitor (C)1) Said third resistance (R)3) One end is an input end of the integrating circuit and is connected with the output end of the voltage follower circuit, and the third resistor (R)3) The other end of the collector is connected with a triode (Q) collector which is a first control end of an integrating circuit and is connected with a first output end of a voltage modulation selection circuit, the base of the triode (Q) is a second control end of the integrating circuit and is connected with a second output end of the voltage modulation selection circuit, and the emitter of the triode (Q) is connected with a capacitor (C)1) Said capacitance (C)1) The other end is connected with the ground terminal, and the third resistor(R3) And the connecting end of the triode (Q) collector is the output end of the integrating circuit.
6. A soft-start circuit according to claim 1, characterized in that the subtraction circuit comprises a third operational amplifier (U)3) A fourth operational amplifier (U)4) A sixth resistor (R)6) A seventh resistor (R)7) Eighth resistor (R)8) And a ninth resistance (R)9) The sixth resistance (R)6) One end of the resistor is a positive input end of the subtraction circuit and is connected with the output end of the voltage follower circuit, and the sixth resistor (R)6) The other end is connected with a seventh resistor (R)7) And a fourth operational amplifier (U)4) Positive input terminal, the seventh resistor (R)7) The other end is connected with the ground terminal, and the third operational amplifier (U)3) The positive input end of the subtraction circuit is connected with the output end of the integrating circuit, and the third operational amplifier (U)3) The inverting input end is connected with a third operational amplifier (U)3) Output terminal, the third operational amplifier (U)3) The output end is connected with an eighth resistor (R)8) Said eighth resistance (R)8) The other end is connected with a ninth resistor (R)9) And a fourth operational amplifier (U)4) An inverting input terminal, the ninth resistor (R)9) The other end is connected with a fourth operational amplifier (U)4) Output terminal, the fourth operational amplifier (U)4) The output end is the output end of the subtraction circuit and outputs a voltage feedback signal.
7. A soft start method of the circuit is characterized in that soft start control is carried out based on the following soft start circuit:
the soft start circuit comprises a voltage division circuit, an integrating circuit, a voltage modulation selection circuit, a voltage follower circuit and a subtraction circuit, wherein the input end of the voltage division circuit is connected with the output voltage of the switching power supply converter, the output end of the voltage division circuit is connected with the input end of the voltage follower circuit and the input end of the voltage modulation selection circuit, the output end of the voltage follower circuit is connected with the input end of the integrating circuit and the positive input end of the subtraction circuit, the first output end of the voltage modulation selection circuit is connected with the first control end of the integrating circuit, the second output end of the voltage modulation selection circuit is connected with the second control end of the integrating circuit, the output end of the integrating circuit is connected with the negative input end of the subtraction circuit;
the voltage divider circuit comprises a first resistor (R)1) And a second resistance (R)2) The first resistance (R)1) One end of the voltage divider circuit is connected with the output voltage v of the switching power supply converteroutThe first resistance (R)1) The other end is connected with a second resistor (R)2) Said second resistance (R)2) The other end is connected with the ground end, and the first resistor (R)1) And a second resistance (R)2) The connecting end of the voltage divider circuit is the output end of the voltage divider circuit;
the voltage follower circuit comprises a first operational amplifier (U)1) Said first operational amplifier (U)1) The positive phase input end is the input end of the voltage follower circuit and is connected with the output end of the voltage division circuit, and the first operational amplifier (U)1) The inverting input terminal is connected with a first operational amplifier (U)1) An output terminal, the first operational amplifier (U)1) The output end is the output end of the voltage follower circuit;
the voltage modulation selection circuit comprises a second comparator (U)2) Diode (D)1) A fourth resistor (R)4) And a fifth resistance (R)5) Said second comparator (U)2) The inverting terminal is the input terminal of the voltage modulation selection circuit and is connected with the output terminal of the voltage division circuit, and the second comparator (U)2) The positive phase terminal is connected with a reference voltage signal VrefAnd a diode (D)1) Anode, said diode (D)1) The cathode is connected with a fourth resistor (R)4) Said fourth resistance (R)4) The other end is a first output end of the voltage modulation selection circuit, and the second comparator (U)2) The output end is connected with a fifth resistor (R)5) The fifth resistance (R)5) The other end is a second output end of the voltage modulation selection circuit;
the integration circuit comprises a third resistor (R)3) Triode (Q) and capacitor (C)1) Said third resistance (R)3) One end is an input end of the integrating circuit and is connected with the output end of the voltage follower circuit, and the third resistor (R)3) The other end of the collector is connected with a triode (Q) collector which is a first control end of an integrating circuit and is connected with a first output end of a voltage modulation selection circuit, the base of the triode (Q) is a second control end of the integrating circuit and is connected with a second output end of the voltage modulation selection circuit, and the emitter of the triode (Q) is connected with a capacitor (C)1) Said capacitance (C)1) The other end is connected with the ground terminal, and the third resistor (R)3) The connecting end of the triode (Q) collector is the output end of the integrating circuit;
the subtraction circuit comprises a third operational amplifier (U)3) A fourth operational amplifier (U)4) A sixth resistor (R)6) A seventh resistor (R)7) Eighth resistor (R)8) And a ninth resistance (R)9) The sixth resistance (R)6) One end of the resistor is a positive input end of the subtraction circuit and is connected with the output end of the voltage follower circuit, and the sixth resistor (R)6) The other end is connected with a seventh resistor (R)7) And a fourth operational amplifier (U)4) Positive input terminal, the seventh resistor (R)7) The other end is connected with the ground terminal, and the third operational amplifier (U)3) The positive input end of the subtraction circuit is connected with the output end of the integrating circuit, and the third operational amplifier (U)3) The inverting input end is connected with a third operational amplifier (U)3) Output terminal, the third operational amplifier (U)3) The output end is connected with an eighth resistor (R)8) Said eighth resistance (R)8) The other end is connected with a ninth resistor (R)9) And a fourth operational amplifier (U)4) An inverting input terminal, the ninth resistor (R)9) The other end is connected with a fourth operational amplifier (U)4) Output terminal, the fourth operational amplifier (U)4) The output end is the output end of the subtraction circuit and outputs a voltage feedback signal;
the control steps are as follows:
step 1, when the power-on is started, the output voltage v of the switching power supply converteroutOutputting a first feedback signal v via a voltage divider circuit1Wherein
In the formula, R1And R2The first resistor and the second resistor of the voltage division circuit are respectively arranged;
step 2, first feedback signal v1Outputting a voltage signal v via a voltage follower circuit2Wherein
Step 3, first feedback signal v1And a reference voltage VrefWhen the first feedback signal v passes through the voltage modulation selection circuit1Less than reference voltage VrefAt the moment, the first output end and the second output end of the voltage modulation selection circuit both output high levels;
step 4, the first output end and the second output end of the voltage modulation selection circuit output high levels to the first control end and the second control end of the integrating circuit, and the triode Q is controlled to be conducted;
step 5, voltage signal v2Outputting a second feedback signal v via an integrating circuit3Wherein
Namely, it is
In the formula, R3And C1A third resistor and a capacitor of the integrating circuit respectively;
step 6, voltage signal v2And a second feedback signal v3The feedback voltage signal v is output through a subtraction circuitFBWherein
Namely, it is
In the formula, R6、R7、R8And a sixth resistor, a seventh resistor, an eighth resistor and a ninth resistor of the subtraction circuit, respectively;
step 7, when the output voltage v isoutReaches the first voltage target value Vt1Then, the second output end of the voltage modulation selection circuit outputs low level to control the disconnection of a triode Q in the integrating circuit, at the moment, the integrating circuit is bypassed, and a second feedback signal v3Is equal to the voltage signal v2；
Step 8, voltage signal v2And a second feedback signal v3Outputting a feedback voltage signal v via the subtraction circuitFBAt this time
Namely, it is
Step 9, the soft start process is finished, and the voltage feedback signal is finally equal to the reference voltage signal Vref。
8. The soft-start method of claim 7, wherein: the first voltage target value Vt1By a voltage divider circuit and a reference voltage signal VrefThe expression is determined as follows:
9. the soft-start method of claim 7, wherein: the whole soft start time tau is measured by a third resistor R in the integral circuit3And a capacitor C1Determining, a third resistance R3And a capacitor C1Are all proportional to the soft start time, i.e.
τ＝R3C1。
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Effective date of registration: 20230922 Address after: No. 567 Yancheng South Road, Wujin National High tech Industrial Development Zone, Changzhou City, Jiangsu Province, 213164 Patentee after: JIANGSU BAOSITE ELECTRICAL TECHNOLOGY Co.,Ltd. Address before: 210094 Xuanwu District, Jiangsu, Xiaolingwei 200, Nanjing Patentee before: NANJING University OF SCIENCE AND TECHNOLOGY |