A soft switching control method

Abstract

The application discloses a soft switch control method, and a switching power supply comprising a switching tube S1, a switching tube S2, a switching tube S3, a switching tube S4, a capacitor C1, an inductor L1, an inductor L2, a controller and a detection module. The detection module detects the inductor current state, and the controller controls the switching tube to be turned on according to the current state and the output gain condition, so that the soft opening of the switching tube is realized. The switching power supply can realize the soft switch in a wide gain range through the control method, the loss and electromagnetic interference of the switching tube are effectively reduced, the reverse recovery problem caused by the switching tube is avoided, the device stress can be optimized in practical application, the device selection is facilitated, and the cost is saved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of switching power supply, in particular to a soft switching control method. BACKGROUND

[0002] Switching power supply has the characteristics of small size, high efficiency, large power and strong anti-interference compared with linear power supply, and is widely used in the fields of automobile, photovoltaic, industrial control, medical treatment and handheld device, with the continuous iteration of technology, among which the non-isolated buck is concerned, and in recent years, switching capacitor, three-level buck circuit and series capacitor BUCK circuit reduce the device stress and optimize the loss by series capacitor. However, the power loop is large after series capacitor, and in actual application, the parasitic parameters brought by PCB cannot be ignored, resulting in high voltage stress peak of switching tube, which needs to select higher voltage power MOS tube, which will bring additional loss and cost increase. In order to reduce the stress peak of switching tube and switching loss, the control method of soft switching can be usually used to make the switching tube work in soft switching state, which reduces the switching loss and helps to reduce the peak stress of switching tube.

[0003] Please refer to Figure 1 For the existing two-phase series capacitor BUCK circuit, the control method is 180° out of phase control, which usually works in continuous mode.

[0004] Figure 2 For duty ratio D≤0.5, the gain is less than 1 / 4

[0005] Figure 3 For duty ratio D> 0.5, the gain is greater than 1 / 4

[0006] In actual application, the reverse recovery stress peak brought by switching tube SR1 and switching tube SR2 cannot be ignored, which brings difficulties to the selection of devices in actual application, and also brings greater electromagnetic interference SUMMARY

[0007] In order to solve the stress peak problem of existing series capacitor BUCK in actual application, the purpose of the present application is to provide a soft switching control method, which realizes the soft switching of switching tube with wide gain range, solves the stress influence caused by reverse recovery of switching tube, and soft switching is also beneficial to reduce high frequency loss and electromagnetic interference.

[0008] The specific technical scheme of the present application is:

[0009] In a first aspect, the present application provides a soft switching control method for a switching power supply, the switching power supply comprising a switching tube S1, a switching tube S2, a switching tube S3, a switching tube S4, a capacitor C1, an inductor L1, an inductor L2, a controller and a detection module, the drain of the switching tube S1 being connected to the positive terminal of an input power supply, the source of the switching tube S1 being connected to the drain of the switching tube S2 and the first terminal of the capacitor C1, the source of the switching tube S2 being connected to the drain of the switching tube S3 and the first terminal of the inductor L2, the drain of the switching tube S3 being connected to the detection module, the source of the switching tube S3 being connected to a ground terminal, the second terminal of the capacitor C1 being connected to the first terminal of the inductor L1 and the drain of the switching tube S4 respectively, the drain of the switching tube S4 being connected to the detection module, the second terminal of the inductor L1 being connected to an output load, the second terminal of the inductor L2 being connected to the output load, the source of the switching tube S4 being connected to the ground terminal, the gate of the switching tube S1, the gate of the switching tube S2, the gate of the switching tube S3 and the gate of the switching tube S4 being connected to the controller.

[0010] The soft switching control method comprises:

[0011] According to the duty cycle of the switching tube S1, the duty cycle of the switching tube S2 and a preset duty cycle threshold, the switching tube S1 and the switching tube S2 are controlled to be conducted in opposite phase, so that the switching tube S1 and the switching tube S2 work in a soft on state, and the switching tube S3 and the switching tube S4 work in a zero current off state.

[0012] The opposite phase angle of the opposite phase conduction changes with the duty cycle of the switching tube S1 and the duty cycle of the switching tube S2.

[0013] Optionally, according to the duty cycle of the switching tube S1, the duty cycle of the switching tube S2 and a preset duty cycle threshold, the switching tube S1 and the switching tube S2 are controlled to be conducted in opposite phase, specifically:

[0014] When D1 is less than the duty cycle threshold, the switching tube S1 and the switching tube S2 are conducted in opposite phase by 180°, and the output gain is controlled by modulating the duty cycle and modulating the switching frequency;

[0015] When D1 is greater than or equal to the duty cycle threshold, the switching tube S1 and the switching tube S2 are conducted in opposite phase by ≤360*(1-D1), and the output gain is controlled by modulating the duty cycle, modulating the switching frequency and phase shifting;

[0016] The duty cycle threshold is 0.5, D1=D2, D1 is the duty cycle of the switching tube S1, and D2 is the duty cycle of the switching tube S2.

[0017] Optionally, when D1 is less than the duty cycle threshold, the duty cycle of the switch tube S1, the duty cycle of the switch tube S2 and the preset duty cycle threshold are used to control the switch tube S1 and the switch tube S2 to be opposite phase conduction, so that the switch tube S1 and the switch tube S2 work in a soft on state, and the switch tube S3 and the switch tube S4 work in a zero current off state, specifically: in a working cycle, the following steps are performed:

[0018] In the first stage, the switch tube S1 is soft on, the switch tube S4 is off, the switch tube S2 is off, the switch tube S3 is on, the inductor L1 starts to excite energy storage, the inductor current increases linearly, and the inductor L2 is in a demagnetization stage;

[0019] In the second stage, the switch tube S1 is off, the switch tube S4 is on, the inductor L1 ends excitation at the beginning of the second stage and starts demagnetization, the inductor L2 is still in a demagnetization stage until the end of the second stage, and the inductor L2 is in a negative current state;

[0020] In the third stage, the switch tube S3 is off at the beginning of the third stage, so that the inductor L2 charges the capacitor CoSS3 and discharges the capacitor CoSS2, and when the capacitor CoSS2 is discharged to 0V at the end of the third stage, the switch tube S2 reaches a soft on condition;

[0021] In the fourth stage, the switch tube S2 is soft on, the inductor L2 starts to excite, and the inductor L1 is in a demagnetization state. At the end of the fourth stage, the inductor L2 ends excitation;

[0022] In the fifth stage, the switch tube S2 is off, and the switch tube S3 is on, so that the inductor L2 starts demagnetization, and the inductor L1 is in a demagnetization state until the end of the fifth stage, so that the inductor L1 is in a negative current state;

[0023] In the sixth stage, the switch tube S4 is off at the beginning of the sixth stage, so that the inductor L1 charges the capacitor CoSS4 and discharges the capacitor CoSS1, and when the capacitor CoSS1 is discharged to 0V at the end of the sixth stage, the switch tube S1 reaches a soft on condition.

[0024] Optionally, when D1 is greater than or equal to the duty cycle threshold, the duty cycle of the switch tube S1, the duty cycle of the switch tube S2 and the preset duty cycle threshold are used to control the switch tube S1 and the switch tube S2 to be opposite phase conduction, so that the switch tube S1 and the switch tube S2 work in a soft on state, and the switch tube S3 and the switch tube S4 work in a zero current off state, specifically: in a working cycle, the following steps are performed:

[0025] In the first stage, the switch S2 is turned on, the switch S3 is turned off, the switch S1 is turned on, the switch S4 is turned off, the inductor L2 starts to store energy, the inductor current linearly increases, and the inductor L1 is in the excitation stage;

[0026] In the second stage, the switch S1 is turned off, the switch S4 is turned on, at the beginning of the second stage, the inductor L1 and the inductor L2 stop excitation, the inductor L2 is demagnetized, the inductor L1 is demagnetized through the switch S4, until the end of the second stage, so that the inductor L1 is in a negative current state;

[0027] In the third stage, the switch S2 is turned off, the switch S3 is turned on, and at the beginning of the third stage, the switch S4 is turned off, so that the inductor L1 charges the capacitor CoSS4 and discharges the capacitor CoSS1, so that at the end of the third stage, when the capacitor CoSS1 is discharged to 0V, the switch S1 reaches the soft turn-on condition;

[0028] In the fourth stage, the switch S1 is turned on, the inductor L1 starts to excite, and the inductor L2 is in a demagnetization state, so that until the end of the fourth stage, the inductor L2 is in a negative current state;

[0029] In the fifth stage, at the beginning of the fifth stage, the switch S3 is turned off, so that the inductor L2 charges the capacitor CoSS3 and discharges the capacitor CoSS2, so that at the end of the fifth stage, when the capacitor CoSS2 is discharged to 0V, the switch S2 reaches the soft turn-on condition.

[0030] In a second aspect, the present application also provides a soft switching control method for a switching power supply, the switching power supply comprising 2n switches, n-1 capacitors, n inductors, a controller and a detection module, the drain electrode of the first switch is connected to the positive terminal of an input power supply, the source electrode of the i-th switch is connected to the drain electrode of the (i+1)-th switch and the first terminal of the i-th capacitor, the source electrode of the n-th switch is connected to the drain electrode of the 2n-th switch and the first terminal of the n-th inductor, the source electrode of the 2n-th switch is connected to the ground terminal, the drain electrode of the 2n-th switch is connected to the detection module, the second terminal of the i-th capacitor is connected to the first terminal of the i-th inductor and the drain electrode of the j-th switch, the drain electrode of the j-th switch is connected to the detection module, the second terminals of the i-th inductor and the n-th inductor are connected to an output load, the source electrode of the j-th switch is connected to the ground terminal, and the gate electrodes of the 2n switches are connected to the controller; wherein n is an integer greater than or equal to 2, i is an integer greater than or equal to 1 and less than n, and j is an integer greater than or equal to n+1 and less than 2n;

[0031] The soft switching control method comprises:

[0032] According to the duty cycle of the first switch to the nth switch and a preset duty cycle threshold, the 2n switches are controlled to be conducted in opposite phase, so that the first switch to the nth switch work in a soft on state, and the nth+1 switch to the 2nth switch work in a zero current off state.

[0033] Wherein, the duty cycle of the first switch to the nth switch is equal, and the opposite phase angle of the opposite phase conduction changes with the duty cycle.

[0034] Optionally, according to the duty cycle of the first switch to the nth switch and a preset duty cycle threshold, the 2n switches are controlled to be conducted in opposite phase, so that the first switch to the nth switch work in a soft on state, specifically:

[0035] When the duty cycle is less than the duty cycle threshold, the first switch to the nth switch is conducted in opposite phase (360 / n) °, and the output gain is controlled by modulating the duty cycle and the modulation switching frequency;

[0036] When the duty cycle is greater than or equal to the duty cycle threshold, the first switch to the nth switch is conducted in opposite phase ≤360×(1-D) °;

[0037] Wherein, the duty cycle threshold DZ=1-1 / n, and D is the duty cycle of the first switch to the nth switch.

[0038] The present application has the following beneficial effects compared with the prior art:

[0039] The present application can realize soft switching of the switching power supply in a wide gain range by the control method, effectively reduce the loss and electromagnetic interference of the switch, avoid the reverse recovery problem caused by the switch, optimize the device stress in actual application, facilitate device selection, and save cost. BRIEF DESCRIPTION OF DRAWINGS

[0040] Figure 1 is a two-phase series capacitor Buck circuit diagram;

[0041] Figure 2 is the control timing of the two-phase series capacitor Buck circuit when the duty cycle D≤0.5;

[0042] Figure 3 is the control timing of the two-phase series capacitor Buck circuit when the duty cycle D>0.5;

[0043] Figure 4 is the circuit topology applied in the first embodiment of the present application;

[0044] Figure 5is the circuit topology applied in the present application duty cycle and staggered phase relationship diagram;

[0045] Figure 6 is the control timing diagram of the first embodiment of the present application duty cycle less than 0.5;

[0046] Figure 7 is the control timing diagram of the first embodiment of the present application duty cycle greater than 0.5;

[0047] Figure 8 is the parasitic capacitance discharge diagram of switch S1 when the duty cycle is greater than 0.5 in the first embodiment of the present application;

[0048] Figure 9 is the parasitic capacitance discharge diagram of switch S1 when the duty cycle is greater than 0.5 in the first embodiment of the present application, if the traditional staggered 180° control is still used, so that the parasitic capacitance of switch S1 is clamped by switch S2 and cannot be discharged.

[0049] Figure 10 is the circuit topology applied in the second embodiment of the present application;

[0050] Figure 11 is the circuit topology applied in the third embodiment of the present application. DETAILED DESCRIPTION

[0051] The drawings of the present application are only used for illustrative description, and cannot be understood as the limitation of the present application. In order to better illustrate the following embodiments, some components in the drawings will be omitted, enlarged or reduced, and cannot represent the size of the actual product; for those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings can be omitted.

[0052] Reference Figure 4 , Figure 4For the first embodiment of the application, two-phase series capacitor BUCK; the switching power supply comprises switch S1, switch S2, switch S3, switch S4, capacitor C1, inductor L1, inductor L2, controller and detection module, the drain of the switch S1 is connected to the positive terminal of the input power supply, the source of the switch S1 is connected to the drain of the switch S2 and the first end of the capacitor C1, the source of the switch S2 is connected to the drain of the switch S3 and the first end of the inductor L2, the drain of the switch S3 is connected to the detection module, the source of the switch S3 is connected to the ground, the second end of the capacitor C1 is connected to the first end of the inductor L1 and the drain of the switch S4 respectively, the drain of the switch S4 is connected to the detection module, the second end of the inductor L1 is connected to the output load, the second end of the inductor L2 is connected to the output load, the source of the switch S4 is connected to the ground, the gate of the switch S1, the gate of the switch S2, the gate of the switch S3 and the gate of the switch S4 are all connected to the controller;

[0053] The soft switching control method comprises:

[0054] According to the duty cycle of the switch S1, the duty cycle of the switch S2 and the preset duty cycle threshold, the switch S1 and the switch S2 are controlled to be out of phase and turned on, so that the switch S1 and the switch S2 work in a soft on state, and the switch S3 and the switch S4 work in a zero current off state.

[0055] Wherein, the out of phase angle of the out of phase and turned on varies with the duty cycle of the switch S1 and the duty cycle of the switch S2.

[0056] In this embodiment, the controller outputs stable by modulating frequency + modulating duty cycle + phase shift control, and realizes soft on of the switch S1 and the switch S2, the detection module detects the inductor current state and feeds back to the controller, wherein the capacitor CoSS1, the capacitor CoSS2, the capacitor CoSS3 and the capacitor CoSS4 are the parasitic capacitances of the switch S1, the switch S2, the switch S3 and the switch S4.

[0057] The soft on process of this embodiment is explained in two cases.

[0058] When the duty cycle is less than 0.5, that is, the output gain is less than 1 / 4, the switch S1 and the switch S2 are out of phase and controlled by 180°, and the control mode is modulating frequency + modulating duty cycle to adjust the output gain, as shown in the following figure: Figure 6 ;

[0059] At time t0-t1, the switch S1 is soft on, the switch S4 is off, the switch S2 is off, the switch S3 is on, the inductor L1 starts to store energy, the inductor current linearly increases, and the inductor L2 is in a demagnetization stage.

[0060] At time t1-t2, the switch S1 is off, the switch S4 is on, the switch S2 is off, the switch S3 is on, the inductor L1 ends the excitation at time t1 and starts to demagnetize, the inductor L2 is still in the demagnetization stage until time t2, and the inductor L2 is in a negative current state.

[0061] At time t2-t3, the switch S1 is off, the switch S4 is on, the switch S2 is off, and the switch S3 is off. This stage is the dead time of the switch S2 and the switch S3. At time t2, the switch S3 is off. Because the inductor current cannot be abruptly changed, the inductor L2 charges the capacitor CoSS3 and discharges the capacitor CoSS2. When the capacitor CoSS2 discharges to 0V at time t3, the switch S2 reaches the soft on condition.

[0062] At time t3-t4, the switch S2 is soft on, the inductor L2 starts to excite, and the inductor L1 is in a demagnetization state. At time t4, the excitation of the inductor L2 ends.

[0063] At time t4-t5, the switch S1 is off, the switch S4 is on, the switch S2 is off, the switch S3 is on, the inductor L2 starts to demagnetize, and the inductor L1 is in a demagnetization state. Until time t5, the inductor L1 is in a negative current state.

[0064] At time t5-t0, the switch S1 is off, the switch S4 is off, the switch S2 is off, and the switch S3 is on. This stage is the dead time of the switch S1 and the switch S4. At time t5, the switch S4 is off. Because the inductor current cannot be abruptly changed, the inductor L1 charges the capacitor CoSS4 and discharges the capacitor CoSS1. When the capacitor CoSS1 discharges to 0V at time t0, the switch S1 reaches the soft on condition.

[0065] The cycle ends, and the next working cycle starts, and the above stages are repeated.

[0066] When the duty cycle is greater than 0.5, that is, the output gain is greater than 1 / 4, the switch S1 and the switch S2 are controlled by 360*(1-D)°, the control mode is the modulation frequency + the modulation duty cycle + the phase shift adjustment output gain, and reference Figure 7 ;

[0067] At time t0-t1, the switch S2 is soft on, the switch S3 is off, the switch S1 is on, the switch S4 is off, the inductor L2 starts to store energy, the inductor current linearly increases, and the inductor L1 is in an excitation stage.

[0068] At time t1-t2, the switch S1 is off, the switch S4 is on, the switch S2 is on, and the switch S3 is off. At time t1, the excitation of the inductors L1 and L2 is completed. The inductor L2 is demagnetized through the loop C1→the switch S2→L2→LOAD→the switch S4→C1, and the inductor L1 is demagnetized through the switch S4, until time t2, at which the inductor L1 is in a negative current state.

[0069] At time t2-t3, the switch S1 is off, the switch S4 is off, the switch S2 is off, and the switch S3 is on. This stage is the dead time of the switch S1 and the switch S4. At time t3, the switch S4 is off. Because the inductor current cannot be abruptly changed, the inductor L1 charges the capacitor CoSS4, and the capacitor CoSS1 is discharged. When the capacitor CoSS1 is discharged to 0V at time t3, the switch S1 reaches the soft-on condition.

[0070] At time t3-t4, the switch S1 is soft-on, the inductor L1 starts to be excited, and the inductor L2 is in a demagnetized state, until time t4, at which the inductor L2 is in a negative current state.

[0071] At time t4-t0, the switch S1 is on, the switch S4 is off, the switch S2 is off, and the switch S3 is off. This stage is the dead time of the switch S2 and the switch S3. At time t4, the switch S3 is off. Because the inductor current cannot be abruptly changed, the inductor L2 charges the capacitor CoSS3, and the capacitor CoSS2 is discharged. When the capacitor CoSS2 is discharged to 0V at time t0, the switch S2 reaches the soft-on condition.

[0072] The cycle ends, and the next working cycle starts, and the above stages are repeated.

[0073] In the embodiment, when the duty cycle D is greater than 0.5, the control strategy of phase shift needs to be added. The reason is that the switch S1 needs to discharge the parasitic capacitor CoSS1 to achieve the soft-on condition. If D is greater than 0.5 and the switch S1 and the switch S2 are controlled with a phase difference of 180°, the switch S2 is in a conducting state before the switch S1 is turned on, which causes the parasitic capacitor CoSS1 of the switch S1 to be clamped by the switch S2 and unable to be discharged, so that the switch S1 cannot achieve soft-on. Figure 8 For the current state of the inductor L1 before the switch S1 is turned on in the embodiment, the capacitor CoSS1 is discharged to 0V before the switch S1 is turned on, and the switch S1 achieves soft-on. Figure 9 For the phase difference of 180°, the capacitor CoSS1 is clamped by the switch S2 and unable to be discharged before the switch S1 is turned on, so that the switch S1 cannot achieve soft-on.

[0074] Reference Figure 10 , Figure 10For the second embodiment of the application, the soft switching principle is the same as the first embodiment, and will not be repeated. The difference is that the circuit is a three-phase series capacitor BUCK, the duty cycles of the switch tube S1, the switch tube S2 and the switch tube S3 are equal, when the duty cycle is less than 66%, the switch tube S1, the switch tube S2 and the switch tube S3 are 120° out of phase, and when the duty cycle is greater than 66%, the switch tube S1, the switch tube S2 and the switch tube S3 are ≤360×(1-D)° out of phase.

[0075] Reference Figure 11 , Figure 11 For the third embodiment of the application, a soft switching control method is used for a switching power supply, the switching power supply includes 2n switch tubes, n-1 capacitors, n inductors, a controller and a detection module, the drain of the first switch tube is connected to the positive terminal of the input power supply, the source of the i-th switch tube is connected to the drain of the i+1-th switch tube and the first terminal of the i-th capacitor, the source of the n-th switch tube is connected to the drain of the 2n-th switch tube and the first terminal of the n-th inductor, the source of the 2n-th switch tube is connected to the ground terminal, the drain of the 2n-th switch tube is connected to the detection module, the second terminal of the i-th capacitor is connected to the first terminal of the i-th inductor and the drain of the j-th switch tube, the drain of the j-th switch tube is connected to the detection module, the second terminals of the i-th inductor and the n-th inductor are connected to the output load, the source of the j-th switch tube is connected to the ground terminal, and the gates of the 2n switch tubes are connected to the controller; wherein n is an integer greater than or equal to 2, i is an integer greater than or equal to 1 and less than n, and j is an integer greater than or equal to n+1 and less than 2n.

[0076] The soft switching control method includes:

[0077] According to the duty cycles of the first switch tube to the n-th switch tube and the preset duty cycle threshold, the 2n switch tubes are controlled to be out of phase and turned on, so that the first switch tube to the n-th switch tube work in a soft on state, and the n+1-th to the 2n-th switch tube work in a zero current off state.

[0078] Wherein, the duty cycles of the first switch tube to the n-th switch tube are equal, and the out of phase angle of the out of phase conduction changes with the duty cycle.

[0079] Specific working process:

[0080] When the duty cycle is less than (1-1 / n), the first switch S1 to the nth switch Sn are controlled with a phase difference of (360 / n)°, the switch Sn and the switch S2n are driven complementarily, the switch S2 and the switch Sn+2 are driven complementarily, the switch S1 and the switch Sn+1 are driven complementarily; the output gain is controlled to be stable by controlling the frequency and the duty cycle, and the inductor current is in a negative current state, which prepares for the soft switching of the switch; specifically, the inductor L1 discharges the parasitic capacitance of the switch S1 and the parasitic capacitance of the switch Sn+1, so that the parasitic capacitance of the switch S1 is discharged to 0V, and the soft opening condition of the switch S1 is reached; the inductor L2 discharges the parasitic capacitance of the switch S2 and the parasitic capacitance of the switch Sn+2, so that the parasitic capacitance of the switch S2 is discharged to 0V, and the soft opening condition of the switch S2 is reached; the inductor Ln discharges the parasitic capacitance of the switch Sn and the parasitic capacitance of the switch S2n, so that the parasitic capacitance of the switch Sn is discharged to 0V, and the soft opening condition of the switch Sn is reached.

[0081] When the duty cycle is greater than or equal to (1-1 / n), the first switch S1 to the nth switch Sn are controlled with a phase difference of ≤(360×(1-D))°, the switch S1 and the switch Sn+1 are driven complementarily, the switch S2 and the switch Sn+2 are driven complementarily, the switch Sn and the switch S2n are driven complementarily; the output gain is controlled to be stable by controlling the frequency, the duty cycle and the phase difference, and the inductor current is in a negative current state, which prepares for the soft switching of the switch; specifically, the inductor L1 discharges the parasitic capacitance of the switch S1 and the parasitic capacitance of the switch Sn+1, so that the parasitic capacitance of the switch S1 is discharged to 0V, and the soft opening condition of the switch S1 is reached; the inductor L2 discharges the parasitic capacitance of the switch S2 and the parasitic capacitance of the switch Sn+2, so that the parasitic capacitance of the switch S2 is discharged to 0V, and the soft opening condition of the switch S2 is reached; the inductor Ln discharges the parasitic capacitance of the switch Sn and the parasitic capacitance of the switch S2n, so that the parasitic capacitance of the switch Sn is discharged to 0V, and the soft opening condition of the switch Sn is reached.

[0082] The reason for controlling with a phase difference of ≤(360×(1-D))° is that the switch S2 is in an off state before the switch S1 is turned on, so as to avoid the parasitic capacitance of the switch S1 being clamped by the switch S2 and being unable to be discharged to 0V, thereby failing to achieve the soft opening of the switch S1; the switch Sn is in an off state before the switch Sn-1 is turned on, so as to avoid the parasitic capacitance of the switch Sn-1 being clamped by the switch Sn and being unable to be discharged to 0V, thereby failing to achieve the soft opening of the switch Sn-1.

[0083] The above merely is the preferred embodiment of the present application, it should be pointed out that the above preferred embodiment should not be considered as the limitation of the present application, for the ordinary skilled in the art, within the spirit and scope of the present application, several improvements and decorations can be made, the improvement and decoration of the present application should also be considered as the protection scope of the present application, here no longer use the embodiment to repeat, the protection scope of the present application should be limited by the scope of claims.

Claims

1. A soft-switching control method for a switching power supply, characterized in that: The switching power supply includes switching transistors S1, S2, S3, and S4, capacitor C1, inductor L1, inductor L2, a controller, and a detection module. The drain of switching transistor S1 is connected to the positive terminal of the input power supply. The source of switching transistor S1 is connected to the drain of switching transistor S2 and the first terminal of capacitor C1. The source of switching transistor S2 is connected to the drain of switching transistor S3 and the first terminal of inductor L2. The drain of switching transistor S3 is connected to the detection module. The source of switching transistor S3 is connected to ground. The second terminal of capacitor C1 is connected to the first terminal of inductor L1 and the drain of switching transistor S4. The drain of switching transistor S4 is connected to the detection module. The second terminal of inductor L1 is connected to the output load. The second terminal of inductor L2 is connected to the output load. The source of switching transistor S4 is connected to ground. The gates of switching transistors S1, S2, S3, and S4 are all connected to the controller. The soft-switching control method includes: Based on the duty cycle of the switch S1, the duty cycle of the switch S2, and a preset duty cycle threshold, the switch S1 and the switch S2 are controlled to conduct in opposite phases, so that the switch S1 and the switch S2 operate in a soft turn-on state, and the switch S3 and the switch S4 operate in a zero-current turn-off state. The phase reversal angle of the phase reversal conduction varies with the duty cycle of the switching transistor S1 and the duty cycle of the switching transistor S2.

2. The soft-switching control method according to claim 1, characterized in that, The method of controlling the staggered conduction of switch S1 and switch S2 based on the duty cycle of switch S1, the duty cycle of switch S2, and a preset duty cycle threshold specifically includes: When D1 is less than the duty cycle threshold, the switching transistor S1 and the switching transistor S2 are turned on out of phase by 180°, and the output gain is controlled by modulating the duty cycle and the switching frequency. When D1 is greater than or equal to the duty cycle threshold, the switch S1 and the switch S2 are turned on with a phase misalignment of ≤360*(1-D1), and the output gain is controlled by modulating the duty cycle, modulating the switching frequency and phase shifting. Wherein, the duty cycle threshold is 0.5, D1 = D2, D1 is the duty cycle of the switch S1, and D2 is the duty cycle of the switch S2.

3. The soft-switching control method according to claim 1, characterized in that, When D1 is less than the duty cycle threshold, the step of controlling the switching transistors S1 and S2 to conduct out of phase according to the duty cycle of the switching transistor S1, the duty cycle of the switching transistor S2, and the preset duty cycle threshold, so that the switching transistors S1 and S2 operate in a soft-turn-on state, and the switching transistors S3 and S4 operate in a zero-current turn-off state, specifically, within one working cycle, the following steps are executed: In the first stage, the switch S1 is soft-turned on, the switch S4 is turned off, the switch S2 is turned off, the switch S3 is turned on, the inductor L1 begins to be energized and stores energy, the inductor current increases linearly, and the inductor L2 is in the demagnetization stage. In the second stage, the switch S1 is turned off and the switch S4 is turned on. At the beginning of the second stage, the inductor L1 ends its excitation and begins to demagnetize. The inductor L2 is still in the demagnetization stage until the end of the second stage. The inductor L2 is in a negative current state. In the third stage, at the beginning of the third stage, the switch S3 is turned off, so that the inductor L2 charges the capacitor CoSS3 and the capacitor CoSS2 discharges, so that when the capacitor CoSS2 discharges to 0V at the end of the third stage, the switch S2 reaches the soft turn-on condition. In the fourth stage, the switch S2 is soft-turned on, the inductor L2 begins to be energized, and the inductor L1 is in a demagnetized state. At the end of the fourth stage, the energization of the inductor L2 ends. In the fifth stage, the switch S2 is turned off and the switch S3 is turned on, causing the inductor L2 to begin demagnetizing and the inductor L1 to be in a demagnetized state until the end of the fifth stage, when the inductor L1 is in a negative current state. In the sixth stage, at the beginning of the sixth stage, the switch S4 is turned off, so that the inductor L1 charges the capacitor CoSS4 and the capacitor CoSS1 discharges, so that when the capacitor CoSS1 discharges to 0V at the end of the sixth stage, the switch S1 reaches the soft turn-on condition. Among them, capacitors CoSS1, CoSS2, CoSS3, and CoSS4 are the parasitic capacitances of switching transistors S1, S2, S3, and S4, respectively.

4. The soft-switching control method according to claim 1, characterized in that, When D1 is greater than or equal to the duty cycle threshold, the step of controlling the phase-shifted conduction of switch S1 and switch S2 according to the duty cycle of switch S1, the duty cycle of switch S2, and the preset duty cycle threshold, so that switch S1 and switch S2 operate in a soft-turn-on state, and switch S3 and switch S4 operate in a zero-current turn-off state, specifically, within one working cycle, the following steps are executed: In the first stage, the switch S2 is soft-turned on, the switch S3 is turned off, the switch S1 is turned on, the switch S4 is turned off, the inductor L2 begins to be energized and store energy, the inductor current increases linearly, and the inductor L1 is in the energization stage. In the second stage, the switch S1 is turned off and the switch S4 is turned on. At the beginning of the second stage, the excitation of inductors L1 and L2 ends, inductor L2 is demagnetized, and inductor L1 is demagnetized through the switch S4 until the end of the second stage, so that inductor L1 is in a negative current state. In the third stage, the switch S2 is turned off, the switch S3 is turned on, and the switch S4 is turned off at the beginning of the third stage, so that the inductor L1 charges the capacitor CoSS4 and the capacitor CoSS1 discharges, so that when the capacitor CoSS1 discharges to 0V at the end of the third stage, the switch S1 reaches the soft turn-on condition. In the fourth stage, the switch S1 is soft-turned on, the inductor L1 is energized, and the inductor L2 is demagnetized, so that the inductor L2 is in a negative current state until the end of the fourth stage. In the fifth stage, at the beginning of the fifth stage, the switch S3 is turned off, so that the inductor L2 charges the capacitor CoSS3 and the capacitor CoSS2 discharges, so that when the capacitor CoSS2 discharges to 0V at the end of the fifth stage, the switch S2 reaches the soft turn-on condition. Among them, capacitors CoSS1, CoSS2, CoSS3, and CoSS4 are the parasitic capacitances of switching transistors S1, S2, S3, and S4, respectively.

5. A soft-switching control method for a switching power supply, characterized in that: The switching power supply includes 2n switching transistors, n-1 capacitors, n inductors, a controller, and a detection module. The drain of the first switching transistor is connected to the positive terminal of the input power supply. The source of the i-th switching transistor is connected to the drain of the (i+1)-th switching transistor and the first terminal of the i-th capacitor. The source of the n-th switching transistor is connected to the drain of the 2n-th switching transistor and the first terminal of the n-th inductor. The source of the 2n-th switching transistor is connected to ground. The drain of the 2n-th switching transistor is connected to the detection module. The second terminals of each capacitor are connected to the first terminal of the i-th inductor and the drain of the j-th switching transistor, respectively. The drain of the j-th switching transistor is connected to the detection module. The second terminals of both the i-th and n-th inductors are connected to the output load. The source of the j-th switching transistor is connected to ground. The gates of all 2n switching transistors are connected to the controller. Wherein, n is an integer greater than or equal to 2, i is an integer greater than or equal to 1 and less than n, and j is an integer greater than or equal to n+1 and less than 2n. The soft-switching control method includes: Based on the duty cycle of the first to the nth switching transistors and a preset duty cycle threshold, the 2n switching transistors are controlled to conduct in an out-of-phase manner, so that the first to the nth switching transistors operate in a soft-on state, and the (n+1)th to the 2nth switching transistors operate in a zero-current-off state. Among them, the duty cycles of the first to the nth switches are all equal, and the phase reversal angle of the phase reversal conduction varies with the duty cycle.

6. The soft-switching control method according to claim 5, characterized in that, The method of controlling the phase-shifted conduction of the 2n switches based on the duty cycles of the first to nth switches and a preset duty cycle threshold, so that the first to nth switches operate in a soft-switching state, specifically involves: When the duty cycle is less than the duty cycle threshold, the first to the nth switches are out of phase by (360 / n)°, and the output gain is controlled by modulating the duty cycle and the switching frequency. When the duty cycle is greater than or equal to the duty cycle threshold, the phase misalignment between the first switch and the nth switch is ≤360×(1-D)° and they are turned on. Wherein, the duty cycle threshold DZ = 1 - 1 / n, where D is the duty cycle from the 1st switch to the nth switch.

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