Soft drive method and circuit and switching power supply using the same

Abstract

The soft drive method, circuit and switching power supply applying the same provided in the present application, when the drive voltage of the first switch tube in the switching module changes from the second voltage threshold to the first voltage threshold, a first current is generated based on the change of the voltage at the first end of the switching module, the difference between the first reference current and the first current is input into the operational amplifier as the input, the output of the current input operational amplifier is connected with the gate of the first switch tube, based on the adjustment of the current input operational amplifier and the first switch tube, the change rate of the voltage at the first end of the switching module is stabilized at a certain value in the time period when the drive voltage is the first voltage threshold. Through the above setting, the change rate of the voltage at the first end of the switching module is limited to stabilize at a certain value during the process of turning on or turning off of the first switch tube, the problem of the system application caused by the too fast change rate is avoided, and the requirement for other devices is reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of switch tube driving, in particular to a soft driving method, a circuit and a switching power supply using the same. BACKGROUND

[0002] In the field of switching power supply, energy conversion is carried out by controlling the conduction or turn-off of the switch tube. The switch tube is usually driven by a PWM square wave, which makes the change rate of the drain voltage of the switch tube fast during the conduction or turn-off process. The fast change rate is not conducive to the application of the system or puts forward higher requirements for other devices. For example, in a flyback converter, when the voltage at the connection end of the primary side switch tube and the transformer changes fast, the system may have problems such as EMI (electromagnetic interference) and stress of the secondary side rectifier. Therefore, it is necessary to propose a new driving scheme to solve the problems in the prior art. SUMMARY

[0003] In order to solve the above technical problems, the present application provides a soft driving method, a circuit and a switching power supply using the same.

[0004] The present application provides a soft driving method for driving a first switch tube in a switch module, the switch module being applied to a switching power supply, characterized in that the soft driving method comprises:

[0005] When the driving voltage of the first switch tube changes from a second voltage threshold to a first voltage threshold, a first current is generated based on the change of the first end voltage of the switch module, and the difference between the first reference current and the first current is input to the input of the current input operational amplifier. The output of the current input operational amplifier is connected to the gate of the first switch tube. Based on the adjustment of the current input operational amplifier and the first switch tube, the change rate of the first end voltage of the switch module is stabilized at a certain value during the time period when the driving voltage is the first voltage threshold. The first end is the end whose change rate needs to be controlled.

[0006] Wherein, the driving voltage of the first switch tube is the absolute value of the voltage difference between the gate and the source thereof; the second voltage threshold corresponds to the driving voltage when the first switch tube is in the off state or the fully on state; and the first voltage threshold is close to the Miller platform voltage setting.

[0007] Optionally, when the second voltage threshold corresponds to the driving voltage when the first switch tube is in the off state, when the driving voltage of the first switch tube rises from the second voltage threshold to the first voltage threshold,

[0008] When the first switch tube is an N-type switch tube, the first reference current is a pull-down current, and based on the adjustment of the current input operational amplifier and the first switch tube, the rising rate of the first end voltage of the switch module is stabilized at a certain value in the time period when the driving voltage is the first voltage threshold.

[0009] When the first switch tube is a P-type switch tube, the first reference current is a pull-up current, and based on the adjustment of the current input operational amplifier and the first switch tube, the falling rate of the first end voltage of the switch module is stabilized at a certain value in the time period when the driving voltage is the first voltage threshold.

[0010] Optionally, when the second voltage threshold corresponds to the driving voltage in the fully on state of the first switch tube, when the driving voltage of the first switch tube decreases from the second voltage threshold to the first voltage threshold,

[0011] When the first switch tube is an N-type switch tube, the first reference current is a pull-down current, and based on the adjustment of the current input operational amplifier and the first switch tube, the rising rate of the first end voltage of the switch module is stabilized at a certain value in the time period when the driving voltage is the first voltage threshold.

[0012] When the first switch tube is a P-type switch tube, the first reference current is a pull-up current, and based on the adjustment of the current input operational amplifier and the first switch tube, the falling rate of the first end voltage of the switch module is stabilized at a certain value in the time period when the driving voltage is the first voltage threshold.

[0013] Optionally, when the second voltage threshold corresponds to the driving voltage in the off state of the first switch tube, as the first switch tube is turned on, when the first end voltage of the switch module changes at a rate lower than a preset threshold, the driving voltage of the first switch tube is controlled to increase from the first voltage threshold to the driving voltage in the fully on state of the first switch tube.

[0014] Optionally, when the second voltage threshold corresponds to the driving voltage in the fully on state of the first switch tube, as the first switch tube is turned off, when the first end voltage of the switch module changes at a rate lower than a preset threshold, the driving voltage of the first switch tube is controlled to decrease from the first voltage threshold to the driving voltage in the off state of the first switch tube.

[0015] The present application also provides a soft drive circuit for driving the first switch tube in a switch module, which is applied to a switching power supply, characterized in that the soft drive circuit comprises,

[0016] a first capacitor arranged on a branch between the first end of the switch module and the first node.

[0017] a first reference current source, which is a pull-up or pull-down current source acting on the first node;

[0018] a current input operational amplifier arranged on a branch of the first node and the gate of the first switch tube; when the driving voltage of the first switch tube changes from a second voltage threshold to a first voltage threshold, a first current is generated on a first capacitor based on the change of the first end voltage of the switch module, a difference signal between the first reference current and the first current is connected to the input end of the current input operational amplifier, and the output end of the current input operational amplifier is connected to the gate of the first switch tube; based on the adjustment of the current input operational amplifier and the first switch tube, the change rate of the first end voltage of the switch module is stabilized at a certain value in the time period when the driving voltage is the first voltage threshold;

[0019] wherein the driving voltage of the first switch tube is the absolute value of the voltage difference between the gate and the source thereof; the second voltage threshold corresponds to the driving voltage when the first switch tube is in the off state or the fully on state; and the first voltage threshold is close to the Miller plateau voltage.

[0020] Optionally, when the second voltage threshold corresponds to the driving voltage when the first switch tube is in the off state, the driving voltage of the first switch tube rises from the second voltage threshold to the first voltage threshold,

[0021] when the first switch tube is an N-type switch tube, the first reference current is a pull-up current, and based on the adjustment of the current input operational amplifier and the first switch tube, the falling rate of the first end voltage of the switch module is stabilized at a certain value in the time period when the driving voltage is the first voltage threshold;

[0022] when the first switch tube is a P-type switch tube, the first reference current is a pull-down current, and based on the adjustment of the current input operational amplifier and the first switch tube, the rising rate of the first end voltage of the switch module is stabilized at a certain value in the time period when the driving voltage is the first voltage threshold.

[0023] Optionally, when the second voltage threshold corresponds to the driving voltage when the first switch tube is in the fully on state, the driving voltage of the first switch tube falls from the second voltage threshold to the first voltage threshold,

[0024] when the first switch tube is an N-type switch tube, the first reference current is a pull-down current, and based on the adjustment of the current input operational amplifier and the first switch tube, the rising rate of the first end voltage of the switch module is stabilized at a certain value in the time period when the driving voltage is the first voltage threshold.

[0025] When the first switch tube is a P-type switch tube, the first reference current is a pull-up current, and based on the adjustment of the current input operational amplifier and the first switch tube, the falling rate of the first end voltage of the switch module is stabilized at a certain value in the time period when the driving voltage is the first voltage threshold.

[0026] Optionally, the soft drive circuit comprises a detection circuit,

[0027] When the second voltage threshold corresponds to the driving voltage in the off state of the first switch tube, as the first switch tube is turned on, when the detection circuit detects that the change rate of the first end voltage of the switch module is lower than a preset threshold, the driving voltage of the first switch tube is controlled to rise from the first voltage threshold to the driving voltage when the first switch tube is fully turned on; or,

[0028] When the second voltage threshold corresponds to the driving voltage in the fully turned-on state of the first switch tube, as the first switch tube is turned off, after the detection circuit detects that the change rate of the first end voltage of the switch module is lower than a preset threshold, the driving voltage of the first switch tube is controlled to fall from the first voltage threshold to the driving voltage when the first switch tube is turned off.

[0029] The present application also provides a switching power supply for converting an input voltage into an output voltage to supply power to a load, characterized in that the switching power supply comprises the soft drive circuit described above or controls the first switch tube in the switch module based on the soft drive method described above.

[0030] The beneficial effects of the present application at least include:

[0031] The soft drive method, circuit and switching power supply applying the same provided in the present application, when the drive voltage of the first switch tube in the switching module changes from the second voltage threshold to the first voltage threshold, the first current is generated based on the change of the voltage at the first end of the switching module, and the difference between the first reference current and the first current is input to the operational amplifier as the input, the output of the current input operational amplifier is connected to the gate of the first switch tube, based on the adjustment of the current input operational amplifier and the first switch tube, the change rate of the voltage at the first end of the switching module is stabilized at a certain value in the time period when the drive voltage is the first voltage threshold; wherein the drive voltage of the first switch tube is the absolute value of the voltage difference between the gate and the source thereof; the second voltage threshold corresponds to the drive voltage when the first switch tube is in the off state or the fully on state; the first voltage threshold is close to the Miller platform voltage setting, which can be greater than or equal to the absolute value of the on voltage threshold of the first switch tube. Through the above setting, the change rate of the voltage at the first end of the switching module can be limited to a certain value during the on or off process of the first switch tube, and the problems caused by the too fast change rate of the voltage at the first end of the switching module can be avoided, and the requirements for other devices can be reduced.

[0032] It should be noted that the foregoing general description and the following detailed description are only exemplary and explanatory, and cannot limit the present application. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 The schematic diagram of the soft drive circuit provided in the present application is shown;

[0034] Figure 2 An embodiment of the soft drive circuit during the on process of the N-type switch tube is shown;

[0035] Figure 3 An embodiment of the drive voltage and drive current during the on process of the N-type switch tube is shown;

[0036] Figure 4 An embodiment of the soft drive circuit during the off process of the N-type switch tube is shown;

[0037] Figure 5 An embodiment of the drive voltage and drive current during the off process of the N-type switch tube is shown;

[0038] Figure 6 An embodiment of the soft drive circuit during the on and off processes of the N-type switch tube is shown. DETAILED DESCRIPTION

[0039] For the purpose of facilitating the understanding of the present application, a more complete description of the present application will be provided below with reference to the relevant drawings. The preferred embodiments of the present application are shown in the drawings. However, the present application can be realized in different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present application more thorough and comprehensive.

[0040] The present application provides a soft drive method for driving a first switch tube in a switching module applied in a switching power supply, the method comprising: when the driving voltage of the first switch tube changes from a second voltage threshold to a first voltage threshold, generating a first current based on the change of the first end voltage of the switching module, inputting the difference between the first reference current and the first current as the input of the current input operational amplifier, connecting the output of the current input operational amplifier with the gate of the first switch tube, based on the adjustment of the current input operational amplifier and the first switch tube, stabilizing the change rate of the first end voltage of the switching module at a certain value during the time period when the driving voltage is the first voltage threshold; wherein the driving voltage of the first switch tube is the absolute value of the voltage difference between the gate and the source thereof; the second voltage threshold corresponds to the driving voltage when the first switch tube is in the off state or the fully on state; the first voltage threshold is close to the Miller platform voltage setting, which can be greater than or equal to the absolute value of the on voltage threshold of the switch tube. It should be noted that close to the Miller platform voltage setting can be understood as slightly less than, equal to or slightly greater than the value of the Miller platform voltage. Wherein the first end is the end that needs to control the change rate; for example, in the application of a flyback converter, the primary side of the transformer is connected to the ground through the switching module (a resistor can also be arranged between the switching module and the ground), and the change rate of the end connected to the primary side of the transformer and the switching module usually needs to be limited, so the end connected to the primary side of the transformer and the switching module can be regarded as the first end. Wherein the switching module described herein includes the first switch tube and can also include or not include other devices.

[0041] The present application can realize the limitation of the change rate of the first end voltage of the switching module to a certain value during the on or off process of the first switch tube, avoid the problem of too fast change rate of the system application, and reduce the requirements on other devices.

[0042] The switch tube is generally divided into N-type switch tube and P-type switch tube, and the following is further explained. Specifically, when the second voltage threshold corresponds to the off state of the first switch tube, the driving voltage of the first switch tube rises from the second voltage threshold to the first voltage threshold, when the first switch tube is an N-type switch tube, the first reference current is a pull-up current, and based on the adjustment of the current input operational amplifier and the first switch tube, the rising rate of the first end voltage of the switch module is stabilized at a certain value in the time period when the driving voltage is the first voltage threshold; when the first switch tube is a P-type switch tube, the first reference current is a pull-down current, and based on the adjustment of the current input operational amplifier and the first switch tube, the falling rate of the first end voltage of the switch module is stabilized at a certain value in the time period when the driving voltage is the first voltage threshold.

[0043] When the second voltage threshold corresponds to the fully on state of the first switch tube, the driving voltage of the first switch tube falls from the second voltage threshold to the first voltage threshold, and when the first switch tube is an N-type switch tube, the first reference current is a pull-down current, and based on the adjustment of the current input operational amplifier and the first switch tube, the rising rate of the first end voltage of the switch module is stabilized at a certain value in the time period when the driving voltage is the first voltage threshold; when the first switch tube is a P-type switch tube, the first reference current is a pull-up current, and based on the adjustment of the current input operational amplifier and the first switch tube, the falling rate of the first end voltage of the switch module is stabilized at a certain value in the time period when the driving voltage is the first voltage threshold.

[0044] Further, when the second voltage threshold corresponds to the off state of the first switch tube, as the switch tube is turned on, when the change rate of the first end voltage of the switch module is lower than a preset threshold, the driving voltage of the first switch tube is controlled to rise from the first voltage threshold to the driving voltage when the switch tube is fully on.

[0045] Further, when the second voltage threshold corresponds to the fully on state of the first switch tube, as the first switch tube is turned off, after the change rate of the first end voltage of the switch module is lower than a preset threshold, the driving voltage of the first switch tube is controlled to fall from the first voltage threshold to the driving voltage when the first switch tube is in the off state.

[0046] The present application also provides a soft drive circuit for driving the first switch tube in the switch module, which comprises Figure 1As shown, the soft drive circuit includes a first capacitor C1, a first reference current source I1, a current input operational amplifier IAv, and a switch module, which can include only the first switch tube or can include other devices in addition to the first switch tube (for example, a first switch tube can also be connected in series with other switch tubes, and the switch tube can be always on); the first capacitor C1 is arranged on the branch of the first end (the end shown as VD in the figure) of the switch module and the first node N1; the first reference current source I1 is a pull-up or pull-down current source acting on the first node N1; the current input operational amplifier is arranged on the branch of the gate of the first switch tube and the first node N1; when the drive voltage of the first switch tube changes from the second voltage threshold V2 to the first voltage threshold V1, the first current IC1 is generated on the first capacitor C1 based on the change of the voltage VD of the first end of the switch module, the difference signal Iin between the first reference current source I1 and the first current IC1 is connected to the input end of the current input operational amplifier IAv, and the output end of the current input operational amplifier IAv is connected to the gate of the first switch tube (VG in the figure represents the gate of the first switch tube); based on the adjustment of the current input operational amplifier IAv and the first switch tube M0, the change rate of the voltage VD of the first end of the switch module is stabilized at a certain value in the time period when the drive voltage is the first voltage threshold V1; wherein the drive voltage of the first switch tube is the absolute value of the voltage difference between the gate and the source thereof; the second voltage threshold V2 corresponds to the drive voltage when the first switch tube is in the off state or the fully on state; the first voltage threshold V1 corresponds to the Miller platform voltage setting, which can be greater than or equal to the absolute value of the on voltage threshold VGSth of the switch tube M0, and can be set according to actual application.

[0047] In the following, it is taken that the switch module includes only the first switch tube, and the first switch tube is an N-type switch tube, and its conduction process is taken as an example for description, at this time, the drain voltage of the first switch tube M0 can be regarded as the voltage of the first end of the switch module described above; as shown in the figure, Figure 2 As shown in the figure, the source of the first switch tube M0 is grounded, so its drive voltage can be represented by VG, in other embodiments, the source of M0 can also be connected to the ground through other elements, for example, the source of M0 is connected to the ground through a resistance element. In Figure 2 In the embodiment, the first reference current source I1 is a pull-up current source connected to the first node N1, Figure 3 In order to correspond Figure 2An embodiment of the driving voltage VG of the first switch tube M0 and the gate charging current IG in the process T1, before the time t0, the first switch tube M0 is off, its driving voltage VG is the second threshold voltage V2 (low level threshold), in the time period t0-t1, the driving voltage VG of M0 rises from the second voltage threshold V2 to the first voltage threshold V1, wherein the first voltage threshold V1 is greater than or equal to the on voltage threshold VGSth of the first switch tube M0, and its specific value can be set according to the actual application, for example, when the first switch tube M0 is applied in the scenario of flyback converter, DCM, the first voltage threshold V1 can be set as the on voltage threshold VGSth of M0; when the first switch tube M0 is applied in the scenario of flyback converter, CCM, the first voltage threshold V1 can be set as greater than the on voltage threshold VGSth of M0, and at this time its specific value can be set according to the size of the Miller platform voltage in the system; in this time period, the driving current IG acts on the gate of M0, which is used to realize the rising of the driving voltage VG from the second voltage threshold V2 in the off state to the first voltage threshold V1. After the time t1, the drain voltage VD of the first switch tube M0 will drop, as shown in Figure 2 As shown in the first capacitor C1 in Figure 2a first current IC1 in the direction shown in the figure, where IC1=C1xdVD / dt, at this time, the current Iin input to the current input operational amplifier IAv=I1-IC1, the input current Iin is affected by the current input operational amplifier IAv to generate the output current Iout acting on the gate of M0, in the period of t1-t2, when the falling rate of the drain voltage VD of M0 is fast, the value of the input current Iin will decrease, and the corresponding output current Iout will also decrease, acting on the gate of M0, so that the falling rate of VD is reduced; when the falling rate of the drain voltage VD of M0 is slow, the value of the input current Iin will increase, and the corresponding output current Iout will also increase, acting on the gate of M0, so that the falling rate of VD is increased. Therefore, through the feedback regulation of the current input operational amplifier IAv and M0, the input current Iin can finally be made to be 0, that is, IC1=I1, and then dVD / dt can be calculated to be equal to I1 / C1, that is, the falling rate of the drain voltage VD of M0 is stabilized at a certain value, and the driving voltage VG is also kept unchanged at V1; by reasonably setting the size of I1 and C1, the falling rate of VD can be avoided to be too fast, and thus the processing difficulty of system application is avoided; for example, when it is used in a flyback switching converter, the problems of EMI and secondary side rectifier stress caused by the change of the falling rate of VD can be avoided. In the period of t1-t2, considering the application of the Miller capacitor in the switch tube, there is also a certain current IG at the gate. At time t2, with the opening process of the first switch tube M0, the drain voltage VD drops to a potential close to zero, and the falling rate of the drain voltage VD will slow down, and after the detection circuit detects that the falling rate of VD is lower than the preset threshold, the corresponding driving current IG is set to act on the gate of the first switch tube M0, in the period of t2-t3, for increasing the driving voltage VG to realize the complete conduction of the first switch tube M0; in the period of t3-t4, the first switch tube M0 remains in the completely conductive state.

[0048] Figure 4 For example, the drain voltage of the first switch tube M0 can be regarded as the voltage of the first end of the switching module described above; and Figure 2 The difference between the two is that the first reference current source I1 is a pull-down current source connected to the first node N1, Figure 5 For corresponding Figure 4an embodiment of the driving voltage VG and the gate discharge current IG (or driving current) of the first switch tube M0 in the process of turning off T2, before t0, the first switch tube M0 is in a fully on state, the driving voltage VG is the second threshold voltage V2 (high level threshold), in the period of t0-t1, the driving voltage VG of M0 decreases from the second voltage threshold V2 to the first voltage threshold V1, the first voltage threshold V1 here can be set as a value close to the Miller platform voltage according to the actual application, as described above; in the period of t0-t1, the driving current IG acts on the gate of M0, for realizing the decrease of the driving voltage VG from the second voltage threshold V2 in the on state to the first voltage threshold V1, after t1, the drain voltage VD of the first switch tube M0 will rise, as shown in Figure 4 , a first current IC1 in the direction shown in Figure 4 is generated on the first capacitor C1, where IC1=C1×dVD / dt, at this time, the current Iin acting on the current input operational amplifier IAv is I1-IC1 (the direction is the same as that of the first reference current I1), the input current Iin passes through the current input operational amplifier IAv to generate an output current Iout acting on the gate of M0, in the period of t1-t2, when the rising rate of the drain voltage VD of M0 is fast, the value of the input current Iin will decrease, and the corresponding output current Iout will also decrease, acting on the gate of M0, so as to reduce the rising rate of VD; when the rising rate of the drain voltage VD of M0 is slow, the value of the input current Iin will increase, and the corresponding output current Iout will also increase, acting on the gate of M0, so as to increase the rising rate of VD. Therefore, through the feedback regulation of the current input operational amplifier IAv and M0, the input current Iin can finally be equal to 0, that is, IC1=I1, and dVD / dt can be calculated to be equal to I1 / C1, that is, the rising rate of the drain voltage VD of M0 is stabilized at a certain value, and the driving voltage VG remains unchanged at V1; by reasonably setting the sizes of I1 and C1, the rising rate of VD can be prevented from being too fast, and the problems such as processing difficulty in system application can be avoided. Similarly, in the period of t1-t2, considering the application of the Miller capacitor in the switch tube, there is also a certain current IG at the gate. At t2, with the process of turning off the first switch tube M0, the drain voltage VD will rise to a corresponding high potential, and the rising rate of the drain voltage VD will slow down, and after the detection circuit detects that the rising rate of VD is lower than a preset threshold, a corresponding driving current IG is set to act on the gate of the first switch tube M0, in the period of t2-t3, for reducing the driving voltage VG, so as to realize the complete turn-off of the first switch tube M0; in the period of t3-t4, the first switch tube M0 remains in the off state.

[0049] It should be noted that, Figure 3 and Figure 5 The size of the drive current IG in is only illustrative, and can be set according to actual application. In addition, the detection circuit and the corresponding circuit for generating the drive current IG are not shown in the setting diagram, and structures in the prior art can be used to achieve the same. This will not be described in detail herein. Figure 2 and Figure 4 The connection mode of the circuit in is also only illustrative in the t1-t2 time period. Corresponding switches can also be provided, and the corresponding branches can also be disconnected by controlling the switches in other time periods. For example, a switch is provided between the first reference current source I1 and the current input operational amplifier IAv. In the t1-t2 time period, the switch is closed, and in other time periods, the switch is opened, and the first switch tube M0 is driven by other drive currents IG. Of course, the first reference current source I1 can also be used for driving in other time periods, and the specific application can be set according to actual application. Figure 3 and Figure 5 The three-stage drive voltage VG in is only one of the illustrations herein, and other multi-stage drives can also be set according to actual application. For example, Figure 3 In, after the t2 moment, before the first switch tube M0 is fully turned on, the drive voltage VG is raised to a certain threshold for a period of time by setting the drive current IG, and then the drive voltage VG is raised to the voltage threshold when the first switch tube M0 is fully turned on by setting the drive current IG.

[0050] The above switch tube is taken as an example of an N-type switch tube, and the principles of controlling the change rate of the drain voltage VD of the switch tube in the conduction process and the turn-off process are described above. In specific applications, the change rate of the drain voltage VD can be controlled by corresponding settings only for the conduction process of the switch tube, or by corresponding settings only for the turn-off process of the switch tube, or by setting two reference current sources for the conduction and turn-off processes of the switch tube, as shown in Figure 6 A pull-up reference current source I1 and a pull-down reference current source I1' are provided, and the change rate of the drain voltage VD of the switch tube in the conduction or turn-off process of the switch tube is controlled by switching different reference current sources (switching of different reference current sources is realized by controlling switches S1 and S1'). In the conduction and turn-off processes of the switch tube, a current input operational amplifier IAv can be shared, as shown in Figure 6 or two current input operational amplifiers (not shown in the figure) can be provided correspondingly.

[0051] The above is described by taking the N-type switch tube as an example. The present application is also applicable to the P-type switch tube. The absolute value of the voltage difference between the gate and the source of the P-type switch tube is regarded as the driving voltage. The conduction process of the P-type switch tube can correspond to the turn-off process of the N-type switch tube, and the turn-off process of the P-type switch tube can correspond to the conduction process of the N-type switch tube. Only the circuit needs to be transformed accordingly. The present application will not be described in detail.

[0052] The present application also provides a switching power supply for converting an input voltage into an output voltage to supply power to a load. The switching power supply controls the first switch tube in the switching module by using the soft driving circuit or the soft driving method described above.

[0053] In summary, the soft driving method, the circuit and the switching power supply using the same provided by the present application can generate the first current based on the change of the voltage at the first end of the switching module when the driving voltage of the first switch tube in the switching module changes from the second voltage threshold to the first voltage threshold. The difference between the first reference current and the first current is input into the operational amplifier as the input. The output of the current input operational amplifier is connected to the gate of the first switch tube. Based on the adjustment of the current input operational amplifier and the first switch tube, the change rate of the voltage at the first end of the switching module is stabilized at a certain value during the period when the driving voltage is the first voltage threshold. The driving voltage of the first switch tube is the absolute value of the voltage difference between the gate and the source. The second voltage threshold corresponds to the driving voltage when the first switch tube is in the turn-off state or the fully on state. The first voltage threshold is close to the Miller platform voltage, which can be greater than or equal to the absolute value of the turn-on voltage threshold of the first switch tube. The present application can limit the change rate of the voltage at the first end of the switching module to be stabilized at a certain value during the conduction or turn-off process of the first switch tube in the switching module, thereby avoiding the problem of too fast change rate of the system application and reducing the requirements for other devices.

[0054] Finally, it should be noted that: obviously, the above embodiments are only examples for clearly illustrating the present application, and are not limitations on the embodiments. Based on the above description, those skilled in the art can make other different forms of changes or variations. Here, it is not necessary and impossible to enumerate all the embodiments. The obvious changes or variations derived therefrom are still within the protection scope of the present application.

Claims

1. A soft drive method for driving a first switch tube in a switch module, the switch module being applied to a switching power supply, characterized in that, The soft drive method comprises, The first capacitor is arranged on a branch where the first end of the switch module and the first node are located, and the first reference current is a pull-up or pull-down current source acting on the first node; When the drive voltage of the first switch tube changes from the second voltage threshold to the first voltage threshold, a first current is generated on the first capacitor based on the change of the voltage at the first end of the switch module, and the difference between the first reference current and the first current is input to an operational amplifier as an input, and the output of the operational amplifier is connected to the gate of the first switch tube, so that the change rate of the voltage at the first end of the switch module is stabilized at a certain value in the time period when the drive voltage is the first voltage threshold based on the adjustment of the operational amplifier and the first switch tube; the first end is an end whose change rate needs to be controlled; The drive voltage of the first switch tube is the absolute value of the voltage difference between the gate and the source thereof; the second voltage threshold corresponds to the drive voltage when the first switch tube is in an off state or a fully on state; and the first voltage threshold is close to the Miller platform voltage.

2. The soft driving method according to claim 1, wherein When the second voltage threshold corresponds to the drive voltage when the first switch tube is in an off state, when the drive voltage of the first switch tube rises from the second voltage threshold to the first voltage threshold, When the first switch tube is an N-type switch tube, the first reference current is a pull-up current, and the rising rate of the voltage at the first end of the switch module is stabilized at a certain value in the time period when the drive voltage is the first voltage threshold based on the adjustment of the operational amplifier and the first switch tube; When the first switch tube is a P-type switch tube, the first reference current is a pull-down current, and the falling rate of the voltage at the first end of the switch module is stabilized at a certain value in the time period when the drive voltage is the first voltage threshold based on the adjustment of the operational amplifier and the first switch tube.

3. The soft driving method according to claim 1, wherein When the second voltage threshold corresponds to the drive voltage when the first switch tube is in a fully on state, when the drive voltage of the first switch tube falls from the second voltage threshold to the first voltage threshold, When the first switch tube is an N-type switch tube, the first reference current is a pull-down current, and the rising rate of the voltage at the first end of the switch module is stabilized at a certain value in the time period when the drive voltage is the first voltage threshold based on the adjustment of the operational amplifier and the first switch tube; When the first switch tube is a P-type switch tube, the first reference current is a pull-up current, and the falling rate of the voltage at the first end of the switch module is stabilized at a certain value in the time period when the drive voltage is the first voltage threshold based on the adjustment of the operational amplifier and the first switch tube.

4. The soft driving method according to claim 2, wherein When the second voltage threshold corresponds to the off state of the first switch tube, the driving voltage of the first switch tube rises from the second voltage threshold to the driving voltage when the first switch tube is fully on, and when the voltage variation rate of the first end of the switch module is lower than a preset threshold, the driving voltage of the first switch tube is controlled to rise from the first voltage threshold to the driving voltage when the first switch tube is fully on.

5. The soft driving method according to claim 3, wherein When the second voltage threshold corresponds to the fully on state of the first switch tube, the driving voltage of the first switch tube drops from the second voltage threshold to the driving voltage when the first switch tube is off, and after the voltage variation rate of the first end of the switch module is lower than a preset threshold, the driving voltage of the first switch tube is controlled to drop from the first voltage threshold to the driving voltage when the first switch tube is off.

6. A soft drive circuit for driving a first switch tube in a switching module, the switching module being applied to a switching power supply, characterized in that, The soft drive circuit comprises, a first capacitor arranged on a branch where the first node and the first end of the switch module are located; a first reference current source, which is an up or down pull current source acting on the first node; a current input operational amplifier arranged on a branch where the gate of the first switch tube and the first node are located; when the driving voltage of the first switch tube changes from the second voltage threshold to the first voltage threshold, a first current is generated on the first capacitor based on the voltage variation of the first end of the switch module, a difference signal between the first reference current and the first current is connected to the input end of the current input operational amplifier, and the output end of the current input operational amplifier is connected to the gate of the first switch tube; based on the adjustment of the current input operational amplifier and the first switch tube, the voltage variation rate of the first end of the switch module is stabilized at a certain value in the time period when the driving voltage is the first voltage threshold. The driving voltage of the first switch tube is the absolute value of the voltage difference between the gate and the source thereof; the second voltage threshold corresponds to the driving voltage when the first switch tube is in the off state or the fully on state; and the first voltage threshold is close to the Miller platform voltage.

7. The soft drive circuit according to claim 6, wherein When the second voltage threshold corresponds to the off state of the first switch tube, the driving voltage of the first switch tube rises from the second voltage threshold to the driving voltage when the first switch tube is fully on, and when the voltage variation rate of the first end of the switch module is lower than a preset threshold, the driving voltage of the first switch tube is controlled to rise from the first voltage threshold to the driving voltage when the first switch tube is fully on. When the first switch tube is an N-type switch tube, the first reference current is an up pull current, and based on the adjustment of the current input operational amplifier and the first switch tube, the voltage drop rate of the first end of the switch module is stabilized at a certain value in the time period when the driving voltage is the first voltage threshold. When the first switch tube is a P-type switch tube, the first reference current is a down pull current, and based on the adjustment of the current input operational amplifier and the first switch tube, the voltage rise rate of the first end of the switch module is stabilized at a certain value in the time period when the driving voltage is the first voltage threshold.

8. The soft drive circuit according to claim 6, wherein, When the second voltage threshold corresponds to the fully on state of the first switch tube, the driving voltage of the first switch tube drops from the second voltage threshold to the driving voltage when the first switch tube is off, and after the voltage variation rate of the first end of the switch module is lower than a preset threshold, the driving voltage of the first switch tube is controlled to drop from the first voltage threshold to the driving voltage when the first switch tube is off. When the first switch tube is an N-type switch tube, the first reference current is a pull-down current, and based on the regulation of the current input operational amplifier and the first switch tube, the rising rate of the voltage at the first terminal of the switch module is stabilized at a certain value within the time period when the driving voltage is the first voltage threshold; When the first switch tube is a P-type switch tube, the first reference current is a pull-up current. Based on the regulation of the current input operational amplifier and the first switch tube, the decrease rate of the voltage at the first end of the switch module is stabilized at a certain value within the time period when the driving voltage is the first voltage threshold.

9. The soft drive circuit according to claim 6, wherein, The soft driving circuit includes a detection circuit, When the second voltage threshold corresponds to the driving voltage of the first switch tube when it is in the off state, as the first switch tube is turned on, when the detection circuit detects that the rate of change of the voltage at the first terminal of the switch module is lower than the preset threshold, the driving voltage of the first switch tube is controlled to increase from the first voltage threshold to the driving voltage when the first switch tube is fully turned on; or When the second voltage threshold corresponds to the driving voltage when the first switch tube is in a fully on state, as the first switch tube is turned off, when the detection circuit detects that the rate of change of the voltage at the first terminal of the switch module is lower than a preset threshold, the driving voltage of the first switch tube is controlled to drop from the first voltage threshold to the driving voltage when the first switch tube is in an off state.

10. A switching power supply for converting an input voltage to an output voltage to power a load, characterized by, The switching power supply includes the soft driving circuit according to any one of claims 6 to 9 or controls the first switching tube in the switching module based on the soft driving method according to any one of claims 1 to 5.

Images