Drive power supply circuit, switching power supply and digital power supply

Abstract

This application relates to a drive power supply circuit, a switching power supply, and a digital power supply. The drive power supply circuit includes: a signal control module, a transformer T1, a primary-side drive module, a secondary-side drive module, and a pre-bias control module. The signal control module outputs a first drive signal to the primary-side drive module and a second drive signal to the secondary-side drive module during soft start. The pre-bias control module delays the control of the secondary-side drive module by the second drive signal for a preset delay time, causing the secondary-side drive module to be in asynchronous rectification mode. After the preset delay time, the secondary-side drive module is brought into synchronous rectification mode under the control of the first and second drive signals. This application solves the safety hazard problem of excessive negative current by allowing the secondary-side drive module to first be in asynchronous rectification mode and then enter synchronous rectification mode after a delay time, thus meeting the application requirements of drive power supply circuits under high power conditions.

Description

Technical Field

[0001] The present application relates to the technical field of switching power supplies, and in particular to a driving power supply circuit, a switching power supply and a digital power supply. Background Art

[0002] As the power of power products increases, the loss of secondary side rectifier devices is also increasing, and it is necessary to adopt a secondary side synchronous rectification driving mode. At present, the driving power supply circuit using the secondary side synchronous rectification driving mode includes: a control IC and a transformer; the first drive signal output by the control IC controls the on and off of the MOS tube M1 to control the primary side of the transformer, and the second drive signal output by the second drive signal controls the on and off of the MOS tube M2 to realize the synchronous drive of the secondary side, and there is a large electrolytic capacitor on the secondary side. During the soft start process of the control IC, the duty cycle of the first drive signal increases from small to large, and the duty cycle of the second drive signal decreases from large to small, that is, the secondary side conduction time (Toff period) is relatively long during startup. Since there is a large electrolytic capacitor energy storage on the secondary side output, when the load is relatively light or the power is turned on and off quickly under no-load conditions, the output voltage starts to power on again before it has time to discharge. In this case, the negative current of the transformer will be very large, which may exceed the saturation value, causing the current to run away, posing a safety hazard.

[0003] There is currently no effective solution to the problem in the related technology that when the transformer is powered on quickly after being powered off under light load or no load, the negative current is too large, posing a safety hazard. Summary of the invention

[0004] In this embodiment, a driving power supply circuit, a switching power supply and a digital power supply are provided to solve the problem in the related art that when the transformer is powered on quickly after being powered off under light load or no load, the negative current is too large, posing a safety hazard.

[0005] In a first aspect, a driving power supply circuit is provided in this embodiment, comprising: a signal control module, a transformer T1, a primary side driving module connected to the primary side of the transformer T1, a secondary side driving module connected to the secondary side of the transformer T1, and a pre-bias control module;

[0006] The signal control module is connected to the primary drive module and the secondary drive module respectively, and is used to output a first drive signal to the primary drive module and a second drive signal to the secondary drive module during soft start; there is a dead zone between the first drive signal and the second drive signal, and the signal waveforms are the same;

[0007] The pre-bias control module is connected to the secondary drive module, and is used to delay the control of the secondary drive module by the second drive signal within a preset delay time, so that the secondary drive module is in an asynchronous rectification mode; after the preset delay time is reached, the secondary drive module is placed in a synchronous rectification mode under the control of the first drive signal and the second drive signal.

[0008] In some of the embodiments, the pre-bias control module includes a first switch unit, a second switch unit, a third switch unit, and a fourth switch unit;

[0009] The first switch unit is connected to the secondary side driving module and the second switch unit respectively, and is used to control the conduction or cutoff of the second switch unit under the voltage level signal output by the secondary side driving module;

[0010] The third switch unit includes an RC subunit and a third switch tube;

[0011] The RC subunit is connected to the secondary side driving module, the second switch unit and the third switch tube respectively, and is used to be in a charging process or a discharging process under the voltage level signal output by the secondary side driving module and the conduction or cutoff of the second switch unit, so as to control the cutoff or conduction of the third switch tube;

[0012] The fourth switch unit is connected to the secondary side drive module and the third switch tube respectively, and is used to control the conduction or cutoff of the fourth switch unit when the third switch tube is cut off or turned on, so as to delay the control of the secondary side drive module by the second drive signal.

[0013] In some of the embodiments, the delay time is determined by the time of a charging process or a discharging process of the RC subunit.

[0014] In some of the embodiments, the RC subunit includes a resistor R1, a resistor R2, a resistor R3, a resistor R4 and a capacitor C1;

[0015] One end of the resistor R1 is respectively connected to the output end of the secondary drive module and one end of the resistor R3; the other end of the resistor R1 is respectively connected to one end of the resistor R2, one end of the capacitor C1 and the control end of the third switch tube;

[0016] The other end of the resistor R3 is connected to the first switch unit;

[0017] The other end of the resistor R2 is connected to one end of the second switch unit and the resistor R4 respectively;

[0018] The other end of the resistor R4 and the other end of the capacitor C1 are grounded.

[0019] In some of the embodiments, the RC subunit further includes a diode D1;

[0020] The anode of the diode D1 is connected to the output end of the secondary driving module; the cathode of the diode D1 is connected to one end of the resistor R1 and one end of the resistor R3 respectively.

[0021] In some embodiments, the first switch unit includes a resistor R5, a resistor R6, a capacitor C2 and a first switch tube;

[0022] One end of the resistor R5 is connected to the output end of the secondary drive module; the other end of the resistor R5 is connected to one end of the resistor R6, one end of the capacitor C2 and the control end of the first switch tube;

[0023] The output end of the first switch tube is connected to the second switch unit and the RC subunit respectively;

[0024] The other end of the resistor R6, the other end of the capacitor C2 and the input end of the first switch are grounded.

[0025] In some of the embodiments, the first switch unit further includes a diode D2;

[0026] The anode of the diode D2 is connected to the output end of the secondary driving module; the cathode of the diode D1 is connected to one end of the resistor R5.

[0027] In some embodiments, the fourth switch unit includes a resistor R7, a resistor R8 and a fourth switch tube;

[0028] One end of the resistor R7 is connected to an external power supply; the other end of the resistor R7 is connected to the input end of the third switch tube and one end of the resistor R8 respectively;

[0029] The other end of the resistor R8 is connected to the control end of the fourth switch tube;

[0030] An input end of the fourth switch tube is grounded, and an output end of the fourth switch tube is connected to a control end of the secondary side driving module.

[0031] In some of the embodiments, the secondary driving module includes a first winding, a second winding and a secondary driving unit;

[0032] The turns ratio of the first winding to the second winding is 1:1;

[0033] The first winding is connected to the pre-bias control module and is used to output a voltage level signal;

[0034] The second winding is connected to the secondary driving unit and is used for inputting the first driving signal to the secondary driving unit.

[0035] In some of the embodiments, the secondary side driving unit includes an isolation driving sub-unit and a secondary side driving sub-unit;

[0036] The isolation driving sub-unit is connected to the signal control module and the secondary driving sub-unit respectively;

[0037] The secondary side driving sub-unit is connected to the second winding and the pre-bias control module respectively.

[0038] In a second aspect, a switching power supply is provided in this embodiment, comprising the driving power supply circuit as described in the first aspect above.

[0039] In a third aspect, a digital power supply is provided in this embodiment, comprising the driving power supply circuit as described in the first aspect above.

[0040] Compared with the related art, the driving power supply circuit, switching power supply and digital power supply provided in this embodiment, wherein the driving power supply circuit includes: a signal control module, a transformer T1, a primary side driving module connected to the primary side of the transformer T1, a secondary side driving module connected to the secondary side of the transformer T1 and a pre-bias control module; the signal control module is connected to the primary side driving module and the secondary side driving module respectively, and is used to output a first driving signal to the primary side driving module and output a second driving signal to the secondary side driving module during soft start; there is a dead zone between the first driving signal and the second driving signal, and the signal waveforms are the same; the pre-bias control module is connected to the secondary side driving module, and is used to delay the second driving signal at a preset delay time. The control signal controls the secondary drive module so that the secondary drive module is in a non-synchronous rectification mode; after reaching the preset delay time, under the control of the first drive signal and the second drive signal, the secondary drive module is placed in a synchronous rectification mode. In the related technology, there is a problem that when the transformer is powered on quickly after being powered off under light load or no-load, the negative current of the transformer is too large, which poses a safety hazard. The pre-bias control module is used to delay the control of the secondary drive module by the second drive signal, so that the secondary drive module is placed in a non-synchronous rectification mode in the early stage of soft start, thereby avoiding the problem of excessive negative current; in the later stage of soft start, the secondary drive module is placed in a synchronous rectification mode to meet the application requirements of the drive power supply circuit under high power.

[0041] Details of one or more embodiments of the present application are set forth in the following drawings and description to make other features, objects, and advantages of the present application more readily apparent. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0043] Figure 1 is a circuit diagram of a driving power supply circuit provided in an embodiment of the present application;

[0044] Figure 2 is a circuit diagram of a pre-bias control module provided in one embodiment of the present application;

[0045] Figure 3 is a circuit diagram of a secondary side driver subunit provided in an embodiment of the present application;

[0046] Figure 4 is a circuit diagram of an isolation driving subunit provided in an embodiment of the present application;

[0047] Figure 5 is a circuit diagram of a driving power supply circuit provided in a preferred embodiment of the present application;

[0048] Figure 6 is a simulation circuit diagram of a driving power supply circuit provided in an embodiment of the present application;

[0049] Figure 7 It is a schematic diagram of power-off waveform verification at gate2 provided in an embodiment of the present application;

[0050] Figure 8 It is a schematic diagram of power-on waveform verification at gate2 provided in an embodiment of the present application;

[0051] Fig. 9 It is a schematic diagram of power-off waveform verification at Vdm3 provided in one embodiment of the present application;

[0052] Fig.10 It is a schematic diagram of power-on waveform verification at Vdm3 provided in one embodiment of the present application;

[0053] Fig.11 This is a schematic diagram of the current waveform of a transformer with a pre-bias control module at startup provided by an embodiment of the present application.

[0054] In the figure: 10, signal control module; 20, primary side drive module; 30, secondary side drive module; 31, secondary side drive sub-unit; 32, isolation drive sub-unit; 40, pre-bias control module. DETAILED DESCRIPTION

[0055] In order to make the purpose, technical solutions and advantages of the present application clearer, the present application is described and illustrated below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not intended to limit the present application. Based on the embodiments provided in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present application. In addition, it can also be understood that although the efforts made in this development process may be complex and lengthy, for ordinary technicians in the field related to the contents disclosed in the present application, some changes such as design, manufacturing or production based on the technical contents disclosed in the present application are only conventional technical means, and should not be understood as insufficient contents disclosed in the present application.

[0056] Reference to "embodiments" in this application means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those of ordinary skill in the art that the embodiments described in this application may be combined with other embodiments without conflict.

[0057] Unless otherwise defined, the technical terms or scientific terms involved in this application should be understood by people with ordinary skills in the technical field to which this application belongs. In this application, when an element is referred to as "provided on" another element, it can be directly provided on the other element or there can also be a centered element. When an element is considered to be "provided on" another element, it can be directly provided on the other element or there can be a centered element at the same time. When an element is considered to be "fixed on" another element, it can be directly fixed on the other element or there can be a centered element at the same time. The terms "first", "second", "third" and the like involved in this application are merely used to distinguish similar objects and do not represent a specific ordering of objects. The terms used in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0058] See also Figure 1 In this embodiment, a driving power supply circuit is provided. Figure 1 is a circuit diagram of the driving power supply circuit of this embodiment, such as Figure 1 As shown, the driving power supply circuit includes: a signal control module 10, a transformer T1, a primary side driving module 20 connected to the primary side of the transformer T1, a secondary side driving module 30 connected to the secondary side of the transformer T1, and a pre-bias control module 40;

[0059] The signal control module 10 is connected to the primary drive module 20 and the secondary drive module 30 respectively, and is used to output a first drive signal to the primary drive module 20 and a second drive signal to the secondary drive module 30 during soft start; there is a dead zone between the first drive signal and the second drive signal, and the signal waveforms are the same;

[0060] The pre-bias control module 40 is connected to the secondary drive module 30, and is used to delay the control of the secondary drive module 30 by the second drive signal within a preset delay time, so that the secondary drive module 30 is in an asynchronous rectification mode; after the preset delay time is reached, under the control of the first drive signal and the second drive signal, the secondary drive module 30 is in a synchronous rectification mode.

[0061] Specifically, the signal control module 10 can output a first driving signal and a second driving signal; Figure 2 As shown, there is a dead zone between the first drive signal and the second drive signal, and the signal waveforms are the same, and both can be duty cycle signals. In this embodiment, the duty cycle signals of the first drive signal and the second drive signal first change from small to large, then remain at a high level for a period of time, and then change from large to small, and so on. Among them, the signal control module 10 can be a control IC, etc., which is not limited to this.

[0062] The secondary side driving module 30 is in the non-synchronous rectification mode, which means that the secondary side driving module 30 works under the control of the first driving signal. The secondary side driving module 30 is in the synchronous rectification mode, which means that the secondary side driving module 30 is under the control of the first driving signal and the second driving signal; in the synchronous rectification mode, the damage of the electronic components in the secondary side driving module 30 can be effectively reduced. The delay time can be set by adjusting the parameters of the electronic components in the pre-bias control module 40, or it can be set by the software program in the pre-bias control module 40, and there is no limitation on this.

[0063] Among them, the first drive signal is input to the primary drive module 20 to drive the primary drive module 20; the second drive signal is input to the secondary drive module 30 to drive the secondary drive module 30. If there is no intervention of the pre-bias control module 40; due to the dead zone between the two drive signals, the two drive signals change from small to large or from large to small; then in the early stage of soft start, the conduction time (time to complete the drive) of the secondary drive module 30 is relatively long; if the load is relatively light or the power is turned on and off quickly under no-load conditions, the voltage output by the secondary drive module 30 is affected by the capacitor in the secondary drive module 30 and has no time to discharge. At this time, the power is turned on again, which will cause the negative current of the transformer T1 to be very large, which may exceed the saturation value, causing the current to run away, and there is a safety hazard. In this embodiment, this problem is solved by setting a pre-bias control module 40.

[0064] Specifically: the pre-bias control module 40 is connected to the secondary drive module 30, and it can delay the control of the secondary drive module 30 by the second drive signal. At this time, the secondary drive module 30 is only under the control of the first drive signal, so that the secondary drive module 30 is in a non-synchronous rectification mode, so that the capacitor in the secondary drive module 30 has sufficient time to discharge, avoiding the problem of excessive negative current; then after the preset delay time, that is, the discharge of the capacitor in the secondary drive module 30 is completed, and then under the control of the first drive signal and the second drive signal, the secondary drive module 30 is in a synchronous rectification mode; thereby avoiding the problem of excessive negative current and meeting the application requirements of the drive power supply circuit under high power.

[0065] The following is a detailed description of each of the above modules:

[0066] Combination Figure 2 The pre-bias control module is described.

[0067] In some of the embodiments, the pre-bias control module includes a first switch unit, a second switch unit, a third switch unit, and a fourth switch unit;

[0068] A first switch unit is connected to the secondary side driving module and the second switch unit respectively, and is used to control the conduction or cutoff of the second switch unit under the voltage level signal output by the secondary side driving module;

[0069] The third switch unit includes an RC subunit and a third switch tube;

[0070] The RC subunit is connected to the secondary side driving module, the second switch unit and the third switch tube respectively, and is used to control the cut-off or conduction of the third switch tube when the voltage level signal output by the secondary side driving module and the conduction or cut-off of the second switch unit are in the charging process or the discharging process;

[0071] The fourth switch unit is connected to the secondary drive module and the third switch tube respectively, and is used to control the conduction or cut-off of the fourth switch unit when the third switch tube is cut-off or turned on, so as to delay the control of the secondary drive module by the second drive signal.

[0072] Specifically, the pre-bias control module is mainly composed of four switch units, which delay the control of the secondary drive module by the second drive signal according to the change of the input voltage level signal. Among them, the voltage level signal is output by the secondary drive module, which can be considered as a high and low level signal, which can drive the pre-bias control module to work. The implementation of the first switch unit, the second switch unit, the third switch unit and the fourth switch unit can be realized by electronic components, or by electronic components combined with software programs, and there is no limitation on this.

[0073] Among them, the first switch unit controls the conduction or cutoff of the second switch unit under the voltage level signal to cooperate with the charging process or discharging process of the RC subunit in the third switch unit. The charging process or discharging process of the RC subunit cooperates with the cutoff or conduction of the third switch tube to affect the conduction or cutoff of the fourth switch unit; when the fourth switch unit is turned on, the second drive signal can be pulled down to the ground, so that the second drive signal cannot control the secondary drive module; when the fourth switch unit is turned off, the influence on the secondary drive module (second drive signal) is stopped, so that the second drive signal can control the secondary drive module. In other words, the above process can be considered to use the charging process or discharging process of the RC subunit to determine the delay time, thereby realizing the control of the mode of the secondary drive module.

[0074] Through this embodiment, according to the charging and discharging principle in the RC subunit and in conjunction with the characteristics of the switch unit being turned on or off, the mode of the secondary side drive module is controlled during the power-on and power-off process of the soft start.

[0075] In some of the embodiments, the delay time is determined by the time of the charging process or the discharging process of the RC subunit.

[0076] Specifically, the delay time is determined by the time of the charging process or the discharging process of the RC subunit. When the power is on, that is, when the voltage level signal is a high level signal, the delay time is determined by the time of the charging process; when the power is off, that is, when the voltage level signal is a low level signal, the delay time is determined by the time of the discharging process. Therefore, it can be considered that by adjusting the parameters of the electronic components in the RC subunit to adjust the time of the charging process or the discharging process, the delay time can be adjusted accordingly.

[0077] Through this embodiment, the delay time is determined by utilizing the time of the charging process or the discharging process of the RC subunit, so as to match the high and low level switching of the voltage level signal and improve the stability of the delay time.

[0078] In some of the embodiments, the RC subunit includes a resistor R1, a resistor R2, a resistor R3, a resistor R4, and a capacitor C1;

[0079] One end of the resistor R1 is connected to the output end of the secondary drive module and one end of the resistor R3 respectively; the other end of the resistor R1 is connected to one end of the resistor R2, one end of the capacitor C1 and the control end of the third switch tube respectively;

[0080] The other end of the resistor R3 is connected to the first switch unit;

[0081] The other end of the resistor R2 is connected to the second switch unit and one end of the resistor R4 respectively;

[0082] The other end of the resistor R4 and the other end of the capacitor C1 are grounded.

[0083] Specifically, the charging circuit of the RC subunit includes a resistor R1 and a capacitor C1. When the voltage level signal gata3 (output by the output end of the secondary drive module) is a high-level signal, the capacitor C1 is charged through the resistor R1, and the voltage at the control end of the third switch tube gradually rises. Before the voltage reaches the turn-on voltage of the third switch tube, the third switch tube is always turned off. At this time, the fourth switch unit is always turned on, and the output signal gata2 of the pre-bias control module is forced to be grounded. Until the delay time is reached, the voltage of the capacitor C1 reaches the turn-on voltage of the third switch tube, so that the third switch tube is turned on, thereby turning off the fourth switch unit and not controlling the output signal gata2.

[0084] The RC subunit has two discharge loops, the first of which is capacitor C1, resistor R1, resistor R3 and the first switch unit; the second is capacitor C1, resistor R2, second switch unit or resistor R4. When the voltage level signal gata3 (output by the output end of the secondary drive module) is a low level signal, capacitor C1 starts to discharge, and capacitor C1 first discharges through resistor R1, resistor R3 and the first switch unit (the first switch unit is turned on and grounded at this time). If the first switch is turned off and the second switch unit is turned on, the discharge is through resistor R2 and the second switch unit; if the second switch unit is turned off, the discharge is through resistor R2 and resistor R4. Among them, resistor R2 can be replaced by at least two parallel resistors to improve the stability of operation. In other embodiments, the RC subunit can also be implemented by a computer program or an integrated chip, which is not limited.

[0085] Through this embodiment, simple electronic components are used to form the RC subunit, thereby ensuring the stability and reliability of the delay time.

[0086] In this embodiment, the switch tubes involved in the first switch unit, the second switch unit, the third switch unit and the fourth switch unit can adopt one or more of MOS tubes, field effect tubes and triodes. The gate (G) of the MOS tube corresponds to the control end, the drain (D) corresponds to the output end, and the source (S) corresponds to the input end. The base (B) of the triode corresponds to the control end, the collector (C) corresponds to the output end, and the emitter (E) corresponds to the input end. For example: the switch tubes in the first switch unit, the second switch unit and the third switch unit adopt MOS tubes; the switch tube in the fourth switch unit adopts a triode.

[0087] In some of the embodiments, the RC subunit further includes a diode D1;

[0088] The anode of the diode D1 is connected to the output end of the secondary driving module; the cathode of the diode D1 is connected to one end of the resistor R1 and one end of the resistor R3 respectively.

[0089] Specifically, the diode D1 is used for unidirectional conduction, and the conduction direction is from the positive electrode to the negative electrode. By providing the diode D1, the voltage level signal flows in the direction of the resistor R1 and the resistor R3.

[0090] In some embodiments, the first switch unit includes a resistor R5, a resistor R6, a capacitor C2 and a first switch tube;

[0091] One end of the resistor R5 is connected to the output end of the secondary drive module; the other end of the resistor R5 is connected to one end of the resistor R6, one end of the capacitor C2 and the control end of the first switch tube;

[0092] The output end of the first switch tube is connected to the second switch unit and the RC subunit respectively;

[0093] The other end of the resistor R6, the other end of the capacitor C2 and the input end of the first switch tube are grounded.

[0094] Specifically, resistor R5, resistor R6 and capacitor C2 constitute RC charging and discharging to control the conduction or cutoff of the first switch tube. The RC charging circuit is resistor R5 and capacitor C2; the voltage level signal charges capacitor C2 through resistor R5, and the voltage at the control end of the first switch tube gradually rises (before rising to the turn-on voltage, the first switch tube is cut off), and when it rises to the turn-on voltage, the first switch tube is turned on. The RC discharging circuit is capacitor C2 and resistor R6; capacitor C2 is discharged through resistor R6, and the voltage at the control end of the first switch tube gradually decreases, and when it decreases to the turn-on voltage, the first switch tube is cut off. Among them, resistor R2 can be replaced by at least two parallel resistors to improve the stability of operation. In other embodiments, the first switch unit can also be implemented by a computer program or an integrated chip, which is not limited.

[0095] Through this embodiment, the first switch unit is formed by using simple electronic components, thereby ensuring the stability and reliability of the operation of the first switch unit.

[0096] In some of the embodiments, the first switch unit further includes a diode D2;

[0097] The anode of the diode D2 is connected to the output end of the secondary driving module; the cathode of the diode D1 is connected to one end of the resistor R5.

[0098] Specifically, the diode D2 is used for unidirectional conduction, and the conduction direction is from the positive electrode to the negative electrode. By providing the diode D2, the voltage level signal flows in the direction of the resistor R5.

[0099] In some embodiments, the fourth switch unit includes a resistor R7, a resistor R8 and a fourth switch tube;

[0100] One end of the resistor R7 is connected to the external power supply; the other end of the resistor R7 is connected to the input end of the third switch tube and one end of the resistor R8 respectively;

[0101] The other end of the resistor R8 is connected to the control end of the fourth switch tube;

[0102] An input end of the fourth switch tube is grounded, and an output end of the fourth switch tube is connected to a control end of the secondary side driving module.

[0103] Specifically, resistors R7 and R8 are used to limit current and provide a bias voltage for the control end of the fourth switch tube, so that the fourth switch tube is turned on and the output signal gata2 is grounded. After the third switch tube is turned on, the voltage at the control end of the fourth switch tube drops to the turn-on voltage, and the fourth switch tube is cut off; the drive signal gate2 is not controlled, so that the secondary side drive module enters the synchronous rectification mode. Among them, the external power supply can be a 12V power supply; preferably, the 12V voltage can also be provided by the secondary side, that is, the secondary side outputs a 12V voltage to resistor R7. In normal power-on and power-off applications, the external power supply will drop to zero when shutting down, so the pre-bias module will not affect the drive signal gate2, and will have no effect on other performances of the drive power supply circuit.

[0104] Through this embodiment, the fourth switch unit is formed by using simple electronic components, thereby ensuring the stability and reliability of the operation of the fourth switch unit.

[0105] In some of the embodiments, the secondary driving module includes a first winding, a second winding, and a secondary driving unit;

[0106] The turns ratio between the first winding and the second winding is 1:1;

[0107] The first winding is connected to the pre-bias control module and is used to output a voltage level signal;

[0108] The second winding is connected to the secondary driving unit and is used for inputting the first driving signal to the secondary driving unit.

[0109] Specifically, the primary side of the transformer is the primary winding; the secondary side of the transformer is the secondary winding; the voltage ratio of the primary winding and the secondary winding is equal to the turn ratio of the primary winding and the secondary winding. Therefore, if you want to output different voltages, you can change the turn ratio of the windings. In this embodiment, the secondary winding is divided into a first winding and a second winding, and the turn ratio of the first winding and the second winding is 1:1. If the turns of the primary winding and the secondary winding are also 1:1; then the voltage of the primary winding and the secondary winding is 1:1, and the phase is opposite (because the primary winding and the secondary winding are opposite ends); if the turns ratio of the first winding and the second winding in the secondary winding is 1:1, then the voltage output by the first winding and the second winding is also 1:1, and the phase is the same.

[0110] In this embodiment, the turns ratio is used to adjust the signal output by the first winding and the signal output by the second winding to be the same, so as to improve the accuracy of delay time setting.

[0111] In some of the embodiments, Figure 3 and Figure 4 As shown, the secondary side driving unit includes an isolation driving sub-unit 32 and a secondary side driving sub-unit 31;

[0112] The isolation driving sub-unit 32 is connected to the signal control module and the secondary driving sub-unit 31 respectively;

[0113] The secondary driving sub-unit 31 is connected to the second winding and the pre-bias control module respectively.

[0114] Specifically, Figure 3 As shown, the secondary side driving subunit 31 is respectively connected to the second winding and the pre-bias control module; wherein the secondary side driving subunit 31 includes a diode D3, a MOS tube M4, a resistor R91, a resistor R92, a resistor R93, a resistor R94, a capacitor C91, a capacitor C92, a capacitor C93, a capacitor C94, a capacitor C95, a capacitor C96, a capacitor C97, a capacitor C98, and a capacitor C99; the gate of the MOS tube M4 is connected to the driving signal gete2; the source of the MOS tube M4 is respectively connected to the input end of the second winding, the negative electrode of the diode D3, and the resistor R91 The other end of the resistor R92 and the other end of the resistor R93 are connected; the drain of the MOS tube M4 is respectively connected to the positive electrode of the diode D3, one end of the capacitor C99, the other end of the capacitors C91 to C98, and the other end of the resistor R94; the other end of the capacitor C99 is respectively connected to one end of the resistor R91, one end of the resistor R92, and one end of the resistor R93; one end of the capacitors C91 to C98 is connected to the output end of the second winding; one end of the resistor R94 is connected to the output end of the second winding; one end of the capacitor C97 is also connected to the external 12V power supply. Among them, the resistor R91, the resistor R92, and the resistor R93 can be replaced by an equivalent resistor; the capacitor C91, the capacitor C92, the capacitor C93, the capacitor C94, the capacitor C95, the capacitor C96, the capacitor C97, and the capacitor C98 can be considered as large capacitors and can be replaced by equivalent capacitors, and there is no restriction on this. Due to the presence of large capacitors and the energy storage of large capacitors, when the load is light or no-load, in quick plug-in applications, it is believed that the voltage remains basically unchanged or does not drop significantly; the intervention of the pre-bias control module can solve the problem caused by this.

[0115] Among them, Figure 4As shown, the isolation driving subunit 32 includes a transformer T2, a capacitor C81, a capacitor C82, a diode D4, a diode D5, a transistor Q2, a resistor R81, a resistor R82, a resistor R83, a resistor R84, and a resistor R85; one end of the capacitor C81 is connected to the signal control module to receive the second driving signal; the other end of the capacitor C81 is respectively connected to the input end of the primary side of the transformer T2 and one end of the resistor R81; the other end of the resistor R81 is connected to the output end of the primary side of the transformer T2. The output end of the secondary side of transformer T2 is connected to the cathode of diode D5 and one end of resistor R82 through capacitor C82; the input end of the secondary side of transformer T2 and the anode of diode D5 are grounded; the other end of resistor R82 is connected to one end of resistor R82 and the anode of diode D4; the other end of resistor R82 is connected to the base of transistor Q2; the cathode of diode D4 is connected to the collector of transistor Q2, one end of resistor R84 and one end of resistor R85; the emitter of transistor Q2, the other end of resistor R84 and the other end of resistor R85 are grounded. The collector of transistor Q2 outputs driving signal gate2.

[0116] In this embodiment, the isolation driving sub-unit 32 and the secondary driving sub-unit 31 may also be implemented by a computer program or an integrated chip, which is not limited thereto.

[0117] Through this embodiment, the isolation driving sub-unit 32 and the secondary driving sub-unit 31 are constructed by using simple electronic components, thereby ensuring the stability and reliability of operation.

[0118] Figure 5 is a circuit diagram of the driving power supply circuit of this preferred embodiment.

[0119] In this preferred embodiment, the first switch is MOS tube M1, the second switch is MOS tube M2, the third switch is MOS tube M3, and the fourth switch is triode Q1. Resistor R6 is replaced by resistor R61, resistor R62, and resistor R63 connected in parallel. Resistor R2 is replaced by resistor R21 and resistor R22 connected in parallel.

[0120] The connection relationship of the electronic components in this preferred embodiment can refer to the description in the above embodiments, which will not be repeated here.

[0121] The working principle of this preferred embodiment is described below:

[0122] The signal control module outputs the first drive signal to the primary drive module, and then outputs the voltage level signal gate3 through the first winding of the transformer T1; the signal control module outputs the second drive signal as the input of the isolation drive sub-unit 32 (input to one end of the capacitor C81). At this time, under the control of the external power supply, the resistor R7, and the resistor R8, the transistor Q1 is turned on; so that the drive signal gate2 output by the secondary drive sub-unit 31 is pulled low, and the MOS tube M4 is turned off, so that the isolation drive sub-unit 32 is in the asynchronous rectification mode.

[0123] When the voltage level signal gate3 is a high level signal: the voltage of the gate of the MOS tube M1 (during the charging process of the capacitor C99) gradually rises, turning on the MOS tube M1. After being turned on, the MOS tube M1 pulls down the gate voltage of the MOS tube M2, so that the MOS tube M2 is turned off. The capacitor C1 is charged through the resistor R1, and the gate voltage of the MOS tube M3 gradually rises. Before the voltage reaches the turn-on voltage, the MOS tube M3 is turned off. At this time, the transistor Q1 is turned on all the time, and the output signal gata2 of the pre-bias control module 40 is forced to be grounded. When the charging reaches the delay time, the voltage of the capacitor C1 reaches the turn-on voltage of the MOS tube M3, turning on the MOS tube M3, thereby turning off the transistor Q1 and not controlling the output signal gata2.

[0124] At this time, the MOS tube M1 is turned on, the MOS tube M2 is turned off, the voltage of the MOS tube M3 is high, the MOS tube M3 is turned on, and the transistor Q1 is turned off.

[0125] It can be considered that: when powered on, MOS tube M1 must be turned on quickly, and after MOS tube M1 is turned on, the gate of MOS tube M2 is pulled down, MOS tube M2 is turned off, and the charging current of MOS tube M1 is much larger than the discharging current. The turn-on time of MOS tube M1 can be adjusted by selecting the values ​​of resistor R5, resistor R61 to resistor R63.

[0126] When the voltage level signal gate3 is a low level signal: the gate of MOS tube M1 is discharged through R61, R62, and R63, and the gate of MOS tube M3 is discharged through resistor R1, resistor R3, and MOS tube M1. After the gate of MOS tube M1 is discharged to the turn-on voltage of MOS tube M1, MOS tube M1 is turned off, so that the voltage of the gate of MOS tube M2 quickly rises to the same voltage as the gate of MOS tube M3, and is higher than the full turn-on voltage of MOS tube M2. MOS tube M2 is turned on, accelerating the discharge of capacitor C1, and the discharge loop capacitor C1→resistor R21 and resistor R22→MOS tube M2→grounding, which dominates the entire discharge process. After a period of discharge delay (delay time), the gate voltages of MOS tubes M2 and MOS tubes M3 are lower than the turn-on voltage, MOS tubes M2 and MOS tubes M3 are turned off, transistor Q1 is turned on, and the drive signal gate2 is forced to be pulled low. The main function of resistor R4 is to continue to provide a discharge path for capacitor C1 to discharge after MOS tubes M3 and MOS tubes M2 are turned off.

[0127] It can be considered that: when powering off quickly, the capacitor C1 needs to be discharged to turn on the transistor Q1, complete the reset of the driving signal gate2 forced to be pulled low, and prepare for the next fast power-on. Therefore, the time interval from fast power-off to power-on determines the discharge time of the capacitor C1, and thus determines the selection of the parameters of the resistors R21 and R22.

[0128] Among them, after the pre-bias control module 40 reaches the delay time and does not control the output signal gata2, the output signal gata2 output by the isolation driver subunit 32 controls the cut-off or conduction of the MOS tube M4 in the secondary driver subunit 31, so that the isolation driver subunit 32 is in synchronous rectification mode.

[0129] The parameters of the electronic components in the pre-bias control module 40 may be adjusted to adjust the delay time, thereby meeting the timing control requirements in different applications.

[0130] The delay time is mainly affected by the charging and discharging time of the capacitor C1 in the RC subunit, and is determined by the parameters of the capacitor C1 and the resistor R1.

[0131] Through this preferred embodiment, in the application of fast power-on after power-off under light load or no load, the secondary side driving subunit 31 is operated in the asynchronous rectification mode during the front period of soft start, thereby avoiding the problem of excessive negative current of the transformer.

[0132] The following is a simulation to verify the application of the pre-bias control module 40 in the driving power supply circuit.

[0133] like Figure 6As shown, it is a simulation circuit for the pre-bias control module. The components of the simulation circuit correspond to the pre-bias control module, and will not be repeated here. The simulation result of the simulation circuit is: before power-on, the transistor Q4 is turned on, and the output drive signal SR is forced to be pulled low. After power-on, G1 quickly rises to the turn-on voltage of the MOS tube M51, and then pulls G2 down to cut off the MOS tube M52. At this time, the voltage of the capacitor C53 gradually rises (that is, the gate voltage of the MOS tube M53), and after the RC charging delay (about 500us in the simulation), the voltage of the capacitor C53 reaches the turn-on voltage of the MOS tube M53 and then turns on, the emitter of the transistor Q4 is forced to be pulled low, and the transistor Q4 is cut off, thereby not controlling the output drive signal SR.

[0134] like Figure 7 , Fig. 9 Power-off waveform verification and Figure 8 , Fig.10 The power-on waveform verification is shown. In the figure, the horizontal axis represents the time axis; the vertical axis represents the voltage waveform. Among them, Vgm1 represents the gate voltage of MOS tube M1; Vgm2 represents the gate voltage of MOS tube M2; Vgm3 represents the gate voltage of MOS tube M3; gate2 represents the collector voltage of transistor Q1; Vdm3 represents the voltage of the D pole of MOS tube M3.

[0135] When power is turned off, after 3.82ms, the gate voltage of MOS tube M3 drops to its cut-off voltage, and the gate voltage of MOS tube M3 rises, so that the transistor Q1 is turned on to force the drive signal gate2 to be pulled down, preparing for the following fast power-on. At the beginning of power-on (early soft start), the gate voltage of MOS tube M3 is high, the drive signal gate2 is pulled down, and the secondary side driver sub-unit works in the asynchronous rectification mode. After 1.16ms, after the gate voltage of MOS tube M3 rises to its turn-on voltage, MOS tube M3 is turned on, the transistor Q1 is cut off, and the drive signal gate2 is controlled by the drive signal output by the secondary side driver sub-unit, and the secondary side driver sub-unit is converted into the synchronous rectification mode. It can be seen from the figure that the negative current of transformer T1 at startup is successfully reduced; thus solving the problem of excessive negative current of the transformer when powering on quickly after powering off under light load or no load, and there is a safety hazard, without affecting other performances of the drive power supply circuit.

[0136] like Fig.11 As shown, it is a schematic diagram of the current waveform of the transformer with a pre-bias control module when it starts. In the figure, I_sec represents the secondary transformer current; gate2 represents the collector voltage of the transistor Q1; Vdm3 represents the voltage of the D pole of the MOS tube M3; Vo represents the secondary output voltage.

[0137] Among them, the charging and discharging formula of the capacitor is expressed as: Vt=V0+(Vu-V0)×1[1-exp(-t / RC)];

[0138] Where V0 is the initial voltage value of the capacitor, Vu is the voltage value when the capacitor is fully charged, Vt is the voltage value on the capacitor at any time t, and RC is the value of the resistance R and capacitance C in the loop.

[0139] In practical applications, the device parameters in the pre-bias control module are selected.

[0140] When powered on, it is equivalent to charging capacitor C1 through resistor R1. The initial value V0 is equivalent to the voltage of capacitor C1 (the residual voltage after C1 is discharged when powered off). When it is discharged below the turn-on voltage of MOS tube M3, it can be considered that 0=V0, so Vu is equivalent to the high-level voltage value of gate3. Assuming that the high-level voltage value is E, the charging and discharging formula can be organized into the theoretical pre-bias circuit action time, which is expressed as: t1=RCLn[E / (E-Vt)]. If E=12V, Vt=2V (the turn-on voltage of MOS tube M3), the resistance value of resistor R1 is 249Ω, and the value of capacitor C1 is 10uF; t1=0.5ms can be calculated. If E is 10V and the others remain unchanged, t1=0.6ms. In practical applications, the voltage of capacitor C1 after being fully charged does not reach 12V, which will make the measured waveform slightly longer and the total time longer.

[0141] When the power is turned off, it is equivalent to the capacitor C1 discharging (through resistor R21, resistor R22, and MOS tube M2). The voltage on capacitor C1 is close to the high-level voltage value of gate3 (i.e., the secondary output voltage 12V), i.e., the initial discharge value E. Vt is the turn-on voltage of MOS tube M3, so the discharge time is t2=RCLn[E / Vt]; i.e., after the power is turned off, the time for MOS tube M3 to switch from on to off (gate2 is pulled down to reset). Take the equivalent resistance value of 110Ω, the value of capacitor C1 of 10uF, Vt=2V (the turn-on voltage of MOS tube M3), then t2=2ms. Since the previous MOS tube M2 is not turned on, the discharge current is relatively small, so the total measured time will be slightly longer.

[0142] In other embodiments, the problem of large negative current of the transformer during startup can be solved by optimizing according to the selection of parameters combined with actual measurement without affecting other performances.

[0143] It should be noted that the above modules can be functional modules or program modules, and can be implemented by software or hardware. For modules implemented by hardware, the above modules can be located in the same processor; or the above modules can be located in different processors in any combination.

[0144] In addition, in combination with the driving power supply circuit provided in the above embodiments, a switching power supply may be provided in this embodiment to implement the above embodiments. The switching power supply includes any one of the driving power supply circuits in the above embodiments.

[0145] It should be noted that the specific examples in this embodiment can refer to the examples described in the above embodiments and optional implementation modes, and will not be repeated in this embodiment.

[0146] In addition, in combination with the driving power supply circuit provided in the above embodiments, a digital power supply may be provided in this embodiment to implement the above embodiments. The digital power supply includes any one of the driving power supply circuits in the above embodiments.

[0147] It should be noted that the specific examples in this embodiment can refer to the examples described in the above embodiments and optional implementation modes, and will not be repeated in this embodiment.

[0148] It should be understood that the specific embodiments described herein are only used to explain the application, rather than to limit it. Based on the embodiments provided in this application, all other embodiments obtained by ordinary technicians in this field without creative work are within the protection scope of this application.

[0149] Obviously, the drawings are only some examples or embodiments of the present application. For ordinary technicians in the field, the present application can also be applied to other similar situations based on these drawings without creative work. In addition, it is understandable that although the work done in this development process may be complicated and lengthy, for ordinary technicians in the field, certain changes in design, manufacturing or production based on the technical content disclosed in this application are only conventional technical means and should not be regarded as insufficient content disclosed in this application.

[0150] The term "embodiment" in this application refers to a specific feature, structure or characteristic described in conjunction with the embodiment that can be included in at least one embodiment of the present application. The appearance of this phrase in various locations in the specification does not necessarily mean the same embodiment, nor does it mean that it is mutually exclusive with other embodiments and is independent or optional. It is clearly or implicitly understood by those of ordinary skill in the art that the embodiments described in this application can be combined with other embodiments without conflict.

[0151] The above-mentioned embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of patent protection. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the scope of protection of the present application. Therefore, the scope of protection of the present application shall be subject to the attached claims.

Claims

1. A driving power supply circuit, characterized in that: include: A signal control module, a transformer T1, a primary side driving module connected to the primary side of the transformer T1, a secondary side driving module connected to the secondary side of the transformer T1, and a pre-bias control module; The signal control module is connected to the primary drive module and the secondary drive module respectively, and is used to output a first drive signal to the primary drive module and a second drive signal to the secondary drive module during soft start; There is a dead zone between the first driving signal and the second driving signal, and the signal waveforms are the same; The pre-bias control module is connected to the secondary drive module, and is used to delay the control of the secondary drive module by the second drive signal within a preset delay time, so that the secondary drive module is in an asynchronous rectification mode; after the preset delay time is reached, the secondary drive module is placed in a synchronous rectification mode under the control of the first drive signal and the second drive signal.

2. The driving power supply circuit according to claim 1, characterized in that: The pre-bias control module includes a first switch unit, a second switch unit, a third switch unit and a fourth switch unit; The first switch unit is connected to the secondary side driving module and the second switch unit respectively, and is used to control the conduction or cutoff of the second switch unit under the voltage level signal output by the secondary side driving module; The third switch unit includes an RC subunit and a third switch tube; The RC subunit is connected to the secondary side driving module, the second switch unit and the third switch tube respectively, and is used to be in a charging process or a discharging process under the voltage level signal output by the secondary side driving module and the conduction or cutoff of the second switch unit, so as to control the cutoff or conduction of the third switch tube; The fourth switch unit is connected to the secondary side drive module and the third switch tube respectively, and is used to control the conduction or cutoff of the fourth switch unit when the third switch tube is cut off or turned on, so as to delay the control of the secondary side drive module by the second drive signal.

3. The driving power supply circuit according to claim 2, characterized in that: The delay time is determined by the time of the charging process or the discharging process of the RC subunit.

4. The driving power supply circuit according to claim 2, characterized in that: The RC subunit includes a resistor R1, a resistor R2, a resistor R3, a resistor R4 and a capacitor C1; One end of the resistor R1 is respectively connected to the output end of the secondary drive module and one end of the resistor R3; the other end of the resistor R1 is respectively connected to one end of the resistor R2, one end of the capacitor C1 and the control end of the third switch tube; The other end of the resistor R3 is connected to the first switch unit; The other end of the resistor R2 is connected to one end of the second switch unit and the resistor R4 respectively; The other end of the resistor R4 and the other end of the capacitor C1 are grounded.

5. The driving power supply circuit according to claim 4, characterized in that: The RC subunit further includes a diode D1; The anode of the diode D1 is connected to the output end of the secondary driving module; the cathode of the diode D1 is connected to one end of the resistor R1 and one end of the resistor R3 respectively.

6. The driving power supply circuit according to claim 2, characterized in that: The first switch unit includes a resistor R5, a resistor R6, a capacitor C2 and a first switch tube; One end of the resistor R5 is connected to the output end of the secondary drive module; the other end of the resistor R5 is connected to one end of the resistor R6, one end of the capacitor C2 and the control end of the first switch tube; The output end of the first switch tube is connected to the second switch unit and the RC subunit respectively; The other end of the resistor R6, the other end of the capacitor C2 and the input end of the first switch are grounded.

7. The driving power supply circuit according to claim 6, characterized in that: The first switch unit further includes a diode D2; The anode of the diode D2 is connected to the output end of the secondary driving module; the cathode of the diode D1 is connected to one end of the resistor R5.

8. The driving power supply circuit according to claim 2, characterized in that: The fourth switch unit includes a resistor R7, a resistor R8 and a fourth switch tube; One end of the resistor R7 is connected to an external power supply; the other end of the resistor R7 is connected to the input end of the third switch tube and one end of the resistor R8 respectively; The other end of the resistor R8 is connected to the control end of the fourth switch tube; An input end of the fourth switch tube is grounded, and an output end of the fourth switch tube is connected to a control end of the secondary side driving module.

9. The driving power supply circuit according to claim 1, characterized in that: The secondary side driving module includes a first winding, a second winding and a secondary side driving unit; The turns ratio of the first winding to the second winding is 1:1; The first winding is connected to the pre-bias control module and is used to output a voltage level signal; The second winding is connected to the secondary driving unit and is used for inputting the first driving signal to the secondary driving unit.

10. The driving power supply circuit according to claim 9, characterized in that: The secondary side driving unit comprises an isolation driving sub-unit and a secondary side driving sub-unit; The isolation driving sub-unit is connected to the signal control module and the secondary driving sub-unit respectively; The secondary side driving sub-unit is connected to the second winding and the pre-bias control module respectively.

11. A switching power supply, characterized in that: The invention comprises a driving power supply circuit as claimed in any one of claims 1 to 9.

12. A digital power supply, characterized in that: The invention comprises a driving power supply circuit as claimed in any one of claims 1 to 9.

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