Switching power supply system

Abstract

The utility model discloses a switching power supply system, and belongs to the technical field of switching power supplies. The switching power supply system comprises: a power tube; one end of the target capacitor is grounded; the input end of the subtraction circuit is used for receiving the feedback voltage, and the output end of the subtraction circuit is used for outputting the first voltage; the first voltage is smaller than feedback voltage; the non-inverting input end of the first comparator is connected with the output end of the subtraction circuit, the inverting input end of the first comparator is connected with the other end of the target capacitor, and the output end of the first comparator is connected with the power tube; the non-inverting input end of the second comparator is connected with the input end of the subtraction circuit, the inverting input end of the second comparator is connected with the other end of the target capacitor, and the output end of the second comparator is connected with the power tube. The switching power supply system is good in valley bottom locking effect, audio noise interference is eliminated, and the overall efficiency of the system is improved.

Description

Technical Field

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

[0002] When the input voltage or load of the switching power supply changes, the power tube will be turned on alternately at different valley positions to cause frequency jitter. The power tube needs to be valley-locked to reduce frequency jitter. The commonly used valley-locking technology is valley-locking through switching frequency. This technology compares the detected switching frequency with the set reference frequency. Different reference frequencies correspond to different valley numbers. However, this technology may cause valley-locking failure at the critical point of valley switching. When the input voltage or load fluctuates, the power tube will be turned on alternately at adjacent valleys, which is likely to cause device loss and reduce device service life. The overall efficiency of the switching power supply system is low. Utility Model Content

[0003] The present application aims to solve at least one of the technical problems existing in the prior art. To this end, the present application proposes a switching power supply system, which avoids the situation where adjacent valleys are alternately turned on at the critical load point, and has a better valley locking effect; and avoids the problem that the power tube switches back and forth between adjacent valleys or even multiple valleys due to load fluctuations, and can well achieve valley locking, eliminate audio noise interference, and improve the overall efficiency of the system.

[0004] In a first aspect, the present application provides a switching power supply system, comprising:

[0005] Power tube;

[0006] A target capacitor, one end of which is grounded;

[0007] A subtraction circuit, wherein an input terminal of the subtraction circuit is used to receive a feedback voltage, and an output terminal of the subtraction circuit is used to output a first voltage; the first voltage is smaller than the feedback voltage;

[0008] A first comparator, wherein a non-inverting input terminal of the first comparator is connected to the output terminal of the subtraction circuit, an inverting input terminal of the first comparator is connected to the other end of the target capacitor, and an output terminal of the first comparator is connected to the power tube;

[0009] A second comparator, wherein a non-inverting input terminal of the second comparator is connected to an input terminal of the subtraction circuit, an inverting input terminal of the second comparator is connected to the other end of the target capacitor, and an output terminal of the second comparator is connected to the power tube.

[0010] According to the switching power supply system provided in the embodiment of the present application, a subtraction circuit is set to obtain two turn-off time signals with different generation times, and valley locking can be performed based on the two turn-off time signals, so that the critical load point at the valley jump can be maintained at the conduction valley of the previous cycle for conduction, thereby avoiding the situation where adjacent valleys are alternately turned on at the critical load point, and the valley locking effect is better; and the hysteresis time between the generation times of the two turn-off time signals can be adaptively changed based on load changes, thereby avoiding the problem of load fluctuations causing the power tube to switch back and forth between adjacent valleys or even multiple valleys, and the valley locking can be well achieved, eliminating audio noise interference, and improving the overall efficiency of the system.

[0011] In a switching power supply system according to an embodiment of the present application, the subtraction circuit comprises:

[0012] a first operational amplifier, wherein a non-inverting input terminal of the first operational amplifier is used to receive the feedback voltage, and an inverting input terminal of the first operational amplifier is connected to an output terminal of the first operational amplifier;

[0013] a third current source, one end of which is connected to a power supply, and the other end of which is connected to the output end of the first operational amplifier;

[0014] a first resistor, wherein the third current source is grounded via the first resistor;

[0015] a fourth current source, one end of the fourth current source being connected to one end of the third current source, and the other end of the fourth current source being connected to the non-inverting input end of the first comparator;

[0016] a second resistor, the fourth current source is grounded via the second resistor; the resistance value of the second resistor is equal to the resistance value of the first resistor;

[0017] A fifth current source, one end of the fifth current source is respectively connected to the other end of the fourth current source and the non-inverting input end of the first comparator, and the other end of the fifth current source is grounded.

[0018] In a switching power supply system according to an embodiment of the present application, the subtraction circuit comprises:

[0019] a second operational amplifier, wherein a non-inverting input terminal of the second operational amplifier is used to receive a reference voltage, and an inverting input terminal of the second operational amplifier is connected to an output terminal of the second operational amplifier;

[0020] a third resistor, wherein the third resistor is connected to an output terminal of the second operational amplifier;

[0021] a fourth resistor, the fourth resistor being connected in series with the third resistor;

[0022] a third operational amplifier, wherein a non-inverting input terminal of the third operational amplifier is used to receive the feedback voltage, and an inverting input terminal of the third operational amplifier is connected between the third resistor and the fourth resistor;

[0023] a fourth operational amplifier, wherein a non-inverting input terminal of the fourth operational amplifier is connected to an output terminal of the third operational amplifier, and an inverting input terminal of the fourth operational amplifier is connected to an output terminal of the fourth operational amplifier;

[0024] a fifth resistor, one end of which is connected to the output end of the fourth operational amplifier, and a resistance of the fifth resistor is the sum of resistances of the third resistor and the fourth resistor;

[0025] a sixth resistor, one end of the sixth resistor being connected to the other end of the fifth resistor, and the other end of the sixth resistor being grounded;

[0026] A seventh resistor, one end of the seventh resistor is respectively connected to the output end of the third operational amplifier, the fourth resistor and the non-inverting input end of the fourth operational amplifier, and the other end of the seventh resistor is grounded.

[0027] A switching power supply system according to an embodiment of the present application further comprises:

[0028] A first current source, one end of which is connected to a power supply;

[0029] a first switch, wherein one end of the first switch is connected to the other end of the first current source, and the other end of the first switch is connected to the other end of the target capacitor;

[0030] a second switch connected in parallel with the target capacitor;

[0031] a second current source, the second current source being connected in series with the second switch;

[0032] A third switch is connected in parallel with the target capacitor.

[0033] A switching power supply system according to an embodiment of the present application further comprises:

[0034] A first rising edge detection circuit, wherein an input end of the first rising edge detection circuit is connected to an output end of the first comparator, and an output end of the first rising edge detection circuit is connected to the power tube;

[0035] A second rising edge detection circuit, wherein the input end of the second rising edge detection circuit is connected to the output end of the second comparator, and the output end of the second rising edge detection circuit is connected to the power tube.

[0036] A switching power supply system according to an embodiment of the present application further comprises:

[0037] Valley detection module;

[0038] A valley bottom counting module, the valley bottom counting module is connected to the valley bottom detection module;

[0039] A valley conduction module, wherein the valley conduction module is respectively connected to the valley counting module, the first comparator and the second comparator;

[0040] A driving module is connected to the valley conduction module and the power tube respectively.

[0041] A switching power supply system according to an embodiment of the present application further comprises:

[0042] A PWM comparison module, wherein a positive input terminal of the PWM comparison module is connected to an input terminal of the subtraction circuit, and an inverting input terminal of the PWM comparison module is connected to the power tube;

[0043] A first trigger, wherein the first trigger comprises a first input terminal, a second input terminal and an output terminal, wherein the first input terminal is connected to the valley conduction module, the second input terminal is connected to the PWM comparison module, and the output terminal is connected to the driving module.

[0044] In a switching power supply system according to an embodiment of the present application, the power tube includes: a source, a drain and a gate, the source is connected to the inverting input terminal of the PWM comparison module, and the gate is connected to the driving module; the switching power supply system also includes:

[0045] A primary winding, one end of which is connected to a target voltage, and the other end of which is connected to the drain;

[0046] A first sampling resistor is provided, and the source is grounded via the first sampling resistor.

[0047] In a switching power supply system according to an embodiment of the present application, the valley conduction module includes:

[0048] a first latch, wherein an input terminal of the first latch is connected to an output terminal of the first comparator;

[0049] a second trigger, wherein one input terminal of the second trigger is connected to the output terminal of the first latch, and another input terminal of the second trigger is connected to the valley detection module;

[0050] a second latch, wherein an input terminal of the second latch is connected to an output terminal of the second comparator;

[0051] a first AND circuit, wherein one input end of the first AND circuit is connected to the valley counting module, and another input end of the first AND circuit is connected to the second latch;

[0052] An OR circuit, one input terminal of the OR circuit is connected to the output terminal of the second trigger, and the other input terminal of the OR circuit is connected to the output terminal of the first AND circuit;

[0053] A second AND circuit, wherein one input end of the second AND circuit is connected to the valley detection module, another input end of the second AND circuit is connected to the output end of the OR circuit, and the output end of the second AND circuit is connected to the power tube.

[0054] A switching power supply system according to an embodiment of the present application further comprises:

[0055] A feedback circuit, one end of which is used to receive the output voltage of the switching power supply system, and the other end of which is connected to the subtraction circuit.

[0056] The above one or more technical solutions in the embodiments of the present application have at least one of the following technical effects:

[0057] By setting a subtraction circuit to obtain two turn-off time signals with different generation moments, valley locking can be performed based on the two turn-off time signals, so that the critical load point at the valley jump can be maintained at the conduction valley of the previous cycle for conduction, avoiding the situation where adjacent valleys are alternately turned on at the critical load point, and the valley locking effect is better; and the hysteresis time between the generation moments of the two turn-off time signals can be adaptively changed based on load changes, avoiding the problem of load fluctuations causing the power tube to switch back and forth between adjacent valleys or even multiple valleys, and can well achieve valley locking, eliminate audio noise interference, and improve the overall efficiency of the system.

[0058] Furthermore, by setting a subtraction circuit and a hysteresis time that changes adaptively with the load, two turn-off time signals are generated, so that when the load fluctuates or the input bus voltage fluctuates and the turn-off time changes, the change of the turn-off time within a certain range is shielded by the hysteresis time, so that the power tube is still turned on at the conduction bottom of the previous cycle, and the valley locking effect is better.

[0059] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become apparent from the description below, or will be learned through the practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0061] Figure 1 This is one of the structural schematic diagrams of the switching power supply system provided in the embodiment of the present application;

[0062] Figure 2 This is the second structural schematic diagram of the switching power supply system provided in the embodiment of the present application;

[0063] Figure 3 This is the third structural diagram of the switching power supply system provided in the embodiment of the present application;

[0064] Figure 4 This is the fourth structural diagram of the switching power supply system provided in the embodiment of the present application;

[0065] Figure 5 This is the fifth structural diagram of the switching power supply system provided in the embodiment of the present application;

[0066] Figure 6 This is one of the principle schematic diagrams of the switching power supply system provided in the embodiment of the present application;

[0067] Figure 7 This is the sixth structural diagram of the switching power supply system provided in the embodiment of the present application;

[0068] Figure 8 This is the second principle schematic diagram of the switching power supply system provided in the embodiment of the present application;

[0069] Fig. 9 This is the third principle schematic diagram of the switching power supply system provided in the embodiment of the present application.

[0070] Reference numerals:

[0071] Primary side control circuit 110; secondary side control circuit 120; feedback loop 130; valley detection module 210;

[0072] Valley counting module 220; turn-off time module 230; valley conduction module 240; first trigger 250;

[0073] Driving module 260; PWM comparison module 270; subtraction circuit 310; first rising edge detection circuit 320;

[0074] Second rising edge detection circuit 330; first comparator 340; second comparator 350; first latch 710;

[0075] Second trigger 720; second latch 730; first AND circuit 740; OR circuit 750; second AND circuit 760;

[0076] A first current source I1; a second current source I2; a third current source I3; a fourth current source I4; a fifth current source I5;

[0077] A first switch SW1; a second switch SW2; a third switch SW3; a target capacitor CAP; a first resistor Rs1;

[0078] A second resistor Rs2; a third resistor Re1; a fourth resistor Rf; a sixth resistor Re2; and a seventh resistor Ro;

[0079] A first operational amplifier OP1; a second operational amplifier OP2; a third operational amplifier OP3;

[0080] Fourth operational amplifier OP4; primary winding Np; auxiliary winding Na; secondary winding Ns; first sampling resistor R CS ; second sampling resistor R1; third sampling resistor R2; rectifier tube Q2; power tube Q1. DETAILED DESCRIPTION

[0081] The following will be combined with the drawings in the embodiments of the present application to clearly describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments in the present application belong to the scope of protection of this application.

[0082] The terms "first", "second", etc. in the specification and claims of the present application are used to distinguish similar objects, and are not used to describe a specific order or sequence. It should be understood that the data used in this way can be interchangeable under appropriate circumstances, so that the embodiments of the present application can be implemented in an order other than those illustrated or described here, and the objects distinguished by "first", "second", etc. are generally of one type, and the number of objects is not limited. For example, the first object can be one or more. In addition, "and / or" in the specification and claims represents at least one of the connected objects, and the character " / " generally indicates that the objects associated with each other are in an "or" relationship.

[0083] 1. In the description of the present application, it should be understood that the terms "upper", "lower", "front", "back", "left", "right", "inside", "outside", etc., indicating directions or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore should not be understood as a limitation on the present application.

[0084] 2. In the description of this application, “plurality” means two or more.

[0085] Reference below Figures 1 to 9 The switching power supply system according to the embodiment of the present application is described.

[0086] like Figure 1 and Figure 3 As shown, the switching power supply system includes a power tube Q1 and a turn-off time module 230 , wherein the turn-off time module 230 includes: a target capacitor CAP, a subtraction circuit 310 , a first comparator 340 and a second comparator 350 .

[0087] In this embodiment, the switching power supply is a high-frequency electric energy conversion device, which is a type of power supply.

[0088] Switching power supplies are used to convert a voltage level into the voltage or current required by the user through different forms of architecture.

[0089] Switching power supplies can be used in areas such as fast charging, adapters and chargers.

[0090] The working state of the power tube Q1 includes on or off.

[0091] The power tube Q1 includes a source, a drain and a gate.

[0092] One end of the target capacitor CAP is grounded.

[0093] Capacitor voltage V CAP is the voltage across the target capacitor CAP. When the current for charging and discharging the target capacitor CAP changes, the capacitor voltage will also change.

[0094] The input terminal of the subtraction circuit 310 is used to receive the feedback voltage V FB The output terminal of the subtraction circuit 310 is used to output a first voltage V O .

[0095] The first voltage is less than the feedback voltage, and the relationship between the first voltage and the feedback voltage is: V O =V FB -ΔV(ΔV<V FB , ΔV>0), wherein ΔV can be set to 0.4V, or can be set to other values, which can be customized by the user and is not limited in this application.

[0096] The non-inverting input terminal of the first comparator 340 is connected to the output terminal of the subtraction circuit 310 , the inverting input terminal of the first comparator 340 is connected to the other end of the target capacitor CAP, and the output terminal of the first comparator 340 is connected to the power tube Q1 .

[0097] The non-inverting input terminal of the first comparator 340 is used to receive the first voltage V OThe inverting input terminal of the first comparator 340 is used to receive the capacitor voltage V CAP .

[0098] In V CAP <V O In this case, the first comparator 340 outputs a high level signal.

[0099] When the first comparator 340 outputs a high level, the off-time module 230 may output a first off-time signal.

[0100] The non-inverting input terminal of the second comparator 350 is connected to the input terminal of the subtraction circuit 310 , the inverting input terminal of the second comparator 350 is connected to the other end of the target capacitor CAP, and the output terminal of the second comparator 350 is connected to the power tube Q1 .

[0101] The non-inverting input terminal of the second comparator 350 is used to receive the feedback voltage V FB The inverting input terminal of the second comparator 350 is used to receive the capacitor voltage V CAP .

[0102] In V CAP <V FB In this case, the second comparator 350 outputs a high level signal.

[0103] When the second comparator 350 outputs a high level, the off-time module 230 may output a second off-time signal.

[0104] The first comparator 340 and the second comparator 350 start to work after the power tube Q1 is turned off.

[0105] The structure of the subtraction circuit 310 can be adjusted based on user needs. When the structure of the subtraction circuit 310 or the feedback voltage changes, the first voltage V output by the subtraction circuit 310 is O The size will also change.

[0106] When the first voltage and the feedback voltage are different in magnitude, the time when the capacitor voltage reaches the first voltage is different from the time when the capacitor voltage reaches the feedback voltage, and the time when the first comparator 340 and the second comparator 350 output high-level signals is also different, and the time when the first turn-off time signal and the second turn-off time signal are generated is also different.

[0107] In the actual execution process, when the target capacitor CAP is discharged, the capacitor voltage decreases, and the capacitor voltage will first decrease to the feedback voltage, then the second comparator 350 outputs a high level signal before the first comparator 340, that is, the second shutdown time signal is generated earlier than the first shutdown time signal.

[0108] The hysteresis time between the second off-time signal and the first off-time signal is: T delay =T off -T off_L , where T off is the off time corresponding to the first off time signal, T off_L is the off time corresponding to the second off time signal, and the off time is the duration from the off time of the power tube Q1 within the target switching cycle to the generation time of the off time signal.

[0109] like Figure 6 As shown, the size of the hysteresis time can be determined based on the feedback voltage.

[0110] In the present application, a first off-time signal is generated by a subtraction circuit 310, so that when the power tube Q1 is turned on, valley locking can be performed based on the first off-time signal and the second off-time signal, so that the critical load point at the valley jump can be maintained at the conduction valley of the previous cycle for conduction, avoiding the situation where adjacent valleys are alternately turned on at the critical load point, and the valley locking effect is better.

[0111] According to the switching power supply system provided in the embodiment of the present application, by setting a subtraction circuit 310 to obtain two turn-off time signals with different generation times, valley locking can be performed based on the two turn-off time signals, so that the critical load point at the valley jump can be maintained at the conduction valley of the previous cycle for conduction, avoiding the situation where adjacent valleys are alternately turned on at the critical load point, and the valley locking effect is better; and the hysteresis time between the generation times of the two turn-off time signals can be adaptively changed based on load changes, avoiding the problem of load fluctuations causing the power tube Q1 to switch back and forth between adjacent valleys or even multiple valleys, and can well achieve valley locking, eliminate audio noise interference, and improve the overall efficiency of the system.

[0112] The following is a detailed description of the implementation of the two subtraction circuits 310.

[0113] like Figure 4 As shown, in some embodiments, the subtraction circuit 310 may include: a first operational amplifier OP1, a third current source I3, a first resistor Rs1, a fourth current source I4, a second resistor Rs2, and a fifth current source I5.

[0114] In this embodiment, the non-inverting input terminal of the first operational amplifier OP1 is used to receive the feedback voltage, and the inverting input terminal of the first operational amplifier OP1 is connected to the output terminal of the first operational amplifier OP1.

[0115] One end of the third current source I3 is connected to the power supply, and the other end of the third current source I3 is connected to the output end of the first operational amplifier OP1.

[0116] The third current source I3 is grounded via the first resistor Rs1 .

[0117] One end of the fourth current source I4 is connected to one end of the third current source I3 , and the other end of the fourth current source I4 is connected to the non-inverting input end of the first comparator 340 .

[0118] The fourth current source I4 is grounded via the second resistor Rs2.

[0119] The resistance value of the second resistor Rs2 is equal to the resistance value of the first resistor Rs1.

[0120] One end of the fifth current source I5 is connected to the other end of the fourth current source I4 and the non-inverting input end of the first comparator 340 , respectively, and the other end of the fifth current source I5 is grounded.

[0121] In actual implementation, a current proportional to the feedback voltage can be obtained through the first resistor Rs1.

[0122] The current passes through the third current source I3 and the fourth current source I4 with equal amplitude, and a first voltage V can be obtained on the second resistor Rs2. O =V FB -ΔV, where ΔV = I5*R s1 , I5 is the size of the fifth current source I5, R s1 is the resistance value of the first resistor Rs1.

[0123] By setting the size of the fifth current source I5 and the resistance of the first resistor Rs1 , the size of ΔV can be determined, and thus the size of the first voltage can be determined.

[0124] like Figure 5 As shown, in some embodiments, the subtraction circuit 310 may include: a second operational amplifier OP2, a third resistor Re1, a fourth resistor Rf, a third operational amplifier OP3, a fourth operational amplifier OP4, a fifth resistor, a sixth resistor Re2 and a seventh resistor Ro.

[0125] In this embodiment, the non-inverting input terminal of the second operational amplifier OP2 is used to receive a reference voltage, and the inverting input terminal of the second operational amplifier OP2 is connected to the output terminal of the second operational amplifier OP2.

[0126] The third resistor Re1 is connected to the output terminal of the second operational amplifier OP2.

[0127] The fourth resistor Rf is connected in series with the third resistor Re1.

[0128] The non-inverting input terminal of the third operational amplifier OP3 is used to receive the feedback voltage, and the inverting input terminal of the third operational amplifier OP3 is connected between the third resistor Re1 and the fourth resistor Rf.

[0129] A non-inverting input terminal of the fourth operational amplifier OP4 is connected to the output terminal of the third operational amplifier OP3 , and an inverting input terminal of the fourth operational amplifier OP4 is connected to the output terminal of the fourth operational amplifier OP4 .

[0130] One end of the fifth resistor is connected to the output end of the fourth operational amplifier OP4 , and the resistance of the fifth resistor is the sum of the resistances of the third resistor Re1 and the fourth resistor Rf.

[0131] One end of the sixth resistor Re2 is connected to the other end of the fifth resistor, and the other end of the sixth resistor Re2 is grounded.

[0132] One end of the seventh resistor Ro is respectively connected to the output end of the third operational amplifier OP3, the fourth resistor Rf and the non-inverting input end of the fourth operational amplifier OP4, and the other end of the seventh resistor Ro is grounded.

[0133] In the actual implementation process, the non-inverting input terminal of the second operational amplifier OP2 receives the reference voltage V ref1 , the output terminal of the second operational amplifier OP2 is connected to the inverting input terminal of the third operational amplifier OP3 via the third resistor Re1.

[0134] The non-inverting input terminal of the third operational amplifier OP3 is connected to the reference voltage V FB , the output terminal of the third operational amplifier OP3 is connected back to the inverting input terminal of the third operational amplifier OP3 through the fourth resistor Rf, then the voltage

[0135] The non-inverting input terminal of the fourth operational amplifier OP4 is connected to the voltage Vo1, and the output terminal of the fourth operational amplifier OP4 is grounded via the fifth resistor and the sixth resistor Re2.

[0136] The resistance values ​​of the third resistor Re1 and the sixth resistor Re2 are equal, and the first voltage output by the subtraction circuit 310 is in,

[0137] like Figure 3 As shown, in some embodiments, the switching power supply system may further include: a first current source I1, a first switch SW1, a second switch SW2, a second current source I2 and a third switch SW3.

[0138] In this embodiment, one end of the first current source I1 is connected to a power source.

[0139] One end of the first switch SW1 is connected to the other end of the first current source I1 , and the other end of the first switch SW1 is connected to the other end of the target capacitor CAP.

[0140] When the first switch SW1 is closed, the first current source I1 charges the target capacitor CAP.

[0141] The second switch SW2 is connected in parallel with the target capacitor CAP.

[0142] The second current source I2 is connected in series with the second switch SW2.

[0143] When the first switch SW1 is opened and the second switch SW2 is closed, the target capacitor CAP starts to discharge.

[0144] The third switch SW3 is connected in parallel with the target capacitor CAP.

[0145] When the power tube Q1 is turned on and the third switch SW3 is closed, the target capacitor CAP can be discharged and reset.

[0146] Continue to refer Figure 3 In some embodiments, the switching power supply system may further include: a first rising edge detection circuit 320 and a second rising edge detection circuit 330 .

[0147] In this embodiment, the input end of the first rising edge detection circuit 320 is connected to the output end of the first comparator 340 , and the output end of the first rising edge detection circuit 320 is connected to the power tube Q1 .

[0148] When the first rising edge detection circuit 320 detects that the output signal of the first comparator 340 changes from a low level to a high level, the first rising edge detection circuit 320 generates a first turn-off time signal.

[0149] An input end of the second rising edge detection circuit 330 is connected to an output end of the second comparator 350 , and an output end of the second rising edge detection circuit 330 is connected to the power tube Q1 .

[0150] When the second rising edge detection circuit 330 detects that the output signal of the second comparator 350 changes from a low level to a high level, the second rising edge detection circuit 330 generates a second turn-off time signal.

[0151] In the actual implementation process, when the power tube Q1 is disconnected, the first switch SW1 is closed, and the first current source I1 charges the target capacitor CAP. When the capacitor voltage reaches the maximum value V CAP_MAX In the case of , the first switch SW1 is opened, the second switch SW2 is closed, the target capacitor CAP starts to discharge, and the capacitor voltage gradually decreases.

[0152] The first comparator 340 and the second comparator 350 start to work after the power tube Q1 is turned off. CAP drops below the feedback voltage V FBIn the case of , the output of the second comparator 350 is flipped to a high level, and after passing through the second rising edge detection circuit 330, a second off time signal V is generated. off_L .

[0153] The capacitor voltage V CAP drops below the first voltage V O In the case of , the output of the first comparator 340 is flipped to a high level, and the first turning-off time signal V is generated after passing through the first rising edge detection circuit 320. off .

[0154] When the power tube Q1 is turned on, the third switch SW3 is turned on to discharge and reset the target capacitor CAP.

[0155] The capacitor voltage will drop to V sooner FB , the second off time signal V off_L The generation time is earlier than the first off time signal V off The generation time of the two is: T delay =T off -T off_L .

[0156] like Figure 6 As shown, under heavy load conditions, V FB -ΔV>V CAP_MAX , the voltage V CAP_MAX Set to V FB_MAX -ΔV or lower than V FB_MAX -ΔV.

[0157] For example, you can change V FB_MAX Set to 2.4V, V FB_MAX Corresponding minimum off time T off_min , the feedback voltage V FB Not less than V FB_MAX In the case of , the off time corresponding to the feedback voltage is the minimum off time T off_min .

[0158] When the target capacitor CAP starts to discharge, the first comparator 340 and the second comparator 350 respectively output the first off-time signal V off and the second off-time signal V off_L At this time, the first off-time signal V off The corresponding first off time T off and the second off-time signal V off_L The corresponding second off time T off_L Both are minimum values, and the hysteresis time T between them delay is 0.

[0159] When the load is reduced, the feedback voltage VFB decreases, and V FB -ΔV<V CAP_MAX , V FB >V CAP_MAX In the case of the second comparator 350, the second off-time signal V is outputted immediately when the target capacitor CAP starts to discharge. off_L , the first comparator 340 needs to be at V CAP drops to V FB -ΔV are equal, the first off-time signal V is output off , that is, the first off time T off_L is still the minimum value, and the second off time T off Gradually increases, hysteresis time T delay With the feedback voltage V FB decrease and increase.

[0160] The load continues to decrease until the feedback V FB The voltage is also less than V CAP_MAX In the case of V CAP drops to V FB -ΔV are equal, the first off-time signal V is output off , the second comparator 350 needs to be at V CAP drops to V FB When they are equal, the second off-time signal V is output off_L , that is, the second off time T off_L Also with the feedback voltage V FB The hysteresis time T delay Reach the maximum value T dealy_max , where T dealy_max It is usually set to 2 to 3 times the resonant period. For example, in a switching power supply system with a maximum switching frequency of 100KHz, the resonant period T ring is about 1.6μs, then T dealy_max Set to any value between 3.2μs and 4.8μs.

[0161] According to the switching power supply system provided in the embodiment of the present application, two turn-off time signals are generated by setting a subtraction circuit 310 and a hysteresis time that changes adaptively with the load. When the load fluctuates or the input bus voltage fluctuates, the turn-off time changes. The change of the turn-off time within a certain range is shielded by the hysteresis time, so that the power tube Q1 is still turned on at the conduction bottom of the previous cycle, and the valley locking effect is better.

[0162] like Figure 2 As shown, in some embodiments, the switching power supply system may further include: a valley detection module 210 , a valley counting module 220 , a valley conduction module 240 and a driving module 260 .

[0163] In this embodiment, the valley bottom detection module 210 is used to output at least one valley bottom signal.

[0164] The input signal of the valley detection module 210 is the auxiliary winding voltage sampling signal ZCD.

[0165] The variation trend of the auxiliary winding voltage sampling signal ZCD waveform is consistent with the variation trend of the drain of the power tube Q1 , and the ZCD signal can be used for valley detection.

[0166] When the power tube Q1 is turned off, the valley detection module 210 starts to work, converts at least one detected valley signal valley into a counting signal, and latches the counting signal.

[0167] When the counting signal of the current switching cycle is the same as the counting signal of the previous switching cycle, the valley detection module 210 generates a corresponding control signal and sends it to the valley conduction module 240 .

[0168] The valley counting module 220 is connected to the valley detecting module 210 .

[0169] The valley counting module 220 counts and latches the valley signal valley output by the valley detection module 210, and compares the valley counting signal of the current cycle with the latch signal of the previous cycle. When the valley number of the current cycle is the same as the valley number of the previous cycle, the valley latch signal same is output, and the valley latch signal same is sent to the valley conduction module 240.

[0170] The valley conduction module 240 is connected to the valley counting module 220 , the first comparator 340 and the second comparator 350 respectively.

[0171] like Figure 7 As shown, in some embodiments, the valley conduction module 240 may include: a first latch 710 , a second flip-flop 720 , a second latch 730 , a first AND circuit 740 , an OR circuit 750 , and a second AND circuit 760 .

[0172] In this embodiment, an input terminal of the first latch 710 is connected to an output terminal of the first comparator 340 .

[0173] One input terminal of the second trigger 720 is connected to the output terminal of the first latch 710 , and the other input terminal of the second trigger 720 is connected to the valley detection module 210 .

[0174] The second flip-flop 720 may be a D flip-flop.

[0175] An input terminal of the second latch 730 is connected to an output terminal of the second comparator 350 .

[0176] One input terminal of the first AND circuit 740 is connected to the valley counting module 220 , and the other input terminal of the first AND circuit 740 is connected to the second latch 730 .

[0177] One input terminal of the OR circuit 750 is connected to the output terminal of the second flip-flop 720 , and the other input terminal of the OR circuit 750 is connected to the output terminal of the first AND circuit 740 .

[0178] One input end of the second AND circuit 760 is connected to the valley detection module 210 , the other input end of the second AND circuit 760 is connected to the output end of the OR circuit 750 , and the output end of the second AND circuit 760 is connected to the power tube Q1 .

[0179] In the actual implementation process, the first off-time signal V off The latch signal V is generated by the first latch 710. off_latch , latch signal V off_latch The second trigger 720 samples the falling edge of the valley signal valley. When the second trigger 720 samples the falling edge of the valley signal valley, the second trigger 720 outputs the signal V off_sample , and the signal V off_sample Enter OR circuit 750.

[0180] The second off time signal V off_L The latch signal V is generated by the second latch 730. off_L_latch , latch signal V off_L_latch The same valley latch signal is sent to the first AND circuit 740. off_L_latch When the and valley latch signals same are both at high levels, the first AND circuit 740 outputs a high level signal, and sends the output result of the first AND circuit 740 to the OR circuit 750.

[0181] When any one of the inputs of the OR circuit 750 is at a high level, the OR circuit 750 outputs a high level signal.

[0182] The output signal of the OR circuit 750 and the valley signal valley are sent to the second AND circuit 760. When the output signal of the OR circuit 750 and the valley signal valley are both at high levels, the second AND circuit 760 generates a valley-on signal qr_on.

[0183] The driving module 260 is connected to the valley conduction module 240 and the power tube Q1 respectively.

[0184] The driving module 260 is connected to the gate of the power tube Q1 .

[0185] The driving module 260 is used to control the power tube Q1 to be turned on at a target valley bottom position, and is also used to control the power tube Q1 to be turned off based on a shutdown signal.

[0186] like Figure 2 As shown, in some embodiments, the switching power supply system may further include: a PWM comparison module 270 and a first trigger 250 .

[0187] In this embodiment, the non-phase input terminal of the PWM comparison module 270 is connected to the input terminal of the subtraction circuit 310 , and the inverting input terminal of the PWM comparison module 270 is connected to the power tube Q1 .

[0188] The positive phase input signal of the PWM comparison module 270 is the feedback voltage, and the negative phase input signal is the primary current peak sampling signal V CS .

[0189] The inverting input terminal of the PWM comparison module 270 is connected to the source of the power tube Q1 .

[0190] The primary current can pass through the first sampling resistor to obtain a voltage signal V representing the primary current size. CS The PWM comparison module 270 can determine the magnitude of the primary current according to the magnitude of the feedback voltage and output a shutdown signal Gate_off.

[0191] When the load is heavier and the feedback voltage is larger, the conduction time of the power tube Q1 is longer, the primary winding charging excitation time is longer, and the primary current peak is larger.

[0192] When the load is lighter and the feedback voltage is smaller, the conduction time of the power tube Q1 is shorter, the primary winding charging excitation time is shorter, and the primary current peak is smaller.

[0193] The first trigger 250 includes a first input terminal, a second input terminal, and an output terminal.

[0194] The first input terminal is connected to the valley conduction module 240 , the second input terminal is connected to the PWM comparison module 270 , and the output terminal is connected to the driving module 260 .

[0195] The first trigger 250 may be an RS trigger, wherein the first input terminal is the S terminal, the second input terminal is the R terminal, and the output terminal is the Q terminal.

[0196] The S-terminal input signal of the first trigger 250 is the valley conduction signal qr_on, and the R-terminal input signal is the shut-off signal Gate_off. When the S-terminal detects the rising edge of the valley conduction signal qr_on, the output Q is set to a high level.

[0197] When the rising edge of the shutdown signal Gate_off is detected at the R terminal, the output Q is set to a low level.

[0198] When the Q-terminal output is at a high level, the power tube Q1 can be controlled to be turned on through the driving module 260 .

[0199] When the Q-terminal output is at a low level, the power tube Q1 can be controlled to be turned off through the driving module 260 .

[0200] like Figure 1 As shown, in some embodiments, the switching power supply system may include a primary control circuit 110, a feedback loop 130, a secondary control circuit 120, a power tube Q1, a primary winding Np, an auxiliary winding Na, a secondary winding Ns, a first sampling resistor R CS , a second sampling resistor R1, a third sampling resistor R2 and a rectifier tube Q2.

[0201] In this embodiment, the main structure of the primary control circuit 110 is as follows: Figure 2 As shown, the primary side control circuit 110 may include: a valley detection module 210 , a valley counting module 220 , a turn-off time module 230 , a valley conduction module 240 , a first trigger 250 , a PWM comparison module 270 and a driving module 260 .

[0202] One end of the primary winding Np is connected to the input target voltage Vin, and the other end is connected to the drain of the power tube Q1.

[0203] The gate of the power tube Q1 is connected to the DRV pin of the primary control circuit 110 .

[0204] The source of the power tube Q1 is connected to the first sampling resistor R CS , the first sampling resistor R CS The other end is grounded.

[0205] The first sampling resistor R CS One end connected to the source of the power tube Q1 is connected to the CS pin of the primary control circuit 110 .

[0206] The voltage on the auxiliary winding Na is in phase with the drain voltage of the power tube Q1.

[0207] The auxiliary winding Na is connected to the second sampling resistor R1 and the third sampling resistor R2 at the same end, and the other end of the auxiliary winding Na is grounded.

[0208] The connecting point of the second sampling resistor R1 and the third sampling resistor R2 is connected to the ZCD pin of the primary side control circuit 110 .

[0209] The same end of the secondary winding Ns is connected to the drain of the rectifier tube Q2, and the other end of the secondary winding Ns is grounded.

[0210] The gate of the rectifier tube Q2 is connected to the secondary control circuit 120 , the source of the rectifier tube Q2 is connected to the output capacitor Cout, and the other end of the output capacitor Cout is grounded.

[0211] The output voltage Vout is connected to the FB pin of the primary control circuit 110 through the feedback loop 130 .

[0212] Combine the following Figure 8 and Fig. 9 The execution logic of the switching power supply system described in the above embodiment is specifically described.

[0213] In actual implementation, when the input voltage changes or the load changes, the feedback voltage V FB When the off time module 230 changes, the off time module 230 changes according to the feedback voltage V FB The size of the corresponding first off time T off and the second off time T off_L .

[0214] The valley detection module 210 generates a valley signal according to the ZCD resonant voltage waveform and sends it to the valley locking module.

[0215] The valley conduction module 240 is based on the valley signal and the first off time T off and the second off time T off_L Determine the conduction valley number of the power tube Q1.

[0216] When the input AC voltage is low and the load is heavy, the feedback voltage V FB In the case of a higher voltage, the switching power supply operates at the first valley bottom, and the valley counting module 220 latches the first valley bottom and generates a valley latch signal same at the first valley bottom.

[0217] like Fig. 9 In the first switching cycle shown, the feedback voltage V FB Higher, that is, V FB -ΔV is greater than V CAP_MAX , the first off-time signal V off and the second off-time signal V off_L The two turn-off time signals overlap, and the generation moments of the two turn-off time signals are both before the first valley bottom.

[0218] When the input AC voltage is low, the bus voltage after rectification fluctuates greatly (for example, the bus voltage is 125V at the highest and 85V at the lowest under 90V AC voltage input). When the bus voltage is low, the feedback voltage V FB Higher.

[0219] When the bus voltage is high, the feedback voltage V FB Lower, feedback voltage V FBIt changes with the bus voltage fluctuation.

[0220] like Fig. 9 In the second switching cycle shown, the feedback voltage V FB When the first off time T off Increase, the first off-time signal V off The generation time is after the first valley, and the second off-time signal V off_L The generation time is still before the first valley bottom.

[0221] The same valley latch signal is also generated at the first valley. Figure 7 The first AND circuit 740 can output a high level signal, and after the OR circuit 750, the second AND circuit 760 generates a valley turn-on signal qr_on at the first valley signal valley to maintain the valley unchanged.

[0222] The fluctuation of bus voltage will not cause valley jump, and the hysteresis time T delay This is the hysteresis interval for bottom locking.

[0223] As the load continues to decrease, the feedback voltage decreases to less than V CAP_MAX In the case of the second off time T off_L It increases as the feedback voltage decreases.

[0224] As the load decreases, until the second off-time signal V off_L The generation time of is after the first valley bottom, such as Fig. 9 As shown in the third cycle, the valley latch signal same is still generated at the first valley, but the second off-time signal V is not detected at the rising edge of the first valley signal valley off_L , therefore, no valley-on signal qr_on is generated at the first valley.

[0225] The valley latch signal same remains high until the second off-time signal V is detected at the second valley. off_L ,pass Figure 7 The first AND circuit 740 can output a high level signal, and after the OR circuit 750, the second AND circuit 760 generates a valley conduction signal qr_on at the second valley signal valley to complete the valley switching. At the same time, the valley counting module 220 latches the counting signal with the valley being 2.

[0226] After the valley increases, the switching frequency will decrease, based on the calculation formula of the switching power supply output power: Among them, L p is the primary winding inductance, F sw is the switching frequency, I pk is the primary peak current.

[0227] In order to maintain the power unchanged before and after valley switching, the feedback loop of the switching power supply will increase the feedback voltage and thus increase the primary peak current.

[0228] As the feedback voltage increases, the second off time T off_L will decrease during the second off time signal V off_L When the generation time is again before the first valley, the latch valley number is 2, and the valley latch signal same will be generated at the second valley. Therefore, the output of the first AND circuit 740 becomes a high level at the second valley, and a valley conduction signal qr_on is generated at the second valley to maintain the valley unchanged.

[0229] In the present application, the power tube Q1 will not alternately conduct at adjacent valleys at the critical load point where the valley jump occurs. By setting a hysteresis time that adaptively changes with load changes, the problem of the power tube Q1 switching back and forth between adjacent valleys or even multiple valleys due to load fluctuations is avoided. The valley locking effect is better, audio noise interference is eliminated, and the overall efficiency of the system is improved.

[0230] The embodiments of the present application are described above in conjunction with the accompanying drawings, but the present application is not limited to the above-mentioned specific implementation methods. The above-mentioned specific implementation methods are merely illustrative and not restrictive. Under the guidance of the present application, ordinary technicians in this field can also make many forms without departing from the purpose of the present application and the scope of protection of the claims, all of which are within the protection of the present application.

[0231] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0232] Although the embodiments of the present application have been shown and described, those skilled in the art will appreciate that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present application, and that the scope of the present application is defined by the claims and their equivalents.

Claims

1. A switching power supply system, characterized in that: include: Power tube; A target capacitor, one end of which is grounded; a subtraction circuit, wherein an input terminal of the subtraction circuit is used to receive a feedback voltage, and an output terminal of the subtraction circuit is used to output a first voltage; The first voltage is less than the feedback voltage; A first comparator, wherein a non-inverting input terminal of the first comparator is connected to the output terminal of the subtraction circuit, an inverting input terminal of the first comparator is connected to the other end of the target capacitor, and an output terminal of the first comparator is connected to the power tube; A second comparator, wherein a non-inverting input terminal of the second comparator is connected to an input terminal of the subtraction circuit, an inverting input terminal of the second comparator is connected to the other end of the target capacitor, and an output terminal of the second comparator is connected to the power tube.

2. The switching power supply system according to claim 1, characterized in that: The subtraction circuit comprises: a first operational amplifier, wherein a non-inverting input terminal of the first operational amplifier is used to receive the feedback voltage, and an inverting input terminal of the first operational amplifier is connected to an output terminal of the first operational amplifier; a third current source, one end of which is connected to a power supply, and the other end of which is connected to the output end of the first operational amplifier; a first resistor, wherein the third current source is grounded via the first resistor; a fourth current source, one end of the fourth current source being connected to one end of the third current source, and the other end of the fourth current source being connected to the non-inverting input end of the first comparator; a second resistor, the fourth current source is grounded via the second resistor; the resistance value of the second resistor is equal to the resistance value of the first resistor; A fifth current source, one end of the fifth current source is respectively connected to the other end of the fourth current source and the non-inverting input end of the first comparator, and the other end of the fifth current source is grounded.

3. The switching power supply system according to claim 1, characterized in that: The subtraction circuit comprises: a second operational amplifier, wherein a non-inverting input terminal of the second operational amplifier is used to receive a reference voltage, and an inverting input terminal of the second operational amplifier is connected to an output terminal of the second operational amplifier; a third resistor, wherein the third resistor is connected to an output terminal of the second operational amplifier; a fourth resistor, the fourth resistor being connected in series with the third resistor; a third operational amplifier, wherein a non-inverting input terminal of the third operational amplifier is used to receive the feedback voltage, and an inverting input terminal of the third operational amplifier is connected between the third resistor and the fourth resistor; a fourth operational amplifier, wherein a non-inverting input terminal of the fourth operational amplifier is connected to an output terminal of the third operational amplifier, and an inverting input terminal of the fourth operational amplifier is connected to an output terminal of the fourth operational amplifier; a fifth resistor, one end of which is connected to the output end of the fourth operational amplifier, and a resistance of the fifth resistor is the sum of resistances of the third resistor and the fourth resistor; a sixth resistor, one end of the sixth resistor being connected to the other end of the fifth resistor, and the other end of the sixth resistor being grounded; A seventh resistor, one end of the seventh resistor is respectively connected to the output end of the third operational amplifier, the fourth resistor and the non-inverting input end of the fourth operational amplifier, and the other end of the seventh resistor is grounded.

4. The switching power supply system according to any one of claims 1 to 3, characterized in that: The switching power supply system further comprises: A first current source, one end of which is connected to a power supply; a first switch, wherein one end of the first switch is connected to the other end of the first current source, and the other end of the first switch is connected to the other end of the target capacitor; a second switch connected in parallel with the target capacitor; a second current source, the second current source being connected in series with the second switch; A third switch is connected in parallel with the target capacitor.

5. The switching power supply system according to any one of claims 1 to 3, characterized in that: The switching power supply system further comprises: A first rising edge detection circuit, wherein an input end of the first rising edge detection circuit is connected to an output end of the first comparator, and an output end of the first rising edge detection circuit is connected to the power tube; A second rising edge detection circuit, wherein the input end of the second rising edge detection circuit is connected to the output end of the second comparator, and the output end of the second rising edge detection circuit is connected to the power tube.

6. The switching power supply system according to any one of claims 1 to 3, characterized in that: The switching power supply system further comprises: Valley detection module; A valley bottom counting module, the valley bottom counting module is connected to the valley bottom detection module; A valley conduction module, wherein the valley conduction module is respectively connected to the valley counting module, the first comparator and the second comparator; A driving module is connected to the valley conduction module and the power tube respectively.

7. The switching power supply system according to claim 6, characterized in that: The switching power supply system further comprises: A PWM comparison module, wherein a positive input terminal of the PWM comparison module is connected to an input terminal of the subtraction circuit, and an inverting input terminal of the PWM comparison module is connected to the power tube; A first trigger, wherein the first trigger comprises a first input terminal, a second input terminal and an output terminal, wherein the first input terminal is connected to the valley conduction module, the second input terminal is connected to the PWM comparison module, and the output terminal is connected to the driving module.

8. The switching power supply system according to claim 7, characterized in that: The power tube includes: a source, a drain and a gate, the source is connected to the inverting input terminal of the PWM comparison module, and the gate is connected to the driving module; the switching power supply system also includes: A primary winding, one end of which is connected to a target voltage, and the other end of which is connected to the drain; A first sampling resistor is provided, and the source is grounded via the first sampling resistor.

9. The switching power supply system according to claim 6, characterized in that: The valley conduction module comprises: a first latch, wherein an input terminal of the first latch is connected to an output terminal of the first comparator; a second trigger, wherein one input terminal of the second trigger is connected to the output terminal of the first latch, and another input terminal of the second trigger is connected to the valley detection module; a second latch, wherein an input terminal of the second latch is connected to an output terminal of the second comparator; a first AND circuit, wherein one input end of the first AND circuit is connected to the valley counting module, and another input end of the first AND circuit is connected to the second latch; An OR circuit, one input terminal of the OR circuit is connected to the output terminal of the second trigger, and the other input terminal of the OR circuit is connected to the output terminal of the first AND circuit; A second AND circuit, wherein one input end of the second AND circuit is connected to the valley detection module, another input end of the second AND circuit is connected to the output end of the OR circuit, and the output end of the second AND circuit is connected to the power tube.

10. The switching power supply system according to any one of claims 1 to 3, characterized in that: The switching power supply system further comprises: A feedback circuit, one end of which is used to receive the output voltage of the switching power supply system, and the other end of which is connected to the subtraction circuit.

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