Driving circuit, driving method, and switching power supply

Abstract

The application discloses a driving circuit, a driving method and a switching power supply, and relates to the technical field of power supply, and in particular relates to a driving circuit, a driving method and a switching power supply, which comprises a driving adjustment circuit, an input end of the driving adjustment circuit is used for receiving a driving signal, a first switch, a controlled end of the first switch is connected with an output end of the driving adjustment circuit, a first end of the first switch is connected with a transformer, and a second end of the first switch is grounded, the driving adjustment circuit is used for outputting a first current to the first switch when the driving signal is received, so that the first switch is charged, a feedback circuit, a first end of the feedback circuit is connected with the first end of the first switch, and a second end of the feedback circuit is connected with the controlled end of the driving adjustment circuit, the feedback circuit is used for outputting an adjustment signal when it is detected that the voltage of the first end of the first switch is lower than a preset threshold voltage, the driving adjustment circuit is further used for outputting a second current to the first switch when the adjustment signal is received, and the second current is greater than the first current. The application improves EMI while ensuring conversion efficiency.

Description

Technical Field

[0001] This invention relates to the field of power supply technology, and in particular to a driving circuit, driving method, and switching power supply. Background Technology

[0002] Switching power supplies are widely used in various electronic devices due to their small size, light weight, and high efficiency, and are an indispensable power supply method for the rapid development of today's electronic information industry.

[0003] The basic structure of a switching power supply is as follows: Figure 1 As shown, it typically includes four parts: The first part is the input circuit, where the AC power from the grid is filtered and rectified to obtain a smoother DC voltage; the second part is the core power conversion section, which uses a high-frequency transformer in conjunction with the switching action of a high-voltage power switch to achieve a cyclic charging and discharging process, thereby converting the fluctuating DC input into a precisely controllable power output. The rectification and voltage regulation of the output after power conversion are carried out in the third part, the output circuit. The output circuit usually uses a combination of fast rectifier diodes and filter capacitors to achieve rectification and voltage regulation while also suppressing the reverse transmission of load noise; the fourth part is the control circuit, which usually needs to divide and sample the output voltage, and then send it to the control circuit for modulation to control the drive pulse width of the power switch and modulate the turn-on time, thereby achieving the purpose of adjustable output voltage or output power.

[0004] To improve the reliability and performance of switching power supplies, a drive circuit is typically placed between the control circuit and the power switch. For example, a gate resistor can be added to the gate of the power switch to reduce its switching speed, while a diode can be anti-parallelized across the resistor without affecting the turn-off speed. However, this type of drive circuit struggles to balance EMI (electromagnetic interference) and efficiency: increasing the resistor value results in a smaller drive current and better EMI, but also slower switching speed and lower efficiency; conversely, decreasing the resistor value increases the drive capability and faster power switch turn-on, improving efficiency, but excessively fast turn-on worsens EMI. This demonstrates a trade-off between efficiency and EMI.

[0005] The above content is only used to help understand the technical solution of the present invention and does not represent an admission that the above content is prior art. Summary of the Invention

[0006] The main objective of this invention is to provide a driving circuit, driving method, and switching power supply, aiming to solve the technical problem of EMI and efficiency being difficult to balance due to the existing driving circuit structure.

[0007] To achieve the above objectives, the present invention provides a driving circuit, comprising:

[0008] A drive adjustment circuit, wherein the input terminal of the drive adjustment circuit is used to receive drive signals;

[0009] The first switch has its controlled terminal connected to the output terminal of the drive adjustment circuit, its first terminal connected to the transformer, and its second terminal grounded.

[0010] The drive adjustment circuit is used to output a first current to the first switch when the drive signal is received, so as to charge the first switch.

[0011] A feedback circuit, wherein a first terminal of the feedback circuit is connected to a first terminal of the first switch, and a second terminal of the feedback circuit is connected to a controlled terminal of the drive adjustment circuit; the feedback circuit is used to output an adjustment signal when it detects that the voltage at the first terminal of the first switch is lower than a preset threshold voltage.

[0012] The drive adjustment circuit is further configured to output a second current to the first switch when the adjustment signal is received; wherein the second current is greater than the first current.

[0013] Optionally, the drive adjustment circuit includes a first resistor, a second resistor, and a second switch; the first end of the first resistor and the first end of the second switch are connected, the second end of the first resistor, the second end of the second switch, and the first end of the second resistor are connected, the second end of the second resistor is the output end of the drive adjustment circuit, the common end of the connection between the first resistor and the second switch is the input end of the drive adjustment circuit, and the controlled end of the second switch is the controlled end of the drive adjustment circuit.

[0014] The second switch is turned on when the adjustment signal is received, causing the second resistor to step down the driving signal, thereby outputting a second current.

[0015] Optionally, the second switch includes a first MOSFET; the controlled terminal of the first MOSFET is the controlled terminal of the second switch, the input terminal of the first MOSFET is the first terminal of the second switch, and the output terminal of the first MOSFET is the second terminal of the second switch.

[0016] Optionally, the first switch includes a second MOSFET; the controlled terminal of the second MOSFET is the controlled terminal of the first switch, the input terminal of the second MOSFET is the first terminal of the first switch, and the output terminal of the second MOSFET is the second terminal of the first switch.

[0017] Optionally, the feedback circuit includes a voltage detection unit; a first terminal of the voltage detection unit is connected to a first terminal of the first switch, and a second terminal of the voltage detection unit is connected to the controlled terminal of the drive adjustment circuit.

[0018] The voltage detection unit is used to output an adjustment signal when it detects that the voltage at the first terminal of the first switch is lower than a preset threshold voltage.

[0019] Optionally, the voltage detection unit includes a capacitor; the first end of the capacitor is the first end of the voltage detection unit, and the second end of the capacitor is the second end of the voltage detection unit.

[0020] Optionally, the feedback circuit further includes a clamping unit; the first end of the clamping unit is connected to the second end of the capacitor, the second end of the clamping unit is connected to the first power supply, and the third end of the clamping unit is grounded.

[0021] The clamping unit is used to clamp the voltage at the second terminal of the capacitor.

[0022] Optionally, the clamping unit includes a first diode and a second diode; the anodes of the first diode and the second diode are respectively connected to the first terminal of the capacitor, the cathode of the first diode is connected to a first power supply, and the cathode of the second diode is grounded.

[0023] Furthermore, to achieve the above objectives, the present invention also provides a driving method, wherein the driving method is applied to the driving circuit described above, and the driving method includes the following steps:

[0024] After receiving the drive signal, the drive adjustment circuit outputs a first current to the first switch to charge the first switch; wherein, the feedback circuit detects the voltage at the first terminal of the first switch, and outputs an adjustment signal after detecting that the voltage at the first terminal of the first switch is lower than a preset threshold voltage.

[0025] After receiving the adjustment signal, the drive adjustment circuit outputs a second current to the first switch; wherein the second current is greater than the first current.

[0026] Furthermore, to achieve the above objectives, the present invention also provides a switching power supply, including an input rectifier and filter circuit, a transformer, an output rectifier and filter circuit, a sampling circuit, and a control circuit. The input terminal of the input rectifier and filter circuit is the input terminal of the switching power supply. The output terminal of the input rectifier and filter circuit is connected to the primary coil of the transformer. The secondary coil of the transformer is connected to the input terminal of the output rectifier and filter circuit. The output terminal of the output rectifier and filter circuit is the output terminal of the switching power supply. The sampling terminal of the sampling circuit is connected to the output terminal of the output rectifier and filter circuit. The output terminal of the sampling circuit is connected to the input terminal of the control circuit. The switching power supply further includes a drive circuit configured as described above, wherein the input terminal of the drive adjustment circuit is connected to the output terminal of the control circuit, and the second terminal of the first switch is connected to the primary coil of the transformer.

[0027] The present invention provides a driving circuit, driving method, and switching power supply. When the driving adjustment circuit receives a driving signal, it outputs a first current to charge a first switch, causing the first switch to enter a conducting state. During this stage, the voltage at the first terminal of the first switch begins to decrease. When the feedback circuit detects that the voltage has decreased to a preset threshold, the driving current (first current) input to the first switch is relatively small, resulting in a slower turn-on speed. This effectively suppresses current spikes caused by various parasitic parameters in the circuit, improving the system's EMI. After the first switch begins to conduct, the voltage at its first terminal decreases again. When the feedback circuit detects that the voltage has decreased to the preset threshold, it outputs an adjustment signal to cause the driving adjustment circuit to output a second current to the first switch. Because the driving current (second current) is larger during this stage, the turn-on speed of the first switch is accelerated, thereby shortening the total turn-on time of the first switch, reducing turn-on losses, and improving system efficiency. Therefore, this effectively solves the problem of balancing efficiency and EMI, resulting in a switching power supply system with high conversion efficiency and good EMI. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0029] Figure 1 A schematic diagram of the circuit functional modules of a switching power supply provided by the prior art;

[0030] Figure 2 This is a functional module diagram of an embodiment of the driving circuit of the present invention;

[0031] Figure 3 This is a schematic diagram of the equivalent capacitance of a MOSFET.

[0032] Figure 4 This is a waveform diagram of an embodiment of the driving circuit of the present invention;

[0033] Figure 5 This is a schematic diagram of the circuit structure of an embodiment of the driving circuit of the present invention;

[0034] Figure 6 This is a flowchart illustrating an embodiment of the driving method of the present invention;

[0035] Figure 7 This is a schematic diagram of the circuit functional modules of an embodiment of the switching power supply of the present invention.

[0036] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings.

[0037] Explanation of icon numbers:

[0038]

[0039] Detailed Implementation

[0040] It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0041] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0042] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present invention are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indication will also change accordingly.

[0043] Furthermore, the use of terms such as "first" and "second" in this invention is for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of that feature. Additionally, the technical solutions of the various embodiments can be combined with each other, but only on the basis of being achievable by those skilled in the art. When the combination of technical solutions is contradictory or impossible to implement, such a combination of technical solutions should be considered non-existent and not within the scope of protection claimed by this invention.

[0044] This application proposes a driving circuit, referring to... Figure 2 In one embodiment of this application, the driving circuit includes:

[0045] A drive adjustment circuit 10, the input terminal of which is used to receive drive signals;

[0046] The first switch 20 has its controlled terminal connected to the output terminal of the drive adjustment circuit 10, its first terminal connected to the transformer, and its second terminal grounded.

[0047] The drive adjustment circuit 10 is used to output a first current to the first switch 20 when the drive signal is received, so as to charge the first switch 20;

[0048] Feedback circuit 30, with its first terminal connected to the first terminal of the first switch 20 and its second terminal connected to the controlled terminal of the drive adjustment circuit 10; the feedback circuit 30 is used to output an adjustment signal when the voltage at the first terminal of the first switch 20 is detected to be lower than a preset threshold voltage.

[0049] The drive adjustment circuit 10 is further configured to output a second current to the first switch 20 when the adjustment signal is received, so as to accelerate the opening of the first switch 20; wherein the second current is greater than the first current.

[0050] In this embodiment, the input terminal of the drive adjustment circuit 10 can be connected to the control circuit to receive the drive signal output by the control circuit. The circuit structure of the control circuit can be set according to the actual circuit. The drive signal is a voltage signal to control the first switch 20 to turn on. The feedback circuit 30 can be implemented by means of a voltage detection circuit or the like.

[0051] The drive adjustment circuit 10 may include impedance circuits with different impedances, such as a first impedance circuit with a larger impedance and a second impedance circuit with a smaller impedance. When a drive signal is received from the control circuit, the first impedance circuit divides the drive signal and outputs a smaller first current to the first switch 20, resulting in a smaller drive voltage at the controlled terminal of the first switch 20. When an adjustment signal is received, the second impedance circuit can be used to divide the drive signal, thereby outputting a larger second current to the first switch 20.

[0052] The first switch 20 can be implemented using various transistor circuits, such as MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor), BJT (Bipolar Junction Transistor), IGBT (Insulated Gate Bipolar Transistor), and other composite switching circuits composed of multiple transistors.

[0053] As is understandable, transistors have three states: on, off, and turn-on. The turn-on process of a transistor can be further divided into different stages. Taking a MOSFET as an example... Figure 3 The MOSFET's turn-on (conduction time) consists of three stages: The first stage is when the MOSFET begins to conduct, the drive current flows into the gate G, and simultaneously supplies power to the capacitor C. GS and capacitor C GD Charged to gate-source voltage V GS The voltage rises to the threshold voltage level, i.e., the conduction delay time. At this moment, the voltage at the drain D can be set to the preset threshold voltage; the second stage is V. GS When the threshold voltage is exceeded, the MOSFET starts to conduct, and the gate-drain capacitance C... GD Discharge begins, V GS The drain-source voltage drops rapidly when the voltage V remains constant near the threshold voltage. DS Drop to less than voltage V GS At that time, capacitor C GD The capacitance value rapidly increases to its maximum value. All the driving current is then transferred to capacitor C. GD Voltage V GS The V remains unchanged. GS The time during which it remains unchanged is usually also called V. GS Platform time; the third stage is voltage V DS The voltage is completely reduced to the low voltage level after conduction, and the capacitor C GS Continue charging, voltage V GS Instead of remaining constant, the voltage begins to rise, and the device enters the overdrive phase. GSEventually, it will reach near the maximum value of the driving voltage.

[0054] Power switching losses are one of the most significant sources of loss within a typical switching power supply. These losses can be broadly categorized into switching losses and conduction losses, with switching losses further divided into turn-on losses and cut-off losses. Turn-on losses occur because the voltage across the switching device cannot immediately drop to zero upon startup, while the current has already begun to rise from zero. This results in alternation between voltage and current across the switching transistor, leading to corresponding losses. This solution does not discuss cut-off losses and conduction losses.

[0055] In existing technology, a gate resistor is added to the gate of the power switch. However, if the resistance value of the gate resistor is reduced, the drive current driving the MOSFET gate increases. From the perspective of the device's conduction process, the increased drive current causes the gate-source voltage V to... GS The voltage quickly rises to the drive voltage level, achieving rapid turn-on. This reduces the overlap region between the rising drain-source current and the falling drain-source voltage, lowering the MOSFET's switching losses and improving the power switch's conversion efficiency. However, because the MOSFET turns on quickly, at V... GS When the drain current I rises to the threshold voltage level, i.e., the instant the MOSFET begins to conduct (i.e., the instant between the first and second stages of device turn-on), the drain current I... D Significant sudden changes can occur. Moreover, during rapid start-up, the primary coil of the transformer has leakage inductance. The energy stored in the leakage inductance, together with the drain capacitance of the switching transistor and the primary-side discharge circuit, will form an oscillating signal with spikes. These spikes are superimposed on the drain voltage at this time, forming a turn-off voltage spike. These sudden interferences can enter the control circuit or return to the power distribution system through conductive coupling, not only disrupting the output but also creating excessive risk of component breakdown and EMI problems.

[0056] If the resistance value is increased, the impedance of the charging and discharging path of the drive circuit is increased, which reduces the drive current driving the MOSFET gate. In terms of the device's conduction process, the reduced drive current decreases the gate-source voltage V. GS The voltage gradually rises to the level of the drive voltage, thus extending the time of each turn-on stage and significantly reducing the instantaneous drain current I at the start of conduction. D The current spikes effectively improve the EMI of the power supply system. However, when the MOSFET turns on slowly, the turn-on loss of the MOSFET also increases accordingly. Especially for high-frequency circuits, this will significantly reduce the efficiency of the power supply system and have a greater impact on temperature rise.

[0057] In this embodiment, a preset threshold voltage can be set according to actual needs. For example, the voltage at the first terminal during the instant between the first stage and the second stage of the first switch being turned on can be set as the preset threshold voltage. When the control circuit outputs the drive voltage, the first switch 20 is still in the off state. Since the first current output by the drive adjustment circuit 10 is small, the first switch 20 charges slowly, delaying the arrival at the turn-on point of the first switch 20 (i.e., the instant between the first stage and the second stage of the first switch being turned on). This effectively suppresses the spike current caused by various parasitic parameters in the circuit (such as semiconductor junction capacitance, transformer winding layer junction capacitance, semiconductor reverse recovery time, etc.), significantly improving the EMI of the system. Although this stage is prolonged in time, the peak of the drain current is small, therefore, the loss in this stage does not increase significantly.

[0058] Then, the first switch 20 turns on, entering the second stage of the turn-on process. The voltage at the first terminal begins to drop. The feedback circuit 30 detects that the voltage at the first terminal of the first switch 20 has dropped to a preset threshold voltage and outputs an adjustment signal to drive the adjustment circuit 10 to output a second current. Because the second current is larger, the turn-on process in the second stage is accelerated, the turn-on power is reduced, and the turn-on loss is reduced. Although the turn-on speed is accelerated in this stage, the impact on EMI is not significant.

[0059] Taking the first switch 20 as an example, refer to... Figure 4 (The horizontal axis represents time, and the vertical axis represents the values ​​of each parameter), where DRIVE represents the drive voltage input to the gate, Vds represents the drain-source voltage, Vgs represents the gate-source voltage, and Id represents the drain current. As shown in the graph, in the first stage of MOSFET conduction (Phase 1), Vgs gradually rises to the device threshold voltage, Vds slowly decreases, and Id steadily rises to its maximum value. The Id spike generated instantaneously between the first and second stages of conduction is very small. The MOSFET enters the second stage (Phase 2), where Vgs remains stable, and the device conducts. Due to the increased drive current at this time, the holding time of Vgs shortens, rapidly increasing to near the drive voltage, while Id is pulled down to its minimum value, resulting in a slow and smooth waveform. The instantaneous Vds between the first and second stages of conduction is the preset threshold voltage. When Vds approaches 0, Vgs rises rapidly, further reducing turn-on losses.

[0060] It should be noted that the preset threshold voltage can also be set to the voltage value of the first terminal in other stages of the first switch 20 being turned on, so that the first switch 20 can be adaptively adjusted in each stage of being turned on.

[0061] This solution, by slowing down the opening speed of the first switch 20 during its initial opening phase, effectively suppresses current spikes caused by various parasitic parameters in the circuit, thus improving the system's EMI. In the next phase after the first switch 20 opens, the opening speed is accelerated, effectively reducing opening losses, lowering temperature rise, and improving system efficiency. This effectively solves the problem of balancing efficiency and EMI. Furthermore, it improves the EMI of the switching power supply system while maintaining conversion efficiency. Due to the reduced temperature rise, the heat dissipation of the power supply system can also be reduced accordingly, thereby lowering costs.

[0062] Further, see Figure 5 The structure of the drive adjustment circuit 10 described above can be configured according to actual needs. For example, the drive adjustment circuit 10 includes a first resistor R1, a second resistor R2, and a second switch 21. The first end of the first resistor R1 and the first end of the second switch 21 are connected. The second end of the first resistor R1, the second end of the second switch 21, and the first end of the second resistor R2 are connected. The second end of the second resistor R2 is the output end of the drive adjustment circuit 10. The common terminal connecting the first resistor R1 and the second switch 21 is the input end of the drive adjustment circuit 10. The controlled end of the second switch 21 is the controlled end of the drive adjustment circuit 10 and is connected to the feedback circuit 30.

[0063] The second switch 21 is open when the adjustment signal is not received, causing the first resistor R1 and the second resistor R2 to step down the driving signal, thereby outputting a first current; when the adjustment signal is received, it is turned on, causing the second resistor to step down the driving signal, thereby outputting a second current.

[0064] Understandably, the second switch 21 may include, for example, a MOSFET, BJT, IGBT, or other composite switching circuits composed of multiple transistors, or other switching circuits capable of turning on and off. The initial state of the second switch 21 (i.e., when no adjustment signal is received) is the off state. The driving resistance between the control circuit and the first switch 20 is the equivalent resistance of the first resistor R1 and the second resistor R2 connected in series. The driving signal output by the control circuit is input to the first switch 20 through the first resistor R1 and the second resistor R2. Because the resistance value is relatively large at this time, the output first current is small. When the second switch 21 receives the adjustment signal, it begins to conduct. At this time, the first resistor R1 is short-circuited, and the driving resistance between the control circuit and the first switch 20 becomes the second resistor R2. The driving resistance value decreases, and the second current increases.

[0065] In actual setup, if it is necessary to make the first switch 20 open faster, the resistance value of the second resistor R2 can be set smaller, thereby increasing the second current. Thus, by adjusting the resistance values ​​of the first resistor R1 and the second resistor R2, the driving current and opening speed of the first switch 20 at different opening stages can be adjusted, achieving control of the opening stages of the first switch 20 by outputting two different driving currents from a single driving adjustment circuit 10.

[0066] Furthermore, the second switch 21 may include a first MOSFET Q3; the controlled terminal of the first MOSFET Q3 is the controlled terminal of the second switch 21, the input terminal of the first MOSFET Q3 is the first terminal of the second switch 21, and the output terminal of the first MOSFET Q3 is the second terminal of the second switch 21.

[0067] The first switch 20 includes a second MOSFET Q2; the controlled terminal of the second MOSFET Q2 is the controlled terminal of the first switch 20, the input terminal of the second MOSFET Q2 is the first terminal of the first switch 20, and the output terminal of the second MOSFET Q2 is the second terminal of the first switch 20.

[0068] The first MOSFET Q3 and the second MOSFET Q2 mentioned above can both be replaced by equivalent circuits or independent electronic components, which will not be elaborated here. Furthermore, the types of the first MOSFET Q3 and the second MOSFET Q2 can also be set according to actual needs; the first MOSFET Q3 can be a PMOS transistor, and the second MOSFET Q2 can be an NMOS transistor.

[0069] Understandably, regardless of whether it's an N-type or P-type MOSFET, their working principle is essentially the same: the voltage applied to the gate at the input terminal controls the drain current at the output terminal. As a voltage-controlled device, the MOSFET controls the device's characteristics through the voltage applied to its gate. Unlike transistors used as switches, it doesn't experience the charge storage effect caused by base current. Therefore, this embodiment uses a MOSFET as the switch, which should offer faster switching speeds, higher drive capability, and lower power consumption.

[0070] Furthermore, the feedback circuit 30 includes a voltage detection unit 31; the first end of the voltage detection unit 31 is connected to the first end of the first switch 20, and the second end of the voltage detection unit 31 is connected to the controlled end of the drive adjustment circuit 10.

[0071] The voltage detection unit 31 is used to output an adjustment signal to the drive adjustment circuit 10 when it detects that the voltage at the first terminal of the first switch 20 is lower than a preset threshold voltage.

[0072] The structure of the voltage detection unit 31 can be configured by those skilled in the art with reference to commonly used techniques in the field, and it needs to achieve the corresponding functions described above. The adjustment signal is specifically a high-level signal or a low-level signal to drive the first MOSFET Q3 to turn on or off. This achieves timely detection and control of the on-state of the first switch 20.

[0073] Further, the voltage detection unit 31 includes a capacitor C2; the first terminal of the capacitor C2 is the first terminal of the voltage detection unit 31, connected to the first terminal of the first switch 20 and the transformer; the second terminal of the capacitor C2 is the second terminal of the voltage detection unit 31. Since the voltage of the capacitor C2 cannot change abruptly when the voltage of the first switch 20 drops, the capacitor C2 will discharge to the first MOSFET Q3, pulling down the gate of the first MOSFET Q3, thereby turning on the first MOSFET Q3. Regarding the selection of capacitor C2, if voltage withstand capability is not an issue, a film capacitor can be selected for stability considerations, while a ceramic capacitor can be selected for stability and size considerations; a ceramic capacitor is preferred, with a capacitance value ranging from tens to hundreds of picofarads. This embodiment can quickly monitor the voltage of the first switch 20 using only one capacitor, resulting in a simple circuit structure and low cost.

[0074] Furthermore, the feedback circuit 30 also includes a clamping unit 32; the first end of the clamping unit 32 is connected to the second end of the capacitor C2, the second end of the clamping unit 32 is connected to the first power supply VCC, and the third end of the clamping unit 32 is grounded.

[0075] The clamping unit 32 is used to clamp the voltage at the second terminal of the capacitor C2, ensuring that the voltage of the input drive adjustment circuit 10 is not too high or too low when the capacitor C2 is charging or discharging, so that the circuit is not damaged.

[0076] Specifically, the clamping unit 32 includes a first diode D1 and a second diode D2; the anodes of the first diode D1 and the second diode D2 are respectively connected to the first terminal of the capacitor C2, the cathode of the first diode D1 is connected to the first power supply VCC, and the cathode of the second diode D2 is grounded. When the capacitor C2 is conducting, the first diode D1 clamps the voltage level of the capacitor C2 at -0.7V. After the capacitor C2 is discharged, the potential is around 0.6V, and the stored charge is almost completely discharged. When it is recharged, the second diode D2 is used to clamp the voltage and charge it to VCC, preventing the gate of the first MOSFET Q3 from being pulled upwards indefinitely; this prevents the gate polarity of the first MOSFET Q3 from exceeding the normal range and causing damage.

[0077] It should be noted that the driving circuit may further include a sampling resistor R3, with its first terminal connected to the second terminal of the first switch and its second terminal grounded. Specifically, the sampling resistor R3 may also be connected to a control circuit for sampling the current and feeding it back to the control circuit.

[0078] Based on the above hardware structure, the adaptive driving process of the driving circuit can be as follows:

[0079] When the front-end control circuit sends a drive voltage (i.e., a drive signal), the first MOSFET Q3 is turned off, the first resistor R1 and the second resistor R2 are connected in series, and the first current is output to the gate of the second MOSFET Q2, so that the second MOSFET Q2 is slowly charged to the threshold voltage, which improves the peak of the drain current Id at this time, thereby improving the system EMI.

[0080] When the second MOSFET Q2 starts to conduct, the drain voltage begins to decrease, the voltage at the first terminal of capacitor C2 decreases, and it begins to discharge, pulling down the gate voltage of the first MOSFET Q3, and MOSFET Q3 turns on. The first resistor R1 is short-circuited, and the driving voltage outputs a larger second current through the second resistor R2, accelerating the turn-on of the second MOSFET Q2, thereby reducing turn-on losses and improving efficiency.

[0081] In summary, this solution effectively addresses the challenge of balancing efficiency and EMI, thereby enabling the switching power supply system to achieve both high conversion efficiency and good EMI performance.

[0082] This application also proposes a driving method, which applies the driving circuit described in any of the above embodiments, with reference to... Figure 6 In one embodiment of this application, the driving method includes:

[0083] Step S10: After receiving the drive signal, the drive adjustment circuit outputs a first current to the first switch to charge the first switch; wherein, the feedback circuit detects the voltage at the first terminal of the first switch, and outputs an adjustment signal after detecting that the voltage at the first terminal of the first switch is lower than a preset threshold voltage.

[0084] Step S20: After receiving the adjustment signal, the drive adjustment circuit outputs a second current to the first switch; wherein the second current is greater than the first current.

[0085] In this embodiment, a preset threshold voltage can be set according to actual needs. For example, the voltage at the first terminal during the instant between the first stage and the second stage of the first switch being turned on can be set as the preset threshold voltage. When the control circuit outputs the drive voltage, the first switch 20 is still in the off state. Since the first current output by the drive adjustment circuit 10 is small, the first switch 20 charges slowly, delaying the arrival at the turn-on point of the first switch 20 (i.e., the instant between the first stage and the second stage of the first switch being turned on). This effectively suppresses the spike current caused by various parasitic parameters in the circuit and significantly improves the EMI of the system. Although this stage is prolonged in time, the peak of the drain current is small. Therefore, the loss in this stage does not increase significantly.

[0086] Then, the first switch 20 turns on, entering the second stage of the turn-on process. The voltage at the first terminal begins to drop. The feedback circuit 30 detects that the voltage at the first terminal of the first switch 20 has dropped to a preset threshold voltage and outputs an adjustment signal to drive the adjustment circuit 10 to output a second current. Because the second current is larger, the turn-on process in the second stage is accelerated, the turn-on power is reduced, and the turn-on loss is reduced. Although the turn-on speed is accelerated in this stage, the impact on EMI is not significant.

[0087] It should be noted that the preset threshold voltage can also be set to the voltage value of the first terminal in other stages of the first switch 20 being turned on, so that the first switch 20 can be adaptively adjusted in each stage of being turned on.

[0088] This solution slows down the opening speed of the first switch 20 during its initial opening phase, effectively suppressing peak currents caused by various parasitic parameters in the circuit and improving the system's EMI. In the next phase after the first switch 20 opens, the opening speed is accelerated, effectively reducing opening losses and improving system efficiency. Thus, the problem of balancing efficiency and EMI is effectively solved, further enabling the switching power supply system to have both high conversion efficiency and good EMI.

[0089] This application also provides a switching power supply, as shown in the reference. Figure 7The switching power supply includes an input rectifier and filter circuit 100, a transformer 200, an output rectifier and filter circuit 300, a sampling circuit 400, and a control circuit 500. The input terminal of the input rectifier and filter circuit 100 is the input terminal of the switching power supply. The output terminal of the input rectifier and filter circuit 100 is connected to the primary coil of the transformer 200. The secondary coil of the transformer 200 is connected to the input terminal of the output rectifier and filter circuit 300. The output terminal of the output rectifier and filter circuit 300 is the output terminal of the switching power supply. The sampling terminal of the sampling circuit 400 is connected to the output terminal of the output rectifier and filter circuit 300. The output terminal of the sampling circuit 400 is connected to the input terminal of the control circuit 500. The switching power supply also includes a drive circuit 600, which can be referred to in the above embodiment and will not be described again here. The input terminal of the drive adjustment circuit 20 is connected to the output terminal of the control circuit 500, and the second terminal of the first switch 10 is connected to the primary coil of the transformer 200. Naturally, since the switching power supply of this embodiment adopts the above-described driving circuit technical solution, the switching power supply has all the beneficial effects of the above-described driving circuit.

[0090] The above are merely preferred embodiments of the present invention and do not limit the scope of the patent. Any equivalent structural or procedural transformations made based on the description and drawings of the present invention, or direct or indirect applications in other related technical fields, are similarly included within the scope of patent protection of the present invention.

Claims

1. A driving circuit, characterized in that, include: A drive adjustment circuit, wherein the input terminal of the drive adjustment circuit is used to receive drive signals; The first switch has its controlled terminal connected to the output terminal of the drive adjustment circuit, its first terminal connected to the transformer, and its second terminal grounded. The drive adjustment circuit is used to receive the drive signal and output a first current to the first switch so that the first switch is charged. A feedback circuit is provided, wherein a first terminal of the feedback circuit is connected to a first terminal of the first switch, and a second terminal of the feedback circuit is connected to a controlled terminal of the drive adjustment circuit. The feedback circuit is configured to output an adjustment signal after detecting that the voltage at the first terminal of the first switch is lower than a preset threshold voltage. The feedback circuit includes a voltage detection unit; a first terminal of the voltage detection unit is connected to the first terminal of the first switch, and a second terminal of the voltage detection unit is connected to the controlled terminal of the drive adjustment circuit. The voltage detection unit is configured to output an adjustment signal when detecting that the voltage at the first terminal of the first switch is lower than a preset threshold voltage. The system includes a capacitor; the first terminal of the capacitor is the first terminal of the voltage detection unit, and the second terminal of the capacitor is the second terminal of the voltage detection unit. The feedback circuit also includes a clamping unit; the first terminal of the clamping unit is connected to the second terminal of the capacitor, the second terminal of the clamping unit is connected to a first power supply, and the third terminal of the clamping unit is grounded; the clamping unit is used to clamp the voltage at the second terminal of the capacitor, and the clamping unit includes a first diode and a second diode; the anodes of the first diode and the second diode are respectively connected to the first terminal of the capacitor, the cathode of the first diode is connected to the first power supply, and the cathode of the second diode is grounded. The drive adjustment circuit is further configured to output a second current to the first switch after receiving the adjustment signal; wherein the second current is greater than the first current, and wherein the drive adjustment circuit includes a first resistor, a second resistor, and a second switch; the first end of the first resistor and the first end of the second switch are connected, the second end of the first resistor, the second end of the second switch, and the first end of the second resistor are connected, the second end of the second resistor is the output end of the drive adjustment circuit, the common end connecting the first resistor and the second switch is the input end of the drive adjustment circuit, and the controlled end of the second switch is the controlled end of the drive adjustment circuit; the second switch is turned on when it receives the adjustment signal, causing the second resistor to step down the drive signal, thereby outputting the second current, wherein the adjustment signal is triggered when the gate-source voltage of the first switch exceeds a threshold voltage and the gate-drain capacitance of the first switch begins to discharge.

2. The driving circuit according to claim 1, characterized in that, The second switch includes a first MOSFET; the controlled terminal of the first MOSFET is the controlled terminal of the second switch, the input terminal of the first MOSFET is the first terminal of the second switch, and the output terminal of the first MOSFET is the second terminal of the second switch.

3. The driving circuit according to claim 1, characterized in that, The first switch includes a second MOSFET; the controlled terminal of the second MOSFET is the controlled terminal of the first switch, the input terminal of the second MOSFET is the first terminal of the first switch, and the output terminal of the second MOSFET is the second terminal of the first switch.

4. A driving method, characterized in that, The driving method is applied to the driving circuit as described in any one of claims 1-3, and the driving method includes the following steps: After receiving the drive signal, the drive adjustment circuit outputs a first current to the first switch to charge the first switch; wherein, the feedback circuit detects the voltage at the first terminal of the first switch, and outputs an adjustment signal after detecting that the voltage at the first terminal of the first switch is lower than a preset threshold voltage. After receiving the adjustment signal, the drive adjustment circuit outputs a second current to the first switch; wherein the second current is greater than the first current.

5. A switching power supply, comprising an input rectifier and filter circuit, a transformer, an output rectifier and filter circuit, a sampling circuit, and a control circuit, wherein the input terminal of the input rectifier and filter circuit is the input terminal of the switching power supply, the output terminal of the input rectifier and filter circuit is connected to the primary coil of the transformer, the secondary coil of the transformer is connected to the input terminal of the output rectifier and filter circuit, the output terminal of the output rectifier and filter circuit is the output terminal of the switching power supply, the sampling terminal of the sampling circuit is connected to the output terminal of the output rectifier and filter circuit, and the output terminal of the sampling circuit is connected to the input terminal of the control circuit, characterized in that... The switching power supply further includes a drive circuit, which is configured as the drive circuit described in any one of claims 1-3, wherein the input terminal of the drive adjustment circuit is connected to the output terminal of the control circuit, and the second terminal of the first switch is connected to the primary coil of the transformer.

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