Switching power supply controller, switching power supply and its power supply method

Abstract

The present invention discloses a switching power supply controller, comprising: a power switch transistor, whose drain terminal is connected to an input voltage and is used for controlling the power transmission of a power conversion circuit; a logic control circuit, which is used for generating a control signal for controlling the switching action of the power switch transistor; a driving circuit, which is connected to the gate terminal of the power switch transistor and is used for driving the power switch transistor to conduct or turn off according to the control signal; and a power supply circuit, which is connected to the drain terminal of the power switch transistor and is used for providing a power supply voltage to the driving circuit and the logic control circuit based on the drain terminal voltage of the power switch transistor. Wherein, the driving circuit is further used for clamping the drain terminal voltage of the power switch transistor at a set voltage during the conducting stage of the power switch transistor, thereby saving an external power supply capacitor and an internal layout area and reducing the cost. An embodiment of the present invention also discloses a switching power supply and its power supply method.

Description

Technical Field

[0001] The present invention relates to the technical field of switching power supplies, and particularly to a switching power supply controller, a switching power supply and a power supply method thereof. Background Art

[0002] A switching power supply is a power supply that uses modern power electronics technology to control the on and off time ratio of a switching transistor to maintain a stable output voltage Vo. High-voltage step-down AC-DC switching power supplies are widely used in the fields of household appliances and intelligent module power supply. With the update of technology, the industry has higher and higher requirements for high performance, fewer peripherals and lower cost.

[0003] Figure 1 is a schematic structural diagram of a prior art AC-DC switching power supply. An AC input source AC inputs alternating current to a rectifier circuit DB1 and an input capacitor C1, and then, after being controlled by a control chip U1, outputs a constant voltage Vo through a power conversion circuit 10. The power conversion circuit 10 includes a freewheeling diode D1, an inductor L1, a load capacitor C3 and a load RL. The output voltage Vo is input to the power supply pin VCC of the control chip U1 through a diode D2 and a power supply capacitor C2. The control chip U1 indirectly detects the output voltage Vo therefrom and controls the stability of its output voltage Vo. In addition, an external power supply capacitor C2 provides the energy required for the normal operation of the control chip U1 and the energy required for MOS transistor driving. For this power supply method of the control chip U1, the standby power consumption is good, but an additional power supply capacitor C2 is required, and the output voltage Vo is not directly sampled, but passes through a diode D2. Therefore, the voltage sampled at the power supply pin VCC is the output voltage Vo minus the voltage drop consumed on the diode D2, so the accuracy and dynamic characteristics of its output voltage are relatively poor.

[0004] Figure 2 shows a circuit schematic diagram of a switching power supply controller based on Figure 1 as shown in Figure 1 and Figure 2As shown in the figure, the switching power supply controller charges the power supply capacitor C2 through the connection between the power supply circuit 11 and its VCC port. During the conduction and turn-off of the power switch Q1, the power supply capacitor C2 storing electrical energy supplies power to the logic control circuit 13 and the drive circuit 12 inside the switching power supply controller. Since the power switch Q1 is fully conductive during conduction, the drain of the power switch Q1 is connected to the ground through the power switch Q1 and the current detection module 14, resulting in the voltage at the drain of the power switch Q1 dropping to zero, which is lower than the threshold voltage for the normal operation of the switching power supply controller. Therefore, the power supply circuit 11 does not work. An external or internal energy storage unit, such as the power supply capacitor C2, is required to use the energy stored in the energy storage unit by the power supply circuit 11 during the turn-off of the power switch Q1 to supply power to the logic control circuit 13 and the drive circuit 12 inside the switching power supply controller. So the power supply port VCC is both a power supply port and an output voltage feedback port.

[0005] It can be seen that the prior art must require an energy storage unit to supply power to the switching power supply controller. The switching power supply controller requires many peripheral devices and has a high cost, which is not suitable for the development requirements of small size and low cost of current switching power supplies. Summary of the Invention

[0006] In view of the above problems, the purpose of the present invention is to provide a switching power supply controller, a switching power supply and its power supply method, so as to save an external power supply capacitor.

[0007] According to one aspect of the present invention, there is provided a switching power supply controller for controlling a power conversion circuit, the power conversion circuit being configured to provide an output current to a load according to an input voltage. Wherein, the switching power supply controller includes a power switch, whose drain is connected to the input voltage and is used to control the power transmission of the power conversion circuit; a logic control circuit for generating a control signal for controlling the switching action of the power switch; a drive circuit connected to the gate of the power switch and used to drive the power switch to conduct or turn off according to the control signal; and a power supply circuit connected to the drain of the power switch and used to provide a power supply voltage to the drive circuit and the logic control circuit based on the drain voltage of the power switch. Wherein, the drive circuit is further configured to clamp the drain voltage of the power switch at a set voltage during the conduction stage of the power switch.

[0008] Optionally, the power supply circuit includes a junction field effect transistor, the first conduction end is connected to the drain of the power switch, the second conduction end is connected to the drive circuit, and the control end is grounded; and a low dropout linear regulator, the input end is connected to the second conduction end of the junction field effect transistor, and the output end is connected to the logic control circuit.

[0009] Optionally, the driving circuit includes a first zener diode, the cathode of the first zener diode is connected to the second conduction end of the junction field effect transistor, and the anode is connected to the gate end of the power switch transistor; a first switch, the first end is connected to the gate end of the power switch transistor, the second end is grounded, and the control end receives the control signal.

[0010] Optionally, the first switch is turned on or off in response to the control signal, and when the first switch is turned on, the power switch transistor is turned off, and when the first switch is turned off, the power switch transistor is turned on. During the conduction stage of the power switch transistor, the driving circuit controls the gate voltage of the power switch transistor between the turn-on voltage and the Miller plateau voltage.

[0011] Optionally, the driving circuit includes a comparator for comparing a first voltage at the second conduction end of the junction field effect transistor with a preset reference voltage to obtain a comparison result; a third switch and a second switch connected in sequence between the supply voltage and the ground, a middle node of the third switch and the second switch is connected to the gate end of the power switch transistor; and a drive control circuit for controlling the conduction and turn-off of the second switch and the third switch according to the control signal and the comparison result to control the gate voltage of the power switch transistor.

[0012] Optionally, the drive control circuit is further configured to alternately turn on or off the second switch and the third switch based on the comparison result to control the gate voltage of the power switch transistor to clamp the first voltage at the reference voltage.

[0013] Optionally, the drive control circuit is configured to control the power switch transistor to conduct when the control signal is at a logic high level, and control the power switch transistor to turn off when the control signal is at a logic low level. During the conduction stage of the power switch transistor, the driving circuit controls the gate voltage of the power switch transistor between the turn-on voltage and the Miller plateau voltage.

[0014] Optionally, the driving circuit includes: a fourth switch and a fifth switch connected in sequence between the drain end of the power switch transistor and the ground, a middle node of the fourth switch and the fifth switch is connected to the gate end of the power switch transistor, wherein the fourth switch and the fifth switch are respectively controlled by the logic control circuit to alternately conduct or turn off to control the conduction or turn-off of the power switch transistor.

[0015] Optionally, the driving circuit is configured to control the power switch transistor to conduct when the fourth switch is on and the fifth switch is off, and control the power switch transistor to turn off when the fourth switch is off and the fifth switch is on. During the conduction stage of the power switch transistor, the gate voltage of the power switch transistor is controlled between the turn-on voltage and the Miller plateau voltage.

[0016] Optionally, the switching power supply controller further includes a voltage selection module, with a first end connected to the power supply circuit, a second end connected to the output voltage, and a third end connected to the logic control circuit. The voltage selection module is configured to select the power supply circuit or the output voltage to supply power to the logic control circuit and the drive circuit according to the control signal output by the logic control circuit.

[0017] Optionally, the power conversion circuit includes a buck topology, a flyback topology, or a buck-boost topology.

[0018] Optionally, the switching power supply controller further includes a current detection module, with an input end connected to the source end of the power switch tube and an output end connected to the logic control circuit, for detecting the current flowing through the power switch tube.

[0019] Optionally, the switching power supply controller further includes a voltage detection circuit, with an output end connected to the logic control circuit, for performing periodic voltage sampling on the output voltage, so that the logic control circuit controls the drive circuit to drive the switching action of the power switch tube according to the result of the periodic voltage sampling, and then adjusts the output voltage.

[0020] Optionally, the switching power supply controller further includes a protection module, with an output end connected to the logic control circuit, for ensuring that the switching power supply controller acts in a timely manner under abnormal conditions.

[0021] According to another aspect of the present invention, there is provided a switching power supply, including a power conversion circuit, a sampling resistor, an AC input source, a rectification circuit, and a switching power supply controller. The power conversion circuit is configured to provide an output current to a load according to an input voltage. Wherein, the switching power supply controller includes a power switch tube, whose drain end is connected to the input voltage and is used to control the power transmission of the power conversion circuit; a logic control circuit, for generating a control signal for controlling the switching action of the power switch tube; a drive circuit, connected to the gate end of the power switch tube, for driving the power switch tube to conduct or turn off according to the control signal; and a power supply circuit, connected to the drain end of the power switch tube, for providing a supply voltage to the drive circuit and the logic control circuit based on the drain end voltage of the power switch tube. Wherein, the drive circuit is further configured to clamp the drain end voltage of the power switch tube to a set voltage during the conduction stage of the power switch tube.

[0022] Optionally, the power supply circuit includes a junction field effect transistor, a first conduction end connected to the drain end of the power switch transistor, a second conduction end connected to the drive circuit, and a control end grounded; and a low dropout linear regulator, an input end connected to the second conduction end of the junction field effect transistor, and an output end connected to the logic control circuit.

[0023] Optionally, the drive circuit includes a first voltage regulator diode, a cathode of the first voltage regulator diode connected to the second conduction end of the junction field effect transistor, and an anode connected to the gate end of the power switch transistor; a first switch, a first end connected to the gate end of the power switch transistor, a second end grounded, and a control end receiving the control signal.

[0024] Optionally, the first switch conducts or turns off in response to the control signal, and when the first switch conducts, the power switch transistor turns off, and when the first switch turns off, the power switch transistor conducts. During the conduction stage of the power switch transistor, the drive circuit controls the gate voltage of the power switch transistor between the turn-on voltage and the Miller plateau voltage.

[0025] Optionally, the drive circuit includes a comparator for comparing a first voltage at the second conduction end of the junction field effect transistor with a preset reference voltage to obtain a comparison result; a third switch and a second switch connected in sequence between the supply voltage and the ground, a middle node of the third switch and the second switch connected to the gate end of the power switch transistor; and a drive control circuit for controlling the conduction and turn-off of the second switch and the third switch according to the control signal and the comparison result to control the gate voltage of the power switch transistor.

[0026] Optionally, the drive control circuit is further configured to alternately conduct or turn off the second switch and the third switch based on the comparison result to control the gate voltage of the power switch transistor to clamp the first voltage at the reference voltage.

[0027] Optionally, the drive control circuit is configured to control the power switch transistor to conduct when the control signal is at a logic high level, and control the power switch transistor to turn off when the control signal is at a logic low level. During the conduction stage of the power switch transistor, the drive circuit controls the gate voltage of the power switch transistor between the turn-on voltage and the Miller plateau voltage.

[0028] Optionally, the drive circuit includes a fourth switch and a fifth switch connected in sequence between the drain end of the power switch transistor and the ground, a middle node of the fourth switch and the fifth switch connected to the gate end of the power switch transistor, wherein the fourth switch and the fifth switch are respectively controlled by the logic control circuit to alternately conduct or turn off to control the conduction or turn-off of the power switch transistor.

[0029] Optionally, the drive circuit is configured to control the power switch transistor to turn on when the fourth switch is on and the fifth switch is off, and to control the power switch transistor to turn off when the fourth switch is off and the fifth switch is on. During the on stage of the power switch transistor, the drive circuit controls the gate voltage of the power switch transistor between the turn-on voltage and the Miller plateau voltage.

[0030] Optionally, the switching power supply further includes a voltage selection module, with a first end connected to the power supply circuit, a second end connected to the output voltage, and a third end connected to the logic control circuit. The voltage selection module is configured to select the power supply circuit or the output voltage to supply power to the logic control circuit and the drive circuit according to a control signal output by the logic control circuit.

[0031] Optionally, the power conversion circuit includes a buck topology, a flyback topology, or a buck-boost topology.

[0032] Optionally, the switching power supply further includes a current detection module, with an input end connected to the source end of the power switch transistor and an output end connected to the logic control circuit, for detecting the current flowing through the power switch transistor.

[0033] Optionally, the switching power supply further includes a voltage detection circuit, with an output end connected to the logic control circuit, for performing periodic voltage sampling on the switched output voltage, so that the logic control circuit controls the drive circuit to drive the switching action of the power switch transistor according to the result of the periodic voltage sampling, and then adjusts the output voltage.

[0034] Optionally, the switching power supply further includes a protection module, with an output end connected to the logic control circuit, for ensuring that the switching power supply controller acts in a timely manner under abnormal conditions.

[0035] According to another aspect of the present invention, there is provided a method for supplying power to an electrical circuit in a switching power supply. The switching power supply includes a power switch transistor, whose drain end is connected to an input voltage and is configured to provide an output current to a load according to the input voltage. The method includes using a logic control circuit to generate a control signal for controlling the switching action of the power switch transistor; using a drive circuit to generate a drive signal for driving the power switch transistor to turn on or off according to the control signal; converting the drain voltage of the power switch transistor into a supply voltage to supply power to the electrical circuit; and during the on stage of the power switch transistor, clamping the drain voltage of the power switch transistor at a set voltage through the drive circuit.

[0036] Optionally, the method further includes: when the power switch tube is in the off stage, determining whether the inductor current of the switching power supply enters the discontinuous state; if the inductor current does not enter the discontinuous state, supplying power to the power consumption circuit according to the output voltage of the switching power supply; if the inductor current enters the discontinuous state, converting the drain voltage of the power switch tube into a supply voltage to supply power to the power consumption circuit.

[0037] Optionally, the power consumption circuit includes the logic control circuit and / or the drive circuit.

[0038] Optionally, the method further includes: determining whether the power switch tube is in the on state or the off state according to the level state of the drive signal, wherein when the drive signal is at a logic high level, the power switch tube is in the on state, and when the drive signal is at a logic low level, the power switch tube is in the off state. During the on stage of the power switch tube, the gate voltage of the power switch tube is controlled between the turn-on voltage and the Miller plateau voltage.

[0039] Optionally, the step of determining whether the inductor current of the switching power supply enters the discontinuous state includes: detecting whether the inductor current drops to zero. If the inductor current drops to zero, it is determined that the inductor current enters the discontinuous state; otherwise, it is determined that the inductor current does not enter the discontinuous state.

[0040] Optionally, the set voltage is higher than the threshold voltage that enables the power supply circuit in the switching power supply to work normally.

[0041] The switching power supply controller, switching power supply and its power supply method provided by the embodiments of the present invention always supply power to the logic control circuit and the drive circuit through the power supply circuit. Therefore, the VCC port in the prior art is converted into an output voltage feedback port VFB; during the on period of the power switch tube, the gate voltage of the power switch tube does not exceed the Miller plateau voltage, so that the power switch tube works in the linear working range. Thus, the drain of the power switch tube is not directly connected to the ground, and the drain voltage of the power switch tube is maintained above the normal working threshold voltage of the power supply circuit, so as to ensure that the power supply circuit always works to supply power to the logic control circuit and the drive circuit inside the switching power supply controller, thereby saving external power supply capacitors, and there is no need to increase an energy storage unit inside the switching power supply controller, saving the internal layout area and having a lower cost.

[0042] Further, the switching power supply controller can directly sample the output voltage through a sampling resistor, saving diodes, reducing both costs and avoiding the influence of the voltage drop of the diodes on the output voltage feedback, thereby improving the sampling accuracy of the output voltage.

[0043] Further, in a preferred embodiment, the logic control circuit and the drive circuit are powered by a combination of the output voltage power supply and the power supply circuit; when the switching power supply is just turned on and the power switch tube is turned on, the power supply circuit supplies power to the logic control circuit and the drive circuit; after the power switch tube is turned off and before the inductor current enters the discontinuous state, the output voltage is selected to supply power to the logic control circuit and the drive circuit; after the power switch tube is turned off and the inductor current enters the discontinuous state, the power supply circuit supplies power to the logic control circuit and the drive circuit. Among them, when the power switch tube is turned off and the inductor current does not enter the discontinuous state, in order to avoid using high-voltage power supply and causing large losses in the high-voltage power supply module, the output voltage is used to supply power to the logic control circuit and the drive circuit, saving power consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Through the following description of the embodiments of the present invention with reference to the accompanying drawings, the above and other objects, features and advantages of the present invention will become more apparent. In the drawings:

[0045] Figure 1 Shows a schematic structural diagram of an AC-DC switching power supply according to the prior art;

[0046] Figure 2 Shows a circuit schematic diagram of an AC-DC switching power supply controller based on Figure 1 ;

[0047] Figure 3 Shows a schematic structural diagram of a switching power supply according to an embodiment of the present invention;

[0048] Figure 4 Shows a circuit schematic diagram of a switching power supply controller according to the first embodiment of the present invention;

[0049] Figure 5 Shows a signal timing diagram of a switching power supply controller according to the first embodiment of the present invention;

[0050] Figure 6 Shows a circuit schematic diagram of a switching power supply controller according to the second embodiment of the present invention;

[0051] Figure 7 Shows a signal timing diagram of a switching power supply controller according to the second embodiment of the present invention;

[0052] Figure 8 Shows a circuit schematic diagram of a switching power supply controller according to the third embodiment of the present invention;

[0053] Figure 9 Shows a signal timing diagram of a switching power supply controller according to the third embodiment of the present invention;

[0054] Figure 10Shows a schematic circuit diagram of a switching power supply controller according to a fourth embodiment of the present invention;

[0055] Figure 11 Shows a flowchart of a power supply method for a switching power supply according to an embodiment of the present invention. Detailed implementation manners

[0056] The various embodiments of the present invention will be described in more detail below with reference to the accompanying drawings, but the present invention is not limited to these embodiments. In the respective drawings, the same elements or modules are denoted by the same or similar reference numerals. For clarity, the various parts in the drawings are not drawn to scale.

[0057] It should be understood that in the following description, a "circuit" may include a single or multiple combined hardware circuits, programmable circuits, state machine circuits, and / or elements capable of storing instructions executed by a programmable circuit. When an element or circuit is said to be "connected to" another element or when an element or circuit is said to be "connected between" two nodes, it can be directly coupled or connected to another element or there may be intermediate elements, and the connection between the elements can be physical, logical, or a combination thereof. In contrast, when an element is said to be "directly coupled to" or "directly connected to" another element, it means that there are no intermediate elements between the two.

[0058] At the same time, certain terms are used in this patent specification and claims to refer to specific components. Those of ordinary skill in the art should understand that hardware manufacturers may use different nouns to refer to the same component. This patent specification and claims do not use the difference in names as a way to distinguish components, but use the difference in functions of components as the criterion for distinction.

[0059] It should also be noted that in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprise", "include" or any other variant thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not expressly listed, or also includes elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "comprising one..." does not exclude the presence of additional identical elements in the process, method, article or device including the said element.

[0060] Figure 3 Shows a schematic structural diagram of a switching power supply according to an embodiment of the present invention, as Figure 3As shown, the switching power supply includes an AC input source AC, a rectifier circuit DB1, an input capacitor C1, a sampling resistor Rcs, a power conversion circuit 100, a load RL, and a switching power supply controller U2. The power conversion circuit 100 is used to provide an output inductor current IL to the load RL according to the input voltage Vin. The switching power supply controller U2 is used to control the operating state of the power conversion circuit 100.

[0061] Exemplarily, an embodiment of the present invention provides an AC-DC step-up and step-down switching power supply. The power conversion circuit 100 includes a freewheeling diode D1, a load capacitor C3, and an inductor L1. The cathode of the freewheeling diode D1 is connected to the ground pin GND of the switching power supply controller U2, the second end of the sampling resistor Rcs, and the node A where the first end of the inductor L1 is connected. The anode is connected to the ground terminal. The second end of the inductor L1 is connected to the first end of the load capacitor C3 and the VFB pin of the switching power supply controller U2. The second end of the load capacitor C3 is grounded. The load resistor RL is connected in parallel with the load capacitor C3. The load capacitor C3 is mainly used to filter the output voltage Vo, thereby reducing the ripple of the output current and the output voltage Vo. Since the output voltage Vo is directly connected to the switching power supply controller U2, it can be directly detected by the switching power supply controller U2, and the accuracy of the output voltage Vo is relatively high.

[0062] When the switching power supply operates, the input current source AC inputs alternating current to the rectifier circuit DB1, converts the alternating current into direct current, and then inputs the input voltage Vin to the Drain pin of the switching power supply controller U2 through the input capacitor C1, so that the switching power supply outputs a constant output voltage Vo. The first end of the sampling resistor Rcs is connected to the sampling pin CS of the switching power supply controller U2, and the second end is connected to the middle node between the first end of the inductor L1 and the ground pin GND of the switching power supply controller U2. The sampling resistor Rcs samples the current flowing through the power switch Q1 for relevant protection functions.

[0063] Figure 4 The circuit schematic diagram of the switching power supply controller according to the first embodiment of the present invention is shown. As Figure 4 shown, the switching power supply controller U2 includes a power switch Q1, a power supply circuit 21, a driving circuit 22, a logic control circuit 23, a current detection module 24, and a voltage detection module 25. All units of the switching power supply controller U2 are integrated on the same control chip.

[0064] The drain of the power switch Q1 is connected to the first end of the input capacitor C1 for receiving the input voltage Vin. The source is connected to the sampling pin CS, and the gate is connected to the driving circuit 22 to receive the driving signal Vg. The power switch Q1 is used to control the power transmission of the power conversion circuit 100 according to the driving signal Vg. The sampling resistor Rcs is used to convert the current flowing through the power switch Q1 into a sampling voltage Vcs.

[0065] The power supply circuit 21 is used to provide the normal operating supply voltage VCC for the drive circuit 22 and the logic control circuit 23 according to the drain voltage of the power switch tube Q1. The power supply circuit 21 includes a junction field effect transistor Q2 and a low dropout linear regulator LDO. The first conduction end of the junction field effect transistor Q2 is connected to the drain end of the power switch tube Q1, the second conduction end is connected to the input end of the low dropout linear regulator LDO and the drive circuit 22 to supply power to the drive circuit 22, the control end is grounded, the output end of the low dropout linear regulator LDO is connected to the input end of the logic control circuit 23 to supply power to the logic control circuit 23, and the junction field effect transistor Q2 is always in the conducting state during the operation of the switching power supply.

[0066] The input end of the logic control circuit 23 is connected to the output ends of the current detection module 24, the voltage detection module 25, the protection module 26, and the power supply circuit 21. The logic control circuit 23 is used to generate a control signal Vg-d for indirectly controlling the switching action of the power switch tube Q1, keep the output voltage Vo stable at the set value, and can act in time when the switching power supply is abnormal to avoid danger.

[0067] The drive circuit 22 is used to drive the conduction or cut-off of the power switch tube Q1 according to the control signal Vg-d, and during the conduction stage of the power switch tube Q1, clamp the drain voltage of the power switch tube Q1 at the set voltage, and the voltage value of the set voltage is maintained above the voltage value of the supply voltage VCC. The drive circuit 22 includes a first zener diode Z1 and a first switch S1. The cathode of the first zener diode Z1 is connected to the node B where the low dropout linear regulator LDO in the power supply circuit 21 is connected to the junction field effect transistor Q2, the anode is connected to the node C where the gate end of the power switch tube Q1 is connected to the first end of the first switch S1, the second end of the first switch S1 is grounded, and the control end is connected to the output end of the logic control circuit 23. The first switch S1 is turned on or off under the control of the control signal Vg-d output by the logic control circuit 23, and the node B outputs a drive signal Vg according to the state of the first switch S1 to control the conduction or cut-off of the power switch tube Q1.

[0068] Further, when the first switch S1 is turned on, the power switch tube Q1 is turned off, and the switching power supply is in the freewheeling stage; when the first switch S1 is turned off, the power switch tube Q1 is turned on, and the voltage between the drain end of the power switch tube Q1 and the GND pin of the switching power supply controller U2 is maintained above the normal operating threshold voltage of the power supply circuit, so that the drain voltage of the power switch tube Q1 is clamped at the set voltage. During the conduction stage of the power switch tube Q1, the gate voltage of the power switch tube Q1 is controlled between the turn-on voltage and the Miller plateau voltage.

[0069] The input terminal of the current detection module 24 is connected to the source terminal of the power switch tube Q1, and the output terminal is connected to the input terminal of the logic control circuit 23; the current detection module 24 is used to detect the current flowing through the power switch tube Q1.

[0070] The input terminal of the voltage detection module 25 is connected to the output terminal of the switching power supply, and the output terminal is connected to the input terminal of the logic control circuit 23. The voltage detection module 25 is used to perform periodic voltage sampling on the output voltage Vo of the switching power supply, so that the logic control unit 23 controls the drive circuit 22 to drive the power switch tube Q1 to conduct or turn off according to the result of the periodic voltage sampling, and then adjusts the output voltage Vo of the switching power supply.

[0071] Furthermore, the switching power supply controller U2 further includes a protection module 26, and the protection module 26 is connected to the input terminal of the logic control circuit 23, and is used to ensure that the control chip acts in time under abnormal conditions to avoid danger.

[0072] Figure 5 The signal timing diagram of the switching power supply controller according to the first embodiment of the present invention is shown. Combining Figure 4 and Figure 5 as shown, in the t1 stage, the logic control circuit 23 outputs a high-level control signal Vg-d, the first switch S1 conducts, the node B outputs a low-level drive signal Vg, and the power switch tube Q1 turns off. At this time, the drain voltage of the power switch tube Q1 maintains the first high level, and the power supply circuit 21 supplies power to the logic control circuit 23 and the drive circuit 22 according to the first high level. The inductor current IL gradually decreases from the first current to zero and then remains unchanged; in the t2 stage, the logic control circuit 23 outputs a low-level first control signal Vg-d, the first switch S1 turns off, and the voltage of the node C rises, causing the power switch tube Q1 to conduct, and the drain voltage drops. Finally, the voltage of the drive signal Vg is stabilized between the turn-on voltage and the Miller plateau voltage of the power switch tube Q1, so that the voltage of the node B is higher than the normal operating threshold voltage of the power supply circuit; since the power switch tube Q1 conducts, the inductor current IL rises, and a voltage drop is formed on the on-resistance of the MOS tube. Therefore, the drain voltage of the power switch tube Q1 gradually rises from the second high level to the third high level, and the drive signal Vg gradually rises from the fourth high level to the fifth high level. The voltage value of the second high level always remains above the supply voltage VCC, and the power supply circuit 21 supplies power to the drive circuit 22 and the logic control circuit 23 according to the drain voltage of the power switch tube Q1.

[0073] According to the switching power supply controller U2 provided by the first embodiment of the present invention, the logic control circuit 23 outputs a control signal Vg-d to control the conduction and cut-off of the first switch S1, thereby indirectly controlling the conduction and cut-off of the power switch Q1. During the conduction of the power switch Q1, the voltage between the drain terminal of the power switch Q1 and the GND pin of the switching power supply controller U2 is maintained above the normal operating threshold voltage of the power supply circuit 21, thereby clamping its drain voltage at a set voltage, so that the power supply circuit 21 still supplies power to the drive circuit 22 and the logic control circuit 23, thus saving an external power supply capacitor, and there is no need to add an energy storage unit inside the switching power supply controller U2, saving the internal layout area and having a lower cost.

[0074] Figure 6 The circuit schematic diagram of the switching power supply controller according to the second embodiment of the present invention is shown.

[0075] The structure of the switching power supply controller provided by the second embodiment of the present invention is basically the same as that of the switching power supply controller provided by the first embodiment of the present invention. The differences between the two are only described below.

[0076] In this embodiment, the power supply circuit 31 is also composed of a junction field effect transistor Q2 and a low dropout linear regulator LDO. However, the circuit connections between the junction field effect transistor Q2 and the low dropout linear regulator LDO and the components of the drive circuit 32 are slightly different from those in the first embodiment.

[0077] The drive circuit 32 includes a comparator Cmp, a drive control circuit 321, a second switch S2, and a third switch S3.

[0078] The positive input terminal of the comparator Cmp is connected to the node D where the junction field effect transistor Q2 and the low dropout linear regulator LDO in the power supply circuit 31 are connected. The negative input terminal of the comparator Cmp is connected to the reference voltage Vref. The output terminal of the comparator Cmp is connected to the input terminal of the drive control circuit 321. The comparator Cmp is used to compare the first voltage Vr at the node D and the reference voltage Vref, and output a second control signal Vg_d2 according to the comparison result. The voltage value of the reference voltage Vref can be set according to the actual situation, but it needs to be greater than the supply voltage VCC.

[0079] The third switch S3 and the second switch S2 are connected in sequence between the supply voltage VCC and the ground. The intermediate node E between the third switch S3 and the second switch S2 is connected to the gate terminal of the power switch Q1.

[0080] Another input terminal of the drive control circuit 321 is connected to the output terminal of the logic control circuit 33, and receives the first control signal Vg_d1 output by the logic control circuit 33. One output terminal of the drive control circuit 321 is connected to the control terminal of the second switch S2, and the other output terminal is connected to the control terminal of the third switch S3. The drive control circuit 321 is configured to output a first drive signal Vg1 and a second drive signal Vg2 according to the first control signal Vg_d1 and the second control signal Vg_d2 to control the second switch S2 and the third switch S3 to conduct or turn off alternately, so as to charge or discharge the gate capacitance of the power switch Q1. The node D outputs a drive signal Vg for controlling the power switch Q1 to conduct or turn off according to the states of the second switch S2 and the third switch S3, so as to control the gate voltage of the power switch Q1; during the conduction stage of the power switch Q1, the gate voltage of the power switch Q1 is controlled between the turn-on voltage and the Miller plateau voltage, so as to clamp the first voltage Vr at the reference voltage Vref, that is, to ensure that the drain voltage of the power switch Q1 is clamped at the set voltage.

[0081] Figure 7 Fig. shows the signal timing diagram of the switching power supply controller according to the second embodiment of the present invention. Combining Figure 6 and Figure 7 as shown, when the first control signal Vg_d1 is at a low level, the first drive signal Vg1 is at a high level and the second drive signal Vg2 is at a low level, so the power switch Q1 is turned off, corresponding to Figure 7 the t4 stage in; and when the first control signal Vg_d1 is at a high level, the first drive signal Vg1 and the second drive signal Vg2 are complementary signals generated according to the second control signal Vg_d2 and the first control signal Vg_d1, controlling the second switch S2 and the third switch S3 to conduct alternately, so that the voltage of the node D fluctuates near the reference voltage Vref, corresponding to Figure 7The t3 stage; specifically, in the t3 stage, when the first voltage Vr is higher than the reference voltage Vref, the second control signal Vg_d2 is at a high level. At this time, the first drive signal Vg1 is at a low level, the second drive signal Vg2 is at a high level, the second switch S2 is turned off, the third switch S3 is turned on, the gate voltage of the power switch Q1 rises, and the drain voltage drops; when the first voltage Vr is lower than the reference voltage Vref, the second control signal Vg_d2 is at a low level, the first drive signal Vg1 is at a high level, the second drive signal Vg2 is at a low level, the second switch S2 is turned on, the third switch S3 is turned off, the gate voltage of the power switch Q1 drops, and the drain voltage rises, causing the first voltage Vr to always fluctuate near the reference voltage Vref, so that the voltage between the drain of the power switch Q1 and the GND pin of the switch power supply controller U2 is maintained above the normal operating threshold voltage of the power supply circuit 21, thereby ensuring that the power supply circuit 31 always operates during the conduction of the power switch Q1 and supplies power to the logic control circuit 33 and the drive circuit 32.

[0082] According to the switch power supply controller U2 provided by the second embodiment of the invention, when the power switch Q1 is conducting, the drive circuit 32 alternately turns on or off the second switch S2 and the third switch S3 based on the comparison result of the first voltage Vr and the reference voltage Vref, controls the gate voltage of the power switch Q1 to clamp the first voltage Vr at the reference voltage Vref, so that the voltage between the drain of the power switch Q1 and the GND pin of the switch power supply controller U2 is maintained above the normal operating threshold voltage of the power supply circuit 21, to ensure that the power supply circuit 31 is always operating, thereby saving an external power supply capacitor, and there is no need to add an energy storage unit inside the switch power supply controller U2, saving the internal layout area and having a lower cost.

[0083] Figure 8 Fig. shows a circuit schematic diagram of a switch power supply controller according to the third embodiment of the present invention.

[0084] The switch power supply controller provided by the third embodiment of the present invention has basically the same structure as the switch power supply controller provided by the first embodiment of the present invention. The following only describes the differences between the two.

[0085] The drive circuit 42 includes a fourth switch S4 and a fifth switch S5. The fourth switch S4 and the fifth switch S5 are sequentially connected between the drain of the power switch Q1 and the ground. The intermediate node F between the fourth switch S4 and the fifth switch is connected to the gate of the power switch Q1. The control terminals of the fourth switch S4 and the fifth switch S5 are connected to the output terminal of the logic control circuit 43.

[0086] The logic control circuit 43 is used to output a third driving signal Vg3 and a fourth driving signal Vg4 to control the alternating conduction and turn-off of the fourth switch S4 and the fifth switch S5. The node F outputs a driving signal Vg according to the states of the fourth switch S4 and the fifth switch S5 to control the conduction and turn-off of the power switch Q1, thereby controlling the stability of the output voltage Vo.

[0087] Specifically, when the fourth switch S4 is conducting and the fifth switch S5 is turned off, the power switch Q1 is conducting, and the drain voltage of the power switch Q1 supplies power to the driving circuit 42, and the power supply circuit 41 supplies power to the logic control circuit 43. When the fourth switch S4 is turned off and the fifth switch S5 is conducting, the power switch Q1 is turned off, and the power supply circuit 41 supplies power to the logic control circuit 43 and the driving circuit 42. The power supply circuit 41 is any one of the power supply circuits in the above embodiments.

[0088] Figure 9 Fig. shows the signal timing diagram of the switching power supply controller according to the third embodiment of the present invention.

[0089] Combined with Figure 8 and Figure 9 As shown, when the third driving signal Vg3 is at a low level and the fourth driving signal Vg4 is at a high level, the fourth switch S4 is turned off and the fifth switch S5 is conducting. At this time, the voltage of the node F is at a low level, causing the power switch Q1 to turn off. The drain voltage of the power switch Q1 is maintained at the sixth high level, and the inductor current IL gradually decreases from the second current to zero and then remains unchanged. When the third driving signal Vg3 is at a high level and the fourth driving signal Vg4 is at a low level, the fourth switch S4 is conducting and the fifth switch S5 is turned off. At this time, the voltage of the node F rises, causing the power switch Q1 to conduct, and the drain voltage drops. Finally, the voltage of the driving signal Vg is stabilized between the turn-on voltage and the Miller plateau voltage of the power switch Q1, making the voltage of the node B higher than the normal operating threshold voltage of the power supply circuit. Since the power switch Q1 is conducting, the inductor current IL rises, forming a voltage drop across the on-resistance of the MOS transistor. Therefore, the drain voltage of the power switch Q1 gradually rises from the seventh high level to the eighth high level, and the voltage of the driving signal Vg gradually rises from the ninth high level to the tenth high level. The voltage value of the seventh high level always remains above the supply voltage VCC, and the power supply circuit 41 supplies power to the driving circuit 42 and the logic control circuit 43 according to the drain voltage of the power switch Q1.

[0090] According to the switching power supply controller U2 provided by the third embodiment of the present invention, when the power switch tube Q1 is turned on, the fourth switch S4 is turned on and the fifth switch S5 is turned off. The power switch tube Q1 is turned on, and the drain voltage of the power switch tube Q1 supplies power to the drive circuit 42, and the power supply circuit 41 supplies power to the logic control circuit 43, so that the voltage between the drain of the power switch tube Q1 and the GND pin of the switching power supply controller is maintained above the threshold voltage at which the power supply circuit 41 operates normally, thereby clamping its drain voltage to a set voltage, thus saving an external power supply capacitor, and there is no need to add an energy storage unit inside the switching power supply controller U2, saving the internal layout area and having a lower cost.

[0091] Figure 10 The circuit structure diagram of the switching power supply controller according to the fourth embodiment of the present invention is shown.

[0092] Based on any of the first three embodiments, the switching power supply controller U2 of this embodiment further includes a voltage selection module 57, so that the switching power supply controller U2 can supply power to the logic control circuit 53 and the drive circuit 52 through the output voltage Vo.

[0093] The first end of the power supply circuit 51 is connected to the drain of the power switch tube Q1, the second end of the power supply circuit 51 is connected to the first end of the voltage selection module 57, the second end of the voltage selection module 57 is connected to the output end of the switching power supply, the third end of the voltage selection module 57 is connected to the input end of the logic control circuit 53, and the voltage selection module 57 is used to select the power supply circuit 51 or the output voltage Vo to supply power to the logic control circuit 53 and the drive circuit 52 according to the control signal Vg_g output by the logic control circuit 53. The input end of the power supply circuit 51 is connected to the input end of the drive circuit 52, the input end of the drive circuit 52 is connected to the output end of the logic control circuit 53, and the drive circuit 52 outputs a drive signal Vg to the gate of the power switch tube Q1 to control the conduction or cutoff of the power switch tube Q1.

[0094] Specifically, when the switching power supply is just turned on and the power switch tube Q1 is turned on, the logic control circuit 53 outputs a control signal Vg_g to control the power supply circuit 51 to supply power to the logic control circuit 53 and the drive circuit 52; after the power switch tube Q1 is turned off and before the inductor current IL enters the discontinuous state, the logic control circuit 53 outputs a control signal Vg_g to control the output voltage Vo to supply power to the logic control circuit 53 and the drive circuit 52; after the power switch tube Q1 is turned off and the inductor current enters the discontinuous state, the logic control circuit 53 outputs a control signal Vg_g to control the power supply circuit 51 to supply power to the logic control circuit 53 and the drive circuit 52.

[0095] According to the switching power supply controller U2 provided by the fourth embodiment of the present invention, the logic control circuit 53 and the drive circuit 52 are powered by a combination of the output voltage Vo and the power supply circuit 51; when the switching power supply is just turned on and the power switch tube Q1 is conducting, the power supply circuit 51 powers the logic control circuit 53 and the drive circuit 52; after the power switch tube Q1 is turned off and before the inductor current IL enters the discontinuous state, the output voltage Vo is selected to power the logic control circuit 53 and the drive circuit 52; after the power switch tube Q1 is turned off and the inductor current IL enters the discontinuous state, the power supply circuit 51 powers the logic control circuit 53 and the drive circuit 52, so that the switching power supply controller U2 can directly sample the output voltage Vo through the sampling resistor Rcs, thereby saving external power supply capacitors, and there is no need to add an energy storage unit inside the control chip, saving the internal layout area and having a lower cost.

[0096] The present invention also provides a method for supplying power to an electrical circuit in a switching power supply. The switching power supply includes a power switch tube Q1, whose drain terminal is connected to the input voltage Vin and is used to provide an output current to a load according to the input voltage Vin, as Figure 11 shown, and includes the following steps:

[0097] Step S1: Use a logic control circuit to generate a control signal for controlling the switching action of the power switch tube Q1;

[0098] Step S2: Use a drive circuit to generate a drive signal for driving the conduction or turn-off of the power switch tube Q1 according to the control signal;

[0099] Step S3: Convert the drain voltage of the power switch tube Q1 into a power supply voltage to supply power to the electrical circuit;

[0100] In step S3, the electrical circuit includes a logic control circuit and / or a drive circuit. As an embodiment, the power supply circuit supplies power to the logic control circuit and / or the drive circuit according to the drain voltage of the power switch tube Q1. As another embodiment, the drain voltage of the power switch tube Q1 directly supplies power to the drive circuit, and the power supply circuit supplies power to the logic control circuit according to the drain voltage of the power switch tube Q1.

[0101] Step S4: During the conduction stage of the power switch tube Q1, clamp the drain voltage of the power switch tube Q1 at a set voltage through the drive circuit.

[0102] In step S4, the set voltage is higher than the threshold voltage that enables the power supply circuit in the switching power supply to work normally.

[0103] Step S5: When the power switch Q1 is in the off stage, determine whether the inductor current IL of the switching power supply enters the discontinuous state; if the inductor current IL does not enter the discontinuous state, supply power to the electrical circuit according to the output voltage of the switching power supply; if the inductor current IL enters the discontinuous state, convert the drain voltage of the power switch Q1 into the supply voltage and supply power to the electrical circuit.

[0104] In step S5, the step of determining whether the inductor current IL of the switching power supply enters the discontinuous state includes detecting whether the inductor current IL drops to zero. If the inductor current IL drops to zero, it is determined that the inductor current IL enters the discontinuous state; otherwise, it is determined that the inductor current IL does not enter the discontinuous state.

[0105] In steps S4 and S5, it is possible to determine whether the power switch Q1 is in the on state or the off state according to the level state of the drive signal Vg. When the drive signal Vg is at the logical high level, the power switch Q1 is in the on state; when the drive signal Vg is at the logical low level, the power switch Q1 is in the off state.

[0106] According to the embodiments of the present invention as described above, these embodiments do not describe all the details in detail, nor do they limit the invention to only the specific embodiments. Obviously, according to the above description, many modifications and variations can be made. The purpose of selecting and specifically describing these embodiments in this specification is to better explain the principle and practical application of the present invention, so that those skilled in the art can make good use of the present invention and its modifications based on the present invention. The protection scope of the present invention should be defined by the scope defined by the claims of the present invention and their equivalents.

Claims

1. A switching power supply controller for controlling a power conversion circuit, the power conversion circuit being configured to provide an output current to a load based on an input voltage, wherein, The switching power supply controller includes: A power switch transistor, whose drain terminal is connected to the input voltage and is used to control the power transmission of the power conversion circuit; A logic control circuit, which is used to generate a control signal for controlling the switching action of the power switch transistor; A driving circuit, which is connected to the gate terminal of the power switch transistor and is used to drive the power switch transistor to conduct or turn off according to the control signal; and A power supply circuit, which is connected to the drain terminal of the power switch transistor and is used to provide a supply voltage to the driving circuit and the logic control circuit based on the drain terminal voltage of the power switch transistor. Wherein, the driving circuit is further used to clamp the drain terminal voltage of the power switch transistor at a set voltage during the conduction stage of the power switch transistor, so that the power supply circuit still supplies power to the driving circuit and the logic control circuit.

2. The switching power supply controller according to claim 1, wherein, The power supply circuit includes: A junction field effect transistor, whose first conduction terminal is connected to the drain terminal of the power switch transistor, the second conduction terminal is connected to the driving circuit, and the control terminal is grounded; and A low dropout linear regulator, whose input terminal is connected to the second conduction terminal of the junction field effect transistor, and the output terminal is connected to the logic control circuit.

3. The switching power supply controller according to claim 2, wherein, The driving circuit includes: A first voltage regulator diode, whose cathode is connected to the second conduction terminal of the junction field effect transistor, and the anode is connected to the gate terminal of the power switch transistor; A first switch, whose first terminal is connected to the gate terminal of the power switch transistor, the second terminal is grounded, and the control terminal receives the control signal.

4. The switching power supply controller according to claim 3, wherein, The first switch conducts or turns off in response to the control signal, and when the first switch conducts, the power switch transistor turns off, and when the first switch turns off, the power switch transistor conducts. During the conduction stage of the power switch transistor, the driving circuit controls the gate terminal voltage of the power switch transistor between the turn-on voltage and the Miller plateau voltage.

5. The switching power supply controller according to claim 2, wherein, The driving circuit includes: A comparator, which is used to compare a first voltage at the second conduction terminal of the junction field effect transistor with a preset reference voltage to obtain a comparison result; A third switch and a second switch connected in sequence between the supply voltage and the ground, and an intermediate node of the third switch and the second switch is connected to the gate terminal of the power switch transistor; and A drive control circuit, which is used to control the conduction and turn-off of the second switch and the third switch according to the control signal and the comparison result to control the gate terminal voltage of the power switch transistor.

6. The switching power supply controller according to claim 5, wherein, The drive control circuit is configured to alternately conduct or turn off the second switch and the third switch based on the comparison result to control the gate terminal voltage of the power switch transistor to clamp the first voltage at the reference voltage.

7. The switching power supply controller according to claim 6, wherein, The drive control circuit is further configured to control the power switch transistor to conduct when the control signal is a logic high level, and control the power switch transistor to turn off when the control signal is a logic low level. During the conduction stage of the power switch transistor, the driving circuit controls the gate terminal voltage of the power switch transistor between the turn-on voltage and the Miller plateau voltage.

8. The switching power supply controller according to claim 1, wherein the driving circuit includes: A fourth switch and a fifth switch connected in sequence between the drain terminal of the power switch tube and the ground, and a middle node of the fourth switch and the fifth switch is connected to the gate terminal of the power switch tube. Wherein, the fourth switch and the fifth switch are respectively controlled by the logic control circuit to conduct or turn off alternately, so as to control the conduction or turn off of the power switch tube.

9. The switching power supply controller according to claim 8, wherein, The driving circuit is configured to control the power switch tube to conduct when the fourth switch conducts and the fifth switch turns off, and control the power switch tube to turn off when the fourth switch turns off and the fifth switch conducts. During the conduction stage of the power switch tube, the driving circuit controls the gate voltage of the power switch tube between the turn-on voltage and the Miller plateau voltage.

10. The switching power supply controller according to any one of claims 1-9, wherein the switching power supply controller further comprises: A voltage selection module, with a first end connected to the power supply circuit, a second end connected to the output voltage of the switching power supply, and a third end connected to the logic control circuit. The voltage selection module is configured to select the power supply circuit or the output voltage to supply power to the logic control circuit and the driving circuit according to the control signal output by the logic control circuit.

11. The switching power supply controller according to claim 1, wherein, The power conversion circuit includes a buck topology, a flyback topology or a buck-boost topology.

12. The switching power supply controller according to claim 1, wherein the switching power supply controller further comprises: A current detection module, with an input end connected to the source terminal of the power switch tube and an output end connected to the logic control circuit, for detecting the current flowing through the power switch tube.

13. The switching power supply controller according to claim 1, wherein the switching power supply controller further comprises: A voltage detection module, with an output end connected to the logic control circuit, for performing periodic voltage sampling on the output voltage, so that the logic control circuit controls the driving circuit to drive the switching action of the power switch tube according to the result of the periodic voltage sampling, and then adjusts the output voltage.

14. The switching power supply controller according to claim 1, wherein the switching power supply controller further comprises: A protection module, with an output end connected to the logic control circuit, for ensuring that the switching power supply controller acts in time under abnormal conditions.

15. A switching power supply, comprising a power conversion circuit, a sampling resistor, an AC input source, a rectification circuit, and a switching power supply controller, wherein the power conversion circuit is configured to provide an output current to a load according to an input voltage, where The switching power supply controller comprises: A power switch tube, whose drain terminal is connected to the input voltage, for controlling the power transmission of the power conversion circuit; A logic control circuit, for generating a control signal for controlling the switching action of the power switch tube; A driving circuit, connected to the gate terminal of the power switch tube, for driving the power switch tube to conduct or turn off according to the control signal; and A power supply circuit, connected to the drain terminal of the power switch tube, for providing a supply voltage to the driving circuit and the logic control circuit based on the drain voltage of the power switch tube, Wherein, the driving circuit is further configured to clamp the drain voltage of the power switch tube at a set voltage during the conduction stage of the power switch tube, so that the power supply circuit still supplies power to the driving circuit and the logic control circuit.

16. The switching power supply according to claim 15, wherein, The power supply circuit includes: A junction field effect transistor, with the first conducting end connected to the drain end of the power switch transistor, the second conducting end connected to the drive circuit, and the control end grounded; and A low dropout linear regulator, with the input end connected to the second conducting end of the junction field effect transistor and the output end connected to the logic control circuit.

17. The switching power supply according to claim 16, wherein, The drive circuit includes: A first voltage regulator diode, with the cathode of the first voltage regulator diode connected to the second conducting end of the junction field effect transistor and the anode connected to the gate end of the power switch transistor; A first switch, with the first end connected to the gate end of the power switch transistor, the second end grounded, and the control end receiving the control signal.

18. The switching power supply according to claim 17, wherein, The first switch conducts or turns off in response to the control signal, and when the first switch conducts, the power switch transistor turns off, and when the first switch turns off, the power switch transistor conducts. During the conduction stage of the power switch transistor, the drive circuit controls the gate voltage of the power switch transistor between the turn-on voltage and the Miller plateau voltage.

19. The switching power supply according to claim 16, wherein, The drive circuit includes: A comparator for comparing a first voltage at the second conducting end of the junction field effect transistor with a preset reference voltage to obtain a comparison result; A third switch and a second switch connected in sequence between the supply voltage and ground, with the intermediate node of the third switch and the second switch connected to the gate end of the power switch transistor; and A drive control circuit for controlling the conduction and turn-off of the second switch and the third switch according to the control signal and the comparison result to control the gate voltage of the power switch transistor.

20. The switching power supply according to claim 19, wherein, The drive control circuit is configured to alternately conduct or turn off the second switch and the third switch based on the comparison result to control the gate voltage of the power switch transistor to clamp the first voltage at the reference voltage.

21. The switching power supply according to claim 20, wherein, The drive control circuit is further configured to control the power switch transistor to conduct when the control signal is at a logic high level, and control the power switch transistor to turn off when the control signal is at a logic low level. During the conduction stage of the power switch transistor, the drive circuit controls the gate voltage of the power switch transistor between the turn-on voltage and the Miller plateau voltage.

22. According to the switching power supply of claim 15, the drive circuit includes: A fourth switch and a fifth switch connected in sequence between the drain end of the power switch transistor and ground, with the intermediate node of the fourth switch and the fifth switch connected to the gate end of the power switch transistor, wherein the fourth switch and the fifth switch are respectively controlled by the logic control circuit to alternately conduct or turn off to control the conduction or turn-off of the power switch transistor.

23. According to the switching power supply of claim 22, the drive circuit is set to control the power switch transistor to conduct when the fourth switch conducts and the fifth switch turns off, and control the power switch transistor to turn off when the fourth switch turns off and the fifth switch conducts. During the conduction stage of the power switch transistor, the drive circuit controls the gate voltage of the power switch transistor between the turn-on voltage and the Miller plateau voltage.

24. According to the switching power supply of any one of claims 15-23, the switching power supply controller further includes: A voltage selection module, with its first terminal connected to the power supply circuit, its second terminal connected to the output voltage of the switching power supply, and its third terminal connected to the logic control circuit. The voltage selection module is used to select the power supply circuit or the output voltage to supply power to the logic control circuit and the drive circuit according to the control signal output by the logic control circuit.

25. The switching power supply according to claim 15, wherein, The power conversion circuit includes a buck topology, a flyback topology, or a buck-boost topology.

26. The switching power supply according to claim 15, further comprising: A current detection module, with its input terminal connected to the source terminal of the power switch tube and its output terminal connected to the logic control circuit, for detecting the current flowing through the power switch tube.

27. The switching power supply according to claim 15, further comprising: A voltage detection module, with its output terminal connected to the logic control circuit, for performing periodic voltage sampling on the switching output voltage, so that the logic control circuit controls the drive circuit to drive the switching action of the power switch tube according to the result of the periodic voltage sampling, and then adjusts the output voltage.

28. The switching power supply according to claim 15, further comprising: A protection module, with its output terminal connected to the logic control circuit, for ensuring that the switching power supply controller acts in a timely manner under abnormal conditions.

29. A method for supplying power to an electrical circuit in a switching power supply, the switching power supply including a power switching transistor, the drain terminal of which is connected to an input voltage and is configured to provide an output current to a load according to the input voltage, wherein, The method includes: Using a logic control circuit to generate a control signal for controlling the switching action of the power switch tube; Using a drive circuit to generate a drive signal for driving the conduction or cutoff of the power switch tube according to the control signal; The power supply circuit converts the drain voltage of the power switch tube into a supply voltage to supply power to the power-consuming circuit; and During the conduction stage of the power switch tube, clamping the drain voltage of the power switch tube at a set voltage through the drive circuit, so that the power supply circuit still supplies power to the drive circuit and the logic control circuit.

30. The method according to claim 29, wherein, Further comprising: When the power switch tube is in the cutoff stage, determining whether the inductor current of the switching power supply enters discontinuous conduction; If the inductor current does not enter discontinuous conduction, supplying power to the power-consuming circuit according to the output voltage of the switching power supply; If the inductor current enters discontinuous conduction, converting the drain voltage of the power switch tube into a supply voltage to supply power to the power-consuming circuit.

31. The method according to claim 29, wherein, The power-consuming circuit includes the logic control circuit and / or the drive circuit.

32. The method according to claim 29, wherein Further comprising: Judging whether the power switch tube is in the conduction state or the cutoff state according to the level state of the drive signal, wherein, when the drive signal is at a logic high level, the power switch tube is in the conduction state, when the drive signal is at a logic low level, the power switch tube is in the cutoff state, and during the conduction stage of the power switch tube, the drive circuit controls the gate voltage of the power switch tube between the turn-on voltage and the Miller plateau voltage.

33. The method according to claim 30, wherein, The step of determining whether the inductor current of the switching power supply enters discontinuous conduction includes: Detecting whether the inductor current drops to zero. If the inductor current drops to zero, it is determined that the inductor current enters discontinuous conduction, otherwise it is determined that the inductor current does not enter discontinuous conduction.

34. The method according to claim 29, wherein, The set voltage is higher than the threshold voltage at which the power supply circuit in the switching power supply can operate normally.

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