A control circuit and power supply method for controlling a power switch tube in a switching power supply

Abstract

This invention provides a control circuit and power supply method for controlling a power switching transistor in a switching power supply. The control circuit includes a logic control circuit, a high-voltage power supply circuit, and a power supply control circuit. The high-voltage power supply circuit draws power from the line voltage terminal and stores energy in an energy storage circuit under the control of the power supply control circuit. The control circuit further includes a drive circuit and a current source for powering it. The drive circuit drives the power switching transistor to switch on and off states to adjust the output signal of the switching power supply. The current source draws power from the line voltage terminal and is further coupled to the drive circuit to supply power to the control terminal of the power switching transistor. The control circuit and power supply method provided by this invention reduce fluctuations in the power supply signal of the logic control circuit, improve anti-interference capability, provide controllable turn-on speed of the power switching transistor's control terminal, suppress noise, and have a small energy storage capacity that is easy to integrate.

Description

Technical Field

[0001] This invention relates to the field of electronics, and specifically, but not limited to, a control circuit and power supply method for controlling power switching transistors in a switching power supply. Background Technology

[0002] In switching power supplies, to provide a stable power supply to the control chip, external capacitors are typically used in conjunction with power supply control circuitry to stabilize the power supply to the control chip at a certain value, ensuring its normal operation. With technological advancements, switching power supplies are becoming increasingly integrated. To save costs and improve reliability, more peripheral components are integrated into the chip itself, such as integrating the power supply capacitors into the control chip.

[0003] Meanwhile, control chips typically require two power supplies: one to power lower-voltage units such as logic cells, and the other to power higher-voltage power drive circuits. However, these two power supplies are prone to mutual interference. For example, the power drive circuit requires significant energy, and supplying it can cause voltage drops and signal interference on lower-voltage units, leading to instability in the control circuit signals.

[0004] One approach involves providing two independent power supply paths, with separate capacitors for the logic unit and the power drive circuit, respectively. This reduces the capacitance of individual capacitors while providing interference immunity, thus integrating the capacitors into the integrated circuit. However, this method requires two linear power supplies for each capacitor, resulting in a complex structure, high design difficulty, and high cost.

[0005] In view of this, there is a need to provide a new structure or control method in order to solve at least some of the above problems. Summary of the Invention

[0006] In response to at least one or more of the problems in the background art, the present invention proposes a control circuit and power supply method for controlling power switching transistors in a switching power supply.

[0007] According to one aspect of the present invention, a control circuit for controlling a power switch in a switching power supply includes: a high-voltage power supply circuit, the input terminal of which is coupled to a line voltage terminal and the input terminal of the power switch; a power supply control circuit, the input terminal of which is coupled to the output terminal of the high-voltage power supply circuit, and the output terminal of which is coupled to an energy storage circuit and a logic control circuit for supplying power to the logic control circuit; a logic control circuit, the input terminal of which receives a feedback signal characterizing the output signal of the switching power supply, and the output terminal of which provides a logic control signal; a drive circuit, the input terminal of which is coupled to the output terminal of the logic control circuit, and the output terminal of which is coupled to the control terminal of the power switch, the drive circuit being used to drive the power switch to conduction and cutoff states under the control of the logic control signal, so as to adjust the output signal of the switching power supply; and a current source, the line voltage terminal of which is coupled to draw power from the line voltage terminal, and the current source being further coupled to the drive circuit for supplying power to the control terminal of the power switch.

[0008] Optionally, the control circuit further includes a switch connected in series with a current source, and the control circuit charges the control terminal of the power switching transistor by controlling the switch to turn on and off.

[0009] Optionally, the current source is a constant current source when it is turned on.

[0010] Optionally, the high-voltage power supply circuit includes a junction field-effect transistor, the power supply control circuit includes a low-dropout linear regulator circuit, and the energy storage circuit includes a capacitor. The input terminal of the low-dropout linear regulator circuit is coupled to the output terminal of the field-effect transistor, and the output terminal of the low-dropout linear regulator circuit is coupled to the first terminal of the capacitor and the power input terminal of the logic control circuit. The second terminal of the capacitor is grounded.

[0011] Optionally, the control circuitry can be integrated into a single semiconductor chip.

[0012] Optionally, the current source includes a constant current source and a current mirror, wherein the input arm of the current mirror is coupled to the constant current source and the output arm of the current mirror is coupled to the drive circuit. When the current in the output arm flows to the control terminal of the power switch, the voltage at the control terminal rises to control the power switch to turn on.

[0013] Optionally, the current source further includes a switch and a third transistor, the input arm or output arm of the switch and the current mirror are coupled in series, the input arm of the third transistor and the current mirror are coupled in series, and the driving circuit includes a pull-up transistor and a pull-down transistor, wherein the first end of the pull-up transistor is coupled to the output end of the current mirror, the second end of the pull-up transistor is coupled to the control end of the power switch and the first end of the pull-down transistor, and the second end of the pull-down transistor is grounded; when the logic control signal indicates that the power switch is turned on, the control circuit controls the switch, the pull-up transistor and the third transistor to turn on, and the pull-down transistor to turn off; when the logic control signal indicates that the power switch is turned off, the control circuit controls the pull-up transistor and the third transistor to turn off, and the pull-down transistor to turn on.

[0014] Optionally, the input of the current source can be coupled to the output of the high-voltage power supply circuit.

[0015] According to another aspect of the present invention, a power supply method for a control circuit is proposed, wherein the control circuit is used to control a power switching transistor in a switching power supply. The control circuit includes a logic control circuit and a drive circuit. The drive circuit amplifies the logic control signal output by the logic control circuit to drive the power switching transistor. The power supply method includes: drawing power from the line voltage terminal and providing a voltage source to the energy storage circuit via the power supply control circuit to power the logic control circuit; and drawing power from the line voltage terminal and powering the drive circuit via a controllable current source.

[0016] Optionally, powering the drive circuit by drawing power from the line voltage terminal through a controllable current source includes: when the logic control signal indicates that the power switch is turned on, the controllable current source is turned on, and the current flows from the line voltage terminal to the control terminal of the power switch, increasing the control terminal voltage; when the control terminal voltage is greater than the turn-on threshold, the power switch is turned on.

[0017] The control circuit and power supply method proposed in this invention eliminate or reduce signal interference between the power supply of the drive circuit and the power supply of the logic control circuit. The conduction speed of the control terminal of the power switch is controllable, noise is suppressed, and the second power supply for the drive circuit does not need to use energy storage elements and power supply control circuits, thus reducing circuit complexity and cost. The energy storage elements of the power supply for the logic control circuit are used independently, with small capacity and easy integration. Attached Figure Description

[0018] The accompanying drawings are provided to further illustrate the invention and, together with the description, serve to explain embodiments of the invention, but do not constitute a limitation thereof. In the drawings:

[0019] Figure 1 A control circuit according to an embodiment of the present invention is shown;

[0020] Figure 2 A control circuit according to a specific embodiment of the present invention is shown;

[0021] Figure 3 A power supply drive circuit for driving a power switching transistor according to an embodiment of the present invention is shown;

[0022] Figure 4 A power supply drive circuit according to another embodiment of the present invention is shown;

[0023] Figure 5 A schematic flowchart of a power supply method for a control circuit according to an embodiment of the present invention is shown. Detailed Implementation

[0024] To further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, and not for limiting the scope of the claims of the present invention.

[0025] The description in this section pertains to only a few typical embodiments, and the present invention is not limited to the scope of the embodiments described. Combinations of different embodiments, substitution of some technical features in different embodiments, and substitution of similar or identical prior art with some technical features in the embodiments are also within the scope of the description and protection of the present invention.

[0026] The terms "coupled" or "connected" in this specification include both direct and indirect connections. An indirect connection is a connection made through an intermediate medium, such as a connection through an electrically conductive medium like a conductor, which may contain parasitic inductance or capacitance. It can also be a connection through intermediate circuits or components described in the embodiments of this specification. Indirect connections may also include connections through other active or passive devices that achieve the same or similar function, such as connections through switches, signal amplification circuits, follower circuits, or other circuits or components. "Multiple" or "more" indicates two or more.

[0027] Figure 1A control circuit 100 according to an embodiment of the present invention is shown. The control circuit 100 is used to control the power switch 16 in a switching power supply. Preferably, the control circuit 100 is fabricated on the same semiconductor substrate and integrated into the same semiconductor chip. The control circuit 100 includes two independent power supplies, which are used to power the logic control circuit 13 and the drive circuit 15, respectively. The power supply for the logic control circuit 13 has an independent power supply control circuit 12 and an energy storage circuit C1. The power supply for the drive circuit 15 is provided by a current source 14, which does not draw power from the energy storage circuit C1. This ensures that the drive circuit 15 does not affect the power supply capability and signal fluctuation of the logic control circuit 13 when driving the power switch 16. At the same time, it allows the energy storage circuit C1 to be miniaturized and easily integrated into the chip. By providing power to the drive circuit 15 through the current source 14, the voltage at the control terminal of the power switch 16 gradually increases before it is turned on, eliminating or reducing the noise that may be generated at the moment the power switch 16 is turned on in the prior art. Simultaneously, the second power supply for the drive circuit 15 does not require energy storage components and power supply control circuits, reducing circuit complexity and cost. Specifically, the control circuit 100 includes a high-voltage power supply circuit 11, a power supply control circuit 12, an energy storage circuit C1, a logic control circuit 13, a current source 14, and a drive circuit 15. In one embodiment, the control circuit 100 is fabricated on the same semiconductor substrate and integrated on the same semiconductor chip; the illustrated embodiment shows integration within a single control chip. Chip integration enhances integration density, eliminates external capacitors outside the integrated circuit chip or package, simplifies external circuitry, and increases system reliability. In another embodiment, the energy storage circuit C1 may not be integrated on the same semiconductor substrate but rather packaged in the same electronic package. The input terminal of the logic control circuit 13 receives a feedback signal FB characterizing the output signal of the switching power supply, and the output terminal of the logic control circuit 13 provides a logic control signal CTL. The feedback signal terminal FB can receive a feedback signal characterizing the output voltage Vout of the switching power supply output terminal, or a feedback signal characterizing the output current. The input terminal of the drive circuit 15 is coupled to the output terminal of the logic control circuit 13, and the output terminal of the drive circuit 15 is coupled to the control terminal of the power switch 16. The drive circuit 15 is used to control the conduction and cutoff of the power switch 16 through the power supply of the current source 14 under the control of the logic control signal CTL, so as to adjust the corresponding output signal of the switching power supply. The input terminal of the high-voltage power supply circuit 11 is coupled to the line voltage terminal HV and the input terminal of the power switch 16. The high-voltage power supply circuit 11 is used to obtain energy from the line voltage terminal HV when it is turned on, so as to provide power to the logic control circuit 13 in the control circuit 100. In one embodiment, the line voltage terminal HV is the voltage after full-wave rectification or half-wave rectification of the AC mains power supply and filtering.The input terminal of the power switch 16 is coupled to the line voltage terminal HV. When the power switch 16 is turned on, the switching power supply obtains energy from the line voltage terminal HV and converts the HV voltage source into an output signal of the switching power supply to power the load downstream of the switching power supply, and stores the energy in devices such as inductors and capacitors. When the power switch 16 is turned off, the energy stored in the inductors and capacitors continues to power the load. In one embodiment, the switching power supply includes a buck circuit, the input terminal of the power switch 16 is coupled to the line voltage terminal HV, the output terminal of the power switch 16 is coupled to the first terminal of the rectifier and the first terminal of the inductor, the second terminal of the rectifier is coupled to system ground, and the second terminal of the inductor is coupled to the output capacitor and the load. In one embodiment, when the power switch 16 is turned off and / or its conduction is shallow, the high-voltage power supply circuit 11 is turned on to supply power to the energy storage circuit C1 and the logic control circuit 13 under the control of the power supply control circuit 12, and to selectively control the current source 14 to conduct to supply power to the drive circuit 15, driving the power switch 16 to turn on. Preferably, the current source 14 is a constant current source when it is working normally after being turned on. By controlling the working time of the current source, the voltage at the control terminal of the power switch tube can be easily controlled. The description of a constant current source does not mean that its current is fixed. For example, it is possible that its current will rise during the conduction phase. Under the control of the power supply control circuit 12, the energy storage circuit C1 obtains electrical energy from the output terminal of the high-voltage power supply circuit 11 and provides a first supply voltage VDD to power the logic control circuit 13. Preferably, the input terminal of the power supply control circuit 12 is coupled to the output terminal of the high-voltage power supply circuit 11, the first terminal of the energy storage circuit C1 is coupled to the output terminal of the power supply control circuit 12 and the power input terminal of the logic control circuit 13, the second terminal of the energy storage circuit C1 is coupled to the reference ground, and the first supply voltage VDD on the first terminal of the energy storage circuit C1 is used to power the logic control circuit 13. The power supply control circuit 12 isolates the energy storage circuit C1 from the high-voltage power supply circuit 11, and also isolates it from the current source 14. The power supply control circuit 12 controls the voltage value of the first supply voltage VDD output by the energy storage circuit C1, providing a stable voltage source with appropriate amplitude for the logic control circuit. The input terminal of the current source 14 is coupled to the line voltage terminal HV, and the current source 16 is coupled to the drive circuit 15 to supply power to the control terminal of the power switch 16. The current source 14 draws power from the line voltage terminal HV to power the drive circuit 15, driving the power switch 16. In one embodiment, the current source 14 draws power directly from the line voltage terminal HV without passing through the high-voltage power supply circuit 11. In another embodiment, the current source 14 is coupled to the output terminal of the high-voltage power supply circuit 11, and then coupled to the line voltage terminal HV through the high-voltage power supply circuit 11. Thus, the supply voltage VDD used to power the logic control circuit 13 has an independent power supply control circuit 12 and energy storage circuit C1; the power supply used to power the drive circuit 15 will not interfere with the supply voltage VDD; the logic control circuit 13 is less prone to signal fluctuations; and the system reliability is high.Furthermore, the energy storage circuit C1 is only used to power the logic control circuit 13, so the requirement for the capacitor value is low, which is conducive to its integration into the control chip. The drive circuit 15 is powered by the current source 14, and the voltage at the control terminal of the power switch 16 changes gradually, which has better controllability and helps to reduce noise.

[0028] Figure 2 A control circuit 200 according to a specific embodiment of the present invention is shown. In this embodiment, the high-voltage power supply circuit 21 includes a junction field-effect transistor (JFET), and the power switching transistor 26 includes a metal-oxide-semiconductor field-effect transistor (MOSFET). The drain of the JFET is coupled to the drain of the MOSFET, the source of the JFET is coupled to the input terminal of the power supply control circuit 22, and the gate of the MOSFET is connected to the output terminal of the drive circuit 25. The power supply control circuit 22 includes a low-dropout linear regulator (LDO), and the energy storage circuit C1 includes a capacitor. The input terminal of the low-dropout linear regulator 22 is coupled to the output terminal of the JFET, and the output terminal of the low-dropout linear regulator 22 is coupled to the first terminal of the capacitor C1 and the power input terminal of the logic control circuit 23 to supply power to the logic control circuit 23. The second terminal of the capacitor C1 is coupled to reference ground GND. The power supply control circuit 22 can be an LDO or a switching converter circuit, used to step down the voltage at the output terminal of the high-voltage power supply circuit 21 and convert it into a stable voltage to provide a stable supply voltage VDD to the power input terminal of the logic control circuit 23. In the illustrated embodiment, reference ground GND is coupled to the second terminal of the current sensing resistor Rcs, where the first terminal of the current sensing resistor Rcs is coupled to the source of the power switch 26. In this embodiment, the control circuit 200 includes a switch K connected in series with the current source 24. The control circuit 200 controls the conduction of the power switch 26 by charging the parasitic capacitance of the control terminal of the power switch 26 through controlling the on and off states of the switch K. In a preferred embodiment, the current source 24 includes a constant current source.

[0029] exist Figure 2In the illustrated embodiment, the logic control circuit 23 receives feedback signals FB and CS, representing the output voltage of the switching power supply, and uses them to provide the logic control signal CTL. Signal FB is the output voltage feedback signal, representing the output voltage of the switching power supply; signal CS is the current feedback signal, representing the current flowing through the power switch 26. Specifically, the logic control circuit 23 may include a first comparator circuit 231, a second comparator circuit 232, and a trigger circuit 233. In the illustrated embodiment, the two input terminals of the first comparator circuit 231 are respectively coupled to the output voltage signal feedback terminal FB and the output voltage reference signal Vref. The first comparator circuit 231 is used to compare the feedback signal FB, which describes the output voltage of the switching power supply, and the output voltage reference signal Vref. The output terminal of the first comparator circuit 231 is coupled to the set input terminal of the trigger circuit 233. The two input terminals of the second comparator circuit 232 are respectively coupled to the current sampling terminal CS and the peak reference signal Vipk. The output terminal of the second comparator circuit is coupled to the reset terminal of the trigger circuit 233. When the output voltage is lower than a preset value, the first comparator circuit 231 outputs a high level, the trigger circuit 233 is set, the logic control signal CTL is high, and the drive circuit 25, powered by the controllable current source 24, raises the gate voltage of the power switch 26 based on the high-level logic control signal CTL, turning on the power switch 26. When the current flowing through the power switch 26 rises to the peak threshold, the second comparator circuit 232 outputs a high level, the trigger circuit 233 is reset, and the logic control signal CTL is low, used to turn off the power switch 26. In other embodiments, the logic control circuit may have other structures and control methods. Preferably, the control circuit 200 is fabricated on the same semiconductor substrate, such as a silicon substrate, i.e., integrated into a semiconductor chip, without discrete capacitors, either in or outside its electronic package, thus simplifying the external circuitry.

[0030] Figure 3A power supply drive circuit for driving a power switch 36 according to an embodiment of the present invention is shown. The power supply drive circuit includes a current source, a switch K, a drive circuit, and a third transistor K3. The current source includes a constant current source 31 and a current mirror 32. The drive circuit includes a pull-up transistor K1 for pulling up voltage and a pull-down transistor K2 for pulling down voltage. The input arm of the current mirror 32 is coupled to the constant current source 31, and the output arm of the current mirror 32 is coupled to the drive circuit. The switch K and the input arm of the current mirror are coupled in series. The current source is used to provide a controllable current source for the drive circuit. In another embodiment, the switch K may also be coupled in series with the output arm of the current mirror. The switch K and the third transistor K3 may also be considered as part of the current source. The pull-up transistor K1 in the drive circuit is connected in series with the output arm of the current mirror 32. Specifically, the first terminal of the pull-up transistor K1 is coupled to the output terminal of the current mirror 32, and the second terminal of the pull-up transistor K1 is coupled to the control terminal of the power switch 36. The first terminal of the pull-down transistor K2 is coupled to the control terminal of the power switch 36, and the second terminal of the pull-down transistor K2 is grounded. The control terminals of both the pull-up transistor K1 and the pull-down transistor K2 are controlled by the logic control signal CTL, and their on and off states are complementary. However, the complementary states allow for a dead time to prevent simultaneous conduction. The drive circuit can also be considered as sharing some circuitry with the current mirror, and the pull-up transistor K1 can also be considered as part of the current mirror. The third transistor K3 is connected in series with the input arm of the current mirror, and its control terminal is coupled to the control terminal of the pull-up transistor K1, exhibiting the same on and off states as the pull-up transistor K1. The input terminal of the current source is coupled to the line voltage terminal HV to draw power from the line voltage terminal HV. In another embodiment, the pull-up transistor in the drive circuit can also be located at the input terminal of the current mirror.

[0031] When the logic control signal CTL requires the power switch 36 to be turned on, the switch control circuit 33 controls the switch K, pull-up transistor K1, and third transistor K3 to be turned on, and controls the pull-down transistor K2 to be turned off. The output arm of the current mirror 32 outputs a current proportional to the constant current source 31 and flows to the control terminal of the power switch 36, charging the parasitic capacitance at the control terminal. The control terminal voltage GATE of the power switch 36 increases. When the control terminal voltage GATE rises above the turn-on threshold of the power switch 36, the power switch 36 is turned on. By setting the current value of the constant current source 31 and turning on the switch K for a period of time, the gate voltage of the power switch 36 can be controlled to control the conduction state of the power switch 36. When the power switch 36 is fully turned on, the switch K can be turned off to stop charging the control terminal of the power switch 36 and maintain the control terminal voltage of the power switch 36. When the logic control signal CTL requires the power switch 36 to turn off, the switch control circuit 33 controls the pull-down transistor K2 to turn on, and the pull-up transistors K1 and K3 to turn off. The capacitor at the control terminal of the power switch 36 is rapidly discharged, pulling the voltage GATE down to ground potential, and the power switch 36 turns off. Through this conduction method, the voltage GATE at the control terminal of the power switch 36 can be controlled by a constant current source, allowing control of the turn-on speed of the power switch 36 and suppressing system noise. Before the power switch 36 turns on, the line voltage HV is at a relatively high level, allowing the current source to operate stably until the power switch 36 is fully turned on. With this setup, the power supply circuit for the drive circuit does not require energy storage components; the power switch can be driven simply using a current source, saving costs. Simultaneously, the power supply circuit for the power drive circuit also does not require linear voltage regulator circuits or other power supply control circuits, simplifying the circuit design.

[0032] In another embodiment, the current source may take other forms, such as excluding... Figure 3 The current mirror shown.

[0033] Figure 4 A power supply drive circuit according to another embodiment of the present invention is shown. In this embodiment, the input terminal of the current mirror is coupled to the voltage terminal HV through a JFET 42. The JFET 42 can share a common... Figure 2The high-voltage power supply circuit 21 shown contains a JFET. JFET 42 can also be a JFET independent of the high-voltage power supply circuit 21. The current source includes a constant current source 41 and a current mirror 43. In this embodiment, switch K is coupled to the output arm of current mirror 43. When the logic control signal CTL requires power switch 46 to be turned on, JFET 42 is turned on, switch K, pull-up transistor K1, and third transistor K3 are turned on, and pull-down transistor K2 is turned off. The current output from the output arm of current mirror 43 is proportional to the current from constant current source 41. This current flows to the control terminal of power switch 46 and increases the control terminal voltage GATE. When the control terminal voltage GATE is greater than the turn-on threshold, power switch 46 is turned on. In another embodiment, third transistor K3 may not be included.

[0034] Figure 5 A schematic flowchart 500 of a power supply method for a control circuit according to an embodiment of the present invention is shown. This method can be applied to, for example... Figures 1-4 The control circuit shown is used to control the power switching transistor in the switching power supply. The control circuit includes a logic control circuit and a drive circuit. The drive circuit amplifies the control signal output by the logic control circuit to drive the power switching transistor. The power supply method 500 includes a first step 501: drawing power from the line voltage terminal and providing a voltage source to the energy storage circuit via the power supply control circuit to power the logic control circuit. In one embodiment, when the power switching transistor is off, the power supply control circuit draws power from the line voltage terminal. In another embodiment, the power supply control circuit draws power from the line voltage terminal via a high-voltage power supply circuit. The high-voltage power supply circuit may employ a JFET device. In another embodiment, when the power switching transistor is off and when the power switching transistor is slightly turned on and the line voltage terminal voltage is high, the high-voltage power supply circuit is controlled to turn on, causing the power supply control circuit to draw power from the line voltage terminal. In one embodiment, the power supply control circuit includes an LDO for stabilizing the supply voltage on the energy storage circuit near a preset value, providing a stable voltage source to power the logic control circuit. The method includes a step 502: drawing power from the line voltage terminal and supplying power to the drive circuit via a controllable current source to control the turn-on of the power switching transistor. A controllable current source consists of a current source and a switch that controls its output current. The controllable current source turns on when a logic control signal indicates that the power switch is turned on (e.g., by controlling...). Figure 4(As shown, switch K, pull-up transistor K1, and the third transistor K3 of the current mirror input arm are turned on.) Current flows from the line voltage terminal to the control terminal of the power switch, boosting the control terminal voltage. When the control terminal voltage exceeds the turn-on threshold, the power switch turns on. In this power supply method, the power supply control circuit isolates the energy storage circuit from the line voltage terminal. The energy storage circuit is dedicated to powering the logic control circuit. The current source in the second power supply circuit does not affect the voltage on the energy storage circuit in the first power supply circuit. The logic control circuit will not generate erroneous logic control signals due to fluctuations in the supply voltage, improving the system's anti-interference capability and making the system control more reliable. Preferably, the current source includes a constant current source. The voltage at the control terminal of the power switch can be controlled by controlling the conduction time of the constant current source, thereby reliably turning on the power switch. That is, the power unit is driven by a constant current source, which can control the conduction speed of the power unit and suppress system noise. With this configuration, the second power supply circuit for powering the drive circuit to turn on the power switch does not require an additional power supply control circuit and energy storage circuit, simplifying the circuit design and reducing the system size and cost. The energy storage circuit in the first power supply circuit is only used to power the logic control circuit, which reduces the capacitance requirement of the energy storage circuit, makes it easier to miniaturize and integrate the energy storage circuit, reduces system cost, simplifies the peripheral circuit, and improves system reliability.

[0035] The description and application of the present invention herein are illustrative and not intended to limit the scope of the invention to the embodiments described above. The effects or advantages described in the specification may not be apparent in actual experimental cases due to uncertainties in specific conditions or other factors, and such descriptions are not intended to limit the scope of the invention. Variations and modifications to the embodiments disclosed herein are possible, and various substitutions and equivalents of the components in the embodiments are well known to those skilled in the art. It should be understood by those skilled in the art that the invention can be implemented in other forms, structures, arrangements, proportions, and with other components, materials, and parts without departing from the spirit or essential characteristics of the invention. Other variations and modifications can be made to the embodiments disclosed herein without departing from the scope and spirit of the invention.

Claims

1. A control circuit for controlling a power switching transistor in a switching power supply, comprising: The high-voltage power supply circuit has its input terminal coupled to the voltage terminal of the power switch transistor. The power supply control circuit has its input terminal coupled to the output terminal of the high-voltage power supply circuit, and its output terminal coupled to the energy storage circuit and the logic control circuit to supply power to the logic control circuit. The logic control circuit receives a feedback signal representing the output signal of the switching power supply at its input terminal, and provides a logic control signal at its output terminal. The driver circuit has its input terminal coupled to the output terminal of the logic control circuit, and its output terminal coupled to the control terminal of the power switching transistor. The driver circuit is used to drive the power switching transistor to turn on and off under the control of the logic control signal, so as to adjust the output signal of the switching power supply. as well as The current source is coupled to the voltage terminal, and the current source is further coupled to the drive circuit to supply power to the control terminal of the power switch.

2. The control circuit as described in claim 1 further includes a switch connected in series with a current source, wherein the control circuit charges the control terminal of the power switching transistor by controlling the switch to turn on and off.

3. The control circuit as described in claim 1, wherein the current source is a constant current source in the working state.

4. The control circuit as described in claim 1, wherein the high-voltage power supply circuit includes a junction field-effect transistor, the power supply control circuit includes a low-dropout linear regulator circuit, the energy storage circuit includes a capacitor, the input terminal of the low-dropout linear regulator circuit is coupled to the output terminal of the field-effect transistor, the output terminal of the low-dropout linear regulator circuit is coupled to the first terminal of the capacitor and the power input terminal of the logic control circuit, and the second terminal of the capacitor is grounded.

5. The control circuit as described in claim 1 is integrated into a semiconductor chip.

6. The control circuit as described in claim 1, wherein the current source includes a constant current source and a current mirror, wherein the input arm of the current mirror is coupled to the constant current source, and the output arm of the current mirror is coupled to the drive circuit, and when the current in the output arm flows to the control terminal of the power switch, the voltage at the control terminal rises to control the power switch to turn on.

7. The control circuit of claim 6, wherein the current source further includes a switch and a third transistor, the input arm or output arm of the switch and the current mirror are connected in series, the input arm of the third transistor and the current mirror are connected in series, the drive circuit includes a pull-up transistor and a pull-down transistor, wherein the first end of the pull-up transistor is coupled to the output end of the current mirror, the second end of the pull-up transistor is coupled to the control end of the power switch and the first end of the pull-down transistor, and the second end of the pull-down transistor is grounded; when the logic control signal indicates that the power switch is turned on, the control circuit controls the switch, the pull-up transistor and the third transistor to be turned on, and the pull-down transistor to be turned off; when the logic control signal indicates that the power switch is turned off, the control circuit controls the pull-up transistor and the third transistor to be turned off, and the pull-down transistor to be turned on.

8. The control circuit as claimed in claim 1, wherein the input terminal of the current source is coupled to the output terminal of the high-voltage power supply circuit.

9. A power supply method for a control circuit, wherein the control circuit controls a power switching transistor in a switching power supply, the control circuit including a logic control circuit and a drive circuit, the drive circuit amplifying a logic control signal output by the logic control circuit to drive the power switching transistor, the power supply method comprising: Power is drawn from the line voltage terminal and supplied to the energy storage circuit via the power supply control circuit, which in turn supplies power to the logic control circuit. as well as Power is drawn from the line voltage terminal and supplied to the drive circuit through a controllable current source.

10. The power supply method of claim 9, wherein powering the drive circuit from the line voltage terminal through the controllable current source comprises: When the logic control signal indicates that the power switch is turned on, the controllable current source is turned on, and the current flows from the line voltage terminal to the control terminal of the power switch, increasing the control terminal voltage. When the control terminal voltage is greater than the turn-on threshold, the power switch is turned on.

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