GaN driving power switch power supply system and control circuit thereof

Abstract

The application provides a control circuit used in a GaN-driven power switching power supply system, which is configured to: in the case that the GaN-driven power switching power supply system is in a light load mode, control a first power supply path control switch to be in an off state, and based on a power supply voltage on a power supply capacitor and a first power switch control signal used for controlling the turn-on and turn-off of a GaN power switch, generate a second path switch control signal used for controlling the turn-on and turn-off of a second power supply path control switch and a second power switch control signal used for controlling the turn-on and turn-off of a power drive switch; or in the case that the GaN-driven power switching power supply system is in a non-light load mode, control the second power supply path control switch to be in an off state, and based on the power supply voltage on the power supply capacitor and the first power switch control signal, generate a first path switch control signal used for controlling the turn-on and turn-off of the first power supply path control switch and the second power switch control signal.

Description

Technical Field

[0001] This invention relates to the field of circuits, and more particularly to a GaN-driven power switching power supply system and its control circuit. Background Technology

[0002] As silicon-based power devices approach their theoretical limits, power devices based on wide-bandgap semiconductor materials (such as gallium nitride (GaN)) can significantly improve the operating frequency and efficiency of switching power supply systems due to the absence of body diode effects and lower on-resistance and parasitic capacitance, thus helping to reduce the size and weight of chargers. Currently, the demand for GaN power transistors in the charger market is gradually increasing. Summary of the Invention

[0003] According to an embodiment of the present invention, a control circuit for a GaN-driven power switching power supply system includes a GaN power switch and a power supply capacitor. The control circuit includes a power drive switch connected between the GaN power switch and a circuit reference ground, and a first power supply path control switch and a second power supply path control switch connected in parallel between the GaN power switch and the power supply capacitor. The control circuit is configured to: when the GaN-driven power switching power supply system is in a light-load mode, control the first power supply path control switch to be in a closed state, and generate a second path switch control signal for controlling the opening and closing of the second power supply path control switch and a second power switch control signal for controlling the opening and closing of the power drive switch based on the power supply voltage on the power supply capacitor and the first power switch control signal for controlling the opening and closing of the GaN power switch; or when the GaN-driven power switching power supply system is in a non-light-load mode, control the second power supply path control switch to be in a closed state, and generate a first path switch control signal for controlling the opening and closing of the first power supply path control switch and a second power switch control signal based on the power supply voltage on the power supply capacitor and the first power switch control signal. Attached Figure Description

[0004] The invention can be better understood from the following description of specific embodiments of the invention in conjunction with the accompanying drawings, wherein:

[0005] Figure 1 This is a schematic diagram of the circuit principle of a traditional GaN-driven power switching power supply system.

[0006] Figure 2 This is a schematic diagram of the circuit principle of a GaN-driven power switching power supply system according to an embodiment of the present invention.

[0007] Figure 3 yes Figure 2 The diagram shows the logic structure of the switching power supply control unit.

[0008] Figure 4A yes Figure 2 The diagram shows the waveforms of the main control signals of the GaN-driven power switching power supply system when it is operating normally in non-light load mode.

[0009] Figure 4B yes Figure 3 The power supply voltage detection submodule and drive control module shown are used to implement Figure 4A An example implementation of a portion of the circuitry for the control mechanism shown.

[0010] Figure 4C yes Figure 2 The diagram shows the waveforms of the main control signals of the GaN-driven power switching power supply system when it is operating normally in non-light load mode.

[0011] Figure 5A yes Figure 2 The diagram shows the waveforms of the main control signals of the GaN-driven power switching power supply system when it is operating normally in non-light load mode.

[0012] Figure 5B yes Figure 3 The power supply voltage detection submodule and drive control module shown are used to implement Figure 5A An example implementation of a portion of the circuitry for the control mechanism shown.

[0013] Figure 5C yes Figure 2 The diagram shows the waveforms of the main control signals of the GaN-driven power switching power supply system when it is operating normally in non-light load mode.

[0014] Figure 6 yes Figure 2 The diagram shows the waveforms of the main control signals of the GaN-driven power switching power supply system when it is operating normally under light load mode.

[0015] Figure 7 yes Figure 2 The circuit schematic of a variant of the GaN-driven power switching power supply system is shown.

[0016] Figure 8 yes Figure 7 The diagram shows the waveforms of the main control signals of the GaN-driven power switching power supply system when it is operating normally in non-light load mode.

[0017] Figures 9 to 12 These are various variations of the GaN-driven power switching power supply system according to embodiments of the present invention. Detailed Implementation

[0018] The features and exemplary embodiments of various aspects of the present invention will now be described in detail. Numerous specific details are set forth in the following detailed description to provide a comprehensive understanding of the invention. However, it will be apparent to those skilled in the art that the invention may be practiced without requiring some of these specific details. The following description of embodiments is merely intended to provide a better understanding of the invention by illustrating examples of the invention. The invention is by no means limited to any specific configuration and algorithm presented below, but covers any modifications, substitutions, and improvements to elements, components, and algorithms without departing from the spirit of the invention. Well-known structures and techniques are not shown in the drawings and the following description in order to avoid unnecessarily obscuring the invention. Furthermore, it should be noted that the term "A connected to B" as used herein can mean "A and B are directly connected" or "A and B are indirectly connected via one or more other elements."

[0019] Figure 1 This is a schematic diagram of the circuit principle of a traditional GaN-driven power switching power supply system. For example... Figure 1As shown, the GaN-driven power switching power supply system 100 includes components such as a full-wave rectifier BD1, a switching power supply control unit U1, a high-voltage startup unit U2, a GaN power switch M1, a transformer T1, diodes D1 and D2, an input capacitor C1, an output capacitor C2, a power supply capacitor C3, and a current sensing resistor R2. The switching power supply control unit U1 includes a pulse width modulation (PWM) control module U11, a drive module U12, and a power drive switch M2, used to control the on and off states of the GaN power switch M1. The high-voltage startup unit U2 includes high-voltage components such as a high-voltage resistor or a junction field-effect transistor (JFET) (not shown in the figure), used to charge the power supply capacitor C3 when the system is powered on, enabling the switching power supply control unit U1 to start normally. After the system is powered on, the full-wave rectifier BD1 charges the AC input voltage VAC. The system rectifies and generates a voltage VIN on the input capacitor C1. This voltage VIN charges the power supply capacitor C3 via the high-voltage startup unit U2 and the high-voltage power supply pin (HV pin) and chip power supply pin (VDD pin) of the switching power supply control unit U1. The supply voltage VDD on the power supply capacitor C3 (i.e., the supply voltage VDD of the switching power supply control unit U1) gradually increases. When the supply voltage VDD on the power supply capacitor C3 exceeds the preset undervoltage protection voltage threshold inside the switching power supply control unit U1, the switching power supply control unit U1 begins to control the GaN power switch M1 to turn on and off through the drain of the power drive switch M2 (i.e., the switch control pin (SW pin) of the switching power supply control unit U1). During normal system operation, the supply voltage VDD of the switching power supply control unit U1 is mainly provided by the auxiliary winding L2 of the transformer T1. Here, because the power generation method of supplying power to the switching power supply control unit U1 through the auxiliary winding L2 of the transformer T1 requires additional startup and power supply components, it suffers from drawbacks such as high system cost and low power supply efficiency.

[0020] In view of the above, a GaN-driven power switching power supply system and its control circuit according to an embodiment of the present invention are proposed. Compared with the conventional GaN-driven power switching power supply system 100, the high-voltage starting unit U2 and the auxiliary winding L2 of the transformer T1 can be omitted, thus saving system costs. Furthermore, through internal optimized control, the power supply loss to the switching power supply control unit can be reduced, and stable power supply can be achieved.

[0021] Figure 2 This is a schematic diagram of the circuit principle of a GaN-driven power switching power supply system according to an embodiment of the present invention. Figure 1 and Figure 2As shown, the GaN-driven power switching power supply system 200 differs from 100 in that it omits the high-voltage start-up unit U2 and the auxiliary winding L2 of the transformer T1. Furthermore, the switching power supply control unit U200 includes a PWM control module U201, a power supply module U202, a drive control module U203, a drive module U204, and a power drive switch M2. Specifically, the PWM control module U201 is configured to generate a power switch control signal PWM for controlling the on / off state of the GaN power switch M1, and to generate signals indicating whether the GaN-driven power switching power supply system 200 is in light-load or non-light-load mode. The load mode sensing signal Load_sen is used to generate the power switch control signal PWM_2 for controlling the on and off of the power drive switch M2, based on the load mode sensing signal Load_sen. The power supply module U202 is configured to control the voltage VIN on the input capacitor C1 to charge the power supply capacitor C3 via the GaN power switch M1 based on the load mode sensing signal Load_sen. The drive control module U203 is configured to generate the power switch control signal PWM_2 for controlling the on and off of the power drive switch M2 based on the power switch control signal PWM_2. It should be understood that the PWM control module U201 can generate the power switch control signal PWM through various existing control mechanisms, and can generate the load mode sensing signal Load_sen based on the primary current sensing signal (e.g., the current sensing voltage CS generated by the primary inductor current ILp on the current sensing resistor R2) representing the primary inductor current ILp of the transformer T1 through various existing judgment mechanisms. It should be noted that the power supply capacitor C3 is only charged when the power supply voltage VDD on the power supply capacitor C3 is lower than the preset power supply voltage threshold.

[0022] Figure 3 yes Figure 2 The diagram shows the logic structure of the switching power supply control unit. In some embodiments, such as... Figure 3As shown, the power supply module U202 includes power supply path control switches K102 and K103 connected in parallel between the GaN power switch M1 and the power supply capacitor C3, diode D101, current setting submodule U2021, and power supply voltage detection submodule U2022. Specifically: switch K102 controls the connection between the SW pin and VDD pin of the switching power supply control unit U200; this is a path with a relatively large power supply current. Switch K103 controls the connection between the SW pin of the switching power supply control unit U200 and the VDD pin of the switching power supply control unit U200 via the current setting submodule U201; this is a path with a relatively large power supply current. In terms of the electrical path, this is a path with a relatively small supply current. Diode D101 is located on the power supply path between the SW pin and VDD pin of the switching power supply control unit U200 to prevent current backflow when the voltage at the SW pin of the switching power supply control unit U200 is lower than the voltage at the VDD pin. The current setting submodule U2021 is configured to set the charging current of the power supply capacitor C3. The power supply voltage detection submodule U2022 is configured to detect the supply voltage VCC on the power supply capacitor C3 and optionally generate a power supply voltage indication signal 106 indicating the magnitude comparison between the supply voltage VCC on the power supply capacitor C3 and the corresponding voltage threshold. It should be understood that the current setting submodule U2021 and the power supply voltage detection submodule U2022 can adopt various existing implementation methods, so a detailed description of them is omitted.

[0023] like Figure 3 As shown, in some embodiments, the power supply module U202 further includes a power supply path control switch K104 connected in parallel with switches K102 and K103 between the GaN power switch and the power supply capacitor C3, and the power supply voltage detection submodule U2022 is also configured to generate a power supply path shutdown signal 104 for controlling switch K104 to change from the on state to the off state when the power supply voltage VDD on the power supply capacitor C3 is higher than an internally preset undervoltage protection voltage threshold.

[0024] like Figure 3As shown, in some embodiments, the drive control module U203 is further configured to control switch K102 to be in the off state when the GaN drive power switching power supply system 200 is in a light load mode (e.g., generating a path switch control signal 102 based on the load mode detection signal Load_sen to control switch K102 to be in the off state), and generating path switch control signal 103 and power switch control signal 101 (i.e., power switch control signal PWM_2) based on the supply voltage VDD on the supply capacitor C3 and the power switch control signal PWM; or to control switch K103 to be in the off state when the GaN drive power switching power supply system 200 is in a non-light load mode (e.g., generating a path switch control signal 103 based on the load mode detection signal Load_sen to control switch K103 to be in the off state), and generating path switch control signal 102 and power switch control signal 101 based on the supply voltage VDD on the supply capacitor C3 and the power switch control signal PWM.

[0025] like Figure 2 and Figure 3 As shown, in some embodiments, the operation of the GaN-driven power switching power supply system 200 is as follows: After the system is powered on, switch K104 is in the on state, and switches K102 and K103 are in the off state. The full-wave rectifier BD1 rectifies the AC input voltage VAC and generates a voltage VIN on the input capacitor C1. The voltage VIN charges the power supply capacitor C3 through the GaN power switch M1, switch K104, and current setting submodule U2021. The power supply voltage VDD on the power supply capacitor C3 gradually increases, and the power supply voltage detection unit U2022 detects the power supply voltage VDD on the power supply capacitor C3. When D (i.e., the supply voltage of the switching power supply control unit U200) is higher than the internally preset undervoltage protection voltage threshold, the control switch K104 changes from the on state to the off state. When the system is working normally, the supply voltage detection submodule U2022 provides the supply voltage indication signal 106 to the drive control module U203, and the PWM control module U201 provides the power switch control signal PWM to the drive control module U203. The drive control module U203 generates the power supply path control signals 102 and 103 based on the supply voltage indication signal 106 and the power switch control signal PWM to realize power supply control under different loads.

[0026] Figure 4A yes Figure 2 The diagram shows the waveforms of the main control signals of the GaN-driven power switching power supply system during normal operation in non-light load mode. Figure 4A As shown, in the non-light load mode, the power supply path control signal 103 is at a logic low level (that is, switch K103 is in the off state). Figure 3The switching power supply control unit U200 shown can implement the following control mechanism:

[0027] At time t1, the power switch control signal PWM changes from logic low to logic high (i.e., GaN power switch M1 changes from off to on), the power switch control signal 101 is at logic low (i.e., power drive switch M2 is off), the power supply path control signal 102 changes from logic low to logic high (i.e., switch K102 changes from off to on), and the voltage VIN on the input capacitor C1 begins to supply power to the power supply capacitor C3 through GaN power switch M1 and switch K102.

[0028] During the time interval t1 to t2, the primary inductance current ILp of transformer T1 gradually increases, and the supply voltage VDD on the power supply capacitor C3 gradually increases. When the charging time Tcharge of the power supply capacitor C3 ends (i.e., at time t2), the power switch control signal 101 changes from logic low to logic high (i.e., the power drive switch M2 changes from the off state to the on state), and the power supply path control signal 102 changes from logic high to logic low (i.e., the switch K102 changes from the on state to the off state). The voltage VIN on the input capacitor C1 stops supplying power to the power supply capacitor C3 via the GaN power switch M1 and the switch K102. Here, the charging time Tcharge of the power supply capacitor C3 (i.e., the duration for which switch K102 is in the on state) is negatively correlated with the supply voltage VDD on the power supply capacitor C3; that is, the higher the supply voltage VDD on the power supply capacitor C3, the shorter the charging time Tcharge of the power supply capacitor C3.

[0029] During the period from t2 to t3, the primary inductance current ILp of transformer T1 flows into ground (GND) through GaN power switch M1, power drive switch M2, and current sensing resistor R2 and continues to increase until the power switch control signal PWM changes from logic high level to logic low level (i.e., at time t3).

[0030] During the t3~t4 period, the power switch control signal PWM is at a logic low level, the power switch control signal 101 is at a logic low level (i.e., the power drive switch M2 is in the off state), the power supply path control signals 102 and 103 are both at a logic low level (i.e., switches K102 and K103 are both in the off state), and the primary inductance current ILp of transformer T1 is 0.

[0031] In other words, such as Figure 4AAs shown, when the GaN-driven power switching power supply system 200 is in a non-light load mode, the power supply control unit U200 implements the following control mechanism while controlling switch K103 to be in the off state: when the power switch control signal PWM changes from logic low level to logic high level, it controls switch K102 to change from the off state to the on state and controls power drive switch M2 to remain in the off state; when the power switch control signal PWM is at logic high level and switch K102 changes from the on state to the off state, it controls power drive switch M2 to change from the off state to the on state; and when the power switch control signal PWM changes from logic high level to logic low level, it controls power drive switch M2 to change from the on state to the off state and controls switch K102 to remain in the off state.

[0032] Figure 4B yes Figure 3 The power supply voltage detection submodule and drive control module shown are used to implement Figure 4A An example implementation of a portion of the circuitry for the control mechanism shown. (e.g.) Figure 4B As shown, in some embodiments, when the GaN-driven power switching power supply system 200 is in a non-light-load mode, it can be implemented as follows. Figure 4B The control logic shown is as follows: The power supply voltage detection submodule U2022 generates a power supply voltage divider by dividing the power supply voltage VDD on the power supply capacitor C3, and generates a power supply voltage indication signal 106 using a transconductance amplifier based on the power supply voltage divider and a preset voltage threshold Vth1. Correspondingly, when the power switch control signal PWM is at a logic high level, the drive control module U203 uses a comparator to compare the power supply voltage indication signal 106 with the preset voltage threshold Vth2 to generate a path switch control signal 102, and when the power switch control signal PWM is at a logic low level, it uses a comparator to compare the ground voltage with the power supply voltage threshold Vth2 to generate the path switch control signal 102. In this case, the power supply time Tcharge of the power supply capacitor C3 can be calculated as follows:

[0033] Tcharge = (C11 * Vth2) / (gm * ((VDD * R12 / (R11 + R12) - Vth2)) Equation 1

[0034] Where C11 represents the capacitance value of capacitor C11 connected between the output terminal of the transconductance amplifier and ground, gm represents the transconductance of the transconductance amplifier, and R11 and R12 represent the resistance values ​​of resistors R11 and R12 that form a voltage divider network used to divide the supply voltage VDD on the supply capacitor C3.

[0035] Figure 4C yes Figure 2The diagram shows the waveforms of the main control signals of the GaN-driven power switching power supply system during normal operation in non-light load mode. Figure 4C As shown, in the non-light load mode, the power supply path control signal 103 is at a logic low level (that is, switch K103 is in the off state). Figure 3 The switching power supply control unit U200 shown can implement the following control mechanism:

[0036] When the power switch control signal PWM changes from logic low to logic high, if the supply voltage VDD on the supply capacitor C3 is less than the minimum supply voltage threshold VDD_low, then the control path switch control signal K102 changes from logic low to logic high and controls the power switch control signal 101 to remain at logic low, causing the voltage VIN on the input capacitor C1 to charge the supply capacitor C3 (see...). Figure 4C (at time t1 in the text), otherwise the power switch control signal 101 changes from logic low to logic high and the path switch control signal 102 remains at logic low (see...). Figure 4C At times t4 and t6, the voltage VIN on the input capacitor C1 is not used to charge the power supply capacitor C3;

[0037] When the path switch control signal 102 remains at a logic high level for a preset duration (see...) Figure 4C (t1~t2 in the code), control path switch control signal 102 changes from logic high level to logic low level and control power switch control signal 101 changes from logic low level to logic high level, so that the voltage VIN on input capacitor C1 stops charging power supply capacitor C3.

[0038] In some embodiments, when the GaN-driven power switching power supply system 200 is in a non-light-load mode, it can be implemented as follows: Figure 4C The control logic shown is as follows: The power supply voltage detection submodule U2022 generates a power supply voltage indication signal 106 by comparing the power supply voltage VDD on the power supply capacitor C3 with the minimum power supply voltage threshold VDD_low; correspondingly, when the power switch control signal PWM changes from logic low level to logic high level, if the power supply voltage VDD on the power supply capacitor C3 is lower than the minimum power supply voltage threshold VDD_low, the drive control module U203 controls switch K102 to change from the off state to the on state and controls power drive switch M2 to remain in the off state; otherwise, it controls switch K102 to remain in the off state and controls power drive switch M2 to change from the off state to the on state, and controls switch K2 to change from the on state to the off state when the duration of switch K1 in the on state reaches a preset time.

[0039] Figure 5A yes Figure 2The diagram shows the waveforms of the main control signals of the GaN-driven power switching power supply system during normal operation in non-light load mode. Figure 5A As shown, in the non-light load mode, the power supply path control signal 103 is at a logic low level (that is, switch K103 is in the off state). Figure 3 The switching power supply control unit U200 shown can implement the following control mechanism:

[0040] At time t1, the power switch control signal PWM changes from logic low to logic high (i.e., GaN power switch M1 changes from off to on), the power switch control signal 101 changes from logic low to logic high (i.e., power drive switch M2 changes from off to on), the power supply path control signal 102 is at logic low (i.e., switch K102 is in the off state), and the primary inductance current ILp of transformer T1 begins to increase.

[0041] During the time interval t1 to t2, the primary inductance current ILp of transformer T1 gradually increases until the power switch control signal PWM changes from logic high level to logic low level, the power switch control signal 101 changes from logic high level to logic low level (i.e., the power drive switch M2 changes from the on state to the off state), and the power supply path control signal 102 changes from low level to high level (i.e., the switch K102 changes from the off state to the on state) (i.e., at time t2).

[0042] During the time interval t2~t3, the power switch control signal PWM is at a logic low level, the power switch control signal 101 is at a logic low level (i.e., the power drive switch M2 is in the off state), and the power supply path control signal 102 is at a logic high level (i.e., the switch K102 is in the on state). The voltage VIN on the input capacitor C1 charges the power supply capacitor C3, and the primary inductor current ILp of the transformer T1 continues to increase until the power supply path control signal 102 changes from a logic high level to a logic low level (i.e., the switch K102 changes from the on state to the off state) (i.e., at time t3). Here, the charging time Tcharge of the power supply capacitor C3 (i.e., the duration of the switch K102 being in the on state) is negatively correlated with the supply voltage VDD on the power supply capacitor C3; that is, the higher the supply voltage VDD on the power supply capacitor C3, the shorter the charging time Tcharge of the power supply capacitor C3.

[0043] During the t3~t4 period, the power switch control signal PWM is at a logic low level, the power switch control signal 101 is at a logic low level (that is, the power drive switch M2 is in the off state), and switches K102 and K103 are also in the off state. The primary inductance current ILp of transformer T1 is 0.

[0044] In other words, such as Figure 5AAs shown, when the GaN-driven power switching power supply system 200 is in a non-light load mode, the power supply control unit U200 implements the following control mechanism while controlling switch K103 to be in the off state: when the power switch control signal PWM changes from logic low level to logic high level, the power drive switch M2 is controlled to change from the off state to the on state and switch K102 is controlled to remain in the off state; and when the power switch control signal PWM changes from logic high level to logic low level, the power drive switch M2 is controlled to change from the on state to the off state and switch K102 is controlled to change from the off state to the on state.

[0045] Figure 5B yes Figure 3 The power supply voltage detection submodule and drive control module shown are used to implement Figure 5A An example implementation of a portion of the circuitry for the control mechanism shown. (e.g.) Figure 5B As shown, similarly, in some embodiments, when the GaN-driven power switching power supply system 200 is in a non-light-load mode, it can be implemented as follows. Figure 5A The control logic shown is as follows: The power supply voltage detection module U2022 generates a power supply voltage divider by dividing the power supply voltage VDD on the power supply capacitor C3, and generates a power supply voltage indication signal 106 using a transconductance amplifier based on the power supply voltage divider and a preset voltage threshold Vth1; correspondingly, the drive control module U203 generates a path switch control signal 102 by comparing the power supply voltage indication signal 106 with the preset voltage threshold Vth2 using a comparator when the power switch control signal PWM is at a logic low level, and generates a path switch control signal 102 by comparing the ground voltage with the preset voltage threshold Vth2 using a comparator when the power switch control signal PWM is at a logic high level. In this case, the power supply time Tcharge of the power supply capacitor C3 can be calculated as follows:

[0046] Tcharge = (C11 * Vth2) / (gm * ((VDD * R12 / (R11 + R12) - Vth2)) Equation 2

[0047] Where C11 represents the capacitance value of capacitor C11 connected between the output terminal of the transconductance amplifier and ground, gm represents the transconductance of the transconductance amplifier, and R11 and R12 represent the resistance values ​​of resistors R11 and R12 that form a voltage divider network used to divide the supply voltage VDD on the supply capacitor C3.

[0048] Figure 5C yes Figure 2 The diagram shows the waveforms of the main control signals of the GaN-driven power switching power supply system during normal operation in non-light load mode. Figure 5CAs shown, in the non-light load mode, the power supply path control signal 103 is at a logic low level (that is, switch K103 is in the off state). Figure 3 The switching power supply control unit U200 shown can implement the following control mechanism:

[0049] When the power switch control signal PWM changes from logic high to logic low, if the supply voltage VDD on the supply capacitor C3 is lower than the minimum supply voltage threshold VDD_low, then the control path switch control signal 102 changes from logic low to logic high and controls the power switch control signal 101 to change from logic high to logic low, causing the voltage VIN on the input capacitor C1 to charge the supply capacitor C3 (see...). Figure 5C (at time t1 in the text), otherwise the control path switch control signal 102 remains at a logic low level and the control power switch control signal 101 changes from a logic high level to a logic low level (see...). Figure 5C (times t4 and t6 in the data).

[0050] When the path switch control signal 102 remains at a logic high level for a preset duration (see...) Figure 5C (t1~t2 in the code), control path switch control signal 102 changes from logic high level to logic low level and control power switch control signal 101 changes from logic low level to logic high level, so that the voltage VIN on input capacitor C1 stops charging power supply capacitor C3.

[0051] Similarly, in some embodiments, when the GaN-driven power switching power supply system 200 is in a non-light-load mode, it can be implemented as follows: Figure 5C The control logic shown is as follows: The power supply voltage detection submodule U2022 generates a power supply voltage indication signal 106 by comparing the power supply voltage VDD on the power supply capacitor C3 with the minimum power supply voltage threshold VDD_low; correspondingly, when the power switch control signal PWM changes from logic high level to logic low level, if the power supply voltage VDD on the power supply capacitor C3 is lower than the minimum power supply voltage threshold VDD_low, the drive control module U203 controls switch K102 to change from off state to on state and controls power drive switch M2 to change from on state to off state; otherwise, switch K102 remains off state and power drive switch M2 changes from on state to off state, and when the duration of switch K102 being on state reaches a preset duration, switch K102 changes from on state to off state.

[0052] Figure 6 yes Figure 2 The diagram shows the waveforms of the main control signals of the GaN-driven power switching power supply system during normal operation in light-load mode. Figure 6As shown, in light load mode, the power supply path control signal 102 is at a logic low level (i.e., switch K102 is in the off state). When the power switch control signal PWM is at a logic low level, the power switch control signal 101 is at a logic low level (i.e., power drive switch M2 is in the off state), and the power supply path control signal 103 is at a logic high level (i.e., switch K103 is in the on state), which can realize efficient charging of the power supply capacitor C3.

[0053] Figure 7 yes Figure 2 The variation of the GaN-driven power switching power supply system shown is illustrated. Figure 8 yes Figure 7 The diagram shows the waveforms of the main control signals of the GaN-driven power switching power supply system during normal operation in non-light load mode. It should be noted that, although... Figure 2 The GaN-driven power switching power supply system shown adopts a flyback architecture, but combined with... Figure 2 The switching power supply control unit U200 described in the GaN-driven power switching power supply system shown can also be applied to... Figures 9 to 12 The GaN-driven power switching power supply system shown. That is, the power supply control unit U200 can also be used with a boost architecture (see...). Figure 9 and Figure 10 ), buck architecture (see Figure 11 and Figure 12 GaN-driven power switching power supply systems with either a buck-boost architecture or a step-up architecture. Figures 9 to 12 In the GaN-driven switching power supply system shown, the inductor current IL1 flowing through inductor L1 is related to the system load of the GaN-driven power switching power supply system. At this time, the switching power supply control unit U200 can generate a load mode sensing signal Load_sen that indicates whether the GaN-driven power switching power supply system is in light load mode or non-light load mode based on the current sensing signal characterizing the inductor current IL1 (the current sensing voltage CS generated by the inductor current IL1 on the current sensing resistor R2) through various existing judgment mechanisms.

[0054] This invention can be implemented in other specific forms without departing from its spirit and essential characteristics. For example, the algorithm described in a particular embodiment can be modified without departing from the basic spirit of the invention. Therefore, the present embodiments are to be regarded as exemplary rather than limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and all changes falling within the meaning and scope of the claims and their equivalents are thus included within the scope of the invention.

Claims

1. A control circuit for use in a GaN-driven power switching power supply system, the GaN-driven power switching power supply system comprising a GaN power switch and a power supply capacitor, the control circuit comprising a power drive switch connected between the GaN power switch and a circuit reference ground, and a first power supply path control switch and a second power supply path control switch connected in parallel between the GaN power switch and the power supply capacitor, and the control circuit being configured to: When the GaN-driven power switching power supply system is in light-load mode, the first power supply path control switch is controlled to be in the off state, and a second path switch control signal for controlling the on and off of the second power supply path control switch and a second power switch control signal for controlling the on and off of the power drive switch are generated based on the supply voltage on the power supply capacitor and the first power switch control signal for controlling the on and off of the GaN power switch; or When the GaN-driven power switching power supply system is in a non-light load mode, the second power supply path control switch is controlled to be in the off state, and a first path switch control signal and a second power switch control signal are generated based on the power supply voltage on the power supply capacitor and the first power switch control signal to control the on and off of the first power supply path control switch.

2. The control circuit according to claim 1, wherein, The GaN-driven power switching power supply system also includes a transformer, and the control circuit is further configured to: Based on the primary current sensing signal characterizing the primary inductance current of the transformer, a load mode sensing signal is generated to indicate whether the GaN-driven power switching power supply system is in light load mode or non-light load mode.

3. The control circuit according to claim 1, wherein, The GaN-driven power switching power supply system further includes an inductor, the inductor current flowing through the inductor being related to the system load of the GaN-driven power switching power supply system, and the control circuit is further configured to: Based on the current sensing signal characterizing the inductor current, a load mode sensing signal is generated to indicate whether the GaN-driven power switching power supply system is in light load mode or non-light load mode.

4. The control circuit according to claim 1, wherein, The control circuit further includes a third power supply path control switch connected in parallel with the first power supply path control switch and the second power supply path control switch between the GaN power switch and the power supply capacitor, and the control circuit is further configured to: When the system is powered on, the third power supply path control switch is controlled to be in the on state, and when the power supply voltage on the power supply capacitor is detected to be higher than the undervoltage protection voltage threshold preset inside the control circuit, the third power supply path control switch is controlled to change from the on state to the off state.

5. The control circuit according to claim 1, wherein, When the GaN-driven power switching power supply system is in a non-light load mode, the duration for which the first power supply path control switch is in the on state is negatively correlated with the power supply voltage on the power supply capacitor.

6. The control circuit according to claim 1 is further configured to, when the GaN drive power switching power supply system is in a non-light load mode: When the first power switch control signal changes from logic low level to logic high level, the first power supply path control switch is controlled to change from the off state to the on state, and the power drive switch is controlled to remain in the off state. When the first power switch control signal is at a logic high level and the first power supply path control switch changes from the on state to the off state, the power drive switch is controlled to change from the off state to the on state; and When the first power switch control signal changes from logic high level to logic low level, the first power supply path control switch is kept in the off state and the power drive switch is changed from the on state to the off state.

7. The control circuit according to claim 1 is further configured to, when the GaN drive power switching power supply system is in a non-light load mode: When the first power switch control signal changes from logic low to logic high, if the supply voltage on the power supply capacitor is lower than the minimum supply voltage threshold, then the first power supply path control switch is controlled to change from the off state to the on state and the power drive switch remains in the off state; otherwise, the first power supply path control switch remains in the off state and the power drive switch changes from the off state to the on state. When the first power supply path control switch is in the on state for a preset duration, the first power supply path control switch is controlled to change from the on state to the off state.

8. The control circuit according to claim 1 is further configured to, when the GaN drive power switching power supply system is in a non-light load mode: When the first power switch control signal changes from logic low to logic high, the first power supply path control switch remains off and the power drive switch changes from off to on; and When the first power switch control signal changes from logic high level to logic low level, it controls the first power supply path control switch to change from off state to on state and controls the power drive switch to change from on state to off state.

9. The control circuit according to claim 1 is further configured to, when the GaN drive power switching power supply system is in a non-light load mode: When the first power switch control signal changes from logic high to logic low, if the supply voltage on the power supply capacitor is lower than the minimum supply voltage threshold, then the first power supply path control switch is controlled to change from the off state to the on state and the power drive switch is controlled to change from the on state to the off state; otherwise, the first power supply path control switch remains in the off state and the power drive switch is controlled to change from the on state to the off state. When the first power supply path control switch is in the on state for a preset duration, the first power supply path control switch is controlled to change from the on state to the off state.

10. The control circuit according to claim 1 is further configured to, when the GaN drive power switching power supply system is in a light-load mode: When the first power switch control signal is at a logic low level, the power drive switch is controlled to be in the off state and the second power supply path control switch is controlled to be in the on state.

11. The control circuit according to claim 4 further includes a diode connected between the source of the GaN power switch and the first power supply path switch, the second power supply path switch, and the third power supply path switch, for preventing current backflow when the source voltage of the GaN power switch is lower than the power supply voltage on the power supply capacitor.

12. A GaN-driven power switching power supply system, comprising the control circuit according to any one of claims 1 to 11.

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