CN-114696578-B - Power converter and control circuit thereof

Abstract

The application provides a control circuit of a power converter, which comprises a switching transistor and an output inductor, wherein one end of the output inductor is an output node, the other end of the output inductor is a switching node, the control circuit is used for generating a control signal and controlling the switching transistor in the power converter, the control circuit comprises a resistance capacitance oscillation network, an on-time generation circuit and a control signal generation circuit, the resistance capacitance oscillation network is connected to two ends of the output inductor and is used for generating an oscillation signal containing a feedback slope compensation component according to voltage change on the two ends of the output inductor, when the power converter works in an inductor current interruption mode, the resistance capacitance oscillation network is disconnected with the output inductor in a period that an inductor current is in zero current so that voltage on the two ends of the output inductor does not influence the oscillation signal, and the on-time generation circuit is used for generating the control signal and controlling the switching transistor in the power converter.

Inventors

• SUN SHUNGEN
• YANG HANFEI

Assignees

• 上海晶丰明源半导体股份有限公司

Dates

Publication Date

20260505

Application Date

20201231

Claims (20)

1. 1. A control circuit of a power converter, the power converter comprising a switching transistor and an output inductor, one end of the output inductor being an output node, the other end of the output inductor being a switching node, the control circuit being for generating a control signal for controlling the switching transistor in the power converter, the control circuit comprising: The resistance-capacitance oscillation network is connected to two ends of the output inductor and is used for generating an oscillation signal containing a feedback slope compensation component according to voltage changes at two ends of the output inductor, wherein when the power converter works in an inductor current intermittent mode, the resistance-capacitance oscillation network is disconnected with the output inductor in a period that the inductor current is in zero current so that the voltage at two ends of the output inductor does not influence the oscillation signal; A comparator having a first input for inputting a reference signal, a second input for inputting a feedback signal, and an output for outputting a comparison signal, the oscillation signal being incorporated in the reference signal or the input feedback signal; The on-time generating circuit starts timing according to the comparison signal and generates an on-time signal; And a control signal generating circuit for generating a control signal for controlling a switching transistor in the power converter according to the comparison signal and the on-time signal.
2. 2. The control circuit of claim 1, wherein the oscillation signal is equal to the feedback signal.
3. 3. The control circuit of claim 2, wherein the resistive-capacitive oscillating network comprises a first switch, a first resistor and a first capacitor, the first resistor, the first switch and the first capacitor being serially connected in sequence and then connected across the output inductor, a common terminal of the first switch and the first capacitor outputting the oscillating signal.
4. 4. The control circuit of claim 2, wherein the resistive-capacitive oscillating network comprises a first switch, a first resistor and a first capacitor, the first switch, the first resistor and the first capacitor being serially connected in sequence and then connected across the output inductor, a common terminal of the first resistor and the first capacitor outputting the oscillating signal.
5. 5. The control circuit of claim 1, wherein the feedback signal is generated after superposition of the oscillating signal with a signal representative of the output voltage.
6. 6. The control circuit of claim 5, wherein the RC network comprises a second switch, a single-stage or multi-stage RC circuit, and a differential amplifier, the second switch and the single-stage or multi-stage RC circuit being connected in series and then connected across the output inductor, the differential amplifier having a first input, a second input, and an output, the first input and the second input of the differential amplifier being connected across a capacitor or a resistor in the single-stage or multi-stage RC circuit, the output of the differential amplifier outputting an oscillating signal.
7. 7. The control circuit of claim 6, wherein when the RC network comprises a single-stage RC circuit, the second switch and the resistor and the capacitor in the single-stage RC circuit are sequentially connected in series and then connected across the output inductor, and the first input terminal and the second input terminal of the differential amplifier are respectively connected across the resistor or the capacitor of the single-stage RC circuit.
8. 8. The control circuit of claim 6, wherein when the RC oscillating network includes a multi-stage RC circuit, a resistor and a capacitor in a first stage RC circuit of the multi-stage RC circuit are connected in series with the second switch in sequence and then connected to two ends of the output inductor, and a first input terminal and a second input terminal of the differential amplifier are respectively connected to two ends of a resistor or a capacitor of a highest stage of the multi-stage RC circuit.
9. 9. The control circuit according to claim 3 or 4, further comprising a zero-crossing detection circuit, the zero-crossing detection circuit comprising: A first comparator having a first end, a second end and an output end, wherein the first end receives a sensing signal representing the inductor current of the power converter, the second end receives a zero crossing detection threshold, and the output end outputs a zero crossing prompt signal; and the RS trigger module outputs a zero-crossing detection result signal, and updates the zero-crossing detection result signal based on the zero-crossing prompt signal before the next working period at the end of the current working period.
10. 10. The control circuit of claim 9, wherein the zero crossing detection circuit further comprises a timer, the zero crossing detection result signal causing the first switch to open for a time period greater than or equal to a duration of oscillation of the switching node during a duty cycle when in inductor current interrupt mode.
11. 11. The control circuit according to any one of claims 6 to 8, characterized by further comprising a zero-crossing detection circuit comprising: A first comparator having a first end, a second end and an output end, wherein the first end receives a sensing signal representing the inductor current of the power converter, the second end receives a zero crossing detection threshold, and the output end outputs a zero crossing prompt signal; and the RS trigger module outputs a zero-crossing detection result signal, and updates the zero-crossing detection result signal based on the zero-crossing prompt signal before the next working period at the end of the current working period.
12. 12. The control circuit of claim 11, wherein the zero crossing detection circuit further comprises a timer, the zero crossing detection result signal causing the second switch to open for a duration greater than or equal to a duration of oscillation of the switching node during one duty cycle of the inductor current interrupt mode.
13. 13. A power converter, comprising: a switching transistor; The output inductor is characterized by comprising an output node at one end, and a switch node at the other end; a control circuit, comprising: The resistance-capacitance oscillation network is connected to two ends of the output inductor and is used for generating an oscillation signal containing a feedback slope compensation component according to voltage changes at two ends of the output inductor, wherein when the power converter works in an inductor current intermittent mode, the resistance-capacitance oscillation network is disconnected with the output inductor in a period that the inductor current is in zero current so that the voltage at two ends of the output inductor does not influence the oscillation signal; A comparator having a first input for inputting a reference signal, a second input for inputting a feedback signal, and an output for outputting a comparison signal, the oscillation signal being incorporated in the reference signal or the input feedback signal; The on-time generating circuit starts timing according to the comparison signal and generates an on-time signal; And a control signal generating circuit for generating a control signal for controlling a switching transistor in the power converter according to the comparison signal and the on-time signal.
14. 14. The power converter of claim 13, wherein the oscillating signal is equal to the feedback signal.
15. 15. The power converter of claim 14, wherein the rc oscillating network comprises a first switch, a first resistor and a first capacitor, the first resistor, the first switch and the first capacitor being serially connected in sequence and then connected across the output inductor, a common terminal of the first switch and the first capacitor outputting the oscillating signal.
16. 16. The power converter of claim 14, wherein the rc oscillating network comprises a first switch, a first resistor and a first capacitor, the first switch, the first resistor and the first capacitor being serially connected in sequence and then connected across the output inductor, the common terminal of the first resistor and the first capacitor outputting the oscillating signal.
17. 17. The power converter of claim 13, wherein the oscillation signal is superimposed with a signal representative of the output voltage to generate the feedback signal.
18. 18. The power converter of claim 17, wherein the RC network comprises a second switch, a single-stage or multi-stage RC circuit, and a differential amplifier, the second switch and the single-stage or multi-stage RC circuit being connected in series across the output inductor, the differential amplifier having a first input, a second input, and an output, the first input and the second input of the differential amplifier being connected across a capacitor or resistor in the single-stage or multi-stage RC circuit, the output of the differential amplifier outputting an oscillating signal.
19. 19. The power converter of claim 18, wherein when a single-stage RC circuit is included in the RC network, the second switch and the resistor and capacitor in the single-stage RC circuit are serially connected in sequence and then connected across the output inductor, and the first input terminal and the second input terminal of the differential amplifier are respectively connected across the resistor or capacitor of the single-stage RC circuit.
20. 20. The power converter of claim 18, wherein when the RC oscillating network includes a multi-stage RC circuit, a resistor and a capacitor in a first stage RC circuit of the multi-stage RC circuit are connected in series with the second switch in sequence and then connected across the output inductor, and the first input terminal and the second input terminal of the differential amplifier are respectively connected across a resistor or a capacitor of a highest stage of the multi-stage RC circuit.

Description

Power converter and control circuit thereof Technical Field The present application relates to power electronics, and more particularly, to a power converter and a control circuit thereof. Background The power converter has various control modes, such as a voltage control mode, a current control mode, a hysteresis control mode, a constant time conduction mode and the like. The constant on-time control mode has excellent dynamic response speed and high light load efficiency, and is widely applied to power converters. Meanwhile, in order to realize stable operation of the power converter in both the inductor current continuous mode (Continuous Current Mode, CCM) and the inductor current discontinuous mode (Discontinuous Current Mode, DCM), further requirements are put on the design and implementation of the power converter. Content of the application The application aims to solve the technical problem of providing a power converter, a control circuit and a control method thereof, and the power converter can realize steady-state operation in both an inductor current continuous mode and an inductor current intermittent mode. In order to solve the above technical problems, the present application provides a control circuit of a power converter, the power converter includes a switching transistor and an output inductor, one end of the output inductor is an output node, the other end of the output inductor is a switching node, the control circuit is configured to generate a control signal to control the switching transistor in the power converter, the control circuit includes: The resistance-capacitance oscillation network is connected to two ends of the output inductor and is used for generating an oscillation signal containing a feedback slope compensation component according to voltage changes at two ends of the output inductor, wherein when the power converter works in an inductor current intermittent mode, the resistance-capacitance oscillation network is disconnected with the output inductor in a period that the inductor current is in zero current so that the voltage at two ends of the output inductor does not influence the oscillation signal; A comparator having a first input for inputting a reference signal, a second input for inputting a feedback signal, and an output for outputting a comparison signal, the oscillation signal being incorporated in the reference signal or the input feedback signal; the on-time generating circuit starts timing according to the comparison signal or the control signal and generates an on timing signal; and the control signal generating circuit is used for generating a control signal according to the comparison signal and the on timing signal and controlling a switching transistor in the power converter. In an embodiment of the application, the oscillation signal is equal to the feedback signal. In an embodiment of the present application, the rc oscillation network includes a first switch, a first resistor and a first capacitor, where the first resistor, the first switch and the first capacitor are sequentially connected in series and then connected to two ends of the output inductor, and a common end of the first switch and the first capacitor outputs the oscillation signal. In an embodiment of the present application, the rc oscillation network includes a first switch, a first resistor and a first capacitor, where the first switch, the first resistor and the first capacitor are sequentially connected in series and then connected to two ends of the output inductor, and a common end of the first resistor and the first capacitor outputs the oscillation signal. In an embodiment of the application, the feedback signal is generated after superposition of the oscillating signal with a signal characterizing the output voltage. In one embodiment of the application, the resistor-capacitor oscillation network comprises a second switch, a single-stage or multi-stage RC circuit and a differential amplifier, wherein the second switch and the single-stage or multi-stage RC circuit are connected in series and then connected to two ends of the output inductor, the differential amplifier is provided with a first input end, a second input end and an output end, the first input end and the second input end of the differential amplifier are connected to two ends of a capacitor or a resistor in the single-stage or multi-stage RC circuit, and the output end of the differential amplifier outputs an oscillation signal. In an embodiment of the present application, when the RC network includes a single-stage RC circuit, the second switch and the resistor and the capacitor in the single-stage RC circuit are sequentially connected in series and then connected to two ends of the output inductor, and the first input terminal and the second input terminal of the differential amplifier are respectively connected to two ends of the resistor or the capacitor of the single-stage RC circuit. In an embodiment o