CN-114189133-B - Control circuit of power converter

Abstract

A control circuit of a power converter comprises a sensing circuit, a ramp signal generator, an error amplifier, a comparator and a pulse width modulation circuit. The sensing circuit is coupled to the first output circuit to provide a current sensing signal. The ramp signal generator is coupled to the sensing circuit and receives the current sensing signal to provide a ramp signal. The error amplifier receives the reference voltage and the output feedback voltage of the power converter to provide an error amplified signal. The comparator is coupled to the ramp signal generator and the error amplifier and receives the ramp signal and the error amplified signal to provide a control signal. The pulse width modulation circuit is coupled between the comparator and the first output circuit, receives the control signal and provides a pulse width modulation signal to control the first output circuit. The ramp signal generator adjusts the slope of the ramp signal according to the current sensing signal. The invention can avoid ringing phenomenon of the output voltage of the power converter after pumping/unloading so as to improve the stability of system output.

Inventors

• Hong Weixiu

Assignees

• 力智电子股份有限公司

Dates

Publication Date

20260505

Application Date

20200915

Claims (6)

1. 1. A control circuit of a power converter coupled to a first output circuit, wherein the control circuit comprises: A sensing circuit coupled to the first output circuit for providing a current sensing signal; a ramp signal generator coupled to the sensing circuit and receiving the current sensing signal to provide a ramp signal; An error amplifier for receiving a reference voltage and an output feedback voltage of the power converter to provide an error amplified signal; a comparator coupled to the ramp signal generator and the error amplifier for providing a control signal according to the ramp signal and the error amplification signal, and A pulse width modulation circuit coupled between the comparator and the first output circuit for receiving the control signal and providing a pulse width modulation signal to control the first output circuit, The ramp signal generator adjusts the slope of the ramp signal according to the current sensing signal, and the ramp signal generator comprises a current source, a switch and a voltage source, wherein one end of the current source is coupled between the sensing circuit and the comparator, one end of the switch is coupled with the current source, the other end of the switch is coupled with the voltage source, the voltage source is coupled between the switch and a grounding end, and the switch is controlled by the control signal to be selectively conducted.
2. 2. The control circuit of claim 1 wherein the ramp signal generator generates the falling portion of the ramp signal based on a predetermined current and the current sense signal.
3. 3. The control circuit of claim 1, wherein the sensing circuit comprises a current mirror, the current mirror generates the current sensing signal according to an inductor current in the first output circuit, and the current sensing signal has a proportional relationship with the inductor current.
4. 4. The control circuit of claim 1 wherein the ramp generator comprises a capacitor having one end coupled between the sensing circuit and the comparator and the other end coupled to a ground, the other end of the current source being coupled to the ground.
5. 5. The control circuit of claim 1 wherein the greater the current sense signal, the slower the slope of the ramp signal is adjusted.
6. 6. The control circuit of claim 1, further coupled to a second output circuit, wherein the sensing circuit comprises a current mirror, the current mirror generates the current sensing signal according to a first inductor current in the first output circuit and a second inductor current in the second output circuit, and the current sensing signal has a proportional relationship with the first inductor current and the second inductor current.

Description

Control circuit of power converter Technical Field The present invention relates to power converters, and more particularly, to a control circuit for a power converter. Background In a conventional power conversion circuit, an output capacitor is connected in series between an output terminal and a ground terminal, and the power conversion circuit performs feedback control by using a capacitance value of the output capacitor and an equivalent series resistance (Equivalent series resistor, ESR) thereof. When a capacitive element (e.g., a ceramic capacitor) with a small parasitic resistance is used as the output capacitor, the feedback control of the power conversion circuit is only affected by the output capacitor, so that a phase difference (PHASE DIFFERENCE) is generated between the Ripple (Ripple) of the output voltage and the pwm signal, thereby affecting the stability of the system. For example, as shown in fig. 1, when the resistance of the equivalent series resistance of the output capacitor (hereinafter referred to as the output resistor) is small, the output voltage VOUT of the power conversion circuit generates Ringing (Ringing) that oscillates up and down several times away from the reference voltage VEAP after the load/unload operation, which in turn causes the inductor current IL of the power conversion circuit to become unstable, which seriously affects the stability of the system. Disclosure of Invention In view of the above, the present invention provides a control circuit of a power converter to effectively solve the above-mentioned problems encountered in the prior art. The invention provides a control circuit of a power converter, which comprises a sensing circuit, a ramp signal generator, an error amplifier, a comparator and a pulse width modulation circuit. The sensing circuit is coupled to the first output circuit to provide a current sensing signal. The ramp signal generator is coupled to the sensing circuit and receives the current sensing signal to provide a ramp signal. The error amplifier receives the reference voltage and the output feedback voltage of the power converter to provide an error amplified signal. The comparator is coupled to the ramp signal generator and the error amplifier and provides a control signal according to the ramp signal and the compensation signal. The pulse width modulation circuit is coupled between the comparator and the first output circuit, receives the control signal and provides a pulse width modulation signal to control the first output circuit. The ramp signal generator adjusts the slope of the ramp signal according to the current sensing signal. In one embodiment, the ramp signal generator generates a falling portion of the ramp signal according to the preset current and the current sensing signal. In one embodiment, the sensing circuit includes a current mirror. The current mirror generates a current sensing signal according to the inductance current in the first output circuit, and the current sensing signal and the inductance current have a proportional relation. In one embodiment, the ramp signal generator includes a capacitor and a current source. One end of the capacitor is coupled between the sensing circuit and the comparator, and the other end of the capacitor is coupled to the ground terminal. One end of the current source is coupled between the sensing circuit and the comparator, and the other end of the current source is coupled to the ground. In one embodiment, the ramp signal generator further comprises a switch and a voltage source. One end of the switch is coupled with the capacitor and the current source, and the other end of the switch is coupled with the voltage source. The voltage source is coupled between the switch and the ground. The switch is controlled by the control signal to be selectively conducted. In one embodiment, the greater the current sensing signal, the slower the slope of the ramp signal is. In one embodiment, the control circuit is further coupled to the second output circuit. The sensing circuit includes a current mirror. The current mirror generates a current sensing signal according to a first inductance current in the first output circuit and a second inductance current in the second output circuit, and the current sensing signal has a proportional relation with the first inductance current and the second inductance current. Compared with the prior art, the control circuit of the power converter adjusts the falling slope of the ramp signal according to the sensed output current (inductance current) of the power converter, so that the control circuit of the power converter can effectively avoid Ringing (Ringing) of the output voltage of the power converter after pumping/unloading even if the output resistance is smaller, so that the output current of the power converter is kept stable, and the stability of system output can be effectively improved. The advantages and spirit of the present invention will be