CN-113098416-B - Operational amplifier circuit and switching power supply

Abstract

The invention discloses an operational amplifier circuit and a switching power supply, wherein a bias current signal which is in a certain proportion relation with the input voltage or the output voltage of the switching power supply is generated through a current generating circuit, the bias current signal is controlled to be reduced along with the increase of the input voltage or the output voltage, and the transconductance of the operational amplifier circuit can be adjusted, so that the transconductance of an operational amplifier of the switching power supply is high when the output voltage is low, the transconductance of the operational amplifier is low when the input voltage or the output voltage is high, the bandwidth of a system when the input voltage or the output voltage is high is reduced, and the stability of the system under different conditions is ensured.

Inventors

• DOU XUNJIN

Assignees

• 杰华特微电子（杭州）有限公司

Dates

Publication Date

20260512

Application Date

20210401

Claims (7)

1. 1. An operational amplifier circuit is used in a switching power supply, wherein the operational amplifier circuit comprises a current generating circuit and an error amplifying circuit, The current generation circuit receives an input voltage or an output voltage of the switching power supply to generate a bias current signal proportional to the input voltage or the output voltage, wherein the bias current signal decreases with an increase in the input voltage or the output voltage; The error amplifying circuit comprises a current input end, a first voltage input end and a second voltage input end, wherein the current input end receives the bias current signal, the first voltage input end and the second voltage input end respectively receive differential voltage signals to output error amplifying signals, Wherein the current generating circuit comprises a voltage-current converting circuit and a first current source, The first current source outputs a first current signal, the voltage-to-current conversion circuit receives the input voltage or the output voltage to generate a second current signal according to the input voltage or the output voltage, the second current signal is in a proportional relation with the input voltage or the output voltage, The current generation circuit comprises a second current source, the second current source outputs a third current signal, the third current signal is smaller than the first current signal, the difference value between the first current signal and the second current signal is used as a difference current signal, and the signal obtained by adding the third current signal and the difference current signal is used as the bias current signal.
2. 2. The operational amplifier circuit of claim 1, wherein the current generation circuit comprises a first current mirror circuit, a second current mirror circuit, and a third current mirror circuit, The first current mirror circuit receives the input voltage or the output voltage through a first resistor to generate the second current signal; The first current signal and the second current signal have the same current direction, the input end of the second current mirror circuit is connected to the current branch node of the first current signal and the second current signal, the difference current signal is input to the second current mirror circuit, and the second current mirror circuit outputs a first intermediate current signal; the third current mirror circuit receives the first intermediate current signal to output a second intermediate current signal, the second intermediate current signal and the third current signal have the same current direction, and the signal obtained by superposition of the second intermediate current signal and the third current signal is used as the bias current signal.
3. 3. The operational amplifier circuit of claim 1, wherein when the operational amplifier circuit receives the input voltage, the operational amplifier circuit is connected to an input of the switching power supply to sample a voltage of the switching power supply input as the input voltage; When the operational amplification circuit receives the output voltage, the operational amplification circuit is connected with the output end of the switching power supply to sample the voltage of the output end of the switching power supply as the output voltage.
4. 4. The operational amplifier circuit of claim 1, wherein the switching power supply comprises a main power switch and an inductor, the common node of the main power switch and the inductor being a switching node, When the operational amplifier circuit receives the output voltage, the operational amplifier circuit comprises a filter circuit, and the filter circuit is connected with the switch node to filter the voltage of the switch node and then serve as the output voltage of the switch power supply.
5. 5. The operational amplifier circuit of claim 1, wherein the error amplification circuit is a CMOS transconductance amplifier.
6. 6. A switching power supply includes a power stage circuit and a control circuit, wherein, The power stage circuit receives an input voltage, converts the input voltage into a desired output voltage output through a switching action of a switching tube, The control circuit comprises the operational amplification circuit according to any one of claims 1-5, and the control circuit controls the switching action of a switching tube in the power stage circuit according to an error amplification signal generated by the operational amplification circuit.
7. 7. The switching power supply of claim 6 wherein the operational amplifier circuit receives the output voltage feedback signal and a reference voltage representative of a desired output voltage as a differential voltage signal for the error amplifier circuit.

Description

Operational amplifier circuit and switching power supply Technical Field The invention relates to the technical field of power electronics, in particular to an operational amplifier circuit and a switching power supply. Background In the internal compensation scheme of the power circuit, the same set of compensation parameters are generally adopted to meet the requirements of different application scenes, the transconductance of the operational amplifier is expected to be high at low output voltage, when the feedforward capacitor is present at high output voltage, the system bandwidth can be too large under the condition that the compensation parameters are fixed, and the system is easy to approach or exceed half of the switching frequency, so that the system becomes unstable, and the transconductance of the operational amplifier needs to be properly reduced to reduce the bandwidth and improve the system stability. Therefore, it is difficult for the internal compensation scheme to achieve both dynamic response at low output voltage and stability at high output voltage, and optimization of performance cannot be achieved. Disclosure of Invention In view of the above, the present invention is directed to an operational amplifier circuit and a switching power supply for solving the technical problem that the dynamic response at low output voltage and the stability at high output voltage are difficult to be compatible in the prior art. The technical scheme is that the operational amplification circuit is used in a switching power supply and comprises a current generation circuit and an error amplification circuit, wherein the current generation circuit receives input voltage or output voltage of the switching power supply to generate a bias current signal proportional to the input voltage or the output voltage, the bias current signal is reduced along with the increase of the input voltage or the output voltage, the error amplification circuit comprises a current input end, a first voltage input end and a second voltage input end, the current input end receives the bias current signal, and the first voltage input end and the second voltage input end respectively receive differential voltage signals to output an error amplification signal. Preferably, the current generating circuit comprises a voltage-to-current converting circuit and a first current source, The voltage-current conversion circuit receives the input voltage or the output voltage to generate a second current signal according to the input voltage or the output voltage, and the difference value between the first current signal and the second current signal is used as the bias current signal. Preferably, the second current signal is proportional to the input voltage or the output voltage. Preferably, the current generating circuit includes a second current source that outputs a third current signal smaller than the first current signal, a difference between the first current signal and the second current signal is used as a difference current signal, and a signal obtained by adding the third current signal and the difference current signal is used as the bias current signal. Preferably, the current generating circuit comprises a first current mirror circuit, a second current mirror circuit and a third current mirror circuit, wherein the first current mirror circuit receives the input voltage or the output voltage through a first resistor to generate the second current signal, the first current signal and the second current signal have the same current direction, the input end of the second current mirror circuit is connected to a current branch node of the first current signal and the second current signal, the difference current signal is input to the second current mirror circuit, the second current mirror circuit outputs a first intermediate current signal, the third current mirror circuit receives the first intermediate current signal to output a second intermediate current signal, the second intermediate current signal and the third current signal have the same current direction, and the signal obtained by superposition of the second intermediate current signal and the third current signal is used as the bias current signal. Preferably, when the operational amplifier circuit receives the input voltage, the operational amplifier circuit is connected with the input end of the switching power supply to sample the voltage of the input end of the switching power supply as the input voltage, and when the operational amplifier circuit receives the output voltage, the operational amplifier circuit is connected with the output end of the switching power supply to sample the voltage of the output end of the switching power supply as the output voltage. Preferably, the switching power supply includes a main power switch tube and an inductor, wherein a common node of the main power switch tube and the inductor is a switch node, and when the operational ampli