Slope compensation circuit and method for switching power supply

Abstract

The invention provides a slope compensation circuit and a slope compensation method for a switching power supply. The duty ratio D of the switching power supply ranges from 0 to DMAX, and the DMAX is a maximum duty ratio. The slope compensation circuit comprises a current source, a capacitor, a first switching tube, a voltage-to-current circuit, a first mirror circuit and a second mirror circuit, wherein a first current is generated by the output end of the current source; the capacitor is charged by the first current; voltages at the two ends of the capacitors are recorded as curve voltages; the first end of the first switching tube is connected with the first end of the capacitor, and the second end of the first switching tube is grounded; the first switching tube is switched on to reset the curve voltages when the duty ratio D belongs to [0, DS] and is switched off when the duty ratio D belongs to [DS, DMAX], and the DS is a preset value between 0 and the DMAX; the voltage-to-current circuit is used for following the curve voltages and converting the followed curve voltages into second current; the first mirror circuit is used for mirroring the second current to generate third current for charging the capacitor; the second mirror circuit is used for mirroring the second current to generate compensation current. According to the circuit and the method, a curve compensation mode is adopted, so that a relatively small amount of compensation is achieved under the condition of meeting a slope requirement.

Description

technical field [0001] The invention relates to switching power supply technology, in particular to a slope compensation circuit and method for switching power supply. Background technique [0002] In switching power supplies, slope compensation is a technical solution for continuous mode switching power supplies to maintain system stability when the on-duty cycle exceeds 50%. Specifically, when the current reaches a certain value, the switch is turned off. If the duty cycle exceeds 50%, the rise time of the inductor current in the switching power supply is greater than 50% of the entire cycle, and the current fall time is less than one cycle. 50%, therefore, the current has not had time to return to the static initial value in a short period of time, and the next cycle starts again; the initial current of the next cycle becomes larger, and in the following cycle, the inductor current quickly decreases Rising to the reference point, the on-time becomes shorter and the duty ...

AI Technical Summary

Problems solved by technology

[0009] However, whether it is a linear compensation method or a piecewise linear compensation method, it is close to D MAX At least the slope compensation amount at the position is relatively large, so that the limit value of the detection point is small, which makes the circuit design of the switching power supply very difficult

Images