DC-DC (Direct Current-Direct Current) switching power supply working method based on FCCM (Forced Continuous Conduction Mode) and control circuit

Abstract

The invention discloses a DC-DC (Direct Current-Direct Current) switching power supply working method based on an FCCM (Forced Continuous Conduction Mode) and a control circuit. According to the DC-DC switching power supply working method, inductance current and output voltage are monitored, and a switching state for controlling an upper tube and a lower tube is fed back; the problem in the prior art that a controller is easily damaged because reverse current is larger and larger under the FCCM is solved, and furthermore, a DC-DC switching power supply is safer and more reliable and has good economic and social benefits. The DC-DC switching power supply working method can be widely applied to various DC-DC switching power supply circuits.

Description

technical field [0001] The invention relates to an operating mode of a switching power supply, in particular to a forced continuous conduction DC-DC switching power supply working method and a control circuit. Background technique [0002] FCCM: Forced Continuous Conduction Mode, forced continuous conduction mode. [0003] The working modes of the traditional DC-DC switching power supply under light load include burst mode and pulse skipping mode. When the converter enters the pulse-skipping mode, if the load current continues to decrease, the controller will shield or skip some switching pulses to maintain the regulation of the output voltage, resulting in large output voltage ripple. Similarly, in burst mode, since the high-side switching tube stops working for a long time, the output capacitor will maintain the energy of the output load, and the voltage of the output capacitor will drop greatly, so the ripple voltage of the output capacitor is large, that is, the output ...

AI Technical Summary

Problems solved by technology

Therefore, the output ripple and noise of these two operating modes are large

[0004] In the prior art, the forced continuous conduction mode (FCCM, Forced Continuous Conduction Mode) can solve the problem of large ripple and noise, but when the load suddenly enters the light load state, the FCCM mode has certain risks

The typical FCCM mode works with a fixed clock frequency and regulates the load by adjusting the peak current flowing through the inductor. When the load suddenly changes to a light load but does not reach a steady state, due to the abundant energy stored in the inductor, the upper , In the repeated switching of the lower switching tube on and off, the reverse current in the inductor will become larger and larger, which cannot be reasonably controlled, such as figure 1 As shown, it will cause the switch tube to burn out or the system to be damaged

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