Constant current control system for continuous current mode (CCM) and discontinuous conduct mode (DCM) of primary-side feedback flyback power supply

Abstract

The invention discloses a constant current control system for a continuous current mode (CCM) and a discontinuous conduct mode (DCM) of a primary-side feedback flyback power supply. The control system comprises a current detection module, an output feedback module, a current computation module, an error computation module, a PID module, a PWM module and a drive module; the control system is connected with a controlled switch power supply to form a closed loop; the current detection module and the output feedback module collect basic parameters for achieving a constant current algorithm; the current computation module computes an average current of a primary-side inductor at a switch-on stage of the switch, computes an average current of secondary output currents according to a turns ratio relation between input and output, and works out an output current by averaging integrals of the current on time, the output value executes a compensation algorithm in the digital PID module, a compensation value is transmitted to a PWM module, an appropriate duty ratio is output by the drive module, and thus high precision constant current of the digital power supply is controlled.

Description

technical field [0001] The invention relates to the field of switching power supplies, in particular to a constant current control system in CCM (continuous current mode) and DCM (discontinuous current mode) modes of a primary side feedback flyback power supply. Background technique [0002] The primary side feedback (PSR) eliminates the sampling optocoupler, reduces the number of circuit components, and reduces the complexity of the circuit, so most flyback converters now use PSR control. In order to improve the power application range of the primary side feedback flyback switching power supply, it is necessary to require the switching power supply to have a higher power output. CCM is mainly used for high-power loads, while DCM is mainly used for low-power loads, and the control loop is relatively stable. To achieve high-precision current stability in CCM mode is a top priority and a difficulty. [0003] In order to achieve the stability of the output current, the existin...

AI Technical Summary

Problems solved by technology

However, the disadvantage of these two methods is that if the constant current accuracy needs to be improved, the sampling frequency needs to be increased, and the implementation cost for this is often relatively high.

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