A Constant Current Control System of CCM and DCM Modes of Flyback Power Supply

Abstract

A constant current control system in CCM and DCM modes of flyback power supply, the control system includes a current detection module, an output feedback module, a current calculation module, an error calculation module, a PID module, a PWM module and a drive module, and is connected with the controlled The switching power supply is connected to form a closed loop. The current detection module and the output feedback module collect the basic parameters of the constant current algorithm. The current calculation module mainly calculates the average value of the output current. The output value is implemented in the PID module. Compensation algorithm, the compensation value is submitted to the PWM The control module outputs a suitable duty ratio through the drive module, thereby controlling the high-precision constant current of the digital power supply.

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] Primary-side feedback flyback power supply is widely used in lithium-ion battery chargers of digital products, computer (PC) auxiliary power supplies, and LED drivers. It detects and outputs information on the primary side of the transformer, eliminating the need for secondary sampling circuits. The optocoupler reduces the number of components, reduces the complexity of the overall circuit, and is more efficient and optimized. 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. The control loop of DCM is relatively stable, but it is mainly used in...

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.

[0005] DAC is another way to achieve constant current. One of the methods is to use the peak current control method to control the peak current of the switch tube in the conduction phase, and obtain the average current in the conduction phase, so as to control the output current to be constant. The control The method has higher constant current accuracy, but the control loop is more complicated

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