Digital Control in High Frequency Switching Power Supply

The simple application of digitization in high-frequency switching power supply is mainly protection and monitoring circuits, as well as communication with the system, which has been widely used in communication power supply systems. It can replace many analog circuits, complete power supply startup, input and output over and under voltage protection, output over current and short circuit protection, and overheat protection, etc., through a specific interface circuit, it can also complete the communication with the system. show.

More advanced digital applications include not only the realization of complete protection and monitoring functions, but also the output of PWM waves, the control of power switching devices through the drive circuit, and the realization of closed-loop control functions. At present, TI, ST and Motorola have all introduced dedicated motors and motion control DSP chips. At this stage, the digitalization of the communication power supply mainly adopts the combination of analog and digital. The PWM part still uses a special analog chip, and the DSP chip mainly participates in duty cycle control, and functions such as frequency setting, output voltage adjustment, and protection and monitoring.

In order to achieve faster dynamic response, many advanced control methods have been gradually proposed. For example, ON Semiconductor proposes improved V2 control, Intersil Corporation proposes Active-droop control, Semtech Corporation proposes charge control, Fairchild Corporation proposes Valley current control, IR Corporation proposes multi-phase control, and many universities in the United States also A variety of other control ideas are proposed. Digital control can improve the flexibility of the system, provide better communication interfaces, fault diagnosis capabilities, and anti-interference capabilities. However, in the precision communication power supply, factors such as control accuracy, parameter drift, current detection and current sharing, and control delay will be practical problems that need to be solved urgently.

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