Characteristics of digital control of high-frequency switching power supply

With the increase in the working speed, computing power, integration and cost of various microprocessor chips (such as digital signal processors), the control of switching power supplies can also be achieved through microprocessor software. Compared with analog circuits, digital control has the following advantages:

(1) It can realize some advanced but relatively complex control methods, which cannot or are not easy to realize using analog circuits.

(2) The number of peripheral analog devices is very small. The problem of deterioration of control performance caused by aging and temperature drift of analog devices can be effectively improved, and reliability is greatly improved.

(3) The control algorithm is implemented through software, which can avoid the inconsistency of control characteristics caused by the discreteness of analog device parameters.

(4) The modification cost of control methods or parameters is low and the cycle is short.

(5) To meet the increasing demand for intelligent power modules, control and monitoring can be integrated together and completed by one chip.

The main disadvantage of digital control is that the operation speed of the control algorithm is limited by the operating frequency and computing power of the microprocessor chip, resulting in the discretization of the control point on the time axis, introducing a pure lag link, and may not meet the system control requirements with a wider frequency band. In addition, for small power supply modules, the integration of general microprocessor chips is not satisfactory. However, these problems will be gradually solved with the improvement of control algorithms and the advancement of microprocessor chip technology. Digital switching power supply dedicated chips will gradually replace analog chips.

In fact, digital signal processors (DSP) have been widely used in high-power power converters, such as three-phase uninterruptible power supplies (UPS) and other high-power power supplies. Digital control technology is also applied to some dedicated control chips of voltage regulator modules (VRM).

The control theory of high-frequency converters is constantly developing, and the control strategies and control algorithms are becoming increasingly complex. In addition to traditional control methods such as PID, some nonlinear control strategies, such as sliding mode control, dead beat control, and vector control, are becoming possible with the development of DSP technology. These complex control methods and technologies that require high-speed numerical processing are becoming possible in high-frequency switching converters.