Design of DC switching power supply for single chip microcomputer
The main control method of switch mode power supply is to use pulse width modulation integrated circuit to output PWM pulses, and use analog PID regulator for pulse width modulation. This control method has certain errors and the circuit is relatively complex. This article presents a power switching power supply with a wide range of continuously adjustable output voltage, controlled by the high-performance microcontroller μ psd3354 from ST company. The microcontroller directly generates PWM waves and performs digital control on the main circuit of the switching power supply. The circuit is simple and powerful.
Principle and Overall Design of Power DC Power Supply System
1.1 System Principle
This power DC power supply system consists of two parts: the main circuit of the switching power supply and the control circuit. The main circuit mainly processes electrical energy, while the control circuit mainly processes electrical signals. Negative feedback is used to form an automatic control system. The switching power supply adopts PWM control method, and the deviation is obtained by comparing the given quantity and feedback quantity. The PWM output is controlled by a digital PID regulator to control the output of the switching power supply. Among them, PID regulation and PWM output are both controlled by software using a microcontroller system.
1.2 Overall System Design
The hardware part of the system consists of input and output rectification and filtering circuits, power conversion parts, drive circuits, microcontroller systems, and auxiliary circuits. Figure 1 shows the structural diagram of a DC power supply controlled by a microcontroller.
As can be seen, 50Hz and 220V AC power is filtered by the grid filter to eliminate interference from the grid, and then enters the input rectifier filter for rectification and filtering, converting it into a DC voltage signal. The DC signal is converted into a high-frequency AC signal through a power conversion circuit, and the high-frequency AC signal is then converted into a DC voltage output through an output rectification and filtering circuit [1]. The control circuit adopts PWM pulse width modulation method, and the PWM control signal with adjustable pulse width generated by the microcontroller is processed by the driving circuit to drive the power conversion circuit to work. Using a high-speed ADC conversion channel of a microcontroller to collect output voltage at regular intervals, and comparing it with the expected value, PID adjustment is carried out based on its error. The voltage acquisition circuit realizes the acquisition of DC voltage V0 and matches it with the analog input voltage range of the A/D converter. In the event of overvoltage, overcurrent, and short circuit faults in the switching power supply, the protection circuit plays a protective role for the power supply and load. The auxiliary power supply provides DC power for control circuits, drive circuits, etc.
2. Main circuit design of switch power supply
The main circuit of the switching power supply is used to complete the conversion of DC-AC-DC. The system main circuit adopts a full bridge DC-DC converter, as shown in Figure 2. The power switching device used in this system is the BSM 50GB120DN2 series IGBT module from EUPEC company. Each module is a half bridge structure, so two modules are required in the full bridge system. Each module is embedded with a fast freewheeling diode.
