Design and implementation of digital controlled DC voltage regulated power supply based on single chip microcomputer

DC regulated power supply is one of the commonly used equipment in electronic technology, and is widely used in teaching, scientific research and other fields. The traditional multifunctional DC regulated power supply has simple functions, is difficult to control, has low reliability, large interference, low precision, large size and high complexity. There are many types of ordinary DC regulated power supplies. However, they all have the following problems: the output voltage is adjusted by coarse adjustment (band switch) and fine adjustment (potentiometer). In this way, when the output voltage needs to be accurately output or needs to be changed within a small range (such as 1.02~1.03V), the difficulty is greater. In addition, with the increase of usage time, the band switch and potentiometer will inevitably have poor contact, which will affect the output. Overload is often protected by hardware with current limiting or current cutoff type, the circuit structure is complex, and the voltage stabilization accuracy is not high. This paper designs an intelligent high-precision simple DC power supply with a single-chip microcomputer as the core, which overcomes the shortcomings of traditional DC voltage sources and has high application value.

2 System Hardware Design

2.1 Overall system structure

This system is a digitally controlled DC power supply with AT89S51 single-chip microcomputer as the core controller. It has voltage preset, step adjustment, output voltage signal and preset voltage signal that can be displayed simultaneously. Its hardware principle block diagram is shown in Figure 1. The system consists of eight parts: AT889S51 control circuit, keyboard circuit, power supply circuit, D/A circuit, power amplifier circuit, short circuit protection and alarm circuit, voltage stabilization output circuit, and LED display circuit. The system controls the rise and fall of the preset voltage through the three buttons of "switch", "+", and "-", and displays it through the digital tube. The AT89S51 single-chip microcomputer sends out the corresponding digital signal, outputs the current after D/A conversion, and finally stabilizes after conversion by the integrated operational amplifier LM358, transistor amplification, and RC network filtering. At the same time, the output voltage is displayed by the LED digital tube; the measured value is measured by the digital voltmeter.

2.2 CNC part

It is mainly controlled by the AT89S51 minimum system, which has to complete the functions of keyboard control, preset voltage display control, short circuit protection control and alarm control, etc. The AT89S51 minimum system is shown in Figure 2.

2.2.1 Keyboard interface circuit

The keyboard interface circuit is shown in Figure 3. The keyboard design is controlled by three buttons: the "switch" key, the "+" key, and the "-" key, and three external pull-up resistors are connected to control the keyboard debounce. These three buttons are respectively connected to the P1.0, P1.1, and P1.2 interfaces of the microcontroller for control.

2.2.2 Preset voltage display circuit

The preset voltage display circuit is shown in Figure 4. This design uses the decoder driver 74F244 to drive the LED digital tube to display the preset voltage, which is controlled by the microcontroller P2.0~P2.7 interface. The LED common cathode control end is controlled by the P1.4~P1.6 interface, and the triode 8050 is used to control the LED display.