As an energy storage power source, batteries have been widely used in various industries. However, the charging methods of the finished battery charging power supply are single, most of them have only two-stage charging mode, and some even have simple constant voltage or constant current charging modes. When the battery pack is charged, the life of the battery is shortened, which is not conducive to the long-term effective use of the battery. The control technology of charging power supply can be roughly divided into two categories: The first type uses monolithic integrated PWM control devices. These devices have the advantages of high precision, strong anti-interference, high switching frequency, and few external components. The second category is Using the control technology of single-chip microcomputer or DSP, this kind of controller adopts digital operation and has stable performance, which can realize intelligent control of the system. This paper introduces a battery charging power supply based on the ADUC814 microcontroller and the dedicated integrated PWM controller SG3525, which combines the advantages of two types of control technology.

Figure 1 shows the overall design block diagram of the charging power supply. After the mains input, it is rectified and filtered, and then through the DC/DC conversion circuit, a smooth DC power is generated to charge the battery. The output voltage or current detection signal is sent to the control chip SG3525, compared with the charging reference voltage set by the single chip microcomputer, and the comparison result generates a controllable voltage for controlling the PWM signal output, and the PWM signal is further driven by the IR2113 dedicated control chip. The on-off time of the switch tube in the variable circuit, so as to achieve the purpose of controlling the output voltage. At the same time of generating the driving pulse, the control chip SG3525 can also perform circuit protection according to the detection signal to prevent overvoltage and overcurrent. In addition to processing the detection signal, the MCU can also display the output voltage and current.

Figure 1 Overall design block diagram of the charging power supply

The main circuit adopts the circuit shown in Figure 2. The 220V AC is filtered by the fuse and EMI. After passing through the bridge rectifier filter circuit, it obtains about 300V DC. After the full bridge inverter, the full-wave rectification is adopted on the secondary side of the high-frequency transformer. And the inductor and capacitor filter, finally get the rated 24V DC output, and send it to the battery for charging, its maximum output power can reach 900W.

Figure 2 main circuit

The detection circuit section mainly performs detection of current, voltage and temperature. The purpose of the current and voltage detection circuit is to introduce negative feedback to achieve constant current, constant voltage charging and fault protection. The purpose of temperature detection is to obtain the temperature parameter of the battery during charging to prevent overcharging and damage the battery.

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