Design of Uninterrupted DC Power Supply Circuit Based on LM2596

Overview:

This paper presents an uninterruptible DC power supply design based on LM2596. The uninterrupted DC working power supply designed in this scheme adopts the switching voltage regulator LM2596 for DC-DC conversion, which can output 3 A driving current and has good load regulation characteristics. When the main power supply is cut off, the circuit automatically cuts in the battery through the relay to supply power to the device. When the main power is normal, the battery is charged in different modes: when the voltage is greater than the set value, the constant voltage is charged; when the voltage is lower than the set value, the constant current is charged. Test results prove that the system can protect the circuit from overcurrent and undervoltage through relays. 0 Introduction The design requirements of this design: the battery is 4.2 V, the load is 5 V. For this purpose, the switching voltage regulator LM2596 is used for DC-DC conversion, which has the characteristics of strong driving capability and good linearity. The main features of the uninterruptible DC power supply are as follows: When the main power supply is normal, in addition to supplying power to the equipment, the battery can be charged in different modes. When the voltage is greater than 4.2 V, the constant current charging circuit is cut off, and the constant voltage charging circuit is turned on. When the voltage is lower than 4.2 V, the constant current charging is maintained; the constant voltage charging is composed of W117 and the operational amplifier LM324, and has the characteristics of stable output and small ripple. Constant current charging consists of high-power field tube IRF640 and op amp LM324. It has the characteristics of high output current precision, small ripple, and small output current affected by load. If the main power supply is cut off, the battery will be cut automatically to keep the power supply uninterrupted. . 1 System design scheme 1.1 Overall block diagram of the system According to the system design requirements, the uninterruptible DC power supply has: uninterrupted power supply to the equipment when there is no AC power supply; when there are normal AC power, there are two modes of constant voltage charging and constant current charging; Design requirements, form a system block diagram as shown in Figure 1. (Please read the PDF for details)