Integrated regulated power supply circuit

This is an integrated regulated power supply with a continuously adjustable output voltage. The output voltage is continuously adjustable between 1.25-37V, and the maximum output current can reach 1.5A. The circuit is simple and suitable for electronic enthusiasts to make their own. It can be used to power various small appliances. working principle  　　

The circuit schematic is shown in Figure 1. The output current of LM317 is 1.5A, and the output voltage can be continuously adjusted between 1.25-37V. The output voltage is determined by two external resistors R1 and RP1. The voltage difference between the output terminal and the adjustment terminal is 1.25V. This voltage will generate A few milliamps of current flows through R1 and RP1 to ground. The voltage divided on RP1 is added to the adjustment terminal. The output voltage can be changed by changing RP1. Note that in order to obtain a stable output voltage, the current flowing through R1 is less than 3.5mA. The maximum power consumption of LM317 is 2W without a radiator, and its maximum power consumption can reach 15W with a 200×200×4mm3 heat sink. VD1 is a protection diode to prevent the output of the voltage regulator from being short-circuited and damaging the IC, and VD2 is used to prevent the input from being short-circuited and damaging the integrated circuit. The component selection and production component list is shown in the table below. No. Name Model Quantity R1 Resistor 100Ω 1 RP1 Adjustable resistor 5.1K 1 C1 Electrolytic capacitor 2200u/50V 1 C2 Polyester capacitor 0.33u 1 C3 Electrolytic capacitor 10u/50V 1 C4 Electrolytic capacitor 100u/50V 1 VD1, VD2 Rectifier diode IN4002 2 U Full-bridge rectifier 3A/50V 1 IC adjustable three-terminal voltage regulator LM317 1 T power transformer 28V 1 The machine can be used normally after welding is completed and checked, without debugging. But when welding, please note that capacitor C2 should be close to the input terminal of the IC, and C3 should be close to the output terminal of the IC, so as to better suppress the ripple.