Multifunctional refrigerator DC voltage controller circuit diagram composed of 555

The figure shows the control circuit of a multifunctional refrigerator . The controller consists of overvoltage and undervoltage sampling circuits, delayed start circuits, audible and visual alarm circuits, and step-down rectifier circuits. The buck rectifier circuit provides DC voltage for the entire controller .

The delayed start circuit is composed of IC1 (555), C6, R14, W3, etc. When the power is turned on or power is turned off, the terminal voltage on C6 cannot change suddenly, and the 555 is reset because the potential of pin ⑥ is high. While charging is in progress, when C6 is charged to the point where the potential of pin 2 is lower than 1/3VDD, 555 is set, and the high level output by pin ③ causes relay J to close. The corresponding delay is td=1.1(Rw3+R14)C6, and the delay corresponding to the parameters shown in the figure is about 4 to 10 minutes.

The overvoltage, undervoltage and overcurrent detection and switching circuits are composed of W1, R2, R3, DW1, BG1, BG2, BG3, etc. When overvoltage, undervoltage or overcurrent occurs, BG3 is cut off, and its collector is at high potential. One side of this potential is added to pin ⑥ of IC1 to reset the 555. The low level output by pin ③ causes relay J to release, and contact J2 -2 is disconnected, cutting off the power of the refrigerator, and LED1 is lit at the same time; the other channel divides the voltage through R10 and R1 and then adds it to the IC2④ pin to make IC2 start to oscillate.

IC2, C5, R12, and R13 form a multivibrator. Its oscillation frequency is f=1.44/(R12+R13)C5. The frequency corresponding to the parameters shown in the figure is about 1kHz. Once overvoltage, undervoltage or overcurrent occurs, Ic. The oscillator outputs an oscillation signal, drives the speaker to work, and generates an audio alarm.

The controller can realize automatic protection under overvoltage, undervoltage, and overcurrent conditions, delay start after instantaneous power cutoff, audible and visual alarms for faults, and other functions.