Fully automatic AC voltage regulator circuit diagram

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This fully automatic AC voltage regulator circuit can greatly extend the service life of expensive appliances. When the input voltage is 170V ~ 270V, the stable output voltage range is 200V ~ 240V, the rated power is 2.5kW (as long as the transformer is slightly modified, The rated power can be increased or decreased). The transformer is used to isolate the power supply and sampling to ensure the safety of commissioning and maintenance. The regulator has a high stability reference voltage source and a two-stage control circuit. The whole circuit is based on a single-chip dual op amp integrated circuit, which is stable and reliable, and has good anti-interference performance.

The principle circuit is as shown in the drawing.




The power transformer T takes two sets of 12V voltages in the secondary direction, one set is rectified by VD1~VD4, Cl is filtered to provide dual-operation amplifier LM358 and relays Kl, K2 provide 12V DC working voltage. At the same time, the current limiting resistor R2 is stabilized by VD6 to 5.6V, which is used as the reference reference voltage of the comparator ICA and ICB. The other group is used as the power supply error sampling voltage by VD5 rectification, C2 and C3 denoising filtering, and the potentiometer RP1. RP2 is adjusted to make comparison signals of ICA and ICB. The primary of the power transformer T doubles as a voltage regulator. There are three plugs A (240V), B (220V) and C (200V) for the contacts of the relays Kl and K2. C2 is the output power socket and Fu is the fuse. The input or output voltage is indicated by the voltmeter V (also not required) and the SBI is the selector switch.

When the input voltage VIN=200V～240V, the relays K1 and K2 do not operate, and their contacts are in the normally closed position (the position shown in the figure). Therefore, the input voltage is directly sent to the output socket C2 without any lifting or lowering, then the output voltage VOUT=VIV; when the input voltage is lower than 200V, Kl pulls in, K2 is still in the released state, and the input is connected to T at this time. The C terminal, so that the output voltage is improved. According to the measured data, when VIN=170V～200V, the output VOUT=205V～240V; when the input voltage is higher than 240V, K2 is pulled in, Kl is released, and the input is connected to the B end of T, so that the output voltage is reduced. . When VIN = 240V ~ 270V, VOUT = 210V ~ 240V (measured value).

LED1 is used as the power indicator, and the two-color LED LED2 is used as the input voltage indication: when VIN<200V, LED2 green tube (G) is bright; when VIN>240V, LED2 red tube (R) is bright; when VIN=200V～240V, LED2 is two tubes None of them are bright.

The circuit can be mounted on a printed circuit board and can be debugged after inspection. The debugging method and steps are:
(1) Rotate RPl to the uppermost end and RP2 to the lowermost end.
(2) Plug in the power plug CT, use another high-precision voltage regulator to make the CT input voltage 200V (indicated by the voltmeter), and slowly lower the RP1 so that Kl just picks up and LED2 glows green.
(3) Make the CT input voltage 240V, and slowly increase RP2, so that K2 just picks up and LED2 emits red light.
(4) When the input voltage is in the range of 170V~270V, the output voltage and LED2 illumination should be divided into three sections as shown in the attached table, otherwise it should be readjusted. If the repeated adjustment still differs greatly from the attached table, check whether the IC, VT1, VT2, Kl, K2 are defective and whether the transformer T core is too loose or the air gap is too large.