Homemade AC automatic voltage stabilizer

At present, in remote mountainous areas and rural areas of our country, the power grid voltage is extremely unstable and generally low. Some power grid voltages are only about 120V. In such a power grid, televisions and other household appliances cannot be used normally. Although there are many voltage stabilizers on the market, they are not very effective in use and the price is high. In order to solve this problem, the author specially designed a low-cost voltage regulator with easily purchased components, which is suitable for radio enthusiasts to make their own. Circuit principle: The circuit principle of this voltage regulator is shown in the figure below. It is mainly composed of several unit circuits such as power supply, reference voltage, and voltage sampling comparison. The mains power is input from terminals 1 and 2 of the transformer, terminals 3 and 4 are auto-coupling voltage regulating taps, and terminals 5 and 6 are the power supply and sampling taps of the control circuit. When the mains voltage is normal, because the voltage at point C is always 3V (that is, the voltage obtained by R1 stepping down and DW stabilizing), points A and B are both greater than 3V, so A1 and A2 output low level; when the mains voltage drops, 5, The voltage at terminal 6 also drops, and the voltage at point A also drops. When the voltage at point A drops below 3V, A1 outputs a high level, causing transistor V1 to saturate and conduct, and relay K1 closes, turning the voltage regulator output Adjust to terminals 1 and 3; when the mains voltage continues to decrease, similarly when the voltage at point B is lower than 3V, (VA). On the contrary, if the voltage increases, the voltage at point B also increases. When the voltage at point B is higher than When 3V, A2 outputs low level, V2 is cut off, H2 is released, and the output terminal is adjusted to terminals 1 and 3; when the mains voltage continues to increase, the voltage at point A is higher than 3V, A1 outputs low level, V1 is cut off, and K1 Release, adjust the output end to terminals 1 and 2. A1 and A2 are operational amplifiers, used here as voltage comparators; IC1 is a three-terminal voltage regulator block, which provides power supply for the operational amplifier and relay; VD5 and VD6 are protection diodes. Component selection: LM78L06 is used for IC1. LM358 is used for A1 and V2. 4123 is used for the relay and the voltage is 6V. 1N4007 is used for VD1~VD4 and 1N4148 is used for the transformer core. It can be determined according to the power of the voltage regulator. The author chose E-type 24 iron core. The coil parameters are: 1~2 is wound with 0.22mm enameled wire for 1800 turns; 2~3 is wound with 0.27mm enameled wire for 400 turns; 3~4 Use ?0.27mm enameled wire for 850 turns, and ?0.21mm enameled wire for 145 turns. Other component parameters should be selected as marked in the figure. Installation and debugging: This voltage regulator should be installed in a metal casing and has a relatively small diameter. Good heat dissipation holes. After the circuit assembly is completed, adjust RP1 and RP2 to the maximum resistance value. Use a voltage regulator to adjust the input voltage to 180V. Then adjust RP1 to adjust the voltage at point A to 2.9V. At this time, A1 outputs high level. , V1 is turned on, relay K1 is closed, and the output terminal is automatically adjusted to terminals 1 and 3, the output voltage is about 220V; then adjust the voltage regulator so that the input voltage is 140V (the output voltage is 180V at this time), adjust RP2, Make the voltage at point B be 2.9V. At this time, A2 outputs high level, V2 is turned on, and relay K2 is closed. The output terminal is automatically adjusted to terminals 1 and 4, so that the output voltage rises to about 220V again as shown in the figure. According to the data, when the grid voltage is as low as 120V, the TV can still be viewed normally. It should be noted that since the pull-in current of the relay is greater than the release current, the output voltage will have a certain error, and RP1 and RP2 need to be adjusted repeatedly to achieve the desired output. Best state.