How does the regulated power supply work?
The power frequency AC power supply is stepped down, rectified and filtered by the transformer to become a stable DC power. The rest is the control part that performs voltage regulation and achieves regulation. After the power supply is connected to the load, the output voltage is obtained through the sampling circuit, and the output voltage is compared with the reference voltage. If the output voltage is less than the reference voltage, the error value is amplified by the amplifying circuit and sent to the input end of the regulator, and the output voltage is increased by the regulator adjustment until it is equal to the reference value; if the output voltage is greater than the reference voltage, the regulator is passed Reduce the output.
The voltage regulator circuit is composed of =12V power supply circuit, voltage detection control circuit and overvoltage protection. As shown in Figure 5-51, the l2V power supply circuit consists of the W4 and W5 windings of the voltage regulating transformer T and the rectifier diodes VDl-VD4 and the filter capacitor C1. And C2 composition. The voltage detection control circuit is composed of a resistor R-R7, a potentiometer RP1, Rm, a Zener diode VS, capacitors C3, C4, and an operational amplifier integrated circuit IC (Nl-N3). The overvoltage protection circuit is composed of N3 inside the IC, transistor V3, resistor Rl2, and relay K. The piezoelectric regulating circuit resistor R8-R11, the transistors V1, V2, the direct current motor M, the sliding contact and the W1 - W3 winding of the T are composed. When the large end of the AC voltage regulator is connected to the mains, an induced voltage is generated on the W4 and W5 windings of T. The voltage is rectified by VDl-VD4 and filtered by Cl and C2 to provide an unstable working voltage of IC12 and V1, V2, etc. The +l2V voltage has other effects. After Rl-R3 partial voltage and VS voltage regulation, the reference voltage is provided for the inverting input terminals of Nl-N3 respectively; the working power supply is provided for K and V3 of the overvoltage protection circuit; after being divided by R4, RP2 and R6, The detection voltage is supplied to the non-inverting input terminals of N1 and N2; after being divided by R7, RP1, and R5, the detection voltage is supplied to the non-inverting input terminal of N3.
Nl-N3 compares the detection voltage of the large-phase positive-transistor with the reference voltage of the large-end inverter, and uses the generated error voltage to control the automatic voltage regulation circuit.
When the mains voltage is normal, the output voltages of N1 and N2 are OV, Vl and V2 are both in the off state, and the motor M does not work.
When the mains voltage is low, Nl and N2 output low level, so that V2 is turned on, Vl is turned off, M is rotated counterclockwise, and the sliding contact is driven by the sliding wall arm to contact with the voltage tap corresponding to T (W of T1) A total of 21 voltage taps are set in the W2 winding, and the voltage adjustment range of each gear is 5V. The output voltage is boosted by the W2 winding of T. When the output AC voltage rises to 220V, V2 is turned off and M stops. When the mains voltage is high, Nl and N2 both output a high level, so that Vl is turned on, V2 is turned off, M is rotated clockwise, and the sliding contact is moved by the sliding arm to contact the voltage tap corresponding to T, through T Wl windings to reduce the output voltage. When the output AC voltage drops to 220V, Vl is turned off and M stops. When the mains voltage is higher than 260V, N3 outputs a low level because the voltage of the positive phase input terminal is higher than the voltage of the inverting input terminal, so that V3 is cut off, K is released, and its normally closed contact is connected to the output circuit of the AC voltage. When the mains voltage is 160-260V, N3 outputs a high level because the voltage of the positive phase input terminal is lower than the voltage of the inverting input terminal, so that V3 is turned on, K is pulled in, and its normally closed contact is disconnected, thereby ensuring the load. (Electrical appliances) will not be damaged by overvoltage.
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