Refrigerator power outage protector circuit

The circuit can continue to work for 5 minutes when the power is out, thus protecting the refrigerator.
    The refrigerator power-off protector circuit is shown in Figure 1136. T is the power transformer. The 220V voltage is rectified by VD1~ⅥM bridge to charge Ct
and supply +1ZV voltage to the control circuit. It is used for the first time. Since there is no charge on G, VT2 is cut off and point A is at high potential. , VT3 is cut off,
the bidirectional thyristor VTHZ is turned on due to the triggering of VD7, the load is powered, and the refrigerator starts to work.
    At the same time, R2 charges c2, causing the potential of point B to rise. Through R, it triggers the thyristor VTH1 to turn on. Relay K pulls in, and its normally
open contact K closes; diode VD5 charges G, the voltage is +12y, and the circuit is in a preparatory state for power failure protection.
    Once the circuit is powered off , relay K loses power. The normally open contact K is released. Since c:1 is charged, the voltage is +12V, which is applied to the gate of VT2
. Because there is no current connection between the gate, source and drain. Therefore, the charge on C3 remains basically unchanged. The voltage on C3 is added between
the gate and source of VT2, making VGS greater than the turn-on voltage U of VT2, thus forming a certain conductive
channel . Although the power supply has no voltage, the drain Between plate D and source S, it is equivalent to the closed state of the switch. During this period, if the power comes in, VT2 will be in
the conductive state, making point A at low potential, and the HL light will light up to indicate delayed protection. The transistor VT3 is turned on, point C is at a high potential, the diode
VD7 is cut off, the bidirectional thyristor VTH2 is cut off when there is no trigger current, and the refrigerator does not work.
    during this time. The sampled voltage on R6 always makes the transistor VI'] conduct, point B is at a low potential, the thyristor VTH1 does not trigger, the relay
K does not pull in, the normally open contact K does not act, and the low potential of point A is maintained. The maintenance time of the low potential at point A can be controlled by adjusting the wind.
    As C3 discharges the Bianstone. The charge on G decreases, the drain and source current of field effect transistor VT2 gradually decreases, and the sampling voltage on R decreases
, which eventually causes VT1 to cut off, the potential of point B rises, triggering VTH1 to turn on, and relay K to be energized, making the normally open contact. K closes, VTZ stops.
Point A turns to high potential, point C turns to low potential, diode VD7 is triggered, VTH2 is turned on, and the refrigerator gets power to work.
    Voltage stabilization secondary tube vs. It is used to protect the VT2 field effect crystal. Rg and C4 are connected in series and connected in parallel with VS2 to protect the bidirectional thyristor. VTHZ,
Shu and HL are delay indication circuits .