Power outage automatic lighting circuit

This automatic power outage lighting is necessary and appropriate for every family, because in houses in big cities, problems
such as causing a power outage. Here I will introduce to you such
a small electronic device. It only costs 1 to 2 yuan and a few hours of time to install.
    (1) Circuit Working Principle The power outage automatic lighting only requires a total of 12 components. The circuit is shown in Figure 16-28. How it works is simple
. Usually, the power plug CT is always connected to a socket with AC mains power. When there is no power outage. After the 220V mains power is rectified by the diode VD1, a DC voltage of about 310V is obtained at both ends of the filter capacitor c]. This DC voltage is added to the voltage drop stabilizing circuit
composed of the resistor Ri and the voltage stabilizing diode VS2 . Make both ends of VS2 output a stable current voltage of about 7-9V. Since the polarity is positive up and negative down, a reverse bias voltage is applied to the base of VT1 through . In this way, both VT1 and VT2 are cut off, and no current flows through the power outage lighting EL. Therefore, the EL does not light up normally. 1.     If a power outage occurs, the mains power at both ends of the CT disappears, C. The direct voltage at both ends also disappears, and the reverse bias of VT1 naturally disappears. At this time, the power supply provides base bias current to VT1 through day:, ‰ and wind direction, so that VT1 and VT2 are saturated and turned on at the same time. So almost all of the island was added     E _J to Ⅱ. , so the EL emits light and plays the role of automatic lighting in power outages.