Power outage emergency light circuit

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.
    In areas with frequent power outages, it will bring a lot of inconvenience to people's work and study, especially students will have more difficulty doing homework at night. The power outage emergency light
circuit introduced in this section can usually be used for mains lighting. After a power outage, the transistor ultrasonic Audio oscillator, uses battery to light up 8W fluorescent tube, easy to use and save power. At the same time, it also eliminates the flickering phenomenon of ordinary fluorescent lamps , reduces eye fatigue, and helps protect the eyes.     (1) Circuit working principle The circuit is as shown in the figure. It can be seen from the figure that the inverter circuit is a 6-break oscillator fed back by the transformer . R provides the bias current of VT. C2 stabilizes the oscillation frequency of the lamp , and C is a high DC blocking capacitor to prevent premature blackening of the lamp .