Touch delay lamp circuit using power switch integrated circuit

A touch delay ¨ made using
TWH8778 power switch integrated circuit , can be used for lighting in stairs, walkways and other occasions.     VD1～VD4, VS1, R． and (1. form a simple I resistor step-down , bridge rectifier and voltage stabilizing circuit, which outputs about 12V DC voltage for powering the integrated block TWH8778. Normally, the trapped diode VT1 is cut off, and the screw terminal ⑤ pin of TWH8778 is the low power half, Therefore, the internal switch circuit is disconnected , there is no trigger current output at pins ② and ③, the thyristor VTH is in the off state, and the light E does not light up. When you need to turn on the light, just touch M with your hand, and the miscellaneous signal induced by the human body is deduced. Resistor R. is injected into the base of VT! to turn on VD1 , and the 12V positive voltage is transferred to VT1 to charge C. When charged to 16V, the internal switch circuit of the integrated block is opened, that is, pin ① is connected to pins ② and ③. The 12V positive voltage passes through the TWH8778 and the resistor R. Inject the control electrode of the thyristor VTH , so that VTH quickly turns on the light E and the light E is energized and emits light. After the human hand leaves the electrode sheet M, c: the stored charge is directly transferred to the control terminal ⑤ of the integrated block Discharge, so the switch circuit in the integrated block can still be maintained in the on state, and the lamp E continues to shine. When the voltage at both ends of (j drops to 1. 6V, the TWH8778 is cut off, and the VTH circle loses the trigger current . When the alternating current crosses zero When it is turned off, the light lr goes out. The function of the voltage regulator tube VS2 is to ensure that the maximum allowable voltage of C: does not exceed 45V, thereby ensuring that the TWII8778 integrated block is not damaged due to excessive control terminal voltage. The function of this circuit The delay time is determined by the capacity of C:. The data in the figure is about 25 s. If you want to increase the delay time, you can appropriately increase the capacity of [,,. In addition, the length of the touch time has a certain influence on the circuit delay time. Impact.