Make delayed lighting with TWH8751

The delay lighting circuit made with TWH8751 is shown in Figure 3-50. The circuit consists of a capacitor charge and discharge circuit, a power switch
integrated circuit and a power supply circuit.
    In the figure, diodes VDI~VD5 and capacitors C2 and C3 form a simple capacitor step-down bridge rectifier and voltage stabilizing circuit. After powering on,
it can output a stable DC voltage of about 7V for powering the switch integrated circuit. The gate pin 2 of the switching integrated circuit TWH8751 is connected to the ground, so the state of the output pin 4 can be controlled by the level of
the output pin 1 . Normally, the transistor VT is cut off because there is no base bias current, pin 1 of the integrated block is low level, pin 4 of the output terminal is cut off, and the entire circuit is in a static waiting state. When we press the button SB, the capacitor Cl is quickly filled with charge. At the same time, the transistor VT gets the base bias current and is turned on. The l pin of TWH8751 is high level , the output pin 4 is turned on, and the small electric bead H2 is energized and emits light, which is controllable at the same time. The cathode of the silicon VS is equivalent to grounding, the thyristor VS is turned on, and the lighting Hl lights up and emits light. After SB is released, the charge in the capacitor Cl can be discharged to the VT electrode through the resistor RI, so that VT can continue to maintain the conductive state. Since pin 1 of TWH8751 only needs a current of 100 ~ 200 u A to reliably control the internal power of pin 4 The Darlington tube is on and off, so the vs can be maintained for a long time. Using the graphic data, the light can last for more than half an hour. If you want to change the delay time, you only need to adjust the Rl or Cl data.