The NE555 is a commonly used timer integrated circuit, usually used to generate square-wave signals. To compose a step-down circuit, you can use the PWM (pulse width modulation) function of the NE555. By adjusting the duty cycle of the NE555, you can control the average output voltage to realize the voltage reduction function.
The output pins of the NE555 can be connected to a series circuit of inductors and diodes that, through periodic switching operations, reduce the input voltage to the desired output voltage. In addition, voltage regulator diodes and capacitors can also be used to filter to obtain a more stable output voltage.
Its internal structure consists of three 5k resistors in series, two comparators, an RS flip-flop, a inverter and a discharge switch tube T. Three series resistors are connected to the power supply VCC, and the voltage drop on each resistor is 1\/3VCC.
They are delay timer, long delay timer, segmented timer, anti-interference timer, variable intermittent timer and cycle timer with adjustable on and off time respectively.