The utility model provides a step-down circuit based on discrete components, and relates to the technical field of circuit step-down, the step-down circuit comprises a step-down
control circuit and a step-down
voltage stabilizing circuit, the step-down
control circuit comprises a self-locking button H1, an MOS tube U3 and an MOS tube U2, the self-locking button H1 controls the conduction states of the MOS tube U3 and the MOS tube U2 so as to switch the circuit to be in a step-down mode or a non-step-down mode, and the self-locking button H1 controls the conduction states of the MOS tube U3 and the MOS tube U2. The
voltage reducing and stabilizing circuit comprises a
voltage stabilizing
diode ZD1, a voltage stabilizing
diode ZD3, a
triode Q1 and a
triode Q2, and the voltage stabilizing
diode ZD1 and the voltage stabilizing diode ZD3 jointly form a clamping device; the technical key points are as follows: switching of
voltage reduction modes is realized by ingeniously utilizing a self-locking key, multiple functions of surge resistance, secondary protection, voltage stabilization,
overvoltage protection, filtering,
outage detection and the like are combined, the stability and the safety of the circuit are ensured, and the
voltage reduction circuit is simple, easy to realize, relatively low in cost and relatively high in reliability. And the method can be applied to various electronic devices requiring flexible
voltage regulation.