DC low voltage switching power supply circuit designed by NE555

Probe current voltage pin 420*4450 head diameter 5.0 over current current and voltage pin

1.5PF SOT23-6 Low Capacitance 5V Breakdown Voltage 6V SRV05

description:

The switching power supply is designed not to be automatically regulated. Its function is similar to that of the transformer. It only realizes the light-weight isolation and step-down function. The voltage stabilization function is realized by the following voltage regulator circuit.

The VD1-VD4, R1, C1, and C2 of the switching power supply part constitute a rectifying and filtering circuit. NE555 and R2, R3, C4, VD6 and other components form a multi-resonant circuit with a frequency of about 20KHz. R4, C3, and VD5 form a step-down regulator circuit, which provides 12V working power for NE555. The high power tube VT1 and the transformer T constitute a switching circuit. The working state of VT1 is controlled by the 3 pin of NE555. The on-time is determined by the pulse width. Adjusting R3 can change the pulse width. The pulse width is widened, the output voltage is increased, the pulse width is narrowed, and the output voltage is lowered. VT2 and R8, R9, and C6 form an overcurrent protection circuit. When the load is too heavy or a short-circuit fault occurs, VT2 turns on, forcing the NE555 to reset and stop the vibration, thus protecting VT1 from damage. C7 and R10 are protection networks to prevent the ce junction of VT1 from being pulsed by an instant pulse. The two secondary windings are rectified and filtered to output 20V and 12V respectively.

In order to make the production simple, the switching power supply is designed not to be automatically regulated. Its function is similar to that of the transformer, but it realizes the light-isolated isolation and bucking effect. The voltage-stabilizing function is realized by the following voltage-stabilizing circuit. 12V DC voltage is regulated by 7805 and output +5V voltage; 20V DC voltage is sent to the adjustable voltage regulator circuit. The two are not common, so that the combination of the addition and subtraction outputs a variety of voltages.