LM317 12V Soft Power On

Another LM317 based circuit! This time, it is a soft power on. I got it off the TI datasheet examples. The push button simulates the effect of the circuit just being powered up. The blue LED and resistor are the loads. The blue waveform is the current, and the green waveform is the 12V regulated output. Push the button to reset the circuit. The capacitor is completely discharged. The output voltage will be around 1.9V. Then, let go of the button. The capacitor will slowly charge up, and the output voltage will slowly rise to 12V. This takes ~5 seconds. This is a soft power on because the voltage doesn't immediately go to 12V, but there is no clamp on the maximum current as the voltage rises. Therefore, it is not an inrush current limiter. More details about how this works are on the TI datasheet for the LM317. LM317 Series: Adjustable Voltage Regulator: https://everycircuit.com/circuit/6138847104335872 Constant Current Source: https://everycircuit.com/circuit/5424946364547072 Adjustable Current Source: https://everycircuit.com/circuit/4902539157569536 Simple Battery Charger: https://everycircuit.com/circuit/4594156412076032 CCCV Li-ion Battery Charger: https://everycircuit.com/circuit/5336266329292800 Linear Power Supply: https://everycircuit.com/circuit/6413550326906880

published 2 years ago