Circuit Project Electronic

The UCC3580 (www.ti.com), IC1 in Figure 1, is an active-clamp/reset-PWM IC that has all the requisites of a power-supply IC except for current limit. You can use the shutdown pin (16) for this purpose (see the UCC3580 data sheet). But when the shutdown pin activates, the soft-start capacitor normally connected to Pin 15 discharges, and [...]

You’ve seen them when you’re driving. Mailmen use them, snow plows have them. This is a schematic of the circuit inside.This was taken from a popular unit available at NAPA auto parts stores. It’s amazing how simple it is for a PWM circuit.
It uses a UC3842 (here a TL3842 clone) pulse width modulator to regulate [...]

The first example uses the standard op-amp oscillator circuit to generate a triangular waveform which is level-shifted and fed to a comparator (e.g. LM339) to give the PWM waveform. Most people will want to use two comparators rather than one op-amp and one comparator so that is what we show here.
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