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 [...]

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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Often, people attempt to control DC motors with a variable resistor or variable resistor connected to a transistor. While the latter approach works well, it generates heat and hence wastes power. This simple pulse width modulation DC motor control eliminates these problems. It controls the motor speed by driving the motor with short pulses. These [...]