PWM controller for isolated and non-isolated topologies
The Texas Instruments TL494CDG4 is a fixed-frequency PWM controller that supports buck, boost, flyback, forward converter, full-bridge, half-bridge, and push-pull topologies. It operates from a 7V to 40V supply and delivers two transistor-driver outputs with a maximum duty cycle of 45% per output. The switching frequency range of 1kHz to 300kHz covers the typical operating band for offline flyback converters at the low end and push-pull or half-bridge designs at the high end. The 45% duty-cycle ceiling per output enforces dead time between the two output phases, which prevents transformer saturation in push-pull and half-bridge stages.
Supply rail and control features
The wide Vcc range of 7V to 40V allows the controller to be biased directly from the rectified DC bus in offline supplies without a separate auxiliary winding. The built-in dead-time control and frequency control pins give the designer independent adjustment of the output pulse width and the oscillator timing. The TL494CDG4 does not include a clock-sync input or synchronous rectifier drive — these are external additions when needed. The output configuration is positive, and the single-phase output drives two transistor stages internally.