PWM controller for multi-topology power supplies
The Texas Instruments TL594IDRG4 is a fixed-frequency PWM controller that handles step-up, step-down, and step-up/step-down topologies — buck, boost, flyback, forward converter, full-bridge, half-bridge, and push-pull — from a single 16-SOIC package. Its 7V to 40V supply range directly powers from a 12V or 24V industrial bus without an intermediate regulator, and the 1kHz to 300kHz switching frequency lets the designer trade transformer size against core loss.
Switching frequency and duty cycle — sizing the magnetics
The 1kHz~300kHz oscillator range sets the transformer flux swing and output filter corner. A 100kHz design shrinks the magnetics versus 50kHz, but pushes gate-drive loss higher; the TL594IDRG4's transistor-driver outputs handle the increased sink current. Maximum duty cycle of 97% allows the output to stay on nearly the whole cycle — useful in a boost converter that needs low dropout between input and output, or in a forward converter that must reset the core within the off-time.