Full-bridge PWM controller for high-density power conversion
The UC3875DWP is a full-bridge PWM controller from Texas Instruments designed for offline and DC-DC converters where transformer-coupled isolation and high efficiency are required. Its 1 MHz switching frequency allows the use of smaller magnetics and output capacitors, shrinking the power stage footprint. The controller integrates frequency control, soft-start, and synchronization for multi-phase or paralleled converter designs.
At 1 MHz, the UC3875DWP drives the primary-side switches of a full-bridge topology. The 100% duty cycle capability supports the full-bridge phase-shifted modulation scheme.
Supply range and start-up behaviour
The controller operates from a 9.5 V to 20 V supply and has a start-up threshold of 10.75 V, meaning the bias rail must reach 10.75 V before the PWM outputs begin switching. Below that, the IC stays in undervoltage lockout. This matters for the auxiliary winding design: the bias winding needs to deliver at least 10.75 V during start-up and stay within 9.5 V to 20 V during steady-state operation.
Current limiting fault protection is built in. Soft-start limits inrush during power-up, and the sync input lets multiple units operate at a common frequency.
Housed in a 28-SOIC wide-body package (7.50 mm width), surface-mount for automated assembly. The 28-SOIC footprint is standard for this controller family, making PCB layout straightforward with existing land patterns.