Digital Controller IC for Totem Pole PFC Boasts 2 MHz Switching

Wise Integration has introduced its first digital controller IC, the WiseWare 1.1 (WIW1101). Designed for gallium nitride (GaN) based totem pole power factor correction (PFC) topologies, the controller is engineered specifically to enable high power density and efficiency in AC-DC conversion systems.

The digital controller is designed for AC-DC converters. Image used courtesy of Wise Integration

WiseWare 1.1

The WIW1101 digital controller is designed for high-frequency operation in totem pole PFC architectures. It integrates a proprietary firmware-based control algorithm within a 32-bit microcontroller unit to enforce full zero voltage switching (ZVS) across all switching events, minimizing switching losses even at frequencies up to 2 MHz. According to Wise, the high-speed operation significantly reduces the size of magnetic components and leads to more compact and lighter power converter designs.

Notably, the controller operates in critical conduction model (CrCM), which dynamically adjusts conduction times to ensure ZVS during both the turn-on and turn-off transitions. Asymmetric dead times are optimized based on inductor current and midpoint capacitance, balancing reverse conduction losses and avoiding hard-switching. Under typical conditions, the controller achieves over 98% system efficiency.

Important performance metrics include standby power as low as 18 mW and EMC-compliant operation verified through demoboards. It supports input voltage ranges from 90 VAC to 264 VAC, with a regulated output around 400 VDC, and switching frequencies ranging from 280 kHz up to 800 kHz near zero crossing and peaks at 2 MHz depending on system conditions. It also supports power ratings from 100 W to 1.5 kW.

Application diagram of the WIW1101. Image used courtesy of Wise Integration

Electrical protections are built-in, covering overcurrent, overvoltage, overtemperature, and overpower conditions. The WIW1101 also handles inrush current without requiring a relay or thermistor. During startup and standby, the controller leverages a charge pump and control logic to regulate auxiliary power and bulk voltage.

Zero-Voltage Switching in High-Frequency GaN

Zero-voltage switching is an important tool in high-frequency power conversion, especially when using wide bandgap devices like GaN transistors. ZVS minimizes energy losses associated with the switching transitions by guaranteeing that a transistor is turned on only when the voltage across it is effectively zero. This significantly reduces the power dissipated during switching events and limits electromagnetic interference.

In circuits such as the totem pole PFC stage operating in CrCM, ZVS is typically achieved by managing the timing of switch transitions relative to the current flowing through the inductor. When the switch turns off, the inductor current continues to flow and naturally discharges the voltage across the opposing switch. If this timing is controlled correctly, the opposing switch can be turned on precisely when its drain-source voltage reaches zero.

Maintaining ZVS requires accurate control of inductor current and switching intervals. Parameters such as the boost inductor value and the capacitive load at the switching node influence how quickly the voltage falls. Asymmetrical dead times (i.e., delays between the turn-off of one switch and the turn-on of another) must be adjusted dynamically to accommodate variations in line voltage, load conditions, and circuit impedance. If these intervals are too short or too long, the system risks either partial hard switching or excessive reverse conduction, which degrade efficiency.

Digitally Controlled GaN Power Conversion

The WIW1101 is currently available for volume production, with demonstrated performance in multiple customer reference designs and live demonstrations at industry events such as PCIM Europe.