JAJSLJ6C november 2020 – august 2023 UCC25800-Q1
PRODUCTION DATA
Modern high-voltage, high-power-inverter, and motor-drive applications require floating bias supply voltages to power at least the high-side totem-pole switches, where source (and gate) voltages move up and down with the inverter switch-node. The traditional way of providing small amounts of isolated bias power has been to use a flyback converter. Often a single flyback converter with multiple outputs can generate the required rails for all the switches. However, issues with reliability, redundancy, shock and vibration testing, noise immunity and particularly EMI and common mode current have led to a trend away from the flyback topology and centralized architecture toward distributed open-loop approaches. The open-loop approaches such as 50% duty cycle push-pull, open-loop half bridge or full bridge without an output inductor are deployed while the flyback converter or flybuck (an isolated buck converter) continue to be used by some designs to provide regulated outputs despite the larger common-mode capacitance (transformer primary-side to secondary-side parasitic capacitance). With the adoption of SiC and GaN devices, the inverter power stage switches at a much higher dv/dt. This behavior causes much larger common-mode current injection through the isolated bias transformers and drives the needs for a bias supply design with minimum parasitic capacitance. The need to further reduce the primary-to-secondary capacitance without suffering performance degradation has led some designs to deploy resonant topologies such as the LLC. As the leakage inductance in an LLC is a component of the power train, the topology can enable a higher leakage inductance transformer to be used with an associated reduction in the parasitic primary-secondary capacitance. The UCC25800-Q1 transformer driver is a small, simple controller enabling this topology to be deployed with low component count, integrated protection features, high switching frequency, high parameter tolerance and robust operation. An 8-pin DGN package with thermal pad is used to provide up to 6-W power handling capability with 24-V input.