Switching converter topologies are used for active power factor correction to improve both power efficiency and density. Over the past two decades, one of the most prominent topologies is the boost PFC, which utilizes a single low-side MOSFET, an inductor, and a diode. For efficient AC-to-DC conversion, the MOSFET gate driver must meet certain requirements to drive the MOSFET effectively. Some of these driver requirements include the peak drive current and the switching characteristics. High drive current is needed due to the high-power switches that are required for PFCs. Fast switching characteristics such as rise and fall times as well as propagation delays allow for fast switching transitions, reducing losses and increasing efficiency. This need for fast switching transitions is due to the switching losses in the MOSFETs. The MOSFETs are inefficient during the turn on and off times due to the dynamic voltages and currents that are handled. Other requirements include under voltage lockout and noise handling capabilities. Boost PFCs are often driven by single-channel, low-side, non-isolated gate drivers. Texas Instruments has a large portfolio of drivers that meet or exceed these requirements such as the UCC27517A.

By using a low-side gate driver and a MOSFET for switching, the boost converter PFC forces input current to be in-phase with the input voltage, thus correcting the power factor. This is accomplished by the boost converter controller that is sending PWM pulses to the gate driver that is used to provide voltage and current gain to drive the FET. This approach is typically used for power levels of 100W up to 4kW. Figure 2-1 shows a typical boost converter PFC utilizing the UCC27517A.

Figure 2-1 Boost PFC Using a MOSFET, Rectifier Bridge, an Inductor and a Diode With an Output Capacitor Filter

The UCC27517A is a non-isolated, single-channel low-side gate driver that can be used for driving these high power MOSFETs in the boost topology. This driver has output current capabilities of 4A sink and 4A source and an 18V maximum recommended operation on VDD rating. UCC27517A has a propagation delay of 13ns and a rise time of 9ns and fall time of 7ns on the output to also help maximize efficiency that is needed for these systems. This device features under-voltage lockout (UVLO) to maintain glitch-free operation in power on and off transients to increase system robustness.