Is a digital switch mode AC-DC converter consisting of two power stages: an input semi-bridgeless power factor corrector (SBPFC) controlled by an STM32F051K8, and a regulation stage implemented with an LLC half bridge with synchronous rectification (SR), controlled by an STM32F334C8 microcontroller.

This 500 W AC-DC converter uses the so-called bridgeless PFC topology, with the advantage of lower conduction losses and higher efficiency by eliminating the need for a diode rectifier stage. This choice also allows a reduced component count compared to a standard PFC.

The input stage is typically controlled using an outer voltage loop for bus voltage regulation and an inner control loop to shape the current according to a sinusoidal waveform. The outer loop adjusts the current reference in order to maintain a regulated bus voltage, independent of load or input voltage variations. The output isolation and regulation stage is implemented using a half-bridge LLC topology, operating with constant duty cycle and variable frequency control.

Key Features

• Input AC voltage: 90 V to 264 V
• Input AC frequency: 45 Hz to 65 Hz
• Nominal power: 500 W
• Output voltage: 12 V
• Semi-Bridgeless PFC stage
• DC-DC stage: resonant LLC with synchronous rectification
• Peak efficiency: 94%
• PFC switching frequency: 60 kHz
• DC-DC switching frequency: 80 kHz to 115 kHz (burst mode above)
• HF transformer isolation voltage: 4 kV
• Cooling: natural convection up to 300 W, forced cooling above 300 W
• PFC control: managed by STM32F051K8
• LLC control: managed by STM32F334C8
• Input short-circuit protection
• Input under/overvoltage protection
• Input under/overfrequency protection
• DC Bus under/overvoltage protection
• Output short-circuit protection
• Output under/overvoltage protection
• Overtemperature protection
• RoHS compliant