The 2kW interleaved PFC solution features the performance of analog cycle-by-cycle current regulation and the flexibility of digital control to generate sinusoidal supplies with very high-power factor and very low harmonic distortion.
Digital power control is based on the STNRGPF12 digital PFC controller, which in combination with the TN3050H-12WY thyristor implements digital inrush current limitation and can drive up to two interleaved PFC channels using mixed signal (analog and digital) average current mode control in CCM at fixed frequency.
The aim of this reference design is to provide a flexible PFC converter that can accept a wide input range (90 to 265 V at 50/60 Hz) for high power applications (600 W to 2 kW) that require supply power with very high PF and very low THD, in an efficient and cost effective package that can be easily configured for specific performance criteria. If we equate programmable digital control with flexibility, and analog logic with high performance, then the STNRGPF12 digital controller is the ideal choice, specifically designed for interleaved CCM boost PFC for applications above 600 watts. The controller supports mixed signal (analog/digital) architecture, with an analog loop providing cycle-by-cycle current control and the reference signals for PWM modulation, and a digital voltage loop managing all the non-time-critical functions/protections and calculating rapid feed forward responses to fluctuations in the input voltage or step changes in the load.
Regarding inrush current control, which is a critical protection feature also managed by the STNRGPF12 controller, we use a comprehensive approach involving firing angle control of high side TN3050H-12WY SCRs in a mixed input bridge; the low side of the bridge consists of STBR3012 rectifier diodes. Both silicon devices are well above the required current rating to minimize voltage drops across the bridge and offer low forward voltage drop and surge current/voltage handling. The PFC stage is based on a boost circuit design with two parallel channels to take advantage of the controller's ability to support interleaving through a secondary PWM channel that is phase-shifted 180° with respect to the master channel. While two channels increase circuit complexity, the interleaving operation ensures that there is less ripple and higher apparent switching frequency in the PFC input current, which allow the use of smaller and less expensive input EMI filters, boost inductors and switching devices. The STGW20H65FB IGBTs used for the boost switches are cost effective devices especially designed to minimize losses in power converters thanks to their low VCE (sat) and reduced tail current profile.
- Input voltage range: 90 to 265 VAC
- Line frequency range: 47 to 63 Hz
- Maximum output power: 2 kW at 230 V
- Digital Inrush Current Limiter function performed with SCR
- Output voltage: 400 V
- Power factor: > 0.98 at 20% load
- Total Harmonic Distortion: <5% at 20% load
- Mixed-signal Average Current Mode control, CCM fixed frequency operation
- Switching Frequency (fsw): 60 kHz
- Cycle-by-cycle regulation (analog current control loop)
- Input voltage and load feed-forwards
- Phase shedding
- Current balance
- Burst-mode operation
- Overvoltage protection
- Overcurrent protection
- Thermal protection
- Status indicator LEDs
- Cooling function
Power & Energy Management
The 2 kW interleaved PFC solution (STEVAL-IPFC12V1) consists of a power board with 2-ch interleaved CCM boost power stage, input rectifier controlled bridge and auxiliary power supply, a control board with embedded STNRGPF12 digital controller and analog control circuitry, and a USB to UART (FTDI cable required - not included in the kit) bridge for programming the STNRGPF12 and performance monitoring.
You can use the eDesignSuite software available on the ST website to configure the STNRGPF12 according to specific design requirements for each interleaved PFC.
To perform functional and efficiency testing, you need the following equipment:
- Programmable AC source with power > 2 kW
- DC electronic load or load resistor > 2 kW
- Power analyzer
- Digital oscilloscope
The STEVAL-IPFC12V1 board can be tested up to 2 kW at 230 VRMS and 1 kW at 115 VRMS, in a frequency range between 47 and 63 Hz.
Note: Any load or passive oscilloscope probe must be isolated from the input source of the PFC.
How to connect and start the STEVAL-IPFC12P1 power board
Step 1. Insert the STEVAL-IPFC12C1 control board in connector J301 on the STEVAL-IPFC12P1 power board.
Step 2. Connect one of the following AC supplies to the J100 connector on the STEVAL-IPFC12P1 power board:
- 230 V at 50 Hz
- 115 V at 60 Hz
Step 3. Connect the load wires to the output terminals on J300 of the STEVAL-IPFC12P1 power board. The actual load (electronic dc load, load resistors, inverter, etc.) must remain disconnected until the soft startup sequence has completed. The correct polarity is indicated on the board.
Step 4. Supply one of the following input voltage and frequency ranges while no load is connected on the output:
- 185 – 265 VAC at 47 - 53 Hz
- 90 – 140 VAC at 57 – 63 Hz
The eDesignSuite software tool developed by STMicroelectronics helps you configure ST products power conversion applications. You can use it to customize the PFC controller for a specific application: start by entering the main specifications for your design and then generate an automatic design or follow a sequential process to build a highly customized design.