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Design overview: 2 kW 2-ch interleaved PFC

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.

1.

I/O measurement signals

2.

Analog circuitry

3.

Power stages

4.

Digital control section

2-channel

Interleaved

PFC

Driver

Driver

STNRGPF12

SIN_REF

PWM[0]

OUT_PI[2],[3]

TRIANG_REF

CLOCK

VIN

IOUT

VOUT

Load

AC

input

DC

output

PWM0

PWM1

1

1

1

1

Analog

Current loop

2

EMI

filter

3

3

3

3

SCR

isolated

driving

3

3

4

PWM[1]

SCR1

SCR2

Mixed input

bridge

3

Isolated

Aux

PS

3

+5V +15V

G1

G2

I[0]

I[1]

+5V

ISO

1

1

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

STEVAL-IPFC12V1

Design overview: 2 kW 2-ch interleaved PFC

DB3882 - Rev 2

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