3.6kW Totem-Pole PFCwith active in-rush current limiting

Jeff Halbig

Power Discrete Group – Product Marketing Manager

Agenda

2 ST AC-DC inrush current limiter solutions

3 PFC totem pole topology using SiC MOSFETs and thyristors

2

4 Evaluation board performance

1 3.6kW Totem Pole PFC Introduction

Evaluation Board 3.6 kW Totem Pole PFC

3

Main

Features

▪ Input AC voltage: 85VAC up to 264VAC

▪ DC output voltage: 400VDC

▪ Switching frequency: 72 kHz

▪ Maximum input curent: 16 A RMS (POUT = 3.6KW)

▪ Efficiency: > 97,5%

▪ THD < 10 %

▪ Remove two bulky relays and an NTC resistor thanks

to SCRs progressive start-up

Key Products

▪ TN3050H-12WY → SCR in the Bridge

▪ SCTW35N65G2V → 650V SiC MOSFET

▪ STGAP2S → Isolated Gate Driver

▪ STM32 → 32-bit Microcontroller)

▪ VIPER26LD → HV Converter Controller

STGAP2S

STM32F334 STGAP2S

TN3050H-12WY

SCTW35N65G2V

▪ Compliant to :

• EN 55015 and IEC 61000-4-11 and IEC 61000-3-3

• IEC 61000-4-5 surge: 4kV

• IEC 61000-4-4 EFTY burst : criteria A @ 4kV min

▪ Design for operation with DC/DC converter

▪ Peak inrush current tuning

Available Q2/20

Traditional PFC Totem Pole

4

• A conventional PFC circuit:

• Consists of a full bridge rectifier and a boost pre-regulator

• A large portion of system losses are in the diode bridge

D1 D2

D4D3

L

SC

vIN(t)

iIN (t) Inrushcurrentlimiter

D1

S4

L1

S3

GND

D2

C

IIN

VIN

S2

S1

Inrush

current

limiter

SiC MOSFETs(High Frequency)

Diodes or

MOSFETs(Low Frequency)

• In a traditional totem pole PFC:

• The diode losses are eliminated

• Low frequency switches are diodes or MOSFETs

• Needs an Inrush current limiter (NTC + relays)

Bridge-less TopologiesTotem Pole PFC

5

Device Technology ST Proposal

S1/S2 1200V SiC MOS SCTxxN120

D1/D2 1200V Rectifier STBRxx12W

Driver STGAP2S/D

Control STM32

Device Technology ST Proposal

S1/S2 1200V SiC MOS SCTWxxN120

S3/S4 1200V SiC MOS SCTxxN120

Driver STGAP2S/D

Control STM32

Device Technology ST Proposal

S1/S2 1200V SiC MOS SCTxxN120

T3/T4 1200V SCR TNxx50-12PI

Driver STGAP2S/D

Control STM32

Var. 1 – Cost – Diode Leg Var. 2 – Performance – SiC MOS Leg Var. 3 – Relay-less – SCR Leg

Phase 1

S1

S2

D1

D2

Phase 2

Phase 3

S1

S2

S3

S4

Phase 1

Phase 2

Phase 3

Phase 1

Phase 2

Phase 3

S1

S2

T3

T4

SiC MOSFET mandatory due high DC Voltage and body diode robustness

ST AC-DC Inrush Current Limiter solutions

6

RLIM

S1

S2

• Programmable soft power up control

• Controlled multiple peak current

limitation

• Zero-current Switch

• No Contact Bounce: no spark, no EMI

• Faster line-drop recovery

• Increase switching life expectancy

Low profile design, smaller height thanks

to D²PAK package

SM

AR

TS

AF

ET

YC

OM

PA

CT

IHT008V1 ISF003V1

power500W 7kW2kW

SCR001V1

Latest topology trends

STEVAL-SCR001V1

TN5015H-6G

TN2010H-6G

DPSTPFC1

MCU

+

SCR

TRIAC

+

MCU SCR

+

SCR

Bridgeless PFC

SCRs phase control

77

SCR1

VACHVDC

SCR2

T T T

T_OFF_1 T_OFF_2 T_OFF_3

T T TT

T_OFF_Max

2x∆t 3x∆t 4x∆t∆t 5x∆t

T_OFF_Min

• Bulk capacitor is charged according to time-depending pulse train driving SCR1

and SCR2

• SCR1 and SCR2 are synchronized according to the zero crossing (ZVS) of the

AC line

• SCR1 and SCR2 are alternatively controlled according to the AC line polarity by

reducing the turn-on delay (“T_OFF”) by a constant ∆t at each half AC line cycle

• SCR1 and SCR2 are controlled by phase angle up to the turn-on delay

(“T_OFF”) is lower than “T_OFF_Min”

• Control the inrush-current to charge a DC bus capacitor

• Disconnect the DC bus capacitor from the AC mains when it does not have to operate

LAOD

S2

VAC

IACSCR1

SCR2

S1

HVDC

Evaluation board performanceDesign content

88

Reference Name Description

STEVAL-DPSTPFC0 AC - DC power boardBridgeless Totem Pole boost with auxiliary

supply

STEVAL-DPS334M1 PFC control board 32-bit MCU control board

STEVAL-DPSADP01 Adapter BoardInterface for MCU debugging and USART

communication

Evaluation board performancePFC Totem Pole start-up

9

To ensure a smooth PFC start-up a soft start routines has

been implemented on the MCU firmware:

1) Inrush current limiter: SCRs are controlled with a

progressive phase control and the output capacitor can be

smoothly up to the AC line peak voltage.

2) PFC soft start: The output voltage reference is controlled

from AC line peak voltage to 400 Vdc with a smoothly

voltage ramp.

HVDCVAC

IAC

Inrush current limiter Steady StatePFC soft startPFC OFF

LAOD

S2

VAC

IACSCR1

SCR2

S1

HVDC

Evaluation board performancePFC efficiency / THD measurement

10

VAC = 230 VRMS @ 50 Hz

0

2

4

6

8

10

12

14

16

18

90

91

92

93

94

95

96

97

98

99

500 1000 1500 2000 2500 3000 3500

THD

(%

)

Effi

ien

y (%

)

POUT (W)

Board features

11

• Description of a 3.6kW bridgeless totem pole PFC evaluation board for telecom and industrial applications with an digital Inrush current limiter using SiC MOSFETs and Thyristors.

• The Evaluation board design includes

• A power board bridgeless totem pole boost with an inrush limiter circuit, SiC MOSFET and SCRs switch drivers and an auxiliary power supply

• A control board with its MCU, a PFC/ICL control firmware

• An adapter board for software debug

• Evaluate a full ST solution• SCRs: To control the inrush-current to charge a DC bus capacitor and to fulfill with the IEC 61000-3-3 standard

• SiC MOSFETs: To reduce passive components size and to provide a PFC with a very high efficiency thanks to low reverse recovery diode body

• STGAP2S driver: Dedicated and optimized to control SiC MOSFETs

• STM32 microcontroller: Embedded the PFC control algorithm

11

DC/DC or motor inverter can

be connected to this

evaluation board

L

A

O

D

S2

VAC

IACSCR1

SCR2

S1

HVDC

• Check the stand-by losses • Reduce drastically the stand-by losses of the traditional NTC/PTC Inrush-current limitation

• Disconnect the DC bus capacitor from the AC mains when it does not have to operate

• Without requiring a relay to be added to open the circuit during stand-by

• Check EMC• Immunity to fast transient and surge voltages

• Common mode noise

• This reference design offering:• A high efficiency: > 97,5%

• A low THD distortion lower than 5 % of maximum load

• A high switching lifetime with reduced EMI emissions

• A robust circuit that meets EMC standards up to 4 kV

• SCR allows achieving a smart inrush current limitation at power up or line drop recovery compare to the traditional NTC and relays solution

Benefits

12

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