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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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