Design and implementation of a LLC-ZCS Converter for ... · 1/7/2016 · Infineon Italy s.r.l. ATV...
Transcript of Design and implementation of a LLC-ZCS Converter for ... · 1/7/2016 · Infineon Italy s.r.l. ATV...
Infineon Italy s.r.l.ATV division
Design and implementation of a LLC-ZCS Converter for Hybrid/Electric Vehicles
Davide GIACOMINI Principal, Automotive HVICs
HV Battery LV Battery
M
12Vbus
Traction Network
Power Distribution Network
Hybrid and Full Electric vehicles allow pollution reduction this make them the new generation of transportation
Traction and power distribution networks are highly impacted by this evolutionHV battery in hybrid/electric vehicles allow traction as well as services to run out of the battery for a medium/long time.
Need for clean
22016-01-07 Copyright © Infineon Technologies AG 2016. All rights reserved.
HV Battery LV Battery
M
12Vbus
Traction Network
Power Distribution Network
Variable Min. Typ. Max.
Input HVB [V] 250 350 450
Output LVB [V] 13
Load power [W] 400 2400
System has been designed considering these ranges
Power distribution network: exploiting the energy of a HV battery for traction and services
System Specification
› While the traction inverter is directlysupplied by the HV battery, all services in a car today still run out of a 12V battery, therefore a HV-DC/DC converter is neededto supply this battery line
32016-01-07 Copyright © Infineon Technologies AG 2016. All rights reserved.
1. Galvanic isolated topology2. Soft switching
Lr
LV
n:1
GD
GD
GD
IG1 IG2
IG3 IG4
M1
M2
HV
HV
Gate
Dri
ver
LV Gate Driver
Cr
Controller board
and isolation
• Behaves as current generator intrinsically protected @ short circuit at the output.• ZCS has the advantages of using IGBT with co-packed fast diode;• Simplified output filtering uses only capacitors;• No need to control the DC current through transformer, resonance Cap solves it.
System design: converter topology choice
42016-01-07 Copyright © Infineon Technologies AG 2016. All rights reserved.
Lr
LVB
n:1
GD
GD
GD
IG1 IG2
IG3 IG4
M1
M2
HVB
HV
Gate
Dri
ver
LV Gate Driver
Cr
Analog
ControllerOptocoupler
-
+ Vref
Error Amplifier
Cr voltage
sense
Primary High Voltage Side Secondary Low Voltage Side
Inner Loop
Voltage Control Loop
Cf
IRS27951SSO8 analog controllerGrounded in the HV side
Error amplifier and OV protectionGrounded on the LV side
HV caps protectionloop
System design: control strategy
AU
IRS
11
70
S
1
2
3
4
8
7
6
5
VCC
SYNC
MOT
EN
VGATE
VS
VD
NC
AUIRS1170S synch. Rect.PSO8 analog controller
AU
IRS2191S
AUIRS2191S Fast HVIC driverSO16
52016-01-07 Copyright © Infineon Technologies AG 2016. All rights reserved.
LLC DC/DC board, prototype picture
62016-01-07 Copyright © Infineon Technologies AG 2016. All rights reserved.
Board Layout Resonant Capacitor tank
Pri
mary
sid
e I
GBTs
Resonant Inductor at primary side
Transformer
Center tappedoutput
SynchronousrectificationFets and control IC
Pri
mary
sid
e
gate
dri
vers
Loop control board
Output Capacitors
Layout is optmised for system testing and debugging.
72016-01-07 Copyright © Infineon Technologies AG 2016. All rights reserved.
• It is made with only Organic Conductive Polymer capacitor, 4mF in total no need for output inductor
• System volume and cost are reduced
• SR MOSFET voltage rating = 60V-80V higher power density and cheaper system
Output Flter
• Resonant inductor at primary side reduces size and weight; resonant capacitors also take care of balancing the magnetizing current
Magnetics and Resonant Tank
• Resonant inductor and capacitor values have been optimized vs. load and input voltage variation
Mathlab routine has been implemented in order to design
main parameters
•Magnetizing inductance Lm = abut 6 times resonant inductor value
•Transformer ratio is 16:1+1; Isec. = 170Arms
•Variable frequency from 60kHz to 125kHzTransformer
•Lr = 128uH
•Irms~15A
•System Resonant freq.: 125kHzResonant inductor
•Cr = 12,6nF
•3kV
•C0G (low ESR)Resonant Capacitor
•Rds-on = 2,4mW max, 80V
•3x each leg in parallelSynchronous rectification Fets
•650V – 40A IGBTs
•Vce_sat= 1,80V @125CPrimary switching section
System design: main BOM components
82016-01-07 Copyright © Infineon Technologies AG 2016. All rights reserved.
Simulation results
Transfer Function: switching from 70k to 120kHz at Vin=350V
~70kHz ~120kHz
Simulation at Vin = 350V, Vout = 12V and different power output
92016-01-07 Copyright © Infineon Technologies AG 2016. All rights reserved.
Measurements: Operating Frequency vs Input Voltage and load
96
98
100
102
104
106
108
110
112
200 250 300 350 400 450
Fsw vs Vin at Io=100A
V
KHz
0
20
40
60
80
100
120
25 75 125 175
Fsw vs Io at Vin=350VKHz
A
Low switching frequency variation vs. input voltage and load changes
Good matching with simulation
102016-01-07 Copyright © Infineon Technologies AG 2016. All rights reserved.
Operation at nominal input voltage:400V – 100A
Sec.Center tap current
100A/d
Primary current
25A/d
Capacitor voltage
500V/d
Clean sinusoidal voltage across resonance capacitors, someringing noise visible on transformer‘s secondary current
112016-01-07 Copyright © Infineon Technologies AG 2016. All rights reserved.
Operation at nominal input voltage: 400V – 150A
Sec.Center tap current
100A/d
Capacitor voltage
1kV/d
Primary current
25A/d
Frequency, capacitors voltage and Primary/Secondary currents increase
122016-01-07 Copyright © Infineon Technologies AG 2016. All rights reserved.
Operational waveforms at 400V -180A
Primary current
50A/d
Sec.Center tap current
100A/d
Capacitor voltage
1kV/d
Very close to resonance (~110kHz), waveforms are almost sinusoidal.
132016-01-07 Copyright © Infineon Technologies AG 2016. All rights reserved.
Secondary side synchronous rectification
AU
IRS
11
70
S
1
2
3
4
8
7
6
5
VCC
SYNC
MOT
EN
VGATE
VS
VD
NC
VCC
SYNC
MOT
EN
Vg
Vs
Vd
RMOT
RCC
CVCC
VCC
SYNC
MOT
EN
Vg
Vs
Vd
RMOT
RCC
CVCC
AUIRS1170S AUIRS1170S
VoutLon:1
GND
Cout
Rf
Cf
Rg
Rf
Rg
Cf
• In a LLC converter the secondary current and primary switching voltage are not in phase and their
phase rotation depends on the load, this effect doesn’t allow to use the primary PWM signal to
control the secondary side switches.
• A dedicated IC reading the VDS voltage across the Synch Rectification Fets solves this problem
› Typical application schematicAUIRS1170S
142016-01-07 Copyright © Infineon Technologies AG 2016. All rights reserved.
Secondary side waveforms at 400V and light load
Ch1= Vds [10V/d], Ch3= Vgate1 [5V/d], Ch4= Isec. [20A/d]
Waveform obtained at low current output of 30A only: the signal across the 0,8m W equivalent
Rds-on of the Fets becomes quite small but the gate command signal is regular.
152016-01-07 Copyright © Infineon Technologies AG 2016. All rights reserved.
Secondary side waveforms at 400V and high load
Primary current
25A/d
Sec.Center tap current
100A/d
Blue: Vgs
Light blue: Vds
Waveform obtained at high current output of 160A: the signal across the 0,8m W SR Fets is
much more evident as well as switching noise but the gate command signal is regular.
162016-01-07 Copyright © Infineon Technologies AG 2016. All rights reserved.
Power Losses Breakdown(350Vin)
0
50
100
150
200
250
300
350
400
W
Io=150A
0
20
40
60
80
100
120
140
160
180
200
W
Io=100A
• Primary side losses look still predominat and increase proportionally with the output current;
• High Vcesat of IGBTs still inpact this performances;
• Inductor losses seems to be increasing rapidly with output current, showing undersizing of the component, redesign is advisable;
• Resonant and output Capacitor losses have low inpact in the overall efficiency.
Estimation done though thermal measurement and mathematical estrapolations
172016-01-07 Copyright © Infineon Technologies AG 2016. All rights reserved.
Efficiency results
• Efficiency at light load is high, thanks to the low frequency operation of the input bridge;
• High Vcesat of IGBTs and inductor losses inpact overall system performances;
• At Iout=150A, only 1mW pcb trace resistance in the secondary side means 23W dissipatedand 1,3% efficiency loss.
0.75
0.8
0.85
0.9
0.95
1
40 60 80 100 120 140 160
Eff 300Vin
Eff 350Vin
Eff 400Vin
[A]
182016-01-07 Copyright © Infineon Technologies AG 2016. All rights reserved.
Start up and Vin transients
Fast start: Vin rise time is only limited by the Lab power supply
Vin=400V, Io=25A
Primary current
25A/d
Sec.Center tap current
100A/d
Capacitor voltage
1kV/div
Vin; 100V/div
192016-01-07 Copyright © Infineon Technologies AG 2016. All rights reserved.
Output current
30A
120A
Output voltage
Switching frequency
Experimental results: load transient
Low ESR output caps provide very low output voltage variation at load transients
202016-01-07 Copyright © Infineon Technologies AG 2016. All rights reserved.
Load transients : Iout from 70 to 140A
Primary current
25A/d
Sec.Center tap current
100A/d
Vout ripple
Load increase to 140A (traces 2 and 3 with AC coupling)
212016-01-07 Copyright © Infineon Technologies AG 2016. All rights reserved.
Load transients : Iout from 140 to 70A
Primary current
25A/d
Sec.Center tap current
100A/d
Vout ripple
Load decrease to 70A (traces 2 and 3 with AC coupling)
222016-01-07 Copyright © Infineon Technologies AG 2016. All rights reserved.
1. An Auxiliary DC-DC converter has been designed by using the uncommon LLC ZCS topology
2. System design flow with mathematical and electrical models have been utilized to tune the resonant tank and converter frequency operation range
3. Prototype has been built and verified
4. System efficiency over 90%, limited by high Vce_sat of IGBTs and inductor losses
5. Robustness to load transients has been verified
6. Prototype Max power is limited to around 2.0kW with air forced cooling, because of PCB and heat sinks limitations.
7. Next step: evaluate Super-Junction Mosfets performances in the same topology, adding Ultrafast diodes in parallel.
Conclusions
232016-01-07 Copyright © Infineon Technologies AG 2016. All rights reserved.