60W Auxiliary Power Supply Demonstration board

60W Auxiliary Power Supply Demonstration board
1. DEMONSTRATION BOARD SUMMARY
The CRD-060DD12P is a Cree demonstration board for a single-end Flyback converter design with a
commercially available 1700V Silicon Carbide (SiC) MOSFET to replace conventional two-switch
Flyback converter for high voltage input auxiliary power supply of three phase applications. The
demonstration board is not designed to be a product and is to be only used as a tool to evaluate the
performance Cree switching devices.
2. INTRODUCTION
VCPWR-AN14, RE
o board
wer Supply Dem
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Au
W
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Three-phase applications, such as motor drive, UPS and PV inverter, have a front end AC/DC or DC/DC
converter to boost the DC link voltage up to 600Vdc to 800Vdc. Factoring in a design margin, the
maximum DC link voltage is up to 1000V. To support such systems in practice, an auxiliary power
supply is used to generate power for cooling fans, displays, control logic and system protection functions
with the DC link voltage as its input. For such low power applications, Flyback topology is the most
common type in the industry; however, the conventional single end Flyback topology has difficulty in
meeting high input voltage. The first difficulty is caused by the high input voltage (1000Vdc); the singleend Flyback topology would require high blocking voltage switching devices. Currently, the Silicon
MOSFET only has 1500V blocking voltage, which has low voltage stress design margin and thus affects
the reliability of the power supply. The second challenge is that most of the 1500V Si MOSFETs have
very large on-state resistance, and this will lead to higher losses, higher thermal and lower efficiency,
especially when the whole three-phase system is operating at light output load and auxiliary power losses
occupy most of total system losses. Lastly, to support a wide input voltage range, a pure resistance start
up circuit is normally used. However, the start-up resistance will lead to losses at high input voltage.
Larger start-up resistance will have less losses but lead to long start-up time at low input voltage.
In order to overcome these auxiliary power supply design challenges to supply high input voltage, twoswitch Flyback converter was proposed to use high side and low side 800V Si MOSFETs as shown in
Fig.1, but it has the additional isolation gate drive circuit which increases component counts and
complicates the design. This application note proposes a single-end Flyback converter to replace
complicated two-switch Flyback converter by using 1700V SiC MOSFET. An active start-up circuit is
also introduced to achieve less start-up losses with faster start up time. The 60W experimental reference
design demonstrates that the 1700V SiC MOSFET can reduce total cost and simplify the design of
auxiliary power supply.
Figure 1: A conventional two-switch Flyback converter with 800V Si MOSFET
Subject to change without notice.
www.cree.com
1
3. Cree 1700V SiC MOSFET
Today, SiC devices are characterized by a number of promising properties like high rating voltages, low
switching losses, low on-state resistance, higher operating temperature, and high radiation hardness. A
commercially available 1700V TO-247 packaged SiC MOSFET, C2M1000170D, from Cree Inc is used
for a wide input auxiliary power supply application. The table compares the key parameters between SiC
MOSFET and Si MOSFET with common TO-247 package. From this comparison, SiC MOSFET can
support much higher blocking voltage to 1700V and avalanche voltage above 1800V, while Si MOSFET
only has 1500V blocking voltage with lower avalanche voltage. For the on-state resistance and parasitic
capacitance, the SiC MOSFET has lower value than Si MOSFET to have low conduction losses and low
switching losses. This key difference will value 1700V SiC MOSFET to have high efficiency and high
reliability replacing 1500V Si MOSFET.
Table 1: Parameter comparisons of 1700V SiC MOSFET and 1500V Si MOSFET
Parameters
SiC MOSFET
Si MOS
Si MOS
C2M1000170D
STW4N150
2SK2225DS
V(BR)DSS
1700V
1500V
1500V
Avalanche
>1800V
N/A
N/A
Id @ Tc=25°C
5A
4A
2A
Rdson @150°C
2ohm
9ohm
20ohm
Coss
14pF
120pF
60pF
Tjmax
>150°C
150°C
150°C
Package
TO-247
TO-220, TO-247
TO-3PF
4. ACTIVE START-UP CIRCUIT
In this design, a non-dissipative, active start-up circuit has been implemented to optimize converter
efficiency and fast start-up time. The alternative is to use a pure resistive start-up circuit which
significantly affects converter efficiency and start up times at low input voltages in a negative way. Figure
2 shows the proposed active start-up circuit. When input voltage is increasing, Q6 is turned on by Vbase
from path R31 to R36. The VCC voltage comes from path R22 to R25 when U1 (UCC28C44) is turning
on. Once U1 starts operating, the VCC supply comes from the primary auxiliary winding. When VCC
reaches the startup threshold of U1, the VREF (+5V) goes to high and Q7 is turned on. And then Q6 is
turned off, which disconnects the start-up current path to VCC. The R31 to R36 resistors with large value
are used as the voltage balancing for input capacitors C1 to C3. The startup resistors R22 to R25 feeds the
PWM controller of U1 until the auxiliary supply voltage rises and is disconnected from VCC of U1 and
then there are no more losses from start-up resistors. So the active start-up circuit can reduce the start up
power dissipation, especially at high line input voltage and improve the efficiency. The additional power
dissipation under such normal steady state conditions is due to the balance resistances, and they can be set
at very high values (>6Mohm). More importantly, due to low resistance values for this active start-up
circuit, the start-up time will be short and can be trimmed to meet targeting start-up time. If assuming
minimum start-up time 1s, the VCC capacitance can be calculated as follows:
C start up 
CPWR-AN14, REV 2 60W Auxiliary Power Supply Demo board
IUCC 28C 44 startupTstart up
VUVLO _ on  VUVLO _ off
(1)
This document is provided for informational purposes only and is not a warranty or a specification.
For product specifications, please see the data sheets available at www.cree.com/power. For warranty
information, please contact Cree Sales at [email protected]
From datasheet of UCC28C44: I UCC 28C 44 start up  0.1mA ; VUVLO _ on  14.5V ; VUVLO _ off  9.0V . If C Start up  18F ,
it can select the VCC capacitance is 22uF. The total start-up current may then be calculated using the
below equation:
I start up 
C start upVUVLO _ on
Tstart up

22F  14.5V
 0.319mA
1S
(2)
Hence, the total start-up resistors (R22 to R25) may be calculated as:
Rstart up 
VDC min  VUVLO _ off
I start up

200V  9V
 600 K
0.319mA
(3)
Assuming worse darlington gain hFE is 500, the total balance resistance (R31-R36) may be calculated as:
RBalance 
VDC min  VUVLO _ off
I startup / hFE

200V  9V
 300M
0.319mA
(4)
By using much higher balance resistance, total additional losses can be seen to have no negative impact
on total losses.
HV_DC
J1
1
HV_DC
C1
10uF
450V
R22
150k
R32
1M5
I/P:
200V
to 1000V
R23
150k
VCC
R33
1M5
C2
10uF
450V
J2
R31
1M5
Q5
PBSS4240T
R24
150k
R47
4.7k
R34
1M5
+ C12
22uF
R25
150k
+ C36
NC
+ C10
10uF
C11
0.1uF
1
ZD3
18V
P_GND
C3
10uF
450V
R35
R36
1M5
1M5
Q6
STP03D200
Q7
MMBT2222A
R30
510k
1
2
3
4
U1
COMP VREF
FB
VCC
CS
OUT
RC
GND
8
7
6
C13
0.1uF
5
UCC28C44
Figure 2: The proposed active start-up circuit
CPWR-AN14, REV 3 60W Auxiliary Power Supply Demo board
This document is provided for informational purposes only and is not a warranty or a specification.
For product specifications, please see the data sheets available at www.cree.com/power. For warranty
information, please contact Cree Sales at [email protected]
5. EXPERIMENTAL RESULTS
To demonstrate high performance of 1700V SiC MOSFET, a 60W single-end
end Flyback auxiliary power
supply with proposed active start-up
start
circuit is developed as shown in Figure 3.
Table 2: 60W auxiliary SMPS prototype design specification with 1700V SiC MOSFET
200Vdc to 1000Vdc
Input Voltage
Output Voltage
+12Vdc
+5Vdc
-12Vdc
Output Current
4.5A
0.5A
0.25A
Frequency
75KHz
Efficiency
>83%
Figure 3:: Photo of 60W auxiliary SMPS with 1700V SiC MOSFET
85.0%
84.0%
83.0%
Efficiency (%)
82.0%
81.0%
80.0%
79.0%
78.0%
CREE C2M1000170D
ST STW4N150
77.0%
76.0%
75.0%
200v
400v
600v
800v
1000V
Vin (Vdc)
Figure 4:: 60W auxiliary SMPS efficiency with 1700V SiC MOSFET
CPWR-AN14, REV 4 60W Auxiliary Power Supply Demo board
This document is provided for informational purposes only and is not a warranty or a specification.
For product specifications, please see the data sheets available at www.cree.com/power. For warranty
information, please contact Cree Sales at [email protected]
Figure 4 compares measured efficiency at full load with input voltage varying from 200V to 1000V using
different Si and SiC devices. Due to lower on-state resistance and parasitic capacitance, the 1700V SiC
MOSFET can achieve a higher efficiency when compared to other 1500V Si MOSFET competitors.
Thermal comparison at full load with the same heat sink is shown in Fig.5, SiC MOSFET clearly shows a
lower operating temperature at 45.9°C when compared to Si 1500V MOS at 60°C and 99.9°C. It shows
that 1700V SiC MOSFET can achieve higher reliability. Use of the 1700V SiC MOSFET also allows us
to use a small low cost heat sink due to the fact that a smaller amount of heat needs to be dissipated as
shown in Figure 6. This can save the auxiliary power board size and improve power density.
STW4N150 with large heat sink
C2M1000170D with large heat sink
(a) SiC MOS C2M1000170D
(b) Si MOS STW4N150
2SK2225 with large heat sink
(c) Si MOS 2SK2225
Figure 5: Thermal comparison with same large heat sink and input voltage is 1000Vdc
C2M1000170D with small heat sink
Figure 6: SiC MOSFET Thermal with small low cost heatsink and input voltage is 1000Vdc
Figure 7 shows the start up waveform with the proposed active start-up circuit. At 1000Vdc input, start up
time is less 100ms and at 200Vdc input, start up time is less than 1s. Meanwhile, by trimming the start-up
resistor R22 to R25, it can achieve faster start up time smoothly without sacrificing efficiency.
(a) 1000V input full load
(b) 200V input full load
Figure 7: Start-up sequence waveforms
C2 (pink): Vin, 350V/Div; C3 (blue): Vcc, 10V/Div; C4 (green):Vgs, 20V/Div
CPWR-AN14, REV 5 60W Auxiliary Power Supply Demo board
This document is provided for informational purposes only and is not a warranty or a specification.
For product specifications, please see the data sheets available at www.cree.com/power. For warranty
information, please contact Cree Sales at [email protected]
Figure 8 shows the Vgs and Vds waveforms at difference input voltage and output loading (full load and
light load). It shows that 1700V SiC MOSFET Vgs and Vds waveforms are very clean with fast switching
at 200Vdc and 1000Vdc inputs.
(a) Input: 200Vdc, Light load
(b) Input: 200Vdc, Full load
(c) Input: 1000Vdc, Light load
(d) Input: DC 1000V, Full load
Figure 8: Vgs and Vds waveforms of 1700V SiC MOSFET
C1(yellow): Vgs, 10V/div; C4 (green): Vds, 500V/div
REFERENCES
[1]
[2]
[3]
[4]
[5]
C2M1000170D 1700V SiC MOSFET datasheet, Cree InC.
JinBin Zhao, and FengZhi Dai, “Soft-switching two-switch flyback converter with wide range,” in Industrial
Electronics and Application, 2008. ICIEA 2008.
Robert W, Dragan M, Fundamentals of Power Electronics, Boulder Colorado, 2002.
Lloyd H. Dixon, “Magnetics Design for Switching Power Supplies,” in Unitrode Magnetics Design Handbook, 1990.
Bob Callanan. Application Considerations for Silicon Carbide MOSFETs, Cree InC.
CPWR-AN14, REV 6 60W Auxiliary Power Supply Demo board
This document is provided for informational purposes only and is not a warranty or a specification.
For product specifications, please see the data sheets available at www.cree.com/power. For warranty
information, please contact Cree Sales at [email protected]
Appendix A – Schematic
CPWR-AN14, REV 7 60W Auxiliary Power Supply Demo board
This document is provided for informational purposes only and is not a warranty or a specification.
For product specifications, please see the data sheets available at www.cree.com/power. For warranty
information, please contact Cree Sales at [email protected]
Appendix B - BOM
Part
no.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
C1
C2
C3
C4
C5
C6
C7
C8
C9
C10
C11
C12
C13
C14
C15
C16
C17
C18
C19
C20
C21
C22
C23
C24
C25
C26
C27
C28
C29
C30
C31
C32
C33
C34
C35
C36
C37
C38
C39
C40
C41
D1
D2
D3
D4
D5
D6
D7
D8
D9
D10
J1
J2
J3
J4
J5
L1
L2
L3
Q1
Q4
Value
10uF
10uF
10uF
0.1uF
680uF
0.1uF
1.2nF
100pF
1uF
10uF
0.1uF
22uF
0.1uF
22nF
1nF
0.1uF
NC
10nF
680uF
100nF
100uF
1uF
100nF
220uF
0.1uF
1uF
47uF
1uF
0.22uF
220uF
0.1uF
0.1uF
47uF
1uF
100pF
NC
10nF
1uF
100pF
33pF
33pF
HV_DC
P_GND
CON2
CON2
CON2
3.5uH
2.7uH
2.7uH
1000mohm, 1700V
Manufacturer Part no.
Manufacturer
name
B32794D2106K
B32794D2106K
B32794D2106K
EPCOS
EPCOS
EPCOS
EEU-HD1V681
Panasonic
ECW-H16122JV
Panasonic
Description
MKP, 5%
MKP, 5%
MKP, 5%
CAP CER 100V 10% X7R 0603
CAP CER 100V 10% X7R 0603
CAP CER 100V 10% X7R 0603
CAP CER 100V 10% X7R 1206
ECEA1HKS100
Panasonic
EEA-GA1V220
Panasonic
CAP CER 100V 10% X7R 1206
CAP CER 100V 10% X7R 0603
CAP CER 100V 10% X7R 0603
CAP CER 100V 10% C0G 0603
CAP CER 100V 10% X7R 0603
CAP CER 100V 10% X7R 0603
EEU-HD1V681
Panasonic
UPB1V101MPD
Nichicon
CAP CER 100V 10% X7R 0603
CAP CER 50V 10% X7R 0603
CAP CER 100V 10% X7R 0603
EEU-EB1V221
Panasonic
CAP CER 100V 10% X7R 0603
CAP CER 50V 10% X7R 0603
EEA-GA1V470
Panasonic
R76TR3220SE30K
EEU-EB1V221
Kamet
Panasonic
CAP CER 50V 10% X7R 0603
CAP CER 100V 10% X7R 0603
CAP CER 100V 10% X7R 0603
EEA-GA1V470
Panasonic
CAP CER 50V 10% X7R 0603
CAP CER 100V 10% X7R 0603
CAP CER 100V 10% X7R 0603
CAP CER 50V 10% X7R 0603
CAP CER 100V 10% C0G 1206
CAP CER 100V 10% C0G 1206
CAP CER 100V 10% C0G 1206
RS1M-13-F
STTH1R02A
1N4148
VB30100S-E3/8W
STPS3H100U
STPS3H100U
RS1M-13-F
1N4148
1N4148
1N4148
2 pin, P:5.08mm
2 pin, P:5.08mm
282837-2
282837-2
282837-2
744771003
SWPA5020S2R7NT
SWPA5020S2R2NT
C2M1000170D
PBSS4240T
CPWR-AN14, REV 8 60W Auxiliary Power Supply Demo board
Diodes
ST
Vishay
ST
ST
Diodes
TE
TE
TE
Wurth
Sunlord
Sunlord
CREE
NXP
HV tips terminal
HV tips terminal
Horizontal, P:5.08mm
Horizontal, P:5.08mm
Horizontal, P:5.08mm
1700V, 1000mohm, SiC MOSFET
This document is provided for informational purposes only and is not a warranty or a specification.
For product specifications, please see the data sheets available at www.cree.com/power. For warranty
information, please contact Cree Sales at [email protected]
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
Q5
Q6
Q7
R1
R2
R3
R4
R5
R6
R7
R8
R9
R12
R13
R14
R15
R16
R17
R18
R19
R20
R21
R22
R23
R24
R25
R26
R27
R28
R29
R30
R31
R32
R33
R34
R35
R36
R37
R38
R39
R40
R41
R42
R43
R44
R45
R46
R47
R50
R51
R52
R53
T1
U1
U2
U3
ZD1
ZD2
ZD3
HS1
PBSS4240T
STP03D200
MMBT2222A
220K
10R
2k2
1R3
1R3
220K
1R
NC
11k
0
10k
0
NC
1k
33k
39k
10k
2K
10k
150k
150k
150k
150k
0R
0R
0R
0R
510K
1M5
1M5
1M5
1M5
1M5
1M5
10k
10k
2.4k
5.6k
NC
220K
220K
33
10k
0
4.7k
51R
36R
36R
10R
PQ26/25
UCC28C44
FOD817A
TL431A
22V
5.6V
18V
CRCW25121R30FP
CRCW25121R30FP
NXP
ST
Vishay
Vishay
1W, 1%
RES, 0.25W, 1%, 1206
RES, 0.25W, 1%, 1206
1W, 1%
1W, 1%
1W, 1%
RES, 0.25W, 1%, 1206
RES, 0.1W, 1%, 0603
RES, 0.1W, 1%, 0603
RES, 0.1W, 1%, 0603
RES, 0.1W, 1%, 0603
RES, 0.1W, 1%, 0603
RES, 0.1W, 1%, 0603
RES, 0.1W, 1%, 0603
RES, 0.1W, 1%, 0603
RES, 0.1W, 1%, 0603
RES, 0.25W, 1%, 1206
RES, 0.5W, 200V, 1%
RES, 0.5W, 200V, 1%
RES, 0.5W, 200V, 1%
RES, 0.5W, 200V, 1%
RES, 0.5W, 200V, 1%
RES, 0.5W, 200V, 1%
RES, 0.5W, 200V, 1%
RES, 0.5W, 200V, 1%
RES, 0.25W, 1%, 1206
RES, 0.5W, 200V, 1%
RES, 0.5W, 200V, 1%
RES, 0.5W, 200V, 1%
RES, 0.5W, 200V, 1%
RES, 0.5W, 200V, 1%
RES, 0.5W, 200V, 1%
RES, 0.25W, 1%, 1206
RES, 0.25W, 1%, 1206
RES, 0.1W, 1%, 0603
RES, 0.1W, 1%, 0603
750341672
UCC28C44D
FOD817ASD
TL431AIDBZ
MMSZ5251
MMSZ5232
MMSZ5248
RA-T2X-38E
CPWR-AN14, REV 9 60W Auxiliary Power Supply Demo board
Würth-midcom
TI
Fairchild
TI
Vishay
Vishay
Vishay
Ohmite
1W, 1%
1W, 1%
RES, 0.5W, 200V, 1%
RES, 0.1W, 1%, 0603
RES, 0.5W, 100V, 1%
RES, 0.1W, 1%, 0603
RES, 0.25W, 1%, 1206
RES, 0.25W, 1%, 1206
RES, 0.25W, 1%, 1206
RES, 0.25W, 1%, 1206
PQ2625 transformer
0.5W
0.5W
0.5W
Heatsink
This document is provided for informational purposes only and is not a warranty or a specification.
For product specifications, please see the data sheets available at www.cree.com/power. For warranty
information, please contact Cree Sales at [email protected]
Appendix C – PCB layout
Top side PCB layout
Bottom side PCB layout
CPWR-AN14, REV 10 60W Auxiliary Power Supply Demo board
This document is provided for informational purposes only and is not a warranty or a specification.
For product specifications, please see the data sheets available at www.cree.com/power. For warranty
information, please contact Cree Sales at [email protected]