RD5
®
TOPSwitch-II
Reference Design Board
85 to 265 VAC Input, 20W (30W Peak) Output
Product Highlights
Low Cost Production Worthy Reference Design
• Only 22 components!
• Single sided board
• Low cost thru-hole components
• Fully assembled and tested
• Easy to evaluate and modify
• Extensive performance data
• Up to 80% efficiency
• Light weight – no heat sink required for
TOPSwitch-II
Fully Protected by
TOPSwitch-II
• Primary safety current limit
• Output short circuit protection
• Thermal shutdown protects entire power supply
Designed for World Wide Operation
• Designed for IEC/UL safety requirements
• Meets VDE Class B EMI specifications
Figure 1. RD5 Board Overall Physical Dimensions.
1.69 in.
(43 mm)
®
3.57 in. (91 mm)
1.06
in.
(27 mm)
PI-2058-041698
PARAMETER
Input Voltage Range
Input Frequency Range
Temperature Range
Output Voltage
(I
o
= 1.0A)
Output Power
(continuous)
Output Power
(peak)
Line Regulation
(85-265 VAC)
Load Regulation
(10%-100%)
Efficiency
Output Ripple Voltage
Safety
EMI
LIMITS
85 to 265 VAC
47 to 440 Hz
0 to 50°C
12 V
±
5%
25˚C
20W
50˚C
15W
30W
±
1%
±
1%
78%
±
60 mV MAX
IEC 950 / UL1950
VDE B
(VFG243 B)
CISPR22
Description
The RD5 reference design board is an example of a very low
cost production worthy power supply design using the
TOPSwitch
family of Three-terminal Off-line PWM Switchers
from Power Integrations. It is intended to help
TOPSwitch
users to develop their products quickly by providing a basic
design that can be easily modified to fit a particular application.
In most cases, a minor change to the transformer for a different
output voltage is all that is needed. Multiple output voltages are
obtained just as easily. A constant current or constant power
output may be implemented with the addition of a few low cost
components.
Typical applications include AC-DC adapters for laptops,
notebooks and PDAs, battery chargers for cellular telephones,
power tools and camcorders, VTR/VCR, video game, appliance
and satellite decoder power supplies.
Figure 2. Table of Key Electrical Parameters.
July 1997
RD5
1
7, 8
VR1
P6KE200
5, 6
L2
19 mH
BR1
600 V
C1
47
µF
400 V
C6
0.1
µF
250 VAC
D
D2
50SQ100
C2
560
µF
35 V
L1
3.3
µH
+12V
C3
220
µF
35 V
RTN
D1
UF4005
2
4
D3
1N4148
C4
0.1
µF
T1
3
U2
PC817A
R1
39
Ω
TOPSwitch-II
CONTROL
R2
150
Ω
C
J1
L
N
F1
3.15 A
S
U1
TOP224P
C5
47
µF
R3
6.8
Ω
C7
1 nF
250 VAC
Y1
VR2
1N5241B
11 V
PI-2053-041698
Figure 3. Schematic Diagram of the 12V RD5 Power Supply.
BR1
VR1
C1
D2
D1
L2
C6
POWER
INTEGRATIONS
INC.
J1
F1
RD5
S/N
Rev. A
R3
C5
D3
U2
T1
U1
C4
C7
VR2
C2
L1
R2
R1
J2
+
C3
COMPONENT SIDE SHOWN
PI-2059-062697
Figure 4. Component Legend of the RD5.
General Circuit Description
The RD5 is a low-cost, flyback switching power supply using
the TOP224P integrated circuit. The circuit shown in Figure 3
produces a 12 V, 20 W power supply that operates from 85 to
265 VAC input voltage. The 12 V output is directly sensed by
optocoupler U2 and Zener diode VR2. The output voltage is
determined by the Zener diode (VR2) voltage and the voltage
drops across the optocoupler (U2) LED and resistor R1. Other
output voltages are also possible by adjusting the transformer
turns ratios and value of Zener diode VR2.
AC power is rectified and filtered by BR1 and C1 to create the
high voltage DC bus applied to the primary winding of T1. The
other side of the transformer primary is driven by the integrated
high-voltage MOSFET within the TOP224. D1 and VR1
clamp the leading-edge voltage spike caused by transformer
leakage inductance to a safe value and reduce ringing. The
34
A
7/97
RD5
Component Listing
Reference
BR1
C1
C2
C3
C4
C5
C6
C7*
Value
600 V, 2 A
47
µF,
400 V
560
µF,
35 V
220
µF,
35 V
0.1
µF,
50 V
47
µF,
10 V
0.1
µF,
250 VAC, X
1.0 nF, 400 VAC, Y1*
Part Number
2KBPC06M
381LX470M400H012
ECA-1VFQ561
ECE-A1VGE221
RPE131R104M50
ECE-A1AG470
F1772-410-2000
DE1110E102M ACT4K-KD
(or WKP102MCPE.OK
(or PME294RB4100M
UF4005
50SQ100
1N4148
622LY-3R3M
ELF15N005A
5043CX39R00J
5043CX150R0J
5043CX6R800J
TRD5
TOP224P
PC817A
P6KE200
1N5241B
19372K, 3.15A
Manufacturer
General Instrument
Cornell-Dubilier
Panasonic
Panasonic
Murata
Panasonic
Roederstein
Murata
Roederstein)
Rifa)
General Instrument
International Rectifier
National Semiconductor
Toko
Panasonic
Philips
Philips
Philips
Custom
Power Integrations
Sharp
General Instrument
Motorola
Wickman
D1
D2
D3
L1
L2
R1
R2
R3
T1**
U1
U2
VR1
VR2
F1
600 V, 1A, UFR
100 V, 5A, Schottky
75 V, Switching
3.3
µH,
6.5 A
19 mH, 400 mA
39
Ω,
1/4 W
150
Ω,
1/4 W
6.8
Ω,
1/4 W
200 V Zener TVS
11 V Zener
3.15 A, 250 VAC
Figure 5. Parts List for the RD5 (* Two Series Connected, 2.2 nF, Y2-Capacitors Such as Murata DE7100F222MVA1-KC can replace C7).
** T1 is available from Premier Magnetics (714) 362-4211 as P/N POL-12017, and from Coiltronics (561) 241-7876 as P/N CTX00-13742.
power secondary winding is rectified and filtered by D2, C2,
L1, and C3 to create the 12 V output voltage. R2 and VR2
provide a slight pre-load on the 12 V output to improve load
regulation at light loads. R2 also provides bias current for Zener
VR2 to improve regulation. The bias winding is rectified and
filtered by D3 and C4 to create a bias voltage to the TOP224P.
L2 and Y1-capacitor C7 attenuate common-mode emission
currents caused by high-voltage switching waveforms on the
DRAIN side of the primary winding and the primary to secondary
capacitance. L2 and C6 attenuate differential-mode emission
currents caused by the fundamental and harmonics of the
primary current waveform. C5 filters internal MOSFET gate
drive charge current spikes on the CONTROL pin, determines
the auto-restart frequency, and together with R1 and R3,
compensates the control loop.
The circuit performance data shown in Figures 6-18 were
measured with AC voltage applied to the RD5.
Load Regulation (Figure 6) – The amount of change in the DC
output voltage for a given change in output current is referred
to as load regulation. The 12 V output stays within
±1%
from
10% to 100% of rated load current. The
TOPSwitch
on–chip
overtemperature protection circuit will safely shut down the
power supply under persisting overload conditions. Below
minimum load, the 12 V output rises slightly due to the
TOPSwitch
minimum duty cycle.
Line Regulation (Figure 7) - The amount of change in the DC
output voltage for a given change in the AC input voltage is
called line regulation. The maximum change in output voltage
is within
±
1%.
Efficiency (Line Dependent) – Efficiency is the ratio of the
output power to the input power. The curves in Figures 8 and 9
show how the efficiency changes with input voltage.
Efficiency (Load Dependent) – The curves in Figures 10 and 11
show how the efficiency changes with output power for 115
VAC and 230 VAC inputs.
Power Supply Turn On Sequence – The internal switched, high-
voltage current source provides the initial bias current for
TOPSwitch
when power is first applied. The waveforms shown
A
7/97
35
RD5
General Circuit Description (cont.)
in Figure 12 illustrate the relationship between the high-voltage
DC bus and the 12 V output voltage. Capacitor C1 charges to
the peak of the AC input voltage before
TOPSwitch
turns on.
The delay of 160 ms (typical) is caused by the time required to
charge the auto-restart capacitor C5 to 5.8 V. At this point the
power supply turns on as shown.
Figure 13 shows the output voltage turn on transient as well as
a family of curves associated with an additional soft-start
capacitor. The soft-start capacitor is placed across VR2 and can
range in value from 4.7 uF to 47 uF as shown.
Line frequency ripple voltage is shown in Figure 14 for 115
VAC input and 20 W output. Switching frequency ripple
voltage is shown in Figure 15 for the same test condition.
The power supply transient response to a step load change from
1.25 to 1.67 A (75% to 100%) is shown in Figure 16. Note that
the response is quick and well damped.
The RD5 is designed to meet worldwide safety and EMI (VDE
B) specifications. Measured conduction emissions are shown
in Figure 17 for 115 VAC and Figure 18 for 230 VAC.
Thermal Considerations
The RD5 utilizes the printed circuit copper for
TOPSwitch
heatsinking. For 20 W output, the heatsink area is approximately
1.25 in
2
(8 cm
2
). The copper area required for heatsinking at
15 W output is outlined on the non-component side of the board,
and is approximately 0.56 in
2
(3.6 cm
2
). The RD5 printed circuit
board utilizes 2 oz. copper cladding. Printed circuit boards with
lighter cladding will require apertures in the solder mask to
build-up effective trace thickness.
Transformer Specification
The electrical specifications and construction details for
transformer TRD5 are shown in Figures 19 and 20. Transformer
TRD5 is supplied with the RD5 reference design board. This
design utilizes an EI25 core and a triple insulated wire secondary
winding. The use of triple insulated wire allows the transformer
to be constructed using a smaller core and bobbin than a
conventional magnet wire design due to the elimination of the
margins required for safety spacing in a conventional design.
If a conventional margin wound transformer is desired, the
design of Figures 21-22 can be used. This design (TRD5-1)
uses a EEL22 core and bobbin to accommodate the 3 mm
margins required to meet international safety standards when
using magnet wire rather than triple insulated wire, and has the
same pinout and printed circuit foot print as TRD5. The
transformer is approximately 50% taller than the triple insulated
wire design due to the inclusion of creepage margins required
to meet international safety standards.
PI-2062-070297
Output Voltage (% of Nominal)
100
Output Voltage (% of Nominal)
VIN = 115 VAC
100
IL = 1.67 A
50
100
150
200
250
90
0
0.5
1
1.5
2
90
300
Load Current (A)
110
VIN = 230 VAC
Input Voltage (VAC)
110
100
100
IL = 0.33 A
50
100
150
200
250
300
90
0
0.5
1
1.5
2
90
Load Current (A)
Figure 6. Load Regulation
Input Voltage (VAC)
Figure 7. Line Regulation
36
A
7/97
PI-2063-070297
110
110
RD5
PI-2064-070297
Po = 20 W
Po = 4 W
Output Efficiency (%)
60
Output Efficiency (%)
80
80
60
40
20
40
20
0
0
100
200
300
0
0
100
200
300
Input Voltage (VAC)
Figure 8. Efficiency vs. Input Voltage, 20 W Output
100
VIN = 115 VAC
80
Input Voltage (VAC)
Figure 9. Efficiency vs. Input Voltage, 4 W Output
PI-2067-070297
PI-2066-070297
100
VIN = 230 VAC
80
Output Efficiency (%)
Output Efficiency (%)
60
60
40
20
40
20
0
0
5
10
15
20
0
0
5
10
15
20
Output Power (W)
Figure 10. Efficiency vs. Output Power, 115 VAC Input
PI-2068-070297
Output Power (W)
Figure 11. Efficiency vs. Output Power, 230 VAC Input
0
µF
4.7
µF
10
µF
22
µF
47
µF
PI-2069-070297
DC BUS VOLTAGE
150
100
50
0
15
10
5
0
0
100
10
Output Voltage (V)
8
6
4
2
0
OUTPUT
VOLTAGE
200
0
10
PI-2065-070297
100
100
20
Time (ms)
Time (ms)
Figure 12. Turn On Delay
Figure 13. Output Voltage Turn On Transient vs. Soft Start Capacitor
A
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37
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