RDK-252 Power Integrations, RDK-252 Datasheet - Page 27

• Manufacturer Part Number: RDK-252
• Description: KIT REF DESIGN DG CAPZERO
• Manufacturer: Power Integrations
• Series: CAPZero™r
• Type: Other Power Managementr

Specifications of RDK-252

• Main Purpose: Automatic X Capacitor Discharge
• Embedded: No
• Utilized Ic / Part: CAP014DG, CAP002DG, CAP012DG
• Primary Attributes: Low No-Load Input Power (
• Secondary Attributes: Surge Testing to EN6100-4-5 Class 4
• Input Voltage: 85 V to 264 V
• Board Size: 38.1 mm x 25.4 mm
• Product: Power Management Modules
• Dimensions: 38.1 mm x 25.4 mm
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• For Use With/related Products: CAP014DG
• Other names: 596-1313

the device heatsink. The subsequent thermal and efficiency
data confirmed this choice. The maximum device temperature
was 107°C at full load, 40 °C, 85 VAC, 47 Hz (worst case
conditions) and average efficiency exceeded 83% ENERGY
STAR and EuP Tier 2 requirements.
Transformer Core Selection
•
The size of the magnetic core is a function of the switching
frequency. The choice of the higher switching frequency of
132 kHz allowed for the use of a smaller core size. The higher
switching frequency does not negatively impact the efficiency in
TOPSwitch-JX designs due its small drain to source capacitance
(C
Line Sense Resistor Values
•
Line sensing is provided by resistors R1 and R2 and sets the
line undervoltage and overvoltage thresholds. The combined
value of these resistors was increased from the standard 4 MW
to 10.2 MW. This reduced the resistor, and therefore contribution
to no-load input power, from ~26 mW to ~10 mW. To compensate
the resultant change in the UV threshold resistor R12 was
added between the CONTROL and VOLTAGE-MONITOR pins.
This adds a DC current equal to ~16 µA into the V pin, requiring
only 9 µA to be provided via R1 and R2 to reach the V pin UV
threshold current of 25 µA and setting the UV threshold to
approximately 95 VDC.
Figure 32. Schematic of High-Efficiency 12 V, 30 W, Universal Input Flyback Supply With Very Low No-load.
www.powerint.com
AN-47
OSS
132 kHz switching frequency allowed the selection of smaller
core for lower cost.
Increasing line sensing resistance from 4 MW to 10.2 MW to
reduce no-load input power dissipation by 16 mW.
) as compared to that of discrete MOSFETs.
L
N
85 - 264
3.15 A
VAC
F1
14 mH
L1
No-load Input Power (mW)
Full Load Efficiency (%)
Input Voltage (VAC)
Average Efficiency (%)
275 VAC
100 nF
C1
1N4007
1N4007
81.25
D1
D3
60.8
85
83.94
84.97
61.98 74.74
1N4007
1N4007
115
82 µF
400 V
D2
D4
C3
86.21
85.13
230
14.3 kΩ
5.1 MΩ
5.1 MΩ
R15
1%
R1
R2
TOPSwitch-JX
10 MΩ
10 MΩ
TOP266VG
R3
R4
U1
10 kΩ
1/2 W
R5
P6KE180A
VR1
D
S
FR107
CONTROL
D5
X
V
BAV19WS
4.7 nF
1 kV
191 kΩ
C4
F
D6
R12
1%
C
6
4
NC
This technique does effectively disable the line OV feature as
the resultant OV threshold is raised from ~450 VDC to ~980 VDC.
However in this design there was no impact as the value of
input capacitance (C3) was sufficient to allow the design to
withstand differential line surges greater than 1 kV without the
peak drain voltage reaching the BV
Clamp Configuration – RZCD vs. RCD
•
The clamp network is formed by VR1, C4, R5 and D5. It limits
the peak drain voltage spike caused by leakage inductance to
below the BV
This arrangement was selected over a standard RCD clamp to
improve light load efficiency and no-load input power.
In a standard RCD clamp C4 would be discharged by a parallel
resistor rather than a resistor and series Zener. In an RCD
clamp the resistor value of R5 is selected to limit the peak drain
voltage under full load and over-load conditions. However
under light or no-load conditions this resistor value now causes
the capacitor voltage to discharge significantly as both the
leakage inductance energy and switching frequency are lower.
As the capacitor has to be recharged to above the reflected
output voltage each switching cycle the lower capacitor voltage
represents wasted energy. It has the effect of making the
clamp dissipation appear as a significant load just as if it were
connected to the output of the power supply.
The RZCD arrangement solves this problem by preventing the
voltage across the capacitor discharging below a minimum
100 nF
250 VAC
50 V
NC
C9
EF25
ZMM5245B-7
An RZCD (Zener bleed) was selected over RCD to give higher
light load efficiency and lower no-load consumption.
C11
1 nF
T1
VR3
11,12
1
2
7,8
BAV21WS-
7-F
D7
1/8 W
6.8 Ω
R16
47 µF
25 V
C10
10 Ω
200 V
R9
LTV817D
C12
1 nF
DSS
47 µF
U2B
25 V
C7
SB560
D8,9
rating of the internal TOPSwitch-JX MOSFET.
22 Ω
R17
680 µF
25 V
C14
47 nF
110 Ω
50 V
C18
R18
680 µF
25 V
C15
Application Note
DSS
470 Ω
LMV431A
R19
LTV817D
LL4148
3.3 µH
1%
D10
U3
rating of U1.
U2A
L2
33 nF
50 V
C20
100 µF
25 V
C16
PI-5775-030810
10 kΩ
86.6 kΩ
R23
1%
R21
1%
12 V, 2.5 A
Rev. A 030910
RTN
27