TOP242-250 Datasheet, PDF (32/52 Pages) Power Integrations, Inc. – TOPSwitch-GX Family Extended Power, Design Flexible, EcoSmart, Integrated Off-line Switcher

TOP242-250
Solder Side
Component Side
+
TOP VIEW
Safety Spacing
Y1-
Capacitor
Output Filter Capacitors
HV
-
R1a - 1c
Input Filter
Capacitor
D
S
X
L
C
TOPSwitch-GX
Figure 49. Layout Considerations for TOPSwitch-GX using R Package.
PRI
PRI
BIAS
T
r
a
n
s
f
SEC
o
r
m
e
r
Opto-
coupler
- ^DC +
Out
Maximize hatched copper
areas (
) for optimum
heat sinking
PI-2734-043001
Quick Design Checklist
As with any power supply design, all TOPSwitch-GX designs
should be verified on the bench to make sure that components
specifications are not exceeded under worst case conditions. The
following minimum set of tests is strongly recommended:
1. Maximum drain voltage – Verify that peak V_DS does not
exceed 675 V at highest input voltage and maximum
overload output power. Maximum overload output power
occurs when the output is overloaded to a level just before the
power supply goes into auto-restart (loss of regulation).
2. Maximum drain current –At maximum ambient temperature,
maximum input voltage and maximum output load, verify
drain current waveforms at start-up for any signs of
transformer saturation and excessive leading edge current
spikes. TOPSwitch-GX has a leading edge blanking time of
220 ns to prevent premature termination of the ON-cycle.
Verify that the leading edge current spike is below the
allowed current limit envelope (see Figure 52) for the
drain current waveform at the end of the 220 ns blanking
period.
3. Thermal check – At maximum output power, minimum
input voltage and maximum ambient temperature, verify
that temperature specifications are not exceeded for
TOPSwitch-GX, transformer, output diodes and output
capacitors. Enough thermal margin should be allowed for
the part-to-part variation of the R_DS(ON) of TOPSwitch-GX,
as specified in the data sheet. The margin required can
either be calculated from the tolerances or it can be
accounted for by connecting an external resistance in
series with the DRAIN pin and attached to the same
heatsink, having a resistance value that is equal to the
difference between the measured R_DS(ON) of the device
under test and the worst case maximum specification.
Design Tools
For a discussion on utilizing TOPSwitch-GX in a forward
converter configuration, please refer to the TOPSwitch-GX
Forward Design Methodology Application Note.
Up-to-date information on design tools can be found at the
Power Integrations website: www.powerint.com
32 M
12/04