EPR-32 Datasheet, PDF (25/36 Pages) Power Integrations, Inc. – Engineering Prototype Report for EP-32 − TOPSwitch-GX 25 W Multiple Output DVD, Set-top Box Power Supply Using TOP245P

13-Jul-06
EPR-32 - 25 W Multiple Output TOP245P Supply
11.4 Output Ripple Measurements
All measurements were taken at maximum load on all outputs.
11.4.1 Ripple Measurement Technique
For DC output ripple measurements, a modified oscilloscope test probe must be utilized
in order to reduce spurious signals due to pickup. Details of the probe modification are
provided in Figure 19 and Figure 20.
The 5125BA probe adapter is affixed with two capacitors tied in parallel across the probe
tip. The capacitors include one (1) 0.1 µF/50 V ceramic type and one (1) 1.0 µF/50 V
aluminum electrolytic. The aluminum electrolytic type capacitor is polarized, so proper
polarity across DC outputs must be maintained (see below).
Probe Ground
Probe Tip
Figure 20 − Oscilloscope Probe Prepared for Ripple Measurement (End Cap and Ground Lead Removed).
Figure 21 − Oscilloscope Probe with Probe Master 5125BA BNC Adapter (Modified with Wires for Probe
Ground for Ripple Measurement, and Two Parallel Decoupling Capacitors Added).
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