EPR-000014 Datasheet, PDF (5/28 Pages) Power Integrations, Inc. – Engineering Prototype Report - 3 W Universal Input TinySwitch-II TNY264 Power Supply

22-Feb-2002
3 Schematic
EPR-000014 – 9 V, 0.33 A, 3 W TNY264 Adapter
Figure 2. EP14 Power Supply Schematic
4 Description
The EP14 is a single 9 V_DC output power supply rated at 3 W. The power supply was
designed to operate over an AC input range of 85-265 V_AC, 47-64Hz and provides 9 V_DC
output with ±7% accuracy to no-load. Operating efficiency is 67% worst case at full load
across the entire AC line range. Compliance to CISPR22 / EN55022 Class B conducted
emissions and surge immunity test level 1 (1 kV, 1.2 / 50 µS - IEC1000-4-5) is achieved
with minimum component count. The unit is designed to comply with international safety
standards per IEC950. Minimum parts count enables a space conscious design, with
outside dimensions 1.2” x 2.0” x 0.75”.
TinySwitch-II provides several advantages in this application. The enhanced ON/OFF
control scheme allows tight regulation using a simple, low-cost secondary side Zener
reference and no loop compensation. No-load regulation is achieved without a dummy
load. The enhanced ON/OFF control scheme dynamically alters the internal current limit
as load requirements dictate. This approach reduces cycle skipping when the core flux
density is high; thus minimizing acoustic noise. This eliminates the need for special
construction, the transformer merely needs to be dip varnished.
Increased operating frequency (132 kHz) allows the use of a small EF12.6 core, while
frequency jittering reduces conducted emissions and resulting filtering requirements.
These features, combined with primary-side transformer shielding, allows EP14 to
comply with CISPR22 B (FCC Class B) emissions without the use of a large, expensive
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