EPR-89 Datasheet, PDF (3/32 Pages) Power Integrations, Inc. – Engineering Prototype Report for 2.0 W CV Adapter using LNK362P

08-Nov-2005
EP-89 6.2 V, 322 mA Adapter
1 Introduction
This engineering report describes a 2.0 W CV, universal input, power supply for
applications such as wall adapters. The supply is designed around a LNK362P device,
and is intended as a standard evaluation platform for the LinkSwitch-XT family of ICs.
Figure 1 – EP89, LNK362P, 2.0 W, 6.2 V, CV Charger Board Photograph.
The LinkSwitch-XT family has been developed to replace discrete component self-
oscillating, ringing choke converters (RCC) and linear regulator-based supplies, in low
power adapter applications. The ON/OFF control scheme of the device family achieves
very high efficiency over the full load range, as well as very low no-load power
consumption. The no-load and active-mode efficiency performance of this supply
exceeds all current and proposed energy efficiency standards.
Unlike RCC solutions, the LinkSwitch-XT has intelligent thermal protection built in,
eliminating the need for external circuitry. The thermal shutdown has a tight tolerance
(142 °C ± 5%), a wide hysteresis (75 °C) and recovers automatically once the cause of
the over temperature condition is removed. This protects the supply, the load and the
user, and typically keeps the average PCB temperature below 100 °C. In contrast, the
latching thermal shutdown function typically used in RCC designs usually requires that
the AC input power be removed to reset it. Thus, with an RCC, there is fair probability
that units may be returned after a thermal latch-off, because the customer is not aware of
the reset procedure (unplugging the unit long enough for the input capacitor to
discharge). Regardless of the fact that the units being returned are fully functional, this
makes the design appear to be less reliable to both the OEM and the end customer, and
burdens the power supply manufacturer with the needless handling of perfectly good
units through its RMA process.
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