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Semiconductor Components Industries, LLC, 2012
October, 2012 − Rev. 2
1 Publication Order Number:
EVBUM2148/D
NCP1562-100WGEVB
NCP1562 100 W 48 V
DC-DC Converter
Evaluation Board
User'sManual
Introduction
The NCP1562 PWM controller contains all the features
and flexibility needed to implement an active clamp forward
dc−dc converter. This IC operates from an input supply up
to 150 V, thus covering the input voltages usually found in
telecom, datacom and 42 V automotive systems. One can
also note that the NCP1562 can be used in mains related
applications (e.g. desktop, server, flat TVs) as it can be
supplied by an auxiliary power supply.
The NCP1562 is the ideal choice for new generation
isolated fixed switching frequency dc−dc converters using
the active clamp topology with synchronous rectification to
achieve extremely high conversion efficiency. This
controller will help designers cope with their daily
challenge, “small form factor highly protected module”
through the following features:
Dual Outputs with Adjustable Overlap Delay:
provide design flexibility. Output 1 (OUT1) drives the
main switch in a forward or flyback converter topology.
Output 2 (OUT2) can be used to drive an active
clamp/reset switch, a synchronous rectifier switch, or
both. OUT2 has an adjustable overlap delay to prevent
simultaneous conduction of the switching elements.
Soft−Stop:
discharges the active clamp capacitor prior to turn off to
eliminate unwanted oscillations.
An Internal Startup Regulator:
provides power to the NCP1562 during startup. Once
the system powers up, the regulator is disabled, thus
reducing power consumption. The regulator can be
powered directly from the input line.
Soft−Start:
allows the system to turn on in a controlled manner and
reduce stress on system components.
Adjustable Maximum Duty Ratio:
allows the design to be optimized without a penalty on
drain voltage. Duty ratio is controlled within 5%.
Adjustable Volt-second Limit:
prevents transformer saturation and improve transient
response.
Line Feedforward:
adjusts the duty ratio inversely proportional to line
voltage, allowing the controller to respond in the same
cycle to line voltage changes. It provides the controller
some advantages of current-mode control, while
eliminating noise susceptibility, low power jitter and
the need for ramp compensation.
Dual Mode Overcurrent Protection Circuit:
handles momentary and continuous overcurrent
conditions differently to provide the best tradeoff in
system performance and safety.
Line Under/Overvoltage Detector:
circuits enable the device when the line voltage is
within the pre-selected voltage range. A resistor divider
from the input line biases the under and overvoltage
detectors. The accurate UV limit allows the converter to
operate at high duty ratio without creating additional
component stresses.
Figure 1. NCP1562 Evaluation Board
http://onsemi.com
EVAL BOARD USER’S MANUAL
