Rev. 4.0 5/22/2010
International Rectifier
Page 3 of 16
PROPRIETARY INFORMATION - This document and the information contained therein are proprietary and are not to be reproduced, used or disclosed
to others for manufacture or any other purpose except as specifically authorized in writing by
INTERNATIONAL RECTIFIER.
1 INTRODUCTION
This document details the test procedure for validation of IRS27951 Evaluation Board, featuring the
IRS27951 Resonant Half Bridge controller HVIC. The document includes schematic diagram, test
setup, test procedure, and test results.
2 IRS27951/2 DESCRIPTION
The IRS2795 is an 8 pin, high-voltage, double-ended controller specific for the resonant half-bridge topology. It
provides 50% complementary duty cycle; the high-side and the low-side devices are driven 180° out-of-p hase
for exactly the same time. The IC incorporates additional protection features for robust operation and provides
a high performance solution while minimizing external components, design time, and printed circuit board real
estate, all in an 8 pin SOIC package.
The IC enables the designer to externally program all the following features using a 2 pin oscillator - operating
frequency range (minimum and maximum frequency), startup frequency, dead time, soft-start time and sleep
mode. Each of these functions are programmed as follows –
The minimum frequency is programmed using RT and CT.
The dead time is programmed using CT.
RSS and CSS program the converter soft-start time.
RSS//RT and CT program the converter start-up frequency.
The converter maximum frequency is set by (Rmax//RT) and CT.
Sleep mode is initiated by pulling the CT/SD to COM.
At start-up, to prevent uncontrolled inrush current, the switching frequency starts from a programmable
maximum value and progressively decays until it reaches the steady-state value determined by the control
loop. This frequency shift is non linear to minimize output voltage overshoot and its duration is programmable
as well. Output voltage regulation is obtained by modulating the operating frequency. An externally
programmable dead time is inserted between the turn-OFF of one switch and the turn-ON of the other one
allows device zero-voltage turn-on transitions.
IRS2795 uses IR’s proprietary high-voltage technology to implement a VS sensing circuitry that monitors the
current through the low-side half bridge MOSFET for short circuit faults. By using the R
DSON
of the low-side
MOSFET, the IRS2795 eliminates the need for an additional current sensing resistor, filter and current-sensing
pin. This protection feature is latched and the thresholds are fixed at 2V for IRS27951 and 3V for IRS27952.
Finally, the controller IC also features a micro power startup current (I
CC
<100µA) and a user initiated sleep
mode during which the IC power consumption is less than 200µA (@ Vcc=15V). The sleep mode function
allows system designs with reduced standby power consumption and can be used to meet stringent energy
standards from Blue Angel, Energy Star etc.