International Rectifier IRS27951, IRAC27951 User Manual

Energy Saving Products

101 N.Sepulveda Blvd, EL Segundo 90245 California, USA

IRAC27951-220W

IRS27951 Evaluation Board

User Guide

Rev. 4.0 5/22/2010 International Rectifier Page 1 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.

Table of Contents

1

INTRODUCTION ........................................................................................................................ 3

2

IRS27951/2 DESCRIPTION ....................................................................................................... 3

3

EVALUATION BOARD SPECIFICATIONS ................................................................................ 4

3.1 Board Description ................................................................................................................... 4

3.2 Schematic ............................................................................................................................... 5

3.3 Evaluation Board Picture ........................................................................................................ 6

3.4 Board Component Placement ................................................................................................. 6

3.5 Board PCB Layout .................................................................................................................. 7

3.6 Bill of Materials ....................................................................................................................... 8

4

EVALUATION BOARD OPERATING PROCEDURE ................................................................. 9

4.1 Load Connection..................................................................................................................... 9

4.2 AC/DC Input ......................................................................................................................... 10

4.3 IRS27951 DC Supply Voltage .............................................................................................. 10

4.4 Power-up Sequence ............................................................................................................. 10

5

SYSTEM PERFORMANCE CHARACTERIZATION ................................................................ 11

5.1 Steady-State and Start-up Waveforms ................................................................................. 11

5.2 Short Circuit Protection ......................................................................................................... 12

5.3 Dynamic Load Response & Output Voltage Regulation ....................................................... 13

5.4 User Initiated SLEEP Mode .................................................................................................. 14

5.5 Efficiency Chart..................................................................................................................... 14

5.6 Thermal Data ........................................................................................................................ 15

6

Transformer Spec..................................................................................................................... 15

6.1 Electrical Diagram ................................................................................................................. 16

6.2 Resonant Transformer Winding Position on Coil former ....................................................... 16

6.3 Resonant Transformer Winding Characteristics ................................................................... 16

Rev. 4.0 5/22/2010 International Rectifier Page 2 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
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 (ICC<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.

of the low-side

DSON

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.

3 EVALUATION BOARD1 SPECIFICATIONS

Input Voltage...……….………………………………………………………….. ….280VAC or 400V DC
AC Line Frequency Range…………………………………………………………..47 – 63Hz
Converter Switching Frequency Range……………………………………….. ….70-150 kHz

Converter Outputs ....…… ………………………………………………………….24V/6A & 12V/6A

Maximum Output Power…………………………………………………………......220W

Minimum Load Requirement…………………………………………………………None
Maximum Ambient Operating Temperature………………………………………..40°C2
Efficiency (@ 220W)……...…………………………………………… ……….….. 92%
Short Circuit Protection on both Output Rails...………………………………….. Yes
Single Layer PCB with 2oz Copper

There are high voltages present whenever the board is energized and proper precautions should be
taken to avoid potential shock and personal injury.

3.1 Board Description

The evaluation board consists of a front-end AC-DC rectifier stage cascaded with a half-bridge resonant DC­DC converter with multiple output voltage rails (24V and 12V). The front end is a conventional rectifier stage
with a rectifier bridge and an EMI filter.

The downstream converter is a multi-resonant half bridge LLC converter whose control is implemented with the
IRS27951 (U1) controller HVIC. The controller drives the two half-bridge MOSFETs with a 50 percent fixed
duty cycle with dead-time, changing the frequency according to the feedback signal in order to regulate the
output voltages against load and input voltage variations. As described earlier, in addition to current protection,
all the critical functions needed to control resonant converter designs can be externally programmed using this
8 pin controller IC.

The transformer uses the magnetic integration approach, incorporating the resonant series and shunt
inductances in the power transformer. The transformer configuration chosen for the secondary winding is
center-tap, and the output rectifiers are Schottky diodes. The feedback loop is implemented by means of a
classical configuration using a TL431 (U3) to adjust the current in the optocoupler TLP621 (U2). Weighted
resistive dividers from both voltages are summed at the reference node of the TL431 in order to achieve a

1

Please note that EMI measurements have not been performed on this evaluation board. The primary goal of this board is to verify the functionality of

the IRS27951 controller IC.

2

A fan is recommended whenever operating at the maximum load for a prolonged period of time.

Rev. 4.0 5/22/2010 International Rectifier Page 4 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.

RT

CT

1

1

D5

Rstart1

Rstart2

270k

270k

GBU4J-BPMS-ND

RNTC

265VAC

5

t°

JP1

2
1

Header 3

C1

R1

DNP

F1

N

5A/250V

B1

213

L1

C2

0.1uF/275V-X2

4

0.1uF/275V-X2

C3

0.33uF/630V

+

270uF/450V

C4

VCC

Rdisch

JP3

CDC

510K

2
1

Header 2

COM

33uF/35V

Rvcc

Rstart3

270k

22

1N4148

VCC

DSS

CVcc1

+

RSS

RMAX

CVcc2

1uF

100nF

Dz

18V

RT

3.9k
18k

CT

1N4148

15k

CSS

1uF

HO

1

Dbs

MURS160

U1

1

VCC

2

RT

3

CT/SD

COM4LO

IRS2795

390pF

Dg1

1N4148

8

VB

Cbs

7

HO

220nF

6

VS

5

Dg2

1

1N4148

LO

COM

1

Vbus

STF13NM50N

Rx1

Q1

4.7

Rx2

4.7

DNP = Do Not Populate

Rgs1

DNP

STF13NM50N

Q2

Rgs2

DNP

VS

VTR

1

1

Cr

W1

Jumper

22nF/1kV

610uH

1

COM

Cs

2.2nF/250V

U2

Rg1
22

Rg2

22

9

TX

7
2

5

TLP621

20

19
18

17
14

13
12

11

DNP=Do not Populate

D1

V30100S

Cout1

Cout2

+

D2

V30100S

D3

20TQ040

D4

20TQ040

Rled2

5.6k

Rbias2

Rbias1

2.2k

DNP

COMP

1

U3

TL431

1mF/35V

1mF/35V

Cout6

Cout7

+

1.5mF/25V

1.5mF/25V

Rled1

2.2k

Cf1 DNP

Cf2

Rf2
47k

100nF

3.3uH/10ALf1

Cout3

+

+

Rs4
15k

Rs5

3.9k

Cout4

+

+

Cout5

Rprl1

100nF

1mF/35V

Rs1
33k

FB

Rs2

1

0

Rs3

3.74k

560

1mF/35V

3.3uH/10ALf2

Cout8

+

Cout9

Rprl2

470

1000uF/25V

100nF

24V

1

JP4

1

1

2

2

3

3

4

4

5

5

6

6

Header 6

1

COM2

12V

1

JP5

1

1

2

2

3

3

4

4

5

5

6

6

Header 6

1

COM2

INTERNATIONAL RECTIFIER.

Figure 1 – Evaluation Board Schematic

Rev. 4.0 5/22/2010 International Rectifier Page 5 of 16

better overall output voltage regulation. The optocoupler transistor modulates the current from the RT pin of the

controller IC to modulate the switching frequency, thus achieving output voltage regulation.

3.2 Schematic

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