International Rectifier IRS27951 User manual

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Energy Saving Products
101 N.Sepulveda Blvd, EL Segundo 90245 California, USA
IRAC27951-220W
IRS27951 Evaluation Board
User Guide

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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

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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-phase
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.

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3 EVALUATION BOARD1SPECIFICATIONS
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°C
2
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 DC-
DC 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.

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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
VCC
1
RT
2
CT/SD
3
COM
4LO 5
VS 6
HO 7
VB 8
U1
IRS2795
Q1
STF13NM50N
Rf2
47k
Dbs
MURS160
U2
TLP621
Vbus
VCC
VCC
COM
1
1
2
2
3
3
4
4
5
5
6
6
JP4
Header 6
3.3uH/10ALf1
F1
5A/250V
+C4
270uF/450V
2
1
3
4
B1 GBU4J-BPMS-ND
C1
0.1uF/275V-X2
265VAC
N
1
2
JP1
Header 3
1
RT
610uH
Dg1
1N4148
Rgs1
DNP
D1
V30100S
D3
20TQ040
W1
Jumper
U3
TL431
DNP=Do notPopulate
L1
t°
RNTC
5
DNP=Do NotPopulate 3.3uH/10ALf2
C2
0.1uF/275V-X2
C3
0.33uF/630V
CVcc2
100nF
Cbs
220nF
Cf2
100nF
+
CDC
33uF/35V
Cf1 DNP
+
Cout1
1mF/35V
+
Cout2
1mF/35V
+
Cout3
1mF/35V
+
Cout6
1.5mF/25V
+
Cout7
1.5mF/25V
+
Cout8
1000uF/25V
Cout5
100nF
Cout9
100nF
Cr
22nF/1kV
Cs
2.2nF/250V
CSS
1uF
CVcc1
1uF
CT
390pF
D2
V30100S
D4
20TQ040
Dg2
1N4148
DSS
1N4148
1
CT
1
COM
1
HO
1
LO
1
COM
1
VS
1
VTR
1
24V
1
12V
1
COM2
1
COM2
1
FB
1
COMP
1
2
JP3
Header 2
1
1
2
2
3
3
4
4
5
5
6
6
JP5
Header 6
Q2
STF13NM50N
Rgs2
DNP
Rbias2
DNP
Rg1
22
Rg2
22
Rled1
2.2k
Rled2
5.6k
RMAX
15k
Rprl1
560
Rprl2
470
Rs1
33k
Rs2
0
Rs3
3.74k
Rs4
15k
Rs5
3.9k
RSS
3.9k
RT
18k
Rx1
4.7
Rx2
4.7
R1
DNP
Rbias1
2.2k
Rdisch
510K
270k
Rstart1
270k
Rstart2
270k
Rstart3 D5
1N4148
22
Rvcc
Dz
18V
9
7
14
17
20
11
13
19
2
5
18
12
TX
+
Cout4
1mF/35V
Figure 1 – Evaluation Board Schematic

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3.3 Evaluation Board Picture
Figure 2 – Evaluation Board Photo
3.4 Board Component Placement
Figure 3 – Evaluation Board Component Placement

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3.5 Board PCB Layout
Figure 4 - Board Bottom Layer Copper

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3.6 Bill of Materials
Designator Description Quantity Value/Rating Vendor Part#
B1 Single Phase Bridge Rectifier 1 600V/4A DIGIKEY GBU4J-BPMS-ND
C1, C2 X2 Safety Capacitor 2 100nF/275VAC DIGIKEY P10524-ND
C3 Metal Poly Capacitor 1 0.33uF/630V DIGIKEY P12245-ND
C4 Electrolytic Bulk Capacitor TS-HC 1 270uF/450V DIGIKEY EET-HC2W271LA
Cbs 1206 General Purpose Ceramic SMD 1 220nF/50V DIGIKEY 490-1776-1-ND
Cf2, Cout5, Cout9, CVcc2 1206 General Purpose Ceramic SMD 4 100nF/50V DIGIKEY 490-1775-1-ND
CDC Electrolytic Capacitor FM Radial 1 33uF/35V DIGIKEY P13475-ND
Cf1 Not Used
Cout1, Cout2, Cout3, Cout4 Aluminium Electrolytic Capacitor 105°C 4 1000uF/35V DIGIKEY 565-1581-ND
Cout6, Cout7 Aluminium Electrolytic Capacitor 105°C 2 1500uF/25V DIGIKEY 565-1557-ND
Cout8 Aluminium Electrolytic Capacitor 105°C 1 1000uF/25V DIGIKEY 565-1555-ND
Cr Polypropylene Capacitor High Ripple 1 22nF/1kV DIGIKEY 495-3552-ND
Cs 250VAC Y1 Safety Ceramic Disc Capacitor 1 2.2nF/250V DIGIKEY 445-2411-ND
CSS, CVcc1 1206 General Purpose Ceramic SMD 2 1uF/25V DIGIKEY 445-1592-1-ND
CT 1206 General Purpose Ceramic SMD ±5% 1 390pF/50V DIGIKEY 478-1487-1-ND
D1, D2 TO220AB Power Schottky Rectifier 2 100V/30A DIGIKEY V30100S-E3/45GI-ND
D3, D4 TO220AC Power Schottky Rectifier 2 40V/20A DIGIKEY 20TQ040PBF-ND
D5, Dg1, Dg2, DSS Fast Recovery Diode DO-35 4 75V/0.3A DIGIKEY 1N4148DICT-ND
Dbs Fast Recttifier diode SMB 1 600V/1A DIGIKEY MURS160-FDICT-ND
Dz Zener Diode SMD 1 18V/0.5W DIGIKEY FLZ18VCCT-ND
F1 FUSE IEC FA LBC 5x20 1 250V/5A DIGIKEY F2395-ND
JP1 CONN HEADER 3POS 0.156 VERT TIN 1 DIGIKEY WM4621-ND
JP3 CONN HEADER 2POS 0.1 VERT TIN 1 DIGIKEY WM4200-ND
JP4, JP5 CONN HEADER 6POS 0.156 VERT TIN 2 DIGIKEY WM4624-ND
L1 EMI Common Mode Choke 1 16mH/2.6A DIGIKEY 237-1233-ND
Lf1, Lf2 PCV Series Drum Core Inductor 10mm 2 3.3uH/10A COILCRAFT PCV0332-10L
Q1, Q2 TO-220FP N-Channel Power MOSFET 2 500V/12A DIGIKEY STF13NM50N
R1, Rbias2, Rgs1, Rgs2 Not Used
Rbias1, Rled1 1206 SMD Film RED 1/4W 1% 2 2.2k DIGIKEY RHM2.20kFCT-ND
Rdisch Metal Film Power Resistor 2W 5% 1 510k DIGIKEY BC510KW-2CT-ND
Rf2 1206 SMD Film RED 1/4W 1% 1 47k DIGIKEY RHM47.0kFCT-ND
Rg1, Rg2 1206 SMD Film RED 1/4W 1% 2 22 DIGIKEY RHM22.0FCT-ND
Rled2 1206 SMD Film RED 1/4W 1% 1 5.6k DIGIKEY RHM5.60kFCT-ND
RMAX 1206 SMD Film RED 1/4W 1% 1 15k DIGIKEY RHM15.0kFCT-ND
RNTC Inrush Current Limiter 1 5 DIGIKEY 495-2093-ND
Rprl1 Metal Film Power Resistor 2W 5% 1 560 DIGIKEY PPC560W-2CT-ND
Rprl2 Metal Film Power Resistor 2W 5% 1 470 DIGIKEY PPC470W-2CT-ND
Rs1 1206 SMD Film RED 1/4W 1% 1 33k DIGIKEY RHM33.0KFCT-ND
Rs2 1206 SMD Film RED 1/4W 1% 1 0 DIGIKEY P0.0ECT-ND
Rs3 1206 SMD Film RED 1/4W 1% 1 3.74k DIGIKEY RHM3.74KFCT-ND
Rs4 1206 SMD Film RED 1/4W 1% 1 15k DIGIKEY RHM15.0KFCT-ND
Rs5, RSS 1206 SMD Film RED 1/4W 1% 2 3.9k DIGIKEY RHM3.90KFCT-ND
Rstart1, Rstart2, Rstart3 1206 SMD Film RED 1/4W 1% 3 270k DIGIKEY RHM270KFCT-ND
RT 1206 SMD Film RED 1/4W 1% 1 18k DIGIKEY RHM18.0KFCT-ND
Rvcc 1206 SMD Film RED 1/4W 1% 1 22 DIGIKEY RHM22.0FCT-ND
Rx1, Rx2 1206 SMD Film RED 1/4W 1% 2 4.7 DIGIKEY 311-4.70FRCT-ND
TX Resonant Power Transformer 1 ETD49 PRECISION INC 019-4974-00R
U1 IRS27951 Control IC 1 IR IRS27951S
U2 Photocoupler TRANS-OUT 4-DIP 1 TLP621 DIGIKEY TLP621FT-ND
U3 Programmable Voltage Regulator SOT23-3 1 TL431 DIGIKEY 296-17328-1-ND
W1 Jumper for Primary Current Sensing Loop 1 AWG20

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4 EVALUATION BOARD OPERATING PROCEDURE
CAUTION: Potentially lethal voltages exist on this demo board when powered up. Improper
or unsafe handling of this board may result in serious injury or death.
4.1 Load Connection
Connect a resistive or electronic load, capable of 150W continuous power on the 24V rail to connector JP4 and
a 75W continuous power load on the 12V output rail to JP5. Please note that there is no minimum load
3
requirement for this board.
3
A minimum load has been added on both the output rails to ensure tight voltage regulation for both output rails from no
load to full load.
Figure 5 - Recommended Evaluation Board Test Setup
DC Power
Supply
Electronic or
Resistive
Load
24V/6A
ISOLATION
TRANSFORMER
Variable AC
or HV DC
Source
(Variac or
Electronic)
Electronic or
Resistive
Load
12V/6A

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4.2 AC/DC Input
The use of an isolation transformer on the AC side is highly recommended, so that all the control signals on the
test points can easily be probed by using regular scope probes
Connect a 60Hz AC power source capable of operation up to 280VAC or a 400V DC source to JP1. The
converter can keep the output regulated when the BUS voltage is in the range of 350V DC to 420V DC.
The NTC resistor limits the inrush current upon initial application of full AC line voltage. Once power is applied
to demo board, potentially lethal high voltages will be present on board and necessary precautions should be
taken to avoid serious injury.
4.3 IRS27951 DC Supply Voltage
The board is self-supplied by startup circuit and auxiliary winding of transformer. The startup circuit starts to
work once AC or DC input voltage applies to the board. However, the Vcc will be stable only when BUS
voltage is 350Vdc or above. The VCC voltage is monitored at test points VCC and COM.
If you choose to supply VCC voltage using external DC power supply (in order to study IC VCC UVLO features
etc.) then simply provide DC voltage to connector JP3 or alternatively between Test Points V
CC
and COM. You
should also dis-connect Rvcc and Rstart in order to measure the Vcc supply current from the DC source. The
minimum supply voltage recommended is 12V while a maximum voltage of 18V can be applied without
damaging the IC. The location of the DC power connector and controller IC is shown in Figure 6.
Figure 6 - VCC connector and test points
4.4 Power-up Sequence
Once all the connections are made, the system can be powered up. When using external DC supply to bias
Vcc, power-up the AC supply or 400V DC supply first and then the Vcc circuitry. This sequence is necessary to
ensure soft start operation of the DC-DC converter.
IRS2795
1
and control
components on
bottom layer
VCC COM

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5 SYSTEM PERFORMANCE CHARACTERIZATION
Test Conditions – V
IN
=400V DC; Full Load (24V/6A, 12V/6A); No Load (24V/0A, 12V/0A)
5.1 Steady-State and Start-up Waveforms
Ch 1: Low-side device V
GS
– Ch 3: Voltage at VS pin
Ch 4: Resonant tank current
Full Load Operation No Load Operation
Full Load Start-up No Load Start-up

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5.2 Short Circuit Protection
IRS27951 uses high-voltage technology to sense the current in the low-side MOSFET. The voltage at the VS
node is sensed when the low-side device is turned ON and the system shuts off when a load short-circuit
condition is sensed (i.e. I
D
*R
DSON
exceeds the fixed internal threshold). In this reference design, IRS27951
latched shutdown when primary current exceed 8.9A peak.
Ch 2: 12V Rail Output Voltage
Ch 3: 12V Rail Output Voltage Ch 4: Resonant tank current
24V Rail short-circuit 12V Rail short circuit

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5.3 Dynamic Load Response & Output Voltage Regulation
A load step from full load to no load and no load to full load was applied to test the dynamic response of the
system. The output voltage is tightly regulated within a 3% regulation band over the entire line load range. A
summary of the load performance is also shown below.
Ch 3: 24V Rail output voltage Ch 2: 12V Rail output voltage
Ch 4: Resonant tank current
No Load to Full Load Step Full Load to No Load Step
23.4
23.6
23.8
24
24.2
24.4
24.6
11.8
11.85
11.9
11.95
12
12.05
12.1
12.15
12.2
0123456
Vout (V)
Iout (A)
Load Regulation
12V Output 24V Output
Figure 7 - Output voltage regulation plot

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5.4 User Initiated SLEEP Mode
The CT/SD pin of IRS27951 can be used to disable the IC and enter sleep mode in which the IC power
consumption is highly minimized. The IC enters this mode when the CT/SD pin is externally pulled to COM.
This feature facilitates the implementation of system power management functions for reducing overall standby
power consumption by disabling the down converter when no power is being requested by the converter main
output voltage rails.
Ch 1: Low-side device V
GS
Ch 2: CT/SD pin of IRS27951
Ch 3: High-side device V
GS
Ch 4: Resonant tank current
Sleep mode initiated by externally pulling the CT/SD pin to COM
5.5 Efficiency Chart
The efficiency of IRS27951 demo board was tested at both 270Vac input and 400Vdc input over the load
range. The result is shown in the table below.
270Vac 400Vdc
24Vout
24V
current(A) 12Vout
12V current
(A) Pout(W) Eff c ency Eff c ency
24.176 1.5 11.97 1.5 54.2 90.8% 91.0%
24.2 3 11.92 3 108.4 92.6% 92.6%
24.22 4.5 11.9 4.5 162.5 92.4% 92.9%
24.24 6 11.86 6 216.6 92.2% 92.7%
23.517 6 12.26 0 141.1 92.8%
24.814 0 11.63 6 69.8 89.5%

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The average efficiency of the board at 25%, 50%, 75% and 100% load is 92% at 270Vac input:
90.5%
91.0%
91.5%
92.0%
92.5%
93.0%
93.5%
50.0 70.0 90.0 110.0 130.0 150.0 170.0 190.0 210.0
Efficiency
Output Power (W)
Efficieny vs. Output Power
400Vdc nput
270Vac nput
Figure 8 - Efficiency plot
5.6 Thermal Data
The thermal performance of IRS27951 demo board is tested at 400Vdc input and 220W full load under room
temperature.
Part Case Temperature (°C)
MOSFET Q1 44.5
MOSFET Q2 42.5
U1 IRS27951 41
Transformer 73
24V d odes 72
12V d odes 60
6 Transformer Spec
Core type: ETD49 - 0R44949EC
Minimum operating frequency: 80 kHz
Primary inductance: 585 µH ±10% @1 kHz - 0.25V (Note 1)
Leakage inductance: 125 µH ±10% @1 kHz - 0.25V (Note 2)
Note: 1 Measured between Pins 2 and 5
Note: 2 Measured between Pins 2 and 5 with secondary windings shorted

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6.1 Electrical Diagram
9
7
14
17
20
11
13
19
2
5
18
12
TX
Note: pin19 is shorted to pin18 on PCB, pin13 is shorted to pin12 on PCB.
6.2 Resonant Transformer Winding Position on Coil former
6.3 Resonant Transformer Winding Characteristics
Pins Winding Turn number RMS Current Wire type [mm]
2 - 5 Primary 36 1.8A LITZ - dia. 0.15x30
9 - 7 Auxiliary
2
0.1A Dia. 0.2
20 – 19 Sec. A 4 7A LITZ - dia. 0.20x40
18 - 17 Sec. B 4 7A LITZ - dia. 0.20x40
14 – 13 Sec. C 2 7A LITZ - dia. 0.20x40
12 - 11 Sec. D 2 7A LITZ - dia. 0.20x40
Primar
Auxiliary
Sec A
Sec B
Sec C
Sec D