IRAC27951SR IRS27951 Evaluation Board User Guide

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IRAC27951SR IRS27951 Evaluation Board User Guide | Manualzz

Energy Saving Products

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

IRAC27951SR

IRS27951 Evaluation Board

User Guide

Rev. 4.1 6/1/2011 International Rectifier Page 1 of 23

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 IR11682 DESCRIPTION ............................................................................................................ 4

4 EVALUATION BOARD SPECIFICATIONS ................................................................................ 5

4.1

Board Description ................................................................................................................... 5

4.2

Schematic ............................................................................................................................... 6

4.3

Evaluation Board Picture ........................................................................................................ 7

4.4

Board Component Placement ................................................................................................. 7

4.5

Board PCB Layout .................................................................................................................. 8

4.6

Bill of Materials ....................................................................................................................... 9

5 EVALUATION BOARD OPERATING PROCEDURE ............................................................... 10

5.1

Load Connection................................................................................................................... 10

5.2

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

5.3

IRS27951 DC Supply Voltage .............................................................................................. 11

5.4

Disconnect the Board ........................................................................................................... 11

6 SYSTEM PERFORMANCE CHARACTERIZATION ................................................................ 12

6.1

Steady-State and Start-up Waveforms ................................................................................. 12

6.2

Synchronous Rectifier Waveform ......................................................................................... 15

6.3

Dynamic Load Response & Output Voltage Regulation ....................................................... 16

6.4

Output Ripple ........................................................................................................................ 19

6.5

User Initiated SLEEP Mode .................................................................................................. 20

6.6

Efficiency Chart..................................................................................................................... 21

6.7

Thermal Data ........................................................................................................................ 22

7 Transformer Spec..................................................................................................................... 22

7.1

Electrical Diagram ................................................................................................................. 22

7.2

Resonant Transformer Winding Position on Coil former ....................................................... 23

7.3

Resonant Transformer Winding Characteristics ................................................................... 23

Rev. 4.1 6/1/2011 International Rectifier Page 2 of 23

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 IRAC27951SR-240W Evaluation Board, featuring the IRS27951 Resonant Half Bridge controller and the IR11682 dual-channel synchronous rectification controller. The document includes schematic diagram, test setup, test procedure, and test results.

2 IRS27951/2 DESCRIPTION

The IRS2795(1,2) 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 and printed circuit board area.

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.

Rev. 4.1 6/1/2011 International Rectifier Page 3 of 23

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 IR11682 DESCRIPTION

IR11682 is a secondary-side SmartRectifier

TM

driver IC designed to drive two N-Channel power MOSFETs used as synchronous rectifiers in resonant converter applications. The IC can control one or more paralleled N

MOSFETs to emulate the behavior of Schottky diode rectifiers. The drain to source for each rectifier MOSFET voltage is sensed differentially to determine the level of the current and the power switch is turned ON and

OFF in close proximity of the zero current transition.

When the conduction phase of the SR FET is initiated, current will start flowing through its body diode, generating a negative VDS voltage across it. The body diode has generally a much higher voltage drop than the one caused by the MOSFET on resistance and therefore will trigger the turn-on threshold V

TH2

. When V

TH2 is triggered, IR11682 will drive the gate of MOSFET on which will in turn cause the conduction voltage VDS to drop down to ID*RDSON. This drop is usually accompanied by some amount of ringing, that could trigger the input comparator to turn off; hence, a fixed Minimum On Time (MOT) blanking period is used that will maintain the power MOSFET on for a minimum amount of time.

Once the SR MOSFET has been turned on, it will remain on until the rectified current will decay to the level where VDS will cross the turn-off threshold V

TH1

. Once the threshold is crossed, the current will start flowing again through the body diode, causing the VDS voltage to jump negative. Hence, V

TH2

is blanked for a time duration t

BLANK

after V

TH1

is triggered. When the device VDS crosses the positive reset threshold V

TH3

, t

BLANK is terminated and the IC is ready for next conduction cycle as shown below.

V

TH3

I

DS

V

DS

T1

V

TH1

V

TH2

Gate Drive

T2

Blanking

MOT t

BLANK time

IR11682 further simplifies synchronous rectifier control by offering the following power management features:

- Wide VCC operating range allows the IC to be directly powered from the converter output

- Shoot through protection logic that prevents both the GATE outputs from the IC to be high at the same time

- Device turn ON and OFF in close proximity of the zero current transition with low turn-on and turn-off propagation delays; eliminates reactive power flow between the output capacitors and power transformer

- Cycle-by-cycle MOT protection circuit can automatically detect no load condition and turn off gate driver output to avoid negative current flowing through the MOSFETs

- Internally clamped gate driver outputs that significantly reduce gate losses

Rev. 4.1 6/1/2011 International Rectifier Page 4 of 23

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.

4 EVALUATION BOARD

1

SPECIFICATIONS

Input Voltage...……….……………………………………………………………….280VAC or 400VDC

AC Line Frequency Range…………………………………………………………..47 – 63Hz

Converter Switching Frequency Range…………………………………………….70-150 kHz

Converter Output....…………………………………………………………………..24V/10A

Maximum Output Power…………………………………………………………......240W

Minimum Load Requirement…………………………………………………………None

Maximum Ambient Operating Temperature………………………………………..40

°

C

2

Efficiency (@ 240W)……...…………………………………………….……….……. 95%

Short Circuit Protection………………………....……………………………………. Yes

Double 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.

4.1 Board Description

The evaluation board consists of a front-end AC-DC rectifier stage cascaded with a half-bridge resonant DC-

DC converter with 24V output voltage rail.

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 voltage 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.

IRS27951 is self-supplied in this reference design. The startup resistors Rstart1~Rstart3 provide startup current to IRS27951 during power up and charge the Vcc capacitors (CDC2 and CVcc1). Once Vcc voltage exceeds Vccuv+ threshold, IRS27951 starts operation and the auxiliary winding of power transformer can

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. 4.1 6/1/2011 International Rectifier Page 5 of 23

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.

provide bias to the IC. The voltage of auxiliary winding could vary a lot when 24V load changes from 0A to

10A, so a linear regulator – Dz4, Rvcc and Q2 – is used to keep Vcc regulated at 14.5V.

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. The feedback loop is implemented by means of a classical configuration using a TL431 (U3) to adjust the current in the optocoupler TLP621 (U2). The optocoupler transistor modulates the current from the

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

The secondary rectification is implemented with synchronous rectification controller IR11682 and two PQFN power MOSFETs. Each leg of the output uses one IRFH5006, a 60V MOSFET with 3.5mohm on state resistance (typical). The conduction power loss is greatly reduced by using synchronous rectification. No heatshink is required for 10A continuous output current. PCB area is also saved with the highly integrated dualchannel SmartRectifier

TM

controller IR11682.

The synchronous rectification circuit is connected in a low-side configuration. So IR11682 can directly drive the two SR MOSFETs. A RCD circuit is added to IR11682 VD sensing input to provide leading edge filter and turnoff delay compensation.

IR11682 is biased by 24V output through a simple linear voltage regulator Q1 (a general NPN transistor) and zener Dz2 (12V). In addition, a second zener diode Dz3 (9.1V) is used to prevent the synchronous rectifier circuit be activated when output voltage is still low. The IR11682 will start operation when output voltage is approaching 18V.

4.2 Schematic

Figure 1 – Evaluation Board Schematic

Rev. 4.1 6/1/2011 International Rectifier Page 6 of 23

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.

4.3 Evaluation Board Picture

Figure 2 – Evaluation Board Photo

4.4 Board Component Placement

Figure 3 – Evaluation Board Top Side Component Placement

Rev. 4.1 6/1/2011 International Rectifier Page 7 of 23

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.

Figure 4 – Evaluation Board Bottom Side Component Placement

4.5 Board PCB Layout

Figure 5 - Board Top Layer Copper

Figure 6 - Board Bottom Layer Copper

Rev. 4.1 6/1/2011 International Rectifier Page 8 of 23

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.

4.6 Bill of Materials

Designator Description Quantity

24V, COMP, CT_, FB, Gate1,

Gate2, HO, LO, RT_, Vcc,

VD1, VD2, VS, VTR

Test Point PC Mini 0.040''D

B1 Single Phase Bridge Rectifier

C1, C2

C3

X2 Safety Capacitor

Metal Poly Capacitor

C4

C5

Cbs

CD1, CD2

CDC, CDC2

Electrolytic Bulk Capacitor TS-HC

250VAC Y1 Safety Ceramic Disc Capacitor

1206 General Purpose Ceramic SMD

0805 General Purpose Ceramic SMD

Electrolytic Capacitor FM Radial

1

1

1

2

2

2

1

14

1

Cf1

Cf2, Cout5

Cf3

COM, COM2

CON1

1206 General Purpose Ceramic SMD

1206 General Purpose Ceramic SMD

1206 General Purpose Ceramic SMD

Test Point PC Mini 0.040''D

CONN HEADER 3POS 0.156 VERT TIN

CON3 CONN HEADER 6POS 0.156 VERT TIN

Cout1, Cout2, Cout3, Cout4 Aluminium Electrolytic Capacitor FM RAD

Cr Polypropylene Capacitor High Ripple

CSS, CVcc1

CT

1206 General Purpose Ceramic SMD

1206 General Purpose Ceramic SMD

1

4

1

2

1

1

2

1

2

1

Dz3

Dz4

F1

L1

Lf1

CVcc3, CDC3 1210 General Purpose Ceramic SMD

D1, D2, D5, Dg1, Dg2, DSS Fast Recovery Diode SMD

Dbs Fast Recttifier diode SMB

Dz1

Dz2

Zener Diode SOD80

Zener Diode SOD80

Zener Diode SOD80

Zener Diode SOD80

FUSE IEC FA LBC 5x20

EMI Common Mode Choke

PCV Series Drum Core Inductor

M1, M2

M3, M4

Q1, Q2

Rbias1, Rf3

Rcc1

Rcc2, Rvcc

RD1, RD2

RD3, RD4

RDC

Rf2

TO-220 N-Channel Power MOSFET

N-Channel MOSFET 60V PQFN

NPN General Purpose Amplifier

1206 SMD Film RED 1/ 4W 5%

1206 SMD Film RED 1/ 4W 5%

1206 SMD Film RED 1/ 4W 5%

0805 SMD Film RED 1/ 4W 5%

0805 SMD Film RED 1/ 4W 5%

1206 SMD Film RED 1/ 4W 5%

1206 SMD Film RED 1/ 4W 5%

2

2

2

1

2

2

2

2

2

1

1

1

1

1

1

2

6

1

1

1

Rg1, Rg2, Rvcc1

RgM3, RgM4

Rgs1, Rgs2

RL

RL1

Rled1

RMAX

RNTC

Rs1

Rs2

Rs3

RSS

Rstart1, Rstart2, Rstart3

RT

Rx1, Rx2

TX

U1

U2

U3

U4

1206 SMD Film RED 1/ 4W 5%

1206 SMD Film RED 1/ 4W 5%

1206 General Purpose SMD

Resistor 1W 5%

1210 Resistor 0.5W 5%

1206 SMD Film RED 1/ 4W 1%

1206 SMD Film RED 1/ 4W 1%

Inrush Current Limiter

1206 SMD Film RED 1/ 4W 1%

1206 SMD Film RED 1/ 4W 1%

1206 SMD Film RED 1/ 4W 1%

1206 SMD Film RED 1/ 4W 1%

1206 SMD Film RED 1/ 4W 5%

1206 SMD Film RED 1/ 4W 1%

1206 SMD Film RED 1/ 4W 5%

Resonant Power Transformer

IRS27951 Control IC

Photocoupler TRANS-OUT 4-DIP

Programmable Voltage Regulator SOT23-3 1

Sync Rect Controller 1

1

1

1

2

1

1

1

1

1

3

1

1

1

3

2

2

1

1

Value/ Rating Vendor Part#

22

1

DNP

1K

3K

5.6k

14.7k

5

33k

680

3.9k

8.2k

270K

20k

4.7

TRANSYJ

IRS27951

TLP621

TL431

IR11682

10uF/ 25V

1N4148

MURS160

18V

12V

9.1V

15V

5A/ 250V

Trans Cupl

1uH/ 10A

STF18NM60N

IRFH5006

2N3904

2k

100

2.2K

1.5K

100

200

12k

Red DIGIKEY

GBU4J-BPMS-ND DIGIKEY

0.1uF/ 275V-X2

0.22uF/ 630V

DIGIKEY

DIGIKEY

270uF/ 450V

2.2nF/ 250V

220nF

470pF

33uF/ 35V

DIGIKEY

DIGIKEY

DIGIKEY

DIGIKEY

DIGIKEY

220pF/ 50V

100nF

4.7nF

Black

AC IN

Header 6

1000uF/ 35V

22nF/ 400V AC

1uF/ 25V

390pF

DIGIKEY

DIGIKEY

DIGIKEY

DIGIKEY

DIGIKEY

DIGIKEY

DIGIKEY

DIGIKEY

DIGIKEY

DIGIKEY

5000K-ND

GBU4J-BPMS-ND

P10730-ND

P12173-ND

P14116-ND

445-2411-ND

490-1776-1-ND

311-1119-1-ND

565-1687-ND

478-1484-1-ND

490-1775-1-ND

490-3357-6-ND

5001K-ND

WM4621-ND

WM4624-ND

P12405-ND

495-1329-ND

445-1592-1-ND

478-1487-1-ND

DIGIKEY

DIGIKEY

DIGIKEY

DIGIKEY

DIGIKEY

DIGIKEY

DIGIKEY

DIGIKEY

COILCRAFT

COILCRAFT

445-3942-1-ND

1N4148W-FDICT-ND

MURS160-FDICT-ND

FLZ18VCCT-ND

FLZ12VCCT-ND

FLZ9V1CCT-ND

FLZ15VCCT-ND

F2395-ND

CMT2-6.5-2L

PCV-0-102-10L

DIGIKEY STF18NM60N

INTERNATIONAL RECTIFIER IRFH5006

DIGIKEY 2N3904-APCT-ND

DIGIKEY

DIGIKEY

RHM2.00kFCT-ND

RHM100FCT-ND

DIGIKEY

DIGIKEY

DIGIKEY

DIGIKEY

DIGIKEY

RHM2.20KFCT-ND

RHM1.50KCCT-ND

RHM100CCT-ND

RHM200FCT-ND

RHM12.0kFCT-ND

DIGIKEY

DIGIKEY

DIGIKEY

DIGIKEY

DIGIKEY

DIGIKEY

DIGIKEY

DIGIKEY

DIGIKEY

DIGIKEY

DIGIKEY

DIGIKEY

DIGIKEY

RHM22.0FCT-ND

RHM1.00FCT-ND

NOT USED

RSF100JB-1K0

541-3.0KVCT-ND

RHM5.60KFCT-ND

RHM14.7kFCT-ND

495-2093-ND

RHM33.0KFCT-ND

RHM680FCT-ND

RHM3.90KFCT-ND

RHM8.20KFCT-ND

RHM270KFCT-ND

DIGIKEY

DIGIKEY

YUJING

RHM20.0KFCT-ND

311-4.70FRCT-ND

LP3925H

INTERNATIONAL RECTIFIER IRS27951

DIGIKEY TLP621FT-ND

DIGIKEY 568-4883-1-ND

INTERNATIONAL RECTIFIER IR11682S

Rev. 4.1 6/1/2011 International Rectifier Page 9 of 23

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.

5 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.

Electronic or

Resistive

Load

24V/10A

Figure 7 - Recommended Evaluation Board Test Setup

5.1 Load Connection

Connect a resistive or electronic load, capable of 240W continuous power on the 24V rail to connector CON3.

Please note that there is no minimum load

3

requirement for this board.

5.2 AC/DC Input

The evaluation board can take either AC or DC input voltage. If an AC source is used, 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 an AC power source capable of operation up to 280VAC or a 400V DC source to CON1. 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.

3

A dummy load has been added to the output rail to ensure tight voltage regulation from no load to full load.

Rev. 4.1 6/1/2011 International Rectifier Page 10 of 23

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.

5.3 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.

5.4 Disconnect the Board

It is recommended to discharge the bulk capacitor C4 every time after evaluation is finished:

- Disconnect the high voltage AC or DC source from CON1

- Apply an external 12V DC voltage to primary Vcc and COM test points for a while until bus voltage drops to 0V

Rev. 4.1 6/1/2011 International Rectifier Page 11 of 23

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.

6 SYSTEM PERFORMANCE CHARACTERIZATION

6.1 Steady-State and Start-up Waveforms

Test Conditions – V

IN

= 350V DC; Full Load (24V/10A); No Load (24V/0A)

Ch 1: Low-side device V

GS

– Ch 2 : Voltage at VS pin

Ch 4 : Resonant tank current

Full Load Operation No Load Operation

Ch 2 : Output Voltage Ch 4 : Resonant tank current

Full Load Start-up No Load Start-up

At startup, synchronous rectifier circuit activates when Vout voltage is around 18V. As the voltage drop of SR MOSFET is

0.6V lower than body diode forward voltage drop, the output voltage has a small step-up. It also causes primary current a small peaking due to the charging current of output capacitor.

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INTERNATIONAL RECTIFIER.

Test Conditions – V

IN

= 390V DC; Full Load (24V/10A); No Load (24V/0A)

Ch 1: Low-side device V

GS

– Ch 2 : Voltage at VS pin

Ch 4 : Resonant tank current

Full Load Operation No Load Operation

Ch 2 : Output Voltage Ch 4 : Resonant tank current

Full Load Start-up No Load Start-up

The switching frequency sweeps from 200khz to regulation frequency in 10ms~15ms, prevents high current spike during startup. The output voltage has no overshoot during startup.

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Test Conditions – V

IN

= 420V DC; Full Load (24V/10A); No Load (24V/0A)

Ch 1: Low-side device V

GS

– Ch 2 : Voltage at VS pin

Ch 4 : Resonant tank current

Full Load Operation No Load Operation

Ch 2 : Output Voltage Ch 4 : Resonant tank current

Full Load Start-up No Load Start-up

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6.2 Synchronous Rectifier Waveform

Ch 1: SR gate1 – Ch 2 : SR gate2

Ch 2 : Voltage at VS pin – Ch 4 : Resonant tank current

350Vdc, No Load Operation 350Vdc, Full Load Operation

385Vdc, Full Load Operation 420Vdc, Full Load Operation

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6.3 Dynamic Load Response & Output Voltage Regulation

A load step from full load to no load and from no load to full load was applied to test the dynamic response of the system. The undershoot and overshoot are within +/-3%.

Ch2 : 24V Rail output voltage Ch 4 : Resonant tank current

Load Step at 350Vdc input

No Load to Full Load Step at 350Vdc Full Load to No Load Step at 350Vdc

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Load Step at 390Vdc input

No Load to Full Load Step at 390Vdc Full Load to No Load Step at 390Vdc

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INTERNATIONAL RECTIFIER.

Load Step at 420Vdc input

No Load to Full Load Step at 420Vdc Full Load to No Load Step at 420Vdc

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The output voltage is tightly regulated within a +/-1% regulation band over the entire line load range. A summary of the load performance is also shown below.

Load Regulation

24.00

23.90

23.80

23.70

23.60

23.50

23.40

23.30

23.20

23.10

23.00

0.00

2.00

4.00

Iout (A)

6.00

8.00

10.00

Figure 8 - Output voltage regulation plot

350 VDC Input

390 VDC Input

420 VDC Input

6.4 Output Ripple

The 24V output ripple is very tiny under DC input voltage. It is bigger with AC input. Below is the 24V ripple waveform tested at 270Vac and 10A full load.

The ripple is mainly due to the low frequency (2xfAC ) ripple on primary bus voltage. It will be much smaller if use a PFC pre-regulator in the front stage.

At light load, the Sync Rect circuit could go into standby mode if output current is too small. The gate of

IR11682 will be disabled and the body diode of SR MOSFET will carry output current. Depends on the load condition, IR11682 may have burst output as shown in the waveform. There will be some output ripple due to the burst operation of Sync Rect. The ripple is within 200mV and less than 1% of the rated output.

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IR11682 in burst mode at 390Vdc, no load.

Ch1 is the gate1 of IR11682

6.5 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

Rev. 4.1 6/1/2011 International Rectifier Page 20 of 23

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.

6.6 Efficiency Chart

The efficiency of IRS27951 demo board was tested at 350V, 390V and 420V DC input over the load range.

The result is shown in the table below.

Efficiency vs. Output Power

96.00

95.50

95.00

94.50

94.00

93.50

93.00

92.50

92.00

91.50

91.00

50.00

70.00

90.00 110.00 130.00 150.00 170.00 190.00 210.00 230.00 250.00

Output Power (W)

Figure 9 - Efficiency plot

350VDC Input

390VDC Input

420VDC Input

Rev. 4.1 6/1/2011 International Rectifier Page 21 of 23

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.

6.7 Thermal Data

The thermal performance of IRS27951 demo board is tested at 400Vdc input and 240W full load at room temperature.

Part

MOSFET M1

MOSFET M2

Case Temperature (°C)

51

48

U1 IRS27951

Transformer

MOSFET M3

MOSFET M4

40

69

70

73

7 Transformer Spec

Minimum operating frequency: 80 kHz

Primary inductance: 600 µH

±

10% @1 kHz - 0.25V (

Note 1

)

Leakage inductance: 125 µH

±

10% @1 kHz - 0.25V (

Note 2

)

Note: 1 Measured between Pins 3 and 6

Note: 2 Measured between Pins 3 and 6 with secondary windings shorted

7.1 Electrical Diagram

7 TX 16

Auxiliary

Sec C

11

12

6

3

Sec A

15

10

Primary Sec B

13

14

6

Sec D

9

Note: pin9 is shorted to pin10 on PCB, pin12 is shorted to pin13 on PCB and pin15 is shorted to pin16 on PCB.

Rev. 4.1 6/1/2011 International Rectifier Page 22 of 23

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.

Primary

7.2 Resonant Transformer Winding Position on Coil former

7.3 Resonant Transformer Winding Characteristics

Pins

3 - 6

Winding

Primary

Turn number

36

Wire type [mm]

LITZ - dia. 0.10x60

7 - 6

15 – 12

13 - 10

11 – 16

9 - 14

Auxiliary

Sec. A

Sec. B

Sec. C

Sec. D

2

2

2

2

2

Dia. 0.2

LITZ - dia. 0.10x250

LITZ - dia. 0.10x250

LITZ - dia. 0.10x250

LITZ - dia. 0.10x250

7.4 Resonant Transformer Vender and Part Number

Yu Jing Technology Co., LTD

LP3925H

Rev. 4.1 6/1/2011 International Rectifier Page 23 of 23

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.

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