Energy Saving Products
101 N.Sepulveda Blvd, EL Segundo 90245 California, USA
IRAUDPS3-30V
+/-30V Power Supply for
Class-D Audio Amplifier
Reference Design
User Guide
Rev. 1.2
6/23/2015
International Rectifier
Page 1 of 20
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
2
3
INTRODUCTION ........................................................................................................................ 3
IRS27951/2 DESCRIPTION ....................................................................................................... 3
EVALUATION BOARD SPECIFICATIONS ................................................................................ 4
3.1
Board Description ................................................................................................................... 5
3.2
Schematic ............................................................................................................................... 6
3.3
Board PCB Layout .................................................................................................................. 7
3.4
Bill of Materials ....................................................................................................................... 8
4
EVALUATION BOARD OPERATING PROCEDURE ............................................................... 10
4.1
Load Connection .................................................................................................................. 11
4.2
AC Input ................................................................................................................................ 11
4.3
IRS27952 DC Supply Voltage .............................................................................................. 11
4.4
Disconnect the Board ........................................................................................................... 11
5
SYSTEM PERFORMANCE CHARACTERIZATION ................................................................ 12
5.1
Primary Waveforms .............................................................................................................. 12
5.2
Dynamic Load Response and Regulation Waveforms.......................................................... 13
Test Conditions: Full Load (2A to +B and -B); No Load (0A) ......................................................... 13
5.3
Output Waveforms with Audio Amplifier Load ...................................................................... 14
5.4
Output Ripple ........................................................................................................................ 18
5.5
Efficiency .............................................................................................................................. 18
5.6
Thermal Data ........................................................................................................................ 19
6
Transformer Spec..................................................................................................................... 20
6.1
Electrical Diagram................................................................................................................. 20
6.2
Resonant Transformer Winding Characteristics ................................................................... 20
Rev. 1.2
6/23/2015
International Rectifier
Page 2 of 20
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 performance and test procedure of IRAUDPS3-30V Reference Design,
featuring the IRS27952S Resonant Half Bridge controller. The document includes schematic diagram,
PCB layout, 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 nonlinear 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. 1.2
6/23/2015
International Rectifier
Page 3 of 20
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 BOARD
1
SPECIFICATIONS
AC Voltage Range
88V-132V or 176V-264V
With user selectable 110/220V jumper
The jumper is configured for 110Vac input in default
AC Line Frequency
Output Voltage
47-63Hz
+/-30V, 28V~32V regulation under 120W load.
+15%/-25%, 22.5V~34.5V under maximum pulsed load
Average Load
5 Minutes Cont. Load
Maximum Pulse Load
60W, PS will be designed to thermally support this load
120W, PS will be designed to electrically support this load
200W, 20Hz sinusoid pulse, at Nominal Vin and +20% Vin
150W, 20Hz sinusoid pulse, at -20% Vin (Note
2
)
This load has to be managed by the output capacitors
Efficiency
Converter Switching
Frequency Range
Maximum Ambient
Operating Temperature
Board Size
>88% at 120W load
60-190 kHz
50C
3”x5”x1.5”
Main board: Single layer PCB
Control board: Double layer PCB
There are high voltages present whenever the board is energized and proper precautions
should be taken to avoid potential shock and personal injury.
Please note that EMI measurements have not been performed on this evaluation board. The primary goal of this board is to demonstrate the
performance of the IRS27952 controller IC.
2
1
The LLC resonant half-bridge has narrow line regulation range. At low line the capability of peak power is folded back.
Rev. 1.2
6/23/2015
International Rectifier
Page 4 of 20
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.
3.1 Board Description
The evaluation board consists of a front-end AC-DC rectifier stage cascaded with a half-bridge resonant DC-
DC converter with +/-30V output voltage rails.
The front end is a conventional pi type EMI filter, followed by bridge rectifier stage. Two 200V/680uF bulk
capacitors are connected in series to provide stable DC bus voltage. The rectifier can be configured as full
bridge rectifier for 220Vac input, or voltage doubler rectifier for 110Vac input.
The downstream converter is a multi-resonant half bridge LLC converter whose control is implemented with the
IRS27952 controller HVIC (U101 on the control board). The controller drives the two half-bridge MOSFETs
with a 50 percent fixed duty cycle with pre-defined dead-time. Output voltage regulation is achieved by
changing the switching frequency according to the feedback signal.
IRS27952 is self-supplied in this reference design. The startup resistors R7 and R7A~C provide startup current
to IRS27952 during power up and charge the Vcc capacitors (CP3 and C5 on the main board). Once Vcc
voltage exceeds Vccuv+ threshold, IRS27952 starts operation and the auxiliary winding of power transformer
can provide bias to the IC. The voltage of auxiliary winding could vary a lot when load changes from 0A to full
load, so a linear regulator – Z101, R101 and Q101 (on the control board) – is used to keep Vcc regulated at
12V.
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 (U104) to
adjust the current in the optocoupler PC817 (U103). 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 side has two center-tapped windings for +30V and -30V output. Each rail has full wave rectifier
and filter with the return connected to center-tap. The feedback loop is configured to regulate the rail to rail
voltage to 60V. The balance of +30V and -30V is achieved by the symmetric windings of transformer.
Rev. 1.2
6/23/2015
International Rectifier
Page 5 of 20
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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