|
|
PDF AND8129D Data sheet ( Hoja de datos )
| Número de pieza | AND8129D | |
| Descripción | A 30W Power Supply Operating in Quasi-Square Wave Resonant Mode | |
| Fabricantes | ON Semiconductor | |
| Logotipo |  |
|
Hay una vista previa y un enlace de descarga de AND8129D (archivo pdf) en la parte inferior de esta página. Total 18 Páginas | ||
|
No Preview Available !
AND8129/D
A 30 W Power Supply
Operating in Quasi−Square
Wave Resonant Mode
Prepared by: Christophe Basso
ON Semiconductor
http://onsemi.com
APPLICATION NOTE
INTRODUCTION
Quasi−Square Wave Resonant converters, often noted QR
converters, offer an elegant means to make Flyback supplies
look more friendly on the Electro−Magnetic Interference
(EMI) point of view. By delaying the ON switching event
until the drain−source voltage has decayed to a minimum,
switching losses are reduced and rising slopes lose their
stiffness. Designers get an immediate benefit from this
configuration since the MOSFET runs cooler and the EMI
input filter becomes easier to implement. Designing QR
Switch−Mode Power Supplies (SMPS) requires some
attention but is not an area dedicated to experts only.
You will discover through the following lines how new
ON Semiconductor solutions can help you to quickly turn
your quasi−resonant project into a working device.
What is Quasi−Resonance?
The term quasi−resonance is normally related to the
association of a real hard−switching converter and a
resonant tank. While the operation in terms of control is
similar to that of a standard PWM controller, an additional
network is added to shape the variables around the
MOSFET: current or voltage. Depending on the operating
mode, it becomes possible to either switch at zero current
(ZCS) or zero voltage (ZVS). Compared to a conventional
PWM converter, a QR operation offers less switching losses
but the RMS current circulating through the MOSFET
increases and forces higher conduction losses. However,
one of the main advantage in favor of the quasi−resonance
is the reduced spectrum content either conducted or radiated.
True ZVS quasi−resonance means that the voltage present
on the switch looks like a sinusoidal arch. Figure 1 shows
how such a signal could look.
230
170
Ip
·
ǸLf
Ctot
110
50
−10
1.69U
1.73U 1.77U
1.81U
1.85U
Figure 1. A Truly Resonating Vds Signal on a
Quasi−Resonant Flyback Converter
The main problem with this technique lies in the very high
voltage generated at the switch opening. Most of the time,
these resonant offline designs require around 1.0 kV BVdss
MOSFETs whose price is clearly incompatible with high
volume markets. As a result, designers orientate their choice
toward another compromise called quasi−square wave
resonant power supplies.
Quasi−Square Wave Resonant Converters
As we saw, true resonant operation hampers the MOSFET
selection by imposing a high voltage at the switch opening.
If we closely look at the standard hard−switching waveform
(Figure 2), we can see that there exists a time where the drain
voltage gets minimum. This occurs just after the core reset.
© Semiconductor Components Industries, LLC, 2003
October, 2003 − Rev. 0
1
Publication Order Number:
AND8129/D
1 page  
AND8129/D
3.5
3
2.5
2
1.5
100 150 200 250 300 350 400
VinDC
Figure 9. Peak Current Variations for a 100 W Output
Power with Different Line Voltages
A Quiet EMI Signature
Manipulating sinusoidal (or close−to) variables always
offer a narrower spectrum content compared to
hard−switching systems. Figures 10 and 11 depict the
conducted EMI signature of two systems operated at the
same point but implementing different switching
techniques.
Figure 10. A soft−switching approach reduces the
energy content above 1.0 MHz . . .
Since the MOSFET is reactivated at the lowest drain
level, the classical Coss capacitor discharge at the switch
closing is non−existing and the very narrow peak current
has gone (also this peak is often confusing the
current−sense comparator when it is really energetic, even
sometimes despite the presence of the LEB circuitry). As
a result, Quasi−square wave converters are recommended
where the Switch−Mode Power Supply (SMPS) needs to
operate close to Radio−Frequency section, e.g. Set Top
Boxes, TV sets, etc.
Figure 11. . . . while a hard−switching system
generates a lot of noise in this portion
Detecting the Core Reset Event
Core reset detection is usually done via a dedicated
auxiliary winding whose voltage image is directly linked
to
the
transformer
flux
by
Vaux + N
·
dö
dt
(eq. 20)
.
Depending on the controller device, the polarity of the
observed signal must fit its detection circuitry. In
ON Semiconductor NCP1205, this polarity should be of
Forward type, that is to say, when the MOSFET opens, the
auxiliary voltage (actually the Flyback level) dips below
ground and stays there, safely clamped at –0.7 V, until the
core reset occurs. Figure 12 gives an example of a
demagnetization signal given by an auxiliary winding wired
in both types.
http://onsemi.com
5
5 Page 
Rprim
0.5
VCoil
AND8129/D
X4
XFMR−AUX
RATIO_POW = −0.06
RATIO_AUX = 0.06
D
+
Icoil
Lprim
1.2 mH
X1
MBR20100
Idiode
R6
5.6 k
dem
C6
330 p
Iout
Vout
+
Vout
Resr1
60 m
Cout1
2.2 mF
IC = 16
Rload
9.4
Lleak
15 u
+
Vin
360
dem
R1
22 k
fb
X2
Free Run DT
18
27
36
Free
4 Run 5
Vdrain
+
Id
IReso
Creso
1.5 n
Rsense
0.5
Feedback
fb
Vout
Rled
1k
X7
MOC8101
C5
10 n
D4
BV = 15.6
Figure 17. A Simplified Free−Running Controller Eases the Simulation Setup and Increases Speed
http://onsemi.com
11
11 Page | ||
| Páginas | Total 18 Páginas | |
| PDF Descargar | [ Datasheet AND8129D.PDF ] | |
Hoja de datos destacado
| Número de pieza | Descripción | Fabricantes |
| AND8129 | A 30W Power Supply Operating in Quasi-Square Wave Resonant Mode | ON Semiconductor |
| AND8129D | A 30W Power Supply Operating in Quasi-Square Wave Resonant Mode | ON Semiconductor |
| Número de pieza | Descripción | Fabricantes |
| SLA6805M | High Voltage 3 phase Motor Driver IC. |
 Sanken |
| SDC1742 | 12- and 14-Bit Hybrid Synchro / Resolver-to-Digital Converters. |
 Analog Devices |
|
DataSheet.es es una pagina web que funciona como un repositorio de manuales o hoja de datos de muchos de los productos más populares, |
| DataSheet.es | 2020 | Privacy Policy | Contacto | Buscar |