- 您現(xiàn)在的位置：買賣IC網(wǎng) > PDF目錄378405 > AND8112 (ON SEMICONDUCTOR) A Quasi-Resonant SPICE Model Eases Feedback Loop Designs PDF資料下載
參數(shù)資料
| 型號(hào)： | AND8112 |
| 廠商： | ON SEMICONDUCTOR |
| 英文描述： | A Quasi-Resonant SPICE Model Eases Feedback Loop Designs |
| 中文描述： | 阿準(zhǔn)諧振SPICE模型反饋環(huán)的設(shè)計(jì)更易 |
| 文件頁(yè)數(shù)： | 2/12頁(yè) |
| 文件大?。?/td> | 205K |
| 代理商： | AND8112 |
AND8112/D
http://onsemi.com
2
As in any sinusoidal signal, there are peaks and valleys. When you restart the switch in one valley, where the voltage is
minimum, the MOSFET is no longer the seat of heavy turnon losses engendered by capacitive effects: this is the socalled
QuasiResonance operation where the switching frequency depends on the peak current, the various slopes ON and OFF and
the number of valleys you choose after the core reset. In our study, we will first concentrate on a simplified SPICE version where
the power switch is actuated right after the reset detection point (parasitic ringings are neglected) and later on, a more
sophisticated declination will incorporate parasitic delays.
Modeling the Switch Network
Figure 3 depicts a Flyback topology where the switching
elements generating the above waveforms have been
highlighted: the power switch (usually a MOSFET
transistor) and a diode, performing a rectification job.
During the converter operation, the Pulse Width Modulator
controller (PWM) instructs the transistor to turn ON, in
order to store energy in the primary side. The primary
current builds up until the setpoint imposed by the feedback
loop is reached. At this time, the controller toggles the
transistor to the OFF state and energy transfers to the
secondary side. If the ON and OFF states can be described
by a set of linear equations, there exists a discontinuity
linking these two events. Despite the presence of linear
elements in the converter (capacitors, inductors and
resistors), the presence of the commuting switch clearly
introduces the nonlinearity that prevents us from directly
writing the smallsignal equations
…
When learning electronic circuits at school, there were
some exercises in which we were asked to reveal the transfer
function of bipolar amplifiers. At that time, we learned to
replace the transistor symbol by its equivalent smallsignal
model: the schematic turned into the simple association of
current and voltage sources that greatly simplified the
analysis. In the average circuit modeling technique, we also
follow the same philosophy: the exercise lies in isolating and
replacing the switch network with a set of current and
voltage sources whose electrical architecture do not vary
with time. Therefore, plugging the equivalent model back
into the converter of interest allows us to resolve its transfer
characteristics.
d
s
a
k
2
5
3
1
C
R
Figure 3. A Flyback Power Supply where Switches
have been Isolated
V
(t)
V
2(t)
I
2(t)
V
1(t)
Control
V
g
+
I
1(t)
L
P
I
L(t)
1:N
Figure 4.
and Individual Signals Separately Plotted.
(V(L
P
)
T
S
V
g
V
N
T
S
V
2(t)
V
1(t)
I
2(t)
I
1(t)
I
L(t)
I
P
V
N
Vg
I
P
/N
I
P
V
N
LP
Vg
LP
Vg
LP
V
N2
LP
d
TS
d
TS
N
Vg
V
Deriving Equations
The object of deriving a model consists in writing the
equations that describe the switch network averaged input
and output quantities that a) depend from each other b) obey
to the control input. Let us draw the various waveforms
before starting any line of algebra (Figure 4). From this
picture, we can develop equations that will finally describe
the
averaged
evolution of the values of interest, the input /
output voltage and current of our switch network:
IP
2
I1(t)
d
(eq. 4)
I2(t)
IP
2
N
d
(eq. 5)
V1(t)
V
N
N
Vg
d
(eq. 6)
V2(t)
[V
N
Vg]
d
(eq. 7)
where: V is the output voltage, V
g
the input voltage, I
P
the
primary peak current, N the N
S
/ N
P
turn ratio and d the
dutycycle (d
′
= 1 –d).
Please note that in this first approach, we do not consider
any delay occurring at the switch opening or induced by
equation 3. These events will considered later on, in a more
complex model.
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| AND8116 | Integrated Relay/Inductive Load Drivers for Industrial and Automotive Applications |
| AND8116D | Integrated Relay/Inductive Load Drivers for Industrial and Automotive Applications |
| AND8130 | Analog Switch Allows USB Switching at Low Voltages |
| AND8139 | Ultra-Low Voltage MiniGate Devices Solve 1.2 V Interface Problems |
| AND8139D | Ultra-Low Voltage MiniGate Devices Solve 1.2 V Interface Problems |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| AND8116 | 制造商:ONSEMI 制造商全稱:ON Semiconductor 功能描述:Integrated Relay/Inductive Load Drivers for Industrial and Automotive Applications |
| AND8116D | 制造商:ONSEMI 制造商全稱:ON Semiconductor 功能描述:Integrated Relay/Inductive Load Drivers for Industrial and Automotive Applications |
| AND8130 | 制造商:ONSEMI 制造商全稱:ON Semiconductor 功能描述:Analog Switch Allows USB Switching at Low Voltages |
| AND8130/D | 制造商:ONSEMI 制造商全稱:ON Semiconductor 功能描述:Analog Switch Allows USB Switching at Low Voltages |
| AND8139 | 制造商:ONSEMI 制造商全稱:ON Semiconductor 功能描述:Ultra-Low Voltage MiniGate Devices Solve 1.2 V Interface Problems |
發(fā)布緊急采購(gòu)，3分鐘左右您將得到回復(fù)。