- 您現(xiàn)在的位置：買賣IC網(wǎng) > PDF目錄374731 > SC4809C (Semtech Corporation) High Performance Current Mode PWM Controller PDF資料下載
參數(shù)資料
| 型號： | SC4809C |
| 廠商： | Semtech Corporation |
| 英文描述： | High Performance Current Mode PWM Controller |
| 中文描述： | 高性能電流模式PWM控制器 |
| 文件頁數(shù)： | 9/16頁 |
| 文件大?。?/td> | 328K |
| 代理商： | SC4809C |
9
2005 Semtech Corp.
www.semtech.com
SC4809A/B/C
POWER MANAGEMENT
Application Information (Cont.)
Control-to-Output transfer function for the flyback power
stage operating in CCM is given by:
2
O
2
O
2
z
1
z
P
S
2
I
O
S
ω
Q
S
1
S
1
S
1
N
N
)
D
1
V
dD
dV
+
ω
+
ω
ω
+
=
where:
C
L
R
x
)
D
1
Q
C
L
D
1
L
D
R
)
D
1
C
R
1
1
z
SEC
SEC
O
SEC
2
2
z
C
≈
≈
ω
≈
ω
=
ω
Control-to Output transfer function for the flyback power
stage operating in DCM is given by:
P
SEC
S
P
S
I
O
S
ω
1
1
L
2
T
R
N
N
V
dD
dV
+
=
where:
C
R
2
P
=
ω
Peak current mode control requires simpler
compensation, has pulse-by-pulse current limiting, and
has better load current regulation. Primary and secondary
RMS currents can be up to two times higher for
discontinuous mode than for CCM. Discontinuous
conduction mode would require using a transistor with a
higher current rating. Because the output ripple current
is less than it would be continuous mode were used, the
output capacitors are smaller. Continuous conduction
mode (CCM) was therefore chosen.
The DC transfer function of a CCM flyback converter is:
=
+
max
max
D
)
on
(
Rds
(min)
IN
V
D
O
1
D
N
1
V
V
V
where V
O
= output voltage,
V
D
= forward voltage drop across rectifier D1,
N = turns ratio, equal to N
P
/N
S
,
D = duty cycle.
Transformer Design
The transformer in a flyback converter is actually a coupled
inductor with multiple windings. Transformers provide
coupling and isolation whereas inductors provide energy
storage. The energy stored in the air gap of the inductor
is equal to:
(
)
2
I
L
E
2
PEAK
P
=
where E is in Joules, L
is the primary inductance in
Henries, and I
is the primary peak current in Amperes.
When the switch is on, D1 is reverse biased due to the
dot configuration of the transformer. No current flows in
the secondary windings and the current in the primary
winding ramps up at a rate of:
P
)
on
(
Rds
(min)
IN
V
L
t
L
V
I
=
The output capacitor, C
, supplies all of the load current
at this time. Because the converter is operating in the
continuous conduction mode,
I
is the change in the
inductor current which appears as a positive slope ramp
on a step. The step is present because there is still
current left in the secondary windings when the primary
turns on. When the switch turns off, current flows through
the secondary winding and D1 as a negative ramp on a
step, replenishing C
OUT
and supplying current directly to
the load.
相關PDF資料 |
PDF描述 |
|---|---|
| SC480 | Complete DDR1/2/3 Memory Power Supply |
| SC480EVB | Complete DDR1/2/3 Memory Power Supply |
| SC480IMLTRT | Complete DDR1/2/3 Memory Power Supply |
| SC4810B | High Performance Current Mode PWM Controller with Complementary Output, Programmable Delay |
| SC4810BIMLTRT | High Performance Current Mode PWM Controller with Complementary Output, Programmable Delay |
相關代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| SC4809CIMSTRT | 制造商:Semtech Corporation 功能描述:SC Series 25 mA 1100 kHz High Performance Current Mode PWM Controller - MSOP-10 |
| SC480EVB | 制造商:SEMTECH 制造商全稱:Semtech Corporation 功能描述:Complete DDR1/2/3 Memory Power Supply |
| SC480IMLTRT | 制造商:SEMTECH 制造商全稱:Semtech Corporation 功能描述:Complete DDR1/2/3 Memory Power Supply |
| SC4810B | 制造商:SEMTECH 制造商全稱:Semtech Corporation 功能描述:High Performance Current Mode PWM Controller with Complementary Output, Programmable Delay |
| SC4810BIMLTRT | 制造商:Semtech Corporation 功能描述:Controller IC Leaded Process Compatible: |
發(fā)布緊急采購，3分鐘左右您將得到回復。