参数资料
| 型号： | FSQ211L |
| 厂商： | Fairchild Semiconductor |
| 文件页数： | 9/13页 |
| 文件大小： | 0K |
| 描述： | IC SWIT PWM GREEN UVLO HV 8SOP |
| 标准包装： | 4,500 |
| 输出隔离： | 隔离 |
| 频率范围： | 61 ~ 73kHz |
| 输入电压： | 8 V ~ 20 V |
| 输出电压： | 650V |
| 功率（瓦特）： | 1.4W |
| 工作温度： | 25°C ~ 145°C |
| 封装/外壳： | 8-SOP，8-LSOP |
| 供应商设备封装： | 8-LSOP |
| 包装： | 管件 |
4.1 Overload Protection (OLP): Overload is defined as
the load current exceeding a pre-set level due to an
Drain current
unexpected event. In this situation, the protection circuit
should be activated to protect the SMPS. However,
even when the SMPS is operating normally, the over-
load protection (OLP) circuit can be activated during the
I LIM
2.14ms
7steps
load transition. To avoid this undesired operation, the
OLP circuit is designed to be activated after a specified
time to determine whether it is a transient situation or an
overload situation. If the output consumes more than the
maximum power determined by I LIM , the output voltage
(V O ) decreases below its rating voltage. This reduces
the current through the opto-coupler LED, which also
Figure 19. Internal Soft-Start
t
reduces the opto-coupler transistor current, thus
increasing the feedback voltage (V FB ). If V FB exceeds
3V, the feedback input diode is blocked and the 5μA
current source (I DELAY ) starts to charge C FB slowly up to
V CC . In this condition, V FB increases until it reaches
4.5V, when the switching operation is terminated, as
shown in Figure 18. Shutdown delay is the time required
to charge C FB from 3V to 4.5V with 5μA current source.
V FB
Overload Protection
6. Burst Operation: To minimize the power dissipation
in standby mode, the FSQ211 enters burst mode
operation. As the load decreases, the feedback voltage
decreases. The device automatically enters burst mode
when the feedback voltage drops below V BURL (0.55V).
At this point, switching stops and the output voltages
start to drop. This causes the feedback voltage to rise.
Once is passes V BURH (0.70V), switching starts again.
The feedback voltage falls and the process repeats.
Burst mode operation alternately enables and disables
switching of the power MOSFET to reduce the switching
loss in the standby mode.
4.5V
OSC
3V
t 12 = C FB × (V(t 2 )-V(t 1 )) / I DELAY
V fb
4
5μA
400μA
S
R
Q
GATE
DR IVE R
on/off
t 1
t 2
t
0.70V
/0.55V
Burst Operation Block
t 12 = C FB
V (t 2 ) ? V (t 1 )
I DELAY
;
I DELAY = 5 m A , V ( t 1 ) = 3 V , V ( t 2 ) = 4 . 5 V
Figure 20. Burst Operation Block
Figure 18. Overload Protection (OLP)
4.2 Thermal Shutdown (TSD): The SenseFET and the
control IC are integrated, making it easier for the control
IC to detect the temperature of the SenseFET. When
the temperature exceeds approximately 145 ° C, thermal
shutdown is activated.
5. Soft-Start: The FPS has an internal soft-start circuit
that slowly increases the feedback voltage, together with
the SenseFET current, right after it starts up. The typical
soft-start time is 15ms, as shown in Figure 19, where
progressive increment of the SenseFET current is
allowed during the start-up phase. Soft-start circuit
progressively increases current limits to establish proper
working conditions for transformers, inductors,
capacitors, and switching device. It also helps prevent
transformer saturation and reduces the stress on the
secondary diode.
? 2007 Fairchild Semiconductor Corporation
FSQ211 Rev. 1.0.0
9
V o
Vo set
V FB
0.7V
0.55V
I ds
V ds
t
Figure 21. Burst Operation Function
www.fairchildsemi.com
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