参数资料
型号: FSQ0465RSWDTU
厂商: Fairchild Semiconductor
文件页数: 15/23页
文件大小: 0K
描述: IC SWIT PWM GREEN OVP HV TO220F
标准包装: 400
系列: FPS™
输出隔离: 隔离
频率范围: 48kHz ~ 67kHz
输入电压: 9 V ~ 20 V
输出电压: 650V
功率(瓦特): 70W
工作温度: -25°C ~ 85°C
封装/外壳: TO-220-6 全封装,成形引线
供应商设备封装: TO-220F
包装: 管件
resulting in the termination of the switching operation. To
avoid undesired activation of OVP during normal
operation, V CC should be designed below 19V.
4.5 Thermal Shutdown with Hysteresis (TSD): The
SenseFET and the control IC are built in one package.
This enables the control IC to detect the abnormally high
temperature of the SenseFET. If the temperature
exceeds approximately 140°C, the thermal shutdown
triggers IC shutdown. The IC recovers its operation when
the junction temperature decreases 60°C from TSD
temperature and V CC reaches startup voltage (V start ).
5. Soft-Start: The FPS has an internal soft-start circuit
that increases PWM comparator inverting input voltage
with the SenseFET current slowly after it starts up. The
typical soft-start time is 17.5ms. The pulse width to the
power switching device is progressively increased to
V O
Vo set
V FB
0.55V
0.35V
I DS
V DS
establish the correct working conditions for transformers,
FSQ0465 Rev. 00
time
inductors, and capacitors. The voltage on the output
capacitors is progressively increased with the intention of
t1
Switching
disabled
t2
t3
Switching
disabled
t4
smoothly establishing the required output voltage. This
mode helps prevent transformer saturation and reduces
Figure 32. Waveforms of Burst Operation
stress on the secondary diode during startup.
7. Switching Frequency Limit: To minimize switching
6. Burst Operation: To minimize power dissipation in
standby mode, the FPS enters burst-mode operation. As
the load decreases, the feedback voltage decreases. As
shown in Figure 32, the device automatically enters
burst-mode when the feedback voltage drops below
V BURL (350mV). At this point, switching stops and the
output voltages start to drop at a rate dependent on
standby current load. This causes the feedback voltage
to rise. Once it passes V BURH (550mV), switching
resumes. The feedback voltage then falls and the
process repeats. Burst-mode operation alternately
enables and disables switching of the power SenseFET,
thereby reducing switching loss in standby mode.
? 2008 Fairchild Semiconductor Corporation
FSQ0465RS/RB Rev. 1.0.1
15
loss and Electromagnetic Interference (EMI), the
MOSFET turns on when the drain voltage reaches its
minimum value in quasi-resonant operation. However,
this causes switching frequency to increases at light load
conditions. As the load decreases or input voltage
increases, the peak drain current diminishes and the
switching frequency increases. This results in severe
switching losses at light-load condition, as well as
intermittent switching and audible noise. These problems
create limitations for the quasi-resonant converter
topology in a wide range of applications.
To overcome these problems, FSQ-series employs a
frequency-limit function, as shown in Figures 33 and
Figure 34. Once the SenseFET is turned on, the next
turn-on is prohibited during the blanking time (t B ). After
the blanking time, the controller finds the valley within
the detection time window (t W ) and turns on the
MOSFET, as shown in Figures 33 and Figure 34 (Cases
A, B, and C). If no valley is found during t W , the internal
SenseFET is forced to turn on at the end of t W (Case D).
Therefore, the devices have a minimum switching
frequency of 48kHz and a maximum switching frequency
of 67kHz.
www.fairchildsemi.com
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