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Quasi-Resonant IC FA5530/31/32
Valley
Switching Frequency vs. Output Power
Timing Chart ( FA5531/32 )
Timing Chart ( FA5531/32 )
Po
fsw
Max fsw
(130kHz)
(1kHz)
Vds
最大
fsw
Valley
信号
130kHz
130kHz
最大fsw低下
(最小1kHz)
OUT
パルス
重負荷
中負荷
軽負荷
Example:
1kHz
Maximum Frequency :
65kHz or 130kHz
Output Power Po
Maximum
Frequency
Vds
Valley
Signal
OUT pin
voltage
Heavy
Load
Light
Load
Middle
Load
1/130kHz
1/130kHz
Maximum Period
is 1 / (Minimum
Frequency).
Example :1kHz
•
Low frequency switching such as 1kHz
at light load reduces standby power.
•
Maximum frequency limits EMI noise and switching Loss.
•
Switching at Valley of Vds : Turn-ON Loss and Noise are very small.
•
Low dV/dt of Vds at Turn-OFF by a capacitor connected between Drain and Source
of Power MOSFET : Turn-OFF Loss and Noise are also very small.
Valley
Low dV/dt slope of Drain Voltage “Vds”
Switching Frequency vs. Output Power
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