FAN103 Fairchild Semiconductor, FAN103 Datasheet - Page 11

• Manufacturer Part Number: FAN103
• Description: This third-generation Primary Side Regulation (PSR) and highly integrated PWM controller provides several features to enhance the performance of low-power flyback converters
• Manufacturer: Fairchild Semiconductor

© 2010 Fairchild Semiconductor Corporation
FAN103 • Rev. 1.0.5
Cable Voltage Drop Compensation
When it comes to cellular phone charger applications,
the battery is located at the end of cable, which causes,
typically, several percentage of voltage drop on the
actual battery voltage. FAN103 has a built-in cable
voltage drop compensation, which provides a constant
output voltage at the end of the cable over the entire
load range in CV mode. As load increases, the voltage
drop across the cable is compensated by increasing the
reference voltage of voltage regulation error amplifier.
Operating Current
The operating current in FAN103 is as small as 3.2mA.
The small operating current results in higher efficiency
and reduces the V
Once FAN103 enters deep-green mode, the operating
current is reduced to 0.95mA, assisting the power
supply in meeting power conservation requirements.
Green-Mode Operation
The FAN103 uses voltage regulation error amplifier
output (V
modulates the PWM frequency, as shown in Figure 23.
The switching frequency decreases as load decreases.
In heavy load conditions, the switching frequency is
fixed at 50kHz. Once V
PWM frequency linearly decreases from 50kHz. When
FAN103 enters into deep-green mode, the PWM
frequency is reduced to a minimum frequency of 370Hz,
gaining power saving to help meet international power
conservation requirements.
Frequency Hopping
EMI reduction is accomplished by frequency hopping,
which spreads the energy over a wider frequency range
than the bandwidth measured by the EMI test
equipment. FAN103 has an internal frequency hopping
circuit that changes the switching frequency between
47kHz and 53kHz with a period, as shown in Figure 24.
Figure 23. Switching Frequency in Green Mode
COMV
) as an indicator of the output load and
DD
hold-up capacitance requirement.
COMV
decreases below 2.5V, the
11
High-Voltage Startup
Figure 25 shows the HV-startup circuit for FAN103
applications. The HV pin is connected to the line input or
bulk capacitor through a resistor, R
recommended). During startup, the internal startup
circuit in FAN103 is enabled. Meanwhile, line input
supplies the current, I
capacitor, C
reaches V
blocking I
IC turns on, C
IC consumption current before the PWM starts to
switch. Thus, C
from dropping to V
delivered from the auxiliary winding.
STARTUP
DD-ON
Figure 24. Frequency Hopping
DD
Figure 25. HV Startup Circuit
DD
, through R
, the internal startup circuit is disabled,
DD
is the only energy source to supply the
from flowing into the HV pin. Once the
must be large enough to prevent V
DD-OFF
STARTUP
START
before the power can be
, to charge the hold-up
. When the V
START
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(100kΩ is
DD
voltage
DD