FA5502PM Fuji Electric holdings CO.,Ltd, FA5502PM Datasheet - Page 13

• Manufacturer Part Number: FA5502PM
• Description: Power Factor Correction
• Manufacturer: Fuji Electric holdings CO.,Ltd

8. Description of each circuit
(1) Oscillator section
FA5502P/M
R
C
T
T
between 0.3V and 3.4V by charging and discharging
capacitor. Fig.1 shows the connection. The oscillation
frequency is determined by CT and R
comparator. The oscillator is also used for determining
the maximum duty cycle of output pulses. Concretely,
a signal is sent to the output circuit section and the
OUT pin is forced to be Low level during the C
discharge period (fall time of CT pin voltage).
It is usable for synchronized operation. When it is
desired
free-running frequency (determined by C
must be set about 10% lower than that of external
synchronizing signal.
16k . Usually, a square-wave synchronizing signal is
differentiated by R and C, and the voltage input to
SYNC pin is so arranged to be below 1V within CT
discharge period. Concretely, the waveform must
satisfy the condition in Fig.3.
signal used as external synchronizing signal, the RC
differentiating circuit shown in Fig.2 could not generate
a waveform in Fig.3. In such a case, add a resistor
between SYNC pin and GND so as to clear the
condition in Fig.3.
negative voltage will be applied to SYNC pin while in
the
differentiating circuit. Considering the rated voltage of
SYNC pin, use a Schottky diode of a low forward
voltage.
connect SYNC pin to GND pin to avoid a malfunction.
(see characteristics curve).
The
The oscillator waveform is input to the PWM
SYNC pin (pin 14) is a synchronizing signal input pin.
The input resistance in SYNC pin is approximately
Depending on the amplitude, etc. of square-wave
Fig.5 shows timing chart of synchronized operation.
Note that diode D2 in Fig.2 is required so that no
Unless the external synchronization function is used,
discharge
13
15
oscillator
REF
CT
to
Fig.1 Oscillator circuit
adopt
OSC
period
generates
synchronized
0
of
capacitor
sawtooth
0.3V
3.4V
Dmax
T
.
operation,
Csy in
T
Dead time
waveform
and R
t
the
the
T
T
)
13
CT pin voltage
Synchronizing
signal
SYNC pin
voltage
OUT pin
voltage
synchronizing
signal
synchronizing
signal
Fig.5 Timing chart of synchronized operation
less
than
5V
Fig.3 Condition for SYNC pin signal
2V
1V
Quality is our message
Quality is our message
Quality is our message
Quality is our message
0
Rsy
Rsy
SYNC pin
signal
Fig.2 SYNC pin circuit (1)
Fig.4 SYNC pin circuit (2)
SYNC pin voltage waveform
R14
Csy
Csy
D2
D2
more than 50ns
14
14
SYNC
16k
less than 200ns
SYNC
16k
V
=1.5V(typ)
t
SYNC
OSC
OSC
t
t
t
t