M51995AFP#CF0J Renesas Electronics America, M51995AFP#CF0J Datasheet - Page 30

• Manufacturer Part Number: M51995AFP#CF0J
• Description: IC SWIT PWM SMPS OVP UVLO 20SOIC
• Manufacturer: Renesas Electronics America

Specifications of M51995AFP#CF0J

• Output Isolation: Isolated
• Frequency Range: 170 ~ 207kHz
• Voltage - Input: 9.9 ~ 36 V
• Power (watts): 1.5W
• Operating Temperature: -30°C ~ 85°C
• Package / Case: 20-SOIC (0.200", 5.30mm Width)
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

M51995AP/AFP
Application Note of Type M51995AP/AFP
Design of Start-up Circuit and the Power Supply of IC
1. The start-up circuit when it is not necessary to set the start and stop input voltage
2. The start-up circuit when it is not necessary to set the start and stop input voltage
REJ03D0835-0300 Rev.3.00 Jun 06, 2008
Page 28 of 40
Figure 22 Start-up Circuit Diagram (when it is not necessary to set the start and stop input voltage)
Figure 22 shows one of the example circuit diagram of the start–up circuit which is used when it is not necessary to
set the start and stop voltage.
It is recommended that the current more than 300 µA flows through R1 in order to overcome the operation start-up
current I
operation, so the response time will be long if the product is too much large.
Just after the start-up, the I
supplied from the third winding or bias winding of transformer, the winding ratio of the third winding must be
designed so that the induced voltage may be higher than the operation-stop voltage V
The V
output voltage (V
It is not necessary that the induced voltage is settled higher than the operation start-up voltage V
high gate drive voltage causes high gate dissipation, on the other hand, too low gate drive voltage does not make the
MOS FET fully on-state or the saturation state.
It is recommend to use the third winding of “forward winding” or “positive polarity” as shown in figure 23, when
the DC source voltages at both the IC operation start and stop must be settled at the specified values.
The input voltage (V
current characteristics of type M51995AP/AFP.
The input voltage (V
The V
Where
It is required that the V
V
V
I
V
V
V
V
V
CCL
IN (START)
IN (STOP)
CC
CC(START)
CC(STOP)
F
’IN(P-P)
CC
IN(START)
is the forward voltage of rectifier diode
CC(START)
is the operation start-up current of IC
terminal ≈
voltage is recommended to be 12 V to 17 V as the normal and optimum gate voltage is 10 to 15 V and the
is the peak to peak ripple voltage of
is the operation stop voltage of IC
≈ (V
and V
is the operation start-up voltage of IC
≈ R1 × I
and C
OH
CC (STOP)
) of type M51995AP/AFP is about (V
N
N
IN(STOP)
IN(START)
IN(STOP)
B
P
CCL
IN(START)
VCC
V'
IN RIP (P-P)
CC
+ (
is in the range of 10 to 47 µF. The product of R1 by C
), at which the IC operation stops, is decided by the ratio of third winding of transformer.
Rectified DC
voltage from
smoothing capacitor
− V
are given by following equations.
), at which the IC operation starts, is decided by R1 and R2 utilizing the low start-up
current is supplied from C
R1
R2
F
must be higher than V
) ×
M51995A
+ 1) × V
N
N
P
B
+
V
GND
CC
1
2
CC (START)
V'
IN RIP (P-P)
……… (9)
IN(STOP)
VCC
…… (10)
CC
+
R1
C
, however, under the steady state condition, IC will be
VCC
− 2 V).
.
V
F
Main transformer
Third winding or
bias winding
VCC
CC(STOP)
causes the time delay of
.
CC(START)
, and the