NCP1650DR2 ON Semiconductor, NCP1650DR2 Datasheet - Page 22

• Manufacturer Part Number: NCP1650DR2
• Description: IC CTRLR PWR FACTOR PWM 16SOIC
• Manufacturer: ON Semiconductor

Specifications of NCP1650DR2

• Mode: Continuous Conduction (CCM), Discontinuous Conduction (DCM)
• Frequency - Switching: 100kHz
• Voltage - Supply: 10 V ~ 20 V
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 16-SOIC (3.9mm Width)
• Switching Frequency: 25 KHz to 250 KHz
• Maximum Operating Temperature: + 125 C
• Mounting Style: SMD/SMT
• Minimum Operating Temperature: - 40 C
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Current - Startup: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant
• Other names: NCP1650DR2OSTR

Comparator monitors the output voltage and will shutdown
operation of the PWM circuit if the output voltage exceeds
8% above the normal regulation level. The Overshoot
Comparator signal is fed into the second Set input to the
latch.
AC Reference Buffer
by the AC error amplifier to be converted into a current to
be summed with the ramp compensation signal and the
instantaneous current signal.
Comp
The AC reference buffer converts the voltage generated
The buffer’s transfer function is:
AC
3
Figure 39. AC Reference Buffer Schematic
ERROR
AMP
AC
i out = (2.9 V − V ac )∕7 k
2.9 V
Unity Gain Amplifier
+
+
--
--
CURRENT
MIRROR
i
14 k
1
2 X
16 k
i
1
PWM,
Ramp
Comp
Current
Sense
Amp
http://onsemi.com
22
current by creating a current equal to the voltage difference
between the AC error amplifier output and the 2.9 volt
reference dropped across the 14 kΩ resistor. The bipolar
transistor level shifts the voltage and maintains the proper
current into the current mirror. The current mirror has a 1:2
ratio and delivers the output current to the PWM input. This
current is summed with the currents of the ramp
compensation signal and the instantaneous current signal to
determine the turn- -off point in the switching cycle.
Soft- -Start Circuit
low output level will cause the output duty cycle to go to
zero. This will have the effect of soft- -starting the unit at
turn- -on, since the output is coupled to ground through a
capacitor.
the output current and the resistor at pin 3. For example, if
the output is saturated in the high state at turn on, it will
source 50 mA. If pin 3 is terminated with a 2.2 kΩ resistor
and a 0.01 F capacitor, the initial step will be:
and the rate of rise will be:
or, 560 ms until the output is at 2.9 volts, which corresponds
to full duty cycle.
Figure 29, if additional time is desired.
The buffer amplifier, converts the input voltage to a
The AC error amplifier has been configured such that a
There will be an initial offset of the output voltage due to
An external soft- -start circuit can be added, as shown in
50 mA × 2.2 k = 0.11 volts
50 mA∕0.01 mF = 5 mv∕ms