NCP1651DR2G ON Semiconductor, NCP1651DR2G Datasheet - Page 25

• Manufacturer Part Number: NCP1651DR2G
• Description: IC PFC CONTROLLER CCM/DCM 16SOIC
• Manufacturer: ON Semiconductor

Specifications of NCP1651DR2G

• Mode: Continuous Conduction (CCM), Discontinuous Conduction (DCM)
• Frequency - Switching: 250kHz
• Current - Startup: 8.5mA
• Voltage - Supply: 10 V ~ 18 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: Lead free / RoHS Compliant
• Other names: NCP1651DR2GOS; NCP1651DR2GOS; NCP1651DR2GOSTR

Basic Specifications
of specifications. The following parameters should be
known before you begin:
Po
Vrms
Vrms
f
V
requirements.
Transformer
converter, there is no magic formula to determine the
optimum value of the transformer’s primary inductance.
There are several trade- -offs that should be considered.
These include peak current vs. average current, switching
losses vs. core losses and range of duty cycles over the
operational line and load range. All of these are a function
of inductance, line and load. These parameters determine
when the converter is operating in the continuous
conduction mode and when it is operating in the
discontinuous conduction mode.
ON Semiconductor spreadsheet (NCP1651_Design.xls)
that is available as a design aid for this part can be of help.
Enter various values of inductance as well as the turns ratio
and observe the variation in duty cycle and peak current vs.
average current.
There are two main limitations for the duty cycle. The first
is the output voltage reflected back to the primary, which is
scaled by the turns ratio. This means that with a 10:1
(pri:sec) turns ratio, and a 12 volt output, the power switch
will see the input voltage plus 120 volts (10 x 12 volts) plus
leakage inductance spike. This reflected voltage determines
the maximum voltage rating of the power switch.
Given the flyback converter transfer function, continuous
conduction mode,
cycle and the turns ratio. In general, 10:1 is about the
maximum, although some transformer manufacturers go as
high as 12:1 or even 15:1. Turns ratios of 20:1 and above are
not normally practical as they result in very high values of
leakage inductance, which creates large spikes on the power
switch. They also have a very large reflectovoltage
associated with them.
such as Coiltronics (www.cooperet.com/) or Coilcraft
(www.coilcraft.com/). These companies will design and
manufacture transformers to your requirements.
switch
out
The design of any power converter begins with a basic set
Most of these parameters will be dictated by system
For an average current mode, fixed frequency PFC
If you are designing your own transformer, the
The transformer’s duty cycle is an important parameter.
The second, there are practical limits to the turns ratio.
It is evident that there is a direct relationship between duty
The other option is to contact a transformer manufacturer
max
min
max
(Maximum rated output power)
(Minimum operational line voltage)
(Maximum operational line voltage)
(Nominal switching frequency)
(Nominal regulated output voltage)
V O = V in n (D∕1 − D)
http://onsemi.com
25
parameters, a primary inductance of 330 mH and a turns ratio
of 10:1 would be a good choice.
Limits
Po
Vin
Vin
V
L
f
N
it should provide a minimum of 12.1 volts (to exceed the
UVLO spec) and a maximum of 18 volts. The auxiliary
winding should be connected such that it conducts when the
power switch is off. Near the zero crossings of the line
frequency, the voltage will have a peak voltage equal to the
regulated output voltage divided by the turns ratio. The filter
cap on the V
voltage up over between the zero crossings.
Figure 40. Continuous/Discontinuous and Duty Cycle
switch
P
O
p
100
Using the available spreadsheet, with the following
If an auxiliary winding is desired to provide a bias supply,
max
/N
Figure 39. Switching Current versus Phase Angle
75
50
25
= 330 mH
max
min
= 12 V
0
6
5
4
3
2
1
0
s
0
0
= 100 W
= 100 kHz
= 10
= 85 V
= 265 V
CC
rms
pin needs to be of sufficient size to hold the
rms
45
45
100% = Discontinuous
50% = Continuous
PHASE ANGLE ()
DUTY CYCLE
DEGREES ()
PEDESTAL
CURRENT
MODE
90
90
PEAK CURRENT
135
135
180
180