ncp1651 ON Semiconductor, ncp1651 Datasheet - Page 31

• Manufacturer Part Number: ncp1651
• Description: Single Stage Power Factor Controller
• Manufacturer: ON Semiconductor

needs a gain of −25 dB at 10 Hz, since the forward gain is
equal to 25 dB at this frequency. The high frequency gain of
the error amplifier is:
A
connected from the output of the converter to the input of the
error amplifier. If the output circuit of Figure 42 is used, R
would be 9.31 k + 453 W, or 9.76 kW. A gain of −25 dB is
equal to a divider ratio of:
A
so, R
or, R
The closest standard value resistor is 560 W.
amplifier should have a zero of 2 Hz or slightly higher. For
a 2 Hz zero, the compensation capacitor, C
calculated by:
be a good choice. This solution will provide a phase margin
of close to 90 . In practice the value of capacitance could be
Vhf
V
−10
−15
For a crossover frequency of 10 Hz, the error amplifier
Where R
To offset the 2 Hz pole of the output filter, the error
100 mF is the closest standard value capacitor and would
40
35
30
25
20
15
10
−5
= 10
5
0
fb
fb
= R
0.01
= 0.056 x 9.76 kW = 546 W
/ R
(−25/20)
fb
dc1
dc1
/ R
Figure 45. Forward Gain Plot
= 0.056
is the output voltage divider resistor that is
C fb +
0.1
dc1
= 0.056
2 p R fb 3 Hz
FREQUENCY (Hz)
1
1
+ 95 mF
10
100
fb
can be
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1000
dc1
NCP1651
31
cut in half or more and probably remain stable. This can be
tested in the circuit, or simulated with a model in SPICE or
a similar analysis program.
in Figures 46 and 47. These include the effects of all of the
stages shown.
−20
−40
−105
−120
−135
−150
−165
−180
The gain and phase plots of the completed loop are shown
80
60
40
20
−75
−90
0
0.01
0.01
Figure 47. Loop Phase Plot
0.1
Figure 46. Loop Gain Plot
0.1
FREQUENCY (Hz)
FREQUENCY (Hz)
1
1
10
10
100
100
1000
1000