參數(shù)資料
型號(hào): TK75003
廠商: TOKO Inc.
英文描述: PWM CONTROLLER
中文描述: 脈寬調(diào)制控制器
文件頁(yè)數(shù): 12/14頁(yè)
文件大小: 108K
代理商: TK75003
Page 12
January 1999 TOKO, Inc.
TK75003
BOOST POWER FACTOR CORRECTOR APPLICATION
CIRCUIT
Figure 9 shows a universal-input, 100 W boost Power
factor corrector application circuit. The control technique is
called “current-clamped control.” Both the control technique
and the application circuit with waveforms are described in
the paper “Low-Cost Power Factor Correction/Line-
Harmonics Reduction with Current-Clamped Boost
Converter,” published in the conference proceedings of
Power Conversion Electronics ’95/Powersystems World
’95. A copy of the paper can be obtained by contacting
Toko.
For designers who wish to explore other performance
optimizations of the current-clamped boost power factor
corrector, aside from the conference paper Toko offers a
Mathcad file which can accurately display current
waveforms and predict power factor, harmonic distortion,
and individual harmonic currents. The Mathcad file and the
text which describes how to use it are available from the
Colorado Springs Toko IC Design Center.
The power factor corrector in Figure 9 has been optimized
for general wide-range-input use. In order to obtain the
same performance at power levels other than 100 W, the
control components do not need to change. The power
component values change as follows: C
8
scales in
proportion to the power level, and L
1
and R
8
scales in
inverse proportion to the power level. Typically, although
not directly related to the line-current shaping capability of
the application circuit, C
1
and C
10
would scale in proportion
to the power level. All the components in the power stage
should have a current rating as needed to accommodate
the power level.
Below is a step-by-step design example, showing how to
determine the resistance of R
7
terminating the feedback
pin and the resistance of the current-sense resistor R
8
, for
the boost corrector of Figure 9.
Assumptions:
Output power:
P
OUT
= 100 W
Output voltage:
V
OUT
= 380 Vdc
Minimum line voltage:
V
I(MIN)
= 85 Vrms
Efficiency at 85 Vrms:
EFF = 0.93
APPLICATION INFORMATION (CONT.)
Switching frequency:
f = 100 kHz
Inductance of boost inductor:
L
1
= 2.5 mH
Maximum duty ratio of TK75005:
D
MAX
= 0.88
Peak value of ramp current
flowing out of the FB pin:
I
SC(PK)
= 200
μ
A
Threshold voltage of the
current-control detector:
V
CCD
= 0.98 V
Calculations:
Peak value of minimum line voltage:
V
I(MIN)(PK)
=
2
x V
I(MIN)
= 120 V
PK
Switch duty ratio at peak of minimum line voltage:
D = 1 - V
I(MIN)(PK)
/ V
OUT
= 0.684
Peak-to-peak ripple current in inductor L
1
:
I = V
I(MIN)(PK)
x D / (f x L
1
) = 0.33 A
Input power at minimum line voltage:
P
I
= P
OUT
/ EFF = 107.5 W
Peak current in L
1
(at peak of minimum line voltage):
I
L1(PK)
=
2
x P
I
/ V
I(MIN)(PK)
+ I / 2 = 1.95 A
Resistance of resistor R
7
(Note 1):
R
7
= D
MAX
x V
CCD
/ I
SC(PK)
= 4.312 kohms
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