S ECOND-GENERATION POWER FACTOR CONTROLLER
LX1562/1563
PRODUCT DATABOOK 1996/1997
19
Copyright © 1996
Rev. 1.3a 8/30
P RODUCTION DATA SHEET
APPLICATION INFORMATION
INDUCTOR DESIGN (continued)
Step 2: Choose a core with higher K
g
than the one calculated in
Step 1.
K
g
/core = k
where: k ≡ Winding coefficient (typ. k=0.4)
A
W
≡ Bobbin window area
A
E
≡ Effective core area
l
W
≡ Mean length per turn
K
g
factor for TDK PQ2625:
A
W
= 47.7mm
2
A
E
= 118mm
2
l
W
= 56.2mm
K
g
= 0.4 (mm)
5
= 4.7
*
10
-12
m
5
A
W
A
E
2
l
W
(47.7) (118)
2
56.2
Step 3: Determine number of turns.
N =
N = = 61 turns
A
WIRE
= k = 0.4 = 0.31mm
2
= 480mil
2
choose #22 AWG with r = 0.0165Ω/feet resistance.
R
W
= N
*
l
w
*
r
R
W
= 0.185Ω
L I
LP
B A
E
450
*
10
-6
*
2.4
0.15
*
118
*
10
-6
A
W
N
47.7
61
Step 4: Calculate air gap.
l
g
=
l
q
= = 0.122cm = 48 mil
µ
O
N
2
A
E
L
4π
*
10
-7
*
(61)
2
*
118
*
10
-6
450
*
10
-6
CURRENT SENSE RESISTOR
Current sense resistor, R6 is selected using the minimum multi-
plier output clamp voltage and the maximum inductor peak
current such that:
R6 = = = 0.45Ω
Power dissipation is approximated by:
P
R
≈ I
2 (MAX)
2
(1 - D'
MIN
), where D'
MIN
= 1 -
P
R
≈ (2.4)
2
(1 - 0.61) = 0.374
Select THREE 1.3Ω, ¼W carbon comp resistors in parallel.
V
CLAMP(MIN)
I
L (MAX)
1.1
2.4
1
6
√2 V
AC(MIN)
V
BOOST
1
6
R2
R1 + R2
MULTIPLIER COMPONENT SELECTION
Calculate R1 & R2 resistor values such that under low line AC input
the multiplier output is lower than the minimum clamp voltage.
*
√2 V
AC (MIN)
*
K
*
(V
EA0 (MAX)
- V
REF
) < V
CLAMP (MIN)
where: K ≡ Mult. Gain
V
EA)(MAX)
≡ Maximum error amp output where
multiplier is still in linear range.
This voltage is ≈ 3.5V.
For K = 0.65 & V
CLAMP (MIN)
= 1.1V, the ratio of R1/R2 is:
> 83
Assuming R1 is selected to be:
* R1 = 2.2M (1%)
R2 = = 26.4k (1%) select R
2
= 26.7k (1%)
* For high input applications such as 277V, R1 must be divided
into two resistors in series to meet the maximum rated voltage of
the resistors.
To improve THD further (typ. 2-3%), a high value resistor can
be connected from the supply voltage to this pin to allow an
increase in the switch on-time at the zero crossing by adding an
effective offset at the multiplier output.
ERROR AMPLIFIER COMPONENT SELECTION
Boost voltage is programmed with R7 & R8 resistor dividers using
the following equation:
= -1,
assuming that the product of R7 and the E.A. input bias current
does not cause significant error in the output voltage setting.
Assuming R7 = 1M
ΩΩ
ΩΩ
Ω
(for output voltage of higher than 250V,
two resistors may be added in series to meet the voltage
requirement of the resistor.)
∆V
ERROR
(10
6
) (0.5 * 10
-6
) = 0.5V, which is < 0.25% of the
output voltage.
Calculating R8:
R8 = = 11k (1%)
Worst case output tolerance is the total of ±3.75% which is the sum
of ±1.5% (Ref), ±2% (resistor dividers), and ±0.25% (E.A. input
bias current).
R7
R8
V
BOOST
V
REF
R7
V
BOOST
V
REF
- 1
R1
R2
2.2M
83
OBSOLETE PRODUCT
NOT RECOMMENDED FOR NEW DESIGNS
