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參數(shù)資料
| 型號(hào)： | AN-995A |
| 英文描述： | Electronic Ballasts Using the Cost-Saving IR215X Drivers(153.99 k) |
| 中文描述： | 使用電子鎮(zhèn)流器的成本節(jié)約IR215X驅(qū)動(dòng)器（153.99十一） |
| 文件頁數(shù)： | 3/10頁 |
| 文件大?。?/td> | 153K |
| 代理商： | AN-995A |
Application
Notes
C
ONTROL
I
NTEGRATED
C
IRCUIT
D
ESIGNERS’
M
ANUAL
C-61
It can readily be seen, therefore, that to charge and
discharge the power switch input capacitances, the re-
quired charge is a product of the gate drive voltage and
the actual input capacitances and the input power re-
quired is directly proportional to the product of charge
and frequency and voltage squared:
Power =
QV
2
f
2
×
(3)
The above relationships suggest the following consider-
ations when designing an actual ballast circuit:
1) select the lowest operating frequency consistent
with minimizing inductor size;
2) select the smallest die size for the power switches
consistent with low conduction losses (this reduces the
charge requirements);
3) DC bus voltage is usually specified, but if there is a
choice, use the lowest voltage.
NOTE:
Charge is not a function of switching speed.
The charge transferred is the same for 10 ns or 10 μs
switch times.
Let us now consider some practical ballast circuits
which are possible with the self-oscillating drivers. By
far the most popular fluorescent fixture is the so-called
‘Double 40’ type which uses two standard T12 or T8
lamps in a common reflector.
Two suggested ballast circuits are shown in figures 3
and 4. One is a low power factor circuit, and the other
uses a novel diode/capacitor configuration to achieve a
power factor > 0.95.
Figure 3.
‘Double 40’ ballast using IR2151 oscillator/driver
250 VAC
μ
F
L1
4 x 1N4007
L
1
L
2
200v
μ
F
N
100
μ
F
20V
91K
f
= 45 kHz
P.F. = 0.6 LAG
120 VAC INPUT
USE L
1
-N
230 VAC INPUT
USE L
1
-L
2
+320V
11DF4
IRF
47
μ
F
20V
+
+
+
1
2
8
μ
F
1
V
CC
V
R
T
HO7
I
6
IRF 720
5
22
C
T
V
S
LO
COM
4
15K
0.01
μ
F
3
0.1
μ
F
22
40W
μ
F
0.01
μ
F
0.01
40W
L2
10
+
+
L3
PTC
μ
F
0.001
PTC
*Polyproplylene Capacitor
L1
Core: Micorometals T106-26
μ
H
L2-L3 64T #22 HATP
Inductance 1.35 mH: Gap spacer 0.01 inch
P.T.C. CERA MITE #307C1260BHEAB
The low power factor circuit shown in figure 3 accepts
115 VAC or 230 VAC 50/60/400 Hz inputs to produce a
nominal DC bus of 320 VDC. Since the input rectifiers
conduct only near the peaks of the AC input voltage, the
input power factor is approximately 0.6 lagging with a
non-sinusoidal current waveform. This type of rectifier
is not recommended for anything other than an evalua-
tion circuit or low power compact fluorescents and in-
deed may become unacceptable as harmonic currents in
power distribution systems are further reduced by power
quality regulations.
Note that the International Rectifier IR2151 Control
IC operates directly off the DC bus through a dropping
resistor and oscillates at around 45 kHz in compliance
with the following relationship:
f
=
+
1
1.4 (R
75 ) C
T
T
Power for the high side switch gate drive comes from a
bootstrap capacitor of 0.1 μF which is charged to ap-
proximately 14V whenever V
S
(lead 6) is pulled low
during the low side power switch conduction. The boot-
strap diode 11DF4 blocks the DC bus voltage when the
high side switch conducts. A fast recovery diode (<100
ns) is required to ensure that the bootstrap capacitor is
not partially discharged as the diode recovers and blocks
the high voltage bus.
The high frequency output from the half-bridge is a
square wave with very fast transition times (approxi-
mately 50 ns). In order to avoid excessive radiated noise
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