Datasheet

UCC28089
SLUS623A -- SEPTEMBER 2004 -- REVISED AUGUST 2006
11
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APPLICATION INFORMATION
Using the UCC28089 as a Modified Square Wave Inverter
Remote or dc-only power systems often require a limited amount of 60-Hz ac line power to supply small
appliances. Compatible loads include universal motors, incandescent lamps, and other electronic devices with
switched mode power supplies to convert the 110-V
AC
to lower dc voltages. Many of these devices do not require
a perfect sinusoidal line voltage, and acceptable performance can be obtained with a modified square wave
voltage. Using the circuit in Figure 5, the UCC28089 can provide the appropriate waveform along with primary
side over-current protection. Components RA, RB, and CT are selected to program the desired modified square
waveform with the appropriate dead time.
UDG-04105
CT
0.1 μF
RB
27 kΩ
RA
221 kΩ
NC
200 Ω
47 μF
12 V Bias
V
IN
= 145 V
DC
F1
R
S
4.7 μF
MPSA42
MPSA42
4.7 μF
--145 V
145 V
0V
V
O
110 V
AC(rms)
16.7 ms
NOTE: CS signal should be selected to limit peak inrush current to acceptable levels.
1N4003
2
1
4
3
7
8
5
6
UCC28089
SYNC
DIS
CT
CS
VDD
OUTA
OUTB
GND
+
--
6800 pF
6800 pF
50 Ω
200 Ω
200 Ω
50 Ω
200 Ω
20 Ω
Figure 5. Modified Square Wave Inverter
The high-side gate drives of the inverter in Figure 5 are suitable for low frequency applications with relatively
constant duty ratio. The NPN transistors and the charge pump diodes on the high-side gate drives must be rated
for high voltage (at least 145 V + VDD). The gates are protected from excessive negative voltage by the diodes
shown from gate to source.