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

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

F1

4.7 μF

MPSA42

MPSA42

4.7 μF

--145 V

145 V

0V

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.