DN28

Design Note 28
Issue 2 January 1996
6W Inverter for MOS Logic supplies
The inverter is a simple push-pull circuit
which takes advantage of the high
curre nt handling capability of the
ZTX650 range. It oscillates at a
frequency of approximately 25kHz to
allow it to use a very small transformer
(RM6), and also to render the inverter
inaudible. The output characteristics are
given in Figures 2 and 3. Output ripple is
approximately 150mV peak to peak on
both outputs.
The 6W inverter shown in Figure 1 has
been designed to generate the extra
power supplies required by popular
MOS memories from a normal 5V TTL
supply source. It may be used to supply
up to eight 2808 read only memories
which require supplies of +5V, -5V and
+12V, or if the output components of the
12V section are reversed, the circuit will
power over ten 5204 ROMs which
require +5V and -12V supplies.
ZTX650
7T
0.15mF
2T
+12V
*
BY206
5T
BY206
68mF
16V
*
1K
6T
200
0V
33
+
6T
2T
5T
BY206
7T
BY206
*
ZTX650
TFR1
100mF
10V
0V
100mF
10V
680
-5V
Transformer details:
FX3437 cores wound with:
2-0-2t, 29swg.
5-0-5t, 26swg. Bifilar
13-6-0-6-13t, 29swg.
* REVERSE POLARITY IF
-12V SUPPLY IS REQUIRED
+5V
Figure 1
6W Inverter Schematic.
DN28- 1
Design Note 28
Issue 2 January 1996
Figure 2
Output characteristics of +12V Supply
against Load Current.
Figure 3
Output characteristics of -5V Supply
against Load Current.
Table 1.
Output Voltage of +12V Supply against
Load Current.
Output
Current
Output
voltage
Output
voltage
10
12.2
12.1
100
11.8
11.6
200
11.6
11.4
300
11.4
11.2
400
11.2
11.0
500
10.8
10.7
600
10.6
-
10mA load
on -5V
supply.
250mA load
on -5V
supply.
DN28 - 2
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