NCP1729
www.onsemi.com
21
Figure 49. Combination of a Closed Loop Negative Inverter with a Positive Output Voltage Doubler
+
6
4
2
3
1
OSC
+
V
in
5
−V
out
+
Capacitors = 10 mF
10 k
+
+
R
1
R
2
+V
out
All of the previously shown converter circuits have only single outputs. Applications requiring multiple outputs can be
constructed by incorporating combinations of the former circuits. The converter shown above combines Figures 26 and 32 to
form a regulated negative output inverter with a non−regulated positive output doubler. The magnitude of −V
out
is controlled
by the resistor values and follows the relationship −V
ref
(R
2
/R
1
+ 1). Since the positive output is not within the feedback loop,
its output voltage will increase as the negative output load increases. This cross regulation characteristic is shown in the upper
portion of Figure 50. The dashed line is the open loop and the solid line is the closed loop configuration for the load regulation.
The load regulation for the positive doubler with a constant load on the −V
out
is shown in Figure 51.
Figure 50. Load Regulation, Output Voltage
vs. Output Current
Figure 51. Load Regulation, Output Voltage
vs. Output Current
−4.0
−5.0
−3.0
8.0
I
out
, NEGATIVE INVERTER OUTPUT CURRENT (mA)
V
out
, OUTPUT VOLTAGE (V)
02010 30
8.0
7.0
9.0
I
out
, POSITIVE DOUBLER OUTPUT CURRENT (mA)
V
out
, OUTPUT VOLTAGE (V)
0302010 5
R
1
= 10 kW
R
2
= 20 kW
T
A
= 25°C
40
Negative Inverter I
out
= 15 mA
Negative Inverter
Positive Doubler
I
out
= 15 mA
R
out
= 45 W − Open Loop
R
out
= 2 W − Closed Loop
R1 = 10 k, R2 = 20 k
T
A
= 25°C
Figure 52. Inverter Circuit Board Layout, Top View Copper Side
V
in
GND
IC1 C
1
Inverter Size = 0.5 in x 0.2 in
Area = 0.10 in
2
, 64.5 mm
2
−V
out
GND
C
3
+
C
2
+
SHDN
+
0.5″
