Epson Power Supply IC S1F70000 Technical Manual page 40

Negative Voltage Conversion
S1F76620 can boost input voltage to twice on the positive potential side by using the circuit shown in Figure 6. But
the output voltage drops by the forward voltage V
shown in Figure 6 for example, V
Negative Voltage Conversion + Positive Voltage Conversion
When the 3 times step-up operation shown in Figure 1 and the positive voltage conversion in Figure 6 are combined,
the circuit shown in Figure 7 can be formed and 10V and –3.8V can be obtained from the input 5V. However, the
output impedance is higher than in case of connection of either one only (the negative voltage conversion or the
positive voltage conversion).
1
2
3
4
Figure 7 Negative Voltage Conversion + Positive Voltage Conversion
S1F70000 Series
Technical Manual
of the diode. When GND is 0V, V
F
is calculated as follows: V
O
1
P
OFF
2
GND
3
OSC1
4
OSC2
Figure 6 Negative Voltage Conversion
V
O1
8
P V
OFF O
7
GND CAP1+
+
–
6
OSC1 CAP1–
5
OSC2 V
DD
EPSON
= –5V + 2 0.6V = –3.8V.
O
+ –
8
V
O
7
CAP1+
+ –
6
CAP1–
5
V
DD
Potential Relations Diagram
V
DD
+
V
– I
V
SS
V
O2
S1F76620 Series
is 5V and V is 0.6V as
DD F
V '
O
2 V
I
–V +2 V
I F
•
V
O2
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