Epson Power Supply IC S1F70000 Technical Manual page 103

S1F76640 Series
Negative Voltage Conversion
S1F76640 can boost input voltage to negative power on the negative potential side by using the circuit shown in
Figure 8.6. (In case of 3 times step-up, remove the capacitor C
D . In case of 2 times step-up, remove the capacitor C
4
the output voltage drops by the forward voltage V
shown in Figure 8.6 for example, V
step-up, V is calculated to –10V–3 0.6V = –8.2V, and in case of 2 times step-up, V
O
= –3.8V.)
Figure 8.6 Negative Voltage Conversion (Example of 3 times step-up circuit)
Negative Voltage Conversion + Positive Voltage Conversion
When the 3 times step-up operation shown in Figure 8.1 and the positive voltage conversion in Figure 8.6 are
combined, the circuit shown in Figure 8.7 can be formed and 20V and –12.6V 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 conver-
sion or the positive voltage conversion).
Figure 8.7 Negative Voltage Conversion + Positive Voltage Conversion
2–60
and the diode D
2
of the diode. When GND is 0V, V
F
is calculated as follows: V
O
1 RV V
RI
2 V V
REG O
3 TC1 CAP3+
4 TC2 CAP2+
5 P CAP2–
OFF
6 V CAP1+
SS
7 OSC1 CAP1–
8 OSC2 V
DD
1 RV V
RI
2 V V
REG
3 TC1 CAP3+
4 TC2 CAP2+
5 P CAP2–
OFF
6 V CAP1+
SS
7 OSC1 CAP1–
8 OSC2 V
DD
EPSON
and the diode D and short-circuit the both ends of
3 4
and short-circuit the both ends of D
3
= –15V–4 0.6V = –12.6V(In case of 3 times
O
16
15
14
13
–
+
D
3
–
12
C
2
+
11
D
2
+ –
10
C
1
D
1
9
16
15
O
14
13
+
+ –
–
12
+
11 –
+
+ –
–
10
9
is 5V and VF is 0.6V as
DD
is calculated to –5V–2 0.6V
O
V '
O
C
0
V '
O
V '
O
+
–
S1F70000 Series
Technical Manual
.) But
3