Noise Filter Circuit; Rush Current Protection Circuit; Smoothing/Rectifying Circuit - Toshiba TLP411E Technical Training Manual

2-2. Noise Filter Circuit

The noise filter circuit only protects the noise generated
by the power source from leaking out to AC line and from
entering of the external noise inside the power. This circuit
is effective for both normal and common noise.

2-3. Rush Current Protection Circuit

When AC power is, via D001, rectified and directly ap-
plied to C011 and C012, rush current runs through C011
and C012 as shown in Fig. 1-3. The current degrades the
contact point of SW001. This rush current is controlled
by the circuit shown in Fig. 1-2, preventing the degrada-
tion of the contact point.
Before the power activation, there exists no induced volt-
age in T001. SCR001 is in the OFF state. Rectified AC
current runs through RF001 and charges C011 and C012.
SCR001
AC
+
RF001
AC
Fig. 1-2
Rush current
I
0
Fig. 1-3
With this, RF001 becomes charging resistance and is sup-
pressed less than 30A. Then, when the charging voltage
of C011 and C012 becomes more than the activation
voltage, the inverter starts oscillation (activation) and the
voltage is generated in the T001. This voltage is used for
trigger voltage for SCR001, turns on the SCR001 and short-
circuits the RF001. As a result, the rectified current flows
into C011 and C012, eliminating the power loss by RF001
in the normal operation state.
T001
~
C012
–
~ C011
T

2-4. Smoothing/Rectifying Circuit

The input voltage of the unit is set to work in the range of
AC100 ~ 120V and AC220 ~ 240V. To keep the AC recti-
fication output voltage in almost the constant level, the
voltage doubler rectification is employed for the AC100
~ 120V input and the bridge rectification for the AC220 ~
240V input. An exclusive IC is used to switch the voltage
doubler rectification and the bridge rectification. Figs. 1-
4, 1-5 and 1-6 show the basic circuits.
When the switch is turned off, each of a positive and nega-
tive half-wave voltage of V
C011, and the bridge rectification voltage is developed
from the output terminal. On the other hand, when the
switch is turned on, a positive half-wave voltage of V
is charged to C012 through the circuit shown by
(AC)
and a negative half-wave voltage of V
C011 through the circuit shown by
doubler of the half-wave rectification voltage is developed
from the output terminal.
V
IN(AC)
Fig. 1-4 Bridge rectification (SW: OFF)
V
IN(AC)
Fig. 1-5 Voltage doubler rectification (SW: ON)
1-3
is charged to C012 and
IN (AC)
is charged to
IN (AC)
. The voltage
C012
SWITCH
(IC001)
C011
C012
SWITCH
(IC001)
C011
IN