# Document ```[CIRCUIT IDEAS]
MUDIT AGARWAL
Control AC Power
AC Electric power controller which used the
bidirectional triode thyristor. This circuit can control the
electric power with the one variable resistor. This circuit
is used for the dimmer which changes the light of the
bulb. This circuit changes the quantity of the electric
current which flows through the load with the
bidirectional triode thyristor and controls the electric
power. It is only the alternating voltage that can be
controlled with this circuit and it isn't possible to do the
control of the DC voltage. Because it controls the
passing time of the alternating current by the
bidirectional triode thyristor, the electric current which
flows through the load is not the clean sine wave form.
The thyristor has the three terminals. They are the
T2(The terminal which is equivalent to the anode), the
T1(The terminal which is equivalent to the cathode)
and the gate. In case of the thyristor, the electric current
in the forward direction doesn't flow when the electric
current doesn't flow through the gate. When the trigger
electric current(Pulse) flows through the gate, the
forward direction electric current of the thyristor begins
to flow. The forward direction electric current of the
thyristor to have begun to flow through once always fall
through even if the electric current at the gate passes
away until the forward voltage passes away. The gate
function is again restored when the forward voltage
passes away. So, the forward direction electric current
of the thyristor doesn't flow until the trigger electric
current flows through the gate even if the forward
voltage is applied once again. The bidirectional triode
thyristor is the thyristor which can be used in the
alternating current. It is possible to work the gate
function in each of the alternating current sides of the
TR1(TRI AC)
TB1 2B60
T2
T1
G
VR1
220K
AC
Mains IN
D1
(D1AC)
N413
3
R1
2.2k
2
1
CT
0.1 &micro;F
Vc
R2
15k
MANISH
positive voltage, the sides of the negative voltage.
Because it is, the electric power of the alternating current
can be controlled. The trigger diode has the special
characteristic. In case of usual diode, the forward
direction electric current flows when the forward voltage
is applied but in case of the trigger diode, until the
forward voltage becomes the break over voltage(VBO),
the forward direction electric current doesn't flow. At the
trigger diode, the electric current flows through
bidirectionaly. When the voltage above VBO isn't
applied, the electric current doesn't flow in case of the
positive voltage and the negative voltage. When the
voltage which is applied to the diode crosses VBO, the
diode becomes the ON condition and the voltage of the
both edges of the diode falls rapidly. This characteristic
matches to control the gate of the bidirectional triode
thyristor. Probably, I think that the diode which was
developed to control the bidirectional triode thyristor. To
control the electric power with the bidirectional triode
thyristor, the trigger diode is used for the gate circuit. By
the phase change of the electric current which flows
through the trigger diode, the timing which the
alternating current electric current flows through is
controlled. When the alternating voltage is applied to the
capacitor, the phase of the electric current of the
capacitor progresses by the 90 degrees. Because it is,
the voltage of the both edges of the resistor becomes the
voltage to have advanced towards the alternating
voltage of the input by the 90 degrees. Therefore, the
voltage of the both edges of the capacitor becomes the
voltage to have been 90 degrees behind from the input
alternating voltage. When the resistance value (R) is big,
the delay of Vc is the 90 degrees but the delay becomes
little when the resistance value (R)
becomes small. When the resistance
value (R) is small, the electric charge is
stored up rapidly at the capacitor and
the capacitor voltage rise becomes
fast. Therefore, it becomes short in the
R3
time which reaches the trigger
15k
voltage(VBO) of the trigger diode,
too, and the bidirectional triode
AC
thyristor becomes the ON condition in
OUTLET
the early time with the input alternating
DB
voltage. When the resistance value is
W02G
small, the delay of the capacitor
voltage (Vc) becomes below the 90
degrees. When the bidirectional triode
[CIRCUIT IDEAS]
thyristor becomes the ON condition once, even if the
electric current at the gate passes away, for the half
cycle, the electric current alwayses fall through. When
the bidirectional triode thyristor becomes the ON
condition, the voltage of the C falls and the electric
current which flows through the trigger diode stops.
Because it is, the necessary electric current flows
through the gate of the bidirectional triode thyristor
only in a little time for it to become ON. The speed of
the electric charge which is stored up at the capacitor
becomes slow when the resistance value becomes big.
Therefore, the capacitor both edge voltage rise takes
the time, too, and the bidirectional triode thyristor
becomes the ON condition in the late time with the input
alternating voltage. When the ON timing of the
bidirectional triode thyristor becomes late, it becomes
short in the time which the electric current flows through
and the electric power which is applied to the load
becomes little. When the resistance value becomes
bigger, the voltage of the capacitor both edges becomes
small and Vc gets not to reach the trigger voltage of the
trigger diode. Then, the trigger electric current doesn't
flow through the gate of the bidirectional triode thyristor
and the electric power becomes not supplied to the load.
(It is the same as the switch OFF).
```