[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 µF 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 Load 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).