In the waveform controlled rectifier circuit, found within the forward voltage of the thyristor to withstand every half cycle, the first time issued a trigger pulse are the same, that is, the control angle α and conduction angle θ are equal, then the unijunctions relaxation oscillator exactly how to cooperate with the AC power supply in order to achieve effective control? In order to achieve the rectifier circuit output voltage "controlled", must bear the forward voltage of the thyristor within each half cycle, triggering Circuit issued the first trigger pulse is the same all the time, this way of working with each other SCR BTA312, called a trigger pulse and power synchronization. How can we synchronize? We look at the regulator circuit diagram (Figure 1). Note that the SCR BTA208, where unijunction transistor relaxation oscillator power is taken from the full-wave pulsed direct current voltage output from the bridge rectifier circuit. When thyristor does not turn, the relaxation oscillator capacitor C is charged power, UC exponentially rises to a peak point voltage UP when the unijunction transistor VT conduction, the conduction period of thyristor VS BTA216, load RL the AC voltage and current, at the same time, VS turned down the voltage across the small, forcing the relaxation oscillator to stop working. Triac thyristor structure principle and application of ordinary (VS) essentially belongs to the DC control devices. To control the AC load, must be two parallel thyristor reverse polarity, so that each SCR control a half-wave, for which required two separate trigger circuit, use is not convenient enough. Triac is evolved on the basis of ordinary thyristor, it can not only replace two anti-parallel thyristors polarity, but only a trigger circuit, is the ideal communication switching devices. Its English name that triac TRIAC AC switch means. SCR BTA204, SCR, are fertile Electronics Dongguan City is provided by Wal-Electronic Technology Co., Ltd. Dongguan City is Wal-Electronic Technology Co., Ltd. (www.dgmydz.com) (www.dgmydz.com) strong, credible, FET and other industries in Dongguan, Guangdong has accumulated a large number of loyal customers. The company better work attitude and constantly improving innovative ideas will lead the electronics are fertile and you hand into the brilliant, for a better future!