Thyristor, it is a very important AC control device

How to control the brightness of a light bulb ？ If it is direct current , Feed triode PWM Wave selection controls its brightness .

But what about alternating current ？ For example, in our family 220 v 50 Alternating current at hertz , It is obviously inappropriate to use a triode at this time , Because the voltage of AC is changing all the time , The triode doesn't work at all , The voltage of AC is too high , General triode can not bear such a large voltage .

Is there any way to control the brightness of this lamp ？ Of course there is , That is the thyristor , It is very important , AC control devices , For example, adjust the lighting brightness of AC power , Adjust the water temperature of the electric kettle , There is also a fan stepless speed regulation , Can be realized by thyristor .

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Next, let's talk about how the thyristor adjusts the brightness of the bulb , Before we talk about it , We need to know how to control the opening and closing of thyristors .

This is an ordinary thyristor , When we give G Pole a suitable voltage , It turns on , But if you remove the voltage at this time , It can't cut off , To cut it off, you just need to remove the power supply voltage , Using this characteristic of thyristor , It can be used in the light regulation of AC power .

This is the AC dimming circuit of the thyristor , We just need to turn the sliding rheostat to adjust the brightness of the bulb , Waveform of power supply , When the alternating current increases to A a.m. , Through the rheostat R2 and R1 Partial pressure of ,R2 At this time, the output voltage just turns on the thyristor , At this point, the bulb is lit , Further back , The light bulb stays on , until E spot , The AC voltage drops to zero , Thyristor cut-off , The light bulb goes out again .

Then wait until the next A Point coming , The bulb is lit again , In the process , The waveform on the small light bulb is like this , But because the frequency of alternating current is very fast , We can hardly see its flicker , If we want a brighter bulb , You can slide the rheostat R2 Adjust upwards , such R2 The output voltage will be larger .

Do not wait for AC power to arrive A spot , stay B Touch the thyristor and it will be turned on , Then the same process as above , Wait for the AC to arrive E Firing the thyristor will cut off again , In reciprocating , At this time, the waveform falling on the small bulb is like this , It can be seen that their waveforms are similar , However, the conduction time after adjustment is significantly longer than before .

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So after adjustment , Small light bulbs have more time to participate in lighting , Its brightness is naturally higher , If we want to make the light bulb brighter , Just adjust the sliding rheostat upward , vice versa .

In this circuit , The small bulb can only be turned on for half the time at most , This is because half of the alternating current is reversed , Wait until the negative half cycle of alternating current , The light bulb went out naturally , So the brightest light bulb can only reach half of its usual brightness , So this kind of thyristor is a semi control device , Finally, let me ask you , Is there any way to make the small bulb controllable throughout the AC cycle ？ Don't forget to leave a message in the comment area ,

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