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Working Principal of Inverter Circuit #inverter #inverters
Transcript
00:00Today, I will introduce the working principle of an inverter to you.
00:03The function of an inverter is to convert DC power into AC power.
00:08Let's first look at how an AC square wave signal is generated.
00:12As shown in the video, the circuit includes four switches, a power supply, and an output load.
00:18This inverter is called a full bridge inverter.
00:21When Q1 and Q4 are closed, it outputs positive voltage to the load.
00:26When Q2 and Q3 are closed, it outputs negative voltage to the load.
00:31In actual control, the four switches use four transistors Q1 and Q4 to work simultaneously,
00:38Q2 and Q3.
00:40Two groups work simultaneously and alternately.
00:42This inverter outputs an AC square wave signal.
00:46In practical applications, it cannot smoothly control the torque output of the motor.
00:51How is the sine wave controlled?
00:53The circuit used to realize the sine wave is called the pulse modulation circuit.
00:57We divide the sine wave type into multiple small segments.
01:01Each small segment is controlled by a different duty cycle,
01:04so that the average voltage of each segment is a different point.
01:07The higher the voltage, the greater the duty cycle.
01:10How is it implemented in the actual circuit?
01:13PWM modulation requires two comparators.
01:16The two input terminals of the comparator, one is a normal sine wave signal,
01:20and the other is a carrier signal.
01:22The carrier signal usually uses a triangle wave.
01:25One comparator uses a normal sine wave and the other comparator uses an inverted sine wave.
01:30The first comparator controls Q1 and Q2.
01:33The Q1 and Q2 signals are reverse.
01:36Q1 is high potential and Q2 is low potential.
01:39This ensures that the two switching tubes work alternately.
01:43The second comparator controls Q3 and Q4.
01:46The control logic is the same.
01:47The working logic of the comparator is simple.
01:50When the sinusoidal signal is higher than the triangle wave,
01:53it outputs signal 1, otherwise it outputs signal 0.
01:56So we can see that the higher the voltage of the sinusoidal signal,
02:00the greater the duty cycle of the output.
02:02The two comparators use different signals as shown in the video.
02:06The voltage on both sides is the difference between the two signals
02:09and the waveform shown is obtained.
02:12In this way, a smooth sine wave signal can be obtained.
02:16The higher the frequency of the triangular wave, the smoother the signal obtained.
02:20Hope you understand this.
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