Duty cycle rectangular waveform

For ITs driven by a sinusoidal waveform, the superimposition of a dc potential (U) on the main trapping field (Frf) requires the use of an additional dc power supply. However, in the DIT, the dc component can be generated easily by varying the duty cycle of the rectangular waveform through appropriate variation of the parameter values entered into the control software of the mass spectrometer. 

Then by simple waveform analysis, the average input current (which is the average switch current for this topology) can be calculated from the rectangular waveform of height 2 A with a duty cycle of 0.25. This gives an average input current of 2 A x 0.25 = 0.5 A. So the input power is 20 V x 0.5 A = 10 W. We can see that that is exactly the same as the output power, and therefore we are at 100% efficiency. 

FIG U RE 12.8 Various a/q lines obtained by modulation of the rectangular waveform duty cycle. The gray segments indicates those parts of the lines that fall within the stability region... 

Among all non-resonant activation techniques, BAD has been shown to have unique advantages for the formation of product ions. Due to the necessity to utilize an additional power supply for generating the DC component, such an approach has not been used in any commercial mass spectrometer. Conversely, in the DIT, variation of the duty cycle of the rectangular waveform is controlled at software level and it allows readily introduction of the DC component for BAD experiments. 

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