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Design considerations for High Voltage power supplies in Mass Spectrometry

We tackle 6 of the most common design challenges

 

Overview

In precision analytical applications like mass spectrometry, devices require accurately specified and designed high voltage power supplies.

  • Depending on the application, there are different demands on spectroscopy power supplies – a solution-based approach is needed.
  • Deploying multiple power supplies in the same equipment presents extra challenges.
  • We share how to solve the most common design problems for high voltage power supplies in mass spectrometry.

 

1.  Ripple reduction beyond the power supply 

In mass spectrometry applications, high voltage power supplies are required to deliver high voltage with minimum ripple and noise. In a high voltage DC-DC converter, the ripple frequency is related to the switching frequency of the supply. We specify the frequency of devices in our product datasheets.  

XP Power offers a wide range of miniature high voltage DC-DC converters with low ripple and noise. To further reduce output ripple that’s related to switching frequency, customers can use additional filtering components, such as an RC low pass filter. 

This consists of a resistor and a capacitor connected in parallel mode. The RC low pass filter sets a cut-off frequency, allowing signals with a lower frequency to pass through while reducing higher frequency signals.

      Figure 1: A low pass RC filter

 

2. Designing an RC low pass filter 

First, we determine which frequencies must be filtered out. In the following example, we have selected 120kHz, the switching frequency of high voltage module C80N from XP Power in this circuit setup. 

The cut-off frequency should be sufficiently different from the frequency to be filtered to allow for enough damping of the oscillation.

 

 Figure 2: Calculation for a low pass RC filter   

 

We selected a 150kOhm resistor and a 2nF capacitor. The following oscilloscope diagrams show how the ripple and noise levels are reduced significantly.