Handling Large Capacitive Loads

Capacitance at the input of a DC-DC converter plays a vital role in keeping the converter stable and in providing input EMI filtering. Large amounts of capacitance at the output of the DC-DC converter can provide significant challenges in the power system. Many loads downstream of the DC-DC converter, such as pulsed power amplifiers or other converters, need capacitance at their inputs to ensure proper operation. If the capacitance at the load exceeds the value that the upstream power converter is designed to handle, the converter can exceed its maximum current rating at startup, causing power system stability issues. This can lead to improper system operation and premature power system failure.

Unlike most isolated DC-DC converters, the DCM Converter Module has been designed to handle large capacitive loads, such as stepper motors or radar systems, which are found in a variety of applications. This capability allows the customer to select the DCM based on the average power needs, rather than the peak power of the system, which can help to significantly reduce the cost of the power supply. The peak power pulses are then provided by a storage capacitor, which is continuously charged by the output of the DCM.  DCMs are designed for operation with very large output capacitors, and they can even operate with capacitors significantly above the datasheet limits, as long as the system is equipped with a properly sized precharge circuit to manage startup into the excessive capacitance.

In addition, the DCM can provide additional design benefits, such as:

  • High efficiency and power density
  • High frequency switching
  • Wide input voltage ranges
  • VIA packaging, which offers design simplicity, integrated EMI and transient filtering, chassis or PCB mounting options, and flexible thermal management

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