Flying Capacitor Value Verses Efficiency - HELIX MxC 200 Series Manual

MxC® 200 PoL EVB Manual

11. Flying Capacitor Value Verses Efficiency

The MxC 200 flying capacitors can be reduced in value for lower output power applications. Lower
cost, smaller package size, etc. are tradeoffs that can affect the efficiency performance.
The Flying Capacitor's value is critical to the maximum load operating performance of the
MuxCapacitor. If the flying capacitance is too small the efficiency of the MuxCapacitor decreases.
Too little capacitance for the required output current effectively behaves as an increase in the
impedance of the MuxCapacitor cell.
The effective operating capacitance of ceramic capacitors are subject to a DC Bias derating. As the
DC voltage across the capacitor increases, the capacitor's capacitance value decreases. This DC Bias
effect must be considered when operating the capacitor too close to its maximum rated voltage or
selecting smaller case sizes.
There are other trade-offs that must be analyzed for reliable, efficient and safe capacitor operation.
Figure 26: Typical Capacitance verses DC Bias, 50V Device
1.30.19
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