Analog Circuit Design

13

Parasitic capacitance effects in step-up transformer design

Brian Huffman

One of the most critical components in a step-up design like Figure 13.1 is the transformer. Transformers have parasitic components that can cause them to deviate from their ideal characteristics, and the parasitic capacitance associated with the secondary can cause large resonating current spikes on the leading edge of the switch current waveform. These spikes can cause the regulator to exhibit erratic operating conditions that manifests itself as duty cycle instability. This effect is exacerbated in very high voltage designs. Attention to transformer design will cure this problem.

Figure 13.1 High Voltage Power Supply

Figure 13.2 shows the high frequency current paths ...