April/May 2021

www.power.com/products/MinE-CAP POWER SUPPLY DESIGN 31 www.power-mag.com Issue 2 2021 Power Electronics Europe transformer. The output of the auxiliary winding is rectified using diode D4 and filtered by capacitor C15. An RC snubber can be placed across D4 to suppress voltage spikes, if necessary. Since the output voltage of the charger varies from 5 V to 20 V, the output of the auxiliary winding also varies and depending on the secondary to auxiliary turns ratio as well as the coupling coefficient between the primary and auxiliary. A linear regulator comprising resistors R17 and R18, Zener diode D6, and transistor Q4 provides a relatively stable DC voltage based on the breakdown voltage of D6 at the emitter terminal of Q4. Bias current can then be controlled using resistor R19. Zener diode D5 offers primary sensed over-voltage protection. In case of over- voltage at the output of the converter, the auxiliary winding voltage also increases until D5 breaks down, causing excess current to flow into the BPP pin of the InnoSwitch3 IC. If the current flowing into the BPP pin exceeds the I SD threshold, the controller latches off to prevent any further increase in output voltage. Resistor R20 limits the current injected to the BPP pin during an over-voltage event. MinE-CAP can also be used in applications requiring extended wide-range input (90 VAC to 350+VAC), again with a high percentage of the input capacitance 160 V rated along with either stacked 400 V or 500-600 V rated capacitors of much smaller value than would normally be required. An other application for MinE-CAP are electrical distribution networks with unstable voltages. MinE-CAP reduces the number of high-voltage storage components, and shields lower voltage capacitors from the wild mains voltage swings, substantially enhancing robustness while reducing system maintenance and product returns. Literature “Power GaN Reduces Volume of AC/DC Converters Substantially”, www.power-mag.com MinE-Cap family datasheet Figure 6: With MinE-Cap IC, InnoSwitch3-Pro IC and low-profile planar magnetics, a form factor of 82 mm x 51 mm x 12 mm for the 65 W design was realized