This SEPIC converter reference design is designed for 2-MHz switching frequency. Applying a high switching frequency to a hard-switched topology results in increased switching losses at FET and rectifier as well as increased core losses and AC losses at the windings. To minimize those losses, the FET and dual inductor must be carefully selected. By doing so, an efficiency of almost 90% at peak current 2 A by nonsynchronous rectification is achieved. This reference design is designed for pulsed load, switching from 0.2-A to 2-A continuously and a current transient of 90%. For best load regulation, the loop bandwidth has been tuned to achieve a load-step response of approximately 1% deviation output voltage.
Features
- SEPIC topology able to step-up and step-down wide input to output voltage of 12 V
- Withstands cold cranking as low as 4.5 V and load dump up to 36 VPEAK
- Due to continuous input current SEPIC topology, low conducted emissions and high switching frequency of 2 MHz achieved which is beyond AM broadcast band
- High-switching frequency provides small inductance to support dynamic loads resulting in loop bandwidth around 10 kHz results in transient response 1% for 90% load transient
- Prototype supports as-it-is up to 1.5-A continuous load and up to 2-A pulsed load