SLVSFS6A May 2021 – September 2021 TPS629210-Q1
When the MODE/S-CONF pin is configured for AEE mode, the TPS629210-Q1 provides the highest efficiency over the entire input voltage and output voltage range by automatically adjusting the switching frequency of the converter. The efficiency of a switched mode converter is determined by the power losses during the conversion. Traditionally, the efficiency decreases if VOUT decreases, VIN increases, or both. To keep the efficiency high over the entire duty cycle range (VOUT/VIN ratio), the switching frequency is adjusted while maintaining the ripple current. Equation 4 and Equation 5 shows the typical relationships between the on time and switching frequency and the input and output voltages:
Equation 6 can be used to calculate the inductor ripple current in AEE mode:
Efficiency increases by decreasing switching losses and preserving high efficiency for varying duty cycles, while the ripple current amplitude remains low enough to deliver the full output current without reaching current limit. The AEE feature provides an efficiency enhancement for various duty cycles, especially for lower VOUT values, where fixed frequency converters suffer from a significant efficiency drop. Furthermore, this feature compensates for the very small duty cycles of high VIN to low VOUT conversion, which limits the control range in other topologies.
The TPS629210-Q1 operates in AEE mode as long as the output current is higher than half the ripple current of the inductor. To maintian high efficiency at light loads, the device enters Power Save mode at the boundary to discontinous mode (DCM), which happens when the output current becomes smaller than half the inductor ripple current.