Page 11 - PEN eBook July 2023
P. 11
Cover Story — Design
Example calculation:
▶ Battery with 2,800-mAh capacity
▶ Application load current of 10 mA
▶ Output voltage power module of 1.8 V
▶ Three DC/DC converter efficiencies (20%, 45% and 85%)
The efficiency is given by the following equation:
where η is the efficiency, P is the output power, P is the input power, V is the output voltage,
OUT IN OUT
V is the input voltage, I is the input current and I is the output current.
IN IN OUT
P and I are given by the following equations:
IN IN
The battery life is given by the following equation:
where Q is the battery capacity (in milliampere hours) and T is the battery lifetime (in hours).
Example calculation with η = 20%, η = 45% and η = 85% is as follows:
η = 20%: T = 112 hours
The following results are calculated the same way:
η = 45%: T = 264 hours
η = 85%: T = 480 hours
JULY 2023 | www.powerelectronicsnews.com 11
