Micropelt - preliminary - Datasheet TE-CORE v2.5 | Page 5

Thermoharvesting Module

Micropelt TE-CORE

1.5 Energy Balance

Energy harvesting in general, hence also thermohar-

vesting is suitable for low power, typically duty-cycling

applications. The average energy consumed does not

exceed the energy harvested; i.e. a positive or at least

even energy balance is maintained.

1.5.1 Energy Storage

Any surplus energy which is not used by the application

during its sleep phases is buffered in a storage capaci-

tor (C3) which supplies surge currents during the load’s

active cycle. The size of the capacitor must be matched

to the application’s active cycle energy demand: the

stored energy must be sufficient for at least one cycle.

If the default capacitance is found insufficient the TE-

CORE offers an interface for a user-configurable addi-

tional capacitor (see §3.2 Energy storage).

1.5.2 Hysteresis Voltage Control

The storage capacitor’s charge level must always ex-

ceed the powered system’s operating voltage to ensure

stable supply. The actually available stored energy is

defined by the total storage capacitance and the con-

figured difference of the upper and lower thresholds of

Power dropouts caused by excess surge current

DC-DC Booster and power management of the TE-CORE Thermoharvesting Module

the TE-CORE’s hysteresis control (see p. 11) .

If the voltage of the energy buffer drops below the

configured hysteresis minimum level the output of TE-

CORE switches off to protect the continuous operation

of the DC booster required for re-charging the buffer

capacitor. Once the configured maximum capacitor

voltage is reached, the output turns on again. This cycle

is indicated by a LED: Each flash indicates a ‘virtual ac-

tive cycle’ in replacement of a real load.