Energy harvesting with ASIC power managementEnd the need to replace batteries! Get a maintenance-free long lifetime system! Our ASIC for self-powered IoT sensor applications has integrated energy harvesting power management interfaces.

One of the barriers is the lifetime of the battery in the IoT sensor. One solution to extend the lifetime of the product and to avoid battery maintenance and replacement is to make the devices self-powered. A self-powered system which charges itself from its surroundings, means a service free solution. Depending on the surroundings, the energy can be harvested frommanysources:Light,heat,movement,magneticandelectricalfields.

Realizing a self-powered solution not only requires an energy harvesting generator (e.g. a solar cell, thermal generator, piezo element), it also requires an interface for power management, because no energy harvesting generator has the same output characteristic as a battery. A power management interface converts current and voltage to a level that can drive the IoT application.

Every day, “DELTA - a part of FORCE Technology” works with IoT sensors and energy harvesting in many different industries. OurApplicationSpecificIntegratedCircuit(ASIC)IPsforenergyharvesting offer ASIC power management to minimise power consumption,costandareaalongwiththeflexibilityforaddingextra functionality.

ASIC Power Management The target of the ASIC power management is to interface to a DC voltage output energy harvester like solar cells and thermoelectric generators (TEGs), which harvest energy from light and temperature differences, respectively. It should be noted that kinetic and other AC power sources can be used whencombinedwitharectifierstage.

How do we power IoT sensors, using energy harvesting with ASIC power management?A new wave of information technology is upon us. One in which any product can be smart and connected, via Internet of Things (IoT). When your products are part of IoT, you can deliver new kinds of services, offer costumers more value and compete on more than just price.

Light power sourcesLight is a commonly available power source. The amount of generated power by a solar panel depends on the amount of light reaching the panel, type of light and type of solar cell used. In direct sunlight, the illuminance levels can be 100,000+ lux resulting in 20mW/cm2 generated by a high quality monocrystalline solar cell and 8-10mW/cm2 generated by a cheaper outdoor amorphous silicon solarcell.Indoorlightspectrumisdefinedbythetypeofartificiallightningandhasdrasticeffectontheperformance of solar cells. This effect, combined with low light levels, results in a power output in the range of few μW/cm2 under typical living room light conditions and 10sofμW/cm2onanofficedesk.Asaresult,relativelylarge solar panels are required to power products and need to be placed on well-lit surfaces.

Temperature difference power sourcesThe “Thermoelectric effect” is when a temperature difference is converted into an electrical current. If you maintain a thermal difference across a thermoelectric generator (TEG), it is possible to produce electrical power. Small thermal differences of a few degrees may generate a few mW/cm2 while differences of 100 degrees may generate up to 400mW/cm2. The biggest challenge with thermal energy harvesting is to maintain a temperature difference across the thermoelectric generator. This re-quires large heatsinks which lead heat away but unfortu-nately result in a bulky product. Heat from thermoelectric generators might be a possible candidate for powering wearable devices.

Operation DescriptionTypical IoT products are small devices which require small energy harvesters. Small harvesters gather proportionally lesser amounts of power, thus the power must be generated, stored andusedonlywhensufficientamountofenergyisavailable.

Each step in the power collection, storage and usage must be optimized to provide the most optimal operation of your produ-ct. The ASIC power management is a highly integrated energy harvesting power management solution that is well-suited for meeting the special needs of ultra-low power applications. The product is specially designed to maximize the power collected from a variety of sources like TEGs and solar cells.

The output voltage level of the energy harvester is typically lower than the input voltage level of the typical load connected to the system, hence a boost converter is required. In addition, each harvester needs a customised electronic circuit for optimal function, due to the different output characteristics of energy harvesters.

Effective power collection is achieved by matching the gene-rator impedance to the power management circuit impedance which provides maximum power transfer. When the amount of available power changes, the maximum power point will change, therefore the power management needs to adapt to continue operation at maximum power point. This process is also referred to as” maximum power point tracking”. Once the power is extracted it will be accumulated in a rechargeable battery. The rechargeable battery also allows the system to handle any peak currents that cannot come directly from the input source.

The battery management has different threshold voltages that giveustheflexibilitytopreventdamagetotherechargeablebattery and determine the battery use.

The energy harvesting IC marketsSeveral IC manufacturers have components addressing the energy harvesting power management market and offer several types of power management interfaces for energy harvesting. Their input stage is typically targeted at one or two types of generator. Many solar cell ICs also cover thermoelectric generatorswithlowgradients,sincetheiroutputprofilesaresimilar, and they consequently can be interfaced in the same way. However, there are compromises, and many solutions have broadspecificationstoensurethatthereisawideapplicationrange and high volume.

Similarly, our ASIC power management is targeted at both solar cellsandthermoelectricgenerators.Itsuniquefeaturesare:Lower input voltage operating point in comparison to other IC manufacturersandhigherflexibilitywhenitcomestobatterymanagement due to higher number of thresholds.

One of the most distinct features is the ability to stop harvesting when there is no energy available from the energy harvester. Furthermore, our ASIC prevents rapid successive activations of

the load when the battery is close to being depleted and load activation results in an undervolted disconnect.

How can we help?“DELTA – a part of FORCE Technology” has a deep semicondu-ctor industry expertise, having worked with chip design since 1984. We are partnered with companies from a wide range of industries worldwide. Our ASIC solutions can assist you every step of the way, from design to high-volume delivery.

Typicalprojectphasesare:⋅Idea⋅Specification⋅Design⋅Proof of concept⋅Prototyping⋅Implementation⋅Testing⋅Manufacture

Since 2009, we have designed and implemented customised energy harvesting powered systems. We help you navigate the design space of different harvesters for your product, select appropriate power conditioning modules and energy storage. We work with you in design of algorithms that ensure a stable power supply and operation for your IoT product

Our energy harvesting IP is aimed at collecting energy from light, movement, and thermal difference generators. The power managementmoduleonthechipcontrolsefficientstorageofthe collected power, controls operation of the load, controls the sleep duration of the target application and helps your product achieve an energy neutral operation thus removing the need for battery replacement

Formoreinformationpleasecontactusat:asic@delta.dk or +45 72 19 40 40.

DELTA – a part of FORCE TechnologyVenlighedsvej 42970 HørsholmDenmarkTel. +45 72 19 40 40asic@delta.dk asic.madebydelta.com

Energy Harvesting Power Extractor and Manager

4946.1.18

Features

· Energy Harvesting interface circuit for Photovoltaics, Thermoelectric generators with kinetic energy harvesting

possible with addition of a rectifying stage· Efficientoperationofbothsinglecellandmulticellsolarcells· Energy harvesting from source voltage as low as 30mV· Energy harvesting source output monitoring· Energy harvesting source maximum power point tracking· Low power intelligent power management - Application control through adjustable sleep intervals - Load disconnection - Low power sleep mode” Ready to sleep” line for signaling to the power manager that the load doesn’t require high power - Battery voltage monitoring - Battery Overcharge and over discharge protection· Resistorfixedadjustablevoltagethresholds: - Adjustable minimum and maximum battery operating voltages

- Adjustable energy harvester minimum operating point· Advanced power converters· Low power boost converter· Adjustable low power LDO converter for driving high loads· EfficientPoweronResetcircuitryforlowpoweroperation· Communicationinterface: -SPIinterfaceforconfiguringpowermanagement - Interrupt lines for signalling of alerts to the host processor· Ultra-low operating current (<1uA)· Temperature range -30°C to +100°C· Low power RC oscillator for time keeping with a clock output· Possible crystal oscillator for higher precision time keeping

CONTROL

BOOST

MPPT

INTERFACE

SLAVE

SPI

MANAGEMENT

POWER

BATTERY

SWITCH

REGULATOR

VOLTAGE

PGM

LOW POWER

VOLTAGE

REGULATOR

POWER−ON

RESET

LOW POWER

CRYSTAL

OSCILLATOR

LOW POWER

RC

OSCILLATOR

DIODE

SCHOTTKY

SHUNT

DAC

1.8V

MCU

INTERFACE

THRESHOLD

SETTINGS

COMPARATOR

MPPT

CAPACITOR

VOLTAGE

SELECT

CONFIG

BATTERY

INDUCTOR

1.8V − 3.0V

EXTERNAL SUPPLY

HARVESTER

ENERGY

1.8V

32kHz CRYSTAL

OPTIONAL