GB2617549A

GB2617549A - Waste heat energy harvester for portable electrical appliances

Info

Publication number: GB2617549A
Application number: GB2204989.4A
Authority: GB
Inventors: Jogia Paresh
Original assignee: Individual
Current assignee: Individual
Priority date: 2022-04-05
Filing date: 2022-04-05
Publication date: 2023-10-18
Anticipated expiration: 2042-04-05
Also published as: GB202204989D0; GB2617549B

Abstract

The energy harvesting system comprises a low power energy harvesting circuit and a high-power energy harvesting circuit. The low power circuit comprises a normally on depletion mode FET or JFET in combination with a step-up transformer to form a resonant oscillator to start the circuit at voltages of 20mV or below and drives or triggers the high power energy harvesting circuit which utilizes normally off enhancement mode MOSFETs in combination with one or more step-up transformers configured as a forward converter, as a flyback converter or one or more inductors configured as a boost converter to boost the voltage whose output drives a load. Waste heat energy is harvested from a portable electronic device e.g., a mobile phone by a thermoelectric generator e.g., a Peltier device. The energy harvesting system may be integrated within the electronic device (fig 6) an accessory for the device (fig 8B)or located within an aftermarket case (fig 8C). It provides a supplementary power source for the electronic device.

Description

Field of the Invention

The present invention concerns improvements in and relating to regenerative power from waste heat in general.

The present invention secondly concerns improvements in Energy Harvesting Systems at below 1 Volt and down to millivolts.

The present invention thirdly concerns improvements of harnessing usable power from low level heat (typically 37 to 50 Degrees Celsius) and opens a new field of applications by way of portable products for powering or charging mobile phones, portable audio systems and portable power tools from the waste heat they already radiate during their operation or when switched off after operation during some time. Presently there are none due to the limitations of prior art energy harvesting systems at these low temperatures.

The present invention fourthly concerns improvements in the way power is made available to the device that it is powering or charging. Unlike conventional systems, the power is available instantaneously unlike conventional portable chargers which contain a battery which firstly needs charging up over time before the power is made available to the device it is powering or charging.

The present invention finally concerns the use of zero carbon components that are easily and cheaply obtainable within its design.

Background to the Invention

All modern portable Electrical Appliances will drain their batteries at some point and either require replacing or re-charging. Attempts to utilize ambient energy by way of energy harvesting systems have not been completely successful. The reasons include the fact that the energy is not available all of the time, such as solar or kinetic. Also, by the limitation of the minimum 'Turn On' voltage of Silicon transistors which are required for the mass production for use within these devices or the many thousands of transistors within the microprocessor integrated circuit which is limited to 0.7 Volts. Germanium transistors are an alternative as they have a Turn On voltage of around 0.3 Volts. However, they are not so readily available and do not lend themselves easily to mass produced integrated circuits (IC) unlike Silicon which is widely used in today's world. The term Threshold Voltage is used to define the 'Turn On' or 'Turn Off voltage of transistors.

There are several types of Silicon transistors, the Bipolar Junction Transistor (BJT) and the FET (Field Effect Transistor) being the popular ones. JFETs and MOSFETs (Metal Oxide Field Effect Transistor) are part of the FET family. FETs are different from bipolar transistors in that they have a very high input (Gate) impedance and hence are voltage controlled devices. That is, they require a certain voltage to operate but negligible current to drive them rather than Bipolar transistors which require a relatively high current to drive them as they are current controlled devices. FETs are therefore ideal for low power or energy harvesting applications due to their high input impedance and negligible input (Gate) drive current.

Most popular electronic systems use Enhancement Mode MOSFETs due these factors for portable battery powered systems to high power switching applications as they can behave like almost an ideal switch and Page 1 of 31 have a low RDS(On) (Drain Source Resistance) of less than 1 Ohm ranging to just a few micro ohms. In particular they are used in integrated circuits which have thousands or millions of these devices for analogue and digital logic circuits such as microprocessors. The latter of which use a combination of N Channel and P Channel Enhancement Mode MOSFETS. The difference between them is that an N Channel device requires a positive voltage to turn them on while P Channel device requires a negative voltage to turn them on. They are referred to CMOS or Complimentary MOS where they are used together to switch from between low and high logic levels in digital logic integrated circuits and microprocessors. However, Enhancement Mode MOSFETs, just like bipolar transistors made from silicon, have a minimum 'Turn On' voltage of 0.7 Volts.

The waste heat generated by a portable electrical appliance is typically in the 37 to 50 Degrees Celsius range. At these temperatures, the output voltages are in the region of less than 20 mV (milli Volts) to 100mV. Utilising a Peltier Module as the Thermo Electric Generator (TEG) is advantageous in that it has a low resistance of 1 Ohm or less for a 50mm square unit or 0.5 Ohms or less for a 20mm square unit which could provide sufficient current even at these voltages.

However, it needs to be boosted to over 1 Volt or more by the Energy Harvesting System to operate an electrical appliance due to the threshold voltages of Silicon Transistors which are contained in most modern electronics.

Recent attempts have been made to harness electrical energy from ambient energy below 0.1 Volts by way of a "Normally ON" Depletion Mode FET (Field Effect Transistor) or JFET (Junction FET) which is part of the Depletion Mode FET family, having a high RDS (Drain Source Resistance) in combination with a step-up transformer to form an oscillator to boost the input voltage, a common 'forward converter' topology and charge a capacitor. The capacitor is then used as a power source for the energy harvested powered system. Due to the low IDSS (Drain Source Current) and the relatively high RDS, (Drain Source Resistance) in the order of several to hundreds of Ohms, therefore the current is limited and hence the power obtained is unusable for the applications in the present invention.

There are two types of Depletion Mode FETs:

i) JFET (Junction Field Effect Transistor);

ii) Depletion Mode MOSFET (Metal Oxide Semiconductor Field Effect Transistor).

Depletion Mode devices are different from the common Enhancement Mode device as they are 'On' by default, acting like a resistor which limits current. In the case of an N Channel JFET, the current is increased by applying a positive voltage across the Gate and Source, or 'Turn Off' the device by applying a negative voltage across the Gate and Source of the device. The reverse is true for a P Channel device while the device is still 'On' by default. P Channel devices have holes as majority carriers compared to N Channel devices which have electrons hence N Channel Devices are twice as efficient. A JFET is the simplest form of Field Effect Transistor and can be used as an electronically-controlled switch or as a voltage-controlled resistance.

When there is zero voltage applied across the Gate (G) and Source (5) of the N Channel JFET, some current flows through the Drain (D) and Source. However, the resistance across the Gate and Source is relatively high and some current flows. This is called the Zero Gate Voltage Drain Current IDSS. As a positive voltage Page 2 of 31 is applied to the Gate, the resistance drops and allows more current to flow called 'RDS(On)'. If we reverse the voltage such that there is a negative voltage between the Gate and Source, then the N Channel JFET will stop current from flowing between the Drain and Source. The point at which this happens is called the Gate Source Cut off Voltage 'VGS(Off)'. All JFETs therefore have some key operating specifications. For example, a typical, cheap easily available N Channel JFET such as a J106 has the following specification: IDSS = 200 mA (0.2 Amps) at a VDS of 15 Volts (Drain Source Voltage); RDS(On) = 6 Ohms; VGS(Off) = -2 to -6 Volts.

It can be seen from the J106 JFET specification that when there is no Gate signal applied, the IDSS is very low, even with a Drain Source Voltage of 15 Volts. A Depletion Mode MOSFET has similar performance characteristics to the JFET.

As already outlined in The Energy Harvesting System presented in my granted patents for "Body Heat Generated Power Source for Portable Electrical Equipment" (GB2531855B) and "Body Heat Powered Wireless Transmitter" (EP2966752B1 and US995415662), one example utilizing a Depletion Mode MOSFET is a prior art system comprising of an energy harvesting integrated circuit (IC) LTC1308 by Linear Technology Corporation of 1630 McCarthy Blvd. Milpitas, CA 950357417 as shown in Figure 9A for a heat based energy harvesting system from a Thermo Electric Generator (TEG) in the form of a Peltier module.

The key technology is the step-up transformer of a ratio of 1:100 in combination with an N Channel Depletion Mode MOSFET within the LTC3108 integrated circuit of Figure 9A which acts like an oscillator, a common 'forward converter' topology. The harvested energy is captured to charge a small capacitor to up to 3.3 Volts which is then used as a power source.

Here a TEG outputs a voltage of less than 0.1 Volts. The charge time of the capacitor terminated at 'VOUT' based on the step-up transformer ratio is shown in Figure 9B. It can be seen that the capacitor requires some time to charge first before it can then be used as a power source.

The LTC3108 integrated circuit of Figure 9A is deemed to be the industries best and coined the phrase 'The Missing Link for Energy Harvesting Applications'. Although an RDS of 0.5 Ohms is impressive for a Depletion Mode FET, the output power is limited. This solution is also impressive as the processing is done using a single IC device. However, the IC is expensive, requires a specific type of step-up transformer and requires that the system developer use their device which in turn provides a limited output power that is not instantaneous as can be seen in Figure 9B.

It is possible to build a discrete energy harvesting system using readily available cheap JFETs such as the J106 N Channel JFET and a step-up transformer to perform the step-up from less than 0.1 Volts to 3.3 Volts. Hence a LTC3108 integrated circuit of Figure 9A would not be required. Any further decision making or power processing circuits to power a microprocessor can then be done using other ICs available on the market. However, the energy harvesting circuit power output would again be limited due to the relatively high RDS(On).

Another example as already outlined in The Energy Harvesting System presented in my granted patents for "Body Heat Generated Power Source for Portable Electrical Equipment" (GB2531855B) and "Body Heat Powered Wireless Transmitter" (EP2966752B1 and US995415682) is the ECT310 by Enocean GmbH of Page 3 of 31 Kolpingring 18a, D-82041 Oberhaching, Germany. This is a module containing discrete components and the same 1:100 ratio step-up transformer, the LPR6235-752SMLB by Coilcraft Inc. of 1102 Silver Lake Road, Cary IL 60013, USA which is used for the LTC3108 example described in Figure 9A. It is used as a thermal energy powered energy harvester which works with a peltier module. The ECT310 can operate from 20 mV relating to a 2 Kelvin temperature difference provided by the Peltier module. The 20 mV operating voltage is also the same as the example described in the LTC3108 based system of Figure 9A. The ECT310 module is designed for use with wireless sensor networks. The Enocean radio module would wake up every 2 minutes to transmit a telegram which requires approximately 5 micro watts, (0.000005 watts) once the ECT310 module has charged a small capacitor between 3 to 5 Volts. Hence the power is limited of only 5 microwatts every two minutes.

A further design of thermoelectric energy harvesting device is disclosed in Shuttleworth R et at "Discrete, matched-load, step-up converter for 60-400 mV thermoelectric energy harvesting source" ELECTRONICS LETTERS, lEE STEVENAGE, GB, vol. 49, no. 11, 23 May 2013 (2013-05-23), pages 719-720, XP006044041. This was already highlighted in the search and examination for my granted European patent, "Body Heat Powered Wireless Transmitter (EP2966752B1). It has what could be described as low and high power energy harvesting circuits but these are not independent of each other as they are wound on a single core and cannot operate in a resonance-tuned manner unlike the present invention. This device scavenges heat from boilers and hot water systems and therefore unsuitable for low level heat (below 50 degrees Celsius) unlike the present invention. It needs at least 60mV to operate compared to less than 20mV, is inefficient, takes several seconds to start and bulky. A case for its limitations and differences to the energy harvesting system for my granted European patent, "Body Heat Powered Wireless Transmitter" (EP2966752B1) was presented and accepted.

The US patent US6340787 (SIMERAY) filed in 1997 and since lapsed, has claims concerning detail of thermoelectric generator design and particularly circuits that rely on having a chopper converter to boost voltage from the TEG. This was already highlighted in the search and examination for my granted United Kingdom patent, "Body Heat Generated Power Source for Portable Electrical Equipment" (GB2531855B). It mentions "The use of chopper-step-up circuits allows to extract approximately 50% of the available power in the source". There is no clear distinction between the concept of a "low power" and "high power' energy harvesting circuits, cannot operate in a resonance-tuned manner or extract at least 90% of the available power in the source unlike the present invention. It is also clear that it cannot operate at an input voltage of 20mV or less from the thermoelectric generator because the inductors would require a very large current to utilise Back-EMF to provide output voltages of several volts unlike the present invention. Even when using TEGs integrated in a large area such as a ski-boot and corresponding electronics. A case for its limitations and differences to the energy harvesting system for my United Kingdom patent, "Body Heat Generated Power Source for Portable Electrical Equipment" (GB2531855B) was presented and accepted.

The energy harvesting system of the present invention which utilizes that presented in my granted patents for "Body Heat Generated Power Source for Portable Electrical Equipment" (GB2531855B) and "Body Heat Powered Wireless Transmitter" (EP2966752B1 and US9954156B2) which enable the wireless transmitter or portable electrical appliance to be powered by human body heat (37 Degrees Celsius) by contrast not only is proven to work at 20mV or less producing usable output power at 1 Volt or above but also enables Page 4 of 31 integration within a form factor as small as a watch or key-fob form factor-sized device including the TEG.

Furthermore, all presently available chargers based on harvesting ambient energy such as solar etc all have an internal battery which first needs to be charged by the energy harvested by the source so that the internal battery reaches the operating voltage of the portable electrical device it is charging, for example 3.6 Volts. This can take several hours. The present invention, however, does not have an internal battery but a supercapacitor to act as a buffer or electrical storage device to directly charge or power the portable electrical device. As well as being Zero Carbon and lasting the lifetime of the device, due to its low ESR (Internal Series Resistance), high power density and fast charge time, can provide instantaneous power in seconds in real time which the energy is being harvested unlike the battery, however, has good energy density like a battery so can be used as an electrical storage device so providing a best of both worlds.

Summary of the Invention

According to a first aspect of the present invention there is provided Waste Heat Energy Harvester for Portable Electrical Appliances containing a Thermo Electric Generator (TEG), and an Energy Harvesting System characterised in that it comprises a device to harness waste heat, for example from the casing of a mobile phone, the heatsink or the battery casing and convert it to electrical energy to charge or provide a power source for it.

The Energy Harvesting System utilizes that presented in my inventions whose patents have been granted for "Body Heat Generated Power Source for Portable Electrical Equipment" (GB2531855B) and "Body Heat Powered Wireless Transmitter" (EP2966752B1 and US9954156B2) which enable the wireless transmitter or portable electrical appliance to be powered by human body heat (37 Degrees Celsius) and can operate from 20 mV (0.02 Volts) or less without sacrificing the current and hence the power output.

The highly efficient energy harvesting system is utilized in the Waste Heat Energy Harvester for Portable Electrical Appliances from the waste heat for portable electronic systems rather than body heat. The waste heat can be typically higher than body heat (37 Degrees Celsius). Therefore, the said energy harvesting system can cater for a wider range of applications than from body heat as waste heat from portable electrical appliance can be higher. The waste heat generated by a portable electrical appliance is typically in the 37 to 50 Degrees Celsius range.

The present invention therefore allows for a higher temperature gradient and therefore provide a higher power output. This waste heat includes but not limited to an electrical component, the heatsink or the battery casing of the portable electrical appliance. Also, due to the size of portable electronics such as mobile phones and laptops, a larger surface area is available to harness the heat even if it may be less than 37 Degrees Celsius. This is due to the "Seebeck" effect as a large temperature difference from the TEG can be obtained by having a metal plate or heatsink on the other side of the portable electronic device from which it is scavenging the heat. Also, multiple energy harvesting circuits multiple and/or TEGs can be used in conjunction.

The Energy Harvesting System comprises a low power energy harvesting circuit and a high power energy harvesting circuit. The low power energy harvesting circuit utilises the 'normally ON' Depletion Mode FET or JFET in combination with a step-up transformer to form an oscillator operating in resonant mode to start the Page 5 of 31 circuit at voltages at 20mV or below and drives or triggers the high power energy harvesting circuit which utilizes 'Normally off' Enhancement Mode MOSFETs (Metal Oxide Field Effect Transistor) with low RDS ON of 0.1 Ohms or less and preferably 0.005 Ohms in combination with one or more step-up transformers configured as a forward converter, or configured as a flyback converter or one or more inductors configured as a boost converter to boost the voltage whose output drives the load without sacrificing the current and hence the power output.

Advantageously, the step-up transformers of the low power energy harvesting circuit are wound on a separate core which is independent from the wound components that may form a step-up transformer, fly-back transformer or an inductor in the high power energy harvesting circuit which enables design optimisation of the wound components for both the low and high power energy harvesting circuits for the required application.

Advantageously, the output of the high power energy harvesting circuit delivers at least 90% of the input power to the output load.

Advantageously, the device does not require any batteries or charging up over time and can enable instantaneous power by way of the energy harnessed by the waste heat of the portable electrical appliance. The device can self-start automatically when a heat source is present allowing electrical energy to charge or power the appliance. The device can also harness energy from power sources less than 20mV.

Advantageously, the device is safe to operate as it harnesses usable power from low level heat (typically 37 or less to 50 Degrees Celsius) so does not cause pain or injury from the heat.

The system preferably has one or more Thermo Electric Generators (TEG) to harness the waste heat and convert it electrical power.

The system preferably comprises a Peltier Module as a Thermo Electric Generator (TEG) which utilises the 'Seebeck' effect which is the conversion of temperature differences into voltage which advantageously allows a higher output voltage if one of the sides is significantly cooler by way of a heatsink or a metal enclosure.

The system advantageously utilises a Peltier Module as the Thermo Electric Generator (TEG) by having a low resistance of 1 Ohm or less for a 50mm square unit or 0.5 Ohms or less for a 20mm square unit which could provide sufficient current even at voltages between of 20mV or less to over 100mV from a heat source of 37 to 50 Degrees Celsius. Also, due to the size of portable electronics such as mobile phones and laptops, a larger surface area is available to harness the heat even if it may be less than 37 Degrees Celsius. This is due to the "Seebeck" effect as a large temperature difference from the TEG can be obtained by having a metal plate or heatsink on the other side of the portable electronic device from which it is scavenging the heat. Also, multiple energy harvesting circuits multiple and/or TEGs can be used in conjunction.

The system advantageously comprises an energy harvesting system containing one or more low power energy harvesting circuits and one or more high power energy harvesting circuits.

The low power energy harvesting circuit is configured to operate at a power level that is at least ten times lower than that of the high power energy harvesting circuit and particularly preferably of the order of 100 times lower than that of the high power energy harvesting circuit. Each of the low power energy harvesting circuit and the Page 6 of 31 high power energy harvesting circuit comprise at least one Field Effect Transistor (FET) respectively and the power level of each energy harvesting circuit may be assessed by the RDS (Source Drain Resistance) for the Field Effect Transistor (FED in the respective energy harvesting circuit. As an example, the RDS for the FET of the low power energy harvesting circuit may be of the order of 1 Ohm. That of the high power energy harvesting circuit is of the order of 0.1 Ohms and below and preferably of the order of 0.005 Ohms or less. The electrical energy from the TEG is processed first via the low power energy harvesting circuit and then via the high power energy harvesting circuit.

Particularly preferably the low power energy harvesting circuit comprises one or more Depletion Mode Field Effect Transistors, one or more Enhancement Mode Metal Oxide Semiconductor Field Effect Transistors and one or more step-up transformers. The low power energy harvesting circuit suitably has one or more Depletion Mode Field Effect Transistors or one or more Junction Field Effect Transistors and one or more step-up transformers to form an oscillator operating in resonant mode.

The high power energy harvesting circuit comprises one or more Enhancement Mode Metal Oxide Semiconductor Field Effect and one or more of: a step-up transformer; a flyback transformer; and an inductor. The oscillator of the low power energy harvesting circuit suitably drives the Enhancement Mode Metal Oxide Semiconductor Field Effect Transistor of the high power energy harvesting circuit. In turn the Enhancement Mode Metal Oxide Semiconductor Field Effect Transistor can switch a said step-up transformer to serve as a forward converter and/or said flyback transformer to serve as a flyback converter and/ or said inductor to serve as a boost converter.

The system preferably has a high power energy harvesting system comprising a step-up transformer and an Enhancement Mode MOSFET configured as a 'Forward Converter' which is triggered by a low power energy harvesting system. Once triggered, the high power energy harvesting system then can function off its own accord without the need for the switch or the low power energy harvesting system. The Low Power Energy Harvesting circuit preferably also comprises one or more Enhancement Mode Metal Oxide Field Effect Transistors. A single one may be used to trigger the Enhancement Mode Metal Oxide Field Effect Transistor within the High Power Energy Harvesting circuit which switches a step-up transformer for a forward converter.

Alternatively, the system has a high power energy harvesting system comprising a step-up transformer and an Enhancement Mode MOSFET configured as a 'Forward Converter' or a 'Flyback Converter' with the gate of the Enhancement Mode MOSFET driven by the low power energy harvesting system.

Alternatively, the system has a high power energy harvesting system comprising an inductor and an Enhancement Mode MOSFET configured in as a 'Boost Converter' with the gate of the Enhancement Mode MOSFET driven by the low power energy harvesting system.

Alternatively, one or more further Enhancement Mode Metal Oxide Field Effect Transistor(s) within the Low Power Energy Harvesting circuit is/are used to create a square wave oscillator. This may have adjustable pulse width and duty cycle above 50% with output voltages above 1 Volt peak to peak. In this arrangement Page 7 of 31 the Low Power Energy Harvesting circuit, which may comprise a Depletion Mode Field Effect Transistor and step-up transformer forming an oscillator operating in resonant mode, is suitably used as a forward converter. This may charge a small capacitor to voltages above 1 Volt DC (Direct Current) to provide a power source for the square wave oscillator. The square wave oscillator within the Low Power Energy Harvesting circuit may then be used to drive an Enhancement Mode Metal Oxide Field Effect Transistor within the High Power Energy Harvesting circuit which switches a flyback transformer for a flyback converter or for an inductor for a boost converter.

Preferably the low power energy harvesting circuit comprises a step-up transformer whose core is of a high relative permeability between 5000 and 20,000.

Preferably the high power energy harvesting circuit comprises a step-up transformer whose core is of a high relative permeability between 5000 and 20,000.

Preferably the high power energy harvesting circuit comprises a flyback transformer whose core is of a high relative permeability of at least 20,000.

Preferably the high power energy harvesting circuit comprises an inductor whose core is of a high relative permeability of at least 80,000.

Preferably the high relative permeability core used is Nanoperm(RTM) nanocrystalline magnetic alloy or Metglas(RTM) amorphous magnetic alloy.

The system advantageously allows miniaturization of the inductors or transformers by way of the high relative permeability of at least 5000 core material whereby significant inductance can be achieved by the transformer or inductor with low winding resistance thus high current while achieving a small feature size.

The system advantageously allows miniaturization by way of integrating the core material of the inductors or transformers within a PCB (Printed Circuit Board) due to the use of a high relative permeability core material of at least 5000 whereby the tracks form the windings or tracks and vias form the windings within a multi-layer PCB. Whereby significant inductance can be achieved by the transformer or inductor with low winding resistance thus high current while achieving a small feature size.

The system further advantageously lends itself to miniaturization by way of an IC (Integrated Circuit) whereby any multiple or all of the constituent components can be integrated within the IC. Advantageously, significant inductance can be achieved by the transformer or inductor with low winding resistance thus high current due to the use of a high relative permeability of at least 5000 while achieving a small feature size. Advantageously, significant capacitance can be achieved by the capacitor while maintaining low ESR (Effective Series Resistance) thus high current due to the use of high permittivity dielectric materials while achieving a small feature size.

The system preferably has a supercapacitor of an ESR (Effective Series Resistance) of 0.1 Ohms or less terminated in parallel with the Thermo Electric Generator to provide a high electrical current to the high power energy harvesting system or function as a storage element when heat is not available to the Thermo Electric Generator.

Page 8 of 31 The system preferably has a power processing system comprising a supercapacitor as a storage element or buffer and Voltage and Current Sensing Circuits to determine the voltage level of the battery or other electrical storage system of the Portable Electrical Appliance to determine whether to charge it or directly power it. If the battery is fully charged or an external power source connected via its charging port for example, it may then charge the supercapacitor to be used as a direct power source for the system later.

If excessive current draw is sensed, the supercapacitor may be used as a buffer for high load current situations in addition to the battery due to its low ESR and high power density delivering high current instantaneous power and fast charge time. For example, an electric screwdriver, where the peak current draw may be at start up for when fastening a screw or removing a stubborn one. Alternatively, short pulsed power for a nail gun for example. Here is an ideal example of when the appliance may run directly from the supercapacitor as well due to the short time duration of operation.

The Power Processing System advantageously utilizes low power CMOS (Complementary MOSFET) circuits or nano power (power level in the order of a thousand million times less than a watt) circuits comprising Zero Threshold MOSFETs (Metal Oxide Field Effect Transistor) and operates at a power level that is less than the low power energy harvesting system. This advantageously ensures that 90% of the output power from the high power energy harvesting system is transferred to the output load.

A summary of the features includes but not limited to: * Zero Carbon -No batteries required * Zero maintenance -No moving parts for the energy harvesting system * High power output o The Thermo Electric Generators (TEG) used in the system utilises Peltier Modules of very low resistance of 1 Ohm or less. Therefore a 1 Ohm TEG generating 0.1 Volt would equate to 0.1 Amps which is sufficient to allow the highly efficient energy harvesting system to build up the required voltage and current to directly power or charge the battery within the portable electronic device.

* Instantaneous power in < 1 second * Highly efficient -Hamessing of voltages of less than 20mV (0.02 Volts) and 37 Degrees Celsius * Key technology devised of standard readily available mass-produced cheap components: o Peltier Modules usually used for heating and cooling applications o Enhancement Mode MOSFETs o Standard Depletion Mode MOSFETs and Standard low power JFETs * Small Form Factor -Complete electronics system can be housed within existing battery powered enclosures, such as mobile phone, portable audio system, or portable power tool.

* Manufacturability o Can be manufactured using either through whole or surface mount technology (SMT) o Proposal for an energy harvesting Integrated Circuit (IC) which can be mass produced on standard Silicon Process foundries * Lifetime -Lasts the lifetime of the electronic components contained within the system Page 9 of 31

Brief description of the drawings

The present invention will now be described in greater detail, in the following detailed description, with reference to the drawings, in which: Figure 1 illustrates Waste Heat Energy Harvester for Portable Electrical Appliances; Figure 2 illustrates an expanded view of a Mobile Phone; Figure 3 illustrates the back of a Mobile Phone with the Back Casing removed; Figure 4 illustrates an expanded view of Waste Heat Energy Harvester for integration in Mobile Phone; Figure 5 illustrates completed integration of Waste Heat Energy Harvester inside Mobile Phone; Figure 6 illustrates Waste Heat Energy Harvester on the Outside Back Cover of Mobile Phone; Figure 7 illustrates Waste Heat Energy Harvester integrated in Mobile Phone Case with power port to enable the Mobile Phone to be docked for charging or directly power it; Figure 8A illustrates completed integration inside Portable Electrical Appliance showing Power Processing System with Supercapacitor as a Power Source or Buffer; Figure 8B illustrates Waste Heat Energy Harvester mounted on Outside Back Cover showing Power Processing System with Supercapacitor as a Power Source or Buffer; Figure 8C illustrates integration inside Mobile Phone Case showing Power Processing System with Supercapacitor as a Power Source or Buffer; Figure 9A illustrates a Prior Art Energy Harvesting System based on a step-up transformer and an LTC3108 IC which contains a Depletion Mode FET; Figure 9B illustrates the capacitor charge rate of the Prior Art energy harvesting system illustrated in Figure 9A; Figure 10A is a simple charger circuit represented by the primary of a transformer or inductor in series with a FET; Figure 10B is a resistor model of the charger circuit of Figure 10A showing the effects of RDS(On) of a FET; Figure 11 shows an energy harvesting system using whereby the input voltage is less than the transistors threshold voltage and the circuit is started by a switch; Figure 12 shows an energy harvesting system comprising of a low power and high power circuit, each comprising a step-up transformer, where the high power circuit is automatically started by the low power circuit; Figure 13 shows an energy harvesting system comprising of a low power circuit comprising of a step-up transformer and a high power circuit comprising of a step-up transformer where the gate of the transistor in the high power circuit is driven by the low power circuit; Figure 14A shows an energy harvesting system comprising of a low power circuit comprising of a step-up transformer and a high power circuit comprising of a flyback transformer where the gate of the transistor in the high power circuit is driven by the low power circuit; Figure 14B shows the oscilloscope waveforms of the Energy Harvesting Circuit of Figure 14A. Comparing the behaviour across the primary windings of the flyback transformer 'T3' with the 'Gate' drive of the N Channel Enhancement Mode MOSFET Q2'; Figure 14C shows the oscilloscope waveforms of the Energy Harvesting Circuit of Figure 14A. Comparing the behaviour across the secondary windings of the flyback transformer 'T3' with the 'Gate' drive of the N Channel Enhancement Mode MOSFET '02'; Figure 15A shows an energy harvesting system comprising of a low power circuit comprising of a step-up transformer and a high power circuit comprising of an inductor where the gate of the transistor of high power Page 10 of 31 circuit is driven by the low power circuit; Figure 15B shows the oscilloscope waveforms of the Energy Harvesting Circuit of Figure 15A. Comparing the behaviour across the inductor 'LI with the 'Gate' drive of the N Channel Enhancement Mode MOSFET Q2'; Figure 16A shows a Square Wave Generator using CMOS logic gates with adjustable Pulse Width and Duty Cycle > 50%; Figure 16B shows a CMOS Inverter consisting of a P and an N Channel Enhancement Mode MOSFET which have a high input impedance and low gate capacitance and are easy to drive; Figure 17 shows a Square Wave triggered Flyback Converter Energy Harvesting System based on a modified version of Figure 14A. Here, the Low Power Energy Harvesting Circuit powers CMOS logic gates with adjustable Pulse Width and Duty Cycle > 50% to provide the gate pulses to the High Power Energy Harvesting Circuit; Figure 18 shows a square wave triggered Boost Converter Energy Harvesting System based on a modified version of Figure 15A. Here, the Low Power Energy Harvesting Circuit powers CMOS logic gates with adjustable Pulse Width and Duty Cycle > 50% to provide the gate pulses to the High Power Energy Harvesting Circuit; Figure 19A shows a modified version of the Prior Art LTC3108 energy harvesting integrated circuit illustrated in Figure 9A showing integration of low power and high power energy harvesting circuits. Here, only three additional pins, IN1, IN 2, and IN3 are required on the device; Figure 19B shows a Self-Triggered Forward Converter Energy Harvesting System based on the proposed integrated circuit of Figure 19A; Figure 19C shows a Gate-Triggered Forward Converter Energy Harvesting System based on the proposed integrated circuit of Figure 19A; Figure 19D shows a Flyback Converter Energy Harvesting System based on the proposed integrated circuit of Figure 19A; Figure 19E shows a Boost Converter Energy Harvesting System based on the proposed integrated circuit of Figure 19A; Figure 20A shows a Square Wave triggered Flyback Converter Energy Harvesting System based on a modified version of the proposed Integrated Circuit of Figure 19A adapted to the discrete component design of Figure 17, Here, the Low Power Energy Harvesting Circuit powers CMOS logic gates with adjustable Pulse Width and Duty Cycle > 50% to provide the gate pulses to the High Power Energy Harvesting Circuit; Figure 20B shows a Square Wave triggered Boost Converter Energy Harvesting System based on a modified version of the proposed Integrated Circuit of Figure 19A adapted to the discrete component design of Figure 18, Here, the Low Power Energy Harvesting Circuit powers CMOS logic gates with adjustable Pulse Width and Duty Cycle > 50% to provide the gate pulses to the High Power Energy Harvesting Circuit; Figure 21 shows a transformer integrated within a multi-layer PCB whereby the tracks and vias form the windings within a multi-layer PCB and the transformer core is embedded within the PCB.

Figure 22 shows the comparison graph of Energy Density vs Power Density for the Supercapacitor vs the battery and other electrical storage medium and relative charge and discharge times.

Page 11 of 31

Detailed description of the preferred embodiments

Summary of Problems

The waste heat generated by a portable electrical appliance such as a mobile phone is typically in the 37 to 50 Degrees Celsius range. For example, a mobile phone has a normal temperature range of 37 to 43 Degrees Celsius or higher.

At these temperatures, the output voltages are in the region of less than 20 mV (milli Volts) to 100mV so it needs to be boosted to over 1 Volt or more by the Energy Harvesting System to operate an electrical appliance due to the threshold voltages of Silicon Transistors which are contained in most modern electronics. Due to the power limitations of present energy harvesting systems, although the voltage can be increased as required, utilising a "Normally ON" Depletion Mode FET (Field Effect Transistor) having a high RDS ON (Drain Source Resistance) in the order of several to hundreds of Ohms, therefore the current is limited and hence the power obtained is unusable for such applications.

The solution has already been outlined in that presented in my granted patents for "Body Heat Generated Power Source for Portable Electrical Equipment" (Patent GB2531855B) and "Body Heat Powered Wireless Transmitter" (EP2966752B1 and US9954156B2) which contain a highly efficient energy harvesting system comprising a low power energy harvesting system and a high power energy harvesting system which enable the wireless transmitter or portable electrical appliance to be powered by human body heat (37 Degrees Celsius) and can operate from 20 mV or less without sacrificing the current and hence the power output.

Here, the low power energy harvesting circuit utilises the 'normally ON' Depletion Mode FET or JFET in combination with a step-up transformer to start the circuit at voltages at 20mV or below and drives or triggers the high power energy harvesting circuit which utilizes 'Normally off Enhancement Mode MOSFETs (Metal Oxide Field Effect Transistor) with low RDS ON of 0.1 Ohms or less in combination with one or more step-up transformers or inductors to boost the voltage whose output drives the load while providing sufficient current.

Therefore, can cater for wider range of applications than from body heat. As the waste heat from portable electrical appliances can be higher, this is an ideal application for it. Also, due to the size of portable electronics such as mobile phones and laptops, a larger surface area is available to harness the heat even if it may be less than 37 Degrees Celsius. This is due to the "Seebeck" effect as a large temperature difference can be obtained by having a metal plate or heatsink on the other side of the portable electronic device from which it is scavenging the heat. Also, multiple energy harvesting circuits multiple and/or TEGs can be used in conjunction.

System Overview Figure 1 shows a simplified system overview of the Waste Heat Energy Harvester for Portable Electrical Appliances of the present invention. The electrical appliance for example a mobile phone releases Waste Heat which is captured by the Thermo Electric Generator and converted to electrical energy. The preferred unit for the heat capture is a Peltier Module which utilises the 'Seebeck' effect which is the conversion of temperature differences into voltage. Higher voltages are obtained if the other side is a metal enclosure or Page 12 of 31 heatsink which cools the other side of the Pettier Module. This is then processed via the energy harvesting system to power or charge the portable electrical appliance. This is therefore deemed "Regenerative Power".

The Energy Harvesting System of the present invention utilizes that presented in my granted patents for "Body Heat Generated Power Source for Portable Electrical Equipment" (Patent GB2531855B) and "Body Heat Powered Wireless Transmitter' (EP2966752B1 and US9954156B2) which enable the wireless transmitter or portable electrical appliance to be powered by human body heat (37 Degrees Celsius) and can operate from 20 mV or less without sacrificing the current and hence the power output.

The highly efficient energy harvesting system is utilized in the Waste Heat Energy Harvester for Portable Electrical Appliances from the waste heat for portable electronic systems rather than body heat. The waste heat can be typically higher than body heat (37 Degrees Celsius). Therefore, the said energy harvesting system can cater for a wider range of applications than from body heat as waste heat from portable electrical appliance can be higher. The waste heat generated by a portable electrical appliance is typically in the 37 to 50 Degrees Celsius range. For example, a mobile phone has a normal temperature range of 37 to 43 Degrees Celsius or higher.

The Energy Harvesting System comprises a low power energy harvesting circuit and a high power energy harvesting circuit. The low power energy harvesting circuit utilises the 'normally ON' Depletion Mode FET or JFET in combination with a step-up transformer to form an oscillator operating in resonant mode to start the circuit at voltages at 20mV or below and drives or triggers the high power energy harvesting circuit which utilizes 'Normally off' Enhancement Mode MOSFETs (Metal Oxide Field Effect Transistor) with low RDS ON of 0.1 Ohms or less and preferably 0.005 Ohms in combination with one or more step-up transformers configured as a forward converter, or configured as a flyback converter or one or more inductors configured as a boost converter to boost the voltage whose output drives the load without sacrificing the current and hence the power output. Advantageously, the output of the high power energy harvesting circuit delivers at least 90% of the input power to the output load.

Example Applications

Figure 2 shows an expanded simplified overview of a Mobile Phone. Front Casing (6), Display Panel (7), Main PCB (8), Heatsink (9), Battery (10) and Back Casing (11). The key components which are likely to get hot are the Display Panel (7), Heatsink (9), and Battery (10). Heat may be harnessed from any of these components but not solely limited to them.

Page 13 of 31 Figure 3 shows a simplified overview of the Mobile Phone of Figure 2 in assembled form with the with the Back Casing removed showing key heat sources such as a CPU (Central Processing Unit) Heatsink (13) and Battery (14). These components are likely to radiate their heat to the Rear Casing (15) and captures the heat radiated from these components and therefore represents one of the embodiments of the present invention to harness the heat from such a device as a mobile phone.

Figure 4 shows an expanded view of a Waste Heat Energy Harvester for integration in a Mobile Phone. The present invention utilises the heat radiated by the Heatsink (17) and the Battery (18) with independent Thermo Electric Generators (20) and (21) located between the back of the Mobile Phone (16) and the Back Casing (22) feeding electrical energy to the Energy Harvesting System (19).

Figure 5 shows completed integration of Waste Heat Energy Harvester inside a Mobile Phone showing the Back of the Mobile Phone (23). The Energy Harvesting System (24) is integrated within the main PCB (24) of the expanded view of the Mobile Phone of Figure 2 and the Thermo Electric Generators (25) and (26) mounted on the CPU (Central Processing Unit) Heatsink and Battery respectively.

The other side of the Thermo Electric Generators can be made to be in contact with the Back Casing (27) if they are Peltier Modules to enable a Seebeck effect which is the conversion of temperature differences into voltage. A further temperature difference and hence high voltages are then possible if the Back Casing is made of metal such as alluminium and can act as a heatsink.

Figure 6 shows a Waste Heat Energy Harvester on the Outside Back Cover of Mobile Phone. Here the heat radiated by the internal components such as CPU Heatsink or Battery are captured on the outside back casing of the mobile phone (28). A Thermo Electric Generator (29) is mounted on it together with the Energy Harvesting System (30). The electrical power output is then terminated to the Charging Port of the Mobile Phone via a Cable (32). For convenience, the energy harvesting system output may have a standard socket such as USB to allow connection of charging cables that have come standard with the portable electrical appliance such as a mobile phone.

Figure 7 shows a Waste Heat Energy Harvester integrated in Mobile Phone Case with a power port to enable a Mobile Phone to be docked for charging or directly power it. Here the Mobile Phone Case (33) has a built in Power Connector (37) to allow the Mobile Phone (33) to be docked into it to charge or directly power it. It also has an External Charging Port (39) to allow the phone to be charged by a phone charger. The Thermo Electric Generator (36) is mounted on the front side of the Mobile Phone Case (35) so that the back of the Mobile Phone (33) touches it. The Energy harvesting system (38) is mounted inside the Mobile Phone Case (35).

Power Processing System comprising a Supercapacitor as Power Source or Buffer and Voltage and Current Sensing Circuits The output of the energy harvesting system may further be processed via a Power Processing System comprising a supercapacitor used as a storage element or buffer and a decision making circuit.

All presently available chargers based on harvesting ambient energy such as solar etc all have an internal battery which first needs to be charged by the energy harvested by the source so that the internal battery reaches the operating voltage of the portable electrical device it is charging, for example 3.6 Volts. This can take several hours. The present invention, however, does not have an internal battery but a supercapacitor Page 14 of 31 to act as a buffer or electrical storage device to directly charge or power the portable electrical device. As well as being Zero Carbon and lasting the lifetime of the device, due to its low ESR (Internal Series Resistance), high power density and fast charge time, can provide instantaneous power in seconds in real time from the energy is being harvested unlike the battery, however, has good energy density like a battery so can be used as electrical storage device so providing a best of both worlds.

The system preferably has a Power Processing System comprising a supercapacitor as a storage element or buffer and Voltage and Current Sensing Circuits to determine the voltage level of the battery or other electrical storage system of the Portable Electrical Appliance to determine whether to charge it or directly power it. If the battery is fully charged or an external power source connected via its charging port for example, it may then charge the supercapacitor to be used a direct power source for the system later. If excessive current is sensed, the supercapacitor may be used as a buffer for high load current situations in addition to the battery due to its low ESR (Electrical Series Resistance) of 0.1 Ohms or less and high power density delivering high current instantaneous power and fast charge time. For example, an electric screwdriver, where the peak current draw may be at start up for when fastening a screw or removing a stubborn one. Altematively, short pulsed power for a nail gun for example. Here is an ideal example of when the appliance may run directly from the supercapacitor as well due to the short time duration of operation.

For the Waste Heat Energy Harvesting System integrated in a Mobile Phone of Figure 5, if the battery is fully charged or an external power source is connected via its charging port for example, it may then charge the supercapacitor to be used as a buffer or a direct power source for the system later.

Figure 8A shows the additional integration of the Power Processing System into the mobile phone of Figure 5 but can also apply to a tablet, laptop, audio player or power tools such as an electric screwdriver or nail gun.

Here, the Portable Electrical Appliance (40) shows the Power System (42) comprising the key components, Charge Port (43), Charge Controller (44) and Battery (45). The Waste Heat (46) radiating from the inside of the enclosure (41) of the Portable Electrical Appliance (40) is captured by the Thermo Electric Generator (48) of the Waste Heat Energy Harvesting System (47) and is then processed by the Low Power Energy Harvesting System (49) and High Power Energy Harvesting System (50) whose input is terminated to a Supercapacitor (C1) in parallel to act as a storage device when heat is not available or provide high current to the High Power Energy Harvesting System (50) due its low ESR and high power density.

The Power Processing System (51) may be powered by the Charge Port (43) via D1 or the Battery (45) via D2. The Voltage and Current Sensing Circuit (52) monitors the status to allow an appropriate decision to be made. The Charge Controller (44) may send a signal to the Power Processing System (51) to indicate whether it is charging the Battery (45) via the Charge Port (43) and if not, the Waste Heat Energy Harvesting System (47) may charge it via D3. If the Battery (45) is fully charged, it may charge the Supercapacitor (C2) via D4.

Page 15 of 31 If an excessive current draw is sensed by the Voltage and Current Sensing Circuit (52), then the Supercapacitor (C2) will function as a buffer to complement the Battery (45) during high load conditions. Alternatively, it may directly power the Portable Electrical Appliance (40) from its output port via VIN from the electrical energy processed by the Waste Heat (46) or from the Supercapacitor (C2).

For the Waste Heat Energy Harvesting System mounted on the back cover of a Mobile Phone of Figure 6, it will determine if current is drawn from the charging port to determine whether to charge it or charge the supercapacitor to function as a buffer or a direct power source for the Portable Electrical Appliance later.

Figure 8B shows the addition of the Power Processing System mounted on the back cover of the Mobile Phone of Figure 6 but can also apply to a tablet, laptop, audio player or power tools such as an electric screwdriver or nail gun. Here, the Waste Heat (55) radiating from the Outside Back Cover of the Portable Electrical Appliance (53) is captured by the Thermo Electric Generator (57) of the Waste Heat Energy Harvesting System (56) and is then processed by the Low Power Energy Harvesting System (58) and High Power Energy Harvesting System (59) whose input is terminated to a Supercapacitor (C3) in parallel to act as a storage device when heat is not available or provide high current to the High Power Energy Harvesting System (58) due its low ESR and high power density.

The Voltage and Current Sensing Circuit (61) in the Power Processing System (60) monitors the status to allow an appropriate decision to be made. If it does not sense a current draw from the Power Port (62), it may charge the Supercapacitor (C4) via D5. If an excessive current draw is sensed by the Voltage and Current Sensing Circuit (61), then the Supercapacitor (C2) will function as a buffer during high load conditions. Alternatively, it may charge the Portable Electrical Appliance (53) via the Charging Port (54) from its Power Port (62) from the electrical energy processed by the Waste Heat (55) or from the Supercapacitor (C4). The Power Port (62) may be a standard USB socket to allow it to be connected to the Portable Electrical Appliance (53) via the Charging Port (54) using the charging cable supplied as standard.

For the Waste Heat Energy Harvesting System mounted integrated in a Mobile Phone Case of Figure 7, detects if current is drawn from the Mobile Phone Charging Port and if the External Charging Port is connected to an external power source to determine whether to charge it, charge the supercapacitor to function as a buffer or a direct power source for the Portable Electrical Appliance later.

Figure 8C shows the addition of the Power Processing System integrated in a Mobile Phone Case of Figure 7 but can also apply to other appliances such as a tablet, laptop, audio player or power tools such as an electric screwdriver or nail gun.

Here, the Waste Heat (65) from the Portable Electrical Appliance (63) is captured by the Thermo Electric Generator (67) of the Waste Heat Energy Harvesting System (66) and is then processed by the Low Power Energy Harvesting System (68) and High Power Energy Harvesting System (69) whose input is terminated to a Supercapacitor (C5) in parallel to act as a storage device when heat is not available or provide high current to the High Power Energy Harvesting System (68) due its low ESR and high power density.

This is processed by the Power Processing System (70) comprising a Voltage and Current Sensing Circuit (71) which monitors the status to allow an appropriate decision to be made. If there is a voltage sensed at the External Charging Port (73), or it does not sense a current draw from the Internal Power Port (72), indicating Page 16 of 31 that the battery is fully charged, it may charge the Supercapacitor (C6) via D6 from the electrical energy processed by the Waste Heat (65) for use later.

If an excessive current draw is sensed from the Internal Power Port (72) by the Voltage and Current Sensing Circuit (71), then the Supercapacitor (C6) will function as a buffer during high load conditions. Alternatively, it may charge the Portable Electrical Appliance (63) via its Charging Port (64) from the Internal Power Port (72) from the electrical energy processed by the Waste Heat (65) or from the supercapacitor (C6).

Energy Harvesting System A system used to boost the input voltage to several to hundreds of times the input voltage may adopt the following 'boost converter' topologies: * Forward Converter * Flyback Converter * Boost Converter Electrical power is determined by the following equation: P=Vx1 -(Eq.1) Where P = Power in Watts, V= Voltage in Volts and I = Current in Amps.

For an energy harvesting system to therefore have high power output, both the voltage and current needs to be high.

To explain this in more detail, Figure 10A shows a simplified representation of a charger circuit showing the voltage source, V1, an inductor, the primary side of a step-up transformer, Li, and a FET, Ql. To explain the effect of RDS(On) of the FET, this can be modelled as shown in Figure 10B. Here, the voltage source V1 is of a Thermo Electric Generator (TEG). R2 is represented as the DC resistance of an inductor or the primary side of a step-up transformer. R3 represents the On resistance of the FET, RDS(On).

It can be seen that the current is given by Ohm's law by the following equation: I = V/R -(Eq 2) Example based on the LTC3108 Energy Harvesting IC of Figure 9A.

Depletion Mode N Channel FET RDS (On) = 0.5 Ohms With a low DC resistance of the primary of the transformer or inductor, R2 = 0.1 Ohms and a low RDS FET, R3 = 0.5 Ohms such as the one in the LTC3108 Energy Harvesting IC of Figure 9A. With a TEG voltage, V1 of 0.02 Volts (20 Milli Volts). Then the maximum current is: I = 0.02/(R1+R2) = 0.02/(0.1+0.5) = 0.033 Amps Page 17 of 31 However, to determine the voltage across the primary side of the transformer or inductor, we get: V2 = 0.033 x 0.1 = 0.0033 Volts The voltage across or loss of is then accounted by the FET as: V3 = 0.033 x 0.5 = 0.0165 Volts This means that a higher number of turns would be required on the secondary side to boost the voltage to above 1 Volt. Note that tuning the secondary side of the transformer by the effect of resonance frequency can give higher output voltages and thus reduce the number of secondary turns required. However, there is a limit to this and hence the voltage and current on the primary side pay large factor in determining it. Even with the high output voltage under a resonance tuned circuit, the system is still limited by the current which has been reduced due to the RDS of the FET. Note also, as the secondary turns are increased to step-up the voltage, as so is the current reduced by the same factor. The current is further reduced by the DC resistance caused by the length of wire for the turns for the secondary windings.

Example -Effect of significantly low RDS(On) Enhancement Mode N Channel MOSFET, RDS(On) = 0.005 Ohms.

It is possible to achieve a significant more power output by utilising a switching element with an RDS of 0.005 Ohms therefore increasing the current significantly and therefore the power. With the same TEG voltage V1 of 0.02 Volts: I = 0.02/(R1+R2) = 0.02/(0.1+0.005) = 0.19 Amps To determine the voltage across the primary side of the transformer or inductor, we get: V2 = 0.19 x 0.1 = 0.019 Volts The voltage across or loss of is then accounted by the FET as: V3 = 0.19 x 0. 0.005 = 0.0165 Volts It can therefore be observed that both the current and the voltage to the primary side of the transformer or inductor are increased by a factor of 5.75. Using Eq. 1 we get the following power increase with this example: Power increase = 5.75 x 5.75 = 33 times Therefore, there are significant advantages in the use of the present invention in the charging circuit applications for an energy harvesting system including the following topologies: i) Forward Converter; ii) Flyback Converter; Page 18 of 31 iii) Boost Converter.

The Energy Harvesting System in the present invention may comprise and not be limited to these configurations.

However significantly low RDS(On) of 0.005 Ohms is only achievable with Enhancement Mode MOSFETs which have a 'Turn On' voltage of greaterthan 0.7 Volts typically unlike Depletion Mode FETs which are always 'On' at zero gate voltage and achieve their optimum RDS(On) at their threshold voltage. The next section describes how both of these issues are overcome together with an automatically starting energy harvesting system at ultra-low voltages, typically 20 mV or less.

Forward Converter This is traditional step-up energy harvesting circuit as described in the LTC3108 example of Figure 9A. Here, the output voltage is stepped up using a step-up transformer to boost the low 20 my to 2 Volts using a 1:100 turn step-up transformer in combination with a depletion mode FET. In this example this had an RDS(On) of 0.5 Ohms. We have seen the power limitations of this by way of a resistor model.

However, this invention proposes that it is possible to operate a charger circuit consisting of an Enhancement Mode MOSFET which has a very low RDS(On) of less than 0.1 Ohms and preferably typically 0.005 Ohms and a threshold voltage (Vt) far higher (typically 2 Volts) than the input source voltage (typically 20 mV). Therefore, significant power gains can be achieved where a factor of 33 was calculated compared to a FET with RDS(On) of 0.5 Ohms.

Figure 11 is an example using an enhancement MOSFET with an RDS(On) of 0.005 Ohms together with a step-up transformer. The step-up transformers have been taken from a popular disposable photoflash camera with one primary winding and one secondary winding. They are compact in size in that they or less than 1 square cm footprint. Closing the switch SW1 will allow the input source voltage to be presented across the primary winding (6 Turns). This in turn will be boosted by 291.66 (1750/6) times and switch the gate of the MOSFET as the voltage will be to be greater than 2 Volts.

The circuit will then oscillate once the switch is released. The capacitor C1 forms part of a resonant tank circuit between the inductance of the transformer secondary windings, and the input Gate Source capacitance of the MOSFET. This is to allow the oscillating frequency to be towards the self-oscillating frequency of the transformer to allow it to perform at its optimum. This is called the resonant frequency and given by: F = 1/(2TrNLC)) -(Eq. 3) Where F = Frequency in Hz, L = Inductance (of the secondary windings of the transformer) in Henries, C = Total series capacitance of the tank capacitor 'Cl ' and MOSFET input capacitance in Farads.

At the resonant frequency, higher voltages are achieved. As the RDS(On) of the MOSFET is very low, the primary current of the transformer is also high, hence the output power is high.

Page 19 of 31 C2 is a de-coupling capacitor and together with D1 make the sinusoidal waveform from being centered on the zero volts axis to make the waveform positive only. D2 then acts as a rectifier charging the capacitor C3 on the positive peaks of the waveform. RG1 is a low dropout regulator to provide a constant supply voltage and C4 is used to remove any ripples in the DC supply out voltage.

Self-Triggering Forward Converter We have seen how we can achieve high powers with very low input voltages using an enhancement mode MOSFET with low RDS(On) and a threshold voltage higher than the input voltage of the system that is started by a switch. However, this can be impractical as the available power is not always available. Therefore, an automatic starting circuit is proposed as shown in Figure 12. The system (74) comprises of a low power (75) and a high power energy harvesting circuit (76). The low power energy harvesting circuit (75) takes advantage of a depletion mode FET (always On) together with advantage of a high input impedance of FETs in general.

Q1 is a JFET, pad of the depletion mode FET family. At zero volts it is On and allows a small amount of current through its Drain and Source terminals causing the input source voltage to be presented across the primary winding (6 Turns). This in turn will be boosted by 291.66 (1750/6) times and switch the gate of the JFET off by a negative voltage swing equalling its Turn Off voltage of -2 Volts to -6 Volts.

The circuit will then oscillate by way of a sinusoidal waveform swing of +/-6 Volts. The capacitor Cl forms part of a resonant tank circuit between the inductance of the transformer secondary windings, and the input Gate Source capacitance of the JFET. This is to allow the oscillating frequency to be towards the self-oscillating frequency of the transformer to allow it to perform at its optimum.

This is a low power circuit as the JFET used is a J106 which has an RDS(On) of 6 Ohms and hence although the voltage swings between -6 and 6 Volts, it is of a low current. However, this will be sufficient to turn on the high power circuit (76) by way of the MOSFET, Q2 which has an RDS(On) of 0.005 Ohms and a Turn On voltage of 2 Volts but a very high impedance of tens of millions of ohms which makes it very easy to drive operating at resonant frequency similar to Figure 11. This will be done instantaneously, which is the moment the voltage to the gate of Q2 is above 2 Volts. At this point the input voltage will be presented at the primary of transformer T2 and boosted by 291.66 (1750/6) times and switch MOSFET Q3 on which is the same specification as Q2. The transformer T2 and MOSFET Q2 then form a self-oscillating circuit operating at resonant frequency similar to Figure 11. As the RDS(On) of Q3 is very low at 0.005 Ohms and the JFET Q1 has high RDS(On) of 6 Ohms, once Q3 turns on, it forms a short circuit effect across JFET Q1. Therefore, the power will now be transferred to the high power energy harvesting circuit from the input voltage source and charge the storage element very quickly. In this case less than 1 second to charge the capacitor C4. The low power energy harvesting circuit consumes less than 10 % of the overall power allow 90% to be utilised by the high power energy harvesting circuit to provide power to the output load.

External Gate Driven Forward Converter It is possible to create a forward converter that is not self-triggered like Figure 12. Figure 13 shows an arrangement using the same photoflash disposable camera transformers and operation is the same as that described in Figure 12.

Page 20 of 31 However, the low power forward converter (80) creates pulses to switch the MOSFET Q2 ON and OFF in the High Power Forward Converter Circuit (81). The secondary windings of transformer T2 step the input voltage Vin up by 291.66 (1750/6) and charge the storage element (82).

Here there is no resonant tank circuit between the secondary of the transformer T2 and the Gate Source of the N Channel MOSFET (unlike Figure 11 and 12), in the high power forward converter (81). Instead, the low power forward converter '80' frequency output is set to that of the resonant frequency of the transformer 'T2' in the high power forward converter (81). This is to allow the use of a very wide range of MOSFETs and transformers to be used in the high power forward converter (81). This is because some MOSFETs with very low RDS(ON) may have a high input Gate Source capacitance hence the system can still operate at the transformer T2 resonant frequency for optimum power output. T1 is also tuned such that it operates in resonant mode while its secondary winding is loaded with the gate capacitance of Q2 (resonant tuned) to ensure it can drive it easily and therefore provide sufficient voltage to switch it effectively.

Due to the resonance mode of operation, the low power energy harvesting circuit consumes less than 10 % of the overall power allow 90% to be utilised by the high power energy harvesting circuit to provide power to the output load.

Flyback Converter This type of converter involves using a flyback transformer. Unlike mains transformers and audio transformers, a flyback transformer is designed not just to transfer energy, but also to store it for a significant fraction of the switching period. The current does not flow simultaneously in primary and secondary (output) windings of the transformer. Because of this the flyback transformer is really a coupled inductor rather than a classical transformer, in which currents do flow simultaneously in all magnetically coupled windings. Essentially a flyback transformer was invented as a means to control the horizontal movement of the electron beam in a television cathode ray tube (CRT) and generates very high voltages in the order of 50 KV (Thousand Volts). Here it is referred to as the Line Output Transformer (LOPT). However, miniature ones are used for SMPs (Switched Mode Power supplies).

Essentially, the primary side of the transformer is used as an inductor. To this end, a transformer with a core such as ferrite is used which has a higher relative permeability than the laminations of a conventional transformer such as a mains or audio one. This way it is possible to get high inductance on the primary side with a lower number of windings. The secondary is then used to step the voltage up and it is possible to have additional windings for applications such as TV sets. The flyback converter works on the principle of charging the primary side of the transformer to store energy within the transformer core. Then the energy released when power is removed from the primary side of the transformer and the magnetic field within the core collapses. This is referred to as Back-EMF (Electro Motive Force) and is given by the following equation: V = Ldl/dt -(Eq. 4) Where V = the Back-EMF generated in Volts, L = Inductance, I = Current, t = duration of time when power is removed from the inductor.

Page 21 of 31 Figure 14A shows an arrangement using the same photoflash disposable camera transformers. The Low Power Forward Converter (85) creates pulses to switch the N Channel Enhancement Mode MOSFET 'Q2' in the High Power Flyback Circuit (86). The black dots on the transformer shows the starting of the windings. Here you will notice the actual polarities between primary and secondary are reversed relative to GND. When the gate to Q2 is high, the primary side of the transformer T3 is charged. When it goes low, the energy from the primary side is released. At this point, the secondary windings step this voltage up and charge the capacitor C4 of the storage element (87). The Low Power Forward Converter (85) serves as an oscillator whose frequency is optimised to meet the charge and discharge times of the inductance of the primary winding of flyback transformer T3 of the High Power Flyback Circuit (86). T1 is also tuned such that it operates in resonant mode while its secondary winding is loaded with the gate capacitance of Q3 (resonant tuned) of the High Power Flyback Circuit 86 to ensure it can drive it easily and therefore provide sufficient voltage to switch it effectively. This is because some MOSFETs with very low RDS(ON) may have a high input Gate Source capacitance.

The following observations can be made: i) The output of the Low Power Forward Converter '85' and the High Power Flyback circuit (86) are not 'High' at the same time but rather during opposite times hence less drain on the input power supply; ii) The Back-EMF generated is a factor of the current as well as the inductance of the primary side of the flyback transformer T3, hence a low voltage high current source such as a TEG together with a low RDS(On) of 0.005 Ohms N Channel Enhancement Mode MOSFET Q2 are advantageous even at very low voltages; iii) Due to the high primary current, high voltage peaks are possible with a low number of secondary transformer windings for the flyback transformer T3; iv) A reduced number of secondary windings of T3 means the output current will be high and hence a high output power is possible.

Figure 14B shows the behaviour of this circuit comparing the behaviour across the primary windings of the flyback transformer T3 with the Gate drive of the N Channel Enhancement Mode MOSFET Q2. Waveform 2 shows the output of the Low Power Energy Harvesting Circuit Driving the Gate of Q2 which is also a High Power (100 Amp) N Channel Enhancement Mode MOSFET whose RDS (ON) is of 0.005 Ohms (5 milli Ohms). Waveform 1 shows the primary windings of the Flyback Transformer T3 which releases its stored energy once the Gate signal is low. You will notice that although the supply voltage is less than 50mV, the released energy voltage is 3 times the amount. This means less turns are required for the step-up and hence higher power output.

Page 22 of 31 Figure 14C compares the behaviour across the secondary windings of the flyback transformer T3, waveform 1 with the Gate drive of the N Channel Enhancement Mode MOSFET Q2, waveform 2. It can be seen that the secondary winding of 'T3' show a peak voltage of almost 20 Volts.

Ferrite cores are typically used for wound materials such as inductors or transformers and have a relative permeability 'pr' of around 640 and are useful in the application of Flyback Converter configurations. A good magnetic core material must have high relative permeability. This is the ability of a material to support the formation of a magnetic field within itself. In other words, it is the degree of magnetization that a material obtains in response to an applied magnetic field. Using a dedicated Flyback transformer with a high relative permeability will give a much higher inductance for the primary windings. The secondary windings will then multiply the Back-EMF voltage depending on its number of turns. Using a flyback transformer which is essentially a coupled inductor that is wound on a much higher relative permeability core than ferrite will give higher performance still.

For the purposes of the present invention, the term high relative permeability can be referred to a value that is 10 or 100 times or greater than that of Ferrite and is achieved by using such materials as Nanoperm(RTM) nanocrystalline magnetic alloy or Metglas(RTM) amorphous magnetic alloy.

This is described in further details in the section "High Permeability Materials for Wound Components of the Energy Harvesting System".

Boost Converter A boost converter is a simplified flyback converter whereby only an inductor is used and there is not step-up of the voltage. So, the behaviour of operation is the same. The first three observation points for the flyback topology also apply here. As there is no secondary winding, the current remains the same (that is, it is not stepped down).

It is possible to get high current and reasonable voltages without a step-up transformer or flyback transformer in the proposed invention by using a high inductance inductor with low DC resistance.

The Back-EMF generated is a factor of the current as well as the inductance of the inductor, hence a low voltage high current source such as a TEG together with a low RDS(On) of 0.005 Ohms N Channel Enhancement Mode MOSFET are advantageous even at very low voltages.

It was observed that the Back-EMF generated is a factor of the current as well as the inductance of the primary side of the flyback transformer T3, in the Flyback Converter High Power Energy Harvesting Circuit (86) in Figure 14A. This also holds true for an inductor. Looking at the following equation again: V = Ldl/dt -(Eq. 4) Where V = the Back-EMF generated in Volts, L = Inductance, I = Current, t = duration of time when power is removed from the inductor.

Ferrite cores are typically used for wound materials such as inductors or transformers and have a relative permeability 'pr' of around 640 and are useful in inductors and for the application of boost converter configurations. A good magnetic core material must have high relative permeability. This is the ability of a Page 23 of 31 material to support the formation of a magnetic field within itself In other words, it is the degree of magnetization that a material obtains in response to an applied magnetic field.

However, the inductance per turn can be increased using a core material of higher relative permeability. For the purposes of the present invention, the term high relative permeability can be referred to a value that is 10 or 100 times or greater than that of Ferrite and is achieved by using such materials as Nanoperm(RTM) nanocrystalline magnetic alloy or Metglas(RTM) amorphous magnetic alloy.

Figure 15A shows an energy harvesting system (89) containing a high power boost converter energy harvesting circuit (91) with an inductor, Ll wound on a Nanoperm(RTM) M-102 high permeability Nanocrystalline Soft Magnetic Alloy core by Magnetec GmbH. It has a relative permeability of 90,000. The inductor L1 has 40 windings on SWG 28 copper enamelled wire. This gives an inductance 141 mH (milli Henries) and a measured DC resistance of less than 0.1 Ohms. The Low Power Forward Converter (90) serves as an oscillator whose frequency is optimised to meet the charge and discharge times of the inductor L1 of the High Power boost converter Circuit (91). T1 is also tuned such that it operates in resonant mode while its secondary winding is loaded with the gate capacitance of Q3 (resonant tuned) of the High Power boost converter Circuit (91) to ensure it can drive it easily and therefore provide sufficient voltage to switch it effectively. This is because some MOSFETs with very low RDS(ON) may have a high input Gate Source capacitance.

Figure 15B compares the behaviour across the inductor L1, waveform 1 with the Gate drive of the N Channel Enhancement Mode MOSFET Q2, waveform 2. It can be observed that the inductor releases its stored energy when the Gate is Off giving pulses of short duration. However, they have a peak voltage of over 1 Volt even with a supply voltage of less than 50 mV. This means that it is possible to charge a capacitor via the silicon diode D2 whose nominal forward voltage drop is 0.7 Volts. That is, the diode needs more than 0.7 volts to operate. The inductor winding resistance is less than 0.1 ohm and in combination with the low RDS (On) of the N Channel Enhancement Mode MOSFET of 5 mOhms (5 milli Ohms or 0.005 Ohms) means that although the pulse is around 1 Volt, the current is high and hence it is possible to charge large capacitors quickly.

Note that core materials of a higher relative permeability than 90,000 are possible for the described inductor in the boost converter configuration as it does not operate at a resonant frequency but rather it is based on the charge and discharge times of the primary winding inductance which is a factor of the input current. Using Nanoperm(RTM) nanocrystalline magnetic alloy or Metglas(RTM) amorphous magnetic alloy will also prevent high frequency saturation at high currents. In the present invention it is therefore particularly preferred that the inductor core be of high relative permeability of at least 80,000. Preferred examples are Nanoperm(RTM) nanocrystalline magnetic alloy or Metglas(RTM) amorphous magnetic alloy. The inductor may still be compact in size for portable or small form factor applications while giving significant power and efficiency gains and enabling the circuit of the present invention to operate effectively for the proposed applications.

Page 24 of 31 This is described in further detail in the section "High Permeability Materials for Wound Components of the Energy Harvesting System".

High Permeability Materials for Wound Components of the Energy Harvesting System Conventional wound components and in particular used in energy harvesting systems use Ferrite Core for example for the step-up transformer. This has typically a relative permeability 'pr' of around 640. However, it is possible to get 10 to 100 times the order of relative permeability that of ferrite by using materials as Nanocrystalline or amorphous magnetic alloy.

A typical high relative permeability toroid core such as the Nanoperm M-102 of Magnetec GmbH has a relative permeability of 90,000 compared to that of Ferrite which is typically 640. The term high relative permeability can be referred to a value that is 10 or 100 times that of Ferrite. This means that the inductance will also be 10 to 100 times as shown by the equations for both cylindrical and toroidal core wound inductors: L= poprIPA/1 (For a cylindrical core) -(Eq. 5a) Where L = Inductance in Henries, po = permeability of free space = 41r x 10-7 H/m pi = relative permeability of core material, N = number of turns A = area of cross-section of the coil in square metres (m2), I = length of coil in metres L= poprN2r2/D (For a toroidal core) -(Eq. 5b) Where r = radius of coil winding in metres, D = overall diameter of core in metres.

To date 2714A alloy has the highest relative permeability which is starting to be introduced into the industry. A typical core made of this material could be MP3210P4AF by Manz Electronic Systeme OHG. With this material, even higher output power is achievable at higher frequency without saturation.

The use of high permeability core materials would provide the following advantages: * A smaller wound component o Due to decrease in the core material size and number of windings * Increased power output o Due to a smaller number of windings to achieve the inductance and hence increase in current * Increased Efficiency o Smaller number of windings and hence reduced DCR (DC Resistance), in turn, thicker wire could be used to reduce DC resistance further o Increased coupling between the primary and secondary windings of transformers as a minimum inductance is required for the windings to achieve sufficient coupling. Coupling is the amount of power transfer between the primary and secondary windings * Reduced saturation at high currents Page 25 of 31 o Saturation is when the magnetic flux drops and causes a decrease in the inductance. This particularly prevalent at high frequencies and hence larger sized cores are needed. However, using high relative permeability can prevent this and also allow smaller cores to be used * Higher frequency operation o It is possible to have multiple wires connected and wound in parallel for high frequency due to the 'skin effect' due to the extra space available now as fewer numbers of winding are required to achieve the same inductance To this end, the present invention advantageously utilises high relative permeability core materials for the wound components.

The proposed high relative permeability cores as mentioned in the present application were used mainly for filtering chokes (Nanoperm) and high voltage transformers of 100kVA (Amorphous) in the art, not for purposes similar to the present invention. To date, miniature inductors, step-up transformers, and flyback transformers having the high permeability cores as proposed in the present invention have not been proposed in the industry yet, particularly for low voltage application and certainly not for 0.1 Volt or below operation.

High Permeability Core Materials in High Power Applications The reduction of the number of windings therefore reducing the resistance and hence increasing the current are especially advantageous for the 'Flyback Converter' (Figure 14A) and 'Boost Converter' (Figure 15A) topologies of the present invention as the output voltage is primarily based on converting the input current into voltage for an inductor as in the following equation: E =1,4 LI2 -(Eq. 6) Where E is the energy stored in an inductor in Joules, L is the inductance of the inductor in Henries and I is the current flowing through the inductor in Amps.

This equation also applies to the a 'Flyback Converter' is as it is essentially a 'Boost Converter' whereby the output voltage is multiplied by the secondary windings of the flyback transformer and the current reduced proportionally.

It can be determined by the equation that just halving the DC resistance of the windings of the inductor or the primary windings of the flyback transformer due to using a high permeability core will increase the current by four times and therefore the energy stored.

Optimised Square Wave Gate Triggering for Flyback and Boost Converter Embodiment of the Energy Harvesting Systems Maximum power output can be obtained if the low RDS(ON) Enhancement Field Effect MOSFET is driven by a square wave with at least a 50% duty cycle. So ideally, a PWM (Pulse Width Modulation) system is used.

The square wave shape and longer pulse duration enables the inductor current to be ramped up faster and to Page 26 of 31 be charged for longer each cycle thus providing high current and thus higher power output. However, square wave generators with variable pulse widths of >50% can be complex and consume too much power for such a low voltage energy harvesting system where the available voltage is less than 0.1 Volts, typically 20mV to 50mV from a Peltier element that is 20mm x 20mm. However, a simple PWM with variable duty cycle greater that 50% can be implemented using only 9 components.

One such example is based on a low power Hex 4069 integrated circuit consisting of CMOS logic gates which contains six logic inverters as shown in Figure 16A. Resistor Rosc and capacitor Cosc to provide the duty cycle and frequency. The diode Dosc is biased such that the output of the second inverter provides a duty cycle less than 50%. The third inverter U3 inverts this to generate the square wave with a duty cycle greater than 50%. The CMOS Inverter consists of P and N Channel Enhancement Mode MOSFETs which have a high input impedance and low gate capacitance and are easy to drive. This is shown in Figure 16B. Additional inverters can be used in parallel to provide higher drive capability (such as the three remaining out of the six in the Hex 4069 inverter package).

Figure 17 shows a Square Wave triggered Flyback Converter Energy Harvesting System (94) with adjustable Pulse Width and Duty Cycle > 50% based on a modified version of Figure 14A.

Here, the step-up transformer T1 in the low power energy harvesting circuit (95) is configured as a Forward Converter to charge the capacitor C6 to provide a stable DC voltage of 1 Volt or more to the Square Wave Generator based on the Hex 4069 inverter of Figure 16A to provide the gate pulses to Q2 of the High Power Energy Harvesting Circuit (96). The Hex 4069 inverter can easily be driven by the Forward Converter in Low Power Energy Harvesting Circuit (95) and only a 2.2pF (micro Farads) capacitor C6 is needed to maintain a clean stable 3 Volts when a 20mm x 20 mm TEG is used with an internal resistance of 0.5 Ohms.

To ensure efficient operation, resonant mode operation of the step-up transformer in the low power energy harvesting circuit (95) is maintained by way of a resonant tuned decoupling capacitorC2' to ensure fast start up at very low voltage (20 mV or less) while providing at least 1 Volt output or more to the storage capacitor. Too high a capacitance of C2 would cause too much load for the step-up transformer, too low a capacitance would allow easy start-up but reduce the amount of power to be transferred to the Square Wave Oscillator. Again, due to the resonance mode of operation, the low power energy harvesting circuit consumes less than 10 % of the overall power allow 90% to be utilised by the high power energy harvesting circuit to provide power to the output load.

It could therefore provide a 3 Volt Peak to Peak output with sufficient current to drive the low RDS(ON) 0.005 Ohm N Channel Enhancement Mode MOSFET, Q2, in the High Power Energy Harvesting Circuit (96).

Figure 18 shows a Square Wave triggered Boost Converter Energy Harvesting System of based on a modified version of Figure 15A. Here, the Low Power Energy Harvesting Circuit powers CMOS logic gates with adjustable Pulse Width and Duty Cycle > 50% to provide the gate pulses to the High Power Energy Harvesting Circuit. Again, the decoupling capacitor C2 maintains resonant mode operation of the step-up transformer in the low power energy harvesting circuit.

Page 27 of 31 Supercapacitor as Current Booster A supercapacitor has very high power density and low ESR (Electrical Series Resistance) resulting in high current. The system advantageously utilizes a supercapacitor of 0.1 Ohms ESR or less terminated in parallel with the Thermo Electric Generator to provide a high electrical current to the High Power Energy Harvesting Circuit. This is particularly advantageous for the 'Flyback Converter' and 'Boost Converter' topologies of the present invention as the output voltage is primarily based on converting the input current into voltage for an inductor as in the following equation: V = Ldlidt -(Eq. 4) Where V = the back EMF generated in Volts, L = Inductance, I = Current, t = duration of time when power is removed from the inductor.

Also, as mentioned, the energy stored in the inductor is proportional to the current squared as in the following equation: E = % LI2 -(Eq. 6) Where E is the energy stored in an inductor in Joules, L is the inductance of the inductor in Henries and I is the current flowing through the inductor in Amps.

Supercapacitor as Storage Device for Thermo Electric Generator The system advantageously utilizes a supercapacitor with low ESR of 0.1 Ohms or less terminated in parallel to the Thermo Electric Generator and function as a storage element when heat is not available due to its high power density delivering high current instantaneous power and fast charge time.

Supercapacitor as Output Storage Device of Energy Harvesting System and Output Buffer As mentioned all presently available chargers based on harvesting ambient energy such as solar etc all have an internal battery which first needs to be charged by the energy harvested by the source so that the internal battery reaches the operating voltage of the portable electrical device it is charging, for example 3.6 Volts. This can take several hours. The present invention, however, does not have an internal battery but a supercapacitor to act as a buffer or electrical storage device to directly charge or power the portable electrical device. As well as being Zero Carbon and lasting the lifetime of the device, due to its low ESR (Internal Series Resistance), high power density and fast charge time, can provide instantaneous power in seconds in real time from the energy is being harvested unlike the batter, however, has good energy density like a battery so can be used as electrical storage device so providing best of both worlds. This can be seen by the graph in Figure 22 showing the Energy Density in Watt hours per kilogram vs Power Density in Watts per kilogram for the Supercapacitor vs the Battery and other electrical storage medium and relative charge and discharge times.

Page 28 of 31 Integrated Circuit of Energy Harvesting System The system can be made smaller for ease of integration into portable electronic equipment by way of an integrated circuit.

Figure 19A shows the present invention based on an improvement to the Prior Art LTC3108 Integrated circuit of Figure 9A consisting of a low power and high power energy harvesting circuit.

Figure 19B shows the present invention based on the integrated circuit of FIGURE 19A showing connections to components configured as a 'Self Triggering Forward Converter' in the discrete component design of Figure 12.

Figure 19C shows the present invention based on the integrated circuit of FIGURE 19A showing connections to components configured as a 'External Gate Triggered Forward Converter' in the discrete component design of Figure 13.

Figure 19D shows the present invention based on the integrated circuit of FIGURE 19A showing connections to components configured as a 'Flyback Converter' in the discrete component design of Figure 14A.

Figure 19E shows the present invention based on the integrated circuit of FIGURE 19A showing connections to components configured as a 'Boost Converter' in the discrete component design of Figure 15A.

Figure 20A is based on a modified version of the proposed Integrated Circuit of Figure 19A. It shows a Square Wave triggered Flyback Converter Energy Harvesting System '107' based on the discrete component design of Figure 17 whereby the low power energy harvesting circuit '108' also contains a square wave generator (consisting of only 9 components) with adjustable Pulse Width and Duty Cycle > 50% to provide pulses to the gate of C)3' in the High Power Energy Harvesting Circuit '109' and provide greater current and therefore higher power.

Figure 20B is as Figure 20A, however, is based on a 'Boost Converter' topology of the discrete component design of Figure 18 using an inductor instead of a flyback transformer.

Miniaturization of Components due to the use of Novel Materials PCB integrated Inductors and Transformers As outlined, the preferably comprises transformers or inductors where the core material is Nanocrystalline or amorphous magnetic alloy of a high relative permeability of at least 5000.

Therefore, the system allows miniaturization by way of embedding the core material of the inductors or transformers within a PCB (Printed Circuit Board) whereby the tracks form the windings ortracks and vias form the windings within a multi-layer PCB.

One such example is shown in Figure 21 comprising a multi-layer PCB of 4 metal layers and several vias. The top side of the PCB (110) shows the secondary winding of the transformer and its connections S1 and S2 together with the connections for the primary winding P1 and P2 whose windings are on the bottom side of the PCB (112). The cross-section of the PCB (111) shows the magnetic core material of the transformer M, the vias V1, V2 and V for the primary windings and secondary windings V4 and V5 and the metal layers L1, L2, Page 29 of 31 L3 and L4. The view of the cross section is between arrows (113A) and (113B) as shown on the top of the PCB (110) and between arrows (114A) and (114B) as shown on the bottom of the PCB (112).

Significant inductance can be achieved by the transformer or inductor with low winding resistance thus high current due to the use of a high relative permeability of at least 5000 while achieving a small feature size.

Multi-Component Integrated Circuit The system further lends itself to miniaturization by way of an IC (Integrated Circuit) whereby any multiple or all of the constituent components can be integrated within the IC: * Inductors and Transformers Advantageously, significant inductance can be achieved by the inductor or transformer with low winding resistance thus high current due to the use of a high relative permeability of at least 5000 while achieving a small feature size to allow integration into an IC. High coupling coefficient can also be achieved for the transformers of greater than 90%.

* Capacitors Advantageously, the technology of Supercapacitors is utilised to allow miniaturization with significant orders of magnitude greater capacitance compared to those in present integrated circuits while maintaining low ESR (Effective Series Resistance) thus high current due to the use of high permittivity dielectric materials. Unlike ordinary capacitors, supercapacitors do not use the conventional solid dielectric, but rather, they use electrostatic double-layer capacitance. The double-layer serves approximately as the dielectric layer in a conventional capacitor, albeit with the thickness of a single molecule. Thus, the standard formula for conventional plate capacitors can be used to calculate their capacitance: C = A/d -(Eq. 7) Accordingly, capacitance C is greatest in capacitors made from materials with a high permittivity £, large electrode plate surface areas A and small distance between plates d.

As a result, double-layer capacitors have much higher capacitance values than conventional capacitors, arising from the extremely large surface area of activated carbon electrodes and the extremely thin double-layer distance on the order of a few ingstrOms or 0.3-0.8 nm (nano metres) of order of the Debye length (a measure of a charge carrier's net electrostatic effect in a solution and how far its electrostatic effect persists).

Activated carbon was the first material chosen for EDLC electrodes. Even though its electrical conductivity is approximately 0.003% that of metals which is 1,250 to 2,000 S/m (Siemens per metre), it is sufficient for supercapacitors. It is an extremely porous form of carbon with a high specific surface area. A common approximation is that 1 gram (0.035 oz) (a pencil-eraser-sized amount) has a surface area of roughly 1,000 to 3,000 square metres (11,000 to 32,000 square ft), about the size of 4 to 12 tennis courts. The bulk form used Page 30 of 31 in electrodes is low-density with many pores, giving high double-layer capacitance. Active Carbon is one such example used for a supercapacitor, other materials are also available to include but not limited to Activated carbon fibres, Carbon aerogel, Carbide-derived carbon, Graphene and Carbon nanotubes.

Manufactured Energy Harvesting System The energy harvesting system is the key technology of the present invention and as mentioned utilizes that presented in my granted patents for "Body Heat Generated Power Source for Portable Electrical Equipment" (GB2531855B) and "Body Heat Powered Wireless Transmitter" (EP2966752B1 and U59954156B2). The Prior Arts disclosed by Linear Technology LTC3108 integrated circuit of Figure 9A and Enocean ECT310 were deemed to be already more powerful, efficient and compact than that disclosed in Shuttleworth R et al: "Discrete, matched-load, step-up converter for 60-400 mV thermoelectric energy harvesting source" ELECTRONICS LETTERS, IEE STEVENAGE, GB, vol. 49, no. 11, 23 May 2013 (2013-05-23), pages 719720, XP006044041 and US patent US6340787 (SIMERAY) and any other system on the market utilising heat at body heat (37 Degrees Celsius) and operating at 20mV.

However, a prototype of the Flyback Converter based energy harvesting system embodiment of Figure 14A using discrete components manufactured using mass produced SMT (Surface Mount Technology) has been built and tested operating at 20mV or less from body heat (37 Degrees Celsius). Tests have proved it to be more powerful than any other system on the market utilising heat at body heat (37 Degrees Celsius) with an improvement in the output power by several times over the present invention by Linear Technology LTC3108 integrated circuit of Figure 9A and Enocean ECT310 at an input of 20mV while taking the same footprint of 1.5cm x 1.5cm. This was also outlined in my granted patents for "Body Heat Generated Power Source for Portable Electrical Equipment" (GB2531855B) and "Body Heat Powered Wireless Transmitter" (EP2966752B1 and U59954156B2).

While embodiments of the invention have been illustrated and described, it is not intended that these embodiments illustrate and describe all possible forms of the invention. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the invention.

Page 31 of 31

Claims

1. A heat powered electrical device that comprises a Thermo Electric Generator to harness heat and convert the heat to electrical energy; and an energy harvesting system to process the electrical energy to power a load, wherein the energy harvesting system. comprises a low power energy harvesting circuit and a high power energy harvesting circuit characterized in that the heat powered electrical device is a Waste Heat Energy Harvester for Portable Electrical Appliances to power or charge an electrical appliance and one or more Thermo Electric Generators harness waste heat from a portable electrical appliance such as a mobile phone and converts the heat to electrical energy, the Thermo Electric Generators being connected to the energy harvesting system to power it, wherein the low power energy harvesting circuit comprises one or more step-up transformers forming an oscillator which is operated in resonance mode and is independent of the high power energy harvesting circuit, the high power energy harvesting circuit comprising one or more Enhancement Mode Metal Oxide Semiconductor Field Effect Transistors that have an RDSon of 0.1 ohms or less and the high power energy harvesting circuit comprising one or more of its own step-up transformers, flyback transformers or inductors that are independent of the step-up transformers of the low power energy harvesting circuit, wherein the low power energy harvesting circuit operates at a power level that is at least ten times lower than the high power energy harvesting circuit, the low power energy harvesting circuit power output drives or triggers the gate of the Enhancement Mode Metal Oxide Semiconductor Field Effect Transistors of the high power energy harvesting circuit thereof, driving or triggering the high power energy harvesting circuit to deliver the electrical energy as output power to the portable electrical appliance, whereby the device powers from any heat radiating component of the portable electrical appliance to operate from 20 millivolts DC or less from the Thermo Electric Generators and the output of the high power energy harvesting circuit powers or charges the portable electrical appliance.

2. A heat powered electrical device as claimed in claim 1, wherein the energy harvesting system comprises a transformer or inductor where the core material is Nanocrystalline or Amorphous magnetic alloy of a high relative permeability of at least 5000.

3. A heat powered electrical device as claimed in any preceding claim, wherein the Thermo Electric Generator is mounted to any heat radiating component of the Electrical Appliance to include any or all of the following: a) Battery; b) Heatsink; c) Electrical Component; d) Casing.

4. A heat powered electrical device as claimed in any preceding claim wherein the Waste Heat Energy Harvester is integrated within the Portable Electrical Appliance.

5. A heat powered electrical device as claimed in claim 4 comprises a Power Processing System comprising of a Supercapacitor and Voltage and Current Sensing Circuits to detect the current drawn from the Portable Electrical Appliance and the voltage level of the battery or other electrical storage system and if an external power cable is connected to determine whether to charge it, directly power it or charge the Supercapacitor to act as a buffer or a direct power source for the Portable Electrical Appliance.

6. A heat powered electrical device as claimed in any preceding claim wherein the Waste Heat Energy Harvester is mounted on the outside of the Portable Electrical Appliance and the power output is connected to its Charging Port.

7. A heat powered electrical device as claimed in claim 6 comprises a Power Processing System comprising of a Supercapacitor and Voltage and Current Sensing Circuits, to detect the current drawn from the Portable Electrical Appliance to determine whether to charge it or charge the Supercapacitor to act as a buffer or a direct power source for the Portable Electrical Appliance.

8. A heat powered electrical device as claimed in any preceding claim wherein the Waste Heat Energy Harvester is integrated within an Aftermarket Portable Electrical Appliance Case to include any of the following: a) Mobile Phone Case;b) Tablet Case;c) Laptop Case;

9. A heat powered electrical device as claimed in claim 8 wherein the Waste Heat Energy Harvester output is terminated to a Power Port to enable the Charging Port of the Portable Electrical Appliance to be docked to it to charge it or power it directly and an External Charging Port to allow an external power source to charge or power it directly.

10. A heat powered electrical device as claimed in claim 9 comprises a Power Processing System comprising of a Supercapacitor and Voltage and Current Sensing Circuits, to detect the current drawn from the Portable Electrical Appliance and if the External Charging Port is connected to an external power source to determine whether to charge it, charge the Supercapacitor to act as a buffer or a direct power source for the Portable Electrical Appliance later.

11. A heat powered electrical device as claimed in any preceding claim wherein the Power Processing System utilizes low power CMOS (Complementary MOSFET) circuits or nano power (power level in the order of a thousand million times less than a watt) circuits comprising Zero Threshold MOSFETs (Metal Oxide Field Effect Transistor).

12. A heat powered electrical device as claimed in any proceeding claim, wherein the device comprises an Integrated Circuit comprising any of the electrical components to comprise any multiple of them.

13. A heat powered electrical device as claimed in any proceeding claim, wherein the core material of the transformer or inductor is embedded in a printed circuit board and the windings are formed by a combination of tracks and vias.

14. A heat powered electrical device as claimed in any preceding claim, wherein the Thermo Electric Generator is a Peltier Module with 1 Ohm internal resistance or less.

15. A heat powered electrical device as claimed in any preceding claim wherein a Supercapacitor with Electrical Series Resistance of 0.1 Ohms or less is terminated in parallel to the Thermo Electric Generator to provide a means to deliver high electrical current to the High Power Energy Harvesting Circuit or act as a storage element when heat is not available to the Thermo Electric Generator.