CZ2012981A3 - Feeding unit operating on the energy harvesting principle and method of obtaining and transformation of energy from free sources - Google Patents

Abstract

The invention provides a power harvesting power unit and a method for obtaining and transforming energy from free sources. The power supply unit is a free energy device that is freely accessible from the environment, accumulates it in small amounts and stores it in a supercapacitor. The device comprises a microprocessor unit (1), a MOSFET transistor (2), a transformer (3), a low level input voltage connector (4) from a free energy source (9), a first capacitive block (5) and a second capacitive block (7), one-way rectifier (6) and lithium battery (8). The energy from the free energy source (9) is supplied to the low level input voltage connector (4), which is filtered by the first capacitive block (5) and then transformed from DC to voltage by the MOSFET pulse transistor (2). Pulse Transistor (2) The MOSFET controls the microprocessor unit (1), the pulse voltage being transformed by the transformer (3) to a higher level voltage and rectified by the one-way rectifier (6), and the obtained electric charge is stored in the output second capacitive block (7).

Description

Power supply unit working on the principle of energy harvesting and the method of obtaining and transforming energy from free sources

Field of technology

The device falls into the area of special switching power supplies, which use the possibilities of alternative power supplies instead of conventional inputs.

State of the art

Currently, a growing number of manufacturers are producing similar devices capable of utilizing the surrounding free energy and converting it into an electric charge, as described, for example, in Salemo D., Ultralow Voltage Energy Harvester Uses Thermoelectric Generator for Battery-Free Wireless Sensors, LT Journal of Analog Innovation, October 2010, Volume 20, Number 3.

These sources are able to convert input power in the order of 10 mW. Higher input powers cannot be realized today due to the miniaturization of power management chips and thus also the switching elements contained in them. Due to these limitations, the charging times of these sources are in the order of hundreds to thousands of seconds. These devices are able to operate without any primary power source (battery or accumulator). The achieved efficiencies range from 10 to 44% depending on the input voltage.

The essence of the invention

According to the invention, the term energy harvesting means obtaining energy (small amounts) from alternative sources such as heat, vibration, air flow, etc., its gradual accumulation, transformation and further its use for powering other devices, typically sensors.

The term supercapacity according to the invention represents a capacitor with a higher capacity value.

The term free energy source according to the invention represents an energy source obtained freely from the surrounding environment, such as heat, air flow, solar radiation intensity, etc. Free energy sources are standard types of sources capable of generating electrical power from

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ř of one of the types of surrounding free energies. Examples are thermocouples, or better Peltier cells connected inversely. By this is meant that the areas of standard Peltier cells are at different thermal potentials, thereby generating a voltage proportional to this thermal gradient at its terminals. These cells are composed of a large number of semiconductor elements connected in series-parallel. The surface of the cells is ceramic with a total thickness of about 5 mm. Articles are available in many variants and the source composed of such articles is in the price range of hundreds of crowns. Other sources that are used to obtain free energy are vibrational sources, which convert vibration energy into electrical power (piezoelectric effect). Furthermore, solar panels (cell voltage is around 0.3 to 0.5 V at currents of 50 to 500 mA), or sources capable of converting electromagnetic energy in the vicinity of fluorescent lamps into electrical power (in principle suitably sized antennas).

The term ambient free energy according to the invention represents energy from the environment, i.e. waste heat from various processes, solar radiation intensity, electromagnetic energy emitted by fluorescent lighting fixtures, vibrational energy generated as an undesirable product in rotating machines, etc.

The essence of the invention is a device that works with free energy freely accessible from the environment, accumulates it in small batches and stores it in a large-capacity capacitor, supercapacitor.

The input parameters are in the order of tenths of a volt and tenths of an ampere. The advantage over commercially available circuits is comparable or higher circuit efficiency and the ability to process significantly higher input power, in the order of tens to hundreds of mW, thanks to the use of a MOSFET switching transistor and microprocessor control and evaluation unit. In this case, the microprocessor unit represents the power management unit, ie the unit that ensures the regulation of the output voltage, the generation of the logic signal POWER-GOOD and the generation of excitation pulses for the power switching element transistor MOSFET. The POWER GOOD signal is a logic signal generated by the microprocessor unit that notifies the connected terminals that enough power is available to operate them. These connected devices are usually in SLEEP mode, ie in a state where they consume only negligible energy, but do not do useful work. To wake up from this state, it is necessary to bring a logic signal to their specific inputs, which will wake them up. If the power supply unit has sufficient input energy, it is able to supply itself with energy and store the excess in a large-capacity capacitor (supercapacity). If the capacitor is fully charged, the microprocessor goes into sleep mode and takes only ·

negligible amount of energy (up to 10 μΑ). From this state, the output voltage at the supercapacity is waking up and measured periodically and the switching element MOSFET transistor controls according to the amount of accumulated energy. The output energy in the form of a charge is stored in the output capacitive block II. This block of capacitors serves primarily to filter the output voltage and to accumulate the obtained energy. It consists of three types of capacitors. The small capacitor (10 uF) ceramic capacitor has an extremely low series resistance and is therefore suitable for capturing voltage peaks that arise from the nature of the DC / DC converter function. The electrolytic capacitor is used to compensate for leakage peaks when supplying terminal equipment and its capacity is in the order of hundreds of pF. The current peaks can be quite high, for example when the GSM device is powered, the short-term consumption from the power supply is 2 A. These peaks are in the order of ms and therefore it is necessary to dimension the output electrolytic capacitor well. The third type of capacitors is the above-mentioned supercapacitor. It is an electrolytic capacitor with a low operating voltage, mostly at the level of 5.5 V. However, its capacity is very high, in the order of farads. This type of capacitor acts as an energy accumulator. However, unlike a conventional accumulator, the internal energy is not bound in chemical bonds, but in the form of an electric charge between the electrodes of capacitors. As with the output voltage, the input voltage must be filtered. This voltage is in the order of hundreds of mV, so the demands on capacitors are not very critical. The input capacitive block consists of only two types of capacitors, namely electrolytic and ceramic. A ceramic capacitor with very low hay resistance stops the function of a hard voltage source, while a larger electrolytic capacitor serves as a temporary storage of energy. Current peaks arising on the primary side of the transformer are caused by switching the input voltage on the power element. In addition, the input and output capacitive blocks effectively suppress the interference that occurs during operation of this type of DC / DC converter.

The power supply unit according to the invention consists of nine basic elements: a microprocessor unit, a MOSFET transistor as a power switching element, a transformer, a low-level input voltage connector of J-a-IK capacitive blocks, a one-way rectifier and a battery.

The microprocessor unit here functions as a control element which evaluates and controls the connected peripherals. The integrated analog-to-digital (A / D) converter converts the analog value of the output voltage to its digital image. This then serves as the main variable for the next control logic.

Power switching element - MOSFET transistor switches low voltage input voltage and thus creates a pulse voltage suitable for transformation. This element is crucial because standard bipolar transistor types are not able to switch such low voltages. This is due to their design, when a voltage is required at the terminals of the bipolar transistor that exceeds the threshold level of two semiconductor junctions (N-P, P-N). This threshold voltage normally ranges from around 0.8 to 1.2 V. In contrast, unipolar types of transistors, including the type used here, have only one semiconductor channel and it is therefore possible to switch even very low voltages of the order of tens of mV. In addition, unipolar transistors (MOSFETs) are field-driven, not like bipolar types, which are current-driven to their base. Voltage control is more energy efficient and contributes positively to the entire power consumption. Various types of MOSFET transistors appear to be the most suitable type of N-MOSFET for the purposes of this invention. A ferrite core transformer transforms a low level input voltage to a high level output voltage. The transformer is defined by its gear ratio, which is simply a value that indicates how many times the input voltage will be greater after the transformation. The transformer itself consists of a ferrite core, a primary winding (thread units) and a secondary winding (tens of threads). Due to the very low transmitted power, the core may have a very small active cross section. However, the switching frequency is limited to its minimum limit of 10 kHz. Below this limit, the efficiency of energy transfer decreases sharply, thus increasing losses in the core.

The low level input voltage connector from the free power supply is used to connect one of the power supplies. These are screw terminals with an increased contact area due to the good transmission of current peaks.

The active block k serves to filter the input voltage and as a hard power supply.

The one-way rectifier is used to rectify the AC voltage that is present on the secondary side of the transformer. The rectifier consists of one Schottky diode connected in the forward direction. A schottky diode is required here due to the high operating frequency of the DC / DC converter. The standard type would show too many losses. This type of diode is used as standard in these drives. The only significant disadvantage of a Schottky diode is that it allows a certain minimum current to pass in the reverse direction. This property is taken into account and a type with a reduced closing current has been chosen for the purposes of the present invention.

. . The capacitive block Π serves to filter the output voltage and as a hard voltage source for the connected devices that are supplied by this block.

The lithium battery is used in the present invention to back up power in the absence of sufficient power in the output capacitive block II and to power the microprocessor unit.

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The advantage of the invention over commercially available solutions is comparable or higher efficiency and the possibility to process significantly higher input power, in the order of tens to hundreds of mW. Another indisputable advantage is the power switching element used, a MOSFET transistor, which has a very low resistance in the closed state (Rds-on), of the order of mQ and a switching current in the order of tens to hundreds of amperes. By using this switching element, it is possible to transform a significantly higher current than in commercially available solutions and thus significantly reduce the charging capacity of the supercapacity. The power supply unit working on the principle of energy harvesting is suitable for powering various types of sensors, especially wireless. Modern types of sensors are already energetically advanced, which means the possibility of going into sleep mode. In this state, they have negligible power consumption, which prolongs battery life. The sensors switch from continuous measurement mode to intermittent mode. This reduces the number of measurements per unit time, but significantly reduces the power consumption.

In general, it is an energy source that transforms waste thermal energy into electrical energy capable of powering electronic devices.

The disadvantage of the invention compared to the commercial solution is the need for a backup power source, i.e. a small lithium battery, which in this case has an average life of more than 3 years. Another disadvantage is the relatively larger dimensions of the power supply unit compared to commercial products.

Overview of figures in the drawings

The invention is further elucidated with the aid of the drawings, in which Figure 1 shows a block diagram of the power supply unit as such and Figure 2 shows an electrical diagram of the power supply unit with the indication of the respective blocks.

Example * embodiment of the invention

Example 1

The power supply unit K) according to figure 1, where the basic component of the power supply unit 10 is the microprocessor unit 1 Atmel ATMEGA 8A. It controls the power transistor 2 MOSFET. The input voltage from the low level input voltage connector 4 is switched by a semiconductor switch via a transformer 3 with a defined gear ratio and is transformed to the secondary side of the transformer 3. The increased voltage is then rectified by a one-way rectifier 6 and filtered by a second capacitive block 7.

I S> »block 7 consists of three capacitors. The first capacitor is a very low internal resistance (RESR) ceramic, which efficiently accumulates the short peaks supplied by the drive. The second capacitor of the pair is electrolytic, with low internal resistance and small leakage current with a capacity of hundreds of microfarads. This capacitor serves as a standard filtration capacity. The third capacitor is the so-called supercapacitor with a capacity of 0.44 F, which is suitable for the accumulation of higher energies and thus represents the accumulator. The input low voltage is also filtered by the first capacitive block 5 and serves as a hard voltage source for the transformation. This block consists of only a pair of capacitors - ceramic (microfarad units) and electrolytic (hundreds of microfarads). In case there is enough energy available in the output block of the capacitors from the second capacitive block 7, the microprocessor unit 1 activates the logic signal POWER GOOD and thus signals to the connected devices that they have the possibility to take energy. In the presence of the input voltage, the microprocessor unit f is supplied from this free energy source 9 via the connector 4.

Example 2

The power supply unit JO according to Figure 1, where the basic component of the power supply unit 10 is a microprocessor unit 1, Atmel ATMEGA 8A. It controls the power transistor 2 MOSFET. The input voltage from the low level input voltage connector 4 is switched by a semiconductor switch via a transformer 3 with a defined gear ratio and is transformed to the seconds side of the transformer. capacitors. The first capacitor is a very low internal resistance (RESR) ceramic, which efficiently accumulates the short peaks supplied by the drive. The second capacitor of the pair is electrolytic, with low internal resistance and small leakage current with a capacity of hundreds of microfarads. This capacitor serves as a standard filtration capacity. The third capacitor is the so-called supercapacitor with a capacity of 0.44 F, which is suitable for the accumulation of higher energies and thus represents the accumulator. The input low voltage is also filtered by the first capacitive block 5 and serves as a hard voltage source for the transformation. This block consists of only a pair of capacitors - ceramic (microfarad units) and electrolytic (hundreds of microfarads). The microprocessor unit 1 is powered by a lithium battery 8 when free ambient energy is unavailable.

(several years). If there is not enough power available in the capacitor output block from the second capacitive block 7, the microprocessor unit 1 deactivates the POWER GOOD logic signal, signaling the connected devices to switch to a low-power state and wait until it is in the second capacitive block. block 7 enough energy again. The microprocessor unit 1 is in this case powered by a lithium battery 8.

Example 3

The power supply unit U) according to figure 1, where the basic component of the power supply unit 10 is the microprocessor unit 1 Atmel ATMEGA 8A. It controls the power transistor 2 MOSFET. The input voltage from the low level input voltage connector 4 is switched by a semiconductor switch via a transformer 3 with a defined gear ratio and is transformed to the seconds side of the transformer 3. The increased voltage is then rectified by a one-way rectifier 6 and filtered by a second capacitive block 7. four capacitors. The first two capacitors go ceramic with very low internal resistance (RESR), which efficiently accumulates the short peaks supplied by the drive. The other two capacitors are electrolytic, with low internal resistance and a small leakage current with a capacity of 0.44 F, suitable for the accumulation of higher energies and thus represents a battery. The input low voltage is also filtered by the first capacitive block 5 and serves as a hard voltage source for the transformation. This block consists of only three capacitors - two ceramic (4.7 // F) and electrolytic (470 pF). In case of unavailability of free ambient energy, the microprocessor is powered by a lithium battery 8. This battery 8 is connected in series via an isolating diode D1 (BAT54). As a result, it is possible to switch from a free ambient power supply to a backup source in the form of a lithium battery 8 without interrupting the power supply. GOOD and signals to the connected devices that they have the possibility to take the accumulated energy.

Example 4

The power supply unit W according to Figure 2, where the basic component of the power supply unit 10 is a single-chip microprocessor unit 1 connected without an external oscillator and using an internal clock clock source for its operation. Transistor 2 MOSFET is type NTMFS4833N, capable of switching a current of 191 A. Transformer 3 is a hand-wound type on an El core with

cross section 2 cm. The low level 4 input voltage connector from the free power supply is a standard screw terminal with a spacing of 5 mm. The first capacitive block 5 consists of three capacitors. Two are with a ceramic dielectric, one with an electrolytic dielectric. The one-way rectifier 6 is represented by a schottky type diode D2 with the designation 1N5819 in the SMD design. The second capacitive block 7 consists of two types of capacitors. Two are ceramic (4.7 μι) and two electrolytic with a capacity of 0.22 F rated at 5.5 V. Lithium battery 8 is coupled to two ceramic capacitors Cla C2 to compensate for current spikes when switching transistor 2 MOSFET. A serial communication port UART is led out of the microprocessor unit 1, which allows communication with the power supply unit 10 with the possibility of its setting (operating frequency, value of stabilized output voltage, etc.).

Industrial applicability

The invention, a power unit operating on the principle of energy harvesting, can be used in the field of sensors, in areas without the availability of mains power supply and in places with difficult access for maintenance.

Claims (5)

PATENT CLAIMS Power supply unit (10) operating on the principle of energy harvesting, characterized in that it consists of a microprocessor unit (1), which has a lithium battery (8) connected to the first input, the output from the second capacitive block (7) is connected to the second input. ), the first output (POWER GOOD logic signal) of the microprocessor unit (1) is connected to other energy signaling blocks for their operation and the second output of the microprocessor unit (1) is connected to the primary side of the transformer via the power switching element of the transistor (2). 3), to which a source (9) of free energy is connected via the input connector (4), while the first capacitive block (5) is further connected to the input connector (4) and is connected to the secondary side of the transformer (3) via a one-way rectifier ( 6) the second capacitive block (7) is connected. Power supply unit (10) according to claim 1, characterized in that the MOSFET transistor (2) is an N-MOSFET transistor. Power supply unit (10) according to Claim 1 or 2, characterized in that the microprocessor unit (1) is a microprocessor of the ATMEGA standard. Power supply unit (10) according to any one of the preceding claims, characterized in that the one-way rectifier (6) comprises a Schottky type diode. A method of obtaining and transforming energy from free energy sources (9) by means of a power supply unit (10), characterized in that energy from free energy sources (9) is fed to a low level input voltage connector (4) which is filtered by a first capacitive block (5) and then transformed from DC to voltage by a pulse transistor (2) MOSFET controlled by a microprocessor unit (1), the pulse voltage being transformed by a transformer (3) to a higher level and rectified by a one-way rectifier (6) and the obtained electric the charge is stored in the second output capacitive block (7).