Dc Converters And The Power Crisis Engineering Essay

In existent universe, power crisis was mounting up-and-up provided that utilizations of portable electronic device with other devices were being increased. Majority part of these portable devices operates in DC current. Operating electromotive force of these DC electronics is get downing from 3.3V. So after acquiring the electromotive force lower than 3.3 or depending on the applications, the operation would halt and the remainder of energy would hold lost.

DC/DC convertors could be a alleviation in this instance. DC/DC convertor is a device that converts one degree of DC electromotive force to another degree. This transition could be of different types, depending on different construction of circuit and their applications. Some generic DC to DC convertors were step-up, step-down, and invert. Here concern would be centred to step-up convertors and ‘Maxim MAX756 ‘ [ 1 ] would be up to its extent.

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Fig 1: MAX756 [ Embedded in an application device ]

The vision was doing the automatic measuring systems independent of power beginning in close hereafter. So the aims of this assignment for the device MAX756 was set to followerss.

Investigating alternate electric energy beginning to power a typical existent life application

Measuring a DC/DC convertor [ by experimentation ] how this device can help the proficient solution of low power energy job.

Problem analysis

2.1 Overview

Fig 2: Applications ( 5v ) ca n’t run with Low energy ( below threshold )

From figure-2 above, it can be observed that the applications were unable to run with low power input. Below a threshold electromotive force of the application, the application would turn off. For an illustration: If the threshold electromotive force of the application is of 3.3 V and the low power supply would hold either of the undermentioned state of affairs, the applications would non run.

Below 3.3 Volts

Normally has 5v but on occasion goes lower than 3.3 Volts

So one of the long term and feasible solution would be utilizing the DC/DC convertor like the undermentioned attack, . Here the low energy would be boosted up to the needed energy of the operating electromotive force of the application. But this DC/DC has besides some restrictions. One of them would be the sum of low input scope.

Fig 3: Applications ( 5v ) tally with energy below even threshold with DC/DC convertor

2.2 MAX756

Fig 4: DC/DC convertor circuit

The cardinal portion of the given circuit is MAX756. And the cardinal portion of MAX756 would be exchanging regulator. Here in this circuit MAX756 acts as encouragement regulator. In fact the end product electromotive force is straight controlled by the ON clip of the switch of exchanging regulator. How this controls is being explained here.

2.2.1 Switch ON

Switch is ON when pulsation from the regulator goes high. At this clip most of the current would travel through the inductance and hive awaying the energy to the inductance. By this clip the charge stored in the capacitance would let go of and the changeless electromotive force at end product remains.

Fig 5: Operationss at exchanging ( On ) manner [ 2 ]

2.2.2 Switch OFF

Switch is OFF when pulsation from the regulator is Low. At this clip the energy stored in the inductance would let go of and would bring on a contrary electromotive force across the inductance. This is known as electromotive force boot. Worsening current through the inductance makes rectifying tube as for forward prejudice. This helps Capacitor charge to a electromotive force that is higher than the input electromotive force.

Fig 6: Operationss at exchanging ( Off ) mode [ 2 ]

2.2.3 Changeless End product

If the end product electromotive force would seek to increase at that place would hold implied a less feedback electromotive force. This would impact to hold a less comparator end product, accordingly a less duty rhythm of the frequence generator and less inductive boot. Less inductive boot would bring forth less end product electromotive force.

Again when the end product electromotive force would seek to diminish at that place would hold implied a higher feedback electromotive force. This would impact to hold a high comparator end product, accordingly a high responsibility rhythm of the frequence generator and high inductive boot. High inductive boot would bring forth high end product electromotive force.

Equally good as MAX756 is runing at 500 KHz, DC end product looks really much stalls in world.

2.2.4 Calculations

Min. Duty Cycle ( D_min ) A = 1 – ( Vimax/Vomin ) [ 3 ]

Max. responsibility rhythm ( D_max ) A = 1 – ( Vimin/Vomax ) [ 3 ]

Min. Inductor size ( L ) & gt ; DA * Vin * ( 1-D ) / ( freq * 2 * Iout ) [ 3 ]

Minimum capacitance ( Cap ) & gt ; Iout / ( Vripple * freq ) [ 3 ]

2.3 Applications

2.3.1 Humidity Control

Watering the harvest Fieldss, suites need humidness measurement. Measuring the humidness needs humidness detectors to be used. T. Calculating true comparative humidness demands

Supply electromotive force,

Sensor temperature, and

Output electromotive force

Fig 7: Humidity measurement detector

The undermentioned expression to cipher the comparative humidness ( RH ) could be [ 4 ] .

Sensor RH = ( VOUTA / VSUPPLY ) – 0.16 / 0.0062, [ For 25A°C ]

True RH = detector RH / ( 1.0546 – 0.00216 T ) , where T is in A°C

True RH = detector RH / ( 1.093 – 0.0012 T ) , where T is in A°F

The device usually operates at 5 VDC. But it could run over a 4-5.8 VDC scope. At room temperature, the end product electromotive force ranges from 0.8 to 3.9 VDC as the humidness varies from 0 % to 100 % .

2.3.2 USB IPOD/mobile courser

IPOD or mobile are two most used portable devices today. These devices can be charged with USB overseas telegram though it was known that USB is largely used for reassigning informations, like scanning, publishing etc. But this UBS in this instance would be used as to bear down device straight from power beginning. In this image among four pins, merely two pins demands to be used to acquire power from the beginning. This pins are Vcc and GND. The other two D+ and D- for information pins and would be fresh.

Fig 8: Practical USB connexion ( Lone power here )

2.3. 3 Child Toy

Child playthings are likely to utilize 1,2,3,4 cell battery beginnings. A four cell battery powered toy demands 4*1.5=6 V power to acquire operated. After utilizing a plaything, kids are likely to maintain these batteries connected to this application and the batteries go discharged. So toys need a immense figure of batteries for operation. DC to DC convertor would be one of the solutions for that type of application.

2.3.4 Motion Detection and Lightening

At dark to observe gesture near place, people usually use a device with a set of visible radiation that flashes after holding some motion near. Gesture can be detected by assorted engineerings today.

One of the ways could be utilizing force per unit area detector. Among other possible ways another 1 could be utilizing microwave wireless energy. Receiver waits any reflected energy to resile back. When a individual moves through the microwave energy it changes the sum of reflected energy and trip the action of holding sensed the motion. Ultrasonic sound moving ridges can besides be used to find the gesture by reflected moving ridge [ 10 ] .

2.3.5 Automatic Door

Shops, library, canteen doors open automatically. This automatic doors needs to observe the presence of prosaic. After feeling the presence of prosaic, the door needs to acquire opened and it could hold opened by magnetic initiation and turn overing simple steeper motor for several unit of ammunitions.

Fig 9: Pedestrian Detection for automatic door

2.4 Criteria of Choosing Application

Some standard was considered for taking the right application. Main concern was decided every bit low power ingestion, another concern was the serviceability in day-to-day footing. Other one was the high frequence of serviceability in a peculiar twenty-four hours so that, though it takes little energy its entire energy ingestion goes really high for high frequence utilizing. Automation was chosen as a choice standard because of holding captivation on these types of plants. And eventually whether the application is able to commercially approvable was taken for so.

Table 1:

Comparing and analysing each standard for every application it was found ‘Automatic door ‘ the best suited application among discussed.

2.5 Selected Application

Automatic door was so selected as the application. Here to observe the presence of prosaic it needs to utilize a detector like LDR or other types of detectors. In this instance it was considered to utilize LDR for low costs. Light beginning could be placed at the conveying terminal Tx as in the fig. LDR can be used to observe whether the light beginning has been cut or non. If light beginning would cut, it would recognize that there is person is go throughing / coming towards door. Fig 10: LDR detector system

2.5.1 Premises for Application

Here some premises could be assimilated,

As a accountant, it could be used PIC18f2520 [ 5 ] .

Power demand sing for the accountant and for LDR ( detector ) , and light beginning merely.

Power would be provided merely for the MCLR PIN [ 5 ] .

LDR would take the power from pins RC0.

Light would devour power from RC1.

2.5.2 Operational Description

PIC18f2520 as a microcontroller has got 3 PORTS [ A, B and C ] . Each of the PORT has 8 pins. So there are 24 operational pins in sum. Some of them could be used every bit input every bit good as end product depending on how pins were configured. Here 0 for ‘OUTPUT ‘ and 1 for ‘INPUT ‘ . Pins can take digital every bit good as the parallel input besides.

Fig 11: PIC18f2520 uses C port for I/O.

If 3.3V or greater could be applied to any operational pins it would be in high province. Comparing the high or low province by look intoing the peculiar pin, it could be determined whether in the transition there was any prosaic or non.

2.5.3 Input Output Selection

Equally long as it was used PORT C in this instance, the constellation spot for choosing the pins would be 0b00000000 ( BIN ) or 0x00 ( HEX ) which means all the pins of port C is being used as end product. It could be 0b11111111 ( BIN ) or 0xFF ( HEX ) which would intend all the pins are input.

So as pins C0 and C1 are being used as end product for feeding LDR and the visible radiation, and end product from LDR as input goes to the 3rd pin of C2, the constellation should wish 0b00000100 ( BIN ) / 0x04 ( HEX ) or 0b11111100 ( BIN ) / 0xF4 ( HEX ) . Here pins RC-4 to RC7 were considered do n’t care in this instance.

Table 2:

So by declaring PORT C=0xF4 or PORT C=0x04 it could be configured the input and end product. Here RC3 is being as end product and its map is to give a high pulsation of 1 or low pulsation by which the door would be opened or non. 1 in pin CR3 will open door otherwise non.

2.5.4 Voltage Requirement

As accountant is the critical portion of this system the electrical features of it was taken into history.

Voltage scope of MCLR ( X ) = 4.2 V & lt ; X & gt ; =5.5 V

Operating electromotive force scope ( X ) = 2 V & lt ; X & gt ; =5.5 V

Fig 12: [ 5 ] .

2. 5.5 Current Requirement

Current demand for PIC18f2520 was excavated from datasheet, where current scope was presented for legion scope of frequence. These scopes were compiled in the signifier of table construction for different frequence scope. The Vdd in the undermentioned tabular array is input electromotive force.

Table 3: Compiled from Datasheet for 4 MHz [ 5 ] .

Table 4: Compiled from Datasheet for 1 MHz [ 5 ] .

Table 5: Compiled from Datasheet for 31 kilohertzs [ 5 ] .

2. 5.6 Power Requirement

So if the system was designed to be operated at 4 MHz, the power computation could be like the following tabular array.

Table 6: Compiled from required electromotive force of operation and Current at 4 MHz

So at temperature of 25 grades, if the input electromotive force was set to 3V in a peculiar minute, the maximal power would so be required as 3*2.7=8.1 mW. If the current is greater than 80mA, and the electromotive force at MCLR goes below the Vss, it could do latch up, that ‘s why it was recommended to utilize a resistance of sum 50-100 Ohm in series of MCLR and beginning.

Problem solutions

3.1 Analyze beginning of power

3.1.1 Solar Cell

Solar cells are photovoltaic cells made from Ge, Si. They can bring forth electricity straight from solar visible radiation. Upon heating the visible radiation in signifier of photon, silicon/ Ge atoms release the free negatrons cause bring forthing electricity. A solar cell provides direct current ( DC ) [ 6 ] .

So these types of cell can be used for bring forthing electricity while it is

Abundant in nature

Environmentally friendly

Low/no care cost

But this beginning has some restrictions excessively for practical considerations. But these are non that major sing its overall impactions.

No handiness of power at dark

Dependant on the conditions conditions

Initial cost

As it needs big infinite for installings depends on the applications.

Location of solar panel could impact the efficiency.

Not a good pick for portable device where it needs immense power ( Still now ) . Maximum Cell Power

If a solar cell of radius is 5 centimeter and if it is made of Si so the maximal power from a solar cell would be:

= Ns*Nt *PI*r2

= 0.25*0.85*1000*3.142*25*10^-4

=1.67 W

If each cells are of about 0.45 V, so current would be of 3.74 ampere. Higher Current

Connecting cells in analogue would give the higher. Possible connexion of this type of solar cell would be in fig — .

Fig 13: Parallel Connection of solar Cell Higher Voltage

Connecting cells in series would bring forth the higher electromotive force. Possible connexion of this type of solar cell would be in fig.

Fig 14: Series Connection of Cells

3.1.2 Bicycle Dynamo

Harmonizing to the Faradaies jurisprudence when a magnet is in gesture and if it is invariably cutting the magnetic flux, their current will bring forth [ 7 ] .

Fig 15: Bicycle Dynamo

A dynamo can either be A.C or D.C harmonizing to the coppices and figure of commutators used. The faster the rider rides the faster the alteration in magnetic flux and hence the more power. There are three chief sorts of bike generators. Normally a bottle dynamo can bring forth about 3W of power, 6Volt and 0.5 As. This power was adequate to illume the way while bike equitation.

Hub Generators,

Sidewall Generators, and

Drum Generators

3.1.3 Knee Brace Generator

While walking human musculuss break/slow down articulatio genuss and energy is absorbed. The new knee-brace generator helps the musculuss do this and so “ crops ” Regenerative brakes collect the kinetic energy. This knee brace harvests the energy lost when a human breaks the articulatio genus after singing the leg forward to take a measure [ 8 ] .

Using a series of cogwheels, the articulatio genus brace assists the hamstring in decelerating the organic structure merely before the pes hits the land, whilst at the same time bring forthing electricity. Detectors on the device exchange the generator off for the balance of each measure. In this manner, the device puts less strain on the wearer than if it was invariably bring forthing energy [ 9 ] . Fig 16: Biometric energy Harvester [ 9 ]

Trials of the 1.6kg device produced an norm of 5 Wattss of electricity from a slow walk and explored ways of bring forthing more electricity and found that we can acquire every bit much as 13 Wattss from walking.

3.1.4 Piezo Electric Generator

One of the most promising techniques of mechanical power harvest home is ‘Piezo Electric constituents where distortion is converted to electrical charge via direct piezo electric consequence [ 10 ] . Some stuffs generate an electric charge when placed under mechanical emphasis. Voltage created by an applied emphasis is called piezoelectric effect. Piezoelectric stuffs produce a electromotive force in response to an applied force, normally a uni-axial compressive force.

These stuffs are normally ceramics with a perovskite construction. The perovskite construction exists in two crystallographic signifiers

Tetragonal construction and

Cubic construction.

In the tetragonal province, each unit cell has an electric dipole, i.e. there is a little charge differential between each terminal of the unit cell. A mechanical distortion can diminish the

separation between the cations and anions which produces an internal field or electromotive force. The relationships between a force applied to a piezoelectric ceramic component and the electric field and charge produced by the component are: A E = – ( g33T ) , Q = – ( d33F )


Tocopherol: electric field,

g33: piezoelectric electromotive force invariable

Thymine: emphasis on ceramic component

Q: generated charge

d33: piezoelectric charge changeless Fig 17: Bending Generator [ 10 ]

F: applied force

One of the surveies [ 11 ] has shown that with a resonance frequence of 291 Hz a piezo cantilever can bring forth 96 microwatt power. Noteworthy phenomenon is that the higher the frequence the higher the power. Most curial portion here is vibrator coevals. This can be solved by utilizing spring downside of the crystal home base and a considerable mass upon the crystal.

Table 7: Data [ 11 ]

Fig 18: Voltage coevals Vs Frequency [ 11 ]

3.1.5 Energy from Vibration

Magnetic field converts the mechanical energy to electrical energy. When force per unit area is applied spiral oscillates through the magnetic field created by the lasting magnet. Passing through the flux a little electromotive force is induced in the spiral. Then this electromotive force can be used for the low power applications. Increasing the figure of bends of the spiral and the powerful magnet, power can be increased.

Fig 19: Vibration Generator [ 12 ]

From Faraday ‘s jurisprudence of magnetic attraction it was found that the electromotive force of generated electricity is

V= dI¦/dt ; [ 13 ]

B= magnetic flux denseness in teslas ( T )

I¦= magnetic flux in Webbers ( Wb )

A= Area in square metres ( M2 )

3.2 Criteria of Choosing Source

The standards of taking the beginning was taken into history for the undermentioned factors.

Whether the beginning in environmentally independent or non.Like, solar energy is non possible to reap at dark clip, at cloudy sky. Bicycle dynamo is non excessively much affected by the external environment other than go throughing through a strong magnetic field.

Whether the beginning has clip restriction. Application ca n’t be operated whole twenty-four hours if it was used as the solar power.

Whether the beginning has infinite restriction for its execution.

Whether the beginning produces electricity automatically?

Whether the beginning is more or less tantrums with the practical usage of the application chosen.

Whether the application produces the considerable sum of energy for the application

The summery of the standards could be represented by the comparing table 3. Here it was chosen by the highest figure of beginning proprietor. Piezo electric Generator and Bicycle dynamo had the same weight of 5. However Piezo electric Generator was considered for detector powering of an automatic door as because the individual ‘s force per unit area would make the energy itself so the true mechanization comes.

Table 8: Criteria analysis of taking beginnings

Problem Executions

4.1 Prescribed Power Solution

Fig 20: Prescribed simple power solution

4.1.1 Power Required for Application from Converter

Here application was considered to be operated at 4 MHz and runing temperature was considered from -40 grade Celsius to 85 grade Celsius. So application would hold required holding followerss energy evaluations.

Current: 2.5 mA – 5 ma

Voltage: 4.2 V to 5 Volts

Power: 10.5mW to 25 mW

So this specification would hold to be generated from DC/DC convertor.

4.1.2 Power Required for Converter

Among all the experiment informations, it was found when DC/DC input electromotive force is 1.25 V and the current is 29 ma and as a burden of application would utilize 1K ohm, so the application would viable to be in running manner. Other two close specifications were found that is demoing in the undermentioned tabular array. In this instance the efficiency of DC/DC convertor was found to be happen 53.65 % .

Table 9:

4.1.3 Power Produced by Source

So power beginning would necessitate to supply 1.25 V and 29 ma of current. But the specified beginning was found to be given highest of 287AµA of current with assorted electromotive force scope. This current could be produced merely when the resonance frequence would be of 569 Hz and the size of the cantilever was of 11*25.4 mm2. Here job arises how to bring forth this frequence of about 0.57 kilohertzs of frequence. Human measure ca n’t easy bring forth this type of frequence. That ‘s why the particular type of spring would necessitate to be used to bring forth the frequence for the cantilever in a suited mechanical manner.

Fig 21: Cantilever bring forthing 1.25 V with 550-569 sHz

With this constellation it would necessitate to utilize [ 29 * 1000 AµA / 287 AµA= 101.04 ] 101 of these power points at least in the tract to come in the gate. If it takes a distance of 1.5 pess between two stairss of a human the way manner would necessitate to be at least of 1.5*101 feet= 151.5 feet=50.5 paces long.

4.2 Use of Super capacitance

In this instance as because the energy from the footfalls would sum up to acquire the detector activated, a storage system would hold needed to hive away the electricity. As a storage device super capacitance was considered because it would non necessitate to alter clip to clip like as batteries.

4.3 Power Management

It was non consecutive frontward to accomplish the needed current in the application, as because the needed current is far more than that was found from a individual power generator point. So it

Fig 22: Block diagram for power agreement

was considered parallel connexion of each individual power generator points demoing in the power agreement diagram. This agreement boosts the current by taking current from each of the power points and shops in a ace capacitance. This ace capacitance is connected to a relay system that after hive awaying a peculiar sum of energy, it would acquire contacted and the discharging of the ace capacitance would hold started.

Fig 23: Block Diagram for Sensor System ( Power )

When walker would be near the detector by pressing the power points, the needed sum of power should be generated by the system and would be stored in ace capacitance. And so relay would be connected after acquiring peculiar power, allowing the ace capacitance discharge. Then Sensor would be activated. Light would acquire the power to fall over the detector. If the light gets distracted by the prosaic while his traversing the detector point and the signal

4.4 Prototype

4.4.1 Test Method

The lone manner to measure whether the convertor could bring forth the expected result was utilizing the DC power supply as power input. It was used assorted tonss including system demand of 1k ohm. Input current was measured by series connexion with the millimeter and the circuit. The other burden and input was varied to look into the stableness of the needed electromotive force end product from the convertor. At consequence subdivision it has been presented.


As application needs 2.5 ma to 5.3 mas and 4.2 V to 5 V for its operation as was stated in datasheet of the chief accountant, it was tested with assorted scopes of tonss and the inputs which can originate at existent state of affairs to bring forth the end product for the application. Some relevant end product combinations [ table -9 ] .

Iout=4.41 ma, Vout 4.41

Iout=5.36 ma, Vout 4.29

5.1 Iout=4.41 ma, Vout 4.41

This state of affairs is desirable for the application noted earlier. It was found with the input electromotive force of 1.25V and input current of 28.9, about 29 ma. Here burden was used with1 kOhm. Hence end product current would be 4.41 ma. It ‘s a theoretical operation manner of application with temperature of -43 grade to 83 grade of Celsius.

Fig 24: Iout=4.41 ma, Vout 4.41

5.2 Iout=5.36 ma, Vout 4.59

This was besides a desirable status for the application holding little current scope higher from Iout of 5.3. Here it was used with 800 Ohm [ table -9 ] . Unfortunately this grounds was non captured in a minute that could be presented here.

5.3 Probable Practical Situations

In practical sense, frequence would be variable bring forthing from spring below the cantilever ; hence the electromotive force would be varied from beginning so input electromotive force for the convertor could be changed. One of the same state of affairs was found from the informations while it was experimenting was with 1.5 input Vs direct from the DC to DC input power.

Table 10: Situation holding 1.5 Vin

It shows that, with a high frequence if the electromotive force from the beginning goes higher than 1.25 V say 1.5, the end product from beginning truly exceeds the expected scope of our application generated by the accountant in this its 5.84.

Other two repletions were experimented. With the beginning end product of 1.43V and with some changing current, though current fluctuation non likely to be happened. It shows that thought the current degree is bit close to the expected 5.82 and 6.47 [ 2.5 mas to 5.3 mas ] but the electromotive force exceeds the higher scope demoing in the undermentioned tabular array.

Table 11: Situation holding 1.43 Vin with assorted burden

Discussion of Consequences

Among assorted scope it was examined [ Appendix ] , the operable solutions were compiled in an excel tabular array below. It was found merely individual experiment that shows in tick grade that could work out the entire bundle for existent universe. As any other break was unbearable for the application and the beginning, because of holding restrictions in bring forthing power from beginning and the restriction of bring forthing power for the application by the convertor besides.

Table 12:

So in existent sense, this one is really limited, that does n’t full make full the practical effects, because beginning would bring forth variable scope of input power that does n’t fit for the application. It needs to be changeless that is non practical for the beginning.

This implies that, to do the system feasible for existent word, it would necessitate to hold some alteration to do this convertor applicable for the prescribed application with the beginning mentioned. Table 13: Expected Valuess

To stabilise the application the new design would be like the following tabular array.

Table 14: Converter Property Values ( evaluated by excel )


The successful experiments on MAX657 were made to measure the implacability of the device for a detector based application to do the detector based application independent of power beginning. Experiment reveals the limited pertinence in such application with the constellation of the circuit.

But by reconfiguring the equipments [ inductance, capacitance and Schottky diode- non calculated here though ] would do the circuit applicable to that type of application. That is how universe can salvage a immense sum of power demands for detectors in close hereafter.

Future Work

In this experiment the information was experimented indiscriminately, holding no peculiar dimension or position. While it was known the position, why and which informations should be experimented, it was late. But by now to do this application feasible merely demands few other experiments to look into whether the application is truly suits to the desired degree.

If the experiment consequences fail to turn out this device viable for broad scope, it would necessitate to refashion the design to seek to assist the universe to salvage immense power.


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