Department of Electronic Engineeringlbms03.cityu.edu.hk/studproj/ee/2007eeych154.pdf · 8 R1-R2 Load Table 1 The component name of the whole power circuit Since the power circuit

Final Year Project 2007 (HC-04-BEECE2) Yip Chi Hong John Electronic Car Ignitor

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Department of Electronic Engineering

FINAL YEAR PROJECT REPORT

BEngECE2-2006/07-<HC>-<04 >

<Electronic Car Ignitor >

Student Name: Yip Chi Hong John Student ID: Supervisor: Professor CHUNG , Henry S H Assessor: Professor HUI, Ron Shu-Yuen

Bachelor of Engineering (Honours) in Electronic and Communication Engineering

(Part-time Evening)


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Student Final Year Project Declaration I have read the student handbook and I understand the meaning of academic dishonesty, in particular plagiarism and collusion. I declare that the work submitted for the final year project does not involve academic dishonesty. I give permission for my final year project work to be electronically scanned and if found to involve academic dishonesty, I am aware of the consequences as stated in the Student Handbook.

Project Title : Electronic Car ignitor

Student Name : Yip Chi Hong John

Student ID:

Signature

Date : 26 April 07

No part of this report may be reproduced, stored in a retrieval system, or transcribed in any form or by any means – electronic, mechanical, photocopying, recording or otherwise – without the prior written permission of City University of Hong Kong.


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Abstract

When the voltage of a car battery corrupts, it cannot be able to ignite the car

engine. Therefore, a bi-directional power converter stage is developed. It can extract

the remaining energy stored in the car battery and store it into a bank of

supercapacitor as an alternative power source. Once the voltage of the car battery falls

below the rated voltage and the car engine need to be started, the bank of

supercapacitor can act as an alternative power source to start the car engine. This

power stage consists of a boost power stage and a buck power stage. They are

combined together such that bi-directional energy flow is allowed. When a voltage

corruption of the car battery is detected, the bank of supercapacitor is charged up from

the week battery by the boost power stage and its voltage is regulated at 36V. Under

this condition, if the car engine needs to be ignited, the topology of the power stage

will turn to the buck mode. The current needed in the starting process of the car

engine is then provided by the supercapacitor as the input voltage source and the

output voltage supplied to the car engine is regulated at 12V. This power stage can be

treated as back up facilities for car engine igniting.


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Acknowledgement

I feel an immense gratitude to Professor Chung; he makes me to have idea to

finish this terrific project. He lets me to wide the view to learn more power electronic.

He always says a slogan, “Power electronic is an interesting thing.” Therefore, I also

discover the interesting thing in the power electronics.

Thanks to the senior technician Mr. MAK, W H who is at P1403. He helps me to

make some mechanical part to cell the supercapacitor and he also shares his

experience to me for power electronics.


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Table of the content Student Final Year Project Declaration..........................................................................2 Abstract ..........................................................................................................................3 Acknowledgement .........................................................................................................4 Table of the content........................................................................................................5 Introduction:...................................................................................................................7

Background:...........................................................................................................8 Objective:.............................................................................................................10

Theory and design issue of the power circuit ..............................................................11 Theory of the power circuit..................................................................................11

Boost Converter ...........................................................................................12 Buck Converter ............................................................................................15 The Driving method of the P channel Power MOSFET ..............................18 Supercapacitor..............................................................................................19

Design Issue .........................................................................................................23 The design of component value of the capacitors and the inductor.............23

Control Circuit .............................................................................................................26 Protection circuit ..................................................................................................27 Locked Relay circuit and Relay circuit................................................................28

Locked Relay Circuit ...................................................................................28 Relay Circuit ................................................................................................30

Comparator ..........................................................................................................39 Supercapacitor fully charged indicator ................................................................41 Igniting Detector ..................................................................................................42

Experimental Result.....................................................................................................44 Delay circuit in the control board ........................................................................44 The efficiency of the boost mode.........................................................................45 The efficiency of the buck mode .........................................................................47

In boost mode...............................................................................................48 In buck mode................................................................................................50

Further Improvement ...................................................................................................51 Application...................................................................................................................52 Conclusion ...................................................................................................................53 Appendix......................................................................................................................55

The designator layer of the control PCB layout...........................................57 The BOM of the power Circuit....................................................................57 The schematic of the control board..............................................................58


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The top layer of the control PCB layout ......................................................59 The bottom layer of the control PC1 layout.................................................59 The designator layer of the control PCB layout...........................................60 The BOM of the power Circuit....................................................................60

Reference .....................................................................................................................61


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Introduction:

Since Benjamin Franklin tried to know the lightning (electricity) in 17th century

[1], the development of human went up with a leap until now. People start to use this

type of energy to work efficiently. The electricity is a main energy source in our life.

With the rapid development of power electronic technology, many of the power

converters were developed. Different types of power conversion became available

such as AC-AC, AC-DC, DC-AC and DC-DC.

In 1970s’, the three basic topologies which convert DC at one level to another

level were developed in the Power Electronics Group of Caltech in California, USA:

boost, buck and buck-boost [2]. The boost circuit steps up the DC input voltage; the

buck circuit steps down the DC input voltage and the buck-boost circuit is either

stepping up or stepping down the output voltage but its polarity of the output voltage

is opposite to its input.

Nowadays, this technology of these three power circuit are still applied in our

life. Many designs are based on these three topologies as a building block and are

modified to develop other new applications. For example, the boost circuit and buck

circuit are combined together, the buck circuit is modified to from a flyback converter.

In this report, the boost circuit and buck circuit will be combined together. The

principles of this circuit will be discussed and the experimental result will be showed.


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Background:

In general, the knowledge of people accumulates for our living; the standard of

living is also advanced. The area of the activities of people increases so much.

Therefore, people need a vehicle to travel places they want. Each car contains a

battery which provides energy to start up the car-engine. However, when the car

battery is exhausted and its voltage is dipped, the car engine cannot be ignited. In

traditional, a booster cable (jumper cable) is used to connect a good battery of a car to

the dipped battery of another so at to restore the dipped battery [3]. Figure 1 shows

the connection of the dipped and good battery. In this time, the car can ignite again

and it should be sent to repairing center. On the other hand, if a good battery from

other car is not available, the cat should be towed to car-maintenance center for

repairing.


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-

Fig1. The dipped battery in the car is connected into other good condition of the battery for charging by the booster cable. [4]

Besides, no other alternative system is installed in the car which can make it

move. The car battery is still having the energy but the voltage is not high enough to

ignite the car.


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Objective:

The purpose of this project is to extract the remaining energy from the dipped car

battery and store it to an energy storage device. Therefore, the following task should

be done:

To investigate which components are suitable for used as an energy storage

device for demand of high energy density.

To investigate the circuit of the car especially on the car starter and engine.

To develop whatever power circuits are used for bi-directional power circuit of

which the efficiency should be high.

To develop a control circuit or board for controlling the power circuit.

A experimental prototype is built for investigating the operation and efficiency of

the power circuit.


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Theory and design issue of the power circuit

Theory of the power circuit

-Fig 2. The schematic diagram of the overall power circuit.

Item No. Designator name Component name

1 Q1 Power MOSFET (N-Channel)

2 Q2 Power MOSFET (P-Channel)

3 D1-D2 Ultra-fast recovery Diode

4 D4 Diode ( The large current can be passed)

5 L Inductor

6 C1 Supercapacitor (14 pieces connects in the series)

7 C2 E-capacitor

8 R1-R2 Load

Table 1 The component name of the whole power circuit

Since the power circuit is a bi-directional power-handling stage, it consists of a

boost converter stage and a buck converter stage which are combined together. The

diode D4 is operated in forward bias mode because it will let the current pass through

the D4 while the boost converter is operating. The diode D4 is operating in the

reversed bias when the buck mode is running; it prevents the current from going back


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to the source.

In each of the boost and buck mode of the power circuit shown in figure 2, they

can operate in continuous mode and discontinuous mode [5]. Since the design is

focused on the continuous mode, the following discussion is confined in continuous

of operation.

Boost Converter

Fig 3. The schematic diagram of the boost converter embedded in the overall power

circuit.

From figure 3, the battery is the input voltage source and resistor R1 is the load.

The power circuit is of boost type which is operated in continuous-conduction mode

[6]. The name of the boost converter implies that the output voltage of capacitor C1 is

always greater than the input voltage.


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Fig. 4 The schematic diagram of the operation of the boost converter.

From figure 4, in state 1 (Ton), the switch Q1 is on and connected to ground, then

the diode D1 will be reversed biased. The output is isolated. In this time, the battery

supplies the energy to the inductor L through the D4.

In state 2 (Toff), the switch Q1 is opened, the D1 will be forward biased, so the

output is connected to L again and received the energy from L as well as from the

input.


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In the continuous mode

Fig 5. The voltage and current waveform of the boost converter are showed. [7]

In ideal case shown in the figure5, the voltage (Vs) across Q1 is low when the Q1

is on, then current of L (IL) will be increased, IL increases due to the current of the

source (Is) provides the energy to inductor. No current flow to the output through the

diode, the current of the diode (ID) is zero. Then when the Q1 is off, the Vs across Q1

is high, IL will be decreased since the stored energy will release to the load. Is is zero

because of the open of Q2. Therefore, the voltage of the output (Vo) keeps constant.

Moreover, the voltage of the inductor (VL) depend on the (Vi-Vo), the waveform of

VL is really following the VL=Vi-Vo


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Buck Converter

The name of the buck converter implies that the voltage of capacitor C2 is always

smaller than the voltage of capacitor C1.

In Continuous Mode

D1

R1

L

C1

Q2

D2Q1C2

R2

D1

R1

L

C1

Q2

D2Q1C2

R2

D4

D4

Load

Source

Fig. 6 The schematic diagram of the buck converter embedded in the overall power

circuit.

From figure 6, the voltage of capacitor C1 is the voltage source, R2 is the load.

The power circuit is converted into buck converter which is also operated in

continuous-conduction mode [6].


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D1

R1

L

C1D2Q1C2

R2

D4

Q2

D1

R1

L

C1D2Q1C2

R2

D4

Q2

+-

+ -

State 1

State 2

Fig. 7 The schematic diagram of the operation of the buck converter.

From figure 7, in state 1 (Ton), the switch Q2 is on, the Q2 is connected to the

inductor L, then the diode D2 will be reversed biased. Therefore, the input capacitor

C1 supplies the energy to the load (R2) as well as the inductor L. In this time, the

battery supplies the energy to the inductor L through diode D4.

In state 2 (Toff), the switch Q2 is opened, the D2 will be forward biased. The

direction of the inductor current remains unchanged. Thus, the inductor current will

flow through diode D2 and the inductor will still transfer the energy to the load again.


Page 17


Fig. 8 The voltage and current waveform of the buck converter are showed.[8]

In ideal case of the buck circuit shown in figure 8, when the Q2 is on, the current

of L (IL) will be increased. Since the energy is stored in the inductor directly, the

voltage of inductor (VL) is high. When the switch Q2 is off, IL will be decreased since

the energy stored in L will release to the load. Therefore, the voltage of the output (Vo)

keeps constant. Moreover, the input voltage (Vi) and the voltage of the diode D2 (VD)

are following the Q2, the voltage of the inductor (VL) depend on the (VD-Vo), the

waveform of VL is really following the VL=VD-Vo


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The Driving method of the P channel Power MOSFET

Fig. 9 The driving method of the P channel Power MOSFET

The N-channel Power MOSFET used in the boost converter is driven directly by

the PWM controller. However, the method of driving of the P-channel Power

MOSFET in the buck converter is totally different. Due to the different feature of

these two modes of converters, in figure 9, by using an N-channel Power MOSFET

U103, the P-Channel Power MOSFET U101 can be driven. Also U103 will be driven

by the PWM controller.


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Supercapacitor

Fig. 10 The photo of an ultra-capacitor is showed [9].

Why the supercapacitor is selected to be used in the power circuit? It is because

the supercapacitor has a property of higher energy density compared with

general-purpose capacitor. Also, its equivalent series resistance (ESR) is very low. For

example, The ESR of a supercapacitor with capacitance 650F is 1.15mΩ [10]. It can

sustain high charging and discharging current. On the other hand, its recharging cycle

is over one million times [10]. Its lifetime is longer than the re-chargeable battery.

The target output voltage is 36V, however, a piece of supercapacitor can be only

charged to 2.7V. The 14 pieces of the supercapacitors could be connected in series. In

figure 11, the 14 pieces of the supercapacitors from a bank of the supercapacitor.


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Fig. 11 The two banks of the supercapacitors

Although a series of the supercapacitors can be connected together, the voltage

of each supercapacitor may not be the same. If one of supercapacitors is over voltage,

it may explode. Thus, they need a balance circuit which balances the voltage of each

capacitor in the capacitor-bank. [11]


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Fig. 12 Balance circuit Layout[12]

Fig. 13 The two banks of the supercapacitors [13]

Figure 12 shows the layout of the balance circuit. As shown in figure 12, the


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position 2 and + wire pad and – wire pad are marked. The marking names also appear

in figure 13, since a balance circuit board is the same as a piece of PCB in the figure

12.

The balance circuit board 1 can control Ca and Cb; the balance circuit board 2 can

control Cb and Cc; the balance circuit board 3 can control Cc and Cd. From Figure 13,

the balance circuit consists of an operation amplifier, voltage divider and a negative

feedback resistor. The voltage divider provides an input to the op amplifier. The bank

of the supercapacitor can be configured to equally divide the voltage from the voltage

divider. The feedback information relating the capacitor voltage and another input of

the op amplifier provide the feedback information back to the negative feedback

resistor. If the voltage of one of the supercapacitor is different from the others in this

manner, the op amplifier input will be unbalanced. When the input of voltage divider

and feedback are not matched, the op amplifier will provide the current. Thus it

causes the higher voltage supercapacitor to transfer to lower voltage one.


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Design Issue

The design of component value of the capacitors and the inductor

In the buck mode, the values of the capacitors and the inductor are estimated.

D1

R1

L

C1D2Q1C2

R2

Q2+-

Vout

Iout Idisc9V Car battery

IL

Fig. 11 The schematic diagram of the buck converter embedded in the overall power circuit.

From figure 11, assume the weak battery is 9V. The assumed voltage of the super

capacitor is 36V.

Suppose:

Switching frequency fs: 5 kHz

Output current Iout: 10A

Output voltage Vout: 12V

Discharge time of the super capacitor C1: 5s

The voltage of super capacitor C1 in 5s Vdrop: 9V

The ripple voltage of capacitor C1 Vripple: 1V

The ripple current of inductor IL ΔI: 1A


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The duty ratio of switch Q2 at full voltage of C1 is

31

3612

VVD

1C

outbuck ===

The estimated inductor L is

( ) mH6.115000

31

31136

IfDD1VL

s

buckbuck1C =×

⎟⎠⎞

⎜⎝⎛ −

=Δ

−=

The estimated capacitor C2 is:

( ) F2515000m6.18

31

31136

VfL8DD1VC 2ripple

2s

buckbuck1Cout μ=

×××

⎟⎠⎞

⎜⎝⎛ −

=×××

−=

The duty ratio of switch Q2 at full voltage of C1 is

2512

VVD

1C

outbuck ==

The estimated inductor L is

( ) H124815000

2512

2512125

IfDD1VL

s

buckbuck1C μ=×

⎟⎠⎞

⎜⎝⎛ −

=Δ

−=

The estimated capacitor C2 is:

( ) F251500012488

2512

2512125

VfL8DD1VC 2ripple

2s

buckbuck1C2 μ=

××μ×

⎟⎠⎞

⎜⎝⎛ −

=×××

−=


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The current Idisc and IL are shown in figure 12.

Figure 12. The discharge current and the inductor current

Use the duty ratio 12/25 to estimate the size of the super C1.

The average discharge equals to:

A8.425

1210VVIIin

outoutavg_dis =

×==

For 10s, the voltage of the super capacitor C1 drop 16V

The size of the C1 estimated as

F316

108.4V

tIC

drop

avg_disc1 =

×=

Δ=


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Control Circuit

Control Circuit

Igniting Detector

Supercapacitor fully charged

indicator

PWM controller

Locked Relay Circuit

Relay

Power Circuit

VccBoost Circuit

Buck Circuit

Buck Gate Control Signal

Output voltage sensing

Delay Circuit

Relay Circuit


Protection Circuit

Soft starting Circuit

Relay


Boost Gate Control Signal

Gate Control Signal

Figure 13. The overall block diagram of the control circuit

Figure 13 gives an overview of the control circuit. The gate signal controlling the

power switch in both of buck and boost mode is provided by the PWM controller. The

function of relay circuit is to select the modes of operation (i.e. the buck and boost

mode) by changing the connection of the gate signal and output voltage sensing signal

to the boost or buck stage. Also, it can provide the indication of the fully charged

status of the bank of supercapacitors and detect the dip of the battery voltage when the

voltage of battery is lower than 9V (by the igniting detector) during the ignition

process of the car.


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Protection circuit

Fig. 14 The Block diagram of the protection circuit.

In figure 14, the first part of the control circuit is the protection circuit. It

prevents the control circuit from destroying by short circuit. In this control board, if

all function is operating, the current should not be greater than 300mA. Therefore, the

current rating the fuse is designed at 500mA. Although the input current has a little

fluctuation, it will not be burned and it can protect the control board.


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Locked Relay circuit and Relay circuit


Fig. 15 Relay circuit is controlled by the Locked relay circuit

The aim of the Locked Relay Circuit shown in figure 15 is to force the relay in

on state. It prevents the relays from switching on and off alternatively during charging

the supercapacitor. Thus, a simple circuit design shown in figure 15 is proposed which

can replace the locked relay circuit. It consists of two switches. When both of the


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switches are closed, the coil of winding in relays K1, K2 and K3 are energized. The

system is selected to be operated in boost mode as shown in figure 16.


R21LED1Vcc

Q1B_9V

D2

R20

C_BUCK_DTBoost_DTBuck_N-GBoost_N-G

Feedback

Gate_O

Relay K1

D4

R7

Boost_N-S

Buck_DT

Boost_N-G

C_Buck_DT

( Connected to GND )

R5LED2Vcc

Q4L_9V

Relay K3

D3

R22

Buck_N-S

Buck_P-S

Buck_N-G

Buck_P-G


R22LED3Vcc

Q3B_9V

Relay K2

Relay Circuit

1kΩ

100Ω

100Ω

1kΩ

100Ω

1kΩ

Fig.16 The relay circuit is on by controlling the locked relay circuit


Page 30

Relay Circuit

The next part of discussion is focused on the relay circuit. In Relay Circuit, when

the relays are on, the LED1, LED2 and LED3 will be lighted up. Resister R7, R20 and

R22 provide a path for releasing the energy of the coils in relay. It prevents the relay

from holding on and cannot be turned off. Diodes D1, D4 and D3 are connected in

parallel to the coil of relays K1, K3 and K2 respectively. They will protect the

transistors Q1, Q4 and Q3 respectively from damaging as the back EMF of the

coil-inductance of the relays K1, K3 and K2 may destroyed the transistors Q1, Q4 and

Q3 in their on-state.

Fig.17 The relay circuit for Relay K1


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Figure 17 shows the Relay circuit K1. The terminal marked with “Feedback” is

connected to the output voltage sensing pin of the PWM controller. The terminal

marked with “Boost_DT” is connected to the feedback signal of the output voltage of

boost stage. The terminal marked with “C_Buck_DT” is connected to the terminal

“Buck_DT” shown in figure 18. This terminal is then connected to the feedback

signal of the output voltage of the buck stage. The feedback signal of the output

voltage of the operating converter stage is selected by the relay K1. The terminal

marked with “Gate_O” is connected to the gate-control pin of the PWM controller.

When the terminal “Gate_O” is connected to the terminal “Buck_N-G”, the gate drive

signal given by the PWM controller is connected to gate terminal of the power

MOSFET of the buck stage. When the terminal “Gate_O” is connected to the gate

terminal “Boost_N-G”, the gate drive signal given by the PWM controller is

connected to the gate terminal of the power MOSFET of the boost stage. The

transistor Q1 can drive the Relay K1 depends on the voltage level connected to the

terminal “B_9V”. If the control pin B_9V is high, the Q1 is turned on and the coil of

the relay K1 is energized.


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Fig.17a The relay circuit for Relay K1 in the buck mode

As shown in figure 17a, when the power circuit is operated in buck mode, the

terminal “feedback” is connected to terminal “C_Buck_DT” and the terminal

“Gate_O” is connected to the terminal “Buck_N-G”.

Fig.17b The relay circuit for Relay K1 in boost mode.

As shown in figure 17b, when the power circuit is operated in boost mode, the

terminal “feedback” is connected to the terminal “Boost_DT” and the terminal

“Gate_O” is connected to the terminal “Boost_N-G”.


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Figure 18 shows the Relay circuit K3. The terminal marked with “Boost_N-G” is

connected to the gate terminal of the N-Channel Power MOSFET in boost stage. The

terminal marked with “Boost_N-S” is connected to the source of the N-Channel

Power MOSFET in boost stage. The transistor Q4 can drive the relay K3 on or off

which depends on the voltage level connected to the terminal “L_9V”. If the control

pin L_9V is high, the Q4 is turned on. The coil of relay K3 will be energized.


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Fig.18a The relay circuit for Relay K3 in buck mode

As shown in figure 18a, when the circuit is operated in buck mode, the terminal

“Boost_N-G” is connected to the terminal “Boost_N-S” which is connected to ground.

By using this connection, the unwanted turn-on of the N-channel MOSFET used in

boost stage can be avoided. At the same time, the terminal “C_Buck_DT” is

connected to the terminal “Buck_DT” so as to sense the output voltage of the buck

stage.


Page 35

Fig.18b The relay circuit for Relay K3 in boost mode

As shown in figure 18b, there is no connection between the terminals

“Buck_DT” and “C_Buck_DT” when the circuit system operates in boost mode.



Page 36

Figure 19 shows the Relay circuit K2. The terminal “Buck_N-G” is connected

the gate terminal of the N-Channel Power MOSFET used in buck stage. The terminal

“Buck_P-G” is connected to the gate terminal of the P-Channel Power MOSFET used

in buck stage. The terminal “Buck_N-S” is connected to the source terminal of the

N-Channel Power MOSFET used in buck stage. The terminal “Buck_P-G” is

connected to the gate terminal of the P-Channel Power MOSFET used in the buck

stage. The transistor Q4 can drive the relay K2 on or off depends on the voltage level

connected to the terminal “B_9V”. If the control pin B_9V is high, the transistor Q4 is

turned on and the coil of the relay K2 is energized.

D3

R22

Buck_N-S

Buck_P-S

Buck_N-G

Buck_P-G


R22LED3Vcc

Q3B_9V

Relay K2

100Ω

1kΩ

Fig.19a The relay circuit for Relay K2 in buck mode

As shown the figure 19a, there is no connection between the terminals

“Buck_N-G” and “Buck_P-G” when the circuit is operated in buck mode.


Page 37

Fig.19b The relay circuit for Relay K2 in boost mode

As shown in figure 19b, when the circuit is operated in boost mode, the terminal

“Buck_N-G” is controlled to the terminal “Buck_N-S” of the boost stage which is

connected to ground. The terminal “Buck_P-G” is connected to the terminal

“Buck_P-S” of the boost stage. The unwanted turn-on of the P-channel MOSFET can

be avoided.


Page 38

PWM controller

Fig.21 TL494 block diagram [14]

By using the PWM controller TL494, its oscillating frequency can be found from:

TTosc CR

1.1f =

n68R1.1kHz5

T

=

RT = 3235.29

The PWM controller provides the gate drive which can drive the Power

MOSFET. It has an error amplifier which can perform close-loop control so as to

regulate the output of the power stages. It can generate an internal reference of 5V. If

the voltage of the feedback is more than 5V, the gate control signal will be off. The

dead time of the PWM signal used for the gate driving can also be adjusted [14].


Page 39

Comparator

The comparator is used to make a comparison between two input signals (input

voltage and the reference voltage). The output of the comparator must be pull-high

and it can provide a self-defined voltage output.

Vin can be determined as follow:

⎟⎠⎞

⎜⎝⎛

+×=

2R1R2RVV ccin

The reference voltage is set at 5V in this case.

Fig.22 Circuit 1 of the comparator

In figure 22, for circuit 1, if the input voltage (Vin) is larger than the reference

voltage, the output is high and vice versa.


Page 40

Fig.23 Circuit 2 of the comparator

In figure23, for circuit 2, if the input voltage is smaller than reference voltage,

the output is high and vice versa.


Page 41

Supercapacitor fully charged indicator

R10

R11

5V

36v

V36V_out

R8

9V-12V

+-

Q2

R9

36V

R16

62kΩ

10kΩ

3kΩ

100Ω

2W470Ω

VR650kΩ

Fig.24 Supercapacitor fully charged indicator

By using the circuit 1, the output voltage which is larger than 36V can be

detected by comparing the scaled voltage with the reference voltage of 5V.

⎟⎠⎞

⎜⎝⎛

+×=

11R10R11RVV outcomparsion

V5k10k62

k10V36Vcomparsion =⎟⎠⎞

⎜⎝⎛

Ω+ΩΩ

×=

Therefore, if the voltage of supercapacitor is charged to 36V, the indicating LED

will be lighted up. VR6 is an alternative component for accurately adjusting the

charge-up voltage level.


Page 42

Igniting Detector

R15

R14

5V

9V

V12V_0ut

R8

+-

9V-12V

3kΩ

VR5100kΩ

39kΩ

51kΩ

Fig.25 Igniting Detector

In figure 25, the reference voltage is set to 5V and the input voltage can be

changed by tuning the variable resistor VR5. If the input voltage is smaller than 5V,

the comparator output will be high. If the input voltage is larger than 5V, the

comparator output will be low.

VR5 is an alternative component for accurately adjusting feedback voltage level

of the battery. When the voltage of the battery falls below 9V, the operation of the

system will switch from boost mode to buck mode.

The calculation below should how the variable resistor can give us a selection of the

input voltage of the comparator.

⎟⎠⎞

⎜⎝⎛

+×=

14R15R14RV9Vin

V1.5Vk51k39

k51V9V

in

in

=

⎟⎠⎞

⎜⎝⎛

Ω+ΩΩ

×=


Page 43

Delay Circuit

Fig.26 Delay Circuit

In figure26, the delay circuit is made by simple RC circuit.

The Delay time can estimate by the calculating the time constant RC

s1.0F1000)100(CRt 8181 =μ×Ω==

s22.0F2200)100(CRt 9192 =μ×Ω==

21total ttt +=

s22.0s1.0t total +=

s32.0t total =


Page 44

Experimental Result

Delay circuit in the control board

Fig. 27 The delay time between the buck converter and boost converter

Channel 1: Buck mode Channel 2: Boost mode

As shown in figure 27, the predicted delay time is 320ms. The measured delay

time is 300ms. The estimation agrees with the experimental result.


Page 45

The efficiency of the boost mode

Fig. 28 Channel 1: Vin = 5.75V

Channel 2: Iin = 9.90A Channel 3: Vout = 5.82V Channel 4: Iout = 1.65A x2 =3.3A So the efficiency

925.56206.19

IVIV

PP

inin

outout

in

out =••

==η =33.73%


Channel 2: Iin = 10.2A Channel 3: Vout = 7.91V Channel 4: Iout = 1.68A x2 =3.36ASo the efficiency

728.675776.26

IVIV

PP

inin

outout

in

out =••

==η =39.24

Fig. 30

Channel 1: Vin = 7.39V Channel 2: Iin = 10.2A Channel 3: Vout = 10.0V Channel 4: Iout = 1.67A x2 =3.34ASo the efficiency

378.754.33

IVIV

PP

inin

outout

in

out =••

==η =44.3%



4432.83714.51

IVIV

PP

inin

outout

in

out =••

==η =62%


Page 46

Fig. 32

Channel 1: Vin = 11.7V Channel 2: Iin = 9.93A Channel 3: Vout = 32.3V Channel 4: Iout = 1.67A x2 =3.34ASo the efficiency

181.116882.107

IVIV

PP

inin

outout

in

out =••

==η =92.86%



153.120564.115

IVIV

PP

inin

outout

in

out =••

==η =96.18%

The efficiency is ranged from 62-96%. According to the shown figures, the

efficiency is high in the boost mode.


Page 47

The efficiency of the buck mode

Fig. 34 Channel 1: Vout = 14.5V

Channel 2: Iout = 2.98A Channel 3: Vin = 34.4V Channel 4: Iin = 1.11A x2 =2.22A So the efficiency

368.7621.43

IVIV

PP

inin

outout

in

out =••

==η =56.58%



76.71355.43

IVIV

PP

inin

outout

in

out =••

==η =60.42%

Fig. 36

Channel 1: Vout = 14.4V Channel 2: Iout = 2.94A Channel 3: Vin = 25.8V Channel 4: Iin = 1.29A x2 =2.4A So the efficiency

564.66336.42

IVIV

PP

inin

outout

in

out =••

==η =63.60%



142.65896.40

IVIV

PP

inin

outout

in

out =••

==η =62.78%

The efficiency is ranged from 62-63%. According to the shown figures, the

efficiency is high in the buck mode.


Page 48

In boost mode

Fig. 38

Channel 1: PWM for the gate of N-Channel Power MOSFET

Channel 2: Inductor current Channel 3: Vout Channel 4: Iout

Fig. 39 Channel 1: PWM for the gate of

N-Channel Power MOSFET

Channel 2: Inductor current Channel 3: Vout Channel 4: Iout The operating frequency is 5.17k Hz The positive duty is 87.86%


Fig 40. The voltage and current waveform of the boost converter. [7]

The waveforms are similar to the ideal case.


Page 49

Fig. 41 The signal of the Boost converter Channel 1: PWM for N-Channel Power MOSFET Channel 2: Inductor current

Channel 3: Vout Channel 4: Iout

In the final part of the boost mode, it needs to keep the output voltage at 35.2V, it

will use the a little current to charge the supercapacitor.

The time taken for the voltage of supercapacitor charged to the desire voltage

level in boost mode is about 20mins.


Page 50

In buck mode

Fig. 42

Channel 1: PWM for the gate of N-Channel Power MOSFET

Channel 2: Inductor current Channel 3: PWM for the gate of

P-Channel Power MOSFET

Channel 4: Iout = Discharging from the supercapacitor

The operating frequency is 5.17k Hz The positive duty is 44.69% for the gate of N-Channel Power MOSFET. The positive duty is 44.69% for the gate of P-Channel Power MOSFET.

Fig. 43 Channel 1: PWM for the gate of

N-Channel Power MOSFET

Channel 2: Inductor current Channel 3: PWM for the gate of

P-Channel Power MOSFET

Channel 4: Iout = Discharging from the supercapacitor

Since the voltage is too low that cannot provide enough voltage to drive up the MOSFET.


Fig. 44 The waveform of the voltage of Q2 and the current of L in the buck converter. [8]

The waveforms are similar to the ideal case.


Page 51

Further Improvement

The control system can be implemented by a MCU. Moreover, the circuit could

be designed to operate at the higher switching frequency such as 20k Hz so as to

reduce the charging time of the supercapacitors. Furthermore, at high frequency

operation, the audible noise emitted from the inductor can be eliminated and the size

of the inductor can be reduced.


Page 52

Application

Recently, the idea of the environment protection is considered frequently. The

hybrid vehicle is better than a conventional vehicle since it can reduce the wasted

energy [15]. The investigated power circuit in this project is the hybrid energy storage

system (HESS). It can be installed in vehicles. Thus, it can mix fuel and HESS for the

car.

Also, it can act as a support system in uninterruptible power supply (UPS). Since

the circuit design in this project is bi-directional, it can use another control circuit to

release the energy to source when there is energy shortage occur at the source.


Page 53

Conclusion

In this project, an experimental prototype of proposed bi-directional power

circuit is built and tested. It is observed that the supercapacitors can be charged up to

the required voltage level in the boost mode of operation. The time taken for the

charging process is about 20 minutes. The operation of the boost mode is then

switched to the buck mode with a delay time of 300ms. It is also observed that the

supercapacitors can successfully deliver the energy to the load in the buck mode

operation. Based on the experimental result, it can be shown that the functions of the

proposed system are realized. Therefore, the proposed system can be used in an

energy backup system due to high energy density of the supercapacitor. It is very

useful for the future since the HESS will be used more in future.


Page 54

Fig. 45 The photo of the control PCB

Fig. 46 The photo of the bi-direction Power circuit


Page 55

Appendix

The schematic diagram of the Power board


Page 56

The top layer of the Power board

The bottom layer of the Power board


Page 57

The designator layer of the control PCB layout

The BOM of the power Circuit

Item Qty Part Name Description

1 1 DIODE_MR756

2 3 DIODE_MUR460

3 1 FUSE_SOCKET_13A

4 4 M3_HOLE

5 1 MBR3045_POWER_RECTIFIER

6 2 N_MOSFET

7 1 PCAP200-500U_B 2200uF

8 8 POWER_TERMINAL_DG46G_300V_25A

9 1 P_MOSFET

10 2 R1/4W_FYP 3K

11 1 R1/4W_FYP 51K

12 1 R1/4W_FYP 39K

13 1 R1/4W_FYP 4K7

14 1 R1/4W_FYP 15K

15 8 TERMINAL_2PIN

16 1 VRES-TOP-ADJ_FYP

17 1 VRES-TOP-ADJ_FYP 100K


Page 58

The schematic of the control board


Page 59

The top layer of the control PCB layout

The bottom layer of the control PC1 layout


Page 60

The designator layer of the control PCB layout

The BOM of the power Circuit

Item Qty Part Name Description Item Qty Part Name Description

1 4 2N2222 17 1 R1/4W_FYP 100K

2 5 CAP_FYP 0.1u 18 1 R1/4W_FYP 1M

3 1 CAP_FYP 0.001u 19 1 R1/4W_FYP 47K

4 1 COMPARATOR_LM393 20 1 R1/4W_FYP 51K

5 4 DIODE_IN4001 21 1 R1/4W_FYP 39K

6 1 FUSE_SOCKET_A 22 6 R1/4W_FYP 100

7 3 JUMPER_2P 23 1 R1/4W_FYP 620K

8 4 LED 24 1 R2W_FYP 470

9 4 M3_BRASS_POST 25 3 RY5W-K

10 1 NAND_4011B 26 2 SW_LOCK

11 2 PCAP200-500U 27 6 TERMINAL_2PIN

12 2 PCAP200-500U_B 28 2 TERMINAL_3PINS

13 3 R1/4W_FYP 5K1 29 1 TL494_FYP

14 1 R1/4W_FYP 4K7 30 2 VRES-TOP-ADJ_FYP 50K

15 3 R1/4W_FYP 1K 31 2 VRES-TOP-ADJ_FYP 500K

16 2 R1/4W_FYP 3K


Page 61

Reference

1) http://code-electrical.com/historyofelectricity.html

2) http://www.steve-w.dircon.co.uk/fleadh/mphil/history.htm

3) http://www.answers.com/topic/booster-cable

4) http://www.answers.com/topic/jump-starting-jpg

5) http://en.wikipedia.org/wiki/Boost_converter

6) Power Electronics: Converters, Applications, And Design, 3rd Edition, Mahan,

Undeland, Robbins

7) http://en.wikipedia.org/wiki/Image:Boost_chronogram.svg

8) http://en.wikipedia.org/wiki/Image:Buck_chronogram.svg

9) http://www.maxwell.com/ultracapacitors/products/large-cell/bcap0650.asp

10) http://www.maxwell.com/pdf/uc/datasheets/MC_Cell_Energy_1009323_rev5.pdf

11) integration_kit.pdf from Maxwell

12) integration_kit_manual_1008233_rev2.pdf from Maxwell

13) US patent 6806686.pdf

14) TL494 datasheet of Fairchild, Motorola and OnsemiConductor

15) http://en.wikipedia.org/wiki/Petroleum_electric_hybrid_vehicle

16) Handout from

17) Power electronics 3rd ed. McGraw-Hill, 1993./ Cyril W. Lander.


Page 62

18) Power electronics handbook 3rd ed. Oxford [England] ; Boston : Newnes, 1997/

Fraidoon Mazda.

19) Basic principles of power electronics Berlin : Springer-Verlag, c1986./ Klemens

Heumann.

20) An introduction to power electronics 2nd ed. Chichester [West Sussex] : Wiley,

c1993./ B.M. Bird, K.G. King, D.A.G. Pedder.

21) Power integrated circuits: physics, design, and applications New York:

McGraw-Hill, c1986./ Paolo Antognetti, editor.

22) HKIVE Power Electronic Lecture Handout

23) EE4101 Modern Power Electronics Lecture Handout by Professor CHUNG ,

Henry S H

24) T.I. Application Report SLVA001D - December 2003 − Revised February 2005

25) Engineering Faculty MSc. Course Handout

26) MC_Cell_Power_1009361.pdf from Maxwell

27) relaydrv.pdf from http://www.standards.org.au/

28) IRFP32N50K datasheet

29) IRF9240 datasheet

30) RY12W-K datasheet

31) LM393 datasheet


Page 63

32) MUR460 datasheet

33) MBR3045 datasheet

34) HEF4011BN datasheet

35) 2N2222 datasheet

Documents

Department of Electronic Engineeringlbms03.cityu.edu.hk/studproj/ee/2007eeych154.pdf · 8 R1-R2 Load Table 1 The component name of the whole power circuit Since the power circuit