DOI : 10.17577/IJERTV5IS100029
- Open Access
- Total Downloads : 161
- Authors : Wen-Chih Yang, Yu-Hao Xu, Tong-Qing Wang, Chuan-Xiu Lan
- Paper ID : IJERTV5IS100029
- Volume & Issue : Volume 05, Issue 10 (October 2016)
- Published (First Online): 06-10-2016
- ISSN (Online) : 2278-0181
- Publisher Name : IJERT
- License:
This work is licensed under a Creative Commons Attribution 4.0 International License
Design and Tests of a Programmable Step-Up Converter for Collecting the Residual Electric Power in used Batteries
Wen-Chih Yang Yu-Hao Xu Tong-Qing Wang Chuan-Xiu Lan
Department of Electrical Engineering Taipei City University of Science and Technology
Taipei, R.O.C.
AbstractThis research aims to design and test a programmable step-up converter for collecting the residual electric power in used batteries. Used batteries may have residual electric power. The residual electric power should be recovered in order for people to use it again. The input terminal of the developed programmable step-up converter connects to used batteries and the output terminal connects to normal rechargeable batteries. The developed programmable step-up converter was able to pump the residual electric power in used batteries into normal rechargeable batteries via a pulse width modulation technique even though the used batteries voltages are lower than the normal rechargeable batteries. Therefore, the residual electric power collected by the developed programmable step-up converter can be utilized again by people. This research is effective in energy-saving and
batteries as far as possible. In this paper, the topology and the function of the developed a programmable step-up converter are presented. The results of three tests are also presented and discussed in this paper.
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DESIGN OF THE DEVELOPED CONVERTER
The developed step-up converter was based on a boost circuit. Fig. 1 depicts the function blocks of the developed step-up converter. The detail structure and functions of each component in the developed step-up converter is described as follows.
environment protection.
KeywordsStep-up converter, residual electric power, used battery.
Voltage detector
Voltage detector
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INTRODUCTION
A battery is an element for storing electric power. Currently people use various batteries to supply electricity to mobile phones, flashlights, remote controls, uninterruptible power supplies, vehicles, etc [1]. Because people use lots of batteries every day and thus create a large number of used batteries [2]. Although the used batteries are not used by people any longer, they may still have residual electric power. Perhaps the residual electric power in used batteries is not much, it deserves to be recovered due to the numbers of used
Used battery
Microprcessor
Step-up converter
Driving circuit
Rechargeable battery
DC power source
batteries. If the residual electric power in used batteries can be recovered as much as possible, it will be benefit of environment protection and energy-saving [3,4].
The method for recovering the residual electric power in used batteries is to pump this electric power into normal rechargeable batteries. To achieve this purpose, the first requirement is that used batteries voltages must be higher than normal rechargeable batteries voltages. But used batteries voltages are generally low. Their residual electric power can not be directly released to normal rechargeable batteries. Moreover, the used batteries voltages will continue to fall and the normal rechargeable batteries voltages will continue to rise during the process of pumping the residual electric power of used batteries into normal rechargeable batteries. In this situation, to recover the residual electric power is more difficult. In order to solve this problem, we developed a programmable step-up converter. The developed programmable step-up converter is able to pump the residual electric power of used batteries into normal rechargeable
Fig. 1. Function blocks of the developed step-up converter.
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The step-up converter
Fig. 2 depicts the structure of the developed step-up converter based on a non-isolated boost circuit. The developed step-up converter consisted of an inductor, an n-channel MOSFET, a fast recovery diode and a filter capacitor. The n- channel MOSFET Q is used as a switch and the inductor L is used as an energy-saving element. While the MOSFET Q conducts, the inductor L stores electric power from used batteries. Oppositely, while the MOSFET Q closes, the inductor L and the used batteries will be in series causing a higher voltage to charge the normal rechargeable batteries through the diode D. As a result, the normal rechargeable batteries can store the residual electric power in the used batteries.
IL L
IQ
D ID or
+
+ Q + C
dI L
Used
V Driving
VDS
Rechargeable
L Vout Vub
batteries
ub
– circuit
+ –
VGS
–
Vout
–
batteries
dt
where Vout is the voltage across the normal rechargeable batteries.
Fig. 2. The structure of the developed step-up converter.
The operating principle of the developed step-up is described bellow [5,6].
In this duration, the current IL is decreasing gradually. The decrease in current of the inductor L during the close of MOSFET Q is given by:
-
Mode 1:
When the MOSFET Q conducts at the time t=0, the current IL provided by used batteries flows through the inductor L and MOSFET Q. During this time the diode D is
I
Vout Vub L
toff
L
L
closed due to a reverse voltage. Fig. 3 depicts the equivalet circuit of the developed step-up converter under mode 1. The voltage across the inductor L is
where ton is the period while the MOSFET Q closes.
Assuming that the inductor current is continuous during the whole period T= ton + toff, therefore the (4) is equal to (7).
VL Vub
I I
where Vub is the voltage across the used batteries.
L L
That means
Because the voltage of the inductor L is induced from the
Vub ton Vout Vub toff
current IL, (1) can be represented as follows. L L
The duty cycle is defined as follows.
L dI L V
D ton
dt ub
T
IL L ID
Equation (2) can be rewritten as follows. +
+ C
dI L
Vub
Used
Vub
V Rechargeable
IL L
dt L
batteries
–
out
–
batteries
Used batteries
+
Vub
–
IQ +
C
Vout
–
Rechargeable batteries
Fig. 4. The equivalet circuit of the developed step-up converter under mode 2.
Substituting (9) by (10) yields:
Fig. 3. The equivalet circuit of the developed step-up converter under mode 1.
In this duration, the current IL is increasing gradually. The
in
Vub D T (Vout Vub )( 1 D )T
This can be written as:
Vout 1 Vub
crease in current of the inductor L during the conduction of MOSFET Q is given by:
-
Vub
1 D
Equation (12) represents the voltages of used batteries can be boosted via the developed step-up converter while the duty
IL
L ton
cycleis
higher than 0.5. If the duty cycle is higher, the
where ton is the period while the MOSFET Q conducts.
-
-
Mode 2:
When the MOSFET Q closes at the time t=ton, the voltage polarity of the inductor L will be reversed according to Lenz's law. In this duration, the current IL flows through the diode D and the normal rechargeable batteries. Fig. 4 depicts the equivalet circuit of the developed step-up converter under mode 2. The voltage acros the inductor L becomes
voltages of used batteries are higher, too. When the voltages of used batteries are higher than the normal rechargeable batteries, the former can charge the latter.
-
-
The microprocessor
The microprocessor employed by this research was HT46R24 produced by Holtek Inc. HT46R24 is an 8-bit RSIC microprocessor. It has 28 pins and 4-channel 8-bit PWM outputs. Fig. 5 illustrates the planning of some pins function of the HT46R24 employed by this research.
VL Vout Vub
The pin 27 (PB7) was used to produce PWM signals. The maximum frequency of PWM signals was 32 kHz. The pins 9 and 10 (PB0 and PB1) were used to receive the terminal voltages of used batteries and normal rechargeable batteries, respectively. The maximum input voltage of HT46R24 is DC 5V. Two voltage detectors were used to detect the voltages
Bridge rectifier
Bridge rectifier
Transformer
AC
source
DC 5V for microprocessor
LM7805
LM7805
across the used batteries and normal rechargeable batteries,
Dc 12V for
LM7812
LM7812
optical coupler
respectively. The feedback voltages were all send to the A/D converter inside the microprocessor HT46R24. The pins 3~6, 12~14 and 23~25 were used to control the LCD displayer.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
1
2
3
4
5
6
7
8
9
10
11
12
13
14
HT46R24
HT46R24
28
27
26
25
24
23
22
21
20
19
18
17
16
15
28
27
26
25
24
23
22
21
20
19
18
17
16
15
To driving circuit
Fig. 7. The structure of the DC power source.
To LCD displayer
To voltage detectors
To LCD
displayer
To LCD
displayer
To DC
power source
-
-
-
CONTROLLING STRATEGY FOR COLLECTING
RESIDUAL ENERGY
The voltages of used batteries and normal rechargeable batteries vary at any time while the developed step-up converter pumps the residual electric power in used batteries into normal rechargeable batteries. In order to maximize the recovering benefit, a controlling strategy for the developed step-up converter was proposed and described as follows.
Fig. 5. The planning of some pins function of the HT46R24.
-
The driving circuit
Fig. 6 depicts the structure of the driving circuit. In this research, an optical coupler 4N25 was used as a driving circuit. The driving circuit contains a light source (a LED) which converts the PWM signals from the microprocessor into light and an optotransistor, which detects incoming light and generates PWM signals with the same frequency but higher voltage level. The higher voltage level signals can drive the MOSFET Q easily.
-
The DC power source
The DC power source employed by this research contained an AC/DC rectifier, a filter capacitor and two voltage regulators, LM7805 and LM7812. Fig. 7 depicts the structure of the DC power source. The AC/DC rectifier was used to change an AC voltage at input terminal into a DC voltage. The filter capacitor was used to reduce the ripple rate of the DC output voltage of the AC/DC rectifier. The voltage regulator LM7805 was used to provide DC 5V for the microprocessor HT46R24 and the voltage regulator LM7812 was used to provide DC 12V for the driving circuit.
Firstly, both the voltages of normal rechargeable batteries and used batteries are detected simultaneously and sent to the microprocessor.
Secondly, if the used batteries voltage is lower than the normal rechargeable batteries voltage, the microprocessor produces PWM signals with a bigger duty cycle to the developed step-up converter. Then the developed step-up converter boosts the used batteries voltage. If the output voltage of the developed step-up converter is still lower than the normal rechargeable batteries voltage, the microprocessor increases PWM signals duty cycle continuously until the output voltage of the developed step-up converter is higher than the normal rechargeable batteries voltage.
Thirdly, if the normal rechargeable batteries voltage has reached its upper limit, the microprocessor stops the developed step-up converter.
Finally, if the used batteries voltage has reached its lower limit, the microprocessor stops the developed step-up converter as well.
-
-
TEST RESUTS OF THE DEVELOPED CONVERTER
To the PWM pin of microprocessor
To DC
power source
To the gate of MOSFET
The development of a programmable step-up converter has been achieved. The entity of the developed step-up converter with a LCD displayer, a DC power source, a microprocessor, a driving circuit, two voltage detectors, a normal rechargeable battery and a used battery is shown in Fig. 8. The LCD displayer was used to display the discharging states of the used battery and the charging states of the normal rechargeable battery. Both the used battery and the normal rechargeable battery were lea-acid batteries in this research. Their rating voltages and capacities were all 6V and 4Ah.
Fig. 6. The structure of the driving circuit.
r
Fig. 8. The entity of the developed step-up converter.
There are three tests adopted in this research. The work of each test was defined as follows.
Test 1: To examine the original states of the used battery and the normal rechargeable battery.
Test 2: To pump the residual electric power of the used battery into the normal rechargeable battery and examine the charging/discharging states at any time.
Test 3: To examine the latest states of the used battery and the normal rechargeable battery after a charging/discharging process.
The three tests have been carried out. The results are presented and discussed below.
-
Test 1
In this test, the used battery was disconnected from the input terminal of the developed step-up converter and the normal rechargeable battery was disconnected from the output
-
Test 2
In this test, the used battery and the normal rechargeable battery were connected to the input terminal and the output terminal of the developed step-up converter, respectively. The developed step-up converter started a charging/discharging work. The duration of the test 2 was five hours. The residual electric power in used battery was pumped into the normal rechargeable battery. Results of the test 2 have been arranged and are shown in Fig. 11 to 14.
Fig. 11 illustrates the charging states of the normal rechargeable battery in test 2. The original terminal voltage of the normal rechargeable battery was 5.2V. In order to charge the normal rechargeable battery, the output voltage of the developed step-up converter was controlled at 5.6V. The terminal voltage of the normal rechargeable battery rose gradually from 5.6V to 6.4V during a five-hour charging process. The reason was that the developed step-up converter continually pumped the residual electric power in the used battery into the normal rechargeable battery. The charging current was held at 100mA because a constant current charging method was adopted in this test.
Fig. 12 illustrates the discharging states of the used battery in test 2. When the developed step-up converter started to pump the residual electric power in the used battery, the terminal voltage of the used battery dropped from 5.0V to 4.6V immediately. The discharging current of the used battery increased gradually from 135mA to 254mA. The reason is that the terminal voltage of the used battery dropped continuously and the charging current of the normal rechargeable battery was held at constant. In order to provide enough electric power with the normal rechargeable battery, the sed battery was forced to provide increased current.
V I
terminal of the developed step-up converter. The two voltage detectors detected the original terminal voltages of the used battery and the normal rechargeable battery. They were 5.0V and 5.2V, respectively. The discharging currents of the used battery and the charging current of the normal rechargeable battery were all 0mA. Fig. 9 and 10 show the original states of the used battery and the normal rechargeable battery, respectively.
6.6
6.4
Voltage (V)
Voltage (V)
6.2
6
5.8
5.6
5.4
5.2
0 1 2 3 4 5
Time (hr)
120
100
Current (mA)
Current (mA)
80
60
40
20
0
Fig. 9. The original states of the used battery in test 1.
Fig. 10. The original states of the normal rechargeable battery in test 1.
Fig. 11. Results of the normal rechargeable battery in test 2.
V I Used battery Normal battery
6.6
6.4
Voltage (V)
Voltage (V)
6.2
6
5.8
5.6
5.4
5.2
Current (mA)
Current (mA)
0 1 2 3 4 5
Time (hr)
120
100
80
60
40
20
0
300
250
Current (mA)
Current (mA)
200
150
100
50
0
0 1 2 3 4 5
Time (hr)
Fig. 12. Results of the used battery im test 2.
Figs. 13 and 14 show the comparisons between the terminal voltages and discharging/charging currents of the used battery and the normal rechargeable battery during a five-hour charging/discharging process. The terminal voltages of the used battery and the normal rechargeable battery dropped and rose continuously, respectively. Moreover, the discharging current of the used battery increased continuously and the charging current of the normal rechargeable battery was held at constant at all time. Therefore, the two figures can demonstrate that the developed step-up converter was able to collect the residual electric power from used batteries.
Fig. 15 shows the discharging/charging power of the used battery and the normal rechargeable battery during a five-hour charging/discharging process. This figure demonstrates that the residual electric power of the used battery was surely stored into the normal rechargeable battery. The power converting efficiencies of the developed step-up converter during a five-hour charging/discharging process are also presented in Fig. 15. The efficiency dropped from 90.2% to 84.0%. The major reason was that the discharging current of the used battery increased continuously during discharging process. The larger discharging current caused more power losses in developed step-up converter. The longer the discharging time, the lower the power converting efficiency of the developed step-up converter.
Used battery Normal battery
7
6
Voltage (V)
Voltage (V)
5
4
3
2
1
0
0 1 2 3 4 5
Time (hr)
Fig. 13. A comparison between the terminal voltages of the used battery and the normal rechargeable battery in test 2.
Fig. 14. A comparison between the discharging/charging currents of the used battery and the normal rechargeable battery in test 2.
Used battery
Normal battery
Power Converting efficiency
1000
92
800
90
600
88
86
400
84
200
82
0
80
0
1
2 3
4
5
Time (hr)
Power (mW)
Power (mW)
efficiency (%)
efficiency (%)
Fig. 15. The discharging/charging power of the used battery and the normal rechargeable battery in test 2.
C. Test 3
In this test, the used battery was disconnected from the input terminal of the developed step-up converter and the normal rechargeable battery was disconnected from the output terminal of the developed step-up converter again. The two voltage detectors detected the terminal voltages of the used battery and the normal rechargeable battery to get the latest states of the two batteries. They were 3.3V and 6.0V, respectively. Fig. 16 and 17 show the latest states of the used battery and the normal rechargeable battery, respectively. The terminal voltage of the used battery in test 3 was higher than the voltage at the 5th hour in test 2. The reason was that the discharging current of the used battery in test 3 became 0mA. The voltage drop of the inner resistance in the used battery also became 0V. Therefore, the terminal voltage of the used battery increased 0.3V. Similarly, the charging current of the normal rechargeable battery in test 3 became 0mA after disconnecting from the output terminal of the developed step- up converter. The voltage drop of the inner resistance in the normal rechargeable battery also became 0V. Therefore, the terminal voltage of the normal rechargeable battery decreased 0.4V.
Fig. 16. The latest states of the used battery in test 3.
Fig. 17. The latest states of the normal rechargeable battery in test 3.
-
-
CONCLUSIONS
A programmable step-up converter for collecting the residual electric power of used batteries has been implemented by this research. The programmable step-up converter was developed based on a non-isolated boost circuit. Its output voltage magnitude could be adjusted according to the width of a PWM signal produced by a microprocessor. Therefore, the developed step-up converter could boost used batteries voltages continuously to charge normal rechargeable batteries. Three tests have been carried out by this research. The results presented in this paper have demonstrated that the developed step-up converter has the ability to collect the residual electric power of used batteries.
Up to date, people use more and more batteries and then produce numerous used batteries every year. Used batteries may have residual electric power [7]. People should collect and reuse this residual electric power. The programmable step-up converter is developed for this purpose. It is benefit of environment protection and energy-saving.
ACKNOWLEDGMENT
This research was founded by a grant provided by the Ministry of Science and Technology, Taiwan, R.O.C., under the grant number: MOST 104-2221-E-149-003.
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