Advances in Environmental Sciences, Development and Chemistry
Performance Measure of Switching Device (MOSFET)
in Photo-voltaic System
Kamala J, Janarthanan V, and Santhosh K
College of Engineering Guindy, Anna University, Chennai, Tamil Nadu, India
Abstract — Battery charging circuits utilize switching devices
for its control operations. MOSFET is used as switching device in
the charge control circuits. This paper analyze the characteristics
of Power MOSFET used to charge batteries from solar energy. N
channel and P channel MOSFET Device characteristics are
investigated for two cases of photo-voltaic system. First case study
is done with the device connected between solar panel and battery.
Second case study illustrates the performance of device in Buck
converter used as photo-voltaic battery charger. Switching losses
and efficiency of converter is analyzed for both devices. Results
and discussions of this paper are useful for the selection of
switching device and the operating frequency.
Index Terms — Buck converter, Power MOSFET, Switching
losses, Transfer characteristics.
DC-DC converter is used between solar panel and battery, if
battery voltage does not match with solar panel. Efficiency of
converter depends on the switching losses of the device.
Efficiency of converter is analyzed for various switching
frequencies applied to different types of devices. In this case,
solar panel is connected to battery through buck converter as
shown in figure 2.
I. INTRODUCTION
Photo-voltaic energy storage system uses DC-DC
converters for maximum energy transfer [1]. DC-DC
converters consist of inductance, capacitance and power
electronic semi-conductor devices [2]. Inductor and capacitor
sizing is decided by switching frequency of power electronic
components. Higher frequency leads to smaller values of
inductor and capacitor with improved output regulation [3-5].
Power electronic components are designed with low on state
resistance, fast switching rate, higher voltage and current
carrying capacity [6].
In a battery charging system, source voltage of N-MOSFET
is fixed at battery voltage and the drain current varies with
battery voltage. Therefore, conventional MPPT algorithm does
not deliver maximum current for battery charging [7]. Detailed
analysis of MOSFET characteristics in a photo-voltaic system
is required to find the switching requirements. Transfer
characteristics of the device indicate the required gate drive for
switching. It is derived by connecting the power component
between solar panel and battery, with various gate voltages, as
shown in figure 1. In this case, battery charging is possible only
if solar panel voltage is sufficiently greater than battery voltage.
N channel and P channel MOSFET transfer characteristics
curves are obtained in this paper.
Figure 2 Battery charging through power converter
Photo-voltaic energy storage system with a solar panel of
100Wp, Vmp of 17.5V, and a battery of 12V, 42Ah are
considered in the proposed research work. Section II describes
overall photo-voltaic charging system and its hardware
specifications. Section III discusses the transfer characteristics
of power electronic components connected between solar panel
and battery. Converter efficiency is analyzed in section IV for
various switching frequencies applied to different devices.
Section V discusses the results obtained with the experimental
set-up. Section VI concludes with the power component
requirement and its characteristics applied to battery charging.
II. PHOTO-VOLTAIC BATTERY CHARGING SYSTEM
Specifications of solar panel are given in Table I. Battery
charging is achieved either by connecting switch between solar
panel and battery as shown in figure 3 or by using DC-DC
converter as shown in figure 6.
TABLE I
SPECIFICATIONS OF SOLAR PANEL
Figure 1 Power MOSFET coupled between PV cell and battery
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460
Characteristics
Specification
Rated power, P
Peak power voltage, Vmpp
Peak power current, Impp
Open circuit voltage, Voc
Short circuit current, Isc
100Wp
17.5V
5A
21.4V
6A
Advances in Environmental Sciences, Development and Chemistry
Figure 3 Switch controlled Battery charger
Figure 5 Buck Converter
Important parameters of the switching device are given in
table II
TABLE II SWITCHING DEVICE PARAMETERS
IRFP150N
IRF9530
VDSS = 100V
VDSS = -100V
RDS(on) = 0.036Ω
RDS(on) = 0.3Ω
ID = 42A
ID = 12A
Charge pump circuit required for gate of MOSFET is achieved
by a driver circuit shown in figure 4. Complementary pair
switching transistors 2N2907A and PN2222A are used to
improve the drive strength of signal. Opto-isolator TLP250 [10]
is used as isolator.
Figure 6 Converter based Battery charger
HI
PN2222A
pwm-in
tlp250
1
10
1
2
3
4
10
2N2907A
TL494 [11] pulse width modulator IC is used to generate the
PWM signal of converter. Battery voltage is fed back to PWM
generator circuit, using potentiometer that can be adjusted to
vary the duty cycle of PWM signal. Frequency of PWM signal
is varied by varying the resistance of oscillator circuit. Circuit
shown in figure 7 uses resistance R13 (potentiometer) to vary
frequency and R16 to adjust the duty cycle.
pwm-out
8
7
6
5
1
0
Figure 4 Gate driver circuit
III. MOSFET TRANSFER CHARACTERISTICS COUPLED
BETWEEN PV CELL AND BATTERY
Buck converter capable of handling 500W is designed with
the following requirements
 Switching frequency = 5 MHz maximum
 Current ripple < 0.04A
 Voltage ripple < 0.01V
 Charging current = 10A maximum
 Duty cycle = 5% to 95%
Specifications of converter are given as follows and shown
in figure 5
 Input voltage : varies between 14V-20V
 Output voltage : fixed by battery voltage
 MOSFET used : IRFP150N / IRF 9530 [8,9]
 Diode used:MBR1545
 Inductance: 100µH

Capacitance: 1000µF
ISBN: 978-1-61804-239-2
HEXFET N channel power MOSFET IRFP150N and P
channel device IRF9530 are chosen to study the transfer
characteristics. Connection of MOS devices between PV cell
and battery is shown in figure 8.
In case of N channel MOSFET, higher gate voltage is required to
turn on the device, since the source is at battery potential
approximately 12V. Sufficient drain current flows through the device,
when gate voltage is greater than 16V. Gate to source voltage required
for sufficient drain current is shown in figure 9. Drain current increases
with increase in gate to source voltage.
461
Advances in Environmental Sciences, Development and Chemistry
Figure 7 PWM Generation circuit
Figure 8 MOS device connected between PV cell and battery
Figure 10 Characteristics of PMOS devices
Flow of drain current charges the battery and increases battery
voltage with drain to source voltage decreasing from 7V to 0.15V.
Maximum drain current is 5.36A with single N channel MOS device
and it is increased to 5.41A with two devices in parallel. Parallel
connection of devices reduces on-resistance of device and increases
drain current.
IV. CONVERTER PERFORMANCE WITH DIFFERENT
MOS DEVICES
Conventinal MPPT is not effective for battery charging
system, since the output voltage is at battery voltage, which is
not Vmp of PV cell. Faster Charging is achieved with higher
current flow. This paper analyzes the efficiency of converter by
varying switching frequency for different MOSFET
configurations. Input / output measurements of converter is
taken for four cases of power electronic component as given
below
 Single N channel device
 Two N channel devices in parallel
 Single P channel device
 Two P channel devices in parallel
Figure 9 Characteristics of NMOS device
In case of P channel devices, gate voltage need not be higher
than source. Gate signal can be derived from the input signal
and charge pump circuit is not required. On-resistance of P
channel MOS is higher and drain current is comparatively
reduced. Maximum drain current for this case is 5.16A with
single device and 5.3A with two devices in parallel.
Characteristic curves of PMOS device is shown in figure 10.
The efficiency of the Converter is defind in equation 1,
𝐸𝑓𝑓𝑖𝑐𝑖𝑒𝑛𝑐𝑦 =
Where,
ISBN: 978-1-61804-239-2
462
𝑃𝑜𝑤𝑒𝑟 𝑜𝑢𝑡𝑝𝑢𝑡
𝑇𝑜𝑡𝑎𝑙 𝑃𝑜𝑤𝑒𝑟 𝑖𝑛𝑝𝑢𝑡
(1)
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Output Power =Total input power-Total Power losses
Results of this analysis are shown in figure 11.
(2)
Power losses in the MOSFET is given by
Power Losses = switching power losses + Conduction losses (3)
Where,
𝑃𝑠𝑤 = (
𝑉𝑖𝑛×𝐼𝑜𝑢𝑡
2
) × (𝑇𝑟𝑖𝑠𝑒 + 𝑇𝑓𝑎𝑙𝑙 ) × 𝐹𝑠𝑤
2
𝑃𝑐𝑜𝑛_𝑙𝑜𝑠𝑠 = 𝐼𝑜𝑢𝑡
× 𝑅𝑑𝑠(𝑜𝑛) ×
𝑉𝑜𝑢𝑡
(4)
(5)
𝑉𝑖𝑛
Based on the experimental results the losses can be estimated
for a Single NMOS Device, with following parameters
𝑅𝑑𝑠(𝑜𝑛) = .036; 𝐼𝑖𝑛 = 4.79; 𝑉𝑖𝑛 = 14.39,
𝐼𝑜𝑢𝑡 = 4.89, 𝑉𝑜𝑢𝑡 12.27, 𝐹𝑠𝑤 = 1000 𝐻𝑒𝑟𝑡𝑧,
𝑇𝑟𝑖𝑠𝑒 = 200𝑢𝑠, 𝑇𝑓𝑎𝑙𝑙 = 5𝑢𝑠
𝑃𝑠𝑤 = (
14.39×4.89
2
) × (200 + 5)𝑢𝑠 × 1000 𝐻𝑍
Figure 11 Efficiency of converter with different MOS devices
Efficiency of converter with two NMOS devices is lowered
due to higher switching losses of two devices. PMOS devices
provide comparable efficiency with simple gate driving circuit.
(6)
𝑃𝑠𝑤 = 7.21 𝑊𝑎𝑡𝑡𝑠
𝑃𝑐𝑜𝑛_𝑙𝑜𝑠𝑠 = 4.892 × .036 ×
𝑃𝑒𝑓𝑓𝑖𝑐𝑖𝑒𝑛𝑐𝑦 =
12.27×4.89
14.39×4.79
12.27
= .734 𝑊𝑎𝒕𝒕𝒔
14.39
= .870 = 87%
Figure 12 Experimental Set-up
Buck Converter
Switching Device
PWM Generator
ISBN: 978-1-61804-239-2
463
Advances in Environmental Sciences, Development and Chemistry
V. EXPERIMENTAL SET UP AND RESULTS
Switched Applications, IEEE Transactions on Power Electronics,
Vol. 29, No. 2, pp. 906-919, , Feb 2011
Experimental set-up used to get results is shown in figure 12.
Drain current with Vds and PWM signal is shown in figure 13
and 14.
[6] K.C. Daly, "Power Electronic Switching Devices" [Online]
Available people.physics.anu.edu.au
[7] Nabil Karami, NazihMoubayed and RachidOutbib, "Analysis of
an irradiance adaptativepv based battery floating charger,"
presented in IEEE Photo-voltaic specialists conference 2011.
[8]
International Rectifer, [Online] Available www.irf.com
[9]
Power MOSFET, [Online] Available www.vishay.com
[10] Laszlo Balogh, Design and Application Guide for MOSFET
Gate Drive Circuits, [Online] Available www.ti.com
Fig. 13 Vds and Id
[11] Pulse Width Modulation Control circuits, [Online] Available
www.ti.com
Fig.14 PWM and Id
VI. CONCLUSION
Power electronic components play vital role in the
performance of converters. This paper analyzes various
MOSFET configurations with converter. Results show
choosing PMOS device with low on-resistance delivers better
performance with simple control circuit. N channel MOS
devices operate at maximum effeciency with complex driving
circuit.
ACKNOWLEDGMENT
Authors of this paper would like to thank for the funding
provided by the Centre for Technology Development and
Transfer, Research Support Scheme of Anna University,
Chennai.
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