12 | SAMLEX AMERICA INC.
Series and Shunt types
of charge controller
When the MOSFET Switch is connected in
series with the Solar Panel and the bat-
tery, the Controller is called Series Type.
When it is connected in parallel across the
Solar Panel and the Battery, it is called
Shunt Type. In Series Type, the MOSFET
Switch is kept open when the battery
is fully charged. The Solar Panel stops
supplying current during this period. In
the Shunt Type, when the battery is fully
charged, the MOSFET Switch is kept closed
to shunt (divert) the full Short Circuit Cur-
rent of the Solar Panel away from
the battery.
Advantages of Series type
of charge controller
A Series Type of Charge Controller has the
following advantages over a Shunt Type:
• Power systems experience temporary
over voltage conditions. For example,
when lightning strikes, extremely high
electrostatic energy is discharged. This
energy induces damaging high volt-
age transients in exposed and un-pro-
tected electrical circuit elements like
cables etc and these high voltage tran-
sients are fed to the electrical devices
and cause damage if the device is not
adequately protected. Solar Systems
and associated cabling are installed in
exposed locations and hence, they are
more prone to the damaging effects
of high voltage transients. Large Solar
Systems employ numerous lightning
protection devices like Lightning Rods,
Surge Suppressors, shielded cables etc.
However, in small Solar Systems, these
protections are seldom incorporated.
Because there is less system level pro-
tection, small Solar Charge Control-
lers are more susceptible to damage
by high voltage transients. Transient
Voltage Surge Suppressors (TVSS) are
used to protect the input and output
sections of the Charge Controller. The
TVSS clamps the high voltage of the
transient to a safe level. The Clamping
Voltage is seen by the MOSFET and
temporarily stresses the MOSFET. In a
Series Type of Charge Controller, the
MOSFET Switch is located between
the input terminals and the battery.
Hence, the voltage seen across the
MOSFET Switch during high voltage
transient condition is lower and is
equal to the Clamping Voltage of the
TVSS minus the battery voltage. This
produces lower stress. on the other
hand, in a Shunt Type Charge Control-
ler, the MOSFET Switch sees the full
Clamping Voltage and, therefore, it is
stressed to a higher degree.
• Less switching noise
• During charging, the Shunt MOSFET
Switch experiences higher level of
stress because it is in a high tempera-
ture, reverse bias stand-off condition
• The voltage applied across the Series
MOSFET Switch is lesser and hence, it
experiences lesser stress and is, there-
fore more reliable
SeCtIOn 3-1 |
Supplementary Information
