Shunt Regulator
Shunt Regulator
Find out about the uses of shunt regulators and dump load controllers in renewable energy applications
electronics | electric circuitA
Shunt Regulator is a small electronic component that
clamps a power supply
voltage at a
fixed level. Hundreds of times per second the shunt regulator checks the voltage, and if the voltage is over the
limit then any extra voltage is dissipated as heat through a
resistor or other
dump load. If the supplied voltage is below the set maximum, then
no current passes through the resistor.
Using Shunt Regulators
How can
shunt regulators be useful to
alternative energy generators. Well, for example, a
PV solar panel rated at
12V will actually generate up to 20V in full sunshine. If this panel is to be connected
directly to equipment requiring an input of 12V, that equipment could be damaged - particularly if it draws only a small current and if it contains sensitive electronics. Therefore, by passing the solar panel's generated current through a
shunt regulator circuit, the voltage reaching the equipment can be
clamped at 12V* very accurately.
Rather than dumping any excess generated
power into a
resistor and losing it in the form of dissipated heat, it is possible to put it to better use, for example diverting it to heat or pump water. In such a situation the shunt regulator may also be called a
dump controller since the circuit decides when incoming power (from a
wind turbine or solar panel) should be
dumped - for example into an
immersion heater element.
Shunt regulators are an essential part of any
Solar Charge Controller
*
An alternative way to obtain a fixed 12.0V from a solar panel is to use a 12 Volt Regulator.
Shunt Regulator Components
A common
shunt regulator used in many
solar and other applications is the
LM431 (aka
TL431). This is a
3-terminal adjustable shunt regulator which can have its
output voltage clamped to any value
between 2.5 and 36V by the correct selection of two resistors. This component is available for sale in the
REUK Shop:
buy LM431.
Click here to view the
TL431 programmable shunt regulator datasheet (PDF).
Build a Complete Dump Controller Circuit
The following link to
Hurd Solar takes you to a comprehensive circuit diagram for a dump / shunt controller which will protect a
battery from being
overcharged (and therefore damaged). Unassembled
controller kits are available for sale ($12) or you can purchase the
components and put one together following the detailed assembly instructions and parts lists on that website.
For people in the UK, all required
components are available for sale at
Rapid, and
Maplin.
Article Last Modified: 15:13, 19th Aug 2008
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