HUGO
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Design and Development
From Wikipedia, the
free encyclopedia
An H-bridge is
an electronic circuit which enables a voltage to be
applied across a load in either direction.
These circuits
are often used in robotics and other applications to
allow DC motors to run forwards and backwards. H-bridges
are available as integrated circuits, or can be built
from discrete components.
The term "H-bridge" is derived
from the typical graphical representation of such a
circuit. An H-bridge is built with four switches (solid-state
or mechanical). When the switches S1 and S4 (according
to the first figure) are closed (and S2 and S3 are open)
a positive voltage will be applied across the motor.
By opening S1 and S4 switches and closing S2 and S3
switches, this voltage is reversed, allowing reverse
operation of the motor.
Using the nomenclature above, the switches
S1 and S2 should never be closed at the same time, as
this would cause a short circuit on the input voltage
source. The same applies to the switches S3 and S4.
This condition is known as shoot-through.
The H-Bridge arrangement is generally
used to reverse the polarity of the motor, but can also
be used to 'brake' the motor, where the motor comes
to a sudden stop, as the motor's terminals are shorted,
or to let the motor 'free run' to a stop, as the motor
is effectively disconnected from the circuit.
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