Download Class Discussion 2.2

Class Discussion 2.2
Improper Application of a Voltage Divider
Kyle I. Platt
Mechatronic Systems
EAS 5407
Ohm’s Law
• V = IR
• R = V/I
– If your needed current
output goes up, you
need to step down the
voltage.
– Assuming your load
impedance is
constant.
Voltage Divider
VR
i
 R i 
V s
 N


R j
 j1 



Power
• Power is equal to the
following 3
expressions
2
P
V
R
2
I R
IV
Example Circuit
Problems that can occur:
•If one resistor fails, whole circuit fails
R1
1ohm
•Failure can occur by not using a
resistor with the correct allowable
power rating.
V1
12V
R2
1ohm
•Certain Resistive materials are a
function of voltage.
•If the supply voltage versus the
desired output voltage is to great,
the resistivity values for the
resistor can change.
Power in Voltage Divider Circuits
• If the load, R2, requires a high current and a low
voltage then the following:
– For resistors in series, current is constant
• Power rating for resistor R1 will be high
•For high current devices (operation critical), the
circuitry leading up to that load should be
designed to account for any faults in the system,
including current/voltage spikes.
Conclusions
• For power hungry devices
which are critical to the overall
operation of the deliverable, it
is recommended to use a
voltage regulator.
– Such devices are
inexpensive and are readily
available
– Such devices are designed
to account for high current
and Voltage/Current spikes
Fixed Voltage Regulator
Output
Input
Ground