Tuesday, 16 October 2012

Test Equipment --- Electronic Dummy Load

The most common thing or rather the most frequent thing we circuit designer generally do is design Power Supply to power our circuits. In recent times where there is a buck load of battery driven devices power consumption becomes more important. Gone are those days where using a simple circuit to implement a linear regulator like 7805 which wastes about 5W of power to deliver 1W a rough approximation which can go worse depending on application. The increased power dissipation not only drains more and more battery life but also the heat sink size increases immensely. Here comes the application of rather complex switched mode power supplies.
    However designing either kind the power supply unit must be tested through out its entire range. This piece of test kit exactly does that. Thanks to Dave from EEVblog for this design. If you haven't checked EEVBlog do check it.

Variable electronic dummy load 
What is it?                               :                    A variable electronic dummy load is basically a constant current sink where the value of the sinking current can be set by the user. Once the sinking current is set the device will continue to draw the same current from the test device.
Where it is used?                    :                    It is used to test various power supplies, linear as well as switched mode to check whether the designed power supply really does cater for the whole load range.
Why use it?                             :                    Power supplies can also be tested by connecting a power resistor in series with its output terminal and noting the current through and voltage across it. Now to test the power supply for the entire load range one must have an inventory of numerous values of power resistors and test them individually. This is cumbersome. Here the electronic load comes into play. With just a turn of a potentiometer the user can emulate various power resistor values with ease.