Hi,
Here is a typical LM317 regulator circuit and layout. Nothing fancy but the layout was done using a screw type connector so that the operation of the LM317 could be changed easily for different functions such as current regulation, so it can be used as a voltage regulator, battery charger, etc., just by changing resistor values and their location on the connector. For this problem however it will only be used in the voltage regulation mode so the RCC is not used and so is open.
The circuit is shown on the top and the layout on the bottom of the drawing.
Some notes about the layout:
The layout drawing shows the placement of the parts. It's very close to real life except the heatsink is vertical.
All the wiring is done with #24 gauge wire and the longest length of wire is 8 inches or a little less, so no wires resistance is more than about 0.020 ohms.
The connections are all well soldered and the screws tight.
RCL is a direct short here, Rvs is around 1.5k but the pot + Rvs resistance totals about 2.3k.
The word "tested" appears at the top corner of the drawing, but it was only tested for use as a battery charger, not (as then) as a voltage regulator.
The heatsink is fairly large, not a tiny one.
Symptom:
Poor voltage regulation with a load like a simple resistive load. With the pot set to create 14.2 volts output (total lower resistance around 2.3k), with only a 1 amp resistive load (connected from Vout to GND) the voltage drops to 14.0 volts. That's way too much for this kind of regulator. The input voltage is 20v DC and well filtered and well regulated.
Can you find the flaw?
I can assure you that if you dont know what is wrong with this and you like to use these kinds of three terminal regulators then you will definitely want to see the solution to this. It's also very interesting within general power supply design.
Here is a typical LM317 regulator circuit and layout. Nothing fancy but the layout was done using a screw type connector so that the operation of the LM317 could be changed easily for different functions such as current regulation, so it can be used as a voltage regulator, battery charger, etc., just by changing resistor values and their location on the connector. For this problem however it will only be used in the voltage regulation mode so the RCC is not used and so is open.
The circuit is shown on the top and the layout on the bottom of the drawing.
Some notes about the layout:
The layout drawing shows the placement of the parts. It's very close to real life except the heatsink is vertical.
All the wiring is done with #24 gauge wire and the longest length of wire is 8 inches or a little less, so no wires resistance is more than about 0.020 ohms.
The connections are all well soldered and the screws tight.
RCL is a direct short here, Rvs is around 1.5k but the pot + Rvs resistance totals about 2.3k.
The word "tested" appears at the top corner of the drawing, but it was only tested for use as a battery charger, not (as then) as a voltage regulator.
The heatsink is fairly large, not a tiny one.
Symptom:
Poor voltage regulation with a load like a simple resistive load. With the pot set to create 14.2 volts output (total lower resistance around 2.3k), with only a 1 amp resistive load (connected from Vout to GND) the voltage drops to 14.0 volts. That's way too much for this kind of regulator. The input voltage is 20v DC and well filtered and well regulated.
Can you find the flaw?
I can assure you that if you dont know what is wrong with this and you like to use these kinds of three terminal regulators then you will definitely want to see the solution to this. It's also very interesting within general power supply design.
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