Hello, i have recently purchased a new Korad variable dc power supply.
I find it very useful as i can now test and see different electrical reactions, like the forward voltage of transistors or the avalanche voltage of diodes. Also just being able to power any project that i encounter.
The site advertises "heavy duty single-channel, constant-voltage and constant-current power supply with low ripple and noise.
I just want to make sure this statment is correct. There are 3 different modes on the Korad power supply.
A constant voltage, a constant current and overcurrent protection.
The constant voltage maintains the voltage by changing the current.
The Over protection current lets me set a current then when i exceed this current by giving more and more voltage, the Korad will cut itself off until I either lower the voltage or turn off the overcurrent setting.
The last one that i just learned and am a bit unsure off is the constant current. I am able to set the required current and it seems only when i go over the limit does it kick into constant current mode ( i get constant current means that it must change the input voltage to keep and constant current)
but shouldn't it also go into constant current mode also when it is under the set current? or does it only work as a regulator and not a boost converter?
I hope you guys get what I'm saying. If i set the Korad to 7 ma and i adjust the voltage higher, then eventually once i get to 7 ma the Korad will not let me adjust the voltage any higher to keep the 7ma which makes sense. But when i am at a lower voltage, let's say 4ma constant current won't be activated until i reach 7 ma. So i guess you have to be a the required amperage or higher?
Thanks and any tips or tricks so i dont ruin my new Power supply?
Thanks
You are basically correct however some clarification might help.
Overvoltage protection. This will shut down the supply (not power off) if the output exceeds the the voltage setting by some percentage. It works in both modes (CV and CC)
Constant Voltage
The supply will attempt to maintain whatever voltage you set it to until the load is too much for it to handle and then the voltage will reduce.
The current determined by the load characteristics. current = voltage / resistance or I = V / R
Constant current
The supply can only vary the voltage (as above the load determines the current) however in this mode the supply will attempt to vary the voltage until the set current is attained. Again this is within the limits of the supply.
For instance if you resistor is 100,000 ohms and you want 0.01 ma then the voltage will have to be:
V = I * R = 0.01 * 100,000 = 1000V well your supply cannot generate 1000 volts
The most is can supply is 30V so the highest current you can generate with a 100,000 ohm reisistor is
I = V / R = 30 / 100,000 = 0.0003 amps or 0.3 milliamps
The constant voltage maintains the voltage by changing the current.
No, the load determines the current. The power supply will maintain a constant output voltage regardless of the load being 5 microamps or 5 amps.
The Over protection current lets me set a current then when i exceed this current by giving more and more voltage, the Korad will cut itself off until I either lower the voltage or turn off the overcurrent setting.
Not exactly although I don’t honestly understand what you’re trying to say. The constant current setting only functions when the load current exceeds the current setting of the power supply. When this occurs, the output voltage will drop until the supply output current matches the current (I) pot setting. Turning the current pot to zero will result in zero output volts. Think about a second, it will make sense. If you don’t want any current, you cannot have any voltage.
Under no circumstances will the output voltage rise above the voltage pot setting in an attempt to meet the current pot setting. There are supplies that do behave that way but they will have a selection switch for either constant voltage or constant current mode. The unit you have is does not have that selection and the voltage output is always limited by the pot setting.
The over current protection is very simple, the device will not allow more than 5 amps to flow. If the load demands more than that, the voltage drops to keep the current at 5 amps. This means the supply can operate into a short without damaging and or overheating although the output voltage may only be a few millivolts.
WattsThat:
The over current protection is very simple, the device will not allow more than 5 amps to flow. If the load demands more than that, the voltage drops to keep the current at 5 amps. This means the supply can operate into a short without damaging and or overheating although the output voltage may only be a few millivolts.
Thanks for reponse. What you have said does make sense, but for the overcurrent protection i can also set a specified amperage and if it exceeds this cut off the output.
“Cut off the output” means drop to zero to me. Is that what you mean? If so, then no, that is not correct. The voltage drops to maintain the current. The voltage drop may be small, it may be large, it depends on output current setting and the actual load.
Think of it this way:
Constant voltage: the current varies based on the actual load.
or
Constant current: the voltage varies based on the actual load.