The operation method of DC regulated power supply:
Turn on the power switch first and set the current. Because the output terminal needs to be short-circuited when setting the current, in order to prevent the current impact, first reduce the voltage to about 1Ⅴ, and then short-circuit the output terminals of the power supply together. At this time, the voltage of the voltmeter will drop to around zero volts. And the ammeter starts to display the current value.
Adjust the current to around 1.8A by coarsely adjusting the current knob, and then finely adjust it to 1.8A. Separate the positive and negative poles of the output to end the short-circuit state. At this time, the current disappears and the voltage returns to the state before the setting.
The next voltage adjustment is relatively simple, just adjust the two voltage knobs to adjust the voltage to 12.6V.
It is conditional for this kind of power supply to achieve constant current or constant voltage. It is not that there is a defect in the power supply function, but it is determined by Ohm's law. For example, the above 12.6V and 1.8A, when the load power connected to the power supply is small, the current does not reach 1.8A, and the power supply output is in a constant voltage state. At this time, the current changes from 0 to 1.8A, and 12.6V will remain constant. The current setting has no effect.
If you want to continue to increase the output voltage, you will find that when the current reaches 1.8A, the voltage cannot be raised any more, because the power supply has entered a constant current state since then.
But when the load power increases and the current exceeds 1.8A, for example, a 5Ω high-power resistor is connected. According to Ohm's law U/R=l, 12.6Ⅴ ÷ 5Ω= 2.52A, since the current has been set to 1.8A, the output voltage of the power supply will be actively lowered to 9Ⅴ (1.8Aⅹ5Ω) to meet the requirements of the set current. It can be seen that it is impossible to achieve constant current and constant voltage at the same time, that is, constant current is not constant voltage, and constant voltage is not constant current.
This constant current function is very useful when measuring LED light sources. For example, when measuring 1W lamp beads, the current can be set to 0.3A, and the voltage can be set to 4~5V (slightly higher than ⅤF). If the voltmeter shows 3.15Ⅴ, which is the ⅤF value of the lamp bead, the light source or lamp bead can be easily classified and screened.
