What is the difference between a constant voltage and a constant current power supply?

You may have seen that we sell constant voltage and constant current LED power supplies and might be wondering what the difference is. The short answer is that a constant voltage power supply keeps the output voltage constant while a constant current power supply keeps the output current constant. Below we explain further what exactly this means.

Constant voltage power supplies

Constant voltage power supplies are the most common type of power supplies. These function as a voltage source and thus provide a constant voltage. When more power is needed, the output current becomes higher, but the output voltage remains the same, often 12 or 24 volts.

Most appliances, and of course voltage-controlled LED lighting, need a voltage that stays constant. That's why constant voltage power supplies are suitable for this. This is because you connect components side by side, or in parallel. In parallel circuits, the same amount of voltage runs through each component, but each component can use a different amount of current. When choosing a constant voltage power supply, you must ensure that the output voltage matches the voltage your components need and that the output current is at least as high as the amount of current from each component added together.

Constant current power supplies

With a constant current power supply, the output current remains the same. Thus, this is a current source. When more power is needed, the output voltage becomes higher but the output current remains the same, often 350 or 700 milliamperes.

Because the output current is constant, constant current power supplies are suitable for current-controlled LED lighting. This is because you must connect them in series. In a series circuit, you connect components, such as LED lights, in series, so the - of one is connected to the + of the next. In a series circuit, the same amount of current flows through each component, but the amount of voltage each component uses can vary. The disadvantage of this is that if one component is defective, the circuit is interrupted and therefore the other components will not turn on either. You may recognize this from the lights in your Christmas tree. If you want to buy a constant current power supply, you should choose one whose output current corresponds to the amount of current your components need and whose output voltage is at least as much as the sum of the amounts of voltage your components use.