The question "Do I need to use a regulated power supply with my xxx..." comes up occasionally. The following is an explanation of some of the characteristics of regulated and non-regulated power supplies.
Older linear units still contain a simple transformer, rectifier and capacitor arrangement, but also contain a regulator to eliminate the issues outlined above. Depending on the type of regulator employed in the design, the power supply may generate a fair bit of heat when supplying high current.
Newer units are of the switchmode type. In general these are much more efficient and therefore run much cooler than the equivalent linear types. They are also often available with a universal input voltage range. (usually 90V - 260V, 47Hz - 63Hz)
Line Regulation
This is where the output voltage varies with the mains voltage supply. Although Australia has a nominal 230Vac 50Hz power grid, the actual voltage arriving to your home varies. It can be anywhere between 220Vac and 260Vac depending on your location, time of day, etc. Since an unregulated power supply is not much more than a transformer (with a fixed input to output ratio), rectifier and capacitor, the output voltage will also vary with the input voltage. This is not too much of a problem in most cases as the variations are a fairly small percentage.Load Regulation
This is where the output voltage varies with the current drawn from the output. As an example, the output voltage of an unregulated 12V, 500mA PSU might be close to 12Vdc when you are drawing the full 500mA, but could rise to as high as 17V - 20V with no load. If the manufacturer of the connected device has used components with (for example) a 16V maximum voltage rating and the device only draws 100mA, '''the device may be damaged by the excessive supply voltage'''. The other issue is that the device may use an internal regulator to drop the 12V down to a lower voltage for part of the circuit. If the input voltage is considerably higher than specified, the regulator may (depending on its design) dissipate a lot more heat than it was designed to and be damaged or shut down unexpectedly.Output Ripple
Due to its very simple nature, an unregulated power supply may also have a lot of 50Hz (or 100Hz) ripple on the output. This is because the transformer and rectifier charge up a capacitor on every half cycle of the AC voltage. The capacitor attempts to hold the DC output voltage constant between cycles, but at higher current draw the output voltage can become "lumpy". If the device being powered is designed to be used with a regulated power supply, this ripple bleed through into the circuitry. This may cause erratic operation of digital equipment or audible hum and noise in audio equipment.Regulated Supplies
Regulated power supplies fall into two categories.Older linear units still contain a simple transformer, rectifier and capacitor arrangement, but also contain a regulator to eliminate the issues outlined above. Depending on the type of regulator employed in the design, the power supply may generate a fair bit of heat when supplying high current.
Newer units are of the switchmode type. In general these are much more efficient and therefore run much cooler than the equivalent linear types. They are also often available with a universal input voltage range. (usually 90V - 260V, 47Hz - 63Hz)