There are two types of electrical current – alternating and direct. Known as AC and DC, the two have different applications. The former is the power supplied to your home or business and is currently powering any air-conditioner, heater or fan you may be using. DC is the current in the computer you are using, since it is used for powering electronic devices such as smartphones, televisions and hi-fi amplifiers.
Because of this, sometimes AC needs to be converted to DC. But DC may also need to be converted to a different voltage. Here’s a look at current and voltage conversion practices – and how DC converters save lives.
Converting AC to DC
Since the current supplied by the electrical grid is AC, all the devices that use DC must have a converter inside them. These AC DC converter circuits are usually small and built in to the device or a ‘wall wart’ (e.g. a laptop). When a large piece of DC equipment is used, a dedicated DC converter must be used. The core of any AC to DC converter is its rectifier, which takes alternating current and passes it through a diode, a device that only permits the flow of electricity in one direction. Alternating current takes its name from the fact that during generation the current flow constantly changes direction. To power electronic devices with microchips inside the current must flow only one way – hence ‘direct current’ – and this is what the diode achieves.
Voltage stabilisers for current regulation
There are also times when a DC source is unsteady and needs to be converted to a reliable constant voltage. This can be the case with batteries – the source of any mobile DC supply – which can output a varying amount of charge that subsequently interferes with the equipment it is powering. DC converters can be paired with voltage stabilisers which provide a continuous, regulated supply of power over the life of the battery. This doesn’t mean the battery will never lose its charge, but its gradually diminishing capacity over time will not affect voltage-sensitive equipment.
Stepping down the DC current: DC to DC converters
A DC to DC converter system changes the voltage of a DC current. This is necessary in car sound systems where the 12V battery source needs to be converted to a lower voltage to power a CD player or charge a smartphone. Conversely, step up converters turn the 1.5V of a battery to a stable 5V to power an MP3 player, or boost a car’s 12V to the 40V needed by its stereo amplifier.
Isolated DC converters: A question of safety
There are two types of DC converters, isolated and non-isolated. Non-isolated converters have no barrier between the incoming current and the outgoing.
This is fine when the ratio between the voltages is low or when the risk of the current escaping the device is not high. But imagine a piece of electronic hospital equipment that has leads connected to a patient that carry monitoring signals. The DC converter that supplies the extremely low voltage to the leads needs to be isolated from the original current for critical safety reasons.
If the voltage contained in a device is allowed to escape from a DC converter, the results can be electrical failure and damage to the equipment or even a risk to life. For example, if the low voltage in a USB interface was not isolated from the 240V available at the power source, the results of a malfunction would be catastrophic for you the next time you went to use the USB device.
DC converters are a vital component not only in voltage conversion but in the safety of any DC electrical circuit.
