VI conversion

VI conversion (sometimes called EI conversion) is the name for a process used to make power supplies efficient.

The problem is that in energy terms, a fixed amount of energy at a high voltage means a relatively low current; when converted to low voltage, if the conversion is to be efficient, there must be a higher current. Similarly, a fixed amount of energy at a low voltage means a relatively high current; when converted to high voltage, if the conversion is to be efficient, there must be a lower current.

However, if a power supply takes in a given current (at the supply voltage), and wishes to produce a lower output voltage, then unless it has some way to produce more than that much output current (since otherwise the number of electrons in the current is fixed, and 'electrons out' must equal 'electrons in'), the voltage difference between the two is lost energy, lowering the efficiency.

An equivalent, but inverse problem is encountered when the output voltage needs to be higher than the input. There are a number of different design approaches that can achieve voltage conversion in an efficient manner.

One approach to VI conversion is to use a transformer, which can turn a high-voltage, low-current input into a low-voltage, high-current output. However, transformers only operate on AC.

One circuit which can do VI conversion of low current input is a buck converter.