An apparatus comprising: a Direct Current to Direct Current 'DCDC' converter having a plurality of converter modules (501,502,503) each configured to convert current at a first voltage level to another voltage form wherein the converter modules (501,502,503) are configured to be dynamically enabled or disabled such that only each converter module that has been enabled converts current for an output of the DCDC converter; characterised in that the apparatus further comprises a processor and a memory having stored thereon computer-executable instructions that when executed by the processor implement a selector configured to: determine on an ongoing basis an estimated total power usage for at least one circuit being powered by the DCDC converter by: maintain a look-up table so as to identify, for each of the at least one circuit, power usage as a function of operation of the circuit; for each of the at least one circuit, determine an operating state and a resulting power usage according to the look-up table; and determine the estimated total power usage as a sum of all resulting power usages determined using the look-up table determine which converter module(s) to enable and which converter module(s) to disable based on the estimated total power usage; and dynamically enable the converter modules as load of at least one circuit being powered by the DCDC converter increases and disable converter modules as load decreases. a Direct Current to Direct Current 'DCDC' converter having a plurality of converter modules (501,502,503) each configured to convert current at a first voltage level to another voltage form wherein the converter modules (501,502,503) are configured to be dynamically enabled or disabled such that only each converter module that has been enabled converts current for an output of the DCDC converter; characterised in that the apparatus further comprises a processor and a memory having stored thereon computer-executable instructions that when executed by the processor implement a selector configured to: determine on an ongoing basis an estimated total power usage for at least one circuit being powered by the DCDC converter by: maintain a look-up table so as to identify, for each of the at least one circuit, power usage as a function of operation of the circuit; for each of the at least one circuit, determine an operating state and a resulting power usage according to the look-up table; and determine the estimated total power usage as a sum of all resulting power usages determined using the look-up table determine which converter module(s) to enable and which converter module(s) to disable based on the estimated total power usage; and dynamically enable the converter modules as load of at least one circuit being powered by the DCDC converter increases and disable converter modules as load decreases. determine on an ongoing basis an estimated total power usage for at least one circuit being powered by the DCDC converter by: maintain a look-up table so as to identify, for each of the at least one circuit, power usage as a function of operation of the circuit; for each of the at least one circuit, determine an operating state and a resulting power usage according to the look-up table; and determine the estimated total power usage as a sum of all resulting power usages determined using the look-up table maintain a look-up table so as to identify, for each of the at least one circuit, power usage as a function of operation of the circuit; for each of the at least one circuit, determine an operating state and a resulting power usage according to the look-up table; and determine the estimated total power usage as a sum of all resulting power usages determined using the look-up table determine which converter module(s) to enable and which converter module(s) to disable based on the estimated total power usage; and dynamically enable the converter modules as load of at least one circuit being powered by the DCDC converter increases and disable converter modules as load decreases.