Introduction to DC-TO-DC Converter

 Introduction to DC-TO-DC Converter

DC-to-DC converters convert electrical power provided from a source at a certain voltage to electrical power at a different dc voltage.

Electrical energy, though available extensively from storage sources such as batteries, or from primary converters such as solar cells, distributed ac mains, is hardly ever used as such at the utilization end.

The electrical energy is converted at the utilization end to forms of energy as required (thermal, chemical, light, mechanical and so on).

Electrical power converter interfaces between the available source of electrical power and the utilization equipment (heaters, storage battery chargers, lamps, motors and so on) with its characteristics demands of electrical power.

The need for this interface arises on account of the fact that in most situations the source of available power and the conditions under which the load demands power are incompatible with each other.

An example of such a situation is where a 24V lead acid battery is available as the source of power and the load to be catered consists of digital circuits demanding power at 5V.

DC-to-DC power converters form a subset of electrical power converters. Both the output and input power specications of dc-to-dc converters are in dc.

Most dc loads require a well-stabilized dc voltage capable of supplying a range of required current, or a variable dc current or pulsating dc current rich in harmonics. The dc-to-dc converter has to provide a stable dc voltage with low output impedance over a wide frequency range.

These features of the dc-to-dc converter are known through the output regulation and the output impedance of the converter. Most dc sources are either batteries or derived by rectifying the ac mains.

The source voltage may vary as much as 40% in the case of batteries. It may contain substantial superimposed voltage ripple in the case of rectied supplies. Most dc sources also exhibit a nite source impedance (against the ideal of zero source impedance).

The dc-to-dc converter 

must maintain integrity of the output power in the presence of these non-ideal source characteristics. This capability of the dc-to-dc converters is known through the line regulation, ripple susceptibility, and the input impedance of the converter.

Uses Of DC To DC conversion 

High-voltage direct current

DC-to-DC converters are used in portable electronic devices such as cellular phones and laptop computers, which are supplied with power from batteries primarily. 

Such electronic devices often contain several sub-circuits, each with its own voltage level requirement different from that supplied by the battery or an external supply (sometimes higher or lower than the supply voltage). 

Additionally, the battery voltage declines as its stored energy is drained. Switched DC to DC converters offer a method to increase voltage from a partially lowered battery voltage thereby saving space instead of using multiple batteries to accomplish the same thing.

Most DC-to-DC converter circuits also regulate the output voltage. Some exceptions include high-efficiency LED power sources, which are a kind of DC to DC converter that regulates the current through the LEDs, and simple charge pumps which double or triple the output voltage.

DC-to-DC converters which are designed to maximize the energy harvest for photovoltaic systems and for wind turbines are called power optimizers.

Transformers used for voltage conversion at mains frequencies of 50–60 Hz must be large and heavy for powers exceeding a few watts. 

This makes them expensive, and they are subject to energy losses in their windings and due to eddy currents in their cores. DC-to-DC techniques that use transformers or inductors work at much higher frequencies, requiring only much smaller, lighter, and cheaper wound components. 

Consequently these techniques are used even where a mains transformer could be used; for example, for domestic electronic appliances it is preferable to rectify mains voltage to DC, use switch-mode techniques to convert it to high-frequency AC at the desired voltage, then, usually, rectify to DC. 

The entire complex circuit is cheaper and more efficient than a simple mains transformer circuit of the same output. DC-to-DC converters are widely used for DC microgrid applications, in the context of different voltage levels.