A power processing unit (PPU) is a circuit device that convert an electricity input from a utility line into the appropriate

voltage Voltage, also known as electric pressure, electric tension, or (electric) potential difference, is the difference in electric potential between two points. In a static electric field, it corresponds to the work needed per unit of charge to m ...

and current to be used for the device in question. They serve the same purpose as

linear amplifier A linear amplifier is an electronic circuit whose output is proportional to its input, but capable of delivering more power into a load. The term usually refers to a type of radio-frequency (RF) power amplifier, some of which have output power mea ...

s, but they are much more efficient, since the use of linear amplifiers results in much power loss due to the use of a

resistor A resistor is a passive two-terminal electrical component that implements electrical resistance as a circuit element. In electronic circuits, resistors are used to reduce current flow, adjust signal levels, to divide voltages, bias active el ...

to change the voltage and current. Instead of using a resistor, PPUs use switches to turn a signal on and off quite rapidly in order to change the average current and voltage. In this way, they could be conflated with DC-AC converters, but the frequency at which they switch the signal on and off is a few orders of magnitude higher than that of AC signals. They are used to convert the current and voltage of both

direct current Direct current (DC) is one-directional flow of electric charge. An electrochemical cell is a prime example of DC power. Direct current may flow through a conductor such as a wire, but can also flow through semiconductors, insulators, or even ...

(DC) and

alternating current Alternating current (AC) is an electric current which periodically reverses direction and changes its magnitude continuously with time in contrast to direct current (DC) which flows only in one direction. Alternating current is the form in whic ...

(AC) signals.Ned Mohan. ''Electric Machines and Drives: A First Course.'' Minneapolis: John Wiley and Sons, 2012

Spacecraft

In the context of

spacecraft A spacecraft is a vehicle or machine designed to fly in outer space. A type of artificial satellite, spacecraft are used for a variety of purposes, including communications, Earth observation, meteorology, navigation, space colonization, p ...

, the power processing unit (PPU) is a module containing the electrical subsystem responsible for providing

electrical power Electric power is the rate at which electrical energy is transferred by an electric circuit. The SI unit of power is the watt, one joule per second. Standard prefixes apply to watts as with other SI units: thousands, millions and billions of ...

to other parts of the spacecraft. The PPU needs to be able to cope with varying demands for power output and provide that power in the most efficient manner possible. There are two main constraints placed on PPUs: *

Power generation Electricity generation is the process of generating electric power from sources of primary energy. For utilities in the electric power industry, it is the stage prior to its delivery ( transmission, distribution, etc.) to end users or its stor ...

from, for instance, a

solar array A photovoltaic system, also PV system or solar power system, is an electric power system designed to supply usable solar power by means of photovoltaics. It consists of an arrangement of several components, including solar panels to absorb and co ...

radioisotope thermoelectric generator A radioisotope thermoelectric generator (RTG, RITEG), sometimes referred to as a radioisotope power system (RPS), is a type of nuclear battery that uses an array of thermocouples to convert the heat released by the decay of a suitable radioacti ...

where power generation can vary based on external conditions. * Power utilization, which varies depending on the current internal activities performed by the spacecraft such as burst radio transmission or external demand factors like outside temperature and the need to provide heat to maintain constant internal temperature. Major considerations in building PPUs are

weight In science and engineering, the weight of an object is the force acting on the object due to gravity. Some standard textbooks define weight as a Euclidean vector, vector quantity, the gravitational force acting on the object. Others define weigh ...

size Size in general is the Magnitude (mathematics), magnitude or dimensions of a thing. More specifically, ''geometrical size'' (or ''spatial size'') can refer to linear dimensions (length, width, height, diameter, perimeter), area, or volume ...

and

efficiency Efficiency is the often measurable ability to avoid wasting materials, energy, efforts, money, and time in doing something or in producing a desired result. In a more general sense, it is the ability to do things well, successfully, and without ...

. Most PPUs process and supply

because that is what is generated by a solar array. The PPU is also responsible for

conversion and supplying the required voltage to other subsystems of the spacecraft.

References

{{reflist Spacecraft components Electrical engineering