In electronic engineering, a DC to DC converter is a circuit which converts a source of direct current (DC) from one voltage to another. It is a class of power converter. This article does not cite any references or sources. ... Direct current (DC or continuous current) is the continuous flow of electricity through a conductor such as a wire from high to low potential. ... International safety symbol Caution, risk of electric shock (ISO 3864), colloquially known as high voltage symbol. ... Power conversion is the process of converting power from one form into another. ...

Usage

DC to DC converters are important in portable electronic devices such as cellular phones and laptop computers, which are supplied with power from batteries. Such electronic devices often contain several sub-circuits with each sub-circuit requiring a unique voltage level different than that supplied by the battery (sometimes higher or lower than the battery voltage, and possibly even negative voltage). Additionally, the battery voltage declines as its stored power is drained. DC to DC converters offer a method of generating multiple controlled voltages from a single variable battery voltage, thereby saving space instead of using multiple batteries to supply different parts of the device. Cellular redirects here. ... Laptop with touchpad. ... Symbols representing a single Cell (top) and Battery (bottom), used in circuit diagrams. ...

Conversion methods

Electronic

Linear

Linear regulators drop the input voltage to a lower output voltage. They are inefficient , as they convert the dropped voltage into heat dissipation. The efficiency of an entity (a device, component, or system) in electronics and electrical engineering is defined as useful power output divided by the total electrical power consumed (a fractional expression). ... A wave that loses amplitude is said to dissipate. ...

Linear regulators are much simpler than switching DC-DC converters. However, unlike switching DC-DC converters, linear regulators cannot generate:

• higher voltages
• higher currents
• voltages of the opposite polarity

An even simpler approach to use a resistors in series with the voltage supply. That resistor and the load form a voltage divider resulting is a lower voltage. However, this method offers no regulation. Resistor symbols (non-European) Resistor symbols (Europe, IEC) Axial-lead resistors on tape. ... This article or section does not adequately cite its references or sources. ... In electronics, a voltage divider is a simple device designed to create a voltage (Vout) which is proportional to another voltage (Vin). ...

Switched-mode conversion

Electronic switch-mode DC to DC converters convert one DC voltage level to another, by storing the input energy temporarily and then releasing that energy to the output at a different voltage. The storage may be in either magnetic components (inductors, transformers) or capacitors. This conversion method is more power efficient (often 80% to 98%) than linear voltage regulation (which dissipates unwanted voltage as heat). This efficiency is beneficial to increasing the running time of battery operated devices. Drawbacks of switching converters include cost, complexity and electronic noise (EMI / RFI). Radio Frequency Interference (RFI) is electromagnetic radiation which is emitted by electrical circuits carrying rapidly changing signals, as a by-product of their normal operation, and which causes unwanted signals (interference or noise) to be induced in other circuits. ...

DC to DC converters are now available as integrated circuits needing minimal additional components. DC to DC converters are also available as a complete hybrid circuit component, ready for use within an electronic assembly. Integrated circuit of Atmel Diopsis 740 System on Chip showing memory blocks, logic and input/output pads around the periphery Microchips with a transparent window, showing the integrated circuit inside. ... An electronic circuit consisting of several different levels of components; printed circuits, semiconductors, resistors, capacitors etc. ...

Magnetic

These DC to DC converters convert one DC voltage to another by storing energy into a magnetic component (an inductor or a transformer) for a period of time (usually in the 30 kHz to 5 MHz range). By adjusting the PWM Duty Cycle (the ratio of on/off time), the amount of power transferred can be controlled. Usually, this is done to control the output voltage, though it could be done to control the input current, the output current, or maintaining a constant power. Transformer based converters may provide isolation between the input and the output. In general, the term "DC to DC converter" refers to one of these switching converters. These circuits are the heart of a switched-mode power supply. An inductor is a passive electrical device employed in electrical circuits for its property of inductance. ... Figure 1:Three-phase pole-mounted step-down transformer. ... Pulse-width modulation of a signal or power source involves the modulation of its duty cycle, to either convey information over a communications channel or control the amount of power sent to a load. ... In telecommunication and electronics, the term duty cycle has the following meanings: The duty cycle D is defined as the ratio between the pulse duration () and the period (T) of a rectangular waveform In a periodic phenomenon, the ratio of the duration of the phenomenon in a given period to... A switched-mode power supply, switch-mode power supply, or SMPS, is an electronic power supply unit (PSU) that incorporates a switching regulator — an internal control circuit that switches power transistors (such as MOSFETs) rapidly on and off in order to stabilize the output voltage or current. ...

Many topologies exist. This table shows the most common.

In addition, each topology may be: A buck converter is a step-down DC to DC converter. ... A boost converter (step-up converter) is a power converter with an output dc voltage greater than its input dc voltage. ... A SEPIC (single ended primary inductor converter) is a DC-DC converter which allows the output voltage to be greater than, less than, or equal to the input voltage. ... The buck-boost converter is a type of DC-DC converter that has an output voltage magnatude that is either greater than or less than the input voltage madnatude. ... The buck-boost converter is a type of DC-DC converter that has an output voltage magnatude that is either greater than or less than the input voltage madnatude. ... A push-pull converter is a type of DC to DC converter that uses a transformer to step the voltage of a DC power supply. ... An H-bridge is an electronic circuit which enables DC electric motors to be run forwards or backwards. ... The Flyback converter is a DC to DC converter with a galvanic isolation between the input and the output(s). ...

• Hard switched - transistors switch quickly while exposed to both full voltage and full current
• Resonant - an LC circuit shapes the voltage across the transistor and current through it so that the transistor switches when either the voltage or the current is zero

Magnetic DC to DC converters may be operated in two modes, according to the current in its main magnetic component (inductor or transformer): An LC circuit consists of an inductor, represented by the letter L, and a capacitor, represented by the letter C. When connected together, an electrical current can alternate between them at an angular frequency of where L is the inductance in henries, and C is the capacitance in farads. ...

• Continuous - the current fluctuates but never goes down to zero
• Discontinuous - the current fluctuates during the cycle goes down to zero at the end of each cycle

A converter may be designed to operate in Continuous mode at high power, and in Discontinuous mode at low power.,

Capacitive

Switched capacitor converters rely on alternately connecting capacitors to the input and output in differing topologies. For example, a switched-capacitor reducing converter might charge two capacitors in series and then discharge them in parallel. This would produce an output voltage of half the input voltage, but at twice the current (minus various inefficiencies). Because they operate on discrete quantities of charge, these are also sometimes referred to as charge pump converters. They are typically used in applications requiring relatively small amounts of current, as at higher current loads the increased efficiency and smaller size of switch-mode converters makes them a better choice. They are also used at extremely high voltages, as magnetics would break down at such voltages. A charge pump is an electronic circuit that uses capacitors as energy storage elements to create either a higher or lower voltage power source. ...

Electrochemical

A further means of DC to DC conversion in the kW to many MW range is presented by using redox flow batteries such as the vanadium redox battery, although this technique has not been applied commercially to date. A Flow Battery is a form of secondary battery in which the electrolytes are not confined to within the power cell its self. ... The vanadium redox ( and redox flow ) battery was first patented by the University of New South Wales in Australia in 1986. ...

Terminology

Step down

A converter that outputs a voltage lower than the input.

Step up

A converter that outputs a voltage higher than input.

Continuous Current Mode

Current and thus the magnetic field in the energy storage never reach zero.

Discontinuous Current Mode

Current and thus the magnetic field in the energy storage may reach or cross zero.

See also

• Switched-mode power supply

A switched-mode power supply, switch-mode power supply, or SMPS, is an electronic power supply unit (PSU) that incorporates a switching regulator — an internal control circuit that switches power transistors (such as MOSFETs) rapidly on and off in order to stabilize the output voltage or current. ...

References

• Rudy P. Severns, G. Ed Bloom (1985). Modern DC-DC Switchmode Power Conversion Circuits. Van Nostrand Reinhold. Out of Print.
• George C. Chryssis (1989). High Frequency Switching Power Supplies: Theory and Design. McGraw-Hill. ISBN 0070109516.
• Andre S. Kislovski, Richard Redl, Nathan O. Sokal (1991). Dynamic Analysis of Switching-Mode DC/DC Converters. Van Nostrand Reinhold. ISBN 0442239165.
• Yim-Shu Lee (1993). Computer-Aided Analysis and Design of Switch-Mode Power Supplies. Marcel Dekker. ISBN 0824788036.
• Abraham I. Pressman (1997). Switching Power Supply Design. McGraw-Hill. ISBN 0-07-052236-7.
• Philip T. Krein (1997). Elements of Power Electronics. Oxford University Press. ISBN 0195117018.
• Robert W. Erickson, Dragan Maksimovic (2001). Fundamentals of Power Electronics. Kluwer Academic Publishers. ISBN 9780792372707.
• Ned Mohan, Tore M. Undeland, William P. Robbins (2002). Power Electronics : Converters, Applications, and Design. Wiley. ISBN 0-471-22693-9.
• Chi Kong Tse (2003). Complex Behavior of Switching Power Converter. CRC Press. ISBN 0849318629.

External links

• A general description of DC-DC converters.
• DC-DC Converter Tutorial
• A beginner's guide to switching regulators.
• Power Electronics Books