DC-to-DC converter

A DC-DC converter, also known as DC-DC converter, DC-DC converter English, designates an electric circuit which converts a voltage supplied to the DC input voltage into a DC voltage with higher, lower or inverted voltage levels. The reaction is carried out by using a periodically operating the electronic switch and one or more energy storage devices. DC-DC converters are one of the self -commutated converters. In the field of electrical power engineering, they are also known as DC-DC converter.

The inductance used for the intermediate storage of energy ( inductive transducer ) consisting of a coil and a converter transformer. In contrast transducer with capacitive storage ( capacitive transducer ) are referred to as charge pumps. Charge pumps are used when either - inductors are not available, or when so little output is required, that the use of the expensive coil over the cheap capacitors are not worth it - as in integrated circuits.

  • 3.1 capacitors

Applications

DC-DC converters are part of switching power supplies, with which much more consumers as PC power supplies, notebooks, mobile phones, small motors, hi-fi equipment. be operated. The advantages over linear power supplies are in better efficiency and less heat. Especially the former plays in the conversion of a battery voltage a major role, since the battery life is much higher in a switching power supply: For a linear voltage regulator or a resistor, however, the drop across the series resistance is converted into waste heat. The switching losses occurring during the switching power supply, however, are much lower.

In addition to its purpose as a clocked voltage converter voltage regulator also serves as a filter to keep especially in high power applications the negative impact as low as possible to the power grid ( so-called phase effect ). An example is the active power factor correction (PFC).

DC - DC converters are also offered as a fully encapsulated converter modules, which are partly intended for direct mounting on printed circuit boards. The output voltage may be smaller, equal to or greater than the input voltage depending on the design. Best known are the modules which translate a low voltage on an isolated low voltage. Enclosed DC - DC converters are available for insulation voltages from 1.5 kV to 3 kV and are used to power small consumer in DC networks such as at 24 V in industrial plants or to 48 V in telecommunications or range of electronic components, for example, 5 volts for digital circuits or ± 15 volts for operation of operational amplifiers.

DC-DC converter for high output voltages (eg electronic flash unit ) are also called transverter.

In the electric power engineering and drive technology DC-DC converter are referred to as DC-DC converter. The differences relate primarily to the use and power range. As a switch, referred to in the field of energy technology as valves, while power MOSFET, IGBTs and thyristors are used. DC-DC converter can be used in this application area as a combination in the form of two-or four -quadrant controller. Following this terminology refers to the simple DC chopper as Einquadrantensteller.

Topologies ( basic circuits )

DC-DC converters are classified according to various criteria and divided into different topologies. The assignment of each topology to the main groups forward converter principle flyback converter principle and resonant converter principle is not uniformly established in the literature.

The parameter D in the voltage range column specifies the pulse width factor, which ranges from 0 to 1 may be. The voltage is the input voltage UE with a valid range in relation to the output voltage UA and the gear ratio.

Resonant converter

A custom class represent the resonant converter dar. They are divided into two major groups:

  • For performance applications over 1 kW upwards, with the aim to minimize the power loss during the switching operations in the switching transistors. This resonant converters come in two variants, which are controlled either always switched only at the zero crossing of the voltage or only at the zero crossing of the current. The power-transmitting path, including the transformer forming a resonant circuit with additional capacitance and inductance that determines the switching frequency fixed at these converters.
  • For very compact power supplies less power in the range of some 10 W, which have to make do with a minimum number of components and construction are very cost sensitive. The advantage is to not need a separate resonant circuit, and control of additional electronic components. Examples of use are also referred to as an inverter power supply for cold cathode tubes and energy saving lamps.

Is common to the two groups, that in the switching power supply, no separate oscillator must be present, but the energy transfer components, such as the transformer, if present, are part of the resonant circuit.

Multi- phase converter

Here, each within the above concepts ( topologies ) a plurality of groups, each consisting of a switch connected with the associated inductors, in parallel, the individual elements is controlled in a fixed sequence, but are controlled in accordance with consuming. This principle is known from the three-phase current. The number of phases and links is limited only to the particular structure. The grouping improves the performance and the seamless supply of current flow. Top dead center of each transducer are replaced by a phase-shifted other of the driven group.

Therefore, the characteristics of the transducer change:

  • Increasing the current capability
  • Reduction of the residual ripple (ripple )
  • Reduction of the required capacities
  • Reduction of interference due to lower switching frequencies relative to the strength of the output current

Components in the DC voltage converter

Capacitors

DC-DC converter in the power supply required in general capacitors, which are typically carried in the form of electrolytic capacitors. This requires the capacitor types with a low series resistance (ESR) due to the voltage reserve and adequate surge voltage. Alternatively, the reduction of ESR by parallel connection of electrolytic capacitors can be made.

In DC-DC converter on the main boards in the vicinity of large consumers as the main processor (CPU) can also audible sounds occur in multilayer ceramic chip capacitors ( MLCC). According to periodic low-frequency load variations and intermodulation products they depend as sounds like a whistling or hissing sound perceptible and various influences, such as the structure of the DC-DC converter and its operating parameters. The cause is weak and in this case unwanted piezoelectric effects in the used ceramic materials of Keramikondensatoren that lead to mechanical vibrations.

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