A DC-to-DC converter is an electronic circuit or an electromechanical device that converts a DC direct current from one voltage level to another. This is a type of electric power converter. The power levels range from very low (small batteries) to very high (high voltage power transmission).
Video DC-to-DC converter
Histori
Prior to the development of power semiconductors and allied technologies, one way to convert DC supply voltages to higher voltages, for low power applications, is to convert them into AC by using vibrators, followed by step-up transformers and rectifiers. For higher power electric motors are used to drive the desired voltage generator (sometimes combined into a single "dynamite" unit, the motor and generator are combined into one unit, with one winding that drives the motor and the other produces an output voltage). This is a relatively inefficient and expensive procedure used only when there is no alternative, such as to turn on car radios (which then use thermionic valves/tubes that require much higher voltage than those available from 6 or 12 V car batteries). The introduction of power semiconductors and integrated circuits makes it economically feasible to use the techniques as described below, for example to convert DC power supplies into high-frequency ACs, using transformers - small, lightweight, and inexpensive because of high-frequency-to change voltage, and fix back to DC. Although in 1976 car radio reception transistors did not require high voltage, some amateur radio operators continued to use vibrators and dynamics supplies for mobile transceivers requiring high voltage, even though available power supplies were available.
While it may be possible to lower the lower voltage from a higher by linear electronic circuit, or even resistor, this method discards its excess as heat; energy-saving conversion is only possible with a solid-state switch-mode circuit.
Maps DC-to-DC converter
Usage
DC to DC converters are used in portable electronic devices such as cell phones and laptop computers, which are supplied with power from the battery mainly. Such electronic devices often contain several sub-circuits, each with its own voltage level requirements different from that provided by the battery or external supply (sometimes higher or lower than the supply voltage). In addition, the battery voltage decreases as the stored energy is drained. Switched DC to DC converter offers a method to increase the voltage from a partially lowered battery voltage thus saving space rather than using multiple batteries to achieve the same.
Most DC to DC converter circuits also regulate the output voltage. Some exceptions include a high-efficiency LED resource, which is a type of DC to DC converter that regulates current through LEDs, and a simple charge pump that doubles or multiplies the output voltage.
DC to DC converters are developed to maximize energy harvesting for photovoltaic systems and for wind turbines called power optimizers.
The transformer used for voltage conversion at the main frequency of 50-60 Hz should be large and heavy for power over several watts. This makes them expensive, and they experience energy losses in their scrolls and because of eddy currents at their core. DC-to-DC techniques using transformers or inductors work at much higher frequencies, requiring only much smaller, lighter, and less costly wound components. Consequently this technique is used even when the parent transformer can be used; for example, for household electronics appliances it is preferable to fix the voltage to DC, use the switch-mode technique to convert it into high-frequency AC at the desired voltage, then, usually, fix to DC. All complex circuits are cheaper and more efficient than simple electrical transformer circuits of the same output.
Electronic conversion
Electronic converter is practical using switching technique. DC-to-DC converter Switched mode converts one level of DC voltage to another, which may be higher or lower, by storing the temporary input energy and then releasing that energy to the output at different voltages. Storage may be a magnetic field storage component (inductor, transformer) or an electric field storage component (capacitor). This conversion method can increase or decrease the voltage. Conversion conversion is more power efficient (often 75% to 98%) rather than linear voltage regulation, which removes unwanted power as heat. Semiconductor devices rapidly rise and fall times are required for efficiency; However, this fast transition combines with the effects of parasitic layouts to create challenging circuit designs. The higher efficiency of the switched-mode converter reduces the heatsinking required, and increases the battery life of portable equipment. Efficiency has increased since the late 1980s due to the use of power FETs, which can switch more efficiently with lower switching losses at higher frequencies than bipolar power transistors, and use more complex drive circuits. Another notable improvement in DC-DC converters is to replace the flywheel diodes with synchronous rectification using power FET, which is "at much lower resistance", reducing switching losses. Prior to the wide availability of power semiconductors, low-power DC-to-DC synchronous converters consist of electro-mechanical vibrators followed by voltage transformer transformers that supply vacuum tubes or semiconductor rectifiers, or rectifier rectifiers to vibrators.
Most DC-to-DC converters are designed to move power in only one direction, from special input to output. However, all switching switching topologies can be made in two directions and are capable of moving power in any direction by replacing all diodes with independently controlled active rectifiers. The two-way converter is useful, for example, in applications requiring vehicle regenerative braking, where power is supplied to the wheel while driving, but is provided by the wheel during braking.
Even though they require several components, switching the converter is electronically complex. Like all high-frequency circuits, the components must be carefully determined and physically arranged to achieve stable operation and to maintain switching noise (EMI/RFI) at acceptable levels. Their costs are higher than linear regulators in dropped voltage applications, but their cost has decreased with advances in chip design.
DC-to-DC converters are available as integrated circuits (ICs) that require some additional components. Converter is also available as a complete hybrid circuit module, ready for use in electronic assemblies.
Linear regulators used to produce independent DC outputs stable from input voltages and output loads from higher but less stable inputs by removing excess volt amperes as heat, can be described literally as DC-to-DC converters, but these are unusual usage. (The same can be said about a simple voltage drop resistor, whether it is stable or not by the following voltage regulator or Zener diode.)
There is also a simple capacitive voltage doubler and a Dickson multiplier circuit using diodes and capacitors to multiply DC voltages with integer values, usually giving only small currents.
Magnetic
In this DC-to-DC converter, energy is stored periodically in and out of the magnetic field in the inductor or transformer, usually in the frequency range from 300 kHz to 10 MHz. By adjusting the voltage filling cycle (ie the on/off time ratio), the amount of power transferred to the load can be more easily controlled, although this control can also be applied to input currents, output currents, or to maintain constant power. The transformer-based converter can provide isolation between input and output. In general, the term DC-to-DC converter refers to one of these switching converters. These circuits are the heart of the mode-switched power supply. Many topologies exist. This table shows the most common.
In addition, any topology may be:
- Hard switched
- The transistor switches quickly when exposed to full voltage and full current
- Resonant
- The LC circuit forms the voltage on the transistor and the current through it so that the transistor changes when the voltage or current is zero
The magnetic DC-to-DC converter can be operated in two modes, corresponding to the current in its main magnetic component (inductor or transformer):
- Continue
- Current fluctuates but never goes down to zero
- Discontinuous
- The current fluctuates during the cycle, down to zero at or before the end of each cycle
The converter can be designed to operate in sustainable mode at high power, and in the discontinuous mode at low power.
The half-bridge and flyback topology is similar in energy stored in the magnetic core that needs to be removed so that the core is not saturated. The power transmission in the flyback circuit is limited by the amount of energy that can be stored in the core, while the forward circuit is usually limited by the I/V switch characteristics.
Although MOSFET switches can tolerate full simultaneous currents and voltages (although thermal and electromigration pressures may shorten MTBF), bipolar switches generally can not necessarily require the use of a snubber (or two).
High current systems often use multiphase converters, also called interleaved converters. Multiphase regulators can have better ripple and better response times than single-phase regulators.
Many laptops and desktop motherboards include interleaved buck regulators, sometimes as voltage regulators.
Capacitive
Switched capacitor converters rely on alternately connecting capacitors to inputs and outputs in different topologies. For example, an activated capacitor converter converter may charge two capacitors in series and then release them in parallel. This will produce the same output power (less than the efficiency lost below 100%), ideally, half of the input voltage and twice the current. Because they operate on different amounts of charge, this is also sometimes referred to as pump charge converters. They are usually used in applications that require relatively small currents, because at higher currents, increased efficiency and smaller size of switch mode converters make it a better choice. They are also used at very high voltages, because the magnets will be damaged at such voltages.
Electromechanical conversion
A set of generators, especially for historical purposes, consists of electric motors and generators combined together. A dynamotor combines the two functions into one unit with a coil for the motor and a generator function wrapped around one rotor; both coils have the same outer coil or magnet. Usually the motor coil is driven from the commutator on one end of the shaft, when the generator winds the output to another commutator at the other end of the shaft. All rotor and shaft assemblies are smaller in size than a pair of machines, and may not have an open propulsion shaft.
The motor-generator can convert between a combination of DC voltage and AC voltage and phase standard. The large set of motor generators is widely used to convert a number of industrial power while smaller units are used to convert battery power (6, 12 or 24 V DC) into high DC voltages, which are required to operate the vacuum tube equipment (thermionic valve).
For low power requirements at higher voltages than those provided by vehicle batteries, vibrators or "buzzer" power supplies are used. The vibrator oscillates mechanically, with contacts that change the polarity of the battery many times per second, effectively converting DC into square wave AC, which can then be fed to the required output voltage transformer. It makes a distinctive buzzing noise.
Electrochemical Conversion
A further tool from DC to DC conversion in kilowatts to the megawatt range is presented using redox flow batteries such as vanadium redox batteries.
Chaotic behavior
DC-to-DC converters are subject to various types of chaotic dynamics such as bifurcation, crisis, and intermittence.
Terminology
- Step-down
- Converter where output voltage is lower than input voltage (like buck converter).
- Step-up
- Converter that outputs voltage higher than input voltage (such as converter increase).
- Continuous current mode
- Currently and thus the magnetic field in inductive energy storage never reaches zero.
- Uninterrupted mode
- The current and thus the magnetic field in the inductive energy storage can reach or traverse zero.
- Noise
- Electrical noise and unwanted electromagnetic signals, usually switch artifacts.
- RF noise
- Switching converters inherently emit radio waves at their switching and harmonic frequencies. Switching converters that produce triangular current switching, such as Split-Pi, forward converter, or? Uk converter in continuous current mode, resulting in less harmonic noise than other switching converters. RF noise causes electromagnetic interference (EMI). The acceptable rate depends on the requirements, e.g. proximity to RF circuits requires more oppression than just complying with regulations.
- Input noise
- The input voltage may have non-negligible noise. In addition, if the converter loads the input with the sharp end of the load, the converter can output RF sound from the supplying power line. This should be prevented by proper filtering in the input stage of the converter.
- Output output
- The output of the ideal DC-to-DC converter is a constant and flat output voltage. However, the real converter produces a DC output superimposed on some level of electrical noise. Switching converter produces switching noise at switching and harmonic frequencies. In addition, all electronic circuits have some thermal interference. Some sensitive radio and radio frequency circuits require a power supply with little noise so that it can only be provided by a linear regulator. Some analog circuits that require a relatively low-noise power supply can tolerate some of the noisy switching converters, eg. using a continuous triangular waveform rather than a square wave.
See also
- Displaced mode power supply
References
External links
- DC DC Power Converter sets up an electronic project series
- DC-DC Converter Technology for Electric/Hybrid Electric Vehicles
- Power Electronics Book
- Switch app regulator records for LCD power supply
Source of the article : Wikipedia
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