What is a DC to DC converter and why do we use a DC to DC converter
DC to DC converters are widely used in industrial applications, the performance of these applications can be improved by using a variable DC supply. By using a variable DC supply we can improve the controllability of the equipment too. DC to DC converters are also known as a chopper, constant DC voltage can be controlled with the help of a chopper. DC to DC converter is a static power electronic device which can convert the fixed DC voltage or power to variable DC voltage or power. They can be considered as a high-speed switch that connect and disconnect the load from a source at a high rate in order to get a chopped or variable voltage at the output. DC converters are considered as an AC transformer that provides a variable AC voltage level. DC converters can also be used to increase or decrease the voltage by using some kind of semiconductor switches. We can use DC converters whenever we need to transform DC electrical power efficiently from one voltage level to another. These converters are required because unlike AC power we can simply step up or step down DC power. DC to DC converters is also considered as a DC transformer.
Why do we need a DC to DC converter and where is it used
DC to DC converters are very important in an electronic device, which is powered by batteries, such as laptops and mobile phones. All of these electronic devices are mostly have many sub-circuits, and all of that requires a certain voltage level other than that supplied by the battery. The voltage of the battery will reduce as its stored energy is nearly depleted, keeping it from outputting a constant voltage level. Multiple control voltage can be generated from a single battery voltage and this method was offered by DC to DC converters which would allow the user to save space, without using multiple batteries for different components of the equipment. DC converters are used in trolley cars, marine hoists, forklift trucks, and mine haulers, DC converters are also used in electric automobiles for their speed control and braking. DC to DC converters offers smooth control, high efficiency, fast response, and regeneration.
What are the types of DC to DC converter
There are many types of DC to DC converter, each of which is suitable for some type of applications than for others. Some converters can be used for stepping down voltage while some other can be used for stepping it up
Non–isolating converters
This type of converter is mostly used when the voltage needs to be stepped up or down by a relatively small ratio and there won’t be any problem if the input and output don’t have any dielectric isolation. The major types of non-isolating converters are
Buck converter
Buck converter steps down the supplied DC voltage source and does the CCM operation.
The buck converter function in two modes when the switch is on the input voltage forces the diode into reverse bias region and it won’t conduct. When the switch is turned off the circuit transfers mode to the equivalent circuit, at this time the diode becomes forward biased and the energy stored in the inductor will discharge through the load. The output voltage is stabilized by the capacitor, the effective voltage can be lowered by controlling the duty cycle of the switch.
Boost converter
The boost converter provides a higher output voltage than the input voltage.
The difference between the buck and boost converter is the placement of the inductor diode and switch. Boost converter also operates in one of two oscillatory modes depending upon whether the switch is open or closed. If the switch is closed then the diode is reverse biased and eliminating the portion of the circuit and current flow only through the inductor and switch, and the energy will be stored in the inductor. The stored current in the inductor flows through the forward-biased diode and through the load. The cycle will repeat when the switch is turned on again.
Buck-boost converter
This is the most versatile type of the DC-DC converter
Buck-boost converter is capable of, stepping up or stepping down the supply voltage according to the duty cycle of the switch. If the switch is on then the diode is polarized, during its off state the inductor magnetic field charges and current increases linearly. This will continue until the switch opens, and the inductor instantly switches polarity and draws current through the load and the diode as the inductor discharges linearly.
Charge pump converters
The other non-isolated converters are dependent upon the stored energy in the magnetic field of an inductor for their operation. A charge pump converter is a converter that operates by storing energy as the electric charge in a capacitor. This type of converters can be considered as a development from traditional voltage doubling and ‘voltage multiplying’ rectifier circuits.
Cuk converter
Transfer of energy between the input and output in buck, boost and buck-boost converter is done by using the inductor, analysis is based on voltage balance across the inductor. While the cuk converter uses capacitive energy transfer and analysis is based on the current balance of the capacitor. The circuit configuration of cuk converter is like the combination of the buck and boost converters. The Cuk converter delivers an inverted output like the buck-boost circuit.
Isolated converters
In many DC-DC applications, multiple outputs are required and output isolation needs to be implemented depending upon the application. Because of this input and output isolation may be required for safety or to provide impedance matching. Flyback and forward converters are the types of isolated converters
Flyback converter
This converter can be developed as an extension of the buck-boost converter, but it uses a transformer to store energy instead of an inductor like the buck-boost converter. During the operation of the buck-boost converter, energy is stored in the inductor during the on phase and in the off phase, it is released to the output. With the transformer the energy storage is in the magnetization of the transformer core, a gapped core is used to increase the stored energy.
Forward converter
The forward converter concept is that of the ideal transformer converting the input AC voltage to an isolated secondary output voltage. The forward converter has used the transformer in a traditional way, the transformer is used to transfer energy between the input and output. The most common type of forward converter is a push-pull type.
