What is dc to dc converters? These types of converters convert direct current denoted by “DC” into another direct current “DC” of different voltage or current levels. The inverting polarity converter inverts the input voltage, whereas the non-inverting polarity converter does not change the input voltage polarity.
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The output voltage across the converter can have a value less than the input or greater than the applied voltage. So, what are the main categories of dc to dc converter circuits? We can categorize them into two main types – Step Down and Step-up converters, both serve different purposes and are available at different wattage ratings.
Dc to dc converters working depends on the topology used in the converter circuit. “Dc-Dc converters” circuits are also termed voltage regulator circuits.
Basics of DC to DC Converter
Before diving into the details of dc to dc converter circuits, we must know that these converter circuits only convert one type of dc to another level of dc. As the generation is in AC so the DC voltages are obtained using some other type of converters which we call AC to DC converters. Click here to have an overview of AC to DC converter circuits.
Dc-Dc converters are high-frequency power converting circuits. These circuits use inductors, diodes, and capacitors to generate regulated DC voltages at the output. We categorize these converter circuits on the basis of isolation into two types.
DC to Dc Isolated Converters
Non-Isolated DC to DC Converters
Both schemes have a difference in the ground terminal. In the isolated type, the ground terminal of input and output is not connected but on the other hand, the ground terminal of input and output is connected in the non-isolated. As it is clear from the name, this circuit is only for direct current “DC” and cannot be used for “AC” alternating current.
As we can see in the above figure that when we apply 110 volts of DC to the DC-DC converter, we get 12 volts at the output of the converter. In a similar way, the voltages can be stepped up.
In electrical systems, it’s a common practice that at any stage we require to step up or step down the voltages to operate any electrical component or device.
So, from the above discussion, we are clear about the basics of dc to dc converters. Let’s move one step further and see how many types it has.
Types of DC to DC converter Circuits
On the basis of their working modes, dc-dc converters can be categorized into two types. Linear converters, use the heat dissipation in the resistor and regulate the voltage at the output.
The second dc to dc converter is a power switch mode converter, which preserves the energy from applied voltages and then releases the preserved energy across the Load at a different level. The energy storage occurs in the form of magnetic flux if there is an inductor or even a transformer.
The transformer in the circuit acts as an isolation between the input and output. But in the case of a capacitor, the same energy is stored in the form of an electric field.
So, let’s have a look at the advantages of having a switch mode converter in the circuit.
The inductor in switching mode dc to dc converters stores energy which can be converted into a low voltage value, high voltage value, or the voltage value reverse polarity.
The losses are lower due to high-frequency switching and low values of passive elements in the circuit. The conversion rate is highly efficient in switching mode dc to dc converters.
The main disadvantage of switching mode converters includes the noise problem. They generate noise while switching but due to technological innovation this problem has been minimized. On the other side, when we look at the linear dc-dc converters, we find that the linear converters can only transform the input signal to a lower voltage value.
Non-Isolated includes following
Buck Topology or step-down converter circuit
Boost Topology or step up converter circuit
Buck-boost Topology or polarity inverter.
The main components of these types of dc to dc converters include a switch, diode, resistor, and capacitor.
Buck (Step Down) Dc to Dc converters
A step-down or “buck” topology output strongly relies on the applied voltage and the switching mechanism of the power switch. Which turns on and off with some specific time interval and is termed the duty cycle “D” of the circuit.
The duty cycle is equal to the ratio between output voltages to input voltages. A typical buck dc to dc converter looks like as below.
In the above circuit, when the gate signal is On, the diode will behave as an open circuit. This circuit stores energy in the inductor and capacitor. But during the off time, the switch is off and the diode will behave as a short-circuit and the stored energy is released by the inductor and capacitor at the output.
Boost “Step Up” Dc to Dc converter
A Step up or “boost” topology also uses the same components but they are arranged in such a way that the output voltage across the load resistor, is greater than the applied input voltage. Typical boost dc-dc converters look like as below.
In the above circuit, we can see that during the on-time, the inductor stores the energy, and when the switch is off, the inductor and capacitor release stored energy across the load resistor. The voltages across output are relatively greater than the applied input voltage.
Buck-Boost converter circuit
A Buck-boost circuit of dc to dc converter either increases the input voltage or reduces the input voltage. This increase or decrease relies on the duty cycle of the circuit. But the polarity of the output in buck-boost dc-dc converters reverses. The equation looks like below.
We can also call a dc-dc converter of buck-boost type due to its output a “voltage inverter”. Now, let’s have a look at the buck-boost circuit diagram
These circuits employ the same concepts of inductor and capacitor functions as described in our articles regarding low-pass and high-pass filter circuits. You can follow the links to read more deeply about the inductor and capacitor response toward ac signal. Further, you can also read about oscillator circuits to have a basic understanding of oscillations. Read about amplifier circuits.
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