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How Does a Voltage Regulator Work?
A Voltage Regulator produces a fixed output voltage of a particular preset magnitude that remains constant regardless of changes to load conditions or input voltage. You can find voltage regulators stabilizing the DC voltages for computer power supplies and even in motor vehicles by matching the output voltage of the generator to both the electrical load and the charging requirements of the car battery. To become more familiar with voltage regulators, this blog will cover different types, distinguishing characteristics, and their importance for a number of applications.
A voltage regulator is an integrated circuit (IC) that depends on the topology of the circuit within to generate a fixed output voltage. As such, this section will cover two types of IC voltage regulators: linear and switching, each containing different circuit layouts. Moreover, they are often used for DC/DC power conversion, but in some instances, they can perform AC/AC or AC/DC power conversion as well. In this case, we will be focusing on DC/DC voltage regulators.
Linear regulators consist of a pass transistor, error amplifier, voltage reference, and resistor feedback network. One of the inputs to the error amplifier is set by two resistors in order to monitor a percentage of the output voltage, while the other input is a stable voltage reference. In addition, they operate with low-efficiency and employ an active pass device such as BJT or MOSFET controlled by the error amplifier. In order to maintain a constant output voltage, the linear regulator adjusts the pass device resistance by comparing the output voltage to the reference internal voltage, driving the error to zero. Additionally, Linear Regulators are step-down converters, meaning that the output voltage is always below the input voltage.
Some advantages of this type of regulator include an easy-to-use design, dependability, cost-efficiency, low noise production, and low output voltage ripple. One of the main disadvantages of a linear regulator includes the fact that it may dissipate large amounts of power in certain applications. With this in mind, it is important to consider the approximate power dissipation of the regulator in any given application, since large input voltages produce high power dissipation that can overheat and damage components. Furthermore, the voltage drop of a linear regulator is similar to the voltage drop across a resistor.
Switching regulators, on the other hand, have a much more complex design. They require selecting external component values, tuning control loops for stability, and a careful layout diagram. Moreover, they come as either step-down converters, step-up converters, or a combination of the two, which makes them incredibly versatile. They operate by converting DC input voltage to a switched voltage applied to a Power MOSFET or BJT switch. Next, the filtered power switch output voltage is delivered back to a circuit that controls the power switch. In this way, the output voltage remains constant despite any changes in load current or input voltage.
Like linear regulators, switching regulators have several advantages. They are more efficient in terms of power conversion, have better thermal performance, and can support higher current applications. However, unlike linear regulators, switching regulators may require additional external components such as Inductors, capacitors, feedback resistors, or FETs. Switching regulators are also less cost-effective, larger in size, and can produce more noise if the external components are not properly selected. As such, it is important to consider the quality of components you are sourcing for your fixed voltage regulators or other internal circuit applications.
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