Current and voltage regulator ICs

Regulators are semiconductor components that are use to regulate current or voltage in circuits. It can be found in many circuits, especially those that requires a stable supply of voltage or current. They are usually use to regulate voltage or current into a stable amount from a large current source. i.e a regulator can be use to regulate 5v DC from 20v DC.  The regulator IC can't regulate high voltage from a low voltage, i.e you can't regulate a voltage of 5v out of 4v, it can only reduce a large voltage to a fixed amount of voltage. Types of regulator ICs. 

 

Types of regulator ICs.

There are just two types of regulators, they are listed below.

•Voltage regulators. 

A voltage regulator is a circuit that creates and maintain a fixed output voltage, irrespective of changes to the input voltage or load conditions. Voltage regulators keep the voltage from a power supply within a range compatible with the other electrical components. They are mostly used for DC to DC power conversion, some can perform AC to AC  voltage regulation, or AC to DC voltage regulation as well. This tutorial focus DC to DC voltage regulator ICs. 

Types of voltage regulators.

There are two main types of voltage regulators: 

linear and switching. 

Both types regulate a system's voltage, but linear regulator operate with low efficiency. In high efficiency switching regulators, most of the input power is transferred to the output without dissipation. Linear regulators.

1. linear voltage regulator.

It utilizes an active pass device (such as a BJT or MOSFET), which is controlled by a high-gain operational amplifier. 

To maintain a constant output voltage, the linear regulator adjusts the  pass device resistance by comparing the internal voltage refrence to the sampled output voltage, and then driving the error to zero. Linear regulators are step-down converters, so by definition the output voltage is always below the input voltage. However, these regulators offer a few advantages: they are generally easy to design, dependable, low cost, efficient, and offer low noise as well as a low output voltage ripple. Linear regulators, such as the MP2018, only require an input and output capacitor to operate. Their simplicity and reliability make them intuitive and simple devices for engineers, and are often highly cost-effective 

2.Switching regulators.

A switching regulator circuit is generally more complicated to design than a linear regulator, and requires selecting external component values, tuning control loops for stability, and careful layout design. Switching regulators can be step-down converters, stepup converters, or a combination of the two which makes them more versatile than a linear regulator.

Advantages of a switching regulators include that they are highly efficient, have better thermal performance, and can support higher current and wider VIN/VOUT applications. They can achieve greater than 95% efficiency depending on the applications. They can achieve greater than 95% efficiency depending on the applications requirements. Unlike linear regulators, a switching power supply system may require additional external components, such as inductors, capacitors, FETs, or feedback resistors. The HF920 is an example of a switching regulator that offers high reliability and efficient power regulation. 

  Limitations of voltage regulators. 

One of the main disadvantages for linear regulators is that they can be inefficient because they dissipate large amounts of power in certain use cases. The voltage drop of a linear regulator is comparable to a voltage drop of a linear regulator is comparable to a voltage drop across a resistor. For instance with a 5v input voltage, there is a 12v drop between the terminals, and the efficiency is limited to 3v/5v (60%). This means linear regulators are the best suited for applications with lower VIN/VOUT differentials. It's important to consider the estimated power dissipation of a linear regulator in application, since using larger input voltages results in high power dissipation that can overheat and damage components.  Another limitation of linear volatage regulators is that they are only capable of buck (step-down) conversion, which also offer boost (step-up) and buck-boost conversion.  Switching regulators are highly efficient, but some disadvantages includes that they are generally less cost-effective than linear regulators, larger in size, more complex, and can create more noise if their external components are not carefully selected. Noise can be very important for a given application, as noise can affect circuit operation and performance, as well as EMI performance. 

Switching regulator Topologies.

Step down, stepup, linear, LDO, and adjustable. There are various topologies for linear and switching regulators. Linear regulators often rely on low dropout topologies. For switching regulators, there are three common topologies: step-down converters, stepup converters and buck boost converters. Each topology is described below. 

LDO regulators. 

One popular topology for linear regulators is a low dropout regulator (LDO). Linear regulators typically require the input voltage to be at least 2v above the output voltage. However, an LDO regulator is designed to operate with a very small voltage difference between the input and output terminals sometimes as low as 100mV.

 

Stepdown and step-up converter. 

Step down converters are also known as buck converters. They take a higher input voltage and produce a lower output voltage.  Conversely, stepup converters also called boost converters take a lower input voltage and produce a higher outpit voltage. Buck-boost converter. A bulk boost converter is a single stage converter that combines  the functions are if a buck and a boost converter to regulate the output over a wide range of input voltage that can be greeater it less than the output voltage.

Voltage regulator control.

The four fundamental components of a linear regulator are a pass transistors error amplifier, voltage refrence, and resistor feedback network. One of the inputs to the error amplifier is set by two resistors (R1 and R2) to monitor a percentage of the output voltage . The other input is a stable voltage refrence (VREF). If the sampled voltage output changes relative right VREF, the error amplifier changed the pass transistor's resistance to maintain  a constant output voltage (VOUT). Linear regulators typically only require an external imoutr and output capacitor to operate, making them easy to implement. On the other hand, a switching regulator requires more compine be to create the circuit. The power stage switches between VIN  and ground to create charge packets to deliver to the output similar to a linear regulator, there is an operational amplifier that samples the DC output voltage from the feedback network and comparws it to an internalvikatega reference. Then the error signal is amplified, compensated, and filtered. This signal is used to modulate the PWM duty cycle yo pull the output back into regulation for example, if the load current increases rapidly and causes an output voltage drop, the control loop increases the PWM sure cycle to supply more charge to the load and bring the back to regulation

Current regulators.

A circuit designed to keep the current flowing through a circuit at a constant rate is a current regulator. A good example of this is a power supply for an LED light. These work best at a constant current level. Too much and the LED may burn up and fail. Too little and it will not light. Different LEDs, even the exact same type from the same manufacturer may have different voltages where they work best, so a voltage regulator will not help if you don’t know what the voltage can or should be. Here a current regulator comes to the rescue. 

Like a voltage regulator, or an air pressure regulator, there is a limit to what a current regulator can do. If not supplied with enough power in the form of a voltage pressure, of course the regulator will not be able supply enough to control the current. If too high, it could prove to be too much for the regulator to “stay in compliance” and it may allow too much current. All types of voltage regulators have practical limits. This is sometimes best defined as the minimum and maximum load resistance that it can drive and remain in a regulated mode. Like everything in the world, there are good and poorly performing current regulators. 

A precision laboratory instrument would likely need a much more precise regulator, requiring many expensive parts. A much more cost-effective current regulator can be made with a single transistor or two, and one or more resistors. Like any regulator, this requires some form of a feedback, or a closed-loop system. The output is measured (in a current regulator it can be easily measured by sensing the voltage across a small resistance in the current path.)

This is compared with a reference level, and the amount over or under the desired amount is used to throttle the current up or down depending on how far off it is. Improving the basic current regulator involves usually one of three areas of poor performance. 

1. the circuit may be very temperature dependent, so more advanced circuitry will compensate for this and improve its performance in a wider range of temperatures.

2.The regulator is not regulating precise enough, this can be improved by amplifying the sensed current to a greater signal that can be used to adjust the output current. The other remedy is to create a more accurate and stable reference to compare the measured current to.

3.Simple current regulators can be such that they will try to provide too much power and destroy themselves. Improving circuitry tries to make sure that it is not self-destructive. Most of these issues can be solved with just a few more components, additional transistors or reference diode.