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Difference Between Smps And Linear Power Supply Pdf

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While linear power supplies may not be as efficient as switch mode power supplies, they offer the best performance and are therefore used in many applications where noise is of great importance.

Linear power supplies are a very familiar power supply since they were the normal standard before switch mode power supplies were introduced into the power supply industry. These power supplies have many benefits and drawbacks depending on the intended application. Advantages for linear mode power supplies include simplicity, reliability, low noise levels and low cost. These power supplies, also known as linear regulators LR , have a very simple design in that they require few components making it an easy device for design engineers to work with.

Linear vs Switching Power Supplies

While linear power supplies may not be as efficient as switch mode power supplies, they offer the best performance and are therefore used in many applications where noise is of great importance.

One major area where linear power supplies are almost always used is for audio visual applications, hi-fi amplifiers and the like. Here the noise and switching spikes from switch mode power supplies can cause issues - that said SMPSs are improving in performance all the time, but linear supplies tend to be used most of the time.

Linear regulated power supplies gain their name from the fact that they use linear, i. The term linear power supply implies that the power supply is regulated to provide the correct voltage at the output.

The voltage is sensed and this signal is fed back, normally into some form of differential amplifier where it is compared with a reference voltage, and resulting signal is used to ensure the output remains on the required voltage.

Sometimes the sensing of the voltage may be accomplished at the output terminals, or on some occasions it may be achieved directly at the load. Remote sensing is used where there may be ohmic losses between the power supply and the load.

Often laboratory bench supplies have this capability. Different linear power supplies will have different circuits and incorporate different circuit blocks if additional capabilities are required, but they will always include the basic blocks as well as some optional additional ones.

As many regulated power supplies take their source power from an AC mains input, it is common for linear power supplies to have a step down or occasionally a step up transformer. This also serves to isolate the power supply from the mains input for safety. The transformer is typically a relatively large electronic component, especially if it is used in a higher power linear regulated power supply. The transformer can add significant weight to the power supply, and can also be quite costly, especially for the higher power ones.

Dependent upon the rectifier approach adopted, the transformer may be a single secondary, or it may be centre tapped. Also additional windings may be present if further voltages are required. For vintage radios and other vintage electronic electronics, multiple secondary windings were commonplace. Normally the main secondary winding was centre tapped to enable full wave rectification with a double diode valve or tube rectifier, and further secondary windings were required for the valve or tube heaters - often 5 volts for the rectifier and then 6.

As the input from an AC supply is alternating, this needs to be converted to a DC format. Various forms of rectifier circuit are available. The simplest form of rectifier that could be used in a power supply is a single diode, providing half wave rectification. This approach is not normally used because it is more difficult to satisfactorily smooth the output. Normally full wave rectification, using both halves of the cycle is used. This provides a waveform that can be more easily smoothed.

There are two main approaches to providing half wave rectification. One is to use a centre tapped transformer and two diodes. The other is to use a single winding on the power supply transformer and to use a bridge rectifier with four diodes. As diodes are very cheap, and the cost of providing a centre tapped transformer is more, the most common approach these days is to use a bridge rectifier.

Diode rectifier circuits are used in many areas from mains power supplies to radio frequency demodulation. The diode rectifier circuits use the capability of the diode to only pass current in one direction. There are several varieties from half wave to full wave, bridge rectifiers, peak detectors and more. Read more about Diode Rectifier Circuits. Even for DC powered regulators, a rectifier may be placed at the input to guard against inverse connection of the supply. Once rectified from an AC signal, the DC needs to be smoothed to remove the varying voltage level.

Large reservoir capacitors are used for this. The smoothing element of the circuit uses a large capacitor. This charges up as the incoming waveform from the rectifier rises to its peak.

As the voltage of the rectified waveform falls away, once the voltage is below that of the capacitor, the capacitor starts to supply charge, holding the voltage up, until the next rising waveform from the rectifier. The smoothing is not perfect, and there will always be some residual ripple, but it enables the huge variations in voltage to be removed.

Most power supplies these days provide a regulated output. With modern electronics it is quite easy and not too costly to include a linear voltage regulator. This provides a constant voltage output regardless of the load - within the specified limits. With many electronic components and electronic devices, etc requiring accurately maintained supplies, a regulated power supply is a necessity.

The power supply is designed for a given current, and wit the load applied, the shunt regulator absorbs any current not required by the load so that the output voltage is maintained. In this block diagram, a reference voltage is used to drive the series pass element which may be a bipolar transistor or a FET.

The reference may just be a voltage taken from a reference voltage source, e. The more usual approach is to sample the output voltage and fed this into a differential amplifier to compare the output with a reference, and then used this to drive the final pass element circuitry. Both of these types of linear regulator are used in power supplies, and although the series regulator is more widely used, there are instances where the shunt regulator is also used.

The use of any technology is often a careful balance of several advantages and disadvantages. This is true for linear power supplies which offer some distinct advantages, but also have their drawbacks.

Despite the disadvantages, linear regulated power supply technology is still widely used, although it is more widely used where low noise and good regulation are needed. One typical application is for audio amplifiers where the linear supply is able to provide optimum performance for powering all the stages of the amplifier. Typical variable linear power supply for bench laboratory use Linear power supply basics Linear regulated power supplies gain their name from the fact that they use linear, i.

Power supply input transformer As many regulated power supplies take their source power from an AC mains input, it is common for linear power supplies to have a step down or occasionally a step up transformer. Note on Diode Rectifier Circuits: Diode rectifier circuits are used in many areas from mains power supplies to radio frequency demodulation. Read more about. Capacitor smoothing. Shunt regulator. Series regulator.

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Linear Power Supply: linear regulated supply

Most electronic and electrical devices require DC voltage in order to function. These devices, especially electronic devices with integrated circuits, should be supplied with a reliable, distortion-less DC voltage for them to work without malfunctioning or burning. The purpose of a DC power supply is to supply clean DC voltage to these devices. DC power supplies are categorized into linear and switched-mode, which are the topologies involved to make AC mains supply into smooth DC. Linear power supply uses a transformer to directly step-down the AC mains voltage into a desired level while SMPS converts AC to DC using a switching device which helps to obtain an average value of the desired voltage level.

Linear power supplies are designed for low noise and are often considered quiet since there is no high-frequency switching. A linear power supply typically uses a large transformer to drop voltage from an AC line to a much lower AC voltage, and then uses a series of rectifier circuitry and filtering process to produce a very clean DC voltage. The disadvantages are weight, size, and low efficiency. Switching power supplies are designed for high efficiency and small size. They incorporate a switching regulator to convert electrical power efficiently. Switching DC power supplies regulate the output voltage through a process called pulse width modulation PWM.

Difference Between SMPS and Linear Power Supply

Switch mode power supplies differ from linear power supplies in how the primary AC voltage is converted into the output DC voltage. Switch mode power supplies use a power transistor to produce a high frequency voltage that is passed through a small transformer and then filtered to remove both the AC component and noise. Linear power supplies deliver DC by passing the primary AC voltage through a transformer and then filtering it to remove the AC component. Switching power supplies feature higher efficiencies, lighter weight, longer hold up times, and the ability to handle wider input voltage ranges.

Related FAQs

Everyday electronic devices, especially those with integrated circuits, require a reliable DC voltage source that can supply powers at all times without any hiccups. The power supply that you choose ultimately comes down to your requirements for efficiency, space, output regulation, transient response time, and cost. Linear regulators were the power supplies of choice until the s for converting alternating current AC into a steady direct current DC for electronic devices. They might be bulky, but linear regulated power supplies are noise-free. Image source. The main component that allows a linear regulator to function is a steel or iron transformer.

The linear power supply and Switch mode power supply, both supplies DC power to electrical and electronic circuits but the similarities end here. The crucial factor which differentiates linear power supply and SMPS is the working procedure.

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AN-140: Basic Concepts of Linear Regulator and Switching Mode Power Supplies

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4 Comments

Slittaterge 05.05.2021 at 08:18

The main difference between the switching power supply and the linear power supply is that the switching supply does not operate at normal power line.

Jude P. 05.05.2021 at 10:26

Comparative analysis between the switch mode power supply (SMPS) using IC Tlcn transformer based on power supply linear. To cite this article: A Azis H et al difference being its mechanism of action. For more details, can be seen.

Unegriha 07.05.2021 at 09:56

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JГјrgen W. 07.05.2021 at 13:23

This article explains the basic concepts of linear regulators and switching mode power supplies SMPS.

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