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  • When should you use a switching power supply?

    A power supply is like the heart of an electronic device. It breathes life into circuits, enabling them to perform their functions as intended. Choosing the right power supply, therefore, is crucial to achieving optimal performance from your electronics. Amongst the multiple types of power supplies available, Linear and Switching Power Supplies have carved a unique place for themselves. They cater to different needs and thus understanding their functionalities, advantages, and drawbacks is essential not only for electronics enthusiasts but also for anyone interested in the dynamics of everyday-use electronic devices. In this blog post, we’re going to delve into these two types of power supplies, demystifying their workings and helping you choose the right fit for your needs. Let’s get started.

    An adjustable switched-mode power supply for laboratory use source:https://en.wikipedia.org/wiki/Switched-mode_power_supply

    Definition of Power Supplies

    Power supplies—sounds complex, doesn’t it? But in actuality, you’re probably more familiar with them than you realize. Let’s simplify this.

    Power supplies are devices that provide electrical power to one or more electric loads. They take in electrical energy from a power source and convert it into the correct form needed by the loads. Like a translator, they ‘translate’ the source power (which could be from a wall outlet, battery, or renewable source like a solar panel) into a language (form of power) that the electrical device can understand and work with.

    Most power supplies convert electricity from Alternating Current (AC) to Direct Current (DC), bring out your phone charger for instance. The AC power from your wall outlet is translated into the DC form that your phone battery needs to charge. Other power supplies may have a different purpose, like stepping down or up voltages (transformers), stabilizing currents or voltages (regulators), or even converting DC power back to AC.

    Hence, power supplies are like backstage heroes—quietly ensuring our devices run smoothly, effectively, and safely. They’re tucked away in our devices, out of sight, but definitely never out of action.

    Types of Power Supplies

    Power supplies come in a variety of types, each designed to cater to specific devices and applications. However, categorically, they broadly fall under two main categories:

    Linear Power Supply: This is one of the oldest and simplest types of power supply. It operates by converting the mains AC supply into a low voltage DC supply using a transformer. It then uses a rectifier to convert the alternating current into a direct current, and a capacitor to remove any remaining fluctuations. Despite being less efficient and bulkier, linear power supplies are preferred in applications where low output noise is required, like audio and medical equipment.

    Switched-Mode Power Supply (SMPS or Switching Power Supply): This is a more complex but highly efficient type of power supply. It quickly switches a power transistor between saturation (full-on) and cutoff (completely off) with a variable duty cycle whose average is the desired output. This allows it to convert voltage and current efficiently, minimising heat wastage. Their light-weight, small size, and efficiency make them the preferred choice in computer and server power supplies, as well as other high-power applications.

    Uninterrupted Power Supply (UPS): This is a secondary source of power supply that comes into action when the primary supply fails, ensuring continuous operation of the device. Used extensively in computer systems, UPS provides a means to save data before safely shutting down during power blackouts.

    DC Power Supply: This is a power supply that uses a DC voltage source to output a DC current.

    AC Power Supply: As opposed to DC power supplies, AC power supplies convert a DC voltage input into an AC voltage output.

    Programmable Power Supply: These are power supplies that can be remotely controlled through analogue signals or digital interfaces, allowing automatic control of output voltage or current.

    The right type for your specific requirement would depend on multiple factors – the device you’re powering, its power requirements, efficiency needs, space constraints, and so on.

    Understanding Linear Power Supplies:

    How They Work:

    Linear power supplies work in a sequence of stages. First, the Alternating Current (AC) enters the power supply, passing through a transformer. This transformer then steps down the incoming AC voltage to a lower value. The rectifier stage follows, converting the AC power into Direct Current (DC), resulting in a waveform of pulsed DC voltage. Finally, the power supply uses a regulator to stabilize the DC voltage to a fixed value, which is then outputted to power the device. The regulator also maintains this fixed output voltage despite variations in the input voltage or output load.


    Linear Power Supplies



    Simple design and easy to maintain

    Inefficient energy conversion results in heat generation

    Lower rippling effect, which decreases noise

    Can’t step up input voltage

    Excellent load and line regulation

    Larger size and heavier weight compared to switching power supplies

    Less susceptible to output noise

    Need for considerable cooling efforts

    Linear power supplies can be the perfect fit for sensitive applications where output voltages need to remain free from any noise—like in audio processing and broadcasting. However, its inefficiencies and size could be limiting factors, particularly in applications where power consumption, device size, and weight are key considerations.

    How They Work

    Switching power supplies also kick-off operations with the AC power passing through a transformer. However, in contrast to linear power supplies, switching power supplies add an extra step. The input power is ‘switched’ on and off rapidly by power semiconductors (transistors), resulting in a quick succession of power pulses and zero power. This stepped down DC voltage is then smoothed out and regulated to produce the required DC output. A heat sink is often used to regulate the heat produced during this process.


    Switching Power Supplies



    High energy efficiency, reducing energy consumption and making it a more environmentally friendly choice

    Higher cost and complexity in design

    Smaller and lighter compared to linear power supplies due to the absence of large transformers

    Noise caused by the fast-switching transistors can interfere with other electronic devices

    Capable of stepping up the input voltage

    Diagnosis and repair need more expertise due to the complexity

    Less heat production due to high energy efficiency

    Potential for higher electromagnetic emissions

    In conclusion, switching power supplies hold the upper hand when it comes to efficiency, size, and adaptability to different input voltages. However, things can get a bit noisy due to the switching process, which is something to keep in mind when used with sensitive electronic equipment.


    Choosing between a linear and a switching power supply is equivalent to finding the right tool for the right job. Both types have their unique strengths and weaknesses which make them suitable for different applications.

    Linear power supplies, with their simplicity and outstanding regulation, serve as an excellent choice for sensitive applications such as audio processing, where signal quality is paramount. That said, their efficiency drops as power demands increase, making them less viable for high-power applications.

    On the other hand, switching power supplies steal the show when it comes to high-power, high-efficiency applications. Their compact and lightweight design coupled with their energy-saving characteristics make them an excellent choice for everything from home appliances to industrial equipment. While they do generate more electrical noise, the impact is negligible in most situations.

    In conclusion, the battle between linear and switching power supplies is not about which one is better. Instead, it’s about understanding their strengths, weaknesses, and identifying the right power supply for your specific needs and constraints. As technology continues to advance, both types will keep evolving, getting better and better.

    This marks the end of our deep dive into Linear and Switching Power Supplies, hope you found it informative and helpful.

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