1.1 Transformers & Rectifiers 1.3 Power Supply Basics Quiz Section 1.0 Power Supply Basics. Basic functions of a power supply. Safety aspects of working on power supplies. Section 1.1 Transformers & Rectifiers. Section 1.2 Filter Circuits. Section 1.3 Power Supply Basics Quiz. Test your knowledge of basic power supplies Parts of a Power Supply Ideally, A DC Power Supply Unit (commonly called a PSU) deriving power from the AC mains (line) supply performs a number of tasks: 1.  It changes (in most cases reduces) the level of supply to a value suitable for driving the load circuit. 2.  It produces a DC supply from the mains (or line) supply AC sine wave. 3.  It prevents any AC from appearing at the supply output. 4.  It will ensure that the output voltage is kept at a constant level, independent of changes in: a. The AC supply voltage at the supply input. b. The Load current drawn from the supply output.

To do these things the basic PSU has four main stages, illustrated in Fig. 1.0.1 Fig. 1.0.1 Power Supply Block Diagram Power supplies in recent times have greatly improved in reliability but, because they have to handle considerably higher voltages and currents than any or most of the circuitry they supply, they are often the most susceptible to failure of any part of an electronic system. Modern power supplies have also increased greatly in their complexity, and can supply very stable output voltages controlled by feedback systems. Many power supply circuits also contain automatic safety circuits to prevent dangerous over voltage or over current situations. The power modules on Learnabout-electronics therefore introduce many of the techniques used in modern power supplies, the study of which is essential to an understanding of electronic systems. If you are considering building or repairing a power supply, especially one that is powered from mains (line) voltages the power supply modules on this site will help you understand how many commonly encountered circuits work.

However you must realise that the voltages and currents present in many power supplies are, at best dangerous, and can be present even when the power supply is switched off! At worst, the high voltages present in power supplies can, and from time to time do KILL. The information provided on this site will not alone, qualify you to work safely on power supplies. You must also have the skills and equipment to work safely, and be fully aware of locally relevant health and safety issues.air conditioning unit will not come on Please act responsibly, the author of this information and owners of this site will accept no responsibility or liability for any damage or injury caused to persons or to any third parties, property or equipment arising from the use or misuse of the information provided on the learnabout-electronics web sites.air handling unit selection software

DC Power Supply Basics Tutorial - summary or tutorial about the basics of DC power supplies, PSU, detailing linear and switching types and their advantages and disadvantages. Power supplies or power supply units, PSU, form an essential part of very many items of electronics equipment. The most common form takes in AC power from the mains supply and delivers a DC voltage to the item requiring power. Accordingly power supplies are widely used in a variety of forms - some large supplying high levels of current, other power supplies, much smaller providing lower levels of power.installing window ac unit metal window The aim of a DC power supply is to provide the required level of DC power to the load using an AC supply at the input. Different applications require different attributes, but more often than not these days DC power supplies provide an accurate output voltage - this is regulated using electronic circuitry so that it provides a constant output voltage over a wide range of output loads.

In most power supplies there are number of different elements. These may not all be present in every design. Input transformer:   The input transformer is used to transform the incoming line voltage down to the required level for the power supply. Typically the input transformer provides a step down function. It also isolates the output circuit from the line supply. Rectifier:   The power supply rectifier converts the incoming signal from an AC format into raw DC. Either half wave or more commonly full wave rectifiers may be used as they make use of both halves of the incoming AC signal. Smoothing:   The raw DC from the rectifier is far from constant falling to zero when the AC waveform crossed the zero axis, and then rising to its peak. The addition of a reservoir capacitor here fills in the troughs in the waveform, enabling the next stage of the power supply to operate. Large value capacitors are normally used within this stage. Regulator:   This stage of the power supply takes the smoothed voltage and uses a regulator circuit to provide a constant output virtually regardless of the output current and any minor fluctuations in the input level.

There are two basic forms of power supply used in electronics equipment: Unregulated:   This form of power supply was the only type used many years ago. It simply consisted of a rectifier section and this was followed by capacitor or capacitor and inductor smoothing. There was no regulation to steady the voltage. If a large current was drawn the voltage would fall as a result of the resistive losses, and also the smoothing would not be as effective and the level of hum would rise. Voltage regulated:   As transistor circuitry became more commonplace, regulated power supplies became more common. Today they are almost universally used. They typically incorporate a voltage reference, and the output voltage is compared to this and altered accordingly by control circuitry within the regulated power supply. In addition to this, regulated power supplies may be further subdivided: Linear regulated power supply:   Linear regulated power supplies use an analogue approach.

A series element - a semiconductor transistor or FET - is controlled allow the correct voltage at the output for any current within the operating range. Note on Linear Power Supplies: Linear power supplies are widely used for applications where low noise and ripple are required. As the name suggests, they use linear technology - typically a series linear regulator element to drop voltage. As such they dissipate power, but without any switching mode, they are able to offer high levels of eprformance Click on the link for a Linear power supply tutorial Switching regulator power supply:   The switching regulator format for a power supply uses a large output reservoir capacitor. A series element - a transistor or FET - is switched on and off to keep the voltage on the capacitor within the required limits. Note on Switch Mode Power Supplies: Switch mode power supplies and switch mode regulators have many advantages in terms of efficiency, size and weight. Their design can be more involved than might be thought at first.

Yet with a good understanding, these switch mode power supplies, SMPSs, switch mode regulators and switch mode controllers can be successfully designed and built.. Click on the link for a Switch Mode Power Supply tutorial Each type of power supply regulation technique has its own advantages and disadvantages. As a result different types of regulator are used in different applications, although with technology improving, switching regulators are being used increasingly. Very low level of noise Low level of efficiency High levels of heat may need to be dissipated Large size compared to switching regulator Can be made very compact Low amounts of heat need to be removed Ripple and noise can be higher than linear regulator EMC issues need to be addressed as switching spikes can cause interference As a result of the different properties of each type of power supply regulator, linear regulators tend to be used in applications where very low levels of noise and ripple are required and heat dissipation may not be such a problem.

Hi-fi amplifiers are one such area. Switching mode regulators are used more widely as they can be made very compact, they are very efficient and the levels of ripple, spikes and noise can normally be low enough for most applications. . . . .   Want more like this? Register for our newsletter TV White Space technology ready for real-world commercial applicationsNokia expands LTE portfolio with Cloud Packet Core solutionToshiba adds N-channel devices to U-MOS IX-H MOSFET family1 - 6 Watt DC-DC converters for surface mount applications unveiledArrow Electronics to market full Electric Imp IoT platform     . . . . National InstrumentsSmarter Technology Requires Smarter Test SystemsRahman Jamal looks at Living in a Smarter World: Smarter Test Systems on the Verge of Conquering the Market Online - Designing GaN Power Amplifier MMICs Learn how to design high performance GaN power amplifier MMICsMore training courses mmWave The Battle of the Bands 5G mobile communications will use mmWave for many short range wide band links - but which microwave band will be used?