Power Supply Basics | What to Know About
Any electronic system needs power to function, and the power supply provides that power. Selecting the proper source can make all the difference between a gadget operating at peak performance and one that might produce erratic results.
Direct current (DC) to alternating current (AC) power supplies and DC to DC converters are both options. A DC-to-DC converter might be a better design option if DC is already present in your system rather than the AC that is explained below. Power supply for direct current is either uncontrolled or regulated. There are various types of regulated supply, including battery-based, switching, and linear.
In many pieces of electronic equipment, power supplies are a crucial component. While some are powered by batteries, others require mains power sources, and the electrical circuitry and design of the power supply are crucial to the effective operation of the entire piece of equipment.
Circuits for power supply electronics can be divided into a variety of parts or units. While each is essential to the overall functioning of the power supply, the proper operation of the entire unit depends on the performance of each area of the power supply electronics.
Types of Power Supply
Three primary types of power supplies are available. Each has its own benefits and drawbacks; thus, each is applied in slightly different situations. There are three main categories of electronic power supply:
- Rectified Power Supply: The simplest kind of electronics power supply is the rectified and smoothed power supply, which is typically employed in non-critical applications where performance is not a big concern. The fact that it was difficult to regulate supplies and that sometimes the criteria were not very stringent led to the widespread usage of this form of power supply in thermionic valve or vacuum tube equipment.
- Linear Regulated Power Supply: The performance level of a linear regulated power supply, a type of electronics power supply, is quite high. It can, however, be relatively inefficient due to the fact that it employs a series regulator element, squandering a sizable percentage of the incoming power as heat. However, these power supplies can provide extremely high levels of control, minimal ripple values, etc.
- Switch Mode Power Supply: Electronics circuits control the output of this type of power supply through switching technology. Spikes are present in the output, but because of their great efficiency, they can be contained in considerably smaller packets than their linear counterparts.
Major electronic blocks for power supplies:
A power supply can be divided into a number of components, each of which performs a specific task for the power supply as a whole. These parameters are obviously rather arbitrary and may differ significantly depending on the actual power supply design, but they can be used as a general, illustrative guide.
- Power input filtering: In some cases, it’s required to make sure that noise from the power supply doesn’t get into the power lines or that spikes from the power line don’t get into the power supply. This is accomplished by placing circuitry at the power supply’s input to filter out noise and restrict the effects of incoming spikes. While more complex circuits may be utilized for specialized supply, filtering at this point is often relatively minimal.
- Input Transformer: The input of a power supply that uses mains or line voltage of 110- or 240-volts AC typically incorporates a transformer to raise the incoming line voltage to the level needed for the power supply’s design.
- Rectifier: A device that converts an incoming AC waveform into a DC waveform is required. An AC rectifier circuit is utilized for this. Full wave and half wave rectifier circuits are the two types that can be employed. These efficiently block a portion of the waveform in one sense and let the waveform pass in the other.
- Over voltage protection: In some instances, the output voltage from the power supply may grow to a level that could harm the circuitry being powered in the case that the regulator fails. Over-voltage protection circuitry can be employed to stop this from happening. This circuit element monitors the output voltage level and trips if the voltage starts to climb above its safe limits. This stops the supply to the regulator and typically clamps the output of the regulator to zero volts, shielding the remaining circuitry from harm.
- Regulation: There may still be sizable amounts of residual hum even after the rectified voltage has been smoothed. Additionally, as different amounts of current are drawn, the voltage will change. A voltage regulator circuit is necessary to deliver a consistent voltage output from the power supply with low lingering hum and noise. Depending on the need, regulators can deliver a stable voltage at a fixed or variable level. To get the needed output voltage, either linear or switching mode approaches may be used.
- Smoothing of the rectifier’s output: The waveform that emerges from the AC rectifier circuit ranges as of zero volts to 1.414 times the RMS input voltage. This needs to be smoothed out before it can be used by electrical circuits. A capacitor is utilized to accomplish this. It will charge for a portion of the cycle, then provide the circuit with current as the voltage drops while recharging as the voltage increases.
Power Supply Specifications:
Following are the power supply specifications to look into:
- Voltage and current: The voltage and current output parameters are the main power supply specs. The power source may be fixed in terms of voltage or it may have a variable output. Checking whether the power supply has a fixed or variable output is necessary.
- Line Regulation: Line regulation for power supplies include numbers for a parameter called “line regulation.” It has been discovered that a minor difference may be visible on the output when the line or input voltage varies. This modification is seen in the line regulation figure. Make sure the line regulation is such that it does not fall outside the compulsory output voltage limits with the predicted line performance if the output voltage is critical. The load management, time and temperature stability, and any other power supply output voltage fluctuations must all be added to this.
- Load Regulation: It is a term used to describe another crucial power supply parameter. It has been discovered that the voltage at the terminals of a power supply may somewhat decrease when a load is added to the output. Since the output voltage should, in a perfect world, remain perfectly constant, this is obviously undesirable.
- Ripple and Noise: Another crucial power supply spec is the ripple and noise parameters. The output of the circuit that is being powered may be affected by noise and other impulses on the power line. The power cables must be kept as clean as possible in order to reduce this, especially for sensitive circuits. The output’s ripple and noise are merged into a single specification. The ripple frequency for linear supply is typically twice as high as the line frequency. Because of the supply’s action of switching, ripples and spikes will result.
- Temperature constancy: One of the primary factors influencing circuit conditions is temperature, which can affect the output voltage of power supplies, including both linear and switch mode power supplies. Other electronic components, primarily resistors, can alter as well as voltage references, which can be one of the main sources of voltage change.
- Stability over time: It is not surprising to learn that power supplies, but linear regulator and switch mode power supplies both fluctuate by a tiny amount with time. This is because all components gradually change their values over time. Although the amounts of change are typically negligible, in some situations they can be significant. Because of this, information about the voltage output stability over time is frequently provided in the general power supply requirements.
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The aforementioned power supply basics are often the most common, other ones could appear and could be crucial for particular applications that are more specialized. Generally speaking, it is feasible to interpret them, at least generally, and have a fair notion of how the power supply must operate.
Although power supplies have significantly increased in reliability in recent years, they are still frequently the most prone to failure of any component of an electronic system because they must handle voltages and currents that are significantly higher than any or most of the circuitry they supply.
Modern power supplies are incredibly complicated and can deliver output voltages that are tightly controlled by feedback mechanisms. Automatic safety circuits are also present in many power supply circuits to guard against harmful over voltage or over current conditions.