difference between ac and dc power supply pdf

Difference between ac and dc power supply pdf

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What is AC Current?

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AC vs. DC (Alternating Current vs. Direct Current)

What is AC Current?

The flow of electricity pulled under the highest dc load value must be listed on product labels for compliance to safety agency standards. Most ac power is generated at either 50 or 60 Hz cycles per second. Switching Power Supplies typically accept any frequency between Hz nominal. The nominal ac input voltage that a power supply will accept during normal operation. For example, a switching power supply labeled with a nominal to Vac input range will actually operate over 90— Vac input range.

The instantaneous current drawn when the power supply is turned on cold. Smaller power supplies generally incorporate a thermistor to limit this amount. It is most important in considering an ac switch rating. Traditional switched mode power supplies draw current from the ac line in short pulses, and as a result, the input current of such basic switched mode power supplies has high harmonic content.

This creates extra load on utility lines and increased heat of utility transformers and may cause stability problems to the entire ac Line Especially in Europe.

Active Power Factor Correction controls the input current of a supply so that the current wave form is proportional to the ac waveform a sine wave.

The maximum altitude at which a supply can be operated without derating. Supplies must often be de-rated due to the thinner air which is required to cool the power supply. A metal surface to which circuit components are mounted in such a way as to draw heat away from components. It is common with this type of connection for there to be a short pin called last-mate which enables the supply to be on, in order to prevent arcing or powering of the supply until it is firmly seated into its mating connector.

A boost converter step-up converter is a power converter with an output dc voltage greater than its input dc voltage. The breakdown voltage of an insulator is the minimum voltage that causes a portion of an insulator to fail and become conductive. A switching supply topology that employs four switching elements full bridge or two switching elements half bridge. Bridge converters provide high output power and low ripple, but are significantly more complex than other types of supply topologies.

Operating newly manufactured supplies under defined load conditions for a specified period to eliminate faulty power supplies from shipping. Most power supplies will typically fail in the first few hours of operation referred to as infant mortality. The time period and conditions input power cycling, load switching, temperature, etc.

This is the temperature range at which a supply will meet its specifications as measured at the center of the top surface of the supply. Enclosed in a metal or perforated metal cover assembly.

Often referred to as Enclosed or Covered. Typically, a cased power supply is covered on all 6 surfaces for finger safe operation. A document which is designed to include the necessary tests and measurements approvals required among differing national safety test standards. CE marking Communaute European, European Committee indicates that all applicable EC directives pertaining to the power supply have been met.

California Energy Commission, energy efficiency targets for external power supplies in the USA was largely voluntary except in California where state law made it mandatory. A chassis ground is a connection to the main chassis of a piece of electronic or electrical equipment. It is sometimes called common ground. It provides a reference that can be considered to have zero voltage. All other circuit voltages positive or negative are measured or defined with respect to it.

Ideally, all chassis grounds should lead to earth grounds. The power supply offers one ore more surfaces for mounting a power supply directly to a system chassis or other metal. A conductive path used as a return for two or more circuits.

The term Common is often used interchangeably with ground, which is not technically correct unless it is connected to earth. The noise at an electrically fixed point usually chassis ground common to both dc output and return lines. A power supply that regulates its output current to within a specified current range regardless of changes of output load. Current limiting circuit that holds output current at some maximum value whenever an overload of any magnitude is experienced.

The process of removing heat generated by normal operation of a power supply. Typical methods are convection, forced air and conduction.

This typically refers to a supply of either open-frame PCB construction or mounted on some type of bracket L-Bracket or U-Frame that has a cover option, These type of products are typically covered on 4 sides, leaving the ends open, though 6-sided covers are not uncommon.

The shortest distance between two conductors typically one conductor primary and one conductor secondary. On many multiple output power supplies, the secondary outputs may be affected by the loading conditions of the primary output s.

Multiple output power supplies often require minimum loads in order for the supply to achieve stated regulation specifications. Preload resistors may be employed at the system level to overcome these issues. An overvoltage protection circuit which places a low resistance shunt across the power supply output terminals, if a predetermined voltage is exceeded. The independent Canadian organization Canadian Standards Association which tests to see that public safety regulations are met.

A circuit that protects a supply or load from damage during an overload condition. The output current is limited to a predetermined, safe value. Typically, normal operation is automatically restored when the overload condition is removed. The range over which the protective current limit set-point can be adjusted and the means of adjustment. The point at which current is limited foldback on the plot of output voltage vs output current.

See Foldback Current. Multiple power supplies or dc-dc supplies are often connected redundantly to increase system reliability or in parallel to increase system power. In power supplies and dc-dc converters, derating is the specified reduction of the output current when operating under defined conditions, typically elevated operating temperatures.

Diagram below is current derating under various airflow cooling measured in linear feet per minute LFM. A supply may not bear any safety agency approvals, but when installed and used properly, should meet the official safety requirements of an electronic system. Typically a safety agency standard is referenced: eg Design to meet UL That component of noise measured with respect to output or input to its returns; it does not include common mode noise. See Ripple and Noise.

A DIN rail is a metal track or rail to which PLCs and other industrial control devices can be easily attached or removed. The DIN rail mount can be a part the enclosure for a device. It can also be an adapter bracket that can be attached to an industrial control device that does not have an integral mounting bracket.

An additional layer of insulation to protect one from high voltage potential, often referred to as supplementary or reinforced insulation a common requirement of medical applications and transportation equipment. Often referred to as Supplementary Insulation or Reinforced Insulation. The variation of output voltage of a supply over a specified period of time, following a warm up period, with all other operating parameters such as line, load and ambient temperature held constant.

The function of paralleling two power supplies to share a load without any active circuit to control how the load is shared. The current-sharing accuracy is directly related to the output-voltage set-point accuracy of the paralleled supplies. Considering that output voltage will vary based upon varying line, load, temperature and other conditions, it is strongly advised that droop sharing only be utilized for redundant operation, not for increased power.

The ability of a multiple output supply to provide maximum current from any combination of outputs without cross regulation issues. This is usually achieved through independent regulation circuits for each output within the supply.

A load condition that changes rapidly. A European Directive defining no load power consumption limits and minimum efficiency levels of external power supplies. A measurement of Output power divided by Input Power. The values will vary depending on the load and ac input voltage. Typical Values shown are usually measurements of a supply at nominal input and output conditions.

A performance curve that describes how the efficiency varies with input voltage. Usually one or more load values are plotted i. Electromagnetic Compatibility, is the compliance of the power supply and its components to standards for electromagnetic emissions and susceptibility immunity.

Electronic interferences that impair the performance of electronic device is referred to as Electromagnetic Interference. Conducted EMI is unwanted high frequency energy caused by the switching transistors, rectifiers, and transformers in power supplies and dc-dc. The noise that is generated on the input and output lines of a power supply is known as Conducted EMI. Switch mode power supplies and dc-dc converters may be filtered by using an EMI filter on their input or primary side to meet applicable EMC standards.

It is the final equipment that must conform to EMC regulations. So, specifying a supply which meets the EMI classes is not a guarantee that final equipment will be compliant and does not remove the need for testing and possible additional filtration required for final equipment.

Radiated EMI is unwanted high frequency energy caused by the switching transistor, output rectifiers, and zener diodes in switching power supplies and dc-dc supplies and emitted into the area surrounding a supply. Electromagnetic radiation emitted into the atmosphere from the power supply. Conducted is that energy sent down the ac line cord; radiated is sent into the air. Final equipment must meet both standards while many supplies may be rated only for conducted emissions.

Hermetically sealed and contained encapsulated in a thermally conductive epoxy resin or similar plastic. A law effective July 1, which states that external power supplies should meet no load power consumption limits and minimum efficiency limits identical to California Energy Commission CEC limits. Effective the end of the calendar year , Energy Star will no longer govern External Power Supplies and their no load power consumption or efficiency levels.

See ErP for the latest in consumption and efficiency requirements. Covered in a metal or perforated metal cover assembly. Often referred to as Cased or Covered. Typically, an enclosed power supply is covered on all 6 surfaces for finger safe operation. A current produced by the static charge of two objects when they are close enough to produce a discharge or arc.

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The conducting materials have free electrons which move from one atom to another when the potential difference is applied across them. This flow of electrons in a closed circuit is called current. On the basis of the direction of movement of electrons in a closed circuit, the electric current is mainly classified into two types, i. One of the major differences between the alternating and direct current is that in alternating current the polarity and the magnitude of the current changes at the regular interval of time whereas in direct current it remains constants. Some of the differences are explained below in the form of the comparison chart by considering the various factors;.

Both AC and DC describe types of current flow in a circuit. In direct current (DC), the electric charge (current) only flows in one direction. Electric.

AC vs. DC (Alternating Current vs. Direct Current)

The AC current changes its polarity and magnitude periodically and continuously with respect to time. The Ac current can be produced with a device named alternator that produces the alternating current. Suppose a piston is inserted inside a pipe and connected with a rotating rod as in the pin pic below. Here the piston has two strokes one towards upward and the other towards backward on the upward stroke, the water moves in a clockwise direction and the backward direction the water displaces in an anticlockwise direction so in this way water direction changes its direction periodically with oscillation of the piston.

Power is the backbone of any electronic system and the power supply is what feeds the system. Choosing the right supply can be the critical difference between a device working at optimum levels and one that may deliver inconsistent results. Direct current power supplies are either unregulated or regulated.

However, the two appear to be more recently coming together to exist in harmony. Alternating and reversing direction 60 times per second 50 in Europe , AC current could be converted to different voltages more easily using a transformer. However, in recent years, DC has seen a bit of a renaissance. While both AC and DC current deliver electricity, the way in which that electricity arrives at its end destination differs. What are your appliances and electronics eating?

Comparison chart

Latest Articles in "Industry News". Electricity comes in two forms—alternating current AC and direct current DC. Both are essential to enable the functioning of our electronics, but do you know the difference between the two and what they apply to? Alternating current AC power is the standard electricity that comes out of power outlets and is defined as a flow of charge that exhibits a periodic change in direction. AC 's current flow changes between positive and negative because of electrons—electrical currents come from the flow of these electrons, which can move in either a positive upward or negative downward direction.

What Is The Difference Between AC and DC?

When the electricity was invented many changes have taken place over the years.


  • Sulamita T. 08.05.2021 at 14:23

    The consistent and constant voltage of DC power supplies electronics that use a battery, such as your mobile device or smartphone. Like the battery powering your.

  • Tilly C. 11.05.2021 at 03:36

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