question: What's the difference between an input of 110-240V 1.5A and 2A on a power supply?
comment: The difference is 0.5 Amperes. One of the supplies is less efficient than the other, and thereby draws more current. Alternatively, they could be nearly the same efficiency, but they specify the current draw in different ways. One could be quoting average and the other one quoting peak, for example.
passages: Voltage regulation is a measure of change in the voltage magnitude between the sending and receiving end of a component, such as a transmission or distribution line. It is given in percentage for different lines.
  
  Mathematically, voltage regulation is given by,
  
  formula_2
  
  Section::::Line Parameters of AC transmission.
  
  The AC transmission has four line parameters, these are the series resistance & inductance, and shunt capacitance and
  
  admittance. These parameters are responsible
  
  for distinct behavior of voltage and current waveforms along the
  
  transmission line. Line parameters are generally represented in their
   Some "universal" replacement power supplies allow output voltage and polarity to be switched to match a range of equipment. With the advent of switch-mode supplies, adapters which can work with any voltage from 110 VAC to 240 VAC became widely available; previously either 100–120 VAC or 200–240 VAC versions were used. Adapters which can also be used with motor vehicle and aircraft power "(see EmPower)" are available.
   BULLET::::1. For "carefully monitored applications where peak transient capability must be maintained, a system should be powered with an amplifier capable of delivering twice its IEC rating." As an example, a studio monitor rated at 300 watts IEC, can be safely driven by a 600 watts (RMS) amplifiers, provided that "peak signals are normally of such short duration that they hardly stress the system's components".
   This is the current version of the ATX12V spec, published in April 2013. It is specified in Revision 1.31 of the 'Design Guide for Desktop Platform Form Factors', which names this as ATX12V version 2.4.
  
  Section::::Power supply.:ATX power supply derivatives.
  
  Section::::Power supply.:ATX power supply derivatives.:SFX.
   If the SMPS has an AC input, then the first stage is to convert the input to DC. This is called "rectification". An SMPS with a DC input does not require this stage. In some power supplies (mostly computer ATX power supplies), the rectifier circuit can be configured as a voltage doubler by the addition of a switch operated either manually or automatically. This feature permits operation from power sources that are normally at 115 V or at 230 V. The rectifier produces an unregulated DC voltage which is then sent to a large filter capacitor. The current drawn from the mains supply by this rectifier circuit occurs in short pulses around the AC voltage peaks. These pulses have significant high frequency energy which reduces the power factor. To correct for this, many newer SMPS will use a special PFC circuit to make the input current follow the sinusoidal shape of the AC input voltage, correcting the power factor. Power supplies that use active PFC usually are auto-ranging, supporting input voltages from , with no input voltage selector switch.
   For loads other than incandescent lamps, such as fluorescent lamps, high-intensity discharge lamps, and electrical home appliances, the triac-based electronic switching in the lamp module is unsuitable and an "appliance module" must be used instead. These modules switch the power using an impulse relay. In the U.S., these modules are generally rated to control loads up to 15 amperes (1800 watts at 120 V).
   All voltages are root mean square voltage; the peak AC voltage is greater by a factor of , and the peak-to-peak voltage greater by a factor of 2.
  
  Section::::Plugs.
   BULLET::::- C7/C8 connectors for up to 10 A (IEC maximum is 2.5 A)
  
  BULLET::::- C13/C14 and C15/C16 connectors for up to 15 A (IEC maximum is 10 A)
  
  BULLET::::- C19/C20 and C21/C22 connectors for up to 20 A (IEC maximum is 16 A)
  
  Given the 120 V (±5%) mains supply used in the United States and Canada, these higher ratings permit devices with C6 and C8 inputs to draw more than 114 V × 2.5 A = 285 W from the mains, and devices with C14 inputs to draw more than 1140 W from the mains.
   Low voltage and low current signals (i.e., at the secondary of a voltage transformers and current transformers) are brought into a low pass filter that removes frequency content above about 1/3 of the sampling frequency (a relay A/D converter needs to sample faster than twice per cycle of the highest frequency that it is to monitor). The AC signal is then sampled by the relay's analog-to-digital converter from 4 to 64 (varies by relay) samples per power system cycle. As a minimum, magnitude of the incoming quantity, commonly using Fourier transform concepts (RMS and some form of averaging) would be used in a simple relay function. More advanced analysis can be used to determine phase angles, power, reactive power, impedance, waveform distortion, and other complex quantities.
   Two different breakdown voltage measurements of a material are the AC and impulse breakdown voltages. The AC voltage is the line frequency of the mains. The impulse breakdown voltage is simulating lightning strikes, and usually uses a 1.2 microsecond rise for the wave to reach 90% amplitude, then drops back down to 50% amplitude after 50 microseconds.
  
  Two technical standards governing performing these tests are ASTM D1816 and ASTM D3300 published by ASTM.
  
  Section::::Gases and vacuum.
   BULLET::::- For an arbitrary periodic waveform formula_24 of period formula_25:
  
  BULLET::::- For a sinusoidal voltage:
  
  BULLET::::- For a triangle waveform centered about zero
  
  BULLET::::- For a square waveform centered about zero
  
  Section::::Mathematics of AC voltages.:Example.
  
  To illustrate these concepts, consider a 230 V AC mains supply used in many countries around the world. It is so called because its root mean square value is 230 V. This means that the time-averaged power delivered is equivalent to the power delivered by a DC voltage of 230 V. To determine the peak voltage (amplitude), we can rearrange the above equation to:
   Section::::Development.:12 V–only supplies.
  
  Since 2011, Fujitsu and other tier-1 manufacturers have been manufacturing systems containing motherboard variants that require only a 12 V supply from a custom-made PSU, which is typically rated at 250–300 W. DC-DC conversion, providing 5 V and 3.3 V, is done on the motherboard; the proposal is that 5 V and 12 V supply for other devices, such as HDDs, will be picked up at the motherboard rather than from the PSU itself, although this does not appear to be fully implemented .
   - AC: up to 690 V, up to 250 A
  
  - DC: up to 600 V, up to 400 A.
  
  Typical connectors and inlets that were built according to this edition of the standard used spring-loaded butt contacts and were made by Avcon and Maréchal Electric.
   An off line regulator can be a complete integrated circuit with all capabilities necessary to provide clean power to a small portable or handheld device, or it may be used as part of a larger switched mode power supply (SMPS) or DC-DC converter.
  
  Section::::Characteristics.
  
  Although alternating current is commonly described as being "120 V" or "240 V", this is the root mean square of the actual full peak voltage of the AC sinewave, which is +/- 169 V for 120 V and +/- 338 V for 240 V.
   This is a practical guidance what to mix and what not to mix:
  
  BULLET::::- Older systems (before Pentium 4 and Athlon XP platforms) were designed to draw most power from 5 V and 3.3 V rails.
  
  BULLET::::- Because of the DC-DC converters on the motherboard that convert 12 V to the low voltages required by the Intel Pentium 4 and AMD Athlon XP (and subsequent) processors, such systems draw most of their power from the 12 V rail.
   A distinction should be made between the voltage at the point of supply (nominal voltage at the point of interconnection between the electrical utility and the user) and the voltage rating of the equipment (utilization voltage). Typically the utilization voltage is 3% to 5% lower than the nominal system voltage; for example, a nominal 208 V supply system will be connected to motors with "200 V" on their nameplates. This allows for the voltage drop between equipment and supply. Voltages in this article are the nominal supply voltages and equipment used on these systems will carry slightly lower nameplate voltages. Power distribution system voltage is nearly sinusoidal in nature. Voltages are expressed as root mean square (RMS) voltage. Voltage tolerances are for steady-state operation. Momentary heavy loads, or switching operations in the power distribution network, may cause short-term deviations out of the tolerance band and storms and other unusual conditions may cause even larger transient variations. In general, power supplies derived from large networks with many sources are more stable than those supplied to an isolated community with perhaps only a single generator.
   An AC power supply typically takes the voltage from a wall outlet (mains supply) and uses a transformer to step up or step down the voltage to the desired voltage. Some filtering may take place as well. In some cases, the source voltage is the same as the output voltage; this is called an isolation transformer. Other AC power supply transformers do not provide mains isolation; these are called autotransformers; a variable output autotransformer is known as a variac. Other kinds of AC power supplies are designed to provide a nearly constant current, and output voltage may vary depending on impedance of the load. In cases when the power source is direct current, (like an automobile storage battery), an inverter and step-up transformer may be used to convert it to AC power. Portable AC power may be provided by an alternator powered by a diesel or gasoline engine (for example, at a construction site, in an automobile or boat, or backup power generation for emergency services) whose current is passed to a regulator circuit to provide a constant voltage at the output. Some kinds of AC power conversion do not use a transformer. If the output voltage and input voltage are the same, and primary purpose of the device is to filter AC power, it may be called a line conditioner. If the device is designed to provide backup power, it may be called an uninterruptable power supply. A circuit may be designed with a voltage multiplier topology to directly step-up AC power; formerly, such an application was a vacuum tube AC/DC receiver.
   The ATX specification requires the power supply to produce three main outputs, +3.3 V, +5 V and +12 V. Low-power −12 V and +5 V (standby) supplies are also required. The −12 V supply is primarily used to provide the negative supply voltage for RS-232 ports and is also used by one pin on conventional PCI slots primarily to provide a reference voltage for some models of sound cards. The 5 V supply is used to produce trickle power to provide the soft-power feature of ATX when a PC is turned off, as well as powering the real-time clock to conserve the charge of the CMOS battery. A −5 V output was originally required because it was supplied on the ISA bus; it was removed in later versions of the ATX standard, as it became obsolete with the removal of the ISA bus expansion slots (the ISA bus itself is still found in any computer which is compatible with the old IBM PC specification (e.g., not found in the PlayStation 4.)
   Since the first revision of the ATX standard, PSUs were required to have a 3.3 V output voltage rail. Rarely, a linear regulator generated these 3.3 V, supplied from the 5 V and converting the product of voltage drop and current to heat. In the most common design this voltage is generated by shifting and transforming the pulses of the 5 V rail on an additional choke, causing the voltage to rise delayed and rectified separately into a dedicated 3.3 V rail and getting the rising idle voltage cut by a device type TL431, which behaves similar to a zener diode. Later regulators managed all the 3.3, 5 and 12 V rails. Cutting the pulse by the voltage regulator the rato of the 3.3 and 5 V is controlled. Some of these PSUs use two different chokes, feeding the to the 3.3 V rail from the transformer to manage changing loads by pulse with ratio between the 3.3 and the 5 V outputs. In designs using identical chokes, the pulse width manage the ratio.
   Section::::Applications.:Home appliances.
  
  Harness of white goods products can be reduced significantly by use of AC/DC-BUS between its modules. The new architecture use only two 24 V DC wires and two 110/220 V AC wires connecting all modules within the white goods products. Yamar’s semiconductors use these lines for data communication over noisy power lines; activating loads and reading sensors without need for extra wires.
   Other variants include plug/sockets with a rating of 10 A using a round earth pin, which is used on "special use" circuits, such as storage heaters in classrooms; and a 110 V 10 A version that has round active & neutral pins with a flat earth pin. The latter is rated at only 110 V (since certain [foreign] 110 V plugs could be inserted into the socket-outlet) and may be used on PAR 64 lights, where two 110 volt 1000 watt lamps are used in series.
   Take a transformer that is rated at 10 kVA and 240/100 V. The secondary side has an impedance equal to 1∠0° Ω. The base impedance on the secondary side is equal to:
  
  formula_34
  
  This means that the per unit impedance on the secondary side is 1∠0° Ω / 1 Ω = 1∠0° pu When this impedance is referred to the other side, the impedance becomes:
  
  formula_35
  
  The base impedance for the primary side is calculated the same way as the secondary:
  
  formula_36
   Generally, supply voltages must be within ±5% of their nominal values at all times. The little-used negative supply voltages, however, have a ±10% tolerance. There is a specification for ripple in a 10 Hz–20 MHz bandwidth:
   most practical standards operate in the range 70–96 GHz. Table 1 lists a typical set of junction parameters for a commonly used design.
  
  Section::::Array design.
   The BC548 is an example of the modern low-cost member of this family, still in a through-hole package, while the BC848 is the Surface-mount version.
  
  Section::::Table of BC107 to BC860 Variants.
  
  (see also:  for a neat summary of some of the family).
  
  Noise Figure (at 1kHz, for 2 kilohm source, BW=200Hz, I=0.2mA/V=5V) is 10dB for those not tabulated as "Low Noise".
  
  Section::::Current Ratings.
  