Practical-3
Aim:- To study SMPS and UPS.
SMPS
A Switched-mode power supply (also Switching-mode power supply, SMPS, or
simply Switcher) is an electronic Power Supply Unit (PSU) that incorporates a switching
regulator in order to provide the required output voltage. An SMPS is actually a power converter
that transmits power from a source (e.g., a battery or the electrical power grid) to a load (e.g., a
personal computer) with ideally no loss. The function of the converter is to provide a reliable
output voltage often at a different level than the input voltage.
Interior view of an ATX SMPS:
Below A - input EMI filtering
A - Bridge rectifier
B - Input filter capacitors
Between B and C - Primary side heat sink
C - Transformer
Between C and D - Secondary side heat sink
D - Output filter coil
E - Output filter capacitors
The coil and large yellow capacitor below E are additional input filtering components that are
mounted directly on the power input connector and are not part of the main circuit board .
Classification
SMPS can be classified into four types according to the input and output waveforms:
AC in, DC out: rectifier, off-line converter input stage
DC in, DC out: voltage converter, or current converter, or DC to DC converter
AC in, AC out: frequency changer, cycloconverter, transformer
DC in, AC out: inverter
Applications:
Switched-mode PSUs in domestic products such as personal computers often have universal
inputs, meaning that they can accept power from most mains supplies throughout the world, with
rated frequencies from 50 Hz to 60 Hz and voltages from 100 V to 240 V (although a manual
voltage range switch may be required). In practice they will operate from a much wider
frequency range and often from a DC supply as well. In 2006, at an Intel Developers Forum,
Google engineers proposed the use of a single 12 V supply inside PCs, due to the high efficiency
of switch mode supplies directly on the PCB.
Switched mode mobile phone charger
SMPS Connectors:
Amphenol connector gives power supply to Mother Board
Mole x gives power supply to IDE drives
Mini Molex gives power supply to floppy drive.
UPS
An uninterruptible power supply, also uninterruptible power source, UPS or battery
backup, is an electrical apparatus that provides emergency power to a load when the input power
source, typically the utility mains, fails. A UPS differs from an auxiliary or emergency power
system or standby generator in that it will provide instantaneous or near-instantaneous protection
from input power interruptions by means of one or more attached batteries and associated
electronic circuitry for low power users, and or by means of diesel generators and flywheels for
high power users. The on-battery runtime of most uninterruptible power sources is relatively
short—5–15 minutes being typical for smaller units—but sufficient to allow time to bring an
auxiliary power source on line, or to properly shut down the protected equipment.
Technologies
The general categories of modern UPS systems are on-line, line-interactive or standby. An on-
line UPS uses a "double conversion" method of accepting AC input, rectifying to DC for passing
through the battery (or battery strings), then inverting back to 120V/240V AC for powering the
protected equipment. A line-interactive UPS maintains the inverter in line and redirects the
battery's DC current path from the normal charging mode to supplying current when power is
lost. In a standby ("off-line") system the load is powered directly by the input power and the
backup power circuitry is only invoked when the utility power fails. Most UPS below 1 kVA are
of the line-interactive or standby variety which is usually less expensive.
For large power units, Dynamic Uninterruptible Power Supply are sometimes used. A
synchronous motor/alternator is connected on the mains via a choke. Energy is stored in a
flywheel. When the mains power fails, an Eddy-current regulation maintains the power on the
load. DUPS are sometimes combined or integrated with a diesel-generator, forming a diesel
rotary uninterruptible power supply, or DRUPS.
A Fuel cell UPS has been developed in recent years using hydrogen and a fuel cell as a power
source, potentially providing long run times in a small space.
Applications
N+1
In large business environments where reliability is of great importance, a single huge UPS can
also be a single point of failure that can disrupt many other systems. To provide greater
reliability, multiple smaller UPS modules and batteries can be integrated together to provide
redundant power protection equivalent to one very large UPS. "N+1" means that If the load can
be supplied by N modules, the installation will contain N+1 modules. In this way, failure of one
module will not impact system operation
Multiple redundancy
Many computer servers offer the option of redundant power supplies, so that in the event of one
power supply failing, one or more other power supplies are able to power the load. This is a
critical point - each power supply must be able to power the entire server by itself.
Redundancy is further enhanced by plugging each power supply into a different circuit (i.e. to a
different circuit breaker).
Outdoor use
When a UPS system is placed outdoors, it should have some specific features that guarantee that
it can tolerate weather with a 'minimal to none' effect on performance. Factors such as
temperature, humidity, rain, and snow among others should be considered by the manufacturer
when designing an outdoor UPS system. Operating temperature ranges for outdoor UPS systems
could be around −40 °C to +55 °C.
Internal systems
UPS systems can be designed to be placed inside a computer chassis. There are two types of
Internal UPS. The first type is a miniaturized regular UPS that is made small enough to fit into a
5.25″ CD-ROM slot bay of a regular computer chassis. The other type are re-engineered
switching power supplies that utilize dual power sources of AC and/or DC as power inputs and
have an AC/DC built-in switching management control units.
