Switching Power Supply

1. Unit 3 Electronic System
Components
Lesson 7 Switching Power Supply

2. Switching Power Supply
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A switched-mode power supply (SMPS) is an electronic
power supply that incorporates a switching regulator to
convert electrical power efficiently.

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Lesson 7 Switching Power Supply
• Backgrounds
• Text tour
• Language in use
– Vocabulary

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• Terminology
– Domino effect
Backgrounds

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Terminology

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Domino effect
• A cumulative effect produced when one event sets off a
chain of similar events.
• The domino effect of increasing the speed limit in one of
several contiguous states.
Example:
(Top) Dominoes
are standing.
(Bottom)
Dominoes are in
motion.

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Text tour
• Outline
– Linear versus Switching Power Supplies
– Basic Converters
• Forward-Mode Converter Fundamentals
• Boost-mode Converter Fundamentals
– Topologies

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• The linear regulator
– It operates by reducing a higher i/p voltage down to the
lower voltage by linearly controlling the conductivity.
– only 30 to 50 percent efficient
– uneconomical above 10 watts for small applications
• Switching regulator
– operates the power devices in the full-on and cutoff
states
– efficiencies of between 70 to 90 percent
– an attractive choice for output powers greater than 10
watts or where multiple outputs are desired
Linear vs. Switching Power Supplies

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Figure 3.1. Forward-Mode Converter Operation
Basic Converters
Forward-Mode Converter Fundamentals

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Figure 3.1. Forward-Mode Converter Operation
Basic Converters
Forward-Mode Converter Fundamentals

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Figure 3.2. Schematic of a Boost Converter
Basic Converters
Boost-mode Converter Fundamentals

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Figure 3.3. Waveforms for a Boost Converter
Basic Converters
Boost-mode Converter Fundamentals

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• Vocabulary
– load , cutoff, flux, barrier, effect, condition
Language in use

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Vocabulary

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Load in dictionary
• A weight or mass that is supported:
• The overall force to which a structure is subjected in supporting a
weight or mass or in resisting externally applied forces.
• Something that is carried, as by a vehicle, a person, or an animal:
• The quantity that is or can be carried at one time.
• The share of work allocated to or required of a person, a machine, a
group, or an organization.

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Load in text
• Historically, the linear regulator was the primary method
of creating a regulated output voltage. It operates by
reducing a higher input voltage down to the lower output
voltage by linearly controlling the conductivity of a series
pass power device in response to changes in its load. This
results in a large voltage being placed across the pass unit
with the load current flowing through it.

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Load in use
• admissible load
• capacitive load
• circuit load
• inductive load
• ohmic load
• output load
• safe load
• unmatched load

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Cutoff in dictionary
• A designated limit or point of termination.
• A shortcut or bypass.
• The act or an instance of cutting off:
• Designating a limit or point of termination:
• The point of degradation, due to attenuation or distortion, at which a
signal becomes unusable.

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Cutoff in text
• The switching regulator operates the power devices in the
full-on and cutoff states. This then results in either large
currents being passed through the power devices with a
low “on’’ voltage or no current flowing with high voltage
across the device.

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Cutoff in use
• current-gain cutoff
• grid-current cutoff
• grid-voltage cutoff

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Flux in dictionary
• A flow or flowing.
• A continued flow; a flood.
• The lines of force of a magnetic field.
• Constant or frequent change; fluctuation.
• A substance that aids, induces, or otherwise actively
participates in fusing or flowing

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Flux in text
• During the “on” period, energy is being stored within the
core material of the inductor in the form of flux. There is
sufficient energy stored to carry the requirements of the
load during the next off period.

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Flux in use
• electric flux
• magnetic flux
• core flux
• non-oxygen flux
• rosin flux
• scalar flux
• short-circuit flux

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Barrier in dictionary
• A structure, such as a fence, built to bar passage.
• Something immaterial that obstructs or impedes:
• A boundary or limit.
• Something that separates or holds apart.

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Barrier in text
• Non-isolated switching power supplies are typically used
for board-level regulation where a dielectric barrier is
provided elsewhere within the system.

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Barrier in use
• air barrier
• collector barrier
• contact (potential) barrier
• customs barrier
• emitter barrier
• fire barriers
• language barrier
• sonic barrier
• water barrier

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Effect in dictionary
• Something brought about by a cause or an agent; a result.
• The power to produce an outcome or achieve a result;
influence:
• A scientific law, hypothesis, or phenomenon:
• Advantage; avail:
• The condition of being in full force or execution:
• A particular impression:

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Effect in text
• The companies building their own power systems are
leaning toward transformer isolation in as many power
supplies as possible since it prevents a domino effect
during failure conditions

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Effect in use
effect consequence result outcome
• An effect is produced by the action of an agent or a cause and
follows it in time:
• A consequence also follows a cause and is traceable to it, but the
relationship between them is less sharply definable
• A result is an effect, or the last in a series of effects, that is viewed
as the end product of the operation of the cause:
• An outcome is a result but more strongly than result implies finality
and may suggest the operation of a cause over a relatively long period:

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Condition in dictionary
• A mode or state of being:
• A state of readiness or physical fitness.
• A disease or physical ailment:
• Social position; rank.
• One that is indispensable to the appearance or occurrence of another;
prerequisite:
• One that restricts or modifies another; a qualification.

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Condition in text
• A crowbar is a latching SCR which is fired when the
output is sensed as entering an overvoltage condition.

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Condition in use
• abnormal operating conditions
• adverse conditions
• housing conditions
• normal running conditions
• oscillating condition
• short-circuit condition

33. Thank You
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