Strand 2 (Electrical/Electronics) — Power Supplies: From Mains AC to Usable DC and Back Again

Power Supply

A circuit that takes an available source of electrical energy and delivers the required voltage, current, and waveform to a load.

Transformer-powered Supply

A power supply that uses a mains-frequency transformer to provide galvanic isolation and to step voltage up or down.

Line-connected Supply

A power supply connected directly to the mains without a mains-frequency isolation transformer.

Galvanic Isolation

A condition where there is no direct conductive path from the mains to the low-voltage output, enhancing safety.

Capacitive Dropper Supply

A line-connected supply using capacitive components for voltage reduction, typically for small current applications.

Resistive Dropper Supply

A line-connected supply that uses resistors to reduce voltage, often wasteful and intended for tiny loads.

Switch-mode Power Supply (SMPS)

A type of regulated power supply that uses switching technology to convert power efficiently, often without galvanic isolation.

Load Current

The current drawn by the circuit or device that requires power.

Ripple

The AC component superimposed on the DC output of a rectifier, representing voltage variation.

Linear Regulator

A type of voltage regulator that maintains a constant output voltage by dissipating excess voltage as heat.

Duty Cycle

The fraction of time a signal is in an active state, used in PWM to control the average power delivered to a load.

Smoothing Capacitor

A capacitor used in power supplies to reduce voltage ripple after rectification.

Transformer Utilization Factor (TUF)

A measure of how effectively a transformer is used in relation to its capacity.

Full-wave Rectifier

A type of rectifier that uses two diodes to convert both halves of the AC waveform to DC, resulting in lower ripple.

Peak Inverse Voltage (PIV)

The maximum voltage a diode can withstand in the reverse direction without breaking down.

Surge Current

A short burst of high current that occurs when devices like capacitors or inductors switch on.

Fuse

A protective device that melts and breaks the circuit when current exceeds a certain threshold.

Thermal-magnetic Circuit Breaker

A circuit breaker that uses both thermal and magnetic elements to trip under overload or short-circuit conditions.

Capacitance

The ability of a component to store charge per volt, typically measured in Farads (F).

H-Bridge

A circuit configuration used in inverters to drive a load with AC by reversing the polarity of the output.

Pulse Width Modulation (PWM)

A technique used to control the average voltage delivered to a load by varying the width of the pulses in a signal.

Electrolytic Capacitor

A type of capacitor that uses an electrolyte to achieve a large capacitance, sensitive to polarity.

DC to AC Converter

An inverter that converts direct current (DC) into alternating current (AC) for powering AC loads.

Inrush Current

The initial surge of current required to start a device, often considerably higher than its running current.

High-Voltage DC Bus

A system used in some inverters to step up DC voltage to high levels for further processing.

Breaking Capacity

The maximum fault current that a fuse or circuit breaker can safely interrupt.

Headroom

The minimum voltage differential required between input and output for regulators to operate effectively.

Voltage Rating

The maximum voltage that a component can handle safely without failure.

Isolation Transformer

A transformer used to isolate a circuit from the mains supply, providing safety from electrical shocks.