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What is Power supply? (Basics of Power Supply) | Matsusada Precision

Outline of Power Supply

Power supplies generally refer to generators, power plants, batteries, and solar cell (photovoltaic cell). This section describes the basic knowledge of power supply units (power supply circuit) that convert power into a power suitable for electrical appliances.

Many electronic devices use DC voltages. However, commercial power supplied from an outlet is alternating current (AC) of a fixed voltage 100V or 200V. Therefore, a power supply unit (power supply circuit) is used for the operation of the electronic devices to convert AC to DC and regulate voltages. For example, AC adapter is commonly used as a power supply device. Power supplies built into electronic equipment are also called AC/DC power supplies or switched-mode power supplies. Some power supply circuits are known as DC/DC power supplies to convert an unstable DC into a stabilized DC. These power supplies have a constant output voltage that cannot be varied.

AC adapter

We often see AC adapters at home. They are used for electronic devices like computers and a smartphone charger. Many of them have a compact square design, and we can plug them directly into an outlet or connect to a cord that plugs into an outlet.

In the past, adapters used to be too big and heavy to carry. Thanks to innovative voltage conversion methods, more compact and lightweight design can be adopted to them. Devices that supplies a defined voltage, frequency, etc. are required to use dedicated ones.

AC adapter
AC/DC power supply
AC/DC power supply refers generally to a power supply device that converts AC to DC. Electronic equipment that uses DC incorporates a power supply circuit to supply from an outlet. AC adapter is also a kind of AC/DC power supply.
Switched-mode power supply
The switched-mode power supply has a switch mode to convert AC to DC, similarly to AC/DC power supply. New advancements in AC adapter design led to higher efficiency with smaller and lighter units, as mentioned in the AC adapter. In fact, it is due to the switching method replacing the linear method.
DC/DC power supply
The DC/DC power supply, also called DC/DC converter, is designed to input a DC voltage and output a different DC voltage. As the operating voltages vary depending on the electronic devices, a voltage needs to be converted to the appropriate voltage to operate their respective devices.

Power supply classification and application

A variety of power supplies are used in the development and evaluation of electrical equipment and production line.

Power source we use in daily life is an outlet. However, electricity supplied from an electrical outlet generates noise following momentary voltage drops. The power frequency for commercial AC power is 50Hz or 60Hz and the electricity is normally 100V or 200V.

Stable, noise-free electricity is a must in using electricity for operating and testing various electrical equipment. And different voltages, frequencies, and not only AC but DC are essential for such purposes. Power supply unit is used for providing stable electricity.

The device converts and supplies electricity of the required voltage and frequency, excluding noise from the electricity obtained from an electrical outlet. Power supplies are classified by applications for available DC, AC, and output voltage ranges.

Programmable DC power supply

The programmable power supply is used for stable DC power supply. At Matsusada Precision, the programmable DC power supplies are classified to DC power supplies. Separating them from high voltage power supplies mentioned below, products with output voltage up to 1000 V are classified as DC power supplies.

They are used in experiments on electronic circuits, factory operation of production equipment, inspections, and research.

Moreover, it is also available to reproduce the electricity supplied by a battery during the inspection and testing of battery powered equipment.

The programmable power supplies are further classified into series and switching regulator power supplies based on circuit method. A series regulator power supply is also referred to as a linear power supply, and it converts AC voltage to DC with a transformer.

On the other hand, a switching power supply has a feature that converts a switching current into high-frequency AC using coils and semiconductors, and then converts it back to DC for control.

As for the difference between linear and switching power supplies, see "Difference between Linear Power Supply and Switching Power Supply"

Programmable DC power supply is classified into "DC constant voltage power supplies" and "DC constant current power supplies" according to whether the output voltage or output current is stabilized. In general, the voltage and current in a power supply circuit will change as the load (resistance) changes, based on Ohm's law.

Therefore, the operation of the circuit depends on which of the two is stabilized when the load changes. In other words, a DC constant-voltage power supply has a stable output voltage even when the load changes, and a DC constant-current power supply has a stable output current.

High voltage power supply

The high voltage power supply is a programmable DC power supply that provides high output voltage over thousands to tens of thousands of volts.

It has various shapes suitable for different applications: benchtop, rack mount, module, and PCB mount types. Some models has AC/DC input.

High voltage power supplies are suited for scanning electron microscopes, X-ray inspection system, X-ray CT scanning, etc. As these devices are used for electronic detection or control, they require a very strong electric field to detect and control electrons in operation. HIgh voltage is essential to generate such a strong electric field.

If noise and stability are still far satisfactory in performance, the devices would have serious negative impact on images due to the noise. High voltage power supplies provide high stability and low ripple solution.

Programmable AC power source (AC power source)

The programmable power supply can provide a stable and reliable AC power supply. While programmable DC power supplies need to deliver stable voltage, programmable AC power sources must also provide stable AC waveforms.

Programmable AC power sources can be broadly classified into two types: AC voltage stabilizers and frequency converters. AC stabilizers are used to stabilize output voltage and output waveforms. Frequency converters have features of maintaining a constant output frequency or outputting an arbitrary frequency.

The method of AC stabilizers is classified into the slidac, tap-switching, and phase control methods. And the frequency converters are broadly classified by the linear amplifier and inverter methods. Some frequency converters can also output DC.

Type Method Compact size Efficiency Cost-effective Fast response Waveform quality Features
AVR
AC stabilizer
Slidac method Good      
Tap switching method Good    
Phase control method Good Good Bad Highly reliable
Having high distortion
Linear amplifier method Good Bad Bad Good Outstanding in output waveform
CV/CF
frequency converter
Linear amplifier system Good Bad Bad Good output waveform quality
Varying output voltage and frequency at any time.
Switching method     Outstanding in waveform quality, size, efficiency, and cost-effective Well-balanced
Matsusada AC power sources: DRK, DRS, DRJ series
Inverter method
(Single range)
Good Good   DC output available for some types
Inverter method
(Wide range)
Good Good   DC output available for some types
Evaluation scale:   : Excellent  : Very good  Good: Good  Bad: Bad