Electromagnetic Compatibility (EMC)

Electromagnetic Compatibility, also known as EMC, is the ability of a device and systems to operate in the electromagnetic environment without impairing functions and without faults.

Say, for example, that you use a microwave in your house. The microwave can affect the wireless LAN and Bluetooth connections and cause some problems. It is a case where the microwave is causing electromagnetic interference to devices via wireless LAN or Bluetooth.
Similar cases are found when a vacuum cleaner or hair dryer is used near the TV. Many forms of electromagnetic interference may prevent regular operation. The EMC measure ensures that a variety of different items of electronic equipment can operate nearby without causing any undue interference.
In other words, the EMC has compatibility to suppress noise emissions as well as immunity to noise.
The Electromagnetic Interference, also known as emissions, is related to the noise generated by electronic equipment and components during operation. And Electromagnetic Susceptibility or EMS refers to the sensitivity of electromagnetic equipment and components to noise during operation, also called immunity.
Nowadays, many things are electronic, and many wirelessly connected electronic devices operate simultaneously. EMC is of increasing importance.

Electromagnetic Compatibility (EMC) | Technical Terms:Power Supplies | Matsusada Precision
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Arc discharge

Arc discharge can be defined as an electrical discharge of high current at low voltage. It has a characteristic of sustaining discharge while emitting many thermal electrons from a high-temperature cathode.

The arc dischrage has two methods: hot cathode arc discharge and cold cathode arc discharge. The hot cathode arc discharge occurs under the cathode is heated and emits thermal electrons.
Hot cathode arc discharge is used to generate plasma for fluorescent lamps, xenon lamps, metal hydride lamps, mercury lamps, and other light sources, as well as thermal plasma and plasma torches.
In cold cathode arc discharge, on the other hand, electrons are directly emitted by a very strong electric field on the cathode surface. A different discharge phenomenon, glow discharge, is used for cold cathode discharge lamps (CCFLs).

Fluorescent lights are the most typical applications in arc discharge. The heat electrons emit and collide with mercury electrons inside the fluorescent tube, generating ultraviolet light. Then, the phosphor-coated inside the tube is emitted by the ultraviolet.
The arc discharge is also used in metal processing, such as arc welding and electrical discharge machining, while it involves many risks because of its high temperatures. Matsusada Precision offers arc discharge solutions and high voltage power supplies to prevent unwanted arc discharge.

Arc discharge | Technical Terms:Power Supplies | Matsusada Precision
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Isolation refers to the electrical and physical separation of individual components or points in a circuit. Isolation is used in power circuits, high-speed and long-distance communications. There are five types of insulation: Functional insulation, Basic insulation, Supplementary insulation, Double insulation, and Reinforced insulation. The commonly used insulation methods are galvanic, optical, magnetic, and capacitive insulations.

When used in high-voltage power circuits, the isolation prevents equipment malfunctions and electric shock to users due to current surges, etc. In high-speed and long-distance communications, it prevents noise generation due to ground loops by connecting the grounds of each communication point.

The isolation system is mostly used in programmable power supplies or motor control system, industrial sensors and various interfaces, and measurement devices. Isolators have certain important parameters to select: power supply current, input signal current, and ranges of power supply and signal voltage. Creepage distance and spatial distance are also important in parameters.
The isolation system comprises of isolation amplifiers, digital isolators, optical isolators, photocouplers, transformers, coils, and other devices. They are to follow individual standards depending on the applications in various areas of industry, information technology, medication, home, measurement, control, and telecommunication.

Isolation | Technical Terms:Power Supplies | Matsusada Precision
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Impedance is the opposition to current flow in an AC circuit. The ratio of voltage and current indicates it, and the unit is "Ω" as with electrical resistance. In a DC circuit, coils and capacitors do not interfere with the current.

In AC circuits, however, not only resistors, but also coils, capacitors, and the circuit itself act like resistors to block current.
As for a coil, if the voltage is constant, the current is also constant. However, when the voltage is not constant, electromagnetic induction tries to oppose the change, resulting in a phenomenon that interferes with the current. Because of it, the coil will be an impedance.

Thus, things that interfere with current in an AC circuit are all regarded as impedance.
Impedance has the property of resistance. It does not change the values by the frequency of electrical resistance. On the other hand, reactance is the property that changes values with frequency. The use of self and mutual impedances in a circuit that could cause equipment malfunction requires particular attention.

Impedance | Technical Terms:Power Supplies | Matsusada Precision
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Sequence Control

Sequence is a sequence of successive actions. Sequential control system refers to the control for successively advancing each step of a control procedure according to a predetermined order or an order determined according to a fixed logic.

For example, a washing machine has presetting modes selectable in advance and proceeds with washing, rinsing, and dehydration in specific methods. This is unlike an air conditioner that keeps the room temperature constant and controls the operation by feedback based on information sent from the sensor.
A washing machine is not controlled by feedback but performs in a series of predetermined operation modes, which is some kind of a sequence control.

For developing advanced solutions and flexibility of the production system, Matsusada Precision provides a broad lineup of programmable DC power supplies, Bipolar amplifiers, and DC electronic loads employing effective sequential programs; pulse sequence, ramp sequence, step control, and other programs. Furthermore, Matsusada's products are suited to your various purposes and applications, including models featuring advanced program functions with detailed output patterns and complex sequence settings without a computer.

Image of sequence programs
Sequence Control | Technical Terms:Power Supplies | Matsusada Precision
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Relative humidity

Relative humidity (RH) is the ratio of water vapor actually in the air compared to the maximum amount of water vapor allowed (Saturated water vapor amount).
It is expressed as a percent and an important tool in weather forecasting as it references the water vapor content in the air. In general, "humidity" refers to Relative humidity, and the measurement method is defined in the Japanese Industrial Standard JIS Z 8806.

Saturated water vapor amount in the air changes with temperature. Even if the amount of moisture in the air is the same, the relative humidity also changes as the temperature changes.
Another way to measure humidity is Absolute humidity. It represents the water vapor in the air regardless of temperature. It is expressed as grams cubic meter of air (g/m3). If the amount of moisture in the air does not change, absolute humidity will not change with changes in temperature.

Relative humidity is widely used to describe the environment in daily life and manufacturing and inspection areas of products. Absolute humidity is not commonly used since relative humidity affects how we feel the temperature.
During product manufacturing, Condensation on the products could affect quality. Using relative humidity is easy to maintain the optimal environment where condensation is less likely to occur.
Generally, relative humidity between 45 to 50 percent feels comfortable for electronic equipment usage. If the humidity is too high, the possibility of condensation increases, and if it is too low, the possibility of static electricity increases.

Relative humidity | Technical Terms:Power Supplies | Matsusada Precision
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Rating can be seen in equipment specifications and performance features under certain conditions. The power supply ratings are provided for voltage, current, frequency, output, load, etc. Absolute maximum ratings, continuous ratings, instantaneous maximum ratings, short-time ratings, etc., are also available.

For example, in using a regulated power supply (RKT80-50 (800W)) with a rated voltage of 80 V, a rated current of 50 A, and a power consumption of 800 W, the maximum output voltage is the rated 80 V.
As the power consumption is 800W or less, up to 10 A will be available within the rating. As for the current of 50 A, the voltage is up to 16 V with 800 W limited.

Rating | Technical Terms:Power Supplies | Matsusada Precision
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Equivalent circuit

The equivalent circuit is another circuit whose terminal current, voltage, and frequency characteristics are equal to those of the original circuit. The equivalent circuit simplifies a complex device's internal elements, representing the characteristics of a substitute circuit.

For example, a circuit with a DC motor is modeled using the equivalent circuit with resistance, inductance, mechanical elements to friction, etc. Thus, you can obtain information on the voltage/current characteristics similar to those of the motor.
Using an LCR meter that measures Inductance (l), Capacitance (C), and Resistance (R), all the parameters of the equivalent circuit model can be calculated in a "series" or "parallel" circuit" depending upon capacitance, inductance, or resistance.

The equivalent circuit helps secure better solutions to your measurement application by simplifying complex objects under certain conditions to make it easier to observe phenomena.
The equivalent circuit can also simulate things that are not electric circuits, such as mechanical vibrations. Therefore, it is available in various analysis fields, including impedance models of living organisms.

Series equivalent circuit
Series equivalent circuit | Technical Terms:Power Supplies | Matsusada Precision
Parallel equivalent circuit
Parallel equivalent circuit | Technical Terms:Power Supplies | Matsusada Precision
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Rush current

When turning on a regulated DC power supply, the Inrush current flows higher than the rated current instantaneously.

At turn-on, a high current exceeding the rated value flows through the circuit immediately, reaching the peak current value. The current value then drops and gradually converges to the rated current value. The inrush current may put a lot of stress on the circuit and be regarded as an overload or short circuit. In some cases, it may cause the breaker to trip or the voltage to drop, and shut down the equipment connected.

Inrush currents could cause by several reasons. In the case of equipment with capacitors, a high current may flow because the capacitors must first be charged. Regarding the devices with filaments, as the resistance of the filament is low before heating the filament, there is highly possible the current flowing gets very high.

Matsusada Precision provides a broad product lineup of power supplies to protect the circuit from the inrush current occurrence. Also, our products are available to support supply power while adjusting to operating within their ratings.

Inrush current | Technical Terms:Power Supplies | Matsusada Precision
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Pulse is an English word meaning heart rate or heartbeat. Electrically, it means a current or radio wave that flows for a very short time. It is also known as impulse current. A series of very short duration ON/OFF currents, such as high-frequency pulses, is also called a pulse. There is some case of a single wave. Waves with the same width at the top and bottom are called square waves.

Pulses are used to control stepping motors and servo motors, as well as to signal CDs and DVDs.
Matsusada Precision offers SK series, AMP series, AP series, and a broad lineup of high voltage amplifiers that can supply high-voltage pulses. Our high voltage amplifiers are suited for various applications such as beam deflection, corona discharge, and dielectric strength testing, in addition to solar cell panel evaluation and piezo drivers.
Note that, however, pulse signals can be a source of noise because the power supply is repeatedly turned on and off. When you use some models in Japan, they apply to "High-frequency use equipment" depending on the output device of high voltage pulses. The products require a license for use from the Minister of Internal Affairs and Communications under the provisions of Article 100 of the Radio Law. The requirement applies to use in Japan. Please follow the laws of the country or region as of usage.
Before installation, confirm the necessary parameters and also requirements of the high-frequency use equipment facility.

Continuous pulse
Continuous pulse | Technical Terms:Power Supplies | Matsusada Precision
Single-shot pulse
Single-shot pulse | Technical Terms:Power Supplies | Matsusada Precision
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Input Voltage

It is the warranty range of input voltage according to the specification. In terms of AC input, it shows the root mean squared value. In terms of AC input, there are single-phase input and 3-phase input which is often used for high power.

Input Current

It flows into the power supply which is shown by root mean squared values. Because of their built-in rectifier circuits in capacitor input type, the input currents of series method as well as switching method generate sine wave but waveform as shown in the figure below. With PFC (power factor improvement circuit), the input current is a sine wave.

Input Power (Input Capacity)

It is indicated as a power to input into the power supply. In terms of the power supply, all of the supplied power are not always consumed. Taking account of this, we consider that there are two types of input powers; one is apparent power which flows into the power supply, the other is effective power to be consumed by the power supply. The difference power between the two powers is not used in the power supply and returns to the commercial power part.


It is provided by the ratio between the output power and the effective input power. The specification is described with rated output power, and as the output current decreases, the efficiency deteriorated

Power Factor

It is provided by the ratio between the apparent power and the effective power. Basically, the value is 0.6 in capacitor input type, or 0.9 with PFC (power factor improvement circuit).

Inrush Current

In switching power supply, high current flows more than ten times to several hundred times which is greater than in normal operations. It shows the wave height value of current flowing at the moment when the input voltage is applied to the power supply. In series power supply, there are two types of current, one for rectifier circuits in capacitor input type at the secondary side and another for saturated transformers after the power is supplied in the 0-phase.

Leakage Current

From the view point of safety, the current is stipulated in the safety regulation in most countries. It flows into the ground via stray capacitance both of parts at primary side and transformers between primary and secondary sides. It also runs through grounded capacitances of the noise filter. The measurement is to be conducted as indicated in the figure below.

Line Regulation

It is a voltage fluctuation to move within the specification.

Load Regulation

[ Static Load Regulation ]
It shows the output alteration moving from null load to the rated capacity.

[ Dynamic Load Regulation ]
It is also called as transient response. It is the output response of the voltage rapidly moving from no-load to the rates capacity.


It is a component which is synchronized to the input frequency as well as switching frequency superimposed to the output voltage, and the value is provided with peak-peak. If a new capacitor is installed at the output side in the switching power supply, the component to synchronize with the switching frequency will be attenuated. Meanwhile, the component synchronized to the input frequency remains unchanged. The output voltage of series power supply only includes components synchronized to the input frequency.

Ripple Noise

The output noise only indicates noise components except certain ripples superimposed to the output voltage, and the value is provided with peak-peak. As most of the switching power supplies are equipped with inverters with rectangular wave, noises occurred from switching transistor and rectifier diode are made in the output.

Overvoltage protection (O.V.P)

This function is essential for protecting the power supply to prevent from applying the voltage to the load exceeding the regulated level. When the protection circuit against overvoltage is activated, the power supply is suspended the operation.

Heat Radiation Design

As power converters, power supplies emit heat of the difference in conversion efficiency. One of the main points in designing is how to release the heat effectively.

[ Natural Air cooling ]
The heat is released by radiation and convection without using forced cooling. You need to secure a sufficient space to pass the air for radiation, taking into account that the heat is released by convection. In using cases, make sure to install the outside air opening to prevent the heated air from increasing inside. In this case, you should adopt a larger size of discharge opening at the stage of designing compared with the inlet. Make sure to install the power supply in the appropriate direction before operating.

[ Forced Air colling ]
As the power supply itself is built in the fan for forced-air cooling, you can regulate the ambient temperature only (of air influx). Be careful not to close the two openings for air influx or discharge.

Remote Controlling

The operation is used for turning on or off the output of power supply from far way, or to spare the time for startup or shutdown in several power supplies. In this function, the output of power supply is turned on or off with external signal. It is available with such devices like relay contact, transistor, and IC. Please confirm respective specifications depending on types of turning on with LOW, turning off with HIGH, or vice versa.

Withstand Voltage

[ Insulation resistance ]
It shows the resistance value to apply regulatory DC voltage between specified terminals.

[ Withstand Voltage ]
It is a voltage without having spark discharges or causing no damage to the power supplies as AC voltage is applied between certain terminals. When it comes to withstand voltage testing, the applied voltage must be raised slowly starting 0V, the voltage needs to be applied using a zero-cross switch.

Working Temperature

It is the warranty range of ambient temperature in operation according to the specification of power supply. The temperature value is provided as the power supply is horizontally placed in no wind. No other option is accepted in installing except the above. Concerning power supplies with built-in fan for forced air cooling inside, the value indicates the temperature of flesh air. The service life of power supply could be shortened by half whenever the temperature increases by 10 degrees. As long as you use the power supply with the lowest-level of temperature, you can extend service life of the equipment.

Storage Temperature

It is an ambient temperature for storage to prevent power supplies from worsening the performance in non-operating status. Be careful not to store power supplies in high temperature for lengthy periods of time which might lead to further deterioration of electrolytic capacitors.