Power Conversion Terminology

Power Conversion Terminology

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Absolute Maximum Ratings

A limit specified in the operating and environmental conditions of electronic equipment which, if exceeded, can cause permanent damage to the converter.

AC Filter

A filter circuit that suppresses or weakens unwanted frequencies in alternating current.

AC-DC Converter

An electronic component that converts AC(alternating current voltage) to DC(direct current voltage).


Operating the newly manufactured power supply at a rated load for a period of time to troubleshoot initial component failures or other potential defects.

Ambient Temperature

The temperature of the still air around a power supply while it is operating.


Balun Filter

Balun filter is commonly used in DC-DC converters, it will be connected to the input power line, it shows low impedance for differential signals; It shows high impedance for common mode signals.


In terms of stability, the lower the bandwidth, the more stable the power supply; From the perspective of dynamic indicators, the higher the bandwidth, the better the dynamic performance of the power supply, the higher the power density and the lower the cost.

Base Plate

A piece of metal which all of the converter installed on and is designed to carry away the heat generated by the electronic components.

Battery Backup

The voltage that damages the insulation of electronic products and causes leakage of electricity or even sparks. For power modules, the breakdown voltage is the maximum AC or DC voltage that can be applied from input to output.

Burn In

Operating the newly manufactured power supply at a rated load for a period of time to troubleshoot initial component failures or other potential defects.



An electronic component that stores electric charge. It has the function of passing alternating current and isolating direct current.

Case Temperature

The case temperature of the power supply in normal operation.


CFM means cubic feet per minute (cu ft/min). It is a measurement of the velocity at which air flows into or out of a space.


A passive components used for filtering to meet the power requirements of electronic equipment.

Common Mode Filter

It is equivalent to combining two inductors together to make the current difficult to pass, in order to play the role of common mode current non-circulation and differential mode current circulation

Common Mode Noise

Stray current, such as stray capacitance, that passes through the ground and returns to the power line.

Conduction Cooled

Use a radiator or place the power module on the metal to dissipate heat .

Convection Cooled

A form of cooling in which heat is dissipated by the flow of gases.

Copper Loss

It refers to the heat generated by the current flowing through the thermal conduction in the winding wires of transformers or other electronic equipment, which is the loss of energy.

Cross Regulation

It refers to the rate of change of the output voltage of the whole power supply when the load current of one circuit of the multi-circuit output power supply changes, which is an important index to examine the multi-circuit output power supply.


When an overvoltage is detected, the product will be shut down to protect the load.

Current Limiting

Control the output current of the power supply to prevent damage to the load and power supply due to excessive current.

Common Mode Filter

It is equivalent to combining two inductors together to make the current difficult to pass, in order to play the role of common mode current non-circulation and differential mode current circulation.

Current Limit Knee

A value of the output current of a power supply, beyond which the current begins to be limited, that is, it remains at its maximum output.

Current Mode Control

It is an improvement from the voltage mode and can be used to replace the triangle wave to detect the inductive current of the circuit. It can also be used to replace the inductive current of the circuit with the current of the transistor or the resistance of the electric flu to detect the current.

Current Transformer

When the line current is too high, the test will be calculated at a rate of low current.


DC Filter

A filter circuit that suppresses or weakens unwanted frequencies in direct current and uses capacitance to filter the output waveform more smoothly.

DC-DC Converter

A power supply that converts an unstable direct current to a stable output direct current of different voltages for use in electronic equipment.

DCR (DC Resistance)

Refers to the resistance generated when direct current passes through electronic components, that is, the inherent static resistance of the components.


Electronic components are deliberately operated at less than their maximum operating capacity so that they can operate at higher temperatures.


A dielectric (or dielectric material) is an electrical insulator that can be polarized by an applied electric field. It is an excellent capacitor material.

Dielectric Withstand Voltage

The maximum voltage that the dielectric can withstand without damage.

Differential Mode

Voltage and current are transmitted through two wires as a round trip line, respectively.

Differential Mode Noise

Differential Mode Noise

Distributed Capacitance

Distributed capacitance exists between two conductors with voltage difference and mutual insulation, which emphasizes the uniformity of distribution. Generally speaking, the smaller the distributed capacitance of an inductor is, the higher its natural vibration frequency is. The larger the distributed capacitance is, the lower the natural frequency will be.


Other things being equal, the variation of output voltage with time after heating process is called drift.

Duty Cycle

The ratio of working time to total time in a period.

Dynamic Load Regulation

The rate of change of the output voltage when the output current changes rapidly.

Dynamic Response

The response of a control system to its output from its initial state to its final state under typical input signals.



The ratio of total output power to output power is expressed as a percentage.

Electronic Load

A equipment that controls current, voltage and resistance.

Electrostatic Discharge (ESD)

It is the transfer of electrostatic charges between two objects with different electrostatic potentials that can cause current thermal effects, such as sparks and electromagnetic interference./p>

Electromagnetic Interference (EMI)

Electronic devices interfere with other electronic devices through electromagnetic waves.

Equivalent Series Inductance (ESL)

It is an equivalent inductance in a circuit element, used to describe the inductance component of the impedance in the circuit element.

Equivalent Series Resistance (ESR)

An ideal capacitor does not lose any energy on its own, but in practice, because the material used to make it has resistance, the dielectric of the capacitor has losses. This loss is external and behaves like a resistor in series with a capacitor, so it is called "equivalent series resistance". The lower the ESR, the lower the loss, the higher the output current, and the higher the quality of the capacitor.

Electromagnetic Compatibility (EMC)

The ability of a device or system to operate normally in its electromagnetic environment without causing intolerable electromagnetic disturbance to anything in the environment. Includes EMI and EMS.


Failure Mode

Reasons why converters do not meet the requirements or become non-compliant with technical specifications.

Faraday Shield

It is an electrostatic shield that reduces the capacitance between the primary and secondary windings. This shield reduces the common-mode noise and transient amplitude caused by passing through the transformer.

Faulty Mode Current

The input current absorbed by the converter when the output is short-circuited.

Federal Communications Commission (FCC)

The Federal Communications Commission (FCC) is an independent agency of the United States government that regulates communications by radio, television, wire, satellite, and cable across the United States. The FCC maintains jurisdiction over the areas of broadband access, fair competition, radio frequency use, media responsibility, public safety, and homeland security.

Feed Forward

By directly detecting the input voltage of the converter to improve the voltage stability performance, the system can be processed according to the predicted information before deviation occurs.

Floating Output

The output or input pin of the circuit didn’t link together, resulting in unexpected results, so that the circuit or program inexplicable output or even crashed.

Flyback Converte

The flyback converter is a power supply topology that uses mutually coupled inductor, to store energy when current passes through and releasing the energy when the power is removed. It has simple structure, low cost, is the commonly used industry architecture.

Foldback Current Limiting

It is similar to constant-current control, the voltage decreases as the load resistance goes to zero, and the current decreases.

Forced Air Cooling

Use a fan to force air circulation to dissipate heat.

Forward Converter

When the switching tube is closed, the positive excitation mainly relies on the energy storage inductance and the flyback diode to maintain the output, and the transformer does not store energy.

Full Load

The instantaneous maximum power that the power supply can withstand.


It is a disposable component connected to the circuit to protect the circuit from damage by blowing a fuse when the current is too high, causing an open circuit and interrupting the current.



Electrical connection to the ground (or to some conductor to the eart


Hall Effect Sensor

It is a transducer that converts a changing magnetic field into an output voltage.

Heat Sink

It is used to cool down hot electronic components.

Hiccup Mode

A protective mode in which the power is disconnected due to an output fault and the internal power consumption is maintained at a safe level until the fault is eliminated.

High Line Input

The maximum continuous voltage which is allowed to be input to the converter while maintaining normal operation of the converter.

High Potential Test (Hi-Pot Test)

A test to determine whether the breakdown voltage of a transformer or power supply exceeds the minimum requirements.

Hold-Up Time

The length of time for which the output voltage can normally maintain the output alignment during shutdown or power failure of the power supply. This test condition is set at rated voltage and full load.

Hot Swap

Insert or remove a circuit board on a backboard that is running on electricity without causing the host or peripheral devices to burn out, and can detect and use new devices in a timely manner.



It is a general term of resistance, inductance and electric melting in the circuit.

Input Curren

When the converter is in operation, it absorbs ground current from the input power supply.

Input Reflected Ripple Current

The component of AC current reflected from the module power supply to the battery or DC power supply. If the reflected current loop is large, the input reflected ripple current will generate electromagnetic fields and cause EMI problems.

Input Voltage Range

The lowest and highest input voltages when the converter is in operation.

Inrush Current

Refers to the peak current flowing into the power supply immediately after the power is switched on. Because the input filter current is charged rapidly, the peak current is much higher than the steady state input current.


To separate the charged body by using a nonconductive substance.

Insulation Resistance

The resistance between two conductors separated by an insulating material.

Internal Power Dissipationt

The power consumption generated inside the converter during normal operation.

International Electrotechnical Commission (I.E.C)

It is a worldwide standardization organization composed of various electrotechnical committees. Its purpose is to promote the standardization in the field of electrotechnics and electronics in the world. Its purpose is to promote the international cooperation on standardization and related issues in the field of electrical and electronic engineering and to enhance the international mutual understanding.


RIt is to convert direct current into alternating current.


To separate the charged body by using a nonconductive substance.

Isolation Voltage

This is the maximum insulation voltage that two systems without direct electrical connection can withstand.


Leakage Current

In order to reduce interference, the power supply must be equipped with an EMI filter circuit. Due to the EMI circuit, when the switching power supply is connected to power, there is a small current to ground, which is called leakage current.


The unit of measurement of air velocity used to cool a power converter.

Life Test

A test that allow the converter to run for a period of time to estimate its lifespan.

Line Regulation

Other things being equal, the percentage of variation in output voltage. The lower the percentage, the better.

Linear Power Transformer

Using cored wire to convert voltage, its disadvantages are large volume, heavy weight, low conversion efficiency, but the price is cheap.

Linear Regulation

The voltage regulator's resistance varies with the load and input voltage so that the output voltage is stable.


Usually refers to the electronic component to which the output of a circuit is connected.


The filter element is attached to both ends of the load to reduce noise.

International Electrotechnical Commission (I.E.C)

It is a worldwide standardization organization composed of various electrotechnical committees. Its purpose is to promote the standardization in the field of electrotechnics and electronics in the world. Its purpose is to promote the international cooperation on standardization and related issues in the field of electrical and electronic engineering and to enhance the international mutual understanding.

Load Regulation

When the output load changes, the change in output voltage is expressed as a percentage. The lower the percentage, the better.

Long Term Stability

Other things being equal, the output voltage of the converter changes over time.

Low Line Input

The minimum continuous voltage allowed to be input to the converter while maintaining normal operation of the converter.


Maximum Ambient Operating Temperature

The maximum ambient temperature at which the circuit is expected to operate normally.

Maximum Load

The maximum output load to which the converter can be connected under normal operation.

Mean Time Between Failure (MTBF)

This is the average continuous trouble-free time of the product during operational use or testing.

Minimum Load

The minimum output load to which the converter can be connected under normal operation.

Minimum Operating Temperature

The minimum ambient temperature at which the circuit is expected to operate normally.


No Load Voltage

The voltage on the output pin when the converter is not connected to the load.

Nominal Input

The normal values of the input voltage range.

Nominal Value

The quantification of a declared or targeted value.

Normal Operating Current

It is the maximum current that flows through the circuit when the device is working.


Off-Line Power Supply

A source of power supplied by an AC grid.

Open Frame

A power module without a case.

Operating Temperature Range

The temperature range within which an electronic component can maintain its proper function and function.

Output Current Rating

The standard value of the DC output current of a power supply.

Output Filter

The output impedance determines how much the output voltage of a source circuit decreases when it is connected to a load. The smaller the output impedance, the stronger the load capacity, and the larger the input impedance, the better the isolation effect from the external circuit. Impedance matching is to eliminate the influence between each circuit functional module.

Output Voltage Accuracy

Under normal input voltage and full load, the accuracy is the percentage difference between the actual measured output voltage and the output voltage specified in the specification. The smaller the output precision, the more stable the output.

Overcurrent Protection

A protective mechanism that turns off the power supply when the output current exceeds a preset value.


In signal processing, control theory, electronics, and mathematics, overshoot is when a signal or function exceeds an expected value and is a characteristic of transient response. This is commonly seen in the step response phase of a band-limited system such as a low-pass filter, which is usually followed by an accompanying ringing.

Overtemperature Protection

When the internal temperature of the power supply is too high, the overtemperature protection will be started to stop the power supply immediately, so as not to burn out due to the internal parts overheating.

Overvoltage Lockout (OVLO)

the power supply voltage in the electronic device is higher than a certain standard value, to protect the circuit, the function of OVLO is activated to cut off the power supply circuit.

Overvoltage Protection (OVP)

TA protective mechanism that shuts off the power supply when the output voltage exceeds a preset value.


Parallel Operation

The positive pole and the positive pole of the power supply are connected, and the negative pole and the negative pole are connected, called parallel connection. When the power is connected in parallel, the output voltage does not increase, but the battery's workload is halved and its life is doubled.

Peak On-Stage Surge Current

The current flowing through the element in the on state.

Peak Pulse Curren

The maximum rated pulse current of the rated amplitude and waveform.


The filter consists of two capacitors and an inductor with a low impedance input and output to reduce the reflected ripple current.

Positive Temperature Coefficient (PTC)

It means that the resistance value of a material will rise with the rise of temperature. If the resistance temperature characteristic of a material can be used as an engineering application, it is generally required that the resistance value will change greatly with the temperature, that is, the temperature coefficient is large. The larger the temperature coefficient is, the more the resistance increases under the same temperature change.

Power Density

It is power per unit volume (the rate of energy transfer).

Power Density

It is power per unit volume (the rate of energy transfer).

Power Dissipation

Power dissipation is generated by the current flowing through and the voltage across the two ends of the element in the actuating state.

Power Factor Correction (PFC)

To improve the power factor.

Power Rating

A steady output of power over a long period of time.

Pulse Frequency Modulation (PFM)

P FM has a fixed ON time type and a fixed OFF time type. When the load becomes large, the number of ON times in the period of time will be increased to meet the load. In other words, the frequency becomes higher when the load is heavy, and lower when the load is light.

Pulse Transformers

It is a transformer which changes the input sinusoidal voltage into a narrow pulse output voltage by using the magnetic saturation property of the core.

Pulse Width Modulation (PWM)

A technique that converts analog signals into pulses. Generally, the period of the pulse is fixed after conversion, but the operating period of the pulse varies depending on the size of the analog signal.

Push-Pull Converter

It is a derivative circuit of step-down converters. It is a combination of two forward converter operating in opposite phase with a maximum operating cycle of less than 0.5. It is commonly used in DC DC converters.


Rated Current

Rated current = rated power/rated voltage, which is the maximum safe current.


A device, such as a diode, that allows current to flow in one direction.

Redundant Operation

A repetitive component or function that is deliberately configured in a system to improve its reliability.


A measure that stabilizes the output voltage of a power source or supply device when the power supply voltage or load changes.

Reverse Current

The current passing through the diodes is the reverse current formed by the drift motion of the minority carriers. This reverse current is also known as the reverse saturation current or leakage current. The reverse saturation current of a diode is greatly affected by temperature.

Reverse Voltage Protection

The function of preventing internal device damage when the input and output terminals of the converter are polarity reversed.


The abbreviation for “Radio Frequency Interference”, the noise from radio frequency sources.

Ripple and Noise

Ripple is namely ripple wave, a pulsating component of DC voltage output; Noise is the noise signal on the ripple wave.

Ripple Voltage

It is an AC component of DC voltage, which is obtained by alternating current rectification and filtering.


Secondary Winding

The winding in a transformer which is not directly connected to an AC power supply.

Self Resonant Frequency (SRF)

Self Resonant Frequency (SRF)

Series Operation

The series operation achieves the highest effect on the system with high resistance.


A method of blocking electromagnetic interference, it is used to protect components, equipment, and devices that are sensitive to electromagnetic interference.

Short Circuit Protection

A short circuit fault will occur when electrical appliances or wiring insulation in the electrical control line is damaged, load short circuit, or when wiring error occurs.

Six-sided Shielding

The converter is housed in a metal case. This metal shield reduces any electromagnetic interference (EMI) emitted from the converter element.

Soft Start

"Soft start" is a function that allows gradual increase of the output of electronic devices to at least 100%, often starting the motor on the start. Soft start can make the motor start slowly under the action of voltage, and achieve stable start by suppressing the starting current value.


It provides electrical power to electrical loads for electrical installations. The main function is to convert the current from the source to the correct voltage/current/frequency to supply the load.

Standby Current

The current consumed by the converter when the converter is not loaded but the power is not turned off.

Step Change

Step response refers to the time domain characteristics of the output of the system as the input of the system changes from 0 to 1 in a very short time.

Storage Temperature Range

Temperature range within which electronic components can be safely stored.

Surface Mount Devices (SMD)

Surface welded parts, generally those electronic parts that can use SMT processes or techniques.

Surface Mount Technology (SMT)

A technique for welding electronic components to the surface of a circuit board.

Switch Mode Power Supply

Switching power supply inputs are mostly AC or DC power supplies, while outputs are mostly devices that require DC power

Switching Frequency

The switching frequency in electronic systems refers to the frequency at which electronic switches are switched and, in some electronic systems, is also the carrier frequency.

Switching Regulator

A switching voltage regulator is a voltage regulator that uses switching elements to convert the input power supply into a pulse voltage, and then uses capacitors, inductors and other elements for smoothing. Supply power from input to output by switching on a switch (MOSFET) until the desired voltage is reached. Once the output voltage reaches a default value, the switch element will turn off without consuming any input power. Repeating this operation at high speed allows for efficient voltage supply and less heat generation.


Thermally Sensitive Resistance

It is very sensitive to temperature changes, using its sensitivity to temperature, through the change of resistance value, and using TSR conversion circuit converted into temperature value. The structure is made of metal oxide semiconductor materials. Among them, the change of resistance is divided into "positive temperature coefficient", "negative temperature coefficient" and "critical temperature coefficient".

Temperature Coefficient (TC)

A measure of a change in error due to the change in temperature

Thermal Conductivity

The ability of a material to conduct heat, or thermal conductivity. Thermal conductivity “K” refers to the material's ability to conduct heat directly, or thermal conductivity. Thermal conductivity is defined as the heat energy directly conducted by a material of unit cross section and length in unit temperature difference and unit time.

Thermal Gasket

It can fill in the gap to complete the heat transfer between the heat generating part and the heat dissipating part, as well as insulating, shock absorbing and sealing.

Thermal Joint Compound

It is used as sealing, bonding, insulation, moisture-proof, anti-vibration materials, as electronic components, semiconductor equipment, electronic and electrical equipment bonding and sealing materials; Or for the heat dissipation of electronic appliances, power supply, transistor and thermistor heat dissipation, bonding and sealing, PTC bonding insulation, etc., especially suitable for high thermal conductivity of the bond seal requirements.

Thermal Protection

Thermal protection is a method of detecting overheat and disconnecting electrical circuits. The protective device protects against fire or damage to electronic components caused by overheating of power supplies or other equipment.

Thermal Resistance

The ability of an object to resist heat transfer in the presence of a temperature difference. The better the thermal conductivity, the lower the thermal resistance.

Thermal Resistivity

The greater the thermal resistance, the worse the heat transfer performance. On the contrary, the lower the thermal resistance rate, the better the heat transfer.

Three-Terminal Regulator

The three-terminal voltage regulator has only three pins, namely the input end, the output end and the ground (common end). According to the function, it can be divided into fixed voltage regulator circuit and adjustable voltage regulator circuit. The fixed voltage is fixed, while the adjustable voltage can get a wide range of regulation through external components.


The main uses are to lift AC voltage, change impedance and separation circuit.


Transient means a short period of time. For example, after the oscillator is temporarily disturbed and suppressed, it takes some time to return to equilibrium. Or system variables are permanently altered to achieve a new equilibrium. This short period of time between states of equilibrium is called "transient time".

Transient Recovery Time

Transient recovery time is the specification of DC power supply. It describes how quickly the power supply recovers from the transient load state on the power supply output.

Transient Suppression

Transient voltage suppression diodes, abbreviated as TVS devices, when subjected to a high-energy transient overvoltage pulse under specified reverse application conditions, the operating voltage can immediately replace a very low conductance value, allowing large currents to pass through, clamping the series voltage to a pre-determined level, and thus effectively protecting delicate components in the electronic circuit.

Thermal Resistivity

The greater the thermal resistance, the worse the heat transfer performance. On the contrary, the lower the thermal resistance rate, the better the heat transfer.

Transient Voltage Suppressor

It is an overvoltage protection component. It is small in size, low in price, extremely fast in response and stable in clamping voltage. It is often used as overvoltage protector in various instruments, household appliances and automatic control devices, and can also protect the power tube of switching power supply and voltage sensitive devices.

Turn Ratio

The ratio of turns is equal to the ratio of the first and second induced electromotive forces. The ratio of turns is proportional to the voltage ratio, and it is inversely proportional to the current ratio.

Twisted Pair

TIt is a kind of universal wiring made of two mutually insulated conductors wrapped together according to a certain specification (usually clockwise wound). It belongs to the transmission medium of information communication network. It has been used in the telephone network for more than 100 years. Twisted-pair wires used to transmit analog signals, but now they are used for digital signals as well.


Underwriters Laboratory (UL)

UL is an independent product safety certification organization. The main business is product safety and establishes standards and test procedures for a wide range of products, materials, parts, tools and equipment.

Uninterruptible Power Supply (UPS)

A device that continuously supplies back-up AC power to electrical load equipment and maintains normal electrical operation in the event of a power grid anomaly (e.g., power failure, undervoltage, interference, or surge). In general, an uninterruptible power system is used to maintain the uninterrupted operation of critical commercial equipment or precision instruments such as computers (especially servers) or switches to prevent the loss of computer data, the interruption of telephone communication networks, or the loss of instrument control.

Undervoltage Lockout (UVLO)

When the input current is lower than the default value, no output current will be generated.


Voltage Balance

Voltage balance is the difference in amplitude, in percentage, between two output voltages that have equal nominal voltage amplitudes but opposite polarity. When referring to dual power sources, voltage balancing is usually used. This is the difference in percentage between the magnitude of the positive output voltage and the negative output voltage. Ideally, this value should be zero, but this is hardly feasible in most power supplies.


Withstand Voltage

This test is conducted by applying a high voltage to the input power line of the electrical product within a specified period of time to the specified high voltage value of each product type by the safety authority, and this test provides that an arc breakdown (or crash) shall not occur during the application of the high voltage.