(1) Rated voltage
This indicates a range of voltage to be used.
Electric characteristics of power supply is guaranteed within the
(2) Input frequency
This indicates a usable range of input frequency.
Efficiency is obtained as output power (W) is divided by input power
(Efficiency)｡・Output power)｡・Input active power)
That is, it shows how much energy (W) is effectively converted.
It is in the neighborhood of 70% at general multi-output power supplies.
Nipron aims at 80% or more under the business philosophy to guard
(4) Power factor
Power factor is obtained as active power (W) is divided by apparent
(Power factor)｡・Active power)｡・Apparent power)
In general switching power supplies, rectification circuit is placed
in front to rectify AC input voltage and smooth it with capacitors.
This circuit generates low frequency harmonic current in input due
to its non-linearity to AC input.
This harmonic current leads to not only direct trouble, such as
malfunction of devices and unusual heat buildup in components, but
also social problems like increase of power loss in power transmission
and distribution installation due to poor power factor caused by
increased total loss.
That is why harmonic regulations and rules across the world are
in progress based on International standard (IEC61000-3).
Power factor needs to be close to 1 (= 100%) as counter-measures
against harmonic current. Corresponding to this movement, there
are two circuit systems in general, which are called PFC (Power
Factor Correction) circuit. One is active filter system with electronic
control, the other is passive filter system with passive components.
(5) Inrush current
In switching power supply, peak current flows momentarily to charge
smoothing capacitors when input voltage is turned on. This current
is called inrush current. It varies according to timing when input
voltage is turned on, or soft-start circuit, and it is from several
times up to tens of times of normal input current.
For low input voltage power supplies or when several power supplies
are connected together to supply mains, in particular, switches
or fuses on the line may be damaged.
Careful selection of those is required.
Also, if inrush current is too small, startup of switching power
supply may be too slow.
(6) Input VA
Input VA is a capacity of input block of electric/ electronic circuit
and shown as a product of voltage and current.
(7) Battery discharge cut-off voltage
The minimum discharge voltage at which battery can safely discharge.
When the voltage falls down to the discharge cut-off voltage, the
power supply shuts down output voltage.
When the battery keeps on discharging beyond the cut-off voltage,
the battery goes to "Over discharge."
(8) Maximum current and power
This indicates continuous maximum current and power.
(9) Peak current and power
This indicates current and power beyond the maximum current and
power to be obtained. However, the period of those are specified
by model and needs to be confirmed.
(10) Minimum load
This indicates minimum current load required to run all output voltages
(11) Voltage drift
This mainly indicates output voltage drift in power supply, and
divided into two categories. One depends on environments, (hereinafter
described as drift), the other on the fluctuation of input voltage/output
load (hereinafter described as fluctuation). They are changes in
voltage against the change of external conditions, and show stability
of power supply in "mV," or "%."
1. Initial drift
This indicates the change of output voltage until the components
inside power supply reach the temperature at continuous operation
since input voltage is turned on (normally 30 minutes).
2. Time-lapse drift
This indicates the change of output voltage as times go by after
initial drift. The measurement period is 30 minutes to 8 hours after
input voltage is turned on.
3. Temperature drift (fluctuation)
This indicates the change of output voltage against the change of
ambient temperature to be measured at maximum and minimum operating
temperature, and at normal temperature.
4. Static input fluctuation
This indicates the change of output voltage against slow change
of input voltage to be measured at maximum and minimum input voltage
range, and at rated input voltage.
5. Static load fluctuation
This indicates the change of output voltage against slow change
of output current (load) to be measured at maximum and minimum output
current range, and at the middle of the range.
6. Dynamic input fluctuation
This indicates the change of output voltage against rapid change
of input voltage to be measured when input voltage is changed anywhere
between maximum and minimun input voltage.
7. Dynamic load fluctuation
This indicates the change of output voltage against rapid output
current (load) change to be measured with any change within load
8. Total voltage accuracy
This is total change of "1" to "7" above which
can be regarded as the minimum guaranteed value of output voltage
range of the power supply. However, in many cases, rapid change
such as item "6" or "7" is specified
(12) Maximum ripple and spike noise (voltage)
Output voltage of power supply contains marginal AC component which
is called ripple with UOM of "mV." Acceptable ripple varies
depending on loads so that it should be provided according to each
Also, output voltage contains noise generated by switching devices
and secondary diodes. This noise is indicated in "mV"
and called spike noise. (Figure 1.19)
Figure 1.19 Ripple and Spike noise
(13) Overcurrent protection
This function operates to limit output current when load current
incenses for any reason.
The primary purpose of overcurrent protection is for protection
of power supply. Accordingly, protection of load comes next.
(14) Overvoltage protection
This function protects load when output voltage of power supply
increases excessively. In general, overvoltage detection circuit
in switching power supply operates in a way that control signals
shut down. This shutdown situation is kept until energy inside the
power supply is emitted. Or input voltage needs to be turned off
(15) Timing sequence
This is output sequence in general. This includes rising and falling
timing of Input/Output and sequence of each output, or control of
them at multi-output power supply. They are shown in timing sequence
(16) Operating temperature and humidity
This indicates acceptable operating temperature and humidity.
(17) Storage temperature and humidity
This indicates the acceptable temperature and humidity in storage.
(18) Vibration test
Vibration test is carried out provided that harmonic oscillation
is applied to products (components/devices) during operation or
transportation. Harmonic oscillation is mainly generated by torque,
steady pulsating force or periodic force including vibration in
ships, airplanes, vehicles, helicopters, and space devices, or caused
by machinery and earthquakes.
(19) Mechanical strength (surface dropping) test
This test is simplified test to duplicate hammering and quick vibration
possibly caused by rough handling during repairing or operation
of the product on the workbench.
(20) Dielectric strength
In the case that high voltage is applied between input, output,
and chassis, it may cause arc or insulation break-down to damage
human body or devices connected to. To prevent this, the design
is carried out considering creepage distance in PWB and coil structure
Also, every product is tested with high voltage applied to verify
the safety at final test (Dielectric strength test).
(21) Insulation resistance
Insulator has high resistance (tens of M Ω or more).
However, but it may deteriorate when the unit has absorbed lots
of humidity during lying neglected or due to surface breakdown of
(22) Leakage current
Switching power supply uses grounding capacitrs in primary side
to deal with noise and allows few current.
This current is called leakage current (leak current).
The more grounding capacitors are used, the more effective countermeasures
against noise is. However, leakage current increases. If it increases
too much, the leakage current activates leakage breaker installed
on supply mains to which the power supply is connected to shut down
the systems. This leakage current shall be 1mA or less in general.
(23) Line noise
This is impulsive electric noise generated by arc discharge between
contacts of switch when motors or glow-ramp fluorescent bulbs are
(24) Electrostatic discharge
This discharge is occurred by discharge through fingers of human
body when highly charged by rubbing shoes, clothes, floors, and
shelves each other, in general, or through keys or metal materials
held by hand.
(25) Radiated, radio-frequency electromagnetic field
This is effect under electromagnetic environment which electromagnetic
wave affects by electromagnetic radiation emitted from transceivers,
mobile phones, fixed radio and broadcasting stations, and in-car
walkie-talkies, for example.
(26) Fast transient burst
This is impulsive electric noise containing harmonic components
generated by arc discharge between contacts of switch when motors
or glow-ramp fluorescent bulbs are turned off.
(27) Lightning surge
This is large current and high voltage caused by electric field
effect related to lightning, thundercloud, and power lines generating
electrical change in the neighborhood.
(28) Conductive radio-frequency electromagnetic field
This is electromagnetic wave interference caused by transceivers
with frequency range of 9kHz to 80MHz.
(29) Power frequency magnetic field
This is magnetic field with supply mains frequency (50Hz or 60Hz)
caused by large transformers in the vicinity of high voltage lines,
power stations or substations.
(30) Voltage dipps and fluctuation
This is temporary fluctuation of input voltage caused by troubles
on the power line or ON/OFF operation by large machinery connected
to the same supply mains.
(31) Conducted emission
This is noise that is generated in the switching power supply and
emitted along with input line to affect other devices connected
to the same supply mains.
(32) Harmonic current regulation
In terms of substation and power distribution installation, harmonic
current component becomes noise to cause additional amount of power
distribution when the component is large. As capacitor-input type
switching power supply, in particular, has large harmonic current,
the regulation should be implemented because the existing installations
are burdened too much.
1. Acoustic noise
This is audible noise. Audio frequency is 20KHz or low in general.
It gives metallic sound at higher frequency, and dull clank at lower
2. Feedback noise (Conducted emission) Though the noise generated
in switching power supply is attenuated by built-in filter, it still
leaks to AC line. This is called feedback noise.
3. Radiant noise
Noise generated in swathing power supply is emitted as radio waves.
This is called radiant noise. Metal closure is effective to prevent
this noise from emission.
(34) Cooling system
Forced air cooling: A cooling system by fan(s) to meet specification.
Natural air cooling: A cooling system by natural air convection
to meet specification.
Semi-self cooling: A cooling system by switching natural air cooling
and forced air cooling detecting temperature.
(35) Output GND grounding
It indicates grounding condition of output GND (0V and COM) to FG.
For many general business machines such as PCs, GND grounding is
adopted. Capacitor-grounding or floating is required for use in
industry such as factory.
(36) Buildup characteristics
It indicates rising time of output voltage and characteristics of
its waveform. It varies in specification according to loads.
(37) Instantaneous characteristics (Dynamic characteristics)
This indicates output voltage characteristics including the fluctuation
at rapid change of input voltage and load. This characteristics
is provided when the load changes quickly or power supply is required
to operate with unstable input condition.
(38) Output hold-up time
This indicates hold-up time of output voltage since input is turned
(39) Low voltage
This indicates detection level of output voltage when the output
voltage falls below the operation voltage of load devices due to
blackout, etc. This detection level is set to send a signal and
provided mainly for 5V output.
(40) Rising time
This indicates the period for output voltage to start up since input
voltage is turned on.
(41) MTBF (Mean Time Between Failure)
MTBF is a rough guide to know lifetime of the same type of product
or series product, although it is too hard to know the exact lifetime
individually. MTBF is just a rough guide as it comes from reciprocal
of failure probability under specific conditions.