Power Supply Units
Table of Contents
1.Input Overview
1.Input Current
2.Inrush Current
3.Input Fuse
2. Mounting Method, Wiring, and Connection
1.Mounting Method
2.Connection
3. Safety
1.Input Voltage Range
2.Leakage Current
3.Wiring Materials
4.Electric Shocks and Burns
4. EMI
1.Separation of Wiring
2."Heavy and Short"
3.Grounding
4.Electric Shocks and Burns
5. Reliability
1.Ambient Temperature and Service Life
2.Overhaul

TECHNICAL NOTESHow to Use Switching Power Supplies
Switching power supplies are compact, lightweight, and highly efficient. Used correctly,
they can improve the reliability of your electric equipment.

Input Overview
There are many types of switching power supplies
manufactured and used worldwide, some for AC and somefor DC operation. Before using your switching power supply,
check the local voltage and whether it is AC or DC, theallowable voltage range, and the input selection method.
The RUBYCON resonant power supply can be used with
input voltage between 85 Vac and 264 Vac and frequency
between 47 Hz and 63 Hz. Input outside the specified range
may damage the power supply. Even if the input voltage iswithin the specified range, distortion in the input voltage may
impair the proper functioning of the power supply.

Power supply voltage (AC) around the world

Input Current
Although there are some exceptions, in switching power
supplies that directly rectify AC input, the most common
method of rectification is the capacitor input method, in whichcurrent runs through a smoothing capacitor. In such cases,
the input current is determined by the output power, input
voltage, power factor and efficiency.

Input fuse

Inrush current
prevention circuit

PFC
Output power*Input current =Input voltage x Power factor x Efficiency

In general, the power factor of switching power supplies
using the capacitor input method is between 0.4 and 0.6.
However, the power factor of the RUBYCON resonant power
supply is approximately 1, due to the use of a PFC (PowerFactor Collection) circuit. This means that the input current
requirement is lower than for other switching power supplies.

Input rectifying and smoothing circuit
Power Factor Collection circuit* PFC:
Rubycon resonant switching power supply:
Other switching power supplies:

Built-in PFC circuit
No PFC circuit

Inrush Current
In switching power circuits, when the power is turned onpeak current flows while the input smoothing capacitor ischarging. This current is called "inrush current". The inrush
current varies depending on the input timing and whether or
not an inrush current prevention circuit is employed, and it
occurs between 10 and 20 times before the normal operating
condition is reached.
If several switching power supplies are used at once, theinrush current increases. This is an important point toconsider when selecting power cables, fuses, and switches.

Input voltage

Input current

Inrush current

Input Fuse
If the input fuse blows (opens), it may mean that there is aproblem with the switching power supply. Do not replace thefuse but report the problem to your local RUBYCON sales
office or distributor.

Input
smoothingcapacitor

Mounting Method, Wiring, and Connection
Even the most sophisticated switching power supply will not provide the expected performance if it is notinstalled, wired, and connected properly. Please observe the precautions outlined below.

Mounting Method(1) Heat Radiation(2) Output Deratinga. Ensure proper ventilation.

The output power depends on the operating temperature.

b. Make sure the switching power supply faces in theproper direction.

Please refer to the derating diagram for the model you
are using.

c. Allow for thermal conductivity.
d. If you are installing a number of switching power
supplies side by side, leave at least 60 mm of open
space between them.

ExhaustExhaustSpace in between

With coverOutput power (%)

e. If necessary, consider the use of forced air-cooling.

Without coverForced air coolingAmbient temperature (˚C)

Derating characteristic (Example)(3) Mounting Screws

Air intake

Air intake

Single use

Multiple use

Make sure the screws that you use to mount the power
supply are no more than 50 mm long. Tighten thescrews to a torque of no more than 1.56 Nm (16 kgfcm).
Set Chassis

Power Supply Chassis
Mounting screw

Clamping Torque 1.56 Nm or less

Length of screw inside power supply 50 mm or lessConnection(1) Input and Output Wiring(2) Groundinga. Keep the input and output wires separate to protect
the output from external surges in the input lines andto prevent an increase in conductive noise in theinput.

To ensure safety and reduce noise, ensure that thegrounds for the power supply and the device are “heavyand short”.

b. Ensure that the output wires are “heavy and short”, tooptimize output current.
Switching power supply

Equipment ground

Input wires
Output wires

Power supply ground(3) Wiring for Remote ON / OFF Control andRemote Sensing(4) Correct Terminal Connection
When wiring the switching power supply, use screws ofa suitable diameter, apply appropriate pressure, and use
suitable tools and wires.

Output wires(including voltage sensing wire)

Remote ON/OFF control

Wiring conceptual diagram

SafetyIn general, switching power supplies are DC stabilized power supplies that are designed to be installedinside electrical devices. Please use them for this purpose only.

Input Voltage Range
The input voltage range for the standard RUBYCON power
supply is between 85 Vac and 264 Vac. The frequency range
is between 47 Hz and 63 Hz. Using input outside of theseranges could damage the power supply or cause it tomalfunction. To avoid damaging the power supply or hostequipment, do not apply input voltage in excess of 264 Vac.
To ensure the stable operation of the equipment, ensure thatthe input voltage is more than 85 Vac.

Fuse

Leakage Current
The leakage current of the noise filter built into the switching
power supply is below the maximum leakage current
specified in the applicable safety standards. The leakage
current increases when more than one unit is used. To
prevent electric shocks, be careful to ground the unit(s)properly.

Example of branch wiring on secondary side

Wiring Materials
To prevent overheating of wires when the switching power
supply is overloaded, use wires that are appropriate for theoutput current capacity of the switching power supply. Be
especially careful when wiring to more than one load. If thinwires are used as the branch lines, the overcurrent
protection may not operate in the event of a short circuit. In
such cases, it is necessary to prevent problems by suchmeans as inserting fuses in the wiring. It is also necessary tobe aware of the rated voltage of the wires you are using.

HotElectricshock

Requirement: Switching power supplies of the built-in typeare subject to the national safety standards
that apply to the final products in which they
are used. Before using a power supply, besure to check the various specifications forthe applicable safety standards.

Electric Shocks and Burns
Switching power supplies contain parts that generate highvoltage and high heat. Take the appropriate precautions toprevent electric shocks and burns.

HotEMIRUBYCON switching power supplies are designed to meet EMI requirements. However, the input power
supply, load, wiring, and grounding can all affect the characteristics of a switching power supply. Keepthe following principles in mind when using a switching power supply.

Separation of Wiring“Heavy and Short”

If the input wires are close to the output wires, conductive
noise and radiant noise may increase. Similarly, if the input
wires are close to the internal wiring (especially digitalcircuits), external noise may cause the equipment tomalfunction. Ensure that the input wires are kept away fromthe output wires.

Ensure that the input and output wires used in the equipment
are “heavy and short”. Looped wires can decrease noiseperformance.

Grounding
Use short, heavy wires to connect the power supply housing
ground and the equipment ground, and ensure that theconnections are made securely.

Reliability
Ambient Temperature and Service Life

OverhaulSwitching power supplies are compact, lightweight, andhighly efficient. However, their service life is affected by theambient temperature. In particular, the electrolytic capacitor
that is used as a smoothing filter is very sensitive to theambient temperature because of the chemical reactions that
occur within the capacitor. In general, the effect oftemperature on the service life of an electrolytic capacitor
follows the Arrhenius rule*, and the service life of a switching
power supply is affected accordingly.

There is increasing demand to extend the service life ofswitching power supplies. To extend the life of a switching
power supply, overhaul it at an appropriate time given theconditions of use. The appropriate timing of an overhaul
depends on the ambient temperature in which it is used andthe number of hours of continuous operation. The following
may be useful as a guideline.

ShortService lifeLong* Arrhenius rule: For every 10˚C increase in ambienttemperature, the service life decreases
by 1/2, and for every 10˚C decrease inambient temperature, the service life
doubles.

Ambient temperature
Low

High

In general, the relationship between ambient temperatureand the service life of a switching power supply is as shownin the figure above. To extend the service life of a switching
power supply, it may be necessary to overhaul it, forexample by replacing the electrolytic capacitor.

Ta = 40°C - 45°C
Ta = 35°C - 40°C
Ta = 30°C - 35°C

Every 3 years
Every 4 years
Every 5 years

Contact RUBYCON sales for more information on overhauls
and power supply life.