Question 1

Why is the primary side fuse of the power supply in the live side (L phase)?

Accepted Answer

﻿	Q.Why is the primary side fuse of the power supply in the live side (L phase)?Power Supplies > Switching Power Supply > AC-DC Power Supplies/DC-DC ConvertersA.The primary side fuse is in the live side (L phase).Fuses on live sides can melt when there are short circuits between L-FG or N-FG inside power supplies.The primary side fuse is in the live side (L phase) because there is the possibility of electric shock with fuses not melting when there are short circuits between L-FG or N-FG if the fuse is in the neutral side (N phase).						Related Information					   Power Supplies Product Information										Power Supplies Tech Notes										 Contact Information			  Inquiries on products&#44 sales and technical matters

Question 2

Please explain the specs of the vibration test.

Accepted Answer

﻿	Q.Please explain the specs of the vibration test.Power Supplies > Switching Power Supply > AC-DC Power Supplies/DC-DC ConvertersA.Standard number: JIS60068-2-6Standard name: Sinusoidal vibration test methodThe conditions in “instruments used for large power-generating equipment and general industry” for sweep endurance tests have been extracted with the assumption that there are vibrations during transportation.						Related Information					   Power Supplies Product Information										Power Supplies Tech Notes										 Contact Information			  Inquiries on products&#44 sales and technical matters

Question 3

Please explain the difference between the rating voltage on the nameplate seals and specifications.

Accepted Answer

﻿	Q.Please explain the difference between the rating voltage on the nameplate seals and specifications.Power Supplies > Switching Power Supply > AC-DC Power Supplies/DC-DC ConvertersA.The input ranges shown on power supplies (nameplates) are the figures used when applications for safety standards are submitted so approval of the safety standards is already granted at the time of use within these ranges.Furthermore&#44 the specifications shown on documents such as catalogs are the input ranges of the operational assurance that we offer. Therefore&#44 assurance for use within the specifications is given for use exceeding the ranges shown on the power supplies (nameplates) although the safety standards are excluded.						Related Information					   Power Supplies Product Information										Power Supplies Tech Notes										 Contact Information			  Inquiries on products&#44 sales and technical matters

Question 4

Please explain the heat dissipation methods for power modules / onboard power supplies.

Accepted Answer

﻿	Q.Please explain the heat dissipation methods for power modules / onboard power supplies.Power Supplies > Switching Power Supply > AC-DC Power Supplies/DC-DC ConvertersA.They can be classified into two major types depending on the structure of the products.(1) The type where the heat generated from mounted components is directly dissipated in the surrounding airThe heat generated from components mounted on products with exposed mounting boards is directly dissipated in the surrounding air.The electrical power that can be outputted with this type of product can be increased when it is forcedly cooled with external fans (CC-E series have cases to cover their mounting boards but are classified as this type because they have intake ports for surrounding air and mold resin is not used).The operable temperatures are specified in the ambient temperatures with the type above.Refer to the specifications&#44 output deratings&#44 and instruction manuals of the products for details.(2) The type where heatsinks are attached for the use of heat conduction and dissipation in the surrounding airAluminum baseplate-type products (with heat-generating components mounted on aluminum plates) require the attaching of appropriate heatsink on their baseplates.With this type&#44 the heat generated from mounted components placed on the baseplates undergoes heat conduction (conduction cooling) in the heatsink through the baseplates and is efficiently dissipated in the surrounded air with the heatsink.This type is different from the one described above in that the operable temperatures are specified in the baseplate temperatures. It is adopted by products that have relatively large capacity and high levels of heat generation. It allows electrical power that can be outputted to be designed freely through the shape of the heatsink and forced cooling of the heatsink with an external fan (please contact us for details).						Related Information					   Power Supplies Product Information										Power Supplies Tech Notes										 Contact Information			  Inquiries on products&#44 sales and technical matters

Question 5

Is it alright to clean the products?

Accepted Answer

﻿	Q.Is it alright to clean the products?Power Supplies > Switching Power Supply > AC-DC Power Supplies/DC-DC ConvertersA.Washing only the terminal pins by brush with IPA (isopropyl alcohol) is recommended&#44 with the exception of some products (cleaning solutions that enter the products may cause deterioration of the components used).Refer to the instruction manuals of the respective products for details.						Related Information					   Power Supplies Product Information										Power Supplies Tech Notes										 Contact Information			  Inquiries on products&#44 sales and technical matters

Question 6

Is it a problem if the load currents of each output are not equal in ±2 output products with insulated onboard power supplies?

Accepted Answer

﻿	Q.Is it a problem if the load currents of each output are not equal in ±2 output products with insulated onboard power supplies?Power Supplies > Switching Power Supply > AC-DC Power Supplies/DC-DC ConvertersA.Please note that the output voltages can fluctuate significantly. The output voltages can be stabilized by controlling the voltages between +Vout and -Vout in circuits such as the one shown in the Figure below as±2 output products are compact.Figure 1The output voltages fluctuate with the current values of each output because each output voltage does not undergo stabilized controlling individually. We recommend use combined with a single-output converter when load currents of each output are unequal and precise output voltages are required.						Related Information					   Power Supplies Product Information										Power Supplies Tech Notes										 Contact Information			  Inquiries on products&#44 sales and technical matters

Question 7

What do the terms such as EHFP and HFP at the end of the product nameplates mean?

Accepted Answer

﻿	Q.What do the terms such as EHFP and HFP at the end of the product nameplates mean?Power Supplies > Switching Power Supply > AC-DC Power Supplies/DC-DC ConvertersA.They are identification codes that we use.						Related Information					   Power Supplies Product Information										Power Supplies Tech Notes										 Contact Information			  Inquiries on products&#44 sales and technical matters

Question 8

Please explain power loss of power supplies.

Accepted Answer

﻿	Q.Please explain power loss of power supplies.Power Supplies > Switching Power Supply > AC-DC Power Supplies/DC-DC ConvertersA.The power loss of power supplies is the difference between input active power and output power and is calculated with the formulas below.Power loss= input active power - output powerInput active power can be calculated with the output power ÷ efficiency&#44 sopower loss= (output power ÷ efficiency) - output power.(example) When calculating the power loss in HWS1500-48 with the maximum output power when the input voltage Vin = 200VAC and the ambient temperature Ta = 25°C：The power loss is as shown below because the efficiency is 90% of the specifications with the maximum output power (1536W). Power loss = (1536W ÷ 0.9) - 1536W = 171W						Related Information					   Power Supplies Product Information										Power Supplies Tech Notes										 Contact Information			  Inquiries on products&#44 sales and technical matters

Question 9

Please explain how to interpret the output power when the set voltage is used after being raised above the rated output voltage.

Accepted Answer

﻿	Q.Please explain how to interpret the output power when the set voltage is used after being raised above the rated output voltage.Power Supplies > Switching Power Supply > AC-DC Power Supplies/DC-DC ConvertersA.The maximum output power is calculated with the formulas below.Maximum output power = rated output voltage × maximum output currentPlease note that there are specifications on the maximum output power when the set voltage is raised above the rated output voltage and that the levels of the maximum output currents that can be used will be lowered.(example) When HWS100A-5 is set at 5.5V and used:The maximum output current that can be used = maximum output power ÷ set voltage=100W÷5.5V = 18.2A						Related Information					   Power Supplies Product Information										Power Supplies Tech Notes										 Contact Information			  Inquiries on products&#44 sales and technical matters

Question 10

Please explain how to interpret the output power when the set voltage is used after being lowered below the rated output voltage.

Accepted Answer

﻿	Q.Please explain how to interpret the output power when the set voltage is used after being lowered below the rated output voltage.Power Supplies > Switching Power Supply > AC-DC Power Supplies/DC-DC ConvertersA.The maximum output current that can be used increases if the set voltage is lowered when “maximum output power = rated output voltage × maximum output current” is used&#44 but please use at the specified values of the maximum output current or below because there is the danger of damage due to factors such as the generation of heat in the components inside the power supply.						Related Information					   Power Supplies Product Information										Power Supplies Tech Notes										 Contact Information			  Inquiries on products&#44 sales and technical matters

Question 11

Please describe the power consumption (loss).

Accepted Answer

﻿	Q.Please describe the power consumption (loss).Power Supplies > Switching Power Supply > AC-DC Power Supplies/DC-DC ConvertersA.The power consumption (loss) is the difference between input power and output power and is calculated with the formulas below.Pd: Power consumption (W)Pin: Input power (W）　Pin = Vin × IinPout: Output power (W）　Pout = Vout × Ioutη: EfficiencyVin: Input voltage (V)Iin: Input current (A)Vout: Output voltage (V)Iout: Output current (A)Example 1) The efficiency is 92.5% of the specifications with the maximum output (30W) when the input voltage of the CC30-4805SFP-E is 48V and the ambient temperature is 25°C.The power consumption (loss) in this case is Pd = (30 ÷ 0.925) – 30 = 2.43W with the formula above.Example 2) The following figures were produced when the DC-DC converter was operated and the input power voltage and output power current were measured.Input voltage (Vin) = 47.996VInput current (Iin) = 0.348AOutput voltage (Vout) = 5.014VOutput current (Iout) = 2.998AThe power consumption (loss) in this case is Pd = (47.996 × 0.348) – (5.014 × 2.998) = 1.67W with the formula above.						Related Information					   Power Supplies Product Information										Power Supplies Tech Notes										 Contact Information			  Inquiries on products&#44 sales and technical matters

Question 12

How much output power (current) can actually be used?

Accepted Answer

﻿	Q.How much output power (current) can actually be used?Power Supplies > Switching Power Supply > AC-DC Power Supplies/DC-DC ConvertersA.The specifications stipulate the maximum output current and maximum output power. It is necessary to use the products under conditions where none of these figures are exceeded so that it can be operated safely.Please note that they will be as shown below particularly when using an output voltage variable function.(1) When the output voltage is equal to the rated output voltage (initial settings)　　The maximum output power = the maximum output current × the rated output voltage so there is no problem if it is confirmed that one of them is not exceeded.(2) When setting the output voltage higher than the rated output voltage　　The maximum output power < the maximum output current × the set output voltage so it is limited with the maximum output power (the output current must be decreased).(3) When setting the output voltage lower than the rated output voltage　　The maximum output power > the maximum output current × the set output voltage so it is limited with the maximum output current (the output power must be decreased).Output derating by operating temperature is also specified for each product. This must also be taken into consideration along with the other factors.Example) The maximum output current is 2A and the maximum output power is 10W under the specifications if the output voltage of the CC10-4805SF-E is adjusted to 6V with an ambient temperature of 85°C and convection cooling is used&#44 but the output current is decreased so that it does not exceed the maximum output power when the output voltage is set higher than the rated output voltage.It is necessary to make a further decrease down to 40% or below during use with an ambient temperature of 85°C with output derating.Therefore&#44 the maximum output current is as follows:Maximum output current = maximum output power ÷ set output voltage × 0.4 = 10 ÷ 6 × 0.4 = 0.66A    Figure 1						Related Information					   Power Supplies Product Information										Power Supplies Tech Notes										 Contact Information			  Inquiries on products&#44 sales and technical matters

Question 13

Are there specifications for input surge currents (inrush currents) with DC input power modules / on-board power supplies?

Accepted Answer

﻿	Q.Are there specifications for input surge currents (inrush currents) with DC input power modules / on-board power supplies?Power Supplies > Switching Power Supply > DC-DC ConvertersA.There are regularly no stipulations in the specifications.Please refer to the typical waveforms listed in the data for the models of the respective products.Input surge currents (inrush currents) are charging currents that flow into capacitors that are connected between input lines when the power is turned on. These currents also flow when input voltage is instantly applied with a device such as a switch in DC input power modules / on-board products. However&#44 the values of the input surge currents (inrush currents) change according to the capacity of input capacitors that are additionally connected outside or impedance components of wiring patterns.    Figure 1*The input surge current (inrush current) is the total value of the charging current that flows into the capacitor inside the product ① and the charging current that flows into the input capacitor Cin that connects to the exterior ②.						Related Information					   DC-DC Converters Product Information										Power Supplies Tech Notes										 Contact Information			  Inquiries on products&#44 sales and technical matters

Question 14

Please explain how to interpret the ambient temperature of power supplies.

Accepted Answer

﻿	Q.Please explain how to interpret the ambient temperature of power supplies.Power Supplies > Switching Power Supply > AC-DC Power Supplies/DC-DC ConvertersA.The intake temperature of the power supply is defined as the ambient temperature of the power supply with forced air cooling type power supplies.    Forced air cooling type power suppliesThe location that is not affected by the heat generated from the power supply is defined as the ambient temperature with convection cooling type power supplies. Also&#44 please be careful so that there is no exposure to radiation heat from the power supply.Convection cooling type power supplies						Related Information					   Power Supplies Product Information										Power Supplies Tech Notes										 Contact Information			  Inquiries on products&#44 sales and technical matters

Question 15

What is MTBF?

Accepted Answer

﻿	Q.What is MTBF?Power Supplies > Switching Power Supply > AC-DC Power Supplies/DC-DC ConvertersA.MTBF (Mean Time Between Failures) is the numerical value that determines the number of repair parts prepared for products that are operating in the market.(example) If there are 1&#44000 products operating in the market; the number of units that will fail after 100 hours is estimated and the number of products that must be prepared is determined.The calculation formula used in this case is “1&#44000 units × 100 hours = 100&#44000 hours/units”.The forecasted number of failures is 100&#44000 ÷ 50&#44000 = 2 units if the MTBF is 50&#44000 hours.Therefore&#44 there should be replacements ready for 2 units if 1&#44000 of these devices are used for 100 hours.MTBF calculation values vary according to manufacturer as their calculation methods and calculation conditions are different.There are two kinds of calculation methods and various environmental conditions depending on how they are combined.Basic failure rates for parts are figures produced by the American Military Standard MIL STD 217&#44 the JEITA&#44 and so on. This is why there are multiple forms of calculation results.Calculations are based on parts stress reliability projections and parts count reliability projections.The generic failure rates for parts are classified by usage environments&#44 and with our part count reliability projections;Ground&#44 benign: An environment fixed on the ground where people can liveGround&#44 fixed: An environment fixed on the ground for devicesare assumed for calculations. “Ground&#44 benign 						Related Information					   Power Supplies Product Information										Power Supplies Tech Notes										 Contact Information			  Inquiries on products&#44 sales and technical matters

Question 16

How can I check the useful life of a product?

Accepted Answer

﻿	Q.How can I check the useful life of a product? Power Supplies > Switching Power Supply > AC-DC Power Supplies/DC-DC ConvertersA.In many cases&#44 the useful life of a product depends on the life span of its electrolytic capacitors.Various types of electrolytic capacitors with different Lo  and rated temperatures are used&#44 and the useful life varies depending on these characteristics.For details&#44 check the Electrolytic Capacitor Lifetime in the reliability data on the technical data pages for each product on the product information website (TDK Product Center).(For fan-embedded products&#44 check the Electrolytic Capacitor Lifetime and Fan Life Expectancy.)The useful life of an electrolytic capacitor is generally controlled by a phenomenon whereby the electrolyte evaporates to the outside of the product through a seal. The pace of evaporation depends on the temperature. The Arrhenius equation (the rate doubles for each 10°C increase in temperature) is presented as a representative example of a formula used for calculating the estimated useful life of electrolytic capacitors.The Electrolytic Capacitor Lifetime in the reliability data indicates the useful life calculated according to the Arrhenius equation assuming use for 24 hours per day&#44 and therefore&#44 the actual useful life may differ depending on the operational status of the customer’s device.Even in cases where a longer useful life is projected as a result of shorter operating times or lower temperature&#44 however&#44 it is necessary to take into consideration degradation of the electrolytic capacitor seal rubber. It is generally said that it takes 15 years for the seal rubber to degrade.						Related Information					   Power Supplies Product Information										Power Supplies Tech Notes										 Contact Information			  Inquiries on products&#44 sales and technical matters

Question 17

There are products that indicate time to failures with MTBF and those that indicate time to failures with MTTF&#44 but what is the difference between the two?

Accepted Answer

﻿	Q.There are products that indicate time to failures with MTBF and those that indicate time to failures with MTTF&#44 but what is the difference between the two?Power Supplies > Switching Power Supply > AC-DC Power Supplies/DC-DC ConvertersA.MTBF (Mean Time Between Failures) indicates the average time it takes for a product to become faulty from the time it is first used or from the time it becomes faulty after it has been once recovered.MTTF (Mean Time To Failure)&#44 on the other hand&#44 indicates the time until a product becomes faulty after initial use.The same calculation methods are used for both&#44 but MTBF is generally used in reference to products that can be repaired and MTTF is generally used in reference to products that cannot be repaired.We normally use MTBF to represent the reliability of power supply products&#44 but also particularly use MTTF to represent products that are obviously difficult to repair such as compact on-board products.						Related Information					   Power Supplies Product Information										Power Supplies Tech Notes										 Contact Information			  Inquiries on products&#44 sales and technical matters

Question 18

Please explain what the FIT rate is as the failure rate.

Accepted Answer

﻿	Q.Please explain what the FIT rate is as the failure rate.Power Supplies > Switching Power Supply > AC-DC Power Supplies/DC-DC ConvertersA.FIT (Failure In Time) is a unit that represents failure rates and how many failures occur every 109 hours.For example&#44 there is the occurrence of 10 failures for every 109 hours in the case of 10FIT.FIT values can be calculated with the formulas below with the MTBF or MTTF shown in the reliability data.    (Formulas)						Related Information					   Power Supplies Product Information										Power Supplies Tech Notes										 Contact Information			  Inquiries on products&#44 sales and technical matters

Question 19

What is the specific area where the temperature must be measured to find the ambient temperature?

Accepted Answer

﻿	Q.What is the specific area where the temperature must be measured to find the ambient temperature?Power Supplies > Switching Power Supply > AC-DC Power Supplies/DC-DC ConvertersA.The ambient temperature is the temperature of the atmosphere around the product so please measure the internal temperature of the device to be mounted on the product.Please make the measuring point about 5 centimeters horizontally away from the product. If it is on the upper part of the product&#44 it will be affected by factors such as the increasing of self-generated heat and natural convections. Please also note that it can be affected by radiation from the power supply and thus preventing accurate measurements from being made if it is too close.    Figure 1There are also separate measuring methods for products that are compliant with forced air cooling (products with exposed mounting boards). Refer to the instruction manuals of the respective products for details.						Related Information					   Power Supplies Product Information										Power Supplies Tech Notes										 Contact Information			  Inquiries on products&#44 sales and technical matters

Question 20

What should be done if the input side fuse of the power supply has become fused?

Accepted Answer

﻿	Q.What should be done if the input side fuse of the power supply has become fused?Power Supplies > Switching Power Supply > AC-DC Power Supplies/DC-DC ConvertersA.If the power fuse has become fused&#44 this may be due to damage of the internal components of the power supply.Therefore&#44 please avoid making replacements by yourself as there is the danger of secondary failures.>br>We ask that you please contact the retailer who you purchased your product from as our service department does repairs and analyses.						Related Information					   Power Supplies Product Information										Power Supplies Tech Notes										 Contact Information			  Inquiries on products&#44 sales and technical matters

Question 21

What happens during use if the sensing wires are accidentally left open?

Accepted Answer

﻿	Q.What happens during use if the sensing wires are accidentally left open?Power Supplies > Switching Power Supply > AC-DC Power Supplies/DC-DC ConvertersA.The output voltage cannot be controlled and the voltage increases if the +V and +S along with the -V and -S of the power supply are open.This starts the overvoltage protection function and interrupts the output. Therefore&#44 please short the areas between the +V and +S as well as the -V and -S using the accompanying parts when not using the remote sensing function.						Related Information					   Power Supplies Product Information										Power Supplies Tech Notes										 Contact Information			  Inquiries on products&#44 sales and technical matters

Question 22

Please explain the checkpoints for when there is an operational failure.

Accepted Answer

﻿	Q.Please explain the checkpoints for when there is an operational failure.Power Supplies > Switching Power Supply > AC-DC Power Supplies/DC-DC ConvertersA.Problems occurring in the operation of switching power supplies do not indicate malfunctions in power supplies&#44 but often are results of improper use or handling. Please first confirm the following checkpoints for when there is an operational failure.    Figure 1						Related Information					   Power Supplies Product Information										Power Supplies Tech Notes										 Contact Information			  Inquiries on products&#44 sales and technical matters

Question 23

Please explain the checkpoints for when there are no outputs.

Accepted Answer

﻿	Q.Please explain the checkpoints for when there are no outputs.Power Supplies > Switching Power Supply > AC-DC Power Supplies/DC-DC ConvertersA.[Cause (1)] The proper input voltage is not being applied:Please check the connections of the input voltage&#44 input switching terminals&#44 and output terminals.[Cause (2)] The over voltage protection function is operating:The output is interrupted by the over voltage protection function if the output voltage variable trimmer (V.ADJ) is turned too far or the settings of the over voltage value adjustment trimmer are too low.[Cause (3)] The remote sensing is open:The output is interrupted by the over voltage protection function if the short piece between the S terminal and the DC output terminals is disconnected.[Cause (4)] The over current protection function is operating:The over current protection function operates in cases such as when the over current value adjustment trimmer is turned too far or if the load is short.[Cause (5)] The remote ON/OFF has shorted:The output will be interrupted by the remote ON/OFF function when there is a short between the RC terminals or if the “L” level signal is inputted.[Cause (6)] The capacity of the external capacitor is too great：There are models where the capacities of the external capacitors are limited. There are cases where the output does not start up when excessive capacity is connected to the load or if there is load that indicates low impedance characteristics during startup as with DC-DC converters.						Related Information					   Power Supplies Product Information										Power Supplies Tech Notes										 Contact Information			  Inquiries on products&#44 sales and technical matters

Question 24

Please explain the checkpoints for when the output voltages are low.

Accepted Answer

﻿	Q.Please explain the checkpoints for when the output voltages are low.Power Supplies > Switching Power Supply > AC-DC Power Supplies/DC-DC ConvertersA.[Cause (1)] The settings for the output voltage values are too low:This is when the settings for the output voltage are too low in areas such as the V.ADJ or output voltage external variable function.[Cause (2)] A current value below the minimum output current:When a V1 (5V) output current is below the minimum output current with a multi-output power supply&#44 there are cases where regular voltages are not being outputted with other outputs.[Cause (3)] The proper input voltage is not being applied:The output voltage may be too low if it is lower than the input voltage.[Cause (4)] The over current protection function is operating:Excessive currents flow and the over current protection function operates in cases such as when the load is short.［Cause (5)］ The load is too great：The load current becomes greater and the over current protection function operates.						Related Information					   Power Supplies Product Information										Power Supplies Tech Notes										 Contact Information			  Inquiries on products&#44 sales and technical matters

Question 25

Please explain the checkpoints for when the outputs are abruptly stopped.

Accepted Answer

﻿	Q.Please explain the checkpoints for when the outputs are abruptly stopped.Power Supplies > Switching Power Supply > AC-DC Power Supplies/DC-DC ConvertersA.[Cause (1)] The over voltage protection function is operating:The output is interrupted by the over voltage protection function if the output voltage variable trimmer is turned too far or the settings of the over voltage adjustment trimmer are too low.[Cause (2)] The over current protection function is operating:Excessive currents flow and the over current protection function operates in cases such as when the load is short.[Cause (3)] The thermal protection function is operating:The output is stopped by the thermal protection function in cases such as where the ambient temperature is high or when the forced air cooling device malfunctions.						Related Information					   Power Supplies Product Information										Power Supplies Tech Notes										 Contact Information			  Inquiries on products&#44 sales and technical matters

Question 26

Please explain the checkpoints for when the outputs are unstable.

Accepted Answer

﻿	Q.Please explain the checkpoints for when the outputs are unstable.Power Supplies > Switching Power Supply > AC-DC Power Supplies/DC-DC ConvertersA.[Cause (1)] The connection of the terminals is incomplete:The output is unstable due to factors such as loose screws in the output terminals or load terminals&#44 or poor contact due to rust.[Cause (2)] The over current protection function is operating:The over current protection function operates in cases such as when the load is short or when there are excess load currents.[Cause (3)] A current value below the minimum output current:When a V1 (5V) output current is below the minimum output current with a multi-output power supply&#44 there are cases where regular voltages are not being outputted with other outputs.						Related Information					   Power Supplies Product Information										Power Supplies Tech Notes										 Contact Information			  Inquiries on products&#44 sales and technical matters

Question 27

Please explain the checkpoints for when the ripple and noise are high.

Accepted Answer

﻿	Q.Please explain the checkpoints for when the ripple and noise are high.Power Supplies > Switching Power Supply > AC-DC Power Supplies/DC-DC ConvertersA.[Cause (1)] Input-output wiring:Long wiring or wiring where the input and output are not isolated lead to the generation of noise.[Cause (2)] The input voltage is low:The ripple and noise increase when the input voltage becomes low.［Cause (3)］ The load current is high：The ripple and noise increase when there is excessive load.						Related Information					   Power Supplies Product Information										Power Supplies Tech Notes										 Contact Information			  Inquiries on products&#44 sales and technical matters

Question 28

Please explain the effects of motor drive applications on switching power supplies.

Accepted Answer

﻿	Q.Please explain the effects of motor drive applications on switching power supplies.Power Supplies > Switching Power Supply > AC-DC Power Supplies/DC-DC ConvertersA.Problems such as the generation of counter electromotive force due to inductance of the coil and lowered output of the power supply can occur if a standard switching power supply were to be used for motor drive applications.These phenomena are found in mainly output capacitance types of below 300W that do not have independent auxiliary power supplies in their power supplies.About DC370V of boosted voltage is applied on both ends of the input capacitor (C1) of the smoothing circuit from the rectifier circuit through the harmonic current suppression circuit when the power supply is turned on. Furthermore&#44 voltage is then supplied to the VCC of the PWM control IC (hereunder “IC”) through the starting resistance R1. The MOS FET (Q1) starts switching when this VCC reaches or exceeds the activation start voltage of the IC and the IC starts to move. The driving voltage of the IC receives a supply from the auxiliary winding tap (winding 3) from the main transformer after that. In other words&#44 the voltage that passes through the R1 is only used only for starting up the IC during the startup of the system (steady operation).Here is an explanation of the mechanism where the output voltage is decreased when the motor is not running with the waveform of the parts in the block diagram of Figure 1.    Figure 1　Waveforms of parts when the motor is not runningA counter electromotive force is generated if the motor stops during the steady operation of the power supply. The counter electromotive current flows into the secondary side of the power supply&#44 the output voltage increases&#44 and the IC tries to make the pulse narrow in order to decrease the output voltage after detecting its increase. However&#44 the pulse cannot be made narrow instantly due to lag in the control system and a phenomenon where the output voltage exceeds the rated voltage occurs (1).The IC is in then a state where the pulse is closed for a while without the output voltage instantly returning to the rated voltage because there is an output capacitor (C2) on the secondary side of the power supply.However&#44 the Q1 stops operating and the voltage supply from the auxiliary winding tap of the main transformer gets cut off if the pulse of the IC is closed. The VCC therefore gradually decreases (2). Furthermore&#44 the system will be in reboot mode if the VCC is decreased to the stop voltage of the IC (3) and the voltage will be supplied to the VCC of the IC through the starting resistance R1 again so tens of ms time are required for making an increase up to the starting voltage of the IC. The output voltage therefore decreases during this time (5).Because of this&#44 it is necessary to prevent the voltage of the output end of the power supply from increasing due to counter electromotive force when connecting the motor load to the switching power supply. It is therefore recommended that a diode for preventing reverse currents is connected to the outside of the power supply. (Please use one of our products such as the backflow prevention module RP-60-20.)						Related Information					   Power Supplies Product Information										Power Supplies Tech Notes										 Contact Information			  Inquiries on products&#44 sales and technical matters

Question 29

Please provide precautions for when conducting insulation / withstand voltage tests.

Accepted Answer

﻿	Q.Please provide precautions for when conducting insulation / withstand voltage tests.Power Supplies > Switching Power Supply > AC-DC Power Supplies/DC-DC ConvertersA.Insulation / withstand voltage tests can cause deterioration and require special attention. In input systems&#44 output systems&#44 and FG (frame grounding)&#44 it is necessary to execute them with the same potentials in the systems (short in the same systems).A preferable test device is one that starts up gently when the test is ON and automatically discharges charged energy when it is OFF. Please use resistance of 100kW to 1MW when discharging energy manually after a test (please avoid discharging with low impedance as it may cause deterioration).Sufficient safety measures for preventing electric shock are also necessary in any of these cases.						Related Information					   Power Supplies Product Information										Power Supplies Tech Notes										 Contact Information			  Inquiries on products&#44 sales and technical matters

Question 30

Can power modules / on-board power supplies be operated just by connecting input-output terminals to power supplies and load devices?

Accepted Answer

﻿	Q.Can power modules / on-board power supplies be operated just by connecting input-output terminals to power supplies and load devices?Power Supplies > Switching Power Supply > AC-DC Power Supplies/DC-DC ConvertersA.There are power supplies that cannot be operated just by connecting input-output terminals to power supplies and load devices. Please be sure to note the following precautions.- Products with sensing functions require the sensing terminals to be connected with the output sides.- Products with remote ON/OFF control functions sometimes require connections with the -Vin terminals or +Vin terminals.- Some products require peripheral components such as capacitors or choke coils.Refer to the instruction manuals and basic connections of the respective products for details.						Related Information					   Power Supplies Product Information										Power Supplies Tech Notes										 Contact Information			  Inquiries on products&#44 sales and technical matters

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