Question 1

What power supplies can be used for battery charging?

Accepted Answer

Q.What power supplies can be used for battery charging? Stromversorgungen > Schaltnetzteil > AC-DC-Netzgeräte A. Constant current control power supplies and power supplies with a CVCC function are recommended for battery charging. These power supplies can be found under the Constant Voltage/Constant Current (CVCC) power supply category or AC-DC Power Supplies (AC-DC Converters) > Simple Constant Current Control on the Power Supply portal site of the product information website (TDK Product Center). However, there are cases where a power supply with an overcurrent protection function is used for battery charging. The overcurrent protection function is intended to prevent deterioration of and damage to the power supply by suppressing the current value when the power supply is overloaded and the current exceeds the rated current value. Here, operation of the current value suppression function diverts the current, and the diverted current is used for constant current to charge the battery. It should be noted that some overcurrent protection characteristics are not suitable for battery charging. Figure 1 As shown in Figure 1, there are three main power supply overcurrent protection characteristics. The most appropriate method for charging batteries among them is with a power supply that has constant current voltage drooping type characteristics where a constant current range is used for charging batteries with a constant current. Caution must be exercised when selecting power supplies because other power supplies with overcurrent protection characteristics are not appropriate for charging batteries. Furthermore, the constant current range is the state where overcurrent protection for avoiding deterioration and damage in the power supply is operating as explained above, and its use is the exceeding of the rated current stipulated in the specifications of the power supply (rated current < overcurrent protection setting current). In this case, a substandard for changing the overcurrent protection setting current value of the power supply is needed so that the overcurrent protection setting current < the rated current. There is also a method of controlling constant currents by connecting the external circuitry to the power supply in addition to the method explained previously where the overcurrent protection function is diverted. This is a concrete explanation using our HWS1000 as an example (Figure 2). Figure 2　Constant current circuitry for charging batteries when using the HWS1000 Shunt resistance (1) is applied to the load line of the power supply, a voltage conversion for the output current is made with the shunt resistance, and the output current is detected (2). A conditioning circuit for constant current drooping points is then designed and a set standard voltage for over currents is established (3). The voltage of (2) and (3) is compared in the operational amplifier (4) and the output voltage of the power supply is controlled in the photo coupler (5). This method is an example of a constant current circuit configuration of power supplies with external controls of output voltages (PV variable functions) and always requires use at the rated power or below. Also, be sure to use lithium-ion and other such batteries with a battery management system (BMS*). When charging and discharging are repeatedly performed, differences in the charging capacity of the individual cells occur, and if discharging occurs in this condition, overcharging can occur. Consequently, a BMS that monitors the voltage of each cell and suspends charging/discharging if a single cell over charges or over discharges should be used to ensure safety and prevent deterioration. * A system that monitors and controls the status of battery modules (battery packs). Also referred to as a battery management unit (BMU). Related Information AC-DC Power Supplies Product Information Power Supplies Tech Notes Contact Information Inquiries on products, sales and technical matters

Question 2

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.Stromversorgungen > Schaltnetzteil > AC-DC-Netzgeräte/DC-DC-Wandler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.)						Weiterführende Informationen					   Power Supplies Product Information										Power Supplies Tech Notes										 Kontakt			  Fragen zu Produkten&#44Vertrib oder bei technischen Fragen

Question 3

I noticed that storage conditions in the instruction manual differ from the storage conditions in the specifications. What is the reason for this difference?

Accepted Answer

﻿	Q.I noticed that storage conditions in the instruction manual differ from the storage conditions in the specifications. What is the reason for this difference?Stromversorgungen > Schaltnetzteil > DC-DC-Wandler/AC-DC-NetzgeräteA.●Storage temperature and humidity listed in the instruction manualThe temperature and humidity are shown as an approximate guide for storage in a customer warehouse before installing the power source in the equipment.●Storage humidity and temperature listed in the specificationsThe specifications show the temperature and humidity at which storage is possible when the power source is built into the equipment and it is not operating.						Weiterführende Informationen					   Power Supplies Product Information										Power Supplies Tech Notes										 Kontakt			  Fragen zu Produkten&#44Vertrib oder bei technischen Fragen

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