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Engineer Blog

Good Use of Electronic Load (1)

Bias power supply

An electronic load is one of the forms of direct current power supply called a shunt regulator, as shown below.

Normally, electronic load have the minimum operating voltage predefined. This is because the Vce of a transistor does not work at 0V. Therefore, when you want to perform a "reverse-polarity test of the battery", a DC power supply called a bias power supply is inserted in a series.

With the power supply inserted, it compensates for the minus voltage from the battery. For example, even when the battery outputs -1V, 4V can be secured at Vce, which allows the electronic load to keep discharging. I think that "bias" in this case means "offset", which makes more sense.

In reality, since the voltage also drops due to a loss in a load cable, etc., when the bias power supply outputs 5V, approximately 2V can be secured at Vce at the lowest. Of course, if you make the load cable "thicker and shorter", the voltage drop will decrease, which further increases Vce.

Our electronic load with an "A" at the end of their product model names (e.g. PLZ664WA) have a built-in bias power supply. Since PLZ70UA also ends with an "A", its operation range is "from 0V".

Note that the "additional power supply (5V/60A) SPEC70548" shown in the following figure is a fixed voltage power supply specially designed for charging/discharging systems. It uses the chassis of the PWR400L.

We do not have a fixed voltage output power supply as a standard product. However, we can accept special orders such as housing a commercially available fixed voltage power supply in a case and attaching the ON/OFF switch and forced air cooling fan to it to produce a reliable product. If you are interested, we would be delighted to provide you with a cost estimate. Please contact us.

Yoshinori Hara
Yoshinori Hara, Senior Staff, SE Section, Solution Business Promotion Department

[Major achievements in product development]
Custom-ordered charging/discharging power supply devices, charging/discharging power supply devices PFX20W-12 and PFX2000 series
Direct current stabilized power supply PMR series, power supply controller PIA4800 series
Custom-ordered charging/discharging systems (e.g. PFX2500 series)
Custom-ordered power supply systems, custom-ordered electronic load systems, and custom-ordered fuel battery evaluation systems

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