When in constant voltage mode, the load current flowing into the electronic load depends on the set load voltage. At this time, the load current increases until the load voltage is equal to the set value, that is, the load voltage remains unchanged. The constant voltage circuit of the electronic load can be used to test the charger.

500kw load bank
 

The constant voltage circuit adopts a three-terminal voltage regulator integrated circuit scheme, supplemented by a soft-start circuit and a voltage compensation circuit.

The voltage regulator circuit is composed of an integrated three-terminal voltage regulator, the output voltage adjustment range is 1.25-37V, the output current can reach 1.5A, built-in overload protection circuit, high voltage regulation accuracy, working reliability, etc. Since the regulator has a stable reference voltage U (1.25 V), there are:

U0=U*(1+R5/R3)= 1.25*(1+R5/R3)

R3 is a fixed resistor, so set the output voltage U0 of R5 to be adjustable. The soft-start circuit consists of transistor T, resistors R2, R4 and capacitor C3.

Its function is to slowly increase the circuit output voltage U0 to match the start-up characteristics of the inductive load. When the input voltage UI is turned on, since the voltage on C3 cannot be abruptly changed, because the base potential is high, T will saturate and conduct, so U2 and U3 are very low, so U0 is very small, when C is charged, the base potential of T falls, the collector potential (ie U2) rises.