Novel strategy to control battery recharging, complying with EN61000.3.2

Abstract

In order to recharge a battery, it is mandatory to transfer the energy from the mains, complying with the EN61000.3.2 regulation concerning the current spectrum. The traditional method uses the cascade triac-single output transformer-diode bridge. The triac firing angle control allows the precise adjustment of the power transferred to the battery. The other, less precise method uses a transformer with as many outputs as the number of power steps. The outputs are connected via mechanical switches or relays. The first method has the drawback of exceeding the harmonics level stated by the EN61000.3.2. The second one generates less harmonics, but it becomes more and more difficult to construct the transformer as the number of outputs increases. Hence, the number of power steps is limited. The purpose of the circuit proposed is to put together the advantages of the two previous strategies. The cascade triac-multiple outputs transformer-diode bridge is able to comply with the EN61000.3.2 standard, still using a small-size passive filter.