In an electrical power converter, an input circuit performs switching for converting a supply voltage of a power source to alternating-polarity voltage pulses which are applied to the primary winding of a transformer. Each voltage pulse is controlled (e.g., pulse width or amplitude is adjusted) based on a detected value of current flow in the primary winding, where the value has been detected an even-numbered plurality of voltage pulses previously. Any DC component of current flow in the primary winding, caused by manufacturing deviations between switching elements in the input circuit, can thereby be suppressed, and DC flux bias in the transformer thereby suppressed.