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1. (WO2011151101) METHOD AND APPARATUS FOR DETERMINING A ZERO CROSSING OF A PHASE CURRENT OF AN ELECTRONICALLY COMMUTATED ELECTRICAL MACHINE, IN PARTICULAR FOR DETERMINING A ROTOR POSITION OF THE ELECTRICAL MACHINE

Pub. No.:    WO/2011/151101    International Application No.:    PCT/EP2011/055882
Publication Date: Dec 8, 2011 International Filing Date: Apr 14, 2011
IPC: H02P 6/18
Applicants: ROBERT BOSCH GMBH
FRICKER, David
Inventors: FRICKER, David
Title: METHOD AND APPARATUS FOR DETERMINING A ZERO CROSSING OF A PHASE CURRENT OF AN ELECTRONICALLY COMMUTATED ELECTRICAL MACHINE, IN PARTICULAR FOR DETERMINING A ROTOR POSITION OF THE ELECTRICAL MACHINE
Abstract:
The invention relates to a method for determining a time for a zero crossing of a phase current in a polyphase electrical machine (2), wherein the electrical machine (2) is driven with the aid of a driver circuit (31; 50) comprising power switches (36, 37; 52, 53) in order to provide a plurality of phase voltages which are applied to connecting nodes (A1, A2, B1, B2) of the electrical machine (2) which are associated with corresponding phases, wherein at least some of the power switches (36, 37; 52, 53) can be driven cyclically in accordance with pulse width modulation with a duty factor in order to apply different potentials alternately to one of the connecting nodes (A1, A2, B1, B2), comprising the following steps: - driving the driver circuit (31; 50) for providing the phase voltages to operate the electrical machine (2); - deactivating the pulse-width-modulated driving by at least one of the power switches (36, 37; 52, 53), with the result that no potential is applied to the connecting nodes (A1, A2, B1, B2) by the driver circuit (31; 50), at least during a time segment in each cycle of the pulse width modulation; - detecting a diode voltage via a freewheeling diode, with which the deactivated power switch (36, 37; 52, 53) has been provided, within the time segment; - fixing the time for the zero crossing of the phase current as the time after which there is no longer a diode voltage present across the freewheeling diode (40; 54) within the time segment.