An electrical motor system and a method for operating the electrical motor system are disclosed. The electrical motor system comprises a direct current (DC) source, a filter connected in parallel with the DC source and an electric motor with at least two sets of windings. A voltage signal is provided from the DC source to the inverter circuit where the signal is modulated. The modulated signal is then supplied from the inverter circuit to each set of windings with a respective time offset between each set of windings respectively, providing a very efficient DC bus ripple reduction. Hereby, it is e.g. possible to use small filter capacitors/capacitor banks in electrical motor systems.

A power conversion apparatus includes: DC input terminals for inputting a DC voltage; AC output terminals for outputting an AC voltage; a switching element; a first resonant capacitance connected across the switching element; a first LC resonance circuit that has an inductance and a capacitance connected in series and is connected together with the switching element between the AC output terminals; and a second LC resonance circuit connected in series together with the switching element between the DC input terminals. The second LC resonance circuit includes a first connector portion connected to one DC input terminal and a second connector portion connected to the switching element, and has a first current path, which includes an inductance, and a second current path, which includes a series circuit with an inductance and a capacitance, formed between the first connector portion and the second connector portion.

A power conversion apparatus includes: DC input terminals for inputting a DC voltage; AC output terminals for outputting an AC voltage; a switching element; a first resonant capacitance connected across the switching element; a first LC resonance circuit that has an inductance and a capacitance connected in series and is connected together with the switching element between the AC output terminals; and a second LC resonance circuit connected in series together with the switching element between the DC input terminals. The second LC resonance circuit includes a first connector portion connected to one DC input terminal and a second connector portion connected to the switching element, and has a first current path, which includes an inductance, and a second current path, which includes a series circuit with an inductance and a capacitance, formed between the first connector portion and the second connector portion.

A driving circuit for a vibration type actuator includes an inductor and a capacitor which are connected in series to an electric-mechanical energy conversion element, in which, in a case where a series resonance frequency based on the inductor and the capacitor is set as fs, and a resonance frequency in a vibration mode other than vibration used for driving of the vibrator is set as fu, 0.73.Math.fu<fs<1.2.Math.fu is satisfied.

A driving circuit for a vibration type actuator includes an inductor and a capacitor which are connected in series to an electric-mechanical energy conversion element, in which, in a case where a series resonance frequency based on the inductor and the capacitor is set as fs, and a resonance frequency in a vibration mode other than vibration used for driving of the vibrator is set as fu, 0.73.Math.fu<fs<1.2.Math.fu is satisfied.

A switching power supply device includes a switching element to which a DC input is supplied, a frequency control circuit which controls a switching frequency of the switching element, a frequency detection circuit which detects the switching frequency of the switching element, and a duty ratio control circuit which controls a switching duty ratio based on the frequency detected by the frequency detection circuit. The duty ratio control circuit controls the switching duty ratio such that the switching frequency becomes an approximately maximum frequency.

A driving circuit for a vibration type actuator includes an inductor and a capacitor which are connected in series to an electric-mechanical energy conversion element, in which, in a case where a series resonance frequency based on the inductor and the capacitor is set as fs, and a resonance frequency in a vibration mode other than vibration used for driving of the vibrator is set as fu, 0.73.Math.fu<fs<1.2.Math.fu is satisfied.

There is provided a high frequency AC inverter comprising a DC-DC circuit having a variable output, an output power circuit and a load circuit and a controller, the load circuit comprising a load circuit detector configured to detect the electrical parameters of the load circuit. The output power circuit comprises a DC to AC driver having a variable frequency output, a HFAC driver circuit comprising a resonant network and a transformer coupled to the HFAC driver circuit and the load circuit. The controller is configured to control the output of the DC to DC circuit to control the current on the load circuit to maintain it within a predetermined range.

Method to control a quasi-resonant inverter (13) in an induction cooking appliance (1) provided with an induction heating coil (4). A switching device (21) is electrically connected to the induction heating coil (4) by a node (20) having a first voltage (VC(t)) which is indicative of the voltage across the power switching device (21). The method includes: providing to the switching device (21) an enabling signal (K1) comprising a plurality of pulses, in order to switch-on and switch-off the switching device (21) for a switch-on period (tON) and a switch-off period (tOFF), determining a second voltage (VCmin) indicative of the minimum value of the first voltage (VC(t)) during the switch-off period (tOFF), regulating the switch-off period (tOFF) based on the second voltage (VCmin), and regulating the enabling signal (K1) based on the regulated switch-off period (tOFF).

Method to control a quasi-resonant inverter (13) in an induction cooking appliance (1) provided with an induction heating coil (4). A switching device (21) is electrically connected to the induction heating coil (4) by a node (20) having a first voltage (VC(t)) which is indicative of the voltage across the power switching device (21). The method includes: providing to the switching device (21) an enabling signal (K1) comprising a plurality of pulses, in order to switch-on and switch-off the switching device (21) for a switch-on period (tON) and a switch-off period (tOFF), determining a second voltage (VCmin) indicative of the minimum value of the first voltage (VC(t)) during the switch-off period (tOFF), regulating the switch-off period (tOFF) based on the second voltage (VCmin), and regulating the enabling signal (K1) based on the regulated switch-off period (tOFF).