Passive common mode filter and method for operating a passive common mode filter
AssigneeInternational Rectifier Corporation
InventorBrian Pelly
Life of this patent
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Abstract
An electromagnetic interference filter for filtering common mode current in an inverter device, the filter comprising: an inductor coupled in a least one power supply line to the inverter device; the inverter device having a ground return line, a capacitor coupled between the inductor and the ground return line; and a controlled switch coupled in series with the capacitor between the inductor and ground return line, and a control unit controlled in accordance with commutations in said inverter device whereby said switch is turned on when common mode current is drawn by said inverter device and turned off when common mode current ceases substantially to be drawn by said inverter device.
Claims26
An electromagnetic interference filter for filtering common mode current in an inverter device, the filter comprising:
- a common mode inductor having a common core and at least two winding inductors wound on the common core, each in series with a respective supply line supplying power to the inverter device, the inverter device further having a separate ground return line;
- at least one capacitor coupled between each inductor and the ground return line;
- and
- a controlled switch coupled in series with the at least one capacitor between the inductor and ground return line;
- and
- a control unit controlled in accordance with commutations in said inverter device whereby said switch is turned on when common mode current is drawn by said inverter device and turned off when common mode current ceases substantially to be drawn by said inverter device.
An electromagnetic interference filter for filtering common mode current in an inverter device, the filter comprising:
- an inductor coupled in a least one power supply line to the inverter device;
- the inverter device having a ground return line;
- a capacitor coupled between the inductor and the around return line;
- and
- a controlled switch coupled in series with the capacitor between the inductor and around return line;
- and
- a control unit controlled in accordance with commutations in said inverter device whereby said switch is turned on when common mode current is drawn by said inverter device and turned off when common mode current ceases substantially to be drawn by said inverter device;
- wherein the inverter device receives control signals from a controller for controlling commutations of the inverter, further comprising a delay circuit for delaying said control signals for a period of time to enable said switch to respond when a commutation occurs and said inverter device draws common mode current.
A method of filtering electromagnetic interference due to common mode current in an inverter device, the method comprising:
- providing power to the inverter device on at least two power supply lines each having an inductor on a common core in series with the inverter device;
- switching common mode current pulses in the at least two supply lines supplying power to the inverter device through a capacitor coupled between each supply line and a separate ground return line for the inverter device only when common mode current is drawn by the inverter device.
A method of filtering electromagnetic interference due to common mode current in an inverter device, the method comprising:
- switching common mode current pulses in a supply line including an inductor to the inverter device through a capacitor coupled between the sunny line and a around return line for the inverter device only when common mode current is drawn by the inverter device;
- further wherein the step of switching comprises providing a controlled switch in series with said capacitor and switching said switch on when the inverter device draws common mode current and switching the switch off when a common mode current pulse terminates, whereby said switch is on only during the duration of a pulse of common mode current;
- further comprising providing a resistive shunt in parallel to said switch whereby said capacitor is able to track input line voltage when said controlled switch is off.
A method of filtering electromagnetic interference due to common mode current in an inverter device, the method comprising:
- switching common mode current pulses in a supply line including an inductor to the inverter device through a capacitor coupled between the supply line and a ground return line for the inverter device only when common mode current is drawn by the inverter device;
- further comprising controlling said controlled switch with a control signal related to a control signal provided to said inverter device to control commutation of said inverter device whereby said controlled switch is turned on during a commutation in said inverter device to shunt a common mode current pulse between said supply line and said ground return line;
- further comprising delaying the control signal to commutate said inverter device thereby to allow said controlled switch to switch on substantially simultaneously or slightly before a common mode current pulse is drawn by said inverter device.
Dependencies are inferred from the claim text.