Abstract: Each cell of a cell assembly for a converter may include: first and second terminals, switching elements, and a capacitor. The cells are connected in series such that, for each pair of neighbouring cells, the first terminal of a first cell is connected to the second terminal of a second cell. Each cell includes a bypass connected to the first and second terminals that bypasses switching elements in a short circuit configuration and does not bypass the switching elements in an open circuit configuration. Each cell has a cell controller providing control signals to the sw itching elements to connect the capacitor to the first and second terminals or to bypass the capacitor. The cell controller provides a control signal to the bypass unit of neighbouring cells to change its configuration between the short circuit and open circuit configurations.

Abstract: A method for voltage balancing series-connected power switching devices (IGBTs) each connected in parallel with a respective diverter having controllable impedance to controllably conduct current diverted from the associated power switching device, the method comprising the step of controlling each diverter to follow a series of at least two successively higher impedance states during an OFF period of the power switching devices. The series of impedance states for each diverter comprises a first impedance and then a second, higher impedance, the first impedance occurring in response to an indication of a start of the OFF period. The first impedance state preferably occurs during a tail current of the power switching device in parallel with the respective diverter and the second or later impedance state during a leakage current of that power switching device.

Abstract: A power switch driver for driving a control terminal of a power switch to drive a load, the power switch driver having a negative feedback circuit to control current delivered to the control terminal. The negative feedback circuit has a current output circuit having a current source and a current sink and serving for providing the current of the control terminal and configured to receive an output current control signal to control a magnitude of the current provided by the current output circuit, a terminal voltage input circuit for receiving a voltage from the control terminal and to output an indication of the voltage, an amplifier coupled to the terminal voltage input circuit for amplifying the terminal voltage indication to generate an amplifier output, and a reference voltage input circuit for receiving a reference voltage, having at least one resistor, and coupled to a charge supply input of the amplifier.

Abstract: The invention generally relates to power converters, and more particularly to a communications method for controlling at least one power switching device of a power converter, a communications system for a power converter, and a power converter comprising the communications system.

Abstract: A method for voltage balancing series-connected power switching devices (IGBTs) each connected in parallel with a respective diverter having controllable impedance to controllably conduct current diverted from the associated power switching device, the method comprising the step of controlling each diverter to follow a series of at least two successively higher impedance states during an OFF period of the power switching devices. The series of impedance states for each diverter comprises a first impedance and then a second, higher impedance, the first impedance occurring in response to an indication of a start of the OFF period. The first impedance state preferably occurs during a tail current of the power switching device in parallel with the respective diverter and the second or later impedance state during a leakage current of that power switching device.

Abstract: Power switch driver for driving a control terminal of a power switch to drive a load, the power switch driver having a in negative feedback circuit to control current delivered to the control terminal, the negative feedback circuit comprising:—a current output circuit comprising at least one of a current source and a current sink, the current output circuit for providing a said current of a said control terminal and configured to receive an output current control signal to control magnitude of the current provided by the current output circuit;—a terminal voltage input circuit for receiving a voltage from a said control terminal and to output an indication of said voltage;—an amplifier coupled to amplify the terminal voltage indication to generate an amplifier output; and—a reference voltage input circuit for receiving a reference voltage, comprising at least one resistor, the reference voltage input circuit coupled to a charge supply input of the amplifier, wherein—the power switch driver is configured to ge

Abstract: The invention generally relates to methods and circuits for controlling switching of parallel coupled power semiconductor switching devices (3), for example for use in a power converter.

Abstract: An SMA actuation apparatus comprises a support structure, a movable element movably supported on the support structure and an arrangement of three or more SMA actuator wires mechanically connected between the support structure and the movable element. The SMA actuator wires have an interconnection at the movable element that electrically connects the group of SMA actuator wires together. This avoids the need to make a separate electrical connection to the movable element.

Abstract: The invention generally relates to power converters, and more particularly to a communications method for controlling at least one power switching device of a power converter, a communications system for a power converter, and a power converter comprising the communications system.

Abstract: The invention generally relates to methods and circuits for controlling switching of parallel coupled power semiconductor switching devices (3), for example for use in a power converter.

Abstract: A camera apparatus capable of providing optical image stabilization comprises: a support structure; a camera unit comprising an image sensor and a lens system; a suspension system comprising a plurality of flexure elements supporting the camera unit on the support structure in a manner allowing the camera unit to tilt; and a plurality of SMA actuators each formed as SMA wire connected between the camera unit and the support structure and arranged on contraction to drive tilting of the camera unit. The SMA wire may be fixed to the camera unit at its ends and hooked over an element of the support structure. A vibration sensor, whose output is used as the basis for generating drive signals, may be mounted on the camera unit.

Abstract: An SMA actuation arrangement comprises: an SMA actuator arranged on contraction caused by heating to drive movement of a movable element relative to a support structure; a current source operative to supply drive current through the SMA actuator to heat the SMA actuator; and a detector circuit operative to detect a measure of the resistance of the SMA actuator. While detecting a measure of the resistance of the SMA actuator and controlling the drive current on the basis of the measure of the resistance of the SMA actuator; there is derived a measure of an electrical characteristic of the SMA actuator that is representative of the ambient temperature. While applying closed-loop control an offset is added to the control signal which reduces the steady-state value of an error between the measure of the resistance of the SMA actuator and a target value.

Abstract: An SMA actuation apparatus comprises a support structure, a movable element movably supported on the support structure and an arrangement of three or more SMA actuator wires mechanically connected between the support structure and the movable element. The SMA actuator wires have an interconnection at the movable element that electrically connects the group of SMA actuator wires together. This avoids the need to make a separate electrical connection to the movable element.

Abstract: An SMA actuation apparatus comprises: an SMA actuator arranged to drive movement of a movable element; a current supply supplying a drive current; a detection circuit detecting a measure of the resistance of the SMA actuator; and a control unit operative to generate a closed-loop control signal supplied to current supply for controlling the power of the drive current to drive the resistance of the SMA actuator to a target value. The control unit derives: an estimate of a characteristic temperature of the SMA actuation apparatus on the basis of the supplied power, using a thermal model; and a resistance offset on the basis thereof. The closed-loop control signal is generated on the basis of the error between the measure of the resistance of the SMA actuator and the target value of the resistance of the SMA actuator, adjusted by the resistance offset to compensate for variations in resistance.

Abstract: A miniature camera lens actuation apparatus comprises a support structure, a camera lens element supported on the support structure by a suspension system; and an SMA actuator connected between the support structure and the movable element to drive movement of the camera lens element. The control circuit may include a drive circuit and a sensor circuit which have separate electrical connections to the SMA actuator to reduce the impact of the resistance of the electrical connections on the sensing. The control circuit may vary the drive signal in response to a temperature signal indicative of the ambient temperature. An endstop limits movement to prevent extension of the SMA actuator in its unheated state beyond a maximum length which is at or below the length corresponding the local maximum resistance of the resistance-length curve. Control of position is effected using resistance of the SMA actuator as a measure of position.

Abstract: A camera lens actuation apparatus for driving motion of a camera lens supported on a support structure by a suspension system. The apparatus incorporates a subassembly comprising SMA wire connected to at least one mounting member which is mounted to the support structure. At least one pair of lengths of SMA wire are held in tension between the camera lens element and the support structure at respective acute angles to the optical axis applying a tensional force having a component along the optical axis. The lengths of SMA wire in the pair are held at angle as viewed along the optical axis. There may be plural pairs with a balanced arrangement in which the forces generated have no net component perpendicular to the optical axis and generate no net torque around any axis perpendicular to the optical axis. A control circuit controls heating of the SMA wire in response to a measure of its resistance.

Abstract: An SMA actuation apparatus comprises: an SMA actuator arranged to drive movement of a movable element; a current supply supplying a drive current; a detection circuit detecting a measure of the resistance of the SMA actuator; and a control unit operative to generate a closed-loop control signal supplied to current supply for controlling the power of the drive current to drive the resistance of the SMA actuator to a target value. The control unit derives: an estimate of a characteristic temperature of the SMA actuation apparatus on the basis of the supplied power, using a thermal model; and a resistance offset on the basis thereof. The closed-loop control signal is generated on the basis of the error between the measure of the resistance of the SMA actuator and the target value of the resistance of the SMA actuator, adjusted by the resistance offset to compensate for variations in resistance.

Abstract: A camera apparatus capable of providing optical image stabilisation comprises: a support structure; a camera unit comprising an image sensor and a lens system; a suspension system comprising a plurality of flexure elements supporting the camera unit on the support structure in a manner allowing the camera unit to tilt; and a plurality of SMA actuators each formed as SMA wire connected between the camera unit and the support structure and arranged on contraction to drive tilting of the camera unit. The SMA wire may be fixed to the camera unit at its ends and hooked over an element of the support structure. A vibration sensor, whose output is used as the basis for generating drive signals, may be mounted on the camera unit.

Abstract: An SMA actuation arrangement comprises: an SMA actuator arranged on contraction caused by heating to drive movement of a movable element relative to a support structure; a current source operative to supply drive current through the SMA actuator to heat the SMA actuator; and a detector circuit operative to detect a measure of the resistance of the SMA actuator. Whilst detecting a measure of the resistance of the SMA actuator and controlling the drive current on the basis of the measure of the resistance of the SMA actuator; there is derived a measure of an electrical characteristic of the SMA actuator that is representative of the ambient temperature. Whilst applying closed-loop control an offset is added to the control signal which reduces the steady-state value of an error between the measure of the resistance of the SMA actuator and a target value.

Abstract: A miniature camera lens actuation apparatus comprises a support structure, a camera lens element supported on the support structure by a suspension system; and an SMA actuator connected between the support structure and the movable element to drive movement of the camera lens element. The control circuit may include a drive circuit and a sensor circuit which have separate electrical connections to the SMA actuator to reduce the impact of the resistance of the electrical connections on the sensing. The control circuit may vary the drive signal in response to a temperature signal indicative of the ambient temperature. An endstop limits movement to prevent extension of the SMA actuator in its unheated state beyond a maximum length which is at or below the length corresponding the local maximum resistance of the resistance-length curve. Control of position is effected using resistance of the SMA actuator as a measure of position.