Abstract: An AC-to-AC converter includes input terminals, pairs of output terminals, a plurality of bridge arms, and a control unit. The bridge arms are connected in parallel to the input terminals and comprise a respective bridge arm for each pair of output terminals and a common bridge arm. Each bridge arm comprises a pair of switches and a node between the switches. Each pair of output terminals comprises a first output terminal connected to the node of the respective bridge arm, and a second output terminal connected to the node of the common bridge arm. The switches have a plurality of configurations for selectively connecting the output terminals to the input terminals in one of a plurality of arrangements. The control unit is operable to control the switches to apply an alternating output voltage to the output terminals. Over each half-cycle of the input voltage, the switches transition between different configurations.

Abstract: A liquid heater is described including a chamber for receiving a liquid, pairs of electrodes located within the chamber for applying electric current to the liquid, input terminals for connection to a power supply, a plurality of bridge arms connected in parallel to the input terminals, and a control unit for controlling switches of the bridge arms. The plurality of bridge arms includes a respective bridge arm for each pair of electrodes and a common bridge arm, and each bridge arm includes a pair of switches and a node located between the switches. A first electrode of each pair of electrodes is connected to the node of the respective bridge arm, and a second electrode is connected to the node of the common bridge arm. The switches have a plurality of different states for selectively connecting pairs of electrodes to the input terminals in one of a plurality of electrode configurations, the electrodes having a different total electrical resistance in each electrode configuration.

Abstract: A gate driver is described for driving switches. The gate driver includes an input for receiving a signal indicative of a polarity of a voltage or current, and outputs for outputting gate signals for driving the switches. In response to a fault condition, the gate driver generates gate signals at the outputs that depend on the polarity of the voltage or current.

Abstract: A drive circuit for a brushless motor is described. The drive circuit includes a converter for connection to a phase winding of the motor, and a controller. The converter includes a plurality of switches and the controller controls the states of the switches to configure the converter in one of a plurality of configurations. In a first configuration, current is permitted to flow through the phase winding in a first direction and in a second opposite direction. In a second configuration, current is permitted to flow through the phase winding in the first direction and is prevented from flowing through the phase winding in the second direction. The controller includes an input for receiving a signal indicative of current in the converter, and the controller configures the converter from the first configuration to the second configuration in response to a characteristic of the current.

Abstract: A hairstyling apparatus having heating elements, and a sensor for determining voltage and/or current output of an electrical energy source, and outputting a signal indicative of the determined voltage and or/current output. Switching components are connected with the heating elements. The switching components are controlled to reconfigure current flows through the plurality of heating elements in reliance on the signal.

Abstract: A buck-boost converter is described that includes input terminals, output terminals, a first group of devices, a second group of devices, an inductor, a capacitor, and a controller. Each group of devices includes a first switch, a second switch, and a third switch or diode connected in series. Each group of devices further includes a first node located between the first switch and the second switch, and a second node located between the second switch and the third switch or diode. A first of the input terminals is connected to the first node of the first group of devices, and a second of the input terminals is connected to the first node of the second group of devices. The inductor is connected between the second node of the first group of devices and the second node of the second group of devices.

Abstract: An AC-to-AC converter includes input terminals for connection to an AC source, output terminals for connection to a load, a transformer having a primary winding and a secondary winding, a primary-side switch, a pair of secondary-side switches, and a control circuit to control the switches. Closing the primary-side switch causes a primary current to be drawn from the AC source and through the primary winding to store energy in the transformer. Closing one of the secondary-side switches causes a secondary current to be output at the output terminals to transfer energy from the transformer to the load. The secondary current has the same polarity as the primary current when a first of the secondary-side switches is closed, and the opposite polarity when a second of the secondary-side switches is closed. The control circuit is operable to control the switches such that an alternating current is output at the output terminals.

Abstract: A gate driver is described for driving switches. The gate driver includes an input for receiving a signal indicative of a polarity of a voltage or current, and outputs for outputting gate signals for driving the switches. In response to a fault condition, the gate driver generates gate signals at the outputs that depend on the polarity of the voltage or current.

Abstract: A buck-boost converter is described that includes input terminals, output terminals, a first group of devices, a second group of devices, an inductor, a capacitor, and a controller. Each group of devices includes a first switch, a second switch, and a third switch or diode connected in series. Each group of devices further includes a first node located between the first switch and the second switch, and a second node located between the second switch and the third switch or diode. A first of the input terminals is connected to the first node of the first group of devices, and a second of the input terminals is connected to the first node of the second group of devices. The inductor is connected between the second node of the first group of devices and the second node of the second group of devices.

Abstract: A drive circuit for a brushless motor is described. The drive circuit includes a converter for connection to a phase winding of the motor, and a controller. The converter includes a plurality of switches and the controller controls the states of the switches to configure the converter in one of a plurality of configurations. In a first configuration, current is permitted to flow through the phase winding in a first direction and in a second opposite direction. In a second configuration, current is permitted to flow through the phase winding in the first direction and is prevented from flowing through the phase winding in the second direction. The controller includes an input for receiving a signal indicative of current in the converter, and the controller configures the converter from the first configuration to the second configuration in response to a characteristic of the current.

Abstract: A liquid heater is described including a chamber for receiving a liquid, pairs of electrodes located within the chamber for applying electric current to the liquid, input terminals for connection to a power supply, a plurality of switches for connecting the pairs of electrodes to the input terminals, and a control unit for controlling the switches. The switches have a plurality of different states for selectively connecting pairs of electrodes to the input terminals in one of a plurality of electrode configurations, the electrodes having a different total electrical resistance in each electrode configuration.

Abstract: A liquid heater is described including a chamber for receiving a liquid, pairs of electrodes located within the chamber for applying electric current to the liquid, input terminals for connection to a power supply, a plurality of bridge arms connected in parallel to the input terminals, and a control unit for controlling switches of the bridge arms. The plurality of bridge arms include a respective bridge arm for each pair of electrodes and a common bridge arm, and each bridge arm includes a pair of switches and a node located between the switches. A first electrode of each pair of electrodes is connected to the node of the respective bridge arm, and a second electrode is connected to the node of the common bridge arm. The switches have a plurality of different states for selectively connecting pairs of electrodes to the input terminals in one of a plurality of electrode configurations, the electrodes having a different total electrical resistance in each electrode configuration.

Abstract: A liquid heater is described including a chamber for receiving a liquid, a pair of electrodes located within the chamber for applying electric current to the liquid, input terminals for connection to a power supply, a plurality of bi-directional switches for connecting the electrodes to the input terminals, and a control unit for controlling the switches. The power supply supplies an alternating voltage having a frequency no greater than 60 Hz, and the control unit controls the switches such that the electrodes are energised with an alternating voltage having a frequency no less than 150 kHz.

Abstract: A battery system comprising positive and negative charge-discharge terminals, first and second batteries, first and second unidirectional switches, and a bridging switch. The first battery and the first unidirectional switch are connected in series across the charge-discharge terminals such that the first unidirectional switch provides a conductive path from the positive charge-discharge terminal to a positive terminal of the first battery. The second battery and the second unidirectional switch are connected in series across the charge-discharge terminals such that the second unidirectional switch provides a conductive path from the negative terminal of the second battery to the negative charge-discharge terminal. The batteries and the bridging switch are connected in series across the charge-discharge terminals, with the bridging switch being located between the positive terminal of the first battery and the negative terminal of the second battery.

Abstract: A method of controlling a brushless motor that includes sensing a temperature and using the sensed temperature to define a current limit. A lower current limit is then defined for a lower sensed temperature. A winding of the motor is sequentially energized and de-energized, with the winding being de-energized when current in the winding exceeds the defined current limit.

Abstract: A battery system comprising positive and negative charge-discharge terminals, first and second batteries, first and second unidirectional switches, and a bridging switch. The first battery and the first unidirectional switch are connected in series across the charge-discharge terminals such that the first unidirectional switch provides a conductive path from the positive charge-discharge terminal to a positive terminal of the first battery. The second battery and the second unidirectional switch are connected in series across the charge-discharge terminals such that the second unidirectional switch provides a conductive path from the negative terminal of the second battery to the negative charge-discharge terminal. The batteries and the bridging switch are connected in series across the charge-discharge terminals, with the bridging switch being located between the positive terminal of the first battery and the negative terminal of the second battery.

Abstract: A power supply that operates in two modes comprising input terminals for connection to an AC source, output terminals for connection to a load, an AC-to-DC stage, and a battery. When operating in the first mode, the load draws current from the battery only. When operating in the second mode, the load draws current from both the battery and the AC-to-DC stage. The current drawn by the load is then greater than the current output by the AC-to-DC stage during first periods, and is less than the current output by the AC-to-DC stage during second periods. The load draws current from the battery and the AC-to-DC stage during the first periods such that the battery discharges, and the load and the battery each draw current from the AC-to-DC stage during the second periods such that the battery charges.

Abstract: A battery charger comprising input terminals for connection to an AC source, output terminals for connection to a battery to be charged, and a power factor correction (PFC) circuit connected between the input terminals and the output terminals. The PFC circuit comprises a current control loop for regulating an input current drawn from the AC source. The voltage at the output of the PFC circuit is regulated by the voltage of the battery which is reflected back to the PFC circuit. As a result, the battery charger acts as a current source that outputs an output current at the output terminals, and the waveform of the output current is periodic with a frequency twice that of the input current and a ripple of at least 50%.

Abstract: A vacuum cleaner comprising a vacuum motor and a power supply. The power supply comprises input terminals for connection to an AC source, output terminals connected to the vacuum motor, an AC-to-DC stage, and a battery. The AC-to-DC stage converts alternating current drawn from the AC source into direct current that is supplied to the battery and the vacuum motor. The power supply operates in a first mode when disconnected from the AC source and a second mode when connected to the AC source. In the second mode, the vacuum motor operates in either a low-power state or a high-power state. In the low-power state, the vacuum motor and the battery each draw power from the AC source such that the battery charges. When the vacuum motor operates in the high-power state, the vacuum motor draws power from both the AC source and the battery such that battery discharges.

Abstract: A battery charger comprising input terminals for connection to an AC source supplying an alternating input voltage, output terminals for connection to a battery to be charged, and a power factor correction (PFC) circuit connected between the input terminals and the output terminals. The battery charger monitors the voltage of the battery and operates in a first mode when the voltage is below a threshold. The battery charger then switches to a second mode when the voltage exceeds the threshold. The PFC circuit regulates an input current drawn from the AC source such that the waveform of the input current when operating in the first mode is different to that when operating in the second mode.