Abstract: An inverter logic circuit includes a bipolar junction transistor and a zener diode. The zener diode is connected between the base of the bipolar junction transistor and ground (or other reference voltage). The zener diode is reverse biased such that a leakage current through the zener diode allows for sufficient current through the emitter-base terminals of the bipolar junction transistor when a voltage is applied across the emitter and base terminals of the bipolar junction transistor to turn the transistor ON in the absence of an external signal to the base. As such the bipolar junction transistor functions as a normally ON bipolar junction transistor.

Abstract: A circuit including: a transistor, a base of the transistor being switchably connectable to a signal source; and a first diode connected between the base and a reference voltage. The circuit is arranged such that when the signal source is not connected to the base of the transistor, a voltage applied at an emitter of the transistor causes a current flow through the base of the transistor and through the first diode such that the transistor is in an ON state, and when the signal source is connected to the base of the transistor, current flow through the base reduces such that the transistor switches to an OFF state. The circuit includes a second diode, and the signal source is connectable to the base of the transistor through the second diode.

Abstract: A controller adapted to operate a driver circuit of Bipolar Junction Transistors (BJT) such that within each ON-OFF switching cycle of the BJT, the output of the driver circuit is in the floating state for longer than it is in either the ON or OFF state. In the floating state the driver circuit is not drawing power and so power efficiency is improved. The circuit may include a bypass connection between the base and collector terminals of the BJT. The resistance of the bypass connection is selected to decay charge in the drift region whilst the transistor is ON to reduce the switching time of the BJT.

Abstract: A bipolar transistor having a semiconductor structure that includes a channel of semiconductor type that is the same as the collector and emitter regions. The channel is significantly shallower than the base region with which it interfaces. The semiconductor structure provides improved current gain. It also enables the device to operate, when on, selectively either with primarily unipolar conduction or with primarily bipolar conduction by control of the voltage across the emitter and collector terminals of the transistor.

Abstract: A transistor device includes a transistor and programmable controller. The controller has an output that controls operation of the transistor. The controller includes analog computing circuitry and optionally digital computing circuitry that may be used to setup the analog computing circuitry. In addition to two connectors for connecting the transistor into an external circuit, the device includes a further connector that provides an input to the controller and through which the control can be programmed post manufacture. The transistor device may be a discrete component in which transistor and controlling circuitry are held in packaging, the three connectors exposed through the packaging in order to connect the device to an external circuit.

Abstract: A structure and method for guarding a high voltage region at a semiconductor surface from a low voltage region at the semiconductor surface. The structure comprising at least two trenches between the high and low voltage regions to isolate the high voltage region from the low voltage region. The trenches are spaced apart so as to define a sub-region therebetween. To prevent breakdown across the trenches, an intermediate voltage, i.e., of a value between the voltages of the high and low voltage regions, is applied to the sub-region so as to reduce the voltage drop across each trench. Preferably this is achieved by providing an integrated voltage divider circuit that connects between the high and low voltage regions and has an output connected to the sub-region by which the intermediate voltage is applied to the sub-region.

Abstract: A circuit including: a transistor, a base of the transistor being switchably connectable to a signal source; and a first diode connected between the base and a reference voltage. The circuit is arranged such that when the signal source is not connected to the base of the transistor, a voltage applied at an emitter of the transistor causes a current flow through the base of the transistor and through the first diode such that the transistor is in an ON state, and when the signal source is connected to the base of the transistor, current flow through the base reduces such that the transistor switches to an OFF state. The circuit includes a second diode, and the signal source is connectable to the base of the transistor through the second diode.

Abstract: A method of subdividing a semiconductor wafer is described with trenches in order to provide separate, electrically isolated regions that can be used to hold components that operate at different voltages. There is also described a masking and etching process of forming collector and emitter regions of a lateral bipolar transistor, from a layer of polysilicon deposited on a patterned later of silicon dioxide.

Abstract: An inverter logic circuit includes a bipolar junction transistor and a zener diode. The zener diode is connected between the base of the bipolar junction transistor and ground (or other reference voltage). The zener diode is reverse biased such that a leakage current through the zener diode allows for sufficient current through the emitter-base terminals of the bipolar junction transistor when a voltage is applied across the emitter and base terminals of the bipolar junction transistor to turn the transistor ON in the absence of an external signal to the base. As such the bipolar junction transistor functions as a normally ON bipolar junction transistor.

Abstract: A transistor device includes a transistor and programmable controller. The controller has an output that controls operation of the transistor. The controller includes analog computing circuitry and optionally digital computing circuitry that may be used to setup the analog computing circuitry. In addition to two connectors for connecting the transistor into an external circuit, the device includes a further connector that provides an input to the controller and through which the control can be programmed post manufacture. The transistor device may be a discrete component in which transistor and controlling circuitry are held in packaging, the three connectors exposed through the packaging in order to connect the device to an external circuit.

Abstract: A power adaptor is disclosed, which comprises an input for connection to an AC power supply, a resonant circuit coupled to the input that provides an output suitable for driving a load, at least one half-bridge drive circuit for providing a drive signal to the resonant circuit, and a switch controller for the half-bridge drive circuit. The switch controller is adapted to provide one or more of the following, in at least one mode: (i) to provide the high-side switch and the low-side switch with on-times of different durations, (ii) to provide the high-side switch and the low-side switch with on-times that overlap, and (iii) to provide the high-side switch and the low-side switch with on-times that are synchronous. This may be utilised to control the current delivered to the output without any need to change the frequency at which the resonant circuit is driven.

Abstract: A power adaptor including an input for connection to an AC power supply, an output for connection to a load, and a resonant circuit coupled to the input that provides power to the output suitable for driving the load, is provided. The resonant circuit has two or more resonant frequencies, which are not harmonics of each other. The power adaptor includes a controller adapted to drive the resonant circuit at, or near, each of the two or more resonant frequencies to select different characteristics of the current drawn from the AC power supply, in use.

Abstract: A power adaptor including an input for connection to an AC power supply, an output for connection to a load, and a resonant circuit coupled to the input that provides power to the output suitable for driving the load, is provided. The resonant circuit has two or more resonant frequencies, which are not harmonics of each other. The power adaptor includes a controller adapted to drive the resonant circuit at, or near, each of the two or more resonant frequencies to select different characteristics of the current drawn from the AC power supply, in use.

Abstract: A power adaptor is disclosed, which comprises an input for connection to an AC power supply, a resonant circuit coupled to the input that provides an output suitable for driving a load, at least one half-bridge drive circuit for providing a drive signal to the resonant circuit, and a switch controller for the half-bridge drive circuit. The switch controller is adapted to provide one or more of the following, in at least one mode: (i) to provide the high-side switch and the low-side switch with on-times of different durations, (ii) to provide the high-side switch and the low-side switch with on-times that overlap, and (iii) to provide the high-side switch and the low-side switch with on-times that are synchronous. This may be utilised to control the current delivered to the output without any need to change the frequency at which the resonant circuit is driven.

Abstract: A rectifier circuit is disclosed comprising input terminals adapted to receive an alternating current voltage, and output terminals adapted to provide an output having a rectified output voltage. The rectifier circuit has a diode bridge in which the diodes are each adapted to be by-passed by a low-impedance path on activation of an associated electronic switching device (Q1,Q2,Q3,Q4). Furthermore, the rectifier circuit is adapted to control activation of one or more electronic switching devices (Q1,Q2,Q3,Q4), such that the flow of current relative to one of the output terminals is in one direction only.

Abstract: A power adaptor (20) is provided, comprising an input (22) for connection to an AC power supply, and a resonant circuit (34) coupled to the input (22) that provides an output suitable for driving a load (50). The capacitance and inductance of the resonant circuit (34) are selected to provide a pre-determined change in effective voltage, and a corresponding pre-determined change in effective current, between the input (22) and the output (24) of the power adaptor (20).

Abstract: A power adaptor for a lighting unit, comprising an input for coupling to an electrical power supply and a controller adapted to monitor the input and operable to provide at least two independent electrical outputs, each output having a power level based on an amount of power available at the input. The independent electrical outputs may be used to supply and control an intensity and/or colour characteristic of a solid state lighting unit, comprising at least two separately controllable coloured emitters.

Abstract: A lighting controller is used to independently control variable output intensity of both a first, relatively high power lighting unit and a second, relatively low power lighting unit. A control device is operable within an overall range of operation between first and second end points, for varying the light intensity output of both the first and second lighting units. The overall range of operation is divided into (i) a first range over which the intensity of the first lighting unit is varied between a first level and a second level and over which the intensity of the second lighting unit is held substantially constant at a third level, and (ii) a second range over which the intensity of the first lighting unit is held substantially constant at a fourth level and over which the intensity of the second lighting unit is varied between a fifth level and a sixth level.