GB2624624A

GB2624624A - Apparatus and method

Info

Publication number: GB2624624A
Application number: GB2217167.2A
Authority: GB
Inventors: Mottley Sam; Kitchin Richard; Slater Patrick
Original assignee: Visive Group Ltd
Current assignee: Visive Group Ltd
Priority date: 2022-11-16
Filing date: 2022-11-16
Publication date: 2024-05-29
Also published as: WO2024105401A1; GB202217167D0

Abstract

A power supply circuit 1 for a set of loads 10, including a first load 10A such as a light-emitting diode (LED) array, comprising an array of semiconductor junction devices including a first semiconductor junction device, the power supply circuit comprising: a power supply 20, configurable in a series of states including: a first “ON” state S1, during which the first semiconductor junction device is biased into conduction; and a second “OFF” state S2, during which the first semiconductor junction device is not biased into conduction; a load characteristics sensor 30, configured to sense one or more of: a voltage level across the first load, a current level through the first load, a resistance of the first load, a capacitance of the first load and an inductance of the first load; and a controller 40, configured to synchronously control: the power supply to switch between the first state and the second state at a first frequency F1 and/or with a first duty cycle DC1 (e.g. employing pulse-width modulation); and the load characteristics sensor to sense the set of load characteristics of the first load selectively during the series of states.

Description

APPARATUS AND METHOD

Field

The present invention relates to power supply circuits for semiconductor junction devices.

Background to the invention

Typically, an illuminated sign or display panel comprises an array of semiconductor diodes (i.e. a load), respectively capable of emitting optical radiation when forward biased at a voltage sufficient to bias the semiconductor diodes into conduction. Such semiconductor diodes are usually referred to as light emitting diodes (LEDs), notwithstanding that the radiation may not be in the visible spectrum. Such LEDs, in common with other semiconductor junction devices, used as loads, exhibit load conduction characteristics (also known as load characteristics) which are non-linear in respect of obeying Ohm's law. Herein, the term 'load conduction characteristics' is used to mean the extent to which the load, in passing a current (I) is accompanied by a voltage drop (V) thereacross that is indicative of the I-V characteristics of any devices or components comprising the load.

As is well known in the art, the conduction characteristic of a so-called linear load which obeys Ohm's law is that the voltage across the load is directly proportional to the current passing therethrough, even for small values of current, and the power dissipated therein as heat increases as the product of current and voltage, or alternatively as the square of the current. This may be contrasted with a single junction semiconductor device, such as an LED, having, when forward biased, an I-V characteristic in which a small but significant threshold voltage (of the order of 0.5 to 1 V) exists before and for the passage of even very small currents whereas thereafter, significant current levels can pass without a significantly large increase in the voltage drop across the single junction semiconductor device. That is, the single junction semiconductor exhibits a non-linear forward conduction characteristic which in part enables such a device to pass large currents and emit radiation whilst generating relatively little internal heat.

Notwithstanding that a semiconductor junction device is formed from at least one body of conductive material which exhibits some ohmic resistance when conducting, it is usual to drive such a semiconductor junction device from a current limiting source. Typically, when a large number of semiconductor junction devices are grouped together to provide intense illumination in a product, for example in providing edge illumination of display panels of plastics materials, the semiconductor junction devices may be housed so that ventilation to the surroundings, such as via ventilation apertures, is necessary to dissipate heat produced within the semiconductor junction devices and notwithstanding that this may conflict with a desire that the emitted radiation is not directly visible through the ventilation apertures.

Hence, the use of large numbers of LEDs forming light sources for lighting articles, such as illuminated signs and display panels, requires the semiconductor junction devices to be operated with current and voltage values within the capacity of the articles to dissipate such heat as is generated, and such parameters are often fixed as part of the overall design of the lighting articles.

It will be appreciated that such lighting articles are vulnerable both to the generation significant additional heat per se and to the generation and dissipation of even small amounts of additional heat locally in regions where the thermal balance is disturbed.

In certain circumstances, electrical breakdown of a semiconductor junction within such a semiconductor diode, supplied from a current-limiting source, may result in the semiconductor diode instead exhibiting an ohmic resistance and, notwithstanding in likely reduction in current flow caused by the resistance, become a source of heat which may adversely affect other components coupled thereto electrically or thermally, spreading component failure or escalating generation of additional heat, that may lead to a fire.

The generation of additional heat and resultant component failure and/or fire may also result from failures of non-semiconductor components or of the circuit structure itself, typically due to the formation of unintentional and unregulated conductive paths between conductors of the circuit by breakdown of insulating materials or ingress of contaminants of an electrically conductive, chemically or electrochemically, reactive nature.

It will be appreciated that that whereas the effects of such contaminant ingress to the load may be a permanent change in its conduction characteristics, the presence of contaminants may affect other characteristics of the load in ways that may not be immediately apparent from how the load handles operating current provided by the source but which, in being inconsistent with the correctly operating semiconductor device load, are nevertheless indicative of a physical state of the load which portends operation from which the circuit requires protection.

For example, loads comprising LEDs may have the LEDs connected in linear 'strings' and contained within transparent housings for protection from the environment or apertured thereto for ventilation. If the sealing of any such housing is breached or ventilation apertures incorrectly positioned, it is possible for the housing to fill with rain water or atmospheric moisture. Such water, as a liquid or vapour, may act as a weak electrolyte and when in contact with dissimilar metals, form a voltaic cell or battery and generate a voltage across the load.

Alternatively or additionally, such water may act as a dielectric between conductors and effect a capacitance tending to store any voltage applied to the load.

Whilst neither of these situations necessarily affects operation of the load when supplied with power by the source, they are indicative of such sealing breach and point to the load operating other than as intended and thus do have a bearing in determining the desirability of applying operating power to the load, that is, its protection.

It will be seen that if the circuit is operated for prolonged periods, it is possible for such changes in load characteristics which depend upon the presence of water or other contaminants to occur randomly with any such ingress and possibly disappear with drainage or evaporation, so that it is desirable to identify and act upon changes to the characteristics of the load caused thereby, if and when they occur.

It will be appreciated that such LEDs and the application and configuration outlined above represent only one example of a load comprising one or more semiconductor junction devices for which a change in conduction or other characteristics (i.e. load characteristics) of the circuit may lead to the need for protection of other components and/or the circuit as a whole, and in general, any electronic circuit wherein a load contains one or more semiconductor junction devices which are biased into conduction by a current from a power supply may benefit from protection against adverse effects caused by changes in characteristics of the load, particularly introducing a current path with an Ohmic resistance and thereby an unwanted source of heat.

Hence, there is a need to improve protection of loads, comprising semiconductor junction devices, from anomalies which may lead to detrimental and/or dangerous conditions..

Summary of the Invention

It is one aim of the present invention, amongst others, to provide a power supply circuit which at least partially obviates or mitigates at least some of the disadvantages of the prior art, whether identified herein or elsewhere. For instance, it is an aim of embodiments of the invention to provide a power supply circuit that XXX. For instance, it is an aim of embodiments of the invention to provide a XXX that XXX.

A first aspect provides a power supply circuit for a set of loads, including a first load comprising an array of semiconductor junction devices including a first semiconductor junction device, the power supply circuit comprising: a power supply, configurable in a series of states including: a first state, wherein the power supply is configured to supply a first current through the first load at a first voltage sufficient to bias the first semiconductor junction device into conduction; and a second state, wherein the power supply is configured to supply a second current through the first load at a second voltage insufficient to bias the first semiconductor junction device into conduction; a load characteristics sensor, configured to sense a set of load characteristics of the first load, including one or more of: a voltage level across the first load, a current level through the first load, a resistance of the first load, a capacitance of the first load and an inductance of the first load; and a controller, configured to synchronously control: the power supply to switch between the first state and the second state at a first frequency and/or with a first duty cycle; and the load characteristics sensor to sense the set of load characteristics of the first load selectively during the series of states.

A second aspect provides an electronic circuit comprising a power supply circuit according to any previous claim and a set of loads, including a first load comprising an array of semiconductor junction devices, including a first semiconductor junction device.

A third aspect provides a method of controlling a power supply circuit according to the first aspect, the method comprising: synchronously controlling: the power supply to switch between the first state and the second state at the first frequency and/or with the first duty cycle; and the load characteristics sensor to sense the set of load characteristics of the first load selectively during the series of states.

Detailed Description of the Invention

According to the present invention there is provided a power supply circuit, as set forth in the appended claims. Also provided is an electronic circuit and a method. Other features of the invention will be apparent from the dependent claims, and the description that follows.

Power supply circuit The first aspect provides a power supply circuit for a set of loads, including a first load comprising an array of semiconductor junction devices including a first semiconductor junction device, the power supply circuit comprising: a power supply, configurable in a series of states including: a first state, wherein the power supply is configured to supply a first current through the first load at a first voltage sufficient to bias the first semiconductor junction device into conduction; and a second state, wherein the power supply is configured to supply a second current through the first load at a second voltage insufficient to bias the first semiconductor junction device into conduction; a load characteristics sensor, configured to sense a set of load characteristics of the first load, including one or more of: a voltage level across the first load, a current level through the first load, a resistance of the first load, a capacitance of the first load and an inductance of the first load; and a controller, configured to synchronously control: the power supply to switch between the first state and the second state at a first frequency and/or with a first duty cycle; and the load characteristics sensor to sense the set of load characteristics of the first load selectively during the series of states.

In this way, the load characteristics of the first load are sensed on-line during intended operation of the first load such as illumination of LEDs thereof i.e. during the series of states, for example during the first state, wherein the power supply is configured to supply the first current through the first load at the first voltage sufficient to bias the first semiconductor junction device into conduction and/or during the second state, wherein the power supply is configured to supply the second current through the first load at the second voltage insufficient to bias the first semiconductor junction device into conduction, synchronously with the power supply switching between the first state and the second state at a first frequency and/or with a first duty cycle. In other words, the load characteristics of the first load are sensed without interruption of the power supply to the to the first load. For example, the power supply circuit comprises and/or provides a pulse width modulation power supply (i.e. by the controller controlling the power supply) for the first load, which operates continuously (i.e. switching between the first state and the second state at the first frequency and with the first duty cycle) while the load characteristics sensor synchronously senses the set of load characteristics of the first load. In contrast, conventional power supply circuits for such set of loads sense the load characteristics off-line, requiring interruption of the power supply. By sensing the load characteristics of the first load on-line, a fidelity, for example an accuracy and/or precision, of the sensed load characteristics is relatively improved, compared with conventional off-line sensing, since the load characteristics are sensed during operating conditions, rather than during predetermined test conditions of conventional off-line sensing. In this way, identification of anomalies of the sensed load characteristics is improved, compared with conventional off-line sensing. For example, some anomalies may only manifest and/or may only be identifiable during intended operation of the first load such as illumination of LEDs thereof i.e. during the series of states. Additionally and/or alternatively, since the load characteristics of the first load are sensed on-line, the load characteristics of the first load may be sensed relatively more frequently, compared with conventional off-line sensing, thereby enabling identification of intermittent, periodic and/or aperiodic anomalies that do not manifest coincident in time with conventional off-line sensing and/or determination of temporal trends the load characteristics of the first load, such as increases over time in the resistance of the first load.

Herein, the term off-line is used in relation to a load in respect of its function when operating power is absent from the load and is used in relation to associated circuit components and their function to indicate operation, intended or actual, when the load is off-line. In contrast, the term on-line is used in relation to the load in respect of its function when operating power, including PVVM power for example, is applied and is used in relation to associated circuit components and their function to indicate operation, intended or actual, when the load is on-line.

The first aspect provides the power supply circuit for the set of loads, including the first load comprising the array of semiconductor junction devices including the first semiconductor junction device. It should be understood that the power supply circuit is an electrical and/or electronic circuit suitable for supplying electrical power to the set of loads. It should be understood that the respective loads of the set of loads each comprise arrays of semiconductor junction devices. In one example, the set of loads includes L loads, including the first load, wherein L is a natural number greater than or equal to 1, for example 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 or more, for example wherein each of the L loads is as described with respect to the first load mutatis mutandis. In one example, the set of loads includes a second load, for example wherein the second load is as described with respect to the first load mutatis mutandis. It should be understood that a load may be known as a channel. In one example, the power supply circuit is configured to supply power and/or to control the respective loads of the set of loads mutually independently or dependently. For example, independent RGB LEDs may be configured as three loads: one load for each of the respectively one or more (i.e. a plurarlity of) R, G and B LEDs, enabling independent control of the frequency and/or the duty cycle of each of the three loads and hence control of the overall colour as well as the brightness. For example, the first load may comprise, instead of a single LED, a plurality of LEDs connected in parallel and/or in series without changing the operating principle, that the power supply provides current at an operating voltage across the or each semiconductor junction device sufficient to bias it into full forward conduction and draw current to the extent permitted by any limiting or regulating device. Once the LED load is fully conducting the voltage dropped thereacross is substantially invariant even if the current varies. It should be understood that the respective arrays, for example regular arrays On which the respective semiconductor junction devices are logically and/or physically arranged regularly, for example linearly or in a matrix) or irregular arrays (in which the respective semiconductor junction devices are logically and/or physically arranged irregularly, for example non-linearly), each comprise semiconductor junction devices, which may be mutually electrically coupled, for example via one or more electrical interconnects, in series and/or in parallel and dependently couplable, for example via one or more electrical connectors, or independently electrically couplable to the power supply, for example via one or more electrical connectors. In one example, the first load consists of the array of semiconductor junction devices, including the first semiconductor junction device, optionally one or more electrical interconnects and optionally one or more one or more electrical connectors. That is, such a first load does not include other resistive, capacitive and/or inductive electrical components notwithstanding that failure of the array of semiconductor junction devices, including the first semiconductor junction device, optionally one or more electrical interconnects and optionally one or more one or more electrical connectors. In one example, the array of semiconductor junction devices includes D semiconductor junction devices, including the first semiconductor junction device, wherein D is a natural number greater than or equal to 1, for example 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000 or more, for example wherein each of the D semiconductor junction devices is as described with respect to the first D semiconductor junction device mutatis mutandis. In one example, the first semiconductor junction device is a light emitting diode.

The power supply circuit comprises the power supply, configurable in the series of states. It should be understood that the power supply is electrically couplable, directly or indirectly, to the set of loads, for example via one or more electrical connectors. Suitable power supplies are known.

The series of states includes the first state, wherein the power supply is configured to supply the first current through the first load at the first voltage sufficient to bias the first semiconductor junction device into conduction. That is, the first state is an ON (also known as high) state, in which, in use, the first semiconductor junction device is biased, particularly forward biased, into electrical conduction. For example, a LED would thus radiate light during the first state. In one example, the first voltage is in a range from 3 V to 60 V, preferably in a range from 12 V to 48 V, for example 3 V. 6V, 12 V, 24 V, 36 V, 48 V or 60 V, i.e. above a threshold voltage (of the order of 0.5 to 1 V) for a single junction semiconductor device, such as an LED. It should be understood that the first voltage may be adjusted, thereby changing the first current, or may be fixed, for example for a particular load. It should be understood that the first current depends on the I-V characteristics of the first load and on the first voltage. It should be understood that, in normal use and without adjustment, the first voltage and the first current are respectively constant, within ripple of the power supply.

The series of states includes the second state, wherein the power supply is configured to supply the second current through the first load at the second voltage insufficient to bias the first semiconductor junction device into conduction. That is, the second state is an OFF (also known as low) state, in which, in use, the first semiconductor junction device is not biased, particularly forward biased, into electrical conduction. For example, a LED would thus not radiate light during the second state. In one example, the second voltage is in a range from 0.01 V to 1 V, preferably in a range from 0.1 V to 0.5 V, for example 0.01 V, 0.05 V, 0.1 V, 0.2 V, 0.3 V, 0.4 V, 0.5 V i.e. below a threshold voltage (of the order of 0.5 to 1 V) for a single junction semiconductor device, such as an LED. It should be understood that the second voltage may be adjusted, thereby changing the second current, or may be fixed, for example for a particular load. It should be understood that the second current is nominally 0 A and depends on the I-V characteristics of the second load and on the second voltage. It should be understood that, in normal use and without adjustment, the second voltage and the second current are respectively constant, within ripple of the power supply.

The power supply circuit comprises the load characteristics sensor, configured to sense the set of load characteristics of the first load, including one or more of: the voltage level across the first load, the current level through the first load, the resistance of the first load, the capacitance of the first load and the inductance of the first load. It should be understood that the load characteristics sensor is electrically couplable to the set of loads load, for example between the power supply and the set of loads. In one example, the power supply is indirectly electrically couplable to the set of loads via the load characteristics sensor. In one example, the load characteristics sensor comprises a first set of sensors, including one or more of: a voltage sensor, a current sensor, a resistance sensor, a capacitance sensor and an inductance sensor, configured to respectively sense the voltage level across the first load, the current level through the first load, the resistance of the first load, the capacitance of the first load and the inductance of the first load. Suitable sensors are known. In one example, the load characteristics sensor is configured to sense the respective sets of load characteristics of the respective set of loads, including the first load, including one or more of: the respective voltage levels across the respective set of loads, the respective current levels through the respective set of loads, the respective resistances of the respective set of loads, the respective capacitances of the respective set of loads and the respective inductances of the respective set of loads. In this way, the respective sets of load characteristics of the respective loads of the set of loads may be sensed, for example independently. For example, the load characteristics of 4 channels of LEDs may be sensed separately. In one example, the load characteristics sensor comprises S sets of sensors, including the first set of sensors, wherein S is a natural number greater than or equal to 1, for example 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 or more, for example wherein each of the S sets of sensors is as described with respect to the first set of sensors mutatis mutandis and/or for example wherein respective sets of sensors are configured to sense the respective sets of load characteristics of the respective loads of the set of L loads, as described previously. In other words, the load characteristics sensor may include a separate set of sensors for each load. In one example, the load characteristics sensor is configured to sense the set of load characteristics of the first load, for example the respective load characteristics of the set of load characteristics of the first load, for a duration in a range from from 1 ps to 10 ms, preferably in a range from 10 ps to 5 ms.

Suitable load characteristics sensors are known, for example as described in WO 03/073798 and/or EP1479271B1, the subject matter of which is incorporated herein in entirety. Thus insofar as the load characteristic being sensed is its conduction, the load characteristic sensor may be considered as load conduction sensing means, comprising voltage sensing means, couplable to the first load and operable to derive at least one sensor voltage level representative of current passed by the first load as described more fully below, and the controller operable to compare the sensed load voltage level with a threshold value and responsive to a difference therebetween, having regard to the current passing through the first load, that is indicative of said sensed voltage level representing a load conduction characteristic consistent with or inconsistent with a correctly functioning semiconductor junction device to produce a threshold comparison decision that is favourable or unfavourable.

In one example, the controller includes an input port means to receive at least one sensor voltage level from the voltage sensing means, and supply gating logic which is responsive to a threshold comparison decision to inhibit or permit provision of an enabling signal at an output port means, for example to a switch as described herein.

In one example, the voltage sensing means is coupled to the first load where fed with operating power, for example via a switch, at a tapping point or node, and is arranged to effect a representation of the conduction behaviour of the first load to current absent supply, that is, with the first load in the second state, and during said second state passing through the first load a sensing current having a value that is less, for a semiconductor junction device, than the forward conduction threshold thereof, and sensing the voltage level across the first load in response to said sensing current. In one example, the load characteristics sensor comprises a generator of said sensing current in the form of a source resistance connected between the power supply and said node. The value of the source resistance is chosen having regard to the master source voltage and voltage drop expected across the load to permit a current of about 200pA to be drawn by the load with the supply switch inhibited, that is, a current insufficient to bias the semiconductor junction or junctions of the load into full conduction.

In one example, the voltage sensing means comprises a voltage reading resistor connected between the node and an output terminal and an optional capacitor connected between the output terminal and ground, which serves to decouple from the read node voltage any high frequency electrical disturbances internally or externally of the circuit.

The power supply circuit comprises the controller, for example including a processor and a memory, wherein the processor is configured to execute instructions to implement the control provided by the controller. For example, the controller may comprise and/or be provided by discrete or integrated components operating logically upon signal levels or may be provided by one or more microprocessors or a general purpose computer in accordance with a stored program, the precise nature and structure of the controller being secondary to the functions it performs. For example, the controller may comprise and/or be provided by a processor, having one or more input ports and one or more output ports, and/or a plurality of interrelated function blocks and one or more input ports and one or more output pods. It should be understood that such pods represent interfacing between signals levels derived and utilised by the remainder of the power supply circuit and logical processes occurring within the controller.

The controller is configured to synchronously control: the power supply to switch between the first state and the second state at the first frequency and/or with the first duty cycle; and the load characteristics sensor to sense the set of load characteristics of the first load selectively during the series of states.

That is, the controller synchronises selective sensing of the set of load characteristics of the first load with controlling of the switching, such that power supply to the first load is not interrupted while sensing, as described previously. For example, the power supply circuit comprises and/or provides a pulse width modulation power supply (i.e. by the controller controlling the power supply) for the first load, which operates continuously (i.e. switching between the first state and the second state at the first frequency and with the first duty cycle) while the load characteristics sensor synchronously senses the set of load characteristics of the first load. It should be understood that the term selectively means that the set of load characteristics are sensed appropriately according to the first state or the second state depending on which particular load characteristic is to be sensed, as understood by the skilled person, for example wherein the load characteristics sensor senses the capacitance of the first load during, for example only during, the second state, the resistance of the first load during, for example only during, the second state and/or the current level through the first load during, for example only during, the first state. It should be understood that the series of states are switched periodically, at the first frequency. In one example, the first frequency is in a range from 10 Hz to 100 kHz, preferably in a range from 30 Hz to 10 kHz, for example 30 Hz, 50 Hz, 100 Hz, 1 kHz, 2 kHz, 3 kHz, 5 kHz or 10 kHz. It should be understood that the first duty cycle is the ratio of the temporal duration (also known as pulse width) of the first state to a periodicity (i.e. a time period, determined as the reciprocal of the first frequency), typically expressed as a percentage. In one example, the first duty cycle is in a range from 1% to 99%, preferably in a range from 10% to 90%, for example 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80% or 90%.

In one example, the power supply circuit comprises a switch and the controller is configured to synchronously control the power supply to switch between the first state and the second state at the first frequency and/or with the first duty cycle by actuating (i.e. activating or deactivating appropriately) the switch, for example by providing an enabling signal thereto.

In one example, the controller is configured to synchronously control the load characteristics sensor to consecutively (i.e. successively, in sequence, serially) sense the set of load characteristics of the first load selectively during the series of states. That is, the set of load characteristics of the first load may be sensed separately (i.e. not simultaneously, not concurrently), for example in the same or in different first states and/or second states.

In one example, the controller is configured to synchronously control the load characteristics sensor to sense the set of load characteristics of the first load selectively during the series of states responsive to the switch between the first state and the second state, to the first state and/or to the second state. For example, responsive to a switch to the second state, such as a switch from the first state to the second state, the controller may synchronously control the load characteristics sensor to sense the capacitance of the first load during the second state and/or the resistance of the first load during the second state. For example, responsive to a switch to the first second state, such as a switch from the second state to the first state, the controller may synchronously control the load characteristics sensor to sense the current level through the first load during the first state by measuring the current level through the first load during the first state. In one example, the controller is configured to detect a switch between the first state and the second state, to the first state, such as from the second state to the first state, and/or to the second state, such as from the first state to the second state, for example by correspondingly detecting a trailing voltage edge or a leading voltage applied by the power supply across the first load and wherein the controller is configured to synchronously control the load characteristics sensor to sense the set of load characteristics of the first load selectively during the series of states responsive to the detected switch between the first state and the second state, to the first state and/or to the second state. In this way, the controller controls the load characteristics sensor reactively (i.e. in response to the switch, which triggers the sensing) rather than in according to a timing schedule and using a clock, for example. In this way, timing of the sensing does not require predetermining (e.g. calculating) and hence is relatively more amenable to changes of the first frequency and/or the first duty cycle.

In one example, the controller is configured to synchronously control: the power supply to switch between the first state and the second state at the first frequency and/or with the first duty cycle; and the load characteristics sensor to sense the set of load characteristics of the first load selectively during the series of states; according to a timing schedule and using a clock. In this way, timing of the sensing may be predetermined.

In one example, the controller is configured to synchronously control the load characteristics sensor to sense the set of load characteristics of the first load selectively during the series of states, after a temporal delay following the switch between the first state and the second state, to the first state and/or to the second state. In this way, the voltage across or current through the first load may settle, before the set of load characteristics is sensed. In one example, the temporal delay is in a range from 1 ps to 100 ms, preferably in a range from 10 ps to 10 ms.

Capacitance sensing In one example, the controller is configured to synchronously control the load characteristics sensor to sense the capacitance of the first load by sensing the voltage level across the first load during, for example only during, the second state, for example by measuring decay of the voltage level during the second state, as understood by the skilled person. If, as discussed above, the physical load structure is contaminated with a poorly conductive material that effects a storage capacitance at any time during circuit operation, when the relatively high power supply first voltage is removed, the capacitance will have the effect of causing the voltage across the first load to decay relatively slowly, notwithstanding sensing current source resistor. It will be appreciated that instead of comparing the actual load voltage decay during the second state with a predetermined threshold value of decay for the same time period, the threshold comparison means may determine from voltage levels sensed during the second state a rate of decay of the load voltage upon switching from the first state to the second state and the controller may effect threshold comparison with a threshold value representing a minimum rate expected during the second state from a purely semiconductor or resistive load, the controller being responsive to a sensed load voltage decay rate less than the threshold value to provide to the supply gating logic an unfavourable threshold comparison decision.

Resistance sensing In one example, the controller is configured to synchronously control the load characteristics sensor to sense the resistance of the first load by controlling the power supply to supply an additional current through the first load at a voltage insufficient to bias the first semiconductor junction device into conduction during the second state and to measure the corresponding voltage level across the first load. It should be understood that the supplying the additional current thus corresponds with injection of the additional current during the second state, as understood by the skilled person. Hence, the corresponding voltage across the first load may be measured during injection of the additional current during the second state and the resistance of the first load calculated therefrom trivially for a purely resistive load.

Current sensing In one example, the controller is configured to synchronously control the load characteristics sensor to sense the current level through the first load during, for example only during, the first state.

Repetitive sensing In one example, the controller is configured synchronously control the load characteristics sensor to repetitively, for example periodically or aperiodically, sense, for example M repetitions (wherein M is a natural number greater than or equal to 2 such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100 or more) the set of load characteristics of the first load selectively during the series of states and optionally, wherein the sensed set of load characteristics of the load comprise averaged, for example mean, mode and/or median, and/or summed load characteristics of the first load, for example calculated using the repetitively sensed set of load characteristics of the first load. That is, the set of load characteristics of the first load are repetitively sensed (for example, a plurality of measurements) during the first state and/or during the second state, for example at least one of the load characteristics of the first load is repetitively sensed during each first state and/or during each second state. In this way, an accuracy and/or precision of the sensed set of load characteristics of the first load is improved, for example according to counting statistics. In one example, the sensed set of load characteristics of the first load excludes one or more outlier sensed load characteristics, for example wherein the one or more outlier sensed load characteristics are more than 2 standard deviations away from the mean thereof. In this way, transient noise, such as electrical interference, may be excluded. In one example, the sensed set of load characteristics of the first load includes one or more outlier sensed load characteristics, for example wherein the one or more outlier sensed load characteristics are more than 2 standard deviations away from the mean thereof. In this way, high frequency anomalies, such as electrical spikes, may be identified. In one example, the sensed set of load characteristics of the first load is the one or more outlier sensed load characteristics, for example wherein the one or more outlier sensed load characteristics are more than 2 standard deviations away from the mean thereof. In this way, high frequency anomalies, such as electrical spikes, may be prioritised.

Frequency and/or duty cycle control In one example, the controller is configured to change the first frequency to a second frequency and/or to change the first duty cycle to a second duty cycle. In this way, a luminosity (also known as intensity or brightness) of LEDs may be increased, for example, by increasing the frequency (i.e. the second frequency is greater than the first frequency) for a given duty cycle and/or by increasing the duty cycle (i.e. the second duty cycle is greater than the first duty cycle) and vice versa. In this way, a radiated colour of RGB LEDs, configured as three loads, may be changed by changing the respective frequencies and/or duty cycles for the respective loads. In one example, the power supply circuit comprises a frequency controller and/or a duty cycle controller, such as a dimmer controller and/or a colour controller, communicatively coupled to the controller, for example for setting luminosity and/or colour.

Comparator In one example, the controller is configured to compare the respective sensed set of load characteristics of the first load with a corresponding set of threshold values and to control the power supply to not switch to the first state, based on a result of the comparing. In this way, upon identification of an anomaly, the controller may inhibit the power supply from supplying power to the first load, which is thus effectively switched off, for example by deactivating a switch as described previously. In this way, the power supply circuit provides load protection, for protecting the power supply circuit and/or the set of loads from load anomalies which may lead to detrimental and/or dangerous conditions. It should be understood that the corresponding set of threshold values and the comparing are appropriate for the particular load characteristic. For example, when sensing the capacitance of the first load by measuring the voltage level across the first load during the second state, as described previously, the sensed voltage level should be smaller than the corresponding threshold value. For example, when sensing the resistance of the first load by injecting a current and measuring the voltage across the first load during the second state (i.e. providing the third state), as described previously, the sensed voltage level should be larger the corresponding threshold value. For example, when sensing the current level through the first load during the first state, as described previously, a sensed delta on a moving window average current level should be smaller than the corresponding threshold value.

In one example, the controller is configured to repeatedly, for example periodically or aperiodically such as at a reducing frequency, compare the respective sensed set of load characteristics, for example the resistance and/or the capacitance, of the first load, for example without switching to the first state, with the corresponding set of threshold values and to selectively control the power supply to switch to the first state, based on a result of the repeated comparing. In this way, upon identification of an anomaly and inhibiting the power supply from supplying power to the first load, the controller may confirm (i.e. anomaly present) or deny (i.e. anomaly present or false positive) the anomaly and if the anomaly is denied, the controller may control the power supply to resume supplying power to the first load. By repeating the comparisons at a reducing frequency (i.e. increasingly extending time intervals between the comparisons), the controller may attempt to restart power supply after the load dries out, for example. However, if repeated comparisons are unsuccessful, the controller may stop further comparisons and instead, perform an action such as flag an error.

In one example, the controller is configured to modify the corresponding set of threshold values, based on a result of the repeated comparing. In this way, the controller may customise the corresponding set of threshold values for the first load, for example to improve sensitivity to anomalies by decreasing upper threshold limits and/or by increasing lower threshold limits.

In one example, the controller is configured to determine respective rates of change of the sensed set of load characteristics of the first load and optionally, to compare the respective rates of change of the sensed set of load characteristics of the first load with a corresponding set of threshold rates and to control the power supply to not switch to the first state, based on a result of the comparing. In this way, the controller may identify a trend, for example towards a threshold, before the threshold is breached. For example, the sensed resistance of the first load may rise relatively slowly, indicative of breakdown of insulating materials, ingress of contaminants and/or electrical breakdown of a semiconductor junction.

In one example, the power supply circuit comprises a transmitter and the controller is configured to control the transmitter to transmit a signal based on the sensed set of load characteristics of the first load. In this way, the controller may perform an action such as flag an error.

In one example, the power supply circuit comprises a receiver and the controller is configured to receive a received message from the receiver, for example to inhibit the power supply from supplying power to the first load and/or modify the corresponding set of threshold values.

Electronic circuit The second aspect provides an electronic circuit comprising a power supply circuit according to the first aspect and a set of loads, including a first load comprising an array of semiconductor junction devices, including a first semiconductor junction device.

The set of loads, the array of semiconductor junction devices and/or the first semiconductor junction device may be as described as with respect to the first aspect.

In one example, the first semiconductor junction device is a light emitting diode, as described as with respect to the first aspect.

Method The third aspect provides a method of controlling a power supply circuit according to the first aspect, the method comprising: synchronously controlling: the power supply to switch between the first state and the second state at the first frequency and/or with the first duty cycle; and the load characteristics sensor to sense the set of load characteristics of the first load selectively during the series of states.

The method may include any of the steps as described with respect to the first aspect.

Definitions Throughout this specification, the term "comprising" or "comprises" means including the component(s) specified but not to the exclusion of the presence of other components. The term "consisting essentially of" or "consists essentially of' means including the components specified but excluding other components except for materials present as impurities, unavoidable materials present as a result of processes used to provide the components, and components added for a purpose other than achieving the technical effect of the invention, such as colourants, and the like.

The term "consisting or or "consists of' means including the components specified but excluding other components.

Whenever appropriate, depending upon the context, the use of the term "comprises" or "comprising" may also be taken to include the meaning "consists essentially of' or "consisting essentially of', and also may also be taken to include the meaning "consists or or "consisting of'.

The optional features set out herein may be used either individually or in combination with each other where appropriate and particularly in the combinations as set out in the accompanying claims. The optional features for each aspect or exemplary embodiment of the invention, as set out herein are also applicable to all other aspects or exemplary embodiments of the invention, where appropriate. In other words, the skilled person reading this specification should consider the optional features for each aspect or exemplary embodiment of the invention as interchangeable and combinable between different aspects and exemplary embodiments.

Brief description of the drawings

For a better understanding of the invention, and to show how exemplary embodiments of the same may be brought into effect, reference will be made, by way of example only, to the accompanying diagrammatic Figures, in which: Figure 1 schematically depicts a power supply circuit according to an exemplary embodiment; Figure 2 schematically depicts a method according to an exemplary embodiment; Figure 3 schematically depicts the power supply circuit of Figure 1, in more detail; and Figure 4 schematically depicts a method according to an exemplary embodiment.

Detailed Description of the Drawings

Figure 1 schematically depicts a power supply circuit according to an exemplary embodiment.

The first aspect provides a power supply circuit 1 for a set of loads 10, including a first load 10A (not shown) comprising an array of semiconductor junction devices 11 including a first semiconductor junction device 11A, the power supply circuit 1 comprising: a power supply 20, configurable in a series of states including: a first state Si, wherein the power supply 20 is configured to supply a first current 11 through the first load 10A at a first voltage V1 sufficient to bias the first semiconductor junction device 11A into conduction; and a second state S2, wherein the power supply 20 is configured to supply a second current 12 through the first load 10A at a second voltage V2 insufficient to bias the first semiconductor junction device 11A into conduction; a load characteristics sensor 30, configured to sense a set of load characteristics of the first load 10A, including one or more of: a voltage level across the first load 10A, a current level through the first load 10A, a resistance of the first load 10A, a capacitance of the first load 10A and an inductance of the first load 10A; and a controller 40, configured to synchronously control: the power supply 20 to switch between the first state Si and the second state 52 at a first frequency Fl and/or with a first duty cycle DC1; and the load characteristics sensor 30 to sense the set of load characteristics of the first load 10A selectively during the series of states In this example, the set of loads 10 includes L loads (not shown), including the first load 10A, wherein L is a natural number greater than or equal to 1, wherein each of the L loads is as described with respect to the first load 10A mutatis mutandis. In this example, the power supply circuit 1 is configured to supply power and/or to control the respective loads of the set of loads 10 mutually independently. In this example, the first semiconductor junction device 11A is a light emitting diode.

In this example, the first voltage V1 is 48 V. In this example, the second voltage V2 is in a range from 0 0.1 V to 0.5 V. In this example, the power supply 20 is indirectly electrically couplable to the set of loads 10 via the load characteristics sensor 30. In this example, the load characteristics sensor 30 comprises a first set of sensors 31A, including: a voltage sensor 32A, a current sensor 33A, a resistance sensor 34A and a capacitance sensor 35A, configured to respectively sense the voltage level across the first load 10A, the current level through the first load 10A, the resistance of the first load 10A, the capacitance of the first load 10A and the inductance of the first load 10A. In this example, the load characteristics sensor 30 is configured to sense the respective sets of load characteristics of the respective set of loads 10, including the first load 10A, including one or more of the respective voltage levels across the respective set of loads 10, the respective current levels through the respective set of loads 10, the respective resistances of the respective set of loads 10, the respective capacitances of the respective set of loads 10 and the respective inductances of the respective set of loads 10. In this example, the load characteristics sensor 30 comprises S sets of sensors, including the first set of sensors, wherein S is a natural number greater than or equal to 1, wherein each of the S sets of sensors is as described with respect to the first set of sensors mutafis mutandis and wherein respective sets of sensors are configured to sense the respective sets of load characteristics of the respective loads of the set of L loads, as described previously, noting the comment 'Per CSC Output'. In this example, the load characteristics sensor 30 is configured to sense the set of load characteristics of the first load 10A, for example the respective load characteristics of the set of load characteristics of the first load 10A, for a duration in a range from 10 ps to 5 ms.

In this example, the first frequency Fl is 2 kHz. In this example, the first duty cycle DC1 is in a range from 10% to 90%.

In this example, the power supply circuit 1 comprises a switch 50A and the controller 40 is configured to synchronously control the power supply 20 to switch between the first state S1 and the second state S2 at the first frequency Fl and/or with the first duty cycle DC1 by actuating (i.e. activating or deactivating appropriately) the switch 50A, for example by providing an enabling signal thereto.

In this example, the controller 40 is configured to synchronously control the load characteristics sensor 30 to consecutively (i.e. successively, in sequence, serially) sense the set of load characteristics of the first load 10A selectively during the series of states.

In this example, the controller 40 is configured to synchronously control the load characteristics sensor 30 to sense the set of load characteristics of the first load 10A selectively during the series of states responsive to the switch between the first state Si and the second state 52, to the first state Si and/or to the second state S2. In this example, the controller 40 is configured to detect a switch between the first state Si and the second state 52, to the first state Si, such as from the second state S2 to the first state Si, and/or to the second state 52, such as from the first state Si to the second state S2, for example by correspondingly detecting a trailing voltage edge or a leading voltage applied by the power supply 20 across the first load 10A and wherein the controller 40 is configured to synchronously control the load characteristics sensor 30 to sense the set of load characteristics of the first load 10A selectively during the series of states responsive to the detected switch between the first state Si and the second state S2, to the first state Si and/or to the second state S2.

In this example, the controller 40 is configured to synchronously control the load characteristics sensor 30 to sense the set of load characteristics of the first load 10A selectively during the series of states, after a temporal delay following the switch between the first state Si and the second state S2, to the first state S1 and/or to the second state S2. In this example, the temporal delay is in a range from 10 ps to 10 ms.

In this example, the controller 40 is configured to synchronously control the load characteristics sensor 30 to sense the capacitance of the first load 10A by sensing the voltage level across the first load 10A during, for example only during, the second state 52, for example by measuring decay of the voltage level during the second state 52, as understood by the skilled person.

In this example, the controller 40 is configured to synchronously control the load characteristics sensor 30 to sense the resistance of the first load 10A by controlling the power supply 20 to supply an additional current through the first load 10A at a voltage insufficient to bias the first semiconductor junction device 11A into conduction during the second state and to measure the corresponding voltage level across the first load 10A.

In this example, the controller 40 is configured to synchronously control the load characteristics sensor 30 to sense the current level through the first load 10A during, for example only during, the first state Si.

In this example, the controller 40 is configured synchronously control the load characteristics sensor 30 to repetitively, for example periodically or aperiodically, sense, for example M repetitions (wherein M is a natural number greater than or equal to 2 such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100 or more) the set of load characteristics of the first load 10A selectively during the series of states and optionally, wherein the sensed set of load characteristics of the load comprise averaged, for example mean, mode and/or median, and/or summed load characteristics of the first load 10A, for example calculated using the repetitively sensed set of load characteristics of the first load 10A. In this example, the sensed set of load characteristics of the first load 10A includes one or more outlier sensed load characteristics, for example wherein the one or more outlier sensed load characteristics are more than 2 standard deviations away from the mean thereof In this example, the controller 40 is configured to change the first frequency Fl to a second frequency and/or to change the first duty cycle DC1 to a second duty cycle. In this way, a luminosity (also known as intensity or brightness) of LEDs may be increased, for example, by increasing the frequency (i.e. the second frequency is greater than the first frequency Fl) for a given duty cycle and/or by increasing the duty cycle (i.e. the second duty cycle is greater than the first duty cycle DC1) and vice versa. In this example, the power supply circuit 1 comprises a dimmer controller 60.

In this example, the controller 40 is configured to compare the respective sensed set of load characteristics of the first load 1OA with a corresponding set of threshold values and to control the power supply 20 to not switch to the first state 81, based on a result of the comparing.

In this example, the controller 40 is configured to repeatedly, for example aperiodically such as at a reducing frequency, compare the respective sensed set of load characteristics, for example the resistance and/or the capacitance, of the first load 10A, for example without switching to the first state Si, with the corresponding set of threshold values and to selectively control the power supply 20 to switch to the first state Si, based on a result of the repeated comparing.

Figure 2 schematically depicts a method according to an exemplary embodiment.

Particularly, Figure 2 shows, as synchronously controlled by the controller, the power supply switching between the first state (48 V in this example) and the second state (about 0.5 V in this example) at the first frequency and/or with the duty cycle; and the load characteristics sensor sensing the set of load characteristics of the first load selectively during the series of states.

responsive to the switch between the first state and the second state. In this way, the first frequency and/or the first duty cycle may be changed and the sensing of the load characteristics continues to operate independently thereof.

In this example, the controller is configured to synchronously control the load characteristics sensor to sense the set of load characteristics of the first load selectively during the series of states responsive to the switch between the first state and the second state.

In this example, the controller is configured to synchronously control the load characteristics sensor to sense the capacitance of the first load by measuring the voltage level across the first load during the second state, responsive to the switch from the first state to the second state.

In this example, the controller is configured to synchronously control the load characteristics sensor to sense the resistance of the first load by controlling the power supply to supply an additional current through the first load at a voltage insufficient to bias the first semiconductor junction device into conduction during the second state and to measure the corresponding voltage level across the first load, responsive to the switch from the first state to the second state On this example, during the subsequent second state compared with sensing the capacitance).

In this example, the controller is configured to synchronously control the load characteristics sensor to sense the current level through the first load during the first state by measuring the current level through the first load during the first state, responsive to the switch from the second state to the first state.

Figure 3 schematically depicts the power supply circuit 1 in more detail.

In this example, the power supply circuit 1 comprises a transmitter 70 and the controller 40 is configured to control the transmitter to transmit a signal based on the sensed set of load characteristics of the first load 10A. In this way, the controller 40 may perform an action such as flag an error.

Figure 4 schematically depicts a method according to an exemplary embodiment.

The method is of controlling a power supply circuit, for example the power supply 1, the method comprising: synchronously controlling: the power supply to switch between the first state and the second state at the first frequency and/or with the first duty cycle (S401); and the load characteristics sensor to sense the set of load characteristics of the first load selectively during the series of states (S402).

Although a preferred embodiment has been shown and described, it will be appreciated by those skilled in the art that various changes and modifications might be made without departing from the scope of the invention, as defined in the appended claims and as described above. Notes

Attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

All of the features disclosed in this specification (including any accompanying claims and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at most some of such features and/or steps are mutually exclusive.

Each feature disclosed in this specification (including any accompanying claims, and drawings) may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

The invention is not restricted to the details of the foregoing embodiment(s). The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

Claims

CLAIMS1. A power supply circuit for a set of loads, including a first load comprising an array of semiconductor junction devices including a first semiconductor junction device, the power supply circuit comprising: a power supply, configurable in a series of states including: a first state, wherein the power supply is configured to supply a first current through the first load at a first voltage sufficient to bias the first semiconductor junction device into conduction; and a second state, wherein the power supply is configured to supply a second current through the first load at a second voltage insufficient to bias the first semiconductor junction device into conduction; a load characteristics sensor, configured to sense a set of load characteristics of the first load, including one or more of: a voltage level across the first load, a current level through the first load, a resistance of the first load, a capacitance of the first load and an inductance of the first load; and a controller, configured to synchronously control: the power supply to switch between the first state and the second state at a first frequency and/or with a first duty cycle; and the load characteristics sensor to sense the set of load characteristics of the first load selectively during the series of states.
2. The power supply circuit according to claim 1, wherein the controller is configured to synchronously control the load characteristics sensor to sense the set of load characteristics of the first load selectively during the series of states responsive to the switch between the first state and the second state.
3. The power supply circuit according to any previous claim, wherein the controller is configured to synchronously control the load characteristics sensor to sense the capacitance of the first load by measuring the voltage level across the first load during the second state.
4. The power supply circuit according to any previous claim, wherein the controller is configured to synchronously control the load characteristics sensor to sense the resistance of the first load by controlling the power supply to supply an additional current through the first load at a voltage insufficient to bias the first semiconductor junction device into conduction during the second state and to measure the corresponding voltage level across the first load.
5. The power supply circuit according to any previous claim, wherein the controller is configured to synchronously control the load characteristics sensor to sense the current level through the first load during the first state by measuring the current level through the first load during the first state.
6. The power supply circuit according to any previous claim, wherein the controller is configured synchronously control the load characteristics sensor to repetitively sense the set of load characteristics of the first load selectively during the series of states and optionally, wherein the sensed set of load characteristics of the load comprise averaged load characteristics of the first load.
7. The power supply circuit according to any previous claim, wherein the controller is configured to change the first frequency to a second frequency and/or to change the first duty cycle to a second duty cycle.
8. The power supply circuit according to any previous claim, wherein the controller is configured to compare the respective sensed set of load characteristics of the first load with a corresponding set of threshold values and to control the power supply to not switch to the first state, based on a result of the comparing.
9. The power supply circuit according to claim 8, wherein the controller is configured to repeatedly compare the respective sensed set of load characteristics of the first load with the corresponding set of threshold values and to selectively control the power supply to switch to the first state, based on a result of the repeated comparing.
10. The power supply circuit according to any of claims 8 to 9, wherein the controller is configured to modify the corresponding set of threshold values, based on a result of the repeated comparing.
11. The power supply circuit according to any previous claim, wherein the controller is configured to determine respective rates of change of the sensed set of load characteristics of the first load and optionally, to compare the respective rates of change of the sensed set of load characteristics of the first load with a corresponding set of threshold rates and to control the power supply to not switch to the first state, based on a result of the comparing.
12. The power supply circuit according to any previous claim, comprising a transmitter and wherein the controller is configured to control the transmitter to transmit a signal based on the sensed set of load characteristics of the first load.
13. The power supply circuit according to any previous claim, wherein the set of loads includes a second load.
14. An electronic circuit comprising a power supply circuit according to any previous claim and a set of loads 10, including a first load comprising an array of semiconductor junction devices, including a first semiconductor junction device.
15. The electronic circuit according to claim 14, wherein the first semiconductor junction device is a light emitting diode.
16. A method of controlling a power supply circuit according to any of claims 1 to 13, the method comprising: synchronously controlling: the power supply to switch between the first state and the second state at the first frequency and/or with the first duty cycle; and the load characteristics sensor to sense the set of load characteristics of the first load selectively during the series of states.