Parallel channel switching with balanced output branches

Abstract

The invention relates to circuits and methods for parallel channel switching in a multi-channel design which makes use of a common current source that provides power to multiple output channels, each having a series switch. A make-before-break circuit is introduced to prevent simultaneous disconnection of all output channels. The make-before- break circuit may be an integral part of gate drive circuits of the series switches, so that a series switch of one output channel can only be turned off if another series switch of another output channel is turned on. This allows the output channels to have load branches with same length or at least substantially the same forward voltage.

Description

[0001] 2024PF80304

[0002] 1

[0003] Parallel channel switching with balanced output branches

[0004] FIELD OF THE INVENTION

[0005] The invention relates to the field of power supplies for lighting systems, such as - but not limited to - solid-state lighting systems or other loads, for use in various different applications for home, office, retail, hospitality and industry.

[0006] BACKGROUND OF THE INVENTION

[0007] A luminaire can be any type of lighting unit or lighting fixture which comprises one or more light sources (e.g., visible or non-visible (infrared (IR) or ultraviolet (UV)) light sources) for illumination and / or communication purposes and optionally other internal and / or external parts necessary for proper operation of the lighting, e.g., to distribute the light, to position and protect the light sources and ballast (where applicable), and to connect the luminaires to a power supply.

[0008] Solid-state lighting (SSL) is a type of lighting that uses semiconductor lightemitting diodes (LEDs), organic light-emitting diodes (OLED), or polymer light-emitting diodes (PLED) as sources of illumination rather than electrical filaments, plasma (used in arc lamps such as fluorescent lamps), or gas. Solid state electroluminescence is used in SSL, as opposed to incandescent bulbs (which use thermal radiation) or fluorescent tubes. Compared to incandescent lighting, SSL creates visible light with reduced heat generation and less energy dissipation.

[0009] A driver is required to deliver a highly stable constant current to the luminaire(s) irrespective of variations in the luminaire characteristics or the supply voltage while complying with increasingly stringent regulations covering input power requirements such as power factor and total harmonic distortion.

[0010] Lighting designs frequently choose to apply an electrical isolation within the LED driver such that the electrical design requirements on the LED board and optical window can be relaxed. From cost point of view, medium power LEDs are also favourable such that e.g., safety extra low voltage (SELV) multi-channel designs with medium output power (e.g., 25W to 60W) make use of a single current source and parallel channel 2024PF80304

[0011] 2 switching. In such designs, one output channel with the highest forward voltage may permanently be connected to the current source while other channels include a series switch. This topology ensures that at least one load is applied to the current source at all times (also during transition from switching between LED strings). A drawback of such a topology is a substantial forward voltage difference between the permanently connected LED string and the switchable LED strings, so that power demultiplexing characteristics are largely determined by the power demultiplexing switches instead of dynamic resistances of the LED loads and / or forward volage differences of the LED strings.

[0012] SUMMARY OF THE INVENTION

[0013] It is an object of the present invention to provide a multi-channel design with demultiplexing characteristics that are less dependent on power demultiplexing switches.

[0014] This object is achieved by a multi-channel driver circuit as claimed in claim 1, by a luminaire as claimed in claim 11, by a lighting system as claimed in claim 12, by a method as claimed in claim 13, and by a computer program product as claimed in claim 14.

[0015] According to a first aspect, a multi-channel driver circuit for suppling current to at least two loads (e.g., LED strings) via at least two output channels is provided, the driver circuit comprising: at least two switching elements for switching on and off the current supplied to the at least two loads; an interlocking circuitry comprising and interconnecting at least two drive circuits for controlling the switching elements, the drive circuits comprising integrated make- before-break (MBB) circuits or functions that are configured to prevent one of the switching elements from switching off the current before another one of the switching elements has switched on the current.

[0016] Furthermore, according to a second aspect, a luminaire comprising a driver circuit of the first aspect is provided.

[0017] Additionally, according to a third aspect, a lighting system comprising one or more driver circuits of the first aspect for driving respective luminaires is provided.

[0018] Moreover, according to a fourth aspect, a method of controlling a multichannel driver circuit that supplies current to at least two loads is provided, the method comprising: 2024PF80304

[0019] 3 controlling respective drive circuits interconnected via an interlocking circuitry to switch on and off the current supplied to the at least two loads by at least two switching elements; wherein the controlling step comprises an MBB function that prevents one of the switching elements from opening before another one of the switching elements has or is closed. Finally, according to a fifth aspect, a computer program product is provided, that comprises code means for producing the steps of the method of the fourth aspect when run on a controller circuit (e.g., implementing the drive circuits of the first aspect) of a multi-channel driver device.

[0020] The above aspects are intended to cover the two situations of (i) sequential switching where only one channel is active at a time and (ii) more than one active channel at a time, e.g., RGB color mixing.

[0021] Accordingly, the proposed interlocking circuitry and / or the controller circuit with the MBB function or circuit can be provided to overcome the initially mentioned restriction of requiring a higher forward voltage LED string to be permanently connected to the current source while ensuring a nearly perfect transition of the power demultiplexing by applying an MBB approach.

[0022] Advantageously, the proposed solution can be implemented without complex software and / or hardware changes to ensure that at least one channel remains switched on at all times, so that all output channels can be made switchable. It is thus low in cost and very effective for the intended purpose.

[0023] Moreover, timing of the switching control software of the multi-channel driver becomes less critical, because the proposed solution ensures a sufficient load at the current source.

[0024] According to a first option of any of the first to fifth aspects, the interlocking circuitry may comprise an interlocking network with a plurality of interlocking connections between the drive circuits to provide feedback to each of the drive circuits about a switching status of one or more switching elements of other ones of the drive circuits.

[0025] According to a second option of any of the first to fifth aspects, which may be combined with the first option, wherein the MBB circuits or functions of the drive circuits may be configured to control the switching elements in a manner to switch off an output channel only when at least one output channel is switched on.

[0026] According to a third option of any of the first to fifth aspects, which may be combined with the first or second option, the drive circuits may comprise control terminals 2024PF80304

[0027] 4 for allowing a controller circuit of a power conversion stage of the driver circuit to apply control signals for controlling switching functions of the switching elements.

[0028] According to a fourth option of any of the first to fifth aspects, which may be combined with any one of the first to fourth options, the drive circuits may comprise a level shifter stage with a level-shifting transistor and a pull-up resistor configured to pull up the voltage at a collector of the level-shifting transistor to a supply voltage whenever the levelshifting transistor is switched off in response to a respective one of the control signals, wherein the MBB circuits may each comprise a respective interlocking transistor connected in series with the respective level-shifting transistor to ensure that the level-shifting transistor can only be set to a conductive state if the interlocking transistor is set to the conductive state.

[0029] According to a fifth option, the interlocking transistor of one of the drive circuits may be controlled by a feedback voltage from another one of the drive circuits.

[0030] According to a sixth option, the feedback voltage of the fifth option may be obtained at a control terminal of the switching element or the collector of the level-shifting transistor and provided to the interlocking transistor via a respective interlocking connection.

[0031] According to a seventh option which may be combined with the fifth or sixth option, the drive circuits may comprise a voltage divider for dividing the feedback voltage to set a switch-on instant of a first one of the drive circuits and a delayed switch-off instant of a second one of the drive circuits, wherein the first one and the second one of the drive circuits are connected via an interlocking connection.

[0032] According to an eighth option which may be combined with any one of the fourth to seventh options, the drive circuits may each comprise a capacitor connected between the gate of the interlocking transistor and ground to determine a time delay between the switch-on instant and the delayed switch-off instant.

[0033] According to a ninth option of any of the first to fifth aspects, which may be combined with any one of the first to eighth options, the drive circuits may each comprise a push-pull circuit implemented by a complementary pair of transistors.

[0034] It is noted that the above driver circuit may be implemented based on discrete hardware circuitries with discrete hardware components, integrated circuits, or arrangements of integrated modules, or based on signal processing devices or integrated circuits controlled by software routines or programs stored in memories, written on a computer readable media, or downloaded from a network, such as the Internet.

[0035] It shall be understood that the driver circuit of claim 1, the luminaire of claim 11, the lighting system of claim 12, the method of claim 13, and the computer program 2024PF80304

[0036] 5 product of claim 14 may have similar and / or identical preferred embodiments, in particular, as defined in the dependent claims.

[0037] It shall further be understood that a preferred embodiment of the invention can also be any combination of the dependent claims or above embodiments with the respective independent claim.

[0038] These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter.

[0039] BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In the following drawings:

[0041] Fig. 1 shows schematically a circuit diagram of a multi-channel LED driver with permanently connected output channel;

[0042] Fig. 2 shows schematically a circuit diagram of an exemplary implementation of a multi-channel LED driver according to a first embodiment;

[0043] Fig. 3 shows schematically a circuit diagram of a further exemplary implementation of a multi-channel LED driver according to a second embodiment;

[0044] Fig. 4 shows schematically a circuit diagram of another exemplary implementation of a multi-channel LED driver with more detailed inhibition circuitry, according to a third embodiment; and

[0045] Fig. 5 shows schematically exemplary waveforms to explain a make-before- break operation of the multi-channel LED driver of the second embodiment.

[0046] DETAILED DESCRIPTION OF EMBODIMENTS

[0047] Various embodiments of the present invention are now described, which are applicable to luminaires of a solid-state lighting system, such as semiconductor LEDs, semiconductor lasers, vertical -cavity surface emitting lasers (VCSELs), organic lightemitting diodes (OLED), or polymer light-emitting diodes (PLED) as sources of illumination or light sources in visible or non-visible light spectra.

[0048] More specifically, the following embodiments are directed to LED luminaires. They can be implemented in connection with any type of LED module or board and are applicable to various kinds of LED drivers or converters of luminaires.

[0049] Fig. 1 shows schematically a circuit diagram of a multi-channel LED driver with permanently connected output channel. 2024PF80304

[0050] 6

[0051] It is noted that - throughout the present disclosure - the structure and / or function of blocks or circuit components with identical reference numbers that have been described before are not described again, unless an additional specific functionality is involved. Moreover, only those structural elements and functions are shown, which are useful to understand the embodiments. Other structural elements and functions are omitted for brevity reasons.

[0052] The driver circuit of Fig. 1 comprises a first power conversion stage (SI) 103 and a second power conversion stage with a controller circuit (CC) 200 for controlling a total of n-1 controllable switches (e.g., field effect transistors (FETs)) 303, 404, ... via control signals 302, 402, . . . applied to control terminals (e.g., gate electrodes of the FETs) to select at least one of n-1 output channels with respective output loads (e.g., LED strings) 301, 401, . . ., while the n-th output channel with its output load nOl does not comprise any controllable switch and is therefore permanently connected to the output line 201 of the controller circuit 200.

[0053] The first power conversion stage 103 may be supplied with power via supply terminals 101 and 102. More specifically, a power supply AC voltage (e.g., a power grid voltage of 110 or 220V at a mains frequency of 50 or 60Hz) may be supplied to an electromagnetic interference (EMI) filter (not shown) which is an electronic device that attenuates electromagnetic interference from the power system to limit the noise in the system and lower a risk of malfunctioning of the luminaire driver.

[0054] The first power converter stage 103 thus serves to convert the input AC voltage into a DC voltage while meeting power intake requirements such as power factor (PF) and total harmonic distortion (THD). A smoothening capacitor 107 may be applied between output terminals 105 and 106 of the first power conversion stage to reduce a volage ripple.

[0055] The constant voltage with reduced ripple is then converted by the controller circuit 200 of the second power conversion stage into a ripple-free (mains-ripple-free) constant current.

[0056] The controller circuit 200 may comprise independent digital inputs 202 (e.g., parallel or serial digital or analog input) to control application of the individual control signals (e.g., pulse width modulation (PWM) signals) 302, 402, ... to the controllable switches 303, 403,. . . of the switched output channels.

[0057] As the second power conversion stage is designed as a current source, it operates to keep constant its output current through output line 201, while its output voltage 2024PF80304

[0058] 7 can vary instantly. However, this requires that at least one load is connected to the output line 201 at all times (unless it is disabled). Therefore, as mentioned above, the driver circuit shown in Fig. 1 has a permanent load nOl and multiple switchable loads 301, 401, ... . As a result, for proper control of the current flow, respective forward voltages of the switchable channels need to be significantly lower compared to the permanently connected (switched- on) output channel to compensate for the controllable switches 303, 403,. . . . Note that such a topology also needs to take tolerances into account, which may worsen the problem.

[0059] The required volage difference between the switched output channels and the permanently connected output channel can be established by providing different numbers and / or types of LEDs, which may however complicate the optical design. Especially, designs with phosphor-converted LEDs with cool and warm white LEDs may be subject to this problem, as their forward voltages are almost identical to each other.

[0060] Fig. 2 shows schematically a circuit diagram of an exemplary implementation of a multi-channel LED driver according to a first embodiment.

[0061] In the first embodiment, each of the parallel output channels connected to the output line 201 of the second power conversion stage has a respective LED string (load string) 301 to nOl with a respective series switch 303 to n03. This allows the strings to have the same length and / or at least closely same forward voltage. Additionally, an interlocking circuitry (“make-before-break”) has been introduced to prevent simultaneous disconnection of all LED strings 301 to nOl.

[0062] A simple explanation for the term “make” is the act of closing a (normally open) switch contact, while the term “break” corresponds to the act of opening the switch contact to break a circuit flow. Make-before-break (MBB) occurs in switches that are controlled to complete a new circuit before breaking the old one. Open contacts are thus controlled to close, hence “make,” before the closed contacts open, hence “break.”

[0063] Such an MBB control function is achieved by the proposed interlocking circuitry which is configured to interconnect the series switches 303 to n03 of the output strings of the parallel output channels. The interlocking circuitry comprises gate drive circuits 320 to n20 with integrated MBB circuits / functions that are interlocked by an interlocking network 221 which may consist of a plurality of interlocking connections between the gate drive circuits 320 to n20. The interlocking network 221 is configured to ensure that each of the gate drive circuits 320 to n20 is made aware (e.g., by a feedback signal) of the switching status of one or more of the other serial switches, so that at least one of the serial switches 303 to n03 is in a closed state. 2024PF80304

[0064] 8

[0065] The gate drive circuits 320 to n20 may comprise control terminals 302 to n02 for allowing the controller circuit 200 of the second power conversion stage to apply control signals for controlling the switching functions of the respective serial switches 303 to n03.

[0066] The MBB circuit / function is an integral part of each of the gate drive circuits 320 to n20 of the serial switches 303 to n03 and may be implemented as a software routine of a controller of the gate drive circuits 320 to n20 or as an integrated circuit (e.g., an application-specific integrated circuit (ASIC) or a programmable gate array (PGA), etc.) or as discrete circuit (as described below with reference to Fig. 3).

[0067] In embodiments where the MBB function is implemented as a software routine, the gate drive circuits 320 to n20 may each comprise a programmable controller or may be combined in at least one programmable controller, which are / is controlled by the software routine to switch on and off the current supplied to the LED strings 301 to nOl via the serial switches 303 to n03 in response to the control signals 302 to n02, wherein the control is configured to prevent one of the serial switches 303 to n03 from opening before another one of the serial switches 303 to n03 has closed.

[0068] Fig. 3 shows schematically a circuit diagram of a further exemplary implementation of a multi-channel LED driver according to a second embodiment.

[0069] In the second embodiment, the MBB function may be implemented in the gate drive circuits 320 to n20 based on feedback information (e.g., (divided) voltage from respective ones of gate terminals 311 to nl 1 or level shifters of the remaining other gate drive circuits 320 to n20 of the serial switches 303 to n03. In this case, the control signals 302 to n02 can be modified based on the MBB function responsive to the feedback information from all other output channels.

[0070] In an alternative embodiment, the feedback information from the gate terminals 311 to nl 1 may be directly provided to the controller circuit 200 which may then generate MBB-modified control signals 302 to n02 to be supplied to the gate drive circuits 320 to n20. In this case, the MBB function or circuit is provided at the controller circuit instead of the gate drive circuits 320 to n20.

[0071] In embodiments, the MBB circuit / function of the gate drive circuits 320 to n20 or the controller circuit 200 can be configured to establish (switch on) a new connection path (i.e., output branch controlled by the respective one of the serial switches 303 to n03) before a previous connection path (i.e., currently closed output branch controlled by a respective other one of the serial switches 303 to n03) is opened. This ensures that the output of the second power conversion stage (current source) never copes with an open circuit. 2024PF80304

[0072] 9

[0073] Thus, the proposed interlocking circuitry ensures that a serial switch of one output branch can only be turned off if another switch of another output branch is turned on. Such an interlocking circuitry works with at least two output branches (e.g., LED strings with serial switches.

[0074] Thus, in embodiments, a multi-channel LED driver comprises at least two LED output channels in parallel, each channel having a respective serial switch 303 to n03, wherein an interlocking circuitry with gate drive circuits 320 to n20 and integrated MBB circuits / functions is provided that prevents a serial switch from opening before another serial switch has closed.

[0075] Furthermore, in embodiments, the gate drive circuits 320 to n20 of the switches are interconnected by the interlocking network 221 (interlocking connections).

[0076] Fig. 4 shows schematically a circuit diagram of another example of a multichannel LED driver with a more detailed implementation of the gate drive circuits 320 to n20 as discrete circuits, according to a third embodiment.

[0077] According to the third embodiment, the discrete gate drive circuits 320 to n20 are connected between the power supply output terminals 105, 106 of the first power conversion stage 103 and comprise respective level shifter stages each implemented by a level-shifting transistor 305 to n05 and a pull-up resistor 304 to n04 that pulls up the voltage at the collector of the level-shifting transistor 305 to n05 to the supply voltage at terminal 106, whenever the level-shifting transistor 305 to n05 is switched off by the respective control signal 302 to n02.

[0078] Furthermore, the discrete gate drive circuits 320 to n20 comprise respective push-pull circuits (amplifiers) each implemented by a complementary pair of transistors 309 to n09 and 310 to nlO. The push-pull circuit uses the complementary pair of transistors 309 to n09, 310 to n 10 to alternately supply current to, or absorb current from, the gate of the serial switches 303 to n03. Thereby, switching speed and efficiency can be increased compared to a single-ended "class-A" amplifier.

[0079] Additionally, the proposed MBB circuit is implemented by respective interlocking transistors (e.g., metal oxide semiconductor (MOS) transistors) 306 to n06 each connected in series with the respective level-shifting transistors 305 to n05 to ensure that the level-shifting transistors 305 to n05 can only be set to the conductive state if the interlocking transistors 306 to n06 are set to conductive state.

[0080] Each of the interlocking (MOS) transistors 306 to n06 is controlled by the respective other level shifter stages of other output branches. In the example shown in Fig. 4, 2024PF80304

[0081] 10 among others, the interlocking (MOS) transistor 306 of the left output branch (comprising LED string 301) is controlled by respective interlocking connections of gate control signals 411 to nl 1 of the other serial switches 403 to n03 via respective decoupling diodes 414 to nl4).

[0082] As an example, it is assumed that a voltage at the collector of the levelshifting transistor 405 of the middle output branch is set to high level (via the pull-up resistor 404) due to a switch of the control signal 402 to low level. In response, a gate voltage 411 (of gate voltages 311 to nl 1) of the respective serial switch 403 is set to high level via the respective push-pull circuit to which the collector voltage of the level-shifting transistor 405 is supplied as input voltage 408. As a result, the serial switch 403 of the middle output branch is set to the conductive state and the interlocking transistors 306 and n06 of the left and right output branches shown in Fig. 4 are set to the conductive state via the feed interlocking connections between the gate drive circuit of the middle output branch and the gate drive circuits of the left and right output branches (i.e., feedback from the middle output branch to the left and right output branches), which allows the level-shifting transistor 305 of the left output branch to pull down the level shifter output voltage at its collector and eventually switch off the serial switch (MOS transistor) 303 of the left and / or right output branch after a small delay, if required. However, as long as the serial switch 403 of the middle output branch is switched off, the feedback voltages via the feedback interlocking connections inhibits a switch-off operation of the serial switches 303 and n03 of the left and right output branches.

[0083] As shown in Fig. 4, the interlocking connections are provided between each of the gate control terminals 311 to nl 1 through respective ones of the diodes 314 to nl4 and respective voltage dividers 312 / 313, 412 / 413 to nl2 / nl3. By using these voltage divider 312 / 313 to nl2 / nl3, the interlocking threshold (i.e., the gate-source voltage of interlocking (MOS) transistor 306) can be set to a lower level with respect to gate control voltage 311 to nl 1 of the serial switches 403 to n03 such that the switching transitions point can be set / adjusted in order to ensure optimal transition between switching on one output channel and switching off the other output channel. Thereby, fast transitions with minimal overlap of two output channels conducting at the same time can be achieved.

[0084] Fig. 5 shows schematically exemplary signal waveforms of the MBB operation of the multi-channel LED driver of the second embodiment based on the above example. 2024PF80304

[0085] 11

[0086] The upper waveform of Fig. 5 corresponds to a voltage U402 of the control signal 402 for controlling the serial switch 403 of the middle output branch with LED string 401. In an example, the voltage may be switched between a high level of 3.3V and a low level of 0V. The lower waveforms correspond to a load current I301 through the left output branch with LED string 301 (as switched by the serial switch 303) and a load current I401 through the middle output branch with LED string 401 (as switched by the serial switch 403). In an example, the load currents I301 and I401 may be switched between 0mA and 500mA.

[0087] As shown in Fig. 5, the transition of the voltage U402 to low level triggers a switch-on of the serial switch 403 of the middle output branch. Thus, the current I401 through the LED string 401 changes to the high level. As a result of the highgate voltage 411 of the middle output branch, the interlocking transistor 306 of the left output branch is switched on via the interlocking connection and allows a switch-off of the serial switch 303 of the left output branch. Thus, the current I301 through the LED string 301 of the left output channel is only allowed to change from the initial high level to the low level after the current I401 through the LED string 401 of the left output channel has changed to the high level, thereby fulfilling the MBB requirement.

[0088] As explained above, the switch-on instant of the serial switch 403 of the middle output branch and the delayed switch-off instant of the serial switch 303 of the left output branch can be set more precisely by providing the voltage divider comprising a first divider resistance 412 and a second divider resistor 413. Such first and second divider resistors 312 to nl2, 313 to nl3 are provided in all gate control circuits. The voltage divider can be configured to set a divided feedback voltage 307 to n07 to a voltage value that provides a proper switch-on process / timing of the interlocking transistor 306 to n06.

[0089] Optionally, the time delay (channel overlapping time) between the above switch-on instant and the above switch-off instant may be increased by providing a capacitor 315 to nl5 connected between the gate of the interlocking transistors 306 to n06 and ground (e.g., terminal 105 of the first power conversion stage).

[0090] In an alternative embodiment, the feedback voltage provided to the interlocking transistors 306 to n06 via the respective interlocking connections may be obtained at the collectors of the level-shifting transistors 305 to n05 (i.e., at the input 308 to n08 of the push-pull circuit), instead of the gate terminals of MOS transistors 303 to n03.

[0091] To summarize, circuits and methods for parallel channel switching in a multichannel design have been described, which makes use of a common current source that provides power to multiple output channels, each having a series switch. An MBB circuit or 2024PF80304

[0092] 12 function is introduced to prevent simultaneous disconnection of all output channels. The MBB circuit or function may be an integral part of gate drive circuits of the series switches, so that a series switch of one output channel can only be turned off if another series switch of another output channel is turned on. This allows the output channels to have load branches with the same length or at least substantially the same forward voltage.

[0093] While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive. The invention is not limited to the disclosed embodiments concerning solid-state luminaires (e.g., LED luminaires). The proposed embodiments can be applied in connection with any type of loads, any types of DC / DC converters and any number of output channels (including a single output channel). Moreover, the MBB function of power multiplexing can be implemented by various different discrete circuits or signal processing functions or processor routines.

[0094] More specifically, elements and components mentioned in the above embodiments may be embedded in one or more integrated circuits (ICs), e.g., application specific ICs (ASICs) or programmable logic arrays (PLAs) or the like.

[0095] The above embodiments may be implemented in (e.g., integrated or combined with) various high-efficiency products such as office luminaires, outdoor lighting, LED strips, color-tuneable spots or the like.

[0096] Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure and the appended claims. In the claims, the word “comprising” does not exclude other elements or steps, and the indefinite article “a” or “an” does not exclude a plurality. A single processor or other unit may fulfil the functions of several items recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. The foregoing description details certain embodiments of the invention. It will be appreciated, however, that no matter how detailed the foregoing appears in the text, the invention may be practiced in many ways, and is therefore not limited to the embodiments disclosed. It should be noted that the use of particular terminology when describing certain features or aspects of the invention should not be taken to imply that the terminology is being re-defined herein to be restricted to include any specific characteristics of the features or aspects of the invention with which that terminology is associated. 2024PF80304

[0097] 13

[0098] A single unit or device may fulfill the functions of several items recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

[0099] The described procedures of the controller circuit 200 can be implemented as program code means of a computer program and / or as dedicated hardware of the receiver devices or transceiver devices, respectively. The computer program may be stored and / or distributed on a suitable medium, such as an optical storage medium or a solid-state medium, supplied together with or as part of other hardware, but may also be distributed in other forms, such as via the Internet or other wired or wireless telecommunication systems.

Claims

2024PF8030414CLAIMS:

1. A multi-channel driver circuit for suppling current to at least two loads (301 to nOl) via at least two output channels, the multi-channel driver circuit comprising: at least two switching elements (303 to n03) for switching on and off the current supplied to the at least two loads (301 to nOl); an interlocking circuitry comprising and interconnecting at least two drive circuits (320 to n20) for controlling the switching elements (303 to n03), the drive circuits (320 to n20) comprising integrated make-before-break, MBB, circuits or functions that are configured to prevent one of the switching elements (303 to n03) from switching off the current before another one of the switching elements (303 to n03) has switched on the current, wherein the drive circuits (320 to n20) comprise:- control terminals for allowing a controller circuit (200) of a power conversion stage of the driver circuit to apply control signals (302 to n02) for controlling switching functions of the switching elements (303 to n03), and- a level shifter stage with a level-shifting transistor (305 to n05) and a pull-up resistor (304 to n04) configured to pull up the voltage at a collector of the level-shifting transistor (305 to n05) to a supply voltage whenever the level-shifting transistor (305 to n05) is switched off in response to a respective one of the control signals (302 to n02), and wherein the MBB circuits each comprise a respective interlocking transistor (306 to n06) connected in series with the respective level-shifting transistor (305 to n05) to ensure that the level-shifting transistor (305 to n05) can only be set to a conductive state if the interlocking transistor (306 to n06) is set to the conductive state.

2. The multi-channel driver circuit of claim 1, wherein the interlocking circuitry comprises an interlocking network (221) with a plurality of interlocking connections between the drive circuits (320 to n20) to provide feedback to each of the drive circuits (320 to n20) about a switching status of one or more switching elements of other ones of the drive circuits (320 to n20).2024PF80304153. The multi-channel driver circuit of claim 1 or 2, wherein the MBB circuits or functions of the drive circuits (320 to n20) are configured to control the switching elements (303 to n03) in a manner to switch off an output channel only when at least one output channel is switched on.

4. The multi-channel driver circuit of claim 1, wherein the interlocking transistor (306 to n06) of one of the drive circuits (320 to n20) is controlled by at least a feedback voltage from another one of the drive circuits (320 to n20).

5. The multi-channel driver circuit of claim 4 when depending on claim 2, wherein the feedback voltage is obtained at a control terminal (311 to nl 1) of the switching element (303 to n03) or at the collector of the level-shifting transistor (305 to n05) and provided to the interlocking transistor (306 to n06) via a respective interlocking connection.

6. The multi-channel driver circuit of claims 4 or 5, wherein the drive circuits (320 to n20) comprise a voltage divider (313 to nl3, 314 to nl4) for dividing the feedback voltage to set a switch-on instant of a first one of the drive circuits (320 to n20) and a delayed switch-off instant of a second one of the drive circuits (320 to n20), wherein the first one and the second one of the drive circuits (320 to n20) are connected via an interlocking connection.

7. The multi-channel driver circuit of claim 6, wherein the drive circuits (320 to n20) each comprise a capacitor (315 to nl5) connected between the gate of the interlocking transistor (306 to n06) and ground to determine a time delay between the switch-on instant and the delayed switch-off instant.

8. The multi-channel driver circuit of any one of the preceding claims, wherein the drive circuits (320 to n20) each comprise a push-pull circuit implemented by a complementary pair of transistors (309 to n09, 310 to nlO).

9. A luminaire comprising a multi-channel driver circuit of any one of the preceding claims.2024PF803041610. A lighting system comprising one or more multi-channel driver circuits of any one of preceding claims 1 to 8 for driving respective luminaires.

11. A method of controlling a multi-channel driver circuit that supplies current to at least two loads (301 to nOl), the method comprising: controlling respective drive circuits (320 to n20) interconnected via an interlocking circuitry to switch on and off the current supplied to the at least two loads (301 to nOl) by at least two switching elements (303 to n03); wherein the controlling step comprises a make-before-break, MBB, function that prevents one of the switching elements (303 to n03) from opening before another one of the switching elements (303 to n03) has or is closed.

12. A computer program product comprising code means for producing the steps of claim 11 when run on a controller circuit (320 to n20) of a multi-channel driver device.

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