Power supply circuit

Abstract

A power supply circuit for a communication bus. The power supply circuit includes a power output interface for connecting to the communication bus, a power converter circuit for supplying the power output interface with power and a first grounding capacitor. The first ground capacitor connects the power output interface to a ground reference. The power supply circuit further comprises a unidirectional conduction component connected in series with the power output interface, the first ground capacitor and the ground reference. The unidirectional conduction component is adapted to prevent the first grounding capacitor from bidirectionally buffering a signal on the communication bus via a different power supply circuit connected to the communication bus and the ground reference (PE) and via the ground reference or the first grounding capacitor is electrically connected in series with the power output interface and the ground reference.

Description

[0001] 2024PF80281

[0002] 1

[0003] Power supply circuit

[0004] FIELD OF THE INVENTION

[0005] The present invention relates to the field of power supply circuitry, and in particular to power supply circuits for a communication bus.

[0006] BACKGROUND OF THE INVENTION

[0007] There is an ongoing demand for reliable and flexible communications to electronic devices, such as lighting devices and / or sensors for lighting devices. One approach for facilitating communication between different electronic devices is the use of a communication bus shared between the electronic devices. Communications are sent over the communication bus, between different electronic devices.

[0008] One example communication protocol that uses a communication bus is known as the Digital Addressable Lighting Interface (DALI ®). This provides a mechanism for providing addressable communication to each of a plurality of connected devices in a network, as well as providing power for one or more low power devices (e.g., DALI remote controller or sensors) in the network.

[0009] In some forms of communication protocol, such as DALI, it would be advantageous to provide or supplement a power on the communication bus. This can ensure more reliable communication and / or provide power for devices that are powered only by the communication bus.

[0010] There is therefore a demand for reliable and robust power supply circuits for a communication bus.

[0011] KR20110138996A discloses a boost converter with a capacitor and a diode. CN104115556B discloses a flyback converter with output buffer capacitors and output diodes.

[0012] SUMMARY OF THE INVENTION

[0013] One disadvantage to power supply circuits for connection to a communication bus is that of electromagnetic interference. In particular, the connection to a communication bus provides a current path for common mode current, which can create significant 2024PF80281

[0014] 2 electromagnetic interference in the power supply circuit (particularly if passing through a switch of the power supply circuit.

[0015] One approach to overcoming this problem is to provide a grounding capacitor between the output of the power supply circuit and a protective earth. However, if two power supply circuits with such grounding capacitors are connected to the same communication bus, with opposite polarity, then an equivalent differential capacitor is effectively created between output terminals of each power supply circuit. This differential capacitor causes a smoothing or reduced pulse rise-slope for signals provided by the communication bus to the power supply circuit and influence the performance of the communication. Such connections in opposite polarity are allowed by the communication standard, thus the existence of the equivalent differential capacitor is unavoidable and the performance of the communication tends to be lower than expected.

[0016] The present disclosure proposes to provide a unidirectional conduction component connected between the output interface of a power supply circuit and the grounding capacitor. This prevents grounding capacitors of different power supply circuits from forming a differential capacitor with bidirectional power flow between two terminals of any one power supply circuit, thereby preventing or reducing a risk of affecting the pulse rise-slope for signals on the communication bus. Note that having a unidirectional conduction component near the output interface of a power supply is already known but the non-obviousness of the present application is using such a unidirectional conduction component in combination with a grounding capacitor and for solving the problem of grounding capacitors accumulating into a differential capacitor across the communication bus via the ground reference in case of multiple power supply circuit connected in opposite polarity.

[0017] The invention is defined by the claims.

[0018] According to examples in accordance with an aspect of the invention, there is provided a power supply circuit for a communication bus. The power supply circuit includes a power output interface for connection to the communication bus, a power converter circuit connected to the power output interface and configured to provide power to the power output interface, a first grounding capacitor electrically connected between the power output interface and a ground reference, wherein the first grounding capacitor is configured to attenuate, from the power output interface, electromagnetic interference produced by the power converter circuit, and a unidirectional conduction component connected in series with the power output interface, the first grounding capacitor and the ground reference, wherein, the unidirectional conduction component is adapted to prevent the first grounding capacitor from bidirectionally 2024PF80281

[0019] 3 buffering a signal on the communication bus via a different power supply circuit connected to the communication bus and the ground reference and via the ground reference, or the first grounding capacitor is electrically connected in series with the power output interface and the ground reference.

[0020] This configuration allows the grounding capacitor to effectively shunt EMI to ground thus providing effective attenuation of electromagnetic interference (EMI) produced by the power converter circuit. Furthermore, the unidirectional conduction component only allows the ground capacitor to conduct current flow with respect to the power output interface in one direction while blocking current flow in the opposite direction, preventing the capacitor from bidirectionally buffering the signal on the power output interface, thus preventing the capacitor from interfering with the communication on the communication bus (at least from a long term perspective). It is noted that permitting bidirectional buffering of the signal on the power output interface could otherwise interfere with communication signals on the power output interface in both short- and long-term perspectives. If a herein proposed power supply circuit is used with a traditional power supply circuit, only one direction of current flow of the grounding capacitors is allowed and the grounding capacitors would therefore not continue to buffer the communication signal after they are fully buffered (because they cannot be discharged). If two of such power supply circuits are used together, no direction of current flow of the grounding capacitors is allowed since the two unidirectional conduction components are oppositely biased thus the ground capacitors would not buffer the communication signal from both short-term perspective (the very beginning) and long term perspective.

[0021] More particularly, this configuration reduces a risk that multiple power supply circuits connected to the same communication bus will interfere with each other through their respective grounding capacitors, maintaining signal integrity on the bus.

[0022] In some examples, the anode of the unidirectional conduction component is connected to the power output interface and the cathode of the unidirectional conduction component is connected to the ground reference, e.g., via the first grounding capacitor. In other words, the unidirectional conduction component may be forward biased from the power output interface to the ground reference,

[0023] In some embodiments, the unidirectional conduction component comprises a diode forward biased from the power output interface to the ground reference. The use of a diode advantageously provides a robust and reliable approach for providing a unidirectional conduction component. As discussed above, the problem of differential capacitor is caused by co grounding of two power supply circuit thus this embodiment solves this problem. 2024PF80281

[0024] 4

[0025] In some embodiments, the power converter circuit comprises an isolated power converter circuit defining a primary side and a secondary side magnetically coupled together, wherein the power output interface and the first grounding capacitor are electrically connected to the secondary side. The isolated power converter design provides electrical isolation between input and output, enhancing safety and reducing noise coupling between primary and secondary sides. A grounding capacitor is often essential for isolated power converter circuits to reduce noise in the power output interface, but this also means such existing power converter circuits tend to interfere with the communication signal. Thus, the proposed approach is particularly useful for solving the problem with the isolated power converter circuits.

[0026] In some embodiments, the power converter comprises a switch arrangement electrically connected to the primary side and configured to control power flow in the primary side, wherein the switch arrangement is adapted to produce the electromagnetic interference.

[0027] It is recognized that the switch arrangement of a power converter circuit is a primary source of EMI, which is then at least partially addressed by the subsequent grounding capacitor. As such, the proposed configuration is particularly advantageous when employed with a power converter that includes a switch arrangement.

[0028] In some embodiments, the power converter comprises a capacitor connected between the primary side and the secondary side, wherein the capacitor is adapted to couple the electromagnetic interference produced by the switch arrangement to the power output interface. This capacitor, while inherent for the converter's operation, can inadvertently couple EMI from the primary to the secondary side, necessitating additional EMI mitigation measures. Thus the grounding capacitor is effectively used to handle this capacitor. As such, the proposed configuration is particularly advantageous when employed with such an arrangement.

[0029] In some embodiments, the capacitor is a parasitic capacitance between the primary side and the secondary side. This embodiment recognizes that even unintended capacitances in the converter design can contribute to EMI coupling, making the EMI reduction technique with the grounding capacitor particularly advantageous for use with power converters. Thus, the present invention can be used to avoid the grounding capacitor from interfering the communication bus.

[0030] In some embodiments, the first grounding capacitor is adapted to shunt the electromagnetic interference to the ground reference thereby away from the power output interface, and the power supply circuit further comprises a second grounding capacitor connected between the primary side and the ground reference and adapted to route back the electromagnetic interference from the ground reference to the power converter circuit. 2024PF80281

[0031] 5

[0032] This dual-capacitor arrangement creates a low-impedance path for EMI, effectively shunting it away from the power output and back to its source, reducing EMI emission from the circuit. The herein proposed approach is particularly useful with this arrangement.

[0033] In some embodiments, the power supply circuit further comprises a power input interface configured to receive an AC input power, and a rectifying arrangement connected between the power input interface and the primary side of the power converter circuit, wherein the second grounding capacitor is connected to a node located between the power input interface and the rectifying arrangement. This placement of the second grounding capacitor helps to attenuate and / or filter EMI (or other high frequency noise) at the input stage, preventing it from propagating through the power converter circuit.

[0034] The unidirectional conduction component may be connected between the power output interface and the first grounding capacitor and is coupled in a loop of the power to the output interface and decoupled from a loop through which a common mode current and / or EMI portion of a power supply flows. This improves the EMI attenuation performed by the first grounding capacitor, as the unidirectional conduction component does not block any common mode current and / or EMI.

[0035] In some examples, the unidirectional conduction component couples in a loop through which a common mode current and / or EMI portion of a power supply flows and is decoupled from a loop of the power to the output interface. This removes the unidirectional conduction component from a power loop for the power output interface to improve the power efficiency of the power supply circuit. Based on experiments, at least a portion of the common mode current and / or EMI can still pass the unidirectional conduction component via its parasitic capacitance and be shunted to the ground reference via the grounding capacitor, and the overall EMI is still acceptable.

[0036] In some embodiments, the power output interface is configured for connecting to an external electronic device for powering the electronic device. In this way, the power supply circuit is able to perform a dual function of providing power to a communication bus and a second external electronic device. This reduces a need or demand for a dedicated power supply circuit for the communication bus.

[0037] In some embodiments, the power supply circuit further comprises a control signal interface configured to connect to the communication bus, wherein the control signal interface is connected to the power output interface. 2024PF80281

[0038] 6

[0039] In this embodiment, the power supply circuit does not only provide power but also communicate via the communication bus, and it is a double function device.

[0040] In some embodiments, the power supply circuit further comprises control logic circuitry connected to the control signal interface and configured to control an operation of the power supply circuit responsive to a control signal received from the communication bus via the control signal interface. This enables dynamic control of the power supply circuit based on commands received through the communication bus, allowing for adaptive power management and / or control of the power provided to an external device.

[0041] In some embodiments, the control signal interface comprises a positive control signal terminal, the power output interface comprises a positive power output terminal, and a current limiting circuit connecting the positive power output terminal to the positive control signal terminal. The current limiting circuit protects the control signal interface (and communication bus) from excessive currents that may be present on the power output, enhancing reliability and safety, particularly to any other devices connected to the same communication bus.

[0042] In some embodiments, the control signal interface comprises a negative control signal terminal, and the power output interface comprises a negative or neutral power output terminal connected to the negative control signal terminal. This common connection provides a simple circuit design while maintaining the necessary signal and power paths.

[0043] In a second aspect, it is provided a semiconductor light source driving apparatus, comprising the power supply circuit as mentioned above.

[0044] In a third aspect, it is provided a luminaire comprising the semiconductor light source driving apparatus as mentioned above, and a semiconductor light source.

[0045] There is also provided a system comprising a plurality of different power supply circuits, at least one of which is the power supply circuit described above, and the communication bus comprising a first bus line and a second bus line connected to the control signal interface of each power supply circuit. When the control signal communication interfaces of the different power supply circuits are connected to the communication bus with opposite polarities, the first grounding capacitors of the different power supply circuits are coupled together between the first bus line and a second bus line and the unidirectional conduction component is adapted to prevent the first grounding capacitors of the different power supply circuits from bidirectionally buffering a signal on the communication bus via the power supply circuits connected to the communication bus and the ground reference and via the ground reference. 2024PF80281

[0046] 7

[0047] This system-level configuration ensures that multiple power supply circuits can coexist on the same communication bus without interfering with each other, regardless of their connection polarity. The unidirectional conduction components prevent unwanted signal paths through the grounding capacitors, maintaining signal integrity across the communication bus. More specifically, the grounding capacitors are prevented from bidirectionally buffering the communication signal thus, at most, only one direction of current flow of the grounding capacitors is allowed and the ground capacitors would not buffer the communication signal at least from long term perspective after they are buffered (if they can).

[0048] In some embodiments, at least two of the plurality of different power supply circuits is the power supply circuit described above, and the unidirectional conduction component of each power supply circuit is configured such that, when the control signal communication interfaces of the different power supply circuits are connected to the communication bus with opposite polarities, the unidirectional conduction components of said power supply circuit are opposite biased with each other and in series with the first grounding capacitors of the different power supply circuits between the first bus line and a second bus line, thereby preventing any of the first grounding capacitors from buffering signal on the communication bus in any of two directions.

[0049] This configuration ensures more robust protection against bidirectional buffering, even when multiple power supply circuits are connected with different polarities. The opposite biasing of the unidirectional conduction components functions to prevent (positive) signals attempting to pass through the grounding capacitors in either direction, preserving the integrity of communication on the bus from the very start (i.e., from initial power up) and thereafter.

[0050] These and other aspects of the invention will be apparent from and elucidated with reference to the embodiment(s) described hereinafter.

[0051] BRIEF DESCRIPTION OF THE DRAWINGS

[0052] For a better understanding of the invention, and to show more clearly how it may be carried into effect, reference will now be made, by way of example only, to the accompanying drawings, in which:

[0053] Figure 1 illustrates a power supply circuit known in the art;

[0054] Figure 2 represents equivalent circuits for a system comprising the power supply circuit;

[0055] Figure 3 illustrates a proposed power supply circuit; 2024PF80281

[0056] 8

[0057] Figure 4 represents equivalent circuits for a system comprising the proposed power supply circuit;

[0058] Figure 5 represents equivalent circuits for another system comprising the proposed power supply circuit;

[0059] Figure 6 represents another proposed power supply circuit;

[0060] Figure 7 represents another proposed power supply circuit;

[0061] Figure 8 represents equivalent circuits for a system comprising a proposed power supply circuit; and

[0062] Figure 9 shows the EMI curves of the embodiments in figure 3 / 6 and in figure 7.

[0063] DETAILED DESCRIPTION OF THE EMBODIMENTS

[0064] The invention will be described with reference to the Figures.

[0065] It should be understood that the detailed description and specific examples, while indicating exemplary embodiments of the apparatus, systems and methods, are intended for purposes of illustration only and are not intended to limit the scope of the invention. These and other features, aspects, and advantages of the apparatus, systems and methods of the present invention will become better understood from the following description, appended claims, and accompanying drawings. It should be understood that the Figures are merely schematic and are not drawn to scale. It should also be understood that the same reference numerals are used throughout the Figures to indicate the same or similar parts.

[0066] The invention provides a power supply circuit for a communication bus. The power supply circuit includes a power output interface for connecting to the communication bus, a power converter circuit for supplying the power output interface with power and a first grounding capacitor. The first ground capacitor connects the power output interface to a ground reference. The power supply circuit further comprises a unidirectional conduction component connected in series with the power output interface, the first ground capacitor and the ground reference.

[0067] Figure 1 schematically illustrates a power supply circuit 100 known in the art. The power supply circuit is designed for providing power to a communication bus 190, such as a communication bus used for the Digital Addressable Lighting Interface (DALI ®) communication protocol.

[0068] In the illustrated example, the communication bus 190 comprises a pair of bus lines 191, 192. Thus, the communication bus 190 comprises a first bus line 191 and a second 2024PF80281

[0069] 9 bus line 192. By convention, the first bus line 191 may represent a positive bus line and the second bus line 192 may represent a negative bus line.

[0070] The power supply circuit comprises a power output interface 110, a power converter circuit 120 and (in the illustrated example) a control signal interface 130.

[0071] The power output interface 110 is designed for connection to the communication bus, e.g., via a control signal interface 130. In particular, the power output interface 110 may comprise a positive power output terminal 111 and a negative or neutral power output terminal 112.

[0072] Similarly, if present, the control signal interface may comprise a positive control signal terminal DA+ and a negative control signal terminal DA-. The positive control signal terminal DA+ is configured to connect to the positive bus line 191 and the negative control signal terminal DA- is configured to connect to the negative bus line 192.

[0073] The positive power output terminal 111 may connect to the positive control signal terminal DA+, e.g., via a current limiter CL. The negative or neutral power output terminal 112 may connect to the negative control signal terminal DA-, e.g., directly.

[0074] The power output interface 110 may also be designed for providing power to another (electronic) device, such as a DALI remote control device which does not have its own power supply. In other words, the power output interface may be configured for connecting to an external electronic device for powering the electronic device.

[0075] In alternative arrangements, instead of the power output interface 110 connecting to the communication bus 190 via a control signal interface 130, the power output interface may directly connect to the communication bus 190. Thus, in this approach, the power output interface effectively functions as the control signal interface (and can be associated with the corresponding labels).

[0076] The power converter circuit 120 is connected to the power output interface 110 and configured to provide a power to the power output interface. By way of example, the power converter circuit 120 may connect to an input interface 140 of the power supply circuit 100 and convert an input power provided at the input interface 140 (e.g., a mains power or a battery power) to a power for the power output interface. Examples of suitable power converter circuits are well known in the art.

[0077] The power supply circuit may further comprise control logic circuitry 150. The control logic circuitry is configured to connect to the communication bus, e.g., via the control signal interface. The control logic circuitry 150 may be configured to control an operation of 2024PF80281

[0078] 10 the power supply circuit 100 responsive to a control signal received from the communication bus via the control signal interface.

[0079] Although not illustrated, the control logic circuitry may comprise an appropriate diode arrangement to pass any signal(s) carried by the communication bus to a control logic processor.

[0080] It is common for a capacitance CY2 to exist between an input to the power converter circuit 120 and a protective earth PE (i.e., a ground or reference voltage). This capacitance may be due to at least to a dedicated capacitor CY2, designed to create a low impedance path for EMI to / from the PE at the input to the power converter or a parasitic capacitance. Similarly, in practice, since the external electronic device connected to the communication bus is often grounded to the same protective earth PE, an electrical path will exist between the communication bus 190 (e.g., the second bus line 192) and the protective earth PE via the external electronic device. This provides a path or loop for a common mode / EMI current to flow through the external electronic device via the communication bus, which can create significant electromagnetic interference (EMI) out leakage and influence the external electronic device.

[0081] One existing solution to reduce this electromagnetic interference is to shorten the loop for the common mode current by electrically connecting a first grounding capacitor CY1 between the power output interface and a ground reference. The first grounding capacitor is thereby configured to attenuate, from the power output interface, electromagnetic interference produced by the power converter circuit.

[0082] More particularly, the first grounding capacitor CY1 may connect between the negative or neutral power output terminal 112 and the ground reference PE (e.g., the protective earth). Thus, the electromagnetic interference created by the power converter 120 is circulated via the two capacitors CY1 and CY2 internally within the power supply circuit 100 without leaking out.

[0083] Although the above approach can cope with the EMI out leakage, the present disclosure recognizes that this approach introduces a new potential point of failure or error for a system comprising a plurality of power supply circuits connected to a same communication bus. In particular, consider a scenario in which two power supply circuits (embodied as illustrated in Figure 1) are connected to a same communication bus, but with opposite polarities, which is a common and permitted installation in many forms of communication protocol such as DALI. In this scenario, for each power supply circuit, the terminals of the power output interface and control signal interface of the power supply circuit will be effectively connected 2024PF80281

[0084] 11 by a differential capacitor. This will significantly reduce a rise time of a voltage provided on the communication bus, causing a failure of the system.

[0085] This potential point of failure is illustrated by Figure 2, which demonstrates equivalent circuits from the perspective of a pair of control signal interfaces that are connected to a same communication bus with opposite polarities.

[0086] When the control signal interfaces 211, 221, of two different power supply circuits 210, 220 are connected to the communication bus with opposite polarities, they also connect to the same protective earth and a differential capacitor is formed by their respective first grounding capacitors CY1 A, CY2B between the two terminals DA1+, DAI- of the power output interface (and control signal interface) of the power supply circuits. This would cause a smoothing of a signal provided on the communication bus 190, interfering with communication on the communication bus.

[0087] The present disclosure proposes a mechanism to overcome this problem.

[0088] In particular, by providing a power supply circuit with a unidirectional conduction component in series with the power output interface, the first grounding capacitor and the ground reference, the current flow between corresponding terminals of the power output interface with respect to the first grounding capacitor will be restricted, whilst still permitting current to flow from the power output interface to a protective earth for the purposes of attenuating noise resulting from at least EMI.

[0089] Figure 3 schematically illustrates a proposed supply circuit 300 for providing power to a communication bus 390, such as a communication bus used for the Digital Addressable Lighting Interface (DALI ®) communication protocol.

[0090] The power supply circuit comprises a power output interface 310, a power converter circuit 320 and (in the illustrated example) a control signal interface 330. This may be embodied as previously described.

[0091] The power supply circuit 300 differs from the previously described power supply circuit (Figure 1) by further comprising a unidirectional conduction component DI, such as a diode, connected in series with the power output interface, the first grounding capacitor and the ground reference. In the illustrated example, the unidirectional conduction component is connected between the power output interface 310 and the first grounding capacitor CY 1 , specifically from the power output interface 310 to the first grounding capacitor CY1. The first grounding capacitor thereby connects the unidirectional conduction component to the ground or protective earth PE. Other examples of unidirectional conduction components could be employed. 2024PF80281

[0092] 12

[0093] More specifically, the anode of the unidirectional conduction component DI is connected to the power output interface 310 and the cathode of the unidirectional conduction component DI is connected to the ground reference (here: via the first grounding capacitor CY1). More specifically, the anode of the unidirectional conduction component DI may connect to the negative or neutral power output terminal 112 and the cathode of the unidirectional conduction component may connect to the ground reference, e.g., via the first grounding capacitor CY1.

[0094] Put another way, the unidirectional conduction component is here forward biased from the power output interface to the ground reference,

[0095] When employed, the unidirectional conduction component DI functions to prevent the first grounding capacitor from bidirectionally connecting bus lines of the communication bus 190 for the power supply circuit (i.e. , via a different power supply circuit connected to the communication bus with an opposite polarity).

[0096] In other words, the unidirectional conduction component DI functions to prevent a bidirectional capacitive connection forming between terminals on a power output interface 310. This effectively means that the grounding capacitors of two different power supply circuits are unable to function as a differential bidirectional capacitor between the two terminals on the power output interface 310 of a single power supply circuit.

[0097] Figure 3 further illustrates optional embodiments for the components of the proposed supply circuit.

[0098] In the illustrated example, the power converter circuit 320 comprises an isolated power converter circuit 325 defining a primary side PS and a secondary side SS magnetically coupled together. The power output interface 310 and the first grounding capacitor CY1 are electrically connected to the secondary side SS. Positioning the first grounding capacitor CY1 on the same side as the power output interface 310 facilitates improved attenuation of noise resulting from EMI produced by the power converter circuit 320.

[0099] More specifically, the isolated power converter circuit 325 is implemented as a flyback converter and comprises a transformer T1 formed from a pair of windings, namely a first winding wl and a second winding w2. The windings wl, w2 are magnetically coupled together, but electrically isolated from one another (ignoring any shared protective earth). The first winding defines the primary side PS, such that any electrical component electrically connected to the first winding can be considered to connect to the primary side. The second winding w2 defines the secondary side SS, such that any electrical component electrically connected to the second winding can be considered to connect to the secondary side. 2024PF80281

[0100] 13

[0101] The power converter circuit 320 also further comprises a switch arrangement QI, 550 electrically connected to the primary side. The switch arrangement QI, 550 is configured to control power flow in the primary side, e.g., using a switched-mode logic technique. In the illustrated example, the switch arrangement QI, 550 comprises a single switch QI (e.g., a MOSFET or other transistor) and switch control circuitry 550. The switch control circuitry 550 controls the switching of the switch QI to thereby control current flow through the primary side PS (particularly the first winding), and thereby the current flow to the power output interface via magnetically coupling of the secondary side.

[0102] Although here illustrated as a separate component - in practice, the switch control circuitry 550 may form part of the control logic circuitry 150. In any event the operation of the switch control circuitry may be responsive to signals and / or data produced by the control logic circuitry (e.g., responsive to any signals carried by the communication bus 190).

[0103] The first grounding capacitor CY1 is connected between the power output interface and a ground reference. More particularly, the first grounding capacitor CY1 may connect between the negative or neutral power output terminal 112 and the ground reference PE (e.g., the protective earth). Even more particularly, the first grounding capacitor may be connected to an intermediate node N2 between the second winding and the power output interface, such that the first grounding capacitor is also connected between the second winding and the ground reference PE. The intermediate node may, for instance, be connected to the negative or neutral power output terminal 112 of the power output interface 310.

[0104] The first grounding capacitor is thereby configured to attenuate, from the power output interface, electromagnetic interference produced by the power converter circuit.

[0105] The power converter circuit 320 also comprises a secondary side rectifier Dss and a smoothing capacitor Cs configured to convert the current flow in the secondary winding w2 to a DC voltage. In the illustrated example, the secondary side rectifier takes the form of a single diode connecting the secondary winding to the power output interface, specifically the positive output terminal of the power output interface.

[0106] The secondary side rectifier Dss allows current to flow in only one direction, effectively transforming the bidirectional AC waveform from the secondary winding w2 into a unidirectional pulsating DC. This pulsating DC is then smoothed by the smoothing capacitor Cs to produce a more stable DC voltage suitable for powering external devices or supplying the communication bus.

[0107] The smoothing capacitor Cs thereby functions to reduce ripples in the DC output voltage at the power output interface. In this way, the smoothing capacitor Cs acts as a low- 2024PF80281

[0108] 14 pass filter, attenuating high-frequency fluctuations in the rectified voltage from the secondary side rectifier DSS. This filtering action helps to produce a more stable and consistent DC voltage at the power output interface.

[0109] The illustrated power converter circuit 320 takes the form of a flyback converter, and the switch arrangement is designed as such. However, the skilled person would readily understand that the power converter circuit 320 can be readily replaced with another form of power converter (e.g., a boost converter, buck converter, a push-pull converter, other forms of buck-boost converter, a Cuk converter, a resonant such as LLC converter, a synchronous converter and so on).

[0110] Regardless of the specific arrangement, it will be appreciated that the power converter circuit 320 may take the form of a (e.g., isolated) switched-mode power supply having a switch arrangement QI, 550 that will produce electromagnetic interference. In particular, a common mode current passing through the switch arrangement will naturally produce electromagnetic interference.

[0111] There will be a defined capacitance, representable by a capacitor Cp, between the primary side PS and the secondary side SS of the isolated power converter circuit 325 (i.e., between the first winding wl and the secondary winding w2). This defined capacitance may, for instance, result from a parasitic capacitance that will naturally exist between the primary side PS and the secondary side.

[0112] The capacitor Cp may therefore result or be a parasitic capacitance between the primary side and the secondary side. Alternatively, in some variants, the capacitor Cp may be an electrical component connected between the primary side PS (i.e., the first winding wl) and the secondary side SS (i.e., the secondary winding w2).

[0113] As previously mentioned, the first grounding capacitor Cyl may be adapted to shunt the electromagnetic interference to a / the ground reference PE and thereby away from the power output interface 310.

[0114] In some examples, the power supply circuit further comprises a second grounding capacitor CY2 connected between the primary side PS and the ground reference PE and adapted to route back the electromagnetic interference from the ground reference PE to the power converter circuit.

[0115] The power supply circuit 300 and / or power converter circuit 325 may also comprise any additional components required or advantageous for producing power at the power output interface. 2024PF80281

[0116] 15

[0117] For instance, the power supply circuit may further comprise the power input interface 140 configured to receive an AC input power; and a rectifying arrangement R1 connected between the power input interface 140 and the primary side PS of the power converter circuit 120. If present, the second grounding capacitor CY2 is connected to a node N1 located between the power input interface 140 and the rectifying arrangement Rl.

[0118] Although illustrated as a single diode, the skilled person will appreciate that the rectifying arrangement Rl may be replaced by any suitable form of rectifying arrangement, e.g., a diode bridge arrangement, a half-bridge, a synchronous rectifier and so on.

[0119] The power supply circuit may further comprise input interface coils T2. The input interface coils comprise a pair of windings magnetically coupled to one another, one of which connects a first terminal of the input interface 140 to the rectifying arrangement and another of which connects a second terminal of the input interface 140 to the rectifying arrangement. This functions to perform a filtering process on the AC input power, e.g., to further reduce EMI.

[0120] The power supply circuit may may further comprise output interface coils T3. The output interface coils comprise a pair of windings magnetically coupled to one another, one of which connects the power converter circuit 325 to a first terminal (e.g., the positive output terminal) of the power output interface and another of which the power converter circuit 325 to a second terminal (e.g., the negative output terminal) of the power output interface. This functions to perform a filtering process on the AC input power, e.g., to further reduce EMI or common mode noise.

[0121] In the illustrated example, the output interface coils T3 are connected between the power output interface and the intermediate node N2 (to which the first grounding capacitor CY1 connects).

[0122] The unidirectional conduction component DI may be connected between the power output interface and the output interface coils T3. More particularly, the unidirectional conduction component DI may be connected between the negative or neutral terminal 112 of the power output interface 310 and the output interface coils T3.

[0123] Alternative configurations are later illustrated and described.

[0124] Figure 4 illustrates equivalent circuits for a portion of a system comprising a pair of power supply circuits 100, 300. The power supply circuits comprise a known power supply circuit 100 (e.g., as described with reference to Figure 1) and a proposed power supply circuit 300. 2024PF80281

[0125] 16

[0126] As such, each power supply circuit comprises a power output interface for connection to the communication bus 190; a power converter circuit connected to the power output interface and configured to provide a power to the power output interface; and a first grounding capacitor electrically connected between the power output interface and a ground reference. The first grounding capacitor of each power supply circuit is configured to attenuate, from the power output interface, electromagnetic interference produced by the power converter circuit.

[0127] The power supply circuit 300 further comprises a unidirectional conduction component DI, such as a diode, connected between the power output interface and the first grounding capacitor CY1.

[0128] When the control signal interfaces 130, 330 of these two different power supply circuits 100, 300 are connected to the communication bus with opposite polarities, a differential capacitor formed by the respective first grounding capacitors CY1A, CY2B is again formed between the two terminals DA1+, DAI- of the power output interface (and control signal interface) of the power supply circuits. Note that the polarity of DA1+ and DAI- can be swapped namely the DAI- becomes positive and DA1+ becomes negative.

[0129] However, due to the presence of the unidirectional conduction component DI in one of the power supply circuits, bidirectional power flow between the two power supply circuits is prevented. As such, in operation, in case that the DAI- is positive and DA1+ is negative, each first grounding capacitor may be charged in one direction to a peak voltage and in this duration the communication signal is buffered; but they are subsequently unable to discharge, and as such, they will no longer interfere / buffer with signals carried by the communication bus. Therefore, at least from long term perspective, the communication functionality of the communication bus is recovered.

[0130] In other words, the unidirectional conduction component functions to prevent the first grounding capacitors of the different power supply circuits from bidirectionally buffering a signal on the communication bus via the power supply circuits connected to the communication bus and the ground reference and via the ground reference.

[0131] A more preferred embodiment is that all the power supply circuits in the system are that proposed by the application. Figure 5 illustrates equivalent circuits for a portion of a system comprising a pair of power supply circuits 510, 520. Each power supply circuit is embodied according to any herein proposed power supply circuit 300 (Figure 3).

[0132] As such, each power supply circuit 510, 520 comprises a power output interface for connection to the communication bus 190; a power converter circuit connected to the power 2024PF80281

[0133] 17 output interface and configured to provide a power to the power output interface; and a first grounding capacitor electrically connected between the power output interface and a ground reference. The first grounding capacitor of each power supply circuit is configured to attenuate, from the power output interface, electromagnetic interference produced by the power converter circuit.

[0134] Each power supply circuit 510, 520 further comprises a unidirectional conduction component DI, such as a diode, connected between the power output interface and the first grounding capacitor CY1.

[0135] The unidirectional conduction components in the power supply circuits prevent unidirectional and bidirectional power flow between the two power supply circuits. As such, in operation, none of the two first grounding capacitors is effectively charged by the signal carried by the communication bus across DA1+ and DAI. As such, it will not interfere with signals carried by the communication bus either from short term perspective (i.e., from initial power up) or long term perspective. Note that the polarity of DA1+ and DAI - can be swapped namely the DAI- becomes positive and DA1+ becomes negative but the two first grounding capacitors are neither allowed to be charged by a signal carried by the communication bus DAI + and DAI.

[0136] Figure 6 illustrates a variation to the proposed power supply circuit 600. The power supply circuit 600 differs from the previously described and illustrated power supply circuit 300 (Figure 3) in the placement of the unidirectional conduction component.

[0137] In this variant, the unidirectional conduction component is connected between the output interface coils T3 and the first grounding capacitor CY1. More specifically, the anode of the unidirectional conduction component DI connects to the output interface coils T3 and the cathode of the unidirectional conduction component connects to the first grounding capacitor.

[0138] More particularly, in this variant, the unidirectional conduction component is connected between the output interface coils T3 and the first grounding capacitor CY1. More specifically, the unidirectional conduction component DI is connected between the output interface coils T3 and the intermediate node N2.

[0139] Figure 7 illustrates another variation to the proposed power supply circuit 700. The power supply circuit 700 differs from the previously described and illustrated power supply circuit 300 (Figure 3) in the placement of the unidirectional conduction component.

[0140] For completeness, Figure 8 illustrates equivalent circuits for a portion of a system comprising a pair of power supply circuits 100, 700. The power supply circuits 2024PF80281

[0141] 18 comprise a known power supply circuit 100 (e.g., as described with reference to Figure 1) and a proposed power supply circuit 700.

[0142] With reference to Figure 7, in this variant, the unidirectional conduction component is connected between the first grounding capacitor CY1 and the ground reference PE. More specifically, the anode of the unidirectional conduction component DI connects to the first grounding capacitor CY1 and the cathode of the unidirectional conduction component connects to the ground reference PE. Alternatively, the positions of the unidirectional conduction component DI and the first grounding capacitor CY1 can be swapped.

[0143] This variant causes the unidirectional conduction component to be in the EMI attenuation loop. In particular, to be shunted to the ground reference, an EMI portion of the power provided at the secondary side will need to pass the unidirectional conduction component (which is avoided by the previously proposed examples). Nonetheless, the inherent parasitic capacitance of the unidirectional conduction component will conduct at least some of the EMI at the secondary side SS.

[0144] It will be appreciated that the amount of attenuation of EMI is reduced (particularly at higher frequencies) in the power supply circuit 700 compared to previously described circuits.

[0145] Figure 9 shows a first set of EMI curves 92 and a second set of EMI curves 90. The first set of EMI curves 92 are EMI curves of the power supply circuit 700 illustrated in Figure 7 and the second set of EMI curves 90 are EMI curves of the either of the power supply circuits 300, 600 illustrated by Figures 3 and 6. The second set of EMI curves 90 should be the same as the EMI curves for the existing design for the power supply circuit 100 (as illustrated in Figure 1) because the diode DI in figure 3 / 6 is not in the EMI loop and would not influence EMI.

[0146] For frequencies less than 5MHz, it can be seen that the EMI curves 92 are substantially similar as the EMI curves 90; for frequencies higher than 5MHz, the curves 92 are higher (indicating more EMI noise) than the curves 90 but are still considered acceptable. The power supply circuit of the present variant has, whilst maintaining an acceptable EMI, effectively removed the unidirectional conduction component from the power loop for the power output interface, reducing power loss in generating the power for the power output interface.

[0147] Turning back to Figure 8, is it noted the function of the unidirectional conduction component from the perspective of the control signal interfaces is similar to that of a system comprising previously proposed power supply circuits. In particular, the 2024PF80281

[0148] 19 unidirectional conduction component DI prevents bidirectional power flow between the two power supply circuits. In other words, the unidirectional conduction component functions to prevent the first grounding capacitors of the different power supply circuits from bidirectionally buffering a signal on the communication bus via the power supply circuits connected to the communication bus and the ground reference and via the ground reference.

[0149] In another variant (not illustrated), the unidirectional conduction component DI is instead connected between the intermediate node N2 and the first grounding capacitor CY1. In particular, the anode of the unidirectional conduction component DI may be connected to the intermediate node N2 and the cathode of the unidirectional conduction component DI is connected to the first grounding capacitor CY1.

[0150] 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.

[0151] Functions implemented by a processor may be implemented by a single processor or by multiple separate processing units which may together be considered to constitute a "processor". Such processing units may in some cases be remote from each other and communicate with each other in a wired or wireless manner.

[0152] 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.

[0153] A computer program may be stored / 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.

[0154] If the term "adapted to" is used in the claims or description, it is noted the term "adapted to" is intended to be equivalent to the term "configured to". If the term "arrangement" is used in the claims or description, it is noted the term "arrangement" is intended to be equivalent to the term "system", and vice versa.

[0155] Any reference signs in the claims should not be construed as limiting the scope.

Claims

2024PF8028120CLAIMS:

1. A power supply circuit (300) for a communication bus (190), the power supply circuit (300) comprising: a power output interface (310) for connection to the communication bus (190); a power converter circuit (320) connected to the power output interface (310) and configured to provide a power to the power output interface (310); a first grounding capacitor (CY1) electrically connected between the power output interface (310) and a ground reference (PE), wherein the first grounding capacitor (CY 1 ) is configured to attenuate, from the power output interface (310), electromagnetic interference produced by the power converter circuit (320); and a unidirectional conduction component (DI) connected in series with the power output interface (310), the first grounding capacitor (CY1) and the ground reference (PE), wherein the unidirectional conduction component (DI) is adapted to prevent the first grounding capacitor (CY1) from bidirectionally buffering a signal on the communication bus (190) via a different power supply circuit connected to the communication bus (190) and the ground reference (PE) and via the ground reference (PE), or the first grounding capacitor (CY1) is electrically connected in series with the power output interface (310) and the ground reference (PE).

2. The power supply circuit of claim 1, wherein the unidirectional conduction component (DI) comprises a diode (DI) forward biased from the power output interface (310) to the ground reference (PE).

3. The power supply circuit of claim 1 or 2, wherein the power converter circuit (320) comprises an isolated power converter circuit defining a primary side (PS) and a secondary side (SS) magnetically coupled together, wherein the power output interface (310) and the first grounding capacitor (CY1) are electrically connected to the secondary side (SS).

4. The power supply circuit of claim 3, wherein the power converter circuit (310) comprises a switch arrangement (QI) electrically connected to the primary side (PS) and2024PF8028121 configured to control power flow in the primary side (PS), wherein the switch arrangement (QI) is adapted to produce the electromagnetic interference.

5. The power supply circuit of claim 4, wherein the power converter circuit (320) comprises a capacitor (Cp) connected between the primary side (PS) and the secondary side (SS), wherein the capacitor (Cp) is adapted to couple the electromagnetic interference produced by the switch arrangement (QI) to the power output interface (210).

6. The power supply circuit of any one of claims 3 to 5, wherein said first grounding capacitor (CY1) is adapted to shunt the electromagnetic interference to the ground reference (PE) thereby away from the power output interface (310), and the power supply circuit further comprises a second grounding capacitor (CY2) connected between the primary side (PS) and the ground reference (PE) and adapted to route back the electromagnetic interference from the ground reference (PE) to the power converter circuit (320).

7. The power supply circuit of any one of claims 1 to 6, wherein the unidirectional conduction component (DI) is connected between the power output interface (310) and the first grounding capacitor (CY1) at a position such that the unidirectional conduction component (DI) is coupled in a loop of the power to the power output interface (310) and decoupled from a loop through which the first grounding capacitor (CY1) attenuates the electromagnetic interference.

8. The power supply circuit of any one of claims 1 to 6, wherein the unidirectional conduction component (DI) is connected at a position such that the unidirectional conduction component (DI) is decoupled in a loop of the power to the power output interface and (310) coupled in a loop through which the first grounding capacitor (CY1) attenuates the electromagnetic interference.

9. The power supply circuit of any one of claims 1 to 8, wherein the power output interface (310) is configured for connecting to an external electronic device for powering the electronic device.2024PF802812210. The power supply circuit of any one of claims 1 to 9, further comprising a control signal interface (330) configured to connect to the communication bus (190), wherein the control signal interface (330) is connected to the power output interface (310), and a control logic circuitry (150) connected to the control signal interface (330) and configured to control an operation of the power supply circuit responsive to a control signal received from the communication bus (190) via the control signal interface.

11. The power supply circuit of claim 10, wherein: the control signal interface (330) comprises a positive control signal terminal (DA+); the power output interface (310) comprises a positive power output terminal (111); and a current limiting circuit (CL) connecting the positive power output terminal (111) to the positive control signal terminal (DA+); and the control signal interface (330) comprises a negative control signal terminal (DA-); the power output interface (310) comprises a negative or neutral power output terminal (112) connected to the negative control signal terminal (DA-).

12. A semiconductor light source driving apparatus, comprising the power supply circuit of any one of claims 1 to 12.

13. A luminaire comprising the semiconductor light source driving apparatus of claim 12, and a semiconductor light source.

14. A system comprising: a plurality of different power supply circuits, at least one of which is the power supply circuit according to any one of claims 1 to 13; and the communication bus (190) comprising a first bus line (191) and a second bus line (192) connected to the control signal interface (330) of each power supply circuit, wherein when the control signal communication interfaces (330) of the different power supply circuits are connected to the communication bus (190) with opposite polarities, the first grounding capacitors (CY1A, CY1B) of the different power supply circuits are coupled together between the first bus line (DA+) and a second bus line (DA-) and the unidirectional2024PF8028123 conduction component (DI) is adapted to prevent the first grounding capacitors (CY1A, CY1B) of the different power supply circuits from bidirectionally buffering a signal on the communication bus (190) via the power supply circuits connected to the communication bus (190) and the ground reference (PE) and via the ground reference (PE).

15. The system of claim 14, wherein at least two of the plurality of different power supply circuits is the power supply circuit according to any one of claims 1 to 13, the unidirectional conduction component (DI A, DIB) of the at least two power supply circuits is biased in same relative direction within respective power supply circuit, and the unidirectional conduction component (DI A, DIB) of each power supply circuit is configured such that, when the control signal communication interfaces (330) of the different power supply circuits are connected to the communication bus (190) with opposite polarities, the unidirectional conduction components (D1A, DIB) of said power supply circuit are opposite biased with each other and in series with the first grounding capacitors (CY1A, CY1B) of the different power supply circuits between the first bus line (191) and a second bus line (192), thereby preventing any of the first grounding capacitors (CY1A, CY1B) from buffering signal on the communication bus (191) in any of two directions.

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