Classifications

• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
  • H02M3/00—Conversion of dc power input into dc power output
  • H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
  • H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
  • H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
  • H02M3/325—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal
  • H02M3/335—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
  • H02M3/33507—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of the output voltage or current, e.g. flyback converters
  • H02M3/33523—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of the output voltage or current, e.g. flyback converters with galvanic isolation between input and output of both the power stage and the feedback loop
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
  • H02H9/00—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection
  • H02H9/02—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection responsive to excess current
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
  • H02M3/00—Conversion of dc power input into dc power output
  • H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
  • H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
  • H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
  • H02M3/325—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal
  • H02M3/335—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
  • H02M3/33507—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of the output voltage or current, e.g. flyback converters
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
  • H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
  • H05B45/30—Driver circuits
  • H05B45/36—Circuits for reducing or suppressing harmonics, ripples or electromagnetic interferences [EMI]
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
  • H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
  • H05B45/50—Circuit arrangements for operating light-emitting diodes [LED] responsive to malfunctions or undesirable behaviour of LEDs; responsive to LED life; Protective circuits
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
  • H05B47/00—Circuit arrangements for operating light sources in general, i.e. where the type of light source is not relevant
  • H05B47/10—Controlling the light source
  • H05B47/175—Controlling the light source by remote control
  • H05B47/18—Controlling the light source by remote control via data-bus transmission
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
  • H02H9/00—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection
  • H02H9/04—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection responsive to excess voltage

Definitions

• the present disclosure relates to lighting technology, and in particular to a power supply for a lighting control bus.
• Lighting control buses according to the Digital Addressable Lighting Interface (DALI) specifications use a single pair of wires for both communication and powering. Signals are sent by briefly shorting the bus to a low voltage level, wherein power supplies of the lighting control bus are required to tolerate this, limiting the current to 250 mA by means of a current limiter circuit.
• DALI Digital Addressable Lighting Interface
• such current limiter circuits are typically arranged between the lighting control bus and the power supply for the same, and comprise an analog circuit including a reference diode for low temperature drift and a Field Effect Transistor (FET) for limitation of the flow of current on the lighting control bus if any of the gears (e.g., drivers, sensors, controls) attached to the lighting control bus communicate.
• FET Field Effect Transistor
• the prompt response may result in a partial return to the high voltage level or a ringing, which in turn may affect the communication on the lighting control bus.
• a signal level change on the lighting control bus is preferably monotonic.
• a control loop of the power supply may behave hysteresis-like. Therefore a ripple of an output current of the power supply may be significant.
• Stacking i.e. parallel connection, of power supplies for a lighting control bus, such as specified by the Digital Illumination Interface Alliance (DiiA) in connection with its D4i certification, introduces the possibility of mutually reverse polarity when multiple power supplies are connected to the lighting control bus.
• DIiA Digital Illumination Interface Alliance
• the aforementioned FET of the current limiter may be subject to an excess DC voltage, which may ultimately destroy the FET.
• DALI Digital Addressable Lighting Interface
• Such power supplies are usually based on the Flyback concept, which subdivides the power supply into inductively coupled primary and secondary sides separated by a galvanic isolation barrier.
• Flyback converters comprise a switch on the primary side for controlling a duration of an ON period of a switching cycle of the switch, which in turn determines a primary side peak current.
• a regulation of the secondary side (i.e., output) voltage normally involves a secondary side voltage measurement.
• a communication of the measurement result across the isolation barrier to the control circuit is expensive.
• an output voltage drift is considerable due to factors such as inductive coupling, converter efficiency, temperature drift etc.
• the present disclosure thus seeks to provide
• a first aspect of the present disclosure relates to a current limiter for a power supply of a lighting control bus.
• the current limiter comprises a resistor and a first switch arranged serially in a current path of the lighting control bus.
• the first switch is configured to gate a current of the lighting control bus in accordance with a voltage of the lighting control bus applied to a control terminal of the first switch.
• the resistor is configured to sense the current gated by the first switch as a voltage drop there across.
• the current limiter further comprises a reference diode configured to shunt the voltage applied to the control terminal of the first switch in accordance with the voltage drop across the resistor; and a capacitor connected in parallel to the reference diode.
• the control terminal of the first switch may be connected to a high-side rail of the lighting control bus; and the first switch may be interposed in a low-side rail of the lighting control bus.
• a control terminal of the reference diode may be connected to a common terminal of the resistor and the first switch; and the reference diode may be interposed between another terminal of the resistor and the control terminal of the first switch.
• the capacitor may have a capacity between 3 nF and 20 nF, and preferably between 5 nF and 15 nF, for a monotonic signal level change on the lighting control bus in less than 1 ps.
• the lighting control bus may comprise a DALI bus.
• the first switch may comprise a FET.
• the reference diode may comprise an adjustable shunt regulator circuit.
• a second aspect of the present disclosure relates to a current limiter for a power supply of a lighting control bus.
• the current limiter comprises a first switch arranged in a current path of the lighting control bus.
• the first switch is configured to gate a current of the lighting control bus in accordance with a voltage of the lighting control bus applied to a control terminal of the first switch.
• the current limiter further comprises a voltage divider connected in parallel to the current path.
• the current limiter further comprises a second switch interposed between the control terminal of the first switch and an outer terminal of the voltage divider.
• the second switch is configured to shunt the voltage applied to the control terminal of the first switch in accordance with a current into the control terminal of the second switch.
• the current limiter further comprises a Zener diode interposed between the control terminal of the second switch and an inner terminal of the voltage divider.
• the Zener diode is configured to gate the current into the control terminal of the second switch in accordance with a voltage drop between the inner terminal and the outer terminal of the voltage divider in excess of a reverse breakdown voltage of the Zener diode.
• the control terminal of the first switch may be connected to a high-side rail of the lighting control bus; and the first switch may be interposed in a low-side rail of the lighting control bus.
• the lighting control bus may comprise a DALI bus.
• the first switch may comprise a FET.
• the second switch may comprise an NPN BJT.
• the Zener diode and an emitter diode of the second switch may be oppositely directed.
• the Zener diode may be designed for the reverse breakdown voltage of at least 9 V.
• a third aspect of the present disclosure relates to a power supply for a lighting control bus.
• the power supply comprises: an interface DC/DC (isolated power) converter configured to inductively supply power from a primary side of the converter to a secondary side of the converter.
• the secondary side comprises output terminals connectable to the lighting control bus.
• the primary side comprises a switch, and a control circuit configured to control, in a first conduction mode of the switch, a duty cycle of the switch in dependence of a variation of an output voltage of the power supply measured on the primary side, and configured to adjust, in a second conduction mode of the switch, a duration of the switching period of the switch in dependence of a variation of an average output current of the power supply measured on the primary side.
• the control circuit may further be configured to adjust a reference value of the output voltage of the power supply in dependence of an estimated output power of the power supply.
• the control circuit may further be configured to estimate the output power of the power supply in dependence of an actual value of the output voltage of the power supply and an actual value of an input current of the power supply.
• the control circuit may further be configured to measure the actual value of the output voltage of the power supply in accordance with a first measurement on the primary side.
• the primary side may further comprise a series connection of a diode and a capacitor arranged in parallel to the switch; and a low-pass filter connected downstream of a midpoint between the diode and the capacitor and upstream of the control circuit.
• the control circuit may further be configured to measure an average peak voltage dropping across the capacitor when the switch is in a non-conducting state. The average peak voltage may be indicative of the actual value of the output voltage of the power supply.
• the control circuit may further be configured to measure the actual value of the input current of the power supply in accordance with a second measurement on the primary side.
• the primary side may further comprise a shunt connected downstream of the switch.
• the control circuit may further be configured to measure a voltage dropping across the shunt when the switch is in a conducting state, the voltage being indicative of the actual value of the output current of the power supply.
• the control circuit may further be configured to measure a zero-crossing of the output current of the power supply in accordance with a third measurement on the primary side.
• the control circuit may further be configured to measure a zero-crossing of the voltage dropping across the shunt when the switch is in a conducting state, the zero-crossing of the voltage being indicative of the zero-crossing of the output current of the power supply.
• the control circuit may further be configured to perform a transition of a conduction mode of the switch between the first conduction mode and the second conduction mode in dependence of the estimated output power of the power supply.
• the control circuit may further be configured to adjust a peak amplitude of a primary-side current passing through the switch when the switch is in a conducting state in dependence of the estimated output power of the power supply, the peak amplitude being indicative of the average output current of the power supply.
• the interface DC/DC converter may comprise a Flyback converter, and/or the switch may comprise a MOSFET.
• the first conduction mode may comprise a discontinuous conduction mode
• the second conduction mode may comprise a boundary/borderline conduction mode
• the secondary side may further comprise an overcurrent protection for limiting the output current to a nominal value in case of a short-circuit of the output terminals, and/or an overvoltage protection.
• a fourth aspect of the present disclosure relates to a power supply for a lighting control bus, the power supply comprising an interface DC/DC converter configured to supply the lighting control bus off an externally provided logic supply DC voltage; and a current limiter of the first or second aspects or any of their implementations interposed between the interface DC/DC converter and the lighting control bus.
• the power supply may further comprise an interface control circuit configured to operate the interface DC/DC converter.
• the interface DC/DC converter may comprise a galvanic isolation.
• the interface DC/DC converter may comprise a Flyback converter or a resonant converter.
• a fifth aspect of the present disclosure relates to a driver for at least one LED.
• the driver comprises: a power factor correction, PFC, AC/DC converter configured to supply a DC bus off an AC mains supply; a first DC/DC converter configured to supply the at least one LED off the DC bus; a second DC/DC converter configured to provide a logic supply DC voltage off the DC bus; and a power supply of the third or fourth aspects or any of their implementations configured to supply a lighting control bus connectable to the driver off the logic supply DC voltage provided by the second DC/DC converter.
• the driver may further comprise: a communications interface entity configured to communicate via the lighting control bus; and a control entity configured to operate the first DC/DC converter in accordance with instructions receivable by the communications interface entity.
• a sixth aspect of the present disclosure relates to a lighting control system.
• the lighting control system comprises a driver of the fifth aspect or any of its implementations for at least one LED; and at least one bus participant.
• the driver is connected to a lighting control bus and configured to drive the at least one LED in accordance with a lighting control instruction receivable via the lighting control bus.
• the at least one bus participant is also connected to the lighting control bus and configured to issue the lighting control instruction for the driver via the lighting control bus.
• the at least one bus participant may comprise at least one of: a sensor, and a control.
• the present disclosure provides a current limiter for a power supply of a lighting control bus, in particular a DALI bus, wherein a capacitor is provided parallel to the reference diode’s anode and cathode terminals, thereby softening a switching behaviour of the FET.
• a current limiter for a power supply of a lighting control bus, in particular a DALI bus, wherein a capacitor is provided parallel to the reference diode’s anode and cathode terminals, thereby softening a switching behaviour of the FET.
• the present disclosure further provides an overvoltage-protected current limiter for a power supply of a lighting control bus, in particular a DALI bus, in which a first FET-type switch for overcurrent protection is overvoltage-protected by a second BJT-type switch.
• the second switch becomes conducting (closed, on, switched through) when an excess DC voltage on the lighting control bus triggers a reverse breakdown of a reverse-biased Zener diode connected to the control terminal of the second switch.
• This shunts shorts, short-circuits, hot-wires the voltage applied to the control terminal of the first switch, which is derived from a high-side rail of the lighting control bus, to a low-side rail of the same, so that the first switch becomes non-conducting (open, off).
• the first FET-type switch is switched off / protected by the second BJT-type transistor.
• the protection is generally against overheat / overload, not only against wrong polarity of power supplies.
• the overvoltage-protected current limiter may give rise to less customer complaintss (when power supplies are wrongly installed).
• the protection is a temperature-stable function despite the deployment of a low-cost BJT transistor.
• the present invention provides a power supply for a lighting control bus which
• FIG. 1 illustrates a driver in accordance with the present disclosure for at least one LED
• FIG. 2 illustrates a power supply in accordance with the present disclosure for a lighting control bus
• FIG. 3 illustrates a current limiter in accordance with the present disclosure for the power supply of FIG. 1;
• FIG. 4 illustrates an overvoltage protection for the current limiter of FIG. 3.
• FIG. 1 illustrates a driver 3 in accordance with the present disclosure for at least one LED 5.
• the driver 3 comprises a PFC AC/DC converter 31 configured to supply a DC bus voltage, such as 400V, to a - schematically illustrated - dual rail DC bus 32 off an AC mains supply 4; a first DC/DC converter 33 configured to supply a load supply DC voltage to the at least one LED 5 off the DC bus 32; a second DC/DC converter 34 configured to provide a logic supply DC voltage, such as 12V, off the DC bus 32; and a power supply 2 of the third or fourth aspects or any of their implementations.
• the power supply 2 is configured to supply a lighting control bus 6, such as a DALI bus, connectable to the driver 3 off the logic supply DC voltage provided by the second DC/DC converter 34.
• the driver 3 may further comprise a communications interface entity 35, such as a DALI communications interface, configured to communicate bidirectionally via the lighting control bus 6; and a control entity 36, such as a microcontroller, configured to operate the first DC/DC converter 33 in accordance with instructions receivable by the communications interface entity
• the control entity 36 may be configured to dim the at least one LED 5 in accordance with such instructions received from one or more sensors 7 or one or more controls 8, such as Serial DIMmer communications (S-DIM) controls or DALI controls.
• S-DIM Serial DIMmer communications
• a lighting control system of the sixth aspect comprises a driver 3 of the fifth aspect or any of its implementations for the at least one LED 5; and at least one bus participant 7, 8.
• the driver 3 is connected to a lighting control bus 6 and configured to drive the at least one LED 5 in accordance with a lighting control instruction receivable via the lighting control bus 6.
• the at least one bus participant 7, 8, such as at least one of a sensor 7 and a control 8, is connected to the same lighting control bus 6 and configured to issue the lighting control instruction for the driver 3 via the lighting control bus 6.
• driver 3 may be connected to the same lighting control bus 6.
• the power supply 2 comprises an interface DC/DC converter 22, 1 configured to supply the lighting control bus 6 off an externally provided logic supply DC voltage, such as the logic supply DC voltage provided by the second DC/DC converter 34 of the driver 3; and a current limiter 23 of the first or second aspects or any of their implementations interposed between the interface DC/DC converter 22, 1 and the lighting control bus 6.
• an interface DC/DC converter 22, 1 configured to supply the lighting control bus 6 off an externally provided logic supply DC voltage, such as the logic supply DC voltage provided by the second DC/DC converter 34 of the driver 3; and a current limiter 23 of the first or second aspects or any of their implementations interposed between the interface DC/DC converter 22, 1 and the lighting control bus 6.
• the power supply 2 may further comprise an interface control circuit 21, 106, such as an integrated circuit (IC), configured to operate the interface DC/DC converter 22, 1.
• the interface DC/DC converter 22, 1 may comprise a galvanic isolation, and particularly comprise a Flyback converter or a resonant converter.
• the driver control entity 36 and the interface control circuit 21, 106 may be combined as one joint control entity, e.g. as one integrated circuit, performing both functions.
• FIG. 2 illustrates a power supply 2 in accordance with the present disclosure for a lighting control bus 6.
• the interface DC/DC converter 22, 1 (also herein called isolated power converter) is configured to inductively supply power from a primary side 102 of the interface DC/DC converter 22, 1 to a secondary side 103 of the interface DC/DC converter 22, 1.
• the inductive coupling may be realized by a transformer 131, which comprises a coupled inductor with a gapped core.
• the secondary side 103 comprises output terminals 104 connectable to the lighting control bus 6, such as a Digital Addressable Lighting Interface (DALI) bus, a rectifying diode 116 and a smoothing capacitor 117.
• the lighting control bus 6 such as a Digital Addressable Lighting Interface (DALI) bus
• DALI Digital Addressable Lighting Interface
• DALI as used herein may refer to a series of technical standards (IEC 62386) specifying requirements for networking-enabled products of lighting control.
• the secondary side 103 may further comprise an overcurrent protection (OCP) 114 for limiting an output current 108 to a nominal value in case of a short-circuit of the output terminals 104, and/or an overvoltage protection (OVP) 115.
• OCP overcurrent protection
• OVP overvoltage protection
• an OCP may be realized based on a shunt regulator, and an OVP may be implemented using a Zener diode.
• the primary side 102 comprises a switch 105, such as a Metal Oxide Semiconductor Field Effect Transistor (MOSFET) or a bipolar transistor.
• a switch 105 such as a Metal Oxide Semiconductor Field Effect Transistor (MOSFET) or a bipolar transistor.
• MOSFET Metal Oxide Semiconductor Field Effect Transistor
• a duty cycle as used herein is a fraction of a (recurring) period, such as the duration T of the switching cycle, in which a switch is active/conductive/closed/ON.
• an input voltage (such as 12 V DC) supplied by a voltage source 124 is applied to a primary winding of the transformer 131, and energy is stored in the gap of the core.
• the combination of winding polarity (identified by the polarity dots) biases the diode 116 in a reverse direction to ensure that no energy is transferred to the secondary side 103.
• a primary side current ramps up over time to store energy.
• this energy is transferred to a secondary winding of the transformer 131 to provide energy to a load, such as the lighting control bus 6, which is represented as a resistor in FIG. 2.
• the switch 105 When the switch 105 is opened, the output current 108 is at its peak and ramps downward as the stored energy is transferred to the load.
• the switch 105 may further be operated in one of a first conduction mode, such as a discontinuous conduction mode (DCM), and a second conduction mode, such as a boundary/borderline conduction mode (BCM).
• a first conduction mode such as a discontinuous conduction mode (DCM)
• a second conduction mode such as a boundary/borderline conduction mode (BCM).
• DCM discontinuous conduction mode
• BCM boundary/borderline conduction mode
• DCM and a BCM as used herein may refer to modes of operation of a power converter wherein an energy stored in an energy storage element (inductor) of the power converter is fully depleted in each switching cycle.
• the Flyback converter supplies an output voltage V out , 107 in dependence of the input voltage Vin, a number of turns N s of the secondary winding, a number of turns N p of the primary winding and the afore-mentioned duty cycle D according to:
• the output voltage V out , 107 may be controlled by the duty cycle D, or its constituents, i.e., the duration TON of the ON period and the duration T of the switching cycle, respectively.
• the primary side 102 further comprises the interface control circuit 21, 106 configured to control, in the first conduction mode (DCM) of the switch 105, the duty cycle D of the switch 105 in dependence of a variation of the output voltage Vout , 107 of the power supply 1 measured on the primary side 102, and configured to adjust, in the second conduction mode (BCM) of the switch 105, the duration T of the switching cycle of the switch 105 in dependence of a variation of the average input current of the power supply 1 measured on the primary side 102.
• DCM first conduction mode
• BCM second conduction mode
• the interface control circuit 21, 106 may in particular comprise a controller 128, such as a PID controller, and a PWM signal generator 129 for generating a pulse- with modulation (PWM) drive signal (represented asD in FIG. 2) for the switch 105 in accordance with the duty cycle D and/or the duration T of the switching cycle.
• a controller 128, such as a PID controller such as a PID controller
• PWM signal generator 129 for generating a pulse- with modulation (PWM) drive signal (represented asD in FIG. 2) for the switch 105 in accordance with the duty cycle D and/or the duration T of the switching cycle.
• PWM pulse- with modulation
• the interface control circuit 21, 106 may further be configured to measure a quantity V sense indicative of the actual value of the output voltage 107, Vout of the power supply 1 in accordance with a first measurement A on the primary side 102.
• the primary side 102 may further comprise a series connection of a diode 110 and a capacitor 111 arranged in parallel to the switch 105.
• the diode 110 and the capacitor 111 constitute a "peak tracker" (in fact a peak hold with average function) of the secondary side / output voltage 107, Vout implemented on the primary side 102. This means that regulation of the secondary side / output voltage 107, Vout takes place without measurement effort on the secondary side 103.
• a potential of a midpoint between the diode 110 and the capacitor 111 is tapped by a voltage divider 118, 119.
• a low-pass filter 112 is connected downstream of a midpoint of the voltage divider 118, 119, and thus downstream of the midpoint between the diode 110 and the capacitor 111, and upstream of the interface control circuit 21, 106.
• the interface control circuit 21, 106 may further be configured to measure an average peak voltage dropping across the capacitor 111 when the switch 105 is in a non-conducting state. This average peak voltage may be indicative of the actual value of the output voltage 107, V ou t of the power supply 1, and may be provided to the interface control circuit 21, 106 as the first measurement
• the interface control circuit 21, 106 may further be configured to measure a quantity I sen se indicative of the actual value of the input current of the power supply 1 in accordance with a second measurement B on the primary side 102.
• the primary side 102 may further comprise a shunt resistor 113 connected downstream of the switch 105.
• a potential of a midpoint between the switch 105 and the shunt 113 is tapped and provided to the interface control circuit 21, 106.
• the interface control circuit 21, 106 may further be configured to measure a voltage dropping across the shunt 113 when the switch 105 is in a conducting state. This voltage may be indicative of the actual value of the input current of the power supply 1, and may be provided to the interface control circuit 21, 106 as the second measurement B.
• the interface control circuit 21, 106 may further be configured to adjust a reference value 109 of the output voltage 107 of the power supply 1 in dependence of an estimated output power P ou t of the power supply 1, and to estimate the output power P ou t of the power supply 1 in dependence of actual values of the output voltage 107, V ou t and the input current of the power supply 1. More specifically, the quantities V se nse, Isense indicative of the actual values of the output voltage 107, Vout and the input current may be determined in accordance with the explanations above.
• An analog/digital conversion (ADC) unit 125 of the interface control circuit 21, 106 may receive these quantities, and a power estimation unit 126 of the interface control circuit 21, 106 may multiply these quantities to estimate the output power P ou t.
• ADC analog/digital conversion
• Variations of this estimated output power P ou t reflect a load-dependent drift of the output voltage 107, Vout.
• the load dependence of the output voltage 107, V ou t may be compensated for by an opposite load-dependent adjustment of the reference value 109 of the output voltage 107.
• the reference value 109 of the output voltage 107, V ou t is made load-dependent.
• a compensation function 127 may be provided, which may be realized as a lookup table, for example.
• an adjusted reference value 109’ may be retrieved/obtained as a function of the nominal reference value 109 and the output power P out estimated by the power estimation unit 126. Accordingly, the output voltage 107, V out can be kept stable, even though the first and second measurements A, B are made on the primary side 102 of the interface DC/DC converter 22, 1.
• the usually utilized DCM leads to relatively large transformer sizes. This is because of the inductance tolerance of the transformer 131. For example, small inductances and air gaps are subject to high tolerance (approx. 15% up to 25%).
• the converter design has to reflect reserves (i.e., a large safety margin) which do not allow for an optimization for smallest size.. This means that the transformer 131 must be designed larger than theoretically required. This can be overcome by a load-dependent BCM to DCM mode transition.
• CCM continuous conduction mode
• continuous conduction mode may refer to a mode of operation of the power converter wherein the energy stored in the energy storage element of the power converter is not fully depleted in each switching cycle.
• the interface control circuit 21, 106 may further comprise a mode switching unit 130 configured to toggle between the first conduction mode (DCM) and the second conduction mode (BCM) in dependence of the output power P out of the power supply 1.
• the interface control circuit 21, 106 may further be configured to measure a zero-crossing of the input current of the power supply 1 in accordance with a third measurement C on the primary side 102.
• the interface control circuit 21, 106 may further be configured to measure a zero-crossing of the voltage dropping across the shunt 113 when the switch 105 is in a conducting state. This zero crossing of the voltage may be indicative of the zero-crossing of the input current of the power supply 1.
• the primary side 102 may further comprise a voltage divider 122, 123, which taps a potential of a midpoint between the primary winding of the transformer 131 and the switch 105. In turn, a potential of a midpoint of the voltage divider 122, 123 may be provided to the interface control circuit 21, 106 as the third measurement C.
• the interface control circuit 21, 106 may further be configured to perform a transition of a conduction mode of the switch 105 between the first conduction mode and the second conduction mode in dependence of the estimated output power P out of the power supply 1.
• measuring a zero-crossing of the input current is a requirement for the second conduction mode, and the estimated output power P out of the power supply 1 may be compared with reference value, such as a power threshold.
• the interface control circuit 21, 106 may further be configured to adjust a peak amplitude of a primary-side current passing through the switch 105 when the switch 105 is in a conducting state in dependence of the estimated output power of the power supply 1. This peak amplitude is indicative of the average output current 108, I out of the power supply 1. As a result, the output power may virtually be maintained constant when switching between DCM and BCM.
• FIG. 3 illustrates a current limiter 23 in accordance with the present disclosure for the power supply 2 of FIG. 1.
• the current limiter 23 comprises in this implementation a resistor 231 and a first switch 232 arranged serially in a current path of the lighting control bus 6.
• the first switch 232 may comprise a FET.
• the control terminal of the first switch 232 may be connected to a high-side rail of the lighting control bus 6; and the first switch 232 may be interposed in a low-side rail of the lighting control bus 6.
• the first switch 232 is configured to gate a current I of the lighting control bus 6 in accordance with a voltage V of the lighting control bus 6 applied to a control terminal of the first switch 232. This may also refer to a fraction of said voltage V, as may be derived from the voltage V by means of a voltage drop across one or more resistors (not shown) provided at the control terminal of the first switch 232.
• gate may refer to controlling a passage or pass-through (of a current/voltage) with a gate, such as a gate of a transistor, in dependence of some other parameter.
• a high-side rail may refer to a particular one of a pair of electrical connections between a power supply (such as the power supply 2) and a load (such as the sensors 7 or controls 8 connected to the lighting control bus 6) having a higher electrical potential of the pair
• a low-side rail may refer to the other one of the pair having a lower electrical potential of the pair.
• the resistor 231 is configured to sense the current I gated by the first switch 232 as a voltage drop across the resistor 231.
• the current limiter 23 further comprises a reference diode 233, such as a TL431 adjustable shunt regulator circuit.
• the reference diode 233 is configured to act as a temperature- compensated variable/adjustable Zener diode.
• a control terminal of the reference diode 233 may be connected to a common terminal of the resistor 231 and the first switch 232; and the reference diode 233 may be interposed between another terminal of the resistor 231 and the control terminal of the first switch 232.
• the current limiter 23 is configured to shunt the voltage V applied to the control terminal of the first switch 232 in accordance with the voltage drop across the resistor 231.
• shunt may refer to tapping (a voltage) in dependence of some other parameter.
• shunting a voltage may be a gradual tapping / function of said parameter.
• the current I is limited by the current limiter 23 if any of the gears (i.e., sensors 7, controls 8 or drivers 3) connected to the lighting control bus 6 communicate by briefly shorting the high-side and low side rails of the lighting control bus 6 to a low voltage level.
• the current limiter 23 further comprises a capacitor 234 connected in parallel to the reference diode 233.
• the capacitor 234 may have a capacity between 3 nF and 20 nF, and preferably between 5 nF and 235 nF, for a monotonic signal level change on the lighting control bus 6 in less than 1 ps. That is to say, the capacitor 234 provided parallel to the anode and cathode terminals of the reference diode 233 soften a switching behaviour of the first switch 232.
• FIG. 4 illustrates an overvoltage protection for the current limiter 23 of FIG. 3.
• the current limiter 23 comprises in this implementation a first switch 232 arranged in a current path of the lighting control bus 6.
• the first switch 232 may comprise a FET.
• the control terminal of the first switch 232 may be connected to a high-side rail of the lighting control bus 6; and the first switch 232 may be interposed in a low-side rail of the lighting control bus 6.
• the first switch 232 is configured to gate a current I of the lighting control bus 6 in accordance with a voltage V of the lighting control bus 6 applied to a control terminal of the first switch 232. This may also refer to a fraction of said voltage V, as may be derived from the voltage V by means of a voltage drop across one or more resistors (not shown) provided at the control terminal of the first switch 232.
• the current limiter 23 may further comprise a resistor 231 arranged in series with the first switch 232. The resistor 231 may be configured to sense the current I gated by the first switch 232 as a voltage drop across the resistor 231.
• the current limiter 23 may further comprise a reference diode 233, such as a TL431 adjustable shunt regulator circuit.
• the reference diode 233 is configured to act as a temperature-compensated variable/adjustable Zener diode.
• a control terminal of the reference diode 233 may be connected to a common terminal of the resistor 231 and the first switch 232; and the reference diode 233 may be interposed between another terminal of the resistor 231 and the control terminal of the switch 232.
• the current limiter 23 is configured to shunt the voltage V applied to the control terminal of the switch 232 in accordance with the voltage drop across the resistor 231.
• the current I is limited by the current limiter 23 if any of the gears (i.e., sensors 7, controls 8 or drivers 3) connected to the lighting control bus 6 communicate by briefly shorting the high-side and low side rails of the lighting control bus 6 to a low voltage level.
• gears i.e., sensors 7, controls 8 or drivers
• the current limiter 23 may further comprise a capacitor 234 connected in parallel to the reference diode 233 for softening a switching behaviour of the first switch 232.
• the first switch 232 of the current limiter 23 may be subject to an excess DC voltage as follows:
• the power supply 2 of one driver 3 may regulate the bus supply voltage to a value of 15 V, for example. If a power supply 2 of another driver 3 is connected to the lighting control bus 6 with reverse polarity of 15 V, a total of almost 30 V must drop across the first switch 232 (and the resistor 1 in series). As a result, the second switch 232 may ultimately be destroyed.
• An overvoltage protection (including a protection against wrong polarity) of the current limiter 23 may be achieved as follows.
• the current limiter 23 further comprises a voltage divider 235, 236 connected in parallel to the current path.
• the current limiter 23 further comprises a second switch 237 interposed between the control terminal of the first switch 232 and an outer terminal of the voltage divider 235, 236.
• the second switch 237 may comprise an NPN BJT.
• the second switch 237 is configured to shunt the voltage applied to the control terminal of the first switch 232 in accordance with a current I B into the control terminal of the second switch 237.
• the current limiter 23 further comprises a Zener diode 238 interposed between the control terminal of the second switch 237 and an inner terminal of the voltage divider 235, 236.
• the Zener diode 238 is configured to gate the current I B into the control terminal of the second switch 237 in accordance with a voltage drop between the inner terminal and the outer terminal of the voltage divider 235, 236 in excess of a reverse breakdown voltage of the Zener diode 238.
• Zener diode 238 may be designed for the reverse breakdown voltage of at least 9 V.
• the current I B into the control terminal of the second switch 237 increases sharply, so that the second switch 237 becomes conducting (closed, on, switched through) and shunts (shorts, short-circuits, hot-wires) the voltage applied to the control terminal of the first switch, which is derived from a high-side rail of the lighting control bus, to a low-side rail of the same, so that the first switch becomes non conducting (open, off).
• the first FET-type switch 232 is protected by the second BJT- type transistor 237.
• the Zener diode 238 and an emitter diode of the second switch 237 may be oppositely directed.
• a temperature coefficient (TC) of the Zener diode 238 compensates for a TC of the BJT base-emitter junction.
• the overvoltage protection is a temperature-stable function despite the deployment of the low-cost BJT 237.

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• 2021
  • 2021-03-17 EP EP21163025.6A patent/EP4060887B1/de active Active
  • 2021-08-13 WO PCT/EP2021/072569 patent/WO2022194400A1/en active Application Filing
  • 2021-08-13 CN CN202180095364.0A patent/CN117044092A/zh active Pending
  • 2021-08-13 EP EP21751826.5A patent/EP4275272A1/de active Pending

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