WO2020187669A1 - Court-circuit de del amélioré et détection de charge ouverte avec une seule broche de commande - Google Patents

Court-circuit de del amélioré et détection de charge ouverte avec une seule broche de commande Download PDF

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Publication number
WO2020187669A1
WO2020187669A1 PCT/EP2020/056545 EP2020056545W WO2020187669A1 WO 2020187669 A1 WO2020187669 A1 WO 2020187669A1 EP 2020056545 W EP2020056545 W EP 2020056545W WO 2020187669 A1 WO2020187669 A1 WO 2020187669A1
Authority
WO
WIPO (PCT)
Prior art keywords
voltage
current
led driver
signal
representing signal
Prior art date
Application number
PCT/EP2020/056545
Other languages
English (en)
Inventor
Jagjitpati SHUKLA
Deepak MAKWANA
Harald Netzer
Stefan Stark
Original Assignee
Tridonic Gmbh & Co Kg
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Tridonic Gmbh & Co Kg filed Critical Tridonic Gmbh & Co Kg
Priority to EP20715280.2A priority Critical patent/EP3935919A1/fr
Publication of WO2020187669A1 publication Critical patent/WO2020187669A1/fr

Links

Classifications

    • 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
    • H05B45/58—Circuit arrangements for operating light-emitting diodes [LED] responsive to malfunctions or undesirable behaviour of LEDs; responsive to LED life; Protective circuits involving end of life detection of LEDs
    • 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
    • H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
    • H05B45/30—Driver circuits
    • H05B45/37—Converter circuits
    • H05B45/3725—Switched mode power supply [SMPS]
    • H05B45/382—Switched mode power supply [SMPS] with galvanic isolation between input and output
    • 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
    • H05B45/37—Converter circuits
    • H05B45/3725—Switched mode power supply [SMPS]
    • H05B45/39—Circuits containing inverter bridges

Definitions

  • the invention relates to a switched isolated LED driver with a circuitry for detecting a short circuit and an open load condition on the secondary side of an isolation stage.
  • the first approach makes use of two separate controller (microcontroller or ASIC) pins, wherein one pin is used to evaluate the sensed output (LED) voltage e.g. to detect an open load condition when the secondary side voltage exceeds a given threshold. Another pin is used to evaluate the sensed output (LED) current.
  • the first pin utilizes a comparator to detect over voltage (open load) conditions
  • the second pin utilizes a comparator to detect over current (short circuit) conditions.
  • the output voltage sensing module generates the voltage signal V SNS which is given as input in a pin of a controller
  • the output current sensing module generates the current signal I SNS _PK which is given as input to another pin of the controller.
  • the sensing circuity uses peak hold circuits (namely, rectifier diode and filter capacitor) the sensed voltage can follow the real output voltage very fast in positive going direction. However, it follows slow in negative going direction as it takes some time for the filter capacitor to discharge.
  • the second approach makes use of only one controller pin, wherein only the output (LED) voltage is evaluated.
  • Two comparators are used: one to detect over voltage (open load) conditions and one to detect under voltage (short circuit) conditions.
  • reaction times depend on the filtering of the sensed output voltage signal. If the sensed secondary side voltage of the LLC (output voltage) is fed to a peak hold circuit (namely, rectifier diode and filter capacitor), over voltage conditions can be detected very fast (because peak hold capacitor is charged immediately). However, under voltage (short circuit) conditions are detected delayed, because it takes some time for the peak hold capacitor to discharge. This leads to the problem that high output currents flow for several milliseconds that could probably destroy parts of the circuit.
  • a peak hold circuit namely, rectifier diode and filter capacitor
  • an isolated LED driver with open circuit and short-circuit at one pin comprises a control unit controlling at least one switch on the primary side of an isolation stage of the LED driver, means for detecting the voltage on the secondary side of the isolation stage and producing a voltage-representing signal, means for detecting the current flowing on the secondary side, and especially the current through an LED load when connected at supply terminals of the LED driver, and producing a current-representing signal, and means combining for a current- representing signal, optionally the decoupled AC component of the current representing signal, with the voltage representing signal and feeding it to an input pin of the control unit.
  • this aspect of the invention allows fast detections of both over voltage and over current conditions.
  • two different signals one representative for the output voltage and one representative for the output current
  • the current representing signal is supplied to a further input of the control unit for a feedback control of the LED load current.
  • control unit is a microcontroller or an application-specific integrated circuit, ASIC.
  • the means for detecting the voltage on the secondary side of the isolation stage comprise an analog to digital converter, ADC.
  • the LED driver comprises a LLC converter.
  • control unit is further configured to compare the current representing signal with a threshold value in order to derive regulation values for the LLC current transformer, for example, a frequency, a duty cycle value or an actuating variable.
  • the means for combining the current representing signal further comprises a diode for combining the current representing signal with the voltage representing signal to obtain a total signal.
  • control unit further comprises a comparator configured to compare the total signal to a threshold value and, if the total signal is higher than the threshold value, to detect a short-circuit condition or an over voltage condition.
  • the comparator is a comparator with variable reference and polarity.
  • the comparator is a comparator with single reference.
  • control unit is configured to switch off the means for combing the current representing signal in the short-circuit condition or over voltage condition.
  • a method for an isolated LED driver comprises the steps of: controlling at least one switch on the primary side of an isolation stage of the LED driver, detecting the voltage on the secondary side of the isolation stage and producing a voltage-representing signal, detecting the current flowing on the secondary side, and especially the current through an LED load when connected at supply terminals of the LED driver; producing a current-representing signal; combining for a current-representing signal, optionally a decoupled AC component of the current representing signal, with the voltage representing signal; and feeding it to an input pin of the control unit.
  • an isolated LED driver with open circuit and short-circuit at one pin comprises a control unit controlling at least one switch on the primary side of an isolation stage of the LED driver, means for detecting the voltage on the secondary side of the isolation stage and producing a voltage-representing signal, a comparator supplied with the voltage representing signal at its non-inverted input, wherein the reference level of the comparator and, in synchronization therewith, the polarity of the comparator output signal are switched in order to produce a signal indicating, in time multiplex a LED load open circuit and short-circuit indicating signal.
  • a method for an isolated LED driver comprises the steps of controlling at least one switch on the primary side of an isolation stage of the LED driver; detecting the voltage on the secondary side of the isolation stage and producing a -voltage-representing signal; and switching the reference level of a comparator and, in synchronization therewith, the polarity of the comparator output signal in order to produce a signal indicating, in time multiplex, a LED load open circuit and short-circuit indicating signal, wherein the comparator is supplied with the voltage representing signal at its non-inverted input.
  • Fig. 1 shows an exemplary circuit of an LED driver according to prior art
  • Fig. 2 shows an exemplary embodiment of a circuit of an isolated LED driver according to the invention
  • Fig. 3 shows exemplary behaviors of current ILED and voltage V LED in an isolated
  • Fig. 4 shows an exemplary embodiment of a comparator according to the invention
  • Fig. 5 shows an exemplary embodiment of an LED driver according to the invention
  • Fig. 6 shows exemplary embodiments of behaviors of a voltage V in an isolated LED driver as a function of time according to the invention
  • Fig. 7 shows a method for an isolated LED driver according to an embodiment
  • Fig. 8 shows a further method for an isolated LED driver according to an embodiment.
  • the aspect of the present invention might contain integrated circuits that can be readily manufactured using conventional semiconductor technologies, such as complementary metal-oxide semiconductor technology, short "CMOS".
  • CMOS complementary metal-oxide semiconductor technology
  • the aspects of the present invention may be implemented with other manufacturing processes for making optical as well as electrical devices.
  • FIG. 2 an exemplary embodiment of a circuit of an isolated LED driver 200 with open circuit and short-circuit at one input terminal (“pin”) of a preferably integrated control circuitry in according to the invention is shown.
  • the isolated LED driver 200 comprises a control unit (not shown in Fig. 2) controlling at least one switch on the primary side of an isolation stage of the LED driver 200.
  • the switching of the switch determines the power supplied to a LED load and especially the LED current.
  • the LED current may be feedback-controlled back to the control circuitry by a current signal representing the LED current.
  • the control circuitry compares LED current signal with a nominal value (which may be varied for a dimming control) and controls the switching of the switch.
  • the LLC comprises a half-bridge DC/AC converter with two serially connected switches (FETs), M40, M41.
  • the half-bridge arrangement M40, M41 is fed with a DC voltage.
  • the mid-point of the switches M40, M41 is connected to a resonance capacitor C51 and the primary side winding L51a of the transformer of the LLC.
  • the primary side winding L51a of the transformer of the LLC is coupled with a secondary side winding L51b connected to a rectifier, which in the example is a diode arrangement D52a, D52b, D52c and D52d.
  • the diodes may be Schottky diodes.
  • the shown example represents a full-bridge rectifier. However, alternatively a middle-tapped rectifier may be used.
  • the output of the rectifier (diode arrangement) is fed to a capacitor C52, the DC voltage of which is applied to output terminals LED+ and LED- for supplying a LED load.
  • the primary side windings of the sensing transformers L52b, L52c are coupled with a secondary side of the sensing transformer L52a.
  • a signal ISNS_PK indicating the peak current of the LED current is generated as well as a further signal ISNS AVG indicating the average value of the LED current.
  • Both signals ISNS_PK and ISNS AVG can be used by the control circuitry 2 as feedback signals in order to set the clocking of the half-bridge switches M40, M41.
  • the AC component of the LED current is decoupled via a transformer L53a, L53b in order to generate a signal which may be sent to a sensing terminal OVP SCP PIN of the control circuitry.
  • this signal representing the decoupled AC component of this sensed LED current is thus combined with a signal produced by the circuitry 202 sensing, using a further transformer L51c, L51b, the voltage on the secondary side of the power transformer of the transformer L51a, L51b of the LLC.
  • the LED driver 200 comprises means for detecting the voltage on the secondary side of the isolation stage 202 and producing a voltage-representing signal.
  • the LED driver 200 comprises means for detecting the current flowing on the secondary side 204, and especially the current through an LED load when connected at supply terminals of the LED driver, and producing a current-representing signal, means combining for a current- representing signal, optionally the decoupled AC component of the current representing signal, with the voltage representing signal and feeding it to an input pin of the control unit OVP SCP PIN in Fig. 2.
  • the control unit can further be configured to compare the current representing signal with a threshold value in order to derive regulation values for the LLC current transformer, for example, a frequency, a duty cycle value or an actuating variable.
  • the control unit can be a microcontroller or an application-specific integrated circuit (ASIC).
  • ASIC application-specific integrated circuit
  • ADC analog-to-digital converter
  • a comparator 206 can be used to detect over voltage conditions (when the voltage at that pin rises above a certain threshold). In this embodiment, the voltage signal is generated by the LED voltage source.
  • a current pulse is generated in the signal ISNS_PK.
  • This current pulse can be transformed via current transformer to a voltage signal which can then be coupled to the voltage signal at a diode.
  • a peak occurs in this signal, which can be fed to a comparator within the controller. The comparator will detect the peak so that the controller can react to the short-circuit condition.
  • the current signal does not affect the voltage signal during normal operation (where ILED is a constant DC), but it increases the voltage signal during transients of ILED such as in the case of a short circuit of the output.
  • control unit in the short-circuit condition or over voltage condition can be configured to switch off the means for combining the current representing signal.
  • Fig. 3 shows exemplary behaviors of the current ILED and voltage V LED in the isolated LED driver 200 according to the invention.
  • V LED and ILED are combined into a single total signal and then fed to the comparator 206, as shown in figure 4.
  • the comparator 206 can be a comparator configured to compare the total signal to a threshold value and, if the total signal is higher than the threshold value, to detect a short-circuit condition or an over voltage condition.
  • the comparator 206 can be a comparator with variable reference and polarity or a comparator with single reference.
  • the circuit shown in Fig. 4 further comprises two diodes D1 and D2, one resistance R1 and one capacitance C1.
  • the signals V LED and ILED pass through the diodes D1 and D2, respectively. Afterwards, they are combined into a single signal PA3 which is fed to the comparator 206 and then compared to the reference voltage V ref,int in order to detect an over voltage or short current condition.
  • Fig. 5 shows an exemplary embodiment of an isolated LED driver 800 comprising a comparator 806 according to the invention.
  • an isolated LED driver 800 with open circuit and short-circuit at one pin comprises a control unit controlling at least one switch on the primary side of an isolation stage of the LED driver, means for detecting the voltage on the secondary side of the isolation stage and producing a voltage-representing signal, a comparator 806 supplied with the voltage representing signal at its non-inverted input, wherein the reference level of the comparator and, in synchronization therewith, the polarity of the comparator output signal are switched in order to produce a signal indicating, in time multiplex a LED load open circuit and short-circuit indicating signal.
  • the LED driver 800 shown in Fig. 5 comprises an LED load, whose voltage V LED is compared to a reference voltage V ref by the comparator 806. Moreover, the LED driver 800 comprises three resistors Rl, R2, and R3 and two capacitors Cl and C2.
  • the comparator 806 can comprise an operational amplifier, wherein the polarity of the operational amplifier output circuit depends on the polarity of the difference between the two input voltages V LED and V ref .
  • Fig. 6 shows exemplary behaviors of the voltage V LED in an isolated LED driver as a function of time according to the invention.
  • the frequency of variation is 1kHz.
  • Fig. 7 shows a method 1000 for an isolated LED driver 200 according to an embodiment.
  • the method 1000 comprises the following steps: controlling 1002 at least one switch on the primary side of an isolation stage of the LED driver 200; detecting 1004 the voltage 202 on the secondary side of the isolation stage and producing a voltage-representing signal; detecting 1006 the current flowing on the secondary side, and especially the current through an LED load when connected at supply terminals of the LED driver 200; producing 1008 a current-representing signal; combining 1010 for a current-representing signal, optionally a decoupled AC component of the current representing signal, with the voltage representing signal; and
  • Fig. 8 shows a further method 1100 for an isolated LED driver 800 according to an embodiment.
  • the method 1100 comprises the following steps: controlling 1102 at least one switch on the primary side of an isolation stage of the LED driver; detecting 1104 the voltage on the secondary side of the isolation stage and producing a - voltage-representing signal; and switching 1106 the reference level of a comparator and, in synchronization therewith, the polarity of the comparator output signal in order to produce a signal indicating, in time multiplex, a LED load open circuit and short-circuit indicating signal, wherein the comparator is supplied with the voltage representing signal at its non-inverted input.

Landscapes

  • Circuit Arrangement For Electric Light Sources In General (AREA)
  • Led Devices (AREA)

Abstract

L'invention concerne un pilote de DEL isolé (200) à circuit ouvert et court-circuit à une broche comprenant une unité de commande commandant au moins un commutateur sur le côté primaire d'un étage d'isolation du pilote de DEL (200), des moyens de détection de la tension (202) sur le côté secondaire de l'étage d'isolation et de production d'un signal de représentation de tension, des moyens de détection du courant (204) s'écoulant sur le côté secondaire et en particulier du courant à travers une charge de DEL lorsqu'il est connecté à des bornes d'alimentation du pilote de DEL (200) et produisant un signal représentant un courant ainsi qu'un moyen de combinaison pour un signal représentant un courant, éventuellement la composante CA découplée du signal représentant le courant, avec le signal représentant la tension et l'amenant à une broche d'entrée de l'unité de commande.
PCT/EP2020/056545 2019-03-19 2020-03-11 Court-circuit de del amélioré et détection de charge ouverte avec une seule broche de commande WO2020187669A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
EP20715280.2A EP3935919A1 (fr) 2019-03-19 2020-03-11 Court-circuit de del amélioré et détection de charge ouverte avec une seule broche de commande

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
EP19163603.4 2019-03-19
EP19163603.4A EP3713376B1 (fr) 2019-03-19 2019-03-19 Détection améliorée de court-circuit de del et de charge ouverte à l'aide d'une seule broche de contrôleur

Publications (1)

Publication Number Publication Date
WO2020187669A1 true WO2020187669A1 (fr) 2020-09-24

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Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2004057924A1 (fr) * 2002-12-19 2004-07-08 Koninklijke Philips Electronics N.V. Pilote de diodes electroluminescentes
US20180139808A1 (en) * 2016-11-15 2018-05-17 Ledvance Gmbh Lighting system

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR100718828B1 (ko) * 1999-09-17 2007-05-17 코닌클리케 필립스 일렉트로닉스 엔.브이. Ｌｌｃ 컨버터 및 ｌｌｃ 컨버터를 제어하기 위한 방법
US8995156B2 (en) * 2012-12-11 2015-03-31 Eaton Corporation DC/DC converter with resonant converter stage and buck stage and method of controlling the same
US9203318B2 (en) * 2013-12-18 2015-12-01 Texas Instruments Deutschland Gmbh Primary side current regulation on LLC converters for LED driving
CN108702085B (zh) * 2016-02-12 2020-10-30 昕诺飞控股有限公司 Dc/dc谐振转换器和使用谐振转换器的功率因数校正以及对应的控制方法

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2004057924A1 (fr) * 2002-12-19 2004-07-08 Koninklijke Philips Electronics N.V. Pilote de diodes electroluminescentes
US20180139808A1 (en) * 2016-11-15 2018-05-17 Ledvance Gmbh Lighting system

Also Published As

Publication number Publication date
EP3713376B1 (fr) 2024-02-28
EP3713376A1 (fr) 2020-09-23
EP3935919A1 (fr) 2022-01-12

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