EP2936929B1 - Led-converter with frost start function - Google Patents

Description

The invention relates to an LED converter for operating an LED line and a method for operating such an LED line. In particular, the method relates to an LED converter with an electrolytic capacitor (ELKO, ELCAP).

LED converters for operating LED lines are, for example, from the WO 2011/021096 A1 known in which an ELKO is provided, for example after a line filter and / or a rectifier, or in the supply path of the LED section.

When using such an LED converter, however, the problem arises that when used at low temperatures, for example in cold stores, freezers or freezers, but also outdoors, i. H. In general, in environments with low temperatures, for example below -30 ° C or -25 ° C, operation of the LED section cannot be guaranteed.

The reason for this is that at such low temperatures, especially below -25 ° C, the electrolytic capacitor of the LED converter cannot provide enough electrical power for the start-up of the LED path, since part of the electrolyte of the electrolytic capacitor can be frozen.

On the other hand, the internal resistance of the electrolytic capacitor also rises sharply at such low temperatures. Thus, especially if the LED section is to be operated at 100% of its nominal output, there is a risk that the LED section cannot be activated.

It is indeed possible to use electrolytic capacitors which are specified for operation at low temperatures, for example for temperatures below -40 ° C. However, these electrolytic capacitors are much more expensive than the electrolytic capacitors used as standard, so that overall the costs of the LED converter would be greatly increased. Such LED converters would also have to be specially manufactured.

The document is from the prior art WO 2010/108982 A1 known. This document describes that dimming values are limited once during a burn-in process for gas discharge lamps when a converter is started up for the first time.

From the DE 10 2010 006 998 A1 temperature compensation of the luminous flux in LED lights is known. Here, a temperature sensor is electrically connected to a control circuit. If the temperature falls below a threshold, the LED is operated with a reduced current in order to avoid higher energy consumption due to the increasing luminous flux as the temperature decreases.

The document JP 2012 015052 A shows an operating circuit for an LED track. If the operating temperature is low, a frost protection mode is used for starting. The nominal power is limited during a period after the start.

The invention now proposes an LED converter and an operating method to solve the above problem. The LED converter and the method are the subject of the independent claims. Further embodiments of the invention are the subject of the dependent claims.

• wenigstens einen Elektrolytkondensator in einem elektrischen Versorgungspfad, über den die LED-Strecke ausgehend von einer elektrischen Versorgung versorgbar ist, und
• eine Steuerschaltung, die dazu eingerichtet ist, die LED-Strecke zu betreiben,

Die Steuerschaltung ist dazu eingerichtet, die LED-Strecke lediglich in der Betriebsart für tiefe Temperaturen nach jedem Einschalten der elektrischen Versorgung für Zeitdauer mit einer im Vergleich mit der Nennleistung reduzierten Leistung, zu betreiben, und nach Ablauf der Zeitdauer den Betrieb mit nichtreduzierter Leistung freizugeben. Die Zeitdauer ist dabei adaptiv. Die Steuerschaltung ist dabei dazu ausgelegt, die Zeitdauer für den Betrieb mit der reduzierteren Leistung in Abhängigkeit von einer früheren Einschaltdauer und Ausschaltdauer des LED-Konverters zu bestimmen.In a first aspect, the invention provides an LED converter which is set up to selectively operate at least one LED section or other illuminants, depending on a temperature detection, in an operating mode for low temperatures. The LED converter features:

• at least one electrolytic capacitor in an electrical supply path, via which the LED path can be supplied starting from an electrical supply, and
• a control circuit which is set up to operate the LED section,

The control circuit is set up to operate the LED section only in the operating mode for low temperatures after each switch-on of the electrical supply for a period of time with a reduced power compared to the nominal power, and to release the operation with non-reduced power after the time period has expired. The duration is adaptive. The control circuit is designed to determine the period of time for operation with the reduced power as a function of an earlier on period and off period of the LED converter.

The electrolytic capacitor can be supplied starting from an actuator / switching regulator, in particular a DC / DC converter and / or a constant current source. It is only important that the electrolytic capacitor is arranged in the supply path due to its physical properties as a polarized capacitor according to its polarity and is operated with a DC voltage.

The control circuit can be designed as an IC, ASIC, and / or microcontroller.

The control circuit can be set up to change, in particular to increase, the power with which the LED line is operated, after the period of time, preferably to 100% of a nominal power of the LED line and / or a predetermined dimming value. The nominal power can in particular be the power with which the illuminant is operated without derating. The dimming value can be stored in a memory in the LED converter and / or can be transmitted to the LED converter via the bus.

Furthermore, the LED converter can have a temperature sensor which detects the temperature in / on the LED converter, in particular on the electrolytic capacitor and / or the actuator / switching regulator. In particular, a temperature sensor provided to protect the electrolytic capacitor from overheating can be used for the temperature detection.

The parameters influencing the light output of the LED path for the operation of the LED path with reduced power, in particular the duration, and parameters for the subsequent operation of the LED path can be stored as a dimming profile in the control circuit.

• elektrisches Versorgen der LED-Strecke ausgehend von einer elektrischen Versorgung, über einen Versorgungspfad mit wenigstens einem Elektrolytkondensator,
• Betreiben der LED-Strecke,
  wobei das Betreiben der LED-Strecke lediglich in der Betriebsart für tiefe Temperaturen nach jedem Einschalten der elektrischen Versorgung für eine Zeitdauer mit einer im Vergleich der Nennleistung reduzierten Leistung erfolgt, und
• Freigeben eines Betriebs mit nichtreduzierter Leistung nach Ablauf der Zeitdauer. Die Zeitdauer ist dabei adaptiv. Die Zeitdauer für den Betrieb mit der reduzierteren Leistung wird in Abhängigkeit von einer früheren Einschaltdauer und Ausschaltdauer des LED-Konverters bestimmt.

In a further aspect, the invention provides a method for operating an LED link in which the LED link is operated selectively, depending on a temperature detection in an operating mode for low temperatures, with the steps:

• electrical supply of the LED section starting from an electrical supply, via a supply path with at least one electrolytic capacitor,
• Operating the LED line,
  wherein the LED section is operated only in the operating mode for low temperatures after each switching on of the electrical supply for a period of time with a reduced power compared to the nominal power, and
• Enable an operation with non-reduced power after the time period has expired. The time period is adaptive. The time period for the operation with the reduced power is dependent on one earlier on time and off time of the LED converter determined.

In another aspect, the invention provides a control circuit, in particular ASIC or microcontroller, which is designed to carry out a method as described above or for an LED converter as described above.

In yet another aspect, the invention provides an LED light for low ambient temperatures, comprising an LED path and an LED converter, as described above.

Fig. 1

schematisch einen beispielhaften Schaltungsaufbau für einen LED-Konverter gemäß der Erfindung,

Fig. 2

exemplarisch zeitliche Kurvenverläufe für einen erfindungsgemäßen LED-Konverter,

Fig. 3

einen exemplarischen Kurvenverlauf eines Ersatzwiderstandes (ESR, Equivalent Series Resistor) im Verhältnis zur Temperatur, und

temperaturabhängige Zeitdauer mit einer im Vergleich der Nennleistung reduzierten Leistung, insbesondere mit einem bestimmten Dimmwert, und Freigeben eines Betriebs mit nichtreduzierter Leistung nach Ablauf der Zeitdauer.The invention and further aspects of the invention are now also shown with reference to the figures. Show:

Fig. 1

schematically an exemplary circuit structure for an LED converter according to the invention,

Fig. 2

Exemplary temporal curves for an LED converter according to the invention,

Fig. 3

an exemplary curve profile of an equivalent resistor (ESR, equivalent series resistor) in relation to temperature, and

Temperature-dependent period of time with a power reduced in comparison to the nominal power, in particular with a specific dimming value, and release of an operation with non-reduced power after the time period has expired.

In another aspect, the invention provides a control circuit, in particular ASIC or microcontroller, which is designed to carry out a method as described above or for an LED converter as described above.

In yet another aspect, the invention provides an LED light for low ambient temperatures, comprising an LED path and an LED converter, as described above.

Fig. 1

schematisch einen beispielhaften Schaltungsaufbau für einen LED-Konverter gemäß der Erfindung,

Fig. 2

exemplarisch zeitliche Kurvenverläufe für einen erfindungsgemäßen LED-Konverter,

Fig. 3

einen exemplarischen Kurvenverlauf eines Ersatzwiderstandes (ESR, Equivalent Series Resistor) im Verhältnis zur Temperatur, und

Fig. 4

schematisch eine Veränderung der Kapazität des Elektrolytkondensators in Abhängigkeit zur Temperatur.

The invention and further aspects of the invention are now also shown with reference to the figures. Show:

Fig. 1

schematically an exemplary circuit structure for an LED converter according to the invention,

Fig. 2

Exemplary temporal curves for an LED converter according to the invention,

Fig. 3

an exemplary curve profile of an equivalent resistor (ESR, equivalent series resistor) in relation to temperature, and

Fig. 4

schematically a change in the capacitance of the electrolytic capacitor depending on the temperature.

The invention now provides that the LED converter, which is designed for the operation of the LED section at very low temperatures, provides a frost start function (frosty start) that can be activated or fixed. In particular, the LED converter operates an LED section in such a way that each time an electrical supply to the LED converter is switched on for a predetermined time, for example 10 seconds, the LED section is always operated in a strongly dimmed manner, for example with a dimming value of 10% of the Nominal power of the LED track. An operating mode for low temperatures is referred to as the frost start function, the term “frost” generally denoting the occurrence of temperatures below 0 ° C.

In Fig. 1 A circuit is shown as an example, on the basis of which the operation of the LED converter is described below.

The Fig. 1 shows an LED converter 1 with a rectifier 2, which converts an electrical variable supplied to the LED converter 1, for example an alternating current / alternating voltage, into a direct current / direct voltage. However, it can also be provided that the LED converter 1 is supplied by an electrical supply which already supplies a direct voltage / direct current.

In the schematic illustration, an electrolytic capacitor 3 is also connected at the output of the rectifier 2, which is fed, for example, from the mains. In the LED converter, however, the electrolytic capacitor 3 can be provided elsewhere and a plurality of electrolytic capacitors can also be provided. In particular, the electrolytic capacitor 3 can also be provided after an actuator or a switching regulator 4, in this case a DC / DC converter or a constant current source or a PFC circuit.

Overall, the LED converter 1 is used to operate an LED section 5, which can consist of at least one LED. A control circuit 6 is typically also provided, to which an internal or external signal can be supplied and which sets a parameter of the switching regulator 4 (or e.g. the constant current source) which influences the light output of the LED path 5.

In particular, the control circuit 6 can actuate the switch regulator 4 after the predetermined time has elapsed so that the LED section 5 is operated with a higher output, in particular 100% of its nominal output. It is therefore provided that the control circuit (for example an IC, ASIC or a microcontroller, etc.) controls the frost start function, ie the strongly dimmed LED operation for the specified time each time the LED converter is switched on. In particular, this frost start function can be programmed in the software of the control unit 6 of the LED converter 1. The control unit 6 is therefore preferably implemented as an integrated circuit ASIC or as a microcontroller.

In the frost start mode, the electrolytic capacitor 3 can provide sufficient power even at low temperatures to operate the LED section 5 in this strongly dimmed mode. In addition, the current flow through the electrolytic capacitor 3 heats the electrolytic capacitor 3. While the electrolytic capacitor 3 heats up at about 60 ° C. to 70 ° C. at normal temperature, the electrolytic capacitor self-heats to about 20 ° C. to 30 ° even at the low temperatures mentioned C given.

Thus, in strongly dimmed operation, the electrolytic capacitor 3 likewise heats up above a temperature of approximately −25 ° C., as a result of which frozen electrolyte may thaw and the electrolytic capacitor 3 can provide more power.

The time period in which the LED path 5 is operated with reduced power is therefore chosen in particular in such a way that the electrolytic capacitor 3 is sufficiently heated after the time period has expired, that is to say in particular has assumed a temperature of above -25 ° C. After the specified time has elapsed, operation with higher power, in particular with 100% rated power, can then be set.

In general, the time period can be monitored and set by the control circuit 6. In the simplest case, the control circuit 6 has only one timer / timer 8, so that the control circuit determines the time duration Power changed on an internal signal from the timer / timer 8, with which the LED path 5 is operated.

However, the control circuit 6 can also receive an external signal, for example from a bus, in particular from a DALI / DSI bus, and, depending on this, execute the frost start function. In particular, provision can be made to activate / deactivate the frost start function by means of an external signal, or to set the time period for operation with reduced power. It can further be provided that the control circuit does not receive the signal via the bus, but rather receives a signal via the supply lines and interprets it accordingly. This variant is in Fig. 1 not shown. For example, a certain switching sequence and / or a selective rectification of the mains supply could be interpreted in such a way that the time period is set thereby, or the frost start function is activated / deactivated. Such an entry can be made, for example, using a (power) switch or button.

The LED converter 1 can also have a temperature sensor 7. The temperature sensor 7 can be provided on or in the vicinity of the electrolytic capacitor 3 or the converter 4 and / or the LED section 5. If several electrolytic capacitors are used, several temperature sensors 7 can of course also be provided. This means that a frost start can be carried out selectively depending on temperature detection. In particular, when detecting lower temperatures the specified frost start time can be extended. At higher temperatures, the time period can be shortened or the frost start function can be deactivated.

If an external signal can be supplied to the control circuit 6, it is also possible to supply the control circuit with a temperature signal from a temperature detection unit external to the LED converter 1. The time period can thus be dependent, for example, on an ambient temperature, e.g. a (global) outside temperature sensor.

A memory, for example a look-up table, can be provided in the control circuit 6. There it can be stored which time period is to be set for which temperature or for a specific temperature range. With a continuous detection of the temperature, the cold start can also be terminated if the detected temperature is interpreted to mean that the relevant electrolytic capacitor 3 has heated up to a predetermined temperature, for example above -25 ° C. Of course, a temperature sensor can also be used for temperature detection, which is provided to prevent the electrolytic capacitor 3 / the LED converter 1 from heating up beyond a threshold value, for example in order to avoid overheating. In this case, the evaluation of the recorded temperature is modified accordingly in order to implement the frost start function. The control circuit 6 is preferably adapted accordingly in order to also evaluate the low temperatures accordingly.

It should also be understood that the LED converter can be designed to generally, i.e. even after frost start, to enable dimming operation of LED section 5. However, this is not necessary. In particular, the LED converter 1 can also be a so-called fixed output device that always operates the LED section with 100% of its nominal power. Only one actuator is to be provided in this case, which the strongly dimmed operation, ie. H. Operation with greatly reduced (light) power allowed after each switch-on (mains reset) of the electrical supply of the LED converter.

If it can be concluded from the detected temperature that the temperature at the electrolytic capacitor 3 is sufficiently high, the frost start can be deactivated. If, for example, the temperature, directly or indirectly, of the electrolytic capacitor 3 is evaluated such that the temperature of the electrolytic capacitor 3 is sufficiently high, the operation can be immediately set to 100% or another dimming value.

The control circuit 6 can, however, also detect a switch-on / switch-off period of the LED converter, for example with the aid of the timer / timer 8. Thus, in the sense of a time measurement, the control circuit 6 can, for example, detect whether a switch-on period is sufficiently long and / or a switch-off period is sufficient was short, so that based on the time measurement it can be assumed that the electrolytic capacitor 3 is still sufficiently heated. So in the memory of the control circuit For example, a table can also be stored which specifies the time period as a function of the switch-off time period. If, for example, the LED converter has already been switched off for a longer period of time, the time period can be selected longer, whereas if the switch-off period is short, no frost start may be necessary.

The frost start function of the LED converter 1 is preferred, comparable to a dimming profile, stored in the control circuit on the part of the manufacturer, or the frost start function is implemented by a dimming profile.

It should be noted that the method mentioned cannot be used, for example, for gas discharge lamps, since too much power is required for starting in gas discharge lamps, so that it cannot be provided by the electrolytic capacitor 3 at the low temperatures. The cold start function can also be carried out by changing the software / firmware of the control circuit 6.

If several electrolytic capacitors 3 are used, a temperature sensor 7 can also be provided for each electrolytic capacitor, and the temperature at the electrolytic capacitors can be recorded individually. The duration of the frost start function can then be set, for example, as a function of a recorded maximum / minimum temperature value or an average of the recorded temperatures.

Fig. 2 now shows a curve for an LED converter 1 according to the invention. The vertical axis shows the capacitor temperature T _c in degrees Celsius, an ambient temperature T _a (ambient temperature) in degrees Celsius and a dimming value DL (dimming level) in percent of the nominal power . The equivalent resistance (ESR, Equivalent Series Resistance) is also plotted. Time is plotted on the transverse axis.

Is shown in Fig. 2 that at the time (1) at a temperature of approximately -30 ° C., the operation of the LED converter 1 takes place with a low dimming value, for example 10% of the nominal power of the LED path 6 (ie in particular 10% of the light power).

The electrolytic capacitor 3 now heats up to the point in time (2) to approximately -25 ° C. continuously. At the same time it can be seen that the equivalent resistance (ESR), which at time (1) is still approximately ten times the equivalent resistance of the electrolytic capacitor 3 at approximately 20 ° C., is continuously decreasing.

At time (2), i.e. after the period of time, the power with which the LED sections 5 are to be operated is continuously increased in a relatively short time (fade in, fade to 100%) until a predetermined light output, here 100%, is reached.

It can also be seen at time (3) that the temperature of the electrolytic capacitor 3 has risen steadily and the equivalent resistance is significantly lower and itself in the direction of the equivalent resistance with a factor of 1. At time (3), the operating temperature of the electrolytic capacitor 3 is reached and the capacitance of the electrolytic capacitor 3 and its equivalent resistance normalize.

Fig. 3 shows the course of the equivalent resistance (ESR) for several frequencies (upper curve 100Hz, middle curve 1KHz, lower curve 100KHz) at different temperatures in a temperature range from -40 ° C to approx. 80 ° C. It can be clearly seen that at a temperature of -40 ° C to -30 ° C the equivalent resistance of the electrolytic capacitor is about ten times higher than at a temperature of 10 ° C to 20 ° C or 60 ° C to 80 ° C.

Fig. 4 also shows that the capacitance of the electrolytic capacitor increases continuously as the temperature rises, and thus at higher temperatures, ie after self-heating of the electrolytic capacitor 3, a higher output can be called up from the LED path 5 or the LED path through the control circuit 6 can be operated with a higher output.

Overall, the invention thus has the advantages that the reduced capacitance and the high equivalent resistance of the electrolytic capacitor 3 are not a problem at low temperatures and the LED path 5, which initially represents a low load for LED converters 1, is nevertheless operated reliably can. In addition, the temperature ranges in which the LED converter can be increased by the method according to the invention and the converter according to the invention 1 can be used. Thus, in particular, the costs for producing the LED converter 1 can be reduced or remain the same, since no electrolytic capacitors are required which are specified / certified for temperatures below -25 ° C, -30 ° C or -40 ° C.

It is also advantageous that LEDs work highly efficiently at low temperatures and even have a longer lifespan. In addition to LEDs, however, other illuminants can also be operated which can be started with an initially reduced output, in particular in strongly dimmed operation.

Claims (12)

1. An LED converter (1), which is configured to operate at least one LED series (5) selectively, depending on a temperature detection in an operating mode for low temperatures, having:

   - at least one electrolytic capacitor (3) in an electrical supply path, via which the LED series (5) can be supplied starting from an electrical supply, and

   - a control circuit (6), that is configured to operate the LED series (5),

   wherein the control circuit (6) is configured to operate the LED series (5) only in the operating mode for low temperatures every time the electrical supply is switched on for a period of time at a reduced power compared with a nominal power, and after expiry of the period of time to enable an operation at non-reduced power,
   characterized in
   that the period of time is adaptive, and that the control circuit (6) is designed to determine the period of time for the operation at the reduced power in dependence on a previous switched-on time and switched-off time of the LED converter (1).
2. The LED converter (1) according to Claim 1,
   wherein the electrolytic capacitor (3) is designed, in order to be supplied from an actuator/switching regulator (4).
3. The LED converter (1) according to any one of the preceding claims,
   wherein the control circuit (6) is designed as an IC, ASIC, and/or microcontroller.
4. The LED converter (1) according to Claim 3,
   wherein the control circuit can be connected to a bus, wherein the bus, in particular, is a DALI bus or a DSI bus.
5. The LED converter (1) according to Claim 3 or 4,
   wherein the control circuit (6) is configured to increase the power, with which the LED series is operated, after a period of time, or wherein the control circuit (6) is configured to increase the power, at which the LED series is operated after a period of time to 100% of the nominal power of the LED series (5) and/or to increase to a different dimming value, wherein the different dimming value is stored in a memory of the LED converter (1) and/or is transmitted via the bus to the LED converter (1).
6. The LED converter (1) according to any one of the preceding claims, which further has a temperature sensor (7), which detects the temperature in/at the LED converter (1), and/or at the electrolytic capacitor (3) and/or at the actuator/switching regulator (4), or wherein temperature sensor (7) provided to protect the electrolytic capacitor (3) from an overheating is used for the temperature detection.
7. The LED converter (1) according to Claim 6, wherein the control circuit (6) is designed to set the period of time for the operation at the reduced power in dependence on a temperature detected at the electrolytic capacitor (3) and/or at the actuator/switching regulator (4), and
   wherein the control circuit (6) sets the period of time in dependence on a stored value corresponding to the detected temperature.
8. The LED converter (1) according to Claim 5, wherein the parameters determining the light output of the LED series (5), and parameters for the operation of the LED series (5) are stored in the memory, preferably as a dimming profile, in the control circuit (6).
9. The LED converter (1) according to any one of the preceding claims, wherein the reduced power corresponds to 5-15%, of the nominal power, of the LED series (5).
10. A method for the operation of an LED series (5), wherein the LED series is operated selectively, depending on a temperature detection in an operating mode for low temperatures,
    wherein the method has the following steps:

    - electrical supply of the LED series (5) starting from an electrical supply, via a supply path with at least one electrolytic capacitor (3) and

    - operation of the LED series (5),

    wherein the operation of the LED series (5) takes place only in the operating mode for low temperatures after each switching on of the electrical supply for a period of time at a reduced power compared to a nominal power, and
    wherein an enabling of an operation at non-reduced power takes place after expiry of a period of time,
    characterized in
    that the period of time is adaptive, and
    that the period of time for the operation at the reduced power is determined in dependence on a previous switched-on time and switched-off time of the LED converter (1).
11. A control circuit (6), which is designed for carrying out a method according to Claim 10 or for an LED converter according to any one of Claims 1 to 9.
12. An LED light for low ambient temperatures, having an LED series (5) and an LED converter (1) according to any one of Claims 1 to 9.

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