EP4637270A1

EP4637270A1 - Driver system and method of operating a driver system

Info

Publication number: EP4637270A1
Application number: EP24170915.3A
Authority: EP
Inventors: Miguel Philipp Schneider; Fabio Romano
Original assignee: Tridonic GmbH and Co KG
Current assignee: Tridonic GmbH and Co KG
Priority date: 2024-04-18
Filing date: 2024-04-18
Publication date: 2025-10-22

Abstract

The invention relates to driver system (10) for electrically supplying at least one load (20). The driver system (10) comprises: two or more drivers (11) which are connected in parallel; wherein each of the two or more drivers (11) is configured to supply a regulated nominal DC output voltage; and wherein, upon being switched on, each of the two or more drivers (11) is configured to regulate its DC output voltage for a defined time period to an intermediate voltage level, which is lower than a voltage level of its nominal DC output voltage.

Description

TECHNICAL FIELD OF THE INVENTION

The invention relates to the field of drivers, in particular LED drivers, which are connected in parallel for supplying a load.

BACKGROUND OF THE INVENTION

When connecting multiple LED drivers in parallel, it is important to ensure that the connected drivers are started (e.g., after switching on a mains supply voltage) at the same time. However, this is difficult to realize if the drivers do not directly communicate with each other.
For instance, if the start of a single LED driver in a system of parallel drivers is delayed, the remaining LED drivers will attempt to provide the full electrical power to the load by themselves. However, they are typically not designed to provide this performance over a longer period of time which may cause problems, such as an error shutdown of these drivers.
For protecting an LED driver and the connected load, the drivers typically comprise numerous such error shutdowns. A detection of an error may cause a driver to shut down and automatic restart to comply with all standards (so-called second cycle). An incorrectly detection of an error condition can also cause a switch on delay for an individual driver, preventing a synchronous start of all drivers.

SUMMARY OF THE INVENTION

Thus, it is an objective of the invention to provide an improved driver system and an improvised method of operating a driver system, which avoid the above-mentioned disadvantages.
The object of the present invention is achieved by the solution provided in the enclosed independent claims. Advantageous implementations of the present invention are further defined in the dependent claims.
According to a first aspect, the invention relates to a driver system for electrically supplying at least one load. The driver system comprises: two or more drivers which are connected in parallel; wherein each of the two or more drivers is configured to supply a regulated nominal DC output voltage; and wherein, upon being switched on, each of the two or more drivers is configured to regulate its DC output voltage for a defined time period to an intermediate voltage level, which is lower than a voltage level of its nominal DC output voltage.
This achieves the advantage that the switch-on of parallel connected LED drivers can be synchronized. Regulating the DC output voltage to the intermediate level (also referred to as: intermediate voltage) can represent a signaling by which a driver indicates to the other drivers of the system that it was switched on and will provide its nominal DC output soon (i.e., after the defined time period has lapsed). Detection of this intermediate signal can prompt the other drivers to switch on at a certain (synchronous) point in time as well.
For instance, the intermediate voltage level is chosen such that the resulting current through the load is zero (e.g., in case of LED loads) or so low that the electrical power to be provided for a certain amount of time can be provided by a single driver. Thus, the intermediate voltage level is lower than a voltage level of the nominal DC output voltage of the driver.
The at least one load can comprise at least one LED load, e.g. an LED luminaire and/or at least one DCDC converter.
Thus, each of the two or more drivers can be an LED driver and the driver system can be an LED driver system.
The two or more drivers can be essentially identical in construction and/or their respective nominal DC voltage can be identical.
Hereby, switching on a driver may refer to a switching on of its supply voltage. Thus, the driver being switched on may refer to the driver being activated or turned on. Likewise, the driver being switched off may refer to the driver being deactivated or turned off (i.e., it does not provide the DC output voltage).
In an embodiment, each of the two or more drivers is configured to regulate its DC output voltage from the intermediate voltage level to the level of its nominal DC output voltage after the defined time period has passed. This achieves the advantage that after the "synchronization phase", the drivers can provide their nominal output voltage to power the load.
In an embodiment, each of the two or more drivers comprises a voltage sensing circuit configured to detect a voltage level on its output side when the driver is switched off.
For example, the voltage sensing circuit is configured to measure a voltage which is applied at the output terminals of the driver when the driver is switched off.
In an embodiment, each of the two or more drivers, which is switched off, is configured to switch on again if the detected voltage level on its output side corresponds to the intermediate voltage level.
In an embodiment, upon detecting that the voltage level on its output side corresponds to the intermediate voltage level, the respective driver is configured to switch on again immediately or after a defined waiting time has lapsed. This achieves the advantage that the switch on of the drivers can be synchronized.
In an embodiment, upon being switched on due to detecting that the voltage level on its output side corresponds to the intermediate voltage level, the respective driver is configured to regulate its DC output voltage immediately to its nominal DC output voltage.
In an embodiment, upon being switched on due to detecting that the voltage level on its output side corresponds to the intermediate voltage level, the respective driver is configured to regulate its DC output voltage to a further intermediate voltage level which is between the intermediate voltage level and the voltage level of its nominal DC output voltage.
For instance, the driver regulates its DC output voltage to the further intermediate voltage level for a further defined time period after which it regulates its DC output voltage to its nominal DC voltage.
In other words: if a driver is switched on due to detecting the intermediate voltage on its output, indicating that another driver of the system was just switched on, the driver may not regulate its output voltage to the same intermediate voltage, but to a further intermediate voltage (higher than the intermediate voltage). This may constitute to the sending of a handshake signal by which the driver indicates its readiness to provide its nominal DC output voltage. Alternatively, when being switched on due to detecting an intermediate voltage level, the driver may directly regulate its output voltage to its nominal DC output voltage (foregoing any intermediate voltage level).
In an embodiment, each of the two or more drivers comprises a respective control unit which is configured to regulate its DC output voltage. For instance, the control unit is an integrated circuit (IC), such as an ASIC.
According to a second aspect, the invention relates to a lighting system comprising: at least one LED load; and a driver system according to the first aspect of the invention.
In particular, the driver system supplies the at least one LED load.
According to a third aspect, the invention relates to a method of operating a driver system, wherein the driver system comprises two or more drivers which are connected in parallel, wherein each of the two or more drivers is configured to supply a regulated nominal DC voltage. The method comprises: regulating a DC output voltage of one of the drivers for a defined time period upon being switched on to an intermediate voltage level, which is lower than a voltage level of its nominal DC output voltage.
In an embodiment, the method further comprises: regulating the DC output voltage of the driver from the intermediate voltage level to its nominal DC voltage after the defined time period has passed.
In an embodiment, the method further comprises: detecting the intermediate voltage level on an output side of at least one further driver of the two or more drivers, which is switched off.
In an embodiment, the method further comprises: switching on the at least one further driver if the detected voltage level on its output side corresponds to the intermediate voltage level.
For instance, the at least one further driver can be switched on immediately or after a defined waiting time has lapsed.
In an embodiment, upon being switched on due to detecting that the voltage level on its output side corresponds to the intermediate voltage level, the DC output voltage of the at least one further driver is regulated to its nominal DC output voltage immediately.
In an embodiment, upon being switched on due to detecting that the voltage level on its output side corresponds to the intermediate voltage level, the DC output voltage of the at least one further driver is regulated to a further intermediate voltage level which is between the intermediate voltage level and the voltage level of its nominal DC output voltage.
The method according to the third aspect of the invention can be carried out by the driver system according to the first aspect of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be explained in the followings together with the figures.

Fig. 1: shows a schematic diagram of a driver system according to an embodiment;
Fig. 2: shows a schematic diagram of a driver according to an embodiment;
Figs. 3A-B: show changes of an output voltage during operation of a driver system according to an embodiment; and
Fig. 4: shows a flow diagram of a method of operating a driver system according to an embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Fig. 1 shows a schematic diagram of a driver system 10 for electrically supplying at least one load 20 according to an embodiment.
The driver 10 system comprises: two or more drivers 11 which are connected in parallel; wherein each of the two or more drivers 11 is configured to supply a regulated nominal DC output voltage; and wherein, upon being switched on, each of the two or more drivers 11 is configured to regulate its DC output voltage for a defined time period to an intermediate voltage level, which is lower than a voltage level of its nominal DC output voltage.
Thus, when starting a driver 11 of the system 10, the driver 11 may regulate its DC output voltage not immediately to the nominal DC output voltage, but to the reduced intermediate level for the defined time period. The output voltage at the intermediate level may represent a signaling. For instance, the output voltage at the intermediate level signals the other drivers 11 of the system 10 that the driver providing the output voltage at the intermediate level was switched on. The output voltage at the intermediate level can be a first signal of a handshake sequence between the drivers 11 of the system 10.
The intermediate voltage level is lower than a voltage level of the nominal DC output voltage of the driver 11. For instance, the intermediate voltage level is chosen such that the resulting current through the load 20 is zero (e.g., in case of LED loads) or so low that the electrical power to be provided for a certain amount of time can be provided by a single driver 11.
Each of the two or more drivers 11 can be configured to regulate its DC output voltage from the intermediate voltage level to the level of its nominal DC output voltage after the defined time period has lapsed. Thus, after signaling the switch-on (or start-up) via the intermediate voltage level, the driver 11 can start its normal operation.
The at least one load 20 can comprise at least one LED load, e.g. an LED luminaire and/or at least one DCDC converter.
Thus, each of the two or more drivers 11 can be an LED driver and the driver system 10 can be an LED driver system.
The two or more drivers 11 can be essentially identical in construction and/or their respective nominal DC voltage can be identical.
The system 10 shown in Fig. 1 comprises two parallel connected drivers 11, each providing an electrical power of 100 W, which supply a load at 200 W. However, the number of drivers and loads and their performance parameters in Fig. 1 are just an example. The system 10 could comprise a larger number of drivers 11 which are regulated to different DC output voltages and/or a larger number of loads.
Hereby, "switching on" a driver 11 may refer to a switching on of its supply voltage. After the driver 11 is switched on, it may convert the supply voltage to the DC output voltage which is provided at its output terminals. Thus, the driver 11 being switched on may refer to the driver being started, activated or turned on. Likewise, the driver being switched off may refer to the driver being stopped, deactivated or turned off (i.e., it does not provide the DC output voltage).
For instance, if a driver 11 is switched on after a restart, e.g. an automatic restart due to an error detection, it regulates its output voltage to the intermediate voltage level for the defined time period. However, if the driver is switched on due to receiving an intermediate voltage level from another driver in the system it might immediately regulate its DC output level to its nominal value or to a further intermediate voltage level (as will be discussed below).
The supply voltage which is received by each driver 11 can be an AC supply voltage, e.g. a mains voltage.
The driver system 10 and the at least one LED load 20 as shown in Fig. 1 can form a lighting system.
Fig. 2 shows a schematic diagram of a driver 11 of the system 10 according to an embodiment. For instance, each driver 11 of the system shown in Fig. 1 can be configured as shown in Fig. 2.
The driver 11 comprises input terminals 14 for receiving the supply voltage (e.g., the mains supply) and output terminals 15 for providing the DC output voltage. Each driver may further comprise a converter circuit 16 configured to convert the AC input signal to the DC voltage signal.
The driver 11 may further comprise a control unit 13 which is configured to regulate its DC output voltage.
The control unit 13 can be an integrated circuit (IC), such as an ASIC. For example, the control unit 13 controls an internal switch of the driver (e.g., of the converter circuit 16) to control its DC output voltage.
The driver 11 can have an automatic restart capability. For instance, after an error shutdown (e.g., a shutdown due to an error detection) the driver 11 can carry out an automatic restart (so-called "second cycle"). For instance, an error could be caused by an incompatible load which draws too much power from the driver 11.
The driver 11 may further comprise a voltage sensing circuit 12 which is configured to detect a voltage level on its output side when the driver 11 is switched off (i.e., when the driver does not provide its DC output voltage).
The voltage sensing circuit 12 can be configured to measure a voltage or more specifically a voltage level which is applied at the output terminals 15 of the driver 11.
For instance, by means of its voltage sensing circuit 12, a switched off driver 11 can detect if another driver 11 of the system 10, which is connected in parallel, provides a DC output voltage at the intermediate level indicating that it was just switched on.
For example, the intermediate voltage level may be detected if the voltage sensing circuit 12 senses that the voltage level on the output side of the driver 11 is lower than a threshold value or between a first and a second threshold value.
If a switched-off driver 11 detects a DC voltage at the intermediate level on its output side, it can be configured to switch on in a defined time period after said detection of the intermediate voltage signal.
For instance, upon detecting that the voltage level on its output side corresponds to the intermediate voltage level, the driver 11 can switch on immediately or after a defined waiting time has lapsed. By appropriately choosing this waiting time, the switch on of the drivers in the system can be synchronized such that all drivers 11 start to provide their nominal DC output voltage simultaneously.
Moreover, when a driver is switched on due to detecting the intermediate voltage level, it could also immediately regulate its DC output voltage to its nominal DC output voltage.
Alternatively, when being switched on after detecting the intermediate voltage signal, the driver 11 can be configured to regulate its DC output voltage to a further intermediate voltage level which is between the intermediate voltage level and the voltage level of its nominal DC output voltage. For instance, the driver regulates its DC output voltage to the further intermediate voltage level for a further defined time period after which it regulates its DC output voltage to its nominal DC output voltage.
By issuing the further intermediate voltage signal, it can be signaled to the driver 11 which issued the intermediate voltage signal that the other parallel driver(s) 11 of the system 10 are operational and ready to start.
Figs. 3A-B show changes of an output voltage of the driver system 10 during operation according to an embodiment. Thereby, a driver system 10 which comprises two drivers 11 is assumed. However, the principles shown in Figs. 3A-B also apply to more complex driver systems 10 with a larger number of drivers 11.
The two bottom curves in Figs. 3A-B indicate the activation and deactivation of the first and second driver drv1, drv2 of the system 10. The upper curve shows the DC output voltage of the system 10. For instance, both drivers drv1, drv2 provide an identical nominal DC output voltage of e.g. 48 V.
In both Fig. 3A and 3B, the driver drv1 switches off due to an error detection. Since the further driver drv2 cannot provide the load of 200 W by itself, the further driver drv2 also switches off due to an error and the DC output voltage of 48 V collapses.
If an automatic restart is possible, both drivers drv1, drv2 will immediately start to monitor the voltage level on their output sides after their respective switch-off, e.g. using their respective voltage sensing circuits 12.
As shown in Fig. 3A, the driver drv1, which was switched off first may wait for a certain time interval after its switch off (e.g., 400 ms), and then regulate its DC output voltage to the intermediate voltage level V_scr (second cycle ready, e.g., 30 V). By providing its DC output voltage at this intermediate voltage level, the driver can signal to the other drivers in the system 10 that it will provide its nominal DC output voltage at a certain time in the future, namely exactly after the defined time period (e.g., 50 ms). The other drivers in the system (in Fig. 3A: driver drv2) can detect the intermediate voltage signal V_scr immediately and start to provide their nominal DC output voltage after the defined time period (e.g., 50 ms). Thus, as shown in Fig. 3A, all drivers of the system can start to provide their nominal DC output voltage at the same time.
However, in the example shown in Fig. 3A, the driver drv1 might not know if the driver drv2 is ready for a restart. If driver drv2 is not operational, this might cause a situation where only driver drv1 is switched on and regulated to its nominal voltage, causing again a switch-off of driver drv1 because the total load is too high. To avoid this situation, a plurality of voltage levels can be added.
Fig. 3B shows an example where the "handshake" between drivers is further extended and improved.
Upon receiving the intermediate voltage signal (e.g., 30 V), from one of the drivers, the further driver(s) of the system (in Fig. 3B, driver drv2) can regulate their DC output voltage to the further intermediate voltage signal (e.g., 35V). In this way, the further driver(s) can signal their readiness for a restart.
After the further driver(s) have signaled their readiness, all drivers can regulate their DC output voltage to their respective nominal voltage level after a defined fixed time interval (e.g., 100 ms).
For example, the load 20 might not be an ohmic resistance which draws current at any applied voltage, but a DCDC converter or LEDs. Thus, the load 20 might only have a high power consumption when a minimum voltage level is reached (e.g., 46 V). The intermediate voltage level(s) can be chosen to be lower than the minimum voltage level at which the load 20 draws power. This can prevent an unwanted restart of a drivers providing an intermediate voltage signal. At most, the intermediate voltage(s) might charge a number of electrolytic capacitors of the load 20.
In summary, the intermediate voltage(s) allow for a synchronization of an automatic restart (second cycle) of parallel connected drivers 11 without requiring a direct communication between the drivers. Not requiring such a communication allows to reduce the complexity of the drivers 11.
Fig. 4 shows a flow diagram of a method 40 of operating the driver system 20 according to an embodiment. The driver system 20 can be a system as shown in Fig. 1 which comprises two or more drivers 11 which are connected in parallel, wherein each of the two or more drivers 11 is configured to supply a regulated nominal DC output voltage.
The method 40 comprises: regulating 41 the DC output voltage of one of the drivers 11 for the defined time period upon being switched on to the intermediate voltage level, which is lower than the voltage level of its nominal DC output voltage.
The method 40 may comprise the further step of: regulating 42 the DC output voltage of the driver 11 from the intermediate voltage level to the level of its nominal DC output voltage after the defined time period has passed.
For instance, the method 40 further comprises: detecting 43 the intermediate voltage level on an output side of at least one further driver of the two or more drivers 11, which is switched off; and switching on 44 said at least one further driver 11 if the detected voltage level on its output side corresponds to the intermediate voltage level. This switch on can be carried out immediately or after a certain waiting time after detecting the intermediate voltage level.
For instance, upon being switched on after detecting that the voltage level on its output side corresponds to the intermediate voltage level, the DC output voltage of the at least one further driver 11 is regulated to its nominal DC output voltage immediately.
Alternatively, upon being switched on after detecting that the voltage level on its output side corresponds to the intermediate voltage level, the DC output voltage of the at least one further driver 11 can be regulated to the further intermediate voltage level which is between the intermediate voltage level and the voltage level of its nominal DC output voltage.
Although the invention has been illustrated and described with respect to one or more implementations, equivalent alternations and modifications will occur to those skilled in the art upon the reading of the understanding of the specification and the annexed drawings. In addition, while a particular feature of the invention may have been disclosed with respect to only of the several implementations, such features may be combined with one or more other features of the other implementations as may be desired and advantage for any given or particular application.

Claims

A driver system (10) for electrically supplying at least one load (20), comprising:
two or more drivers (11) which are connected in parallel; wherein each of the two or more drivers (11) is configured to supply a regulated nominal DC output voltage; and

wherein, upon being switched on, each of the two or more drivers (11) is configured to regulate its DC output voltage for a defined time period to an intermediate voltage level, which is lower than a voltage level of its nominal DC output voltage.
The driver system (10) of claim 1,
wherein each of the two or more drivers (11) is configured to regulate its DC output voltage from the intermediate voltage level to the level of its nominal DC output voltage after the defined time period has passed.
The driver system (10) of claim 1 or 2,
wherein each of the two or more drivers (11) comprises a voltage sensing circuit (12) configured to detect a voltage level on its output side when the driver (11) is switched off.
The driver system (10) of claim 3,
wherein each of the two or more drivers (11), which is switched off, is configured to switch on again if the detected voltage level on its output side corresponds to the intermediate voltage level.
The driver system (10) of claim 4,
wherein, upon detecting that the voltage level on its output side corresponds to the intermediate voltage level, the respective driver (11) is configured to switch on again immediately or after a defined waiting time has lapsed.
The driver system (10) of claim 4 or 5,
wherein, upon being switched on due to detecting that the voltage level on its output side corresponds to the intermediate voltage level, the respective driver (11) is configured to regulate its DC output voltage immediately to its nominal DC output voltage.
The driver system (10) of claim 4 or 5,
wherein, upon being switched on due to detecting that the voltage level on its output side corresponds to the intermediate voltage level, the respective driver (11) is configured to regulate its DC output voltage to a further intermediate voltage level which is between the intermediate voltage level and the voltage level of its nominal DC output voltage.
The driver system (10) of any one of the preceding claims,
wherein each of the two or more drivers (11) comprises a respective control unit (13) which is configured to regulate its DC output voltage.
A lighting system comprising:
a driver system (10) of any one of the preceding claims; and

at least one LED load (20).
A method (40) of operating a driver system (10), wherein the driver system (10) comprises two or more drivers (11) which are connected in parallel, wherein each of the two or more drivers (11) is configured to supply a regulated nominal DC output voltage, the method comprising:
regulating (41) a DC output voltage of one of the drivers (11) for a defined time period upon being switched on to an intermediate voltage level, which is lower than a voltage level of its nominal DC output voltage.
The method (40) of claim 10,
regulating (42) the DC output voltage of the driver (11) from the intermediate voltage level to the level of its nominal DC output voltage after the defined time period has passed.
The method (40) of claim 10 or 11,
detecting (43) the intermediate voltage level on an output side of at least one further driver of the two or more drivers (11), which is switched off.
The method (40) of any one of claim 12,
switching on (44) the at least one further driver (11) if the detected voltage level on its output side corresponds to the intermediate voltage level.
The method (40) of claim 13,
upon being switched on (44) due to detecting that the voltage level on its output side corresponds to the intermediate voltage level, the DC output voltage of the at least one further driver (11) is regulated to its nominal DC output voltage immediately.
The method (40) of claim 13,
upon being switched on (44) due to detecting that the voltage level on its output side corresponds to the intermediate voltage level, the DC output voltage of the at least one further driver (11) is regulated to a further intermediate voltage level which is between the intermediate voltage level and the voltage level of its nominal DC output voltage.