Converter module for lamps with load detection function and method for operating a converter module for lamps with load detection function

Abstract

Converter module for operating a load in the form of at least one light source, preferably at least one LED, with - a potential-isolated clocked converter, which is controlled on the primary side by a control unit, - wherein the converter can be supplied on the primary side from a supply voltage, preferably an AC voltage, and wherein the illuminant can be supplied from the secondary side of the converter, - wherein the converter module further comprises a load identification circuit (1) on the primary side, which is designed to select an operating mode of the control unit by means of signals only on the primary side, depending on a load that can be supplied from the secondary side, and which is designed to detect a primary-side current and an applied supply voltage and to relate the detected current and the detected supply voltage and to select the operating mode depending on the relationship, - wherein the load identification circuit (1) comprises a resistor (R35), wherein detection of the load by the load identification circuit (1) is carried out by monitoring the supply voltage across the resistor (R35), wherein the voltage drop across the resistor (R35) is compared with a reference value which varies proportionally to the average supply voltage, and - wherein the reference value is generated by a detection circuit (2) on a voltage divider and a capacitor to form an average value.

Description

[0001] The invention relates to a converter module for lighting devices, in particular for operating at least one LED or an LED string, which enables dimmable operation of lighting devices. The invention preferably relates to a converter module for use in ballasts or luminaires, to which, in particular, the lighting device to be operated can be connected. Dimming of the lighting devices can be achieved using a phase dimmer or triac, which are still widely used as infrastructure for dimming incandescent lamps.

[0002] The converter module can be designed to operate at least one LED lamp, e.g., an LED retrofit lamp. Alternatively or additionally, the converter module can also be part of an LED lamp, for example, as a module integrated into the lamp. The converter module according to the invention can, in particular, be a driver module for LED retrofit lamps, in particular for MR16-type retrofit lamps.

[0003] The converter module according to the invention preferably has a clocked potential-isolating converter (flyback converter, flyback converter) that galvanically or potentially isolates a primary side of the converter module from a secondary side of the module. The converter is clocked on the primary side by means of a switch and can be supplied from a mains voltage. The at least one light source can be operated / supplied from the secondary side. The switch can be controlled by a control unit, for example a microcontroller, an ASIC, or an IC, and can be provided either in the control unit or separately.

[0004] The invention is based on the desire to be able to operate various loads on a single converter module. The ability to operate various loads allows for flexible selection of the light sources used, while also allowing forward voltage tolerances to be easily handled. These problems are particularly prevalent in converter modules for retrofit lamps, particularly MR16 operating modules, since a user can connect a varying number of lamps to the converter module, each of which may have different wattages or belong to different power classes. Furthermore, lamps can be freely connected and removed by the user, and it is important that the remaining lamps continue to operate properly even when dimmed.

[0005] However, a variable load poses a problem in many dimming applications, especially for inexpensive dimming solutions with phase-cut dimming. This problem arises from the fact that existing dimming techniques reduce the primary-side peak current to achieve dimming of the lamp, i.e., to reduce the light output of the lamp.

[0006] The resulting effect, however, is that the power output from the module is reduced, rather than the current output, when dimming down. Therefore, if the current load is less than the maximum load, the load will always operate at reduced power because the forward voltage is lower. For example, a dimmer itself must first dim by a certain degree before the module's output drops enough to actually dim the sub-maximum load.

[0007] On the other hand, the minimum dimming value to be achieved is higher than what could be achieved at maximum load. This means that at reduced load, the light cannot be dimmed as far as would be possible at maximum load. This results in an undesirably reduced dimming range, as the lower limit for the adjustable dimming value is raised.

[0008] LED drivers that provide different power levels are known from the state of the art. However, these require manual selection of the respective power range using a jumper, a switch, or separate output terminals. This is cumbersome and requires user intervention.

[0009] WO 2011 / 008635 A1 discloses an LED lamp that adjusts the light intensity based on the input voltage, detects the dimmer type and generates appropriate control signals to serve as a direct replacement for incandescent lamps in wiring with conventional dimmer switches.

[0010] DE 102012209780 A1 discloses a method for operating an (LED) lamp using a circuit arrangement in which a load characteristic of at least one light source is detected and an output variable (IOUT, UOUT, P) to be controlled and / or a setpoint for controlling the output variable is determined as a function of the detected load characteristic.

[0011] WO 2012 / 110973 A1 discloses a lighting driver that detects mains current or the type of connected ballast, regulates a bus voltage accordingly and provides the current to operate LEDs via a switching power supply.

[0012] US 2012 / 0112638 A1 discloses a lighting system that distributes excess energy using a controller that controls multiple power dissipation circuits according to a thermal management strategy.

[0013] EP 2369897 A2 discloses a load determination device that detects the type of a lighting load by measuring current and voltage, comparing them with a threshold value and operating the lighting load accordingly with a nominal voltage.

[0014] The aim of the invention is to overcome these disadvantages and to automatically select a range for the output power depending on the supplied load.

[0015] The problem is solved according to the invention by a device and a method according to the independent claims. Further embodiments of the invention are the subject of the dependent claims.

[0016] In a first aspect, the invention provides a converter module for operating a load in the form of at least one luminous means, preferably at least one LED, with a potential-isolated clocked converter which is controlled on the primary side by a control unit, wherein the converter can be supplied on the primary side from a supply voltage, preferably an AC voltage, and wherein the luminous means can be supplied from the secondary side of the converter, wherein the converter module further has a load identification circuit on the primary side which is designed to select an operating mode of the control unit depending on a load which can be supplied from the secondary side by means of signals only on the primary side, and which is designed toto detect a primary-side current and an applied supply voltage and to relate the detected current and the detected supply voltage and to select the operating mode depending on the relationship, wherein the load identification circuit has a resistor, wherein the load is detected by the load identification circuit by monitoring the supply voltage across the resistor, wherein the voltage drop across the resistor is compared with a reference value that varies proportionally to the average supply voltage, and wherein the reference value is generated by a detection circuit on a voltage divider and a capacitor to form an average value.

[0017] By relating them, a signal can be generated that represents the operated load on the secondary side of the switched-mode potential-isolated converter.

[0018] The load identification circuit may comprise a latch circuit having at least two switching elements.

[0019] The control unit may be in a high power operating mode after a mains reset and switch to a lower power operating mode when a load below the maximum load is detected.

[0020] The latch circuit can activate / deactivate a circuit part that changes a reference value supplied to the control circuit.

[0021] An unchanged reference value can be supplied to the control unit when the latch circuit is in a first state, in particular conductive, and the control unit can operate the converter with low power in this state.

[0022] The changed reference value can be supplied to the control unit when the latch circuit is in a second state, in particular when it is not conductive, and the control unit can operate the converter at high power in this state.

[0023] The latch circuit can hold the first state until a mains reset, in particular regardless of a dimming value / dimming value change.

[0024] Preferably, no signal is supplied to the control unit from the secondary side of the converter.

[0025] The supply voltage can be detected via the detection circuit.

[0026] In another aspect, the invention provides a lamp, in particular an LED retrofit lamp, with a converter module as described above.

[0027] In a further aspect, the invention provides a ballast for lighting means, in particular at least one LED or an LED line, with a converter module as described above.

[0028] In yet another aspect, the invention provides a luminaire with a converter module as described above.

[0029] In yet another aspect, the invention provides a method for operating a converter module for operating at least one luminous means, preferably at least one LED, wherein a primary-side control unit controls a potential-isolated converter which can be supplied on the primary side from a supply voltage, preferably an AC voltage, and wherein the luminous means can be supplied from the secondary side of the converter, wherein a primary-side load identification circuit of the converter module selects an operating mode of the control unit depending on a load which can be supplied from the secondary side by means of signals only on the primary side and detects a primary-side current and the applied supply voltage and relates the detected current and the detected supply voltage and selects the operating mode depending on the relationship, wherein the load identification circuit has a resistor,wherein the load is detected by the load identification circuit by monitoring the supply voltage across the resistor, wherein the voltage drop across the resistor is compared with a reference value that varies proportionally to the average supply voltage, and wherein the reference value is generated by a detection circuit across a voltage divider and a capacitor to form an average value.

[0030] The invention will now be described with reference to the figures, which show: Fig. 1 schematically shows a block diagram of the device according to the invention. Fig. 2 a circuit arrangement according to the invention.

[0031] In general, the invention is designed to enable smooth and flicker-free dimming, particularly in conjunction with common phase-control dimmers. At the same time, the number of required circuit elements should be kept as low as possible, while also enabling operation with different control units.

[0032] An essential feature of the invention is that the control unit, which is arranged on the primary side of the converter, selects a lower value for the maximum power when a changed load is detected in order to provide improved dimming behavior.

[0033] The invention now provides for a simple circuit arrangement which can gradually switch between several operating modes depending on a detected load, for example between two operating modes, ie an operating mode with higher power and an operating mode with lower power, when dimming, ie a reduction of the dimming value, takes place.

[0034] A load identification circuit has a detection resistor (in Fig. 2 e.g. resistor R35), at which a current applied on the input side, ie primary side, is detected. In addition, a detection circuit for the applied voltage is provided (in Fig. 2 in particular the resistors R21, R39, R24 with the capacitance C11), whereby the voltage can change when dimming.

[0035] If the current and the supply voltage are now related, a signal can be obtained that represents the operated load on the secondary side of the clocked potential-isolated converter.

[0036] This is in Fig. 1, which shows a converter module KM according to the invention. A voltage detection circuit VE detects the supply voltage, while a current detection circuit IE on the primary side detects the current originating from the converter W. A signal from both detection circuits VE, IE is fed to a load identification circuit LI, which preferably has a latch circuit, which relates the two signals. Identification then also occurs depending on threshold values ​​set in the circuit, which are determined, for example, by appropriately dimensioning the resistors used or the switching elements (transistors) of the load identification circuit LI, in particular the latch circuit. In particular, the load identification circuit LI can logically perform a subtraction / addition of the signals.

[0037] An output signal of the load identification circuit LI is then fed to the control unit SE, which selects an operating mode based thereon and, depending on the selected operating mode, then controls the switch (which can also be provided internally in the control unit SE) of the converter W accordingly.

[0038] Schematically shown in Fig. 1 also the galvanically insulating barrier B, which divides the converter module KM into a primary side P and a secondary side S.

[0039] Fig. 2 shows an example of a circuit arrangement which allows the output power to be controlled / regulated according to the invention.

[0040] The converter module is supplied with a supply voltage, e.g., an alternating voltage / current (AC), from the primary side terminals labeled "Live" and "Neut," which represent the phase and neutral conductors, respectively. The supply voltage is rectified by a rectifier D1. It can also be designed for the converter module to be directly supplied with a direct voltage / current, thus eliminating the need for a rectifier.

[0041] On the secondary side, output terminals are provided (labeled 0V and +12V) from which the lamp can be supplied.

[0042] The control unit U1, which is located in the circuit arrangement in Fig. 2 is used, for example, is an LED driver HV LED 815 from ST Microelectronics, which is designed as a dimmable driver for LED retrofit lamps.

[0043] The operating mode is selected by a load identification circuit 1.

[0044] In Fig. 2, an identification signal output by the load identification circuit 1 is used to externally switch a resistance circuit 3 so that different voltage levels U1 are supplied to the control unit and thus the reference voltage of the control unit U1 can be changed.

[0045] In a more complex design, which is Fig. 2 is not shown, the identification signal is supplied, for example, to the pin of the control unit (IC, ASIC, microcontroller, ...) whose operating mode or operating parameters can be set depending on this identification signal.

[0046] In the Fig. In the embodiment shown in Figure 2 with external circuitry (trick circuit for the control unit U1), a latch circuit is provided which, in the event that a low power state is detected, maintains this state even if the dimming levels subsequently change.

[0047] The latch circuit is only reset when the supply voltage is switched off (mains reset). Upon restart, the circuit normally returns to the high power state and remains in this state until a correlation between the input current and the applied voltage triggers switching to the low power mode.

[0048] The load identification can be evaluated in different ways with a more intelligent primary-side control unit (microcontroller, ASIC, IC).

[0049] For example, it can be used to detect a lamp voltage. This has the advantage that no secondary-side lamp voltage detection is required, and thus, for example, no signal needs to be routed from the secondary side to the primary side via the potential isolation (e.g., an insulating SELV barrier). This allows the lamp path to be operated with a specified lamp current without secondary-side detection. For this purpose, the current through the primary side of the isolated converter is detected, and the load identification signal is also used.

[0050] The load is detected by the load identification circuit 1 by monitoring the supply voltage at a first resistor R35, which is Fig. 2 is circled.

[0051] Since the current also drops when dimming, the voltage drop across the first resistor R35 is not compared to a fixed reference value. Instead, it is compared to a reference value that varies proportionally to the average supply voltage. This reference value is generated by a detection circuit 2 across a first voltage divider formed by resistors R23, R39, and R24, and a capacitor C11 for averaging.

[0052] Thus, the load can be detected when the supply current or the voltage drop across the first resistor R35 is low while the supply voltage is high.

[0053] The basic function of the Fig. The circuit shown in Figure 2 is as follows: The currently selected load state, i.e., the operating mode for the detected load, is stored by a simple latch circuit formed by the switching elements Q4 and Q7. The switching elements Q4 and Q7 are implemented as transistors (bipolar transistors, FETs, MOSFETs) or a combination thereof.

[0054] The latch circuit can either be conductive, i.e. both switching elements Q4, Q7 can be switched on (conductive) or the LED circuit can be non-conductive when both switching elements are switched off.

[0055] After power-on (mains reset), the latch circuit is initially in a non-conductive state, which selects the high output power setting by the control unit. In this state, the collector of the switching element Q4 is connected to a voltage V CCpulled, thereby turning on the switching element Q6 (MOSFET, FET, bipolar transistor). The switching element Q6 is shown in circuit section 3.

[0056] As a result, the voltage divider formed by resistors R30 and R31 is activated, reducing the reference voltage signal fed back from the secondary side to the CS (current sense) input of the control unit, which is sensed by the control unit via resistor R11. The converter then operates at full power.

[0057] The monitoring of the connected load is carried out as described below: The voltage drop across resistor R35 is averaged by resistor R34 and capacitor C16, resulting in a negative DC voltage at the emitter of switching element Q4. This is indicated by the arrow in Fig. 2 indicated.

[0058] The positive reference voltage (proportional to the supply voltage) is added to the negative voltage by the voltage divider consisting of resistors R32 and R33. The switching element Q3 is connected as a diode to prevent a voltage drop in the base-emitter voltage V BE to compensate for the base-emitter voltage drop across the switching element Q4. This further improves temperature stability.

[0059] The resulting voltage is applied to the base of switching element Q4. Reducing the supply current will increase this applied voltage, while reducing the supply current will also reduce the supply voltage.

[0060] If the current is small relative to the supply voltage, the switching element Q4 will switch the latch circuit into the conducting state.

[0061] When the latch circuit is in the conducting state, the collector of switching element Q4 is pulled to or close to 0V, turning off switching element Q6 (MOSFET). The full feedback voltage is then sensed by the control unit via current sense resistor R11, and the converter operates at reduced power.

[0062] Once the circuit is in a low power state, the supply voltage must preferably be interrupted to return to the high power state.

[0063] The switching element Q5 prevents the latch circuit from triggering during the start-up phase, i.e., after power-on or a power reset. The Zener diode Z2 further prevents triggering until the voltage VCC reaches a certain value, for example, 15 volts, and in particular, 10-20 volts.

[0064] As a result, the circuit arrangement according to the invention dims in a low-power state even at a load of 20-40, preferably 30% of the maximum load, just as it does at maximum load in high-power mode.

[0065] In summary, the invention therefore provides improved dimming behavior at reduced load, i.e., load below the maximum load value, while the circuit arrangement can be implemented cost-effectively. It should be understood that the circuit arrangement can also be operated with other control units.

[0066] For example, the invention prevents flickering of the lamp when dimming, for example when an LED retrofit lamp is replaced by halogen transformers.

[0067] The invention therefore allows the operation of a varying load with a single converter module. As mentioned, the load differences can result from connecting a different number of lamps / lighting devices, so the load can vary, for example, from 3 watts (for one lamp) to the maximum specification of the driver module.

[0068] Since the circuit arrangement according to the invention automatically switches between different power ranges, gentle dimming can take place in each of the power ranges.

[0069] This allows a light source to be operated at a specified current without secondary-side detection. As mentioned above, the current is detected through the primary side of the isolated converter and the load identification signal is also used.

Claims

[1] Converter module for operating a load in the form of at least one light source, preferably at least one LED, with - a potential-isolated clocked converter, which is controlled on the primary side by a control unit, - wherein the converter can be supplied on the primary side from a supply voltage, preferably an AC voltage, and wherein the illuminant can be supplied from the secondary side of the converter, - wherein the converter module further comprises a load identification circuit (1) on the primary side, which is designed to select an operating mode of the control unit by means of signals only on the primary side, depending on a load that can be supplied from the secondary side, and which is designed to detect a primary-side current and an applied supply voltage and to relate the detected current and the detected supply voltage and to select the operating mode depending on the relationship, - wherein the load identification circuit (1) comprises a resistor (R35), wherein detection of the load by the load identification circuit (1) is carried out by monitoring the supply voltage across the resistor (R35), wherein the voltage drop across the resistor (R35) is compared with a reference value which varies proportionally to the average supply voltage, and - wherein the reference value is generated by a detection circuit (2) on a voltage divider and a capacitor to form an average value. [2] Converter module according to claim 1, wherein the relating generates a signal representative of the driven load on the secondary side of the switched-mode potential-isolated converter. [3] Converter module according to claim 1 or 2, wherein the load identification circuit (1) comprises a latch circuit with at least two switching elements. [4] Converter module according to one of the preceding claims, wherein the control unit is in a high power operating mode after a mains reset and changes to a lower power operating mode when a load below the maximum load is detected. [5] Converter module according to one of the preceding claims, wherein the latch circuit activates / deactivates a circuit part which changes a reference value supplied to the control circuit. [6] Converter module according to one of the preceding claims, wherein an unchanged reference value is supplied to the control unit when the latch circuit is in a first state, in particular conductive, and the control unit operates the converter with low power in this state. [7] Converter module according to one of the preceding claims, wherein the changed reference value is supplied to the control unit when the latch circuit is in a second state, in particular is not conductive, and the control unit operates the converter at high power in this state. [8] Converter module according to one of the preceding claims, wherein the latch circuit maintains the first state until a mains reset, in particular independently of a dimming value / a dimming value change. [9] Converter module according to one of the preceding claims, wherein no signal is supplied to the control unit from the secondary side of the converter. [10] Converter module according to one of the preceding claims, wherein the supply voltage is detected via the detection circuit (2). [11] Lamp with a converter module according to one of the preceding claims. [12] Ballast with a converter module according to one of the preceding claims 1-10. [13] Luminaire with a converter module according to one of the preceding claims 1-10. [14] A method for operating a converter module for operating at least one luminous means, preferably at least one LED, wherein a primary-side control unit controls a potential-isolated converter which can be supplied on the primary side from a supply voltage, preferably an AC voltage, and wherein the luminous means can be supplied from the secondary side of the converter, wherein a primary-side load identification circuit of the converter module selects an operating mode of the control unit by means of signals only on the primary side, depending on a load which can be supplied from the secondary side, and detects a primary-side current and the applied supply voltage, relates the detected current and the detected supply voltage, and selects the operating mode depending on the relationship, wherein the load identification circuit (1) comprises a resistor (R35), wherein detection of the load by the load identification circuit (1) is carried out by monitoring the supply voltage across the resistor (R35), wherein the voltage drop across the resistor (R35) is compared with a reference value which varies proportionally to the average supply voltage, and wherein the reference value is generated by a detection circuit (2) at a voltage divider and a capacitor to form an average value.

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