DE102011003937A1 - Control circuit for controlling lamps switched into series, has electronic switches arranged parallel to lamps and short circuited during activation of lamps that are switched into series and comprise common reference potential - Google Patents

Abstract

The circuit has multiple electronic switches (139-145) controlled based on rectified main voltage and arranged parallel to lamps (101-108). The electronic switches are short circuited during activation of the lamps that are switched into series and comprise a common reference potential. The lamps comprise a group of semiconductor light elements i.e. LEDs. The rectified main voltage is detected and evaluated based on a control unit, and the lamps are activated via the electronic switches based on amount of the detected main voltage. The electronic switches are semiconductor switches e.g. transistors, bipolar transistors and/or MOSFETs.

Description

The invention relates to a circuit for driving a plurality of series-connected bulbs or an integrated circuit for controlling a plurality of series-connected bulbs.

Basically, it is a problem semiconductor elements, z. As light emitting diodes (LED) or LED systems to operate directly on an electrical power network, in particular when the semiconductor light elements are dimmable and should have at least approximately a sinusoidal current consumption.

Known approaches use up or down converters to set a supply voltage to the semiconductor light elements. Also, a mesh capacitor is used after the mains rectification to keep the current in the semiconductor light elements at a nearly constant level. Such solutions are not dimmable. Furthermore, the current flow through the semiconductor light elements is not sinusoidal, which leads to a disadvantageous load or unwanted disturbances of the AC network.

The object of the invention is to avoid the abovementioned disadvantages and, in particular, to provide a solution for efficiently operating dimmable semiconductor light elements over a mains voltage and disturbing the power network as little as possible (by a non-sinusoidal current consumption).

This object is achieved according to the features of the independent patent claims. Further developments of the invention will become apparent from the dependent claims.

• – umfassend eine Steuereinheit und mehrere elektronische Schalter, wobei die mehreren elektronischen Schalter in Abhangigkeit von einer gleichgerichteten Netzspannung ansteuerbar sind,
• – wobei die mehreren elektronischen Schalter parallel zu den Leuchtmitteln angeordnet sind,
• – wobei jeder der mehreren elektronischen Schalter bei Aktivierung jeweils mindestens eines der in Reihe geschalteten Leuchtmittel kurzschließt,
• – wobei die mehreren elektronischen Schalter ein gemeinsames Bezugspotential aufweisen.

To solve the problem, a circuit or a circuit arrangement is proposed for controlling a plurality of lamps connected in series,

• Comprising a control unit and a plurality of electronic switches, wherein the plurality of electronic switches are controllable as a function of a rectified mains voltage,
• - wherein the plurality of electronic switches are arranged parallel to the lighting means,
• Each of the plurality of electronic switches, when activated, short-circuits at least one of the series-connected lamps,
• - Wherein the plurality of electronic switches have a common reference potential.

In particular, depending on the height of the rectified mains voltage, different electronic switches are activated. Thus, different electronic switches can be gradually activated via the rectified mains voltage and thus a different number of series-connected lamps can be activated or deactivated. The course of a pulsating DC voltage can thus be used to activate or deactivate different numbers of the lamps depending on their voltage value.

The electronic switches are arranged parallel to the lighting means. In particular, each electronic switch when it is activated a different number of bulbs over (or short circuit). It is advantageous if the electronic switches are arranged so that upon activation of a first electronic switch one of the lamps, upon activation of a second electronic switch two of the lamps, upon activation of a third electronic switch three of the lamps, etc. are überberbar. When the last electronic switch is activated, for example, all but one of the lamps connected in series are printed.

The common reference potential of the electronic switches ensures, for example, that each of the electronic switches can be activated with the same switching voltage.

A further development is that the lighting means comprises at least one semiconductor light-emitting element, in particular a group of semiconductor light-emitting elements.

The semiconductor light element can be a light-emitting diode (LED).

Another development is that based on the control unit, a detection and evaluation of the rectified mains voltage takes place and depending on a high of the detected mains voltage more or less many lamps can be activated via the electronic switch.

Thus, the voltage of the rectified mains voltage (eg in pulsating half-wave form with twice the frequency of the mains AC voltage) is used to control the electronic switches and depending on the level of the mains voltage different number of series-connected bulbs on or off.

In particular, it is a further development that a dimmable control of the lighting means takes place on the basis of the control unit.

Thus, by means of a reference voltage, which can be changed by a user, a brightness control (dimming) of the series-connected bulbs take place.

It is also a development that the control unit has a voltage follower for detecting the mains voltage whose output signal is passed to a comparator bank, by means of which the electronic switches can be controlled depending on the level of the mains voltage.

Instead of the voltage follower, each circuit can be used for voltage detection. The comparator bank comprises, for example, an arrangement of a plurality of operational amplifiers whose non-inverting inputs may be assigned different values of a reference voltage. These values can be z. B. be obtained via a voltage divider from a reference voltage. Each output of a comparator is used to drive an electronic switch. In particular, the output of the comparator may be connected via a driver to the electronic switch.

Furthermore, it is a development that the control unit and the electronic switches are executed together integrated in a circuit.

In the context of an additional development, the circuit has a voltage-controlled current source which can be operated via the rectified mains voltage and which is arranged in series with the plurality of series-connected lighting devices.

By controlling the voltage-controlled power source by means of z. B. sinusoidal-like pulsed rectified mains voltage is achieved that at low voltage values (in which only one lamp or a few lamps are activated) and a correspondingly adapted smaller current flows through the lamps than at high voltage values (in which, for example, all lamps are activated ). Thus, the voltage controlled current source provides a current suitable for the currently active number of lamps. Both the number of active lamps and the current through these lamps is therefore influenced or adjusted by the waveform of the rectified mains voltage. This advantageously leads to a nearly sinusoidal current consumption and thus minimizes disturbances, which act on the power network starting from the circuit.

A next development is that the control unit, the electronic switches and the voltage-controlled current source are arranged together in an integrated circuit.

One embodiment is that the electronic switches comprise semiconductor switches, in particular transistors, bipolar transistors and / or MOSFETs.

An alternative embodiment is that the control unit has drivers for controlling the electronic switches.

The above object is also achieved by an integrated circuit comprising the control unit and the electronic switches as described herein.

Optionally, the voltage-controlled current source described here can also be part of the integrated circuit.

A development is that the integrated circuit is at least partially executed as an ASIC, an FPGA or a microcontroller.

Exemplary embodiments of the invention are illustrated and explained below with reference to the drawings.

Show it:

1A to 1C a schematic diagram of the operation of several series-connected LEDs on an AC line voltage;

2 a schematic block diagram illustrating the approach for driving bulbs.

1A to 1C show a schematic diagram of the operation of several series-connected LEDs 101 to 108 at an AC mains voltage 109 ,

It should be noted that the right side of 1A about connections 150 to 158 with the left side of the 1B connected is. Furthermore, the right side of the 1B over the connections 159 to 167 with the left side of the 1C connected. These connections are also referred to as nodes in the following description of the circuit.

The AC mains voltage 109 is about a rectifier 110 converted into a (pulsating) DC voltage. The DC voltage is after the rectifier 110 at the node 111 (positive supply voltage) and 112 (Ground potential) available.

The knot 111 is a voltage divider comprising a series connection of a resistor 113 and a resistance 114 with the node 112 connected. A center tap between the resistors 113 and 114 is connected to the noninverting input of an operational amplifier 115 connected. The inverting input of the operational amplifier 115 is connected to the output of the operational amplifier 115 connected further to the inverting input of an operational amplifier 122 connected is.

A reference voltage 123 is via a series circuit comprising resistors 124 to 131 with the node 112 connected.

A tap between the resistances 124 and 125 is connected to the noninverting input of an operational amplifier 116 connected, a tap between the resistors 125 and 126 is connected to the noninverting input of an operational amplifier 117 connected, a tap between the resistors 126 and 127 is with the noninverting input of an operational amplifier 118 connected, a tap between the resistors 127 and 128 is with the noninverting input of an operational amplifier 119 connected, a tap between the resistors 128 and 129 is with the noninverting input of an operational amplifier 120 connected, a tap between the resistors 129 and 130 is with the noninverting input of an operational amplifier 121 connected and a tap between the resistors 130 and 131 is with the non-inverting input of the operational amplifier 122 connected.

Further, the inverting inputs are the operational amplifiers 116 to 122 with each other or with the output of the operational amplifier 115 connected.

The operational enhancers 116 to 122 are preferably operated as comparators.

The output of the operational amplifier 116 is about a driver 132 and about a resistance 148 with the node 160 and thus to the gate terminal of an n-channel MOSFET 145 connected.

The output of the operational amplifier 117 is about a driver 133 and about a resistance 168 with the node 161 and thus to the gate terminal of an n-channel MOSFET 144 connected.

The output of the operational amplifier 118 is about a driver 134 and about a resistance 169 with the node 162 and thus to the gate terminal of an n-channel MOSFET 143 connected.

The output of the operational amplifier 119 is about a driver 135 and about a resistance 170 with the node 163 and thus to the gate terminal of an n-channel MOSFET 142 connected.

The output of the operational amplifier 120 is about a driver 136 and about a resistance 171 with the node 164 and thus to the gate terminal of an n-channel MOSFET 141 connected.

The output of the operational amplifier 121 is about a driver 137 and about a resistance 172 with the node 165 and thus to the gate terminal of an n-channel MOSFET 140 connected.

The output of the operational amplifier 122 is about a driver 138 and about a resistance 173 with the node 166 and thus to the gate terminal of an n-channel MOSFET 139 connected.

The source connection of the Mosfets 139 to 145 is with the node 167 (and thus also with the node 112 ) connected.

The drain connection of the mosfet 139 is with a tap between the light emitting diodes 101 and 102 connected, the drain connection of the mosfet 140 is with a tap between the light emitting diodes 102 and 103 connected, the drain connection of the mosfet 141 is with a tap between the light emitting diodes 103 and 104 connected, the drain connection of the mosfet 142 is with a tap between the light emitting diodes 104 and 105 connected, the drain connection of the mosfet 143 is with a tap between the light emitting diodes 105 and 106 connected, the drain connection of the mosfet 144 is with a tap between the light emitting diodes 106 and 107 connected and the drain connection of the mosfet 145 is with a tap between the light emitting diodes 107 and 108 connected.

The knot 111 is via the nodes or connections 150 and 159 via a voltage-controlled current source 146 with the anode of the LED 101 connected and the cathode of the light emitting diode 108 is with the node 167 or the node 112 connected.

The drivers 132 to 138 are preferably designed to work for the Mosfets 139 to 145 provide a suitable gate (or base current if transistors are used as a semiconductor switch), preferably to a Volistandiges through switching the Mosfets 139 to 145 to ensure. The one from the drivers 132 to 138 provided gate current can be dimensioned so that the switching behavior of the mosfets 139 to 145 within a network period is sufficiently fast. Also, the gate current can be dimensioned so low that high system efficiency is achieved by a low power consumption.

In an exemplary implementation, the values of the resistances 113 . 114 . 124 to 131 be highly dimensioned. The selected height results, for example, as a compromise of immunity of the circuit in terms of Input currents of the comparators 116 to 122 , For example, the resistors 113 . 114 . 124 to 131 in a range of 10 kOhm to 1 MOhm. The resistance 168 to 173 and 148 For example, each can be 1 kOhm.

The knot 160 is over a diode 174 with the base of an npn transistor 195 whose collector is connected to the node 161 and its emitter with the node 167 connected is.

The knot 160 is over a diode 176 with the base of an npn transistor 196 whose collector is connected to the node 162 and its emitter with the node 167 connected is. Furthermore, the node 161 over a diode 175 with the base of the transistor 196 connected.

The knot 160 is over a diode 179 with the base of an npn transistor 197 whose collector is connected to the node 163 and its emitter with the node 167 connected is. Furthermore, the node 161 over a diode 178 and the node 162 over a diode 177 each with the base of the transistor 197 connected.

The knot 160 is over a diode 183 with the base of an npn transistor 198 whose collector is connected to the node 164 and its emitter with the node 167 connected is. Furthermore, the node 161 over a diode 182 , the knot 162 over a diode 181 and the node 163 over a diode 180 each with the base of the transistor 198 connected.

The knot 160 is over a diode 188 with the base of an npn transistor 199 whose collector is connected to the node 165 and its emitter with the node 167 connected is. Furthermore, the node 161 over a diode 187 , the knot 162 over a diode 186 , the knot 163 over a diode 185 and the node 164 over a diode 184 each with the base of the transistor 199 connected.

The knot 160 is over a diode 194 with the base of an npn transistor 147 whose collector is connected to the node 166 and its emitter with the node 167 connected is. Furthermore, the node 161 over a diode 193 , the knot 162 over a diode 192 , the knot 163 over a diode 191 , the knot 164 over a diode 190 and the node 165 over a diode 189 each with the base of the transistor 147 connected.

The diodes 174 to 194 are each aligned so that their cathode is toward the base of the respective transistor 195 to 199 and 147 shows.

It should be noted that center tap or tap denotes a possibility of contacting between two components. This corresponds electrically to a node that may be connected to multiple components.

Each light-emitting diode 101 to 108 can be designed as at least one light emitting diode or at least one semiconductor element. In particular, each light emitting diode 101 to 108 comprise a group of light-emitting diodes. A setpoint voltage for a group of light-emitting diodes can in particular correspond to the total voltage by the number of light-emitting diodes per group.

By means of the operational amplifier 115 (which is connected as a voltage follower) is a voltage detection. The detected voltage is applied to a comparator bank comprising the operational amplifiers 116 to 122 forwarded, depending on the magnitude of the detected voltage, the comparators 116 to 122 switch through and control the mosfets via the connected inverting driver.

The Mosfets 139 to 145 be controlled depending on the height of the detected voltage and thus the mains voltage or activated. For example, the mosfet 139 at a sensed voltage of 35 V, the mosfet 140 at a detected voltage of 70 V, the mosfet 141 at a detected voltage of 105 V, the mosfet 142 at a detected voltage of 140 V, etc. activated.

Preferably, it becomes dependent on the magnitude of the voltage at the center tap between the resistors 113 and 114 only one of the mosfets 139 to 145 activated. Alternatively, it is also possible that at a predetermined minimum voltage all mosfets 139 to 145 be activated and with each voltage level an additional mosfet is opened or deactivated.

It is advantageous that the electronic switch 139 to 145 as well as the voltage controlled current source 146 integrated, z. B. in a common electronic integrated circuit, can be executed. Alternatively, it is also possible that the voltage-controlled power source 146 discrete.

The control of the voltage-controlled current source 146 is done via the at the node 111 provided pulsating DC voltage (with a frequency of eg 100 Hz or 120 Hz). Depending on the course of the rectified half-wave of the pulsating DC voltage, a correspondingly large current from the voltage-controlled current source 146 for operation of the LEDs 101 to 108 provided. If the half-wave of the pulsating DC voltage has only a low voltage value, on the one hand, this voltage of the operational amplifier 115 detected and evaluated by the connected comparator so that only one LED or a few LEDs are active; for this one LED or these few LEDs, on the other hand, the appropriate current - also based on the magnitude of the instantaneous value of the pulsating DC voltage - from the voltage controlled current source 146 provided. Thus, the current controller is at an operating point, it is done in an efficient manner, a voltage adjustment to the respective load.

By the use of semiconductor switches (in the example of 1 based on the Mosfets shown 139 to 145 ) with common potential of the source terminal (corresponding npn transistors can be used, whose collectors are at a common potential) simplifies the control of the semiconductor switches, since the voltage between the gate terminal and the source terminal can always have the same reference potential. Furthermore, so the semiconductor switches together for. B. be integrated on silicon basis. Optionally, the drivers 132 to 138 be executed integrated with the semiconductor switches together.

Depends on that of the Operationsverstarker 115 detected current mains voltage is always driven or switched from a predetermined minimum value always a Mosfet.

Depending on the voltage detected, one (or none) of the comparators will switch 116 to 122 , At the output of each comparator there is a suitable for the Mosfet electrical driver 132 to 138 , This controls the gate connection of the mosfet 139 to 145 (or the base of a transistor) accordingly.

Depending on the level of the instantaneous mains voltage is due to the voltage-controlled current source 146 which may be integrated or discrete, a chain of light emitting diodes of different lengths 101 to 108 effective. At a low mains voltage z. B. the Mosfet 139 be turned on, thereby the light-emitting diodes 102 to 108 überbruckt and only the light emitting diode 101 via the voltage-controlled current source 146 fed. As is the voltage-controlled current source 146 Depending on the level of the mains voltage impresses a current, the light emitting diode 101 fed in this case with a suitable current for them. This current is different from a significantly higher current, the z. B. from the voltage controlled current source 146 is imprinted to all the LEDs 101 to 108 to operate (if all mosfets 139 to 145 lock and the rectified half-wave of the mains voltage z. B. is in or near its maximum).

To optimize the power factor is the voltage controlled current source 146 mains-guided, ie the current is for example proportional to the mains voltage and varies with the course of the mains voltage. Thus, voltage and current are approximately in phase and have a similar time course.

2 shows a schematic block diagram illustrating the approach presented here for driving bulbs 205 illustrated.

At the bulbs 205 For example, they are semiconductor light elements or groups of semiconductor light elements connected in series with each other. In particular, groups of lamps can each be controlled jointly.

A pulsating DC voltage 201 at twice the frequency of an AC line voltage is a control unit 202 fed to. The control unit 202 can z. B. as in 1 be shown shown. Alternatively, the control unit 202 also have a processor and / or a (micro) controller, which depends on the course of the pulsating DC voltage 201 switch 203 controls. The switches 203 can the in 1 Mosfets shown correspond.

In principle it is possible to use other electronic switches, eg. B. (bipolar) transistors to use.

The control unit 202 evaluates the course of a half wave of the pulsating DC voltage 201 depending on the height of the voltage of the half-wave one or more of the switches 203 is / are controlled, so that adapted to the voltage progressively the bulbs 205 over the switches 203 be activated (this can gradually the number of activated bulbs 205 be increased according to the height of the voltage curve). For this purpose, the half-wave is preferably divided into steps or switching thresholds, so that with increasing voltage gradually the bulbs 205 be switched on and with decreasing voltage of the half-wave gradually the bulbs 205 be switched off again.

Furthermore, the pulsating DC voltage 201 also a voltage-controlled current source 204 zugefuhrt, by means of which a current through the bulbs 205 depending on the voltage of the half-wave provided (in particular limited) is. Thus it can be achieved that also the current through the bulbs 205 is essentially in phase with the mains voltage, which has a favorable effect on the power factor and reduces or prevents disturbing influences of the circuit on the power grid.

Alternatively, it is possible that the control unit 202 the voltage controlled current source 204 controls.

The presented solution has in particular the following advantages:
The arrangement can be constructed largely integrated. This makes a compact and inexpensive production possible. By the reference voltage 123 a flexible dimmability can be achieved. Furthermore, the solution for a variety of possible bulbs is flexibly scalable by z. B. the thresholds for the individual comparators are selected accordingly. The circuit allows a nearly sinusoidal current consumption, which minimizes power system disturbances. It is also advantageous that the approach shown for high performance is easy to implement. Furthermore, it is an advantage that parts of the circuit can be monolithically integrated (common substrate potential in the case of silicon) due to the common ground potential.

To optimize the efficiency, a voltage at the input of the Operationsverstarkers 115 or at other points of the circuit so that the switching threshold width of a switching step corresponds to the rated voltage of an LED sub-string (in the above example: 35 V).

It is also advantageous that, when adapted to a different mains voltage, the number of LEDs connected in series and consequently the switching threshold width can be flexibly adjusted.

The comparator bank may preferably be designed such that, during a switching transition, the (two) adjacent electronic switches also briefly execute a switching operation in order to avoid current peaks at the voltage-controlled current source. This prevents short-term opening of all electronic switches during a switching transition, thereby generating current peaks. In particular, it is advantageous to control the electronic switches with low switching currents, because so the electronic switches go slower in a saturation state, which contributes to an additional reduction of current peaks.

LIST OF REFERENCE NUMBERS

101 to 108

Light emitting diode or group of semiconductor light elements

109

AC line voltage

110

rectifier

111, 112

node

113, 114

resistance

115

Operational amplifier (voltage follower for detecting the high of the pulsed rectified mains voltage)

116 to 122

Operational amplifier (operated as a comparator)

123

Reference voltage, in particular for setting the dimming (brightness control)

124 to 131

connected in series resistances

132 to 138

Driver (eg Schmitt trigger)

139 to 145

electronic switches (n-channel mosfets)

146

voltage-controlled current source

150 to 167

Connections or nodes

148, 168-173

resistance

174 to 194

diode

195 to 199, 147

npn transistor

201

rectified pulsating mains voltage (double the frequency compared to the mains (alternating) voltage)

202

control unit

203

electronic switches

204

voltage-controlled current source

205

Light source (eg series connection of semiconductor light elements or series connection of semiconductor light systems, each semiconductor light system having at least one semiconductor element)

Claims (12)

Circuit for driving a plurality of lamps connected in series ( 101 - 108 ; 205 ), Comprising - a control unit ( 202 ) and several electronic switches ( 139 - 145 ; 203 ), wherein the plurality of electronic switches ( 139 - 145 ; 203 ) as a function of a rectified mains voltage ( 201 ) are controllable, - wherein the plurality of electronic switches ( 139 - 145 ; 203 ) parallel to the bulbs ( 101 - 108 ; 205 ) are arranged - each of the several electronic switches ( 139 - 145 ; 203 ) when activated in each case at least one of the series-connected bulbs ( 101 - 108 ; 205 ), the plurality of electronic switches ( 139 - 145 ; 203 ) have a common reference potential. Circuit according to Claim 1, in which the lighting means ( 101 - 108 ; 205 ) comprises at least one semiconductor element, in particular a group of semiconductor elements. Circuit according to one of the preceding claims, wherein on the basis of the control unit ( 202 ) a detection and evaluation of the rectified mains voltage takes place and depending on a level of the detected mains voltage more or fewer bulbs ( 101 - 108 ; 205 ) via the electronic switches ( 139 - 145 ; 203 ) are activated. Circuit according to one of the preceding claims, in which by means of the control unit ( 202 ) a dimmable control of the bulbs ( 101 - 108 ; 205 ) he follows. Circuit according to one of the preceding claims, in which the control unit has a voltage follower ( 115 ) for detecting the mains voltage whose output signal to a comparator bank ( 116 - 122 ), by means of which the electronic switches ( 139 - 145 ; 203 ) are controllable depending on the height of the mains voltage. Circuit according to one of the preceding claims, in which the control unit ( 202 ) and the electronic switches ( 139 - 145 ; 203 ) are executed together integrated in a circuit. Circuit according to one of the preceding claims, comprising a voltage-controlled current source ( 146 ; 204 ), which exceed the rectified mains voltage ( 201 ) and in series with the plurality of lamps connected in series ( 101 - 108 ; 205 ) is arranged. Circuit according to Claim 7, in which the control unit ( 202 ), the electronic switches ( 203 ) and the voltage-controlled current source ( 204 ) are arranged together in an integrated circuit. Circuit according to one of the preceding claims, in which the electronic switches comprise semiconductor switches, in particular transistors, bipolar transistors and / or MOSFETs. Circuit according to one of the preceding claims, in which the control unit has drivers for controlling the electronic switches. An integrated circuit comprising the control unit and the electronic switches according to one of the preceding claims. An integrated circuit according to claim 11, which is at least partially implemented as an ASIC, an FPGA or a microcontroller.

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