DE102016223998A1 - Synchronous buck converter for operating one or more lamps, associated method and operating device - Google Patents

Abstract

The invention relates to a synchronous buck converter for operating one or more light sources, wherein the synchronous buck converter is configured to operate in a first mode of operation or in a second mode of operation wherein in the first mode of operation of the synchronous buck converter alternating current flows through the synchronous buck converter and decreases, and wherein in the second mode of operation, the current waveform of the current flowing through the synchronous buck converter over a predetermined period of time swings. Furthermore, the invention relates to a corresponding method for operating one or more light sources and to an operating device which has the synchronous down converter and is designed to operate from the one or more light sources.

Description

The present invention relates to a synchronous buck converter for operating one or more light sources, a method for operating a synchronous buck converter for operating one or more light sources and an operating device for operating one or more light sources. The one or more bulbs include e.g. one or more light-emitting diodes (LEDs).

Synchronous buck converters are well known. Compared to a standard or conventional buck converter, in a synchronous buck converter the diode is replaced by a switch so that the synchronous buck converter has a second switch in addition to the primary switch. Since the synchronous buck converter is composed of two switchable switches, the second switch must be operated in push-pull to the primary or first switch. If the first switch becomes conductive, the second opens, and vice versa.

Since a diode always causes a voltage drop in the forward direction, not inconsiderable losses occur at the latter and thus at a standard or conventional down converter. On the other hand, synchronous buck converters have much lower losses, so the implementation of a buck converter as a synchronous buck converter or as a synchronous converter can improve the efficiency.

Another advantage of the synchronous buck converter is the lack of discontinuous operation. In a standard or conventional buck converter, with a low average output current, the current through the inductor periodically becomes zero and the diode turns off. In this discontinuous operating range, the output voltage no longer depends linearly on the input voltage and the pulse width ratio, which makes the regulation more difficult. In contrast, in a synchronous buck converter, the current due to the reverse conductivity of the switches after its zero crossing increases negatively, energy flows from the output capacitance back to the input, providing linearity and thus easy controllability independent of the load. Another advantage of this mode of operation is that the negative current range lowers the time average of the current.

Although in a synchronous buck converter the current can be lowered in the time average, the amplitude of the current also decreases relatively strongly. The result of the strong drop in the current is a high current amplitude. The switching frequency of the synchronous buck converter is relatively low.

Even though a high current amplitude, such as that caused by the sinking of the current in the synchronous buck converter, has the advantage that it is not affected by short bursts in the signal, the problem with a synchronous buck converter operating one or more lamps already exists due to the high current amplitude, a slight time deviation or fluctuations in the switching on and off of the switches can lead to an optically visible flickering of the one or more light sources (eg one or more LEDs) which is supplied with power via the synchronous down converter.

It is therefore the object of the present invention to enable an improved supply of the current to one or more light sources.

This object is achieved by the features of the independent claims. The dependent claims indicate further embodiments of the invention.

More particularly, the present invention is based on the idea of reducing the presence of the high amplitudes in the synchronous buck converter by introducing a further mode of operation in which the amplitudes are reduced as the current increases and decreases, and particularly as the current sinks. According to the present invention, in the second mode of operation, a deceleration of the current flow is implemented.

According to one aspect of the present invention, there is provided a synchronous buck converter for operating one or more light sources, wherein the synchronous buck converter is configured to operate in a first operating mode or in a second operating mode, wherein in the first mode of operation of the synchronous buck converter Down converter flows alternately increases and decreases and wherein in the second mode of operation, the current waveform of the current flowing through the synchronous buck converter current over a predetermined period of time swings.

According to one embodiment, when the current sinks in the first operating mode, the current first decreases in the direction of zero and then flows in a negative direction.

In one embodiment, the synchronous buck converter is configured to transition from the first mode of operation to the second mode of operation when the current in the first mode of operation rises and reaches zero, or when the current in the first mode of operation increases and is a predetermined distance from the zero line.

According to one embodiment, the synchronous buck converter is configured to change from the second mode of operation to the first mode of operation after the lapse of the predetermined period of time

According to one embodiment, the predetermined period of time is predetermined by a predetermined number of settling cycles.

According to one embodiment, after a change from the second mode of operation to the first mode of operation, the current flowing through the synchronous buck converter increases.

According to one embodiment, the synchronous buck converter has a first switch and a second switch for controlling the current flow of the current flowing through the synchronous buck converter.

According to one embodiment, the synchronous buck converter is configured such that, in the first mode of operation, the current flowing through the synchronous buck converter increases by turning on the first switch and turning off the second switch, and decreasing by turning off the first switch and turning on the second switch.

In one embodiment, the synchronous buck converter is configured such that in the second mode of operation, the first switch and the second switch are turned off.

According to one embodiment, the first switch is switched off when changing from the first operating mode to the second operating mode.

According to one embodiment, the first switch is switched on when changing from the second operating mode to the first operating mode.

In one embodiment, in the first mode of operation, the current flowing through the synchronous step-down switch rises to a first threshold and / or decreases to a second threshold.

According to one embodiment, the current flowing through the synchronous step-down switch in the first mode of operation increases until the expiration of a first period of time and / or decreases until the expiration of a second period of time.

According to one embodiment, the synchronous buck converter is configured to be connectable to the one or more light sources and, when connected to the one or more light sources, is configured to supply the one or more light sources with the current flowing through the synchronous buck converter.

According to one embodiment, the one or more light sources comprise one or more light emitting diodes, LEDs.

According to one aspect of the present invention, there is provided a method of operating a synchronous buck converter configured to operate one or more light sources, the method comprising operating the synchronous buck converter in a first mode of operation or in a second mode of operation, wherein in the first one Operating mode of the synchronous buck converter by the synchronous buck converter alternately rises and falls and wherein in the second mode of operation, the current waveform of the current flowing through the synchronous buck converter current over a predetermined period of time.

According to one embodiment, the operating device has a synchronous buck converter for operating the one or more light sources, and the synchronous buck converter is a synchronous buck converter as indicated above and / or as shown in more detail below.

According to one embodiment, the operating device has a controller that is designed to drive the synchronous buck converter.

In one embodiment, the controller controls the operation of the synchronous buck converter in the first mode of operation and the second mode of operation, a change of operation of the synchronous buck converter from the first mode of operation to the second mode of operation, and a change of operation of the synchronous buck converter from the second mode of operation first operating mode.

The height of the current amplitudes is reduced on average by the present invention. This will cause flickering on bulbs such as light bulbs. LEDs, which is optically visible (especially at low dimming levels), avoided or at least significantly reduced. In this way, an improved supply of the current to one or more lighting means is realized by a synchronous down converter, since the current has a more stable change of the current levels.

• 1 eine Ausgestaltung eines Betriebsgeräts zum Betreiben von Leuchtmitteln gemäß einer Ausführungsform der vorliegenden Erfindung,
• 2 einen beispielhaften Stromverlauf durch einen synchronen Abwärtswandler in zwei Betriebsmodi des synchronen Abwärtswandlers gemäß einer Ausführungsform der vorliegenden Erfindung,

Other features, advantages and features of the present invention will now be apparent from the figures of the accompanying drawings and the detailed description of embodiments will be explained. This shows

• 1 an embodiment of an operating device for operating lamps according to an embodiment of the present invention,
• 2 an exemplary current waveform through a synchronous buck converter in two operating modes of the synchronous buck converter according to an embodiment of the present invention,

Hereinafter, components having the same or similar functions will be denoted by the same reference numerals in the figures. In addition, it should be noted that the embodiments discussed herein may be combined with each other unless a combination is explicitly excluded.

1 shows an exemplary embodiment of a control gear 1 for operating one or more lamps 13 according to an embodiment of the present invention.

The one or more light sources comprise one or more light-emitting diodes (LEDs) according to an embodiment. The LEDs may be variously configured, and the present invention is not limited to any particular configuration of the LEDs. According to one embodiment, the LEDs comprise inorganic and / or organic LEDs. The arrangement of the LEDs can be designed in various ways. Thus, according to one embodiment, the LEDs are connected in series, whereas according to a further embodiment, the LEDs are connected in parallel. According to a further embodiment, the LEDs are connected in more complex arrangements, for example in a plurality of series circuits connected in parallel with one another. In 1 are exemplified by three lightweight, such as LEDs 13 shown. However, the present invention is not limited to this example and allows using any number of bulbs such as LEDs 13 ie using at least one light source (eg at least one LED).

The operating device 1 or the operating circuit 1 serves the operation of the one or more bulbs 13 (eg LEDs). In particular, the operating device is used 1 the supply of the one or more bulbs 13 such as LEDs with power. The operating device 1 a supply voltage V _{in is} supplied. The supply voltage V _in is, for example, a DC voltage or a rectified AC voltage. In one embodiment, the operating device includes a power factor correction circuit (not shown) that provides the supply voltage V _in .

The operating device 1 or the operating circuit 1 has a synchronous buck converter 11 (also known as "subscript", "buck,""buckconverter," or "step down converter") as a converter. The down converter 11 reduces the voltage from the input to the output of the buck regulator 11 , The current goes from the input to the output of the down-converter 11 elevated.

The synchronous buck converter 11 has a first switch 111 and a second switch 112 on, with the second switch 112 replaced the diode of the conventional or standard buck converter. The first and the second switch 111 . 112 are controllable. According to further embodiments, the first and / or the second switch 111 . 112 designed as a power switch, field effect transistor, bipolar transistor or insulated gate transistor. The present invention allows various suitable embodiments of the first and second switches 111 . 112 the synchronous buck converter 11 , By switching the first and the second switch 111 . 112 is via the synchronous buck converter 11 Current i _L from the supply voltage V _in to the at least one light source 13 transferred (eg LED). The synchronous buck converter 11 has energy storage: a coil 113 and possibly a capacitor 114 which supplies the at least one light source 13 (eg LED) with current i _L in the phases of the operation of the synchronous buck converter 11 make sure in which the first switch 111 switched on or is open.

The current i _L usually flows in the switched-on state of the first switch 111 by the at least one light source 13 (eg LED) and through the coil 113 which is magnetized by it. The sink 113 is charged with energy. The second switch 112 is usually off in this state. After switching off the first switch 111 becomes the second switch 112 turned on, and the coil 113 drives the current i _L flowing through it through the at least one lighting means (eg LED) 13 and the second switch 112 , The in the magnetic field of the coil 113 stored energy discharges. In parallel, at the beginning of turning on the first switch 111 the capacitor 114 getting charged. During the switch-off phase of the first switch 111 , the capacitor may be 114 discharged and contributes to the flow of current through the at least one light source 13 (eg LED). With suitable dimensioning of the capacitor 114 this can lead to a smoothing of the current through the at least one lighting means 13 lead (eg LED).

In the embodiment of the 1 are the first switch 111 and the coil 113 in series between the entrance and the exit of the synchronous buck converter 11 connected. If that at least one light source 13 (eg LED) with the synchronous buck converter 11 connected are the first switch 111 , the sink 113 and that at least one light source 13 (eg LED) according to the present embodiment connected in series. The capacitor 114 is parallel to the at least one light source 13 (eg LED) and the coil 113 switched (if the second switch 112 closed is). The capacitor 114 is parallel to the output terminals according to the present embodiment 115 . 116 switched so that the capacitor 114 connected in parallel to the at least one light-emitting means (eg LED). The capacitor 114 is an optional element of the synchronous buck converter 11 , The capacitor 114 can through the supply line to the bulb 13 be formed or may be integrated on an LED module.

The operating device 1 moreover has a controller or a control circuit 12 which is used to drive the synchronous buck converter 11 is designed. In particular, the controller 12 designed, the first and the second switch 111 . 112 the synchronous buck converter 11 to control what is in 1 through by the controller 12 to the counters 111 . 112 is represented by leading arrows.

In one embodiment, the controller operates 12 the first and the second switch 111 . 112 the synchronous buck converter 11 in a pulsed mode, so that in each case an output current is provided in the form of pulse packets. For example, in this embodiment, at smaller dimming levels, pulse packets are generated to adjust the average current level and thus the brightness perceived by the eye.

The present invention allows various embodiments of the controller 12 , For example, the controller 12 According to one embodiment, a semiconductor integrated circuit or comprises a semiconductor integrated circuit. According to further embodiments, the controller is 12 as a processor, a microprocessor, a controller, a microcontroller, an application specific integrated circuit (ASIC) or a combination of said units configured.

The synchronous buck converter 11 is configured to be operated in a first operating mode or in a second operating mode. In the first mode of operation of the synchronous buck converter 11 rises and falls through the synchronous buck converter 11 flowing electricity i _L. The sinking and the increase of the current i _L occur alternately. According to one embodiment, the current i _L first sinks in the direction of zero when sinking and then flows in a negative direction. When the current i _L rises in the first operation mode and reaches the zero line or when the current i _L rises in the first operation mode and has a predetermined distance from the zero line, according to the embodiment, a change from the first operation mode to the second operation mode is made. According to a further embodiment, this is done after a predetermined number of sinking or rising of the current i _L in the first operating mode.

In the second mode of operation, the current waveform of the oscillates through the synchronous buck converter 11 flowing current i _L over a predetermined period of time. In one embodiment, this predetermined period of time is predetermined by a predetermined number of settling cycles. After the lapse of the predetermined period of time, the operation of the synchronous buck converter changes 11 from the second operating mode to the first operating mode.

The operation of the synchronous buck converter according to the invention 11 is in 2 by illustrating the various current waveforms in the two modes of operation of the synchronous buck converter 11 shown.

2 shows an exemplary current waveform through the synchronous buck converter 11 in the two modes of operation of the synchronous buck converter 11 according to an embodiment of the present invention. It should be noted that the number and duration of the various phases in the respective modes of operation are merely exemplary and provide a better understanding of the present invention.

In 2 the time axis is represented by the horizontal axis and the height or level of the current is indicated by the vertical axis. The horizontal axis intersects the vertical axis in the embodiment of FIG 2 at a zero point. This corresponds to the horizontal axis in 2 also a zero line.

The current flow in the first operating mode is in 2 as an example divided into three phases, the present invention is not limited to this exemplary classification. The first and second phases of the first mode of operation show the alternating rising and falling of the synchronous buck converter 11 flowing electricity i _L.

In the first phase of the first mode of operation, it rises through the synchronous buck converter 11 flowing current i _L on. This is done by turning on the first switch 111 and by turning off the second switch 112 reached. The Turning on and off the switches 111 . 112 is done accordingly by the controller 12 driven. According to one embodiment, the current i _L increases until an upper limit or threshold, also referred to as the upper shutdown threshold, has been reached. According to another embodiment, the current i _L increases until a predetermined period of time has elapsed. If the upper limit has been reached or the predetermined time period has elapsed, the flow of the current i _{L is} lowered (see the second period of the first operating mode in FIG 2 ). This is achieved according to the present embodiment in that the first switch 111 is turned off and the second switch 112 is turned on.

As already mentioned, the driving of the first and the second switch takes place 111 . 112 according to the present embodiment by the controller 12 , With regard to the first mode of operation is the controller 12 configured to check whether the rising current i _{L has reached} the upper limit or whether the predetermined time period has expired. If the upper limit has been reached by the rising current i _L or the predetermined time period has expired, the controller controls 12 the synchronous buck converter 11 to change the current direction in the first operating mode. For example, the controller controls 12 the first switch 111 so on, that the first switch 111 is turned on, and the second switch 112 so on, that the second switch 112 is turned off.

In the second phase of the first mode of operation, this decreases due to the synchronous buck converter 11 flowing electricity i _L. This is done by turning off the first switch 111 and by turning on the second switch 112 reached. As explained, the switching on and off the switches 111 . 112 through the controller 12 driven. According to one embodiment, the current i _L decreases until a lower limit or threshold, also referred to as the lower shutdown threshold, has been reached. According to another embodiment, the current i _L decreases until a predetermined period of time has elapsed. When the lower limit value has been reached or the predetermined time period has elapsed, the flow of the current i _{L is made} to rise (see the third period of the first operation mode in FIG 2 ). This is achieved according to the present embodiment in that the first switch 111 is turned on and the second switch 112 is turned off.

As already mentioned, the driving of the first and the second switch takes place 111 . 112 according to the present embodiment by the controller 12 , Regarding the first mode of operation and the decreasing current flow is the control 12 configured to check whether the decreasing current i _{L has reached} the lower limit or whether the predetermined time period has expired. When the lower limit has been reached by the decreasing current i _L or the predetermined time period has elapsed, the controller controls 12 the synchronous buck converter 11 to change the current direction in the first operating mode. For example, the controller controls 12 the first switch 111 so on, that the first switch 111 is turned on, and the second switch 112 so on, that the second switch 112 is turned off.

The rise and fall of the current i _L as represented by the first phase and the second phase of the first operating mode in FIG 2 may be repeated a predetermined number of times (eg, N times, where N is a positive integer). When the predetermined number of repeated rises and falls of the current in the first operating mode has been reached, the change from the first operating mode to the second operating mode is made. This can also be done by the control 12 respectively. The control 12 checks, for example, whether the predetermined number of repeated rise and fall of the current has been reached in the first operating mode, and causes the changeover from the first operating mode to the second operating mode when the predetermined number is reached.

From the first operating mode to the second operating mode is changed when the current in the first operating mode increases and reaches the zero line or when the current in the first operating mode increases and has a predetermined distance from the zero line. This can also be done by the controller 12 be recorded. When the zero line is reached or the rising current is at a predetermined distance from the zero line, it is changed to the second operating mode (see 2 the transition from the third phase of the first operating mode to the second operating mode). In the second mode of operation, the current waveform of the oscillates through the synchronous buck converter 11 flowing current over a predetermined period of time. So that the synchronous buck converter 11 is operated in the second operation mode, according to the present embodiment, the first switch 111 off and the second switch 112 is switched off or left off. The appropriate control of the switch 111 . 112 eg by the controller 12 performed. Further, the controller 12 According to the present embodiment, it is configured to check if the predetermined time has elapsed. The predetermined period of time is predetermined by, for example, a predetermined number of settling cycles. When the predetermined period of time has elapsed (eg, the predetermined number of settling cycles has been reached), which is also done by the controller 12 can be determined, a change from the second operating mode is made in the first operating mode. This is also by the controller according to the present embodiment 12 controllable.

In order to make the change from the first operation mode to the second operation mode, according to the present embodiment, the first switch becomes 111 switched on while the second switch 112 is switched off or remains off. The appropriate control of the switch 111 . 112 is done by the controller according to the present embodiment 12 ,

The further course of the first operating mode and the subsequent changeover from the first operating mode to the second operating mode and back are continued as discussed above.

The first mode of operation of the synchronous buck converter 11 According to one embodiment, it is a synchronous threshold mode, also referred to as "synchronous borderline mode".

According to another embodiment of the present invention, the first switch 111 in the phase of the first operating mode in which the changeover from the first operating mode to the second operating mode will take place (see in FIG 2 the third phase of the first operating mode with the first switch turned on 111 and off the second switch 112 ) switched on. Remains the first switch 111 opened, the negative current flow (with the decrease of the amplitude in the third phase of the first operating mode) via a body diode of the switch 111 taken over when the switch 111 as a field effect transistor (FET) is designed.

According to one embodiment, operating the synchronous buck converter in the two modes of operation is used at low dimming values for the one or more LEDs (e.g., an LED track) because in that range the brightness variations are particularly noticeable. At low dimming levels, the eye often reacts particularly sensitively to brightness fluctuations. Further, the relative brightness change corresponding to a clock rate change is often greater at low dimming values than at higher dimming values.

As stated above, the present invention relates to a synchronous buck converter 11 for operating one or more lamps 13 , wherein the synchronous buck converter 11 is configured to be operated in a first operating mode or in a second operating mode, wherein in the first operating mode of the synchronous buck converter 11 through the synchronous buck converter 11 flowing current alternately increases and decreases, and wherein in the second mode of operation, the current flow through the synchronous buck converter 11 flowing current over a predetermined period of time swings. Furthermore, the invention relates to a corresponding method for operating one or more light sources 13 and a control gear 1 that is the synchronous buck converter 11 and for operation of the one or more bulbs 13 is designed.

LIST OF REFERENCE NUMBERS

1

control gear

11

Synchronous buck converter

111

first switch

112

second switch

113

Kitchen sink

114

capacitor

115

output port

116

output port

12

control

13

one or more bulbs (e.g., LEDs)

Claims (19)

A synchronous buck converter for operating one or more light sources, wherein the synchronous buck converter is configured to operate in a first mode of operation or in a second mode of operation, wherein in the first mode of operation of the synchronous buck converter, current flowing through the synchronous buck converter alternately rises and falls, and wherein in the second mode of operation, the current waveform of the current flowing through the synchronous buck converter will settle over a predetermined period of time. Synchronous down-converter after Claim 1 In the first operating mode, when the current sinks, the current initially decreases in the direction of zero and then flows in a negative direction. Synchronous down-converter after Claim 1 or 2 wherein the synchronous buck converter is configured to switch from the first mode of operation to the second mode of operation when the current in the first mode of operation rises and reaches zero, or when the current in the first mode of operation increases and is a predetermined distance from the zero line. A synchronous buck converter according to any one of the preceding claims, wherein the synchronous buck converter is configured after the expiration of the predetermined period of time to change from the second operating mode in the first operating mode Synchronous down-converter after Claim 4 wherein the predetermined period of time is predetermined by a predetermined number of settling cycles. The synchronous buck converter of any one of the preceding claims, wherein after a transition from the second mode of operation to the first mode of operation, the current flowing through the synchronous buck converter increases. The synchronous buck converter of any one of the preceding claims, wherein the synchronous buck converter has a first switch and a second switch for controlling the current flow of the current flowing through the synchronous buck converter. Synchronous down-converter after Claim 7 wherein the synchronous buck converter is configured such that, in the first mode of operation, the current flowing through the synchronous buck converter increases by turning on the first switch and turning off the second switch, and decreases by turning off the first switch and turning on the second switch. Synchronous down-converter after Claim 7 or 8th wherein the synchronous buck converter is configured such that in the second mode of operation, the first switch and the second switch are turned off. Synchronous buck converter to one of the Claims 7 to 9 wherein, when changing from the first operating mode to the second operating mode, the first switch is turned on. Synchronous buck converter to one of the Claims 7 to 10 wherein, when changing from the second operating mode to the first operating mode, the first switch is turned on. A synchronous buck converter according to any one of the preceding claims, wherein the current flowing through the synchronous step-down switch in the first mode of operation increases to a first limit and / or decreases to a second limit. Synchronous buck converter to one of the Claims 1 to 11 wherein the current flowing through the synchronous down switch in the first mode of operation increases until the expiration of a first period of time and / or decreases until the expiration of a second period of time. A synchronous buck converter as claimed in any one of the preceding claims, wherein the synchronous buck converter is connectable to the one or more light sources and is configured to be connected to the one or more light sources comprising the one or more light sources Down converter to supply flowing electricity. A synchronous buck converter according to any one of the preceding claims, wherein the one or more lighting means comprises one or more light emitting diodes, LEDs. A method of operating a synchronous buck converter configured to operate one or more light sources, the method comprising operating the synchronous buck converter in a first mode of operation or in a second mode of operation, wherein in the first mode of operation of the synchronous buck converter, flowing through the synchronous buck converter Current alternately increases and decreases and wherein in the second mode of operation, the current waveform of the current flowing through the synchronous buck converter current over a predetermined period of time swings. An operating device for operating one or more light sources, wherein the operating device has a synchronous buck converter for operating the one or more light sources, and wherein the synchronous buck converter is a synchronous buck converter according to any one of Claims 1 to 15 is. Operating device after Claim 17 wherein the operating device comprises a controller configured to drive the synchronous buck converter. Operating device after Claim 18 wherein the controller controls the operation of the synchronous buck converter in the first mode of operation and in the second mode of operation, a change of operation of the synchronous buck converter from the first mode of operation to the second mode of operation, and a change of operation of the synchronous buck converter from the second mode of operation to the first mode of operation controls.

Images