WO2015007468A1

WO2015007468A1 - Voltage transformer, lighting device, and method for transforming a voltage

Info

Publication number: WO2015007468A1
Application number: PCT/EP2014/063233
Authority: WO
Inventors: Dieter Nietfeld
Original assignee: Hella Kgaa Hueck & Co.
Priority date: 2013-07-16
Filing date: 2014-06-24
Publication date: 2015-01-22
Also published as: DE102013107536A1

Abstract

The invention relates to a voltage transformer, wherein the voltage transformer comprises an input having a first input terminal and a second input terminal and the voltage transformer comprises a step-up transformer and an output having a first output terminal and a second output terminal and wherein the voltage transformer comprises a switch, which is designed to pull the second output terminal either to the potential of the first input terminal or to the potential of the second input terminal. The invention further relates to a lighting device for a vehicle having such a voltage transformer and to a corresponding method for transforming a voltage.

Description

Voltage transformer, lighting device and method for converting a voltage

description

The requirements for control devices or voltage transformers for signal functions in motor vehicles (for example LEDs) are becoming ever higher. To date, the converter topology (Buck, Buck Boost, Boost, Flyback, etc.) is chosen based on the specific application based on the number of LEDs. However, a control unit suitable for different numbers of LEDs, e.g. for both a position light (an LED) and a daytime running light (e.g., 14 LEDs).

If the output voltage range of various topologies is calculated with respect to the input voltage range of the vehicle electrical system, the forward voltage range of the LED and the minimum and maximum duty cycle of converters, no fixed-frequency converter, which is the most common method, will meet the requirements the output voltage of about 2V to about 50V just.

This requirement is met today with multi-level converters. First, a correspondingly high output voltage is generated with a boost converter in order then to generate the required application-specific output voltage with a buck converter. Firstly, two-stage systems have the disadvantage of high costs and, secondly, the disadvantage of lower efficiency compared to single-stage systems.

A system with a high output voltage without transformer delivers eg a pure boost converter. Depending on the parameters (LED voltage, duty cycle, input voltage) listed above, the system can control via 14 LEDs. Operation with only one LED is thus not possible because the switching element (transistor) is not placed in series between input voltage and output voltage, in contrast, for example, a buck converter, and thus in the off mode of the switch unimpeded by a current the LED would flow that is uncontrollable. The task is thus to increase the application flexibility. In addition, preferably a high efficiency should be achieved. Preferably, the cost of implementation should be kept low or reduced.

The object is achieved in particular by a voltage converter (1), wherein the voltage converter (1) has an input (10) with a first input terminal (11) and a second input terminal (12) and the voltage converter (1) has an up-converter (20). and an output (30) having a first output terminal (31) and a second output terminal (32), and wherein the voltage converter (1) comprises a switch (40) arranged to connect the second output terminal (32) either to the potential of to pull the first input terminal (11) or to the potential of the second input terminal (12).

The object is further achieved according to the invention by, in particular, a method for converting a voltage by means of a voltage converter (1) having an input (10) with a first input terminal (1) and a second input terminal (12) and an up-converter (20) and an output (30) having a first output terminal (31) and a second output terminal (32), wherein the following steps are performed:

a) upconverting an input voltage (13);

b) setting one of at least two possible switching states of a switch (40), wherein in a first switching state, the second output terminal (32) is pulled to the potential of the first input terminal (11) and in a second switching state, the second output terminal (32) on the Potential of the second input terminal (12) is pulled.

In this way, due to the switch or due to the setting of the switching state between two topologies, the voltage converter can be switched or placed in one of two topologies. It is thus possible to adapt the converter or wall element to the respective load and / or input voltage. In the first topology, a voltage is preferably present between the output terminals of the output, which voltage is given by the difference between the output potential of the boost converter at the first output terminal and the potential at the first input terminal. plus the voltage dropped across the switch. In the second topology, a voltage is preferably present between the output terminals of the output, which voltage is the difference between the output potential of the boost converter at the second output terminal and the potential at the first input terminal minus the voltage dropped across the switch. With only one boost converter, it is thus possible to achieve different load voltages without great losses or complicated circuit combinations, and thus different load configurations at the output of the voltage converter are possible.

In the method according to the invention, the setting of a switching state can also be done once, e.g. before installation of the voltage converter and e.g. by means of a DIP switch or a hardwiring.

The voltage converter is preferably a DC-DC converter (DC / DC), particularly preferably a non-inverting DC-DC converter. A clamp is understood to be descriptive in the circuitic sense, i. there must be no physical terminal, but a terminal is (also) understood as a virtual / fictitious input point or starting point of a circuit.

The boost converter is preferably a converter in which the magnitude of the input voltage (voltage between the input terminals) is equal to or less than the magnitude of the output voltage (voltage between the output terminals - preferably with load coupled to the output terminals). Particularly preferably, the boost converter is a non-inverting converter.

Preferably, the two input terminals and the first output terminal are directly connected to the boost converter.

Pulling to a potential is preferably done by switching between the switching state of a connection from the second output terminal to the first input terminal (pulling on the potential of the first input terminal) and the switching state of a connection from the second output terminal to the second input terminal (pulling on the potential of the second input terminal). A connection is preferably an electrically conductive path, particularly preferably low impedance, for example below 100Ω, preferably below 10Ω, more preferably below 5Ω. No compound is preferably present, if there is no electrical connection or this is high impedance, for example over 500Ω, preferably over ^ Ω, more preferably above 1 Ω. The connection is preferably present in the through-connected state at least in one direction, preferably in the direction of the potential difference between the second output terminal and the first or second input terminal. Particularly preferably, a connection is present in the respective through-connected state at least in the direction of the second output terminal and the first or second input terminal.

In reality, the potential of the second output terminal and the potential of the input terminal to which the second output terminal is pulled by the switch will differ by a voltage which drops across the switch in the conductive path between the second output terminal and the corresponding input terminal the voltage dropping across the switch is preferably designed as small as possible, eg less than or equal to 2.6V (e.g., Darlington transistor as part of the switch), preferably less than or equal to 1V (also Darlington transistor), more preferably less than or equal to 0.3V (e.g., silicon transistor). Preferably, the potential of the second output terminal is pulled to the potential of the first / second input terminal when the magnitude of the potential difference between the second output terminal and the first / second input terminal is less than the magnitude of the potential difference between the second output terminal and the second / first input terminal.

The switch is preferably a changeover switch, which switches an XOR connection, ie either one path or a connection is switched through or low impedance while the other path or the other connection is not switched through or high impedance and vice versa. In the first switching state of the switch, there is preferably a connection from the second output terminal to the first input terminal, in the second switching state a connection from the second output terminal to the second input terminal. Preferably, only the first and second switching state are possible switching states of the switch. Particularly preferably, the switch is a switch which connects in one direction only (eg in the direction from the second output terminal to the first input terminal). constantly switching on or low-impedance switching (first switching state and second switching state) and another connection to (first switching state) or switching off (second switching state) or low resistance (first switching state) or high resistance (second switching state) switches. The switch is preferably understood in circuit technology sense as a changeover switch and has three connections. Preferably, it is a mechanical switch, particularly preferably it is an electronic switch, which is realized for example from semiconductor elements. The second output terminal is preferably connected to the common center connection (COM) of the (change) switch.

In a preferred embodiment of the voltage converter according to the invention, the switch (40) has a switching element S2 (41) and a blocking element (42).

As a result, the switch can be realized by means of two simple components.

The switching element S2 is preferably a (mechanical) 1-pole switch, particularly preferably a transistor (for example bipolar transistor or (junction) field-effect transistor, MOS-FET). The switching element S2 is preferably connected between the second output terminal and the second input terminal and, depending on the switching state, current-permeable or low-resistance or current-impermeable or high-resistance.

The blocking element is preferably set up to block current flow in one direction, at least in a specific voltage range. It is preferably a diode (e.g., pn diode), more preferably a transistor. Preferably, the blocking element is connected between the second output terminal and the first input terminal. It preferably blocks a current flow via the switching element S2 (if this is permeable / low-resistance) between the first and second input terminal and thus prevents a short circuit in this switching state. For example, it blocks current from the first input terminal to the second output terminal and is permeable to current in the other direction or low impedance, provided that in this direction a voltage is applied, which is higher than a possibly necessary forward voltage or threshold voltage.

In a preferred embodiment of the voltage converter according to the invention, the blocking element (42) can be switched and the voltage converter (1) is furthermore inserted. directed, the blocking element (42) clocked, preferably with variable duty cycle, to switch. This additionally makes it possible to modulate the average value of the output voltage of the voltage converter by means of the cyclic activation, for example by means of a PWM control. For example, the brightness of LEDs connected as load to the output terminals can be dimmed. For this purpose, the blocking element is preferably a transistor which is connected as a controllable switch between the second output terminal and the first input terminal.

In a preferred embodiment of the voltage converter according to the invention, the latter is set up to switch the switching element S2 (41) clocked, preferably with a variable duty cycle. This opens up a further possibility to modulate the mean value of the output voltage of the voltage converter, e.g. by means of a PWM control. For example, Thus, the brightness of LEDs connected as load to the output terminals can be dimmed. For this purpose, the switching element S2 is preferably a transistor which is connected as a controllable switch between the second output terminal and the second input terminal.

Preferably, both the switching element S2 and the blocking element are clocked controlled. In a preferred process according to the invention, one or both of the following steps are carried out:

- Clockwise switching of a blocking element (42) of the switch (40);

- Clockwise switching of a switching element S2 (41) of the switch (40).

This increases the flexibility to be able to adjust or set different operating points of the combination of voltage converter and connected load.

In a preferred embodiment of the voltage converter according to the invention, the boost converter (20) has an inductor (21), a switching element S1 (22), a diode (23) and a capacitor (24). As a result, with simple elements a boost converter can be realized (so-called boost converter), which has a high efficiency. The inductance is eg a coil or choke, the switching element S1 eg Transistor, the capacity eg a capacitor. The voltage converter is preferably set up to switch the switching element S1 clocked.

In a preferred embodiment of the voltage converter according to the invention, this is set up to switch the switching element S1 (22) clocked with a variable duty cycle. In a preferred method according to the invention, the step is further carried out:

Clockwise switching of a switching element S1 (22) of the step-up converter (20) with a variable duty cycle.

As a result, the degree of voltage conversion of the boost converter is adjustable.

Preferably, both the switching element S1 and the switching element S2 and / or the blocking element are clocked, preferably with variable duty cycle, controllable, thereby further increasing the flexibility to set different operating points of the combination of voltage converter and connected load. Preferably, the diode of the boost converter is a switch, e.g. as a transistor, executed and this switch and the switching element S1 are synchronously switchable, or operated synchronously or are synchronously switched or operated. As a result, a so-called synchronous boost converter or synchronous converter with simple components and high efficiency can be realized.

The object is further achieved according to the invention by a particular

Lighting device for a vehicle, wherein the lighting device comprises a voltage converter according to the invention (1) and at least one lighting means (51) which is connected to the output (30) of the voltage converter (1).

In this way, a lighting system according to the invention is flexibly adaptable to the number of connected lamps, in particular LED, or different input voltages, and a high efficiency is achieved in that instead of a conventional buck converter, a switch of the voltage converter according to the invention for switching between two topologies is present. Preferably, 1 to 14 LEDs are connected in series. Especially preferred 1 to 20 LEDs are connected in any series and / or parallel connection.

Embodiments of the invention are explained below with reference to the drawings. Show it:

1 shows a voltage transformer according to the invention,

Fig. 2 shows a voltage converter according to the invention, wherein the switch by means of a

Locking elements and a switching element is realized,

Fig. 3 shows a voltage converter according to the invention, wherein the boost converter a

Inductance, a switching element S1, a diode and a capacitance, Fig. 4 shows a lighting device according to the invention with a voltage converter according to the invention.

1 shows a voltage converter 1 according to the invention. It has an input 10 with a first input terminal 11 and a second input terminal 12. These are connected to an up-converter 20. The voltage converter 1 also has a switch 40 and an output 30 with a first output terminal 31 and a second output terminal 32. The output terminal 31 is connected to the boost converter 20 and the output terminal 32 is connected to the common center terminal of the switch 40, here a changeover switch. The two other terminals of the switch 40 are connected to one of the input terminals 11, 12, respectively. The switch 40 is thus arranged to switch the second output terminal 32 either to the first input terminal 11 (as shown) or to the second input terminal 12. To the output terminals 31, 32, a load is switchable to the input terminals 11, 12, a voltage source. In one topology (as shown), the voltage between the output terminals 31, 32, ie, the output voltage, is the potential difference between the first output terminal 31 and the first input terminal 11. In the second topology, the output voltage is the potential difference between the first output terminal 31 and the second input terminal 12 , each less a possible voltage drop across the switch 40. During operation of the voltage converter 1, a switching state of the switch 40 is set depending on the load used. The boost converter 20 converts the voltage applied to the input terminals 11, 12 into a greater or equal voltage.

In this way, by means of the switch 40, the output voltage, adjustable in two stages by means of two topologies.

FIG. 2 shows a voltage converter 1 according to the invention, wherein, in contrast to FIG. 1, the switch 40 is realized by means of a blocking element 42 and a switching element S2 41. Between the second output terminal 32 and the first input terminal 11, the blocking element 42 is connected. Between the second output terminal 32 and the second input terminal 12, the switching element S2 41 is connected.

During operation of the voltage converter 1, the blocking element 42 blocks a current between the input terminals 11, 12 via the switching element S2 41 when it is turned on or low impedance.

Thus, a short circuit is prevented when the switching element S2 41 is turned on or low impedance, on the other hand, a current path between the second output terminal 32 and the first input terminal 11 is possible.

FIG. 3 shows a voltage converter 1 according to the invention, wherein the up-converter comprises, preferably consists of, an inductance 21, a switching element S1 22, a diode 23 and a capacitor 24. The inductor 21 is connected to the first input terminal 11 and connected in series with the diode 23 between the first input terminal 11 and the first output terminal 31. The switching element S1 22 is connected to one terminal between the inductor 21 and the diode 23 and with the other Connection to the second input terminal 12 or ground. The capacitance 24 is connected between the first output terminal 31 and the second input terminal 12 or ground. The input voltage 13 between the input terminals 11, 12 is positive, as well as the output voltage 33 between see the output terminals 31, 32. There is a load 50 at the output 30 indicated. The blocking element 42 is a diode which is connected in such a way that it blocks a flow of current from the first input terminal 11 to the second output terminal 32.

In the operation of the invention, the input voltage 13 is converted via the inductor 21, the switching element S1 22, the diode 23 and the capacitor 24, as a result, the voltage between the first output terminal 31 and the second input terminal 12 is greater than or equal to the input voltage 13. The conversion takes place according to the known principle of up-conversion. In this case, the switching element S2 22 is controlled clocked. By means of (one-time) switching or setting or setting of the switching element S2 41, that of the two possible topologies is selected which better realizes an operating point desired for the load 50. If the switching element S2 41 is turned on or low resistance, then the load 50 is connected by means of the output terminal 32 to ground or reference potential of the second input terminal 12. This current path of the load 50 corresponds to a classic boost topology. If the switching element S2 41 is not turned on or high impedance, the current flows through the load 50 through the diode 42 to the first input terminal 11. This current path of the load 50 corresponds to the so-called buck-boost topology.

In this way, the voltage converter 1 according to the invention or the method according to the invention for voltage conversion with the possibility of switching the topology for adapting the voltage converter 1 to the connected load 50 and / or the input voltage 13 with simple components is possible. Thus, depending on the input voltage 13 and / or number of e.g. LEDs are switched as loads the topology to achieve the best possible mode for driving the LEDs.

4 shows an illumination device according to the invention with a voltage converter 1 according to the invention. The illumination device also has an LED 51 as a load. It is connected to the cathode to the second output terminal 32. In contrast to the voltage converter 1 shown in FIG. 3, this has Voltage converter 1 in addition to an input-side smoothing capacitor 25. Furthermore, a battery 14 is connected to the input 10 and the switching elements S1 and S2 S2 41 are implemented as MOS-FETs, which are each controlled by a control signal 26 and 43 respectively.

In operation of the illumination device, the smoothing capacitor 25 smoothes voltage fluctuations, e.g. occur by other connected to the battery 14 consumers.

The control signal 26 is a constant clock signal (e.g., 400kHz), preferably a variable duty cycle PWM signal. Thus, the strength or the degree of up-conversion is adjustable. For example, Dimming of the LEDs with approx. 200Hz is carried out via an ON / OFF operation with a varying duty cycle. This has the advantage that this dimming is cheaper than a dimming by means of a circuit breaker.

By means of the control signal 43, depending on the number and / or interconnection of the connected LEDs, a switchover to the most suitable topology is carried out. The input voltage is e.g. 28V. If the switching element S2 43 is turned on or low impedance, the sum of the forward voltages of series connected between the output terminals 31, 32 LEDs in the strand must be greater than the input voltage to prevent unwanted, no longer influenced, current. If the forward voltage of an LED is e.g. 2V and if less than 14 LEDs are connected in series at the output 30, then the topology with non-switched or high-impedance switching element S2 43 is selected. In this example, it thus follows that the switching element S2 43 is open or high-resistance until approximately 14 LEDs, and the current flows via the blocking element 42. With a higher number of connected LEDs, it is advantageous to drive the switching element S2 43 conductive or low resistance.

In a variant, the diode 42 is designed as a transistor and is like the switching element S2 43 driven by a signal. This signal is preferably a clocked PWM signal with a variable duty cycle. As a result, a dimming of the LEDs is also feasible. In a further variant, the switching signal 43 is a PWM signal with a variable duty cycle. In this way, a dimming of the LEDs is feasible in another or additional way.

With this invention, a voltage converter, a lighting device and a method for converting a voltage has thus been provided for the first time, which allow a flexible adaptation to different loads (eg different numbers and / or interconnections of LEDs) and different input voltages with a simple switching structure. In particular, a first topology and a second topology can be selected by means of a switch, one of these topologies corresponding to a bottom topology and the other to a buck-boost topology (preferably non-inverting), or simulating its effect. By means of the switch is the second output terminal, which is preferably that output terminal which is not directly connected to the up-converter, either switchable to one or the other input terminal. The potential of the second output terminal can be coupled to two different potentials. Thus, different output voltages of the voltage converter can be easily realized with high efficiency. The preferred implementation of the switch by an electronically controllable switching element S1, such as a transistor in combination with a blocking element such as a diode or a transistor, is extremely compact and inexpensive. The use of switchable transistors as a switching element S1 and / or switching element S2 and / or as a blocking element allows flexible adjustment of an operating point of the circuit with the load connected under adjustment of the control parameters of the switch, including, for example, the duty cycle or the duty cycle of a PWM control counting. The more PWM-driven transistors are used, the greater the flexibility, and for each PWM drive also higher costs incurred. LIST OF REFERENCE NUMBERS

I voltage converter 10 input

I I First input terminal

12 second input terminal

13 input voltage

14 battery

20 boosters

21 inductance

22 switching element S1

23 diode

24 capacity

25 smoothing capacitor

26 control signal

30 output

31 First output terminal

32 Second output terminal

33 output voltage

40 switches

41 switching element S2

42 blocking element

43 control signal

50 load

51 bulbs, LED

Claims

- 1 - Voltage transformer, lighting device and method for converting a voltage claims

1. voltage converter (1), wherein the voltage converter (1) has an input (10) with a first input terminal (11) and a second input terminal (12) and the voltage converter (1) has a boost converter (20) and an output (30) having a first output terminal (31) and a second output terminal (32),

characterized in that

the voltage converter (1) comprises a switch (40) arranged to pull the second output terminal (32) either to the potential of the first input terminal (11) or to the potential of the second input terminal (12).

2. Voltage converter (1) according to claim 1, wherein the switch (40) has a switching element S2 (41) and a blocking element (42).

3. voltage transformer (1) according to claim 2, wherein the blocking element (42)

is switchable and the voltage converter (1) is further arranged to switch the blocking element (42) clocked.

4. voltage converter (1) according to one of claims 2 to 3, wherein the voltage converter (1) is arranged to switch the switching element S2 (41) clocked.

A voltage converter (1) according to any one of the preceding claims, wherein the boost converter (20) comprises an inductor (21), a switching element S1 (22), a diode (23) and a capacitor (24).

6. voltage converter (1) according to claim 5, wherein the voltage converter (1) is adapted to switch the switching element S1 (22) clocked with a variable duty cycle. - 2 -

7. lighting device for a vehicle,

characterized in that

the lighting device has a voltage converter (1) according to one of the preceding claims and at least one lighting means (51) which is connected to the output (30) of the voltage converter (1).

8. A method for converting a voltage by means of a voltage converter (1) having an input (10) with a first input terminal (11) and a second input terminal (12) and having a boost converter (20) and an output (30) with a a first output terminal (31) and a second output terminal (32), wherein the following step is performed: a) upconverting an input voltage (13);

characterized in that

the following step is carried out:

The method of claim 8, wherein additionally one or both of the following steps are performed:

- Clockwise switching of a blocking element (42) of the switch (40);

- Clockwise switching of a switching element S2 (41) of the switch (40).

10. The method of claim 8 to 9, further comprising the step of: