DE202016007136U1 - DC converter - Google Patents

Abstract

A voltage converter (100) comprising: - an input terminal (101), - an output terminal (131), - a first switching element (102), - a storage inductor (111) connected in series with the first switching element (102), A second switching element (182) selectively connecting a point between the first switching element (102) and the storage inductor (111) in a multi-state conducting state selectively to ground or the input terminal, - a secondary inductor (112) inductively connected to the Memory choke (111), and - a driver circuit (280) arranged to provide a signal generated by the secondary choke (112) to operate the second switching element (182) in the plurality of states.

Description

TECHNICAL AREA

The invention relates to a voltage converter. In particular, the invention relates to a voltage converter having a first switching element and a second switching element, a storage choke and a secondary choke, and a driver circuit which is adapted to provide a signal generated by the secondary choke for operating the second switching element in a plurality of states.

BACKGROUND

Voltage transformers make it possible to convert a DC voltage having a first amplitude into a DC voltage having a second amplitude. Voltage transformers are used in different technical fields. For example, voltage converters may be used to convert an input voltage to an output voltage, wherein the output voltage is used to drive a light emitting diode. For example, voltage transformers can be used in conjunction with a rectifier. Conventionally, voltage converters comprise a switching element, a storage choke and a freewheeling diode.

In many applications, it may be desirable to reduce the power consumption of the voltage converter. Sometimes a freewheeling diode of the voltage converter is replaced or supplemented by another switching element. Namely, a switching element, such as a field effect transistor, typically has a particularly low resistance, so that little energy is dissipated.

However, prior art reference implementations which replace a freewheeling diode of the voltage converter or supplement it with another switching element have certain limitations and disadvantages. For example, the control of the switching element can be comparatively complicated and complicated. This may require additional electronic components.

BRIEF SUMMARY OF THE INVENTION

Therefore, there is a need for improved voltage transformers. In particular, there is a need for such voltage transformers which alleviate or overcome the above limitations and disadvantages.

This object is solved by the features of the independent claims. The features of the dependent claims define embodiments.

In one example, a voltage converter includes an input terminal and an output terminal. The voltage converter also includes a first switching element and a storage choke. The storage choke is connected in series with the first switching element. The voltage converter also includes a second switching element. The second switching element selectively connects a point between the first switching element and the storage inductor in a conductive state to ground or to the input terminal. The conductive state is one of a plurality of states of the second switching element. The voltage converter also includes a secondary choke inductively coupled to the storage choke. In addition, the voltage converter also includes a driver circuit configured to provide a signal generated by the secondary choke to operate the second switching element in the plurality of states.

For example, the first switching element and / or the second switching element could each be operated in a conductive state (sometimes referred to as a closed state) and a non-conductive state (sometimes referred to as an open state).

For example, the driver circuit could include a diode connected in series with the secondary choke.

For example, the driver circuit could have a resistor which couples an interface of the driver circuit to the second switching element with a reference potential of the second switching element.

For example, the interface of the driver circuit to the second switching element could be implemented by an electrical connection to a control terminal of the second switching element.

The driver circuit may, for example, exclusively comprise passive electronic components. This means that the driver circuit may not have any active electronic components in some examples.

It would be possible for the driver circuit to comprise only analog electronic components, i. H. no components that implement digital signal processing.

It would be possible for the turns ratio of windings of the storage choke to windings of the secondary choke to be unequal to one, ie one Transformation of the voltage takes place. By transforming the voltage, the control of the second switching element can be tuned to specific requirements of the second switching element, for example a voltage level at the control terminal of the second switching element.

For example, the driver circuit could be configured to switch the second switching element to the conducting state in synchronization with a zero crossing of a throttle current through the storage inductor. Such an operation may, for example, be referred to as zero-current switching. Alternatively or additionally, however, it would also be possible for the driver circuit to be set up in order to switch the second switching element to the conducting state synchronized with a transient of a midpoint voltage at a point between the first switching element and the second switching element. Such an operation may be referred to as zero voltage switching, for example. Such techniques allow a particularly low energy consumption.

A control unit of the voltage converter could z. B. configured to operate the first switching element according to a latching operation of the voltage converter or according to a limiting operation of the voltage converter in the plurality of states of the first switching element, d. H. For example, switch between conductive state and non-conductive state back and forth. By using different operating modes of the voltage converter z. B. the luminous intensity of the LED can be changed in response to a dimming signal.

A controller of the voltage converter may be configured to switch the first switching element based on the signal generated by the secondary choke. In this way, the signal of the secondary choke can be reused, both for switching the first switching element, as well as for switching the second switching element. This allows a high integration density.

The voltage converter could also have a freewheeling diode which is connected in parallel to the second switching element. By the freewheeling diode, a finite switching time of the second switching element can be compensated.

In a disclosed method, a second switching element is alternately operated in a conducting state and a non-conducting state. The second switching element selectively connects a point between a first switching element element and a storage inductor of a voltage converter to ground or an input terminal of the voltage converter in the conductive state. The method further comprises providing a signal generated by a secondary inductor inductively coupled to the storage inductor by means of a driver circuit for operating the second switching element in the conducting state and the non-conducting state.

The features and features set out above, which are described below, can be used not only in the corresponding combinations explicitly set out, but also in other combinations or isolated, without departing from the scope of the present invention.

BRIEF DESCRIPTION OF THE FIGURES

1 schematically illustrates a voltage converter with a high side switching element according to reference implementations.

2 schematically illustrates a voltage converter with a high since switching element according to reference implementations.

3 schematically illustrates a voltage converter with a low side switching element according to reference implementations.

4 schematically illustrates a voltage converter with a high side switching element according to reference implementations.

5 schematically illustrates a voltage converter with a high side switching element and with a secondary choke and a driver circuit according to various embodiments.

6 schematically illustrates a voltage converter with a low side switching element and with a secondary choke and a driver circuit according to various embodiments.

7 schematically illustrates a voltage converter with a high side switching element and with a secondary choke and a driver circuit according to various embodiments.

8th schematically illustrates a time history of various signals of a voltage converter according to various embodiments.

9 FIG. 10 is a flowchart of a disclosed method. FIG.

DETAILED DESCRIPTION OF EMBODIMENTS

The above-described characteristics, features, and advantages of this invention, as well as the manner in which they will be achieved, will become clearer and more clearly understood in connection with the following description of the embodiments, which will be described in detail in conjunction with the drawings.

Hereinafter, the present invention will be described with reference to preferred embodiments with reference to the drawings. In the figures, like reference characters designate the same or similar elements. The figures are schematic representations of various embodiments of the invention. Elements shown in the figures are not necessarily drawn to scale. Rather, the various elements shown in the figures are reproduced in such a way that their function and general purpose will be understood by those skilled in the art. Connections and couplings between functional units and elements illustrated in the figures may also be implemented as an indirect connection or coupling. Functional units can be implemented as hardware, software or a combination of hardware and software.

Hereinafter, techniques related to a voltage converter will be described. The voltage converter may be configured to receive an input signal at an input terminal. For example, the input signal may be a DC voltage having a certain amplitude. The voltage converter may be configured to output an output signal at an output terminal. In this case, the output signal from the voltage converter can be determined based on the input signal. The output signal may in turn be a DC voltage with a certain amplitude, wherein the amplitude of the output signal may differ from the amplitude of the input signal. It is both up-converters - where the amplitude of the DC voltage at the output terminal is greater than the amplitude of the DC voltage at the input terminal - and down-converters - where the amplitude of the DC voltage at the output terminal is smaller than the amplitude of the DC Voltage at the input connection - possible.

For example, it would be possible for a light-emitting diode to be connected to the output terminal of the voltage converter. The light emitting diode may be operated by the voltage converter to emit light. For this purpose, the output signal can be matched to the operating characteristics of the LED. However, other loads could generally be connected to the output terminal of the voltage converter.

1 illustrates aspects related to a reference implementation of a voltage converter 100 , In the example of 1 includes the voltage converter 100 an input terminal 101 and a high side switching element 102 , In the in 1 shown state is the switching element 102 operated in a non-conductive state. In response to a control signal 160 , which may be received, for example, from a control circuit implemented by a microprocessor, may be the switching element 102 between the non-conductive state and a conductive state are switched back and forth.

The voltage converter 100 further includes a storage throttle 111 , as well as one with the storage choke 111 inductively coupled secondary choke 112 , The storage throttle 111 and / or the secondary choke 112 can be implemented as coils with multiple windings. The secondary choke 112 can in a region with significant stray magnetic field of the storage choke 111 be arranged.

In addition, the voltage converter includes 100 a freewheeling diode 103 , The freewheeling diode 103 connects a point between the switching element 102 and the storage choke 111 to ground, ie the switching element 102 is adjacent to the input terminal 101 arranged. Therefore, the switching element 102 referred to as high side switching element. In 1 is also a light emitting diode 130 shown as an exemplary load.

In a conductive state of the switching element 102 a choke current flows through the storage choke 111 by the at the input port 101 supplied input signal is fed. The freewheeling diode 103 is poled against the direction of flow and there is a voltage, which is the voltage of the input signal 101 corresponds to mass. The freewheeling diode 103 prevents a flow of current from the input terminal 101 flowing directly to ground; therefore, the inductor current is fed by the input signal. The storage throttle 111 is magnetized.

When the switching element 102 is operated in a non-conductive state, the inductor current remains through the storage choke 111 first his direction at (induction law). The voltage across the freewheeling diode 103 decreases until the freewheeling diode becomes conductive. There are different operating modes of the voltage converter 100 possible. For example, the switching element could 102 for a comparatively short time in the non-conductive Condition to be operated. Then the inductor current drops through the storage inductor 111 not down to zero. Such operation is often referred to as continuous operation. In other examples, the switching element could 102 be operated in the non-conductive state for a comparatively long time. Then the inductor current drops through the storage inductor 111 down to zero and remain at zero for a certain period of time, or even take negative values. Such an operation is often referred to as a lopsided operation. Logically, as the transition between the lopsided operation and the continuous operation of the so-called boundary operation is settled, in which the inductor current drops to zero and then immediately the switching element 102 is switched from the non-conductive state to the conductive state. The basic operation of the voltage converter 100 according to the reference implementation in 1 is known in the art, so no further details need to be described here.

Depending on the operating mode of the voltage transformer 100 it may be desirable, the inductor current through the storage choke 111 to monitor. This may include, for example, determining the instant at which the inductor current becomes zero. Then, based on the monitoring of the inductor current, a controller (in 1 not shown) a control signal 160 spend to the switching element 102 in the conducting state or the non-conducting state according to the selected operating mode of the voltage converter 100 to operate.

The monitoring of the inductor current may be based on one of the secondary inductor 112 generated signal can be implemented. Due to the inductive coupling of the storage throttle 111 with the secondary choke 112 can namely a voltage that is above the secondary choke 112 drops, indicative of the inductor current through the storage choke 111 be.

2 illustrates aspects related to a reference implementation of a voltage converter 100 , The example of 2 basically corresponds to the example of 1 , In the example of 2 is the inductor current through the storage choke 111 but not monitored by a secondary choke. For monitoring the inductor current through the storage choke 111 are in the example of 2 a diode 171 and a resistance 172 intended. As a result, in particular, a center point voltage at the point between the switching element 102 and the storage choke 111 are measured, wherein the midpoint voltage is in turn indicative of the inductor current.

3 illustrates aspects related to a reference implementation of a voltage converter 100 , The example of 3 basically corresponds to the example of 1 , However, in the example of 3 the switching element 102 arranged adjacent to ground and the freewheeling diode 103 connects a point between the switching element 102 under storage throttle 111 with the input connector 101 , Therefore, the switching element 102 Also referred to as low side switching element.

4 illustrates aspects related to a reference implementation of a voltage converter 100 , The example of 4 basically corresponds to the example of 2 , In 4 is the LED 130 not shown as a load, but rather an output terminal 131 ,

It is also in 4 a control unit 173 represented, which is adapted to the control signal 160 issue. The control unit 173 can for example be implemented by a microcontroller (In 4 as μC). Other examples include an implementation of the controller 173 as an application-specific integrated circuit (ASIC) or as a field-programmable array (FPGA). The control unit 173 is in particular set up to the control signal 160 based on monitoring the inductor current through the storage inductor 111 by means of electronic components 171 . 172 to create.

In addition, the controller 173 set up a control signal 174 for another switching element 182 to generate and output to this. The switching element 182 is parallel to the freewheeling diode 103 connected. The switching element 182 can depending on the control signal 174 optionally be operated in a conducting state or a non-conducting state. When the switching element 182 is operated in the conductive state, the comparatively large resistance of the diode 103 bypassed. This results in a lower energy consumption.

The voltage converter 100 according to the example of 4 is comparatively complex. In particular, it may be necessary for the controller 173 has a dedicated output to the control signal 174 for the switching element 182 provide. Hereinafter, techniques for reducing the power consumption by the switching element will be described 182 even with a comparatively simpler architecture of the voltage converter 100 to reach.

The control of the switching element 182 by means of the control unit 173 can be relatively expensive. For example, in some examples, it may be necessary to have an extra pin of a microcontroller for the switching element 182 provided. The following are techniques described that a particularly simple control of the switching element 182 enable.

5 illustrates aspects related to a voltage transformer 100 according to various examples. The voltage converter 100 in the example of 5 basically corresponds to the voltage transformer 100 according to the example of 1 , The voltage converter 100 according to the example of 5 also includes the input port 101 and the output terminal 131 , For example, a light emitting diode or other load could be applied to the output terminal 131 be connected. The voltage converter 100 also includes the switching element 102 which in turn is based on the control signal 160 is controlled. For this purpose, a control device may be provided (in 5 not shown), z. B. the controller 173 , The switching element 102 is adjacent to the input terminal 101 arranged as a high side switching element. The freewheeling diode 103 and the switching element 182 are connected in parallel. The freewheeling diode 103 and the switching element 182 are between a point between the switching element 102 and the storage choke 111 and mass arranged. When the switching element 182 is operated in a conductive state, connects the switching element 182 the point between the switching element 102 and the storage choke 111 with mass.

In the example of 5 is a driver circuit 280 provided, which is set up by the secondary choke 112 generated signal for operating the switching element 182 to provide in the conductive state or the non-conductive state. By such a direct coupling between the secondary choke 112 and the switching element 182 can be achieved that the switching element 182 is operated very simply and little complex in the different states. In particular, it may be dispensable, for example, that a control unit has a dedicated output for providing a control signal for the switching element 182 has (compare 4 ).

6 illustrates aspects related to a voltage transformer 100 according to various examples. The voltage converter 100 in the example of 6 basically corresponds to the voltage transformer 100 according to the example of 5 , However, this is the switching element 102 not adjacent to the input port 101 arranged; Rather, the switching element 102 arranged adjacent to ground. Therefore, the switching element implements 102 in the example of 6 a low side switching element. The freewheeling diode 103 and the switching element 182 are between a point between the switching element 102 and the storage choke 111 , as well as the input connection 101 arranged. When the switching element 182 is operated in a conductive state, connects the switching element 182 the point between the switching element 102 under storage throttle 111 with the input connector 101 ,

For the voltage converter 100 according to the example of 6 Effects can be achieved, as already stated above with respect to the voltage transformer 100 according to the example of 5 have been described.

7 illustrates aspects related to a voltage transformer 100 according to various examples. The voltage converter 100 according to the example of 7 basically corresponds to the voltage transformer 100 according to the example of 5 , Illustrated 7 the voltage converter 100 and in particular the driver circuit 280 in greater detail. Also 7 implements a high side switching element 102 , In which case a low side switching element would be possible.

The driver circuit 280 includes a diode 281 in series with the secondary choke 112 is switched. In addition, the driver circuit includes 280 a resistance 282 , which is the interface of the driver circuit 280 to the switching element 182 connects to mass. Here mass forms in the implementation according to 7 a reference potential for the switching element 182 out. For example, in an arrangement of the switching element 182 adjacent to the input terminal 101 (see. 6 ) another reference potential by means of the resistor 282 be contacted.

In the various examples described herein, it would be possible for the switching element 182 is designed as a bipolar transistor or as a field effect transistor. Accordingly, it would be possible for the interface of the driver circuit 280 a base terminal of the bipolar transistor or a gate terminal of the field effect transistor contacted as a respective control terminal.

By using simple electronic components like the diode 281 and the resistance 282 can the driver circuit 280 be implemented particularly simple and robust. In particular, it is not necessary, digital logic, such as a microcontroller, etc., to control the switching element 182 to use.

In general it would be possible for the driver circuit 280 exclusively passive electronic components. It would also be possible for the driver circuit 280 includes only analog electronic components. In addition to a reduction in the complexity of the control of the switching element 182 can often also a smaller space for the voltage converter 100 will be realized.

Depending on the type of switching element used 182 It may be necessary for the driver circuit 280 a drive signal to the switching element 182 which provides the requirements of the switching element 182 , for example, in terms of amplitude, etc., is tuned. This can be done, for example, by suitable dimensioning of the parameters of the secondary coil 112 respectively. For example, it would be possible for the turns ratio of windings of the storage choke 111 to windings of the secondary reactor 112 is not equal to one.

7 also illustrates a capacitor 191 and a resistance 192 between the storage choke 111 and the output terminal 131 are arranged. For example, the capacitor could 191 and the resistance 192 cause a smoothing of the output signal. In the various other examples of the voltage converter described herein 100 it would also be possible to use the capacitor 191 and / or the resistance 192 provided.

8th illustrates aspects related to the operation of a voltage converter according to various examples. For example, could 8th the operation of the voltage converter 100 according to the example of 7 illustrate. 8th represents various temporal signal curves for an exemplary voltage converter.

In 8th , above is first the time course of the inductor current 301 through the storage throttle 111 shown. Illustrated 8th an example in which, for example, the controller 173 is set up to the switching element 102 operate in accordance with the intermittent operation. This means that the inductor current 301 a zero crossing 350 and then maintain a value of zero for a certain period of time. In other examples, however, it would also be possible to implement, for example, a continuous operation or a limit operation. This can be done by suitable control of the switching element 102 respectively. For this it would be possible, for example, that the control unit 173 also one of the secondary choke 112 generated signal to the switching times for the switching element 102 to determine accordingly. This means that the control unit 173 could be set up based on by the secondary choke 112 signal generated the switching element 102 to switch. The control unit 173 So could be set up based on by the secondary choke 112 signal generated the control signal 160 to create.

In 8th , Middle is also the time course of the choke voltage 302 at the storage throttle 111 shown. During a period of time in which the inductor current 301 increases, indicates the choke voltage 302 a positive sign. This is the case because, during the so-called switch-on time, a choke voltage is applied to the storage choke, which is the difference between the input voltage at the input terminal 101 and the output voltage at the output terminal 131 results. During a period of time in which the inductor current 301 decreases, indicates the choke voltage 302 however, a negative sign on. This is the case because during the so-called off-time, the inductor voltage equals the negative value of the output voltage at the output terminal 131 is.

The choke voltage at the secondary choke 112 Due to the inductive coupling, it typically has the same qualitative time characteristic as the choke voltage 302 at the storage throttle 111 , The choke voltage at the secondary choke 112 typically has the opposite sign as the choke voltage 302 at the storage throttle 111 , The amplitudes may vary, depending on the turns ratio.

In 8th , below is still the timing of the control signal 303 the driver circuit 280 shown. By using the diode 281 only the positive choke voltages of the secondary choke 112 as a control signal 302 to the switching element 182 output. This will be the switching element 182 optionally in the conductive state 361 and the non-conductive state 362 operated. From the example of 8th it can be seen that the driver circuit 280 is set up to the switching element 182 synchronized with the zero crossing 350 of the inductor current 301 through the storage throttle 111 in the conducting state 361 to operate.

In relation to 9 a method is disclosed. 9 is a flowchart of the method.

In step 1001 For example, a second switching element is alternately operated in a conducting state and a non-conducting state. For this purpose, the second switching element between the conductive state and the non-conductive state can be switched back and forth. The second switching element selectively connects a point between a first switching element of a voltage converter and a storage inductor of the voltage converter in the conducting state to ground or to an input terminal of the voltage converter. For example, the second switching element could connect the point between the first switching element of the voltage converter and the storage choke of the voltage converter in the conductive state to ground, when the first switching element is a high side switching element; Accordingly, the second switching element could connect the point between the first switching element of the voltage converter and the storage inductor of the voltage converter in the conductive state to the input terminal when the first switching element is a low side switching element.

In step 1002 By means of a driver circuit, a signal generated by a secondary choke for operating the second switching element in the conducting state and the non-conducting state is provided. The secondary choke is inductively coupled to the storage choke. For example, the driver circuit could comprise only passive electronic components and / or only analog electronic components.

Of course, the features of the previously described embodiments and aspects of the invention may be combined. In particular, the features may be used not only in the described combinations but also in other combinations or per se, without departing from the scope of the invention.

For example, various voltage transformers have been described above, in which the freewheeling diode is connected in parallel with another switching element. These examples could also be modified to the effect that no dedicated free-wheeling diode is present. The provision of a freewheeling diode may in particular have advantages if the switching element has a finite switching time in order to switch from the non-conducting state into the conducting state. During this switching time then the freewheeling diode already allow a current flow. In some examples, it would also be possible for the corresponding functionality to be provided via a body diode of a field effect transistor implementing the further switching element.

For example, various implementations have been described above with respect to a high side switching element between the input terminal and the storage choke. However, the corresponding implementations could be modified to use a low side switching element adjacent to ground.

Further, various implementations have been described above with respect to the switching of switching elements in response to a choke current through the storage choke. It would also be possible, however, that in addition to or as an alternative to the inductor current, a midpoint voltage between the switching element and the storage inductor is taken into account.

Claims (10)

Voltage transformer ( 100 ), comprising: - an input terminal ( 101 ), - an output terminal ( 131 ), - a first switching element ( 102 ), - a storage choke ( 111 ) connected to the first switching element ( 102 ) is connected in series, - a second switching element ( 182 ), which is a point between the first switching element ( 102 ) and the storage choke ( 111 ) in a multi-state conducting state selectively connects to ground or the input terminal, - a secondary choke ( 112 ), which are inductively connected to the storage choke ( 111 ), and - a driver circuit ( 280 ), which is set up by the secondary choke ( 112 ) generated signal for operating the second switching element ( 182 ) in the multiple states. Voltage transformer ( 100 ) according to claim 1, wherein the driver circuit ( 280 ) a diode ( 281 ) in series with the secondary choke ( 112 ) is switched. Voltage transformer ( 100 ) according to claim 1 or 2, wherein the driver circuit ( 280 ) a resistor ( 282 ) comprising an interface of the driver circuit ( 280 ) to the second switching element ( 182 ) with a reference potential of the second switching element ( 182 ) couples. Voltage transformer ( 100 ) according to one of the preceding claims, wherein the driver circuit ( 280 ) only passive electronic components ( 281 . 282 ). Voltage transformer ( 100 ) according to one of the preceding claims, wherein the driver circuit ( 280 ) only analog electronic components ( 281 . 282 ). Voltage transformer ( 100 ) according to one of the preceding claims, wherein the turns ratio of windings of the storage choke ( 111 ) to windings of the secondary reactor ( 112 ) is not equal to one. Voltage transformer ( 100 ) according to one of the preceding claims, wherein the driver circuit ( 280 ) is arranged to the second switching element ( 182 ) synchronized with a zero crossing ( 350 ) of a throttle current ( 301 ) through the storage throttle ( 111 ) in the conductive state. Voltage transformer ( 100 ) according to any one of the preceding claims, further comprising: - a control device ( 173 ), which is adapted to the first switching element ( 102 ) according to a latching operation of the voltage converter ( 100 ) or according to a limit operation of the voltage converter ( 100 ) in the multiple states. Voltage transformer ( 100 ) according to any one of the preceding claims, further comprising: - a control device ( 173 ) arranged to be based on the energy produced by the secondary reactor ( 112 ) generated the first switching element ( 102 ) to switch. Voltage transformer ( 100 ) according to one of the preceding claims, further comprising: - a freewheeling diode ( 103 ) parallel to the second switching element ( 182 ) is switched.

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