Provision of two mutually different electrical DC voltages by means of an energy converter

Abstract

The invention relates to a method for providing two mutually different electrical DC voltages (12, 14) by means of a clocked energy converter (10) by using a converter switching unit (16) to apply electrical energy from an electrical energy source (20) to a storage inductor (18) and to supply electrical current of the storage inductor (18) to a first electrical capacitor (22), wherein the operation of the converter switching unit (16) is controlled depending on a result of a first comparison of the first DC voltage (12) with a first voltage comparison value. According to the invention, the electrical current of the storage inductor (18) is supplied to the first electric capacitor (22) depending on a switching state of a secondary switching unit (26), wherein the electrical current of the storage inductor (18) is supplied to a second electrical capacitor (24) depending on the switching state of the secondary switching unit (26), wherein the switching state of the secondary switching unit (26) is controlled depending on a result of a second comparison of the second DC voltage (14) with a second voltage comparison value.

Description

[0001] PROVIDING TWO DIFFERENT ELECTRICAL DC VOLTAGES USING AN ENERGY CONVERTER

[0002] DESCRIPTION

[0003] The invention relates to a method for providing two mutually different electrical direct voltages, wherein a first of the two direct voltages, which has a greater voltage value than a second of the two direct voltages, is provided by means of a clocked energy converter in that a converter switching unit of the energy converter supplies a storage inductance of the energy converter with electrical energy from an electrical energy source and an electrical current of the storage inductance is supplied to a first electrical capacitor at which the first direct voltage is provided, wherein the operation of the converter switching unit is controlled depending on a result of a first comparison of the first direct voltage with a first voltage comparison value.Furthermore, the invention relates to a clocked energy converter for providing two mutually different electrical direct voltages, wherein the energy converter has a converter switching unit that can be electrically coupled to an electrical energy source, a storage inductance that is electrically coupled to the converter switching unit, and at least one first electrical capacitor for providing a first of the two direct voltages that has a greater voltage value than a second of the two direct voltages, wherein the first electrical capacitor is electrically coupled to the storage inductance, wherein the energy converter is designed to control an operation of the converter switching unit depending on a result of a comparison of the first of the two direct voltages with a first voltage comparison value.

[0004] Generic procedures as well as generic clocked

[0005] Energy converters are extensively known in the art, so that in principle no special written proof is required for this. Generic clocked energy converters are generally used to provide two different electrical direct voltages essentially simultaneously during normal operation. Preferably, the two direct voltages to be provided use a common electrical reference potential or a common reference ground. Depending on requirements, however, the direct voltages can also be electrically separated from one another, for example galvanically separated, by providing a suitable galvanic isolation unit.

[0006] DC voltages can be used to supply electrical power to electronic units, such as control units or the like, as may be used for sensors, particularly in the automotive sector, but also for lighting devices, such as ballasts or the like. It is particularly difficult to adjust or regulate both DC voltages with sufficient precision using a single clocked energy converter. Especially when the loads on the two DC voltages vary, problems can arise in the current state of the art during normal operation.In the state of the art, it is therefore provided that the clocked energy converter has a large setting reserve for the provision of both direct voltages, as a result of which a correspondingly high power loss generally occurs, particularly in a partial load range, for example in a sleep mode (English: sleep mode, standby mode).

[0007] In this context, EP 2 716 134 B1 discloses a method for controlling LED light sources and an associated device. Furthermore, US 10 447 168 B2 discloses an electronic converter and an associated method for operating an electronic converter. Even if this prior art has proven itself, there is still room for improvement. In particular, when the power requirement for the first and second direct voltages of electrical consumers or electronic devices connected thereto is low, it is desirable to improve the efficiency. For example, this concerns the sleep mode of the device supplied by the clocked energy converter, for example the lighting device or the like.In standby mode, a particularly low power consumption is generally desired in order to keep the load on the electrical energy source as low as possible, particularly when the switch-mode energy converter is permanently electrically coupled to the electrical energy source. This should enable overall energy savings.

[0008] It is the object of the invention to improve a generic method and a generic clocked energy converter in such a way that the energy efficiency can be improved, in particular in the partial load range, particularly preferably in a standby mode.

[0009] As a solution, the invention proposes a method and a clocked energy converter according to the independent claims.

[0010] Advantageous further developments arise from features of the dependent claims.

[0011] With regard to a generic method, the invention particularly proposes that the electrical current of the storage inductance is supplied to the first electrical capacitor as a function of a switching state of a secondary switching unit when the secondary switching unit assumes a first switching state, wherein the electrical current of the storage inductance is supplied to a second electrical capacitor as a function of the switching state of the secondary switching unit when the secondary switching unit assumes a second switching state, wherein the second DC voltage is provided at the second electrical capacitor, wherein the switching state of the secondary switching unit is controlled as a function of a result of a comparison of the second DC voltage with a second voltage comparison value.

[0012] With regard to a generic clocked energy converter, the invention proposes in particular that the energy converter has a second electrical capacitor for providing the second DC voltage, and a secondary switching unit electrically coupled to the storage inductance and the first and second electrical capacitors in order to supply the electrical current of the storage inductance either to the first electrical capacitor or to the second electrical capacitor depending on a switching state of the secondary switching unit, and wherein the energy converter is designed to control the switching state of the secondary switching unit depending on a result of a comparison of the second DC voltage with a second voltage comparison value.

[0013] The invention is based on a clocked energy converter which is designed to provide a single direct voltage. Such a clocked energy converter can be designed, for example, as a step-up converter (booster), as a step-down converter (buck), as a combination thereof, in the manner of a DC-DC converter or the like. The clocked energy converter can be designed to be supplied with a direct voltage from the electrical energy source. In principle, however, it is also possible for the clocked energy converter to be designed to be supplied with an alternating voltage from the electrical energy source. Combinations of these can of course also be provided. The energy converter can be designed in one stage or in multiple stages.An energy converter of the generic type, in particular a single-stage one, usually has at least one electronic switching element, in particular a transistor, a thyristor, or the like, which interacts with the storage inductance. This switching element is frequently combined with a diode in order to achieve the desired conversion effect. Instead of the diode, a second electronic switching element can of course be used. The transistor can be, for example, a bipolar transistor, but also a field-effect transistor, in particular a MOSFET, an IGBT, or the like. In principle, however, a thyristor arrangement, in particular a GTO or the like, can also be used as the electronic switching element.

[0014] On the lighting device side, it is particularly proposed that the lighting device comprise a clocked electronic energy converter according to the invention, which, as a consumer, supplies a lighting device with electrical energy in a controllable manner. Consequently, the lighting device according to the invention has the same effects and advantages as the energy converter according to the invention.

[0015] The invention is based, among other things, on the idea of ​​being able to provide the second DC voltage by means of the energy converter providing the first DC voltage, without placing a load on the first DC voltage itself during normal operation, for example, by an electrical actuator extracting electrical energy from the first electrical capacitor and supplying it to the second electrical capacitor. Rather, in the invention, the energy supply for the first and second electrical DC voltages is provided directly from the storage inductance via the secondary switching unit.

[0016] Regarding the first DC voltage and the

[0017] For this purpose, the voltage regulation characteristic, which is controlled by the converter switching unit depending on the result of the first, can be retained, as with an energy converter that only needs to provide a single DC voltage. Thus, with respect to the first DC voltage, which has the higher voltage value than the second DC voltage, essentially no changes need to be made with respect to the clocked energy converter. In this respect, the invention is even suitable for retrofitting already known designs for clocked energy converters.

[0018] The invention now uses the secondary switching unit to be able to feed the electrical current provided by the storage inductance, in particular either to the first capacitor or to the second capacitor, depending on its switching state. This means that in a first switching state of the secondary switching unit it is preferably provided that the electrical current of the storage inductor is fed to the first capacitor and electrical energy can thus be made available for electrical consumers connected to the first DC voltage. In a second switching state of the secondary switching unit the current supply from the storage inductance to the first electrical capacitor is preferably interrupted. Instead the electrical current is now fed to the second electrical capacitor.

[0019] Even during this second switching state, the control functionality with regard to the converter switching unit is preferably maintained essentially unchanged. This means that if the first comparison of the first direct voltage with the first voltage comparison value results in an energy requirement for the first direct voltage, this energy requirement preferably continues to be decisive for the control of the converter switching unit. Because the electrical current supplied by the storage inductance to the second electrical capacitor is not available for the first direct voltage, this control state is at least maintained; depending on the load on the first direct voltage, the power requirement may even increase.However, the electrical power converted by the energy converter and the converter switching unit is now fed to the second electrical capacitor and the electrical loads connected to the second electrical DC voltage. This allows the second DC voltage to be maintained or increased if sufficient electrical power is supplied. As soon as the secondary switching unit switches back to the first switching state based on the result of the second comparison, the electrical current of the storage inductance is fed back to the first capacitor, and the first DC voltage is supported accordingly.

[0020] The first voltage comparison value is a voltage comparison value that corresponds to a desired value of the first DC voltage, for example a first target value. The first voltage comparison value is preferably a value that corresponds to a desired voltage value for the first DC voltage. The same applies to the other voltage comparison values, in particular to the second voltage comparison value. The voltage comparison value can also have an upper and a lower value that are spaced apart from one another and can, for example, define a tolerance band.

[0021] The control of the switching of the secondary switching unit from the first switching state to the second switching state or vice versa is controlled depending on the result of the second comparison. The second voltage comparison value is preferably a value that corresponds to a desired voltage value for the second direct voltage. This second voltage comparison value is therefore generally smaller than the first voltage comparison value. If the second comparison shows that an actual value of the second direct voltage is greater than the second voltage comparison value, a corresponding switching signal can be output to the secondary switching unit, which then switches from the second switching state to the first

[0022] Switching state switches, so that the electrical current of the storage inductance is no longer supplied to the second electrical capacitor, but instead to the first electrical capacitor. This allows a complete control loop to be created with respect to the first DC voltage.

[0023] The capacitance values ​​of the first and second electrical capacitors are suitably selected so that a desired predetermined control tolerance with respect to the first and / or the second electrical DC voltage can be achieved.

[0024] From the above functional description it can be seen that in the first switching state of the secondary switching unit the clocked energy converter basically functions like a clocked energy converter of the prior art which is only able to provide a single electrical direct voltage. By additionally arranging the secondary switching unit in conjunction with the second electrical capacitor the generation of the second electrical direct voltage can be set up in addition without having to intervene in the existing control or regulation concept of the clocked energy converter with regard to the first direct voltage. Instead a separate regulation can be used here to branch off electrical power from the first control loop for the second control loop with regard to the second direct voltage as required.This allows for a particularly simple and cost-effective concept, which also allows for particularly low energy consumption, especially at low power levels, especially in idle mode. This allows for significant energy savings, especially when the switch-mode energy converter is essentially permanently supplied with electrical energy from the electrical energy source.

[0025] The storage inductance of the energy converter is preferably an electronic component, for example in the form of an electronic coil or a transformer, which can be coupled to the electrical energy source as required by means of the converter switching unit. For this purpose, the converter switching unit can comprise one or more electronic switching elements, in particular transistors.

[0026] A switching element or an electronic switching element, in particular a semiconductor switch, within the meaning of this disclosure is a preferably controllable electronic switching element, for example a transistor, a thyristor, combination circuits thereof, in particular with parallel-connected freewheeling diodes, for example a metal oxide semiconductor field effect transistor (MOSFET), an insulated gate bipolar transistor (IGBT), preferably with integrated freewheeling diodes, or the like. The switching element is operated in switching mode.

[0027] The switching operation of the semiconductor switch in the form of a transistor means that in an on-state a very low electrical resistance is provided between the terminals of the transistor forming the switching path, so that a high current flow is possible with a very low residual voltage. In the off-state the switching path of the transistor has a high impedance, i.e. it provides a high electrical resistance, so that even when a high voltage is applied to the switching path there is essentially no current flow or only a very low, in particular negligible, current flow. This differs from linear operation in transistors. The secondary switching unit can also have one or more electronic switching elements in order to be able to provide the desired switching functionality.The switching elements are preferably provided with a control terminal that is electrically coupled to a corresponding control unit of the clocked energy converter. This allows the switching elements to be supplied with corresponding switching signals by the control unit, so that the desired switching operation can be realized. The secondary switching unit is preferably a component of the energy converter. The function of the second comparison can be provided by the energy converter, in particular the secondary switching unit. The function of the second comparison can be provided, for example, by means of the control unit.

[0028] The control unit can take over or provide functions relating to the control of the converter switching unit and the secondary switching unit, in particular with regard to the operation of the switching elements, the provision of the direct voltages by the energy converter and / or the like. The control unit can be designed to be electrically insulated from the converter switching unit and / or the secondary switching unit and can preferably be connected to them in a galvanically isolated manner. The control unit itself can be provided as a separate structural unit. However, it is preferably a component of the energy converter and particularly preferably arranged so as to be integrated therein. The control unit can basically be designed at least partially or even completely as an electronic hardware circuit.Furthermore, the control unit can also be formed, at least partially or entirely, by a computer unit controlled by a suitable computer program in order to be able to provide the desired functionality. The secondary switching unit and / or the converter switching unit can also have one or more diodes for proper operation.

[0029] The invention thus makes it possible to improve energy efficiency, particularly in the partial load range, compared to the prior art. The inventive addition enables a reliable, stable concept for providing two electrical direct voltages to be implemented with minimal effort. Therefore, the operation of the secondary switching unit generally does not interfere with the operation of the converter switching unit.

[0030] According to a further development, it is proposed that the switching state of the secondary switching unit is controlled independently of a switching operation of the converter switching unit. The invention specifically allows the operation of the secondary switching unit to be decoupled from the switching operation of the converter switching unit. This makes it possible to provide independent controls or regulations with regard to the switching operation of the converter switching unit and with regard to the switching operation of the secondary switching unit with regard to their at least two switching states. This also makes it possible for the clocked energy converter to have a modular design, whereby the outlay for its production can be reduced. Furthermore, reliable operation under a wide variety of load and / or operating conditions can be achieved in a simple manner.A clock rate of the secondary switching unit can thus deviate from a clock rate of the converter switching unit, preferably even vary substantially independently thereof.

[0031] It is further proposed that the switching state of the secondary switching unit is controlled as a function of a result of a third comparison of the electrical current of the storage inductance with a current comparison value. This development is preferably provided at least for the second switching state of the secondary switching unit or even only for the second switching state of the secondary switching unit. For example, this can ensure that a predetermined current is not undershot and / or not exceeded. It can be achieved in a particularly advantageous manner that, in particular in the second switching state of the secondary switching unit, a minimum current can be permanently guaranteed. This can be advantageous for intended operation, as will be explained in more detail below.In addition, however, it can also be provided that, by appropriately selecting the current comparison value, the supplied electrical current becomes zero for at least a predetermined period of time or - depending on the design - can possibly even become negative. This can - depending on the design of the secondary switching unit - support the reliable operation of the secondary switching unit. Overall, the function of the clocked energy converter can be further improved. The third comparison can be carried out at predetermined times and / or in one or more predetermined time periods. It can be provided that the third comparison is not carried out continuously.

[0032] According to a further development, it is proposed that the switching state of the secondary switching unit is controlled as a function of an operating state of a series regulator unit connected to the second electrical capacitor. The series regulator unit can serve to provide a third direct voltage which is dependent on the second direct voltage and which is provided with a high quality, in particular with a high level of stability and accuracy. In particular, voltage fluctuations, for example due to the switching operation of the secondary switching unit and / or the converter switching unit, can be reduced. This is advantageous, for example, for voltage-sensitive electronic consumers which are to be supplied with electrical energy via the second direct voltage and whose reliable, intended operation requires a voltage supply which is as stable as possible.For example, the longitudinal regulator unit can be provided to supply a computer unit, for example in the form of a microcontroller, an analog-to-digital converter, a digital-to-analog converter and / or the like, with electrical energy. Depending on a voltage supply requirement for the longitudinal regulator unit, the operation of the secondary switching unit can thus be controlled so that the longitudinal regulator unit is able to provide a third direct voltage that is as stable and precise as possible, which is supplied with electrical energy from the second direct voltage. This also makes it possible, for example, to keep a voltage difference between the second direct voltage and the third direct voltage, which is responsible for a corresponding power loss at the longitudinal regulator unit, as small as possible.

[0033] It is further proposed that electrical energy from the first electrical capacitor is supplied to the second electrical capacitor via a coupling circuit depending on a result of a fourth comparison of the second direct voltage with a third voltage comparison value. The third voltage comparison value is preferably smaller than the second voltage comparison value. This embodiment makes it possible, if necessary, to branch off additional electrical energy from the first direct voltage to the second direct voltage. This is particularly advantageous, for example, in the event of faults in the electrical energy supply via the electrical energy source, for example in the event of a voltage failure or power failure or in the event of undervoltage or the like.This allows for additional backup of the second DC voltage if the intended operation of the pulsed energy converter can no longer guarantee the provision of the DC voltage. Because the coupling circuit can at least temporarily allow the second DC voltage to be supplied with power, it is possible for loads connected to the second DC voltage to back up data and store operating states based on a corresponding control signal before the power supply from the second DC voltage fails.

[0034] This can improve overall reliability and operational safety.

[0035] The coupling circuit can, for example, have a voltage sensor that makes it possible to detect a corresponding disturbance. The voltage sensor can transmit a corresponding control signal to an electronic switching and / or control element, for example, a transistor or the like, in order to establish a corresponding energy coupling so that electrical energy can be transferred from the first capacitor to the second capacitor or to the series regulator. This allows the second or third DC voltage to be maintained for as long as possible.

[0036] It is further proposed that the second DC voltage be regulated by the secondary switching unit to a voltage value that is greater than the minimum electrical voltage required for proper operation of the series regulator unit. This can improve the reliable operation of the series regulator unit.

[0037] It is further proposed that a clock rate of the secondary switching unit is, on average over time, greater than half the clock rate of the converter switching unit. This makes it possible to achieve rapid regulation or control, so that the second direct voltage can also be set or regulated with high precision and speed. The clock rates can be selected in a range from a few hundred Hertz up to a few 100 kHz. It is also proposed that a value which is at least 1 V lower than the first voltage comparison value be selected as the second voltage comparison value. This makes it possible to further improve the reliable function of the secondary switching unit. In particular, decoupling of the first direct voltage from the second direct voltage can be supported.

[0038] It is further proposed that the secondary switching unit comprise a power converter unit. The power converter unit is a unit which permits the electric current to flow only in one preferred direction. The power converter unit can generally comprise one or more diodes. Alternatively or additionally, the power converter unit can also comprise one or more transistors which are controlled accordingly by means of the control unit so that the desired current flow can be achieved. Combinations thereof can of course also be provided. For example, the power converter unit can comprise two diodes which are electrically connected to one another on the cathode side or the anode side, depending on the type of clocked energy converter, the center connection formed thereby being electrically coupled to the electrical storage inductance.The respective other electrodes of the two diodes can then be electrically coupled to the respective first or second electrical capacitor. This makes it possible to direct the flow of the electrical current either to the first electrical capacitor or to the second electrical capacitor. In order to be able to control the flow of current to the first or second electrical capacitor, a corresponding switching element is preferably provided in the secondary switching unit, by means of which the flow of current to the second electrical capacitor can be controlled. Because the second DC voltage has a lower voltage value than the first DC voltage, it can thus be achieved that when the switching element is switched on, the flow of current is automatically directed to the second capacitor via the power converter unit.If, however, the switching element is in the off state, this automatically results in a flow of electrical current via the power converter unit to the first electrical capacitor. This combination allows the function of the secondary switching unit to be realized. Of course, other designs capable of providing corresponding functionality are also possible.

[0039] For example, the converter unit itself can be provided with two switching elements that are alternately operated in switching mode and that, when connected in series, provide a center terminal that is electrically coupled to the storage inductance. The other terminals are electrically coupled to the respective first and second electrical capacitors. Thus, the flow of the electrical current of the storage inductance can also be controlled here by alternating switching.

[0040] The power converter unit preferably has at least one diode, one electrode of which is electrically connected to the storage inductance and the second electrode of which is electrically coupled to the first electrical capacitor. This allows the first electrical direct voltage to be electrically decoupled from the second electrical direct voltage. In the case of a positive electrical first and second direct voltage, an anode electrode of the diode is preferably electrically connected to the storage inductance and a cathode electrode of the diode is electrically coupled to the first electrical capacitor. In this case, the secondary switching unit can also be connected to the storage inductance, preferably directly, or electrically coupled to it.

[0041] It is particularly advantageous to propose that the

[0042] Power converter unit has at least two diodes, the anode electrodes or cathode electrodes of which are electrically connected to one another and to the storage inductance, the respective other electrodes being electrically coupled to the respective electrical capacitors. This makes it possible to achieve particularly simple control of the current flow of the electrical current of the storage inductance with respect to the first or second electrical capacitor. It is particularly advantageous in this regard that the diodes do not need to be controlled, and corresponding expenditure can therefore be saved. As already explained above, only a single switching element is required. The diode between the storage inductance and the second electrical capacitor can, among other things, serve to set a function of the secondary switching unit, as will be explained in more detail below.To provide positive DC voltages, the anode electrodes of the diodes are preferably electrically connected to one another and to the storage inductance. However, in principle, it could also be provided to provide negative DC voltages. In this case, for example, the cathode electrodes of the diodes can be electrically connected to one another and to the storage inductance.

[0043] It is particularly advantageously proposed that the secondary switching unit has a thyristor functional unit which is at least partially connected in series with the power converter unit with regard to the electrical current supplied to the second capacitor. The thyristor functional unit can preferably be connected to the storage inductance, preferably directly, or electrically coupled to it. The thyristor unit has the advantage that control expenditure can be kept low. The thyristor functional unit provides the function of a thyristor. For example, the thyristor functional unit can be formed by a single component as a thyristor. However, the thyristor functional unit can particularly advantageously be implemented by a circuit comprising two transistors, which makes it possible to set specific functional variables of the thyristor functional unit, for example a holding current or the like.For example, the diode of the converter unit between the storage inductance and the second electrical capacitor can serve, among other things, to at least partially adjust the function of the thyristor functional unit, particularly with regard to the holding current. This makes it possible to create a fast-reacting and specifically designed thyristor functional unit with little effort.

[0044] The thyristor functional unit can assume the function of the switching element in the secondary switching unit. Depending on requirements, two or more thyristor functional units can be provided, which can be connected in parallel or in series as required. Furthermore, a thyristor functional unit can also be provided for each coupling to the first or second electrical capacitor. Other designs are conceivable.

[0045] It is further proposed that the thyristor functional unit has a thyristor circuit with two bipolar transistors and at least one electrical resistor electrically coupled to a collector of one of the transistors in order to set a holding current of the thyristor functional unit by means of the electrical resistor. This makes it possible to achieve a particularly cost-effective and simple implementation of the thyristor functional unit. By using bipolar transistors, moreover, a high switching speed can be achieved, so that, in particular in cooperation with the first converter switching unit, good functionality can be achieved which allows a high level of accuracy with regard to setting the second DC voltage.In particular, the diode between the storage inductance and the second electrical capacitor can, among other things, be used to at least partially adjust the holding current when connected in series with the electrical resistor. For example, a non-linear characteristic curve can also be achieved, for example, to enable a "harder" characteristic curve compared to using the resistor alone. Furthermore, a smaller resistance value can be selected when using the diode because a relevant electrical voltage is present across the diode even at a comparatively small electrical current. This means that power loss in this range can also be low.

[0046] It is further proposed that the thyristor circuit arrangement comprise a stability capacitor which is connected at least between the collector of one of the transistors and an emitter of the other of the transistors. The function of the thyristor circuit arrangement can thereby be stabilized. An undesirable tendency of the thyristor circuit arrangement to oscillate can be reduced. The capacitance of the stability capacitor can preferably be selected to be as small as possible, but sufficiently large to ensure stable functionality during normal operation. For example, the capacitance can be a few pF to a few nF. Advantageously, the capacitance lies in a range from approximately 330 pF to approximately 3.3 nF.

[0047] According to a further development, it is proposed that the energy converter have a potential circuit which is designed to apply a preferably fixed, predetermined electrical potential to a control terminal of the thyristor functional unit during normal operation. The potential circuit serves to apply a predetermined electrical potential to the control terminal. In particular, this can also provide the second electrical comparison voltage at the same time. For example, the function of the second comparison can also be provided at least partially by the thyristor functional unit itself. Separate means for carrying out the second comparison can thus be at least partially eliminated.The thyristor functional unit can then be triggered, for example, if a potential difference between the control terminal and a terminal of the thyristor functional unit that is electrically coupled to the second electrical capacitor exceeds a predetermined value. This allows the second comparison to be carried out. The potential circuit can use a constant voltage source and / or a constant current source to provide the constant electrical potential and can, for example, have corresponding electronic components. This can reduce the control effort required for the thyristor functional unit to a minimum. This also allows the second comparison to be carried out by the thyristor functional unit itself, so that the control unit does not need to be used.

[0048] The features and combinations of features mentioned above in the description as well as the features and combinations of features mentioned below in the description of the figures and / or shown alone in the figures can be used not only in the respective combination specified but also in other combinations without departing from the scope of the invention.

[0049] The exemplary embodiments explained below are preferred embodiments of the invention. The features and combinations of features specified above in the description, as well as the features and combinations of features mentioned in the following description of exemplary embodiments and / or shown alone in the figures, can be used not only in the respective combination specified, but also in other combinations. Thus, embodiments are also encompassed by the invention or are to be regarded as disclosed which are not explicitly shown and explained in the figures, but which arise from and can be produced by separate combinations of features from the explained embodiments.The features, functions, and / or effects illustrated by the exemplary embodiments may, in and of themselves, represent individual features, functions, and / or effects of the invention that can be viewed independently of one another, and which also further develop the invention independently of one another. Therefore, the exemplary embodiments are intended to encompass combinations other than those in the embodiments explained. Furthermore, the described embodiments may also be supplemented by further features, functions, and / or effects of the invention already described.

[0050] In the figures, the same reference symbols designate the same features or functions.

[0051] It shows :

[0052] Fig. 1 shows a schematic circuit diagram of an energy converter for providing two electrical DC voltages, wherein a first of the two DC voltages has a higher voltage value than a second of the two DC voltages, wherein the second DC voltage supplies a series regulator for providing a third DC voltage;

[0053] Fig. 2 shows a schematic diagram using respective graphs to show representations of the first, second and third direct voltages and a fourth graph to show a current flow through a storage inductance of the energy converter according to Fig. 1 over time; Fig. 3 shows a schematic diagram as in Fig. 2 with an enlarged temporal section from the diagram according to Fig. 2, the direct voltages supplying electrical consumers (not shown) with electrical energy during normal operation;

[0054] Fig. 4 is a schematic diagram like Fig. 2, wherein the energy converter is operated in a standby mode in which the first DC voltage is substantially unloaded and the second or third DC voltage is loaded with a small standby current in the range of about 3 mA;

[0055] Fig. 5 is a schematically enlarged diagram like Fig. 3 for the operating state according to Fig. 4.

[0056] Fig. 1 shows a schematic circuit diagram of an energy converter 10 in the form of a DC / DC converter. The energy converter 10 serves to provide two different electrical direct voltages 12, 14. A series regulator 28, which provides a third direct voltage 46, is connected to the second direct voltage 14. The first direct voltage 12 and the third direct voltage 46 are provided at undesignated electrical terminals of the energy converter 10. Electrical consumers can be connected to these terminals for the purpose of supplying electrical energy.

[0057] The energy converter 10 is connected on the input side to an electrical energy source 20, which in this case provides a pulsating direct voltage. The pulsating direct voltage can be provided, for example, by rectifying an alternating voltage, for example an alternating voltage from a public power grid or the like. In principle, however, the direct voltage can also be provided as a smoothed direct voltage, for example from an electrical energy storage device such as a battery, an accumulator, a power supply unit and / or the like. The basic function of a buck converter is known to those skilled in the art, which is why detailed explanations thereof will be omitted.

[0058] The energy converter 10 further comprises a converter switching unit 16 that can be electrically coupled to the electrical energy source 20 and that, together with a storage inductance 18 and a diode D1 that are electrically coupled to the converter switching unit 16, provides the function of a step-down converter. In the present case, the converter switching unit 16 is formed by an integrated circuit that, in addition to a switching element, which in this case is formed by a field-effect transistor (not shown), also includes a required control unit 58 for operating the switching element.

[0059] The storage inductance 18 is embodied here as an electronic coil. The storage inductance 18 is electrically connected to the switching element of the converter switching unit 16, so that the storage inductance 19 can be connected to the electrical energy source 20 depending on a switching state of the switching element of the converter switching unit 16 operating in switching mode.

[0060] The energy converter 10 further comprises two capacitors which are connected in parallel in the present case and which have a first electrical capacitor 22 for providing the first of the two direct voltages 12, 14. The first direct voltage 12 in the present case has a voltage value which is approximately 12 V. The first electrical capacitor 22 is electrically coupled to the storage inductance 18, as will be explained in more detail below. Even if a parallel circuit comprising two capacitors is provided for the first electrical capacitor 22 in the present case, a single capacitor 22 can also be provided as a component here - depending on the design.

[0061] The energy converter 10 further comprises the control unit 58. The control unit 58 for the energy converter 10 is presently integrally comprised by the converter switching unit 16.

[0062] In this case, the first DC voltage 12 also serves to supply power to the converter switching unit 16 via a diode D4 and a capacitor C2. Furthermore, a voltage divider comprising the electrical resistors R2, R3 is provided in parallel with the capacitor C2. A center tap of this series circuit is also connected to the converter switching unit 16. It serves to detect the first DC voltage 12 for the purpose of regulation. This involves detecting the actual value of the first DC voltage 12.

[0063] The control unit 58 of the converter switching unit 16 compares this detected voltage value and performs a first comparison with a first voltage comparison value. This voltage comparison value corresponds to a voltage value of approximately 12 V. As a result, a control functionality is provided by the control unit 58 of the converter switching unit 16 by operating the switching element of the converter switching unit 16 in switching mode such that the first DC voltage is regulated to 12 V.

[0064] The energy converter 10 further comprises a second electrical capacitor 24 for providing the second DC voltage 14. The second DC voltage 14 has a lower voltage value than the first DC voltage 12, which in this case is approximately 4.5 V.

[0065] Furthermore, the energy converter 10 has a secondary switching unit 26 electrically coupled to the storage inductance 18 and the first and second electrical capacitors 22, 24, in order to supply the electrical current of the storage inductance 18 either to the first electrical capacitor 22 or to the second electrical capacitor 24 depending on a switching state of the secondary switching unit 26. The secondary switching unit 26 is designed to control the switching state of the secondary switching unit 26 depending on a result of a second comparison of the second DC voltage 14 with a second voltage comparison value. The second voltage comparison value is approximately 4.5 V in the present case.

[0066] In this case, the secondary switching unit 26 has a power converter unit 32, which in turn has two diodes 34, 36, the anodes of which are electrically connected to one another and to the storage inductance 18. The respective other electrodes or cathodes of the diodes 34, 36 are electrically coupled to the respective electrical capacitors 22, 24. In this case, the cathode of the diode 34 is directly coupled to the first electrical capacitor 22, whereas the cathode of the second diode 36 is electrically coupled to the second electrical capacitor 24 via a thyristor functional unit 38 described below. The function of the secondary switching unit 26 results from an interaction of the power converter unit 32 with the thyristor functional unit 38, as will be explained below.The thyristor functional unit 38 is connected in series with the power converter unit 32 with respect to the electrical current supplied to the second capacitor 24.

[0067] In the present embodiment, it is provided that the thyristor functional unit 38 has a thyristor circuit with two bipolar transistors 40, 42. The transistor 40 is an NPN transistor, whereas the transistor 42 is a PNP transistor. A collector of the transistor 42 is connected to a base of the transistor 42 via an electrical resistor R5, whereas a collector of the transistor 42 is electrically coupled to the base of the transistor 42 via an electrical resistor R6. An emitter of the transistor 42 is further electrically connected to the storage inductor 18 and the anodes of the diodes 34, 36. An emitter of the transistor 40 is electrically connected to the second electrical capacitor 24. The collector of the transistor 40 is further electrically connected to the cathode of the diode 36 via an electrical resistor 44. The electrical resistor 44 can be used to set a holding current of the thyristor function circuit 38.

[0068] The thyristor function circuit 38 basically provides the function of a thyristor. The basic function of a thyristor is known to those skilled in the art, which is why detailed explanations in this regard are omitted here. As will be explained below, a control connection is provided at the collector of the transistor 42 via an electrical resistor R7. This control connection serves to switch on the thyristor function unit 38 formed by the transistors 40, 42 and the aforementioned corresponding further components. As is known, the thyristor function unit 38 is switched off again when the holding current falls below the limit. This will be explained in more detail below.

[0069] As long as the thyristor functional unit 38 is in the switched-off state, the electrical current of the storage inductance 18 is fed to the first electrical capacitor 22 via the diode 34. In this operating state, the energy converter 10 functions as intended like a conventional step-down converter for providing the first direct voltage 12. This is regulated to the predetermined voltage value by means of the converter switching unit 16. For this purpose, the switching element (not shown) of the converter switching unit 16 is operated, for example, in pulse width modulation (PWM) mode. This operating principle is basically also known to those skilled in the art, which is why detailed explanations in this regard are also omitted here.

[0070] The thyristor functional unit 38 can be switched on by providing a suitable voltage difference between the emitter of the transistor 40 and the collector of the transistor 42. For this purpose, the electrical potential at the resistor R7 is stabilized via a voltage divider comprising electrical resistors R8, R9 and a voltage reference U260. This voltage divider is supplied from the first regulated DC voltage 12. A substantially constant electrical potential is thus provided at the control terminal. A potential difference between the control terminal and the terminal of the thyristor functional unit 38, which is electrically coupled to the second electrical capacitor, thus serves to trigger the thyristor functional unit 38.

[0071] Furthermore, a capacitor C3 is connected to the electrical resistor R7. This allows a hysteresis to be realized with respect to the switching function of the thyristor functional unit 38, so that the thyristor functional unit 38 does not switch to the off state too early, for example, when the holding current is reached.

[0072] With increasing energy consumption in the range of the second DC voltage 14 or the third DC voltage 46, the second DC voltage 14 decreases in the switched-off state of the thyristor functional unit 38. As long as a sufficient voltage difference is available across the series regulator unit 28, the third DC voltage 46 can be kept constant by means of the series regulator unit 28.

[0073] Due to the decrease of the second DC voltage 14, the potential difference between the collector of the transistor 42 and the emitter of the transistor 40 increases, so that when a switching threshold is exceeded, the thyristor functional unit 38 switches to the switched-on state.

[0074] The switching state changes, in the same way as it basically happens with a thyristor. The thyristor function unit 38 therefore carries out a second comparison. As a result of this, and because the second direct voltage 14 is lower than the first direct voltage 12, the electrical current from the storage inductor 18 is no longer conducted via the diode 34 to the first capacitor 22, but instead via the second diode 36 and the thyristor function unit 38 to the second capacitor 24, where it charges this capacitor.

[0075] The current flow is maintained until the holding current of the thyristor functional unit 38 is undershot. The current to the second electrical capacitor 24 decreases as the second DC voltage 14 increases. As soon as the holding current of the thyristor functional circuit 38 is undershot, the thyristor functional circuit 38 switches to the off-state. The electrical current of the storage inductance 18 then commutates via the diode 34 to the first capacitor 22.

[0076] When the thyristor functional unit 38 is in the switched-on state, the control loop with respect to the converter switching unit 16 is maintained. However, because the electrical current from the storage inductance 18 does not reach the first electrical capacitor 22, energy continues to be provided via the converter switching unit 16 by means of suitable switching operation, and this energy is used to charge the second capacitor 24. Only when the second capacitor 24 is sufficiently charged is the charging of the first electrical capacitor 22 enabled again by switching off the thyristor functional unit 38, so that the control functionality of the converter switching unit 16 can be completed again. This construction according to the invention therefore makes it possible to divert energy from the higher-level control loop with respect to the first DC voltage 12 for providing the second DC voltage 14.The control function with respect to the first DC voltage 12 is essentially not affected.

[0077] The series regulator unit 28 has, in a known manner, an NPN transistor Q3, the collector of which is electrically connected to the second capacitor 24 and the emitter of which provides the third DC voltage 46. A base of the transistor Q3 is connected to the voltage reference U260, which in turn is coupled to a center connection of a voltage divider comprising electrical resistors R10, R11. The voltage divider is connected to connection terminals for the third DC voltage 46. In this way, series regulation can be provided in a manner known to those skilled in the art. The base of the transistor Q3 is further connected to the resistor R9, so that a power supply is available for the control element U260.

[0078] As will be shown below, the value of the second DC voltage 14 is selected such that the intended operation of the series regulator unit 28 can be realized. At the same time, however, the value of the second DC voltage 14 is selected so small that the power loss at the transistor Q3 is as small as possible during intended operation.

[0079] In the present embodiment, it is provided that the first and second electrical direct voltages 12, 14 are connected to one another via a coupling circuit 30. The coupling circuit 30 is intended to ensure, in the event of a fault in the voltage supply, for example of the electrical energy source 20, that the second direct voltage 14 or the third direct voltage 46 can be maintained for as long as possible, so that electrical consumers connected thereto can enter a safe operating state and / or save data. For this purpose, the coupling circuit 30 has a series circuit comprising an NPN transistor Q4 and an electrical resistor R13, wherein a collector of the transistor Q4 is connected to a positive electrical potential of the first direct voltage 12 and an emitter is connected via the electrical resistor R13 to the positive electrical potential of the second direct voltage 14.A collector of transistor Q4 is electrically connected to a base of transistor Q4 via a resistor R12. The base of transistor Q4 is further electrically connected to the control element U260 via a diode D5. The base is connected to an anode of diode D5, whereas the control element U260 is connected to a cathode of diode D5.

[0080] If the second DC voltage 14 falls below a voltage value that is determined by the design of the coupling circuit 30, the transistor Q4 goes into an electrically conductive state, so that electrical energy is diverted from the first capacitor 22 to the second capacitor 24. This makes additional electrical energy available for the series regulator 28, so that the third DC voltage 46 can be maintained for as long as possible if, due to a fault in the power supply, normal operation can only be maintained to a limited extent. Such a fault can be caused, for example, by a voltage failure at the electrical energy source 20 or by an undervoltage or the like.

[0081] As long as the second DC voltage 14 is sufficiently greater than the electrical voltage applied to the voltage reference U260, the coupling circuit 30 is in the switched-off state. Only when the second DC voltage 14 is small enough does the coupling circuit 30 enter the electrically conductive state. The coupling circuit 30 then performs a fourth comparison.

[0082] In the present embodiment, it is further provided that the first, second and third direct voltages 12, 14, 46 use the same electrical reference potential.

[0083] Fig. 2 shows, in a schematic diagram representation with graphs 48, 50, 52, 54, temporal signal curves of the first, second and third direct voltages 12, 14, 46 and with the graph 54 a temporal curve of the electrical current of the storage inductance 18. In the present embodiment, it is provided that the graph 48 represents a voltage curve of the first direct voltage 12, whereas a graph 50 represents the voltage curve of the second direct voltage 14. A graph 52 represents the voltage curve of the third direct voltage 46. The abscissa is assigned to the time axis of the time in ms. It can be seen that the first direct voltage 48 is regulated to approximately 12 V by means of the converter switching unit 16. From the graph 50, it can be seen that the second DC voltage 14 fluctuates approximately in a sawtooth shape around the voltage value of 4.5 V. However, the second DC voltage 14 generally remains greater than approximately 4 V.The third DC voltage 46, which is represented by the graph 52, is set with great precision to a DC voltage of approximately 3.3 V. This leaves the series regulator 28 with sufficient voltage reserve to reliably regulate the third DC voltage 46 to the desired value. At the same time, the second DC voltage is so small that the power loss at the series regulator 28, in particular at the transistor Q3, remains as small as possible.

[0084] The electrical current of the storage inductance 18 is shown by graph 54. It can be seen that temporally successive current pulses of approximately 200 mA to approximately 300 mA peak occur. The current pulses charge the first and second electrical capacitors 22, 24 accordingly—as previously explained.

[0085] Fig. 3 shows, in a schematic diagram like Fig. 2, but with a greater temporal resolution, the signal curves as previously explained with reference to Fig. 2. It can be seen that, for example, at a point 56 a kink occurs in the sawtooth-shaped curve of the current according to the graph 54. At this point, the thyristor functional unit 38 is switched to the off switching state, in particular the transistor 40 is switched off. The current flow thus commutates as previously explained with reference to Fig. 1.

[0086] Figures 2 and 3 show the signal curves for a given load situation of the direct voltages 12, 14, 46. In this case, the first direct voltage 12 is loaded with an electrical current of approximately 5 mA. The third direct voltage 46 is loaded with a current of approximately 30 mA.

[0087] Figures 4 and 5 show schematic diagram representations corresponding to the schematic diagrams in Figures 2 and 3, but now for a rest mode or standby mode. In this operating state or mode, the first DC voltage is essentially unloaded. However, there is still energy consumption for the converter switching unit 16's own power supply. The current consumption for the converter switching unit 16 can be in a range from approximately 0.3 mA to approximately 5 mA. The third DC voltage 46 is loaded with approximately 3 mA in this operating state. This results in the corresponding voltage curves or current curves shown in Figures 4 and 5.

[0088] The figures show that, due to the low energy requirement, the clock rate of the converter switching unit 16 is significantly reduced. Furthermore, it can be seen that the fluctuation of the second DC voltage 14 is significantly smaller, as shown in graph 50. 56 again designates a commutation point at which the thyristor functional unit 38 switches to the off-state.

[0089] Even if the thyristor functional unit 38 is formed by a transistor circuit in the present case, a thyristor element can also be provided. However, the thyristor functional unit 38 selected here, with discrete transistors 40, 42, has the advantage that its properties can be easily adjusted, for example, with respect to the holding current or the like. Furthermore, a high switching speed can also be achieved.

[0090] The invention can achieve the following advantages:

[0091] - Low costs

[0092] - Compact design, especially because only a single storage inductance is required,

[0093] - Good availability of the required components, especially because no specific components are required,

[0094] - High efficiency during normal operation and also in standby mode,

[0095] - Full support of a Dexal standard,

[0096] - Good stability for both DC voltages, especially due to independent controls for the first DC voltage and the second DC voltage,

[0097] - Compact size, in particular by using small electrical capacitors at a sufficiently high frequency in relation to the sharing of the electrical current of the storage inductance,

[0098] - High voltage accuracy and especially low ripple for the third DC voltage if a series regulator is used for the third DC voltage.

[0099] The exemplary embodiments serve solely to explain the invention and are not intended to limit it. LIST OF REFERENCE SYMBOLS

[0100] 10 energy converters

[0101] 12 first DC voltage

[0102] 14 second DC voltage

[0103] 16 converter switching unit

[0104] 18 Storage inductance

[0105] 20 electrical energy source

[0106] 22 first electrical capacitor

[0107] 24 second electrical capacitor

[0108] 26 Secondary switching unit

[0109] 28 longitudinal regulators

[0110] 30 coupling circuit

[0111] 32 converter unit

[0112] 34 Diode

[0113] 36 diodes

[0114] 38 Thyristor functional unit

[0115] 40 transistors

[0116] 42 transistors

[0117] 44 electrical resistance

[0118] 46 third DC voltage

[0119] 48 Graph

[0120] 50 graphs

[0121] 52 Graph

[0122] 54 Graph

[0123] 56 positions

[0124] 58 Control unit

[0125] C2 capacitor

[0126] Dl, D4, D5 diode

[0127] R2, R3, R5 to R13 resistance

[0128] Q3 , Q4 transistors

[0129] U 260 voltage reference

Claims

Patent claims 1. A method for providing two different DC voltages (12, 14), wherein a first of the two DC voltages (12), which has a higher voltage value than a second of the two DC voltages (14), is provided by means of a clocked energy converter (10) by supplying a converter switching unit (16) of the energy converter (10) with electrical energy from an electrical energy source (20) to a storage inductor (18) of the energy converter (10) and supplying an electric current of the storage inductor (18) to a first electrical capacitor (22) at which the first DC voltage (12) is provided, wherein the operation of the converter switching unit (16) is controlled depending on the result of a first comparison of the first DC voltage (12) with a first voltage comparison value, characterized in thatthat the electric current of the storage inductor (18) is supplied to the first electric capacitor (22) depending on a switching state of a secondary switching unit (26) when the secondary switching unit (26) assumes a first switching state, wherein the electric current of the storage inductor (18) is supplied to a second electric capacitor (24) depending on the switching state of the secondary switching unit (26) when the secondary switching unit (26) assumes a second switching state, wherein the second DC voltage (14) is provided at the second electric capacitor (24), wherein the switching state of the secondary switching unit (26) is controlled depending on a result of a second comparison of the second DC voltage (14) with a second voltage comparison value.

2. Method according to claim 1, characterized in that the switching state of the secondary switching unit (26) is independent is controlled by a switching operation of the converter switching unit (16).

3. Method according to one of the preceding claims, characterized in that the switching state of the secondary switching unit (26) is controlled depending on a result of a third comparison of the electric current of the storage inductance (18) with a current comparison value.

4. Method according to one of the preceding claims, characterized in that the switching state of the secondary switching unit (26) is controlled depending on an operating state of a longitudinal control unit (28) connected to the second electrical capacitor (24).

5. Method according to one of the preceding claims, characterized in that electrical energy from the first electrical capacitor (22) is supplied to the second electrical capacitor (24) via a coupling circuit (30) depending on the result of a fourth comparison of the second DC voltage (24) with a third voltage comparison value.

6. Method according to one of the preceding claims, characterized in that the second DC voltage is regulated by means of the secondary switching unit (26) to a voltage value which is greater than a minimum electrical voltage required for the intended operation of the longitudinal control unit (28).

7. Method according to one of the preceding claims, characterized in that the clock rate of the secondary switching unit (26) is, on average over time, greater than half the clock rate of the converter switching unit (16).

8. Method according to one of the preceding claims, characterized in that the second voltage comparison value is A value is chosen that is at least 1 V smaller than the first voltage comparison value.

9. Switched-mode power converter (10) for providing two different DC electrical voltages (12, 14) , wherein the power converter (10) - a converter switching unit (16) that can be electrically coupled to an electrical energy source (20) , - a storage inductor (18) electrically coupled to the converter switching unit (16) and - has at least one first electrical capacitor (22) for providing one of the two DC voltages (12) which has a higher voltage value than one of the two DC voltages (14), wherein the first electrical capacitor (22) is electrically coupled to the storage inductor (18), - wherein the energy converter (10) is configured to control the operation of the converter switching unit (16) depending on the result of a first comparison of the first of the two DC voltages (12) with a first voltage comparison value, characterized by - a second electrical capacitor (24) to provide the second DC voltage (14) , - a secondary switching unit (26) electrically coupled to the storage inductor (18) and the first and second electrical capacitors (22, 24) to supply the electric current of the storage inductor (18) either to the first electrical capacitor (22) or to the second electrical capacitor (24) depending on a switching state of the secondary switching unit (26), and - wherein the energy converter (10) is configured to control the switching state of the secondary switching unit (26) depending on the result of a second comparison of the second DC voltage (14) with a second voltage comparison value.

10. Switched-mode power converter according to claim 9, characterized in that the secondary switching unit (26) comprises a power converter unit (32).

11. Switched-mode power converter according to claim 10, characterized in that the power converter unit (32) has at least two diodes (34, 36) whose anode electrodes or cathode electrodes are electrically connected to each other and to the storage inductance (18), wherein the respective other electrodes of the diodes (34, 36) are electrically coupled to the respective electrical capacitors (22, 24).

12. Switched-mode power converter according to one of claims 9 to 11, characterized in that the secondary switching unit (26) has a thyristor functional unit (38) which is at least partially connected in series with the power converter unit (32) with respect to the electric current supplied to the second capacitor (24).

13. Clocked energy converter according to claim 12, characterized in that the thyristor functional unit (38) has a thyristor circuit arrangement with two bipolar transistors (40, 42) and at least one electrical resistor (44) electrically coupled to a collector of one of the transistors (40) in order to set a holding current of the thyristor functional unit (38) by means of the electrical resistor (44).

14. Clocked energy converter according to claim 13, characterized in that the thyristor circuit arrangement has a stabilizing capacitor which is connected at least between the collector of one of the transistors (42) and an emitter of the other of the transistors (40).

15. Switched-mode energy converter according to one of claims 12 to 14, characterized by a potential circuit configured to provide a control connection of the To subject the thyristor functional unit ( 38 ) to a predetermined electrical potential during intended operation.

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