NL2028098B1

NL2028098B1 - Parasitic resonant tuning for reduced switching node ringing in power converters.

Info

Publication number: NL2028098B1
Application number: NL2028098A
Authority: NL
Inventors: Peters Elmar
Original assignee: Elmar Solar
Priority date: 2021-04-29
Filing date: 2021-04-29
Publication date: 2022-11-10
Also published as: WO2022229457A1; TW202312646A

Abstract

A commutation cell for connecting a first power element to a second power element, said commutation cell comprising a switch arranged for, in an ON- state, enabling a first current path in said commutation cell, and, in an OFF-state, enabling a second current path in said commutation cell, wherein said first current path is different to said second current path, a rectifier element provided in said second current path, a controller for controlling said switch between said ON-state and said OFF-state, wherein a resonance circuit is provided in said second current path, said resonance circuit being formed by at least any of parasitic capacitance in any of said switch and said rectifier element, and parasitic inductance of any of said second power element, said switch, said rectifier element and interconnections provided in said commutation cell, such that, when said controller controls said switch from said ON- state to said OFF-state, said resonance circuit causes a current in said second current path to oscillate, wherein a relationship exists between an amplitude of said oscillation of said current in said second current path, and an amount of current in said first current path when said controller controls said switch from said ON-state to said OFF- state, said relationship having a plurality of local maxima in said amplitude for given amount of current, said controller is arranged for controlling said switch from said ON- state to said OFF-state based on said local maxima in said relationship.

Description

Title Parasitic resonant tuning for reduced switching node ringing in power converters.

Technical field The present disclosure is directed to power converters and, more specifically, to a commutation cell for connecting a first power element to a second power element wherein said commutation cell is arranged for reducing oscillations occurring in a current caused by switching of a switch in said commutation cell.

Background In recent years, wide bandgap semiconductor devices have emerged as promising devices for high frequency an high efficiency conversion due to a better figure of merit, FOM, than comparable silicon transistors.

As the switching frequency increases the size of the passive components can be decreased, increasing the power converter density.

In order to maintain high efficiency at high switching frequencies switching losses need to be minimized.

Zero voltage switching, ZVS, operation schemes are used to eliminates turn on losses associated with the capacitive discharge of the parasitic capacitance’s of the switches at turn-on.

ZVS operation allows for a further increase in switching frequency while maintaining high efficiency.

When using ZVS operation, losses and voltage overshoots due to parasitic resonance effects become the limiting factor in converters.

The parasitic power loop inductance introduced by, for example, the output capacitor, semiconductor switches, interconnections and packaging can lead to undesired large voltage spikes during turn-off transients of active switches.

The undesired voltage spikes can potentially exceed the device's voltage ratings and have significant impact on the safe operation of fast switching devices.

Next to the safe operation the parasitic power loop inductance becomes critical to high efficiency.

It has been identified that the power loop inductance may be of importance. Conventionally, people have tried to reduce the loop inductance as much as possible, making all kinds of compromises. When the loop inductance can’t be reduced enough, switch turn-off and turn-on speed are typically limited to reduce ringing, i.e. oscillation, but this increases losses.

A different way of dealing with the switch node ringing could potentially allow more loop inductance and therefore the use of more spacious semiconductor packages that allow for better cooling, larger capacitors, placement of the capacitors further away from the semiconductors / outside of the power module for cooler operating of the capacitors and allow for easier to design and cheaper PCB's.

One of the drawbacks of the power converters in the prior art is related to oscillation that occurs when switching from the ON-state of the switch to the OFF- state of the switch.

Summary It is an object of the present disclosure to provide for an improved commutation cell that has a reduced oscillation effect. It is a further object to provide for corresponding methods, a controller and a computer readable medium.

In a first aspect, there is provided A commutation cell for connecting a first power element to a second power element, said commutation cell comprising: - a switch arranged for, in an ON-state, enabling a first current path in said commutation cell, and, in an OFF-state, enabling a second current path in said commutation cell, wherein said first current path is different to said second current path; - a rectifier element provided in said second current path; - a controller for controlling said switch between said ON-state and said OFF- state; wherein a resonance circuit is provided in said commutation cell, said resonance circuit being formed by at least any of: o parasitic capacitance in any of said switch and said rectifier element;

o parasitic inductance of any of said second power element, said switch, said rectifier element and interconnections provided in said commutation cell; such that, when said controller controls said switch from said ON-state to said OFF-state, said resonance circuit causes a current in said resonance circuit to oscillate; characterized in that a relationship exists between co an amplitude of said oscillation of said current in said resonance circuit, and o an amount of current in said first current path when said controller controls said switch from said ON-state to said OFF-state, said relationship having a plurality of local maxima in said amplitude for given amount of current, said controller is arranged for controlling said switch from said ON-state to said OFF-state based on said local maxima in said relationship.

It was the insight of the inventors that there is a relationship between the amplitude of the oscillation of the current in the resonance circuit and the amount of current tin the first current path when the controller controls the switch from the ON- state to the OFF state.

More specifically, the amount of current flowing through the switch at the moment that the controller controls the switch from the ON-state to the OFF-state is an aspect that determines the amplitude of the oscillation that will occur in the current in resonance circuit. It is noted that the oscillation above is provided with respect to the oscillation occurring in the current. The oscillation may also be provided with respect to the voltage, for example the voltage over the switch.

The inventor has found that the relationship between these two is not random. The relationship has a plurality of local maxima in the amplitude for given amount of current. That is, the relationship may not be strictly monotone increasing, ie. the amplitude of the oscillation may not strictly increase by increasing amount of current in the first current path, when switching from ON-state to OFF-state of the switch.

The amplitude of the oscillation is thus a function of the amount of current when switching from the ON-state to the OFF-state of the switch, and the function has multiple local maxima. The moving average of the function may be strictly monotone increasing, but the function itself is not. The function itself has multiple local maxima.

The inventor has found that it may be undesirable to set the controller in such a way that the switch is switched OFF when the current trough the switch is such that the amplitude would be in a local maximum. This would lead to an undesired oscillating effect.

It may therefore be wise to set the controller based on the local maxima in the relationship. That is, the controller may be tuned to a particular set point based on the location of the local maxima in the relationship.

It is noted that, in accordance with the present disclosure, the switch is arranged to be in an ON-state or in an OFF-state. The switch is, for example, a Field Effect Transistor, FET, like a N-Metal Oxide Semiconductor, NMOS, a PMOS FET, GaN FETs, SiC MOSFETs, HEMTs or anything alike. In another example, the switch is a GaN transistor which is very suitable for high frequency switching.

The rectifier element may, for example, be a diode or anything alike. In the present disclosure, the rectifier may also be encompassed by a further switch or a further switch may be placed in parallel over the rectifier element.

In case of a further switch, the further switch may be turned on once the current crosses zero amperes, or anything close to that.

The controller may, for example, be an integrated circuit, IC, a Field Programmable Gate Array, FPGA, an Application Specific IC, ASIC, micro controller, or anything alike.

The controller may thus control the switch with a control signal having a particular frequency and a particular duty cycle. The control signal determines when the switch is turned ON, i.e. conducting, and when the switch is turned OFF, i.e. non- conducting.

It is noted that the switch may not behave perfectly ideal in the sense that the transition between the ON state and the OFF state is infinitely small. As the switch may be a semiconductor device, the transition between the states may take sever nano-seconds, but is at least much smaller compared to the time period of the oscillation signal.

The resonance circuit may be identified by a plurality of parasitic capacitances and parasitic inductances of the different elements. In addition to the 5 parasitic capacitances and parasitic inductances, additional capacitance and/or inductance may be incorporated. In any case, the presence of the resonance circuit causes the current the current in the resonance circuit to oscillate, and thus also a output voltage to oscillate, for example the voltage over the switch.

It is noted that the parasitic inductance as referenced to in this particular disclosure may be considered as the inductance formed by the magnetic flux that flows through the corresponding element.

As mentioned above, the inventor has found that there is a relationship between the amplitude of the oscillation of the current in the resonance circuit and the amount of current in the first current path at the moment when the controller controls the switch from the ON-state to the OFF-state, and that the relationship has a plurality of local maxima in the amplitude for given amount of current.

The above does not necessarily mean that the relationship as such is implemented in the controller. The above means that knowledge of such a relationship is used by setting the controller at a particular operating point.

Multiple options exist for setting the controller at a particular operating point. For example, during design of a particular Switched Mode Power Supply, SMPS, an electrical engineer may use the knowledge of the relationship for determining one, or more, points in the relationship at which the controller is to be operated.

Another option is that there is provided a feedback loop to the controller for feeding back information with respect to the amplitude of the oscillation, for example a voltage or anything alike, and that this information is used for adjusting the setpoint of the controller. By knowing that the relationship may comprise multiple minima, the controller may adjust the setpoint in such a way that it is searching for the most promising minima. The controller may thus know that, for example, even though the set point is currently in a local minimum, another local minimum exists which may be suitable as well.

Yet another option is that the average current is measured and fed back to the controller. Using the average current, it is possible to calculate the actual current through the switch.

In an example, the controller is arranged for controlling said switch from said ON-state to said OFF-state such that said plurality of local maxima are substantially avoided.

The advantage hereof is that the controller is set such that oscillations having a maximum amplitude are avoided as much as possible. This, thus, does not necessarily mean that the controller is set such that no oscillations in the output current occur, but that at least the controller is set such that oscillations witch a maximum amplitude are avoided as much as possible.

The controller may be set to fully avoid the local maxima. This could mean that although it is preferred to set the controller such that the switch turns OFF at a particular set point, which setpoint is actually located in a local maxima, the controller is set to a different set point to avoid the local maxima. The controller may, for example, interpolate between two local minima, surround the local maxima, in such a way that the average current at which the switch is turned OFF is actually substantially equal to the average current at the local maxima, but due to the fact that the switch is controller in two local minima the oscillations at the output current, and the output voltage, are maintained to a minimum.

In a further example, the controller is arranged for controlling said switch from said ON-state to said OFF-state such that said amplitude of said oscillation is below a predefined threshold.

The advantage hereof is that it may occur that certain components used for building a Switch Mode Power Supply, SMPS, may have a voltage or current rating. The predefined threshold may be used during the development phase for assuring that the components are not substantially used outside their voltage or current rating.

In a further example, the relationship has a plurality of local minima, and wherein said controller is arranged for controlling said switch from said ON-state to said OFF-state in any of said local minima.

The above described example may be considered a preferred example as, in this case, the amplitude of the oscillation signal at the output is contained to a minimum.

In a further example, the controller is arranged for controlling said switch from ON-states to OFF-states at different amount of currents.

That is, the controller may switch the switch to the OFF-state at different amounts of currents, i.e. using interpolation, for obtaining a desired or minimum oscillation signal.

In a second aspect of the present disclosure, there is provided a method for operating a commutation cell in accordance with any of the previous examples, wherein said method comprises the steps of: - controlling, by said controller, said switch from said ON-state to said OFF-state based on said local maxima in said relationship.

It is noted that the advantages as explained with respect to the first aspect, being the commutation cell, correspond to the advantages with respect to the second aspect, being the method for operating a commutation cell.

In an example, the step of controlling further comprises: - controlling, by said controller, said switch from said ON-state to said OFF-state such that said plurality of local maxima are substantially avoided.

In a further example, the step of controlling further comprises: - avoiding, by said controller, said local maxima.

In another example, the step of controlling further comprises: - controlling, by said controller, said switch from said ON-state to said OFF-state such that said amplitude of said oscillation is below a predefined threshold.

In yet another example, the relationship has a plurality of local minima, and wherein said step of controlling further comprises: - controlling, by said controller, said switch from said ON-state to said OFF-state in any of said local minima.

In an example, the step of controlling further comprises: - controlling, by said controller, said switch from ON-states to OFF- states at different amount of currents.

In a third aspect of the present disclosure, there is provided a Switched Mode Power Supply, SMPS, comprises a commutation cell in accordance with any of the previous examples.

It is noted that the advantages as explained with respect to the first aspect, being the commutation cell, correspond to the advantages as explained with respect to the third aspect, being the SMPS.

In a fourth aspect, there is provided a controller arranged for operating in a commutation cell in accordance with any of the examples as provided above.

In a fifth aspect, there is provided a computer program product comprising a computer readable medium having instructions stored thereon which, when executed by a controller, cause said controller to implement a method in accordance with any of the method examples as provided above.

These and other aspects of the invention will be apparent from and elucidated with reference to the embodiment(s) described hereinafter. Brief description of the Drawings Figure 1 discloses an example of a commutation cell in accordance with the present disclosure; Figures 2a-2d disclose examples of current paths in the commutation cell in accordance with figure 1; Figure 3a discloses an example of a timing diagram of the voltage over the switch as well as the voltage over the rectifier element; Figure 3b discloses an example of a timing diagram of the voltage over the switch over time when the switch is turned from the ON-state to the OFF-state; Figure 4 discloses the voltage over the switch over time for different amounts of current through the switch when the switch is being switched to the OFF- state; Figure 5 discloses the overshoot voltage as function of input current; Figure 6 discloses an example of a Switched Mode Power Supply, SMPS, in accordance with the present disclosure; Figure 7a — 7c disclose another examples of current paths in a commutation cell in accordance with the present disclosure.

Detailed description Figure 1 discloses an example of a commutation cell 1 in accordance with the present disclosure.

The commutation cell 1 is arranged for connecting a first power element 3 to a second power element 2. The first power element 3 may be any of a voltage source, a current source, an inductor, a capacitor, a load or anything alike. The second power element 2 may be any of a voltage source, a current source, a capacitor, a load or anything alike. Ground is indicated with reference numeral 4.

First, a switch 8 is provided in the commutation cell 1 that is controlled by the controller 9. The switch 8 may be switched ON in which the switch provides for a conducting path and may be switched OFF in which the switch does not provide for a conducting path. Of course, some sort of transition time may exist when turning the switch ON and OFF.

The switch 8 may, for example, be a Metal Oxide Semiconductor, MOS, Field Effect Transistor, FET or a Gallium nitride, GaN transistor or anything alike.

The switch 8 may have a parasitic capacitance as indicated with reference numeral 5. Such a parasitic capacitance is typically an undesired capacitance as it may put upper limits to the speed of the switch 8.

The switch 8 is arranged for, in an ON-state, enable a first current path in the commutation cell, and, in an OFF-state, enable a second current path in the commutation cell, wherein the first current path is different to the second current path. This is explained in more detail with respect to figures 2a — 2d.

A rectifier element 7 is provided in the second current path. The rectifier element may comprise a PN-junction, for example a diode. The rectifier element 7 may also be encompassed by a switch, or a switch may be placed in parallel over said rectifier element 7. The rectifier element 7 allows the current to flow in one direction, i.e. from the anode to the cathode.

The rectifier element 7 may also comprise a parasitic capacitance as indicated with reference numeral 6.

The inventor has found that a resonance circuit may be provided in the mutation cell 1, wherein the resonance circuit may be formed by at least any of the parasitic capacitance 5 in any of the switch 8 and the parasitic capacitance 6 in the rectifier element 7 as well as the parasitic inductance in any of the second power element 2, the switch 8, the rectifier element 7 and interconnections provided in the commutation cell 1. The interconnections may be modelled by an inductance as indicated with reference numeral 10.

The resonance circuit may not necessarily equal any of the first current path and the second current path as the parasitic capacitances and the parasitic inductances play a role as well. This is explained in more detail when referring to figures 2a — 2d.

The present disclosure describes the relationship between the amplitude of the oscillation of the current in the resonance circuit and the amount of current in the first current path when the controller controls the switch from the ON-state to the OFF-state.

It may be desired to reduce the above identified amplitude to a minimum. The inventor has noted that the relationship has a plurality of local maxima in the amplitude for given amount of current, and has found that this knowledge may be used by the controller 9 in controlling the switch 8.

That is, the controller 9 is arranged for controlling the switch 8 from the ON-state to the OFF-state based on the local maxima in the relationship. It is noted that, preferably, the parasitic capacitance of the switch 8 equals the parasitic capacitance of the rectifier element 7. In an example, the rectifier element 7 is provided in a further switch, for example the body diode of the further switch. In that case, it would be beneficial if the two switches are of the same type.

Figures 2a-2d disclose examples of current paths in the commutation cell in accordance with figure 1.

It is noted that the same reference numerals are used in figures 2a-2d compared to the reference numerals in figure 1 for improving the readability of the figures.

Figure 2a discloses an example of the commutation cell 1 of figure 1 wherein the first current path in the commutation cell 1 is highlighted. The first current path is indicated with reference numeral 11.

Figure 2b discloses an example of the commutation cell 1 of figure 1, wherein the second current path in the commutation cell 1 is highlighted. The second current path is indicated with reference numeral 12.

Figure 2c discloses an example of a third current path in the commutation cell 1 of figure 1, wherein the third current path in the commutation cell 1 is highlighted. The third current path is indicated with reference numeral 13.

Figure 2d discloses an example of the first and second current path in the commutation cell 1 of figure 1, wherein the first and second current path in the commutation cell 1 are highlighted. The first and second current path are indicated with reference numerals 15 and 14, respectively.

When turning from an OFF-state to an ON-state, typically current paths are in the order of figure 2a, then figure 2d, then figure 2b. Figure 2d may be considered the power loop that oscillates in section B as well as section C of figure 3.

It is noted that the oscillation may occur in the third current path as indicated with reference numeral 13. Reference numeral 13 may also be used for indicating the resonance circuit in the commutation cell 1.

Figure 3a discloses an example of a timing diagram of the voltage over the switch as well as the voltage over the rectifier element.

Here, the X-axis indicates the time, for example in nanoseconds or milliseconds or anything alike and the Y-axis resembled to voltage.

At point 24, the switch 8 is controlled such that it switches from the ON- state to the OFF-state. At point 25, a switch placed in parallel over the rectifier element 7 may be switched from the OFF-state to the ON-state.

The line having reference numeral 26 indicates the voltage over the switch 8 and the line having reference numeral 28 indicates the voltage over the rectifier element 7. The amplitude of the current of the oscillation relates to the amplitude of the voltage of the oscillation and is indicated with reference numeral 27.

So, in this particular case, initially, the switch 8 is closed. This is indicated with the reference numeral “A”. Then, the switch 8 opens, i.e. switches to the OFF-state, and the switch node voltage, i.e. the voltage over the switch 8, begins to rise as the parasitic capacitance 5 begins to charge. The parasitic capacitance 6 of the rectifier element shifts the voltage on the cathode of the rectifier element above the output voltage, the current through the inductance 10 rises and the oscillation is initiated. The above is indicated with reference numeral “B”.

In the situation indicated with reference numeral “C”. a clear oscillation pattern is shown having an amplitude as indicated with reference numeral 27. The amplitude of the oscillation 27 thus relates to the current flowing through the switch 8 at the time indicated with reference numeral 24. This relationship has a plurality of maxima.

The magnitude of this overshoot is linked to the energy stored in the oscillation. In any realistic converter at least a little bit of damping is present which makes that the energy initially stored in the oscillation is mostly lost before the start of the next switching transition. Furthermore, the low side semiconductor device has to be rated for the overshoot voltage as indicated with reference numeral 27. Devices with higher voltage ratings usually have a worse switching FOM resulting in higher losses. Both of these losses combined have a negative impact on the total efficiency of the converter. Therefore, a low overshoot voltage is preferred, i.e. it is preferred to keep the amplitude of the oscillation relatively low.

Figure 3b discloses an example of a timing diagram of the voltage over the switch over time when the switch is turned from the ON-state to the OFF-state.

Here, it is shown that the oscillation starts in the B region and continues over to the C region.

Figure 4 discloses the voltages 31 over the switch over time for different amounts of current through the switch when the switch is being switched to the OFF- state.

On the vertical axis the normalised voltage over the switch 8 is plotted and on the horizontal axis the time is plotted.

The line having reference numeral 34 shows the oscillation behaviour of the voltage over the switch 8 for a first current. The line having reference numeral 35 shows the oscillation behaviour of the voltage over the switch 8 for a second current.

The line having reference numeral 36 shows the oscillation behaviour of the voltage over the switch 8 for a third current. The line having reference numeral 37 shows the oscillation behaviour of the voltage over the switch 8 for a fourth current. In this particular case the first current > the second current > the third current > the fourth current.

The above shows that, apparently, some optimum amount of currents exist in which the oscillation is non-existing, or at least low.

The above is also shown in figure 5, wherein the overshoot voltage is shown as function of input current.

Figure 5 is an example of the relationship 41 between the amplitude of said oscillation of said current in said resonance circuit, and an amount of current in said first current path when said controller controls said switch from said ON-state to said OFF-state.

The above identified amount of current is provided on the horizontal axis 43, the above identified amplitude of the oscillation is provided on the vertical axis 42.

As shown, there are some so-called sweet spots, i.e. local minima, in which the amplitude is relatively low. These sweet spots are, amongst other, indicated with reference numerals 44, 46 and 48. IN these sweet sports the oscillation reaches a local minimum.

As also shown, there are some so-called worst-case spots, i.e. local maxima, in which the amplitude is relatively high. These worst-case sports are, amongst other, indicated with reference numerals 45, 47 and 49.

Figure 6 discloses a Switched Mode Power Supply, SMPS, 51 in accordance with the present disclosure. The method as described in the appended claims may be provided in the controller 52.

Figure 6 is just an example of many possible topologies, i.e. many possible SMPSs. The inductor without the core is the power loop induction. The inductor with the core may be considered the first power element. The voltage sources combined may be considered the second power element.

The advantages of the present disclosure have been explained with respect to a boost converter being the commutation cell. It is however noted that the advantages of the present disclosure are applicable for all kinds of converters, for example buck converters as well as isolated converters like a flyback converter, and may be applicable for an N-phase inverter.

Figure 7a — 7c disclose another examples of current paths in a commutation cell in accordance with the present disclosure.

Here, the switch and the rectifier element are switched from position to clarify that the commutation cell may also operate in a different manner. The present disclosure is directed to both options, such that both options are covered by the commutation cell in accordance with the claims of the present disclosure.

Figure 7 and figure 2 are commutations that an both be implemented on the invertor, depending on the directions of the current through the inductor and, to chose one of the switches as active rectification, or synchronous rectification.

Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims.

In the claims, the word “Comprising” does not exclude other elements or steps, and the indefinite article “a” or “an” does not exclude a plurality.

The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

Any reference signs in the claims should not be construed as limiting the scope thereof.

Claims

CONCLUSIESCONCLUSIONS

1. Een commutatiecel voor het verbinden van een eerste vermogenselement met een tweede vermogenselement, waarbij de commutatiecel omvat: - een schakelaar die is ingericht om, in een AAN-toestand, een eerste stroompad in de commutatiecel vrij te geven, en in een UIT-toestand een tweede stroompad in de commutatiecel mogelijk te maken, waarbij het eerste stroompad anders is dan de tweede huidige pad; - een in het tweede stroompad voorzien gelijkrichtelement; - een controller voor het besturen van de schakelaar tussen de AAN- toestand en de UIT-toestand; waarbij een resonantiecircuit is voorzien in de mutatiecel, waarbij het resonantiecircuit wordt gevormd door ten minste één van: o parasitaire capaciteit in een van de schakelaar en het gelijkrichtelement; o parasitaire inductantie van een van het tweede vermogenselement, de schakelaar, het gelijkrichtelement en onderlinge verbindingen die zijn aangebracht in de commutatiecel; zodanig dat, wanneer de controller de schakelaar bestuurt van de AAN- toestand naar de UIT-toestand, het resonantiecircuit ervoor zorgt dat een stroom in het tweede resonantiecircuit oscilleert; gekenmerkt door dat er een relatie bestaat tussen o een amplitude van de oscillatie van de stroom in het resonantiecircuit, en o een hoeveelheid stroom in het eerste stroompad wanneer de controller de schakelaar bestuurt van de AAN-status naar de UIT-status, waarbij de relatie meerdere lokale maxima heeft in de amplitude voor een gegeven hoeveelheid stroom, genoemde controller is ingericht voor het besturen van genoemde schakelaar van genoemde AAN-toestand naar genoemde UIT-toestand op basis van genoemde lokale maxima in genoemde relatie.A commutation cell for connecting a first power element to a second power element, the commutation cell comprising: - a switch arranged to release, in an ON state, a first current path in the commutation cell, and in an OFF state state to allow a second current path in the commutation cell, the first current path being different from the second current path; - a rectifying element provided in the second current path; - a controller for controlling the switch between the ON state and the OFF state; wherein a resonant circuit is provided in the mutation cell, the resonant circuit being formed by at least one of: o parasitic capacitance in one of the switch and the rectifying element; o parasitic inductance of any of the second power element, switch, rectifier element and interconnections provided in the commutation cell; such that when the controller controls the switch from the ON state to the OFF state, the resonant circuit causes a current to oscillate in the second resonant circuit; characterized in that there is a relationship between o an amplitude of the oscillation of the current in the resonant circuit, and o an amount of current in the first current path when the controller controls the switch from the ON state to the OFF state, the relationship being has multiple local maxima in the amplitude for a given amount of current, said controller is adapted to control said switch from said ON state to said OFF state based on said local maxima in said relationship.

2. Commutatiecel volgens conclusie 1, waarbij: de genoemde regelaar is ingericht voor het besturen van de genoemde schakelaar van de genoemde AAN-toestand naar de genoemde UIT-toestand, zodat de genoemde meerdere lokale maxima in hoofdzaak worden vermeden.The commutation cell of claim 1, wherein: said controller is adapted to control said switch from said ON state to said OFF state so that said plurality of local maxima are substantially avoided.

3. Commutatiecel volgens conclusie 2, met het kenmerk, dat de controller is ingericht om de lokale maxima volledig te vermijden.3. A commutation cell according to claim 2, characterized in that the controller is arranged to completely avoid the local maxima.

4. Commutatiecel volgens één van de voorgaande conclusies, waarbij: de genoemde regelaar is ingericht voor het besturen van de genoemde schakelaar van de genoemde AAN-toestand naar de genoemde UIT-toestand, zodanig dat de genoemde amplitude van de genoemde oscillatie onder een vooraf bepaalde drempel ligt.A commutation cell according to any one of the preceding claims, wherein: said controller is adapted to control said switch from said ON state to said OFF state such that said amplitude of said oscillation is below a predetermined threshold is located.

5. Commutatiecel volgens één van de voorgaande conclusies, waarbij: de relatie meerdere lokale minima heeft, en waarbij de controller is ingericht voor het besturen van de schakelaar van de AAN-toestand naar de UIT- toestand in een van de lokale minima.A commutation cell according to any one of the preceding claims, wherein: the relationship has multiple local minima, and wherein the controller is adapted to control the switch from the ON state to the OFF state in one of the local minima.

6. Commutatiecel volgens één van de voorgaande conclusies, waarbij: genoemde controller is ingericht voor het besturen van genoemde schakelaar van AAN-toestanden naar UIT-toestanden bij verschillende hoeveelheden stromen.A commutation cell according to any one of the preceding claims, wherein: said controller is adapted to control said switch from ON states to OFF states at different amounts of current.

7. Werkwijze voor het bedrijven van een commutatiecel volgens een van de voorgaande conclusies, waarbij de werkwijze de stappen omvat van: - het door de controller besturen van de omschakeling van de AAN- toestand naar de UIT-toestand op basis van de lokale maxima in de relatie.A method of operating a commutation cell according to any one of the preceding claims, wherein the method comprises the steps of: - the controller controlling the switching from the ON state to the OFF state based on the local maxima in the relation.

8. Werkwijze volgens conclusie 7, waarbij genoemde regelstap verder omvat: - het besturen, door de besturing, van de omschakeling van de AAN- toestand naar de UIT-toestand, zodat het aantal lokale maxima in hoofdzaak wordt vermeden.A method according to claim 7, wherein said controlling step further comprises: - controlling, by the controller, the switching from the ON state to the OFF state so that the number of local maxima is substantially avoided.

9. Werkwijze volgens conclusie 8, waarbij genoemde regelstap verder omvat: - het vermijden, door genoemde controller, van genoemde lokale maxima.A method according to claim 8, wherein said controlling step further comprises: - avoiding, by said controller, said local maxima.

10. Werkwijze volgens een van de conclusies 7 - 9, waarbij de stap van het besturen verder omvat: - het door de controller regelen van de schakelaar van de AAN-toestand naar de UIT-toestand zodat de amplitude van de oscillatie onder een vooraf bepaalde drempel ligt.A method according to any one of claims 7 to 9, wherein the step of controlling further comprises: - the controller controlling the switch from the ON state to the OFF state so that the amplitude of the oscillation falls below a predetermined threshold is located.

11. Werkwijze volgens een van de conclusies 7 - 10, waarbij de relatie meerdere lokale minima heeft, en waarbij de stap van het besturen verder omvat: - het besturen, door de controller, van de schakelaar van de AAN- toestand naar de UIT-toestand in een van de lokale minima.A method according to any one of claims 7 to 10, wherein the relationship has multiple local minima, and wherein the step of controlling further comprises: controlling, by the controller, the switch from the ON state to the OFF state. state in one of the local minima.

12. Werkwijze volgens een van de voorgaande conclusies, waarbij de stap van het besturen verder omvat: - het besturen, door de controller, van de omschakeling van AAN- toestanden naar UIT-toestanden bij verschillende hoeveelheden stromen.A method according to any one of the preceding claims, wherein the step of controlling further comprises: - controlling, by the controller, the switching from ON states to OFF states at different amounts of currents.

13. Schakelende voeding, SMPS, omvattende een commutatiecel volgens een van de conclusies 1-6.A switching power supply, SMPS, comprising a commutation cell according to any one of claims 1-6.

14. Controller ingericht voor het werken in een commutatiecel volgens een van de conclusies 7-12.A controller adapted to operate in a commutation cell according to any one of claims 7-12.

15. Een computerprogrammaproduct dat een computerleesbaar medium omvat waarop instructies zijn opgeslagen die, wanneer uitgevoerd door een controller, ervoor zorgen dat de controller een methode implementeert in overeenstemming met een van de conclusies 7-12.A computer program product comprising a computer readable medium storing instructions which, when executed by a controller, cause the controller to implement a method in accordance with any of claims 7-12.