DE102013104376B3 - Boost converter with resonant circuit - Google Patents

Abstract

The invention relates to a step-up converter (1) with an HSS choke (2) and an HSS diode (3) connected in series with the HSS choke (2) as well as a first shunt arm (9) and a second shunt arm (14), which branch off between the HSS choke (2) and the HSS diode (3). An HSS switch (4) is arranged in the first shunt arm (9), the HSS switch (4) having a regular current flow direction and the first shunt arm (9) for a current opposite to the regular current flow direction of the HSS switch (4 ) Is blocked. A resonant circuit is arranged in the second shunt arm (14), which has a capacitor (16) and a series circuit (17) connected in parallel to the capacitor (16) and made up of a coil (18) and a switch (19). Furthermore, the second shunt arm (14) has a diode (20) which is connected in series with the resonance circuit (15). The forward direction of the diode (20) from the HSS choke (2) is opposite to the forward direction of a freewheeling diode (21) of the switch (19) and the same direction as the regular current flow through the HSS switch (4).

Description

TECHNICAL FIELD OF THE INVENTION

The invention relates to a step-up converter (HSS) with an HSS choke, an HSS diode connected in series with the HSS choke, an HSS switch which is arranged in a first transverse branch branching off between the HSS choke and the HSS diode and having a regular current flow direction, and a resonant circuit arranged in a second transverse branch branching between the HSS inductor and the HSS diode and comprising a capacitor and a series circuit of a coil and a switch connected in parallel with the capacitor. Furthermore, the invention relates to the use of such a boost converter.

Such a step-up converter can be used, for example, in railway technology in a vehicle power converter, which serves the power supply of auxiliary systems for propulsion, air conditioning, lighting o. Ä. In railway vehicles to be used for adaptation between a example of a battery, a traction converter or directly from the Contact wire provided voltage and a higher voltage for the supply of DC loads or as a DC link voltage of a subsequent inverter stage. Furthermore, such a step-up converter can be used for adaptation between a voltage provided by a photovoltaic generator and a higher voltage of an input intermediate circuit of an inverter, with which electrical energy from the photovoltaic generator is fed into an AC network. In this case, the boost converter can be provided to adjust the operating point of the photovoltaic generator at a constant intermediate circuit voltage so that the photovoltaic generator provides a maximum electrical power under the current operating conditions.

The regular current flow direction of an HSS switch is the direction in which the current flows through the HSS switch to energize the HSS reactor. In operation of a conventional boost converter, the current flowing in the regular current flow direction is interrupted by opening the HSS switch.

In the following, when it is said that the transmission directions of two or more diodes are directed the same from a reference point, it is meant that either a current flowing from the reference point through the diodes or through the diodes to the reference point flowing current is passed through by all these diodes. This is equivalent to the fact that their blocking directions are aligned the same from the reference point. On the other hand, when two diodes have opposing directions of passage from the reference point, it means that a current flowing from the reference point toward the diodes or a current flowing from the diodes toward the reference point is allowed to pass through the one diode while it is passing is blocked by the other diode.

STATE OF THE ART

In a conventional step-up converter, one of two lines connected to a DC voltage source has an HSS choke connected in series with an HSS diode. Behind the HSS diode is connected between this one and the other line in which no electrical component is provided, an intermediate circuit capacitor to which a high of the boost converter relative to its input voltage output voltage is applied. Between the HSS-choke and the HSS-diode leads from the one line a shunt branch to the other line in which the HSS switch is arranged. By closing the HSS switch, the HSS reactor is energized with a current flowing through the HSS switch. By opening the HSS switch, this energy is delivered through the HSS diode to the DC link capacitor.

At one of the US 2006/0018138 A1 known boost converter is connected between two input terminals for an input voltage, a series circuit of an HSS choke, an HSS diode and an intermediate circuit capacitor. Between the HSS choke and the HSS diode, a first shunt branch branches off with an HSS switch. The HSS switch is formed by an IGBT switch with a parallel-connected freewheeling diode. In order to minimize switch-on losses when closing the HSS switch, a second shunt branch with a resonance circuit is connected in parallel to the first shunt branch. The resonant circuit has a capacitor to which a series circuit of an IGBT switch and a coil is connected in parallel. Between the coil and the IGBT switch of the resonant circuit, a path with a diode branches off to the output side of the HSS diode connected to the intermediate circuit capacitor. In this case, the transmission directions of the HSS diode and the diode of the path are the same as seen from the output-side connection of the HSS diode. During operation of the boost converter, the IGBT switch of the resonant circuit is first switched so that the resonant circuit is closed and the capacitor discharges via the coil and the IGBT switch. After discharging the capacitor, no voltage is applied to the HSS switch. This can then be de-energized, ie closed, whereby a current flow through the HSS switch and the HSS throttle is possible. Switch-off losses, which are associated with a subsequent opening of the HSS switch, can not be counteracted by the second transverse branch.

At one of the EP 1 519 475 A1 Known boost converter branches between its HSS choke and its HSS diode from two shunt branches. In the first transverse branch, an HSS switch is provided. In the second shunt branch, a diode whose forward direction, viewed from the HSS choke, is equal to a regular current flow direction of the HSS switch, is connected in series with a capacitor, which is charged when the HSS switch is opened, and thus a switch relief for the HSS Switch provides. To discharge the capacitor, an auxiliary boost converter with an auxiliary HSS coil, an auxiliary HSS diode and an auxiliary HSS switch is provided. The auxiliary HSS diode leads to the output side, connected to an intermediate circuit capacitor connection of the HSS diode. The transmission directions of the HSS diode and the auxiliary HSS diode are the same when viewed from the output side connection of the HSS diode. In order to discharge the capacitor in the output side DC link capacitor, the auxiliary HSS switch is clocked at higher frequency with the HSS switch closed again.

OBJECT OF THE INVENTION

The invention has for its object to provide a boost converter whose efficiency is improved with little effort. Furthermore, the invention has the object to show a use of a boost converter, in which the efficiency of the boost converter is improved with little effort.

SOLUTION

The object of the invention is achieved with the features of independent claim 1 and the independent claims 10 and 11. Further preferred embodiments according to the invention can be found in the dependent claims.

DESCRIPTION OF THE INVENTION

An inventive step-up converter has an HSS switch, which is arranged in a first transverse branch, and a resonant circuit, which is arranged in a second transverse branch. The first and the second transverse branch branch off between an HSS throttle and an HSS diode of the boost converter.

According to the invention, the HSS switch is designed such that a current in a regular current flow direction of the HSS switch can flow through the HSS switch, wherein the first shunt branch is blocked for a current counter to the normal current flow direction of the HSS switch. In particular, a current flow in the first transverse branch is prevented against the regular current flow direction even when the HSS switch is closed.

The resonant circuit in the second shunt branch has a capacitor and a capacitor connected in parallel to the series arrangement of a coil and a switch, to which a free-wheeling diode is connected in parallel. Furthermore, the second transverse branch has a diode which is connected in series with the resonant circuit. The diode is arranged such that its forward direction seen from the HSS throttle from the forward direction of the freewheeling diode is directed against, while their forward direction seen from the HSS throttle from the regular direction of current flow through the HSS switch is the same direction. This ensures, on the one hand, that charging or discharging of the capacitor when the switch of the resonant circuit is open is possible due to a current flow in the forward direction of the freewheeling diode. A loading or unloading due to a current flow in the opposite direction, however, can only be done with the switch closed. On the other hand, the same orientation of the forward direction of the diode in the second shunt arm and the regular current flow direction through the HSS switch ensures that the capacitor of the resonant circuit can not be discharged via the first shunt arm, in particular even then, as seen from the HSS choke when the HSS switch is closed. For a current flowing through the first shunt arm during a discharge of the capacitor, the forward direction of the diode is directed in the opposite direction to the regular current flow direction by the HSS switch.

If the capacitor of the resonant circuit is charged in its initial charging state in such a way that a current flow is required against the forward direction of the freewheeling diode for its discharge, its discharge can not take place until the switch of the resonant circuit is closed. Then, during a first quarter of a resonant oscillation, the capacitor is discharged across the coil and the switch of the resonant circuit. In the second quarter of the resonant oscillation, the capacitor is charged with reverse polarity. Discharge from its initial state of charge and reverse polarity charging from its initial state of charge will also be referred to hereinafter as "reloading" of the capacitor.

With the discharge of the capacitor, a voltage applied to the opened HSS switch reduces, which could drive a current in the regular current flow direction through the closed HSS switch. With the subsequent charging of the capacitor with reverse polarity compared to its initial state of charge, although a voltage of opposite polarity builds up over the first transverse branch; for a current counter to the regular current flow direction of the HSS switch but the first transverse branch is locked according to the invention. Therefore, if the HSS switch is closed after discharging the capacitor, no current flows at first. Rather, a renewed current flow through the HSS switch takes place only when the capacitor of the resonant circuit is no longer charged opposite to its initial state of charge, because the voltage drop across the first shunt only allows current again, ie a current in the regular current flow direction drives the HSS switch. Thus, during the entire period in which the capacitor is charged with opposite polarity to its initial state, the HSS switch can be closed without current and therefore lossless, ie without power losses.

When the capacitor is reversely charged from its initial charge state, i. H. when the voltage applied to the capacitor has changed sign, in the third and fourth quarters of the resonant oscillation, i. H. When the capacitor is now discharged in the reverse direction and then recharged to its initial state of charge, current flow also occurs through the freewheeling diode of the switch of the resonant circuit. The switch can therefore be opened during the second half-period of the resonant oscillation, without interrupting the return of the capacitor to its initial state of charge. The capacitor thus returns automatically after opening the switch back to its initial state of charge. For a further resonance oscillation and thus a renewed reloading of the capacitor, the switch of the resonant circuit must be closed again.

If the switch of the resonant circuit is closed when the HSS switch is closed, d. H. while a current is flowing through the HSS switch, a recharging of the capacitor occurs (analogous to the previous embodiments). Reloading the capacitor results in the disappearance of the current flowing through the closed HSS switch, which also causes the voltage across the HSS switch, which drives the current through the HSS switch in the regular current flow direction, to zero goes back. The HSS switch can then be opened lossless as long as the capacitor is in a reverse charge state compared to the initial charge state, since the first shunt arm is disabled for current against the normal current flow direction of the HSS switch.

Overall, therefore, a currentless closing and opening of the HSS switch is made possible by the resonant circuit of the boost converter according to the invention. Thus, switching losses when switching the boost converter according to the invention, d. H. both when closing and when opening the HSS switch minimized.

In a preferred embodiment, in the first shunt branch, an auxiliary diode is connected in series with the HSS switch, wherein the auxiliary diode is aligned such that it blocks the first shunt arm for a current flow against the regular current flow direction through the HSS switch. The HSS switch can then also be a bidirectional switch, by which alone (at least when it is closed), a current flow contrary to the regular current flow direction through the HSS switch would be possible. By the auxiliary diode is connected in series with the bidirectional switch, it can nevertheless be ensured that a current flow through the first shunt arm and thus also through the HSS switch only in the direction of its regular current flow direction, which corresponds to the forward direction of the auxiliary diode, is possible.

When the auxiliary diode is connected in series with the HSS switch, the voltage applied to the HSS switch remains zero or near zero after discharging the capacitor from its initial charging state until the polarity of the voltage across the capacitor returns to the polarity the voltage is in its initial state of charge. In this case, the HSS switch can not only be de-energized and voltage-free for a prolonged period of time, providing a current in the regular Current flow direction through the closed HSS switch could drive, but completely tension-free "closed.

However, the HSS switch does not necessarily have to have an auxiliary diode connected in series with the HSS switch to ensure that current flow in the first shunt branch is blocked against the regular flow direction of the current through the HSS switch. For example, this is not necessary if the HSS switch of the boost converter according to the invention is formed with a unidirectional switch, such as an IGBT semiconductor switch. In this case, once the capacitor has been recharged to reverse polarity, it is not possible to completely close the HSS switch without voltage. However, the reverse polarity voltage then applied to the HSS switch can not drive current in the regular current flow direction through the closed HSS switch, and for a current in the opposite direction, the first shunt arm is blocked. The closing of the HSS switch is therefore also in this case so that a current flow through the HSS switch does not begin immediately, and therefore lossless.

According to a preferred embodiment, a freewheeling diode common for semiconductor switches is connected in parallel with the HSS switch. For example, the HSS switch can be formed with an IGBT semiconductor switch, to which the free-wheeling diode of the HSS switch is connected in parallel. The freewheeling diode can also be an inherent freewheeling diode of a semiconductor switch. If the auxiliary diode is connected in series with the HSS switch in the first shunt branch, the forward directions of the free-wheeling diode and the auxiliary diode are directed counter to one another, thus preventing current flow through the first shunt branch when the HSS switch is open. However, the HSS switch of the boost converter according to the invention can also be designed without a freewheeling diode, without the boost converter thereby being impaired in its operation.

If the switch of the resonant circuit is already opened during the charging of the capacitor, d. H. while one of the forward direction of the freewheeling diode of the switch of the resonant circuit opposite current flows through the switch, this may result in an overvoltage at the switch. To counteract this, a voltage limit for the switch can be provided. For example, the step-up converter may have a discharge path with a further diode, which branches off between the coil and the switch of the resonant circuit and which is connected to the output-side terminal of the HSS diode. The forward direction of the further diode is seen from the output side terminal of the HSS diode from the same as the forward direction of the HSS diode. However, it is not necessary in the HSS according to the invention and to minimize switching losses also not preferred to open the switch of the resonant circuit already during the reloading of the capacitor. If such an opening is excluded, the discharge path can be dispensed with.

During operation of the boost converter according to the invention, provision is made for discharging or reloading of the capacitor from its initial charge state only when the switch of the resonant circuit is closed. To ensure that the capacitor does not remain in its charged state after the end of the operation of the HSS according to the invention, but is automatically discharged with its decommissioning, the boost converter can have a discharge circuit for the capacitor. According to a particularly simple embodiment of the boost converter according to the invention, a discharge resistor can be provided for this purpose, which is connected in parallel with the capacitor. About this discharge resistor, the capacitor is discharged automatically when no input voltage is applied to the boost converter.

For the operation of the boost converter, it may be necessary that this has a fast switching behavior, so that the HSS switch can be switched at short intervals. In order to ensure that the HSS switch is always switchable in its "de-energized" state, in which no current flows through the HSS switch and also no voltage is applied to the HSS switch, the current in the regular current flow direction through the closed HSS switch can drive, the capacitor must be reloaded accordingly fast and can also quickly return to its initial state of charge. Consequently, it is advantageous if the resonant circuit has a short oscillation period in relation to the length of the switching cycle of the boost converter. Such a comparatively short oscillation period can be achieved by suitably dimensioning the coil and the capacitor of the resonant circuit. Preferred oscillation durations of the resonant circuit are in the ms to μs range, with which switching frequencies of the HSS switch can be achieved up to a few hundred kHz.

In a particular embodiment of the boost converter according to the invention, the switch of the resonant circuit is designed for a larger current flow than the HSS switch. Preferably, the switch of the resonant circuit is designed so that this (without being damaged) can carry a current that is at least twice, preferably at least three times, for example, about four times as large as the current for which the HSS switch is designed , Thus, the fact can be taken into account that in a resonant discharge circuit typically a larger current compared to the input current can occur.

The boost converter according to the invention may have a single first and a single second transverse branch or a plurality of first transverse branches and also a plurality of second transverse branches. In this case, a separate second transverse branch can be provided for each first transverse branch. If a plurality of first transverse branches are actuated offset by a control device, however, it is sufficient if the first plurality of transverse branches is assigned a single, common second transverse branch. The resonant circuit of the second shunt branch is then designed so that it has a period of oscillation which is smaller than a time interval between the switching of the HSS switches of the plurality of first shunt arms. It is then ensured that the capacitor has returned to its initial state of charge before the next switching and is thus ready to be reloaded in order to bring the corresponding HSS switch for lossless switching into its de-energized state.

According to a further embodiment of the boost converter according to the invention, this comprises a pair of Teilhochsetzstellern having a common HSS inductor, and a DC voltage intermediate circuit with two series-connected DC link capacitors. The one partial boost converter of the pair comprises the first and second shunt arms and the HSS diode. In this case, the first and second shunt branches lead to a mid-point of the DC voltage intermediate circuit between the two DC link capacitors, and the partial boost converter of the pair charges the one of the two DC link capacitors. The other partial boost converter of the pair charges the other of the two DC link capacitors. In this case, first and second shunt branches and an HSS diode of the other Teilhochsetzstellers with respect to the center of the DC intermediate circuit up to their current flow and transmission directions mirror images of the first and second shunt branches and the HSS diode of a Teilhochsetzstellers of the pair. In a further embodiment, a bridge circuit may be connected to the DC intermediate circuit, wherein a center of the bridge circuit is connected to one end of a primary winding of a transformer and wherein the other end of the primary winding is connected to the center of the DC intermediate circuit.

According to an alternative embodiment of the boost converter with a plurality of partial boost converters, each partial boost converter (with otherwise identical design) has its own HSS throttle.

The invention further relates to the use of a boost converter according to the invention, wherein for closing or opening the HSS switch, the switch of the resonant circuit is closed in order to reload the capacitor (as already described above). During the entire time that the capacitor is charged with the polarity reversed from its initial state of charge, there is no voltage across the HSS switch that could drive current in the regular current flow direction through the HSS switch. Thus, when the initially open HSS switch is now closed, a current does not flow immediately through the HSS switch. When the HSS switch is initially closed, the current is reduced to zero when it is opened during this time. The HSS switch is therefore both closed and opened when it is in its above-defined de-energized state, in which he is powerless and thus lossless switchable.

After reloading the capacitor, the switch of the resonant circuit is opened again, so that the capacitor can indeed return to its initial state of charge, but then does not recharge. There is time until the capacitor has returned to its initial state of charge. After the capacitor has returned to its initial state of charge, the capacitor is available for a next transfer and thus for a subsequent switching operation of the HSS switch.

For closing or opening the HSS switch, it is sufficient if the capacitor is recharged only once, causing a voltage on the open HSS switch to disappear or its polarity reversed, or to cause a current through the closed HSS switch. Switch disappears. For a particularly fast switching behavior of the switch of the resonant circuit is therefore preferably controlled such that in the resonant circuit for exactly one full oscillation period of the resonant circuit, a current flows. That is, the capacitor is once transhipped to switch the HSS switch, and then returns to its initial state of charge so that it is subsequently available for reloading and thus re-switching the HSS switch. Usually, the resonant circuit is designed so that its oscillation period is in the range of 5 to 100 μs. Accordingly, the switch of the resonant circuit is typically closed for a period of 2.5 to 50 μs. This switching frequencies of the HSS switch in the kHz range, in particular up to several hundred kHz, can be achieved. For time-controlled switching, the switch can be controlled, for example, with a control signal having a corresponding signal width, which is provided by a control device provided for this purpose.

Its currentless state reaches the open or closed HSS switch when the capacitor is completely discharged from its initial state of charge and its reloading begins in the opposite to the initial state of charge inversely charged state. The de-energized state of the HSS switch ends only after the recharged capacitor has been discharged again and it is recharged to its initial charge state. The HSS switch does not need to be switched at an exact time, but there is a longer period available in which the HSS switch can be switched lossless. Accordingly, it is not mandatory for the operation of the boost converter, a time To use particularly accurate control device for the HSS switch.

Specifically, the currentless state of the HSS switch begins and ends respectively with the change of sign of the voltage applied to the capacitor. This corresponds to the times of a quarter and three quarters of the oscillation period of the resonant circuit. Therefore, according to a preferred embodiment, the HSS switch is driven so that the HSS switch is switched at a time after a current has already flowed in the resonant circuit for a quarter of the oscillation period, but before the current for three quarters of the oscillation period in the resonant circuit flowed. An exact observance of an exact time for the voltage-free or currentless switching is not required. Rather, it is sufficient if the switching takes place within this period of half a period of oscillation. Therefore, a relatively large time window is available for switching the HSS switch.

To ensure that the capacitor is available for further lossless switching of the HSS switch, it must be ensured that the capacitor returns to and remains in its initial charge state after reloading. This can be achieved by the switch of the resonant circuit is opened after a current flow in the resonant circuit is at least partially by the freewheeling diode of the switch of the resonant circuit. As described above, in spite of the open switch, the capacitor then returns to its initial charging state. By opening the switch, however, it is achieved that the capacitor is not reloaded after returning to its initial state of charge. At the latest, the switch must therefore be open at the time of return to the initial state of charge. Also for the opening of the switch of the resonant circuit so a relatively large time window is available.

Furthermore, it can be provided in the use of the boost converter according to the invention, that a switch of a single second shunt branch is controlled such that each of offset-controlled HSS switches several first shunt arms is switched in its de-energized state. In this case, the staggered driving of the HSS switches and the oscillation period of the resonant circuit are preferably matched to one another such that a time span of at least one full oscillation period of the resonant circuit lies between the switching of the HSS switches. This ensures that the capacitor, after being reloaded for a first lossless switching of an HSS switch, can return to its initial state of charge before the next switching begins for a lossless switching of an HSS switch.

Advantageous developments of the invention will become apparent from the claims, the description and the drawings. The advantages of features and of combinations of several features mentioned in the description are merely exemplary and can take effect alternatively or cumulatively, without the advantages having to be achieved by embodiments according to the invention. Without altering the subject matter of the appended claims, as regards the disclosure of the original application documents and the patent, the following applies: Further features can be found in the drawings. The combination of features of different embodiments of the invention or of features of different claims is also possible deviating from the chosen relationships of the claims and is hereby stimulated. This also applies to those features which are shown in separate drawings or are mentioned in their description. These features can also be combined with features of different claims. Likewise, in the claims listed features for further embodiments of the invention can be omitted. The features mentioned in the patent claims and the description are to be understood in terms of their number that exactly this number or a greater number than the said number is present, without requiring an explicit use of the adverb "at least".

If, for example, an HSS switch and / or a transverse branch is mentioned, this is to be understood as meaning that precisely one HSS switch and / or one transverse branch, two HSS switches and / or two shunt branches or more HSS switches and / or more shunts are present. These features may be supplemented by other features or be the only characteristics that make up the product in question. The reference numerals contained in the claims do not limit the scope of the objects protected by the claims. They are for the sole purpose of making the claims easier to understand.

BRIEF DESCRIPTION OF THE FIGURES

In the following the invention will be further explained and described with reference to preferred embodiments shown in the figures.

1 shows a boost converter according to the invention.

2 schematically shows a time course of control signals for an HSS switch and for a switch of a resonant circuit of the boost converter according to 1 and a resulting voltage and current waveform for the HSS switch and for the switch of the resonant circuit.

3 shows a boost converter according to the invention with a discharge path.

4 shows a boost converter according to the invention with a discharge path and a discharge resistor.

5 shows a boost converter according to the invention with a pair of Teilhochsetzstellern.

DESCRIPTION OF THE FIGURES

1 shows a boost converter according to the invention 1 , The typical for a boost converter interconnection of an HSS throttle 2 , an HSS diode 3 and an HSS switch 4 having. The HSS throttle 2 and the HSS diode 3 are in a lead 5 between an entrance 6 and an exit 7 of the boost converter 1 connected in series. An input or output voltage are at the input 6 or the output 7 each opposite earth 8th at. The HSS switch 4 is in a first transverse branch 9 of the boost converter 1 arranged between the HSS throttle 2 and the HSS diode 3 branches off and with earth 8th connected is. At the in 1 embodiment shown is a freewheeling diode 10 to the HSS switch 4 connected in parallel. At the exit 7 is a DC link capacitor 11 between the line 5 and earth 8th connected. From the of the DC link capacitor 11 formed DC link becomes a load 12 provided. Unlike in 1 shown, the boost converter must 1 but not necessarily have grounded connections.

In the first transverse branch 9 is an auxiliary diode 13 with the HSS switch 4 connected in series. In this case, the forward direction of the auxiliary diode 13 equal to a regular flow direction of the current through the HSS switch. The forward direction of the freewheeling diode 10 of the HSS switch 4 is the forward direction of the auxiliary diode 13 directed against. Through the auxiliary diode 13 becomes a current flow through the first shunt branch 9 with the HSS switch open 4 prevented. With closed HSS switch 4 is a current flow only in the forward direction of the auxiliary diode 13 possible.

In addition to the first transverse branch 9 branches from the pipe 5 between the HSS throttle 2 and the HSS diode 3 a second transverse branch 14 from. In the second transverse branch 14 is a resonant circuit 15 arranged, a capacitor 16 and one to the capacitor 16 parallel series connection 17 from a coil 18 and a switch 19 having. With the resonant circuit 15 is a diode 20 connected in series across which the resonant circuit 15 with earth 8th connected is. In this case, the forward direction of the diode 20 the forward direction of the auxiliary diode 13 from the HSS throttle 2 Seen from the same direction. By this arrangement and orientation of the auxiliary diode 13 and the diode 20 it is achieved that the capacitor 16 no matter how charged, even when the HSS switch is closed 4 not over the first transverse branch 9 can discharge because in a circuit from the one terminal of the capacitor 16 to the line 5 over the first transverse branch 9 after Earth 8th and from there through the diode 20 to the other terminal of the capacitor 16 the forward directions of the diode 20 and the auxiliary diode 13 are directed against each other. Furthermore, the forward direction of the diode 20 from the HSS throttle 2 seen from the forward direction of a freewheeling diode 21 of the switch 19 of the resonant circuit 15 directed against. So is open switch 19 of the resonant circuit 15 also discharging the capacitor charged from the input voltage to its initial charging state 16 over the resonant circuit 15 prevented. A discharge of the capacitor 16 over the resonant circuit 15 takes place only when the switch 19 is closed.

In 2 is shown very schematically, as the HSS switch 4 and the switch 19 of the resonant circuit 15 by means of control signals 22 . 23 be switched ( 2 , above) and which voltage curves 24 . 25 or current characteristics 26 . 27 from it for the HSS switch 4 ( 2 , Middle) and for the switch 19 ( 2 , below).

For the following explanations it is assumed that at the entrance 6 one opposite earth 8th positive voltage is applied and the capacitor 16 by this voltage in its initial charging state opposite to the forward direction of the freewheeling diode 21 charged.

As by the control signal 23 for the switch 19 and the control signal 22 for the HSS switch 4 indicated, the switch is 19 time before the HSS switch 4 closed. With the closing of the switch 19 it falls on the switch 19 voltage applied 25 against zero. At the same time, a current flow in the resonant circuit 15 against the forward direction of the freewheeling diode 21 allows. The capacitor 16 can thus be over the switch 19 and the coil 18 discharged, ie with the closing of the switch 19 begins a resonance oscillation of the resonant circuit 15 with the oscillation period T.

With the discharge of the capacitor 16 in the second transverse branch 14 it sinks at the first one transverse branch 9 and thus at the HSS switch 4 voltage applied 24 from. The at the HSS switch 4 voltage applied 24 is finally disappearing when the capacitor 16 is completely discharged. This corresponds to the time 28 in which the through the switch 19 flowing electricity 27 has reached its positive maximum value.

In the further course of the resonance oscillation of the resonant circuit 15 becomes the capacitor 16 charged with opposite polarity to its initial state of charge. The auxiliary diode prevents this 13 that is the capacitor 16 in its charged opposite to the initial state of charge with reverse polarity state over the first transverse branch 9 can discharge, especially if the HSS switch 4 closed is. After the complete transfer of the capacitor 16 That is, after the first half-period of the resonance oscillation, the capacitor becomes 16 unload again. The remains at the HSS switch 4 voltage applied 24 as long as disappeared on the capacitor 16 voltage applied again changes its sign and charging the capacitor 16 begins in its initial state of charge. This corresponds to the time 29 in which the through the switch 19 flowing electricity 27 reaches its negative maximum value.

For a lossless closing, the HSS switch 4 as based on the control signal 22 for the HSS switch 4 apparent between times 28 and 29 closed, between those on the capacitor 16 a voltage with opposite to the initial state of charge opposite sign is applied. By closing the HSS switch 4 is not a direct current flow through the closed HSS switch 4 associated. Rather, by the auxiliary diode 13 Achieved that through the HSS throttle 2 effected current flow through the HSS switch 4 can only take place when this in the direction of the forward direction of the auxiliary diode 13 he follows. This starts the flow of electricity 26 through the HSS switch 4 only at the time 29 ie if the on the capacitor 16 applied voltage and thus also on the first transverse branch 9 applied voltage again positive to earth 8th is. Between the times 28 and 29 is the HSS switch 4 So in its de-energized state, where no current through the HSS switch 4 can flow even when it is closed. A discharge of the capacitor 16 over the first transverse branch 9 is through the diode 20 prevented.

At the end of the resonant oscillation of the resonant circuit 15 , ie after the period of oscillation T, is the capacitor 16 returned to its initial state of charge. In this case, the return to the initial charging state does not mean that at the end of the resonance oscillation, a voltage across the capacitor 16 must be present, which in terms of their value is identical to the voltage before the resonance oscillation on the capacitor 16 has been on.

When the switch 19 would be closed after the end of the first resonant oscillation, the resonant circuit would 15 perform another resonance oscillation. If continue the HSS switch 4 not already closed during the first resonance oscillation, then the at the still open HSS switch 4 voltage applied 24 during the period of a quarter and three quarters of the period of oscillation T disappears again, which again a loss-free closing of the open HSS switch 4 is possible. Preferably, the HSS switch 4 however, already closed during the first resonance oscillation, so that a further resonance oscillation is undesirable. Therefore, in the in 2 illustrated example of the switch 19 reopened before the capacitor 16 reaches its initial state of charge. This can be done by the switch 19 be opened during a period of time in which the current flow in the resonant circuit 15 in the direction of the forward direction of the freewheeling diode 21 he follows. That the switch 19 is opened in this period, is for the maintenance of the current flow in the resonant circuit 15 until the return of the capacitor 16 in its initial state of charge irrelevant, since the current flow then over the freewheeling diode 21 to be led.

Furthermore, in 2 shown as the HSS switch 4 and the switch 19 be controlled to achieve that the closed HSS switch 4 can be opened in the de-energized state. First, the opened switch 19 closed. With the closing of the switch 19 with closed HSS switch 4 ie during a stream 26 through the HSS switch 4 flows, as described above, a transhipment of the capacitor 16 in the course of the resonance oscillation of the resonant circuit 15 , After discharging the capacitor 16 the current goes from the first shunt branch 9 on the second transverse branch 14 over, causing the switch through the HSS 4 flowing electricity 26 disappears. The HSS switch 4 can then be opened without loss, as long as the capacitor 16 is in a relation to the initial charging state inversely charged state. This corresponds to the period between a quarter and three quarters of the oscillation period T of the resonant circuit 15 , After reloading the capacitor 16 ie, during the second half period of the resonant oscillation, the switch becomes 19 opened again. Opening the switch 19 takes place preferably from the time to which the current in the resonant circuit 15 in the direction of the forward direction of the freewheeling diode 21 flows. After opening the switch 19 he returns capacitor 16 automatically returns to its initial state of charge and remains in this, bringing the resonant circuit 15 for a new switching operation for lossless closing of the HSS switch 4 ready.

In 3 is another embodiment of the boost converter 1 shown, in contrast to the in 1 illustrated embodiment additionally a discharge path 30 having. The discharge path 30 branches between the coil 18 and the switch 19 off and is with an output-side connection 31 the HSS diode 3 connected. In the discharge path 30 is another diode 32 arranged, whose forward direction of the output-side terminal 31 the HSS diode 3 seen from the forward direction of the HSS diode 3 is addressed the same. With the discharge path 30 will prevent overvoltages at the switch 19 occur from an opening of the closed switch 19 during one of the forward direction of the freewheeling diode 21 opposite directed current through the switch 19 flows, can result.

At the in 4 illustrated embodiment of the boost converter 1 is in continuing education in 3 illustrated embodiment, a discharge resistor 33 for the capacitor 16 provided to the capacitor 16 is connected in parallel. About the discharge resistance 33 can the capacitor 16 discharged when no input voltage at the input 6 is applied. This can ensure that the capacitor 16 automatically discharges when the boost converter 1 is taken out of service.

In 5 is an embodiment of the boost converter according to the invention 1 shown as a three-step boost converter with downstream bridge circuit, in which the boost converter 1 a pair of partial boosters 34 . 35 which is between two input terminals 36 . 37 of the boost converter 1 are switched. The basic structure of a three-point boost converter with downstream bridge circuit and its basic operation is for example from the document DE 197 50 041 C1 known.

The partial boosters 34 . 35 have the HSS throttle as the common HSS throttle 2 on, and each partial boost converter 34 . 35 loads a DC link capacitor 11a . 11b , Here are the two DC link capacitors 11a . 11b connected in series and together form a DC voltage intermediate circuit. The one partial boost converter 34 includes two first transverse branches 9a and 9b , for every first transverse branch 9a . 9b an HSS diode 3a . 3b which also become a single HSS diode of a partial boost converter 34 could be summarized, and a second transverse branch 14 , The first transverse branches lead here 9a . 9b and the second transverse branch 14 to a center 39 of the DC intermediate circuit. The other partial boost converter 35 also includes two first transverse branches 46a and 46b with HSS switches 4c . 4d , for every lateral branch 46a . 46b an HSS diode 3c . 3d which also becomes a single HSS diode of the other sub-converter 35 could be summarized, and a second transverse branch 47 , The first transverse branches 46a and 46b , the second transverse branch 47 and the HSS diodes 3c . 3d of the other partial uploader 35 are in relation to the center 39 the DC intermediate circuit except for their current flow and passage directions mirror image of the first transverse branches 9a . 9b , the second transverse branch 14 and the HSS diodes 3a . 3b of a partial boost converter 34 educated. The current flow and passage directions in the two Teilhochsetzstellers 34 and 35 are directed against each other. For those over the DC link capacitors 11a and 11b falling DC bus voltage is a bridge circuit 38 provided, with a center point 40 the bridge circuit 38 via a primary winding 41 a transformer 42 with the center 39 between the DC link capacitors 11a and 11b connected is. One over the transformer 42 voltage transmitted to the secondary side is at the in 5 illustrated embodiment with a rectifier 43 rectified and is then as DC voltage to an output capacitor 44 at. The on the output capacitor 44 applied DC voltage can, as in 5 represented by means of an inverter 45 z. B. be converted into a three-phase AC voltage.

If the HSS switch 4a . 4b respectively. 4c . 4d the first transverse branches 9a . 9b or or 46a . 46b By means of a control device, not shown here, each controlled offset, it is often sufficient if for the first transverse branches 9a . 9b respectively. 46a . 46b each sub-step-up converter 34 and 35 in each case a single second transverse branch 14 respectively. 47 is provided, as in 5 is shown. If the distance between the offset switching of the HSS switch 4a . 4b respectively. 4c . 4d at least one full oscillation period T of the resonant circuit 15a . 15b is, ensures that the capacitor 16a . 16b of the respective second transverse branch 14 respectively. 47 before the next switching is in its initial state of charge. The capacitor 16a . 16b is then ready again for a reload to the switching HSS switch 4a . 4b respectively. 4c . 4d bring into its de-energized state and thus switch lossless.

Optionally, in 5 not shown additional discharge paths for the second transverse branches 14a . 14b be provided. Furthermore, optional to each of the capacitors 16a . 16b a discharge resistor may be connected in parallel across which the capacitor 16a . 16b can discharge if there is no input voltage between the inputs 36 . 37 of the boost converter 1 is applied.

LIST OF REFERENCE NUMBERS

1

Boost converter

2

HSS throttle

3

HSS diode

4

HSS switch

5

management

6

entrance

7

output

8th

earth

9

(first) transverse branch

10

Freewheeling diode

11

Link capacitor

12

load

13

auxiliary diode

14

(second) transverse branch

15

resonant circuit

16

capacitor

17

series connection

18

Kitchen sink

19

switch

20

diode

21

Freewheeling diode

22

control signal

23

control signal

24

voltage curve

25

voltage curve

26

current profile

27

current profile

28

time

29

time

30

discharge path

31

connection

32

diode

33

discharge resistor

34

Part-up converter

35

Part-up converter

36

input port

37

input port

38

bridge circuit

39

Focus

40

Focus

41

primary coil

42

transformer

43

rectifier

44

output capacitor

45

inverter

46

transverse branch

47

transverse branch

T

period of oscillation

Claims (15)

Boost converter ( 1 ) with - an HSS throttle ( 2 ); - one with the HSS throttle ( 2 ) in series HSS diode ( 3 ); - an HSS switch ( 4 ), which in a first between the HSS throttle ( 2 ) and the HSS diode ( 3 ) branching transverse branch ( 9 ) and having a regular current flow direction; and a resonant circuit ( 15 ), in a second between the HSS throttle ( 2 ) and the HSS diode ( 3 ) branching transverse branch ( 14 ) and the one capacitor ( 16 ) and one to the capacitor ( 16 ) series connection in parallel ( 17 ) from a coil ( 18 ) and a switch ( 19 ), wherein the first transverse branch ( 9 ) for a current contrary to the normal current flow direction of the HSS switch ( 4 ), - whereby the switch ( 19 ) of the resonant circuit ( 15 ) a freewheeling diode ( 21 ) is connected in parallel, - wherein in the second transverse branch ( 14 ) a diode ( 20 ) with the resonant circuit ( 15 ) is connected in series and - wherein the forward direction of the diode ( 20 ) from the HSS throttle ( 2 ) seen from the forward direction of the freewheeling diode ( 21 ) and the regular current flow direction through the HSS switch ( 4 ) is the same. Boost converter ( 1 ) according to claim 1, characterized in that in the first transverse branch ( 9 ) an auxiliary diode ( 13 ) with the HSS switch ( 4 ) is connected in series, the first shunt branch ( 9 ) for the current contrary to the regular current flow direction of the HSS switch ( 4 ) locks. Boost converter ( 1 ) according to claim 1 or 2, characterized in that the HSS switch ( 4 ) a freewheeling diode ( 10 ) is connected in parallel. Boost converter ( 1 ) according to one of the preceding claims, characterized in that between the coil ( 18 ) and the switch ( 19 ) of the resonant circuit ( 15 ) a discharge path ( 30 ) with another diode ( 32 ), which is connected to the output ( 31 ) of the HSS diode ( 3 ), wherein the transmission directions of the further diode ( 32 ) and the HSS diode ( 3 ) from the output side port ( 31 ) of the HSS diode ( 3 ) are seen from the same direction. Boost converter ( 1 ) according to one of the preceding claims, characterized in that the capacitor ( 16 ) a discharge resistor ( 33 ) is connected in parallel. Boost converter ( 1 ) according to one of the preceding claims, characterized in that the switch ( 19 ) of the resonant circuit ( 15 ) is designed for a larger current flow than the HSS switch ( 4 ). Boost converter ( 1 ) according to one of the preceding claims, characterized in that a plurality of first transverse branches ( 9 ) and a single second shunt branch ( 14 ), and in that a control device for staggered driving of the HSS switches ( 4 ) of the plurality of first transverse branches ( 9 ) is provided. Boost converter ( 1 ) according to one of the preceding claims, characterized in that the boost converter ( 1 ) a pair of partial boosters ( 34 . 35 ) and a DC link with two series-connected DC link capacitors ( 11 ), where: - the partial boosters ( 34 . 35 ) a common HSS throttle ( 2 ), - of which a partial boost converter ( 34 ) of the pair the first and second transverse branches ( 9 . 14 ) and the HSS diode ( 3 ), wherein the first and second transverse branches ( 9 . 14 ) to a midpoint ( 3 ) of the DC intermediate circuit between the two DC link capacitors ( 11 ) and where the one partial ( 34 ) one of the two DC link capacitors ( 11 ), and - first and second shunt branches ( 46 . 47 ) and an HSS diode ( 3 ) of the other sub-contractor ( 35 ) of the pair with respect to the midpoint ( 39 ) of the DC intermediate circuit except for their current flow and passage directions mirror images of the first and second shunt branches ( 9 . 14 ) and the HSS diode ( 3 ) of one sub-packager ( 34 ), wherein the other partial boost converter ( 35 ) the other of the two DC link capacitors ( 11 ) loads. Boost converter ( 1 ) according to claim 8, characterized in that a bridge circuit ( 38 ) is provided, which is connected on the input side to the DC voltage intermediate circuit and whose center ( 40 ) to one end of a primary winding ( 41 ) of a transformer ( 42 ), the other end of the primary winding ( 41 ) to the center ( 39 ) of the DC intermediate circuit is connected. Use of a boost converter ( 1 ) according to one of the preceding claims, characterized in that - the switch ( 19 ) of the resonant circuit ( 15 ) is closed to the capacitor ( 16 ) of the resonant circuit ( 15 ) and then recharge with opposite polarity to its initial charging state, - the switch ( 19 ) of the resonant circuit ( 15 ) after charging the capacitor ( 16 ) is opened again with respect to its initial charging state of opposite polarity, - the capacitor ( 16 ) of the resonant circuit ( 15 ) returns to its initial state of charge, and - the HSS switch ( 4 ) is closed or opened while the capacitor ( 16 ) is charged with opposite polarity to its initial charging state. Use of a boost converter ( 1 ) according to one of claims 1 to 9, characterized in that - the switch ( 19 ) of the resonant circuit ( 15 ) is closed to the capacitor ( 16 ) of the resonant circuit ( 15 ) and then recharge with opposite polarity to its initial charging state, - the switch ( 19 ) of the resonant circuit ( 15 ) after charging the capacitor ( 16 ) is opened again with respect to its initial charging state of opposite polarity, - the capacitor ( 16 ) of the resonant circuit ( 15 ) returns to its initial state of charge, and - the HSS switch ( 4 ) is opened or closed in a deenergized state in which no current flows through the HSS switch and no voltage is applied across the HSS switch which could drive a current in the regular current flow direction through the HSS switch. Use of a boost converter ( 1 ) according to claim 10 or 11, characterized in that the switch ( 19 ) of the resonant circuit ( 15 ) is controlled such that in the resonant circuit ( 15 ) for exactly one full oscillation period (T) of the resonant circuit ( 15 ) a current flows. Use of a boost converter ( 1 ) according to claim 12, characterized in that the HSS switch ( 4 ) is controlled such that it is closed and / or opened only after a quarter of the oscillation period (T) of the resonant circuit ( 15 ) a current in the resonant circuit ( 15 ), but before the current for three-quarters of the period of oscillation (T) in the resonant circuit ( 15 ) has flowed. Use of a boost converter ( 1 ) according to one of claims 10 to 13, characterized in that the switch ( 19 ) of the resonant circuit ( 15 ) is triggered in such a way that it is opened when one in the resonant circuit ( 15 ) flowing current at least partially through the freewheeling diode ( 21 ) of the switch ( 19 ) to be led. Use of a boost converter ( 1 ) according to one of claims 10 to 14, characterized in that the switch ( 19 ) of a single second transverse branch ( 14 ) is controlled in such a way that the HSS switches ( 4 ) of a plurality of first transverse branches ( 9 ) offset losses are switchable.

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