DE4431665A1 - Method and device for avoiding switching losses in converters - Google Patents

Abstract

The invention relates to a method for avoiding switching losses in converters (2) for producing positive and/or negative voltage pulses from a voltage source (5), in that the power supply to a load (18) is cyclically interrupted and/or commutated. The power is fed back to the voltage source via a feedback device during and/or after the interruption of the power supply to the load (18). During the switching operation for the purpose at least of switching out the load (18), the current present at the load (18) is routed in parallel past the switching device (1) and, in so doing, the switching device (1) is essentially dead (deenergised, free from current). Prior to the opening of a main switch (11, 13), preferably a half- or full-bridge or a three-phase bridge, the current flowing through the load (18) is divided between an auxiliary half-bridge (27) and a feedback circuit, whereupon a capacitor (33) of a resonant circuit (32) between the main switches (11, 13) and the auxiliary half-bridge (27) is charged. The capacitor (33) is charged by a current which is greater than or less than the value of the current taken up by the load (18). The main switch (11) of the half-bridge (10) is opened and thereupon the further main switch (13) of the half-bridge (10) is closed, whereupon the capacitor (33) is charged further. After the capacitor (33) has been recharged, a [lacuna] inductively in the resonant circuit (32) or between the latter and the voltage source (5) ... Original abstract incomplete. <IMAGE>

Description

The invention relates to a method and a device for avoiding switching losses in converters, as in the preambles of claims 1 and 8 be are written.

There are relief circuits, which he a currentless switching of main switches possible, known from the prior art, such. B. the delete circuits after McMurray. Low loss relief circuits for such half bridges are very complex and usually require regenerative power supplies and start-up circuits. You produ also adorn own losses. They make it possible due to the relief effect against a higher switching frequency of the main switch and thus a lowering of the Inverters generated faults, but they do not allow any significant improvements overall efficiency.  

The present invention has for its object a method or a direction to avoid switching losses in converters to create a current enable the circuit breaker to be switched off and with which one if the excess energy is also fed back into the voltage source can be.

This object of the invention is achieved by the features in the characterizing part of the patent claim 1 . The advantage of this solution is that the excess energy can be fed back into the voltage source without a complicated structure of the power supply units. In addition, no starting circuits are required with this method. Due to the sinusoidal current curves and the linear voltage curves during the switching processes, a converter that is relieved of load relieves considerably less interference. In addition, the auxiliary switches only have to switch off the magnetizing current of the transformer and, like the other components, can be designed for very low current loads. In addition, there is almost no switching stress on this auxiliary switch. Another surprising and unpredictable advantage is that the relief effect increases with increasing load, ie increasing load current, and the overall degree of efficiency is significantly improved. In addition, a smaller construction is also possible when using the method or the device according to the invention, since the use of smaller power circuits and heat sinks is sufficient.

A procedure according to claim 2 is also advantageous. This ensures that by reloading the capacitor the current in the resonance circuit over the load current rises, causing a free-wheeling diode to become conductive and thus the main switch to be de-energized and can be switched off without loss, or when the load current through the current flowing through the resonance circuit, only the difference between them the manifold flows during the switching process via the main switch and thus a much lower load on the main switch is achieved than if the Main switch must be switched under the full current load.

But it is also possible to proceed according to claim 3, whereby the current for split the auxiliary half bridge and the current load of the auxiliary switches of the auxiliary half bridge is low, since the auxiliary switch only with the residual current in the transformer stored residual energy is loaded.  

But the measures according to claim 4 are also advantageous, since the in ductility stored energy is returned to the voltage source without a regenerative power supply must be installed in the switching device. About that In addition, this procedure also ver overloads the capacitor prevents.

The measures according to claim 5 enable the voltage to the main switches increases linearly after they are switched off, which makes them considerably less Low voltage peaks occur at the main switches and therefore for a low lower voltage load can be designed. Furthermore, the request entire voltage rise achieved an even better switch-off relief, because of the Main switches a lower power loss must be dissipated, which the The life of the main switch is significantly extended.

Furthermore, a process sequence according to claim 6 is also possible. This he possible to return the energy stored in the transmitter to the Power source without the use of a complicated regenerative power supply.

When using the measures according to claim 7 it is achieved that by bypassing the current at the main switches these are de-energized or when the load current only slightly exceeds the current flowing in the resonance circuit Current load, namely the difference between the load current and that by the Resonant circuit flowing current can be switched off with little loss.

The invention also includes a device for avoiding switching loss Most in converters, as described in the preamble of claim 8.

This device is characterized by the features in the characterizing part of claim 8 featured. It is advantageous in this embodiment that with relatively few components len achieves a de-energized switching in the half-bridge, at the same time a feedback the excess energy into the voltage source is made possible with simple means and in addition no switch-on losses occur when a main switch is switched on Turns on when the freewheeling diode of the other main switch current leads.

The configuration according to claim 9 ensures that after closing of the main switch, the current can only slowly increase, causing switch-on losses  be avoided.

However, the use of components according to claim 10 is also advantageous a faster switching frequency with a longer service life of the main switch chen.

An inexpensive solution with a long service life can also be achieved through the staltung according to claims 11 and 12 can be achieved.

The invention is described below with reference to that shown in the drawings Exemplary embodiments explained in more detail.

Show it

Figure 1 is a circuit diagram of a switching device according to the invention for generating positive and / or negative voltage pulses.

Fig. 2 is a diagram in which the capacitor current is plotted against the capacitor voltage of the capacitor of a switching device according to the invention according to Fig. 1;

Fig. 3 shows a DC-DC full bridge converter in a schematic representation whose half bridges are equipped with the switching device according to the invention;

Fig. 4 shows a further embodiment of the switching device according to the invention for generating positive and / or negative voltage pulses;

Fig. 5 is a diagram in which the capacitor current through the capacitor clamping voltage of the capacitor of a switching device according to the invention according to Fig. 5 applied.

In Figs. 1 and 2, a switching device 1 is shown as a converter 2, z. B. in the exemplary embodiment, a pulse width modulated buck converter acts. The Schaltvorrich device 1 is connected via terminals 3 , 4 to a voltage source 5 and supplied via a line 6 with the positive intermediate circuit voltage and via a line 7 with the negative intermediate circuit voltage. Supply lines 8 and 9 ver share the intermediate circuit voltage supplied by the voltage source 5 within the switching device.

The switching device 1 has a half bridge 10 , which is formed from a main switch 11 and an antiparallel connected freewheeling diode 12 and a further main switch 13 with a further antiparallel connected freewheeling diode 14 . From the output of the main switch 11 is connected via a line 15 to the input of the main switch 13 . The input of the main switch 11 is connected via a line 16 to the supply line 8 and the output of the main switch 13 via a line 17 to the supply line 9 .

Between the main switches 11 and 13 is a. Inductive load 18 , z. B. a motor, a welding unit, a compressor or the like. Via a line 19 is connected. At the connection point of line 19 to line 15 , a bridge midpoint 20 is formed. The load 18 usually has a sufficiently large ductility or is switched on, so that in the functional description of the switching device 1 the load current can be assumed to be constant during a period of the switching frequency or a switching cycle.

A relief circuit 21 is arranged parallel to the half bridge 10 . In the discharge circuit 21 each main switch 11 and 13 auxiliary switches 22 and 23 are assigned , which in turn are connected to each other via a line 24 . The auxiliary scarf tern 22 , 23 is also associated with an antiparallel connected freewheeling diode 25 , 26 . The auxiliary switches 22 , 23 with their anti-parallel diodes 25 , 26 form a further auxiliary half-bridge 27 , which in turn has a bridge center 28 . The auxiliary switch 22 is connected via a line 29 to the supply line 8 and the auxiliary switch 23 via a line 30 to the supply line 9 .

Between the bridge center 20 of the half bridge 10 and the bridge center 28 of the auxiliary half bridge 27 there is a resonance circuit 32 in a line 31 , which is composed of a capacitor 33 and an inductor 34 and a first part 35 of a transformer 36 is interposed. Between the capacitor 33 and the inductor 34 , clamping diodes 37 and 38 are connected to the line 31 via a line 39 . The clamping diode 37 is connected from its cathode via a line 40 to the supply line 8 and the anode of the clamping diode 38 via a line 41 to the supply line 9 . The arrangement of the clamping diodes 37 , 38 creates a further bridge center point 42 at the connection point between the lines 31 and 39 .

Additional clamping diodes 43 and 44 are arranged parallel to the auxiliary half bridge 27 . The cathode of the clamping diode 43 is connected to the supply line 8 and the ano de of the clamping diode 44 to the supply line 9 . The clamping diodes 43 , 44 are connected to one another via a line 45 and form a further bridge center 46 . Between the bridge center 28 of the auxiliary half bridge 27 and the bridge center 46 of the clamping diode 43 , 44 , a second part 47 of the transmitter 36 is interposed in a line 48 . The second part 47 of the transmitter 36 has more than the first part 35 of the transmitter 36 , z. B. twice as many turns.

The switching device 1 also has a current measuring device 49 which is arranged in a line 50 between the supply line 8 and the load 18 . The output from the current measuring device 49 is connected to a controller 51 . The controller 51 is in turn connected to a control device 52 . The control device 52 controls the main switches 11 , 13 and the auxiliary switches 22 , 23 via lines.

The converter 2 consists of the voltage source 5 , the half bridge 10 and the load 18 . The function of the converter 2 with the relief circuit 21 is described in successive periods as shown in FIG. 2.

In this case 2, a U-ZI diagram is shown in Fig., The ordinate of ZI, where Z is the impedance of the resonant circuit 32, and I is the current through the inductor and on the abscissa the capacitor voltage U of the capacitor is applied 33rd The successive points of a characteristic curve 53 running in the direction of the arrow thus describe the successive states in the resonant circuit 32 .

The switching device 1 is started up by applying an intermediate circuit voltage 54 from the voltage source 5 , the capacitor 33 not charging during the voltage build-up. After completion of the voltage build-up it is assumed that a constant load current flows through the load 18 and the capacitor 33 according to arrow 55 to the negative intermediate circuit voltage 54 , shown in Fig. 2, and shown by an arrow 55 in Fig. 1, charged is, as can be seen in a state 56 in FIG. 2, the charging of the capacitor 33 being explained in more detail below in the functional description of the switching device 1 . Furthermore, it is assumed that the main switch 13 is already switched on and the constant load current flows from the load 18 via the main switch 13 to the supply line 9 .

In order to switch off the main switch 13 with little loss, the auxiliary switch 23 is switched on to a state 56 , as a result of which the capacitor 33 charged according to arrow 55 discharges. As a result, the current that previously flowed through the main switch to the supply line 9 now flows partly through the capacitor 33 of the inductor 34 , the first part 35 of the transformer 36 to the auxiliary switch 23 and from this back to the supply line 9 . Because of the current applied to the first part 35 of the transformer 36 , a current is transformed to the second part 47 of the transformer. Since the second part 47 of the transformer 36 is equipped with a higher, in particular double the number of turns than the first part 35 of the transformer 36 , the current flowing into the first part 35 of the transformer 36 is divided, e.g. B. halved, ie the current flowing in half flows through the auxiliary switch 23 to the supply line 9 and the other half via the second part 47 of the transmitter 36 and via the clamping diode 43 to the supply line 8 . Since a current flow is established via the second part 47 of the transformer 36 , the Klemmdio de 43 becomes conductive in the direction of passage, as a result of which the current can flow to the supply line 8 .

Due to the conductive clamping diode 43 and the auxiliary switch 23 switched on, the intermediate circuit voltage is present in the positive direction on the second part 47 of the transformer 36 . Since the transformer 36 consists of two parts 35 , 47 , the intermediate circuit voltage 54 applied to the second part 47 is transformed to the first part 35 of the transformer 36 and is one part, preferably half the intermediate circuit voltage 54 , in the positive direction.

The negative intermediate circuit voltage 54 continues to be present at the resonant circuit 32 according to arrow 55 , as a result of which the capacitor 33 is discharged via a center point 57 , ie by half the negative intermediate circuit voltage 54 . Because of this from the state 56 on the first part 35 of the transformer 36 voltage, with which the resonance circuit 32 is also applied, the discharge of the capacitor 33 begins from the center point 57 , which is shown in Fig. 2 and half of the negative DC link voltage 54 corresponds. The discharge curve of the capacitor 33 describes a circular arc which can be seen in FIG. 2 on the characteristic curve 53 between the state 56 and a state 58 . The center of the arc for discharging the capacitor 33 is located in the center 57 , that is to say on the negative half intermediate voltage 54 .

In a state 59 it can be seen from the characteristic curve 53 that the current in the resonant circuit 32 exceeds a load current 60 of the load 18 , as a result of which the main switch 13 between states 59 and 58 is de-energized and can be switched off. Since the current in the resonant circuit 32 is greater than the load current 60 , the freewheeling diode 14 at the main switch 13 becomes conductive, as a result of which the load current 60 flows from the load 18 via the resonance circuit 32 to the first part 35 of the transformer 36 via the auxiliary switch 23 to the supply line 9 . The current now flows back from the supply line 9 via the freewheeling diode 14 to the resonant circuit 32 . By switching the free-wheeling diode 14 no more current can flow through the main switch 13 , whereby this can be switched off between the states 59 and 58 without current. If, for example, the load current 60 shown with dash-dotted lines exceeds the current in the resonance circuit 32 , the current flowing via the main switch 13 between the states 59 and 58 is very small and corresponds to the difference between the load current and the current in the resonance circuit 32 . Thus, the load on the main switch 13 is kept extremely low in this case and the advantageous effect according to the invention can also be used in this case.

If the discharge curve of the capacitor 33 has progressed so far that the current flow in the intermediate circuit again corresponds to the load current 60 - this occurs in state 58 - the current from the load 18 tries to flow again via the main switch 13 . Since the state 58 of the main switch 13 is already switched off, the constant load current 60 now flows through the resonant circuit 32 and via the first part 35 of the transmitter 36 , which divides the current into two halves, one half via the auxiliary switch ter 23 to the Supply line 9 and the other half flows back to the supply line 8 via the second part 47 of the transformer 36 and via the clamping diode 43 .

By flowing through the resonant circuit 32 of the constant load current 60 , the voltage across the inductor 34 collapses and the voltage at the bridge center point 20 jumps to the value of half the intermediate circuit voltage plus the capacitor voltage of the capacitor 33 at state 58 . From the U-ZI diagram in Fig. 2 it can be seen that the voltage of the capacitor 33 at state 58 is greater than zero and that this voltage becomes smaller with increasing load current 60 . The voltage at the main switch 13 therefore jumps to a maximum of half the intermediate circuit voltage. The capacitor 33 is charged with the constant load current 60 .

In state 61 , the main switch 11 is now switched on with little loss. The verlustar me switching on the main switch 11 takes place in that a voltage is already present via the main switch 13 and the freewheeling diode 14 and therefore the full blocking capability of the main switch 13 and the freewheeling diode 14 is reached. By switching on the main switch 11 , half the intermediate circuit voltage is now applied at the bridge center 20 , according to arrow 62 , in the positive direction of the capacitor 33 to the resonant circuit 32 , whereby a new oscillation process occurs in the resonant circuit 32 . This oscillation in the resonant circuit 32 describes the characteristic curve 53 between the states 61 and 63 .

It can again be seen that the new oscillation process in the resonant circuit 32 charges the capacitor 33 in a circular arc by half the positive intermediate circuit voltage 64 . If state 63 is reached, capacitor 33 is charged to a full positive intermediate circuit voltage 65 μm.

At state 63 , the current in the resonant circuit 32 is already very low and the clamping diode 38 begins to conduct, since otherwise the capacitor 33 would be overloaded. Furthermore, the freewheeling diode 12 becomes conductive and takes over the full load current 60 of the load 18 , as a result of which no more current can flow through the capacitor 33 and the capacitor 33 remains charged to a positive intermediate circuit voltage 65 .

The energy contained in the inductance 34 of the resonance circuit 32 is now fed back from the state 63 to a state 66 to the voltage source 5 . The current flows from the inductor 34 in the first part 35 of the transmitter 36 , which divides it into two parts, one part via the auxiliary switch 23 to the supply line 9 and another part via the second part 47 of the transmitter 36 and Clamping diode 43 flows back to the supply line 8 . The auxiliary switch 23 is now switched off, which only has to switch off the magnetizing current of the transmitter 36 . The energy that is present in the transformer 36 is now supplied to the voltage source 5 via the freewheeling diode 25 and the supply line 8 .

In state 66 , the deletion process for the main switch 11 is initiated, ie the auxiliary switch 22 is switched on. A new discharge of the capacitor 33 is caused.

By switching on the auxiliary switch 22 , the clamping diode 44 begins to conduct, where the negative intermediate circuit voltage is applied to the second part 47 of the transformer 36 . Half the negative intermediate circuit voltage is now transmitted to the first part 35 of the transformer 36 , since the bridge center point 28 is now at a positive intermediate circuit voltage 65 , half the positive intermediate circuit voltage 64 is again applied to the resonant circuit 32 . The center point of the circular arc in the U-ZI diagram, which describes this oscillation, is therefore again equal to half the positive intermediate circuit voltage 64 . The resonant circuit 32 therefore oscillates from the state 66 to a state 67 . In a state 68 of the characteristic curve 53 , the main switch 11 is switched off by the control device 52 . If the state 67 is reached, the main switch 13 is turned on by the control device 52 . After switching on the main switch 13 , the capacitor 33 is again charged to the negative intermediate circuit voltage around the center point 57 . The resonant circuit 32 oscillates from the state 67 to the state 56 around the center 57 .

After reaching state 56 , the capacitor 33 is charged again to the full negative intermediate circuit voltage 54 and the auxiliary switch 22 is switched off by the Steuerervor device 52 , whereby the initial state for switching off from the main switch 13 is reached again.

The load current 60 on the load 18 can be set by the duty cycle of the switch-on times between the main switch 13 and the main switch 11 . The load current 60 is detected by the current measuring device 49 and leads to the controller 51 . A specific current value can now be set on the controller 51 . The load current 60 is then compared with the set current and the result, whether the load current 60 has to be increased or decreased, is passed to the control device 52 . The control device 52 calculates the corresponding duty cycle between the main switches 13 and 11 and controls this and the auxiliary switches 22 and 23 via lines.

In order to obtain the values assumed when the switching device 1 was put into operation, ie the charging of the capacitor 33 to the negative intermediate circuit voltage 54 and a load current 60 , the switching state is based on the state 56 via the states 59 , 58 , 61 , 63 , 66 , 68 and 67 , wherein the main switch 13 is switched on first and then the auxiliary switch 22 . Switching on the main switch 13 creates a current flow from the supply line 8 via the load 18 and the main switch 13 to the supply line 9 .

In Fig. 3 another embodiment of the Schaltvorrich device 1 according to the invention is shown. Two half bridges 69 , 70 are connected together to form a full bridge 71 , the half bridges 69 , 70 corresponding to the half bridge 10 . The supply of the two half bridges 69 , 70 in turn takes place via a voltage source 5 , which supplies the two half bridges 69 , 70 via the supply line 8 and 9 with the positive and negative potential. The two half bridges 69 , 70 are each provided with a relief circuit 21 .

At the bridge center point 20 of the half bridges 69 , 70 , the two half bridges 69 , 70 are connected via a line 72 , with the intermediary of the primary side of a converter 73 . The connection of the half bridges 69 , 70 via the line 72 corresponds to the arrangement of the load 18 in FIG. 1.

The secondary side of the converter 73 is formed by three connection points 74 , 75 and 76 ge. The connection points 74 , 76 are interconnected via a line 77 with the interposition of diodes 78 , 79 . The diodes 78 , 79 form a rectifier 80 which supplies a load 83 with the positive potential via a line 81 with the interposition of an inductor 82 . The load 83 is connected to the connection point 75 via a line 84 and is thereby supplied with the negative potential.

The main switches 11 , 13 shown in the half bridges 69 , 70 are controlled via lines 85 to 88 by the control device 52 . The Ent load circuit 21 shown in Fig. 1 is shown schematically in Fig. 2 as a block. The auxiliary circuit 22 , 23 arranged in the discharge circuit 21 are also controlled by the control device 52 via lines, which, however, are not shown for the sake of clarity.

The function of the individual half bridges 69 , 70 is no longer described, since it corresponds to the functional description of the exemplary embodiment shown in FIG. 1.

By turning on the main switches 11 , 13 in the half-bridges 69 , 70 from the control device 52 in the opposite direction, the direction of the current flow can be changed. This is done in that the control device 52 turns on the line 88 the main switch 13 of the half-bridge 69 and via line 86 the further main switch ter 11 of the half-bridge 70 , thereby causing a current flow from the supply line 8 to the main switch 11 of the half-bridge 70 the line 72 , the main switch 13 of the half bridge 69 continues to the supply line 9 . As a result of the current flowing through the primary side of converter 73 , a current is induced on the secondary side of converter 73 and rectified via rectifier 80 and fed to load 83 via lines 81 , 84 . If the main switch 13 of the half-bridge 69 and the main switch 11 of the half-bridge 70 are now switched off, the control device 52 controls the auxiliary switches 22 and 23 arranged in the relief circuit 21 , as described in FIG. 1. After the main switch 13 of the half-bridge 69 and the main switch 11 of the half-bridge 70 have been turned off, the main switch 13 of the half-bridge 70 and the main switch 11 of the half-bridge 69 are, as described in FIG. 1, from the control device 52 via the lines 85 , 87 switched on, which results in a new current curve. The new current curve now takes place from the supply line 8 via the main switch 11 , the line 72 , the main switch 13 of the half-bridge to the negative potential of the supply line 9 , as a result of which the direction of the current course in line 72 changes and that in the U- ZI diagram shown in Fig. 2 current curve from state 56 to state 66 in the U-ZI diagram by mirroring at the zero point the same curve from state 66 to state 56 results in the currentless switching off of the individual half bridges 69 and 70 .

In Figs. 4 and 5 is another embodiment of the invention Schaltvor direction 1, wherein the same reference numerals apply for the same parts were ver. The difference from the embodiment shown in FIG. 1, switching device 1 is that it is arranged in the lines 16 and 17 are each an inductor 89, 90. In Fig. 5, a U-ZI-diagram is shown, the capacitor voltage of the capacitor U is plotted on the ordinate and on the abscissa ZI.

The switching device 1 is started up by applying an intermediate circuit voltage from the voltage source 5 , the capacitor 33 not charging during the voltage build-up. After completion of the voltage build-up, it is assumed that a constant load current 60 flows through the load 18 and the capacitor 33 , according to arrow 55 , is charged to the negative intermediate circuit voltage 54 , where after charging the capacitor 33 to the negative intermediate circuit voltage 54 after the functional description of the switching device 1 is explained in more detail. The resonance circuit 32 is in state 91 of a characteristic curve 92 in FIG. 5. Furthermore, it is assumed that the main switch 13 is already switched on and the constant load current 60 flows from the load 18 via the main switch 13 to the supply line 9 .

In order to switch off the main switch 13 with little loss, the auxiliary switch 23 is turned on, whereupon the capacitor 33 is discharged via the inductors 90 , 34 in a vibration. When the auxiliary switch 23 is switched on , the load current 60 , which previously flowed from the load 18 via the main switch 13 to the supply line 9 , now flows partly through the capacitor 33 of the inductor 34 , the first part 35 of the transformer 36 through the auxiliary switch 23 and from these to the supply line 9 back. The starting point of the oscillation is the state prevailing in state 91 in the resonance circuit 32 , ie the capacitor 33 is charged to the negative intermediate circuit voltage 54 . Due to the voltage lying on the resonance circuit 32 from state 91 , above the center 57 of the U-ZI diagram as can be seen from the characteristic curve 92 shown in FIG. 5, one of the oscillation-writing circuit of the discharge of the capacitor 33 from the State 91 to a state 93 enforced.

Since the bridge center point 20 is here between two parts of the inductors 34 , 90 , the bridge center point 20 assumes the negative potential in the state 91 with respect to the supply line 9 . At state 94 , the current in the resonance circuit 32 exceeds the load current 60 of the load 18 , as a result of which the main switch 13 between states 94 and 93 can be switched off without current. Since the current in the resonance circuit 32 is greater than the load current 60 , the freewheeling diode 14 at the main switch 13 becomes conductive, whereby the load current 60 from the load 18 via the resonance circuit 32 , the first part 35 of the transmitter 36 and the auxiliary switch 23 to the supply company device 9 flows. From the supply line 9 , the current now flows back via the freewheel diaphragm 14 to the resonant circuit 32 . By switching the freewheeling diode 14 no more current flows through the main switch 13 , whereby this can be switched off between the states 94 and 93 without current. The control device 52 thus switches the main switch 13 from state 95 without current.

In state 93 , the current in the resonant circuit 32 again reaches the size of the load current 60 , as a result of which the load current 60 would like to flow again via the main switch 13 . However, since the main switch 13 was switched off in the state 95 , the constant load current 60 flows through the resonant circuit 32 , whereby the voltage at the bridge center point 20 linearly to the value of half the positive intermediate circuit voltage 64 plus the capacitor voltage, which in the state 93 at the capacitor 33 of the Re resonance circuit 32 is applied and is now charged with the constant load current 60 , where linearly increases by the voltage at the main switch 13 and thus the potential at the bridge center 20 , since the inductance 90 is de-energized.

In state 96 , the main switch 11 , as already described in FIG. 1, is switched on with little loss. By turning on the main switch 11 , half the positive intermediate circuit voltage, according to arrow 62, is applied to the resonant circuit 32 via the transformer 36 , whereby the resonant circuit 32 now consists of the inductor 34 , the capacitor 33 and the inductor 89 . By switching on the main switch 11 a new oscillation process on the resonant circuit 32 is started. This oscillation describes the circular arc beginning in state 96 in the U-ZI diagram in FIG. 5 with the center point of half the intermediate circuit voltage 64 . The Ra dius of this circuit of the new oscillation process depends on the switch-on time of the main switch 11 or on the state 96 in which the resonant circuit 32 is at the switch-on time. If the main switch 11 is switched on in the state 96 , the oscillation ends in a state 97 , as described in FIG. 1. The energy contained in the inductance 34 of the resonance circuit 32 is now fed back from the state 97 to a state 98 to the voltage source 5 , as has already been described in detail in FIG. 1.

However, if the main switch 11 is not switched on at the time when the resonant circuit 32 is in the state 96 , the linear charge interval, which is represented by the dashed line 99 , extends to a state 100 . In the dashed line 99 , the resonant circuit 32 is at the switch-on time of the main switch 11 in the state 100 . When the main switch 11 is switched on, the resonance circuit 32 oscillates from state 100 to state 101 , around the point of half the intermediate circuit voltage 64 . As shown in Fig. 5, the capacitor 33 is not yet charged to the full positive intermediate circuit voltage 54 in state 101 . The capacitor 33 is now forwarded from the state 101 to the state 98 via the main inductance of the transformer 36 . Since the main ductility of the transformer 36 is substantially greater than the resonance inductance, ie the inductance 34 plus the inductance 89 or the inductance 90 , this process can be done in UZ-I diagram with an approximation by a straight line between the state 101 and the State 98 to be described.

In state 98 , the capacitor 33 is charged to the full positive intermediate circuit voltage 65 . The current in the resonance circuit 32 , which is very small in this state 98 , is taken over by the clamping diode 38 , as already described in FIG. 1, as a result of which an overloading of the capacitor 33 is prevented. As described in Fig. 1, the freewheeling diode 12 is now conductive and thus carries the load current 60 , and through the capacitor 33 no more current flows. It therefore remains charged to the positive intermediate circuit voltage 65 .

If the auxiliary switch 22 is now switched off by the control device 52, the auxiliary switch 23 now only switches off the magnetizing current of the transformer 36 , whereupon the first part 35 and the second part 47 of the transformer 36 are demagnetized via the free-wheeling diode 25 against the intermediate circuit voltage.

In state 98 , the deletion process for the main switch 11 by switching on the auxiliary switch 22 , as described in FIG. 1, is initiated by the control device 52 . The capacitor 33 can now discharge via the main switch 11 , the inductor 89 , the auxiliary switch 22 , the transformer 36 , in which the current is as described in FIG. 1, and discharge via the inductor 34 , as a result of which the clamping diode 44 becomes conductive and half the intermediate circuit voltage is present in the positive direction on the resonant circuit 32 and has a renewed swinging around the capacitor 33 . This oscillation of the capacitor 33 describes the circuit from state 98 via a state 102 to a state 103 with a center point which corresponds to half the positive intermediate circuit voltage 64 . In state 102 , the main switch 11 is switched off by the control device 52 . If the state 103 is reached, the capacitor 33 is completely discharged.

In state 103 , in which the resonant circuit 32 is currently de-energized and the capacitor voltage of the capacitor 33 has just become zero, the Steuerervor device 52 switches the main switch 13 again with little loss. After turning on the main switch 13, the current commutates linearly from the freewheeling diode 12 to the main switch 13 . Due to the inductive voltage division, the bridge center point 20 is at half the positive intermediate circuit voltage, as a result of which the resonant circuit 32 remains in state 103 . Only after completed commutation, - ie the freewheeling de 12 is de-energized, and the main switch 13 carries the load current 60 - switches the free-wheeling diode 12 off, as a result of which half the intermediate circuit voltage is present again in the negative direction on the resonant circuit 32 . The resonance circuit 32 oscillates in the U-ZI diagram, as can be seen in FIG. 5, now automatically from the state 103 via the center point 57 to the output voltage of the negative intermediate circuit voltage 54. This occurs between the states 103 and 91 . If the state 91 is reached, the capacitor 33 is charged to the full negative intermediate circuit voltage 54 and a new switch-off process for the main switch 13 can begin. Furthermore, the auxiliary switch 22 is switched off at state 91 .

In order to obtain the values assumed when the switching device 1 was started up , the switching state is carried out from the state 103 to the state 91 , as a result of which the capacitor 33 is charged to the maximum negative intermediate circuit voltage 54 .

In the description of the present method for avoiding switching losses, a switching cycle is understood to mean a switching process which extends from state 56 via state 66 back to state 56 , in the diagram according to FIG. 2. To supply the load 18 , such switching cycles or switching processes are seamlessly connected when the method according to the invention is used.

Of course, it is also possible within the scope of the invention that the described benen circuit elements can be replaced by any other circuit parts nen. So z. B. the main switch or auxiliary switch by insulated gate bipolar Transistors (IGBTs), transistors, diodes ect. be educated.

For the sake of order it should be noted that individual parts of the previously be written circuits in any combination the subject of standalone can form gene solutions according to the invention.

Above all, the individual, in FIGS. 1, 2; 3; 4 and 5 form the subject of independent, inventive solutions. The relevant tasks and solutions according to the invention can be found in the detailed descriptions of these figures.

Reference list

1 switching device
2 inverters
3 connection terminal
4 connection terminal
5 voltage source
6 line
7 line
8 supply line
9 supply line
10 half bridge
11 main switch
12 freewheeling diode
13 main switch
14 freewheeling diode
15 line
16 line
17 line
18 load
19 management
20 bridge center
21 relief circuit
22 auxiliary switches
23 auxiliary switches
24 line
25 freewheeling diode
26 freewheeling diode
27 auxiliary half bridge
28 bridge center
29 line
30 line
31 line
32 resonant circuit
33 capacitor
34 inductance
35 part
36 transformers
37 clamping diode
38 clamping diode
39 Management
40 line
41 line
42 bridge center
43 clamping diode
44 clamping diode
45 line
46 bridge center
47 part
48 line
49 current measuring device
50 line
51 controller
52 control device
53 characteristic curve
54 DC link voltage
55 arrow
56 condition
57 center point
58 condition
59 state
60 load current
61 state
62 arrow
63 condition
64 DC link voltage
65 DC link voltage
66 state
67 state
68 state
69 half bridge
70 half bridge
71 full bridge
72 line
73 converters
74 connection point
75 connection point
76 connection point
77 line
78 diode
79 diode
80 rectifiers
81 line
82 inductance
83 load
84 line
85 line
86 line
87 line
88 management
89 inductance
90 inductance
91 condition
92 characteristic curve
93 state
94 condition
95 state
96 state
97 state
98 state
99 characteristic curve
100 condition
101 state
102 state
103 condition.

Claims (12)

1. A method for avoiding switching losses in inverters for the produc- tion of positive and / or negative voltage pulses from a voltage source in which the power supply of a load is interrupted and / or reversed, the energy during and / or after the interruption of the power supply Load is fed back to the voltage source via a feedback device and the current applied to a load is passed parallel to the switching device in parallel during the switching process, at least to switch off the load, and the switching device is essentially currentless, characterized in that the load ( 18 ) flowing current before opening a main switch ( 11 , 13 ), preferably a half or full bridge or a three-phase bridge is divided into an auxiliary half bridge ( 27 ) and a feedback circuit, whereupon a capacitor ( 33 ) of a resonant circuit ( 32 ) between the Main switches ( 11 , 13 ) and the auxiliary half bridge ( 27 ) is charged and that while the capacitor ( 33 ) is loaded with a current that is above or below the value of the current consumed by the load ( 18 ), one of the main switches ( 11 ) of the half-bridge ( 10 ) is opened and then the further main switch ( 13 ) of the half-bridge ( 10 ) is closed or closes, whereupon the capacitor ( 33 ) is charged and that after the capacitor ( 33 ) has been recharged, one in the resonant circuit ( 32 ) or between it and the voltage source ( 5 ) inductively stored energy is supplied to the voltage source ( 5 ) and then the auxiliary half-bridge ( 27 ) is opened, whereupon by switching the main switch ( 11 , 13 ) of the half-bridge ( 10 ) and an auxiliary switch ( 22 , 23 ) the auxiliary half-bridge ( 27 ) the capacitor ( 33 ) is recharged to the original voltage. 2. The method according to claim 1, characterized in that between the half-bridge ( 10 ) and the auxiliary half-bridge ( 27 ), a resonance circuit ( 32 ) is arranged and the capacitor ( 33 ) in the resonance circuit ( 32 ) within a switching cycle from the negative voltage peak to positive voltage maximum value of the intermediate circuit and then transferred back to the negative voltage value of the intermediate circuit. 3. The method according to claim 1 or 2, characterized in that the current flowing through the resonance circuit ( 32 ) by means of a transformer ( 36 ) via Klemmdio ( 43 , 44 ) to supply lines ( 8 , 9 ) is passed on to the positive or negative potential of the voltage source ( 5 ) and each of these positive or negative potential supply lines ( 8 , 9 ) via the auxiliary switch ter ( 22 , 23 ) of the auxiliary half-bridge ( 27 ) with the center of the transformer ( 36 ) is connected, so that according to a turn ratio, in particular 1: 2, of the transmitter ( 36 ) on both sides of the center, a portion of the current via the auxiliary switches ( 22 , 23 ) and the remaining portion via one of the clamping diodes ( 43 , 44 ) into the supply lines ( 8 , 9 ) flows. 4. The method according to one or more of claims 1 to 3, characterized in that the electrical energy stored in an inductance ( 34 ) of the resonant circuit ( 32 ) after opening the main switch ( 11 , 13 ) of the half-bridge ( 10 ) from alternating over the transformer ( 36 ) and two depending on the flow direction of the current de clamping diodes ( 37 , 44 ) or ( 38 , 43 ) is fed back into the voltage source ( 5 ). 5. The method according to one or more of claims 1 to 4, characterized in that the voltage rise at the main switch ( 11 , 13 ) of the half-bridge ( 10 ) is delayed and / or slowed down when the main switch ( 11 , 13 ) is opened. 6. The method according to one or more of claims 1 to 5, characterized in that the transformer ( 36 ) after opening an auxiliary switch ( 22 or 23 ) via the other auxiliary switch ( 23 or 22 ) parallel-connected freewheeling diode ( 25 or 26 ) demagnetized against the voltage source ( 5 ). 7. The method according to one or more of claims 1 to 6, characterized in that the current is passed in parallel to the main switch ( 13 ) of the half-bridge ( 10 ) through the resonance circuit ( 32 ) and the main switch ( 13 ) or the antipa switched in parallel Free-wheeling diode ( 14 ) when the main switch ( 13 ) turns off the dif current, ie the load current ( 60 ), less the current through the resonant circuit ( 32 ). 8. Device for avoiding switching losses in converters, to which a load, for. B. an electric motor with high power is connected via a half bridge of the converter between a supply line connected to the positive potential of the voltage source and the bridge center and that a white tere auxiliary half bridge connected in parallel to the half bridge is arranged and the brid ken centers of the half bridge and the auxiliary half bridge with interposition egg Nes resonant circuit are connected to each other, characterized in that the bridge center ( 28 ) of the auxiliary half-bridge is formed by the center of a transformer ( 36 ) and the first part ( 35 ) of the transformer ( 36 ) between the resonant circuit ( 32 ) and the center of the Transformer ( 36 ) has a smaller, in particular 50% of the number of turns than the second part ( 47 ) of the transformer ( 36 ) between the bridge center ( 28 ) of the auxiliary half bridge ( 27 ) and the bridge center ( 42 ) of the clamping diodes ( 37 , 38 ) and that between the capacitor ( 33 ) un d the inductivity ( 34 ) of the resonant circuit ( 32 ) the bridge center ( 42 ) of parallel to the half-bridge ( 10 ) connected clamping diodes ( 37 , 38 ) is connected and that the main and auxiliary switches ( 11 , 13 , 22 , 23 ) the half and auxiliary half bridge ( 10 , 27 ) free-wheeling diodes ( 12 , 14 , 25 , 26 ) are connected in parallel. 9. The device according to claim 8, characterized in that an inductance ( 89 , 90 ) is arranged between the supply lines ( 8 , 9 ) and the main switches ( 11 , 13 ). 10. Apparatus according to claim 8 or 9, characterized in that the main switches ( 10 , 13 ) and / or auxiliary switches ( 22 , 23 ) are formed by insulated gate bipolar transistors (IGBTs) or other power switches. 11. Device according to one of claims 8 to 10, characterized in that the auxiliary switches ( 22 , 23 ) in the auxiliary half-bridge ( 27 ) are formed by transistors. 12. The device according to one or more of claims 8 to 11, characterized in that the main switch ( 11 ) is formed by a diode.