DE10045093A1 - Circuit arrangement for energy supply for a control circuit of a power semiconductor switch and method for providing the control energy for a power semiconductor switch - Google Patents

Abstract

The invention relates to the minimisation of power losses in the energy supply of a control circuit for a power transistor (T), whereby a circuit component (SNT), or another switching transformer means, is electrically connected in parallel with a capacitor (C1), the output therefrom is electrically connected to a feed voltage capacitor (C>S<) and said component transforms the input energy to the C>S< voltage level. The R>L< load (control circuit) is thus adequately supplied and only the absolutely necessary balancing current (I1) flows, due to the balancing resistance R>S< in a power transistor switch (T).

Description

The invention relates to a circuit arrangement for Power supply for a control circuit of a power semiconductor switch with an electrically parallel ge switched series connection from a resistor and one first capacitor, which can be charged via the resistor is, and with a parallel connection from a second Kon capacitor and a power consumer.

Power semiconductors offer the possibility of raw electrical Energy (e.g. in the kW or MW range) using a low Switching control energy of a few watts. Here comes the Provision of the control energy for power semiconductors in High voltage applications become very important.

This control energy must be made available on the emitter or source potential of the power semiconductor. According to the known prior art, the following principles are known as solutions for providing this energy at the adequate potential:
A cost-effective solution is the transmission through a transformer. The AC voltage for the transformer is generated by a switching power supply, for example from the intermediate circuit voltage of a converter for converter drives or from an auxiliary voltage. However, this conventional solution is only suitable for transmission over a relatively low voltage level, since otherwise the required transformer will be very expensive. Above 40 k volts, the problem of partial discharges can hardly be mastered.

Another known supply voltage circuit uses optical transmission using a laser diode and a Energy converter: This solution is very expensive and also has problems with life duration of such a supply voltage circuit. That too is transferable power limited to a range below 200 mW.

Another known supply voltage circuit uses hence the following principle of decoupling from the Be circuit of the power semiconductor. Such a circuit For example, order is from the conference report "Novel Gate Power Supply Circuit Using Snubber Capacitor Energy for Series-Connected GTO Valves ", printed in the conference volume EPE '97 Trondheim, pages 1,576 to 1,581.

A circuit arrangement for energy supply for a control circuit on a power semiconductor switch according to the preamble of claim 1 is shown in FIG. 7 Darge closer. This supply voltage circuit for a control circuit of a power semiconductor switch, in particular a thyristor T that can be switched off, has a protective circuit in the form of a switch-off relief.

According to the conference report mentioned above, a capacitor Cb and a resistor Rb form a series circuit 4 and, in conjunction with a diode Db electrically connected on the anode side at node 6 of the series circuit 4, a protective circuit 10 of the power semiconductor switch T. The diode Db is closer to the cathode side via one below Overload protection 11 explained with a parallel circuit 2 of a supply voltage capacitor C _S and an electrical consumer - here in the form of a load resistor R _L - electrically connected.

At the supply voltage capacitor C _S , a supply voltage U _CS drops, which is supplied to the drive circuit of the power semiconductor switch T T. For reasons of clarity, this control circuit is not shown in detail.

The protective circuit 10 has the task of limiting the voltage rise to a predetermined value. The voltage rise is limited by the capacitor Cb. When the power semiconductor switch T is switched on, this capacitor Cb is discharged via the resistor Rb. Due to the requisite protective circuit 10 , losses in the resistor Rb must be accepted with each switching operation. The power loss that occurs is proportional to the switching frequency of the power semiconductor switch T.

The current that occurs through the protective circuit 10 of the power semiconductor T is, however, conducted via the supply voltage capacitor C _S on the control module (not shown) and charges it.

An overload protection or a voltage limiter circuit 11 is switched electrically in parallel with the supply voltage capacitor C _S. When the supply voltage capacitor C _S is overloaded, a protective thyristor TY is ignited, which takes over the wiring current. The thyristor is electrically connected in parallel with a counter-pole diode D2 in a further series circuit 7 to the supply voltage capacitor C _S , the node 8 of this series circuit 7 being electrically connected to the cathode-side terminal of the diode Db. The control connection of the thyristor TY is electrically connected via a Zener diode Z to the cathode-side connection of the diode D2.

This method is suitable for the highest voltage levels since it does not require electrical isolation. However, the following disadvantages of this solution also occur:

• - There must be a circuit, e.g. B. in the form of the protective circuit 10 shown.
• - This solution does not work with a pulse block, but only in the pulse mode of the power semiconductor switch T, since in the case of a pulse block there is no current flow through the appropriate circuitry and therefore no charging of the supply voltage capacitor C _S.
• - Large currents flow through the control module, the supply voltage capacitor C _S and the protective thyristor TY, which results in an undesirably high power loss.

The object of the present invention is therefore a food to create voltage circuit without a circuit gets along and where the power loss compared to the be known prior art is significantly minimized.

According to the present invention, this object is achieved solved that a circuit arrangement for energy supply for a control circuit of a power semiconductor switch further developed according to the preamble of claim 1 is that a switching means of transformation to Trans formation of the energy stored in the first capacitor to the required voltage level of the second condenser Tor is provided, which is electrically on the input side is connected to the first capacitor, and that on the output side is electrically connected to the parallel circuit.

It has proven to be particularly advantageous if a switching power supply or a switching device as transformation means controller is provided.

For a particularly stable operation in the event that the Infeed delivers more energy than in the control scarf device is consumed, according to another advantageous Design electrically parallel to the first capacitor Voltage limiting device arranged.

To avoid discharge of the supply voltage condenser according to an advantageous embodiment of the scarf line arrangement according to the invention in the series circuit additionally  a diode polarized in the flow direction is provided, the preferably between the resistor and the first condenser gate or between the knot from the resistance with the span voltage limiting device and the first capacitor is arranged.

A particularly advantageous voltage limiting device has voltage detection means, a means of comparison to compare a measurement voltage with a reference voltage and a switching means for discharging the capacitor in the case of the reference voltage being exceeded by the measurement voltage.

According to the invention, this becomes particularly simple and inexpensive thereby achieved that the first capacitor is electrical voltage divider connected in parallel to determine the measurement voltage, with which the non-inverting input of a Comparator is applied, its inverting input the reference voltage leads, the output of the comparator drives a semiconductor switch, which is electrically in Series with a resistor the first capacitor electrical is connected in parallel.

At the switching frequency of the switching means or semiconductor scarf limit, the comparison means or the compa rator according to a further advantageous embodiment of the Er find a hysteresis.

As a particularly simple and effective realization of the hyster Rese has proven to be part of the output voltage of the comparison means or comparator on the reference chip switch on.

According to a further advantageous embodiment of the scarf The arrangement of the invention can be particularly compact ter structure by connecting the voltage supply to the ver equal means or the comparator from the voltage of the  second capacitor, the supply voltage capacitor, he follows.

For a particularly easy achievement of a defined one switching state can be the output of the comparator a resistor electrically with the power semiconductor side Connect the first capacitor.

Alternatively, the voltage limiting device has one Zener diode as measuring means, which is a switching means for Ent charging of the supply voltage capacitor triggers.

According to a further advantageous embodiment of the scarf arrangement of the invention can be achieved that too an operation with impulse lock and at the same time with strong mini mated power loss is possible by between the Power semiconductor switch and the series connection one Protective circuit device is provided, in particular by placing between the power semiconductor switch and the rei another series connection with a third Capacitor and a downstream resistor electrically is connected in parallel and one of the tie points of the provided cross branch connecting two series connections which has a diode polarized in the direction of flow.

According to a further advantageous embodiment of the invention can be a plurality of electrically connected in series Power semiconductor switches particularly effective with one each Weil associated circuitry according to the invention Power supply for a control circuit of this Lei operate semiconductor switch when each power half conductor switches each have a parallel resistor has and the electrical series connection of this counter stands for the static symmetrization of the blocking voltages of the Power semiconductor switch serves by any symmetry Resistance for charging the respective first capacitor the assigned circuit arrangement is used.  

It has proven to be particularly advantageous if that Switching power supply or the switching regulator with the highest possible on output voltage is operated, whereby the input current and associated power loss is minimized.

The overall circuit with a plurality of electrically in series switched power semiconductor switches with one scarf each arrangement according to the invention can also advantageously serve to transmit electrical energy (HVDC).

Further advantages and details of a possible embodiment the circuit arrangement for energy supply for an Control circuit of a power semiconductor switch after the Invention result from the following description nes advantageous embodiment and in connection with the figures. There are elements with the same functionality marked with the same reference numerals. It shows:

Fig. 1 shows a circuit arrangement according to the invention,

Fig. 2 shows the basic structure of a switching power supply,

Fig. 3 shows a circuit arrangement of the invention with about sätzlicher limiting circuit,

Fig. 4a shows a possible embodiment of the limiting circuit,

FIG. 4b is an alternative embodiment of a limit TIC,

Fig. 4c shows a modified arrangement of the series diode,

Fig. 5 shows a circuit arrangement of the invention with Ver supply from the balun and an addi tional circuitry,

Fig. 6 shows a bridge branch of a converter circuit with a series connection number 'two' and

Fig. 7 shows a circuit arrangement for extracting energy from a wiring network according to the prior art technology.

After the circuit arrangement on the basis of the representation according to FIG. 7 for extracting energy from a wiring network has already been recognized at the beginning as prior art, a circuit arrangement according to the invention is to be compared in the following. Such is shown in the illustration in FIG. 2.

Here, a power semiconductor switch T is a series circuit 1 of a resistor R _S and a capacitor C1 of the collector-emitter path electrically connected in parallel. In addition, the series circuit 1 additionally has a diode D _S polarized in the direction of flow, which is arranged between the resistor R _S and the first capacitor C1. The diode D _S serves to prevent the capacitor C1 from discharging via R _S when the power semiconductor T is switched on. It must be able to block the voltage of capacitor C1.

The capacitor C1 is charged by the resistor R _S parallel to the power semiconductor. The resistor R _S is required for applications with a high reverse voltage and thus series connection of power semiconductors for static voltage balancing anyway (cf. FIG. 6). In addition, a parallel circuit 2 is provided from a second capacitor C _S and a power consumer R _L , which represent the drive circuit (not shown) for the power semiconductor T.

If the voltage from the capacitor C1 were used directly to supply the load R _L , the entire load current I2 would have to flow through R _S. Since the voltage U _CS across R _{L is} only approx. 1% of the reverse voltage U _{CE of} the component, the circuit would work at best with an efficiency of 1% and cause very high losses in R _S. In order to avoid this, a switching power supply SNT or another switching transformation means is connected electrically in parallel with C1, which is electrically connected on the output side to the parallel circuit 2 and transforms the energy to the voltage level of C _S. The result of this is that the load R _{L is} supplied with sufficient power and only the balancing current I1 which is required anyway flows through R _S.

In FIG. 2, the basic structure of a switching power supply SNT is shown. Switching power supplies are clocked Stromversorgun conditions, ie they "chop" a DC voltage. It is essential for the operation of the switching power supply SNT that a semiconductor element, for. B. a transistor, works exclusively as a scarf ter S. This only results in switching losses and transmission losses, which results in a high efficiency of a clocked power supply in comparison to other methods.

A rectified input voltage Uc1 is by the Switch S chopped, from which an AC voltage Uz of Rectangular, trapezoidal or occasionally sinusoidal shape advantage. A regulation via the switch S. usually one discrete MOSFET transistor, takes place via a control logic ST either by changing the duty cycle T at constant frequency of the AC voltage Uz, or by Change of frequency with fixed or variable duty cycle nis T.

The thus chopped voltage Uz can be transformed into any other voltage by transmitting the power via a transformer U and rectifying the voltage via a rectifier G which follows it. This results in the desired converted DC voltage, here U _CS . The transformer U also serves for a desired network separation. The control loop is closed by feeding this rectified output voltage U _{CS to} a control amplifier RV, which is connected on the output side for potential isolation, for example, to an optocoupler P, via which the control logic ST is controlled. In the illustration according to FIG. 2, the voltage profiles of the described components of the switched-mode power supply SNT resulting on the output side are illustrated in the form of a diagram of the voltage U over time t. If a switched-mode power supply is not connected to the mains but to a direct current source, this is also referred to as a "switching regulator". A simple step-down converter can also be used.

Such switching power supplies or switching regulators are characterized by due to a very high efficiency of up to 90%, good control dynamics and constant voltage as well as low Volume and weight.

The switching power supply SNT is expediently to be operated with the highest possible input voltage U _C1 in order to be able to work with a given power in R _L with a minimum input current I1. Since in the switched-mode power supply SNT - as mentioned - a discrete MOSFET transistor is usually used, this input voltage is limited to a level of approximately 1500 V be. If the reverse voltage of the power semiconductor T1 is below this level, the switched-mode power supply can also be connected in parallel in a series connection directly to the power semiconductor T from FIG. 1.

The resistance R _S is advantageously dimensioned such that:

(U _CE - Uc1) / R _S ) .Uc1.q <Ucs.I2 (1)

Q denotes the efficiency of the switching power supply.

Otherwise the load is greater than the infeed and this cannot supply the load. If the feed provides more energy than is consumed in the load, the capacitor voltage Uc1 will rise. This is practically always the case with correct dimensioning, since both the load and the energy fed in change with the operating conditions and the above inequality ( 1 ) must be fulfilled at all times.

For this reason, a limiting circuit B for Cl as shown in FIG. 3 is advantageous. This is connected in parallel to the capacitor C1.

A basic embodiment of the limiting circuit is shown in Fig. 4a. The voltage at C1 is measured via a voltage detection device from a voltage divider 3 with resistors R3, R4. This measuring voltage Um is compared with a reference voltage Uref. The measuring voltage Um is applied to the non-inverting input + of a comparator K, whose inverting input - carries the reference voltage Uref, the output of the comparator K driving a semiconductor switch Tx. The latter is electrically connected in series with a resistor R2 to the capacitor C1 in parallel.

If the measurement voltage exceeds the value of the reference voltage Uref, the switch Tx, e.g. B. a transistor switches and C1 over the other with the switch Tx elect Discharge R2 connected in series. Sinks Voltage on C1 thereby, the transistor Tx becomes again off.

The comparator K is expediently provided with a hysteresis provided to limit the switching frequency of Tx. This can e.g. B. by connecting a part of the output voltage of the comparator to the reference voltage Uref ge Schehen.

The voltage supply of the comparator K is advantageous usually from the supply voltage capacitor Cs. Since at the arrival circuit C1 and thus also Cs are still uncharged, in this case the comparator K also has no Ver supply voltage. By another resistor R5, which between the output of the comparator K and the emitter of the Transistor Tx is switched in this operating state the transistor Tx safely turned off. This will make one Capacitor C1 can be charged.  

The illustration in Fig. 4b shows a simpler alternative for voltage limitation. The voltage of the supply voltage capacitor C1 is limited here by triggering the switching means Tx via a Zener diode Dx1, which forms a voltage divider 3 'with a further Zener diode Dx2, both of which are connected in series in the reverse direction, which is connected in parallel with the supply voltage capacitor C1.

The junction of this voltage divider 3 'is electrically connected to the control connection of the switching means Tx. The Zener diode Dx1 is also connected in series with a resistor Rx1, which limits the current through Dx1. The Zener diode Dx2 limits the voltage at the control input of the switching means Tx, provided that this is a field-controlled component (e.g. a MOSFET or an IGBT). A resistor Rx2 electrically connected in parallel to the Zener diode Dx2 prevents parasitic positive charging of the control connection or gate of Tx.

If the switching means Tx is a bipolar transistor, then the Zener diode Dx2 is eliminated. The resistor Rx2 then causes a leak flows from Dx1.

FIG. 4c shows a further advantageous variant of the inclusion of the voltage limiting circuit B. By comparing the circuit of Fig. 1 modified arrangement of the series diode Ds, a lower switching frequency of the switching means Tx can be obtained. For this purpose, the switching means Tx, like the resistor R2, is not only connected electrically in parallel with the supply voltage capacitor C1, but also with the series diode Ds. This variant is advantageous because, when the switching means Tx is switched on, the supply voltage capacitor C1 is not discharged via the resistor R2.

In the illustration of FIG. 5 is a circuit variant shows ge that can be used when the principle of the present invention described is to be used, even though an additional switching-off 10 of the described initially on the basis of the prior art of FIG. 7 type is available.

Between the power semiconductor switch T and the series circuit 1 , a further series circuit 4 with a further capacitor Cb and a downstream resistor Rb is then electrically connected in parallel. The connection points 5 and 6 of the two series connections 1 and 4 are connected by a transverse branch 9 from a diode Db polarized in the direction of flow.

The energy from the circuit 10 is then used in addition to the energy from the balancing R _S for the supply. This avoids the disadvantage of the prior art that the circuit only works in pulse mode. With the circuit variant shown in FIG. 5, operation with impulse blocking (for example when starting a converter) can then also be achieved.

The illustration according to FIG. 6 serves to illustrate the integration of the circuit arrangements according to the invention described above in a converter and the already mentioned problem of balancing that occurs in this context.

In order to realize higher intermediate circuit voltages U _ZK , several power semiconductor switches T1 to T4 are electrically connected in series. In FIG. 6, a bridge arm of a multi-phase inverter circuit is shown. In this bridge branch, each circuit breaker is realized by two series-connected power semiconductor switches T1, T2 and T3, T4. Since only two power semiconductor switches are used per circuit breaker, there is a series connection number of 'two' for the converter.

Each power semiconductor switch T1 to T4 has a free-wheeling diode DF1 to DF4 and a resistor R _S1 to R _S4 , which is connected to a supply voltage circuit according to the invention, which is used to supply a respective control circuit A1 to A4 assigned to the power semiconductor switch T1 to T4.

The level of the intermediate circuit voltage U _{ZK on} the input side is limited by the blocking capability of a power semiconductor switch T1 to T4. A respective voltage U _CE1 to U _CE4 drops at each power _{semiconductor switch} T1 to T4.

In the clock operation of the converter, the respective clamping voltage U is _CE1 to _CE4 U about each power semiconductor switch T1 to T4 due to the series connection number of 'two' half of the intermediate circuit voltage U _ZK. In this case, the intermediate circuit voltage U _{ZK can be designed} for twice the operating voltage of a power semiconductor switch T1 to T4.

The resistors R _S1 to R _S4 serve the static symmetry of the blocking voltages U _CE1 to U _CE4 via each power semiconductor _switch T1 to T4. If these lock all, e.g. B. when starting up the intermediate circuit voltage U _ZK , the load tap L is at a potential of U _ZK / 2. In continuous-off operation, the operating voltage across each circuit breaker T1 to T4 is equal to U _ZK / 4 with a series connection number of 'two'.

With the circuit device according to the invention, the energy for charging the supply voltage capacitor C _S can now be obtained from the respective balancing resistor R _S1 to R _S4 without a separate connection of the power semiconductor switch T1 to T4 being necessary.

Claims (16)

1. Circuit arrangement for the power supply for a control circuit (A) of a power semiconductor switch (T) with a series circuit ( 1 ) which is electrically connected in parallel ( 1 ) from a resistor (R _S ) and a first capacitor (C1) which is connected to the Resistor (R _S ) is chargeable, and with a parallel circuit ( 2 ) comprising a second capacitor (C _S ) and a power consumer (R _L ), characterized in that a switching transformation means (SNT) for transforming the in the first capacitor ( C1) stored energy to the required voltage level of the second capacitor (C _S ) is provided, which is electrically connected on the input side to the first capacitor (C1), and which is electrically connected from the output side to the parallel circuit ( 2 ). 2. Circuit arrangement for energy supply for a control circuit (A) of a power semiconductor switch (T) after Claim 1 characterized in that a switching power supply (SNT) or a as a means of transformation Switching regulator is provided. 3. Circuit arrangement for energy supply for a control circuit (A) of a power semiconductor switch (T) after Claim 1 or 2, characterized in that a span electrically parallel to the first capacitor (C1) tion limiting device (B) is arranged. 4. Circuit arrangement for supplying energy for a control circuit (A) of a power semiconductor switch (T) according to one of the preceding claims, characterized in that the series circuit ( 1 ) additionally has a diode (D _S ) which is polarized in the direction of flow and which is preferably resistive between the wi (R _S ) and the first capacitor (C1) or between the node from the resistor (R _S ) with the voltage limiting device (B) and the first capacitor (C1) is net angeord. 5. Circuit arrangement for energy supply for a control circuit (A) of a power semiconductor switch (T) after Claim 3 or 4, characterized in that the voltage limiting device (B) via voltage sensing means (R3, R4), a comparison means for comparison ner measuring voltage (Um) with a reference voltage (Uref) and a switching means (Tx) for discharging the capacitor (C1) in If the reference voltage (Uref) is exceeded by the Measuring voltage (Um). 6. Circuit arrangement for energy supply for a control circuit (A) of a power semiconductor switch (T) after Claim 5 characterized in that a electrically connected in parallel with the first capacitor (C1) ter voltage divider (3, R3, R4) for determining the measuring span voltage (Um), with which the non-inverting input (+) ei Nes comparator (K) is applied, its inverting Input (-) carries the reference voltage, the output of the Comparator controls a semiconductor switch (Tx), which (Tx) electrically in series with a resistor (R2) the first Capacitor (C1) is electrically connected in parallel. 7. Circuit arrangement for energy supply for a control circuit (A) of a power semiconductor switch (T) after Claim 5 or 6, characterized in that the comparison means or the comparator (K) for limitation the switching frequency of the switching means or semiconductor switch (Tx) have a hysteresis.   8. Circuit arrangement for energy supply for a control circuit (A) of a power semiconductor switch (T) after Claim 7 characterized in that to achieve the hysteresis part of the output voltage of the Comparison means or comparator (K) on the reference chip (Uref) is activated. 9. Circuit arrangement for energy supply for a control circuit (A) of a power semiconductor switch (T) according to one of claims 5 to 8, characterized in that the voltage supply of the comparison means or the comparator (K) from the voltage of the second capacitor (C _S ) he follows. 10. Circuit arrangement for the energy supply for an control circuit (A) of a power semiconductor switch (T) according to claim 9, characterized in that the output to achieve a defined switch-on state of the comparator (K) electrically via a resistor (R5) the connection of the first condenser on the power semiconductor side sators (C1) is connected. 11. Circuit arrangement for energy supply for an control circuit (A) of a power semiconductor switch (T) according to claim 3 or 4, characterized in that the voltage limiting device (B) via a zener diode (Dx1) as measuring device, which has a switching device (Tx) for Discharge of the capacitor (C1) triggers. 12. Circuit arrangement for power supply for a control circuit (A) of a power semiconductor switch (T) according to one of claims 1 to 11, characterized in that between the power semiconductor switch (T) and the series circuit ( 1 ) a protective circuit device (10, Cb, Rb , Db) is provided, so that operation with pulse inhibit is possible even in the connected mode. 13. Circuit arrangement for supplying power to a control circuit (A) of a power semiconductor switch (T) according to claim 12, characterized in that between the power semiconductor switch (T) and the series circuit ( 1 ) a further series circuit ( 4 ) with a third capacitor (Cb ) and a downstream opposing stand (Rb) is electrically connected in parallel and a connecting point ( 5 , 6 ) of the two series connections ( 1 , 4 ) connecting transverse branch ( 9 ) is provided, which has a polarized in the direction of flow diode (Db). 14. A plurality of electrically connected in series power semiconductor switches (T1, T2, T3, T4) with an associated circuit arrangement (V1, V2, V3, V4) for energy supply for a control circuit (A1, A2, A3, A4) this Power semiconductor switch according to one of the preceding claims, wherein each power semiconductor switch (T1, T2, T3, T4) each have a parallel resistor (R _S1 , R _S2 , R _S3 , R _S4 ) and the electrical series connection of these resistors (R _S1 , R _S2 , R _S3 , R _S4 ) for the static symmetry of the blocking voltages of the power semiconductor switches, characterized in that each balancing resistor (R _S1 , R _S2 , R _S3 , R _S4 ) for charging the respective first capacitor (C1) of the associated circuit arrangement ( V1, V2, V3, V4) is used. 15. A method for providing the control energy for egg NEN power semiconductor switch (T) with a circuit arrangement for energy supply for a control circuit (A) of the power semiconductor switch (T) according to any one of claims 2 to 13, characterized in that the switching power supply (SNT) or Switching regulator is operated with the highest possible input voltage (U _C1 ). 16. Use a plurality of ge in series switched power semiconductor switches (T1, T2, T3, T4) with a respectively assigned circuit arrangement (V1, V2, V3, V4) according to one of the preceding claims 1 to 14 for transferring carrying electrical energy.