DE3501925A1 - Circuit arrangement for a half-controlled electronic branch pair - Google Patents

Abstract

For half-controlled electronic branch pairs, a circuit is specified which enables inductive (current-impressing) currents to be commutated with a predetermined pulse frequency to two different potentials with the aim of controlling the current and voltage variation in, for example, direct-current pulse controllers, link-circuit converters and direct converters. In this arrangement, the powers which have hitherto been produced in the electronic branch pairs during the switching-over process are reduced to such a level that relieving circuits can be minimised or can be omitted. The basic and/or parasitic inductances responsible for the production of the power losses from the direct-voltage circuit in which such a branch pair is arranged are blocked by a parallel capacitor (Cp) which is connected in parallel with the branch pair (ZP) directly and with low inductance. <IMAGE>

Description

Title of the invention

Circuit arrangement for a semi-controlled electronic pair of branches Field of application of the invention The circuit arrangement according to the invention is for Commutation of inductive (current-impressing) currents provided. the Commutation can be carried out at two different potentials at a predeterminable pulse frequency with the aim of controlling the current and voltage curve. The invention semi-controlled electronic branch pairs are preferably in DC pulse controllers, DC link converters, but also in direct converters, can be used.

Characteristics of the known technical solutions in counter operation working self-switching semiconductor cells, such as bipolar transistors, Unipolar transistors and G20 hyrietors, which are also known as one-way switches since their main flow of current is operationally one-way, are to relieve dynamic losses as much as possible, so that the relatively sensitive ones and self-disconnecting devices that are expensive to manufacture trending semiconductor cells can be used to the maximum by the load current (combined with static losses) can.

Such non-ideal switching one-way switches, those to drain of the induced by the inductive load component when the one-way switch is switched off Current a free-wheeling valve is connected in anti-parallel, are of the principle-related To relieve energy losses that occur during the switching process, in the period of time until the free-wheeling valve can take over the current, caused by the current due to parasitic series inductances that are always present when the One-way switch by this not suddenly, but in a finite period of time decreases, but the voltage between the main electrodes increases rapidly. In addition discharge networks are known which are arranged over the one-way switch and which take over the output current from a certain voltage increase. Such Relief networks generally known as RO elements, RCD elements or as LD-RCD elements but have the disadvantage that they convert the supplied energy into ohmic losses realize. If the one-way switch is switched over frequently, high loads occur for the ohmic resistance. Generally these cause relief shifts with a few exceptions (in switched-mode power supplies) a deterioration in efficiency for the converter.

Solutions have also already become known, the shutdown relief networks include, which work without losses due to the principle (DE-PS 26 39 589).

These lossless relief circuits require a substantial Expenditure on components and lead to the restriction of the application possibilities (Pulse rate, safety times, active protection) and to the lesser Utilization of the semiconductors by the load currents, due to additional oscillating currents from the relief circuit. In addition, these relief circuits worsen, since they largely contain a large number of electronic components, the overall reliability of the converter considerably.

The known wiring networks have further disadvantages if two pairs of branches consisting of a series connection of one-way switch and pre-run diode can be joined together to form an anti-parallel connection, e.g. to convert inverters build up.

For this reason, DE-OS 31 20 469 made a one-way switch and flow valve existing between the poles of a DC voltage source A pair of branches proposed a switch-on discharge choke, a switch-off discharge capacitor and a unipolar operated storage capacitor as a third energy storage device, which temporarily stores the energy of the other two dummy elements. In addition to a second pre-run valve, a switch-off relief diode is also installed for each branch pair and a blocking diode is required. With an anti-parallel connection of two such pairs of branches, of which one for a positive load current and one for a negative load current must be designed, there is the possibility of the load current in both directions respectively. To do this, however, the pairs of branches must use diodes and / or inductances still to be decoupled.

Such an anti-parallel connection of pairs of branches can be simplified as it is proposed in DE-OS 32 15 589, but also when individual Components are shared for both pairs of branches, the effort is always still considerable.

It must also be taken into account that the knew Relief circuits with the development of new current and voltage ranges (up to 250 A and 1000 V) for self-switching semiconductor cells more and more complex and are more lossy, since the dynamic losses are proportional to the current and Tension rise. The use of both lossy and lossless relief circuits leaves no technically and economically sensible solutions in this electricity range to.

OBJECT OF THE INVENTION The invention aims to provide a circuit arrangement for those working in switch mode on the basis of self-switching semiconductor cells to create semi-controlled pairs of electronic branches which, even under the toughest load conditions, such as can be found in drive technology, for example, with little wiring effort or circuit-free structure, an efficiency-optimized commutation of inductance-affected Enable (atroma-impressing) currents.

Explain the essence of the invention The technical problem posed by the invention is achieved.

The object of the invention is to provide the during the Umachaltvorganges self-switching semiconductor cell of a semi-controlled electronic branch pair resulting energies that were previously in lossy or lossy relief circuits were diverted to reduce them to such a level of semiconductor and device technology, that the relief circuits are minimized or omitted entirely can and thus also universally applicable modular self-switching power electronics Semiconductor components-Kuhlkbrper-arrangements can be realized, their internal Overvoltages on the half-letter cells regardless of the load conditions remain small, and actively slotted from overcurrents by the control circuit will.

Features of the invention The object is achieved according to the invention by that to block the principle-related and / or parasitic inductances the DC voltage circuit in which the pair of branches is located, the series connection of one-way switches and Pre-run valve a capacitor is connected in parallel, and that the parallel connection Low inductance is achieved by connecting the capacitor directly to the electrodes of the elements of the series circuit connected to the DC voltage source stay in contact.

In an advantageous development of the invention, there is a reduction in of overvoltages at the one-way switch when the one-way switch is switched off, the free-wheeling valve a switch-on diode connected directly in parallel.

An even more favorable puncture method results when reducing of overvoltages at the one-way switch when the one-way switch is switched off, the pre-run valve the collector-emitter path of a transistor is connected in parallel so that the collector of the transistor with the cathode of the free-wheeling valve and the emitter of the transistor is connected to the anode of the free-wheeling valve.

In an expedient embodiment of the invention, as one and electronic one-way switch that can be switched off a bipolar transistor, a unipolar transistor, but a GTO thyristor can also be used.

When connected in parallel, a positive output current carries A pair of branches with a negative output current can be the parallel capacitor be assigned to both pairs of branches.

EXEMPLARY EMBODIMENT The invention is intended below with the aid of embodiments play are explained in more detail. The drawings show: FIG. 1: an according to the invention semi-controlled branch pair for positive output current; Fig. 2s an according to the invention half-controlled branch pair for negative output current; Fig. 3: the current-voltage-time curve on a half-controlled branch pair with parallel capacitor taking into account parasitic line inductances; Fig. 4: a DC pulse generator with a pair of branches according to the invention; Fig. 5: an intermediate circuit converter with inventive Twig pairs; 6: Low-inductance component cooling element arrangements of the invention Branch pair for positive output current.

The invention assumes that the parasitic (in the circuits usually not shown) generation inductances from the DC voltage circuit, in which such a pair of branches is located, must be reduced to such an extent that the dynamic Losses drop to such an extent that relief circuits are omitted or can be minimized. It should be noted, that on everyone Piece of line on which the currents at the current rate of change achieved (in the tis range) can be switched on and off during the commutation process internal overvoltages arise.

Fig. 1 shows one from the series connection of one that can be switched on and off One-way switch T and an uncontrolled free-wheeling valve D1 existing branch pair ZP +. The one-way switch T is a self-switching semiconductor cell, in the exemplary embodiment a bipolar transistor is provided. But it is also possible to use a unipolar transistor for this or use a switchable GTO thyristor. The freewheel valve Dl is one non-self-switching semiconductor cell, for example a diode in its Switching state "conducting" or "blocking" from the one-way switch T is performed. In the polarity shown, this pair of branches is suitable when the one-way switch T is switched on, to carry positive output current (ia> O) at load connection point L.

According to the series arrangement of the Eineg switch T and free-wheeling valve Dl a capacitor Cp connected in parallel, its connections directly to the electrodes E1, E2 of the pair of branches ZP + are arranged.

As a result, the parasitic line inductances (L6 in Fig. 4 and 5) of the DC voltage circuit to which the branch pair ZP + is connected, bridged or blocked.

Basically the same functionality of a pair of branches results if the polarity of the DC voltage source Ud, the polarity of the one-way switch X and the polarity of the free-wheeling valve D1 are reversed. This creates a Branch pair ZP-, which is suitable for carrying negative output current (generally <0) (Fig. 2). In a parallel connection, the two positive or negative output current leading pairs of branches ZP +, ZP- for controlling an alternating current (ia a °) such parallel connection of a pair of branches ZP + carrying a positive output current with a negative output current-carrying branch pair ZP- can use both branch pairs ZP +, ZP- be assigned a parallel capacitor Cp together.

The capacitor Cp is used in such a way that during the switchovers (commutations) of the load current from the one-way switch T to the freewheeling valve D1 and vice versa inductive components of the input current id or

of the output current generally flow through the capacitor Cp.

When the current is commutated in such a pair of branches ZP taking into account the parasitic generation inductances in the diagrams the Fig. 3 indicated current-voltage-Zeitver runs. The commutation process from the diode D1 to the transistor T of the branch pair is via the control terminal St of the transistor T by means of the control current, Fig. 3b is controlled. After expiration After the switch-on delay time td, the transistor T begins to take over the current (Collector current iC in Fig.3a).

Since the current flow id from the DC voltage source via the transistor T builds up slowly due to the line inductance (Fig. 3d), the capacitor Cp provide the output current ia for this short time until the current id has built up from the DC circuit. At the same time the capacitor ap during the commutation of the output current generally from the diode D1 to the transistor s the task of providing reactive current to block diode D1.

This allows the transistor T in the blocking delay time of the diode D1 be operated in the active area (high power dissipation in the transistor). The tear-off process of the USE current of the diode D1 generates in the actively operated benen transistor T, since only minimal parasitic line inductances are still present, only still minimal overvoltages. This allows a switch-on relief for the transistor T are omitted, the output current ia to be temporarily provided by the capacitor Cp and the breaking current iF for the diode Dl add up to the capacitor current $ p, from which the developing current id is to be subtracted from the DC voltage circuit (Fig. 3d).

In Fig. 3c, the line 1 denotes during the switch-on process in the current application or voltage drop time tr is the distinctive point at which the Voltage at load connection point L switches from diode D1 to transistor T.

If the transistor T should generally output the output current again, what takes place by reversing the control current iSt (Fig. 3b, line 2), flows for the storage time t5 of the transistor 2 the current ic in the collector of the transistor 2 continues until the beginning of the fall time tf. At the same time, the collector-emitter voltage increases UcE due to the principle, because only when the collector-Rmitter voltage UcE When the voltage of the DC circuit has reached Ud, the diode D1 can be conductive and take over the output current da during the fall time tf. The stream id The line inductances continue for a short time from the DC voltage source Ud driven.

This current is taken over by the capacitor Cp as a result of which the capacitor voltage Ucp increases somewhat (Fig. 3d).

The low-inductance arrangement of the capacitor 0p thus enables the rapid commutation of the load current ia from the transistor T to the diode Dl and back, with internal overvoltages on transistor T, resulting from the non-ideal Switching behavior of diode D1 and rapid current changes at internal Inductors, remain small and relief circuits can be minimized or omitted.

In voltage-impressing DC pulse controllers and voltage-impressing DC link converters (Fig. 4 or 5) under the condition LdX LG) reduced the capacitor Cp as a backup capacitor that commutates the output current parasitic line inductances that influence the constructive-technological conditional minimum that is specified by the component manufacturer. The condenser For the commutation process, Cp represents the output current generally from the non-self-switching Semiconductor cell D1 to the self-switching semiconductor cell T the commutation reactive current ready. This creates a clearly defined commutation circuit regardless of the device structure realized, which in turn, a defined commutation process, if necessary, under Utilization of the active work area (by shaping the control current or voltage) the self-switching semiconductor cell. This applies to the most diverse Use of the branch pairs ZP in converter devices and regardless of the amount of the to commutating output current ia.

The use of the capacitor Cp is a prerequisite for implementation current-impressing direct current pulse controller and current-impressing DC link converter (Fig. 5 or 6 assuming Cd = 0) with self-switching semiconductor cells. It serves to limit the intermediate circuit voltage Ud and adjusts after each Switching process in the current-impressing pulse generator or inverter Equalizing reactive currents ready.

In addition to limiting internal overvoltages in the branch pair, the The parallel capacitor Cp im is suitable for limiting the intermediate voltage Working with the diode D1 also generally to limit external Overvoltages.

The technical realization of a single capacitor as a parallel capacitor Cp for the pair of branches according to the invention is state of the art. It becomes a low inductance and low-loss metal-paper or metal-polypropylene film capacitors up to high frequencies used with a narrow end-contact winding.

It is particularly advantageous in its switch-on and switch-off behavior Optimized and adapted to the transistor T diode D1 to connect a second diode D2 in parallel (Figures 1 and 2). The use of two semiconductor cells D1 and D2 not self-switching Type as a free-wheeling valve allows separate semiconductor technology optimization, adapted to the self-switching semiconductor cell. During D1 optimally to the switch-on behavior is adapted to the self-switching semiconductor cell (connection reactive current, capacitive currents), D2 essentially determines the switch-off behavior of the self-switching Semiconductor cell (voltage increase, load current commutation curve). The diode D2 must be quicker to switch on compared to diode D1 in order to switch from T to D1 to take over commutated load current a for a certain time and only one Allow small dynamic forward voltage, which in turn prevents the self-switching Semiconductor cell with impermissible voltages that are significantly greater than the intermediate circuit voltage Ud are claimed. Because the static plus voltage of D2 is higher is determined as that of D1, it is achieved that the load current ia after a certain Time is automatically commutated from D2 to D1.

When connected in parallel, a positive output current carries Branch pair ZP + with a branch pair SP-, which carries negative output current, can, so- remote from the electronic one-way switch that can be switched on and off U In each case there is one transistor, the transistor of the branch pair ZP- with a negative output current in the pair of branches ZP + with positive output current at the same time the function of Take over the diode D2 to be connected in parallel with the free-wheeling valve D1 or the transistor of the branch pair ZP + the function of the diode D2 in the branch pair ZP-. With reverse voltage changes at the diodes D1 and D2, as they occur during the switching processes, also occur at the same time capacitive displacement currents in the diodes. In contrast to the pn structure npn and pnp structures, capacitive displacement currents in the semiconductor in the event of reverse voltage changes Reinforce dUR / dt. Therefore you can use a transistor instead of a diode D2 the displacement currents are advantageously amplified. In the event of a reverse voltage change at the pnp structure dUdt <0, the capacitive current ig2 can be increased to that extent be that it reaches the order of magnitude of the load current ia. The current through the called pnp structure reduces the current through the self-turning semiconductor cell T (with the load current remaining approximately constant) during the increasing voltage UCE in the switch-off process.

It causes a significant reduction in the load on the self-switching semiconductor cell T by a significant reduction in the switch-off loss work in the switch-off time peat 'a faster return of the reverse voltage UcE, combined with a shortening the switch-off time tofi, and increases the safety when using transistors against the 1st (voltage) and the 2nd breakthrough (momentary loss of work).

In the event of a change in the reverse voltage on the pnp structure, dUdt> O (inverse Operation) the capacitive current iD2 is not amplified, so that there is no load for the self-switching semiconductor cell T in the switching process arises. In addition to the reactive commutation current for switching off D1, there are no further loads during the switch-on time ton for the semiconductor cell T.

Since the energies stored in the capacitor lines are self-sustaining Semiconductor cell T converted into heat in a very short time (tr or tf in FIG. 3) has a low-inductance structure with a circuit-free branch pair decisive influence on the electrical function.

The geometric (spatial) structure of the required connections determines the parasitic inductances of the branch pair according to the invention. the 6 shows a few possible examples of such low-inductance component / heat sink arrangements for positive output current leading pairs of branches ZP +, which are the basis for the circuit-free Represent operation. At the same time, the components-heat sink arrangements shown make it possible the most effective use of lossy or lossless relief circuits, which may be necessary due to component-specific problems, if these can be realized geometrically advantageous again.

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Claims (5)

Patent claims a 'circuit arrangement for a semi-controlled electronic Branch pair consisting of a series connection of at least one control connection having electronic override switch that can be switched on and off and an uncontrolled Freewheel valve, the pair of branches so between the poles of a DC voltage source lies that the one-way switch in the forward direction to the DC voltage source and the free valve is polarized in the reverse direction to the DC voltage source and the common point of the series connection of one-way switch and free-wheeling valve is the connection point forms for the load, gekennseicilnet by the fact that the principle-related to the blocking and / or parasitic inductances from the DC voltage circuit in which the branch circuit (ZP) the series connection of one-way switch (T) and free-wheeling valve (D1) is a capacitor (Cp) is connected in parallel, and that the parallel connection is low-inductance, by connecting the connections of the capacitor (Cp) directly to the electrodes (Ei; E2) of the Elements of the series circuit (T; D1) are performed with the DC voltage source (Ud) connected. 2. Circuit arrangement for a semi-controlled electronic pair of branches according to item 1, characterized in that to reduce overvoltages on One-way switch (g) when switching off the one-way switch (T) of the free-running valve (D1) a fast-switching diode (D2) is connected directly in parallel. 3. Circuit arrangement for a semi-controlled electronic pair of branches according to item 1, characterized in that to reduce overvoltages on One-way switch (T) when switching off the one-way switch (T) of the free-wheeling valve (D1) the collector-emitter path of a transistor is connected in parallel so that the collector of the transistor with the cathode of the free-wheeling valve (D1) and the emitter of the transistor is connected to the anode of the PreilauRventils (D1). 4. Circuit arrangement for a semi-controlled electronic pair of branches according to item 1 to 3, characterized in that the on and off switchable electronic One-way switch (T) a bipolar transistor, a unipolar transistor or a GTO thyristor can be. 5. Circuit arrangement for a semi-controlled electronic pair of branches according to item 1 to 4, characterized in that the parallel capacitor (0) at a p parallel connection of a pair of branches carrying a positive output current (ZP +) with a branch pair carrying a negative output current (ZP-) two branch pairs (ZP +; ZP-) is assigned jointly.