DE2639589C2 - Arrangement without principle-related losses to relieve electrical or electronic one-way switches from their power dissipation when they are switched off - Google Patents

Description

Arrangement without losses due to the principle of operation to relieve electrical or electronic one-way switches

of their power loss when they are switched off.

Electrical or electronic one-way switches are used in very numerous areas of electrical engineering. They have two main power connections and a device with the help of which they can be switched from the conductive to the blocking state and back. A flow of the main current is operationally only provided in one direction, namely from the main current electrode E (input) to the main current electrode A (output). The designation one-way switch results from this operational restriction to one direction of current flow. In the conductive state, the one-way switch opposes a current flowing from electrode f to electrode A / almost no resistance. In this conductive state χ , the voltage applied to the one-way switch is consequently almost zero. Conversely, the one-way switch offers a very high resistance to a current flowing from electrode £ to electrode A in the blocking state. In this blocking state β , this current is consequently almost zero even when there is a considerable voltage between the electrodes E and A Switches with mechanical contact used in one-way operation.

For economic reasons, efforts are made to keep the thermal stress on such one-way switches as low as possible. On the one hand, this is done by realizing the states χ (one-way switch is conductive) and β (one-way switch is blocked) as ideally as possible, such that in state χ the voltage at the switch and in state β the current through the switch each have their lowest possible values assume in order to achieve in this way that the product U · I, which represents the power dissipation converted into heat in the switch, is as small as possible. During the transition from the state χ to the state β and vice versa, the one-way switch experiences, without additional precautions, a significant current and voltage load at the same time, which results in considerable momentary power losses during this transition. On the other hand, efforts are therefore made to make these transitions from state χ h to state β and vice versa extremely quickly so that the energy loss per switching process is as low as possible.

But even with a high switching speed and thus a short transition time from one to the other switching state, the simultaneous loading of the one-way switch with considerable values of current and voltage is undesirable. This is because of the loss of useful energy and because of the electrical stress on the one-way switches, which often represents the decisive limit for their load-bearing capacity. This applies in particular to the switch-off process of the one-way switch, ie the transition from the conductive state χ to the blocking state ß.

These statements are illustrated by an example. F i g. 1 shows an arrangement in which a mixed ohmic-inductive loads (1) with the interposition of an electronic one-way switch (2) - which is implemented here as an example of an npn transistor - from a DC voltage source (3) is fed. So that when the * Transistor (2) in the consumer-induced current can flow away, the two-pole consumer is one Freewheeling diode (4) aritiparallel connected

If the one-way switch (2) in Fig. 1 is now switched from the conductive state χ to the blocked state β (in the case of the transistor assumed as an example, because its base current is reduced), the resistance effective between the two main current electrodes and A initially increases very low to a very high value. During this very rapid process, the current through the consumer bipole (1) practically does not change its size due to the choke contained there.As a result, the voltage between the main current electrodes E and A of the one-way switch increases from an initially very small value to ever higher values. Only when the voltage U between the main current electrodes of the one-way switch (2) has become as large as the sum of the source voltage U ₀ and the lock voltage of the freewheeling diode (4) does the current begin to flow through the consumer bipole via this diode, and only when this state is reached is reached, the current goes through the one-way switch (2) back to a very low value. This does not happen suddenly, but also in a finite period of time due to the circuit inductances that are always present.

The described time courses of the current / through the one-way switch and the voltage U between its two main current electrodes are shown in FIG. The product U (t) · I (t), which is also shown in FIG. 2, is determined in a simple manner from these time courses U (t) and I (t). One can clearly see the already described high power loss peak in the one-way switch when it is switched off.

In order to reduce this power loss peak, it is necessary to pass the current through the one-way switch take back to harmless values before the voltage between its main current electrodes has risen to considerable values.

For this purpose, it makes sense to create a capacitor-diode bypass path between the two main current electrodes of the one-way switch to provide which when switching off the one-way switch the until then through this The current that has flowed takes over and the charge taken up the next time the one-way switch is switched on via this and interposed ohmic resistances emits again.

F i g. 3 shows the arrangement according to FIG. 1 after expansion by such a known discharge network, consisting of the capacitor C, the diode D and the discharge resistor R. In this arrangement, the one-way switch (2) was initially switched on for a long time and the capacitor Cin as a result discharged to the voltage Uc = O and is then If the one-way switch is switched from the conductive state χ to the blocking state β , the current through the load bipole begins to change over from the one-way switch (2) to the bypass path formed by the diode D and the capacitor C as soon as the voltage LJ between the main current electrodes of the one-way switch reaches the value the lock voltage of diode D has reached. If the capacitance of the capacitor C is sufficiently large, the current through the one-way switch has already dropped to an insignificant V / erte before the voltage across the capacitor and

so that those between the main current electrodes of the one-way switch have also assumed a significant amount. The time courses of the current / through the one-way switch and the voltage U between its two main current electrodes and the current ic through the capacitor C are shown in FIG. 4 shown. The product U (t) · I (t), which is also plotted in FIG. 4, is determined in a simple manner from the time courses U (t) and 1 (X). It can be seen that the desired effect is achieved, ie the critical power dissipation peak when switching off is omitted. Relief arrangements of this type, however, have a serious disadvantage. The electrical energy supplied to the diode-capacitor secondary branch during the switch-off process is converted into ohmic losses after the next switch-on of the one-way switch in preparation for the discharge when the switch is switched off again Reloading the discharge capacitor after switching on the one-way switch again claimed ohmic resistance must be designed for high loads.

The arrangement presented with this invention avoids these disadvantages. It is for the relief of One-way switches can be used universally from their power dissipation stress when switching off and has no losses due to the principle - unavoidable when using ohmic resistors -. In the The following description of their function should be considered that electrical or electronic one-way switches are usually used in such a way that one of its two main current electrodes when switching off the current flowing through them their electrical potential compared to the previously feeding electrical system does not change significantly

It is referred to below, in accordance with the property described, as the switch electrode with constant potential (in the example according to FIG. 1 this is the output electrode A). In relation to it, the potential of the respectively remaining main current electrode changes to a considerable extent when the one-way switch is switched off in accordance with its function. According to this property, this second main current electrode is referred to as the switch electrode with jumping potential (in the example according to FIG. 1 this is the input electrode E). After switching off, this switch electrode with jumping potential assumes a positive or negative voltage Us _P compared to that with constant potential (in the example according to FIG. 1, this is the voltage U _{0 if the very low gate voltage of the diode (4) is neglected} ).

There is usually a point in the overall circuit which, compared to the switch electrode with constant potential, has an approximately equal, but largely constant over time or only relatively slowly changing voltage (in the example according to FIG. 1, this is the upper connection electrode of the DC voltage source (3 ) or the galvanically connected point P) If, in deviation from the usual, no point with this property can be found in the original circuit itself, such a point can be found either by regrouping the existing components or with the help of passive and, if necessary, additional active electrical and electronic components can also be created in a simple manner in addition ". Regardless of this, this circuit point i is referred to as the point with blocking voltage potential constant; Voltage which is approximately as large as - * that reverse voltage Usp, which the switch electrode '* "with jumping potential compared to the switch electrode' with constant potential following the! ' Switching off the one-way switch assumes.: '

According to the invention, a circuit point is now formed with the aid of active and / or passive electrical and / or electronic components,, V. which compared to the switch electrode with constant potential has a voltage which is approximately half the value of the voltage which the point with reverse voltage potential has compared to the switch electrode with constant potential. (. Eg as a center tap of a battery) should already exist ■% ig a resilient circuit point with this property in ^ the original circuit, can also _■: these are used in the manner described below>".; was in both cases. This Pj circuit point is referred to as a point with half reverse voltage potential. According to the invention, a relief network is now inserted between the circuit points explained, which consists of a capacitor, two diodes and a choke. One of the two connection electrodes of this choke is connected to the point with half reverse voltage potential. The remaining connection electrode the choke is connected to the circuit point with blocking voltage potential via two diodes connected in series, the connection direction of both diodes being the same and chosen so that there is no continuous flow of current between the point with half blocking voltage potential and the circuit point with blocking voltage ng potential is possible The connection point between the two diodes - in which the anode of one and the cathode of the other diode are brought together - is connected to the switch electrode with jumping potential with the interposition of the capacitor. This network thus fulfills the desired relief function described below. Immediately after the one-way switch is switched on, the capacitor is charged via the one-way switch itself, the choke and the diode directly connected to it, so that that capacitor electrode to which the two diodes are connected has a capacitor terminal connected to the switch electrode Voltage which is approximately as large as the reverse voltage that the switch electrode with jumping potential assumes compared to the switch electrode with constant potential after the one-way switch has been switched off.If the one-way switch is switched off again, the next time the one-way switch is switched off by a rapid increase in the resistance between its main current electrodes, it can be initiated the voltage between these main current electrodes only grow as quickly as the capacitor is discharged again by the current that previously flowed through the one-way switch. If the capacitance of the capacitor is large enough, the current is through. the one-way switch then already dropped to insignificant ra values before the voltage between the

it M I

Main current electrodes of the one-way switch has assumed a significant amount. So that is without principle-related losses achieved that the one-way switch from its power loss during Switching off is relieved.

These statements are illustrated by an example. F i g. 5 shows the arrangement according to FIG. 1 after expansion by such a discharge network, which works without losses due to the principle, consisting of the discharge capacitor (5), the discharge diode (6), the charging choke (7) and the charging diode (8). In the example according to FIG. 5 is - as can be seen immediately - the input electrode E of the one-way switch, the switch electrode with jumping potential; Thus, the upper Anschlußelektrcde the supplying DC ^ voltage source (3) or of the node with reverse voltage potential and the center tap of the supply DC voltage source or the hereby electrically connected point Q with this galvanically connected point P is the point at half blocking voltage potential. If in the overall arrangement according to F i g. 5, the one-way switch (2) off after a longer operating time for some time, the current is discharged through the mixed ohmic-inductive load via the freewheeling diode (4) Then, the discharge capacitor (5) is almost fully discharged, its voltage Uc therefore virtually zero. If the one-way switch (2) in Fig. 5 is now switched from the blocked state to the conductive state, on the one hand the consumer current that has flowed through the freewheeling diode changes back to the one-way switch and on the other hand the discharge capacitor (5) is almost charged to the voltage U ₀ and then maintains the value reached because of the blocking effect of the charging diode (8). The time interval for this charging process is determined in a known manner by the product of the inductance L of the charging choke (7) and the capacitance C of the discharge capacitor (5), while the maximum value of the capacitor current that occurs is determined by the quotient of these two variables. If the one-way switch (2) in FIG. 5 is now switched from the conductive state to the blocking state again, the current through the consumer two-pole (1) begins to change over from the one-way switch (2) to the ⁴ ^ by the discharge diode (6) and the discharge capacitor (5) as soon as the sum From the initially still constant capacitor voltage Uc and the rising voltage U between the main current electrodes of the one-way switch, the sum of the voltage U _{0 of} the direct voltage source (3) and the - small - sluice voltage of the discharge diode (6) has become so large. Since previously uc "U _0, this change-over takes place of the current already at a very low voltage U between the main current electrodes of the one-way switch rather than With a sufficiently high capacity C of the snubber capacitor (5) of the current is then decreased by the one-way switches are already on insignificant values before the voltage across the discharge capacitor (5) is abgesuncen significantly and thus the voltage between the main current electrodes of the one-way switch adopted a nenlenswerten amount has the waveforms of the current / ler voltage through the one-way switch and ^M U between its two Hauptstromilektroden and the current icdurch the discharge probe crystallizer and at this voltage Uc are shown in FIG. 6 shown. From the time characteristics U (t) and I (t) is determined in a simple manner the product of U (t) · I (t), which in F i g. 6 is also applied. It can be seen that the desired effect has been achieved, ie the critical power loss peak when switching off has been eliminated.

To demonstrate the wide range of application of the invention, a few examples are given listed.

F i g. 7 largely corresponds to the arrangement according to FIG. 5 with the exception of the fact that the order of the one-way switch and two-pole consumer is reversed and, as a result, the output electrode A of the one-way switch represents the switch electrode with jumping potential

F i g. 8 shows a so-called boost converter, in which a switch-off relief network according to the present invention is inserted. This step-up converter transfers electrical energy from the DC voltage source (3) connected on the left with the voltage U ₀ to the DC voltage system to be connected on the right with the - greater - voltage U ₃ . Here - as can be seen again immediately - the input electrode E of the one-way switch is the switch electrode with jumping potential; Thus the upper connection electrode of the fed DC voltage source or the point P galvanically connected to it is the circuit point with blocking voltage potential and the - existing or supplementary - center tap of the fed DC voltage system or the point Q galvanically connected to it is the point with half blocking voltage potential.

F i g. 9 again largely corresponds to the arrangement according to FIG. 8 with the exception of the fact that the sequence of one- way switch (2) and storage choke (9) is reversed and, as a result, the output electrode A of the one-way switch represents the switch electrode with jumping potential

Fig. 10 shows a so-called. Buck converter (engl. Buck converter), in which also a turn-off snubber circuit is inserted according to the present invention this step-down converter transfers electric power from the left-connected DC voltage source (3) with the voltage U ₀ in the right to be connected DC voltage system with the - smaller - voltage U * Here - as can be seen again immediately - the input electrode E of the one-way switch is the switch electrode with jumping potential; Thus, the upper connection electrode of the feeding DC voltage qucüc or the point P galvanically connected to this is the circuit point with blocking voltage potential and - the existing or supplementary - center tap of the feeding DC voltage source or the point Q galvanically connected to it is the point with half blocking voltage potential.

The following Fig. 11 again largely corresponds to the arrangement according to FIG. 10 with the exception of the circumstances that the sequence of one- way switch (2) and storage choke (9) is reversed and, as a result, the output electrode A of the one-way switch represents the switch electrode with jumping potential and that here for example a pnp transistor acts as a one-way switch

FIG. 12 finally shows a so-called step-up and step-down converter (buck-boost converter) in which again a switch-off relief network according to

9 10

present invention is incorporated. This high and voltage divider is for other branches of the exchange-buck converter electrical energy can from the left judge overall circuit a point half-barrier-affiliated DC voltage source (3) with the voltage potential and can therefore also as connecting voltage U ₀ point in the right to be connected DC- are used for their relief branches, transmission system regardless of whether its 5 F i g. 15a shows, as a further example, the described voltage U _{a is} greater or less than U ₀ . Here - besides the paired use of one-way switches, as can also be seen immediately - the input-elect single-ended flow converter. Here, too, P \ of the switching electrode E of the one-way switch is the switch electrode with the switching point with blocking voltage potential for the upper jumping potential; thus the lower connection one-way switch, Pi is the corresponding node electrode of the fed DC voltage system or io for the lower one-way switch. The center tap of the point P, which is galvanically connected to this, of the capacitive voltage divider circuit point initially sketched on the right with blocking voltage potential and the circuit point Q, is also here for both - existing or supplementary formed - center point of one-way switch, the point with half blocking voltage Q between the two lower electrodes of the potential. Electrical charge is withdrawn from it via the discharge network of the feeding and the fed DC voltage system 15, the lower one-way switch, with a point with half the blocking voltage potential. men and through the relief network of the upper

13 again largely corresponds to the arrangement of the one-way switch supplied with electrical charge Im

according to FIG. 12 with the exception of the fact that the contrast to the arrangement according to FIG. 14 takes place

Sequence of one-way switch (2) and Speicherdros- charge supply and charge discharge here but during

Let (9) be interchanged and consequently the output electrodes of the same time intervals. This means that the capacitive

trode A of the one-way switch the switch electrode with ve voltage divider can also be omitted, the two

represents jumping potential. Charging chokes (7) may be combined and

In the examples described so far, one of the two charging diodes (8) has been omitted

clearly that when the switch electrode can with. The arrangement that then arises is shown in FIG. 15b

jumping potential through the input electrode of the 25 and impresses with its particularly simple

One-way switch is formed from the switching point structure.

with half the reverse voltage potential electrical La- This particularly advantageous variant dung flows through the relief network and that the invention can only be used, however, vice versa, if the switch electrode with if in an overall circuit one-way switch in the jumping potential through the output electrode 30 described type are used in pairs and of the one-way switch is formed, for the circuit, in addition, one such pair is formed at the same time is electrical tet with half the reverse voltage potential. This is e.g. B. also given if the Charge flows over the relief network. Then single-cycle flow controller according to FIG. 15b by adding when two further one-way switches form a push-pull switch in an overall one-way circuit are used in pairs in such a way that the 35 flow plate is supplemented or the latter under one half of the one-way switch each the input omission of the output rectifier and possibly electrodes the switch electrodes with jumping also of the output transformer as a bridge alternating potential and that the judge is operated in the other half. Such an arrangement is shown in One-way switch each the output electrodes the F i g. 16 shown

40 Finally, two of the listed ones are shown

len, the point with half the reverse voltage potential explains in examples how, if in a total

extremely simple, yet power-loss-free circuit, one-way switches as individual elements, d. H. not

Way to be used in pairs by a capacitive voltage divider, the required point

see those two circuit points is formed, with half the reverse voltage potential on simple,

which are formed in addition to the 45 power loss-free way for one half of the one-way switches

Can represent the circuit point with reverse voltage potential.

len or it can be this circuit point with half In Fig. 17 is the step-up converter according to Fig. 8

Reverse voltage potential also completely omitted, if sketched again and around a practically loss-free

it is ensured that this existing or only working center point builder for the initial voltage

still imagined point about the relief networks 50 voltage U _a added, which in the dashed box (11)

the one-way switch electrical charge is drawn both pull-down and exemplarily made up of two small ones

leads to a stable multivibrator, two

Fig. 14 shows an example of the first-mentioned auxiliary diodes, a choke with a center tap and

Possibility of a branch of an inverter circuit, a small storage choke and two smoothing con-

with two one-way switches (2) and an output capacitor 55 This midpoint builder sets that

electrode (10). P \ is the circuit point with the blocking potential of the point Q in the desired manner

Voltage potential for the upper one-way switch, Pi half the reverse voltage potential and leads to the

the corresponding circuit point for the lower point Q assigns the required electrical charge.

One-way switch. The center tap of the opposite sketched on the right, however, must be a corresponding center-forming element

capacitive voltage divider, the circuit point Q, 60 for the in F ig. 18 illustrated high and low setting

For both one-way switches, the point with half of the point Q entered there is electrical charge

Reverse voltage potential. It is taken from him via the discharge. Fig. 18 shows an example of how this is done with

stungsnetzwerk of the lower one-way switch electrical can happen to a center point that the

See charge removed and via the relief network contains the same components as that in FIG. 17

plant of the upper one-way switch electrical charge 65 shown, only in a slightly changed configuration

fed tion.

The sketched center tap of the capacitive span

In addition 12 sheets of drawings

Claims (7)

Patent claims: 1. Arrangement without losses due to the principle to relieve electrical or electronic one-way switches of their power loss stress when switching off, characterized in that, that between three points of the overall circuit in which the one-way switch (2) is operated, a electrical discharge network is inserted, which from a capacitor (5) - hereinafter referred to as a relief capacitor -, a choke (7) - hereinafter referred to as the charging throttle - and two diodes (6) and (8) and that a connection electrode of the discharge capacitor (5) with that main current electrode of the One-way switch - hereinafter referred to as switch & ktrode rmt jumping potential - is connected, when the current flowing through the one-way switch (2) is switched off, compared to its electrical potential the previously feeding electrical system changed significantly and that the remaining, second connection electrode of the discharge capacitor on the one hand via one of the two diodes - hereinafter referred to as the discharge diode (6) - with one point of the overall circuit - in the following circuit point called reverse voltage potential - is connected, which opposite that main current electrode of the one-way switch - in the further switch electrode with called constant potential - which occurs when the one-way switch (2) is switched off Current largely its electrical potential compared to the previously feeding electrical system maintains a voltage which is approximately as large as the reverse voltage, which the Schaher electrode with jumping potential compared to the switch electrode with having constant potential after completion of a disconnection of the one-way switch (2) and that the remaining, second connection electrode of the discharge capacitor (5) to the other via the second of the two diodes - in the further charging diode (8) - and which this downstream charging choke (7) is connected to a point Q of the overall circuit - referred to below as half the blocking voltage potential - which has a voltage with respect to the constant potential Schaher electrode which is approximately half as high as the blocking voltage , which has the switch electrode with jumping potential compared to the Schaher electrode with constant potential after the one-way switch (2) has been switched off and that the connection direction of the relief diode (6) is chosen so that it prevented a continuous flow of current between the circuit point with reverse voltage potential and the circuit point Q with half reverse voltage potential via the relief network even if ^ω one would short-circuit the charging diode (8) and
that the connection direction of the charging diode (8) is also chosen so that it prevented a continuous flow of current between the circuit point with reverse voltage potential and the circuit point Q with half the reverse voltage potential via the discharge network even if the discharge diode (6) were to be short-circuited. 2. Arrangement according to claim 1, characterized in that then, a loadable circuit point with the described property of the circuit point Q with half the blocking voltage potential is not present in the original overall circuit, a circuit point Q with these properties with the aid of active and / or passive electrical and / or electronic components is formed in addition. 3. Arrangement according to claim 1 or 2, characterized in that when a resilient Circuit point with the described property of the circuit point with reverse voltage potential does not exist in the original overall circuit, a circuit point with these properties either by regrouping the existing components or with the help of active and / or passive electrical and / or electronic components formed in addition will. 4. Arrangement according to claim 1 or 3, characterized in that in overall circuits in which electrical or electronic one-way switches (2) are used in pairs such that in one half of those main current electrodes of the one-way switch (2) through which the current enters them , are operated as switch electrodes with jumping potential and that in the other half those main current electrodes of the one-way switch (2), through which the current exits from them, are operated as switch electrodes with jumping potential, point Q with half the reverse voltage potential in a very simple and loss-free manner is formed by a capacitive voltage divider between the two circuit points, which represent the circuit point with reverse voltage potential for one half of the one-way switch (2). 5. Arrangement according to claim 4, characterized in that in overall circuits in which the electrical or electronic one-way switches (2) used in pairs are operated in such a way that in each case a one-way switch from one half is switched on simultaneously with a one-way switch from the other half, the two relief networks of these two one-way switches with those connections of the charging chokes (7) which are not to be connected to the charging diodes (8), are not connected to the circuit point Q with half the blocking voltage potential but, dispensing with this, are connected to one another. 6. Arrangement according to claim 5, characterized in that in the interconnected Relief networks one of the two charging diodes (8) and the two charging chokes (7) be summarized. 7. Arrangement according to claim 2 or 3, characterized in that the circuit point Q is generated with half the reverse voltage potential with a loss-free working, between the Schaher electrode with constant potential and the circuit point with reverse voltage potential inserted center point (11).