GB2031677A - Switching arrangement - Google Patents

Abstract

An arrangement for switching a transistor, useable in switching transistor power supplies has a base coil (50) connected between the base and emitter of the transistor (7). By controlling the polarity of pulses to a control coil (40) which is inductively coupled to the base coil (5), current is induced to flow in the base coil (50) in one direction or in the opposite direction, respectively to switch the transistor (7) ON and OFF. When the transistor (7) has been switched ON it is maintained ON by positive feed back via a feedback coil (60) inductively coupled to the base coil (50). Push pull arrangements are described, and different embodiments include various circuitry for preventing permanent magnetisation of the transformer core (8). <IMAGE>

Description

SPECIFICATION Driving circuit arrangement for controlling switched mode of operation transistors The subject of the invention is a driving circuit arrangement for switched mode control of transistors which can be advantageous applied for controlling switched mode of operation power supply units and similar circuits by realizing single beat or pushpull mode of control.

One of groups of the driving circuits, realizing switched mode of control of transistors includes the widely known direct coupled driving circuits. These circuits, however, have a restricted scope of application since the galvanic separation is a basic requirement in most applications. Therefore, transformer coupled driver circuits are generally used. The energy, necessary for powering the driving stage, comes from an auxiliary voltage source often with bad circuit efficiency. Such a solution has been described in M.C. Basell's article entitled as "30 V 8A Switched Mode Power Supply Operating from - 50 V Post Office Exchange Supplies" (Mullard Technical Note 20). Some data about the power consumption of the driving circuit have been reported in the Mullard Enterprise's article: "5 V 20 A and 40 A switched Mode Power Supplies (Mullard Technical Note 32).

The disadvantages of the mentioned solutions beyond the considerable power consumption - are: switching transistors operated in push-pull mode need two separated driving circuits; the short and constant switch-off time cannot be ensured, furthermore, the possibility of simultaneous opening of the push-pull operated transistors is not excluded.

A substantially similar solution has been reported by B. W. Dudley and R. D. Peck in their article: "High Efficiency Modular Power Supplies Using Switching Regulators" (HP Journal, 1973, Dec.). Although, this solution diminishes the switching off period by the help of an additional circuit, it does not eliminate the above enumerated further disadvantages.

Related to the above briefed solutions the firm Advance-Gould utilizes a more up-to-date way in its switching mode power supply units, manufactured in large series. This solution is suitable for realizing push-pull mode control, it offers better circuit efficiency than the above mentioned solutions, and owing to a separate current monitoring stage the base current is nearly proportional to the collector current. This proportionality, however, exists only up to a certain value of the collector current, and beyond this value the transistor may get into the active mode of operation which trouble, however, characterizes all the other solutions, too. The driving stage has relatively high power consumption and does not eliminate completely the possibilty of simultaneous opening of the transistors.

The disadvantages of the known solutions have made necessary to seek such a driving circuit which is free of the enumerated troubles, has considerably less power consumption, than the already known driving circuits, ensures the proportionality of the base current to the collector current as a result of the circuit construction, excludes the possibility of operation of the transistors in their active domain, ensures well defined switch-on and switch-off processes and significantly decreases the possibility of simultaneous opening of the transistors when realizing push-pull control mode.

The fundamental conception of the invention is the perception, that the switching mode control of the transistor can be easily carried out by such a circuit arrangement, in which the base-coil, inserted between the base and the emitter of the transistor, realizes the switching on process of the transistor when the base coil is generated in one direction, and when this same base coil is generated in the other direction, the switching off process will take place; after switching on the transistor its conducting state can be prolonged by feeding-back its collector current, suitably by the positive voltage feed-back, what happens as a consequence of the current inductively with the base coil; the switching on and switching off processes are realized by alternating the direction of the generating current, forced through the control coil - being inductively coupled with the base coil expediently by pulses of inverse polarity.

The driving circuit arrangement, suggested by the invention, serves for controlling the switched mode operation of transistor(s). It has been constructed by applying inductive coupling elements. The main point of the arrangement is, that the transistor has three coils, coupled in the following way: the first coil (or the base coil) is inserted between the emitter and the base of the transistor; the second coil (orthe feed-back coil) is connected to one of the main electrodes of the transistor and has inductive coupling with the first coil; the third coil (or the control coil) has inductive coupling with both the first and the second coil. At least the first terminal of the third coil joins the first terminal of the auxiliary power supply source through the first switch, and the second terminal of the auxiliary power supply source through the second switch.The end of the third coil is linked, according to necessity, with the terminal (or terminals) of the auxiliary power supply source through a demagnetizing circuit.

These three coils, the first, the second and the third one, are placed upon a common iron core, what means the most advanced implementation form of the circuit arrangement.

If the circuit arrangement includes electronic switching elements, namely transistors, then is advisable to join the first diode in series with the first or/and second switch for protecting them from return currents; this first diode must be inserted in forward direction related to the terminals of the auxiliary power supply.

One of implementation ways of the single beat control mode circuit arrangement with a demagnetizing circuit has a shifted break-point response diode, connected between the first terminal of the third coil and the second terminal of the auxiliary power supply source; the anode of this diode, the anode of the second diode and the anode of the Zener diode have a mutually common wire. The second terminal of the third coil links with the second terminal of the auxiliary power supply source directly.The other advantageous implementation varient of the single beat control mode circuit arrangement includes a demagnetizing circuit as well, although, the second terminal of the third coil and the second terminal of the auxiliary power supply source here are interconnected with the first capacitor and the third diode in parallel, furthermore, the second terminal of the third coil and the first terminal of the auxiliary power supply source are interconnected with the fourth diode. The third diode and the fourth diode are connected to the terminals of the auxiliary power supply source, foreseeing the reverse direction. The fifth diode, connected in parallel with the second switch, is provided for shunting the current that would needlessly load the transistors, realizing the switching function.

The duration between the starting of the switch-off process and the closing of the transistor can further be decreased in this implementation way by applying a current gage unit. The second terminal of the third coil joins the first terminal of the auxiliary power supply source through the switching circuit, being under the control of the transistor current gage unit in this realization.

The push-pull control mode can advantageously be implemented as the circuit arrangement in which each transistor has its own first coil. Each transistor has either its own separate second coil or the transistors, that belong together, have one common second coil. The third coil can be common for the two transistors. The second terminal of the third coil joins the first terminal of the auxiliary power supply resource through the third switch, furthermore, the same second terminal of the third coil joins the second terminal of the auxiliary power supply source, but here through the fourth switch. There is a fifth diode connected in parallel with the second and/or the fourth switch; this fifth diode is provided for shunting the current that would needlessly load the transistors, accomplishing the switching function.

A further push-pull control mode version can be carried out by the implementation form in which each transistor has its own first coil and its own third coil; each transistor either has its own separate second coil or the two transistors, belonging to the same push-pull circuit, have one common second coil. Each first terminal of the third coils joins the second common switch through the sixth diode.

The other implementation way of realizing pushpull control mode of operation utilizes separate first coil and separate third coil for each transistor; a separate second coil can belong to each transistor, or else the two transistors of the push-pull circuit have only one common second coil. Each first terminal of the third coils is connected to the common second switch through the sixth diodes. The second terminals of the third coils are interconnected and their common wire -through the first capacitor and the third diode connected in parallel - joins the second terminal of the auxiliary power supply source, where the third diode is connected to the second terminal of the auxiliary power supply arrangement, foreseening the reverse direction.This realization allows further shortening of the duration between the starting of the switch-off process and the closing of the transistor, owing to application of a current gage unit, if the common wire of the interconnected second ends of the third coils joins the first terminal of the auxiliary power supply source via the switching circuit, being controlled by the current gage unit, gauging the currents of the transistors.

The driving circuit of the suggested invention ensures the saturation in switched on state of the transistor and the proportionalness of the base current to the collector current, according to the principle of operation of the driving circuit. The low power consumption of the circuit can be explained by the fact, that only the starting of the positive feed-back process requires some minimal energy. Owing to the positive feed-back the switching on process is very fast. The switching off time is determined by the charge storage properties of the controlled transistor; its value can be diminished by increasing the base extracting current. The protection against disturbances is ensured by short-circuiting the third coil (control coil) in pause periods.The application of the arrangement in push-pull driving stages ensures a simpler control and less chance of cross-opening, than the circuit solutions applied until now, for the collector current, flowing through the feed-back coil, represents a protection against false control cases and pulses derived from disturbances.

The further more detailed demonstration of some advantageous implementation versions of the invention will be based upon the following diagrammatic circuit diagrams enclosed with these description.

Fig. 1: Circuit diagram of the arrangement of the invention.

Fig. 2a: Diagrammatic circuit diagram of the low consumption single beat driving stage.

Fig. 2b: Signal forms, characterizing the operation of the single beat driving stage, illustrated in Fig. 2a.

Fig. 3a: Diagrammatic circuit diagram of the driving stage, having short switching off time; Fig. 3b: Signal forms, explaining the operation of the circuit arrangement, shown in Fig. 3a.

Fig. 4a: Diagrammatic circuit diagram of a power consumption push-pull driving circuit arrangement.

Fig. 4b: Signal forms, characterizing the operation of the push-pull mode driving circuit, shown in Fig.

4b.

Fig. 5a: Diagrammatic circuit diagram of an other push-pull mode driving circuit arrangement with reduced number of switches.

Fig. 5b: Wave forms, explaining the operation of the circuit arrangement, shown in Fig. 5a.

Fig. 6a: Diagrammatic circuit diagram of a further push-pull mode driving circuit arrangement, characterized by short switching off time.

Fig. 6b: Signal forms for explaining the operation of the circuit arrangement, illustrated in Fig. 6a.

The simplified circuit diagram shown in the Fig. 1 and demonstrating mostly the principle of operation of the circuit arrangement recalls the control of the transistor 7. The first coil 50 - or base coil - links the base of the transistor 7 with its emitter. The emitter of the transistor 7 is connected in series with the second coil 60 - or feed-back coil. The first coil 50 and the second coil 60 are arranged on the common iron core 8. The third coil 40 - or control coil - is arranged on the iron core 8 as well. The first terminal of this coil 40 is attached to the first terminal 2 of the .direct current auxiliary power supply source through the first switch 10 and to the second terminal 4 of the auxiliary power supply source via the second switch 20. The second terminal of the third coil 40 joins the second terminal 4 of the auxiliary power supply source directly.The first coil 50, the second coil 60 and the third coil 40 are in mutual inductive coupling each with the other two.

The transistor 7 can be operated by switching on the first switch 10, i.e. by ensuring its conducting state, while the second switch 20 is presumably interrupted. At that moment a current starts from the first terminal 2 of the auxiliary power supply source through the first switch 10 and the third coil 40. This current induces a voltage of such magnitude in the first coil 50 which leads the transistor 7 into conducting state. The starting collector current of the transistor flows through the second coil 60 and results in positive current feed-back owing to the inductive coupling between the second coil 60 and the first coil 50 what will keep the transistor 7 in conducting state.

While the transistor 7 is in conducting state it is quite indifferent matter wether the first switch 10 is in conducting or interrupted state. But, if the first switch 10 is in interrupted state then for switching off the transistor 7 the second switch 20 has to be put into a durable conducting state. Now the second switch 20 short-circuites the third coil 40 what will result in short-circuiting the base circuit of the transistor 7 in consequence of the indicative coupling.

The ceasing collector currents puts and end to the positive feed-back what leads to the switching off of the transistor 7.

The Fig. 2a shows another version of the circuit arrangement shown on the Fig. 1. The additional element on the Fig. 2 is a demagnetizing circuit, namely a shifted break-point response diode, inserted between the first terminal of the third coil 40 and the second terminal 4 of the auxiliary power supply source according to its inverse direction. The circuit includes the second diode 80 having common anode point with the anode of the Zener diode 83.

The first diode 82 is connected in series with the second switch 20 and attaches to the terminals of the auxiliary power supply source keeping the conducting direction, preventing the switch 20 this way from being flown through by reverse direction currents.

The operation of the driving circuit otherwise is quite identical to the operation of the circuit, shown on the Fig. 1. The briefly described demagnetizing circuit speeds up the operation of the driving circuit by reducing the magnetic energy - accumulated in the coil 40 and the iron core 8 during the switched on state of the driving circuit- up to a zero level immediately after switching off. The magnetizing up of the iron core and its getting saturated because of the quickly repeating switchings on becomes avoidable this way. The demagnetizing circuit seizes the inverse sense voltage induced in the third coil 40 on the level of the break-point voltage and makes the demagnetizing and the dropping of the flux up to zero possible.

The Fig. 2b shows the alternation of the collector current le of the transistor 7 in time and the interrupted or conducting state of the first switch 10 or second switch 20 depend,ing on the control signal of the switches. The interrupted state of the switches is shown by "0" level while the conducting state is marked by "1" level. The switching on of the first switch occurs at the t, point of time. Until that point the second switch 20 has been in conducting state and simultaneously with the switching on of the first switch 10 it gets into interrupted state. The switching on of the first switch 10 starts the collector lc of the transistor 7. After switching on the further conducting or interrupted state of the first switch 10 is quite an indifferent matter.During the switching off process what begins at the time point t by controlling the second switch 20 into conducting state-while the first switch 10 is in interrupted state - the collector current lc of the transistor 7 rests unchanged until the switching off of the transistor, then is drops onto zero at the moment t3. During the switching off state the second switch 20 is closed for ensuring the insensibilty of the driving circuit to disturbances.

The driving circuit shown on the Fig. 3a is a third version of the circuit presented on the Fig. 1. There is the first diode 81 connected in series with the first switch 10 what hinders the forming of inverse direction currents. The fifth diode 84 is connected in parallel with the second switch 20 for preventing it from reverse direction currents. The demagnetizing circuit consists of the first condenser 90 and the third diode 85, inserted between the second terminal of the third coil 40 and the second terminal 4 of the auxiliary power supply source, furthermore, of the fourth diode 86 interconnecting the second terminal of the third coil 40 and the first terminal 2 of the auxiliary power supply source. The third diode 85 and the fourth diode 86 are connected to the terminals of the auxiliary power source in closing direction arrangement.

The circuit operates like the circuit shown on the Fig. 1. The current, started by switching on the first switch 10 charges the first condenser 94 through the first diode 81 and the third coil 40 up to the voltage of the auxiliary power supply source. Simultaneously the transistor 7 switches on as that was explained above. Now, following the closing of the second switch 20 - while the first switch 10 is in the open state - the transistor 7 switches off; the closing direction voltage of the first condenser 94, discharging through the third coil 40, promotes the fast switching off of the transistor 7 until its charge drops up to zero. After that the conducting state of the third diode 85 ensures the short-circuiting of the third coil 40 and the switching off of the transistor 7. The demagnetizing current of the iron core 8 begins again to charge the first condenser 94 up to the voltage of the auxiliary power supply source and when this voltage value will be attained it will be limited by getting into conducting state of the fourth diode 86.

The demagnetizing current flows on through the fifth diode 84, switch 20, coil 40 and fourth diode 86 until the stored up magnetic energy will be fed back into the auxiliary power supply source. Following the demagnetizing the first condenser 94 will be again discharged through the coil 40 and the second switch 20. The speed of the discharging process can be increased by the first resistor 96, connected in parallel with the third coil 40 in the more advanced implementation form of the circuit arrangement.

The delay between the starting of the switching off process and the real switching off of the transistor 7 can further be shortened by applying the fifth switch 91 connected between the second terminal of the third coil 40 and the first terminal 2 of the auxiliary power supply source; this fifth switch 91 is operated by the current gage unit 90, gauging the collector current. The fifth switch 91 gets into conducting state simultaneously with the starting of the collector current.After the switching off its closed state will keep the second terminal of the third coil 40 just upon the potential of the first terminal 2 of the auxiliary power supply source, i.e. it hinders the discharging of the first condenser 94 as long as the switching off of the transistor 7 will be finished; meanwhile, the first terminal of the third coil 40 keeps being upon the potential of the second terminal 4 of the auxiliary power supply source via the closed second switch 20, ensuring hereby inverse closing sense voltage for the third coil 40 of the transistor 7 until the closing process of its base will be completed.

The Fig. 3b shows the succession of operation of the first switch 10, the second switch 20, the collector current lc and the fifth switch 91. After switching on the circuit the first switch 10 gets into conducting state at the moment of time t1, simultaneously with that the second switch 20 gets interrupted, the collector current lC begins to flow, what results in turning the fifth switch 91 into conducting state. If the circuit and the transistor 7 are in switched on state then the state of the first switch 10 has no importance. The switching off process starts with turning the second switch 20 into conducting state at the point of time t2; the interrupted state of the first switch 10 is an indispensable condition in this case.

The switching off process comes to its end at the momentt3, when the collector current of the transistor becomes equal to zero and simultaneously the fifth switch 91 turns into interrupted state.

The Fig. 4a shows the circuit arrangement suitable for push-pull mode controlling two transistors 71 and 72. Each transistor has its own first - base - coil 51 or 52, but the two transistors have a common second - the feed-back- coil 60. One end of the second coil 60 joins the common terminal of the emitter of the first transistor 71 and of the collector of the second transistor 72.

The two transistors are connected in series with the terminals of the auxiliary power supply source which is not shown on the figure. The first coils 51 and 52 and the second -feeding-back- coil 60, common for the two transistors, are arranged on the iron core 8. The third coil 40the controlling coil - is common for the two transistors and is arranged on the iron core 8, too. The first terminal of this third coil 40 links the first terminal 2 of the auxiliary power supply source through the first switch 10, and the second terminal 4 of the auxiliary power supply source via the second switch 20. The fifth diode 84 connected in parallel with the second switch keeps reverse direction regarding the polarity of the termi nals of the auxiliary power supply source.The second terminal of the third coil 40 joins the first terminal 2 of the auxiliary power supply circuit through the third switch 11, and the second terminal 4 of the auxiliary power supply source through the fourth switch 21. The other fifth diode 89 connected in parallel with the fourth switch 21 keeps the reverse connecting direction, regarding the polarity of the auxiliary power supply source.

The operation of the circuit can be traced on the base of the Fig. 4b. The second switch 20 and the fourth switch 21 are of conducting state in their basic condition, the first 10 and the third 11 switches, however, are interrupted. The second transistor 72 can be switched on at the moment of time t, by turning the first switch 10 into conducting state; simultaneously the second switch 20 must be put into its interrupted state.

The current of the third coil 40, flowing along the fourth switch 21 and the first switch 10, induces current in the first coil 52 what opens the second transistor 72, the starting collector current of which forwards through the second coil 60 and arises positive feed-back, what keeps the second transistor 72 in conductive state. Meanwhile, the second transistor 72 is in switched on state, the further state of the first switch 10 has no importance. At the moment of time t2 the second transistor 72 can be switched off by turning the second switch 20 into conducting state, while the first switch 10 is interrupted. Then the third coil 40 gets short circuited through the conducting fourth switch 21 and second switch 20.The shortcircuit current, flowing through the fifth diode 89 and disburdening the fourth switch 21, induces current in the first coil 52 what closes the second transistor 72.

The collector current of the second transistor 72 ceases at the moment ta.

Following the moment of time t3 the magnetizing current, keeping the flux of the iron core 8 unchanged, flows through the fifth diode 84, the fourth switch 21 and the third coil 40; this magnetizing current is of inverse direction related to the short circuit current of the coil 40. At the moment t4 the third switch 10 turns into conducting state, the fourth switch 21 gets into interrupted state, what carries the first transistor 71 into switched on state like the previous processes. After switching on the first transistor 71 the actual state of the third switch 11 has no importance. The closing of the first transistor 71 can occur at the moment t5 on condition that the fourth switch 21 is closed; the closing process occurs according to the description, given above.

The Fig. 5a shows another solution suitable for push-pull controlling the transistors 71 and 72. Both transistors of this driving circuit have separate first (base) coils 51 and 52, separately arranged second (feeding-back) coils 61 and 62, and the third (control) coils 41 and 42. The second coils 61 and 62 can also be arranged as a common single one. Each of these coils is arranged on the common iron core 8. The second coil 61 and the other second coil 62 are inserted into the main circuit of the correspondent transistor. The third coils 41 and 42 have common second terminal, joining the second terminal 4 of the auxiliary power supply source.The first terminal of the third coil 42 links the first terminal 2 of the auxili ary power supply source through the first switch 10 and the first terminal of the third coil 41 joins the first terminal 2 of the auxiliary power supply via the third switch 11. Furthermore, the first terminal of the third coil 42 joins also the sixth diode 87b, similarly the first terminal of the third coil 41 joins also the sixth diode 87a; the other terminals of these sixth diodes are interconnected and their common point links the second terminal 4 of the auxiliary power supply source via the second switch 20, being common for the two third coils.

The operation of the circuit can be traced on the base of the Fig. 5b. The initial states for the first switch 10 and for the third switch 11 are interruptions, while the second switch 20 is in conducting state. The switching on process of the second transistor 72 starts with turning the first switch 10 into conducting state, and the second switch 20 into interrupted state. The current, starting through the first switch 10 and third coil 42, induces a current in the first coil 52, which switches on the second transistor 72, and its starting collector current lC2 flows through the second coil 62, what keeps the second transistor 72 in conducting state.

During the conducting state of the second transistor 72 the actual state of the first switch 10 has no importance. Whilethefirst switch 10 is in interrupted state the second transistor 72 can be switched off on condition that the second switch 20 must be turned into conducting state. The short circuited third coil 42, leads the second transistor 72 into switched off state through the sixth diode 87b and the second switch 20. At the moments3 the collector current lc2 of the second transistor drops up to zero, and following that the magnetizing current, keeping up the flux in the iron core 8, flows through the third coil 41, sixth diode 87a and the second switch 20. At the moment 4 the second switch 20 is controlled into interrupted state, the third switch 11 into conducting state, and the first transistor 71 gets switched on.

The current of the third coil 41 induces the first coil 51 and the induced current carries the first transistor 71 into conducting state. The starting collector current lC1 flowing through the second coil 61 produces positive feed-back and supports the conducting state of the first transistor 71, during which the actual state of the third switch has no importance. The first transistor 71 can be switched off by closing the second switch 20 at the moment t5, when the third coil 41 gets short-circuited through the further sixth diode 87a and the second switch 20; its current switches off the first transistor 71.At the moment t6 the collector current comes to an end after which the magnetizing current, supporting the flux of the iron coil 8, flows through the third coil 42, the sixth diode 87b and the second switch 20.

The driving circuit shown on the Fig. 6a is also suitable for push-pull controlling the transistors 71 and 72, in fact has the construction similar to the circuit, presented on the Fig. 5a. The only difference between them is the way of connecting the third coils 41 and 42 with the second terminal 4 of the auxiliary power supply source, since this connection is done here by inserting the first condenser 94 connected in parallel with the third diode 85, considering that it should be connected in reverse direction related to the polarity of the auxiliary power supply source.The circuit of the present realization version is completed with the current gauge unit 90, gauging the collector current of whichever of transistors 71 and 72, and with the fifth switch 91, interconnecting the common second terminals of the third coils 41 and 42 and the first terminal 2 of the auxiliary power supply source. In addition, the circuit includes the first diode 81 connected in series with the first switch 10, preventing the switches from currents of undesirable direction; the diode 82 should be connected according to its opening direction related to the polarity of the auxiliary power supply source.

The operation of the circuit can be explained on the base of the Fig. 6b. The switching on of the second transistor 72 at the moment t1 - considering, that the second switch 20 and the third switch 11 are in interrupted state - can occur by closing the first switch 10. The current, starting through the first switch 10, the first diode 81 and the third coil 40 turns the second transistor 31 into conducting state on the one hand, as it was explained earlier, and charges up the first condenser 94 on the other.The current gage unit 90, gauging the starting collector current Ica, closes the fifth switch 91, keeping the voltage of the first condenser 94 this way during the period of closed state of the switch - what is as long as the period of flowing of the collector current on the potential of the auxiliary power supply source.

During the switched on state of the second transistor 72 the actual state of the first switch 10 has no importance. The switching of the second transistor 72 while the first switch 10 is interrupted - requires the closing of the second switch 20 at the momentt2.

The second transistor 72 will be switched off by the current of inverse direction, starting from the first terminal 2 of the auxiliary power supply source through the third coil 42 and the other sixth diode 87b as it was explained above. The ceasing of the collector current at the momentt3 results in the opening of the fifth switch 91 and, as a consequence, the first condenser 94 discharges until the opening of the third diode 85 through the third coil 41 or 42, ensuring this way the current, supporting the flux in the iron core 8. Following the opening of the third diode 85 the magnetizing current of the iron core 8 flows through the third coil 41, the sixth diode 87 and the second switch 20.The switching on of the first transistor 71 while the second switch 20 is in opened state requires the closing of the third switch 11 at the moment t4, when the current, switching on the first transistor 71, charges the first condenser 94 - through the third switch 11, first diode 81 and the third coil 41 - up to the voltage of the auxiliary power supply. The fifth switch 91 gets into conducting state under the influence of the starting collector current Cl Meanwhile the firsttransistor71 is in conducting state, the actual state of the third switch 11 has no importance. The switching off of the firsttransistor7l, while the third switch 11 is interrupted, occurs by turning the second switch 20 into closed state at the moment tS, when the reverse direction current, starting through the fifth switch 91, the third coil 41 and the other sixth diode 87a, results in closing the first transistor 71 and ceasing its col lector current lC1. After the opening of the fifth switch 91 the discharging of the first condenser 94 occurs until the opening of the third diode 85 as it was described above, while the magnetizing current gets through the diode 85, the third coil 41, the sixth diode 87a and the second switch 20.

CLAIMS 1. Driving circuit arrangement for switching mode control of transistor(s) (7,71,72) by applying elements of inductive coupling, characterized as follows: the transistor (7,71,72) has a first coil - base coil (50, 51, 52) - inserted between its emitter and base, a second coil - or feeding-back coil (60,61, 62) - connected with one of main electrodes of the transistor, and having inductive coupling with the first coil (50, 51, 52), furthermore, a third coil - control coil (40,41,42) - having inductive coupling with the first coil (50, 51, 52) and second coil (60,61,62); at least the first terminal of the third coil (40,41,42) joins the first terminal (2) of the auxiliary power supply source through the first switch (10), and the second terminal (4) of the auxiliary power supply source through the second switch (20), whilst the other terminal of the third coil (40,41,42) links the terminal (or terminals) of the auxiliary power supply source, through a demagnetizing circuit.

2. The implementation form of the circuit arrangement according to the claim 1, characterized as follows: the first coil (50, 51, 52), the second coil (60, 61,62) and the third coil (40,41,42) are arranged on the common iron core (8).

3. The implementation form of the circuit arrangement according to whichever of the claims 1 to 2, characterized as follows: the first diode (81,82), connected in series with the first switch (10) and/or the second switch (20) joins the terminals of the auxiliary power supply source, observing the opening direction of the first diode, considering the polarity of the auxiliary power supply source.

4. The implementation form of the circuit arrangement, according to whichever of the claims 1 to 3, characterized as follows: the second terminal of the third coil (40) joins the second terminal (4) of the auxiliary power supply source directly.

5. The implementation form of the circuit arrangement, according to whichever of the claims 1 to 4, characterized as follows: the demagnetizing circuit of the circuit arrangement is composed of the shifted break-point response diode, the second diode (80) and the Zener Diode (83) having common anode point; this demagnetizing circuit is inserted between the first terminal of the third coil (40) and the second terminal (4) of the auxiliary power supply, keeping the return direction of the diodes, considering the polarity of the auxiliary power supply source.

6. The implementation form of the circuit arrangement, according to whichever of the claims 1 to 4, characterized as follows: the demagnetizing circuit has its first condenser (94), connected between the second terminal of the third coil (40) and the second terminal (4) of the auxiliary power supply source; the third diode (85) is connected in parallel with the first condenser (94), furthermore, the fourth diode (86) of the demagnetizing circuit is connected between the second terminal of the third coil (40), and the first terminal (2) of the auxiliary power supply source; both the third diode (85) and the fourth diode (86) are connected in reverse direction arrangement, related to the polarity of the auxiliary power supply source.

7. The implementation form of the circuit arrangement for push-pull mode control of the two transistors (71,72), according to whichever of the claims 1 to 3, characterized as follows: each transistor (71,72) has its own first coil (51, 52); each transistor (71,72) and/orthe push-pull transistor pair (71, 72) has common second coil (60) and common third coil (40); the second terminal of the third coil links the first terminal (2) of the auxiliary power supply source, through the third switch (11), and the second terminal (4) of the auxiliary power supply source through the fourth switch (21).

8. The implementation form of the circuit arrangement for push-pull mode control of two transistors (71,72), according to whichever of the claims 1 to 4, characterized as follows: each transistor (71,72) has its own first coil (51, 52) and its own third coil (41,42), furthermore, either the common second coil (61,62) for the push-pull transistor pair (71,72), or separate second coils (61,62) for each transistor (71,72); each first terminal of the third coils (41,42) joins the sixth diodes (87a, 87b), the interconnected other terminals of which link the common second switch (20).

9. The implementation form of the circuit arrangement for push-pull mode control of two transistors (71,72), according to whichever of the claims 1 to 3, characterized as follows: each transistor (71,72) has its own first coil (51, 52) and its own third coil (41,42); furthermore, either a common second coil (61,62) for the push-pull transistor pair (71,72), or separate second coils (61,62) for each transistors (71,72); each first terminal of the third coils (41,42) join the sixth diodes (87a, 87b), connected with their interconnected second terminals to the common second switch (20); the second terminals of the third coils (41,42) are interconnected and their common wire joins the first condenser (94) and the third diode (85) connected in parallel with it; their other common terminal links the second terminal (4) of the auxiliary power supply source, considering the closing direction of the third diode (85), related to the polarity of the second terminal (4) of the auxiliary power supply source.

10. The implementation form of the circuit arrangement, according either to the claim 6 or 9, characterized as follows: the second terminal of the third coil (40,41,42) is connected with the first terminal (2) of the auxiliary power supply source through the switch (91), controlled by the current gage unit (90), gauging the current of the transistor(s) (71,72).

11. The implementation form of the circuit arrangement, according to whichever of the claims 1 to 4 and 6, characterized as follows: the fifth diode (84,89) is connected in parallel with the second switch (20) and/orthefourth switch (21).

Reference numbers and letters have been used in the appended claims purely for illustration and not for limitation.

Claims (12)

1. Driving circuit arrangement for switching mode control of transistor(s) (7,71,72) by applying elements of inductive coupling, wherein the transistor (7,71,72) has a first coil or base coil (50, 51, 52) inserted between its emitter and base, a second coil or feed-back coil (60,61, 62) connected with one of main electrodes of the transistor, and having inductive coupling with the first coil (50, 51,52), furthermore, a third coil or control coil (40,41,42) - having inductive coupling with the first coil (50, 51, 52) and second coil (60, 61,62);; at least the first terminal of the third coil (40,41,42) is connected to the first terminal (2) of an auxiliary power supply through a first switch (10) and to the second terminal (4) of the auxiliary power supply source through a second switch (20), whilst the end or other terminal of the third coil (40,41,42) is connected to the terminal (or terminals) of the auxiliary power supply through a demagnetizing circuit, as required.

2. The circuit arrangement according to the claim 1, wherein the first coil (50, 51, 52), the second coil (60, 61, 62) and the third coil (40,41,42) are arranged on a common iron core (8).

3. The circuit arrangement according to claim 1 or 2, wherein a first diode (81, 82) is connected in series with the first switch (10) and/orthe second switch (20) is connected the terminals of the auxiliary power supply source, in the opening direction of the first diode, considering the polarity of the auxiliary power supply.

4. The circuit arrangement according to any of claims 1 to 3, wherein the second terminal of the third coil (40) and the second terminal (4) of the auxiliary power supply are directly connected.

5. The circuit arrangement according to any of claims 1 to 4, wherein the demagnetizing circuit of the circuit arrangement is composed of a shifted break-point response diode, preferably having a common anode with a second diode (80) and a Zener diode (83); this demagnetizing circuit being inserted between the first terminal of the third coil (40) and the second terminal (4) of the auxiliary power supply, the diode being connected in the closing direction relative to the polarity of the auxiliary power supply.

6. The circuit arrangement according to any of claims 1 to 4, wherein the demagnetizing circuit has a first capacitor (94) connected between the second terminal of the third coil (40) and the second terminal (4) of the auxiliary power supply; a third diode (85) is connected in parallel with the first capacitor (94); furthermore, a fourth diode (86) of the demagnetizing circuit is connected between the second terminal of the third coil (40) and the first terminal (2) of the auxiliary power supply; both the third diode (85) and a fourth diode (86) are connected in reverse direction arrangement, related to the polarity of the auxiliary power supply.

7. The circuit arrangement for push-pull mode control of two transistors (71,72), according to any of claims 1 to 3, wherein each transistor (71,72) has its own first coil (51,52); each transistor (71,72) and/orthe push-pull transistor pair (71,72) had a common second coil 60, and a common third coil (40); the second terminal of the third coil links the first terminal (2) of the auxiliary power supply through the third switch (11), and the second terminal (4) of the auxiliary power supply through the fourth switch (21).

8. The circuit arrangement for push-pull mode control of two transistors (71,72), according to any of claims 1 to 4, wherein each transistor (71,72) has its own first coil (51,52) and its own third coil (41, 42), as well as either the common second coil (61,62) for the push-pull transistor pair (71,72), or separate second coils (61, 62) for each transistor (71,72); each first terminal of the third coils (41,42) joins sixth diodes (87a, 87b) the interconnected other terminals of which link the common second switch (20).

9. The circuit arrangement for push-pull mode control of two transistors (71,72), according to any of claims 1 to 3, wherein each transistor (71, 72) has its own first coil (51,52) and its own third coil (41,42) as well as either common second coil (61,62) for the push-pull transistor pair (71,72), or separate second coils (61, 62) for each transistor (71, 72); each first terminal of the third coils (41,42) join the sixth diodes (87a, 87b), connected with their interconnected second terminals to the common second switch (20); the second terminals of the third coils (41,42) are interconnected and their common lead joins the first capacitor (94) and the third diode (85) connected in parallel with it; their other common terminal links the second terminal (4) of the auxiliary power supply, considering the closing direction of the third diode (85), related to the polarity of the second terminal (4) of the auxiliary power supply.

10. The circuit arrangement according to claim 6 or 9, wherein the second terminal of the third coil (40,41,42) is connected with the first terminal (2) of the auxiliary power supply through a switch (91) controlled by a current sensing unit (90) for sensing the current in the transistor(s) (71,72).

11. The circuit arrangement according to any of claims 1 to 4 and 6, wherein: the fifth diode (84, 89) is connected in parallel with the second switch (20) and/or the fourth switch (21).

12. Atransistor control circuit arrangement substantially as herein described with reference to and as shown in Figure 1 or Figures 2a and 2b, or Figures 3a and 3b, or Figures 4a and 4b or Figures 5a and 5b or Figures 6a and 6b of the accompanying drawings.