DE4040841A1 - Circuit producing DC feed voltage for at least one load - delivers DC voltage essentially between two terminals with at least one user fed across converter system contg. inductance and switch in series - Google Patents

Abstract

The series circuit contg. the inductance (3) and the switch (4) is arranged between the terminals (1,2) of the source. The circuit arrangement also includes a capacitor (10), which with a first diode (11) and the load (8) form a series circuit, which is arranged between a tapping (9) of the inductance (3) and one terminal of the switch (4). Also included is a smoothing capacitor (12) arranged parallel to the load (8), and a second diode (13), which at one side is connected to the junction point between the capacitor (10) and the first diode (11), and from the other side a coupling is provided to the junction point between the load (8) and the terminal of the switch (4) connected with it. USE/ADVANTAGE - Circuit arrangement for producing DC feed voltage. Can be fed also with pulsing DC voltage as well as constant DC voltage. Compact and simply designed. Supply voltage for load can be delivered selectively with positive or negative polarity.

Description

The invention relates to a circuit arrangement for Generating a DC supply voltage for at least one Load.

From DE-PS 36 12 147 is a circuit arrangement for Generation of a DC voltage from a sinusoidal Input voltage known for at least one load. These Circuit arrangement comprises a rectifier, the Output with smoothing connected in parallel with the load capacitor is coupled, and a consumer that between the two output terminals of the rectifier is arranged. A capacitor with a first The output connection of the rectifier is coupled via a first diode arrangement and the consumer can be discharged. Furthermore, one of the first diode arrangements is parallel switched series connection provided that from a second diode arrangement, via which only the charging current of the Capacitor flows, and from at least one with one Connection of the consumer connected parallel connection a load and a smoothing capacitor. In this Circuitry have the load and the consumer a common connection point.

The known circuit arrangement is preferably immediate by an input AC voltage, especially the Mains voltage, fed.

It turns out that in the known circuit arrangement Difficulties arise when the load is higher Has power requirements. In this case, you can  Distortions in the input current of the entire Circuit arrangement are caused, which the load supplying sinusoidal input voltage. The Smoothing capacitor connected in parallel with the load is then necessary to achieve sufficient smoothing the voltage on the load is relatively high Have capacity value, because the reload with the double the frequency of the input voltage corresponding to the Rectifier is supplied. This frequency is however relatively low. In addition, the known circuit arrangement that a flawless Function, in particular a proper supply of the Load, when supplying an at least approximately constant DC voltage at the input, such as from Batteries or accumulators are supplied, no more is guaranteed.

The invention has the task of a circuit arrangement of the type mentioned at the outset, by means of one Supply voltage for the load optionally with positive or can be supplied with negative polarity, and the both with a DC voltage and with a AC voltage is operable at the input. The Circuit arrangement should be simple, especially with components of small dimensions, and the source that feeds them, especially one Power supply network, a distortion-free electricity remove.

This object is achieved by a Circuit arrangement for generating a food DC voltage for at least one load from one between two connections essentially a DC voltage source, with at least one consumer who is fed via a converter arrangement, the one  Series connection of an inductance and a switch contains elements between the connectors of the source is inserted with a capacitor connected to a first Diode arrangement and the load forms a series circuit, that between tapping the inductance and one Connection of the switch element is arranged with a Smoothing capacitor parallel to the load and a second Diode arrangement on the one hand at the connection point between the capacitor and the first diode array is connected and on the other hand a coupling to the point of connection between the load and that with it connected connection of the switch element is provided.

The circuit arrangement according to the invention can be both be supplied from a source that is an exact or at least largely exactly constant DC voltage emits, for example from a battery or Accumulator or a stabilized power supply, as also from a source with pulsating DC voltage such as for example a line rectifier. So that's it Circuit arrangement according to the invention particularly suitable for battery-backed, mains-operated consumers who via a converter arrangement, in particular a switching network part to be supplied with energy. The load or loads preferably provide one or more taxes circuits, of which the consumer feeds Converter arrangement is controlled.

The circuit arrangement according to the invention can be advantageous can be combined with a mains rectifier, via which then either a DC voltage or one AC voltage can be supplied. In addition, can be parallel to the mains rectifier, d. H. between input ports the circuit arrangement according to the invention, a buffer Insert accumulator for optional feeding.  

In the circuit arrangement according to the invention Voltage generation for the load advantageous in the Converter arrangement included, so that the reloading of the Smoothing capacitor for the load with the switching frequency the converter arrangement, d. H. with the switching frequency of the Switch element takes place. This can make the smoothing capacitor are dimensioned very small, so that a compact and inexpensive design can be achieved. This is also favored in that the invention Circuit arrangement characterized by low power losses distinguished.

In the circuit arrangement according to the invention, the Capacitor charged when the switch element of the Converter arrangement is locked. The charging current for the The capacitor flows over the during this time interval first diode arrangement. If the switch element is conductive is switched, the capacitor can Inductance, the switch element and the second diodes unload arrangement. The diode arrangements can at least one diode, one transistor, one thyristor or the like.

The connection of the capacitor to the tap of the Inductance causes no fluctuations in the Potentials appear on the capacitor and possibly one very low sinusoidal current through the capacitor flows. This eliminates any distortion of the Source of current drawn is negligibly small.

According to an advantageous development of the invention the second diode array with the connection point between the load and the connection of the Switch element galvanically connected. The load will then fed a positive voltage. In particular, too  the connection point between the load and that with it connected connection of the switch element from a Connection of the source are formed. This will especially for the consumer, the converter arrangement and the load a common connection, especially one common ground connection, enables.

According to another embodiment of the invention, the second diode arrangement is connected to the connection point between the load and the connection of the switch element connected to it via a further load. This additional load is then fed with a negative voltage. In particular, the further load can be connected to a further smoothing capacitor in parallel. With this arrangement, a positive voltage is still supplied to the first-mentioned load. If, on the other hand, the first-mentioned load is short-circuited, ie the first diode arrangement is connected directly to the corresponding connection of the switch element, an arrangement is obtained which - as in FIG. 2 of DE-PS 36 12 147 - contains only one load supplied with a negative voltage.

Will be in the circuit arrangement according to the invention Switch element used by at least one of the Controlled loads and switched on by the consumer is switched when the voltage on this load A threshold is preferably reached circuit for feeding the load until reaching the Threshold provided. When commissioning the Circuit arrangement then becomes the capacitor and also the smoothing capacitor associated with the corresponding load charged until the threshold is reached. First then the load is used to control the switch element in their active operating state and thereby the Switch element actuated so that the further supply of the Load can take place via the converter arrangement.  

Further advantageous embodiments of the invention are in the remaining subclaims.

Some embodiments of the invention are in the Drawing shown and are described in more detail below described. Show it

Fig. 1 shows a first embodiment with a supplied by a positive voltage load,

Fig. 2 shows a second embodiment with two loads, Fig. 3 shows a third embodiment with a load in modification of the arrangement of FIG. 1.

In the circuit arrangement of FIG. 1, a converter arrangement is connected to the terminals 1 , 2 of a source, which comprises a series circuit comprising an inductor 3 and a switch element 4 . The switch element can preferably be designed as a transistor, thyristor or the like. In parallel to the switch element 4 there is a series connection of a freewheeling diode 5 and a consumer 6 , to which a capacitive energy store 7 is connected in parallel for smoothing the applied voltage. The switch element 4 is periodically switched on and off by a control circuit designated as load 8 . The frequency of these switching operations is preferably 20 to 200 kHz. In the time intervals in which the switching element 4 is turned on in the inductor 3 of the source here accumulated energy in the intervals in which the switching element 4 is locked via the freewheeling diode 5 to the load 6 and the capacitive energy storage device 7 in the usual way supplied with a switching power supply.

To supply power to the load 8 , a tap 9 is provided on the inductor 3 , to which a capacitor 10 is connected with one of its connections. The capacitor 10 forms with a first diode arrangement 11 , in the present example represented by a simple diode and can be configured in practice as a diode, as a diode chain, transistor or the like, and the load 8 forms a series connection between the tap 9 of the inductance 3 and one of the connections the switch element 4 . In the present example, this is the connection of the switch element 4 which is connected to the second connection 2 of the source and is here connected to ground potential. In contrast, the first connection 1 of the source carries a positive voltage to ground. A smoothing capacitor 12 is arranged in parallel to the load 8 . A second diode arrangement 13 is connected on the one hand to the connection point between the capacitor 10 and the first diode arrangement 11 . A second connection of the second diode arrangement 13 is coupled to the connection point between the load 8 and the connection of the switch element 4 connected to it. In the present example according to FIG. 1, this coupling consists of a galvanic connection to the switch element 4 , to the load 8 , and thus also to the smoothing capacitor 12 and to the second connection 2 of the source.

A Zener diode 14 is also arranged parallel to the load 8 to limit and stabilize the voltage at the load 8 . With the polarity of the voltages specified here, the cathode of the Zener diode 14 is connected to the connection point between the load and the first diode arrangement 11 .

The consumer 6 can be of any design; in particular, it can include a (further) switching power supply, which in turn feeds a gas discharge lamp or any other device.

In the operation of the present circuit arrangement, in the time intervals in which the switch element 4 is conductive, the voltage supplied by the source at the terminals 1 , 2 is applied to the inductor 3 . The potential at the tap 9 of the inductor 3 compared to the ground potential at the second terminal 2 of the source then corresponds to a fraction of the voltage of the source, determined by the winding ratio of the tap 9 . A continuously increasing current flows through the inductor 3 , through which energy from the source is stored in the inductor 3 . In the same flow direction flows through the occupied between the tap 9 and the switch element 4 part of the inductor 3, a discharge current of the capacitor 10 , the circuit closes via the switch element 4 and the second Diodenanord voltage 13 . Energy is thus returned from the capacitor 10 to the inductor 3 .

If the switch element 4 is blocked, the potential at the tap 9 increases by an amount which is determined by the voltage at the consumer 6 and the ratio of the winding components of the inductor 3 with respect to the tap 9 , as long as the freewheeling diode 5 is conductive. From the first terminal 1 of the source, a current now flows through the inductance 3 , the tap 9 , the capacitor 10 and the first diode arrangement 11 in the parallel connection of the load 8 , the smoothing capacitor 12 (in the energy for the operation of the load during the rest Time of the period of the switch element 4 is stored) and optionally the zener diode 14 , provided that the voltage across the load exceeds the zener voltage. The capacitor 10 and the smoothing capacitor 12 are charged in this time interval. In the next time interval in which the switch element 4 is again conductive, the capacitor 10 can then discharge again via the inductance 3 , the switch element 4 and the second diode arrangement 13 . A rectangular voltage with the switching frequency of the switch element 4 is present at the capacitor 10 , neglecting compensation processes.

The dimensioning of the smoothing capacitor 12 is determined from the pulse duty factor between the conductive and the blocked state of the switch element in accordance with the time intervals of the recharge via the first diode arrangement 11 and the discharge via the load 8 . The voltage at the load 8 must not fall below a minimum value necessary for its operation.

The dimensioning of the capacitor 10 and the winding ratio for the tap 9 of the inductor 3 is measured according to the power consumed by the load 8 , the winding ratio of the tap 9 also according to the ratio of the voltage of the source, the voltage at the consumer 6 and that for the Load 8 necessary voltage. Due to the high switching frequency of the switch element 4 and thus short recharge cycles for the smoothing capacitor 12 and the capacitor 10 , both can be dimensioned very small, which contributes significantly to the compact structure of the entire circuit arrangement. This also has the advantage of extremely low losses when supplying the load 8 , since the Zener diode 14 is always de-energized when the dimensions are correct and thus low losses occur only in the diode arrangements 11 , 13 .

In addition, if special requirements are placed on the uniformity of the voltage across the load 8 , this can be obtained by means of a control transistor 15 connected in parallel with the second diode arrangement 13 , which is controlled by the load 8 such that the voltage across the load 8 is constant. The control transistor 15 is preferably switched on in the time intervals in which the charging of the smoothing capacitor 12 takes place in such a way that from the capacitor 10 only just the amount of charge required on average for supplying the load 8 via the first diode arrangement 11 in the smoothing condensers sator 12 (and in the load 8 ) flows.

The circuit arrangement of Fig. 1 further comprises a starter circuit 16 via the smoothing capacitor 12 and the load 8 during the commissioning of the circuit arrangement, ie with initially fully discharged Glättungskonden sator 12 and provide such a capacitor 10, energy is supplied. This is particularly important if the load 8 , which forms a control circuit for the switch element 4 , is only put into operation when it is supplied with a voltage that exceeds a threshold value. When commissioning, the converter arrangement 3 , 4 is then not yet in operation, so that the smoothing capacitor 12 cannot be charged via the inductor 3 and the capacitor 10 . The starter circuit 16 comprises a voltage divider consisting of an ohmic resistor 17 and a zener diode 18 , which determines the voltage at the base connection of an npn transistor 19 , the collector connection of which was connected via a series resistor 20 to the first connection 1 of the source and the emitter connection to the smoothing capacitor 12 whose connection point is connected to the first diode arrangement 11 . When the circuit arrangement is started up, the base-emitter voltage at the npn transistor 19 is initially positive as long as the smoothing capacitor 12 is not or only slightly charged. Correspondingly, a charging current for the smoothing capacitor 12 flows through the collector-emitter path of the npn transistor 19 until the npn transistor 19 is blocked by an increase in the voltage at the smoothing capacitor 12 . The breakdown voltage of the Zener diode 18 is dimensioned such that the voltage obtained in this way at the smoothing capacitor 12 and thus at the load 8 is sufficient to activate the load 8 and thus both the consumer 6 and the load 8 via the converter arrangement 3 , 4 continue to feed with energy.

FIG. 2 shows a modification of the exemplary embodiment according to FIG. 1, in which elements which have already been explained are again provided with the same reference symbols. In addition, the exemplary embodiment according to FIG. 2 comprises a further load 21 , to which a further smoothing capacitor 22 and a further Zener diode 23 are connected in parallel. In this exemplary embodiment, the second diode arrangement 13 is connected to the connection point between the load 8 and the connection of the switch element 4 connected to it via the further load 21 . Otherwise, however, the diode arrays 11, 13 with respect to the capacitor 10 are polarized in such a manner again that via the first diode array 11 is a charge and via the second diode array 13, a discharge takes place of the capacitor 10 degrees. The load 8 is supplied with a positive voltage as in FIG. 1, while the further load 21 is now supplied with a negative supply voltage. The two loads 8 , 21 can each control a switch element; in the present case, the sketched switch element 4 is controlled by the load 8 as in FIG. 1, while the further load 21 acts on one or more further switch elements, not shown.

In the embodiment according to FIG. 2, the charging current for the capacitor 10 flows in the same manner, already described for FIG. 1, via the first diode arrangement 11 for simultaneous charging of the smoothing capacitor 12 , while the discharge current of the capacitor 10 when the switch element is switched on 4 of this no longer reaches the second diode arrangement 13 directly, but via the further smoothing capacitor 22 (and the further load 21 ), via which the circuit for the discharge current then closes again.

The starter circuit 16 is connected except for the Zener diode 18 as in Fig. 1; the Zener diode 18 is now led to the connection between the second diode arrangement 13 and the further smoothing capacitor 22 or the further load 21 instead of to the second connection 2 of the source. The Zener diode 18 is dimensioned such that the starter circuit 16 now both the smoothing capacitor 12 and the further smoothing capacitor 22 are loaded in series when the circuit arrangement is started up, the loads 8 , 21 and, if appropriate, the Zener diodes 14 , 23 being compensated for Distribution of the voltage on the two smoothing capacitors 12 , 22 can act.

In operation, the control transistor 15 , which in turn is connected in parallel to the second diode arrangement 13 , is now controlled by the additional load 21 .

Fig. 3 shows a further modification of the embodiment example of FIG. 1. Again, the elements already described are provided with identical reference numerals. In contrast to the previously described exemplary embodiments, in which the connection point between the load 8 and the connection of the switch element 4 connected to it was formed by the second, ground connection 2 of the source, this connection point is now formed by the connection between the inductor 3 and the switch element 4 is formed. With this connection point, the anode of the second diode arrangement 13 , the connection of the smoothing capacitor 12 associated with this anode, the anode of the Zener diode 14 and the emitter connection of the control transistor 15 are consequently linked, these components also having the function already described. However, the load 8 is now fed via the first diode arrangement 11 with respect to the connection point between the inductor 3 and the switch element 4 (and related to this connection point) positive voltage. The load 8 is therefore not at a fixed potential (z. B. ground) as in the previous embodiments, but is connected to the fluctuating potential of the connection point described. Such circuit arrangements are preferably used for synchronous rectifiers, for example.

In the arrangement according to FIG. 3, the charging current of the capacitor 10 is conducted via the first diode arrangement 11 into the parallel connection of the load 8 with the smoothing capacitor 12 , while the discharging current of the capacitor 10 flows via the second diode arrangement 13 . These circuits each close via the tap 9 of the inductor 3 and its part facing the switch element 4 . As in the previous figures, the polarity of the diode arrangements with respect to the capacitor 10 is also carried out in FIG. 3 in such a way that a diode arrangement is used separately for the recharging processes in the capacitor 10 for each current flow direction.

Claims (11)

1. Circuit arrangement for generating a DC supply voltage for at least one load ( 8 ) from a source that supplies a DC voltage essentially between two connections ( 1 , 2 ), with at least one consumer ( 6 ) that is fed via a converter arrangement ( 3 , 4 ) is, which contains a series circuit of an inductance ( 3 ) and a switch element, which is inserted between the connections ( 1 , 2 ) of the source, with a capacitor ( 10 ) connected to a first Diodenanord voltage ( 11 ) and the load ( 8 ) forms a series circuit which is arranged between a tap ( 9 ) of the inductance ( 3 ) and a connection of the switch element ( 4 ), with a smoothing capacitor ( 12 ) parallel to the load ( 8 ) and a second diode arrangement ( 13 ) which on the one hand is connected to the connection point between the capacitor ( 10 ) and the first diode arrangement ( 11 ) and on the other hand a coupling to the connection point between the load ( 8 ) and the connection of the switch element ( 4 ) connected to it is provided. 2. Circuit arrangement according to claim 1, characterized in that the second Diodenanord voltage ( 13 ) is galvanically connected to the connection point between the load ( 8 ) and the connection of the switch elements ( 4 ) connected to it. 3. Circuit arrangement according to claim 1 or 2, characterized in that the connection point between the load ( 8 ) and the connection of the switch element ( 4 ) connected to it is formed by a connection ( 2 ) of the source. 4. Circuit arrangement according to claim 1 or claim 3 in conjunction with claim 1, characterized in that the second Diodenanord voltage ( 13 ) with the connection point between the load ( 8 ) and the connection of the switch elements ( 4 ) connected to it via a further Load ( 21 ) is connected. 5. Circuit arrangement according to claim 4, characterized in that the further load ( 21 ), a further smoothing capacitor ( 22 ) is connected in parallel. 6. Circuit arrangement according to claim 1 or 2, characterized in that the connection point between the load ( 8 ) and the connection of the switch element ( 4 ) connected to it is formed by the connection between the inductance ( 3 ) and the switch element ( 4 ). 7. Circuit arrangement according to one of the preceding claims, characterized in that the diode arrangements (11, 13) of the capacitor (10) are polarized in such a respect that through the first diode arrangement (11) comprises a charging and over the second diode arrangement (13), a discharge of the capacitor ( 10 ) takes place. 8. Circuit arrangement according to one of the preceding claims, characterized in that a Zener diode ( 14 , 23 ) is arranged in parallel with each load ( 8 , 21 ). 9. Circuit arrangement according to one of the preceding claims, characterized in that the consumer ( 6 ) is controlled by at least one of the loads ( 8 , 21 ). 10. Circuit arrangement according to claim 9, in which the consumer of at least one of the loads ( 8 , 21 ) is switched on when the voltage at this load ( 8 , 21 ) reaches a threshold value, characterized by a starter circuit ( 16 ) for feeding the load ( 8 , 21 ) until the threshold value is reached. 11. Circuit arrangement according to one of the preceding claims, characterized by a control transistor ( 15 ) connected in parallel with the second diode arrangement ( 13 ), which is controlled by at least one of the loads ( 8 or 21 ) in such a way that the voltage (s) at the ( load (s) ( 8 or 21 ) is (are) constant.