DE2355061A1 - Inductive aerial excitation device - is used where aerial is tuned by series capacitance is energised by saturated transistors - Google Patents

Abstract

Two transformer couplings are provided between the oscillating circuit and transistors, one of which is a current transformer whose primary winding is in series with the oscillating circuit, and the secondary winding supplies driving current for oscillating circuit transistors through coupling transformers whose secondary widnings are connected to the base and emitter of the transistors. Driving current is for the positive and negative half-wave switched over by an electronic switch from the current to the coupling transformer; the end of the series circuit is connected to the centre tapping of a D.C. voltage source, while its other end is periodically connected to the voltage source positive or negative terminal. If the voltage source is not divided, the oscillating circuit capacitor consists of two halves.

Description

LICENTIA PATENT-VERWALTUNGS-GMBH. 6 Frankfurt / Ma in 70, ■ -Theo dor-Stern.-Kai 1

HH 73/33 November 1, 1973

S a / ro

"Device for exciting an inductive antenna"

The invention relates to a device for exciting a inductive antenna, which is tuned to resonance with a series capacitance and which works in saturation mode Transistors can be operated.

A battery is often used to feed such antennas. In such a case, especially if it is a non-rechargeable battery of a mobile system, it must be included a wide range of the supply voltage can be expected.

The structure of a driver circuit for the resonant circuit transistors is, however, with strongly fluctuating supply voltage with a relatively high effort and a poor degree of efficiency tied together. This disadvantage can be especially common with mobile Plants are of great importance.

This disadvantage can be avoided in a known manner if the resonant circuit transistors through transformers whose primary windings are in series with the resonant circuit, directly from the Resonant circuit are coupled to the base of the transistors. By selecting the gear ratio accordingly

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it can be achieved that the resonant circuit transistors are driven with the optimal base current at every moment will.

This solution, which is optimal in terms of effort and efficiency, is, however, a self-exciting circuit, which cannot be guided by an externally specified frequency. In addition, the resonant circuit transistors inevitably always activated during a half-wave, so that a phase control for regulating the resonant circuit current not possible. In those cases where frequency guidance and / or phase control is required the direct coupling between the resonant circuit and the transistor by means of a transformer is ruled out.

The object on which the invention is based is to be seen in creating a device for frequency guidance and phase control with the advantages of the transformer coupling between the resonant circuit and the base of the resonant circuit transistors are connected. This object is achieved according to the invention in that between the resonant circuit and transistors two transformer couplings are provided, one of which is a current transformer, its primary winding is in series with the resonant circuit and its secondary winding over the driver current for the resonant circuit transistors Coupling transformer supplies whose secondary windings are connected to the base and emitter of the resonant circuit transistors.

Further developments of the device are in the subclaims marked.

The main advantage of the device according to the invention is that an almost ideal coupling of the Schalttran--

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sistors is reached, as was previously only possible with self-excited, unregulated series resonance loops was possible.

In the drawing are exemplary embodiments according to the invention shown in principle.

Figure 1 shows the antenna resonant circuit with the excitation circuit, Figure 2 shows another type of power supply from a battery, FIG. 3 shows a circuit arrangement for avoiding the inverse. Operation of the transistors,

Figures 4 to 7 different driver circuits and Figure 8 diagrams for currents, voltages and signals.

1 and 2, the two halves of a battery are indicated in FIG. 1 The series resonant circuit consists of the resonant circuit capacitor 4 and the inductive antenna 5 »To extract the control power for the resonant circuit transistors 7 and 8, a current transformer 6 with its primary winding l4 is connected in series with the resonant circuit by coupling transformers 9 and 10. The secondary windings 17 of these transformers are connected to the bases and emitters of the resonant circuit transistors 7 and 8. The feed is via the primary winding 16 by a driver circuit which is explained in more detail with reference to FIGS.

The driver _{current X 1} for the resonant circuit transistors is fed from the secondary winding 15 of the current transformer 6 into the driver circuit.

At the end of the resonant circuit capacitor 4, the inductive Antenna 5 and the current transformer 6 existing series circuit

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is at a center tap of the two halves 1 and 2 existing battery. The other end is periodically switched to the positive resp. negative output of the battery switched.

In the exemplary embodiment according to FIG. 2, the feed takes place by the battery 3 »which is designed without a center tap. The resonant circuit capacitor is here in two equal halves 12 and 13 split.

The feed current consists of rectified half-sine waves. The alternating current component contained therein is partly short-circuited by the capacitor 11.

If both transistors are blocked at the same time when the phase control is used, transistor 8 (7) is operated inversely when the resonant circuit current i is positive (negative). Even if the switching of the resonant circuit transistors does not occur in an instant when the frequency is external
an inverse operation comes about «

Resonant circuit transistors does not occur in the zero crossing of i,

Since the inversely operated transistor has a high reverse recovery ■ time, it occurs when the current passes over to the opposite one Transistor to harmful current spikes.

According to FIG. 3, the freewheeling diodes k5 and 46 are used to avoid the inverse operation. With these alone, however, the inverse operation is not completely prevented, since the transistors 7 and 8 are not during the entire time in which an inverse operation is possible within a period , are biased by a positive base emitter voltage.

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It is therefore customary in such a case to use a diode in each collector circuit to control the inverse current direction; To block. However, this results in additional "diode flux losses, which can be reduced to approximately 10% by using a diode 4 parallel to a capacitor 48 ± n series with the secondary winding 17 of the coupling transformers 9 and 10 instead of using collector diodes, whereby a negative base bias of about 0.4 volts to 1 volt is built up, which is sufficient to completely prevent the inverse operation.

In this context, the known options for implementing the series resonance circuit should be mentioned:

The resonance circuit can also be in a bridge circuit with four diagonally driven transistors are arranged. A matching transformer can be installed between the resonant circuit and the resonant circuit transistors be arranged.

The primary winding of the adapter transformer can be in a Bridge circuit to be arranged "

The matching transformer can also be operated in push-pull connection. In this case there are only two oscillating circuit transistors necessary.

The driver circuits shown in Figures 4 to 7 » are suitable for each of the above embodiments of the antenna resonant circuit with excitation circuit.

In the driver circuit according to Figure 4, the secondary current I. of the current transformer 6 via the driver transistor pair 18/19 perio-

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disconnected to the coupling transmitter 9 and 20 or over the short-circuit traiisistor pair 20/21 short-circuited. The collector diodes 22, 23, 24 and 25 prevent inverse operation. Both transistors in a pair are controlled or blocked at the same time. The blocking phases of both couples are allowed do not overlap so that the secondary circuit of the current transformer remains closed. Which of the two coupling transformers 9 or 10 is current when the driver transistor pair is controlled leads, depends on the polarity of the current i ^.

The switching frequency of the electronic switches can be specified externally (externally controlled) as well as with the natural frequency of the resonant circuit formed from the inductive antenna and the series capacitance are synchronized (self-guided).

To accommodate the inductive switch-off routine in the primary winding The diode 26 and the Zener diode 27 are used for the coupling transmitter.

It is also possible to implement the frequency control and / or phase control only by controlling a half-wave of the resonant circuit current i ₀ . If, for example, only the positive half-wave is controlled, the resonant circuit transistor 8 remains controlled during the entire negative half-wave and the transistor 20, the diode 2k and the circuitry of the transformer 10 consisting of diode 26 and Zener diode 27 can then be omitted. The transistor 18 is replaced by a short circuit (collector-emitter).

The driver circuit according to FIG. 5 is modified in such a way that the secondary current i. of the current transformer from the diode bridge 31-33 is rectified. As a result, here is in opposition

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for the exemplary embodiment according to FIG. k, the control of the resonant circuit transistors is no longer permanently assigned to the current direction of i_ _t but rather to the driver transistors 37, 3 ^. The control of these driver transistors must therefore take place in a complementary manner over a current conduction angle of max. _

While both driver transistors are blocked, the flows impressed, rectified secondary current in the voltage source 36. Compared to that used in the example according to FIG Procedure to short-circuit the secondary current has this measure the following advantages: -

The effort for the short circuit was omitted The circuit does not depend on the correct switching of the short-circuit transistor.

Also less the power for the resonant circuit transistors The resonant circuit is removed, a supply voltage source is less for the control of the driver transistors Performance required. This can take over the function of the voltage source 36.

The starting resistor 35 supplies the current required to fan the resonant circuit. About 1 - 5% of the secondary current i »flowing in normal operation is sufficient for this.

In the driver circuit according to FIG. 6, as in the example according to Figure 4t, the control of the resonant circuit transistors fixed to the, Direction of current assigned by i_. During the joint lock · » phase of both resonant circuit transistors, the secondary current flows of the current transformer via the voltage source 36. The connections of the coupling transformers are shown in the examples according to FIGS Figure 6 identical

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The driver circuits according to FIGS. K and 6 are not readily suitable for fanning the resonant circuit. Furthermore, all previously described driver circuits can only work in unipolar operation of the coupling transmitter. Therefore, only about 20 to 30 % of their voltage-time area can be used, which led to relatively large type dimensions for the given transformer power.

These deficiencies can now be remedied by _{smoothing the impressed 8} rectified® secondary current of the current transformer and routing it via j © a® reverse magnetization winding of the coupling transformer. Such a circuit arrangement is shown in FIG. Compared to the embodiment according to FIG. 5 , it has two coupling transformers 28, 29 with an additional reverse magnetization winding 42 ₉ which has about 5 to 10 % of the turns of the primary winding 16. The back τ magnetization windings of both transformers are connected in series with the smoothing choke 43 and absorb the direct current component of the secondary current. The alternating current component flows through the capacitor 44. This is parallel to a series circuit formed from a choke 43 and the back magnetization windings 42.

In the diagram according to Figure 8:

i i resonant circuit current

A; Blanking signal (L = both resonant circuit transistors

locked)

CE8 t collector-emitter voltage of transistor 8

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± _c , η : collector current of transistor 7/8 with parallel

Free-wheeling diode Sum of collector and diode current

^U EB ' ^: base-emitter voltage of the transistor i.

The off tasi: signal A can be supplied, for example, by a controller which _{regulates the resonant circuit current i Q} or the resonant circuit voltage. If the frequency of the blanking signal A does not match the resonance frequency, it is asymmetrical to the zero crossing of i _n>

In the case of driver circuits according to FIGS. K and 6, frequency control is only possible by means of a blanking signal. In the case of driver circuits according to FIGS. 5 and 7, on the other hand, guidance is also conceivable without a blanking signal.

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Claims (8)

HH 73/33 PATENT CLAIMS 1. / device for exciting an inductive antenna, which is ^{tuned to resonance with v} - a series capacitance and can be operated with transistors operating in saturation mode, characterized in that two transformer couplings (9 , IO) are provided, one of which is a current transformer (6) whose primary winding (l4) is in series with the resonant circuit (4, 5) and whose secondary winding (15) transfers the driver current for the resonant circuit transistors (7 »8) Coupling transformer (9, 10) supplies whose secondary windings (1?) Are connected to the base and emitter of the resonant circuit transistors (7, 8). 2. Device according to claim 1, characterized in that the switching of the driver current from the current transformer (6) to the Coupling transformer (9, 10) for the positive or negative Half-wave takes place with the help of an electronic switch. 3. Device according to claim 1, characterized in that one end of the series circuit at the center tap of a DC voltage source consisting of two halves, while the other end is periodically switched to the positive or negative output of the DC voltage source is switched. k . Device according to Claim 1, characterized in that, with an undivided DC voltage source, the resonant circuit capacitor consists of two identical halves (12, 13) (Fig. 2). 5. Device according to claim 1, characterized in that for Avoiding an inverse operation of the transistors (7, 8) in series with the control winding from a parallel connection a diode (47) and a capacitor (48) is placed. (Fig. 3) 509820/0494 -11- HH 73/33 '■ ■ ": 6. Device according to claim I _9, characterized in that the impressed _s. Rectified secondary _{current Ci 1.} ) Of the current transformer (6) is smoothed via a throttle (4 "3) and via each eirte reverse magnetization winding (42) of the coupling transformer (28, 29) (Fig. 7) 7 · Device according to claim 6, characterized in that the alternating current component of the secondary current via a Capacitor (44) flows, the. parallel to one, from one DrοsseIspule (43) and the Rückma gneti sierungswickrungen (42) formed series connection (Figo 7) 8. Device according to claim 2, characterized in that the electronic switch ₉ operates at a Umschal.tfrequenz, both specified externally (separately performed) as well as with the natural frequency of - from inductive antenna (5) and Serienkäpazität. (4) formed resonant circuit is synchronized (self-guided). 509820/019 Λ