GB2123225A - Pulse power source device - Google Patents

Abstract

A pulse power source device which can supply a pulse power output, the pulse width of which is controlled to be selectively large or small, comprises two oscillation circuits (1, 2) to one of which a timing pulse having a desired delay time is provided from a delay circuit (3) and two square-wave inverters (4, 5) respectively connected to each of the oscillation circuits (1, 2) to receive outputs from the circuits. The inverters receive timing pulses having between them a delay-time and generate square waves which, after combination in a secondary winding (10) coupled to transformers (6, 7), provide power pulses of a pulse width depending on the phase difference between the timing pulses during periods in which the respective timing pulses for the two inverters are both positive or negative, whereby a supply of specifically a large power output of a small pulse width is made possible. <IMAGE>

Description

SPECIFICATION Pulse power source device This invention relates generally to pulse power source devices and, more specifically, to a pulse power source device which can generate a pulse power output of controlled pulse width for use in, for example, electrolytic formation and color development of oxidized anti-corrosive coats on aluminium material.

In obtaining such coated aluminium, generally, there has been a method in which an electrolysis is performed with an aqueous solution of oxalic acid, chromic acid or the like in which an aluminium material is dipped as the anode to have its surface oxidized to form an anti-corrosive coat. In developing or varying the thickness and color of the coat during the anodic oxidation coat formation, on the other hand, the pulse width of a direct current voltage supplied to the anode and opposing cathode during the electrolysis is optimumly varied to be, for example, effectively small.

The present invention aims to provide a pulse power source device which can supply a pulse power output the pulse width of which can be selectively controlled to be large or small.

Another aim of the present invention is to provide a pulse power source device which can make the pulse width of its output to be effectively small even when transistors are employed as arranged in, for example, Darlington circuit for a larger power generation normally resulting in a relatively large pulse width.

According to the invention, there is provided a pulse power source device comprising two oscillation circuits to one of which a timing pulse having a desired delay time is provided, two square-wave inverters respectively connected to each of said oscillation circuits to receive outputs from the circuits, two primary windings respectively wound on each of separate cores and respectively connected to each of said inverters to receive outputs therefrom, and a secondary winding magnetically coupled to said cores on which said two primary windings are wound.

Preferably, the output of the other of said oscillation circuits is partly supplied to a delay circuit, and said timing pulse having said desired delay time is applied from said delay circuit to the said one oscillation circuit. The delay circuit may comprise a timer or a one-shot multivibrator.

The secondary winding may be divided into two which are connected in series with each other and a rectifying circuit may, if desired, be connected to the secondary winding.

The invention will now be further described, by way of example, with reference to the drawings, in which Figures 1A and 18 are diagrams for explaining the operation of general transistors; Figure 2 shows a circuit in a block diagram of one embodiment of a pulse power source device according to the present invention; Figure 3 is a detailed circuit of a practical example of the embodiment shown in Figure 2; and Figures 4Aand 4B are output waveforms appearing at various points in the circuit shown in Figure 2.

Reference will be first made to the general operation of transistors for a better understanding of the invention. Referring to Figures 1A and 1B, an input to the base of a transistor is shown in Figure 1A, while a corresponding transient response of the transistor to the base input, i.e. variations in the collector current, is shown in Figure 1 B. More specifically, the transistor is conducted when an input as shown in Figure 1A is applied to the base of the transistor, due to which the collector current starts to rise with delay from a time tl at which the base input rises and this collector current starts to fall after a fixed period from a time t2 at which the base input falls.That is, as illustrated in Figure 1 B, the collector current is caused to flow in response to the base input, with a delay period td, rising period tr, constant period tc, storing period ts (the time length of which is shown as somewhat exaggerated in Figure 1 B) and falling period tf.

In this case, the storing period ts is, as seen in the drawing, of a duration from the falling time t2 of the base input to the fall starting time of the collector current and, while this duration is relatively long and its initiation is determined by the base input falling time t2, the length itself is substantially constant. In other words, it has been possible to shorten the time length during which the collector current flows by reducing the period between the rising time t1 and the falling time t2 of the base input, but it has not been possible to vary the storing period ts.As a result, it has been impossible to obtain an output of a selectively large or small pulse width only by means of the general transistors, and the provision of a pulse power source device capable of freely controlling the pulse width has been demanded specifically in the field of electrolytic formation and color development of an oxidation coat on aluminium material, in which a pulse output of a large power and a small pulse width has been required.

Referring to Figure 2, there is shown an embodiment of a pulse power source device according to the present invention which can freely control its output pulse width. According to the present invention, the device comprises two inverters respective outputs of which are combined through a transformer and the pulse width of the resultant output of which is freely controlled by varying mutual oscilla tion'phase difference of the inverters, regardless of the length of the storing period of the collector current of the transistor.

More particularly, the pulse power source device according to the present invention includes two oscillation circuits 1 and 2. An output of the oscillation circuit 1 is partly provided to a delay circuit 3 such as a timer or one-shot multivibratorwhich provides an optimum timing signal to the other oscillation circuit 2. Therefore, the delay time made variable by the delay cicuit 3 provides a variable phase difference between the oscillation circuits 1 and 2. The outputs of the oscillation circuits 1 and 2 are also connected to respective push-pull type square-wave inverters 4 and 5 which are connected at their output terminals respectively to each of primary windings 8 and 9 on separate cores 6 and 7 of the transformer.It will be readily appreciated by those skilled in the art that, since the inverters 4 and 5 are of push-pull type, intermediate taps of the primary windings 8 and 9 are connected to the positive side of a power source.

On the other hand, a secondary winding 10 is wound on the cores 6 and 7 so as to be magnetically coupled to them. In this connection, separate secondary windings may be wound in series with each other on the cores 6 and 7 as in the case of the primary windings 8 and 9. Further, the secondary winding 10 is connected to a rectifying circuit 11.

Figure 3 shows a detailed circuit arrangement of a major part of Figure 2, in which blocks corresponding to those in Figure 2 are shown as encircled by broken lines and identified by the same reference numerals as in Figure 2, and its circuit arrangement will be self-explanatory. In the present instance, as will be easily understood by those skilled in the art, the circuit arrangement is not limited only to the one shown in Figure 3 but may be of any other arrangement which achieves the same functions and, if necessary, any proper circuit can be attached to the device for higher accuracy or higher level achievement.

Referring next in detail to the operation of the pulse power source device according to the present invention with reference to Figures 4A and 4B, the output of the oscillation circuit 1 is partly sent to the delay circuit 3 by means of a timing pulse of such waveform as V1, while the delay circuit 3 provides to the other oscillator 2 a timing pulse V2 of the same waveform as V1 but involving a delay time T with respect to V1. On the other hand, signals V4 and V5 are applied to the inverters 4 and 5 respectively from the oscillators 1 and 2 to which the timing pulse V1 and delayed timing pulse V2 are supplied, so that the oscillators 1 and 2 will oscillate mutually with a fixed phase difference.

The inverters 4 and 5 receiving the signals V4 and V5 are thereby driven to provide such square wave outputs as shown by V8 and V9 to the primary windings 8 and 9, respectively. When the outputs of the inverters 4 and 5 are mutually of opposite polarity, no output appears in the secondary winding 10 because outputs induced in the winding 10 are cancelled by each other but, during periods in which the inverter outputs are both positive or negative concurrently, there is generated a pulse output as shown byV10 ofwhich the pulse width corresponds to the phase difference between the inverters 4 and 5. The pulse output V10 is sent to the rectified circuit 11 where such a pulse output as shown by V0 having, for example, only positive polarity is generated.When it is desired to obtain a pulse output having both positive and negative polarities, the rectifier 11 may be omitted.

In the outputs of the inverters 4 and 5, there are contained the storing period ts of the transistor as has been described in connection with Figure 1 B, but the pulse width of the signal induced in the secondary winding 10 is determined solely by the phase difference between the inverters 4 and 5. As a result, by varying the phase difference between the inverters 4 and 5, that is, by adjusting the delay time T of the timing pulse to be supplied to the oscillator 2, an output having a pulse width considerably smaller than the transistor's storing period ts can be obtained. In this case, the resultant pulse output still contains the rising period trand falling period tfof the transistor as shown in Figure 1 B, but they are negligibly smaller than the storing period ts.

As has been disclosed, the pulse power source device according to the present invention can effectively control the pulse width of the output power so that a pulse power output of a considerably smaller pulse width than, for example, the storing period ts of the transistor can be supplied. Therefore, even in the case when the pulse power source device is arranged with transistors of the Darlington circuit for supplying a large power output in which event the storing period ts becomes considerably larger due to the large power, the output pulse width can be sufficiently controlled so as to be able to provide a large power which is still small in pulse width, which is highly useful in particular as a source power employed in the electrolytic formation and color development of oxide coated aluminium. Further, when the winding ratio of the primary and secondary windings is properly selected, it is possible to obtain a large power output with a low source voltage.

It will be also readily appreciated by those skilled in the art that the pulse power source device of the present invention can be applied to other cases than the electrolytic formation and color development of oxide coated aluminium.

Claims (7)

1. A pulse power source device comprising two oscillation circuits to one which a timing pulse having a desired delay time is provided, two squarewave inverters respectively connected to each of said oscillation circuits to receive outputs from the circuits, two primary windings respectively wound on each of separate cores and respectively connected to each of said inverters to receive outputs therefrom, and a secondary winding magnetically coupled to said cores on which said two primary windings are wound.

2. A device according to claim 1, wherein the output of the other of said oscillation circuits is partly supplied to a delay circuit, and said timing pulse having said desired delay time is applied from said delay circuit to the said one oscillation circuit.

3. A device according to claim 2, wherein said delay circuit is a timer.

4. A device according to claim 2, wherein said delay circuit is a one-shot multivibrator.

5. A device according to any preceding claim, wherein said secondary winding is divided into two which are connected in series with each other.

6. A device according to any preceding claim, wherein a rectifying circuit is connected to said secondary winding.

7. A pulse power source device substantially as described herein with reference to the drawings.