JPH0748353B2 - Magnetron power supply circuit - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an improved power supply circuit for energizing a magnetron, and more particularly to a power supply for achieving a regulated output with a low ripple component. It is about circuits.

Prior Art U.S. Pat. No. 4,175,246 (Feinberg et al.) Discloses a power supply circuit for a magnetron, often referred to as a double half wave voltage doubler. This circuit uses two relatively low cost leakage reactance transformers as opposed to using one large and fairly expensive transformer, and more than using a single transformer. In terms of generating a peak magnetron current that is not too large,
This is an advantage compared with the prior art.

The circuit of U.S. Pat. No. 4,175,246 has several drawbacks. For example, the ripple component of the load current may be too large. Since this circuit is a double voltage multiplier, it only produces two half cycles of load current per cycle, which reaches its peak value and drops to zero.

The substantial ripple component produced by this voltage doubler circuit is a band of blurred frequencies produced by the magnetron, instead of a sharply tuned spectral output. Furthermore, the substantial value of the peak current obtained may cause premature defects in the magnetron due to moding.

The present invention has been made in view of the above points, and an object of the present invention is to provide a power supply circuit for a magnetron having a low ripple component.

Configuration According to the present invention, there is provided a three-phase half-wave voltage doubler which eliminates the above-mentioned drawbacks. 3 displaced from each other by 120 °
By superimposing two waveforms, the three-phase half-wave voltage doubler of the present invention provides a regulated load current that has a significantly small ripple component and does not have a peak value as high as in the prior art and does not drop to zero. Supply. This is
It tunes the magnetron more sharply and reduces the possibility of moding and performance degradation.

According to the present invention, a circuit is provided that uses three separate transformers of high leakage reactance type. The primary sides of the transformers are interconnected in a three-phase fashion, while their secondary sides are connected via respective capacitors to blocking diode means, which blocking diode means are connected to the magnetron. .

The resulting magnetron current has a large number of current excursions per cycle, compared to only two half-cycles in the prior art, and substantially reduces the ripple factor. It is possible.

Examples Hereinafter, specific embodiments of the present invention will be described in detail with reference to the accompanying drawings.

The conventional circuit of FIG. 1 is described in the above-mentioned US Pat. No. 4,175,246. This circuit uses two relatively inexpensive transformers 2 and 4 of the leakage reactance type.

The magnetron which this power supply circuit energizes is shown at 6, and it has an anode 8 and a cathode 12 which are grounded at 10.

The secondary windings 14 and 16 of the transformer are connected as shown, and their connecting common terminal 18 is grounded. The feedback path rectifiers 20 and 22 are connected in opposite directions so that the series capacitors 24 and 26 charge in a direction that is phasewise opposite to the polarity of the secondary winding, as indicated by the polarity dot. Rectifiers 28 and 29 commonly connect their anodes to cathode 12.

The magnetron current obtained with the circuit of FIG. 1 is shown in FIG. Two current loops are obtained per cycle, and this current drops to zero between those loops.

FIG. 3 schematically shows the circuit of the invention, which uses three physically separate transformers 30, 32, 34, each of which has a high leakage reactance or It is an iron resonance type. The primary windings of these transformers are interconnected in a three phase fashion and are supplied by a three phase power supply, such as a 208V power supply at 60Hz.

The secondary winding is connected to one end of each capacitor 36, 38, 40, and the other end of each capacitor is connected to each diode 42, 44, 46. The other ends of these diodes are connected to ground, while the diodes 50, 52, 54 are connected between the diodes 42, 44, 46 and the cathode of the magnetron.

The circuit of FIG. 3 achieves balanced operation and produces the load current waveform shown in FIG. As can be seen with reference to FIG. 4, the three-phase version of the present invention has multiple loops per cycle and produces load currents with significantly reduced ripple over conventional ones. Moreover, the current does not drop to zero level between the loops and always maintains a positive value.

FIG. 5 shows a superimposed state of the waveform A obtained by the voltage doubler circuit of FIG. 1 and the waveform B obtained by the circuit of the present invention. The ripple obtained by the present invention is significantly smaller than that obtained by the prior art and is always a positive value.

Since the ripple is reduced, the range of output frequencies for the magnetron is smaller, making it easier to tune the magnetron. This means that FIG. 7 showing the magnetron spectrum obtained by the circuit of the present invention is
No. 6 showing the magnetron spectrum obtained by the prior art
It can be better understood by comparing with the figure. In the case of the present invention, the magnetron can be tuned more sharply, and as a result, the operation of the microwave lamp driven by the magnetron can be made more efficient.

Moreover, under the same power conditions, the invention allows for a smaller transformer than that in the circuit of FIG. 1, and has lower ripple and current drops to zero level. That is, the fact that there is less flicker in the light emitting state of the microwave power source. Furthermore, the higher peak currents tend to cause magnetron modding, so the reduced peak current values obtained with the circuit of the present invention reduce the problem of modding. .

Although specific embodiments of the present invention have been described above in detail, the present invention should not be limited to these specific examples, and various modifications can be made without departing from the technical scope of the present invention. It is a matter of course.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a conventional circuit, FIG. 2 is a graph diagram showing a load current obtained by the circuit of FIG. 1, and FIG. 3 is a circuit constructed according to an embodiment of the present invention. 4 is a schematic diagram showing the load current obtained by the circuit of the present invention, and FIG. 5 shows the load current obtained by the circuit of FIG. 1 and the load current obtained by the circuit of the present invention. FIG. 6 is a graph showing the superimposed state, FIG. 6 is a graph showing the magnetron output spectrum obtained in a circuit with large ripples, and FIG.
The figure is a graph showing a magnetron output spectrum obtained by the circuit of the present invention. (Explanation of symbols) 2,4: Transformer 6: Magnetron 8: Anode 10: Ground 12: Cathode 14, 16: Secondary winding of transformer 18: Common terminal 20, 22: Rectifier 24, 26: Capacitor 28, 29: Rectifier 30,32,34: Transformer 36,38,40: Capacitor 42,44,46: Diode 50,52,54: Diode

Claims (4)

[Claims] 1. A magnetron power supply circuit comprising: a) three leaky reactance type transformers each having a primary side and a secondary side, each having a first lead and a second lead; and (1) the transformer. The primary sides of which are three-phase connected to each other to provide three leads for connection to a three-phase power source, and (2) the same polarity first secondary side leads of the transformer are commonly connected, b) three capacitors, one end of each of which is connected to a secondary lead of one of the three transformers, and c) one of each of the three capacitors, each other Three first diode means connected between an end and a common connection of the first secondary side lead, d) a magnetron, e) connected between the first diode means and the magnetron 3 second diode means A magnetron power supply circuit comprising: 2. The magnetron according to claim 1, wherein the magnetron has an anode and a cathode, the common connection portion is grounded, and the anode of the magnetron is also grounded. Characteristic magnetron power supply circuit. 3. The method according to claim 2, wherein
The diode means is connected to the cathode of the magnetron, the first diode means is connected in a polarity such that its conduction direction is toward ground, and the second diode means is connected in its conduction direction. A magnetron power supply circuit, wherein the magnetron power supply circuit is connected so as to be directed to the first diode means. 4. The magnetron power supply circuit according to claim 4, wherein the three transformers are physically separate from each other.