JPS5943910B2 - Multilayer flyback transformer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a flyback transformer used to generate high rectified voltage in television receivers and the like, and in particular to a flyback transformer in which the windings are divided by diodes and the windings are wound in multilayer windings. The present invention relates to a flyback transformer that suppresses the voltage applied to the diode as much as possible in a transformer.

Generally, equipment that requires high voltage, such as the anode electrode of a picture tube in a television receiver, uses a so-called flyback transformer to step up a predetermined pulse and smooth it to generate a high voltage. use

For example, in a television receiver, horizontal output pulses are applied to the primary side, and the pulses applied to the primary side are boosted and smoothed by a secondary winding consisting of alternating diodes and windings. A flyback transformer is used to obtain high voltage.

In this method, the secondary winding is divided by a diode,
Each of the divided secondary windings (sections) is arranged on the same bobbin in isolation via a diode, and the distributed capacitance between the sections is reduced as much as possible to reduce odd harmonics of the fundamental wave (e.g. It is generally used as a so-called tuned flyback transformer that obtains high voltage by tuning to the third harmonic. In such a tuned flyback transformer,
Although it has the advantage of efficiently generating high voltage, it has the disadvantage of poor regulation of the resulting high voltage. In television receivers, if the regulation of high voltage is poor, the problem arises that brightness and focusing are affected, resulting in deterioration of reproduced images. To deal with this, a multilayer flyback transformer with stable high voltage regulation has been considered, in which the secondary winding is divided by a diode and the secondary winding is multilayered. . The multilayer winding flyback transformer C is different from the above-mentioned tunable flyback transformer, as shown in FIG.
The structure has a coil wound around each of the coils, and the diodes interposed between each winding are arranged all together on the outermost bobbin, and the winding start and winding end of each winding layer are at the predetermined positions of the diodes located on the outermost bobbin. A conductive wire is connected to each electrode. In a multilayer flyback transformer with such a configuration, since each winding layer is close to each other, the free capacitance between each winding layer is significantly larger than that of the above-mentioned tuned flyback transformer. Although it has little effect on obtaining high voltage by tuning its third harmonic, etc., on the other hand, the regulation of the high voltage generated is excellent, which is a basic requirement for equipment such as alleviation receivers that require high voltage. Satisfies the high voltage stability required. (Such a multilayer flyback transformer is described, for example, in British Patent No. 1,090,995.) At the same time, multilayer flyback transformers suffer from problems such as the lack of capacitance between each winding layer as described above. There is a problem in that an excessive voltage in the reverse breakdown voltage direction is applied to the diode interposed between each winding layer, and the diode is damaged. Moreover, since the reverse voltage applied to each diode is not uniform, the diodes must be operated under harsh conditions to fully utilize the function of the multilayer flyback transformer, which has excellent regulation of the generated high voltage. It is necessary to maintain its function as a flyback transformer without damage. This problem becomes particularly problematic when a multilayer flyback transformer is used in a high voltage generating circuit of a television receiver, and when intratubular discharge occurs within the picture tube. The present invention solves the above-mentioned problems and provides a multilayer flyback transformer that can maintain its function without being damaged even under severe conditions such as a short circuit at the output end. With the goal.

The present invention will be explained below with reference to the drawings. As mentioned above, a multilayer flyback transformer has a secondary winding divided by a diode, and each divided secondary winding is multilayered. It is characterized by being wound in layers.

Figure 2 is a schematic diagram to explain how the pulses supplied from the primary side to the output of such a multilayer flyback transformer are stepped up and a high voltage is generated. The primary winding to which the pulse is applied and the secondary winding are the winding layer Lnl diode Dn (n-1, 2, 3, 4
) are connected in series 9, and each winding layer is arranged coaxially. Now, when a pulse P is applied to the primary winding Lp, a pulse PLl is generated in the secondary winding L1, and this pulse PLl is rectified by the stray capacitance between the cathode side of the diode D1 and the ground. and generates a DC voltage whose level is approximately zero.

Then, the primary winding Lp (in response to the FC, the secondary winding L
2, a pulse PL2 is induced, and the induced pulse PL
2 is superimposed on the DC voltage V1 obtained by rectifying the pulse PLl on the cathode side of the diode D1. Then, the pulse PL2 generated in the secondary winding L2, which is superimposed on the DC voltage V1, is rectified by the cathode C on the diode D2 side, and a DC voltage having a level of V2 is generated on the cathode side of the diode D2. The pulses thus induced in the winding Ln are passed through the diode D.

A constant DC voltage is obtained by further rectification, and a pulse induced in the winding Ln+1 is superimposed on this DC voltage to sequentially obtain a high voltage. As a result, the pulse PL4 is smoothed by the capacitance existing on the cathode side of the diode D4, and the pulse P supplied to the primary winding side is finally boosted to a predetermined value. High DC voltage VOUT (=ET
I) is obtained. In the above description, it was stated that the rectification effect occurs when the capacitance on the cathode side of the diode in the secondary winding and the diode intersect, but there is actually a capacitance on the anode side of the diode. The figure shows this situation.For example, there is a capacitance of ℃ between the cathode of diode 1 and the ground.

However, there is a capacitance between the anode of the diode D2 and the ground. Therefore, a positive direction pulse PVA appears on the anode side of the diode D2, and a negative direction pulse PVK appears on the cathode side of the diode D1, but the ratio of the capacitances CK and CA is the peak value PVA. ! :． Since it is equal to the ratio with PVK, by using this relationship and observing the peak value of the positive direction pulse and the peak value of the negative direction pulse for each diode, the capacitance CK and CA can be found. . Therefore, it is possible to grasp the capacitance between both electrodes of each diode and the ground, and the secondary winding Ll,
Each of L2, L3, and L4 can be regarded as an independent transformer in terms of alternating current with respect to the primary winding, and as mentioned above, in terms of direct current, the capacitance on the cathode side of each diode and the level of direct current rectified by each diode The voltages are superimposed.

In this way, the obtained DC voltage is sequentially superimposed on the secondary winding divided by diodes to obtain a predetermined DC high voltage, which is almost the same as the so-called tuned flyback transformer described above. While a type flyback transformer minimizes the capacitance between the windings and tunes to low-order odd-numbered harmonics such as the third order of the fundamental wave, the multilayer flyback transformer according to the present invention has a Next winding Ll, L2, L
3. Place L4 close to each other concentrically to increase the capacitance between the secondary windings, and improve the regulation of the generated high voltage without tuning to the lower odd-order harmonics of the fundamental wave. The essential difference in this point is the same as the above.

In other words, in a multilayer flyback transformer, it is necessary to check the capacitance between the valley windings of the secondary winding, and at the same time to prevent the diode from being damaged even if, for example, an internal discharge occurs in the picture tube. Yes, diode breakdown voltage, 2 each
Sufficient consideration must be given to the capacitance between the next windings, etc.

This problem peculiar to multilayer winding flyback transformers is solved by the present invention, and this point will be explained in detail below. In FIGS. 2 and 3, in order to explain the basic step-up operation of a multilayer flyback transformer, the interlayer capacitance that occurs between the secondary windings in a multilayer flyback transformer is ignored for convenience, but in FIG. A multi-layer winding flyback transformer differs from a tuned flyback transformer in that V) the capacitance between each winding layer is created by arranging the winding layers of each winding on the secondary side close to each other to suppress tuning with lower-order odd harmonics. The second method takes into account
Portions Vc that are the same as those in the figure are given the same reference numerals.

To explain FIG. 4, Lp in the figure is the primary winding, and VC between the winding layers L1 to L4 of the secondary winding is the diode Dl, O.
A diode D4 is connected to the winding end D of the winding layer L4, and the capacitance C between this diode V4 and the cathode side of the diode D4 and the ground (in the case of a television receiver, (usually about 1000 PF) to obtain a predetermined high DC voltage.

In the same figure, CKi and CAi represent the capacitance between the cathode and the ground of the diode Di, and the capacitance between the anode and the ground, respectively (i=1, 2, 3, 4). Furthermore, C, j, and Cij represent the interlayer capacitance between the winding start portion of the winding layer and the interlayer capacitance between the winding end v of the winding layer, respectively (i=1, 2, 3, j=i+
l). In FIG. 4, if a pulse of V1-) is obtained at the end of the winding layer L1 in response to the pulse supplied to the primary winding layer L1, then the cathode side of the diode D is A DC voltage is generated A, and the winding layers L2, L3, L
At the end of winding 4, a pulse of approximately: is obtained as in the end of winding υ of the winding layer L1.

Then, at each of the power nodes of diodes D2 and i)3, a DC level voltage of is generated by the same principle as explained in FIG. 2, and at the DC voltage -EH generated at the cathode of diode D3, , the 21 pulses obtained in the winding A layer L4 are superimposed, and the pulse (anode voltage of diode D4) obtained by superimposing the DC voltage ÷ EH is the capacitance C between the cathode of diode D4 and the ground. etc., and generates a high DC voltage of EH as an output.

In addition, as mentioned above, in a multilayer winding flyback transformer (
(Compared to the case of a tuned flyback transformer), the interlayer capacitance C', which is the comparatively small Asahi capacitance value between each winding layer. ．． ,C
．． ．． Therefore, it is not tuned to low-order IJIJ odd harmonics with respect to the fundamental wave, and therefore a DC high voltage with excellent regulation can be obtained under normal conditions.

Note that during normal operation, the voltage across the capacitor CAI is approximately zero because a 2L pulse with a horizontal period (the DC level is approximately zero) is applied. However, in a multilayer flyback transformer, the interlayer capacitance is small.
This corresponds to the case where 0 is closed.

), an excessive reverse voltage may be applied to the diode and the flyback transformer may be damaged, making it difficult to set the interlayer capacitance and withstand voltage of each diode. Therefore, it is necessary to consider the voltage applied to the diode regarding the internal discharge of the picture tube (when the switch 10 is closed). -CCVO QF) -Cove ゜ ゜ ゜ ゜ ゜ ゜ ゜ (1 No ... (3) ... (4) =VlEH
(1), and assuming that CA=CR-CC=C1, the above equation 12 can be rewritten as the following equation 13.

(-ノ~ And, From the above formula 13, To solve for VA′, character.

Then, FLH-α...(self) is obtained.

Similarly, find VC/, VT)/, and the anode voltage D3A (=VA') of diode D3 is D3A=
LH-7α... (self) The anode voltage D2AEH of diode D2 is D2A-VO'+VO'1-1β.
...16), similarly, the anode voltage DlA of the A diode D1 (1iD1A=VO'=?Sδ...
...(J7)C is given.

By the way, as described above, the reverse voltage Dri(1-1, 2, 3) applied to the cathode side of the diodes Dl, D2, and D3 is applied to the capacitance on the cathode side, that is, the diode D.
) is shown by the following equations 18, 19, and 20. Diode D
Reverse voltage applied to diode D2 Reverse voltage applied to diode D3 In equations 18, 19, and 20 above, α, β, and δ are interlayer capacitances C. Figure 6 shows the relationship when the horizontal axis is the interlayer capacitance C1 and the vertical axis is the reverse voltage applied to the diode. As can be seen from the figure, as the interlayer capacitance increases, the reverse voltage applied to the diode increases, and when the load side is short-circuited, the maximum withstand voltage is applied to the diode D3, which is close to the output diode D4. be done.

Considering these facts, multilayer winding flyback transformers in which the secondary winding is divided by diodes have a phenomenon in which the diodes are damaged due to interlayer capacitance, but if the diodes are damaged due to short circuits on the load side, etc. In order to maintain the function of the flyback transformer without any loss even under the harsh conditions of As can be seen, it is sufficient to use diodes D3, D2, and D, which have different reverse resistances in this order.

The present invention utilizes the above analysis results, and FIG. 7 shows a specific example of reducing the line capacitance and reducing the reverse voltage applied to the diode. It is characterized by being irregular.

That is, in FIG. 7, the winding layer L and the winding layer L adjacent thereto
It is connected to the anode side of the diode nI-1, and by making the winding ends uneven and varying the lengths of the winding layers in the bobbin direction, the interlayer capacitance between the winding layers L and NL+1 is reduced, and n is applied to each diode. This suppresses the reverse voltage generated by the transformer, prevents damage to the diode, and maintains the function of the flyback transformer.

In addition, the effective capacitance between the cathode lead wires of diodes D3 and D4 is increased, and the potential on the cathode side of diode D3, which is easily damaged, is lowered by increasing the effective capacitance between the cathode lead wires of diode D3 and the cathode side of diode D3, which is easily damaged in the event of a short circuit on the load side. To protect D3, for example, as shown in FIG.
A diode D located outside the outermost winding layer L4 of ~L4
Grooves 12,
12, and metal plates 13 may be arranged between the grooves 12, 12 and the lead wires on the cathode side of the diodes D3 to D4, respectively.

9. According to the embodiment shown in FIG. 8, the cathode side of the diode D3, which is connected to the winding start of the winding layer L4 and has a DC potential of -EH during normal operation, and the cathode side of the diode L4 are connected to the winding start part of the winding layer L4. The metal plate forms an effective capacitor for discharging the electric charge accumulated on the cathode side of the diode D3, and when the load is short-circuited, the potential on the cathode side of the diode D3 is lowered and the reverse voltage is applied to the diode D3. Protect the flyback transformer by lowering the voltage in the direction.

An effective capacitance is formed between the cathodes of the diodes D3 and D4 to form a discharge path when the load is short-circuited, and the diode D
The means for protecting D3 is not limited to the embodiment shown in FIG. 8, but may be any means that effectively forms a capacitance between the cathodes of diodes D3 and D4. The reason why the winding ends of the winding layers are uneven is not limited to the adjacent winding layers, and may be any shape that effectively reduces the interlayer capacitance.

As shown in Figure 6, this prevents damage to the diode whose cathode is connected to the bottom of the outermost winding layer, where the highest voltage in the reverse direction is applied among the diodes, and prevents the diode from frying. The function of the back transformer can be maintained. In addition, in the present invention, which utilizes the above analysis results, the reverse withstand voltage of the diode whose cathode is connected to the beginning of winding of the outermost winding layer is selected to be the highest among the diodes that divide the circuit layer. In this way, damage to the flyback transformer can be prevented.

In the above description, we focused on the anode side of the diode Dn for convenience, but the above analysis results show that it is the outermost winding layer where the reverse voltage is most applied at the threshold value. It is known that the diode D3 has its cathode connected at the beginning.

As a result, a capacitor Cs is connected between the cathode of the diode D4 and the cathode of the diode 1)3 to form a discharge path for the electric charge charged in the capacitor on the cathode side of the diode D3 when the load side is short-circuited. This is effective in protecting flyback by promoting a drop in the cathode potential of diode D3 and preventing damage to diode D3. As is clear from the above description, according to the present invention, a plurality of diodes Q (a so-called multilayer flyback transformer VC in which the windings divided into parts are wound in multiple layers) is used to control the reverse voltage applied to the diodes. can be set in advance, damage to the diode can be suppressed, and a highly reliable multilayer winding flyback transformer can be provided.

Furthermore, for convenience of analysis, each layer Cij (1=1,
2, 3...Nj-1+1) were assumed to be equal, but the present invention is not restricted to this assumption, and the number of winding layers and the number of diodes are not limited to the examples.

[Brief explanation of drawings]

Fig. 1 is a schematic perspective view showing a conventional multi-layer winding flyback transformer, Fig. 2 is a circuit diagram for explaining the multi-layer winding flyback transformer according to the present invention, and Fig. 3 shows the connection between both electrodes of the diode and the ground. Circuit diagram explaining distributed capacitance, 4th
5 and 5 are circuit diagrams for explaining the operation of the multilayer winding flyback transformer according to the present invention, and FIG. 6 is a circuit diagram for explaining the operation of the multilayer winding flyback transformer according to the present invention. 7 and 8 are sectional views showing a specific embodiment of the present invention and showing a cross section of a wound layer. 1, 2, 3, 4... Bobbin, Ll, L2, L3
, L4... Secondary winding, Dl, D2, D3, D
4...Dionite, CKlDionite D1 (1-1
, 2, 3, 4), the capacitance between the cathode and ground, CAi・
...Diode D. (1-1,2,3,4) capacitance between the anode and ground, C'Ij (1=1,2,3,
j=i+1)...Diode D of secondary winding L1
1 (1-1, 2, 3, 4) interlayer capacitance on the side to which the cathode is connected, C. ．． (1-1,2,3,j=i+1J1)
・・・・・・Diode of secondary winding L1 (1=1, 2,
The interlayer capacitance on the Q side where the anodes of 3 and 4) are connected, C ・
・・・・Effective capacity for external connection, 11・・・・・・
Lead wire holder, 12... Groove, 13...
...Metal plate.

Claims (1)

[Claims] 1. A reverse voltage applied in a multilayer flyback transformer in which a high voltage winding is divided into a plurality of windings by a plurality of diodes and these windings are wound in multiple layers to obtain a high voltage. A discharge path is provided to actively discharge the charge accumulated on the diode side, where the voltage is maximum, to the reference potential side when the load is short-circuited, and by discharging the charge through this discharge path, the reverse voltage applied to the diode is reduced. A multi-layer winding flyback transformer characterized by: 2. The discharge path is formed by a capacitor connected between the cathode of a diode to which the maximum reverse voltage is applied and the cathode of a high voltage output diode among the plurality of diodes. The multilayer winding flyback transformer according to item 1. 3 As the discharge path, a metal plate provided on the lead wire on the cathode side of the diode to which the applied reverse voltage is maximum, and a metal plate provided on the lead wire on the cathode side of the high voltage output diode among the plurality of diodes. The multilayer flyback transformer according to claim 1, which uses a capacitor formed by a plate.