JP2010284027A - High-frequency ac power supply device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high-frequency AC power supply device that improves the switching frequencies and switching voltages of a plurality of semiconductor switches constituting an inverter, or the like, by improving the configuration of a gate power supply. <P>SOLUTION: A multi-output gate power supply 7 includes a plurality of transformers 15 for mutually supplying the insulated voltage source to each gate drive circuit 19, and a transformer drive circuit 14 for supplying driving power to those transformers; the transformer includes each transformer core 18 forming a closed magnetic path, secondary windings 17, wound around each transformer core, and primary windings 16 penetrating through a hollow part of each transformer core; each secondary winding is connected to each gate drive circuit while the primary windings of the plurality of transformers are connected in series; and the series primary windings 16 and the secondary windings 17 are provided with a space distance, while the series primary windings 16 are arranged on a printed board 28. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a high-frequency AC power supply apparatus that has a plurality of semiconductor switches that constitute an inverter and the like, switches these semiconductor switches, and supplies high-frequency AC power.

In this type of conventional high-frequency AC power supply device, as a method of supplying gate driving power to a plurality of semiconductor switches that switch DC voltage at high speed,
For example, as shown in Patent Document 1, a transformer having a common transformer core and a plurality of different secondary windings is provided, and each secondary winding is connected to a plurality of gate drive circuits that drive semiconductor switches, respectively. Was done.
As another prior art, as disclosed in Patent Document 2, a plurality of annular transformer cores are connected through through a highly insulated cable shape, and each secondary voltage is rectified to form a semiconductor. I was driving a switch.

Japanese Patent No. 3991450 Japanese Patent Laid-Open No. 5-304451

Conventionally, in the method as disclosed in Patent Document 1, for example, driving power is supplied from a gate power source using an insulating transformer to a high-side gate of an inverter circuit configured by a semiconductor switch and switching a high voltage of several kV. In such a case, since the secondary winding of the isolation transformer is floating with respect to GND (ground), the potential difference between the primary and secondary windings of the isolation transformer becomes a high voltage of several kV. . In this case, if there is a void in the insulating material that insulates between the primary winding and the secondary winding of the insulation transformer, a high electric field is locally applied to the void portion and partial discharge occurs.
And the higher the switching frequency of the semiconductor switch, the higher the frequency of partial discharges, and the probability of breakdown due to treeing over time increases and the reliability decreases, so a resin-encapsulated type usually called a mold transformer The transformer had to be used, and there was a problem that the cost was high.
Further, since such a mold transformer cannot be seen inside, it is difficult to grasp the state of deterioration or fouling, and it is necessary to shorten the maintenance cycle. In addition, since the insulating portion is molded even when deterioration or fouling occurs, the function cannot be recovered by a simple method such as cleaning, so that there is a problem that the transformer needs to be replaced and the maintenance cost increases.

On the other hand, as shown in Patent Document 2, a transformer in which the primary winding and the secondary winding are insulated using a cable-shaped primary winding with high insulation is made of an insulating material on the cable surface. Since the dielectric constant is high, the stray capacitance between the primary winding and the secondary winding is usually several hundred to several thousand pF.
When such a transformer is used to operate a semiconductor switch at a high switching frequency, partial discharge is likely to occur in the insulating material portion of the cable surface, and the insulating material on the surface of the primary winding deteriorates due to treeing, and the insulation is eventually made. The destruction of quality and reliability was caused due to destruction.
Further, when the stray capacitance between the primary winding and the secondary winding is large, a common mode current flows through the stray capacitance. Such a common mode current causes noise radiation and causes malfunction of the device and heat generation due to the noise current. Therefore, it is necessary to insert a choke coil and a filter as a component to suppress the common mode current. There was a problem that would be high.

When the switching frequency of the semiconductor switch is increased, the circuit board constituting the choke coil and the filter is increased in size and the size of the device is increased, and the stray capacitance between the circuit board itself and the ground is increased, so that it is difficult to increase the frequency. was there.
Further, in order to suppress the noise radiation, it is necessary to shield the transformer with a metal chassis, which not only increases the cost, but also increases the external size and weight of the transformer and makes it difficult to attach it to the apparatus.

As described in Patent Document 2, when a plurality of transformer cores are passed through a single highly insulated cable as the primary winding, the number of turns of the primary winding is one turn, and the primary inductance Can not be raised.
In order to reduce the size and weight of the transformer core using the same transformer core material, it is necessary to increase the switching frequency of the transformer drive circuit that drives the transformer.
Designing a high-speed transformer drive circuit required high technical capabilities, including element selection, and was difficult to design.
In conventional transformers, it is necessary to use an annular transformer core having a large inner diameter in order to increase the number of turns of the primary winding to two or more turns. Therefore, the shape of the transformer core becomes large, and it is difficult to reduce the size and weight of the high-frequency AC power supply device.

From a transformer having a plurality of different secondary windings and having a common transformer core described in Patent Document 1, each secondary winding is passed through a rectifier circuit and a gate drive circuit that convert the voltage of each secondary winding into a DC voltage. When driving a plurality of semiconductor switches connected in series corresponding to the winding, if one of the gate drive circuits fails and the output of the transformer is short-circuited, the transformer primary side is short-circuited, and the transformer primary side This circuit will also fail in a chain.
In order to prevent this, conventionally, it has been necessary to take measures such as providing a protection circuit for detecting a short-circuit state at the output of each transformer.
In addition, a transformer having a common transformer core needs to use a large transformer core in order to separate and isolate each secondary winding, which makes the transformer heavy and large.
In order to solve the above problems, it is necessary to mold the transformer with an epoxy resin or to use an insulating wire having high insulating performance, resulting in high costs.

In addition, when switching is performed by a plurality of semiconductor switches connected in series, the switching voltage is obtained by using the primary winding of the isolation transformer of the gate power supply for supplying driving power to the gate drive circuit that drives the semiconductor switch, and 2 The voltage is divided by the transformer coupling capacitance due to the stray capacitance between the next winding and the output capacitance of the semiconductor switch. The closer the semiconductor switch is to the output terminal, the higher the shared voltage. There was a problem of increased loss.
In order to solve the above-described problem, conventionally, a capacitor is connected in parallel to each semiconductor switch, and a capacitor having a larger capacity is connected to a semiconductor switch closer to the output terminal so that the voltage is equally shared. For this reason, the number of parts is increased and the cost is increased.

  The present invention has been made to solve the above-described problems, and improves a configuration of a power supply for a gate and can improve a switching frequency and a switching voltage of a plurality of semiconductor switches constituting an inverter or the like. The purpose is to provide.

  A high-frequency power supply device according to the present invention includes a plurality of semiconductor switches connected in series, a plurality of gate drive circuits that respectively drive these semiconductor switches, and a multi-output gate that supplies a voltage source to each of these gate drive circuits. The power supply for multi-output gate includes a plurality of transformers that supply mutually isolated voltage sources to the gate drive circuits, and a transformer drive circuit that supplies drive power to these transformers, The transformer includes a transformer core that forms a closed magnetic path, a secondary winding wound around the transformer core, and a primary winding that penetrates a hollow portion of the transformer core. The winding is connected to each of the gate drive circuits, the primary windings of the plurality of transformers are connected in series, and the series primary winding and the secondary winding set a spatial distance. Disposed Te, and the series primary windings are arranged on the printed circuit board.

According to the present invention, the primary winding passes through the hollow portions of the plurality of transformer cores forming the closed magnetic path around which the secondary winding is wound, and between the primary winding and the secondary winding of each transformer. Is insulated by air. Since air has the lowest dielectric constant of 1.0, partial discharge is unlikely to occur between the primary and secondary windings even when high frequency and high voltage are applied between the primary and secondary windings. . In addition, even if partial discharge occurs, air is not deteriorated like a solid insulating material, so that reliability and safety are greatly improved.
Further, by disposing the primary winding on the printed circuit board, it is possible to penetrate the plurality of primary windings through the transformer core while maintaining a spatial distance between the primary winding and the secondary winding. As a result, the transformer primary side inductance can be increased, so that the transformer core can be reduced in size and weight.

It is a circuit block diagram which shows the basic composition of the high frequency alternating current power supply device which concerns on Example 1 of this invention. 3 is a waveform diagram illustrating an example of an output signal of a control circuit in Embodiment 1. FIG. FIG. 3 is a circuit configuration diagram illustrating a configuration of a main part including a gate power supply according to the first exemplary embodiment. FIG. 3 is a perspective view illustrating a configuration of a transformer part of a gate power supply in the first embodiment. FIG. 3 is a plan view of a principal part illustrating details of a transformer in the first embodiment. It is an equivalent circuit diagram in case a void exists in an insulator. It is a graph showing the relationship between the corona start voltage in air and an insulation distance. It is explanatory drawing which shows the shared voltage of the semiconductor switch which comprises 1 arm of an inverter. It is a perspective view which shows the other structural example of the trans | transformer part of the power supply for gates in Example 1 of this invention. It is a perspective view which shows the structure of the trans | transformer part of the power supply for gates in Example 2 of this invention. FIG. 6 is a plan view of a main part showing details of a transformer in Embodiment 2. FIG. 10 is a plan view of a principal part showing another example of the primary winding of the transformer in the second embodiment.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
Example 1.

FIG. 1 is a circuit configuration diagram showing a basic configuration when a discharge tube for obtaining laser output is connected as a load connected to a high-frequency AC power supply apparatus.
In FIG. 1, a discharge tube 1 as a load includes a dielectric capacitor 2 and a discharge resistor 3. The plurality of high voltage switches 5 constituting the four arms A1 to A4 of the full bridge inverter switch the DC voltage Ea / 2 of the DC high-voltage power supply 8 whose ground is grounded at high speed to convert it to a high frequency AC voltage and output it. It is supplied to the discharge tube 1 through the reactor 4. Each high voltage switch 5 is composed of a plurality of semiconductor switches such as FETs connected in series, and each semiconductor switch is driven by each gate circuit 6. Each gate circuit 6 is supplied with driving power from a gate power supply 7 and supplied with a control signal for on / off from a control circuit 9 via an optical oscillator 10 and an optical fiber 11.

The control circuit 9 is a general PWM generator that controls a full bridge inverter.
FIG. 2 shows an example of a timing chart of the control signals S1 to S4 output from the control circuit 9 and the output voltage Vout.
The control signals S1 to S4 are on / off signals whose on-time is shorter by 2t _d than the off-time, and the control signals S3 and S4 are on / off signals whose phases are advanced or delayed by 90 degrees with respect to the control signals S1 and S2.
As described above, the dead time td is provided so that the rising and falling timings of the control signals S1, S2 and the control signals S3, S4 are not the same by making the on time shorter than the off time by 2t _d .
When the control signals S1 and S2 are on, the output voltage Vout is + Ea, and when the control signals S3 and S4 are on, the output voltage Vout is −Ea and a high-frequency AC voltage of ± Ea is output.
The on / off signals of S1 to S4 are converted into light by the optical oscillator 10 and transmitted to the gate circuit 6 through the optical fiber 11.

  In the above configuration, since the high voltage switch 5 directly switches a high voltage, a step-up transformer is not necessary. Therefore, the inductance from the output end of the full-bridge inverter constituted by the high voltage switch 5 to the load is almost determined by the output reactor 4 to be inserted. When the discharge tube 1 that obtains the laser output as the load is connected, the output reactor 4 can be selected to be sufficiently small, so that the frequency of the inverter can be increased and the discharge power can be increased, resulting in the laser output. Strength can be increased.

FIG. 3 shows details of the high voltage switch 5, the gate circuit 6, and the gate power supply 7, and the figure shows one arm of the full bridge inverter.
The high voltage switch 5 is composed of six semiconductor switches 20 connected in series in multiple stages, and the gate circuit 6 is composed of six gate drive circuits 19 that supply a gate signal to each semiconductor switch 20. The gate power supply 7 includes a commercial power supply 12, an AC / DC converter 13, a gate drive circuit 19, six transformers 15, and six rectifier circuits 27. The transformer drive circuit 14 is a general switching circuit such as a full bridge circuit, and switches the output voltage from the AC / DC converter 13.
Each transformer 15 includes a plurality of transformer cores 18 forming a closed magnetic path, primary windings 16 that pass through these transformer cores and connected in series, and a printed circuit board in which a plurality of primary windings 16 are arranged in an outer layer. 28, and a plurality of secondary windings 17 wound around the respective transformer cores at a spatial distance from the plurality of series primary windings, and the plurality of series primary windings 16 are connected to the transformer drive circuit 14. Each secondary winding 17 is connected to each corresponding gate drive circuit 19 via a rectifier circuit 27 while being connected.

In the above configuration, when the commercial power supply 12 is input to the AC / DC converter 13, a DC voltage for driving the transformer drive circuit 14 is output from the AC / DC converter 13. The transformer drive circuit 14 performs a switching operation, an AC signal flows through the series primary winding 16 in each transformer 15, and the AC voltage generated in each secondary winding 17 is converted into a DC voltage via a rectifier circuit 27. It is supplied to the gate drive circuit 19.
An ON / OFF signal is transmitted to each gate drive circuit 19 through the optical fiber 11, and a switching signal is supplied from the gate drive circuit 19 to each semiconductor switch 20. Since the semiconductor switches 20 are connected in series, the high voltage specification can be satisfied as a whole even if one withstand voltage is small.

4 and 5 are a perspective view and a main part plan view showing a detailed structure of a transformer portion (between A and B in FIG. 3) of the gate power supply 7. FIG. In FIG. 4, a plurality of (six in the figure) transformers 15 each have an annular transformer core 18 and a secondary winding 17 wound around the transformer core so as to form a closed magnetic path. The printed circuit board 28 has a plurality of primary windings 16 that pass through the transformer core 18 and are arranged in series with respect to all the secondary windings 17. The primary winding is connected to the printed circuit board 21 via the multi-pin terminal block 22. It is arranged on the top.
That is, as shown in FIG. 4, a plurality of transformer cores 18 are arranged on the printed circuit board 28 in a state where the transformer cores 18 are mounted on the printed circuit board 21 via the pedestal 23 so that their hollow portions are connected in a row. The series primary windings 16 are arranged so as to pass through the hollow portions of all the transformer cores 18 in a straight line, and both ends thereof are supported on the printed circuit board 21 via the multi-pin terminal block 22, and the multi-pin terminals A primary current is supplied via the base 22. Both ends of each secondary winding 17 are connected to wiring (not shown) on the printed circuit board 21, and supply a DC voltage to the corresponding gate drive circuit 19 via the rectifier circuit 27.
In this transformer structure, the primary winding 16 and the secondary winding of each transformer 15 are insulated by air. For this reason, partial discharge hardly occurs, and even if partial discharge occurs, there is no dielectric breakdown due to deterioration of the insulating material, so that reliability and safety are greatly improved.

In general insulation transformers, where the primary and secondary windings of the transformer are insulated by a solid insulation material, there may be voids or impurities in the insulator, and local areas where there are voids or impurities. The electric field strength increases.
FIG. 6 shows an equivalent circuit in the case where there is one void in the insulator. In the figure, Cv represents the capacitance of the void 25, and C1 to C4 represent the capacitance of the insulator corresponding to the positions in the right figure.
Usually, the void 25 in the insulator 26 is made of a gas such as air, and its size is very small. When a voltage is applied between the electrodes 24 of the insulator 26, a high voltage is applied to the void 25 having a small electrostatic capacity, and the electric field strength at the void portion is locally increased. When the electric field strength is locally increased, the probability of occurrence of partial discharge is increased, and when the switching frequency of the semiconductor switch is further increased, the probability is further increased. When the partial discharge occurs, the insulator is carbonized and eroded, and the eroded portion develops with time and causes local destruction. The treeing phenomenon develops into a dendritic state that leads to the destruction of the whole road.

  A structure in which a plurality of primary windings 16 arranged on a printed circuit board 28 are passed through all the transformer cores 18 like the transformer 15 to insulate between the primary winding 16 and the secondary winding 17 by a spatial distance. By doing so, the stray capacitance between the primary winding 16 and the secondary winding 17 is reduced, and the capacitive reactance Xc in the high frequency region is increased. As a result, the impedance in the high frequency region increases and the common mode current can be prevented from flowing.

As described in Patent Document 2, as a conventional technique, a structure in which the primary winding and the secondary winding are insulated only by a highly insulated cable can not prevent partial discharge, Rather, partial discharge tends to occur.
When the insulation distance is t and the relative dielectric constant is ε _s , the partial discharge corona onset voltage Vc is the Darkin's empirical formula
Vc = 163 * (t / ε _s ) ^ 0.46 [V] (1)
It can be estimated with.
Since the dielectric constant of the insulating material portion on the cable surface is higher than the relative dielectric constant ε _s = 1 of air, partial discharge tends to occur on the cable surface.
Since the insulation material on the cable surface deteriorates due to the partial discharge, there is a problem that a short circuit failure between the primary winding and the secondary winding is likely to occur and the quality and reliability are low.
FIG. 7 is a graph showing the relationship between the corona start voltage in air and the insulation distance from the equation (1).
To prevent partial discharge, use an uninsulated bare conductor and make the field strength uniform by providing a spatial distance between the primary and secondary windings that is greater than the insulation distance obtained from equation (1). Thus, it is necessary to suppress a partial increase in electric field strength between the insulation distances.

  In order to prevent dielectric breakdown due to partial discharge, a resin-encapsulated transformer called a mold transformer is generally used. Mold transformer is an epoxy resin to reduce gaps and voids between windings after winding winding around transformer core with insulating material such as insulating tape sandwiched between primary winding and secondary winding. Molded with an insulating material.

Epoxy resin, which is a typical insulating material used for transformer insulation, has a relative dielectric constant of 2.5 to 6.0, while air is 1.0. The capacitance C can be calculated from C = (ε ₀ ε _s · S) / d, and the capacitance C is proportional to the relative dielectric constant ε _s . Insulating with air with a small relative dielectric constant, the stray capacitance between the primary and secondary windings is 1 compared to the case where the primary and secondary windings are filled with epoxy resin and insulated. /2.5 to 1 / 6.0. Further, since the capacitance C is inversely proportional to the distance d, the stray capacitance can be further reduced by providing a sufficient spatial distance between the primary winding and the secondary winding.

  If the stray capacitance between the primary winding 16 and the secondary winding 17 of each transformer 15 can be reduced, the common mode current flowing through the stray capacitance is reduced, and noise countermeasure parts such as a choke coil and a filter become unnecessary. Further, since noise radiation is also suppressed, the transformer is reduced in weight without requiring a metal chassis, and the transformer can be easily attached to the device.

When a switching operation is performed using a plurality of semiconductor switches 20 connected in series as shown in FIG. 3, the switching voltage is between the primary winding 16 and the secondary winding 17 of each transformer 15 in the gate power supply 7. The voltage is divided by the transformer coupling capacitance due to the stray capacitance and the output capacitance Coes of the semiconductor switch, and the semiconductor switch closer to the output terminal has a higher shared voltage.
The charge / discharge loss Wc at the output capacitance Coes of the semiconductor switch can be calculated as 1/2 · Coes · Vc ^ 2 · f, where Vc is the shared voltage and f is the switching frequency. As it increases, the loss Wc at the output capacitance Coes increases in proportion to the square of the shared voltage Vc. Therefore, there is a problem that the loss Wc increases in some semiconductor switches having a high shared voltage Vc.
In order to solve such a problem, a capacitor is conventionally connected in parallel to each semiconductor switch, and a capacitor having a larger capacity is connected to a semiconductor switch closer to the output terminal so that the voltage is equally shared. For this reason, the number of parts is increased and the cost is increased.

FIG. 8 shows the mobile charge and the shared voltage of each part when the potential of each connection point is as shown in the figure, taking A1 as an example of the four arms A1 to A4 constituting the full bridge inverter of FIG. (In actuality, the electric potential at each connection point varies depending on the voltage dividing state, so the electric charge varies slightly). Assuming that Ea = ± 3 kV is applied as the DC high-voltage power supply 8, the output capacitances of the semiconductor switches Q1 to Q6 constituting the arm A1 are 400 pF, and the coupling capacitance of the transformer is 10 pF, the capacitance values of the respective parts are as shown in FIG.
As shown in FIG. 8 (a), when all of the semiconductor switches Q1 to Q6 constituting the arm A1 are on, A2 is on, and A3 and A4 are off, the voltage across each output capacitor is 0V and the potential at each connection point is + 3kV, transformer coupling capacitance 10pF is charged. As shown in FIG. 8 (b), when all the semiconductor switches Q1 to Q6 constituting the arm A1 are turned off, A2 is turned off, A3 and A4 are turned on, and the potentials at the respective connection points are as shown in the figure, the transformer coupling Mobile charge flows from the capacitance 10 pF into the output capacitance of each semiconductor switch.
10b-60nC in Fig. 8 (b), when Q1-Q6 in Fig. 8 (a) switches from on to off, the voltage applied to the transformer coupling capacitance 10pF is + 2kV as shown in Fig. 8 (b). It represents the charge that moves when it is -3kV.
Further, 400 nC to 550 nC in FIG. 8B represent the electric charge flowing through each output capacitance 400 pF. First, in FIG. 8B, 1 kV is applied to the left end output capacitance 400 pF, and 400 nC (= 400 pF). / 1 kV) of charge flows, and then, the moving charge from the transformer coupling capacitor 10 pF flowing into the connection point is added, and 400 nC to 550 nC of charge flows through each output capacitor.
The amount of mobile charge that flows as the output capacity of the semiconductor switch closer to the output arm flows, and the divided charge of each part divided by the output capacity equivalently represents the shared voltage of the semiconductor switch, and the shared voltage of the semiconductor switch closer to the output arm Becomes higher.
Conventionally, in order to equalize the shared voltage, capacitors are connected in parallel to the semiconductor switches Q1 to Q6, and a capacitor having a larger capacity is connected to a semiconductor switch closer to the output arm.

According to the first embodiment, since the primary winding 16 and the secondary winding 17 of each transformer 15 are insulated by air, the stray capacitance between the primary winding and the secondary winding, that is, the transformer coupling capacitance. Is as small as several pF or less, and there is little transfer charge from the transformer coupling capacitance to the output capacitance.
For this reason, the unbalance of the shared voltage of the semiconductor switch 20 is reduced, the loss due to charging / discharging of the output capacitance can be made uniform, and it is not necessary to connect a capacitor in parallel to the semiconductor switch, thereby reducing the number of parts and the cost. .

Furthermore, conventionally, as a method of supplying driving power to each gate circuit using an isolation transformer to semiconductor switches connected in series in multiple stages, the primary sides of a plurality of isolation transformers are connected in parallel, The gate circuit is connected to the secondary winding via a rectifier circuit, and driving power is supplied.
In this case, if one of the plurality of gate circuits fails and the output of the transformer is short-circuited, the primary side of the transformer is short-circuited, and the transformer drive circuit on the primary side of the transformer also fails in a chained manner. Measures such as providing a protection circuit for short-circuit current detection on the (secondary side) were taken.
According to the first embodiment, even when one of the plurality of gate drive circuits 19 breaks down and the output of the transformer 15 is short-circuited, the transformer primary side is not short-circuited and the transformer 15 continues to another gate drive circuit. Can be supplied with driving power.

That is, when n transformers having a turn ratio N and an inductance L1 connected in series with the input voltage Vin are n · L1 and the inductance conduction time is t, the excitation current Il in this case is Vin · t / ( n · L1).
When one of the n transformers is short-circuited, the short-circuited transformer causes magnetic saturation and the primary inductance becomes zero.
As a result, the primary voltage of the transformer rises to V1 ′ = Vin / (n−1), so the output voltage on the other secondary side (ie, the output voltage of the gate drive circuit = gate voltage) is also V2 ′ = Vin · N. It rises to / (n-1).
Further, the total inductance L = n · L1 on the primary side decreases to L ′ = (n−1) · L1, and the excitation current Il increases to Vin · t / ((n−1) · L1).
Since the primary current I1 is the sum of the secondary current I2 and the excitation current, the primary current I1 increases from I2 + Vin · t / (n · L1) to I2 + Vin · t / ((n-1) · L1). .
In other words, when one of n transformers is short-circuited, the secondary output voltage (gate voltage) increases to V2 '= Vin · N / (n-1) or becomes zero, and the primary current I1 also increases. However, if n is sufficiently large, the increase of the secondary output voltage and the primary current is also small.

In the conventional isolation transformer that does not connect the primary windings in series, if at least one secondary winding is short-circuited, the transformer drive circuit breaks down and the voltage of the other secondary windings decreases, making it impossible to continue operation. Met.
According to the first embodiment in which the primary windings are connected in series, the gate voltage rises to V2 '= Vin · N / (n-1) if a semiconductor switch having a sufficient margin for the required withstand voltage is used. However, the apparatus can continue to operate without stopping.
In addition, when an insulated gate element is used as a semiconductor switch, if the gate voltage increases, the on-resistance decreases and the loss increase is reduced.
The increase in heat generation associated with the increase in the shared voltage of the semiconductor switch is mitigated, and it is possible to continue the operation without stopping the apparatus until the maintenance of the failed part, thereby ensuring a very high reliability.

Further, conventionally, in order to detect a failure of the gate drive circuit 19, it is necessary to monitor each output (secondary side) of the transformer. In the first embodiment, when the secondary side of at least one transformer among a plurality of transformers in which the primary windings are in series is short-circuited, the output voltage on the secondary side of the other transformer is changed from Vin · N / n to Vin · Increase to N / (n-1).
As described above, the output voltage on the secondary side increases to Vin · N / (n-1). However, by using a semiconductor switch having a sufficient margin for the required breakdown voltage, at least one of the plurality of transformers is used. Even if the secondary side of the transformer is short-circuited, high reliability can be obtained because operation can be continued without stopping the apparatus until the apparatus is maintained.
Further, by providing a protection circuit that monitors the secondary side voltage of at least one of the plurality of transformers and stops the operation of the gate drive circuit 19 when the secondary side voltage exceeds a predetermined threshold value. Therefore, it is possible to easily cope with the failure of the gate drive circuit 19.

Further, when the output voltage on the secondary side is monitored as described above, it is necessary to insulate the primary side and the secondary side having the protection circuit with a photocoupler or the like. According to the first embodiment, when the output is short-circuited due to a failure, the primary current is I1 = I2 + Vin · t / ((n−1) · L1), and the primary voltage is V1 ′ = Vin / (n− Increase to 1). Therefore, a protection circuit that monitors the primary current or the primary voltage in the series primary winding and stops the operation of the gate drive circuit 19 when the primary current or the primary voltage exceeds a predetermined threshold value. Even if it is provided, it is possible to easily cope with the failure of the gate drive circuit 19.
According to the first embodiment, since the protection circuit and the monitoring voltage can be protected without being insulated, a complicated circuit is not required and time is not spent for circuit adjustment, thereby shortening the design time and cost. Both can be planned.

Conventional transformers of this type with primary windings connected in series have primary windings wound around each transformer core, and the transformer core is fixed on a printed circuit board with a base or an adhesive, and the primary winding is printed. They were connected in series with the wiring pattern of the board. The conventional transformer in which the primary winding is wound around a plurality of transformers has a large number of assembly steps and is expensive.
In order to solve the above problem, a conductor having high mechanical rigidity such as a copper bus bar is used for the primary winding, a plurality of transformer cores are fixed so that the hollow portions thereof are connected in a row, and then a plurality of transformer cores are used. Are connected through the copper bus bar. This saves the trouble of winding the primary winding around a plurality of transformer cores and greatly improves the assembly man-hours.
However, when the number of turns of the primary winding is 2 turns or more, a plurality of terminal blocks and a large mounting space for mounting the plurality of terminal blocks are required to hold and fix each primary winding. There was a problem that the substrate size was increased.
In addition, a transformer core with a large inner diameter was required to allow a plurality of primary windings to pass through the transformer core. A transformer core with a large inner diameter is large and heavy, so that it is difficult to mount on a printed circuit board, and it is difficult to reduce the size of the entire power supply device, resulting in high costs. Furthermore, in order to improve the vibration resistance of the primary winding, it is necessary to use a bus bar having high mechanical rigidity for the primary winding, which is also expensive.
According to the first embodiment, the plurality of primary windings 16 of the plurality of transformers 15 constituting the gate power supply 7 are arranged on the printed circuit board 28. Since both ends of the plurality of primary windings 16 arranged on the printed circuit board 28 are collectively connected to the wiring on the printed circuit board 21 via the multi-pin terminal block 22, the mounting space is reduced and the assembly is easy. As a result, the apparatus can be reduced in size and the number of assembly steps can be reduced. Furthermore, the wiring pattern which is the primary winding 16 is fixed on the printed circuit board 28, and there is no need to use a copper bus bar or the like. Since the primary winding 16 enables high-density wiring with the manufacturing accuracy of the printed circuit board 28, a transformer core with a small inner diameter can be used even when the number of turns of the primary winding 16 is two or more, thereby reducing the size and cost of the entire power supply device. Can be planned.

Generally, in order to reduce the size of the transformer, the switching frequency is set to a high frequency of several hundred kHz. When the switching frequency of the current flowing through the primary winding becomes a high frequency of several hundred kHz, the primary current does not flow inside the conductor but flows only near the conductor surface due to the skin effect.
Conventionally, as the primary winding, a copper bus bar or the like that is thicker and more expensive than necessary for the purpose of obtaining mechanical rigidity has been used.
When the wiring pattern on the printed circuit board is used for the primary winding as shown in the first embodiment, the thickness of the wiring pattern is sufficiently thinner than the skin depth of the skin effect when the switching frequency is several hundred kHz. The primary current flows through the entire wiring pattern. The wiring pattern is fixed to the printed circuit board, and the printed circuit board is rigid, so that it easily penetrates the plurality of transformer cores.
According to the first embodiment, a primary winding having a high rigidity and a minimum necessary conductor can be obtained at low cost.

Previously, it was difficult to increase the primary inductance by increasing the number of primary winding turns N1 due to manufacturing restrictions such as mounting space and cost reduction. Therefore, the switching frequency was increased and the transformer caused magnetic saturation. It was necessary to suppress the peak current so as not to occur.
A primary current I1 including an exciting current Il and an output current Io flows through the transformer primary winding, and the exciting current Il is obtained from Il = Vin · ton / L1. The primary inductance L1 can be calculated from L1 = μ · S · N1 ^ 2 / l, and the excitation current Il is proportional to the square of the number of turns N1. Conventionally, the excitation current Il is reduced by suppressing the peak current Ipk by increasing the switching frequency, shortening the on-time ton, or increasing the transformer core cross-sectional area S.
According to the first embodiment, the number of turns N1 of the primary winding can be easily increased while suppressing the mounting space, and the excitation current Il is inversely proportional to the square of the number of turns N1, so that the peak current Ipk is not increased without increasing the switching frequency. Can be suppressed.
Lowering the switching frequency not only reduces the frequency of occurrence of partial discharge, but also reduces the common mode current, so that the noise of the power supply can be reduced. Further, since a transformer core having a small core cross-sectional area can be used, the entire power supply device can be reduced in size.
The design of the transformer drive circuit that drives the transformer required high technical skills, including element selection, and was difficult to design. According to the first embodiment, the switching frequency is lowered, and the design load on the transformer drive circuit designer can be reduced.

Furthermore, since the transformer core is reduced in size and weight, a plurality of transformers 15 can be mounted on the printed circuit board 21, and the mounting property is improved and the transformer is fixed by soldering via the pedestal 23. Vibration is improved. Further, due to the noise shielding effect of the wiring pattern on the printed circuit board, radiation noise from the transformer toward the back surface of the printed circuit board 21 is shielded.
By mounting the transformer on the printed circuit board in this way, it is possible to configure a gate power supply that combines a shield member with a structure such as a wiring member, a transformer, and a terminal block, and between the primary winding and the secondary winding of the transformer. Insulation distances such as distance, position, space and creepage distance can be controlled with extremely high precision with printed circuit board manufacturing accuracy, and a low-noise high-frequency AC power supply device with simple wiring can be obtained.

Further, according to the first embodiment, since the secondary winding 17 is wound around the plurality of independent transformer cores 18, the secondary windings 17 are insulated by providing a spatial distance, thereby reducing the size and weight of the transformer core. In addition, since it is not necessary to mold with an epoxy resin, the cost can be reduced.
In addition, according to the first embodiment, each transformer 15 can be configured using widely distributed members, so that it has excellent versatility and the components are extremely inexpensive. In comparison, an inexpensive high-frequency AC power supply device can be obtained.
In addition, according to the first embodiment, it is not necessary to seal each transformer 15 with resin, and the contamination state can be visually confirmed so that the maintenance time can be easily confirmed, and the periphery of the transformer core is cleaned by brushing or the like. By doing so, the function can be easily restored, so that the maintenance cost can be suppressed.

Conventionally, in this type of transformer in which the primary winding passes through a plurality of transformer cores, a copper bus bar or the like is used for the primary winding, and both ends of the primary winding are screwed and fixed to the terminal block. When the screw is tightened, the primary winding also moves in the screw rotation direction, the primary winding is likely to be displaced from the center of the transformer core, and it is difficult to pass the primary winding through the center of each transformer core with high accuracy. It was.
Therefore, the distance between the primary winding and the secondary winding is partially shortened, and the probability of partial discharge is increased at the portion where the distance between the primary winding and the secondary winding is short, and the common mode current is increased. There was a problem such as.
According to the first embodiment, primary windings are arranged on a printed circuit board, and a plurality of primary windings and a multi-pin terminal block 22 having a multi-pin structure are connected by soldering as shown in FIG. Unlike the conventional screw fastening, the primary winding does not move when the primary winding is fixed to the terminal block. Therefore, the primary winding can be passed through the center of each transformer core with high accuracy.
Since the primary winding can be penetrated through the center of each transformer core with high accuracy, the distance between the primary winding and the secondary winding can be kept uniform, and the occurrence of partial discharge can be suppressed. A low-noise, multi-output gate power supply with low current can be obtained.

As described above, according to the high-frequency AC power supply device according to the first embodiment of the present invention, the plurality of semiconductor switches 20 connected in series, the plurality of gate drive circuits 19 that respectively drive these semiconductor switches, and these A multi-output gate power source 7 for supplying a voltage source to each of the gate drive circuits, and the multi-output gate power source 7 includes a plurality of transformers 15 for supplying each gate drive circuit 19 with a mutually isolated voltage source; The transformer includes a transformer drive circuit 14 that supplies driving power to the transformer. The transformer includes a transformer core 18 that forms a closed magnetic path, a secondary winding 17 wound around the transformer core, and a transformer core. The secondary winding is connected to each gate drive circuit, and the primary windings of a plurality of transformers are connected in series. Since the series primary winding 16 and the secondary winding 17 are arranged with a spatial distance, and the series primary winding 16 is arranged on the printed circuit board 28, the primary winding and secondary of the transformer Insulators such as inverters connected in series in multiple stages can improve the insulation performance between windings, reduce stray capacitance, easily make insulation between windings, and can be configured as a small, lightweight, low-cost gate power supply. The switching frequency and switching voltage of the switch can be increased.
In addition, the primary winding is fixed to the printed circuit board, and there is no need to use a copper bus bar, etc. The primary winding is capable of high-density wiring with the manufacturing accuracy of the printed circuit board, so the number of turns of the primary winding is 2 turns or more. Even in this case, a transformer core with a small inner diameter can be used, and the entire power supply apparatus can be reduced in size and cost.

In the first embodiment, a toroidal (annular) transformer core has been described as an example. However, since a closed magnetic path is formed other than the toroidal (annular) transformer core, a square shape as shown in FIG. 9 is formed. Needless to say, the same effect as described in the first embodiment can be obtained with this transformer core as well as the toroidal (annular) transformer core.
In this case, since the transformer core is square, the contact area between the transformer core and the transformer core mounting surface is larger than that of the toroidal (annular) transformer core, so that the transformer core can be stably fixed to the substrate. Therefore, a pedestal is not required, vibration resistance is improved, reliability is improved, and cost and assembly man-hours are reduced.
In general, some rectangular transformer cores can divide the transformer core. After the primary winding is wired, the transformer core is assembled to arrange the primary winding in the hollow portion of the transformer core. This improves assembly.

Further, in the first embodiment, the transformer core having no gap (slit) is described as an example, but even when the transformer core has a slight gap (slit), the magnetic flux is continuous between the gaps (slits), and the transformer core is closed. Since the magnetic path is formed, the same effect as the transformer core having no gap (slit) can be obtained.
In addition, after the transformer core is fixed to the substrate by providing a gap (slit), the primary winding is disposed in the transformer core hollow portion through the gap (slit) without passing the primary winding through the transformer core. As a result, assembly is improved.

In the first embodiment, even if a partial discharge occurs, the primary winding and the secondary winding are insulated by air, so that insulation is caused by a treeing phenomenon that occurs when a partial discharge occurs like a conventional mold transformer. There is no destruction, and the operation can be continued without stopping the apparatus.
Therefore, unlike the first embodiment, when the distance between the primary winding and the secondary winding is short or when the transformer is contaminated, partial discharge is likely to occur. Can be prevented (ozone has repellent effects such as flies and cockroaches and rats, and suppresses insecticidal and pest activity).
When partial discharge occurs between the primary and secondary windings as described above, ozone is generated, and it is possible to prevent malfunctions, short circuit accidents, etc. caused by pests and rats entering the device due to ozone. Increased reliability.

Example 2
10 and 11 are a perspective view and a plan view of a main part showing another configuration example of the transformer part in the gate power supply 7.
In FIG. 10, a plurality of transformer cores 18 are mounted on a printed circuit board 21 via a pedestal 23 so that their hollow portions are connected in a row. The plurality of series primary windings 16 are arranged so as to pass through the inner layer of the multilayer printed circuit board 29 and linearly penetrate the hollow portions of all the transformer cores 18. Both ends of the primary winding 16 are supported on the printed circuit board 21 by a multi-pin terminal block 22, and a primary current is supplied to the primary winding 16 through the multi-pin terminal block 22. Each secondary winding 17 has both ends connected to the wiring on the printed circuit board 21 and supplies a DC voltage to the corresponding gate drive circuit 19 via the rectifier circuit 27.

In the second embodiment, as shown in detail in FIG. 11, in the plurality of transformers 15, the secondary windings 17 are biased from the center of each transformer core 18 toward the printed circuit board mounting portion side (the pedestal 23 side) of the transformer core. The plurality of series primary windings 16 pass through the inner layer of the multilayer printed circuit board 29 and are connected to wiring on the printed circuit board via the multi-pin terminal block 22.
In the case where a plurality of primary windings are arranged in the outer layer as shown in the first embodiment, in order to prevent a short circuit between the plurality of primary windings due to conductive fouling substances, an insulating coating material is provided on the printed circuit board exterior. It was necessary to insulate the primary windings.
In addition, the film thickness of the insulating coating material needs to be managed in order to reliably prevent a short circuit between the primary windings due to fouling substances, but a plurality of primary windings should be arranged in the inner layer of the multilayer printed circuit board 29. The primary windings can be reliably insulated with each other, the reliability against short-circuit failure between the primary windings can be improved, and there is no need to apply an insulating coating material to the printed circuit board. The cost can be reduced by reducing the number.

Generally, the transformer winding is uniformly wound around the entire circumference of the transformer core in order to generate a magnetomotive force uniformly throughout the transformer core. However, when the secondary winding is wound uniformly around the entire core, the primary winding is wound. When the wire passes through the center of the transformer core, the spatial distance between the primary winding and the secondary winding, that is, the insulation performance is maximized and the stray capacitance is minimized. Accordingly, as shown in FIG. 11, the secondary winding 17 is biased toward the transformer core mounting portion side below the center of the transformer core 18 and the primary winding 16 is biased to the secondary winding 17. By biasing to the opposite side and passing through the plurality of transformer cores 18, the spatial distance between the primary winding 16 and the secondary winding 17 is easier than when the primary winding 16 passes through the center of the transformer core 18. Therefore, the transformer core can be reduced in size and weight easily by taking a desired insulation distance.
Further, since the stray capacitance between the primary winding 16 and the secondary winding 17 is inversely proportional to the distance, as described above, the spatial distance between the primary winding 16 and the secondary winding 17 is increased to 1 The stray capacitance between the secondary winding and the secondary winding is reduced, and the common mode current flowing through the stray capacitance can be suppressed.

Furthermore, in general, if the winding moves due to vibration or the like, the winding and the transformer core may rub and the insulation film of the winding may peel off. Therefore, measures such as fixing the winding to the transformer core with an adhesive are taken. However, when the winding is uniformly wound around the entire circumference of the core, it is necessary to apply an adhesive to the entire circumference of the core, which increases the number of assembling steps and processing time, resulting in an increase in cost.
As in the second embodiment, the secondary winding 17 is biased from the center of the transformer core 18 in the direction of the transformer core mounting portion, so that the winding is also bonded at the same time when the core and the mounting surface are bonded. Since it can be fixed, not only can assembly and processing time be improved, but the wiring length of the winding can be shortened, and the cost can be reduced.

In addition, even if it is a case where it is such a structure, it cannot be overemphasized that there exists an effect similar to the said Example 1. FIG.
Further, in the second embodiment, the toroidal (annular) transformer core is described as an example. However, since a closed magnetic path is formed other than the toroidal (annular) transformer core, a square shape as shown in FIG. Needless to say, the same effect as described in the second embodiment can be obtained with this transformer core as well as the toroidal (annular) transformer core.
In this case, since the transformer core is square, the contact area between the transformer core and the transformer core mounting surface is larger than that of the toroidal (annular) transformer core, so that the transformer core can be stably fixed to the substrate. Therefore, a pedestal is not required, vibration resistance is improved, reliability is improved, and cost and assembly man-hours are reduced.
In general, some rectangular transformer cores can divide the transformer core. After the primary winding is wired, the transformer core is assembled to arrange the primary winding in the hollow portion of the transformer core. This improves assembly.

Further, in the second embodiment, the transformer core having no gap (slit) is described as an example. However, even when the transformer core has a slight gap (slit), the magnetic flux is continuous between the gaps (slits) and closed. Since the magnetic path is formed, the same effect as the transformer core having no gap (slit) can be obtained.
In addition, after the transformer core is fixed to the substrate by providing a gap (slit), the primary winding is disposed in the transformer core hollow portion through the gap (slit) without passing the primary winding through the transformer core. As a result, assembly is improved.

1 discharge tube, 2 dielectric capacitor, 3 discharge resistor, 4 output reactor, 5 high voltage switch, 6 gate circuit, 7 power supply for gate, 8 DC high voltage power supply, 9 control circuit, 10
Optical oscillator, 11 Optical fiber, 12 Commercial power supply, 13 AC / DC converter, 14 Transformer gate drive circuit, 15 Transformer, 16 Primary winding, 17 Secondary winding, 18 Transformer core, 19 Gate drive circuit, 20 Semiconductor switch , 21 Printed circuit board, 22 Multi-pin terminal block, 23 Base, 24 Electrode, 25 Void, 26 Insulator, 27 Rectifier circuit, 28 Printed circuit board, 29 Multilayer printed circuit board

Claims (8)

A plurality of semiconductor switches connected in series, a plurality of gate drive circuits that respectively drive these semiconductor switches, and a multi-output gate power supply that supplies a voltage source to each of these gate drive circuits,
The multi-output gate power supply includes a plurality of transformers that supply mutually isolated voltage sources to the gate drive circuits, and a transformer drive circuit that supplies drive power to these transformers,
The transformer includes a transformer core that forms a closed magnetic path, a secondary winding wound around the transformer core, and a primary winding that passes through a hollow portion of the transformer core.
The secondary winding is connected to each of the gate drive circuits;
The primary windings of the plurality of transformers are connected in series,
The series primary winding and the secondary winding are arranged with a spatial distance,
In addition, the high-frequency AC power supply device, wherein the series primary winding is disposed on a printed circuit board.   The plurality of transformer cores constituting the plurality of transformers are arranged so that the hollow portions thereof are connected in a line, the primary winding is constituted by a linear conductor, and the hollow portions of the plurality of transformer cores are collectively arranged. The high frequency alternating current power supply device according to claim 1, wherein the high frequency alternating current power supply device is penetrated.   The high frequency AC power supply device according to claim 1, wherein a gap (slit) is formed in each of the transformer cores.   Each of the secondary windings is wound biased toward the printed circuit board mounting portion side of each of the transformer cores, and the primary winding is biased in a direction opposite to the printed circuit board mounting portion and passes through the transformer core. The high frequency alternating current power supply device according to any one of claims 1 to 3.   The printed circuit board on which the series primary winding is disposed is a multilayer printed circuit board, and the series primary winding is disposed on an inner layer of the multilayer printed circuit board. The high-frequency AC power supply device described.   The primary current or primary voltage in the series primary winding is monitored, and the operation of the gate drive circuit stops when the primary current or primary voltage exceeds a predetermined threshold value. The high frequency alternating current power supply device according to any one of claims 1 to 5.   A secondary side voltage of at least one of the plurality of transformers is monitored, and the operation of the gate drive circuit is stopped when the secondary side voltage exceeds a predetermined threshold value. The high frequency alternating current power supply device as described in any one of Claims 1 thru | or 6.   8. The high-frequency AC power supply device according to claim 1, wherein partial discharge is generated between primary windings and secondary windings of the plurality of transformers, and ozone is generated. 9.