JP2005523570A - Trigger circuit for electronic flash equipment - Google Patents

Abstract

The present invention does not require the use of a separate trigger coil or trigger transformer. This circuit converts a small voltage to a high oscillating voltage to charge the flash (180) and trigger capacitor (150) and provide a trigger voltage to ionize the gas in the flash tube (182). A transformer (120) with additional windings is used to act as a trigger transformer and provide an oscillating voltage to charge the capacitor. When the switch (107) is closed, the trigger capacitor (150) is connected in parallel with the primary coil (122) and the feedback winding (127), which winding is connected to the collector (142) and base (144) of the transistor (140). ) In series. This creates a high voltage on the secondary side of the transformer that is applied to the trigger contact (184) by the rectifier diode (152) to prevent the positive voltage from shorting from the flash capacitor to ground.

Description

  The present invention generally relates to an electronic flash device used in a camera, and more particularly to a circuit suitable for such an electronic flash device.

  The flash device is used in a camera to generate a “flash” in which light is shined when shooting under insufficient light conditions. A special flash tube capable of generating such intense light is used to generate a pulse of intense light sufficient to create an ideal environment for imaging. The flash tube contains the gas in a glass enclosure and the gas must be ionized before flashing. In order to ionize the gas, a sufficient level of voltage must first be released to the surface of the glass container. Once the gas is properly ionized, a capacitor discharge is induced through the flash tube to emit a shining “flash”.

  The trigger voltage required for ionization of the gas in the flash tube is generally about 4 KV. This voltage required to drive the discharge through the flash tube is generally about 300-400 volts. Both of these voltage levels are much higher than a typical portable DC power supply, such as one that a battery can excite. Therefore, it is necessary to prepare an appropriate circuit to convert the battery voltage to a level necessary for operating the flash device.

  A flash device generally requires four main parts: a flash unit, a conversion circuit, a drive circuit, and a trigger circuit.

  In general, a flash unit has a flash tube and a flash condenser. The conversion circuit converts a relatively small DC voltage, for example 1.5-6 volts, to a higher oscillating voltage of about 300-400 volts (referred to as the converter voltage) to charge the flash capacitors in the flash unit.

  The trigger circuit transforms the converter voltage from the conversion circuit to a higher voltage, for example 4 KV. The drive circuit activates the trigger circuit to provide the trigger voltage necessary for ionization of the gas in the flash tube. The general functions of these components are well known to those skilled in the art.

  As a result of improved circuit design, an electronic flash circuit with excellent behavior and low cost has been developed. As a result of such many improvements, circuits with fewer parts and more compact designs have emerged. Major components of the electronic flash circuit are the conversion circuit and the trigger circuit. These components include conversion transformers and trigger coils or trigger transformers.

  There are many trigger circuit structures for flash devices. However, the general function of the trigger circuit is the same, transforming the transducer voltage to the higher trigger voltage required for ionization of the gas in the flash tube. However, typical electronic flash devices require at least two transformers in the circuit. At least one transformer in the conversion circuit and at least one other transformer in the trigger circuit is required. These transformers not only increase the space constraints of the flash device, but also affect the cost.

  A conversion circuit having a trigger capacitor for use in a flash device having a flash capacitor and a flash tube, comprising a switching means, a transformer, a switch, and a trigger contact, the transformer being connected to the switching means and being connected to a DC The power supply voltage is converted into a high vibration voltage to charge the trigger capacitor and the flash capacitor. The transformer has a primary coil and a secondary coil, and the secondary coil has a main winding and a feedback winding. The switch is connected to the trigger capacitor and connects the primary coil to the secondary coil to excite a voltage peak in the secondary coil when the trigger capacitor is discharged. This gives a trigger voltage for ionization of the gas in the flash tube. The trigger contact is connected to the secondary coil and emits a trigger voltage.

  The conversion circuit of the present invention shown in FIG. 1 is particularly suitable for use in the electronic flash device 101. The conversion circuit 105 differs from conventional flash circuits in that it does not require a separate trigger coil or trigger transformer. The conversion circuit 105 functions to convert a relatively small voltage into a high vibration voltage for charging the flash and trigger capacitor, and further provides a trigger voltage for ionizing the gas in the flash tube 182. .

  In general, the electronic flash device 101 is divided into a conversion circuit 105 and a flash unit 109.

  The flash unit 109 includes a flash tube 182, a flash capacitor 180, and a trigger contact 184. The conversion circuit 105 includes a transformer 120 and a switch means 139, and a relatively small DC voltage of about 1.5 to 3 volts is converted to a high vibration voltage of about 300 to 400 volts (conversion voltage for charging the flash capacitor 180). Is called).

  The converted voltage is then transformed to a higher trigger voltage of about 4000 volts. The trigger voltage is used to ionize the gas in the flash tube 182. When the flash tube 182 is sufficiently ionized, a “shiny flash” occurs and the flash condenser 180 discharges the energy stored through the flash tube 182. The general functions of the components described above are well known to those skilled in the art.

  The conversion circuit 105 will be described in more detail. The circuit 105 includes a transformer 120 having a primary coil 122 and a secondary coil 124, and the switch means 139 is composed of a transistor 140. The secondary coil 124 has a feedback lead 132 connected thereto, which divides the secondary coil 124 into a main winding 125 and a feedback winding 127.

  The feedback lead 132 is also connected to the base 144 of the transistor 140. The first end conductor 134 of the secondary coil 124 is connected to the rectifier diode 152, and the second end conductor 130 is connected to the first resistor 156 and the trigger capacitor 150. Trigger capacitor 150 is also connected to charging resistor 154, which is connected to rectifier diode 152.

  The switch 107 connects the trigger capacitor 150 to the second end conductor 128 of the primary coil 122 and the first resistor 156. The first end conductor 126 of the primary coil 122 is connected to the collector 142 of the transistor 140. The second end conductor 128 of the primary coil 122 is connected to the positive side of the DC power source 110. The emitter 146 of the transistor 140 is connected to the negative side of the DC power supply 110.

  Current flows from the DC power source 110 to the base 144 of the transistor 140 through the first resistor 156, the feedback winding 127 and the feedback lead 132 of the secondary coil 124. Transistor 140 is open or switched on, and current flows from DC power source 110 through primary coil 122 and transistor 140 to ground.

  This induces a positive voltage in the feedback winding 127 of the secondary coil 124 and the feedback conductor 132, and this voltage saturates the transistor 140. When transistor 140 saturates, more current flows through primary coil 122 and transistor 140, saturating transformer 120 as well. When the transformer 120 reaches saturation, voltage induction in the feedback winding 127 of the secondary coil 124 is reduced.

  When the induced voltage decreases, the transistor 140 becomes less open, and as a result, the magnetic field polarity in the primary coil 122 changes. Thus, a negative voltage is induced in the feedback winding 127 and the feedback conductor 132 of the secondary coil 124, the base 144 of the transistor 140 becomes a negative voltage, and the transistor 140 is turned off. As a result, the flow of current through the primary coil 122 stops.

  The energy in the transformer 120 becomes zero, the current from the DC power source 110 flows again to the first resistor 156, and the above process is repeated. The voltage of the main winding 125 of the secondary coil 124 corresponds to that of the feedback winding 127 of the secondary coil 124 in polarity and frequency. A voltage of about 300-400 volts across the main winding charges the flash capacitor 180 via the rectifier diode 152.

  The voltage induced in the secondary coil 124 charges the flash capacitor 180 and the trigger capacitor 150. When the switch 170 is closed, the negative voltage of the trigger capacitor 150 is transmitted to the second end conductor 128 of the primary coil 122 of the transformer 120. The positive voltage of the trigger capacitor 150 is transmitted to the second end conductor 130 of the secondary coil 124. The feedback winding 127 of the primary coil 122 and the secondary coil 124 is in series via the collector 142 and the base 144 of the transistor 140. The trigger capacitor 150 is in parallel with the primary coil 122 and the feedback winding 127.

  A negative voltage peak at the second end conductor 128 of the primary coil 122 induces a high positive voltage at the first end conductor 134 of the secondary coil 124. This high positive voltage in the conversion circuit 105 is a trigger voltage and is blocked by the rectifier diode 152. A trigger voltage to the surface of the flash tube 182 via the trigger contact 184 ionizes the gas in the flash tube 182. When the gas in the flash tube 182 is sufficiently ionized, the energy stored in the flash condenser 180 is discharged via the flash tube 182 and a “shining flash” occurs.

  The conversion circuit of the present invention eliminates the use of an additional trigger coil or trigger transformer. In the present invention, the transformer 120 with the feedback winding 127 operates as a trigger transformer in addition to providing an oscillating voltage for charging the capacitor.

  When both the flash capacitor 180 and the trigger capacitor 150 are charged, the trigger capacitor 150 is connected in parallel with the primary coil 122 and the feedback winding 127 by closing the switch 170, and when the switch 170 is closed, the feedback with the primary coil 122 is performed. Winding 127 is connected in series. This results in a very high voltage on the secondary side of the transformer that is directed by the rectifier diode 152 to the trigger contact 184. This prevents the positive voltage from flash capacitor 180 from being shorted to ground. This also applies directly to the circuits of FIGS.

  Conventional transformers for such conversion circuits typically operate at about 40 KHz and do not have sufficient transmission at this frequency to directly replace the trigger transformer. The trigger transformer is required to operate at a frequency level achieved only by a conventional trigger transformer operating at about 1 MHz. A conventional transformer can have a turn ratio of about 200, and when a voltage of 270V is applied from the trigger capacitor 150, it should produce a theoretical voltage in the secondary coil 124 that exceeds 50 kV. . However, the conventional transformer actually only gives a voltage of about 1000V with the same applied voltage (270V).

  In the present invention, by connecting the primary coil 122 of the secondary coil 124 and the feedback winding 127 in series, the turn ratio of the transformer 120 is reduced to about 98 when the feedback winding is in series with the primary coil 122. . Increasing the number of windings resulting from the connection of the primary coil 122 and feedback winding 127 in series increases the inductance correspondingly and also reduces the operating frequency.

  Theoretically, a transformer 120 with a turn ratio of about 98 with the feedback winding connected in series with the primary coil 122 provides a voltage in excess of 25 kV. In practice, a voltage of about 4 kV is generated. This is also true for the circuits of FIGS.

  FIG. 2 is a modification of the circuit of FIG. The flash unit 109 is the same. Some components in the conversion circuit 205 are the same as those in FIG. 1 (transformer 120, transistor 140 and trigger capacitor 150).

  In this circuit, the trigger capacitor 150 is directly connected to the first end conductor 126 of the primary coil 122 and the collector 142 of the transistor 140. When the switch 170 is closed, the negative voltage of the trigger capacitor 150 is connected to the feedback lead 132 of the secondary coil 124 and the positive voltage is connected to the first end lead 126 of the primary coil 122.

  The feedback winding 127 of the primary coil 122 and the secondary coil 124 is connected in series opposite to the conversion circuit 105 of FIG. In the circuit they are via the collector base of transistor 140. The trigger capacitor 150 is in parallel with the feedback winding 127 of the primary coil 122 and the secondary coil 124. Similar to the case of FIG. 1, a high trigger voltage is induced on the first end conductor 134 of the secondary coil 124 to ionize the gas in the flash tube 182.

  The conversion circuit 205 further has “READY” for flash display in the form of an LED (light emitting diode) 260, and the LED 260 illuminates when the flash capacitor 180 is fully charged. The LED 260 is connected in parallel to the first resistor 258 and further connected in series to the second resistor 256. The parallel circuit is further connected to the base 144 of the transistor 140, and the second resistor 256 is connected to the feedback lead 132 of the secondary coil 124 and the switch 170, which is connected to the charging resistor 154.

  FIG. 3 is a modification of the circuit shown in FIGS. The second conductor 128 of the primary coil 122 of the transformer 120 is connected to the collector 142 of the transistor 140, and the second end conductor 130 of the secondary coil 124 is connected to the base 144 of the transistor 140. The first end conductor 126 of the primary coil 122 is connected to the positive side of the DC power source 110 and the trigger capacitor 150.

  The feedback lead 132 of the secondary coil 124 is connected to the switch 170, which is connected to the trigger capacitor 150. “READY” on the flash display is provided by an LED 360 connected to the feedback lead 132 of the secondary coil 124. An input resistor 362 in series with a capacitor 364 connects LED 360 to the emitter 146 of transistor 140 and the negative side of DC power supply 110.

  When the switch 170 is closed after the flash capacitor 180 and the trigger capacitor 150 are fully charged, the negative voltage peak at the first conductor 126 of the primary coil 122 of the transformer 120 is the first end of the secondary coil 125. A negative trigger voltage is induced in the partial conductor 134, which ionizes the gas in the flash tube 182.

  When switch 170 is closed, feedback winding 127 of secondary coil 124 is in series with primary coil 122 via the collector-base coupling of transistor 140. This is the same as the conversion circuit 105 of FIG. In this conversion circuit 305, the polarities of the rectifier diode 152 and the flash capacitor are opposite to those of the circuits of FIGS.

  FIG. 4 is a modification of the circuit of FIG. The feedback lead 132 of the secondary coil 124 is directly connected to the first end lead 126 of the primary coil 122 and the positive side of the DC power source 110. The trigger capacitor 150 is directly connected to the second conductor 130 of the secondary coil 124. Trigger capacitor 150 is connected to second end conductor 128 of primary coil 122 via switch 170.

  When switch 170 is closed, the positive peak voltage from trigger capacitor 150 on second lead 128 of primary coil 122 induces a negative trigger voltage on first end lead 134 of secondary coil 124. The gas in the flash tube 182 is then ionized via contact with the trigger contact 184. The series connection of the primary coil 122 with the feedback winding 127 of the secondary coil 124 is direct and there is no loss compared to the series connection through the collector base of the transistor 140.

  The “READY” indication is made via the LED 460 connected to the first resistor 456 and the input resistor 462 connected to the base 144 of the transistor 140. It may be necessary to protect transistor 140 from voltage peaks at collector 142 when switch 170 is closed using buffer capacitor 464.

  This circuit can be further modified by switching the polarity of the transformer with air gap and the rectifier diode 152. A capacitor replaces LED 460, and first resistor 456 is replaced by a diode. As a result, the conversion circuit 405 is converted into the flyback circuit 405. The flyback circuit has the advantage of fast charging time. This can be done in the same way in the circuits of FIGS.

  FIG. 5 shows a modification of the circuit of FIG. The illustrated conversion circuit 505 is the same as that of FIG. The difference is that the parts of the flash unit 109 are not directly connected to ground. In this circuit, the flash tube 182 and the flash capacitor 180 are directly connected to the base of the transistor.

  FIG. 6 shows a modification of the circuit of FIG. This circuit is the same as the circuit of FIG. The difference between them is that a PNP transistor 640 is used instead of the NPN transistor 140 as in FIGS. Thus, some circuit components change their connections to reflect the change in polarity. The polarity of the rectifier diode 152 and the flash capacitor 180 connected to the first end conductor 134 of the secondary coil 120 are reversed. The positive side of the DC power source 110 is directly connected to the emitter 642 of the transistor 640. This can be done in other circuits as well.

  The circuit shown in FIG. 7 uses a push-pull converter to charge the circuit. The conversion circuit 705 will be described in detail. The conversion circuit 705 includes a transformer 720 having a primary coil 722 and a secondary coil 724, and a switch means 139.

  The switch means 139 of this circuit has first and second transistors 740 and 750. The primary coil 722 has an intermediate conductor 728 that is at an intermediate point of the primary coil 722 and divides the primary coil into a first winding 723 and a second winding 725. Similarly, the secondary coil 724 has an intermediate lead 734 that divides the secondary coil into a first half 727 and a second half.

  The first end conductor 726 of the primary coil 722 is connected to the collector 742 of the first transistor 740. The second end conductor 730 of the primary coil 722 is connected to the collector 752 of the second transistor 750. The trigger capacitor 150 is connected to the collector 742 of the first transistor 740 and the switch 170. The switch 170 is connected to the collector 752 of the second transistor 750. The first resistor 762 is connected between the base 744 of the first transistor 740 and the second end conductor of the primary coil.

  The second resistor 764 is connected between the base 754 of the second transistor 750 and the collector 742 of the first transistor 740. Rectifier diode 152 is connected to first end conductor 736 of secondary coil 724, the positive side of flash capacitor 180 and charging resistor 154.

  The charging resistor 154 is connected to the positive side of the trigger capacitor 150. Another rectifier diode 766 is connected to the second end conductor 732 of the secondary coil 724 and the positive side of the flash capacitor 180. The emitters 746 and 756 of the first and second transistors 740 and 750 are both connected to the ground. The intermediate end conductor 734 of the secondary coil 724 is connected to ground. An intermediate end conductor 728 of the primary coil 722 is connected to the positive side of the DC power supply 110.

  The push-pull converter converts the low voltage from the DC power source into a high vibration voltage and charges the flash capacitor 180 and the trigger capacitor 150. When the flash capacitor 180 and the trigger capacitor 150 are fully charged, the switch 170 is closed, and the first winding 723 and the second winding 725 of the primary coil 722 are connected in series.

  The trigger capacitor 150 is in parallel with the first winding 723 and the second winding 725. The negative peak voltage at the first end conductor 726 of the primary coil 722 induces a negative voltage at the first end conductor 736 of the secondary coil 724. The voltage is blocked by the rectifier diode 152. The gas in the flash tube 182 is ionized by contact with the trigger contact 184.

  In one embodiment of the present invention shown in FIG. 8, the conversion circuit 805 has a transformer 820 having a primary coil 822 and a secondary coil 824. Primary conductor 828 divides primary coil 822 into main winding 825 and feedback winding 823. Primary conductor 828 is directly connected to DC power supply 110. The feedback lead 826 of the primary coil 822 is connected to the LED 860 connected in parallel with the first resistor 856.

  The second resistor 862 is connected to the parallel circuit of the LED 860, the first resistor 856, and the collector 142 of the transistor 140. The collector 142 is connected to a second end conductor 830 of the primary coil 822 and a first capacitor 866 connected to ground. The emitter 146 of the transistor 140 is directly connected to ground.

  The base 144 of the transistor 140 is connected to the primary conductor 828 of the transformer 820 via a third resistor 864. The base 144 is connected to a second end conductor 832 of the secondary coil 824 and a second capacitor 868 connected to ground. The third resistor 864 is connected to the primary conductor 828 of the primary coil 822 and the base 144 of the transistor 140.

  The trigger capacitor 150 is connected between the collector 142 of the transistor 140 and the charging resistor 154. Switch 170 is connected between feedback lead 826 of primary coil 822 and the positive side of trigger capacitor 150. Rectifier diode 152 is connected to first end conductor 836 of secondary coil 824 and trigger contact 184. The rectifier diode 152 and the charging resistor 154 are connected to the flash unit 109.

  When the flash capacitor 180 and the trigger capacitor 150 are charged, the switch 170 is closed, the negative voltage peak from the trigger capacitor 150 is connected to the feedback lead 826 of the primary coil 822, and the positive side of the trigger capacitor 150 is the primary coil 822. To the second end conductor 830. Feedback winding 823 and main winding 825 are in series and induce a voltage peak on first end conductor 836 of secondary coil 824.

  The trigger capacitor 150 is in parallel with the feedback winding 823 and the main winding 825. The voltage peak at secondary coil 824 is blocked by rectifier diode 152. The voltage peak, also called the trigger voltage, ionizes the gas in the flash tube 182 via the trigger contact 184. When the gas in the flash tube 182 is sufficiently ionized, the energy stored in the flash condenser 180 is discharged through the flash tube 182 and a “shining flash” occurs.

1 is a circuit diagram of an embodiment of the present invention incorporated in an electronic flash device. FIG. 6 is a circuit diagram of another embodiment of the present invention incorporated in an electronic flash device. FIG. 6 is a circuit diagram of another embodiment of the present invention incorporated in an electronic flash device. FIG. 6 is a circuit diagram of another embodiment of the present invention incorporated in an electronic flash device. FIG. 6 is a circuit diagram of another embodiment of the present invention incorporated in an electronic flash device. FIG. 6 is a circuit diagram of another embodiment of the present invention incorporated in an electronic flash device. FIG. 6 is a circuit diagram of another embodiment of the present invention incorporated in an electronic flash device. FIG. 6 is a circuit diagram of another embodiment of the present invention incorporated in an electronic flash device.

Explanation of symbols

105: Conversion circuit 107: Switch 109: Flash unit 110: DC power supply 120: Transformer 122: Primary coil 124: Secondary coil 127: Feedback winding 140: Transistor 150: Trigger capacitor 180: Flash capacitor

Claims (18)

  A conversion circuit having a trigger capacitor for a flash device comprising a flash capacitor and a flash tube, comprising a switch means, a transformer, a switch and a trigger contact, the transformer being connected to the switch means and being connected to a DC The voltage from the power source is converted to a high vibration voltage to charge the trigger capacitor and the flash capacitor, and the transformer has a primary coil and a secondary coil, and the secondary coil includes a main winding and a feedback winding. The switch is connected to the trigger condenser and the primary coil is connected to the secondary coil to excite the voltage peak in the secondary coil upon discharge of the trigger condenser, thereby ionizing the gas in the flash tube The trigger contact is connected to the secondary coil to release the trigger voltage. Conversion circuit according to claim.   The converter circuit according to claim 1, wherein the switch connects the primary coil to the feedback winding of the secondary coil.   The converter circuit according to claim 2, wherein the trigger capacitor is in parallel with the primary coil and the feedback winding.   2. The conversion circuit according to claim 1, wherein the switch means includes a transistor. A conversion circuit having a trigger capacitor for a flash device including a flash capacitor and a flash tube, and having a transformer, a transistor, a switch, and a trigger contact, and the transformer includes a primary coil and a secondary coil. Have
The secondary coil has a main winding and a feedback winding. The collector of the transistor is connected to the primary coil, and the base of the transistor is connected to the secondary coil to convert the voltage of the DC power source into a high vibration voltage. The trigger condenser and the flash condenser are charged, and the switch is connected to the trigger condenser and the primary coil is connected to the secondary coil to excite the voltage peak in the secondary coil when the trigger condenser is discharged, A conversion circuit characterized in that a trigger voltage for ionizing a gas is applied, and a trigger contact is connected to a secondary coil to release the trigger voltage.   6. The converter circuit according to claim 5, wherein the switch connects the primary coil in series with the feedback winding of the secondary coil.   7. The converter circuit according to claim 6, wherein the trigger capacitor is in parallel with the feedback winding of the primary coil and the secondary coil.   6. The converter circuit according to claim 5, further comprising a rectifier diode connected between the secondary coil and the flash capacitor, and a charging resistor connected between the trigger diode and the flash capacitor.   6. The conversion circuit according to claim 5, wherein the flash capacitor is directly connected to a DC power source.   The LED is further connected in parallel with the first resistor, and the LED and the first resistor are connected between the base of the transistor and the secondary coil. Conversion circuit.   The conversion circuit according to claim 10, further comprising a second resistor connected in series with the LED and the first resistor.   The conversion circuit according to claim 11, further comprising an LED, a first resistor, and a capacitor connected in series between the secondary coil and ground.   The converter circuit of claim 12, further comprising a second resistor connected between the base of the transistor and the primary coil.   A conversion circuit for a flash device having a trigger capacitor, a flash capacitor, and a flash tube, comprising a switch means, a transformer, and a switch, the switch means having a first transistor and a second transistor. The transformer is connected to the switch means and converts the voltage from the DC power source into a high vibration voltage to charge the trigger capacitor and the flash capacitor. The transformer has a primary coil and a secondary coil. The primary coil has a first winding and a second winding, the switch is connected to the trigger capacitor and the first winding is connected to the second winding, the trigger capacitor During the discharge, a voltage peak is excited in the secondary coil, thereby applying a trigger voltage that ionizes the gas in the flash tube and trigger connection. Converter but which is characterized by releasing the connected to the secondary coil trigger voltage.   15. The converter circuit according to claim 14, wherein the collector and base of the first transistor are connected to the primary coil.   6. The converter circuit according to claim 5, wherein the collector of the second transistor is connected to the primary coil, and the base is also connected to the primary coil and the trigger capacitor.   A conversion circuit having a trigger capacitor for a flash device comprising a flash capacitor and a flash tube, comprising a switch means, a transformer, a switch and a trigger contact, the switch means having a transistor The transformer is connected to the switch means and converts the voltage from the DC power source to high vibration voltage to charge the trigger capacitor and the flash capacitor. The transformer has a primary coil and a secondary coil. The coil has a main winding and a feedback winding, the switch is connected to the trigger capacitor and the main winding is connected to the feedback winding to excite a voltage peak in the secondary coil upon discharge of the trigger capacitor, This gives a trigger voltage to ionize the gas in the flash tube, and the trigger contact Conversion circuit connected to the coil, characterized in that to release the trigger voltage.   6. The conversion circuit according to claim 5, wherein the collector of the transistor is connected to the primary coil, and the base is also connected to the secondary coil.

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