JPH01112814A - Switching circuit - Google Patents

Abstract

PURPOSE:To obtain a switching circuit having a self-hold function by turning on/off a switching means according to the storage content of a storage means, detecting a main current of the switching means by a current detection means and operating a content change means changing the storage content according to the current detection means. CONSTITUTION:A flip-flop (storage means) consists of transistors(TRs) 20, 21 or the like, a switching means consists of a TR 26 or the like, a current detection means consists of a TR 27, a resistor 30 and a rectifier 31 or the like and a content change means consists of a TR 18 and a capacitor 19 or the like respectively. Items mt1, mt2 are main terminals of the switching circuit. A diode 22 prevents a base current of a TR 23 from flowing to the TR 20. The two resistors 30 have a low resistance and convert the main current of the TR 26 into a voltage. The two rectifiers 31 act like a limiter to the voltage to prevent an overcurrent from flowing to the base of the TR 27.

Description

[Detailed Description of the Invention] Technical Field The present invention relates to a switching circuit that is easy to turn off or forcibly kept off to prevent it from turning on due to malfunction, and has a self-holding function. Leap.

Therefore, in addition to being a substitute for thyristors and GTOs (gate turn off thyristors), the present invention provides power conversion circuits (e.g., series inverters) using resonant circuits, and devices to which this power conversion circuit is applied. For example, ignition devices including internal combustion engine starting ignition devices, high voltage generators, ozonizers, etc.
1.9 Background Art Used in Discharge Lamp Lighting Devices, Induction Heating Devices, etc. Conventionally, there is a GTO as a switching means having a self-holding function and a self-extinguishing function. The switching means shown in FIG. 2 has an expanded main current capacity.

(Reference: Icho 1 Honkoku Sho '55-37178) However, in order to turn off the GTO, a current with a magnitude of - several times the magnitude of the anode current is passed from its cathode to its gate. It is necessary to provide means. Moreover, there is a power short circuit! As in the case of an overload condition, the overcurrent
The disadvantage is that when it flows to TO, it is difficult to turn it off.

Furthermore, to force it off so that it does not turn on due to malfunction, there is a means to short its gate and cathode, or to keep its gate potential lower than its cathode potential. It is necessary to provide

Therefore, there is a disadvantage that the means for turning off the GTO and the 2121st switching means or forcibly keeping them off is complicated and expensive.

In addition, immediately after turning off the G 'T' O, in the unlikely event that the G 'T' is turned on due to a malfunction.
Considering pulling the TO back off, it is best in terms of keeping it off to keep the reverse current flowing between its gate and cathode whenever the GTO needs to be off. , its energy consumption increases.

In addition, as shown in Figure 3, PNP type transistors 1 and N
In this case, we can consider the well-known equivalent circuit of a thyristor that includes a PN type transistor 2. In both transistors 1 and 2, the collector current of one becomes the base current of the other, so this The larger the main current of the switching means, the more
The characteristic is that the base current of

Therefore, the maximum value of current that can flow through these collectors is limited by the maximum rated value of these base currents, so
The switching means shown in FIG. 3 has a disadvantage in that the maximum value of the main current is smaller than when transistors 1 or 2 are used alone in the usual way.

This switching means also has difficulty in turning off the transistor 1 or 2 when an excessive current flows through it, such as in a power supply short-circuit condition or an overload condition.
It has the disadvantage of

Incidentally, one guideline for the maximum value that the base currents of transistors 1 and 2 reach is the value of both base currents when the product of the two emitter-grounded direct current amplification times of transistors 1 and 2 becomes 1.

Furthermore, if switching means with high withstand voltage and large current capacity is required, PNP that satisfies these conditions can be used.
Another problem is that the type of transistor 1 is currently not in practical use.

In order to solve these problems, transistor 1.
The switching means shown in FIGS. 4 and 5 have a lower current rating to make it easier to turn off.

(Reference: Japanese Special Public Service No. 56-5098, Kaikai 56-26
No. 216) However, turning off transistors l and 2,
They have the disadvantage that it is still not easy enough to force them off.

This will be explained using the arm pair shown in FIG. This pair of arms consists of two switching means shown in Fig. 5 connected in series.
Each trigger signal is input to the input terminal.1. It is input from t2. The two rectifiers 11 form a pair of oppositely oriented arms.

Both said switching means are controlled such that when one of them is on, the other one is not turned on. The purpose of this is to prevent these from short-circuiting the DC power supply 5 due to malfunction.For this purpose, during the ON period of the switching means shown in the upper part of the figure, the transistor 15
The base current of is transmitted from the DC power supply 5 to this switching means,
Diode 12. Passes through resistor 14.

On the other hand, during the ON period of the switching means at the bottom of the figure, the base current of the transistor 8 passes through the resistor 7, the diode 12, this switching means, and the DC power supply 5.

However, the magnitude of the current flowing through each diode 12 must be smaller than the holding current of each switching means.

Two sets of diodes 12 and a rectifier 13 prevent these currents and the main current of this arm pair from interfering with each other, two diodes 6 protect each emitter junction of transistors 8 to 10.15.16 from reverse surge voltages. Protect.

It is desirable that the diode 12 and the rectifier 13 be of the fast recovery type.

Such an arrangement ensures that transistors 15, 16 keep the lower switching means off when the upper switching means is on, and transistors 8-10 keep the lower switching means off when the lower switching means is on. Keep its upper switching means off.

However, for that purpose, transistors 8 to 10 or 15
．． 16 must be able to turn off transistor 1.2 according to the presence or absence of current in each diode 12 without compromising the magnitude that the base current of transistor 1.2 can reach.

This is because transistors 1.2 can be forcibly kept off, which means that two sets of transistors 1 to 4 may turn on at the same time due to malfunction caused by noise, causing an overload on the base of transistors 1.2. This means that even when current flows, transistor 1 or 2 can be pulled back off.

Therefore, as in this example, it is necessary to amplify the current of each tiny diode 12 in two or three stages (more in some cases), so the means for keeping these off becomes complicated. This means that it is still not easy enough to turn off the I transistor 1.2.

One way to solve this problem is to use a transistor with a small current rating as transistor 1.2 in order to reduce the size that can be achieved by the base current of transistors 1 and 2 in the switching means shown in FIG. The idea is to increase the number of transistors connected to Darlington to account for the smaller size.

However, if this value is increased, the on-state voltage will also increase, which is a drawback.

As mentioned above, each of the switching means shown in FIGS. 4 and 5 has the disadvantage that it is still not easy enough to turn them off or forcibly keep them off. It is in the means.

Then, in the switching means of FIGS. 4 to 5i3,
Another disadvantage is that the switching means that constitute its components are all limited to bipolar transistors.

For example, a l31MO5 composite element in which a power MO3-FE'l' and a bipolar transistor are cascaded,
Alternatively, it would be convenient if a switching means with a low on-voltage, self-holding function, and self-extinguishing function could be constructed using power MOS and FET.

Therefore, one feature of the present invention is that it is easy to turn off the switch and forcibly keep it off to prevent it from turning on due to malfunction, and depending on the configuration, the switching means shown in FIGS. 4 and 5 can be turned off. The object of the present invention is to provide a switching circuit having a self-holding function, which can maintain an on-voltage at or below the on-voltage level, and which can also use switching means other than bipolar transistors.

DISCLOSURE OF THE INVENTION That is, the present invention provides content changing means for changing the stored content by turning the switching means SWl on and off according to the stored content of the storage means, by causing the current detection means CSl to detect the main current (1) of the switching means SWt, and by changing the stored content. MCI operates according to the current detecting means CSl, and when the main current detecting means CSI detects that the magnitude of the main current [l becomes smaller than a predetermined value, the content changing means MCI operates according to the current detecting means CSl. 1 for storage means
11f is a switching circuit that turns off the switching means SWI.

This allows the switching circuit to have a self-holding function.

Also, when the switching means SWl is on, the signal that keeps it on varies depending on the magnitude of the main current 11, and therefore there is no signal to turn off the switching means SWl, or force the switching means SWl to turn off. It's easy to do.

Furthermore, since the switching means SWI only has to be turned on and off according to the above-mentioned memory contents, its type can be bipolar,
Any transistor, power MOS-FET, etc. will do.

Then, the switching means SWI and the current detection means CS
By modifying the configuration of 1, it is possible to maintain the on-voltage of the switching circuit at or below the on-voltage of the switching means shown in FIGS. 4 and 5.

When the present invention is a switching circuit according to claim 2, the switching means SW2 and the current detection means CS2
, each of the content changing means MC2 is connected to the switching means S
It forms a pair with W1, current detection means CSI, and content changing means MCI, and each plays the same role as these.

However, for example, one of the switching means SWI, SW2 follows the positive output of the storage means, and the other follows its complementary output, so that the on/off operations of both are reversed.

Therefore, a power conversion circuit can be constructed by using each of the switching means SWI and SW2 as a component of an arm.

BEST MODE FOR CARRYING OUT THE INVENTION In order to explain the present invention in more detail, the same will be described below with reference to the accompanying drawings. Figure 1, Figure 7 to Figure 11, Figure 1
2 ((a), (b)), FIG. 13, and FIG. 14 show circuit diagrams of the ninth embodiment.

In the embodiment of FIG. 1, transistors 20, 21, etc. serve as a flip-flop (the aforementioned storage means), transistors 26, etc. serve as switching means SW1, transistor 2
7, the resistor 30, the rectifier 31, etc. constitute the current detection means CS1, and the transistor 18, the capacitor 19, etc. constitute the content changing means MCI. mtl and mt2 are main terminals of this switching circuit.

Diode 22 prevents the base current of transistor 23 from flowing towards transistor 20.

The two resistors 30 convert the main current of the transistor 26 into a voltage with low resistance. The two rectifiers 31 act as limiters for this voltage and prevent excessive current from flowing to the base of the transistor 27.

The reference value used to determine whether the magnitude of the main current is smaller than a predetermined value is determined by each of the resistors 28 to 30 and the base-emitter voltage at which the transistor 27 is turned on.

Note that this predetermined value is the same as in the case of a thyristor.While the main current flowing through the thyristor 30 is larger than its holding current, the transistor 27 is on and the transistor 18 is on the capacitor 19.
to charge.

On the other hand, when the main current becomes smaller than its holding current, transistor 27.18 turns off, so capacitor 19 turns off transistor 21, and the memory contents of the flip-flop change. In other words, the state is switched.

Transistor 26 turns off.

Therefore, it can be seen that this switching circuit has a self-holding function.

To trigger this switching circuit, a positive trigger signal may be manually applied to the base of the transistor 21.

If the trigger signal is directly applied to this base manually from the outside, depending on the state of the load connected to the main terminal mal or m1, 2 of this switching circuit, if the main current does not flow through the resistor 30, this switching circuit has the disadvantage that it remains on forever.

Therefore, by manually inputting a trigger signal as shown in the figure to the input terminal L3, the transistor 18 and capacitor 19 trigger the transistor 21.
Even if the main current does not flow, when this trigger <2 rises, the transistor 18 is turned off and the capacitor 19 turns off the transistor 21, so this drawback is eliminated.

Turning off this switching circuit is easy. To do this, first turn on transistor 20 or short-circuit the base and emitter of any of transistors 18, 21, and 23.
All you have to do is turn off one of 21.23.

Furthermore, it is easy to keep this switching circuit strongly off. For that, transistor 21 or 2
The transistor 21 or 23 may be kept off by short-circuiting the base and emitter of the transistor 20, or the current may continue to flow through the base of the transistor 20.

Further, transistor 26 is a power MOS FET, but of course it is not a bipolar transistor or the aforementioned BIMO3 composite element. Therefore,
Switching means other than bipolar transistors can also be used as components of the switching means SW1.

Since the on-voltage of this switching circuit is the sum of the on-voltage of the transistor 26 and the on-voltage of the two rectifiers 31, if a power MOS-FET with a small on-resistance is used for the transistor 26, this on-voltage can be adjusted to The on-voltage of the switching means shown in FIGS. 4 and 5 can be made approximately the same.

Note that the rectifier 32 is preferably provided when a current in the opposite direction flows through the resistor 30.

In the embodiment of FIG. 7, comparator 35 detects the magnitude of the main current of transistor 26 flowing through resistor 36. In the embodiment of FIG. −
Vst represents the magnitude of the reference potential.

Furthermore, since the charging current of the capacitor 19 is prevented from flowing to the base of the transistor 21, a trigger method using this charging current cannot be used.

Therefore, this embodiment has the above-mentioned disadvantage of on-response. Of course, this drawback can be eliminated by removing the two diodes 33 and shorting both ends of the diode 34.

The reason why two diodes 33 are connected in series is to reliably prevent the current that should flow to the base of the transistor 21 from flowing toward the diode 33.

To trigger this switching circuit, input a positive trigger signal to the base of transistor 21,
This can be done by manually applying a negative trigger signal to the base of the transistor 20.

The other functions and effects of this switching circuit are generally the same as those of the circuit of FIG.

In the embodiment of FIG. 8, the Darlington-connected transistors 37 to 39 are also components of the switching means SW1 and the current detection means CSI.

This is because during the on-period of transistor 37, transistor 38.39 and resistor 43.44 play the role of two rectifiers 31 and resistor 30 of the 11th iU, so that the main current of this switching circuit When is large, only a part of it flows through resistor 43.44, and when it is small, most of it flows through resistor 43.44.

Therefore, by detecting the voltage of resistor 43 or 44, it is possible to detect whether this main current is larger than the holding current and the phase of both voltages of resistor 4:3.44 according to the emitter voltage. be.

Note that since the current of the resistor 40 is sufficiently smaller than its holding current, there is no problem in its detection. Alternatively, the amount may be added to the +Ii current for detection.

Then, the magnitude of the holding current is determined by the transistor 27
It is determined by the base-emitter voltage at which the transistor turns on and the values of the resistors 41-44.

To trigger this switching circuit, turn on any of the transistors 20.18.27 or
All you have to do is turn off the transistor 21.

Conversely, to turn off this switching circuit, turn on any of the transistors 20.18.27.
Either the transistor 21 can be turned off or the transistor 21 can be turned on.

The other functions and effects of this switching circuit are generally the same as those of the circuit of FIG.

Note that the on-voltage of this switching circuit is determined by the voltage between the collector and emitter of the transistor 37 and the voltage between the collector and emitter of the transistor 38.
．． Since the phase of the voltage between both bases and emitters of the load resistor 53 and the emitter of the load resistor 53, the embodiment of FIG.
The rolling axle 54 and the commutating capacitor 55 are a series inverter circuit forming a series resonant circuit.

Darlington-connected transistors 50-52, transistors 37-39, and two rectifiers 13 form an arm pair.

Transistor 49.15, rectifier 13 and diode 6
．． 12 etc. are provided to prevent this pair of arms from short-circuiting the DC power supply 5.

As long as transistors 50 to 52 are on, 11 on the top of Figure 1
Since the current of the diode 12 of v4 flows to the base of the transistor 15, the transistor 15 becomes the transistor 37.
Similarly, transistor 49 prevents transistors 50-52 from turning on as long as transistors 37-3 are on.

The diode 6 is a measure against the reverse surge voltage applied between the bases and emitters of the four transistors 15.

By the way, this embodiment corresponds to the switching circuit set forth in claim 5.

The transistors 20, 21, etc. constitute a flip-flop (corresponding to the above-mentioned storage means), and the transistors 50 to 52, etc. and the transistors 37 to 39, etc. constitute a switching means SW1,
SW2, transistor 56.27, rectifier 31.32
and resistor 30 etc. constitute current detection means CS1, CS2, respectively, and transistors 18, 46, 47,
Diodes 33, 34, capacitors 19, 48, etc. constitute content changing means MC1, MC2, respectively. However, if the input terminal t4 is not connected to the ground line, the output f knee of the transistor 47 will be connected to the transistor 4.
6, the predetermined action (content change) on one of them is not performed.

The reason why one end of the resistor 57 is separated from the ground line and used as the input terminal 4 is that by simply doing this, a starting/stopping means for controlling starting and stopping of this series inverter circuit can be easily formed. This is because it is possible.

The operation of this circuit, including this, will be described below. When the operation is stopped, the external input terminal 7-t
The start/stop signal input to 4 is at high level,
Transistors 45,46 are off. A 1-transistor 45 is also included in the activation/deactivation means, with transistor 45 firmly fixing transistor 20 off and transistor 21 on.

Therefore, transistors 50 to 52 are fixed off, and transistors 37 to 39 are fixed on.

Here, when the start/stop signal falls, transistors 45 and 46 are turned on. This signal is low
While at the level, transistor 45 remains on, so transistors 20 and 21 are free to operate as flip-flops.

Further, when the start/stop signal falls, the transistor 46 is turned on, and the charging current of the capacitor 48 flows to the base of the transistor 20, so that the transistor 20 is turned on.

Transistors 37-39 are then turned off and transistors 50-52 are turned on.

As a result, the main current of transistors 50-52 flows to resistor 30 through its series resonant circuit. While this main current is larger than the holding current determined by the characteristics of the transistor 27, the value of the resistor 30, etc., the transistor 27 is on, so the transistor 18 charges the capacitor 19.

Thereafter, when this main current becomes less than its holding current, transistor 27.18 turns off, so that the discharge current of capacitor 19 turns off I transistor 20.

Therefore, the memory contents of that flip-flop change.

In other words, the state is switched and the transistors 50-5
2 is turned off and transistors 37-3 are turned on.

As a result, the commutating capacitor 55 discharges via the load resistor 53, the transistors 37 to 39, the resistor 30, and the like. The main current of transistors 37 to 39 is its "holding current"
When it becomes larger, transistor 56.47 turns on.

At this time, if the start/stop signal is at a low level, the transistor 47 keeps the transistor 46 off during the temporary discharge period, and the capacitor 48 is discharged.

Thereafter, when its main current becomes less than its holding current, transistor 56.47 turns off.

At this time, if the start/stop signal is still at a low level, the transistor 46 is turned on, and the same process is repeated. This repetition continues as long as the start/stop signal remains at a low level.

On the other hand, when the start/stop signal rises during the operation of the circuit, the transistor 20 is forcibly turned off and the transistor 21 is turned on regardless of the state of the free tube flora 1.

Therefore, transistors 50 to 52 are turned off.

Since the transistors 37 to 39 are each fixed on, the oscillating current of the series resonant circuit flows through the transistor 37.
~ 39 or flows through the rectifier 11 and is attenuated.

The embodiment shown in FIG. 1θ is a bridge type series inverter circuit. Darlington connected transistors 58-60.6
1~63.50~52.37~39 and 4 rectifiers 1
3 are connected in a bridge.

The role of the 1-herald resistor 49.15, the rectifier 313, the diode 6.12, etc. is the same as that of the circuit shown in FIG. 9, and is a measure to prevent short-circuiting of the power supply.

If the input terminal L5 is grounded and the DC power supply 5 and its series resonant circuit are removed, this circuit configuration is symmetrical.

The structure of the transistors 27, 56, etc. for detecting the magnitude of the main current of the transistors 50-52, 61-63 or the transistors 58-60, 37-39 is the same as in the circuit of FIG.

Initially, when the DC power supply 17 is connected to this series inverter circuit, the transistor 18 is turned on and the charging current of the capacitor 19 flows to the base of the transistor 20. Therefore, the memory contents of this flip-flop are initialized so that transistor 20 is on and transistor 21 is off.

When the operation of this circuit is stopped and the start/stop signal input to the input terminal falls, the transistor 46 turns on, so the capacitor 4
A charging current of 8 turns transistor 21 on.

Therefore, the memory contents of the flip-flop change,
Transistor 21 is on and transistor 20 is off.

As a result, transistors 58 to 60 and transistor 37
-39 are off, and transistors 50-52 and transistors 61-63 are on.

The main current of transistors 50-52, 61-63 is
The transistor 27 is on while the holding current is greater than the
Since transistor 64 keeps transistor 18 off, capacitor 19 discharges and prepares for the next trigger.

When the main current becomes less than the holding current, the charging current of capacitor 19 turns transistor 20 on.

Therefore, the memory contents of the flip-flop change,
Transistor 20 is on and transistor 21 is off.

As a result, transistors 50 to 52 and transistor 61
-63 is off and transistors 58-60 and transistors 37-39 are on.

The main current of transistors 58-60, 37-39 is
The transistor 56.47 is on while the holding current is greater than the holding current.

At this time, if the start/stop signal is at a low level, the transistor 46 is turned off, and the capacitor 48 is discharged to prepare for the next trigger.

When the main current becomes less than the holding current, if the start/stop signal is still low, transistor 46 turns on, and so on. This repetition continues as long as the start/stop signal remains at a low level.

However, when the main current becomes small, if the start/stop signal is at a high level, transistor 46 remains off. Therefore, the memory contents of the flip-flop remain unchanged as long as the start/stop signal is at a high level.

Therefore, transistors 58-60 and transistors 37-
39 is left on, the current in its series resonant circuit undergoes damped oscillation, and the voltage of the commutating capacitor 55 converges to the voltage of the DC power supply 5.

In this circuit, each main current is detected by detecting the voltage across both emitter resistors (or both emitter junctions) of the transistor 38, 39 or 62, 63.

On the other hand, there is also a method of detecting the voltages of the transistors 59, 60 or 51, 52, such as the method of detecting the circuit of FIG. 11, which will be described later. Or you can use both methods.

In any case, any combination of methods does not matter as long as each main current can be detected.

The embodiment shown in FIG. 11 is an ignition circuit using a series inverter circuit. This main circuit is based on the circuit of FIG. 9, with load circuit 53. A primary coil 69a of an ignition coil 69 is connected instead of the commutation reactor 54.

Two sets of ignition coils 69, an ignition discharge gap 70, a commutating capacitor 55, rectifiers 71-73, etc. are equally connected to the arm pair formed by transistors 50-52, 37-39, etc. If necessary, you can increase the number of pairs.

Two switches 75 determine in which ignition discharge gap 70 or both the spark is generated.

Transistor 74 and rectifier 73 constitute a two-way switch.

Since the rectifiers 71, 72 limit the voltage oscillations of the commutating capacitor 55 to a range from zero to the voltage of the DC power supply 5, the oscillating voltage is stabilized. Therefore, almost no current flows through the two rectifiers 11. These are mainly measures against surge voltage.

Note that the transistors 49, 15, etc. play a role in preventing power supply short circuits, but in this embodiment, the current of each diode 12 is of a magnitude that does not interfere with the current detection of the transistors 68, 56, etc. There needs to be. That is, the magnitude of each current must be sufficiently smaller than the holding current -1.

Alternatively, the current of the diode 12 and its maintenance t! Since each part of the i current is known, it is sufficient to consider detecting the sum from the beginning.

Next, the operation of this main circuit will be described. Immediately after transistors 50-52 are turned on, commutating capacitor 5
Since the voltage of DC power supply 5 is initially zero, the voltage of DC power supply 5 is directly applied to primary coil 69a. Therefore, a high voltage is induced in the secondary coil 69b, and a spark is generated in the ignition discharge gap 70.

Thereafter, when the voltage on commutating capacitor 55 becomes equal to its supply voltage, rectifier 71, which was previously off due to the reverse voltage, turns on.

Therefore, rectifier 71, transistors 50-52, and rectifier 13 serve as a flywheel diode for primary coil 69a, and the voltage of commutating capacitor 55 does not exceed its power supply voltage.

On the other hand, when transistors 37 to 39 are turned on,
The voltage of the commutating capacitor 55, which is not charged to the voltage of the DC power source 5, is applied to the primary coil 69a in the opposite direction.

Therefore, a high voltage in the opposite direction is induced in the secondary coil 69b, and a spark is generated in the ignition discharge gap 70.

Thereafter, when the voltage of the commutating capacitor 55 becomes zero, the rectifier 72, which had been off due to the reverse voltage, turns on.
Turn on. Therefore, both ends of commutating capacitor 55 are short-circuited, and rectifier 13, transistors 37 to 39 and rectifier 7
3.72 is the flywheel for the primary coil 69a.
- Acts as a diode. Therefore, the voltage of the commutating capacitor 55 remains zero, returning to the initial state.

The operation of the control section of this ignition circuit will now be explained. The ignition signal input to the input terminal L6 (this is the start/stop signal in this case).

) is at a high level, its ignition operation is stopped.

Further, at this time, since the transistor 66 is off and the transistor 67 is on, the transistor 67 charges the capacitor 48, fixing the transistor 21 on and the transistor 20 off.

As a result, transistors 50-52 are turned off and transistors 37-39 are fixed turned on.

Now, when the ignition signal falls, transistor 66 turns off transistor 67, so its flip-flop becomes free; at the same time, the discharge current of capacitor 48 turns off transistor 21, so that its flip-flop becomes free. The memory contents of flip-flops change.

Therefore, transistors 37-39 are turned off,
Transistors 50-52 turn on.

Since transistor 68.65 is on while its main current is greater than its "holding current", transistor 18 charges capacitor 19 and capacitor 19 is ready for the next trigger.

When its main current becomes less than its holding current, transistor 68.65.18 turns off, so that the discharge current of capacitor 19 turns off transistor 20.

Therefore, the memory contents of the flip-flop change,
Transistor 20 is off and transistor 21 is on.

Therefore, transistors 50-52 are turned off,
Transistors 37-39 turn on.

Transistor 56.46 is on while its main current is greater than its "holding current". At this time, if the ignition signal is at a low level, transistor 46 charges capacitor 48, and capacitor 118 prepares for the next trigger.

When its main current becomes less than its holding current, transistor 56.46 turns off.

At this time, if the ignition signal is still low level,
The discharge current in capacitor 48 turns transistor 21 off, and so on. This repetition continues as long as the ignition signal remains low.

On the other hand, when the ignition (No. 3) starts up, no matter what state this ignition circuit is in, the transistor 67 fixes the transistor 21 on and the transistor 20 off, and the operation stops.

As a result, the current in the primary coil 69a flows through the rectifier 13,
It is attenuated through the transistors 37 to 39 and the rectifiers 73, 72, or the rectifier 71, the DC power supply 5 and the rectifier 11.

To prevent this from happening while the main current of transistors 50-52 is greater than their holding current, transistor 65
However, in order to do this, the input side of the transistor 66 should be made into an OR circuit, one input to the input terminal L6 as before, and the other to the transistor 66. It is necessary to connect to 65.

The embodiments shown in FIGS. 12(a,) and 12(b) are also ignition circuits using a series inverter circuit. Connection terminals Ct1 to ct5
The same numbers are connected to each other.

In this main circuit, one end of the primary coil 69a is grounded, so the means for stabilizing the oscillating voltage of the commutating capacitor 55 described above is somewhat complicated.

1- Since the transistor 77 is also on while the transistors 50 to 52 are on, the rectifier 13 and the transistor 6
1 to 63 and the rectifier 71 serve as flywheel diodes for the primary coil 69a.

On the other hand, during the ON period of the transistors 37 to 39, the rectifier 7
2.13 and transistors 37-39 play that role.

Further, the transistor 15 needs to keep the transistors 37 to 3 off not only during the on period of the transistors 50 to 52 but also during the on period of the transistors 61 to 63. This is to prevent commutation capacitor 55 from shorting.

Therefore, the transistor 76 detects whether the transistors 61 to 63 are on or off, and sends the output to the transistor 15.

(Reference: PCT/JP87100595) On the contrary,
During the on period of transistors 37 to 39, transistor 4
9 prevents transistors 50-52 from turning on', transistors 79.80 block transistors 77.61-
Prevent 63 from turning on.

However, the current of each diode 12 is the same as that of the transistor 68.
It is necessary that the size is such that it does not interfere with current detection such as 65.27. In other words, the magnitude of each current must be sufficiently small compared to each "holding current".
Alternatively, the amount of current may be taken into account.

Then, transistor 27 etc. are replaced by transistors 61 to 6.
The main current No. 3 is detected and its output No. 15 is transmitted to the transistor 18. Accordingly, transistor 18 receives and receives respective output signals from the two current sensing means. However, the current detection means of the transistor 68 does not need to be provided.

The operation of the control section of this ignition circuit is generally the same as that of the circuit of FIG.

In the embodiment of FIG. 13, the inventor has discovered that the current detection means CS1
Photocoupler 82 (TLP manufactured by Toshiba Corporation) is used as a part of the
5501 is used to connect the resistor 30 and the like to the collector side of the transistor 81.

mt7 and mt8 are the main terminals of this switching circuit.

141st! Examples of 0 m to 9 mt are also possible.

10 is the main terminal of this switching circuit. (2) Ss represents the magnitude of the reference potential.

Related patent: Japanese Patent Publication No. 62-5019 1) CT/JP
No. 87100053 Roki Patent Application No. 61-013938 No. 62-120234 No. 62-170898 1) CT/JP No. 87100595 P CT/JP 87/00 G No. 12

[Brief explanation of the drawing]

114, Fig. 7 to Fig. 11, Fig. 12 t 1), (b
)i Figures 13 and 14 are circuit diagrams showing embodiments of the present invention, Figures 2 to 5 are circuit diagrams showing conventional switching means, and Figure 6 is a circuit diagram showing conventional switching means. This is a circuit diagram showing a pair of arms. (Explanation of symbols) t1~L7... Input terminal, mtl~mLL
. ---Main terminal, 35...Comparator, 53...Load resistance, 54...
... Commutation reactor, 55... Commutation capacitor, 69... Ignition coil, 69a...
...Primary coil, 69b...Secondary coil, 70...Ignition discharge gap, cL
1~c 1, 5... Connection terminal, 82...
...Photo coupler.

Claims (5)

[Claims] (1) Switching means S according to the memory contents of the storage means
W1 is turned on and off, the current detection means CS1 detects the main current I1 of the switching means SW1, and the content changing means MC1 for changing the stored content changes the current detection means CS1.
and when the current detecting means CS1 detects that the magnitude of the main current I1 has become smaller than a predetermined value, the content changing means MC1 stores the switching means S in the storage means.
A switching circuit characterized in that W1 is turned off. (2) The switching means SW2 operates in the opposite direction to the switching means SW1 according to the stored contents, and the current detection means CS2 detects the main current I of the switching means SW2.
content changing means MC2 that detects 2 and changes the memory content;
operates according to the current detecting means CS2, and when the current detecting means CS2 detects that the magnitude of the main current I2 has become smaller than a predetermined value, the content changing means MC2 stores the switching in the storage means. Means S
The switching circuit according to claim 1, characterized in that W2 is turned off. (3) A switching circuit according to claim 2, wherein the switching means SW1 and SW2 form an arm pair. (4) The switching circuit according to claim 2 or 3, wherein each of the switching means SW1 and SW2 is a component of an arm of a series inverter circuit. (5) Claim 4, characterized in that the starting/stopping means changes the stored content or causes the storage means to maintain the stored content based on a starting/stopping signal given from the outside. Switching circuit as described.