JPH0430823Y2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field] This invention relates to an improvement of an inductive load disconnection circuit that disconnects and disconnects an inductive load such as an internal combustion engine ignition coil without contact. The device prevents oscillation of the transistor by controlling the path of the reverse current flowing through the transistor that turns on and off.

[Conventional technology]

FIG. 3 is a circuit diagram showing a conventional inductive load intermittent circuit. In FIG. 3, 1 is an ignition coil for igniting an internal combustion engine (not shown), and 2 is for energizing this ignition coil 1. This is a power supply that generates a direct current electromotive force.

The negative pole of this DC power supply 2 is grounded, and the positive pole is connected to the collector of the subsequent transistor 3b of the switching transistor 3 through the primary coil of the ignition coil 1. This opening/closing transistor 3 has a switching action for cutting off and on the current flowing through the ignition coil 1.

The opening/closing transistor 3 includes a front-stage transistor 3a, a rear-stage transistor 3b, and balancing resistors 3c and 3d.

On the other hand, the control transistor 4 is a transistor for discharging unnecessary charges generated at the base electrode to the ground potential via the resistor 5 when the switching transistor 3 is in an open state.

The collector of the control transistor is connected to the emitter of the power supply transistor 6, and the collector of the power supply transistor 6 is connected to the positive electrode of the DC power supply 2 via a resistor 7.

The power supply transistor 6 is made conductive in order to close the switching transistor 3, and supplies a base current to the switching transistor 3 via the resistor 7 and the resistor 5.

Next, the operation will be explained. As the internal combustion engine (not shown) operates, the power supply transistor 6 and the control transistor 4 are repeatedly and alternately turned on and off in opposite phases by the output signal of the ignition timing detection and signal amplification circuit (not shown). Driven.

That is, when the power supply transistor 6 is in a conductive state, the control transistor 4 is in a non-conductive state, and a base current is supplied to the base electrode of the switching transistor 3 via the resistors 7 and 5.

As a result, the power supply transistor 3 becomes closed, and an energizing current flows from the DC power supply 2 to the ignition coil 1.

On the other hand, when the power supply transistor 6 is in a non-conductive state, the control transistor 4 is in a conductive state, and the base current of the switching transistor 3 is quickly cut off. As a result, the switching transistor 3 becomes open, the current flowing from the DC power supply 2 to the ignition coil 1 is also cut off, and a high voltage is generated at the connection point between the collector electrode of the switching transistor 3 and the ignition coil 1.

This high voltage is induced to increase in the secondary coil 1a of the ignition coil 1, and an electric spark is generated in the ignition plug (not shown) connected to the secondary coil 1a, and the internal combustion engine is ignited, and the base electrode of the switching transistor 3 The unnecessary charges generated in the resistor 5 are led to the ground potential through the control transistor 4. Thereby, the opening/closing transistor 3 can be opened quickly and stably.

On the other hand, an inductive load is usually composed of a coil wound around a magnetic material, so it has a coil line capacitance. When the coil 1a is included, the line capacitance of the secondary coil is multiplied by the square of the turns ratio and equivalently added to the primary side, resulting in a large capacitance value.

The capacitor 8 shown in FIG. 4 has such a capacitance.

[Problem that the invention attempts to solve]

As a result of this capacitor 8 forming a series resonant circuit with the ignition coil 1, the switching transistor 3 becomes open in FIG. Rise and ignition coil 1
Charging of the capacitor 8 stops when the electromotive forces are balanced, and as time passes, current flows from the capacitor 8 to the ignition coil 1, causing a so-called resonance phenomenon.

When _the collector potential of the switching transistor 3 eventually becomes negative due to this resonance phenomenon, the current shown by the arrow _A1 shown in FIG. The transistor 3b is equivalent to being supplied with a positive base current by the parasitic current indicated by the arrow _A2 .

Due to the accumulated charges of the base current, when the collector electrode of the switching transistor 3 becomes a positive potential again due to the continuation of the resonance phenomenon, the switching transistor 3 is momentarily closed and a collector current flows.

Thereafter, when the accumulated charge disappears due to recombination or the like with a time delay, the capacitor 8 is opened again to cut off the collector current, and at this time, the capacitor 8 is charged as the collector potential rises.

As a result of this repetition, the oscillation phenomenon continues without attenuation, and as a result, the opening/closing transistor 3 becomes virtually incapable of opening, causing problems such as thermal runaway destruction due to heat generated by the oscillation.

This idea was devised to solve this problem; by simply adding a few components, the basic circuit configuration remains unchanged, and the area increases slightly when integrating the circuit. An object of the present invention is to provide an inductive load switching circuit that can prevent oscillation of a switching transistor, suppress an increase in current consumption, and be inexpensive.

[Means for solving problems]

The inductive load switching circuit according to this invention is provided with a second control transistor whose emitter and collector electrodes are connected opposite to the collector and emitter electrodes of the control transistor.

[Effect]

In this invention, when a reverse polarity current flows due to the resonance phenomenon when the switching transistor is opened, the second control transistor is made conductive, thereby quickly stopping the oscillation of the switching transistor. It is.

〔Example〕

Hereinafter, an embodiment of the inductive load switching circuit of this invention will be described with reference to the drawings. FIG. 1 is a circuit diagram of one embodiment. In FIG. 1, parts that are the same as those in FIG. 3 are given the same reference numerals, and a description of the structure thereof will be omitted, and the parts that are different from FIG. 3 will be mainly described.

As is clear from comparing FIG. 1 with FIG. 3, a second control transistor 9 is newly connected in parallel to the circuit configuration of FIG. 3.

That is, the emitter of the control transistor 4 is connected to the collector of the second control transistor 9, and the collector of the control transistor 4 is connected to the emitter of the second control transistor 9.

The base of the control transistor 4 is connected through a balance resistor 11, and the base of the second control transistor 9 is connected through a balance resistor 10, respectively. It is now being entered. The other configurations are the same as in FIG. 3.

Next, the operation of this invention will be explained. 1st
In the embodiment shown in the figure, A when the switching transistor 3 is open
A voltage-current characteristic diagram looking to the left of the point is shown in FIG. 2 by a solid line. Note that the broken line in FIG. 2 represents the voltage-current on the same scale when looking to the left of point A of the conventional inductive load intermittent circuit shown in FIG.

As shown by the solid line in FIG. 2, in the embodiment of FIG. 1, when point A becomes negative potential with respect to the ground potential, the current supplied from point A is extremely large.
Most of this is the current supplied through the path indicated by arrow _Y3 in Figure 1.

Therefore, in FIG. 4, when the current indicated by arrow A ₁ is about to flow, as in the conventional inductive load intermittent circuit, the current indicated by arrow A ₃ can flow, so that the parasitic current indicated by broken line arrow A ₄ flows. Parasitic current no longer flows through the transistor 3b in the rear stage of the switching transistor 3, and therefore, the accumulated charge is stored only in the transistor _3a in the former stage due to the current indicated by arrow A3.

As a result, when the collector potential of the switching transistor 3 rises again due to the resonance effect of the series resonant circuit constituted by the ignition coil 1 and the capacitor 8, this accumulated charge is transferred to the resistor 5 and the control transistor 4 in FIG. is quickly rejected to ground potential via Therefore, the switching transistor 3 also quickly becomes open, and the problem of continued oscillation as in the conventional example is solved.

Note that in the above embodiment, the second control transistor 9 is driven at the same time as the control transistor 4 so as to be conductive, but even if it is constantly driven, the power consumption is somewhat low. However, the desired effect of this invention is the same, and the above simultaneous driving is not a necessary condition.

In this case, even if the base of the second control transistor 9 is constantly driven, while the collector and emitter of the second control transistor 9 are reverse biased, the second control transistor 9 Since the control transistor 4 is not closed, the base potential of the switching transistor 3 is never at the ground level regardless of whether the control transistor 4 is open or closed, and simultaneous driving is not necessary.

In addition, although the above embodiment describes the case where an ignition coil is used as an inductive load, the presence or absence of a secondary coil is not a fundamental factor in the effectiveness of this invention, and the above embodiment also applies when a normal solenoid coil is used. It has the same effect as that, but when the capacity is added externally, it can have an even stronger effect.

[Effect of idea]

As explained above, this device connects the second control transistor opposite the control transistor to control the path of the reverse current flowing through the switching transistor to prevent oscillation. It is possible to minimize the increase in power and the number and area of elements, making it suitable for integrated circuits and at low cost.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram of an inductive load intermittent circuit of this invention and an embodiment thereof, and Fig. 2 is a voltage-current diagram of the inductive load intermittent circuit of this invention and a conventional inductive load circuit when looking to the left of point A. A characteristic diagram showing a comparison of characteristics, FIG. 3 is a circuit diagram of a conventional inductive load intermittent circuit, and FIG. 4 is a circuit diagram explaining phenomena during conventional inductive load intermittent operation. 1... Ignition coil, 2... DC power supply, 3... Switching transistor, 4... Control transistor,
9...Second control transistor. In addition, in the figure,
The same reference numerals indicate the same or equivalent parts.

Claims (1)

[Scope of utility model registration request] A load having an inductive impedance, a DC power supply having one electrode connected to the load, and a collector electrode and an emitter electrode connected between the other electrode of the DC power supply and the load to energize the load. a power supply transistor that controls the base current supply to control the opening and closing of the switching transistor; a control transistor whose opening and closing operate in a phase opposite to that of the power supply transistor; An inductive load intermittent circuit comprising a second control transistor whose emitter and collector are respectively connected to the collector and emitter of the transistor and which are enabled to conduct when the switching transistor is opened. .