JPS60147571A - Ignition device - Google Patents

Abstract

PURPOSE:To miniaturize the device by a method wherein a circuit constitution near an output transistor, driving an ignition coil, is improved to permit the formation of a means, preventing the output transistor or an ignition coil from being broken by a high voltage, in a monolithic IC. CONSTITUTION:The ignition device is equipped with an input signal generating unit 1, determining ignition timing, an input detecting circuit 2, shaping the waveform of an input signal and converting it into a pulse, an ON/OFF duty control circuit 3, generating a signal for determining the duties of ON-period and OFF-period of the output transistor Tr5, an output circuit 6 and a constant current control circuit 7. In this case, three sets of resistors 21-23 are connected in series between the collector of said transistor Tr5 and an earth to provide a voltage splitting circuit 20 for dividing the voltage of collector of the transistor Tr5 through resistors. The cathode of a Zenner diode 25 is connected to the series connecting point 24 of the resistors 22, 23, which are the output points of divided voltages, while the anode thereof is connected to the base of the transistor Tr5.

Description

[Detailed description of the invention] [Technical field of invention] The present invention relates to an ignition device for an internal combustion engine.

[Technical background of the invention]

FIG. 1 is a block diagram showing the configuration of a conventional ignition device used in an internal combustion engine. In the figure, reference numeral 1 denotes an input signal generating section for determining the wide fire timing. The input signal generating section 1 supplies an axle-synchronous input signal (rotation signal) obtained from, for example, a magnet-packed pickup coil to an input detection circuit 2 . The input detection circuit 2 shapes the input signal into a pulse signal, and supplies this pulse signal to the on/off duty control circuit 3. The on/off duty control circuit 3 generates a signal that determines the duty of the on period and off period of the output transistor 5 in order to cause current to flow through the ignition coil 4 for an appropriate time, and supplies this signal to the output circuit 6. This output circuit 6 generates a signal for actually controlling the switching of the output transistor 5, and supplies this signal to the output transistor 50. The constant current control circuit 7 limits the collector current value of the output transistor 5 to a constant value based on the energizing current of the ignition coil 4 obtained using resistors 8 to 10, and also controls the subsequent on/off duty control circuit 3. Feedback signals for control. Further, on the secondary side of the ignition coil 4, an ignition plug 11 is provided for causing spark discharge.

In the ignition device configured in this way, the output transistor 5 is turned on to flow a current to the ignition coil 4, and then the output transistor 5 is turned off to cut off the current, and the reverse voltage energy generated causes the ignition coil 402 to flow. A high voltage is generated on the next side, thereby causing spark discharge at the ignition plug 11. Further, in the conventional ignition device, in order to prevent the output transistor 5 and the ignition coil 4 from being destroyed by the high voltage generated on the primary side of the ignition coil 4 when the output transistor 5 is cut off, the collector of the output transistor 5, 12 Zener diodes between the bases
or connected with the polarity shown.

[Problems with back piercing technology]

In the conventional ignition system shown in Fig. 1, in order to achieve miniaturization, low cost, and high reliability, the input detection circuit 2, on/off duty control circuit 3, output circuit 6, and constant Current control circuit 7 is formed within one monolithic IC. Therefore, in order to further reduce the size of the device, the Zener diode 12 is also
It may be formed within C. However, since the Zener diode 12 is selected to have a relatively large Zener voltage, for example, 300 to 400 cm, close to the sustaining voltage VCE l1lU8 between the collector and emitter of the output transistor 5 (for example, about 500 cm), the IC It is difficult to form such a high voltage diode internally.

[Purpose of the invention]

The present invention has been made in consideration of the above circumstances, and its purpose is to form within a monolithic IC a means for preventing destruction of switching transistors and ignition coils due to high voltage. The object of the present invention is to provide an ignition device that can achieve miniaturization of the device.

[Summary of the invention]

In order to achieve the above object, the present invention divides the collector voltage of the output transistor that drives the ignition coil using a resistor, and provides a Zener between the point where this divided voltage is obtained and the pace of the output transistor. Ignition devices are provided that have a diode connection. With such a configuration, a small candy can be selected as the Zener diode's voltage, and it can be formed in a monolithic IC.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 2 is a block diagram showing the configuration of a first embodiment of the ignition device according to the present invention. In addition, in FIG. 2, the first
The same reference numerals are given to the parts corresponding to those in the figure, and the explanation thereof is omitted, and only the parts that are different from those in FIG. 1 will be extracted and explained below.

That is, in the device of the embodiment, instead of connecting the Zener diode 12 between the collector of the output transistor 5 and the ground, first, three resistors 21, 22, and 23 are connected between the collector of the output transistor 5 and the ground. are connected in series to form a voltage divider circuit 20 for resistively dividing the collector voltage of the output transistor 5, and the cathode of a Zener diode 25 is connected to the series connection point 24 of the resistors 22 and 23, which is the divided voltage output point. , and the anodes of the Zener diodes 25 are connected to the output transistor 5. The Zener voltage of the Zener diode 25 is selected to be the same as that used in conventional circuits (a sufficiently small value, for example, 6 to 8 V).

In such a configuration, if the collector voltage of the output transistor 5 reaches a voltage high enough to destroy the output transistor 5 itself and the ignition coil 4,
This collector voltage is multi-divided by the voltage divider circuit 20 and applied to the cathode of the Zener diode 250. Now, when voltage is generated at the collector of the output transistor 5, the cathode voltage of the Zener diode 25 is equal to or higher than the Zener 1 (voltage). If the value is set, after this, the Zener diode 25 with
turns on and current flows. Since this current is supplied to the output transistor 5 as a pace current, the base current 1 flows in a wide area in the output transistor 5, and as a result, the output transistor 5 and the ignition coil 4 are prevented from being destroyed.

Here, the Zener voltage of the Zener diode 25 is 6
Since the Zener diode 25 is selected to have a value of V to 8 V, which is much smaller than the conventional one, the Zener diode 25 is connected to the input circuit 2, on/off duty control circuit 3, and output circuit included within the broken line in FIG. 6 and constant current control circuit 7 in one monolithic IC. Therefore, together with the reduction in the Zener voltage of the Zener diode 25, the device can be made smaller.

By the way, in such a case, it becomes necessary to measure the leakage current of the output transistor 5 after the device is completed. In the conventional device shown in FIG. 1, this leakage current can be measured by directly applying a voltage to the collector of the output transistor 5. However, in this embodiment device, since the voltage dividing circuit zo2 is connected to the collector of the output transistor 5, the leakage current cannot be measured by applying a voltage to the collector as in the conventional method. Therefore, in this embodiment, the voltage divider circuit can be configured with only two resistors, but it can be configured with three resistors.
A check terminal 26 for measuring leakage current is provided at the series connection point of two resistors 21, 22 and 23, as shown in FIG. The leakage current of the output transistor 5 can be measured by applying a predetermined DC voltage to the terminal 26 and measuring the voltage drop across the resistor 21 at this time.

FIG. 3 is a block diagram showing the configuration of a modification of the embodiment circuit shown in FIG. 2. In FIG. In this modified circuit, one end of the voltage dividing circuit L, ie, one end of the resistor 23, is connected to the output transistor 50 instead of being connected to the ground.

FIG. 4 is a block diagram showing a configuration according to another embodiment of the invention. In this embodiment circuit, a resistor 31 and an NPN are connected to the anode Th of the Zener diode 25 in FIG.
) A current amplification circuit 30 consisting of a transistor 32 is newly provided, and the anode of the Zener diode 25 is connected to the pace of the transistor 32. With such a configuration, the collector voltage of the output transistor 5 can be kept at a high voltage as described above, and when the Zener diode 25 is turned on and a current flows, this current is passed through the current amplifier circuit. Since the current is amplified by the current and supplied as a pace current to the output transistor 50 via the emitter of the transistor 32, destruction of the output transistor 5 and the ignition coil 4 is prevented for the same reason as described above. Moreover, since the Zener diode 25 and the current amplifier circuit 30 operate at a voltage as low as the battery voltage, they can be formed in one monolithic IC.

FIG. 5 is a block diagram showing a configuration according to still another embodiment of the present invention. In this embodiment circuit, a voltage comparator 4 is used in place of the Zener diode 25 in FIG.
0 is set.

This voltage conno'? The non-inverting input of the regulator 40 is connected to the series connection point 24 in the voltage divider circuit, so that this input is supplied with the pollution voltage, the inverting input is supplied with a constant DC voltage, and The output terminal is connected to the pace of the output transistor 5, and the output of this voltage comparator 40 is supplied to the pace of the output transistor 5.

In such a configuration, the pressure at the inverting input terminal of the pressure converter 40 at the collector of the output transistor 5 is so high as to destroy this transistor and the ignition coil 4. At times, a load voltage lower than the dividing voltage occurring at the series connection point 24 is applied. Therefore, when the divided Th'1 voltage at the series connection point 24 becomes higher than the constant voltage supplied to the inverting input terminal of the voltage converter A 40, the output of the voltage comparator 40 is set to a high level. A pace current is supplied to the output transistor 5. As a result, output transistor 5 and ignition coil 4 are prevented from being destroyed.

Moreover, in this embodiment as well, since the voltage handled by the voltage comparator 40 is kept low, it can be formed within one monolithic IC.

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to provide an ignition device that can be downsized by M positions.

[Brief explanation of drawings]

Fig. 1 is a block diagram of a conventional ignition device, Fig. 2 is a block diagram of an embodiment of the ignition device according to the present invention, Fig. 3 is a block diagram of a modification of Fig. 2, and Fig. 4 is a block diagram of the invention. FIG. 5 is a block diagram of another embodiment of the present invention. This is a diagram. DESCRIPTION OF SYMBOLS 1... Input signal generation part, 2... Input detection circuit, 3.
...On/off duty control circuit, 4...Ignition coil, 5...Output transistor, 6...Output circuit, 7
... Constant current control circuit, 20 ... Voltage division circuit, 25
...Zener diode, 26...check terminal,
30... Current amplifier circuit, 40... Voltage comparator.

Claims (5)

[Claims] (1) An ignition coil, a switching transistor that drives this ignition coil, a control circuit that supplies a control signal to the pace of this switching transistor, and a first and second transistor connected in series that divides the collector voltage of the switching transistor. impedance means, and the impedance means of the first.
The series connection point of the second impedance means and the switch. 1. An ignition device comprising: a constant voltage control means inserted between a switching transistor pace and a constant voltage control means. (2) The ignition device according to claim 1, wherein the constant voltage control means is a constant voltage diode. (3) The constant voltage control means includes a transistor whose collector is supplied with a predetermined bias and whose emitter is connected to the pace of the switching transistor, and the pace of this transistor and the first . The ignition device according to claim 1, comprising a constant voltage diode r connected between the series connection point of the second impedance means. (4) The constant voltage control means has one input terminal supplied with a constant reference voltage, and the other input terminal supplied with the first. 2. The ignition device according to claim 1, comprising a voltage comparator circuit to which the voltage of the series connection point of the second impedance means is supplied and whose output terminal is connected to the pace of the switching transistor. (5) The first impedance means, one end of which is connected to the collector of the switching transistor, is composed of two resistive elements connected in series, and a check terminal is connected to the series connection point of the two resistive elements. The ignition device according to claim 1, wherein the ignition device is provided with: