JPH0216056B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a transistor circuit that causes a pulse current to flow through an output load.

An internal combustion engine ignition device is an example of a circuit that causes a pulse current to flow through an output load. An internal combustion engine ignition system generates a high voltage on the secondary side of an ignition coil to combust an air-fuel mixture in a cylinder, and an example as shown in FIG. 1 has been developed as a typical conventional circuit configuration. In FIG. 1, 1 is a signal generator, and 2 is a waveform shaping circuit which uses an output signal from the signal generator as an input signal, and is composed of a Schmitt trigger circuit. 8,
9 is an input resistance of the waveform shaping circuit 2. 3 is a drive circuit that drives the output transistor 4 using the output voltage pulse of the waveform shaping circuit 2 as an input signal;
0 constitutes a switch circuit with the output transistor of the drive circuit 3, 5 is the load of the output transistor 4, and 6 is the output transistor of the drive circuit 3.
is the DC power supply line. 7 is a collector resistance of the output transistor of the drive circuit 3. FIG. 2 shows voltage and current waveforms at various parts of the block diagram of FIG. 1. The signal generator 1 generates a signal voltage V ₁ similar to a triangular wave in synchronization with the engine rotation speed, and serves as an input signal to the waveform shaping circuit 2 . Assuming that the conduction level of the waveform shaping circuit 2 is V _ON and the cutoff level is V _OFF , when the input signal becomes lower than the conduction level V _ON , the output voltage of the waveform shaping circuit 2 becomes a high level and the cutoff level V _OFF.
The higher the level, the lower the level. Therefore, the output voltage _V2 of the waveform shaping circuit 2 becomes a rectangular wave as shown in FIG. The output voltage _V2 of the waveform shaping circuit 2 becomes the input voltage of the drive circuit 3, drives the output transistor 4, makes the output transistor 4 conductive, and loads the load 5.
The current I ₅ is determined by the time constant of the inductance and resistance of
flows. Assuming that the inductance on the primary side of the ignition coil of the load 5 is L ₁ and the resistance is R ₁ , the time constant T ₁ of the primary side coil is L ₁ /R ₁ . Assuming that the voltage of the DC power supply line is E and the total resistance on the primary side of the ignition coil is R, the primary side current _I5 of the ignition coil is expressed by equation (1).

_I5 =E/R(1-e ^-TON/T1 ₎ (1) Here, T _ON is the time during which the output transistor 4 is conductive.

In the conventional transistor circuit, the waveform shaping circuit 2
Since the input conduction level and cutoff level are almost constant or change only slightly with respect to the voltage E of the DC power supply line, as is clear from equation (1), the load 5 is The peak value of the flowing current _I5 becomes a large value. This has the disadvantage that the thermal design of the components and packages constituting the circuit becomes extremely difficult, and at the same time has the disadvantage that the output transistor 4 may exceed its breakdown tolerance and be destroyed.

In order to compensate for the above-mentioned drawbacks, the present invention provides a transistor circuit in which the current flowing through the load at low rotation speeds and high voltages does not flow excessively and reaches a suitable and preferable value.

The transistor circuit according to the present invention connects the connection point between the switch circuit for driving the transistor that controls the current supply to the ignition coil and the other end of the resistor, one end of which is connected to the power supply terminal, to the input of the shaping circuit at a constant voltage. The device is characterized in that it is connected via a feedback circuit including an element.

Hereinafter, the present invention will be explained in detail with reference to the drawings.

FIG. 3 shows an embodiment of the present invention, in which 11 is a signal generator that generates a signal synchronized with the engine rotation speed, and 12 is a waveform shaping signal using the signal generated by the signal generator 11 as an input signal. This waveform shaping circuit consists of a Schmitt trigger circuit. 13
20 is a drive circuit that uses the output signal of the waveform shaping circuit 12 as an input signal to drive the output transistor 14;
1 is an output transistor of the drive circuit and constitutes a switch circuit, and 17 is a collector resistor of the transistor 20. 15 is output transistor 1
4 load, 16 is one end of the DC power supply line, 1
8 and 19 are input resistors of the waveform shaping circuit 12, and 22 is a feedback circuit that feeds back a signal from the collector terminal of the output transistor 20 of the drive circuit 13 to the input terminal of the waveform shaping circuit 12. This feedback circuit includes a constant voltage element and A passive element for adjusting the amount of feedback is connected in series. 23 and 24 are connection terminals of the feedback circuit 12.

The output of the signal generator 11 has a waveform close to a triangular wave, as shown as V ₁₁ in FIG. 4, and is supplied to the waveform shaping circuit 2. The waveform shaping circuit 2 has two threshold values V _ON and V _OFF , and when the level of the signal V ₁₁ becomes lower than V _ON , the transistor 20 in the drive circuit 13
conducts, causing output transistor 14 to conduct and a current, shown as I ₁₅ in FIG. 4, to flow through load 15.
When the signal V ₁₁ becomes higher than the threshold value V _OFF of the circuit 2, the transistor 20 is turned off and the output transistor 14 is also turned off. Since the transistor 20 is thus conductive or disconnected, its collector voltage becomes a rectangular wave as shown as _V13 in FIG. The high potential level of this collector voltage V ₁₃ makes the constant voltage element in the feedback circuit 22 conductive, and the low potential level does not make the identification voltage element conductive. Therefore, when the voltage V ₁₃ assumes a high potential level, its level is level-shifted by the feedback circuit 22 and superimposed on the signal V ₁₁ from the signal generator 11 as a DC offset potential, and the superimposed signal becomes the waveform. The signal is supplied to the shaping circuit 12. On the other hand, when voltage V ₁₃ takes a low potential level, signal V ₁₁ is passed directly to circuit 1.
2. As a result, the signal actually supplied to the waveform shaping circuit 12 takes the signal waveform shown by the solid line V ₁₁ in FIG. Indicated by the dashed line in Figure 5.
V ₁₁ indicates the output of the signal generator 11. As is clear from the comparison of these two signal waveforms, the feedback circuit 22
By providing , the timing at which the input level of the waveform shaping circuit 12 becomes lower than the threshold value V _ON of the circuit is delayed. That is, the timing at which the output transistor 14 becomes conductive is delayed. The high potential level of the collector voltage _V13 of the transistor 20, and therefore the DC offset potential superimposed on the output of the signal generating circuit 11, has a dependency on the power supply voltage on the line 16, and increases as the power supply voltage increases.
Further, in an internal combustion engine ignition system, an electromagnetic pickup coil is usually used as the signal generator 11, and such a signal generator 11 outputs a signal V ₁₁ with a smaller peak value as the rotation speed of the internal combustion engine becomes lower.
The higher the rotation speed, the larger the signal V ₁₁ of the peak value is output. Therefore, although the DC offset potential generated by the feedback circuit 22 occurs for all frequencies of the signal V ₁₁ , the lower the frequency of the signal V ₁₁ (lower the rotational speed), the greater the feedback effect. In this way, the higher the power supply voltage is and the smaller the peak value of the signal from the generator 11 is, the later the timing at which the output transistor 14 becomes conductive is delayed. On the other hand, the collector potential V ₁₃
When is at a low potential level, that is, when the output transistor 14 is conductive, the feedback circuit 23 does not work, so the timing at which the input level of the waveform shaping circuit 12 exceeds V _OFF of the circuit does not change.

As described above, the conduction period of the output transistor 14 is shortened by the feedback circuit 22, and the conduction period of the output transistor 14 is shortened.
The current flowing through the feedback circuit 2, shown as the dashed line _I15 , as shown as the solid line _I15 in FIG.
The peak value is smaller than that without 2. The conduction time of the transistor 14 can be reduced by using the power supply line 1.
The higher the voltage of signal V 11 becomes, the lower the peak value of the signal V ₁₁ itself becomes.

Fig. 6 shows a specific embodiment of the present invention, and Fig. 6a shows that when the voltage of the DC power supply line exceeds a certain level, the Zener diode becomes conductive and the feedback circuit 2
2 is operated so that the effect of the present invention is produced, and FIG. The present invention is effective not only in embodiments a and b, but also in combinations of a plurality of diodes and Zener diodes.

Therefore, when the transistor circuit according to the present invention is used as an internal combustion engine ignition device, the conduction time of the output transistor is shortened at low rotation speeds and high voltages.
Since the peak value of the current flowing through the output load is reduced, this is suitable for the breakdown withstand capacity of the output transistor and the thermal design of components and packages constituting the device.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a conventional transistor circuit, FIG. 2 is a voltage and current waveform diagram of each part of FIG. 1, FIG. 3 is a block diagram showing an embodiment of the transistor circuit of the present invention, and FIG. Figure 3 is a voltage and current waveform diagram of each part, Figure 5 is a principle diagram showing the effects of the present invention,
FIGS. 6a and 6b show an embodiment of the feedback circuit of the transistor circuit of the present invention. DESCRIPTION OF SYMBOLS 1, 11... Signal generator, 2, 12... Waveform shaping circuit, 3, 13... Drive circuit, 4, 14... Output transistor, 5, 15... Load, 6, 16... One end of a DC power supply line, 7, 8 ,9,17,18,19
...Resistor, 10, 20... Transistor, 22... Feedback circuit, 23, 24... Connection terminal of feedback circuit.

Claims (1)

[Claims] 1. A signal generation circuit that generates a triangular wave signal that is synchronized with the rotational speed of an internal combustion engine and whose peak value increases in proportion to the increase in the rotational speed, and a signal generation circuit that is connected to this signal generation circuit and generates the triangular wave signal. A drive circuit having a waveform shaping circuit that shapes the pulse signal into a pulse signal, a switch circuit that is connected to the waveform shaping circuit and switches in response to the pulse signal, and a drive circuit that is connected to the drive circuit and that switches in response to the switching operation of the switch circuit. In a transistor circuit comprising a transistor for controlling current supply to an ignition coil, a resistor is connected between the switch circuit and a power supply terminal, and a connection point between the switch circuit and the resistor is connected to a feedback circuit including a constant current element. A transistor circuit, characterized in that the transistor circuit is connected to the input of the waveform shaping circuit via.