JPH0116341B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pulse current control circuit, and particularly to a pulse current control circuit that uses a coil as an output load and controls a pulse current flowing through the output load.

An internal combustion engine ignition system is a typical circuit that generally uses a coil as an output load. An internal combustion engine ignition system generates high voltage on the secondary side of the ignition coil to combust the air-fuel mixture in the cylinder, but in order to supply sufficient ignition energy, the secondary side of the ignition coil must have a voltage higher than the specified value. High voltage must be applied. To do this, the magnitude of the current flowing through the primary side of the ignition coil (hereinafter referred to as primary side current) must be greater than a specified value. However, a conventional typical circuit of this type is shown in a block diagram in FIG. In the figure, 1 is a signal generator, and 2 is a waveform shaping circuit for shaping the waveform of an output signal from the signal generator as an input signal, which is a Schmitt trigger circuit. 3 uses the output signal of the waveform shaping circuit as an input signal, and an output transistor 4
5 is the load of the output transistor, 6 is a DC power supply line, and 7 is the other end (ground terminal) of the DC power supply line. In FIG. 1, a signal generator 1 generates a signal voltage V ₁ synchronized with the engine speed and supplies an input signal to a waveform shaping circuit 2 . Set the ON level of waveform shaping circuit 2 to V _ON ,
When the OFF level is set to V _OFF , when the input signal becomes lower than V _ON , the output voltage of the circuit goes to high level, and V _OFF
The higher the level, the lower the level. Waveform shaping circuit 2
The output voltage V ₂ becomes the input voltage of the drive circuit 3,
The output transistor 4 is driven, making it conductive and causing a current I ₅ determined by the time constant of the inductance and resistance of the load 5 to flow through its collector. The relationship among the output voltage V ₁ of the signal generator 1, the output voltage V ₂ of the waveform shaping circuit 2, and the current I ₅ flowing through the load 5 is as shown in FIG. Now, ignition coil 1 of load 5
If the next side inductance is L ₁ and the resistance is R ₁ , then
The time constant T ₁ of the primary coil is L ₁ /R ₁ . If the voltage of the DC power supply line is E, and the total resistance on the primary side of the ignition coil is R, then the ignition coil primary side current I ₅
is as shown in equation (1).

Here, T _ON is the time during which the output transistor 4 is conductive, and if the period of the signal is T ₀ and the ratio of the time T _ON during which the output transistor 4 is conductive to the period T ₀ is D, then ( Equation 1) can be expressed as the following equation.

Here, in the conventional pulse current control circuit, the ratio D between the period during which the output transistor 4 is conductive and the period is
is designed to be almost constant with respect to the engine speed, so as is clear from equation (2), when the rotation speed is low - T ₀ is large, sufficient current flows, but as the rotation speed increases When the early −T ₀ is small, the value of the current I ₅ becomes small. Therefore, using the method shown in Figure 1, if T ₁ is selected so that the specified primary current can be obtained at high speeds, the primary current will flow too much at low speeds, resulting in high power consumption. This has the disadvantage that it becomes extremely difficult to thermally design the components, packages, etc. that make up the circuit. Another method of preventing excessive current is to attach a resistor in series with the primary coil, but this has the disadvantage of increasing costs. On the other hand, in order to reduce power consumption at low speeds, if the time constant T ₁ is selected so that the primary current is at the specified value, at high speeds it will be below the specified value from equation (2), and the secondary side of the ignition coil will be The drawback was that sufficient ignition energy could not be obtained.

Therefore, the present invention provides a current control circuit capable of controlling the primary side current to a preferable value over the entire rotational speed range in order to compensate for the above-mentioned drawbacks.

Hereinafter, the present invention will be explained in detail according to Examples.

FIG. 3 is a circuit connection diagram mainly a block diagram showing an embodiment of the present invention, in which 1 is a signal generator that generates a signal synchronized with the engine rotation speed, and 2 is an output generated from signal generator 1. A waveform shaping circuit that shapes the waveform of a signal and consists of a Schmitt trigger circuit. 8
3 is an adder circuit that ORs the output pulse of the waveform shaping circuit and the output pulse of the waveform shaping circuit 12 (to be described later), 3 is a drive circuit that drives the output transistor 4 with a signal synchronized with the output of the adder circuit, and 5 is an output. The load of the transistor 4, 6 is the DC power supply line 7 is the other end (ground terminal) of the DC power supply line, 9
10 is a peak value hold circuit that converts the signal voltage generated in the signal generator 1 into a DC voltage; 10 is a time constant circuit that converts the DC voltage converted by the peak value hold circuit into a current to charge the capacitor 28;
A switch circuit 11 discharges the charge accumulated in the capacitor 28, and discharges in synchronization with the output pulse of the waveform shaping circuit 2. 12 is the above capacitor 2
This is a waveform shaping circuit that shapes the waveform when the voltage at No. 8 reaches a specified level, and consists of a Schmitt trigger circuit. The peak value hold circuit 9 is made up of a resistor 21, a diode 22, and a capacitor 23 connected in series, the time constant circuit 10 is made up of a diode 24, transistors 25, 26, a resistor 27, and a capacitor 28, and the switch circuit 11 is made up of a transistor. 29 Rinaru. 30 is another DC power supply line.

In FIG. 3, a signal voltage V ₁ generated by a signal generator 1 becomes an input signal to a waveform shaping circuit 2. In FIG. The waveform shaping circuit 2 is similar to the waveform shaping circuit 2 in FIG.
If the ON level is V _ON and the OFF level is V _OFF , the output voltage of the circuit will be high level when the input signal is lower than V _ON , and low level when it is higher than V _OFF . Therefore, the signal voltage V ₁ is triggered by V _ON and V _OFF , and the output voltage of the waveform shaping circuit 2 has a pulse waveform as shown in FIG. That is, first, to explain the case where the engine speed is low, the signal voltage generated by the signal generator 1 has a waveform close to a triangular wave as shown in FIG. is converted to DC voltage. However, at low speeds, the peak value of the signal voltage V ₁ is small in proportion to the rotation speed, and its period Ta is long, so the level of the DC voltage V ₉ converted by the pink value hold circuit 9 is low, so The voltage appearing across the resistor 27 of the constant circuit 10 is also small. resistance 27
The voltage appearing across the resistor 27 is converted into a current by the current mirror circuit composed of the diode 24 and the transistor 25. However, as mentioned above, since the voltage level appearing across the resistor 27 is small, the current mirror 24, 25 The current value charged to the capacitor 28 through the capacitor 28 is also small. Therefore, capacitor 28
Before the voltage _V10 reaches the ON voltage of the waveform shaping circuit 12, the transistor 29 of the switch circuit 11, which discharges in synchronization with the output voltage of the waveform shaping circuit 2, becomes conductive and brings the voltage level of the capacitor 28 to zero. I end up. Therefore, the voltage across capacitor 28 V ₁₀
is below the ON level of the waveform shaping circuit 12, the output of the waveform shaping circuit 12 is at a low level, and only the output pulse _V2 of the waveform shaping circuit 2 is applied to the adder circuit 8, and the conduction period of the output transistor is equal to the waveform It is determined by the conduction period of the shaping circuit 2. As described above, at low speeds, the current I5 flowing through the load ₅ corresponds to the conduction cutoff state of the waveform shaping circuit 2.

As the engine speed increases, the signal voltage V ₁
Since the peak value increases and the period Tb becomes shorter as the rotation speed increases, the level of the DC voltage converted by the peak value hold circuit 9 also increases as the rotation speed increases. Therefore, the voltage appearing across the resistor 27 of the time constant circuit 10 also increases, and as described above, this voltage is converted into a current via the current mirror circuits 24 and 25, and the capacitor 28 is charged. This charging causes the voltage V ₁₀ of the capacitor 28 to increase to the waveform shaping circuit 12.
When the ON voltage is reached, the circuit becomes conductive, and the output voltage V ₁₂ of the waveform shaping circuit 12 remains at the level until the switch circuit 11 becomes conductive and the waveform shaping circuit 12 is cut off. Therefore, the waveform shaping circuit 2 is included in the adder circuit 8.
The output pulse of the waveform shaping circuit 12 is added to the output pulse of the waveform shaping circuit 12, and the output voltage _V12 of the circuit 8 becomes as shown in FIG. 4b. This output pulse drives the output transistor 5 via the drive circuit 3. Therefore, when the engine speed is high, the output pulse V ₁₂ is generated from the waveform shaping circuit 12, is added to the adder circuit 8, and the conduction time of the output transistor 4 is lengthened, so that the output pulse V12 flows to the load 5 - the primary side of the ignition coil. The current is increased to provide sufficient ignition energy.

Therefore, when the pulse current control circuit according to the present invention is used as an internal combustion engine ignition device, the output pulse V ₂ of the waveform shaping circuit 2 at low rotation speeds is the output pulse V 2 of the waveform shaping circuit 2, and the output pulse V ₂ of the same circuit 2 and the waveform shaping circuit 12 at high rotation speeds. The sum of the output pulses V ₁₂ determines the conduction period of the output transistor 4, and it is possible to flow the primary current so as to supply sufficient ignition energy to ignite at all rotational speeds. Further, according to the present invention, a voltage value corresponding to the engine speed is held in the peak hold circuit 9, and the time constant is set to an arbitrary value, so that it is extremely easy to obtain the optimum pulse width. Can be done.

The present invention is not limited to the above-mentioned internal combustion engine ignition system, but also applies to a pulse current control circuit that uses a coil as an output load, and is intended to regulate the current value flowing through the load to a set value regardless of the cycle of the input signal. Needless to say, the present invention can be applied to circuits that

[Brief explanation of drawings]

Figure 1 is a block diagram of a conventional pulse current control circuit, Figure 2 is a voltage and current waveform diagram of each part of Figure 1, and
FIG. 3 is a circuit connection diagram showing an embodiment of the pulse current control circuit of the present invention. Figures 4a and b show the third rotation speed when the engine speed is slow and fast, respectively.
FIG. 4 is a diagram of voltage and current waveforms at various parts in the figure. 1... Signal generator, 2, 12... Waveform shaping circuit, 3... Drive circuit, 4... Output transistor,
5...Load, 6...One end of the DC power supply line,
7...The other end of the DC power supply line (ground terminal),
8...Addition circuit, 9...Peak value hold circuit,
10... Time constant circuit, 11... Switch circuit, 2
1, 27...Resistor, 22, 24...Diode,
23, 28... Capacitor, 25, 26, 29...
...transistor.

Claims (1)

[Claims] 1. A first waveform shaping circuit that shapes the waveform of a signal generated by a signal generator, an adder circuit that receives the output pulse of the first waveform shaper as an input, and a drive circuit that receives the output of the adder circuit as an input. a peak value hold circuit that converts a signal generated from the signal generator into a DC voltage, the peak value hold circuit comprising an output transistor that allows current to flow through a load inductance driven by the output of the drive circuit; a second waveform shaping circuit that converts the converted DC voltage into a current according to its level, applies the current to a time constant circuit, and receives the output voltage of the time constant circuit as an input;
a switch circuit that returns the time constant circuit to an initial state in synchronization with the output voltage of the first waveform shaping circuit, and a switch circuit that returns the time constant circuit to an initial state in synchronization with the output voltage of the first waveform shaping circuit; The output voltage pulse is added to an adder circuit, a logical sum is taken, and the conduction period of the output transistor is adjusted by changing the width of the output voltage pulse of the second waveform shaping circuit so that a current exceeding a specified value flows through the output transistor. A pulse current control circuit characterized by: