JPS63239368A - Ignition device for internal combustion engine - Google Patents

Abstract

PURPOSE:To obtain stable ignition by providing a temperature compensating function to a reference voltage generating circuit producing a constant voltage irrespective of variations in power source voltage, and by controlling the primary current of an ignition coil in accordance with the reference voltage. CONSTITUTION:In a system composed of a power source 1, an ignition coil 2 and an ignition device 3, the input terminal of the ignition device 3 is connected to a power transistor 301 and a constant current control circuit 308, and the output terminal thereof s connected to the collector of the power transistor 30. Further, a primary current detecting resistor 302 for the ignition coil 2 is disposed between the emitter of the power transistor 301 and the ground, and the divided point between resistors 304, 305 connected to both ends thereof is connected to one of input terminals of a comparing circuit composed of transistors 313 through 318 and a resistor 353 in the constant current control circuit 308. Further, the other input terminal of the comparing circuit is connected to a reference voltage generating circuit composed of transistor 319 though 322 and resistors 354 through 356.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to internal combustion engine ignition systems, and in particular to secondary current limiting.

[Conventional technology]

A conventional ignition system of this type is shown in FIG. 3. In FIG. 0, 111 is a power source, (2) is an ignition coil,
3) is the ignition device, (41 (51 is the ignition bag! Resistor and transistor that generates the drive signal.
), the output terminal (31) is connected to the ignition coil (2), the ground terminal (32) is connected, and the input terminal (33
) is connected to the resistor (4) and the transistor (5).

Ignition device (3) by turning on and off the transistor (5)
A signal is supplied to the input terminal (33) of the transistor (
5) is off, the power transistor (
A current flows into the base of the ignition coil (2), the power transistor (301) is turned on, and the negative current of the ignition coil (2) flows.

- The next current detection resistor (302) is the power transistor (3
01) is provided between the emitter of the primary current detection resistor (302) and the ground, and as the negative current increases, the voltage generated across the primary current detection resistor (302) increases.

The base of the transistor (307) is connected to the connection point between the power transistor (301) and the negative current detection resistor (302) via a resistor (304), the emitter is grounded, and the collector is connected to the base of the power transistor (301). Furthermore, a resistor (305) and a transistor (306) are connected between the base and emitter of the transistor (307). - When the voltage generated in the current detection resistor (302) exceeds the on-voltage of the transistor (307), current flows into the base of the transistor (307) and the resistor (305) via the resistor (304).
The collector of the power transistor (307) sinks only the current amplified from the current flowing into the base from the current flowing into the base of the power transistor (301).

Here, the current flowing into the base of the power transistor (301), the voltage generated in the negative current detection resistor (302),
When an equilibrium state determined by the current flowing into the base of the transistor (307), the current amplification factors of the power transistor (301) and the transistor (307), etc. is reached, the primary current of the ignition coil is limited to a constant value.

The transistor (306) has its collector and base shorted and operates as a diode.

This is to compensate for the temperature change in the base-emitter voltage of the transistor (307) with the temperature change in the base-emitter voltage of the transistor (306), so that the current limit value is not affected by temperature. It is provided.

It is known to limit the primary current of the ignition coil, as in the above example, to ensure that the primary current does not exceed the current required for ignition, and to allow the use of smaller rated power transistors.

[Problem that the invention seeks to solve]

However, in the above conventional example, the current supplied to the base of the power transistor (301) changes as the power supply voltage changes, whereas if the primary current of the ignition coil is constant, the transistor (3G?> Since the current value to be sucked is constant, a constant current limit value cannot be obtained with respect to changes in the power supply voltage.

For example, when the power supply voltage increases, the current supplied to the base of the power transistor (301) increases, but in order for the transistor (307) to absorb this increase, the voltage generated across the primary current detection resistor must increase. That is, it is necessary that the -order current increases. Therefore, when the power supply voltage is high, the current limit value becomes high because the circuit is balanced with a large primary current value, and conversely, when the power supply voltage is low, the current limit value decreases.

In addition, a transistor (306) is provided to reduce the temperature dependence of the current limit value, but this cannot fully offset the temperature change in the base-emitter voltage of the transistor (307). -Next current detection resistor (302)
Since it is usually made of metal, the resistance value changes with temperature, so the current limit value decreases at high temperatures and increases at low temperatures.

Higher current limit values require larger rated power transistors;
Problems include a decrease in output and heat generation.

This invention was made to solve the above problems, and it is possible to keep the current limit value constant even when the power supply voltage changes, and also keep the current limit value constant even when the temperature changes. The object of the present invention is to obtain an internal combustion engine ignition device that can perform the following steps.

[Means to resolve the problem]

The internal combustion engine ignition device according to the present invention includes an ignition coil primary current detection circuit for limiting the ignition coil primary current to a predetermined value;
It includes a reference voltage generation circuit, a comparison circuit, and a control circuit, and the reference voltage generation circuit has a temperature compensation function.

[Effect]

In this invention, the reference voltage generation circuit that generates a constant reference voltage in response to power supply voltage fluctuations is further provided with a temperature compensation function, and the primary current is controlled based on this reference voltage. Unaffected by change.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

In Figure 1, +11 is the power supply, (2) is the ignition coil,
(31 is the ignition device according to the present invention. (5) is a transistor that is turned on and off by the output signal of a control device (not shown), and the collector is a resistor (4) whose one end is connected to the power supply (1) and Ignition I is connected to the input terminal (33) of the ignition device (3) and supplies a drive signal for the ignition device (3).
N+31 has an output terminal (31), a ground terminal (32), and an input terminal (33) as in the conventional example, and the output terminal (31) is connected to the negative terminal of the ignition coil (2) and connected to the ground terminal. The terminal (32) is grounded.

Next, the inside of the ignition device (3) according to the present invention will be explained. The input terminal (33) is connected to the power transistor (301) and the constant current control circuit (30B) via the input protection resistor (303), and the output terminal (31) is connected to the collector of the power transistor (301). The primary current detection resistor (302) of the ignition coil is provided between the emitter of the power transistor (301) and the ground, and the point divided by the resistors (304) and (305) connected to both ends is the constant current control circuit (308). ) internal transistors (313), (314), (315),
(316), (317), (31B) and a resistor (353), it is connected to one input terminal of a comparison circuit via a resistor (352). Transistors (319) and (320) are connected to the other input terminal of the comparison circuit.
, (321).

(322) and resistance (354), (355),
(356) is connected to the output of the reference voltage generation circuit. Transistor (325) and resistor (358)
), (359) constitute a starting circuit for the reference voltage generation circuit and comparison circuit, and transistors (323), (
324) and a resistor (357) are circuits for turning off the starting circuit after the reference voltage generation circuit and comparison circuit start operating.

Next, the operation will be explained.

First, as shown in Figure 2(a), when the base voltage of the transistor (5) becomes 0-level, the transistor (5)
is turned off, and resistor (4) and resistor (303
), current flows into the base of the power transistor (301), turning on the power transistor (301).

At this time, the base voltage of the power transistor (old 3) is the voltage between the base and emitter when the power transistor is on.As shown in Figure 2(d), as the primary current increases, the voltage generated across the primary current detection resistor (302) increases. The base voltage of the power transistor becomes a voltage obtained by adding the voltage generated in the primary current detection resistor to the base-emitter voltage. The base voltage waveform of this power transistor is
Normally, the base-emitter voltage of a Darlington-connected power transistor used in an ignition device is about 1.5V. When the base voltage when the power transistor is turned on is applied to the constant current control circuit (30B), the transistor (325) is first turned on, and the transistor (31B) forms a current mirror circuit.

Current is sucked from the bases of (319), (320), and (323) through the resistor (35B), and the current from the collector of the zero-order transistor (320) turns on the transistor that constitutes the current mirror circuit. 322) and (321) are turned on,
The resistance (3
A voltage is generated at 56), and this generated voltage and resistance (356)
The current of the current mirror circuit is set by . Also,
A voltage is generated across the resistor (357) by the current supplied from the transistor (323), and the transistor (324)
is turned on and the transistor (325) of the starting circuit is turned off.

Generally, the current amplification factor of a transistor is sufficiently large, so the emitter current of the transistor is equal to the collector current, and the sum of the resistor (354) and resistor (355) connected between the base and emitter of the transistor (321) is set to be large. Then, the current flowing from the resistor (355) to the resistor (356) becomes smaller than the emitter current of the transistor (321), and the current flowing from the collector of the transistor (320) to the resistor (354) becomes smaller than the emitter current of the transistor (321).
0), the emitter current of the transistor (321) is equal to the current flowing through the resistor (356), and the emitter current of the transistor (322) is equal to the collector current of the transistor (320). Here, the current ■1 flowing through the resistor (356) is the difference Δvl! between the base-emitter voltage of the transistor (322) and the base-emitter voltage of the transistor (321).
and resistance (356).

! 1 and ΔVat are given by the following equations.

Δv,, ink Boltzmann constant T - Absolute temperature q - Charge of electrons Transistor (321) and transistor (3) of formula (2)
The emitter current density ratio of 22) is determined by the resistance (35
4) If (355) is set, the error component can be ignored, so it is given by the following equation.

Emitter current density of transistor (321) Emitter area of transistor (321) Emitter area of transistor (322) Base 11! The reference voltage Vrer output from the voltage generation circuit is generated by a resistor (354) and a resistor (355) connected between the base and emitter of the transistor (321).
*Vref, which is supplied from the midpoint to the base of the transistor (317) which is one of the comparator circuits, is as shown by the broken line in FIG. 2(c), and is given by the following equation.

Vref=△V at +V 5z (321) XV
IE (321): ) The pace-emitter voltage method quasi-voltage generation circuit of the transistor (321) is such that the base voltage of the power transistor (301) is the base voltage of the power transistor ≧V*1 (322)
+V s t (320) −(5) vat(
322) : ) Base-emitter voltage Vci of transistor (322) (320) : Collector-emitter saturation voltage of transistor (320) or base voltage of power transistor ≧Vli! +Va
t (321) + V II! (319) -f
6) V ct (321): ) transistor (32),
) Collector-emitter saturation voltage VI (319): ) The transistor will operate if it satisfies the base-emitter voltage of the transistor (319). The emitter voltage is 0. Although IV, ΔV lt < 0.25, it always operates with the base voltage when the Darlington-connected power transistor is turned on.

As is clear from equations (2) and (4), the reference voltage Vref has a positive temperature change rate in Δv1 of the first term on the right side of equation (4), while V It (321) Since the temperature change rate is normally -2 mV/l, the second term on the right side of equation (4) can be set to a negative temperature change rate by setting the resistors (354) and (355), and overall, vref can be set arbitrarily to the temperature. You can set the rate of change.

On the other hand, the voltage generated in the -order current detection resistor (302) is divided by the resistor (304) and the resistor (305), and the voltage generated in the negative current detection resistor (302) is connected to the base of the transistor (314), which is the input of the comparison circuit, through the resistor (352). Man-powered. Transistor (314
The base voltage V, (314) of ) is as shown by the solid line in FIG. 2(c), and is given by the following equation.

V 1 (314) = (Primary current of ignition coil x resistance 302) Resistance (304) + Resistance (305) If V shown by equation (7), (314) exceeds Vref shown by equation (4) Then, the collector of the transistor (313) which is the output of the comparator circuit and the transistor (
A current is supplied from the connection point of 316) to the Darlington-connected transistors (312) and (311), and absorbs the base current of the power transistor. Therefore, (4
) Vref shown by equation (7) and V++(
314) are equal, the circuit is balanced and limits the primary current in the ignition coil to a constant current value.

In this comparison circuit, the base voltage of the power transistor (301) is the base voltage of the power transistor ≧Vref +V c
t(315) + V BE(313) −(8
1V ci (315): ) Transistor (315) base-emitter saturation voltage V IE (313): Transistor (313) It will operate if the collector-emitter voltage is satisfied, so when the Darlington-connected power transistor is on. It always operates with a base voltage of Furthermore, the operating voltage of the transistor that sinks the base current of the power transistor is V at (311) +
V at (312) + V ct (313) −
(91v, t(311): Transistor (311)
Base-emitter voltage V 5z (312): l” transistor (312) base-emitter voltage Vct (313): Transistor (313) collector-emitter saturation voltage, which is the base-emitter voltage when the Darlington-connected power transistor is turned on. is approximately equal to the emitter voltage, but transistors (311) and (312) are required to operate when the primary current increases, at which time the power Since the base voltage of the transistor is increasing, the base voltage of the power transistor (301) becomes considerably higher than the voltage shown in equation (9).

Therefore, since the constant current control circuit (308) operates with the base voltage of the Darlington-connected power transistor (301), the current limit value can be kept constant regardless of the power supply voltage, and the temperature change rate can be adjusted arbitrarily. A configurable reference voltage generation circuit can be realized, and a constant current limit value can be achieved regardless of temperature.

〔Effect of the invention〕

As described above, according to the present invention, the primary current of the ignition coil can be limited to a constant level without being affected by changes in power supply voltage or temperature, so that a power transistor with a small rating can be used. Further, since no increase in heat generation is caused, reliability of the device can be improved. Furthermore, there is an effect that a stable and constant secondary output of the ignition coil can be obtained.

[Brief explanation of drawings]

FIG. 1 is a circuit configuration diagram showing an internal combustion engine ignition system according to an embodiment of the present invention, FIG. 2 is an operating waveform at each point in the circuit configuration shown in FIG. FIG. (11 is the power supply, (2) is the ignition coil, (3) is the ignition device, (31) is the output terminal of the ignition device, (32) is the ground terminal of the ignition device, (33) is the input terminal of the ignition device, ( 301) is a power transistor, (3
02) is the −order current detection resistor, (303). (304), (305) are resistors, (308) are constant current control circuits, (311) to (325) are transistors, (351) to (359) are resistors, (4) is resistor,
(5) is a transistor Note that the same reference numerals in the figure indicate the same or corresponding parts.

Claims (1)

[Claims] It has a transistor that intermittents the primary current of the ignition coil,
In the device that generates a high voltage for ignition by switching on and off the transistor, the reference voltage generation circuit includes a reference voltage generation circuit having a temperature compensation function, a primary current detection circuit that generates a voltage according to the primary current of the ignition coil, and the reference voltage generation circuit. A comparison circuit that compares a reference voltage output from the primary current detection circuit with an output voltage of the primary current detection circuit, and a control circuit that controls the base current of the transistor based on the output of the comparison circuit are provided. Internal combustion engine ignition system.