JP3269184B2 - Switch signal input circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a switch signal input circuit, and more particularly, to an electronic control circuit for a vehicle, a MOS / IC switch for inputting output voltages of various switches such as an idle switch or a neutral switch. The present invention relates to a signal input circuit.

[0002]

2. Description of the Related Art Conventionally, an input circuit of this type receives an output voltage of a switch 7 such as an idle switch or a neutral switch to which a stabilized power supply voltage Vcc is supplied via a pull-up resistor 8, as shown in FIG. Thus, the inverter circuits 9 and 10 are configured so that the stabilized power supply voltage Vcc is supplied to the inverter circuits 9 and 10 similarly to the switch 7. Here, the stabilized power supply voltage Vcc is an output voltage of the regulator 4 to which the battery power supply voltage + B is input, as shown in FIG.
B has characteristics as shown in FIG.

[0003]

However, in the above-mentioned prior art, since the switch is supplied with the stabilized power supply voltage Vcc of 5 V in order to prevent crosstalk in the MOS-IC, the inverter circuits 9 and 10 are not provided.
The internal reference voltage Vth must be set to 2.5 V, and therefore, as shown in FIG. 5, a noise margin when the switch 7 is on and a noise margin when the switch 7 is off However, there is a problem that a case where the switch signal cannot be correctly detected due to noise is apt to occur because both are as small as 2.5 V.

However, recently, it has become possible to prevent crosstalk by using a MOS IC having a structure as shown in FIG. This structure prevents a parasitic transistor from being formed between the substrate and another terminal through the substrate by using a P-type substrate.
By lowering the concentration of the well and lowering the resistance of the well, the generation of a potential difference is suppressed, and by providing a double guard between the adjacent terminal, the terminal is completely separated from the adjacent terminal. Things.

The present invention has been made in view of the emergence of such MOS-ICs, and has an increased noise margin.
An object of the present invention is to prevent erroneous detection of a switch signal.

[0006]

In order to solve the above problems, an input circuit for a switch signal according to the present invention comprises a battery.
MOS / IC having a comparison circuit for comparing an output voltage of a switch to which a power supply voltage is supplied from the switch with a reference voltage of a reference voltage generation circuit, wherein a stabilized power supply voltage lower than the battery voltage is supplied to the comparison circuit Wherein the reference voltage generation circuit is configured to receive power from the battery.
When the source voltage is equal to or higher than the stabilized power supply voltage, a reference voltage slightly lower than the stabilized power supply voltage is generated.

[0007]

Operation and effect of the present invention Battery power supply voltage (normally 12 V)
Fluctuates due to battery consumption and load fluctuation. Therefore,
The output voltage of the switch to which the battery power supply voltage is supplied is
It fluctuates according to the fluctuation of the battery power supply voltage. However, when the battery power supply voltage is equal to or higher than the stabilized power supply voltage (normally 5V), the reference voltage is set to a voltage slightly lower than the stabilized power supply voltage, for example, 4V. Therefore, when the battery power supply voltage is equal to or higher than the stabilized power supply voltage (for example, when the battery power supply voltage is 12 V), the noise margin when the switch is off is 8 V (= 12-4), while the switch is on. In this case, the noise margin is 4 V (= 4-0), and as is apparent from comparison with the 2.5 V noise margin in the prior art, the noise margin is greatly increased, and the switch signal is erroneously detected. Can be significantly reduced.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 shows a circuit configuration centering on a switch signal input circuit according to one embodiment.

Referring to FIG. 1, an input circuit 1 constitutes a part of an electronic control circuit for a vehicle, and a MOS-I circuit for preventing crosstalk as described above.
It is made into C.

The input circuit 1 has a comparison circuit 2 and a reference voltage generation circuit 3. Comparison circuit 2 and reference voltage generation circuit 3
Are supplied with a stabilized power supply voltage Vcc. As shown in FIG. 2A, the stabilized power supply voltage Vcc is an output voltage of the regulator 4 to which the battery power supply voltage + B is input.
It has characteristics as shown in FIG. 2B with respect to the battery power supply voltage + B. The reference voltage generating circuit 3 is composed of divided resistors 5 and 6 having a resistance ratio of, for example, 1: 4. Is done. The output voltage of the switch 7 is input to the (+) side of the comparison circuit 2 as an input voltage Vin.
The comparison circuit 2 compares the output voltage Vin of the switch 7 with the reference voltage V
Compare with th and output a voltage signal to the CPU.

The switch 7 is an idle switch, a neutral switch, or the like. The switch 7 is supplied with a battery power supply voltage + B via a pull-up resistor 8.
When V is off, an output voltage Vin of + B (12 V) is output.

Since the input circuit 1 is configured as described above, the characteristics of the input voltage Vin and the reference voltage Vth with respect to the battery power supply voltage + B can be represented as shown in FIG.
While the output voltage Vin at the time of OFF is always equal to the battery power supply voltage + B, the reference voltage Vth is a value proportional to the battery power supply voltage + B when the battery power supply voltage + B is between 0 V and 5 V. Up to 4V,
When the battery power supply voltage + B is 5 V or more, it is fixed at 4 V. Therefore, when the battery power supply voltage + B is 12 V, the noise margin when the switch 7 is on is 4 V, while the noise margin when the switch 7 is off is 8 V. Is greatly expanded, thereby significantly reducing the false detection of the switch signal.

In the embodiment described above, the reference voltage Vth
Is set to 4 V, but the reference voltage Vth is basically
It is sufficient if the voltage is slightly lower than the stabilized power supply voltage Vcc.
It is not limited to only 4V.

[Brief description of the drawings]

FIG. 1 is a circuit configuration diagram centering on a switch signal input circuit according to an embodiment;

FIG. 2 is an explanatory diagram of a stabilized power supply voltage.

FIG. 3 is a characteristic diagram of an input voltage Vin and a reference voltage Vth.

FIG. 4 is a circuit configuration diagram of a conventional example.

FIG. 5 is a characteristic diagram of an input voltage Vin and a reference voltage Vth.

FIG. 6 is a structural diagram of a MOS-IC on which the present invention is based;

[Explanation of symbols]

 1 input circuit 2 comparison circuit 3 reference voltage generation circuit 7 switch

Continuation of the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) H03K 17/00-17/70 G01R 19/00-19/32

Claims (2)

(57) [Claims] 1. A power supply voltage (+ B: 0 to 1) from a battery.
2V) output voltage (Vin) of the switch (7) supplied
The reference voltage has a comparator circuit for comparing (2) and (Vth), a low regulated supply voltage than the battery voltage (12V) of the reference voltage generating circuit (3) to (Vcc: 5V) said comparator circuit
MOS / IC input circuit supplied to (2)
(1) wherein the reference voltage generating circuit (3) is configured to supply power from the battery.
A source voltage (+ B: 0 to 12 V ) is equal to the stabilized power supply voltage (V
cc: 5 V) or more, the stabilized power supply voltage (Vcc: 5 V).
V) A switch signal input circuit configured to generate a reference voltage slightly lower than V) (Vth: 4V) . 2. The power supply according to claim 1, wherein the reference voltage generation circuit (3) is configured to output power from the battery.
A source voltage (+ B: 0 to 12 V ) is equal to the stabilized power supply voltage (V
cc: 5 V) or less, the power supply voltage from the battery
(+ B : 0 to 12V) and a reference voltage (Vth: 0 to 0V)
4V) for generating a switch signal.