JPH11345090A - Input circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To use a general purpose port in a microcomputer by a using method in proportion to an A/D port. SOLUTION: This input circuit connected to the general purpose port P for fetching the binary signals of a high voltage level signal and a low voltage level signal in the microcomputer is equipped with a comparator CMP for comparing a reference voltage corresponding to a power supply voltage +B with an input signal and outputting a compared result to the general purpose port P and an increase/decrease circuit for increasing/decreasing the reference voltage corresponding to the compared result of the comparator CMP.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an input circuit connected to a general-purpose port for inputting a binary signal of a high voltage level signal (H signal) and a low voltage level signal (L signal) in a microcomputer.

[0002]

2. Description of the Related Art Recently, microcomputers (microcomputers) are used in many electronic devices, and advanced controls are performed. For example, in automobiles, microcomputers are used in the control of various driving systems such as engines, safety devices such as airbags, and in-vehicle AV devices such as audio devices to improve performance, protect the environment, improve safety, and improve comfort. Is being improved.

A microcomputer receives signals from various sensors and signals from an external device such as another microcomputer.
An input port is provided. This input port has H
A general-purpose port for capturing a binary signal of a signal and an L signal, and an A / A port for converting an analog signal into a digital signal and capturing the signal.
There is a D (analog-to-digital conversion) port.

[0004]

There is no problem if the microcomputer is designed exclusively for a product used for control, but a general-purpose microcomputer designed not to be dedicated to a specific product but to be used for various products. Depending on the product used, the input port may be insufficient. The A / D port can be used as a general-purpose port by devising software, but the general-purpose port cannot be used as an A / D port.
The / D port is often short.

On the other hand, for example, in the case of automobile equipment, since the voltage fluctuation of the power supply (battery) is relatively large, the A / D
In the case of conversion, or when judging an H signal or an L signal, it is necessary to correct the power supply voltage. In other words, it is necessary to perform processing such as what percentage of the power supply voltage becomes (A / D conversion), and what percentage or more of the power supply voltage is used as the H signal (determination of the H signal and the L signal). When the input signal changes from the H signal to the L signal or from the L signal to the H signal, if the input signal is affected by noise, the input signal is changed to the H signal and L signal.
The signal moves up and down across the signal threshold, and as a result, the detection result of the input signal becomes unstable. In order to prevent this state, if the detection result of the input signal changes, a process of changing the threshold value in a direction in which the detection result is unlikely to be inverted, that is, a process of providing a so-called hysteresis is required. Since these processes are usually performed by arithmetic processing of the microcomputer, an A / D port is required even if the detection result of the input signal is a binary signal of the H signal and the L signal.

For example, in recent automobiles, many airbags are installed to protect occupants in each seat, but before the vehicle is disposed of, the disposal processing in a disposal apparatus such as an incinerator is performed. The airbag is inflated in advance to prevent damage due to the airbag inflation. However, as the number of airbags has increased and the inflation work of the airbags has become more troublesome, all of the air signals are externally provided by a predetermined combination of the H signal and the L signal that is equal to or higher than a predetermined percentage of the battery voltage. Devices programmed to inflate the bag have been proposed. In such a case, it is basically sufficient to use a general-purpose port for inputting the H signal and the L signal. However, in order to correct the power supply voltage and to provide hysteresis, the A / D port is used.
Port is used.

It is an object of the present invention to make a general-purpose port available in such a case and to effectively use an A / D port of a microcomputer.

[0008]

In order to solve the above problems, an input circuit (1) according to the present invention is a general-purpose port for receiving a binary signal of a high voltage level signal and a low voltage level signal in a microcomputer. A comparator that compares an input signal with a reference voltage corresponding to a power supply voltage and outputs a comparison result to the general-purpose port; and increases or decreases the reference voltage according to the comparison result of the comparator. And an increase / decrease circuit.

According to the input circuit, the input signal is compared with the reference voltage corresponding to the power supply voltage, and the reference voltage changes according to the comparison result of the comparator.
The fluctuation of the power supply voltage is absorbed, and a signal having a hysteresis in the comparison result is input to the general-purpose port.

The input circuit (2) according to the present invention is an input circuit connected to a general-purpose port for taking in a binary signal of a high voltage level signal and a low voltage level signal in a microcomputer. Is applied to the non-inverting input terminal, the input signal is applied to the inverting input terminal,
It is characterized by comprising a comparator for outputting a comparison result to the general-purpose port, and a feedback resistor for feeding back the output of the comparator to the non-inverting input terminal.

According to the input circuit, the input signal input to the inverting input terminal is compared with the divided voltage of the power supply voltage applied to the non-inverting input terminal, and the reference voltage is fed back. Since it changes according to the comparison result of the comparator fed back by a resistor, the fluctuation of the power supply voltage is absorbed,
A signal having hysteresis in the comparison result is input to the general-purpose port.

Further, the input circuit (3) according to the present invention is an input circuit connected to a general-purpose port for taking in a binary signal of a high voltage level signal and a low voltage level signal in a microcomputer. An input transistor that disconnects, an output transistor that disconnects according to a disconnection state of the input transistor, and outputs an output signal of a voltage corresponding to a power supply voltage to the general-purpose port based on the disconnection state;
An adjustment transistor that disconnects according to the disconnection state of the input transistor, and applies a voltage to a terminal of the input transistor so that a voltage at which the disconnection state of the input transistor changes increases or decreases. And

According to the input circuit (3), the output signal of the output transistor changes according to the power supply voltage, and the voltage of the input signal at which the connection state of the input transistor switches is changed to the connection state of the input transistor. Since the voltage varies depending on the state, the fluctuation of the power supply voltage is absorbed, and a signal having a hysteresis in the comparison result is input to the general-purpose port.

The input circuit (4) according to the present invention is an input circuit connected to a general-purpose port for taking in a binary signal of a high voltage level signal and a low voltage level signal in a microcomputer. A first NPN transistor having a collector connected to a power supply;
First and second resistors connected in series between the emitter of the first NPN transistor and ground, the power supply and the first NP
A third resistor connected between the emitters of the N transistors, an emitter connected to the power supply, and a base connected to the first NP
A PNP transistor connected to the collector of the N transistor, the collector connected to the general-purpose port and grounded via a resistor, the collector connected between the first and second resistors, the emitter grounded, and the base The PN
A second NPN transistor to which a voltage corresponding to the voltage of the collector of the P transistor is applied.

According to the input circuit (4), the output signal of the PNP transistor changes according to the power supply voltage, and the voltage of the input signal at which the connection state of the first NPN transistor switches (emitter voltage of the first NPN transistor). Changes according to the connection state of the second NPN transistor whose connection state changes according to the output signal of the PNP transistor. Therefore, the fluctuation of the power supply voltage is absorbed, and a signal having hysteresis in the comparison result is input to the general-purpose port. .

[0016]

Next, a first embodiment of the present invention will be described. FIG. 1 is a circuit diagram showing an input circuit according to the first embodiment of the present invention.

An input terminal IN to which an input signal is input is connected to an inverting input terminal of the comparator CMP via an input resistor R4, and is grounded via a resistor R5. The non-inverting input terminal + of the comparator CMP has a power source (battery) + B
A voltage divided by the resistors R1 and R2 is applied, and a feedback resistor R3 is connected between the output of the comparator CMP and the non-inverting input terminal +. A capacitor C1 for removing high-frequency noise is connected between the non-inverting input terminal + and the inverting input terminal-of the comparator CMP. And the comparator C
The output of MP is connected to the general-purpose port P of the microcomputer 1. Note that, in order to stabilize the voltage applied to the general-purpose port P of the microcomputer 1, a parallel circuit of the resistor R6 and the diode D1 is used. Output Vcc of power supply circuit)
Side is connected to the output of the comparator CMP.

Next, the operation of the input circuit will be described. When the input signal of the input terminal IN does not reach the voltage of the non-inverting input terminal + of the comparator CMP, the output of the comparator CMP becomes an H signal, and the H signal is input to the general-purpose port P of the microcomputer 1,
When the input signal at the input terminal IN exceeds the voltage at the non-inverting input terminal + of the comparator CMP, the output of the comparator CMP becomes an L signal, and the L signal is input to the general-purpose port P of the microcomputer 1.

The voltage V at the non-inverting input terminal + of the comparator CMP when the output of the comparator CMP is an L signal.
L is a divided voltage of the voltage VB of the power supply + B by the parallel circuit of the resistor R1 and the resistors R2 and R3, and is represented by the following equation.

[0020]

(Equation 1)

In addition, when the output of the comparator CMP is an H signal, the voltage VH of the non-inverting input terminal + of the comparator CMP
Is a voltage obtained by applying the output voltage (Vcc) of the comparator CMP by the feedback resistor R3 to the divided voltage of the voltage VB of the power supply + B by the resistors R1 and R2, and is expressed by the following equation.

[0022]

(Equation 2)

That is, according to the input circuit of this embodiment, the input signal is compared with the reference voltage corresponding to the power supply voltage VB, and the reference voltage changes according to the comparison result of the comparator (VL, VH). Therefore, the fluctuation of the power supply voltage is absorbed, and a signal having hysteresis in the comparison result is input to the general-purpose port.

Next, a second embodiment of the present invention will be described. FIG. 2 is a circuit diagram showing an input circuit according to a second embodiment of the present invention.

An input terminal IN to which an input signal is input includes:
NPN transistor TR1 constituting input transistor
The base is connected. And the transistor TR
The collector of 1 is connected to a power supply + B via a resistor R11, and the emitter is grounded via resistors R12 and R13 connected in series and connected to a power supply + B via a resistor R14. The base of the PNP transistor TR2 constituting the output transistor is connected to the collector of the transistor TR1, the emitter is connected to the power supply + B, and the collector is grounded via resistors R15 and R16 connected in series. The collector of the transistor TR2 is connected to the general-purpose port P of the microcomputer 1. Also NP
The base of the N transistor TR3 is connected between the resistors R15 and R16, the collector is connected between the resistors R12 and R13, and the emitter is grounded. In order to stabilize the voltage applied to the general-purpose port P of the microcomputer 1, the diode D2 has a cathode connected to the output Vcc side of the in-apparatus power supply circuit (stabilized power supply circuit for outputting a drive voltage in the apparatus). Connected to the output of the comparator CMP.

Next, the operation of the input circuit will be described. When the transistor TR1 is in the cut-off state, the base voltage of the transistor TR2 is the H signal, so that the transistor TR2 is also in the cut-off state. Therefore, the L signal is input to the collector of the transistor TR2, and the L signal is input to the general-purpose port of the microcomputer 1. In this state, since the base voltage of the transistor TR3 is the L signal and the transistor TR3 is in the cut-off state, the emitter voltage VEL of the transistor TR1, that is, the voltage applied to the base necessary to make the transistor TR1 connected (strictly speaking) It is necessary to further apply a base-emitter voltage necessary for the transistor TR1 to be in a connected state), which is a divided voltage of the resistors R14, R12, and R13, and is represented by the following equation.

[0027]

(Equation 3)

When the transistor TR1 is in the connected state, the base voltage of the transistor TR2 is the L signal, so that the transistor TR2 is also in the connected state. Therefore, the collector of the transistor TR2 becomes an H signal, and the H signal is input to the general-purpose port of the microcomputer 1. In this state, the base voltage of the transistor TR3 is the H signal, and the transistor TR3 is in the connected state.
The emitter voltage VEH of R1, that is, the transistor TR1
The voltage applied to the base, which must be lower to bring the transistor into the cutoff state (strictly, it is necessary to further apply the base-emitter voltage necessary for the transistor TR1 to be in the connected state) is the resistance R14, R12 Is obtained by adding the conduction voltage VTR3 of the transistor TR3 to the divided voltage of the transistor TR3.

[0029]

(Equation 4)

That is, according to the input circuit of the present embodiment, the base voltage for switching the connection state of the input transistor TR1 changes according to the power supply voltage VB, and the connection state of the input transistor TR1 is further changed according to the state of the input transistor TR1. Since the switching base voltage changes (VEL, VEH), the disconnection state changes according to the state of the input transistor TR1, and the output signal of the output transistor TR2 that outputs a corresponding signal to the general-purpose port absorbs the fluctuation of the power supply voltage. Then, the comparison result is output to the general-purpose port as a signal having hysteresis.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an input circuit according to a first embodiment of the present invention.

FIG. 2 is a circuit diagram showing an input circuit according to a second embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Microcomputer CMP ... Comparator P ... General-purpose port TR1, TR2, TR3 ... Transistor R1-R6, R11-R16 ... Resistance

Claims (4)

[Claims] An input circuit connected to a general-purpose port for receiving a binary signal of a high voltage level signal and a low voltage level signal in a microcomputer, compares a reference voltage corresponding to a power supply voltage with an input signal, and compares the comparison result. An input circuit, comprising: a comparator that outputs to the general-purpose port; and an increase / decrease circuit that increases / decreases the reference voltage according to a comparison result of the comparator. 2. An input circuit connected to a general-purpose port for receiving a binary signal of a high voltage level signal and a low voltage level signal in a microcomputer, wherein a divided voltage of a power supply voltage is applied to a non-inverting input terminal, and an inverting input is applied. An input circuit, comprising: a comparator to which an input signal is applied to a terminal and outputting a comparison result to the general-purpose port; and a feedback resistor for feeding an output of the comparator back to the non-inverting input terminal. 3. An input circuit connected to a general-purpose port for receiving a binary signal of a high voltage level signal and a low voltage level signal in a microcomputer, comprising: an input transistor that disconnects according to an input signal; An output transistor for disconnecting according to a disconnection state, outputting an output signal of a voltage corresponding to a power supply voltage to the general-purpose port based on the disconnection state, and disconnecting according to a disconnection state of the input transistor; An input circuit, comprising: an adjustment transistor that applies a voltage to a terminal of the input transistor so that a voltage at which a disconnection state of the transistor changes increases or decreases. 4. An input circuit connected to a general-purpose port for receiving a binary signal of a high voltage level signal and a low voltage level signal in a microcomputer, wherein an input signal is applied to a base and a collector is connected to a power supply. A transistor; first and second resistors connected in series between the emitter of the first NPN transistor and ground; a third resistor connected between the power supply and the emitter of the first NPN transistor; Connected
A PNP transistor having a base connected to the collector of the first NPN transistor, a collector connected to the general-purpose port and grounded via a resistor, a collector connected between the first and second resistors, and an emitter grounded And a second NPN transistor to a base of which a voltage according to a voltage of a collector of the PNP transistor is applied.