JP2002148271A - Signal processing circuit for both analog signal and digital signal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a signal processing circuit which does not require a turnover switch and is capable of converting input signals into pulse signals, even when either analog signal or digital signal is used as the input signal. SOLUTION: A coupling capacitor 25 for converting the level of input signal is provided. By coupling the input signal with the coupling capacitor 25 and comparing the input signal, after coupling with the threshold level formed by a buffer circuit 32, level confirmation of the input signal is conducted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a signal processing circuit capable of converting an input signal into a pulse signal regardless of whether an analog signal or a digital signal is used as an input signal. It is suitable for use in a signal processing circuit.

[0002]

2. Description of the Related Art A navigation device mounted on a vehicle converts a wheel speed signal obtained from the vehicle into a pulse signal by a distance detection unit, and calculates a vehicle traveling distance from the pulse signal, thereby displaying a signal on a display. Used for vehicle position display. However, some vehicles use digital signals as wheel speed signals, while others use analog signals, and the types of signals used as wheel speed signals differ depending on the vehicle. For this reason, conventionally, a distance detection unit having a circuit configuration shown in FIG. 5 is used so that a wheel speed signal can be converted into a pulse signal in both cases where the wheel speed signal is a digital signal and an analog signal. A digital vehicle speed pulse processing circuit unit 101 and an analog vehicle speed pulse processing circuit unit 102 are provided in parallel.
03 and 104, and one of the circuit units 101 and 102 can be selected by the changeover switches 103 and 104.

[0003]

However, in the above-mentioned conventional configuration, since the changeover switches 103 and 104 are used, the changeover switches 103 and 104 must be mounted at a place where the changeover can be easily performed. ,
There is a problem that there are restrictions on the mounting location, and the changeover switch 1
There is a problem that the mounting area of other components is reduced by the mounting area of Nos. 03 and 104. The changeover switch 10
There is also a problem that the cost of parts increases due to the need for 3, 104.

[0004] In view of the above, the present invention does not require a changeover switch, and can convert an input signal into a pulse signal regardless of whether an analog signal or a digital signal is used as an input signal. It is an object to provide a processing circuit.

[0005]

In order to achieve the above object, according to the present invention, one of an analog signal and a digital signal is input as an input signal,
A signal processing circuit configured to recognize the level of the input signal by comparing the input signal with a predetermined threshold level, the signal processing circuit including a coupling capacitor (25) for performing level conversion of the input signal, The signal is coupled by a coupling capacitor, and the level of the input signal is recognized by comparing the input signal after coupling with a threshold level.

[0006] As described above, by coupling the input signal with the coupling capacitor, it is possible to accurately recognize the level of the wheel speed signal whether the wheel speed signal is an analog signal or a digital signal. . Therefore, even if an analog signal or a digital signal is used as an input signal without a changeover switch, the input signal can be converted into a pulse signal.

For example, the level conversion may be performed by a coupling capacitor such that the upper limit or the lower limit of the amplitude of the input signal becomes zero.

According to the present invention, the first and second resistors (26, 2) connected between the power supply and the ground potential point are provided.
7), wherein a coupling capacitor is connected between the first and second resistors. With such a configuration, the amplitude after coupling can be adjusted.

According to the fifth aspect of the present invention, the input signal is a wheel speed signal sent from a wheel speed sensor,
The level of the wheel speed signal is recognized by comparing the wheel speed signal with a threshold level. As described above, the inventions according to claims 1 to 4 can be applied to a signal processing circuit for a navigation device.

[0010] The reference numerals in parentheses of the above means indicate the correspondence with the specific means described in the embodiment described later.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) FIG. 1 is a block diagram showing a schematic configuration of a navigation device provided with a signal processing circuit according to one embodiment of the present invention. This drawing corresponds to a schematic configuration of a so-called in-dash type navigation device configured so that a display for displaying map information or the like can be inserted into a housing portion housed in a dash box. Hereinafter, a schematic configuration of the navigation device will be described with reference to FIG.

The navigation device shown in FIG. 1 includes a position detector 1, a map data input device 2, an operation switch group 3, a remote control sensor 4, a voice recognition unit 5, an external memory unit 6, a display device 7, and a voice output device 8. And a control unit 9 that performs various signal processing upon signal input from each of these units and outputs a control signal to a display device 7 or an audio output device 8 according to the processing result. It has become.

The position detector 1 detects information on the position where the vehicle is currently traveling based on various information. Specifically, the position detector 1 includes a gyroscope (or geomagnetic sensor) 11 for detecting information on the direction of the vehicle, and a distance detection for detecting information on the vehicle traveling distance based on a detection signal from a wheel speed sensor. Part 1
2. A GPS receiver 13 for receiving signals transmitted by GPS satellites is provided, and detection signals from these units 11 to 13 are input to the control unit 9. The distance detector 12 in the position detector 1 corresponds to a signal processing circuit according to one embodiment of the present invention. The details of the distance detection unit 12 will be described later.

The map data input unit 2 reads map data from an information recording medium such as a CD or DVD in which map data is stored. A signal from the map data input unit is transmitted to the control unit 9. Is to be entered.

The operation switch group 3 is provided directly on the frame of the display in the case of the in-dash type as in this embodiment, and a signal corresponding to the operation state of the operation switch group 3 is input to the control unit 9. It is supposed to be.

The remote controller sensor 4 receives a signal from an operation remote controller 14 provided as an accessory to the navigation device. A signal received by the remote control sensor 4 is input to the control unit 9.

The voice recognition unit 5 recognizes voice when the user performs voice input. A detection signal corresponding to a voice input by the voice recognition unit 5 is input to the control unit 9.

The external memory 6 is for the control unit 9 to write, read, and erase based on information input from the operation switch group 3 or the remote control sensor 4.
For example, information on a place selected by the user as the final destination is temporarily stored.

The display device 7 displays information on a display in accordance with the result of the signal processing by the control unit 9.
Specifically, the display device 7 displays the map information on the display based on the map data sent from the map data input device, and based on the information from the position detector 1, the traveling position of the vehicle in the map. Or displays, for example, a final destination and a planned vehicle traveling route (guidance route) to the final destination in the map based on the information stored in the external memory 6.

The voice output device 8 generates voice according to the result of the signal processing in the control unit 9 and provides information to the user by voice. Specifically, the audio output device 8
Is configured to generate a voice in accordance with the planned vehicle travel route from the map data information sent from the map data input device 2 and the information on the final destination stored in the external memory 6 to perform vehicle guidance.

Next, FIG. 2 shows a specific circuit configuration of the distance detecting section 12, and the details of the distance detecting section 12 will be described with reference to FIG.

As described above, the distance detecting section 12 detects information on the vehicle traveling distance based on the detection signal from the wheel speed sensor. That is, the distance detecting unit 12 processes the input wheel speed signal and outputs a processing signal corresponding to the wheel speed signal.

A power source and a GND (ground potential point) are connected to the distance detecting unit 12. A pull-up resistor 21 for fixing the level is arranged between the power supply and the GND, and a noise suppression capacitor 2 connected in parallel with each other is provided.
2, 23 and Zener diode 24 for overvoltage protection
Are connected in series to the pull-up resistor 21. These pull-up resistor 21 and noise countermeasure capacitor 2
A wheel speed signal is input to a connection point A between the wheels 2 and 23 and the Zener diode 24.

A coupling capacitor 25 for converting the signal level of the wheel speed signal is connected to the connection point A. In the subsequent stage of the coupling capacitor 25, there are provided first and second resistors 26 and 27 for voltage division connected between the power supply and GND, and these first and second resistors 26 and 27 are provided. The amplitude of the wheel speed signal whose level has been converted by the coupling capacitor 25 is adjusted.

The level (Hi or Low) of the wheel speed signal, the amplitude of which is adjusted by the first and second resistors 26 and 27, is adjusted by a buffer constituted by three inverter circuits 28, 29 and 30 and a resistor 31. It is recognized by the circuit 32. That is, the level of the wheel speed signal is compared with the threshold level formed by the buffer circuit 32, and is converted into a pulse signal.

The wheel speed signal converted into the pulse signal in this way passes through a filter circuit and a buffer 35 constituted by a resistor 33 and a capacitor 34, and is then sent to the control unit 9 as a processing signal. In addition,
Each resistor 36 provided before and after the filter circuit,
37 is provided for current limitation.

The operation of the distance detecting unit 12 thus configured will be described for the case where an analog signal is used as a wheel speed signal and the case where a digital signal is used. FIG. 3 shows input / output waveforms in the case of an analog signal and a digital signal, and a waveform after coupling by the coupling capacitor 25, and the operation will be described with reference to FIG.

First, when an analog signal is used as a wheel speed signal, as shown in FIG. 3A, for example, a 12V amplitude sine wave analog vehicle speed pulse is input as a wheel speed signal. The amplitude of the analog vehicle speed pulse is coupled by the coupling capacitor 25, and the level of the wheel speed signal is converted. In other words, a sine-wave analog vehicle speed pulse having amplitude centered on the potential 0 is converted into a sine wave having the potential 0 as the lower limit (or upper limit).

The analog vehicle speed pulse thus level-converted is subjected to amplitude adjustment by the first and second resistors 26 and 27, and then input to the buffer circuit 32.
By comparing the wheel speed signal with the threshold level by the buffer circuit 32, the level of the wheel speed signal is recognized and converted into a pulse signal having an amplitude set by the power supply voltage. This pulse signal is output to the control unit 9 as a processed signal after processing by the distance detection unit 12.

On the other hand, when a digital signal is used as the wheel speed signal, as shown in FIG. 3B, for example, a rectangular wave digital vehicle speed pulse having an amplitude of 12 V is input as the wheel speed signal. The amplitude of the digital vehicle speed pulse is coupled by the coupling capacitor 25, and the level of the wheel speed signal is converted. That is, a rectangular wave analog vehicle speed pulse having amplitude centered on the potential 0 is converted into a rectangular wave having the potential 0 as the lower limit (or upper limit).

The digital vehicle speed pulse thus level-converted is amplitude-adjusted by the first and second resistors 26 and 27, and then input to the buffer circuit 32. The buffer circuit 32 generates the wheel speed signal. The level is recognized and converted into a pulse signal having an amplitude set by the power supply voltage. This pulse signal is output to the control unit 9 as a processed signal after processing by the distance detection unit 12.

In such an operation, the analog vehicle speed pulse and the digital vehicle speed pulse are level-converted by the coupling capacitor 25, and a waveform having a potential 0 as an upper limit or a lower limit and a predetermined threshold level formed by the buffer circuit 32 are obtained. Are compared to recognize the level of the wheel speed signal.
Therefore, the following effects can be obtained. This effect will be described with reference to FIG. This figure is
FIG. 4 is a diagram illustrating a relationship between a threshold level formed by a buffer circuit and a level of a wheel speed signal (vehicle speed pulse) detected based on the threshold level.

The digital vehicle speed pulse processing circuit section provided in the above-described conventional apparatus has a configuration in which the coupling capacitor 25 (see FIG. 2) of the distance detecting section shown in this embodiment is substantially eliminated. A buffer circuit is also formed in this digital vehicle speed pulse processing circuit section, and the threshold level formed by the buffer circuit is usually a potential different from the potential 0.

For this reason, as shown in FIG. 4A, if the signal is a rectangular wave digital vehicle speed pulse, there is no problem because the signal level can be determined to be Hi or Low regardless of the threshold level. ), In the case of a sine wave analog vehicle speed pulse, the period in which the signal level is Hi due to the set threshold level and the period Lo
A shift occurs during the period of w, and accurate level recognition cannot be performed.

In particular, the threshold level formed by the buffer circuit has a wide range, and depending on the magnitude of the voltage at which the threshold level is set, the difference between the period in which the signal level is high and the period in which the signal level is low is extremely large. growing.

On the other hand, since the wheel speed signal is level-converted so as to have a waveform having the potential 0 as the upper limit or the lower limit as in the present embodiment, the above-mentioned deviation generated when compared with the threshold level is eliminated. Can be reduced.

As described above, by using the distance detecting section as in the present embodiment, it is possible to accurately recognize the level of the wheel speed signal whether the wheel speed signal is an analog signal or a digital signal. it can. Therefore, by using the distance detection unit of the present embodiment, it is possible to convert the input signal into a pulse signal without using a changeover switch and using either an analog signal or a digital signal as an input signal. it can.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a schematic configuration of a navigation device according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating a circuit configuration of a distance detection unit illustrated in FIG. 1;

FIG. 3 is a diagram showing an input waveform, a coupling unit waveform, and an output waveform when a wheel speed signal is an analog signal and a digital signal, respectively.

FIG. 4 is a diagram showing the difference between input and output waveforms in the case of a digital signal and an analog signal respectively by a conventional digital vehicle speed pulse processing circuit unit.

FIG. 5 is a diagram showing a block configuration of a distance detection unit provided in a conventional navigation device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Position detector, 9 ... Control part, 12 ... Distance detection part, 25
... coupling capacitors, 28 to 30 ... inverter circuits, 32 ... buffer circuits.

Claims (5)

[Claims] 1. A signal processing circuit configured to receive one of an analog signal and a digital signal as an input signal and perform level recognition of the input signal by comparing the input signal with a predetermined threshold level. A coupling capacitor (25) for performing level conversion of the input signal, by coupling the input signal with the coupling capacitor, and comparing the input signal after coupling with the threshold level, A signal processing circuit for both analog signals and digital signals, which performs level recognition of the input signal. 2. The coupling capacitor according to claim 1, wherein said coupling capacitor performs level conversion so that an upper limit or a lower limit of the amplitude of said input signal becomes zero.
4. A signal processing circuit for both analog and digital signals according to claim 1. 3. The signal processing circuit according to claim 1, wherein the threshold level is formed by a buffer circuit. 4. A semiconductor device comprising first and second resistances (26, 27) connected between a power supply and a ground potential point, wherein the first and second resistances and the coupling capacitor are connected between the first and second resistances. The signal processing circuit according to any one of claims 1 to 3, wherein the signal processing circuit is used for both an analog signal and a digital signal. 5. The signal processing circuit according to claim 1, wherein the input signal is a wheel speed signal sent from a wheel speed sensor, and the wheel speed signal is defined as the threshold level. A signal processing circuit for a navigation device, wherein a level of the wheel speed signal is recognized by comparing.