KR100588084B1 - Waveform Shaping Circuit of Remote Control Receiver and Remote Control Receiver of using the Waveform Shaping Circuit - Google Patents

Abstract

Disclosed are a waveform shaping circuit which integrally performs functions of a demodulator, a Schmitt trigger, and an output stage of an infrared receiver, and an infrared receiver using the same. The waveform shaping circuit receives an input signal input from a comparator of the infrared receiver using a plurality of transistors and a plurality of capacitors, and generates a square wave corresponding to a time interval in which a pulse string of the received input signal exists. By implementing a circuit that performs the same function with fewer transistors than in the related art, the area on the semiconductor wafer occupied by the infrared receiver can be reduced, and the yield can be improved by avoiding the complexity of the semiconductor manufacturing process.

Description

Waveform shaping circuit of infrared receiver and infrared receiver using the same {Waveform Shaping Circuit of Remote Control Receiver and Remote Control Receiver of using the Waveform Shaping Circuit}

1 is a block diagram illustrating a general infrared receiver.

FIG. 2 is a timing diagram for describing operations of the demodulator, the Schmitt trigger, and the output terminal illustrated in FIG. 1.

FIG. 3 is a circuit diagram illustrating the Schmitt trigger and output stage shown in FIG. 1.

4 is a circuit diagram showing a waveform shaping circuit according to a first embodiment of the present invention.

FIG. 5 is a timing diagram for describing an operation of the waveform shaping circuit of FIG. 4.

6 is a circuit diagram showing a waveform shaping circuit according to a second embodiment of the present invention.

FIG. 7 is a timing diagram for describing an operation of the waveform shaping circuit of FIG. 6.

8 is a block diagram showing an infrared receiver according to Embodiment 3 of the present invention.

Explanation of symbols on the main parts of the drawings

301 and 401: first waveform shaping unit 303 and 403: second waveform shaping unit

305 and 405: third waveform shaping unit 307 and 407: fourth waveform shaping unit

309, 409: output unit 513: waveform shaping circuit

The present invention relates to a semiconductor integrated circuit, and more particularly, to a demodulation circuit used in a semiconductor device for an infrared receiver.

As a method of transmitting data wirelessly, there is a method using radio waves (RF) or infrared rays. In general, a method using radio waves (RF) is generally preferred because data transmission is performed even if there are obstacles in the propagation path. However, there are drawbacks of legal restrictions due to concerns about malfunction due to interference of surrounding electronic equipment and insufficient radio resources.

In case of using infrared ray which is straight, it can be free from these legal regulations, and it is a good alternative to the method of using radio wave (RF) because it is cost effective.

Infrared signal is converted into data format and transmitted for data communication using infrared rays. This data is in a form promised between the transmitting end and the receiving end. Commonly used in the form of pre-promised data includes the NEC format, the RC5 format, and various other formats.

In general, an infrared transmitter transmits a control signal using a dedicated microcomputer, and the data signal used therein is in the form of binary signals of '0' and '1' called non return to zero (NRZ). If the binary signal is converted into an infrared signal and then transmitted, a communication distance that can be received from the transmitter has a disadvantage of shortening due to interference of other light sources. Therefore, in order to solve this communication distance problem, a carrier having a higher frequency than a data signal is used. In the case of a typical infrared transmitter, the carrier has a frequency of 30KHz to 40KHz, and in particular, a frequency of 37.9KHz is frequently used.

1 is a block diagram illustrating a general infrared receiver.

Referring to FIG. 1, an infrared receiver includes a photodiode 101, a voltage converter 103, an amplifier 105, a band pass filter 107, an automatic gain control circuit 109, a comparator 111, and a demodulator. (113), the Schmitt trigger 115 and the output stage 117.

The photodiode 101 senses an infrared signal and converts it into a current. The amount of current flowing through the photodiode is converted into a predetermined voltage by the voltage converter 103. The input signal converted into the voltage by the voltage converter is input to the amplifier 105. The amplifier 105 amplifies the output of the voltage converter in response to the automatic gain control signal VAGC. In addition, the signal amplified by the amplifier 105 is input to the band pass filter 107, and only the signal corresponding to the predetermined frequency band is output. The output signal fout of the band pass filter 107 is input to the automatic gain control circuit 109 and the comparator 111. The automatic gain control circuit 109 compares the output signal fout of the band pass filter 107 and the predetermined threshold voltage Vt to generate the automatic gain control signal VAGC. The comparator 111 compares the output signal fout of the band pass filter 107 with the reference voltage VREF and outputs the comparison voltage to the demodulator 113. The demodulator 113 demodulates the output signal of the comparator 111 to remove the carrier. In addition, the demodulator 113 has a function of an integrator. That is, the output signal of the comparator 111 input in the form of a pulse train is integrated to form a signal having a predetermined rise time and fall time. The signal from which the carrier is removed by the demodulator 113 is input to the Schmitt trigger 115 and converted into a shaped square wave. The output terminal 117 generates an output signal in response to the shaped square wave which is the output signal of the Schmitt trigger 115.

FIG. 2 is a timing diagram for describing operations of the demodulator, the Schmitt trigger, and the output terminal illustrated in FIG. 1.

Referring to FIG. 2, pulse trains input to the demodulator are integrated in the demodulator. However, in the case of a predetermined number of pulses or more, it has a fixed maximum value. That is, in FIG. 2, the voltage rises to Vt1 for three pulses, reaches a maximum value in the fourth or fifth pulse, and maintains the maximum value for the duration of the pulse. If the pulse no longer occurs, the demodulator output signal will begin to descend at its maximum. Preferably, the rise time and fall time of the demodulator output signal are equal to each other.

The Schmitt trigger has a demodulator output signal as an input. The Schmidt Kriger is used to avoid distortion of the waveform of the demodulator output signal due to the influence of noise when noise or the like is interposed in the demodulator input signal. That is, if the demodulator output signal is greater than or equal to Vt1, the Schmitt trigger and output stage recognize this and output a low level signal. If the demodulator output signal falls below Vt2, the Schmitt trigger and output stage recognize this and output a high level signal. .

FIG. 3 is a circuit diagram illustrating the Schmitt trigger and output stage shown in FIG. 1.

3 and 2, a demodulator output signal having a predetermined rise time and fall time is input to the Schmitt trigger 201.

When the demodulator output signal is equal to or less than Vt2, the comparator COMP outputs a low level to the positive output terminal to operate the current source I1 and inhibit the operation of the current source I2. The transistor Q3 is turned on by the operation of the current source I1, and the transistor Q2 is turned off. That is, in the situation where the voltage of Vt2 + Vbe is applied to the base terminal of transistor Q2 and the voltage of Vt1-Vbe is applied to the base terminal of transistor Q3, transistor Q3 is turned on so that the voltage of the emitter terminals of transistors Q2 and Q3 is Becomes Vt1. Thus, since Vbe of transistor Q2 is below the voltage to be turned on, transistor Q2 is in the off state and transistor Q5 is also in the off state. The transistor Q4 is in the off state because no current is supplied to the resistor R3 when the transistor Q5 is turned off. Therefore, a high level of voltage is generated at the output terminal 203.

When the demodulator output signal rises above Vt1, the positive output terminal of the comparator COMP outputs a high level to operate the current source I2, and inhibits the operation of the current source I1. In order to satisfy KCL in large signal current analysis, a current path consisting of transistors Q5, Q2 and current source I2 is formed. That is, transistor Q2 is turned on and transistor Q3 is turned off so that the voltage at the emitter terminals of transistors Q2 and Q3 has a level of Vt2. On the other hand, a current flows in the resistor R3 by the turn-on of the transistor Q5, and the voltage at the base end of the transistor Q4 rises above a predetermined level. Transistor Q4 is thus turned on and output stage 203 generates a low level voltage.

When the demodulator output signal falls below Vt2, the positive output terminal of the comparator COMP outputs a low level to operate the current source I1 and prevent the operation of the current source I2. In order to satisfy the KCL in the large signal current analysis, a current path is formed which flows into the current source I1 and the transistor Q3. That is, transistor Q3 is turned on and transistors Q2, Q4 and Q5 are turned off. Therefore, the voltage at the emitter stages of the transistors Q2 and Q3 has a level of Vt1, and the output stage 203 generates a high level voltage.

If the demodulator, the Schmitt trigger 201, and the output stage 203 are maintained, the infrared receiver occupies an excessive area. That is, since a large number of transistors, current sources, and functional blocks must be implemented, the area occupied by the infrared receiver on the wafer must be excessive.

In addition, due to the use of a large number of transistors, even when the characteristics of one transistor are abnormal in the semiconductor manufacturing process, the infrared receiver may malfunction, causing a decrease in yield.

Therefore, it will be required to implement a semiconductor circuit that takes up a small area and can replace the functions of the demodulator, the Schmitt trigger, and the output stage with only a few transistor configurations.

The first object of the present invention for solving the above problems is to provide a waveform shaping circuit of an infrared receiver that can replace the functions of the conventional demodulator, Schmitt trigger and output stage by using a small area and a small number of transistors. have.

It is a second object of the present invention to provide an infrared receiver using the waveform shaping circuit.

The present invention for achieving the first object, the first waveform shaping unit for outputting a level corresponding to the time interval in which the pulse train is input in response to the input pulse train; A second waveform shaping unit for receiving an output of the first waveform shaping unit and outputting a signal having a predetermined level transition time from an input time of the pulse train; A third waveform shaping section for receiving an output of the second waveform shaping section and outputting a signal having a predetermined level transition time from an end time of the pulse train; A fourth waveform shaping unit configured to receive an output of the third waveform shaping unit, and have a predetermined delay time with respect to a start time of the pulse train, and form a square wave corresponding to the duration of the pulse train; And an output unit for inverting the output of the fourth waveform shaping unit.

The present invention for achieving the second object, a photodiode for detecting an infrared input signal; A voltage converter configured to convert the voltage into a voltage in response to a current flowing through the photodiode; An amplifier for amplifying an output signal of the voltage converter in response to an automatic gain control signal; A band pass filter for outputting only a signal corresponding to a predetermined frequency band from the output signal of the amplifier; An automatic gain control circuit for generating the automatic gain control signal by comparing the output of the band pass filter with a predetermined threshold voltage; A comparator for comparing the output of the band pass filter with a reference voltage; And a waveform shaping circuit for receiving the output signal of the comparing unit and generating a square wave corresponding to a section in which a pulse string exists.

The waveform shaping circuit may include a first waveform shaping unit configured to output a level corresponding to a time interval in which a pulse train is input in response to an input pulse train; A second waveform shaping unit for receiving an output of the first waveform shaping unit and outputting a signal having a predetermined level transition time from an input time of the pulse train; A third waveform shaping section for receiving an output of the second waveform shaping section and outputting a signal having a predetermined level transition time from an end time of the pulse train; A fourth waveform shaping unit configured to receive an output of the third waveform shaping unit, and have a predetermined delay time with respect to a start time of the pulse train, and form a square wave corresponding to the duration of the pulse train; And an output unit for inverting the output of the fourth waveform shaping unit.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Example 1

4 is a circuit diagram showing a waveform shaping circuit according to a first embodiment of the present invention.

Referring to FIG. 4, the waveform shaping circuit includes a first waveform shaping unit 301, a second waveform shaping unit 303, a third waveform shaping unit 305, a fourth waveform shaping unit 307, and an output unit ( 309).

The first waveform shaping unit 301 includes a transistor Q11, a capacitor C1 for receiving an input signal Vin, and a current source I11 for supplying a current to the transistor Q11 or the capacitor C1.

The second waveform shaping unit 303 includes a transistor Q12, a capacitor C2, and a current source I12 for supplying current to the transistor Q12 or the capacitor C2 to perform a switching operation according to the voltage Va.

The third waveform shaping unit 305 includes a transistor Q13, a capacitor C3, and a current source I13 for supplying a current to the transistor Q13 or the capacitor C3 to perform a switching operation according to the voltage Vb.

The fourth waveform shaping unit 307 includes transistors Q14 and Q15 for performing a switching operation according to the voltage Vc, and a current source I14 for supplying current to the transistors Q15 and Q16.

The output unit 309 is composed of transistors Q16 and Vcc which perform a switching operation according to the voltage Vd and a resistor R11 connected between the transistor Q16.

An input signal in the form of a pulse train is input to the base terminal of the transistor Q11. The input signal corresponds to the output signal of the comparator disclosed in FIG. 1.

When the input signal is at low level, transistor Q11 is turned off and voltage Va remains at high level. Therefore, a predetermined charge is accumulated in the capacitor C1, and the amount of charge accumulated in the capacitor C1 is proportional to the voltage required to turn on the transistor Q12.

When the input signal is at high level, transistor Q11 is turned on and voltage Va drops to low level. Under the influence of the current source I11, the charge accumulated in the capacitor C1 is drastically reduced. When a pulse train having a high frequency is input, even when the input signal is at a low level, it takes time to accumulate charge in the capacitor C1, so that the voltage Va cannot react sensitively to the change in the input. Therefore, in the input signal, Va maintains the low level in the section where the pulse train exists.

When Va is low level, transistor Q12 is turned off. Therefore, charge is accumulated in the capacitor C2 by the current source I12, so that the voltage Vb is maintained at a high level.

The transistor Q13 is turned on by the high level voltage Vb. The turn-on of transistor Q13 brings the voltage Vc to a low level, and the charge accumulated in the capacitor C3 is nearly insignificant. The transistor Q14 is turned off by the low level voltage Vc, and the transistor Q15 is also turned off.

In addition, under the influence of the current source I14, the voltage Vd rises to a voltage sufficient to turn on the transistor Q16, thereby turning on the transistor Q16. Therefore, the output signal Vout is kept at a low level. That is, the waveform shaping circuit forms a square wave having a predetermined time interval corresponding to a section in which an input signal has a pulse train.

FIG. 5 is a timing diagram for describing an operation of the waveform shaping circuit of FIG. 4.

5 and 4, the input signal Vin is input to the base terminal of the transistor Q11 with a predetermined time interval. If a low level is input before the pulse train is input, transistor Q11 is in the off state and voltage Va has a level sufficient to turn on transistor Q12.

When the first pulse is input and Vin maintains a high level, transistor Q11 is turned on, and the charge accumulated in capacitor C1 is drastically reduced under the influence of current source I11, and the base terminal voltage Va of transistor Q12 falls to low level. Done. When the low level is input in the first pulse and the transistor Q11 is turned off for a short time, charge accumulation starts in the capacitor C1 according to the operation of the current source I11, and the charge accumulation time is determined by the capacitance of the capacitor C1 and the corresponding correction. Depends on the number. Therefore, charges gradually accumulate over a predetermined time, and the voltage Va also gradually rises.

When the second pulse is input in the process of increasing the voltage Va and Vin maintains a high level, the rising voltage Va rapidly drops. Accordingly, the voltage Va maintains the low level as a whole in the section in which the pulse train exists, and the low level has the shape of a triangular wave or a sawtooth wave. When the input of the pulse train is terminated and Vin maintains the low level, the transistor Q11 is turned off and the charge is accumulated in the capacitor C1 at a predetermined time constant. Thus, the voltage Va is raised to a level suitable for turning on the transistor Q12.

If a low level signal is input before the input of the pulse train at the input signal Vin, Va maintains a high level, so that the transistor Q12 is in the turn-on state. Therefore, Vb remains at a low level, and the capacitor C2 has almost no charge.

When Va maintains a low level in response to the input of the pulse train, transistor Q12 is turned off, and the capacitor C2 starts to accumulate charge under the influence of current source I12. The accumulation of charge depends on the capacitance and time constant of capacitor C2. Thus, the voltage Vb rises until the transistor Q13 is turned on with a predetermined rise time. When the input of the pulse train is terminated and the voltage Va rises, the transistor Q12 is turned on. As the transistor Q12 is turned on, the charge accumulated in the capacitor C2 is drastically reduced, and the voltage Vb is also lowered to a low level.

When the voltage Vb is kept at a low level due to the absence of a pulse train at Vin, the transistor Q13 is in a turn-off state and the voltage Vc is at a high level. When Vb rises with the input of the pulse train, the transistor Q13 is turned on. As the transistor Q13 is turned on, the voltage Vc drops to a low level, and the charge accumulated in the capacitor C3 decreases rapidly due to the influence of the current source I13. When the voltage Vb is switched from the high level to the low level upon termination of the pulse train input, the transistor Q13 is turned off. As the transistor Q13 is turned off, the capacitor C3 starts to accumulate charge. The time for which the charge is accumulated and the voltage Vc rises above the predetermined level depends on the capacitor C3 and the time constant. Thus, upon termination of the pulse train input, the voltage Vc rises to a level sufficient to turn on the transistors Q14 and Q15 with a predetermined rise time.

When Vc falls from the high level to the low level due to the input of the pulse train, the transistors Q14, Q15 are turned off. Therefore, under the influence of the current source I14, the voltage Vd rises high enough to turn on the transistor Q16. Therefore, the output signal Vout switches from the high level to the low level. When the input of the pulse string is terminated, with a predetermined rise time, Vc rises from the low level to a level sufficient to turn on the transistors Q14, Q15. Accordingly, when the transistors Q14 and Q15 are turned on, the voltage Vd drops to a low level. As the voltage Vd falls, the transistor Q16 turns off and the output signal Vout switches to a high level.

By the above-described process, a square wave corresponding to the duration of the pulse is formed. In addition, the rise time of the voltage Vb does not rise to a level sufficient to turn on the transistor Q13 when a predetermined number of pulses are not input, thereby replacing the function of the Schmitt trigger of the prior art.

In addition, it can be seen that the waveform shaping circuit of the present embodiment replaces the functions of the demodulator, the Schmitt trigger, and the output stage of the prior art.

Example 2

6 is a circuit diagram showing a waveform shaping circuit according to a second embodiment of the present invention.

Referring to FIG. 6, the waveform shaping circuit includes a first waveform shaping unit 401, a second waveform shaping unit 403, a third waveform shaping unit 405, a fourth waveform shaping unit 407, and an output unit ( 409).

The first waveform shaping unit 401 compares the transistor Q21, the capacitor C4 for receiving the input signal Vin, the current source I21 for supplying the current to the transistor Q11, or the capacitor C4, the first reference voltage Vf1 and the voltage Va '. Comparator COMP1.

The second waveform shaping unit 403 includes a current source I22 and a second reference voltage Vf2 for supplying current to the transistor Q22, the capacitor C5, the transistor Q22, or the capacitor C5 which perform a switching operation according to the output level of the comparator COMP1. It consists of a comparator COMP2 for comparing the voltage Vb '.

The third waveform shaping unit 405 is a current source I23 and a third reference voltage for supplying current to the transistor Q23, the capacitor C6, the transistor Q23, or the capacitor C6 performing a switching operation according to the output level of the comparator COMP2. It consists of a comparator COMP3 for comparing Vf3 and voltage Vc '.

The fourth waveform shaping unit 407 includes a transistor Q24 for performing a switching operation according to the output level of the comparator COMP3, and a current source I24 for supplying current to the transistor Q24.

The output unit 409 includes transistors Q25 and Vcc which perform a switching operation according to whether the transistor Q24 is operated, and a resistor R21 connected between the transistor Q25.

The waveform shaping circuit has an input signal Vin having a pulse train, and the input signal Vin is input to the base end of the transistor Q21, and generates a square wave corresponding to a time section of the pulse train as an output signal.

The input signal Vin corresponds to the output signal of the comparator disclosed in FIG. 1.

When the input signal is at the low level, the transistor Q21 is turned off and the voltage Va 'remains at the high level. Therefore, a predetermined charge is accumulated in the capacitor C4, and the amount of charge accumulated in the capacitor C4 is proportional to the voltage required to turn on the transistor Q22 through the comparator COMP1.

When the input signal is at high level, transistor Q11 is turned on and voltage Va 'falls to low level. Under the influence of the current source I21, the charge accumulated in the capacitor C4 is drastically reduced. When a pulse train having a high frequency is input, even when the input signal is at a low level, it takes time to accumulate charge in the capacitor C4, so that the voltage Va 'cannot be sensitively reacted to the change in the input. Therefore, in the input signal section, Va 'maintains a low level in a section where a pulse train exists.

When Va 'is low level, comparator COMP1 outputs low level, and transistor Q22 is turned off. Therefore, electric charges are accumulated in the capacitor C5 by the current source I22, so that the voltage Vb 'is maintained at a high level.

The comparator COMP2 outputs a high level by the high voltage Vb ', and the transistor Q23 is turned on. The turn-on of the transistor Q23 causes the voltage Vc 'to be at a low level, and the charge accumulated in the capacitor C6 is almost insignificant. The comparator COMP3 outputs the low level by the low level voltage Vc ', and the transistor Q24 is turned off.

Further, under the influence of the current source I24, the base terminal voltage of the transistor Q25 rises to a voltage sufficient to turn on the transistor Q25, thereby turning on the transistor Q25. Therefore, the output signal Vout is kept at a low level. That is, the waveform shaping circuit forms a square wave having a predetermined time interval corresponding to a section in which an input signal has a pulse train.

FIG. 7 is a timing diagram for explaining the operation of FIG. 6 according to the present embodiment.

7 and 6, the input signal Vin is input to the base terminal of the transistor Q21 with a predetermined time interval. When the low level is input before the pulse train is input, the transistor Q21 is in the off state, and the voltage Va 'maintains a level higher than the first reference voltage Vf1 of the comparator COMP1. Therefore, the comparator COMP1 outputs a high level to keep the transistor Q22 turned on.

When the first pulse is input and Vin maintains a high level, transistor Q21 is turned on, and the charge accumulated in capacitor C4 under the influence of current source I21 is drastically reduced, and comparator COMP1 outputs a low level. By the operation of the comparator COMP1, the base terminal voltage of the transistor Q22 drops to a low level. When the low level is input at the first pulse and the transistor Q21 is turned off for a short time, charge accumulation starts in the capacitor C4 according to the operation of the current source I21, and the charge accumulation time is determined by the capacitance of the capacitor C4 and thus the correction. Depends on the number. Thus, charge gradually accumulates over a predetermined time, and the voltage Va 'also gradually rises.

When the second pulse is input in the process of increasing the voltage Va 'and Vin maintains a high level, the rising voltage Va' drops rapidly. Therefore, the voltage Va 'maintains the low level as a whole in the section where the pulse train exists, and the low level has the shape of a triangular wave or a sawtooth wave. When the input of the pulse train is terminated and Vin maintains the low level, the transistor Q21 is turned off and charge is accumulated in the capacitor C4 at a predetermined time constant. Therefore, the voltage Va 'rises to a level above the first reference voltage Vf1 of the comparator COMP1.

If a low level signal is input before the input of the pulse train at the input signal Vin, Va 'is kept at a high level, so the transistor Q22 is in the turn-on state. Therefore, Vb 'is kept at a low level, and the capacitor C5 has almost no charge.

When Va 'maintains a low level in accordance with the input of the pulse train, the comparator COMP1 outputs a low level, the transistor Q22 is turned off, and the capacitor C5 starts to accumulate charge under the influence of the current source I22. The accumulation of charge depends on the capacitance and time constant of capacitor C5. Therefore, the voltage Vb 'rises to a level above the second reference voltage Vf2 of the comparator COMP2 with a predetermined rise time. When the input of the pulse train is terminated and the voltage Va 'rises, the comparator COMP1 outputs a high level, and the transistor Q22 is turned on. As the transistor Q22 is turned on, the charge accumulated in the capacitor C5 decreases rapidly, and the voltage Vb 'also falls to a low level.

When the voltage Vb 'is kept at a low level due to the absence of a pulse train at Vin, the comparator COMP2 outputs a low level, and the transistor Q23 is in a turn-off state. Therefore, the voltage Vc 'is maintained at a high level under the influence of the current source I23. When Vb 'rises above the second reference voltage Vf2 of comparator COMP2 in response to the input of the pulse train, transistor Q23 is turned on. As the transistor Q23 is turned on, the voltage Vc 'falls to a low level, and the charge accumulated in the capacitor C6 decreases rapidly under the influence of the current source I23. When the voltage Vb 'is switched from the high level to the low level upon termination of the pulse string input, the comparator COMP2 outputs a low level, and the transistor Q23 is turned off. As the transistor Q23 is turned off, the capacitor C6 starts to accumulate charge. The time at which the charge is accumulated and the voltage Vc 'rises above the predetermined level depends on the capacitor C6 and the time constant. Therefore, with the end of the pulse string input, the voltage Vc 'rises to a level higher than or equal to the third reference voltage Vf3 of the comparator COMP3 with a predetermined rise time.

When Vc 'falls from the high level to the low level due to the input of the pulse train, the comparator COMP3 outputs a low level, and the transistor Q24 is turned off. Therefore, under the influence of the current source I24, the base terminal voltage of the transistor Q25 is raised to a level sufficient to turn on the transistor Q25. Therefore, the output signal Vout switches from the high level to the low level.

When the input of the pulse string is terminated, Vc 'has a predetermined rise time and rises from the low level to a level above the third reference voltage Vf3 of the comparator COMP3. Accordingly, transistor Q24 is turned on, and transistor Q25 is turned off in accordance with turn-on of transistor Q24. Therefore, the output signal Vout is switched to the high level.

By the above-described process, a square wave corresponding to the duration of the pulse is formed. In addition, the rise time of the voltage Vb 'does not rise to a level sufficient to turn on the transistor Q23 when a predetermined number of pulses are not input, thereby replacing the function of the conventional Schmitt trigger. .

In addition, it can be seen that the waveform shaping circuit of this embodiment replaces the functions of the demodulator, the Schmitt trigger, and the output stage of the prior art.

Example 3

8 is a block diagram showing an infrared receiver according to Embodiment 3 of the present invention.

Referring to FIG. 8, the infrared receiver includes a photodiode 201, a voltage converter 203, an amplifier 205, a band pass filter 207, an automatic gain control circuit 209, a comparator 211 and waveform shaping. It consists of a circuit 213.

The photodiode 201 detects an infrared signal and converts it into a current. The amount of current flowing through the photodiode is converted into a predetermined voltage by the voltage converter 203. The input signal converted into the voltage by the voltage converter is input to the amplifier 205. The amplifier 205 amplifies the output of the voltage converter in response to the automatic gain control signal VAGC. In addition, the signal amplified by the amplifier 205 is input to the band pass filter 207, and only the signal corresponding to the predetermined frequency band is output. The output signal fout of the band pass filter 207 is input to the automatic gain control circuit 209 and the comparator 211. The automatic gain control circuit 209 compares the output signal fout of the band pass filter 207 and the predetermined threshold voltage Vt to generate the automatic gain control signal VAGC. The comparison unit 211 compares the output signal fout of the band pass filter 207 with the reference voltage VREF, and outputs the comparison voltage to the waveform shaping circuit 213. The waveform shaping circuit 213 is shown in Embodiments 1 and 2 of the present invention. In addition, the waveform shaping circuit 213 receives an output signal of the comparator 211 and outputs a shaped square wave corresponding to a time interval in which a pulse string exists.

According to the present invention as described above, since the waveform shaping circuit replaces the role of the conventional demodulator, the Schmitt trigger and the output terminal, it is possible to minimize the area occupied by the infrared receiver in the semiconductor wafer. In addition, since the same function is performed with a small number of transistors, it has the advantage of improving the failure rate according to a complicated semiconductor manufacturing process.

Although described above with reference to a preferred embodiment of the present invention, those skilled in the art will be variously modified and changed within the scope of the invention without departing from the spirit and scope of the invention described in the claims below I can understand that you can.

Claims (6)

A first waveform shaping unit configured to output a level corresponding to a time interval in which the pulse string is input in response to the input pulse string; A second waveform shaping unit for receiving an output of the first waveform shaping unit and outputting a signal having a predetermined level transition time from an input time of the pulse train; A third waveform shaping section for receiving an output of the second waveform shaping section and outputting a signal having a predetermined level transition time from an end time of the pulse train; A fourth waveform shaping unit configured to receive an output of the third waveform shaping unit, and have a predetermined delay time with respect to a start time of the pulse train, and form a square wave corresponding to the duration of the pulse train; And Waveform shaping circuit of the infrared receiver including an output unit for inverting the output of the fourth waveform shaping section. The method of claim 1, wherein the first waveform shaping portion, A first transistor for receiving the input pulse train; A first capacitor connected to a collector end of the first transistor and configured to accumulate charge when the first transistor is turned off; And Has a first current source for supplying current to said first transistor or said first capacitor, The second waveform shaping unit, A second transistor for receiving an output of the first waveform shaping unit; A second capacitor connected to the collector end of the second transistor and configured to accumulate charge when the first transistor is turned off; And A second current source for supplying current to the second transistor or the second capacitor, The third waveform shaping unit, A third transistor for receiving an output of the second waveform shaping unit; A third capacitor connected to the collector end of the third transistor and configured to accumulate charge when the third transistor is turned off; And Has a third current source for supplying current to the third transistor or the third capacitor, The fourth waveform shaping unit, A fourth transistor having a base end connected to the third current source and the third capacitor; A fifth transistor having a base end connected to an emitter end of the fifth transistor; And And a fourth current source for supplying current at turn-on of the sixth transistor. The method of claim 1, wherein the first waveform shaping portion, A first transistor for receiving the input pulse train; A first capacitor connected to a collector end of the first transistor and configured to accumulate charge when the first transistor is turned off; A first comparator for comparing a first reference voltage with a voltage of the first capacitor; And Has a first current source for supplying current to said first transistor or said first capacitor, The second waveform shaping unit, A second transistor for receiving an output of the first waveform shaping unit; A second capacitor connected to the collector end of the second transistor and configured to accumulate charge when the first transistor is turned off; A second comparator for comparing a second reference voltage with a voltage of the second capacitor; And A second current source for supplying current to the second transistor or the second capacitor, The third waveform shaping unit, A third transistor for receiving an output of the second waveform shaping unit; A third capacitor connected to the collector end of the third transistor and configured to accumulate charge when the third transistor is turned off; A third comparator for comparing a third reference voltage with a voltage of the third capacitor; And Has a third current source for supplying current to the third transistor or the third capacitor, The fourth waveform shaping unit, A fourth transistor having a base end connected to an output end of the third comparator; And And a fourth current source for supplying current at turn-on of the fourth transistor. A photodiode for sensing an infrared input signal; A voltage converter configured to convert the voltage into a voltage in response to a current flowing through the photodiode; An amplifier for amplifying an output signal of the voltage converter in response to an automatic gain control signal; A band pass filter for outputting only a signal corresponding to a predetermined frequency band from the output signal of the amplifier; An automatic gain control circuit for generating the automatic gain control signal by comparing the output of the band pass filter with a predetermined threshold voltage; A comparator for comparing the output of the band pass filter with a reference voltage; And A waveform shaping circuit for receiving an output signal of the comparator and generating a square wave corresponding to a section in which a pulse train exists; The waveform shaping circuit A first waveform shaping unit configured to output a level corresponding to a time interval in which the pulse string is input in response to the input pulse string; A second waveform shaping unit for receiving an output of the first waveform shaping unit and outputting a signal having a predetermined level transition time from an input time of the pulse train; A third waveform shaping section for receiving an output of the second waveform shaping section and outputting a signal having a predetermined level transition time from an end time of the pulse train; A fourth waveform shaping unit configured to receive an output of the third waveform shaping unit, and have a predetermined delay time with respect to a start time of the pulse train, and form a square wave corresponding to the duration of the pulse train; And And an output unit for inverting the output of the fourth waveform shaping unit. The method of claim 4, wherein the first waveform shaping portion, A first transistor for receiving the input pulse train; A first capacitor connected to a collector end of the first transistor and configured to accumulate charge when the first transistor is turned off; And Has a first current source for supplying current to said first transistor or said first capacitor, The second waveform shaping unit, A second transistor for receiving an output of the first waveform shaping unit; A second capacitor connected to the collector end of the second transistor and configured to accumulate charge when the first transistor is turned off; And A second current source for supplying current to the second transistor or the second capacitor, The third waveform shaping unit, A third transistor for receiving an output of the second waveform shaping unit; A third capacitor connected to the collector end of the third transistor and configured to accumulate charge when the third transistor is turned off; And Has a third current source for supplying current to the third transistor or the third capacitor, The fourth waveform shaping unit, A fourth transistor having a base end connected to the third current source and the third capacitor; A fifth transistor having a base end connected to an emitter end of the fifth transistor; And And a fourth current source for supplying current at turn-on of the sixth transistor. The method of claim 4, wherein the first waveform shaping portion, A first transistor for receiving the input pulse train; A first capacitor connected to a collector end of the first transistor and configured to accumulate charge when the first transistor is turned off; A first comparator for comparing a first reference voltage with a voltage of the first capacitor; And Has a first current source for supplying current to said first transistor or said first capacitor, The second waveform shaping unit, A second transistor for receiving an output of the first waveform shaping unit; A second capacitor connected to the collector end of the second transistor and configured to accumulate charge when the first transistor is turned off; A second comparator for comparing a second reference voltage with a voltage of the second capacitor; And A second current source for supplying current to the second transistor or the second capacitor, The third waveform shaping unit, A third transistor for receiving an output of the second waveform shaping unit; A third capacitor connected to the collector end of the third transistor and configured to accumulate charge when the third transistor is turned off; A third comparator for comparing a third reference voltage with a voltage of the third capacitor; And Has a third current source for supplying current to the third transistor or the third capacitor, The fourth waveform shaping unit, A fourth transistor having a base end connected to an output end of the third comparator; And And a fourth current source for supplying current at turn-on of the fourth transistor.

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