KR101380785B1 - Infrared Signal Receiver of having Gain Hold Function - Google Patents

Abstract

An infrared receiver capable of realizing a fixed gain according to a gain stop signal applied from the outside is disclosed. When it is determined through analysis of the output signal and the carrier signal to be formed that a change in gain through the variation of the gain control signal is not necessary, the gain stop signal is activated. The activated gain stop signal stops the charge / discharge operation of the automatic gain regulator. Therefore, the gain state just before stopping is maintained as it is. When the gain stop signal is deactivated, the automatic gain regulator causes a change in the gain control signal through a charge / discharge operation. Thus, the gain of the infrared receiver is changed.

Description

Infrared Signal Receiver of having Gain Hold Function

The present invention relates to an infrared receiver, and more particularly to an infrared receiver in which the gain is stopped in the state in which the constant gain or noise is removed.

The infrared receiver receives the infrared signal, amplifies and processes it. An infrared signal is transmitted to an electronic product using a remote controller, and the like, and the infrared receiver receives the infrared signal, amplifies it, and converts it into a data format of a promised form.

1 is a block diagram illustrating an infrared receiver according to the prior art.

Referring to FIG. 1, an infrared receiver includes a photodiode 10, a transimpedance amplifier 11, an auto gain amplifier 12, a limiter 13, a band pass filter 14, an auto gain regulator 15, and a threshold voltage. It has an adjustment and comparator 16, an integrator 17, a Schmitt trigger 18 and an output stage 19.

The photodiode 10 receives an infrared signal and converts it into a current. Since the infrared signal has a pulsation with a predetermined frequency, the current formed by the photodiode 10 is also pulsated. The current signal of the photodiode 10 is input to the transimpedance amplifier 11, the transimpedance amplifier 11 converts a signal in the form of current into a voltage signal, and amplifies it.

The converted voltage signal has a larger amplitude while passing through the auto gain amplifier 12, the limiter 13, the band pass filter 14, and the like, and the signal and noise selectivity are improved.

The automatic gain amplifier 12 is controlled by the automatic gain regulator 15 to vary the gain depending on the noise and the shape of the input voltage signal.

The limiter 13 has a function of limiting within a legitimate level so that overvoltage is not applied to the bandpass filter 14, and the bandpass filter 14 improves frequency selectivity of the infrared receiver and passes only signals of a specific band. . Therefore, the noise component included in the processing signal is partially removed. However, in actual hardware implementation, there is a significant difference from the role of the ideal bandpass filter 14. Therefore, the noise component also passes through the band pass filter 14.

The output of the bandpass filter 14 is input to the threshold voltage control and comparator 16, and is formed of a constant signal component. It is input to the demodulation circuit composed of the integrator 17 and the schmitt trigger 18, and generates the output signal Vo of the output stage 19.

The output signal Vo is input to a microcomputer or the like. The microcomputer receives the output signal Vo, extracts information included in the infrared signal through counting or determining a pulse width, and performs a processing operation.

In the operation of the above-described infrared receiver, the noise component included in the infrared signal should be properly removed, and a predetermined gain should be implemented. However, in the infrared receiver, the gain and the noise have opposite characteristics. In other words, increasing the gain increases the noise component, and decreasing the gain reduces the noise.

The output of the infrared receiver is mostly input to the microcomputer. High noise causes a malfunction of the microcomputer, and in order to prevent the microcomputer from outputting a low gain signal, the microcomputer receives a weak signal and does not perform signal processing smoothly.

SUMMARY OF THE INVENTION The present invention has been made in an effort to provide an infrared receiver in which a gain is fixed according to a noise level or a gain state of a specific level.

The present invention for achieving the above object is a trans-impedance amplifier for converting an infrared signal of the current form detected by the photodiode into a voltage signal; An autogain amplifier for amplifying the output of the transimpedance amplifier; A limiter for limiting the output of the auto gain amplifier to a predetermined level or less; A band pass filter for selecting and outputting a signal of a pass band from the output of the limiter; An automatic gain adjuster for receiving an output signal of the bandpass filter, adjusting a gain of the automatic gain amplifier, or implementing a fixed gain; A threshold voltage adjuster / comparator for receiving an output of the bandpass filter and generating a pulse signal according to a set threshold voltage; An integrator for integrating the pulse signal; A Schmitt trigger for receiving the output of the integrator and forming a square wave; An output stage for forming an output signal through an on / off operation according to the square wave; And a carrier signal generator for receiving the output of the Schmitter and the output of the bandpass filter and extracting a carrier signal included in the infrared signal.

According to the present invention described above, the carrier signal and the output signal are analyzed and the noise level of the signal passing through the bandpass filter is sensed. In addition, the appropriateness of the gain of the automatic gain amplifier is determined by analyzing the aspect of the output signal. If the gain is greater than or equal to the reference gain set in the microcomputer and the signal-to-noise ratio that is the noise level is less than the reference ratio, the microcomputer activates the gain stop signal. Therefore, the automatic gain regulator stops adjusting the gain of the automatic gain amplifier according to the charge / discharge operation.

In this case, if it is determined that the noise and the gain are included in a certain range, the infrared receiver can implement a certain gain, and the unstable processing state of the infrared signal due to the increase of the noise level, the decrease or the increase of the gain can be achieved. It can be improved.

1 is a block diagram illustrating an infrared receiver according to the prior art.
2 is a block diagram illustrating an infrared receiver according to a preferred embodiment of the present invention.
3 is a block diagram illustrating the automatic gain adjuster of FIG. 2 in accordance with a preferred embodiment of the present invention.
4 is a timing diagram for describing an operation of the infrared receiver of FIG. 1 according to a preferred embodiment of the present invention.
5 is another timing diagram for describing an operation of the infrared receiver of FIG. 1 according to an exemplary embodiment of the present invention.
6 is a timing diagram for describing an operation of a carrier signal generator according to an exemplary embodiment of the present invention.

The present invention is capable of various modifications and various forms, and specific embodiments are illustrated in the drawings and described in detail in the text. It should be understood, however, that the invention is not intended to be limited to the particular forms disclosed, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention. Like reference numerals are used for like elements in describing each drawing.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms such as those defined in commonly used dictionaries are to be interpreted as having a meaning consistent with the contextual meaning of the related art and are to be interpreted as either ideal or overly formal in the sense of the present application Do not.

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

Example

2 is a block diagram illustrating an infrared receiver according to a preferred embodiment of the present invention.

Referring to FIG. 2, the infrared receiver of the present invention includes a transimpedance amplifier 110, an auto gain amplifier 120, a limiter 130, a band pass filter 140, an auto gain controller 150, and a threshold voltage adjuster / comparator. 160, an integrator 170, a schmitt trigger 180, an output stage 190, and a carrier signal generator 200.

The infrared receiver is connected to the photodiode 100, which is an external component, and a very weak infrared signal is detected in the form of a pulsating current through a photodetecting device such as the photodiode 100.

In order to detect such a weak infrared signal current at a long distance, a plurality of circuits are provided inside the infrared receiver circuit. In particular, a circuit that receives, amplifies, and removes an infrared signal having a weak level serves as an important element of the infrared receiver.

First, the infrared signal received by the photodiode 100 is converted into a current signal, and the converted current signal is input to the trans impedance amplifier 110.

The trans impedance amplifier 110 converts the detected current signal into a voltage signal and amplifies it. The converted signal is input to the auto gain amplifier 120.

The auto gain amplifier 120 receives the output signal of the trans impedance amplifier 110 and amplifies it with a predetermined gain. However, the auto gain amplifier 120 may vary the gain according to the signal-to-noise ratio of the input signal. That is, when there is a lot of noise in the input signal, the gain of the automatic gain amplifier 120 is somewhat reduced. In addition, when the noise of the input signal is small, the gain of the automatic gain amplifier 120 is increased. Such a change in the gain of the auto gain amplifier 120 is made by the operation of the auto gain regulator 150.

Also, when the gain of the auto gain amplifier enters a constant state, the gain is fixed. That is, if a gain equal to or greater than the reference gain is implemented in the output signal of the infrared receiver, and the signal-to-noise ratio is less than the reference ratio, the gain of the auto gain amplifier is fixed. However, if the gain of the infrared receiver is less than the reference gain, or if the signal-to-noise ratio is more than the reference ratio, the gain of the auto gain amplifier is changed.

The automatic gain controller 150 has a set voltage level through the charge and discharge operation, and adjusts the gain of the automatic gain amplifier 120. That is, the automatic gain adjuster 150 receives the output signal of the band pass filter 140 and generates a gain control signal. The generated gain control signal determines the gain of the auto gain amplifier 120. For example, when a signal with less noise is received, the gain of the auto gain amplifier 120 is increased, and when a signal with noisy is received, the gain control signal is operated so that the gain of the auto gain amplifier 120 is decreased.

In addition, the automatic gain regulator 150 receives a gain stop signal from the microcomputer. When the gain stop signal is activated, the gain control signal is fixed. Therefore, the auto gain controller 150 outputs a fixed gain control signal while the gain stop signal is activated. Thus, the auto gain amplifier 120 has a fixed amplification degree and implements gain. In addition, when the gain stop signal is deactivated, the automatic gain controller 150 again forms a variable gain control signal through a charge / discharge operation.

The auto gain amplifier 120 has a gain range set according to the circuit configuration. However, the maximum value of the gain is preferably set to 30dB to 35dB. The output of the auto gain amplifier 120 is input to the limiter 130.

The limiter 130 has a predetermined gain and forcibly sets a level of a signal above a preset level. For example, when the voltage difference between peaks of a signal exceeds 0.7V, this is forcibly set to the voltage difference 0.7V between preset peaks. In addition, in the present invention, the gain of the limiter 130 is preferably set to 15dB to 25dB. The output of the limiter 130 is input to the band pass filter 140.

The band pass filter 140 selectively passes only signals around the center band in the output signal of the input limiter 130. In the present invention, the center frequency of the band pass filter 140 is set to 30kHz to 60kHz, the bandwidth is preferably set to 4kHz to 5kHz. In addition, the gain of the bandpass filter 140 in the vicinity of the center frequency is preferably set to 15dB to 25dB. The signal passing through the band pass filter 140 is input to the automatic gain controller 150, the threshold voltage adjuster / comparator 160, and the carrier signal generator 200.

The output signal of the band pass filter 140 is input to the threshold voltage regulator / comparator 160. According to the threshold voltage set in the threshold voltage regulator / comparator 160, the output signals of the band pass filter 140 are compared. Thus, the output of the threshold voltage regulator / comparator 160 is a kind of pulse waveform having a high level or a low level. The pulse waveform is input to the integrator 170.

The integrator 170 performs an integration operation on the signal of the pulse voltage threshold voltage regulator / comparator 160. The infrared signal is demodulated by the integration operation of the integrator 170. The demodulated signal is input to the Schmitt trigger 180.

The Schmitt trigger 180 receives the output signal of the demodulated integrator 170 to form a square wave. The formed square wave is input to the output stage 190. The transistor Q included in the output stage 190 performs an on / off operation to generate a final output signal Vout through charge / discharge operation.

The output signal of the band pass filter 140 and the output signal of the Schmitt trigger 180 are input to the carrier signal generator 200. The carrier signal generator 200 has a comparator 210 and a logic circuit 200.

The comparator 210 receives the output signal of the band pass filter, which is compared with the center signal Vct. Therefore, the output of the comparator 210 has an improvement in which the high level and the low level are sequentially changed. In addition, the output of the comparator 210 is input to the logic circuit 220, which is ANDed with the output signal of the Schmitt trigger 180. The logic circuit 220 forms pulse signals in a state where the output signal Vout is at a low level. This means that the output signal of the comparator 210 is transmitted only when the output signal of the schmitt trigger 180 is at a high level. The output of the logic circuit 220 is named carrier signal Vcar.

The output signal Vout and the carrier signal Vcar are input to the microcomputer. The microcomputer determines the aspect of the output signal Vout and the carrier signal Vcar. For example, a gain stop signal is formed by analyzing a noise level included in the carrier signal Vcar, or by analyzing the magnitude and noise level of the output signal Vout.

3 is a block diagram illustrating the automatic gain adjuster of FIG. 2 in accordance with a preferred embodiment of the present invention.

Referring to FIG. 3, the automatic gain regulator has a current charge / discharge circuit 151, a charge / discharge switch 152, a charge / discharge capacitor 153, and a voltage current converter 154.

The output signal of the band pass filter is input to the current charge / discharge circuit 151. In addition, the charge / discharge threshold voltage Vth is input. The current charge / discharge circuit 151 compares the output of the band pass filter with the charge / discharge threshold voltage Vth and outputs a charge / discharge signal. Therefore, the charging operation is performed in a section where a signal having a level higher than or equal to the charging / discharging threshold voltage Vth is applied, and the discharge operation is performed in a section where a signal below the charging / discharging threshold voltage Vth is applied. Under normal circumstances, the gain stop signal is deactivated. Therefore, the charge / discharge switch 152 maintains the conduction state, and the charge / discharge capacitor 153 is performed by the charge / discharge signal.

Therefore, when the charging operation is performed, the voltage of the charge / discharge capacitor 153 continuously rises. This is applied to the voltage current converter 154 in the form of a current signal, and the voltage current converter 154 converts it into the form of a voltage signal and outputs it as a gain control signal. Thus, while the charging operation is performed, the level of the gain control signal continuously rises.

In addition, when the discharge operation is performed, the voltage of the charge / discharge capacitor 153 continuously drops. This is applied to the voltage current converter 154 in the form of a current signal. Accordingly, the voltage current converter 154 forms a gain control signal whose level is continuously reduced.

If the gain stop signal is activated, the charge / discharge switch 152 is opened. Therefore, the aspect of the output signal of the band pass filter 140 is not transmitted to the charge / discharge capacitor 153. The charging / discharging capacitor 153 has a predetermined voltage level set just before the charging / discharging switch 152 is opened. This is generated as a gain control signal of a constant level via the voltage current converter 154.

4 is a timing diagram for describing an operation of the infrared receiver of FIG. 1 according to a preferred embodiment of the present invention.

Referring to FIG. 4, an infrared signal is received and an aspect of the signal passing through the bandpass filter 140 is disclosed. When the output signal of the band pass filter 140 is examined, a signal having a substantially constant frequency, but a high level signal appears in a specific time period. The output signal of the bandpass filter 140 having a high level functions as meaningful data in the infrared receiver. The output of the band pass filter 140 is input to the automatic gain regulator 150. This is also compared with the charge / discharge threshold voltage Vth.

The charge / discharge signal forms a charging current in a section in which a level above the charge / discharge threshold voltage Vth appears. Therefore, the voltage and current of the charge / discharge capacitor 153 continuously rise. In FIG. 4, the charging current is displayed at a high level. In the section marked as high level, it means that charging operation occurs.

In addition, the discharge operation is performed by the charge / discharge signal in a section in which the peak value of the output signal of the band pass filter 140 is less than the threshold voltage. This means that the discharge operation is performed in the section where the discharge current is high level. Therefore, in the discharge section, the voltage and current of the charge / discharge capacitor 153 decrease continuously.

When the charging operation occurs, the voltage current converter 154 may generate it as a gain control signal of which the level continuously increases. The automatic gain amplifier 120 implements a low gain when a high level gain control signal is input and implements a high gain when a low level gain control signal is input. Therefore, the gain of the auto gain amplifier 120 is continuously decreased by the gain control signal of which the level continuously increases. This means that the gain is reduced in the section where the output of the bandpass filter 140 has a high level. In a section with a high level, the noise is also included at a high level. Thus, reducing the gain reduces the noise level.

If the discharge operation occurs, the voltage current converter 154 may generate it as a gain control signal of which the level is continuously lowered. The gain of the auto gain amplifier 120 is continuously increased by the gain control signal whose level is continuously reduced. Therefore, the gain of the auto gain amplifier 120 increases in the period in which the discharge operation is performed. Through this, the auto gain amplifier 120 may be set to an appropriate gain.

In particular, when it is determined that the output signal Vout and the carrier signal Vcar have appropriate gains and noise is substantially removed from the carrier signal Vcar and the output signal Vout, the microcomputer activates the gain stop signal. In FIG. 4, the gain stop signal is shown to be activated at a low level. When the gain stop signal is activated, the charge / discharge switch 152 is opened. Therefore, the current path through the current charge / discharge circuit 151 is blocked. In addition, the charge / discharge capacitor 153 does not additionally perform a charge / discharge operation, and the charge / discharge capacitor 153 maintains a voltage level of a constant level. This is represented by a gain control signal with a constant level. Since the gain control signal is constant, the gain of the automatic gain amplifier 120 is also constant, and the gain of the infrared receiver is also maintained at a constant level.

If it is determined that the output signal Vout or the carrier signal Vcar includes a noise to have a signal-to-noise ratio of more than the reference ratio or a low gain of less than the reference gain, the microcomputer determines this and deactivates the gain stop signal. Accordingly, the charge / discharge switch 152 is turned on, the current charge / discharge circuit 151 generates a charge / discharge signal, and performs a charge operation or a discharge operation through the charge / discharge capacitor 153.

5 is another timing diagram for describing an operation of the infrared receiver of FIG. 1 according to an exemplary embodiment of the present invention.

Referring to FIG. 5, the output of the band pass filter 140 is input to the threshold voltage regulator / comparator 160. The threshold voltage regulator / comparator 160 internally forms a threshold voltage Vref and compares it with the output of the bandpass filter 140. The adjustment of the threshold voltage Vref may be changed according to the gain of the auto gain amplifier 120. For example, when the gain of the auto gain amplifier 120 is high, the level of the threshold voltage Vref formed may increase, and when the gain of the auto gain amplifier 120 is low, the level of the threshold voltage Vref formed may decrease.

The formed threshold voltage Vref is compared with the output of the band pass filter 120. If the level of the output signal of the band pass filter 120 is greater than or equal to the threshold voltage Vref, the threshold voltage regulator / comparator 160 forms a high level. Since the bandpass filter 140 has a high peak value in a specific section, the threshold voltage regulator / comparator 160 forms a signal of a pulse train in a specific section. The output of the threshold voltage regulator / comparator 160 is input to the integrator 170.

Integrator 170 integrates the output of threshold voltage regulator / comparator 160. When the integral value reaches the threshold value, the integrator 170 maintains a constant level even though a pulse train signal is applied. In addition, the level of the integrator 170 decreases in a section in which a signal of the pulse train does not appear.

Accordingly, the output of the integrator 170 undergoes a process of charging, maintaining a threshold, and discharging, thereby forming an approximately trapezoidal waveform.

The schmitt trigger 180 forms a square wave according to two preset reference voltages Vt1 and Vt2. For example, the first reference voltage Vt1 has a high level, and the second reference voltage Vt2 has a lower level than the first reference voltage Vt1. Therefore, the hysteresis characteristics are realized through this.

First, when the output of the integrator 170 is greater than or equal to the first reference voltage Vt1, the Schmitt trigger 180 recognizes this as a high signal and outputs a high level. In addition, even if the output level of the integrator 180 becomes less than or equal to the first reference voltage Vt1, the Schmitt trigger 180 maintains a high level state. However, when the output level of the integrator 170 continuously decreases to become less than the second reference voltage Vt2, the Schmitt trigger 180 recognizes this as a low signal and outputs a low level. The output signal of the Schmitt trigger 180 has a certain square wave aspect. In addition, the output of the Schmitt trigger 180 is supplied to the carrier signal generator 200 and the output stage 190.

First, the output stage 190 is composed of n type BJT or n type MOS. The output signal of the Schmitt trigger 180 is input to the gate terminal or the base terminal of the transistor Q. If the output signal of the schmitt trigger 180 is at the high level, the transistor Q is turned on to form the low level output signal Vout. In addition, when the output signal of the Schmitt trigger 180 is at the low level, the transistor Q is cut off, and the power supply voltage VDD outputs the high level via the load Z. As a result, the output stage 190 inverts the output signal of the Schmitt trigger 180.

6 is a timing diagram for describing an operation of a carrier signal generator according to an exemplary embodiment of the present invention.

Referring to FIG. 6, the signal passing through the band pass filter 140 is input to the comparator 210. The center voltage Vct is applied to the other input terminal of the comparator 210. Accordingly, the comparator 210 forms a signal having a frequency corresponding to the center frequency of the band pass filter 140 in all sections. This is input to the logic circuit 220 together with the output of the Schmitt trigger 180. The logic circuit 220 may perform an AND operation. Therefore, the logic circuit 220 transmits the output of the comparator 210 in the section where the output of the Schmitt trigger 180 is a high level. On the other hand, if the output of the Schmitt trigger 180 is at a low level, the logic circuit 220 forms a low level.

Accordingly, the carrier signal Vcar, which is the output signal of the carrier signal generator 200, has a mode of repeating the high level and the low level in a section in which the output signal Vout is at a low level, which is at the center frequency of the band pass filter 140. Close.

The above-described carrier signal Vcar and output signal Vout are input to the microcomputer. The microcomputer may detect the noise level of the signal passing through the band pass filter 140 by analyzing the state of the carrier signal Vcar. In addition, the aspect of the output signal Vout is analyzed to determine the appropriateness of the gain of the automatic gain amplifier 120. If the gain is greater than or equal to the reference gain set in the microcomputer and the signal-to-noise ratio that is the noise level is less than the reference ratio, the microcomputer activates the gain stop signal. Therefore, the automatic gain regulator stops adjusting the gain of the automatic gain amplifier according to the charge / discharge operation.

In this case, if it is determined that the noise and the gain are included in a certain range, the infrared receiver can implement a certain gain, and the unstable processing state of the infrared signal due to the increase of the noise level, the decrease or the increase of the gain can be achieved. It can be improved.

110: trans impedance amplifier 120: auto gain amplifier
130: limiter 140: band pass filter
150: automatic gain regulator 160: threshold voltage regulator / comparator
170: integrator 180: Schmitt trigger
190: output stage 200: carrier signal generator

Claims (6)

A transimpedance amplifier for converting an infrared signal in the form of current detected by the photodiode into a voltage signal;
An autogain amplifier for amplifying the output of the transimpedance amplifier;
A limiter for limiting the output of the auto gain amplifier to a predetermined level or less;
A band pass filter for selecting and outputting a signal of a pass band from the output of the limiter;
An automatic gain adjuster for receiving an output signal of the bandpass filter, adjusting a gain of the automatic gain amplifier, or implementing a fixed gain;
A threshold voltage adjuster / comparator for receiving an output of the bandpass filter and generating a pulse signal according to a set threshold voltage;
An integrator for integrating the pulse signal;
A Schmitt trigger for receiving the output of the integrator and forming a square wave;
An output stage for forming an output signal through an on / off operation according to the square wave; And
And a carrier signal generator for receiving the output of the Schmitt trigger and the output of the bandpass filter and extracting a carrier signal included in the infrared signal. The method of claim 1, wherein the automatic gain adjuster,
A current charge / discharge circuit which receives an output of the band pass filter and forms a charge / discharge signal in comparison with a charge / discharge threshold voltage;
The output signal and the carrier signal are input to the microcomputer, the noise level of the carrier signal is analyzed by the microcomputer, and the signal is turned on according to the gain stop signal generated from the microcomputer by analyzing the magnitude or the noise level of the output signal. A charge / discharge switch performing an on / off operation;
A charge / discharge capacitor configured to perform a charge / discharge operation according to the charge / discharge signal; And
And a voltage current converter configured to sense a current of the charge / discharge capacitor to form a gain control signal for adjusting the gain of the auto gain amplifier. 3. The infrared receiver of claim 2, wherein when the gain stop signal is activated, the charge / discharge switch is turned off, and the voltage / current converter forms a gain control signal having a fixed level. The infrared receiver of claim 3, wherein when the gain stop signal is inactivated, the charge / discharge switch is turned on, and the gain control signal is changed in level by a charge / discharge operation of the charge / discharge capacitor. The method of claim 1, wherein the carrier signal generation unit,
A comparator for receiving an output of the band pass filter and generating a pulse train-type signal through comparison with an input center voltage; And
And a logic circuit for receiving the output of the Schmitter and the output of the comparator, and generating a carrier signal corresponding to the center frequency of the bandpass filter by performing a logical operation on the output of the comparator. 6. The infrared receiver of claim 5, wherein the logic circuit performs an AND operation.

Images