KR101404569B1 - The noise removing circuit of infrared rays receiver - Google Patents

Abstract

The present invention determines and removes a noise with a continuous or periodical type like a noise generated in PDP based on a reference length corresponding to the minimum gap length by measuring the gap length of a signal inputted to an infrared receiver. For this, the present invention includes a gain controller which outputs a first noise detection signal when input time is over preset time by measuring the burst section input time of a signal from a second demodulator and outputs a second noise detection signal when the gap length of the signal inputted from the second modulator is the reference length corresponding to the minimum gap length or less by measuring the gap length of the signal inputted from the second modulator.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a noise canceling circuit for an infrared receiver,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a noise elimination technique for an infrared receiver, and more particularly, to a noise elimination circuit for an infrared receiver adapted to eliminate noise inputted continuously or periodically.

2. Description of the Related Art Generally, an infrared receiver means a device mounted on a consumer electronic product such as a TV and receiving and processing an infrared signal input by a user's remote control key. In the household appliance, a main control unit such as a microprocessor controls the function or operation of the corresponding home appliance according to an infrared signal (code) received and processed by the infrared receiver.

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

       1, the conventional infrared receiver includes an input unit 110, a first stage amplification unit 120, an automatic gain control amplification unit 130, a limit amplification unit 140, a bandpass filter unit 150, A gain controller 160, first and second comparators 170 and 200, first and second demodulators 180 and 210, and an output unit 190.

      The input unit 110 includes a photodiode to convert the inputted infrared signal into an electric signal, and the first stage amplifying unit 120 amplifies the converted electric signal.

The automatic gain control amplifier 130 receives the output of the first stage amplifier 120 and controls the gain. The limit amplifier 140 amplifies the signal passed through the automatic gain control amplifier 130 again. The band-pass filter unit 150 filters only an electric signal of a specific frequency included in the output of the limit amplifier unit 140.

The first comparator 170 compares the first threshold voltage V _th1 with the output of the bandpass filter unit 150 so that the output of the bandpass filter unit 150 is higher than the first threshold voltage V _th1 And the first demodulator 180 demodulates the output signal of the first comparator 170 to output the original signal. The output unit 190 outputs the output signal of the first demodulator 180 to the outside of the infrared receiver.

When the output of the band-pass filter 150 is lower than the first threshold voltage V _th1 , the output of the comparator 200 is not output and is compared with the second threshold voltage V _th2 , And the output signal of the second comparator 200 is demodulated through the second demodulator 210 and output to the gain controller 160.

The gain controller 160 generates a gain control current or a gain control voltage for controlling the gain of the automatic gain control amplifier 130 according to whether the signal output from the second demodulator 210 is a noise or a normal signal.

The threshold voltages of the first and second comparators 170 and 200 are arbitrarily set. The second threshold voltage V _th2 is set to a voltage as low as several tens mV relative to the first threshold voltage V _th1 .

However, input signals coming from the outside to the infrared receiver are not only infrared components, but also unwanted disturbance lights such as fluorescent light or sunlight. These disturbance lights are considered noise components because they are not intended by the designer.

In order for the infrared receiver to operate reliably, such external noise components must be removed or appropriately limited. In order to remove the noise, the infrared receiver uses the gain controller 160 and the automatic gain control amplifier 130.

2 is a view showing a method of removing a noise component by a simple charge-discharge method in an infrared receiver according to the related art.

A method of removing a noise component by a simple charging / discharging method uses a ratio of a burst section, which is a period in which a normal signal is input, and a dormant section, in which a signal is not input, (burst: dormant period = 1: n). In this case, n> 1 in the case of the signal, and n <1 in the case of the noise. In the case of the signal, the gain is increased by discharging as a whole, and in the case of noise, . However, this method has a problem that the noise of a fluorescent lamp having a waveform similar to that of a signal is recognized as a signal, thereby increasing the gain and outputting noise.

In order to solve this problem, a method of using the duration of the idle period instead of adjusting the gain of the automatic gain control amplifier based on the ratio of the burst signal to the idle period has been proposed.

FIG. 3 is a diagram illustrating a method of removing a noise component using a pause detection method in a conventional infrared receiver. Referring to FIG.

In this method, it is judged that noise is short when the rest period is shorter than a preset predetermined period. If the rest period is longer than that predetermined period, the remote control signal is judged to be a normal remote control signal and the fluorescent light noise of about 8 ms is eliminated by continuously charging during the rest period to reduce the gain.

However, this method requires a small current in order to increase the time constant, or requires a capacitor having a relatively large value in the circuit because the charging period is long in the entire charging period when the signal is applied, not the noise, . In addition, there is a problem that there is no problem in a signal having a long idle period, which is generally used, but a signal having a short idle period is recognized as noise and the signal disappears.

In order to overcome such a problem, other prior arts proposed have discriminated the noise and the signal based on the burst. For example, when the burst length is equal to or greater than a predetermined value, the burst length is recognized as noise, and the burst length is limited to a predetermined value or less.

Conventional electronic fluorescent lamps and triple-wavelength fluorescent noise have a burst length of 1 msec or more, so that noise can be removed using other conventional techniques, and bursts below a certain length can be continuously received.

However, in a home appliance including a PDP, such as a PDP (Plasma Display Panel) TV, there is noise emitted from the PDP, which is similar to the form of an infrared signal received from a remote controller. Therefore, the infrared receiver applied to the home appliances including the PDP, such as the PDP TV, can not remove the noise emitted from the PDP or the noise of the similar type using the other conventional technology, thereby causing the malfunction of the corresponding appliances Respectively.

SUMMARY OF THE INVENTION The object of the present invention is to measure a gap length of a signal input to an infrared receiver using a characteristic of a PDP signal received by an infrared receiver and a difference (difference in minimum gap length) between an infrared signal and a minimum gap length Based on the reference length, it is possible to discriminate and remove continuous and periodic noise such as noise generated in the PDP.

According to an aspect of the present invention, there is provided a noise removing circuit for an infrared receiver, including: an input unit including a photodiode for sensing an infrared input signal received from an external source and outputting an electric signal according to the infrared input signal; A first stage amplifier for amplifying an electric signal output from the input unit; An automatic gain control amplifier amplifying an electric signal output from the first stage amplifier and adjusting a gain; A limit amplifier amplifying the electrical signal amplified by the automatic gain control amplifier; A bandpass filter unit for filtering a carrier frequency signal of an infrared signal from an electric signal amplified by the limit amplifying unit; A first comparator for comparing a signal filtered by the band-pass filter with a first threshold voltage; A first demodulator for demodulating the signal output by the first comparator; An output unit receiving an output signal of the first demodulator and outputting the signal to the outside of the infrared receiver; A second comparator for receiving a signal filtered by the band-pass filter and comparing the received signal with a second threshold voltage; A second demodulator for demodulating the signal output by the second comparator; And outputting a first noise detection signal when the input time is equal to or longer than a preset time, measuring a gap length of a signal input from the second demodulator, And outputting a second noise detection signal when the reference length is equal to or shorter than the reference length.

The present invention measures a gap length of a signal input to an infrared receiver to discriminate a noise appearing continuously or periodically based on a reference length corresponding to a minimum gap length to detect a noise emitted from the PDP or a noise Can be reliably removed.

1 is a block diagram of an infrared receiver according to the prior art.
2 (a) to 2 (c) are waveform diagrams showing a method of removing a noise component by a simple charging / discharging method in a conventional infrared receiver.
3 (a) to 3 (d) are waveform diagrams showing a method of removing a noise component by a pause detection method in a conventional infrared receiver.
4 is a block diagram of an infrared receiver including a noise removing circuit according to an embodiment of the present invention.
FIG. 5 is a detailed block diagram illustrating an embodiment of the gain controller in FIG.
6A is a detailed circuit diagram of the charge pump of FIG.
6B is a waveform chart showing a change in the automatic gain control voltage output from the charge pump of FIG.
6C is a graph showing the relationship between the automatic gain control voltage and the gain of the automatic gain control amplifier.
7 is a detailed block diagram of the second noise detector of FIG.
8 is a detailed circuit diagram of the second demodulator of FIG.
9 (a) to 9 (e) are waveform diagrams of respective parts of Fig. 8
10 (a) is a waveform diagram of PDP noise output from a broadband sensor (APD module).
10 (b) is a frequency domain waveform diagram of a signal obtained by performing a fast Fourier transform on the output signal of the wide band sensor.
10 (c) is a waveform diagram of a signal passed through the band-pass filter.
10 (d) is a magnified waveform diagram of a signal that has passed through the band-pass filter.

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

4 is a block diagram of an infrared receiver including a noise removing circuit according to an embodiment of the present invention.

4, the noise elimination circuit of the infrared receiver according to the present invention includes an input section 411, a first stage amplification section 412, an automatic gain control amplification section 413, a limit amplification section 414, An output unit 419, an oscillator 422, and an oscillator trim unit 423. The first and second demodulators 415 and 415, the gain adjuster 416, the first and second comparators 417 and 420, the first and second demodulators 418 and 421,

The noise elimination circuit of the infrared receiver according to the embodiment of the present invention shown in FIG. 4 includes a gain adjusting unit 416, a second demodulator 421, an oscillator 422, and an oscillator trim unit 423, The second demodulator 421, the oscillator 422, and the oscillator trim unit 423 will be described in detail with reference to FIG. It will be omitted.

FIG. 5 is a detailed block diagram illustrating an embodiment of the gain adjustment unit 416 in FIG. 5, the gain adjustment unit 416 according to the present invention includes a noise detection unit 451, a gain control unit 452, and a charge pump 452. The noise detection unit 451 includes a first noise detector 451A and a second noise detector 451B. (453).

The first noise detector 451A measures the input time of the burst section of the signal input from the second demodulator 421 and determines that the first noise is inputted if it is longer than a preset time (for example, 1 ms) And outputs the first noise detection signal DET1. The reason why the first noise detector 451A measures the burst duration input time of the input signal is that the automatic gain control amplifier 413 does not increase the gain over a predetermined period when the length of the burst duration is equal to or greater than a predetermined value It is for this reason. The first noise includes fluorescent light noise and LCD dimming noise.

The second noise detector 451B measures a gap length (time) of a signal input from the second demodulator 421 and outputs a second noise when the second noise detector 451B is less than a reference length corresponding to the minimum gap length (e.g., 7 x 26.3 mu s) And outputs a second noise detection signal DET2 corresponding thereto. The reason why the second noise detector 451B measures the gap length of the signal less than the reference length is because the automatic gain control amplifying unit 413 increases the gain over a predetermined period when the second noise is inputted In order to avoid such problems. The second noise includes noise generated in the PDP. The reference length is based on when the frequency of the clock signal supplied from the oscillator 422 to the second noise detector 451B is 38 KHz and the reference length and the frequency of the clock signal are not particularly limited, Can be appropriately changed in accordance with the design conditions of FIG. When the first noise detection signal DET1 is outputted from the first noise detector 451A or the second noise detection signal DET2 is outputted from the second noise detector 451B, the gain control unit 452 outputs a normal noise period (Vch) in the burst period for 20 ms, which is greater than 8 ms to 16 ms, corresponding to the gain control signal (Vch) and the gain increase control signal (Vdis) . Accordingly, when the first noise and the second noise can not be detected, the gain control signal Vch is outputted in the burst period and the gap period And outputs a gain increase control signal Vdis. Therefore, in the case of a signal, a burst-to-burst gap interval is long, and the gain increases as a whole.

The charge pump 453 generates an automatic gain control voltage Vagc according to the gain decrease control signal Vch and the gain increase control signal Vdis output from the gain control unit 452, 413.

6A is a detailed circuit diagram showing an embodiment of the charge pump 453. As shown in FIG. 6A, the first constant current source Ich, the first switch SW1, and the second constant current source I2 are serially connected between the power supply terminal and the ground terminal. The switch SW2 and the second constant current source Idis are connected between the common connection point of the first switch SW1 and the second switch SW2 and the ground terminal to output the automatic gain control voltage Vagc And a capacitor C1.

6B is a waveform diagram showing a change in the automatic gain control voltage Vagc output from the charge pump 453. FIG.

6A and 6B, when the gain reduction control signal Vch is output from the gain control unit 452 as in the T2 and T6 periods, the gain control signal Vch is applied to the first switch SW1) is turned on. Accordingly, the current of the first constant current source Ich is charged to the capacitor C1 through the first switch SW1, and the level of the automatic gain control voltage Vagc is raised.

However, the second switch SW2 is turned on by the gain increase control signal Vdis while the gain control signal Vdis is output from the gain controller 452 as in the period T4. As a result, the current charged in the capacitor C1 is discharged to the second constant current source Idis, and the level of the automatic gain control voltage Vagc is lowered.

Since the first switch SW1 and the second switch SW2 are all turned off in the periods T1, T3, T5 and T7 except for the above-mentioned intervals, the level of the automatic gain control voltage Vagc becomes the previous level state Lt; / RTI &gt;

The automatic gain control voltage Vagc generated through the above process in the charge pump 453 is supplied to the automatic gain control amplifying unit 413 to control the gain of the automatic gain control amplifying unit 413 do. 6C is a graph showing the relationship between the automatic gain control voltage Vagc and the gain of the automatic gain control amplifier 413. As shown in FIG. 6C, the automatic gain control voltage Vagc, The gain of the adjustment amplifier section 413 is linearly in inverse proportion.

FIG. 7 is a detailed block diagram showing an embodiment of the second noise detector 451B. As shown in FIG. 7, the second noise detector 451B includes a counter 471, a register 472, and a third comparator 473. The number of bits of the counter 471, the register 472, and the third comparator 473 is not particularly limited, and is assumed to be 4 bits in this example.

The counter 471 counts the number of pulses to count the gap length (time) of the signal input from the second demodulator 421 when the output signal of the second demodulator 421 changes from "low" to "high" And the counted gap length value is stored in the register 472 when the output signal of the second demodulator 421 changes from "high" to "low".

The third comparator 473 compares the counted gap length output from the register 472 with the reference length and outputs the second noise detection signal DET2 when the counted gap length is smaller than the reference length do. A typical signal (infrared signal) has a burst length of 10 or more, but a noise such as a PDP signal has a burst length of 7 or less. Therefore, it is preferable to set the reference length to the burst length of about 7.

 8 is a detailed circuit diagram showing an embodiment of the second demodulator 421. As shown in FIG. 8, the shift register 421A, the latch 421B, the gate 421C, the D flip-flop 421D, (421E).

9 (a) to 9 (d) are waveform diagrams of the respective parts in Fig. 8.

Referring to FIGS. 8 and 9, the shift register 421A shifts the clock signal CLK1 shown in FIG. 9 (b) within one cycle (26.3 μs) of the carrier frequency as shown in FIG. The output logic value of the second comparator 420 is received and stored sequentially in response to the instruction to descend. As described above, the output logic value stored in the shift register 421A is shifted each time the clock signal CLK1 is input. The clock signal CLK1 is not particularly limited, and is exemplified by a clock signal having a cycle of ten times of 38KHz outputted from the oscillator 422. In FIG.

 Accordingly, when the number of bits of the shift register 421A is 10, the output logic value is stored in all the bits of the shift register 421A when 10 falling edge signals of the clock signal CLK1 are input as shown in FIG. do. 9A, when the output signal of the second comparator 420 is as shown in FIG. 9A, '1' is stored in the most significant bit and the next bit of the shift register 421A, '0' is stored in the remaining bits.

The latch 421B loads the output logic value stored in the shift register 421A according to a load signal Load supplied for one period (26.3 μs) of the carrier frequency, and outputs the loaded output logic value to the gate 421C .

The O gate 421C performs an OR operation on the output logic value output from the shift register 421A and outputs it to the data input terminal D of the D flip-flop 421D.

The D-type flip-flop 421D outputs a signal corresponding to the data value supplied to the data input terminal D each time the clock signal CLK2 of the carrier frequency (for example, 38KHz) is supplied.

Accordingly, the second demodulator 421 outputs the output logic value of the second comparator 420 by a predetermined number of times (for example, 10 times) in a cycle of the clock signal CLK1 every one cycle of 38 KHz (26.3 ㎲) Level signal as shown in (d) of FIG. 9 when '1' is detected at least once, and finally maintains a logic 'low' during the burst period via the inverter 421E

10 (a) shows a waveform in which a light noise signal output from a PDP panel is input through a wideband sensor. The broadband sensor means an APD module. When the PDP signal passes through the limit amplifying part 414 and the band pass filter part 415, a difference between the original signal and the original signal is shown due to the distortion of the signal. Using the optical module to see the original signal shape.

      FIG. 10 (b) shows a waveform obtained by Fast Fourier Transforming the optical noise signal as shown in FIG. 10 (a). It was confirmed that a signal component of 100 KHz was output in the form of a burst having a length of 150 to 700 ㎲. FIG. 10C shows the output signal of the band pass filter 415 of the infrared receiver, and FIG. 10D shows the waveform of FIG. 10C on an enlarged scale. Signal was found to be about 10 burst lengths, while PDP noise was found to be less than 7 burst lengths. Therefore, as described above, the noise detector 451 measures the burst length of the input signal to determine that it is an infrared signal if the burst length is 7 or more. If the burst length is less than 7, the PDP noise can be determined.

    In FIG. 4, the oscillator 422 is for generating a clock for use in accurately detecting and maintaining the burst and gap lengths and the 20 ms noise holding time constant. The oscillator trim unit 423 is used to calibrate the oscillator frequency at the time of semiconductor production because it has a deviation according to the current and the capacitor value

Although the preferred embodiments of the present invention have been described in detail above, it should be understood that the scope of the present invention is not limited thereto. These embodiments are also within the scope of the present invention.

411: Input unit 412: First stage amplification unit
413: Automatic gain control amplifying unit 414: Limit amplifying unit
415: bandpass filter unit 416: gain control unit
417: first comparator 418: first demodulator
419: Output section 420: Second comparator
421: second demodulator 422: oscillator
423: Oscillator trim part

Claims (7)

An input unit including a photodiode for detecting an infrared input signal received from the outside and outputting an electric signal according to the received infrared input signal;
An automatic gain control amplification unit that amplifies an electric signal input from the input unit through a first stage amplification unit and adjusts a gain;
A band pass filter unit for filtering the carrier frequency signal of the infrared signal from the electric signal amplified by the limit amplifying unit after being output from the automatic gain control amplifying unit;
A first comparator for comparing a signal filtered by the band pass filter with a first threshold voltage and outputting a signal corresponding to the first threshold voltage;
An output unit for receiving a signal demodulated by the first demodulator after being output from the first comparator and outputting the signal to the outside of the infrared receiver; And
And a second comparator for comparing an output signal of the band-pass filter with a second threshold voltage to output a signal corresponding to the second threshold voltage,
A second demodulator for demodulating an output signal of the second comparator; And
And a gain controller for controlling a gain of the automatic gain control amplifier according to an output signal of the second demodulator to remove noise included in the electrical signal,
The gain control unit
Measuring a burst duration input time of a signal input from the second demodulator, outputting a first noise detection signal when the burst duration is longer than a preset time, measuring a gap length of a signal input from the second demodulator, A gain controller for outputting a second noise detection signal when the reference length is less than a reference length;
When the first noise detection signal or the second noise detection signal is output, the gain reduction control signal is outputted in the burst period corresponding to the noise period, and the output of the gain reduction control signal and the gain increase control signal is blocked in the gap period A gain controller; And
And a charge pump for generating an automatic gain control voltage according to the gain reduction control signal and the gain increase control signal and outputting the automatic gain control voltage to the automatic gain control amplification unit.
The apparatus of claim 1, wherein the gain adjuster
A first noise detector for measuring a burst duration input time of a signal input from the second demodulator and outputting a first noise detection signal when the burst duration is longer than a preset time;
And a second noise detector for measuring a gap length of a signal input from the second demodulator and outputting a second noise detection signal when the gap length is equal to or less than a reference length corresponding to a minimum gap length.
3. The apparatus of claim 2, wherein the second noise detector
A counter for starting a count operation to measure a gap length of a signal input from the second demodulator when an output signal of the second demodulator transitions;
A register for storing a gap length value counted by the counter; And
And a third comparator for comparing the counted gap length output from the register with the reference length and outputting the second noise detection signal when the counted gap length is smaller than the reference length. Receiver noise rejection circuit.
The circuit of claim 1 or 3, wherein the reference length is a length corresponding to seven burst lengths based on a 38 kHz carrier frequency in consideration of a PDP signal.
The noise rejection circuit of an infrared receiver according to claim 3, wherein the counter, the register and the third comparator each have a 4-bit structure.
The apparatus of claim 1, wherein the second demodulator
A shift register for receiving an output logic value of the second comparator and sequentially storing the output logic value of the second comparator every time the clock signal falls in one cycle of the carrier frequency;
A latch for loading and outputting the output logic value stored in the shift register according to a load signal supplied every one cycle of the carrier frequency;
An OR gate for performing a logical OR operation on a plurality of the output logic values output from the latch; And
And a D-type flip-flop for outputting a data value supplied from the OR gate to a data input terminal to an output terminal for each rising edge of the clock signal. The noise rejection circuit of an infrared receiver according to claim 1, wherein the second noise detection signal includes a signal generated in a PDP panel.

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