JP2000036924A - Detector for operating state of television receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the detector for an operating state of a television receiver with a novel configuration. SOLUTION: The detector consists of a proximity coil L1, a 1st capacitor C1 in parallel connection with the proximity coil L1, and a resonance circuit 1 comprising a 2nd capacitor C2 and a 1st switching element Q1 and in parallel connection with the 1st capacitor, of a control circuit 2 that applies periodic ON/OFF control to the 1st switching element, of a 2nd switching element Q2 connecting to the resonance circuit 1 and an output hold circuit 3 that connects to an output of the 2nd switching element Q2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a television operating state detecting device.

[0002]

2. Description of the Related Art A conventional television operating state detecting device includes a proximity coil for detecting a horizontal synchronizing signal of a video output signal of a television, and the detection signal is output when an image is reflected on a television screen. It is not output if the image on the screen is off. Such a television operation state detection device is disclosed in, for example, Japanese Patent Application Laid-Open No. 9-93829.
Further, it is disclosed in Japanese Patent Application No. 10-26643 previously proposed by the applicant.

[0003]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a television operating state detecting device having a novel structure.

[0004]

According to a first aspect of the present invention, there is provided a television operating state detecting apparatus, comprising: a proximity coil; a first capacitor connected in parallel to the proximity coil; A resonance circuit including a capacitor and a series circuit including a first switching element and connected in parallel to the first capacitor; a control circuit for periodically controlling on / off of the first switching element; It is characterized by comprising a second switching element to which the resonance circuit is connected, and an output holding circuit connected to the output side of the second switching element.

According to a second aspect of the present invention, there is provided a television operating state detecting device according to the first aspect, wherein the resonance frequency of the resonance circuit is:
When the first switching element is turned on, the first frequency is equal to the horizontal synchronizing signal frequency in the video output signal of the NTSC system television, and when the first switching element is turned off, the first frequency is almost twice as large as the first frequency. 2 is set.

According to a third aspect of the present invention, there is provided a television operating state detecting device according to the first aspect, wherein the control circuit comprises a dual-wave rectifier connected to an AC power supply. And a voltage dividing circuit for dividing the output voltage of the dual-wave rectifier circuit, and a Zener diode connected between the voltage dividing point of the voltage dividing circuit and the first switching element. .

According to a fourth aspect of the present invention, there is provided a television operating state detecting apparatus according to the first aspect, wherein the control circuit comprises a CMOS oscillation circuit. I do.

[0008]

FIG. 1 is a circuit diagram showing an embodiment of a television operating state detecting apparatus according to the present invention. In FIG. 1, reference numeral 1 denotes a resonance circuit, which includes a proximity coil L1, a capacitor C1 connected in parallel to the proximity coil L1, and a series circuit 1a including a capacitor C2 and a switching transistor Q1 and connected in parallel to the capacitor C1. Is done.

Reference numeral 2 denotes a control circuit for periodically turning on / off the switching transistor Q1, which includes a diode bridge type double-wave rectifier circuit 2a connected to an AC power supply (frequency 50/60 Hz), and a double-wave rectifier circuit. 2a, a resistive voltage dividing circuit 2b including resistors R1 and R2, a Zener diode ZD connected to a voltage dividing point of the resistive voltage dividing circuit 2b, and a Zener diode ZD and a base between the Zener diode ZD and the switching transistor Q1. Connected resistor R
And 3.

The resonance circuit 1 includes a switching transistor Q
2 base. The output side of the switching transistor Q2 is connected to a transistor Q3 via a resistor R5.
Connected to the base. A power supply voltage is supplied to the emitter of the transistor Q3 from the dual-wave rectifier circuit 2a via a diode D and a smoothing circuit including a resistor R4 and a capacitor C3, and an output holding circuit including a resistor R6 and a capacitor C4 is provided to a collector. 3 through the output terminal OUT
Is connected.

FIG. 2 is a signal waveform diagram of each part of the apparatus of FIG. 1, wherein (A) is a divided voltage of the resistance voltage dividing circuit 2b, (B) is a control voltage, and (C) and (D) are output terminals OUT. Is the detected output voltage.

The control circuit 2 generates a control voltage (B) for periodically turning on / off the switching transistor Q1, and a method of generating the control voltage (B) will be described below. In the control circuit 2, the zener voltage Vz of the zener diode ZD is output with respect to the divided voltage waveform (A) in which the AC power supply voltage is double-wave rectified by the double-wave rectifier circuit 2a and divided by the resistance voltage divider circuit 2b. The voltage (B) is set to a predetermined value so as to obtain a voltage (B) on the side, and the voltage (B) is supplied to the base of the switching transistor Q1.
The control voltage (B) is set so that the duty ratio between the period during which the voltage becomes zero and the period when the value becomes a value other than zero is 50%.

The voltage waveform (B) has a duty ratio of 50%
As shown in FIG. 3, when the phase of the AC power supply voltage is π / 2, the peak voltage sin (π / 2) = 1 and π
From the relationship with the voltage sin (π / 4) = 0.707 at / 4, the Zener voltage VZ of the Zener diode is changed to V0 × s with respect to the peak voltage V0 of the divided voltage (A) in FIG.
In (π / 4) (= 0.707V0) may be set. Although the fluctuation of the AC power supply voltage affects the duty ratio of the control voltage, the time constant of the output holding circuit 3 may be provided so as to be equal to or higher than the power supply frequency. Although the duty ratio fluctuates in the range of the AC power supply voltage fluctuation, the detection frequency is very high with respect to this.
2 and the holding operation of the output holding circuit 3 are performed without any problem.

In this way, a control voltage (B) that changes at a duty ratio of 50% from the control circuit 2 is obtained and supplied to the base of the switching transistor Q1.

Next, the switching transistor Q1 is turned off during the period when the control voltage (B) becomes zero, and turned on during the period when the control voltage (B) becomes a value other than zero due to the application of the control voltage (B). Repeatedly on / off.

While the switching transistor Q1 is on, the resonance circuit 1 is connected in parallel with the proximity coil L1 and the capacitors C1 and C2, and the resonance frequency f1 at this time is expressed by the following equation (1).

[0017]

(Equation 1)

On the other hand, while the switching transistor Q1 is off, the resonance circuit 1 is connected in parallel with the proximity coil L1 and the capacitor C1, and the resonance frequency f2 at this time is expressed by the following equation (2).

[0019]

(Equation 2)

The proximity coil L1 is connected to the resonance circuit 1
And operates as a link coil for detecting a horizontal synchronization signal of the television receiver. By selecting the inductance of the proximity coil L1 and the capacitance of the capacitors C1 and C2 to appropriate values, the resonance frequency f1 of the resonance circuit 1 when the switching transistor Q1 is turned on can be synchronized with the horizontal synchronization in the video output signal of the NTSC television. The frequency becomes equal to the signal frequency (15.75 kHz), and the resonance frequency f2 of the resonance circuit 1 when the switching transistor Q1 is turned off is the horizontal synchronization signal frequency (31.5 kHz) in the video output signal of the wide-screen television. Equal frequency (in this case, f2 =
2f1).

FIG. 4 shows the frequency characteristic of the resonance output of the resonance circuit 1. The efficiency (coupling) of the proximity coil L1 increases as the frequency increases, and improves by 6 dB at a frequency twice as high as a certain frequency. Therefore, for the resonance output (A) of the resonance frequency f1 equal to the NTSC horizontal synchronization signal frequency (15.75 kHz), the resonance frequency f2 equal to the wide horizontal synchronization signal frequency (31.5 kHz) is used.
In the resonance output (B) of (= 2f1), the range of frequencies in which the response exceeds the switching level Ls of the switching transistor Q2 is widened, and binary frequencies can be detected. In this example, based on the resonance output (B), the wide mode horizontal synchronization signal frequency f2 (31.5 kHz) is used.
z) and the HDTV horizontal synchronization signal frequency f3 (3
(3.75 kHz) can be detected. The actual setting of the switching level Ls is different from that of FIG.
A certain degree of margin is provided as shown in FIG.

Therefore, the television operating state detecting device shown in FIG. 1 is used in the vicinity of a television receiver (for example, above the television receiver).
When this television receiver is, for example, an NTSC television receiver, when the television is turned on and the television screen is displayed, the proximity coil L1 generates a horizontal synchronization signal in the video output signal leaking from the video output circuit. (Frequency 15.7
5 kHz), and during the ON period of the switching transistor Q1, a resonance output (FIG. 4A) of the resonance frequency f1 is obtained from the resonance circuit 1, and this resonance output is applied to the base of the switching transistor Q2. Thereby,
The switching transistor Q2 is turned on from off,
Next, the transistor Q3 is also turned on from off. When the transistor Q3 is turned on, an output voltage (FIG. 2C) is obtained at the output terminal OUT via the output holding circuit 3. At this time, since the switching transistor Q1 is periodically turned on / off, no resonance output is obtained during the off period, so that the transistors Q2 and Q3 are also turned off. However, the resistor R6 of the output holding circuit 3 and the capacitor The output voltage is held by the time constant of C4.

Similarly, when the television operation state detecting device of FIG. 1 is disposed near a television receiver, and this television receiver is, for example, a wide-screen television receiver, when the television is turned on and the television screen is displayed, The proximity coil L1 detects the horizontal synchronization signal frequency (3
1.5 kHz), and detects the resonance frequency f2 from the resonance circuit 1 during the OFF period of the switching transistor Q1.
(FIG. 4B) is obtained, and this resonance output is applied to the base of the switching transistor Q2. As a result, the switching transistors Q2 and Q3 are turned on from off, and the output terminal O is output via the output holding circuit 3.
An output voltage (FIG. 2D) is obtained at the UT. At this time,
Since the switching transistor Q1 is periodically turned on / off, no resonance output is obtained during the on period, so that the transistors Q2 and Q3 are also turned off. Is held.

If the television receiver is a high-definition television system, when the television is turned on and the television screen is displayed,
The proximity coil L1 is a horizontal synchronization signal (frequency: 33.75 kHz) in the video output signal leaked from the video output circuit.
During the off period of the switching transistor Q1, the resonance output of the resonance circuit 1 at the resonance frequency f2 (FIG. 4)
(B)) is obtained, and this resonance output is applied to the base of the switching transistor Q2, so that the output terminal OUT outputs the output voltage (FIG. 2 (D)) as described above.
Is obtained. Meanwhile, the TV is turned off,
When the television screen is not displayed, the proximity coil L1 does not sense the horizontal synchronizing signal, so that no detection output voltage is generated from the output terminal OUT.

As described above, the operation states of a plurality of different types of television receivers can be detected. The power required for detection is only the current flowing through the resistance voltage dividing circuit 2a and the switching transistor Q1.

[0026]

FIG. 5 is a circuit diagram showing another embodiment of the television operating state detecting apparatus according to the present invention. The device shown in FIG. 5 is a device suitable for battery specifications, and the control circuit 2 '
It comprises a CMOS oscillation circuit including MOS inverters I1 and I2, resistors R7, R8 and R9, and a capacitor C5. A DC power supply voltage is supplied from the battery E to the CMOS inverters I1 and I2 of the control circuit 2 'and the emitter of the transistor Q3. The oscillation output of the CMOS oscillation circuit is set to be the same as the control voltage (B) in FIG. 2, and is supplied to the switching transistor Q1 via the resistor R9. The configuration and operation other than those described above are the same as those of the device shown in FIG. 1, and a description thereof will not be repeated. In the configuration of FIG. 5, the only power required for detection is the power consumed by the CMOS oscillation circuit.

Although the embodiments and examples of the present invention have been described above, the present invention is not limited to these, and various changes and modifications are possible.

For example, in the above description, NTS is used as an example.
Although the description has been given of the detection of the operation state of the C, wide, and high-definition television receivers, the synchronization signal frequency of the television receiver of another system and the synchronization signal frequency of the video output circuit in the color mode of the monitor television for a personal computer ( For example, it can be configured to detect 35 kHz).

By setting the inductance of the proximity coil L1 and the capacitances of the capacitors C1 and C2 to appropriate values, the switching transistor Q
When the resonance frequency of the resonance circuit 1 is off, the horizontal synchronizing signal frequency (31.5 kHz = f2), not the horizontal synchronizing signal frequency (31.5 kHz = f2) in the video output signal of the wide-screen television, and the HDTV Horizontal synchronizing signal frequency f3 in the video output signal of the standard television
(33.75 kHz). In this case, the resonance output of the resonance circuit 1 when the switching transistor Q1 is off is indicated by a dotted line as the resonance output (C) in FIG.

[0030]

According to the present invention, a television operating state detecting device having a novel configuration can be obtained.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing one embodiment of a television operating state detecting device according to the present invention.

2 (A) to 2 (D) are signal waveform diagrams of respective parts of the device of FIG. 1;

3 is an AC power supply voltage waveform diagram for explaining a method of obtaining a control voltage having a duty ratio of 50% in the apparatus of FIG.

FIG. 4 shows a resonance output frequency characteristic of a resonance circuit in the device of FIG.

FIG. 5 is a circuit diagram showing another embodiment of the television operating state detecting device according to the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 resonance circuit 2 control circuit 2 ′ control circuit 2 a dual-wave rectifier circuit 2 b resistor voltage divider circuit 3 output holding circuit L1 proximity coil C1 to C5 capacitors R1 to R9 resistor Q1 switching transistor Q2 switching transistor Q3 transistor ZD Zener diode I1 CMOS inverter I2 CMOS inverter OUT output terminal

Claims (4)

[Claims] 1. A proximity coil, a first capacitor connected in parallel to the proximity coil, and a series circuit including a second capacitor and a first switching element and connected in parallel to the first capacitor. A resonance circuit configured; a control circuit for periodically turning on / off the first switching element; a second switching element to which the resonance circuit is connected; and an output side of the second switching element. A television operating state detecting device, comprising: a connected output holding circuit. 2. The television operating state detecting device according to claim 1, wherein a resonance frequency of the resonance circuit is equal to a horizontal synchronization signal frequency in a video output signal of the NTSC television when the first switching element is turned on. A television operating state detecting device which is set to a second frequency when the first switching element is turned off and when the first switching element is turned off. 3. The television operating state detecting device according to claim 1, wherein the control circuit comprises: a dual-wave rectifier circuit connected to an AC power supply; a voltage-divider circuit for dividing an output voltage of the dual-wave rectifier circuit; A television operating state detecting device comprising a voltage dividing point of a voltage dividing circuit and a Zener diode connected between the first switching element. 4. The television operating state detecting device according to claim 1, wherein the control circuit comprises a CMOS oscillation circuit.