JPH0435958B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a signal conversion circuit used, for example, in a detection circuit of an infrared remote control receiving circuit that remotely controls channel switching of a television receiver using infrared rays.

FIG. 1 shows a general infrared remote control receiving circuit. The transmitted infrared rays are converted into electrical signals by the light receiving element 6 connected between the input terminal 3 and the power supply terminal 4 of the amplifier 2.
added to. A filter 8 constituting a tuning circuit is added to the amplifier 2, and an output tuned to a predetermined frequency is extracted from the amplifier 2. That is, the frequency of infrared rays used in this type of remote control is usually 38 kHz, and is tuned by a filter 8 to distinguish it from noise.

The output of the amplifier 2 is applied to a detection circuit 10, its peak value is detected, and after being waveform-shaped by an output circuit 12, it is taken out from an output terminal 14 as a control output to be applied to a predetermined control section.

This type of infrared remote control receiving circuit detects the received signal as a pulse.
If the level of the received signal is above a preset threshold level, a high (H) level output is obtained, and if the level has not reached the threshold level, a low (L) level output is obtained. However, since a remote control transmitter uses a battery as its driving power source, a drop in its voltage affects the level of the transmitted signal, and therefore the level of the received signal also decreases accordingly. Also, if the transmitter is extremely far away from the remote control receiving circuit, even if the level of the transmitted signal on the transmitter side is normal, the level of the received signal received on the receiving circuit side will decrease depending on the distance. Put it away. Setting the threshold level low on the receiving circuit side makes it possible to detect low-level received signals and improve receiving sensitivity, but it also detects noise at the same time, which degrades the S/N ratio. , sufficient detection accuracy cannot be obtained. For this reason, if you try to increase the detection gain to detect a weak received signal, the S/N ratio will decrease, so you will need to take measures such as shielding the entire circuit to block out noise, which will reduce reliability. There were disadvantages such as low production cost and high manufacturing cost.

Therefore, an object of the present invention is to provide a signal conversion circuit for a remote control receiving circuit that eliminates the inconvenience caused by such level discrimination, detects the peak value of a received signal, converts it into a pulse, and improves the detection sensitivity. shall be.

That is, the signal conversion circuit of the remote control receiving circuit of the present invention receives the transmitted infrared rays with the light receiving element 6 and converts the received signal into a pulse signal to be detected. a differential pair consisting of first and second transistors 50 and 52 that are shared in common, the received signal (base current I _b1 corresponds to the received signal) is applied to the base of the first transistor 50, and A capacitor 60 is connected to the base of the second transistor 52 and its charged voltage is applied, and the amplitude level of the received signal and the charged voltage of the capacitor 60 are compared and the second transistor 52 is a first comparator 54 that obtains a first current (I ₁ ) on the side of the first transistor 50 and a second current (I ₂ ) on the side of the second transistor 52; and a discharge circuit connected to the capacitor 60. A resistor 62 and third and fourth transistors 80 and 85 are connected in series, and the third transistor 80 receives the first current (I ₁ ).
At the same time, the second current (I ₂ ) is passed through the fourth transistor 85 to cause the second and third currents ( _{I 2 ,} I ₃ ) to flow.
a switching circuit 92 that generates pulses by installing fifth transistors 94 and 96 that synthesize the current and switch based on the combined current; and a sixth and seventh transistor 10 that have a common emitter.
A reference voltage is applied to the base of the sixth transistor 106, and a pulse generated by the switching circuit 92 is applied to the base of the seventh transistor 108, and the magnitude relationship between the two is determined. a second comparator 104 that obtains a fourth current (I ₀ −I _b1 ) from the sixth transistor 106 according to the second current (I ₂ ) and the fourth current (I _{0 −I b1} ); I _b1 ) and supplies the combined current to the capacitor 60 as a charging current to charge the capacitor 60 (current reversing circuit 70).

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

FIG. 2 shows an embodiment of the signal conversion circuit of the remote control receiving circuit of the present invention, and the same parts as those of the infrared remote control receiving circuit shown in FIG. 1 are given the same reference numerals.

In FIG. 2, a light receiving element 6 is connected via a resistor 16 between the input terminal 3 of the amplifier 2 and the positive power line connected to the power supply terminal 4, and the light receiving element 6 is connected to a capacitor 18. is attached. A filter 8 constituted by a tuned circuit of an inductor 22 and a capacitor 24 is connected between the amplifier 2, the terminal 20, and the positive power supply line, and a resistor 28 and a capacitor 30 are connected to the feedback terminal 26. Further, the reference potential (GND) terminal 32 is grounded.

The infrared light received by the light receiving element 6 is transmitted to the light receiving element 6.
is converted into an electrical signal. The infrared signal obtained by the light receiving element 6 is amplified by the amplifier 2 and then applied to the detection circuit 10. The detection circuit 10 is constituted by a signal conversion circuit according to the present invention, and generates a pulse output corresponding to the output signal of the amplifier 2 installed at the front stage. This pulse output is applied to the output circuit 12, shaped into a waveform, and converted into a predetermined control output.

This embodiment includes a detection circuit 10 and an output circuit 1.
A constant current circuit 34 is installed to supply a predetermined constant current to 2. This constant current circuit 34 includes transistors 35, 36, 38, 40, 42 and a resistor 4.
4 and 46, and a constant voltage of several volts is applied to the terminal 48.

A first comparator 54 is installed in the detection circuit 10 and includes a differential pair consisting of first and second transistors 50 and 52 having a common emitter.
A transistor 56 is provided as a constant current source for setting an operating current, and the base of this transistor 56 is commonly connected to the bases of transistors 35 and 38.

A signal input from the amplifier 2 is applied to the base of the transistor 50 of the comparator 54, and an external terminal 58 formed at the base of the transistor 52
A capacitor 60 to hold the peak value of the input signal is connected between the and the positive power supply line, and a resistor 62 forming a discharge circuit for the capacitor 60 is connected between the external terminal 58 and the reference potential point. is connected.

The comparator 54 is provided with first, second, and third current inversion circuits 64, 66, and 68 as current detection means for detecting and extracting a current based on an input signal. Further, on the output side of the current inverting circuit 64, a fourth current is connected as a current synthesizing means for synthesizing the current flowing through the comparator 54 and the current obtained by a second comparator 104, which will be described later, to obtain a difference current between the two. An inverting circuit 70 is installed.

The first current inversion circuit 64 includes a transistor 7
1, 72, 73 and a resistor 74, and
The transistor 73 is set so that 1/2 of the current flowing through the transistor 71 flows.
The current flowing through the transistor 50 is detected.
The second current inversion circuit 66 includes transistors 76,
The transistor 78 and 80 detect the current flowing through the transistor 73.

The third current inversion circuit 68 includes a transistor 8
2, 83, 84, 85 and a resistor 86,
The current flowing through the transistor 52 is detected.
Further, the fourth current inverting circuit 70 includes transistors 88, 89, and 90, and includes a transistor 84.
Transistors 88 and 90 installed on the input side receive the current flowing through the transistors.

Further, the third transistor 80 of the second current inversion circuit 66 and the fourth transistor 85 of the third current inversion circuit 68 have their collectors connected in common and are connected between the positive power supply line and the common line. is set up. A current corresponding to the current flowing through the comparator 54 flows through the transistors 80 and 85, and a combined current of both currents is obtained on the collector side of both transistors. That is, the switching circuit 92 for obtaining a pulse corresponding to the input signal includes the transistors 80,
85, fifth transistors 94, 96, and resistors 98, 100, 102. Therefore, in the switching circuit 92, the comparator 54
It generates pulses according to the current flowing through it.

The output pulse of this switching circuit 92 is then applied to a second comparator 104 and compared with a reference level. The comparator 104 includes sixth and seventh transistors 106 and 1 having a common emitter.
A transistor 113 is connected between the emitters of the transistors 106 and 108 and the positive power supply line as a constant current source for flowing a reference current. is supplied with a base current from a constant current circuit 34. Diodes 114, 116, 118 are connected to the base of the transistor 106.
A voltage V _b1 as a reference level is applied by the voltage division of the resistor 120. transistor 10
The collectors of 8 are connected to a common line.
Further, the collector of the transistor 106 is connected to the base of the transistor 52 of the comparator 54.

The output circuit 12 includes transistors 122, 12
4, 126, 128, 130, a resistor 132, and a capacitor 136 connected to a terminal 134.

The operation will be explained based on the above configuration.

When the transmitted infrared rays are received by the light receiving element 6, the light receiving element 6 receives an input signal as a level signal having a level corresponding to the received light level. After this input signal is amplified by amplifier 2,
It is added to the detection circuit 10 which is to detect the peak value level of the input signal.

The signal conversion operation in this detection circuit 10 is as follows.

That is, the transistor 56 in the detection circuit 10
is set to sink current at a current value three times the constant current I ₀ supplied from the constant current circuit 34 in the initial state. The constant current I ₀ varies from the regulated voltage V ₀ applied to the terminal 48 to the base-emitter voltage V _BE36 of the transistor 36 and the transistor 3
I ₀ = V _{0 − V BE36} − _{V BE35 / R 0} ...(1) becomes.

Then, since a constant current I ₀ flows into the transistor 113, the currents flowing through each element of the detection circuit 10 are balanced as follows. That is, transistor 1
When the base current of the transistor 52 is I _b1 , the base current of the transistor 52 is I _b2 , and the base current of the transistor 50 is I _b3 , the current I ₂ flowing to the collector of the transistor 52 is I ₂ = I ₀ −I _b1 −I _b2 ...(2), and the current I ₁ flowing through the transistor 50 is: I ₁ = 3I ₀ −I _b2 −I _b3 −(I ₀ −I _b1 −I _b2 )=2I ₀ +I _b1 −I _b3
...(3) becomes.

On the other hand, a current for current reversal operation flows through the transistors 80 and 85, a current I ₂ (=I ₀ −I _b1 −I _b2 ) flows out from the transistor 85, and a current I ₃ is sucked into the transistor 80. I ₃ becomes I ₃ = I ₀ + I _b1 − I _b3 /2 (4). Since the matching between each transistor 50 and 52 is good, the base current of each transistor 50 and 52 is
The magnitude relationship between I _b3 and I _b2 is I _b2 ≒ I _b3 .

Therefore, the magnitude relationship between the currents I ₂ and I ₃ is (I ₀ −I _b1 −I _b2 )<(I ₀ +I _b1 /2−I _b2 /2)……(5
), and the magnitude relationship between the currents I ₂ and I ₃ is I ₂ <I ₃ , so the base of the transistor 94 becomes a low level, the transistor 94 becomes non-conductive, and the base of the transistor 108 becomes a high potential. and maintain the initial state.

Here, it is assumed that a level signal as shown at A in FIG. 3 is applied to the base of the transistor 50 of the detection circuit 10. Normally, the electrical signal obtained by the light receiving element 6 by the received infrared signal on the receiving circuit side is
It is an AC signal of 38kHz, and the signal passed through filter 8 exhibits an AC signal with a peak value and a slow level change, but for the sake of explaining the peak detection operation, it is a sawtooth wave with a clear peak point. Using a signal, the operation when the amplitude level tends to gradually decrease will be explained. Therefore, consider the moment when the base of the transistor 50 changes to a low level. At this time, assuming that the collector current of the transistor 50 decreases by ΔI due to the input of the level signal,
A current of 2I ₀ +I _b1 −I _b3 −ΔI=I ₁ −ΔI ...(6) flows through the collector of the transistor 50, while a current of I ₀ −I _b1 −I _b2 +ΔI= flows through the collector of the transistor 52. A current of I ₂ +ΔI (7) flows, and a current of I ₀ −I _b1 −I _b2 +ΔI=I ₂ +ΔI (8) is drawn into the transistor 89 due to the current reversal effect.

Further, a current of I ₀ −I _b1 −I _b2 +ΔI=I ₂ +ΔI (9) flows out from the transistor 85, and the current of the transistor 80 is I ₀ +I _b1 /2−I _b3 /2−ΔI=I ₃ Since the current of -ΔI...(10) is drawn, the transistors 80 and 85
The current flowing through is (−I _b1 −I _b2 +ΔI)＞(I _b1 /2−I _b3 /2−ΔI)……
(11), the base of the transistor 94 becomes a high potential, and the transistor 94 becomes conductive. As a result, the base of the transistor 108 has a low potential, the constant current I ₀ supplied from the transistor 113 flows to the common line side through the transistor 108, and no current flows to the transistor 106.

In this case, the transistor 89 attempts to absorb a current of I ₀ −I _b1 −I _b2 +ΔI=I ₂ +Δ1 (12), but the transistor 106 shifts to the cutoff state and no current is supplied from anywhere. , Since current is apparently drawn from the positive power supply line through the capacitor 60, the capacitor 60 is charged. As a result, the base potential of the transistor 52 decreases, and the base potential of the transistor 52 decreases.
It follows the decrease in the base potential of 0 and is balanced at a potential slightly higher than that potential.

Furthermore, considering the moment when the base potential of the transistor 50 becomes high level due to the level signal shown in FIG. 3 from this equilibrium state, the transistor 8
The current that the transistor 80 sinks is larger than the current flowing from the transistor 5, and the transistor 94 becomes non-conductive, so the base of the transistor 108 becomes a high potential, and the constant current _I0 supplied from the transistor 113 flows through the transistor 106. . At this time, a current I _b1 flows through the base of the transistor 106, so a fourth current (I ₀ −I _b1 ) flows through the collector of the transistor 106, and this current is supplied to the collector side of the transistor 89. Therefore, the current that the transistor 89 sinks from the capacitor 60 is smaller than the constant current _I0 , so a discharge circuit is formed between the capacitor 60 and the resistor 62, and the base potential of the transistor 52 is reduced by discharging the capacitor 60. will rise.

Such charging and discharging of the capacitor 60 causes charging or discharging between the change points of the input signal shown in A in FIG. 3, and a charging and discharging waveform shown in B in FIG. 3 is generated in the capacitor 60. It turns out.

Since the base potential of the transistor 52 changes in accordance with the base potential of the transistor 50, a voltage corresponding to the input signal is obtained at the capacitor 60 without being affected by noise, and the SNR is high, and input signals can always be detected at the highest temperature.

Furthermore, as a result of the current combination by the transistors 80 and 85, the base of the transistor 94 receives a current corresponding to the change point of the input signal to the detection circuit 10, that is, as shown in B in FIG. Since a current that depends on the current flows into the collector current of the transistor 96, the collector current of the transistor 96 also depends on it, and the emitter of the transistor 96 reaches the midpoint level at the point when the level of the input signal changes rapidly, as shown in FIG. 3C. The transition point from the lower limit level to the upper limit level, the transition point from the lower limit level to the upper limit level, the transition point from the upper limit level to the lower limit level, and the transition point from the upper limit level to the midpoint level, the high level (capacitor 60 A pulse is generated that has a low level (during the charging period of the capacitor 60) or a low level (during the charging period of the capacitor 60).

After this pulse is shaped into a waveform via the output circuit 12, it is taken out from the output terminal 14 and can be used, for example, as a remote control signal for a television receiver.

The circuit of this embodiment is composed of semiconductor integrated circuits except for the light receiving element 6, filter 8, resistors 16, 28, 132, and capacitors 18, 30, 136. As a result, consistency between each element can be obtained, and a highly reliable and low-cost device can be constructed.

Further, the circuit current can be adjusted by a resistor and a capacitor connected to the external terminal, and proper circuit operation and detection sensitivity can be obtained. moreover,
Integration of circuits facilitates shielding and improves detection sensitivity.

As explained above, according to the present invention, the received signal is detected by converting it into a pulse having a rising or falling edge corresponding to the peak value of the received signal, that is, the point of change. Compared to detection using level discrimination, the SN ratio can be significantly improved.
The detection sensitivity of received signals can be improved.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a general infrared remote control receiving circuit, FIG. 2 is a circuit diagram showing an embodiment of the signal conversion circuit of the remote control receiving circuit of the present invention, and FIG. FIG. 3 is a diagram showing operation waveforms of a signal conversion circuit of a remote control receiving circuit. 6... Light receiving element, 10... Detection circuit (signal conversion circuit), 50... First transistor, 52...
Second transistor, 54...first comparator, 6
0...Capacitor, 62...Resistor, 70...Current inversion circuit (current combining means), 80...Third transistor, 85...Fourth transistor, 92...
...Stitching circuit, 94, 96...Fifth transistor, 104...Second comparator, 106...
Sixth transistor, 108...Seventh transistor.

Claims (1)

[Scope of Claims] 1. In a signal conversion circuit of a remote control receiving circuit that receives transmitted infrared rays with a light receiving element and converts the received signal into a pulse signal to be detected, first and second emitters are shared. The received signal is applied to the base of the first transistor, and the charging voltage of a capacitor connected to the base of the second transistor is applied to the received signal. a first comparison in which the amplitude level and the charging voltage of the capacitor are compared to obtain a first current on the first transistor side and a second current on the second transistor side according to the magnitude relationship between the two; A resistor connected to the capacitor to form a discharge circuit, and third and fourth transistors are connected in series, and a third current corresponding to the first current flows through the third transistor. , causing the second current to flow through the fourth transistor to
and a differential pair consisting of a switching circuit that generates a pulse by installing a fifth transistor that combines the current and the third current, and switches using the combined current, and a sixth and seventh transistor that have a common emitter. A reference voltage is applied to the base of the sixth transistor, and a pulse generated by the switching circuit is applied to the base of the seventh transistor, so that the voltage changes from the sixth transistor to the fourth transistor depending on the magnitude relationship between the two. a second comparator that obtains a current; combining the second current and the fourth current;
A signal conversion circuit for a remote control receiving circuit, comprising: current combining means for supplying the combined current to the capacitor as a charging current to charge the capacitor.