JPH10276487A - Reception equipment for remote control signal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily control the center frequency of a band-pass filter by forming the selection resistor of a center frequency control circuit using the ON/OFF of the Zener diode for zapping. SOLUTION: Zener diodes 23-1 to 23-n for zapping are provided, cathodes are connected with the nodes of selection resistors 21-1 to 21-n and pads 22-1 to 22-n, and anodes are grounded. The Zener diodes 23-1 to 23-n are short- circuitted by destroying PN bonding by impressing a high voltage (40 volt, for example,) between anodes and cathodes. Concretely, when the high voltage is impressed to the pads 22-1 to 22-n, the Zener diodes 23-1 to 23-n are short- circuitted, a resistor 17 and any one of selection resistors 21-1 to 21-n are parallelly connected, and the central frequency of the band filter 3 is changed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a receiver for reliably receiving a remote control signal.

[0002]

2. Description of the Related Art FIG. 2 is a block diagram showing a general remote control signal receiving apparatus, which is assumed to be integrated. In FIG. 2, reference numeral (1) denotes a light-receiving diode (reception circuit), which is operated by operating a remote controller, and which is intermittently transmitted on a carrier wave of a predetermined frequency (for example, 38 KHz). It receives a signal and converts it from an optical signal to an electrical signal.
An amplifier (2) primarily amplifies a small current flowing through the light receiving diode (1) in accordance with the remote control signal so that it can be recognized by a microcomputer or the like at a subsequent stage. (3) is a bandpass filter for extracting a frequency component of the carrier wave, that is, a content portion of the remote control signal. Here, FIG. 4 shows the main part of the bandpass filter (3) equivalently. That is, the bandpass filter (3)
As shown in FIG. 4, differential amplifier (4), capacitor (5)
(6) It operates by connecting a resistor (7) and a buffer (8).

Meanwhile, the center frequency of the bandpass filter (3) fluctuates under the influence of variations in element characteristics of the integrated circuit. Once the center frequency of the bandpass filter (3) deviates from the expected frequency (38 KHz), the bandpass filter (3) cannot reliably remove the carrier,
The microcomputer may erroneously recognize the remote control signal and cause the controlled system to malfunction. Therefore, if the center frequency of the bandpass filter (3) changes, it is necessary to correct the change. The center frequency f0, conductance gm, and capacitance C of the bandpass filter (3) in FIG. 4 have a relationship of f0 = gm / 2πC, and the conductance gm is proportional to the size of the current source of the differential amplifier (4). Therefore, if the current amount of the current source of the differential amplifier (4) is adjusted, the center frequency f0 of the bandpass filter (3) can be adjusted.
Can be corrected. This correction means will be described later.

[0004] A detection circuit (9) detects the carrier wave extracted by the bandpass filter (3) and outputs only the component of the remote control signal. An output circuit (10) secondary-amplifies the output of the detection circuit (9) to a level that can be sufficiently recognized by the microcomputer. Reference numeral (11) denotes a center frequency adjusting circuit for adjusting the amount of current of the current source of the differential amplifier (4) constituting the bandpass filter (3), and as a result, changing the center frequency of the bandpass filter (3). Things.

FIG. 3 shows a conventional circuit of the center frequency adjusting circuit (11). In FIG. 3, a PNP transistor (1
2) (13) forms a current mirror circuit, and the emitter is connected to the power supply VCC. The resistors (14) and (15) are connected in series between the power supply VCC and the ground. The base of the NPN transistor (16) is a series resistor (14) (1
5), the collector is connected to the collector of the PNP transistor (12), and the emitter is connected to the resistor (1).
7) is grounded. That is, when the power supply VCC is in a steady state, the NPN transistor (16) is driven at a constant current. The base collector of the NPN transistor (18) is connected to the collector of the PNP transistor (13),
The emitter is grounded. NPN transistor (1
The base of 9) is connected to the collector of the PNP transistor (13), the collector is connected to the current source of the differential amplifier (4) constituting the bandpass filter (3), and the emitter is grounded via the resistor (20). ing. According to the center frequency adjusting circuit of FIG. 3, the center frequency of the bandpass filter (3) is N
Depending on the collector current of the PN transistor (19), N
The collector current of the PN transistor (19) is the resistance (1
7). Therefore, the center frequency of the bandpass filter (3) can be corrected by adjusting the resistance value of the resistor connected to the emitter of the NPN transistor (16).
Note that the resistance value of the resistor (17) depends on the frequency at which the center frequency of the bandpass filter (3) is lower than the expected frequency (for example, 29 KH).
z). Therefore, the selection resistor (21-
1) to (21-n), and an NPN transistor (1
In order to adjust the resistance value of the resistor connected to the emitter of 6), the selection resistors (21-1) to (21-n) are connected in parallel with the resistor (17), but one end thereof is connected to a pad. (22-1) to (22-n). The integrated chip of FIG. 3 is arranged on a printed circuit board, and the pads (22-1) to (22-n) are selectively soldered to the ground line of the printed circuit board. Specifically, when at least one of the pads (22-1) to (22-n) is soldered to the ground line of the printed circuit board, the resistance (17) and at least one of the selection resistances (21) to (25) are changed. The resistance of the resistor connected in parallel and connected to the emitter of the NPN transistor (16) decreases, and the collector current of the NPN transistor (19) increases with the increase of the collector current of the NPN transistor (16). The center frequency of the bandpass filter (3) is corrected to a higher side.

As described above, the pads (22-1) to (22-)
The center frequency of the bandpass filter (3) is corrected to be the expected frequency by selectively soldering any one of n) to the ground line of the printed circuit board.

[0007]

The center frequency of the bandpass filter (3) varies depending on the element characteristics of the integrated chip. Therefore, the manufacturing side of the integrated chip must collect the information by attaching the information of the pad to be soldered to the ground line of the printed circuit board for each integrated chip.
On the other hand, the use side of the integrated chip must selectively connect the pad and the ground line of the printed circuit board to each other by soldering based on the pad information from the manufacturing side. There is a problem that both the manufacturing side and the use side are troublesome and costly.

Accordingly, an object of the present invention is to provide a remote control signal receiving apparatus capable of easily adjusting the center frequency of a band filter.

[0009]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and a receiving circuit for receiving a remote control signal transmitted while being superimposed on a carrier wave of a predetermined frequency. A bandpass filter for extracting a frequency component of the carrier from an output of a receiving circuit, wherein a center frequency of the filter changes when a current amount of a current source of a differential amplifier constituting the filter is adjusted; A detection circuit for detecting an output of the differential amplifier, a circuit for changing a center frequency of the bandpass filter, a transistor for adjusting a current amount of a current source of the differential amplifier, and a plurality of selection resistors for adjusting a control current amount of the transistor. A remote frequency signal receiving apparatus having a center frequency adjusting circuit including: a center frequency of the band-pass filter is adjusted to a carrier frequency of the remote control signal. Oite, select resistance of said center frequency adjustment circuit, and performing with the on-off of the Zener diode for zapping.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be specifically described with reference to the drawings. FIG. 1 is a circuit block diagram showing a remote control signal receiving apparatus according to the present invention, which is applied to the entire block diagram of FIG. 2 and integrated. Note that, in the configuration of FIG. 1, the same components as those of FIG. 3 are denoted by the same reference numerals, and description thereof is omitted.

In FIG. 1, (23-1) to (23-)
n) is a Zener diode for zapping, the cathode is connected to the connection point of the selection resistors (21-1) to (21-n) and the pads (22-1) to (22-n), and the anode is grounded. ing. Zener diode (23-
1) to (23-n) have a structure in which a PN junction is broken and short-circuited by applying a high voltage (for example, 40 volts) between the anode and the cathode. Specifically, when a high voltage is applied between the pads (22-1) to (22-n) and the ground, the Zener diode (23-1)
To (23-n) are short-circuited, the resistor (17) and one of the selection resistors (21-1) to (21-n) are connected in parallel, and the center frequency of the bandpass filter (3) can be changed. . Incidentally, the Zener diodes (23-1) to (2)
The short circuit of 3-n) is performed in a state before the periphery of the chip is molded with resin or the like.

From the above, any one of the selection resistors (21-1) to (21-n) can be selected on the manufacturing side of the integrated chip in accordance with the variation in the center frequency of the bandpass filter (3).
Conventionally, the manufacturing side of the integrated chip has to attach pad information at the time of shipment, and the using side of the integrated chip has to wire between the integrated chip and the ground line of the printed circuit board based on the pad information from the manufacturing side. This eliminates the need for solder connection. Therefore, the user only needs to place the integrated chip delivered from the manufacturing side on the printed circuit board, and the desired electronic device can be quickly put on the market.

In the embodiment of the present invention, the selection resistors (21-1) to (21-n) are connected in parallel to the resistor (17). However, the present invention is not limited to this. The resistors (21-1) to (21-n) are connected in series to the resistor (17), and the Zener diodes (23-1) to (2-1)
3-n) may be arranged in parallel with the selection resistors (21-1) to (21-n), and pads may be provided at both ends of the Zener diodes (23-1) to (23-n).

[0014]

According to the present invention, the center frequency of the bandpass filter is adjusted on the manufacturing side of the integrated chip by using the zener zener diode, and the adjustment on the use side is unnecessary. Therefore, the trouble of attaching the pad information at the time of shipping, which has been a problem on the manufacturing side, and the trouble of connecting the integrated chip and the ground line of the printed circuit board based on the pad information, which has conventionally been a problem, can be omitted. The advantage of being able to get to market quickly is obtained.

[Brief description of the drawings]

FIG. 1 is a circuit block diagram showing a main part of a remote control signal receiving device of the present invention.

FIG. 2 is a block diagram showing the whole of a general remote control signal receiving device.

FIG. 3 is a circuit block diagram showing a main part of a conventional remote control signal receiving device.

FIG. 4 is an equivalent view showing the inside of a bandpass filter.

[Description of Signs] (1) Photodiode (3) Bandpass filter (9) Detection circuit (10) Output circuit (11) Center frequency adjustment circuit (17) Resistance (19) NPN transistor (21-1) to (21-) n) Selection resistance (23-1) to (23-n) Zener diode

Claims (1)

[Claims] 1. A receiving circuit for receiving a remote control signal transmitted in a state of being superimposed on a carrier having a predetermined frequency, and a filter for extracting a frequency component of the carrier from an output of the receiving circuit. A band filter whose center frequency of the filter changes when the current amount of the current source of the dynamic amplifier is adjusted, a detection circuit that detects an output of the band filter, a circuit that changes the center frequency of the band filter, A center frequency adjustment circuit including a transistor for adjusting the amount of current of a current source of the differential amplifier and a plurality of selection resistors for adjusting the amount of control current of the transistor, wherein the center frequency of the bandpass filter is set to the carrier frequency of the remote control signal. In the remote control signal receiving apparatus, the selection resistance of the center frequency adjusting circuit is a zapping zener. Receiver of remote control signals and performs with off the diode.