Transmitter driver for programmable remote control transmitter

A transmitter driver of this invention is applied to a programmable remote control transmitter for receiving remote control codes for remote-controlling various electric devices in the learning mode and for remote-controlling the electric devices according to the received remote control codes in the remote control mode. The transmitter driver has an output transistor for driving a transmitter constituting a part of a load upon reception of electrical pulses representing the remote control codes, a resistor device arranged between the output side of the output transistor and a given reference potential, and a control transistor device, output electrodes of which are arranged between one end of the resistor device at the side of the output transistor and the reference potential. An input terminal of the control transistor device receives a control signal corresponding to an output signal format of remote control codes necessary for controlling an electric device selected by a user.

BACKGROUND OF THE INVENTION 
The present invention relates to a programmable remote control transmitter 
and, more particularly, to an transmitter driver for a programmable remote 
control transmitter to emulate any one of transmitters for 
remote-controlling electrical devices. 
Various types of electronic products have been used at home to provide 
convenience in daily life in recent years. Most electric products have 
so-called remote controllers as transmitters for electrically 
remote-controlling the electric devices. Since every electric device a 
transmission system of a unique type, a another electric device. If the 
number of electric devices is increased, the number of types of 
transmitters is accordingly increased. When a large number of remote 
controllable electric devices are installed in a house, the user is often 
confused of selecting a transmitter appropriate for each electric device. 
In order to solve this problem, the present applicant has proposed a 
programmable remote control transmitter. This programmable remote control 
transmitter receives various remote control codes from all transmitters 
used in the house and decodes these codes. The decoded remote control 
codes are stored in a memory. Where the remote control transmitter is 
used, a type of the electric device to be available is selected and the 
selected electric device is irradiated with ultrasonic waves or infrared 
rays, thereby controlling the electric device in accordance with data 
stored in the memory which corresponds to the remote control codes of the 
selected electric device. Such a conventional programmable remote control 
transmitter is described in detail in Japanese patent prepublication No. 
60-254898 which corresponds to U.S. Pat. No. 4,623,887 issued to K. B. 
Welles, II on Nov. 18, 1986. 
However, with this arrangement, electric devices to be controlled have 
different output signal formats. For this reason, since the operating 
characteristics of a transmitter differ in accordance with the output 
signal formats, it is difficult to drive the transmitter under the optimal 
operating conditions. In other words, a transmitter driver used in the 
remote control transmitter normally comprises an output transistor for 
receiving an electrical signal representing a remote control code and a 
transmitter, such as a light-emitting diode, connected to its output side. 
Therefore, the conventional transmitter used in such a driver has been 
designed with reference to a case wherein a maximum current is supplied 
thereto, e.g., a remote control code signal of a continuous wave format is 
used. In this case, when the different output wave formats are used, a 
current supplied to the transmitter increases or decreases, thus varying 
an effective output of the transmitter. As a result, a controllable range 
of the remote control transmitter differs in accordance with the selected 
electric devices, thus confusing a user. Typical output wave formats will 
be exemplified below. For example, in a continuous wave format, a ratio of 
a pulse burst period to a pulse off period, i.e., a duty ratio, is 50%. In 
a gated carrier format, the duty ratio is 3 to 10%, and in a single pulse 
format, the duty ratio is 0.5 to 1%. Therefore, when a circuit is designed 
such that a current of 100 mA is supplied to a transmitter in the 
continuous wave format, only a current of 20 mA and a current of 2 mA are 
supplied thereto in the gated carrier and single pulse formats, 
respectively. As a result, the transmission distances of the transmitter 
output in the gated carrier and single pulse formats are shorter than that 
in the continuous wave format. 
SUMMARY OF THE INVENTION 
It is therefore an object of the present invention to provide an 
transmitter driver for a programmable remote control transmitter with 
which a remote control range will not be substantially changed regardless 
of different electric devices selected by a user. 
In order to achieve the above object of the present invention, the output 
load of an output transistor in a transmitter driver constituting a remote 
control transmitter is changed in accordance with a selected output wave 
format. With this arrangement, a current supplied to a transmitter can be 
made substantially constant regardless of the output wave formats, and the 
transmission distance of the transmitter output can also be made constant. 
Therefore, this will not confuse a user unlike a conventional transmitter 
in which a remote control range differs in acordance with a selected 
electric device. 
Therefore, according to an aspect of the present invention, there is 
provided a transmitter driver for a programmable remote control 
transmitter for receiving remote control codes for remote-controlling 
various electric devices in a learning mode and for remote-controlling the 
electric devices according to the received remote control codes in a 
remote control mode, comprising an output transistor for driving a 
transmitter constituting a part of a load upon reception of electrical 
pulses representing the remote control code, a resistor device arranged 
between the output side of the output transistor and a given reference 
potential, and a control transistor device, output electrodes of which are 
arranged between one end of the resistor device at the side of the output 
transistor and the reference potential, and an input electrode of which 
receives a control signal corresponding to an output signal format of 
remote control codes necessary for controlling an electric device selected 
by a user.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIG. 1 shows the basic arrangement of a programmable remote control 
transmitter according to an embodiment of the present invention. First, 
the operation of the remote control transmitter will be described with 
reference to FIG. 1. Referring to FIG. 1, the transmitter comprises a 
detector 11 for receiving an infrared or ultrasonic remote control code 
from a transmitter 100 for an electric device in the learning mode. The 
detectcr 11 also has a waveshaping function. The remote control code sent 
from the transmitter 100 for the electric device has variable pulse burst 
and variable pulse off periods, as shown in FIG. 2A. An output from the 
detector 11 is supplied to a register 13 through a gate 12. The register 
13 also sequentially receives outputs from the detector 11 in response to 
one (i.e., a clock CL1) of the clocks sent from a pulse generator 60. Each 
output from the detector 11 is classified into a pulse burst period and 
the subsequent pulse off period. Parallel outputs from the register 13 are 
supplied to a first repetition pattern discriminator 15 through a latch 
14. The first repetition pattern discriminator 15 discriminates which 
predetermined bin pattern corresponds to the pulse burst or pulse off 
pattern represented by the output from the register 13 and performs first 
data compression. The first repetition pattern discriminator 15 measures 
the pulse off period and the number of pulses during the pulse burst 
period. The resultant count and the off period are compared with preset 
bin patterns stored in a reference bin pattern setting circuit 15R built 
into the first repetition pattern discriminator 15. If a coincidence 
between the input data and the stored pattern is detected, a bin code 
corresponding to the bin pattern is sent out from the first repetition 
pattern discriminator 15. Comparison may be performed in units of input 
remote control codes or for all input remote control codes at once. The 
bin code from the first repetition pattern discriminator 15 is supplied to 
a register 21. The register 21 receives the bin code in response to one 
(i.e., a clock CL2) of the clocks from the pulse generator 60. A parallel 
signal is output from the register 21. The parallel signal is supplied to 
a second repetition pattern discriminator 23 through a latch 22. 
The second repetition pattern discriminator 23 operates in a different 
manner from the first repetition pattern discriminator 15. More 
specifically, the second repetition pattern discriminator 23 compares a 
pair of adjacent ones of the bin codes obtained by the first repetition 
pattern discriminator 15 with a reference bin pair code pattern prestored 
in a reference bin pair pattern setting circuit 23R incorporated therein. 
Comparison may be performed in units of bin pair codes or for all bin pair 
codes at once. Data obtained by second data compression in this manner are 
stored in a predetermined area in a memory 24. 
The learning process described above is repeated in units of command or 
operation keys arranged in the transmitter for each electric device, and 
compressed data corresponding to control data sent from each key are 
stored in the memory 24. 
The above operation is performed for several electric devices, and data 
required for remote-controlling them are stored in the memory 24. 
The data stored in the memory 24, as described above, are read out by the 
following circuit arrangement in the normal operation mode, i.e., the 
remote control mode. 
In the remote control mode, the control mcde corresponding to the electric 
device to be remote-controlled by the operator is selected, and an 
operation key (not shown) is operated. A controller 50 accesses the memory 
24 in response to the key data from the operated key, and the compressed 
data is read out from a memory area at the designated address. The readout 
data is supplied to a third repetition pattern discriminator 31. The third 
repetition pattern discriminator 31 performs the operation opposite to 
that of the second repetition pattern discriminator 23, i.e., converts the 
bin pair code to the bin code. The input bin pair code is compared with a 
reference bin pair code pattern prestored in a reference bin pair pattern 
setting circuit 31R and is converted into a corresponding bin code. The 
converted bin code is supplied to a register 33 through a latch 32 and 
stored therein. The register 33 receives the bin code in response to the 
clock CL2 sent from the pulse generator 60. The content of the register 33 
is sent to a fourth repetition pattern discriminator 35. The fourth 
repetition pattern discriminator 35 converts the bin code into an 
electrical signal of a remote control code consisting of pulse burst and 
pulse off components, in a manner opposite to that of the first repetition 
pattern discriminator 15. More specifically, the input bin code is 
compared with a reference bin code pattern prestored in a reference bin 
pattern setting circuit 35R built into the fourth repetition pattern 
discriminator 35 and is converted into a corresponding remote control 
code. The remote control code is stored in a register 37 through a latch 
36. The register 37 sequentially supplies remote control codes to a 
transmitter (LED) driver 38 in response to the clocks CL1 from the pulse 
generator 60. An infrared or ultrasonic remote control code signal is sent 
to an electric device 70 through a transmitter 39 to control the electric 
device 70. The LED driver 38 is a characteristic feature of the present 
invention. When a user selects an electric device to be controlled, an 
output wave format suitable for the selected device is also specified. 
Therefore, a load corresponding to the specified output wave form is 
selected by the controller 50. This will be described later with reference 
to FIGS. 5 and 6. 
Referring to FIG. 1, reference numeral 80 denotes a display for displaying 
functions, modes and commands for operating the remote control 
transmitter. Reference symbol SM denotes a switch for setting a learning 
mode. The switch SM is manually operated. The controller 50 generates 
various control signals at predetermined timings in response to clock 
pulses supplied from the pulse generator 60 so as to control the operation 
of the gate 12, the latches 14, 22, 32, and 36, and the memory 24. The 
control signals can be generated by techniques known to those skilled in 
the art, and a detailed description thereof will be omitted. 
With the above arrangement, the operations of the first to fourth 
repetition pattern discriminators 15, 23, 31, and 35 as the main feature 
of the present invention will be described with reference to FIGS. 2 to 4. 
In the learning mode, the remote control code signal in FIG. 2A is supplied 
as an operation key signal from the transmitter 100 for the electric 
device. Numeric values written on the pulses of the burst periods 
represent the numbers of pulses constituting the pulse burst periods. The 
times written below the signal represent pulse off periods. Therefore, 
there are two types of pulse burst components respectively having five and 
three pulses, and two types of pulse off periods as 100 ms and 50 ms. 
The remote control signal is waveshaped by the detector 11. The waveshaped 
signal is supplied to the first repetition pattern discriminator 15 
through the register 13. The first repetition pattern discriminator 15 
compares the input electrical signal with the reference bin patterns 
stored in the reference bin pattern setting circuit 15R. The conversion 
codes shown in FIG. 3 are stored in the reference bin pattern setting 
circuit 15R. When the electrical signal in FIG. 2A is supplied to the 
first repetition pattern discriminator 15, it converts the pulse burst "5" 
into a bin code "A". The pulse off period "100 ms" following the pulse 
burst "5" is converted into a bin code "C". The pulse burst "3" following 
the pulse off period "100 ms" is converted into a bin code "B". The pulse 
off period "50 ms" following the pulse burst "3" is converted into a bin 
code "D". The electrical signals are sequentially converted into bin codes 
in the same manner as described above. The array of bin codes is shown 
below the corresponding signal components in FIG. 2B. 
The bin code array is supplied to the second repetition pattern 
discriminator 23 through the register 21 and the latch 22. The bin code 
array is compared with the reference bin pair patterns stored in the 
reference bin pair pattern setting circuit 23R. The conversion codes in 
FIG. 4 are stored in the reference bin pair pattern setting circuit 23R. 
The second repetition pattern discriminator 23 discriminates coincidences 
between the bin pair codes shown in FIG. 4 and the combinations each 
consisting of two adjacent bin codes. The first combination "AB" of two 
adjacent bin codes corresponds to a bin pair code "I" and is converted 
thereinto. The second combination "CD" of two adjacent bin codes 
corresponds to a bin pair code "II" and is converted thereinto. The third 
combination "CD" of two adjacent bin codes corresponds to the bin pair 
code "II" and is converted thereinto. The subsequent combinations each 
consisting of two adjacent bin codes are converted into the corresponding 
reference bin pair codes. An array of resultant bin pair codes is shown in 
FIG. 2C below the corresponding bin codes in FIG. 2B. The bin pair codes 
are stored as compressed data in the memory 24. 
The third repetition pattern discriminator 31 converts the bin pair code to 
a combination of two adjacent bin codes in a manner opposite to that of 
the second repetition pattern discriminator 23. Each compressed data, 
i.e., each bin pair code, read out from the memory 24 is converted into 
the corresponding combination of two adjacent bin codes according to the 
conversion codes (FIG. 4) stored in the reference bin pair pattern setting 
circuit 31R built into the third repetition pattern discriminator 31. For 
example, if the bin pair code is "III", the combination "AC" of two 
adjacent bin codes is obtained as a conversion output. Similarly, if the 
bin pair code is "II", the combination "CD" of two adjacent bin codes is 
obtained as a conversion output. If the bin pair code is "I", the 
combination "AB" of two adjacent bin codes is obtained as a conversion 
output. The resultant combinations each consisting of two adjacent bin 
codes are supplied to the register 33 through the latch 32 and stored 
therein. 
The fourth repetition pattern discriminator 35 converts each combination of 
two adjacent bin codes into remote control codes in a manner opposite to 
the first repetition pattern discriminator 15. An array of the bin code 
combinations read out from the register 33 is converted to a remote 
control code electrical signal according to the conversion codes (FIG. 3) 
stored in the reference pattern setting circuit 35R built into the fourth 
repetition pattern discriminator 35. For example, a pulse signal 
constituting the pulse burst "5" is obtained as a conversion output for 
the bin code "A". Similarly, a pulse off period "100 ms" is obtained as a 
conversion output for the bin code "C". A pulse signal constituting the 
pulse burst "3" is obtained as a conversion output for the bin code "B". A 
pulse off period "50 ms" is obtained as a conversion output for the bin 
code "D". 
The array of the remote control codes is sent to the register 37 through 
the latch 36. 
The detailed arrangement and the operation of the LED driver 38 as the main 
feature of the present invention will be described hereinafter with 
reference to FIGS. 5 and 6. 
FIG. 5 is a detailed circuit diagram of the LED driver 38 shown in FIG. 1. 
Referring to FIG. 5, reference symbol T1 denotes an NPN output transistor, 
the base of which receives remote control codes from the register 37 shown 
in FIG. 1 through a resistor R1. The collector of the transistor T1 is 
connected to one end of a light-emitting diode LED constituting the 
transmitter 39 through a resistor R2. The other end of the light-emitting 
diode LED is connected to a power source +V. The emitter of the transistor 
T1 is connected to a ground potential through a resistor R3. Reference 
symbol T2 denotes a control transistor for changing an output load. The 
collector of the transistor T2 is connected to a node between the emitter 
of the transistor T1 and the resistor R1, the emitter is connected to a 
ground potential, and the base is connected to the controller 50 through a 
resistor R4. The controller 50 supplies, to the base of the transistor T2 
through the resistor R4 and a control terminal A, a control signal 
suitable for a load corresponding to the output signal format used in an 
electric device selected by a user. In this case, assuming that the output 
signal formats of electric devices controlled by this remote control 
transmitter include the continuous wave format, the gated carrier format, 
and the single pulse format, the control transistor T2 receives the 
control signals shown in Table 1 from the controller 50. 
TABLE 1 
______________________________________ 
Single Pulse 
Gated Carrier 
Continuous Wave 
Format Format Format 
______________________________________ 
Transistor T2 
ON ON OFF 
______________________________________ 
Since there is only a slight difference between the duty ratios of the 
single pulse format and the gated carrier format, the same load of the 
output transistor T1 is used for these formats. More specifically, in the 
single pulse format and the gated carrier format, the controller 50 
supplies the control signal to the base of the transistor T2 to turn it 
on. Therefore, the emitter of the output transistor T1 is connected 
directly to the ground potential without being through the resistor R3. As 
a result, a large current is supplied to the light-emitting diode LED. In 
contrast to this, in the continuous wave format, no control signal is 
supplied to the base of the control transistor T2. Therefore, the emitter 
of the transistor T1 is connected to the ground potential through the 
resistor R3. As a result, a small current is supplied to the 
light-emitting diode LED. 
In this manner, when the load of the LED driver is changed, a current 
supplied to the transmitter can be made constant regardless of the output 
signal formats. In addition, the transmission distance of the transmitter 
output can be also made constant. Therefore, a user will not be confused 
of different remote control ranges in accordance with selected electric 
devices unlike in the conventional transmitter. 
FIG. 6 shows a modification of the circuit shown in FIG. 5. The load of the 
output transistor can be correctly set with respect to the remote control 
codes in any of the single pulse, gated carrier, and continuous wave 
formats. The same reference numerals in FIG. 6 denote the same parts as in 
FIG. 5. Referring to FIG. 6, the emitter of an output transistor T1 is 
connected to the ground potential through resistors R3 and R5. The 
collector of a control transistor T3 is connected to a node between the 
resistors R3 and R5, and the emitter thereof is connected to the ground 
potential. The base of the control transistor T3 receives a control signal 
from the controller 50 through a resistor R6 and a control terminal B. 
Assuming that the output signal formats of electric devices controlled by 
this remote control transmitter includes the continuous wave, gated 
carrier, and single pulse formats, the control transistors T2 and T3 
receive the control signals shown in Table 2 below from the controller 50. 
TABLE 2 
______________________________________ 
Single Pulse 
Gated Carrier 
Continuous Wave 
Format Format Format 
______________________________________ 
Transistor T2 
ON OFF OFF 
Transistor T3 
OFF ON OFF 
______________________________________ 
In the single pulse format, the controller 50 supplies the control signal 
to the base of the control transistor T2 to turn it on. Therefore, the 
emitter of the output transistor T1 is connected directly to the ground 
potential without being through the resistor R3. As a result, a large 
current is supplied to the light-emitting diode LED. In this case, no 
control signal is supplied to the control transistor T3. Therefore, the 
transistor T3 is kept off. In contrast to this, in the gated carrier 
format, no control signal is supplied to the base of the control 
transistor T2, and a control signal is supplied to the base of the control 
transistor T3. Therefore, the emitter of the output transistor T1 is 
connected to the ground potential through the resistor R3. As a result, a 
medium current is supplied to the light-emitting diode LED. In the 
continuous wave format, no control signal is supplied to the base of the 
control transistor T2. Therefore, the emitter of the transistor T1 is 
connected to the ground potential through the resistors R3 and R4. As a 
result, a small current is supplied to the light-emitting diode LED. 
In this manner, when the load of the LED driver is changed, a current 
supplied to the transmitter can be made constant regardless of the output 
signal formats. In addition, the transmission distance of the transmitter 
output can be also made constant. Therefore, a user will not be confused 
of different remote control ranges in accordance with selected electric 
devices unlike the conventional transmitter. 
The format of the remote control code is not limited to the one used in the 
above description. Other various code formats may be utilized. 
Although NPN transistors are used in the embodiment in FIGS. 5 and 6, other 
type of transistors, e.g., FETs may also be used. 
In the embodiment shown in FIGS. 5 and 6, the bias potentials of the 
transistors are not limited to those described therein, as a matter of 
course. 
In the above embodiment, the operation is performed by hardware. However, 
the same operation as described above may be performed by a combination of 
a computer and software. In this case, the reference bin pattern setting 
circuits incorporated in the first and fourth repetition pattern 
discriminators 15 and 35 can be constituted by a single circuit. The same 
is true for the reference bin pair pattern setting circuits incorporated 
in the second and third repetition pattern discriminators 23 and 31. 
According to the programmable remote control transmitter of the present 
invention as described above, the load of the transmitter driver is 
changed in correspondence with the output signal format, so that a current 
supplied to the transmitter can be made constant regardless of the output 
signal formats, and the transmission distance of the transmitter output 
can also be made constant. Therefore, a user will not be confused of 
different remote control ranges corresponding to selected electric devices 
unlike in a conventional transmitter.