Drive circuit for an infrared remote control transmitter

• US 4,264,982 A
• Filed: 03/29/1979
• Issued: 04/28/1981
• Est. Priority Date: 03/29/1979
• Status: Expired due to Term

• Current Assignee: RCA Corporation
• Original Assignee: RCA Corporation
• Inventors: Sakarya, Dursun
• Primary Examiner(s): Griffin, Robert L.
• Assistant Examiner(s): Orsino, Jr., Joseph A.
• Application Number:
  US06/025,165
• Time in Patent Office: 761 Days
• Field of Search: 250/199, 358/194, 358/194.1, 332/7.51, 331/94.5 H, 331/ 94.5 S, 331/94.5 M, 307/312
• US Class Current: 398/106
• CPC Class Codes: H03J 9/06 using electromagnetic waves other than radio waves, e.g. light

Abstract

An infrared remote control transmitter includes at least one infrared light-emitting diode poled with respect to a point of reference potential so as to be conductive in response to voltages having the opposite polarity of a DC supply voltage and to be nonconductive in response to voltages having the same polarity as the DC supply voltage. A push-pull amplifier is responsive to a pulse signal encoded to represent a remote control message to selectively couple the DC supply voltage or the reference potential to a capacitor coupled in series between the push-pull amplifier and the light-emitting diode. The capacitor is charged and discharged and an alternating drive voltage for the light-emitting diode having portions with polarities both the same as and opposite to the polarity of the DC supply voltage is generated. The push-pull amplifier is arranged so that when a component failure occurs, the portions of the alternating drive voltage having the polarity opposite to the polarity of the DC supply voltage are at least inhibited to prevent the continuous (i.e., DC) emission of infrared radiation.

Claims

1. In an infrared remote control transmitter for controlling a television system, apparatus comprising:

a reference circuit point for receiving a reference potential;

a supply circuit point for receiving a DC supply voltage;

a battery connected with a predetermined polarity connected between said supply and reference circuit points;

at least one light-emitting diode for emitting infrared radiation when rendered conductive, said light emitting diode having a cathode and an anode, one of said cathode and anode being connected to said reference circuit point, said light-emitting diode being poled with respect to said reference circuit point so as to be conductive in response to the application of a voltage to the other one of said cathode and anode having the opposite polarity to said battery with respect to said reference circuit point and non-conductive in response to the application of a voltage to said other one of said cathode and anode having the same polarity as said battery with respect to said reference circuit point;

a source circuit point for receiving an input signal having pulses encoded to represent information for controlling a predetermined function of said television receiver;

a drive circuit point;

a capacitor directly connected between said drive circuit point and said other one of said cathode and anode;

a diode directly connected between said other one of said cathode and anode and said reference circuit point and poled in the opposite sense to said light-emitting diode with respect to said reference circuit point;

push-pull amplifier means for developing a drive voltage at said drive point including first and second bipolar transistors of opposite conduction types, each of said transistors having a collector-emitter path and a base electrode for controlling the conduction of said collector-emitter path, said collector-emitter path of said first transistor being directly connected between said supply circuit point and said drive circuit point, said collector-emitter path of said second transistor being connected between said drive circuit point and said reference point; and

input means coupled between said source circuit point and said bases of said first and second transistors for rendering said collector-emitter path of said first transistor conductive and said collector-emitter path of said second transistor non-conductive in response to a first portion of said pulses of said input signal and for rendering said collector-emitter path of said second transistor conductive and said collector-emitter path of said first transistor non-conductive in response to a second portion of said pulses of said input signal.

2. The apparatus recited in claim 1 wherein:

three light-emitting diodes poled in the same direction are connected in series between said capacitor means and said reference circuit point.

3. The apparatus recited in claim 1 wherein:

a second capacitor is directly connected between said drive point and said other one of said cathode and anode in parallel with said first mentioned capacitor directly connected between said drive point and said other one of said cathode and anode.

4. The apparatus recited in claim 1 wherein:

said input means includes a first capacitor connected between said source circuit point and said base of said first transistor;

first means connected between said supply circuit point and said base of said first transistor for discharging said first capacitor;

a second capacitor connected between said source circuit point and said base of said second transistor; and

second means connected between said base of said second transistor and said reference circuit point for discharging said second capacitor.

5. The apparatus recited in claim 4 wherein:

said first means includes a further diode poled to be conductive when said collector-emitter path of said first transistor is non-conductive and non-conductive when said collector-emitter path of said first transistor is conductive; and

said second means includes a still further diode poled to be conductive when said collector-emitter path of said second transistor is non-conductive and non-conductive when said collector-emitter path of said second transistor is conductive.

6. In an infrared remote control transmitter for controlling a television system, apparatus comprising:

a reference circuit point for receiving a reference potential;

a supply circuit point for receiving a DC supply voltage;

a battery connected with a predetermined polarity connected between said supply and reference circuit points;

three light-emitting diodes which emit infrared radiation when rendered conductive directly connected in series between a voltage application circuit point and said reference circuit point, all of said light-emitting diodes being poled with respect to said reference circuit point so as to be conductive in response to the application of a voltage to said voltage application circuit point having the opposite polarity to said battery with respect to said reference circuit point and non-conductive in response to the application of a voltage to said voltage application circuit point having the same polarity as said battery with respect to said reference circuit point;

a source circuit point for receiving an input signal having pulses encoded to represent information for controlling a predetermined function of said television receiver;

a drive circuit point;

a first capacitor directly connected between said drive circuit point and said voltage application circuit point;

a second capacitor directly connected between said drive circuit point and said voltage application circuit point;

a diode directly connected between said voltage application circuit point and said reference circuit point and poled in the opposite sense to said light-emitting diode with respect to said reference circuit point;

push-pull amplifier means for developing a drive voltage at said drive point including first and second bipolar transistors of opposite conduction types, each of said transistors having a collector-emitter path and a base electrode for controlling the conduction of said collector-emitter path, said collector-emitter path of said first transistor being directly connected between said supply circuit point and said drive circuit point, said collector-emitter path of said second transistor being connected between said drive circuit point and said reference point; and

input means coupled between said source circuit point and said bases of said first and second transistors for rendering said collector-emitter path of said first transistor conductive and said collector-emitter path of said second transistor non-conductive in response to a first portion of said pulses of said input signal and for rendering said collector-emitter path of said second transistor conductive and said collector-emitter path of said first transistor non-conductive in response to a second portion of said pulses of said input signal.