Infrared transmitter circuit and electronic device
First Claim
1. An infrared transmitter circuit, comprising:
- a light emission element; and
a driving circuit which outputs a driving current, being constant, which causes the light emission element to emit light on the basis of a transmission signal constituted of a pulse, said driving circuit including;
(a) a protection circuit for stopping supplying the driving current to the light emission element as a protection operation when the transmission signal is in a state which causes the light emission element to emit light for a certain time or more; and
(b) a reference current source for generating a reference current so as to generate the driving current, whereinthe protection circuit stops supplying the driving current and stops the reference current source,whereinthe protection circuit includes;
a capacitor element which is charged by flow of a current;
a charging control circuit for allowing a charging current to flow to the capacitor element when the transmission signal is active;
a first comparison circuit for comparing a first reference voltage with an inter-terminal voltage of the capacitor element; and
a retention circuit for retaining a protection operation condition of the protection circuit when the reference current source stops, andthe protection circuit begins the protection operation when the first comparison circuit determines the inter-terminal voltage to be not less than the reference voltage.
2 Assignments
0 Petitions
Accused Products
Abstract
An infrared transmitter circuit causes an output current to flow to a light emission diode via a current mirror circuit constituted of three transistors by using a current supplied from a power source circuit, so that the light emission diode emits light. When a voltage V1 varied by charging a capacitor with a current flowing from the power source circuit exceeds a reference voltage (voltage V2), an output of a comparator resets a D flip-flop, so that an output of the D flip-flop varies to “0”. Thus, an output of a NAND gate to which that output and a transmission signal are inputted causes a transistor (N-channel FET) to turn ON so as to stop operation of the current mirror circuit, and causes a transistor (P-channel FET) to turn OFF so as to cut a connection between the power source circuit and a power source line. Thus, it is possible to reduce power consumption in operation of a protection circuit which stops supplying the output current to the light emission diode.
-
Citations
18 Claims
-
1. An infrared transmitter circuit, comprising:
-
a light emission element; and a driving circuit which outputs a driving current, being constant, which causes the light emission element to emit light on the basis of a transmission signal constituted of a pulse, said driving circuit including; (a) a protection circuit for stopping supplying the driving current to the light emission element as a protection operation when the transmission signal is in a state which causes the light emission element to emit light for a certain time or more; and (b) a reference current source for generating a reference current so as to generate the driving current, wherein the protection circuit stops supplying the driving current and stops the reference current source, wherein the protection circuit includes; a capacitor element which is charged by flow of a current; a charging control circuit for allowing a charging current to flow to the capacitor element when the transmission signal is active; a first comparison circuit for comparing a first reference voltage with an inter-terminal voltage of the capacitor element; and a retention circuit for retaining a protection operation condition of the protection circuit when the reference current source stops, and the protection circuit begins the protection operation when the first comparison circuit determines the inter-terminal voltage to be not less than the reference voltage. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
-
-
10. An electronic device, comprising an infrared transmitter circuit which includes:
-
a light emission element; and a driving circuit which outputs a driving current, being constant, which causes the light emission element to emit light on the basis of a transmission signal constituted of a pulse, said driving circuit including; (a) a protection circuit for stopping supplying the driving current to the light emission element as a protection operation when the transmission signal is in a state which causes the light emission element to emit light for a certain time or more; and (b) a reference current source for generating a reference current so as to generate the driving current, wherein the protection circuit stops supplying the driving current and stops the reference current source, wherein the protection circuit includes; a capacitor element which is charged by flow of a current; a charging control circuit for allowing a charging current to flow to the capacitor element when the transmission signal is active; a first comparison circuit for comparing a first reference voltage with an inter-terminal voltage of the capacitor element; and a retention circuit for retaining a protection operation condition of the protection circuit when the reference current source stops, and the protection circuit begins the protection operation when the first comparison circuit determines the inter-terminal voltage to be not less than the reference voltage. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18)
-
Specification