US 2008/0174545 A1 · Control Device, Illumination Device, And Display Device

Abstract

A control device has: an external terminal receiving a control signal; an output setting circuit changing an output state every time a predetermined edge appears in the control signal; an oscillator generating a clock signal; a period detector counting the number of pulses in the clock signal to detect whether or not the control signal has been kept at a predetermined logic level for a predetermined period; an initializing circuit initializing, based on the output of the period detector, the output state specified by the output setting circuit when the control signal is found to have been kept at the predetermined logic level for the predetermined period; and an oscillation control circuit permitting the operation of the oscillator only when the control signal is at the predetermined logic level and inhibiting the operation of the oscillator otherwise.

Claims11

Dependent claims

A control device, comprising:

an external terminal receiving a control signal;
an output setting circuit changing an output state every time a predetermined edge appears in the control signal;
an oscillator generating a clock signal;
a period detector counting a number of pulses in the clock signal to detect whether or not the control signal has been kept at a predetermined logic level for a predetermined period;
an initializing circuit initializing an output state specified by the output setting circuit when, based on an output of the period detector, the control signal is found to have been kept at the predetermined logic level for the predetermined period;
and
an oscillation control circuit permitting operation of the oscillator only when the control signal is at the predetermined logic level and inhibiting the operation of the oscillator otherwise.

4 more elements

A control device supplying a drive current to a light emitting element, comprising:

an external terminal receiving a binary enable signal;
a counter counting a number of pulses by being triggered by an edge in the enable signal which appears when the enable signal turns from a second logic level to a first logic level, the counter outputting a resulting count as digital data;
a digital/analog converter converting the digital data into analog data and outputting the analog data;
a current source generating a drive current whose current level is based on the analog data, the current source supplying the drive current to the light-emitting element;
an oscillator generating a clock signal;
a period detector counting a number of pulses in the clock signal to detect whether or not the enable signal has been kept at the second logic level for a predetermined period;
a voltage detector detecting whether or not a power supply voltage has reached a predetermined voltage level;
an on/off controller formed of a D flip-flop receiving at a data terminal thereof a logic signal in the second logic level, receiving at a set terminal thereof an inverted signal of the enable signal, receiving at a reset terminal thereof an output signal of the period detector, and receiving at a clock terminal thereof an output signal of the voltage detector;
a first AND operator performing an AND operation of an output signal of the on/off controller and the output signal of the voltage detector;
a switch controlling whether or not to supply a drive current to the light-emitting element based on an output signal of the first AND operator,
a second AND operator performing an AND operation of the inverted signal of the enable signal and an output signal of the first AND operator;
and
a third AND operator performing an AND operation of the inverted signal of the enable signal and the output signal of the on/off controller,
wherein
a reset terminal of the counter and an enable terminal of the voltage detector each receive the output signal of the on/off controller,
an enable terminal of the oscillator receives the output signal of the second AND operator, and
a reset terminal of the period detector receives an output signal of the third AND operator.

14 more elements

An illumination device, comprising:

a light emitting element serving as a light source;
and
a light emission control device supplying a drive current to the light emitting element,
wherein
the light emission control device includes:
an external terminal receiving a binary enable signal;
a counter counting a number of pulses by being triggered by an edge in the enable signal which appears when the enable signal turns from a second logic level to a first logic level, the counter outputting a resulting count as digital data;
a digital/analog converter converting the digital data into analog data and outputting the analog data;
a current source generating a drive current whose current level is based on the analog data, the current source supplying the drive current to the light-emitting element;
an oscillator generating a clock signal;
a period detector counting a number of pulses in the clock signal to detect whether or not the enable signal has been kept at the second logic level for a predetermined period;
a voltage detector detecting whether or not a power supply voltage has reached a predetermined voltage level;
an on/off controller formed of a D flip-flop receiving at a data terminal thereof a logic signal in the second logic level, receiving at a set terminal thereof an inverted signal of the enable signal, receiving at a reset terminal thereof an output signal of the period detector, and receiving at a clock terminal thereof an output signal of the voltage detector;
a first AND operator performing an AND operation of an output signal of the on/off controller and an output signal of the voltage detector;
a switch controlling whether or not to supply the drive current to the light-emitting element based on an output signal of the first AND operator;
a second AND operator performing an AND operation of the inverted signal of the enable signal and the output signal of the first AND operator;
and
a third AND operator performing an AND operation of the inverted signal of the enable signal and the output signal of the on/off controller,
a reset terminal of the counter and an enable terminal of the voltage detector each receive the output signal of the on/off controller,
an enable terminal of the oscillator receives the output signal of the second AND operator, and
a reset terminal of the period detector receives an output signal of the third AND operator.

18 more elements

A display device, comprising:

a liquid crystal panel;
and
an illumination device illuminating the liquid crystal panel,
wherein
the illumination device includes:
a light emitting element serving as a light source;
a light emission control device supplying a drive current to the light emitting element,
the light emission control device includes:
an external terminal receiving a binary enable signal;
a counter counting a number of pulses by being triggered by an edge in the enable signal which appears when the enable signal turns from a second logic level to a first logic level, the counter outputting a resulting count as digital data;
a digital/analog converter converting the digital data into analog data and outputting the analog data;
a current source generating a drive current whose current level is based on the analog data, the current source supplying the drive current to the light-emitting element;
an oscillator generating a clock signal;
a period detector counting a number of pulses in the clock signal to detect whether or not the enable signal has been kept at the second logic level for a predetermined period;
a voltage detector detecting whether or not a power supply voltage has reached a predetermined voltage level;
an on/off controller formed of a D flip-flop receiving at a data terminal thereof a logic signal in the second logic level, receiving at a set terminal thereof an inverted signal of the enable signal, receiving at a reset terminal thereof an output signal of the period detector, and receiving at a clock terminal thereof an output signal of the voltage detector;
a first AND operator performing an AND operation of an output signal of the on/off controller and the output of the voltage detector;
a switch controlling whether or not to supply the drive current to the light-emitting element based on an output signal of the first AND operator;
a second AND operator performing an AND operation of the inverted signal of the enable signal and the output signal of the first AND operator;
and
a third AND operator performing an AND operation of the inverted signal of the enable signal and the output signal of the on/off controller,
a reset terminal of the counter and an enable terminal of the voltage detector each receive the output signal of the on/off controller,
an enable terminal of the oscillator receives the output signal of the second AND operator, and
a reset terminal of the period detector receives an output signal of the third AND operator.

21 more elements

Dependencies are inferred from the claim text.

Control Device, Illumination Device, And Display Device

Life of this patent

Control Device, Illumination Device, And Display Device

Life of this patent

Abstract

Claims11