Light emitter driving device and lighting appliance therewith
A light emitter driving device has a decoder portion which monitors a rectified voltage and generates a dimming signal, and a drive current control portion which controls a drive current to a light emitter according to the dimming signal. The decoder portion has a comparator which compares the rectified voltage with a predetermined threshold voltage to generate a comparison signal, a sampling counter which measures high-level and low-level periods of the comparison signal, a duty calculation portion which calculates the duty of the rectified voltage based on the output of the sampling counter, a filter calculation portion which excludes sporadic variation in duty by applying digital filtering to the output of the duty calculation portion, and a dimming signal generation portion which generates the dimming signal based on the output of the filter calculation portion.
1. A light emitter driving device comprising:
a decoder portion that monitors a rectified voltage and generates a dimming signal; and
a drive current control portion that controls a drive current for the light emitter in accordance with the dimming signal; wherein
the decoder portion includes:
a comparator that compares the rectified voltage with a predetermined threshold voltage to generate a comparison signal;
a sampling counter that measures a high level time span and a low level time span of the comparison signal;
a duty calculation portion that calculates a duty of the rectified voltage in accordance with an output from the sampling counter;
a filter operation portion that applies a digital filter process to an output from the duty calculation portion to remove a sudden duty change; and
a dimming signal generation portion that generates the dimming signal based on an output from the filter operation portion, and
wherein the filter operation portion includes a median filter and a hysteresis filter.
2. The light emitter driving device according to claim 1 , wherein
the median filter includes:
a FIFO portion that that stores a group of duties which are successively calculated over a plurality of periods; and
a selection portion that selects a middle value from or a value larger than the middle value from the group of duties stored in the FIFO portion and outputs the value.
3. The light emitter driving device according to claim 1 , wherein the filter operation portion further includes a FIR filter.
4. A light emitter driving device comprising:
a decoder portion that monitors a rectified voltage and generates a dimming signal; and
a drive current control portion that controls a drive current for the light emitter in accordance with the dimming signal; wherein
the decoder portion includes:
a comparator that compares the rectified voltage with a predetermined threshold voltage to generate a comparison signal;
a sampling counter that measures a high level time span and a low level time span of the comparison signal;
a duty calculation portion that calculates a duty of the rectified voltage in accordance with an output from the sampling counter;
a filter operation portion that applies a digital filter process to an output from the duty calculation portion to remove a sudden duty change; and
a dimming signal generation portion that generates the dimming signal based on an output from the filter operation portion;
a frequency calculation portion that calculates a frequency of the rectified voltage in accordance with the output from the sampling counter;
a frequency determination portion that determines whether the frequency of the rectified voltage falls in a predetermined range or not; and
a mask process portion that applies a mask process to the output from the duty calculation portion in accordance with a determination result from the frequency determination portion.
5. A light emitter driving device comprising:
a decoder portion that monitors a rectified voltage and generates a dimming signal; and
a drive current control portion that controls a drive current for the light emitter in accordance with the dimming signal; wherein
the decoder portion includes:
a comparator that compares the rectified voltage with a predetermined threshold voltage to generate a comparison signal;
a sampling counter that measures a high level time span and a low level time span of the comparison signal;
a duty calculation portion that calculates a duty of the rectified voltage in accordance with an output from the sampling counter;
a filter operation portion that applies a digital filter process to an output from the duty calculation portion to remove a sudden duty change;
a dimming signal generation portion that generates the dimming signal based on an output from the filter operation portion;
a mask signal generation portion that generates a mask signal which changes in logic level at every rise of the rectified voltage; and
a mask process portion that applies a mask process to the output from the duty calculation portion in accordance with the mask signal.
6. A lighting appliance comprising:
a light emitter;
a rectification circuit that rectifies an a.c. voltage to generate a rectified voltage;
a smoothing circuit that generates a d.c. voltage from the rectified voltage and supplies the dc voltage to the light emitter;
a switch device that opens/closes an electric current route in which a driving current for the light emitter flows; and
a light emitter driving device that performs on/off control of the switch device; wherein
the light emitter driving device includes:
a decoder portion that monitors the rectified voltage and generates a dimming signal; and
a drive current control portion that controls a drive current for the light emitter in accordance with the dimming signal; wherein
the decoder portion includes:
a comparator that compares the rectified voltage with a predetermined threshold voltage to generate a comparison signal;
a sampling counter that measures a high level time span and a low level time span of the comparison signal;
a duty calculation portion that calculates a duty of the rectified voltage in accordance with an output from the sampling counter;
a filter operation portion that applies a digital filter process to an output from the duty calculation portion to remove a sudden duty change; and
a dimming signal generation portion that generates the dimming signal based on an output from the filter operation portion, and
wherein the filter operation portion includes a median filter and a hysteresis filter.
7. The lighting appliance according to claim 6 , wherein
the drive current control portion performs the on/off control of the switch device such that a current flowing in the switch device becomes equal to a target value which is set based on the dimming signal.
8. The lighting appliance according to claim 6 , further comprising
a bleeder circuit that keeps a hold current of a TRIAC dimmer which performs phase control of the a.c. voltage.
9. The lighting appliance according to claim 6 , wherein the light emitter includes an LED device.
10. The lighting appliance according to claim 9 , wherein
the lighting appliance is a bulb-shaped lamp, an annular-shaped LED lamp, a linear tube-shaped LED lamp, a ceiling light, or a downlight.
11. A lighting appliance comprising:
a light emitter;
a rectification circuit that rectifies an a.c. voltage to generate a rectified voltage;
a smoothing circuit that generates a d.c. voltage from the rectified voltage and supplies the dc voltage to the light emitter;
a switch device that opens/closes an electric current route in which a driving current for the light emitter flows; and
a light emitter driving device that performs on/off control of the switch device; wherein
the light emitter driving device includes:
a decoder portion that monitors the rectified voltage and generates a dimming signal; and
a drive current control portion that controls a drive current for the light emitter in accordance with the dimming signal; wherein
the decoder portion includes:
a comparator that compares the rectified voltage with a predetermined threshold voltage to generate a comparison signal;
a sampling counter that measures a high level time span and a low level time span of the comparison signal;
a duty calculation portion that calculates a duty of the rectified voltage in accordance with an output from the sampling counter;
a filter operation portion that applies a digital filter process to an output from the duty calculation portion to remove a sudden duty change;
a dimming signal generation portion that generates the dimming signal based on an output from the filter operation portion;
a frequency calculation portion that calculates a frequency of the rectified voltage in accordance with the output from the sampling counter;
a frequency determination portion that determines whether the frequency of the rectified voltage falls in a predetermined range or not; and
a mask process portion that applies a mask process to the output from the duty calculation portion in accordance with a determination result from the frequency determination portion.