Protective device
View Patent ↗A protective device that detects an abnormal current in a driving circuit for driving a speaker includes a sound level detector, a current level detector, and a determination section. The sound level detector detects a sound level of an audio signal output to the driving circuit. The current level detector detects a current level of a current flowing in the driving circuit from a power source. The determination section generates, based on a detection signal of the sound level and a detection signal of the current level, a protection command signal when the current level larger than a second threshold is detected when the sound level of the audio signal is smaller than a first threshold.
1. A protective device that detects an abnormal current in a driving circuit for driving a speaker, the protective device comprising:
a sound level detector that detects a sound level of an audio signal output to the driving circuit;
a current level detector that detects a current level of a current flowing in the driving circuit from a power source;
a determination section that generates, based on a detection signal of the sound level and a detection signal of the current level, a protection command signal when the current level larger than a second threshold is detected when the sound level of the audio signal is smaller than a first threshold, and
a duration detector that detects a duration of a state where the sound level of the audio signal is smaller than the first threshold, and disables the detection signal of the sound level output to the determination section until the duration exceeds a second period.
2. The protective device according to claim 1 , further comprising a delay corrector that delays at least one of the detection signal of the sound level and the detection signal of the current level output to the determination section by a first period.
3. The protective device according to claim 1 , further comprising a frequency detector that detects a frequency of a state where the sound level of the audio signal is smaller than the first threshold in a third period, and disables the detection signal of the sound level output to the determination section until the frequency exceeds a predetermined frequency.
4. The protective device according to claim 1 , wherein the duration detector sets the second period such that the second period is not less than a delay time of the detection signal of the current level with respect to the detection signal of the sound level.
5. The protective device according to claim 3 , wherein the frequency detector sets a period from when the third period is started to when the detection signal of the sound level is disabled such that the period is at least not shorter than a delay time of the detection signal of the current level with respective to the detection signal of the sound level.
6. The protective device according to claim 1 , wherein the duration detector sets the second period such that the second period is shorter than a predetermined mute period provided for a time of switching sound data composing a sequence of the audio signal.
7. The protective device according to claim 3 , wherein the frequency detector sets the third period such that the third period is shorter than a predetermined mute period provided for a time of switching sound data composing a sequence of the audio signal.
8. The protective device according to claim 1 , further comprising a first threshold setting unit that sets the first threshold depending on a type of a sound source apparatus of the audio signal.
9. The protective device according to claim 1 , further comprising a second threshold setting unit that detects the current level of current flowing in the driving circuit from the power source in a predetermined mute period, and sets the second threshold based on the current level.
10. The protective device according to claim 1 , wherein the sound level detector is composed of a digital signal processor that calculates digital data.
11. The protective device according to claim 10 , wherein the calculation is an absolute value detection, a square value detection, or a square average detection of the audio signal.
12. A protective device that detects an abnormal current in a driving circuit for driving a speaker, the protective device comprising:
a sound level detector that detects a sound level of an audio signal output to the driving circuit;
a current level detector that detects a current level of a current flowing in the driving circuit from a power source;
a determination section that generates, based on a detection signal of the sound level and a detection signal of the current level, a protection command signal when the current level larger than a second threshold is detected when the sound level of the audio signal is smaller than a first threshold; and
a frequency detector that detects a frequency of a state where the sound level of the audio signal is smaller than the first threshold in a third period, and disables the detection signal of the sound level output to the determination section until the frequency exceeds a predetermined frequency.
13. The protective device according to claim 12 , further comprising a delay corrector that delays at least one of the detection signal of the sound level and the detection signal of the current level output to the determination section by a first period.
14. The protective device according to claim 12 , wherein the frequency detector sets a period from when the third period is started to when the detection signal of the sound level is disabled such that the period is at least not shorter than a delay time of the detection signal of the current level with respective to the detection signal of the sound level.
15. The protective device according to claim 12 , wherein the frequency detector sets the third period such that the third period is shorter than a predetermined mute period provided for a time of switching sound data composing a sequence of the audio signal.
16. The protective device according to claim 12 , further comprising a first threshold setting unit that sets the first threshold depending on a type of a sound source apparatus of the audio signal.
17. The protective device according to claim 12 , further comprising a second threshold setting unit that detects the current level of current flowing in the driving circuit from the power source in a predetermined mute period, and sets the second threshold based on the current level.
18. The protective device according to claim 12 , wherein the sound level detector is composed of a digital signal processor that calculates digital data.
19. The protective device according to claim 18 , wherein the calculation is an absolute value detection, a square value detection, or a square average detection of the audio signal.
20. A protective device that detects an abnormal current in a driving circuit for driving a speaker, the protective device comprising:
a sound level detector that detects a sound level of an audio signal output to the driving circuit;
a current level detector that detects a current level of a current flowing in the driving circuit from a power source;
a determination section that generates, based on a detection signal of the sound level and a detection signal of the current level, a protection command signal when the current level larger than a second threshold is detected when the sound level of the audio signal is smaller than a first threshold; and
a second threshold setting unit that detects the current level of current flowing in the driving circuit from the power source in a predetermined mute period, and sets the second threshold based on the current level.