Design And Implementation Of Micro Speaker Protection Circuit

Nowadays,with the significant improvement of consumers' living standards and the continuous penetration of digital life,portable consumer electronic products are developing rapidly,the size of mobile internet terminals is getting smaller and smaller,and the size of their components is becoming smaller and smaller.As speakers become smaller and smaller,the challenge of getting good sound on mobile devices is growing.Building an amplifier that produces more output power is simple,but the microspeakers used in most mobile devices are very fragile and easily damaged,and can be easily damaged when the diaphragm drifts above the rated limit.This paper uses a model based on the offset protection algorithm to protect the speaker from excessive diaphragm displacement,which is one of the key reasons for speaker failure.Through the analysis of the speaker structure and the damage mechanism of the speaker,the transfer function of the speaker diaphragm displacement and voltage is obtained.A second order switched capacitor filter is used to implement the transfer function.In the design of second-order switched capacitor filters,the design of a high-gain,low-offset gate-folded cascode op amp is described.The common mode level is required in the filter circuit,and the reference voltage generated by the bandgap reference circuit is obtained by proportional amplification.The simulation results show that the temperature coefficient of the reference voltage is 8.95 ppm/°C in the temperature range of-40 °C to 125 °C.After adding chopping modulation,when there is an offset voltage of 5mV at the op amp input,only 13.6?V ripple appears at the output;the integrated noise of the bandgap reference output voltage is only 4.61?V in the range of 0.1Hz~10Hz.The chopper technology and filtering effectively remove the op amp's offset voltage,significantly reducing the output noise of the bandgap reference,especially the inherent 1/f noise.The designed speaker protection circuit is tested.The speaker protection circuit can trigger the comparator to output a high level enable signal when the amplitude of the speaker diaphragm exceeds the threshold value,so that the AGC reduces the gain of the audio signal path,thereby causing the speaker to vibrate.The membrane amplitude is within the safety threshold to protect the speaker from damage and the test results are consistent with the expected results.