Receiver with multiple drive coils

Abstract

The invention provides a moving armature receiver, such as for a hearing aid, with at least two drive coils adapted to be driven by separate drive signal across different frequency ranges. This is achieved by a frequency dividing network adapted to split an audio input signal into first and second audio signals of predetermined different frequency ranges. In preferred two drive coil versions the frequency ranges overlap below 2-3 kHz, whether only one of the drive coils is active above 2-3 kHz. The drive coil being active in the upper frequency range has a lower impedance than the other drive coil. Thus, a more suitable effective impedance characteristics can be obtained. This enables an increased maximum acoustic high frequency output and an enhanced high frequency response of the receiver when driven by a low impedance amplifier, such as a class D amplifier. In a preferred embodiment the receiver is adapted to receive a digital audio input signal, the frequency division is performed digitally and two separate digital signals are applied to two separate digital amplifiers each operatively coupled to drive two separate drive coils. The invention also provides a hearing aid output stage adapted to drive a multiple coil moving armature receiver.

Description

technical field [0001] The present invention relates to moving armature receivers. More precisely, the invention relates to a moving plate receiver suitable for providing a high sound output at high frequencies when driven by an amplifier having a low output impedance. Furthermore, the invention relates to a hearing aid output stage suitable for driving a multi-coil moving plate receiver. Background technique [0002] Today, miniature moving-plate speakers or receivers for hearing aids are increasingly used in voltage-driven applications driven by digital switching amplifiers or Class D amplifiers, such as output amplifiers based on PWM or PDM digital modulation. These digitally modulated amplifiers have output stage characteristics that typically drive the rotor from a very low source impedance, typically 10-50Ω at audio frequency, from a pair of differential amplifier terminals at audio frequency speaker. [0003] Prior art miniature moving plate receivers consist of a ...

AI Technical Summary

Problems solved by technology

[0006] The increased impedance of moving plate receivers results in attenuated audible high-frequency response under small-signal operating conditions, as well as less than expected maximum power output capability in the high-frequency range

These two deficiencies are particularly unacceptable since the vast majority of hearing-impaired people have the greatest hearing loss in the high frequencies and thus most require amplification and output capabilities in the upper parts of the audio range to properly compensate for their respective hearing losses

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