Electromechanical system with predictive back-EMF protection
A predictive back-emf protection methodology for an electromechanical system, including a signal processor that processes a source signal to provide a modified source signal, a driver that converts the modified source signal to a drive signal, and an electromechanical transducer that generates, from the drive signal, a transducer response, and a back-emf signal coupled back to the driver output. A predictive back-emf generator (such as a routine in the signal processor) is characterized by a back-emf transfer function (linear parameterized model of the electromechanical transducer) for transforming an input signal into a transform back-emf representation of a back-emf signal predicted by the back-emf transfer function as a response of the electromechanical transducer to such input signal. The signal processor processes the source signal based on the transform back-emf representation to generate the modified source signal input to the driver. An example application is limiting peaking current in an audio system.
1. An electromechanical system that generates back-emf (electro-motive force), comprising
a signal source to provide a source signal;
a signal driver receiving an input signal based on a modified source signal, and generating a drive signal;
an electromechanical transducer coupled to receive the drive signal, and to generate a transducer output response, and a back-emf signal response;
the signal driver including:
an signal processing module to receive the source signal, and to generate the modified source signal;
an amplifier to receive the modified source signal, and to generate the drive signal, the amplifier having a pre-defined output peak current limit;
the signal processing module including:
a predictive back-emf generator;
a peak current limit control loop including the predictive back-emf generator to generate the modified source signal based on:
the source signal, and
a feedback predictive back-emf signal, and
a peak current reference corresponding to the pre-defined output peak current limit, and
the predictive back-emf generator to generate the predictive back-emf signal based on a pre-defined back-emf transfer function as a representation of the back-emf response of the electromechanical transducer to the modified source signal.
2. The system of claim 1 , wherein the signal processing module including the predictive back-emf generator comprises a routine executed by a digital signal processor.
3. The system of claim 1 , wherein
the signal source is an audio signal source; and
the electromechanical transducer is an audio speaker, where the transducer response is audio signals generated by the audio speaker.
4. The system of claim 1 , wherein the back-emf transfer function is based on a linearized parameterized model of the electromechanical transducer.
5. The system of claim 1 , wherein the peak current limit control loop operates in a voltage domain, with the predictive back-emf signal and the pre-defined output peak current limit corresponding to currents expressed in the voltage domain.
6. The system of claim 1 , wherein based on the modified source signal, the signal driver generates the drive signal so that the amplifier does not exceed the pre-defined output peak current limit.
7. A signal driver circuit for use in a system with a signal source to generate a source signal, and an electromechanical transducer to generate, in response to a drive signal based on the source signal, a transducer output response, and a back-emf signal response, the circuit comprising:
a signal processing module to receive the source signal, and to generate a modified source signal;
an amplifier to receive the modified source signal, and to generate the drive signal, the amplifier having a pre-defined output peak current limit;
the signal processing module including:
a predictive back-emf generator;
a peak current limit control loop including the predictive back-emf generator to generate the modified source signal based on:
the source signal, and
a feedback predictive back-emf signal, and
a peak current reference corresponding to the pre-defined output peak current limit, and
the predictive back-emf generator to generate the predictive back-emf signal based on a pre-defined back-emf transfer function as a representation of the back-emf response of the electromechanical transducer to the modified source signal.
8. The circuit of claim 7 , wherein the signal processing module including the predictive back-emf generator comprises a routine executed by a digital signal processor.
9. The circuit of claim 7 , wherein
the signal source is an audio signal source; and
the electromechanical transducer is an audio speaker, where the transducer response is audio signals generated by the audio speaker.
10. The system of claim 7 , wherein the back-emf transfer function is based on a linearized parameterized model of the electromechanical transducer.
11. The circuit of claim 7 , wherein the peak current limit control loop operates in a voltage domain, with the predictive back-emf signal and the pre-defined output peak current limit corresponding to currents expressed in the voltage domain.
12. The circuit of claim 7 , wherein based on the modified source signal, the signal driver generates the drive signal so that the amplifier does not exceed the pre-defined output peak current limit.
13. A signal processor for use in a system with a signal source to generate a source signal, a signal driver including an amplifier to generate a drive signal based on the source signal, and an electromechanical transducer to generate, in response to the drive signal, a transducer output response, and a back-emf signal response, the signal processor comprising:
a predictive back-emf generator;
a peak current limit control loop including the predictive back-emf generator to generate the modified source signal based on:
the source signal, and
a feedback predictive back-emf signal, and
a peak current reference corresponding to a pre-defined output peak current limit of the amplifier;
the predictive back-emf generator to generate the predictive back-emf signal based on a pre-defined back-emf transfer function as a representation of the back-emf response of the electromechanical transducer to a modified source signal for input to the signal driver.
14. The signal processor of claim 13 , wherein the signal processor including the predictive back-emf generator comprises a routine executed by a digital signal processor.
15. The signal processor of claim 13 , wherein
the signal source is an audio signal source; and
the electromechanical transducer is an audio speaker, where the transducer response is audio signals generated by the audio speaker.
16. The signal processor of claim 13 , wherein the back-emf transfer function is based on a linearized parameterized model of the electromechanical transducer.
17. The signal processor of claim 13 , wherein the peak current limit control loop operates in a voltage domain, with the predictive back-emf signal and the pre-defined output peak current limit corresponding to currents expressed in the voltage domain.
18. The signal processor of claim 13 , wherein based on the modified source signal, the signal driver generates the drive signal so that the amplifier does not exceed the pre-defined output peak current limit.