Over-current protection for a switch mode class D audio amplifier
First Claim
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1. A method for detecting and solving an over-current situation of a pulse-width modulated system comprising the steps of:
- (1) providing a pulse-width modulated system comprising a filter, means to detect an over-current situation, a PWM modulator, a pulse generator, means to multiplex output from pulse generator with output from PWM modulator;
(2) starting normal operation of the pulse-width modulated system;
(3) monitoring continuously data stream out of the PWM modulator in order to detect an over-current situation until the pulse modulated system is switched off;
(4) checking if an over-current situation is detected and, if so, go to step (5), otherwise repeat step (4);
(5) setting an over-current signal;
(6) enabling the pulse generator generating pulses having a supply-scalable duty cycle;
(7) multiplexing the output of the pulse generator with PWM modulator output;
(8) bounding output current by suitable modulation caused by pulses from the pulse generator;
(9) resetting over-current signal after over-current situation is solved; and
(10) resuming normal operation of the pulse-width modulated system and go back to step (4).
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Abstract
Circuits and methods for over-current protection of pulse-width modulation systems such as switch mode class D audio systems, DC-to-DC converters, or switch mode power supplies have been disclosed. Over-current protection has been achieved by introducing supply-scalable pulses to bring the modulation index of PWM pulses to a safe level. Additionally to the over-current protection a recovery circuit and method to be applied right after an over-current situation has been disclosed.
17 Citations
33 Claims
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1. A method for detecting and solving an over-current situation of a pulse-width modulated system comprising the steps of:
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(1) providing a pulse-width modulated system comprising a filter, means to detect an over-current situation, a PWM modulator, a pulse generator, means to multiplex output from pulse generator with output from PWM modulator; (2) starting normal operation of the pulse-width modulated system; (3) monitoring continuously data stream out of the PWM modulator in order to detect an over-current situation until the pulse modulated system is switched off; (4) checking if an over-current situation is detected and, if so, go to step (5), otherwise repeat step (4); (5) setting an over-current signal; (6) enabling the pulse generator generating pulses having a supply-scalable duty cycle; (7) multiplexing the output of the pulse generator with PWM modulator output; (8) bounding output current by suitable modulation caused by pulses from the pulse generator; (9) resetting over-current signal after over-current situation is solved; and (10) resuming normal operation of the pulse-width modulated system and go back to step (4). - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
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18. A circuit for a digital over-current protection of a pulse-width modulation system comprising:
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a filter capable of filtering input signals of the pulse-with modulation system; a PWM modulator having inputs and an output, wherein a first input is the output of said filter, wherein said PWM modulator is capable of receiving triangular pulses at a second input, and wherein said PWM modulator capable of generating a PWM data stream at the output; a detector capable of monitoring said data stream , wherein said detector is capable of receiving clock pulses as input and, when no transitions in the data stream occur within a defined time period, is capable of setting an over-current flag; a pulse generator, while the over-current flag is set, is capable of generating pulses having a supply-scalable duty cycle; a multiplexing means capable of multiplexing pulses generated by said pulse generator with the PWM data stream from the PWM modulator; a power stage having an input and an output, wherein the input is the output of said multiplexing means and the output is connected to a load and to a feedback circuit; and said feedback circuit having an input and an output wherein the input is connected to the output of the power stage and the output of the feedback circuit is connected to the input of the pulse-width modulated system. - View Dependent Claims (19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33)
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Specification