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US 6,476,683 B1Granted
Adaptive switching speed control for pulse width modulation
AssigneeYazaki North America, Inc.
InventorsMasayuki Saito, Kang Li
Life of this patent
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Abstract
A pulse width modulation apparatus and method operates a switch at one of four slew rates to minimize electromagnetic and harmonic interference or switching losses. One of the four slew rates is selected based on a detected over-current condition, with or without a start up operation condition, an over-temperature condition and a normal working mode.
Claims37
A pulse width modulation system comprising:
- at least one switch operating at least one load according to pulse width modulation;
- at least one temperature detector;
- at least one adaptive switching speed controller which operates the switch at varying slew rates according to an ambient temperature detected by the temperature detector;
- and
- at least one current detector disposed at the switch, wherein said adaptive switching speed controller deactivates the switch at a large slew rate when a current detected by said current detector exceeds a current threshold, wherein said large slew rate is larger than any of said varying slew rates.
2 more elements
A pulse width modulation system comprising:
- at least one switch operating at least one load according to pulse width modulation;
- at least one temperature detector;
- and
- at least one adaptive switching speed controller which operates the switch at varying slew rates according to an ambient temperature detected by the temperature detector;
- wherein said adaptive switching speed controller operates the switch at a first slew rate when the ambient temperature detected by said temperature detector is not greater than a temperature threshold and said adaptive switching speed controller operates the switch at a second slew rate when the ambient temperature detected by the temperature detector is greater than the temperature threshold, wherein the second slew rate is larger than the first slew rate.
2 more elements
A pulse width modulation system comprising:
- at least one switch operating at least one load according to pulse width modulation;
- a current detector disposed at a switch;
- at least one adaptive switching speed controller which operates the switch at varying slew rates according to a current detected by a current detector wherein said adaptive switching speed controller is operable to operate the switch at a first slew rate and is operable to deactivate the switch at a second slew rate only when the current detected by the current detector is more than a threshold current,
- wherein the second slew rate is larger than said first slew rate;
- and
- a PWM controller providing an output to the adaptive switching speed controller, said PWM controller detecting a start up mode of operation, wherein said adaptive switching speed controller deactivates the switch at a third slew rate when the PWM controller detects the start up mode of operation, wherein said third slew rate is smaller than said second slew rate and is larger than said first slew rate.
3 more elements
A pulse width modulation system comprising:
- at least one switch operating at least one load according to pulse width modulation;
- a current detector disposed at a switch;
- at least one adaptive switching speed controller which operates the switch at varying slew rates according to a current detected by a current detector wherein said adaptive switching speed controller is operable to operate the switch at a first slew rate and is operable to deactivate the switch at a second slew rate only when the current detected by the current detector is more than a threshold current,
- wherein the second slew rate is larger than said first slew rate;
- and
- at least one control circuit, wherein when the current detected by said detector exceeds the threshold current, said control circuit repetitively activates and deactivates the switch during an on duration of a pulse width modulation cycle.
3 more elements
A method of setting a rise and fall slew rate for a switch in a pulse width modulation system comprising steps of:
- detecting an ambient temperature;
- comparing the detected ambient temperature with a temperature threshold value;
- setting a rise and fall slew rate for a pulse of the switch according to a result of the comparing step.
A method of setting a rise and fall slew rate for a pulse width modulation system comprising steps of:
- detecting a current output at a switch;
- comparing the detected current with a current threshold;
- setting a rise and fall slew rate for a pulse of the switch according to a result of the comparing step,
- wherein said setting step comprises setting a first rise slew rate and first fall slew rate when the detected current is not greater than the current threshold;
- and
- setting a second fall slew rate for a pulse of the switch only when the detected current is greater than the current threshold,
- wherein said second fall slew rate is larger than said first fall slew rate.
4 more elements
A pulse width modulation system comprising:
- at least one switch operating at least one load according to pulse width modulation;
- at least one temperature detector;
- and
- a at least one adaptive switching speed controller which operates the switch at varying slew rates according to an ambient temperature detected by the temperature detector relative to a threshold value;
- wherein said load comprises a vehicle lamp connected to said switch.
2 more elements
A pulse width modulation system comprising:
- at least one switch connected to a vehicle lamp and operating said vehicle lamp according to pulse width modulation;
- a current detector disposed at a switch;
- and
- at least one adaptive switching speed controller which operates the switch at varying slew rates according to the current detected by the current detector relative to a current threshold.
1 more element
A method of setting a rise and fall slew rate for a pulse width modulation system comprising steps of:
- detecting a current output at a switch;
- comparing the detected current with a current threshold;
- setting a rise and fall slew rate for a pulse of the switch according to a result of the comparing step;
- and
- operating a vehicle lamp according to the set rise and fall slew rate for the switch.
2 more elements
Dependencies are inferred from the claim text.