Switching power supply with power feedback to keep lamp's brightness constant
First Claim
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1. A power supply comprising:
- a filter operable to prevent high frequency current from entering input voltage source;
a protection operable to protect the power supply at over current condition;
a bridge rectifier operable to rectify an alternating current (AC) voltage and generate a DC input voltage;
a converter to convert an input voltage to an output voltage for an output device with constant power;
a controller operable to adjust on time of main switch in the converter to keep output at constant power, the controller comprising;
(i) a signal process circuit operable to generate a power feedback signal as multiplication product of voltage feedback signal and current feedback signal;
(ii) a reference operable to set a voltage signal proportional to a predetermined power level;
(iii) an opamp operable to compare power feedback signal with a reference signal and generate a power error signal with gain;
(iv) a saw tooth generator operable to generate a saw tooth signal;
(v) a comparator operable to compare power error signal with saw tooth signal and generate a pulse; and
(vi) a driver operable to control on time of the main switch of the converter to keep output at constant power;
a voltage feedback circuit operable to sample output voltage and send the voltage feedback signal proportional to output voltage back to the controller; and
a current feedback circuit operable to sample output current and send the current feedback signal proportional to output current back to the controller.
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Abstract
A power supply and methods are provided. In one implementation, the power supply includes a switching converter with power feedback circuit to output constant power to keep lamp at constant brightness. The power feedback circuits include a current feedback circuit and a voltage feedback circuit. The power supply further includes a controller operable to adjust on time or duty cycle of main switch to keep the output power constant.
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Citations
5 Claims
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1. A power supply comprising:
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a filter operable to prevent high frequency current from entering input voltage source; a protection operable to protect the power supply at over current condition; a bridge rectifier operable to rectify an alternating current (AC) voltage and generate a DC input voltage; a converter to convert an input voltage to an output voltage for an output device with constant power; a controller operable to adjust on time of main switch in the converter to keep output at constant power, the controller comprising; (i) a signal process circuit operable to generate a power feedback signal as multiplication product of voltage feedback signal and current feedback signal; (ii) a reference operable to set a voltage signal proportional to a predetermined power level; (iii) an opamp operable to compare power feedback signal with a reference signal and generate a power error signal with gain; (iv) a saw tooth generator operable to generate a saw tooth signal; (v) a comparator operable to compare power error signal with saw tooth signal and generate a pulse; and (vi) a driver operable to control on time of the main switch of the converter to keep output at constant power; a voltage feedback circuit operable to sample output voltage and send the voltage feedback signal proportional to output voltage back to the controller; and a current feedback circuit operable to sample output current and send the current feedback signal proportional to output current back to the controller. - View Dependent Claims (2, 3, 4, 5)
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Specification