Switching power supply with power feedback to keep lamp's brightness constant

• US 20120268039A1
• Filed: 04/20/2011
• Published: 10/25/2012
• Est. Priority Date: 04/20/2011
• Status: Active Grant

• Current Assignee: Upright Lighting LLC
• Original Assignee: Upright Lighting LLC, Xi'An Upright Photoeletric Technology Co., Ltd.
• Inventors: Chen, Liang
• Granted Patent: US 8,659,238 B2
• Time in Patent Office: Days
• US Class Current: 315/308
• CPC Class Codes: H02M 1/0003 Details of control, feedback or regulation circuits
• CPC Class Codes: H02M 3/33523 with galvanic isolation between input and output of both the power stage and the feedback loop
• CPC Class Codes: H02M 7/06 using discharge tubes without control electrode or semiconductor devices without control electrode
• CPC Class Codes: H05B 45/14 using electrical feedback from LEDs or from LED modules
• CPC Class Codes: H05B 45/3725 Switched mode power supply [SMPS]
• CPC Class Codes: H05B 45/38 using boost topology
• CPC Class Codes: H05B 45/385 using flyback topology

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.

Claims

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;

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.

2. The power supply of claim 1, wherein the controller comprises:

a signal process operable to generate a power feedback signal as multiplication product of voltage feedback signal and current feedback signal;

a reference operable to set a voltage signal proportional to a predetermined power level;

an opamp operable to compare power feedback signal with a reference signal and generate a power error signal with gain;

a sawtooth generator operable to generate a sawtooth signal;

a comparator operable to compare power error signal with sawtooth signal and generate a pulse; and

a driver operable to control on time of main switch of the converter to keep output at constant power.

3. The power supply of claim 1, wherein the output is connected to an output device, in one implementation, the output device is a lamp.

4. The power supply of claim 1, wherein:

the converter output a constant power to a lamp to keep the lamp at constant brightness.

5. The power supply of claim 1, wherein:

the converter is a flyback converter.

6. The power supply of claim 1, wherein:

the controller is operable to adjust on time of main switch in the converter.

7. A method of operation for a power supply, the method comprising:

rectifying an alternating current (AC) voltage and generating a DC input voltage;

converting the input voltage into an output voltage;

adjusting the on time of main switch in the converter to output a constant power;

sampling current signal that is proportional to output current;

sampling voltage signal that is proportional to output voltage;

generating a power signal that is proportional to output power;

generating a power error signal by comparing power signal to a reference;

generating a pulse by comparing power error signal to a sawtooth waveform; and

sending a pulse to control on time of a main switch of the converter to keep output at constant power.