Single-stage digital power converter for driving LEDs

• US 20060214603A1
• Filed: 03/22/2005
• Published: 09/28/2006
• Est. Priority Date: 03/22/2005
• Status: Active Grant

• Current Assignee: Semiconductor Components Industries LLC (ON Semiconductor Corporation)
• Original Assignee: Fairchild Semiconductor Corporation (ON Semiconductor Corporation)
• Inventors: Oh, In-Hwan, Rayabhari, Madhu
• Granted Patent: US 7,378,805 B2
• Time in Patent Office: Days
• US Class Current: 315/246
• CPC Class Codes: H05B 45/20 Controlling the colour of the light
• CPC Class Codes: H05B 45/3725 Switched mode power supply [SMPS]
• CPC Class Codes: H05B 47/25 Circuit arrangements for protecting against overcurrent
• CPC Class Codes: Y02B 20/30 Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]

Abstract

This invention presents a single-stage power converter for driving many number of Light-Emitting-Diode (LED). The power converter converts an AC input voltage into DC current source and regulates the current flowing into the LED. In addition, the AC input current is controlled to have a sinusoidal waveform synchronized with the AC input voltage so that AC input Power Factor is corrected. Hence, both of Power Factor Correction (PFC) and LED current regulation are obtained simultaneously by using a single power conversion stage. So higher efficiency with low cost can be obtained.

Claims

1. A power converter for driving at least one light-emitting diode (LED), the power converter comprising a single stage operable to provide both power factor correction (PFC) for input power and control of current delivered to the at least one LED.

2. The power converter of claim 1 wherein the single stage uses digital control for control of current delivered to the at least one LED and analog control for over-current protection.

3. The power converter of claim 1 wherein the PFC for input power synchronizes an AC current and an AC voltage of the input power.

4. The power converter of claim 1 wherein the PFC for input power reduces total-harmonic-distortion (THD).

5. The power converter of claim 1 wherein the single stage comprises a sine table module for reducing total-harmonic-distortion (THD).

6. The power converter of claim 1 wherein the single stage comprises means for identifying a synchronization condition for the input power.

7. The power converter of claim 6 wherein the input power has an AC voltage component, and wherein the means for identifying a synchronization condition is operable to identify at least one instance of the AC voltage component crossing a zero point.

8. The power converter of claim 1 wherein the single stage comprises:

a switch through which a current flows according to a duty cycle; and

a controller coupled to the switch for controlling the duty cycle of the switch.

9. The power converter of claim 8 wherein:

when the switch is turned off, more current is delivered to the at least one LED, thus causing the at least one LED to be brighter; and

when the switch is turned on, less current is delivered to the at least one LED, thus causing the at least one LED to be dimmer.

10. A single-stage power converter for driving at least one light-emitting diode (LED) using an input power, the converter comprising:

means for providing power factor correction (PFC) for the input power; and

means for controlling current delivered to the at least one LED.

11. The single-stage power converter of claim 10 wherein the means for providing PFC comprises:

a resistor and a diode for identifying a synchronization condition for the input power; and

a sine table module for synchronizing a current component and a voltage component of the input power.

12. The single-stage power converter of claim 10 wherein the means for controlling current comprises a current sensing device for developing a signal indicative of the amount of current flowing through one branch of the power converter.

13. The single-stage power converter of claim 10 comprising a switch through which a current flows according to a duty cycle, wherein the means for controlling is coupled to the switch for controlling the duty cycle.

14. The single-stage power converter of claim 13 wherein:

when the switch is turned off, more current is delivered to the at least one LED, thus causing the at least one LED to be brighter; and

when the switch is turned on, less current is delivered to the at least one LED, thus causing the at least one LED to be dimmer.

15. The single-stage power converter of claim 10 wherein the means for controlling provides over-current protection.

16. The single-stage power converter of claim 15 wherein the means for controlling uses digital control for controlling current delivered to the at least one LED and analog control for over-current protection.

17. A power converter for driving a plurality of groups of light-emitting diodes (LEDs) using an input power, wherein the diodes in each group are the same color, the converter comprising:

means for providing power factor correction (PFC) for the input power; and

means for controlling current delivered to the at least one LED.

18. A single-stage power converter for driving at least one light-emitting diode (LED) comprising:

an input terminal for receiving a rectified alternating current (AC) input power;

an output terminal at which a driving current is provided to the at least one LED;

a switch operable to be controlled according to a duty cycle for increasing and decreasing the driving current provided to the at least one LED;

means for providing power factor correction (PFC) for input power, said means comprising means for identifying a synchronization condition in the input power;

means for controlling current provided to the at least one LED by adjusting the duty cycle of the switch, said means comprising a current sensing device coupled to the switch for developing a signal indicative of the amount of current flowing to the at least one LED;

a transistor coupled to the primary winding of the transformer for controlling the current flowing through the primary winding;

a current sensing device coupled to the transistor for developing a signal indicative of the amount of current flowing through the power converter, the current sensing device forming part of a current control loop for the power converter;

a controller operable to provide analog control of the current control loop and digital control of the voltage control loop of the power converter.