Method and Apparatus for Driving Low-Power Loads from AC Sources

• US 20100320840A1
• Filed: 06/18/2010
• Published: 12/23/2010
• Est. Priority Date: 06/18/2009
• Status: Active Grant

• Current Assignee: ADSP Consulting, LLC
• Original Assignee: ADSP Consulting, LLC
• Inventors: Fridberg, Mikhail
• Granted Patent: US 8,729,729 B2
• Time in Patent Office: Days
• US Class Current: 307/52
• CPC Class Codes: H02J 1/14 Balancing the load in a network
• CPC Class Codes: H05B 35/00 Electric light sources using a combination of different types of light generation
• CPC Class Codes: H05B 45/3725 Switched mode power supply [SMPS]
• CPC Class Codes: Y02B 20/30 Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]

Abstract

Method and apparatus for providing controllable power to the load via AC-line power source where load is less than minimal required for proper operation of said source. In one example LED lamp connected to AC power source via conventional triac-based dimmer uses less power than minimum required for proper operation of said dimmer. In another example LED lamp connected to AC power source via device known as electronic transformer uses less power than required for proper operation of said electronic transformer.

Claims

1. A driver for driving a load from an output from an AC source, comprising:

a) a rectifier having an AC input coupled to the output from the AC source and a rectified DC output;

b) a current source having an output for driving the load and an input;

c) an energy storage device for storing energy, coupled to the input of the current source for supplying energy to the current source;

d) a controller having an input coupled to the DC output of the rectifier and an output coupled to the energy storage device, comprising;

i) a switch having a control input for controlling an open or closed state of the switch, coupled between the input of the controller and the output of the controller, such that current passes through the controller from the input to the output when a signal at the control input causes the switch to be in the closed state, storing energy in the energy storage device; and

ii) an intelligent controller having an output coupled to the control input of the switch, and a voltage sensing input coupled to the energy storage device;

the intelligent controller being programmed to close the switch at a frequency sufficient for the AC source to operate properly, and maintaining the switch closed for a gate period chosen between;

i) a minimum gate period chosen to provide a minimum required power draw for operation of the AC source; and

ii) a second gate period, longer than the minimum gate period;

the intelligent controller being programmed to chose the second gate period during a charge time period starting when a charge state of the energy storage device as sensed by the voltage sensing input drops below a lower limit.

2. The driver of claim 1, in which the charge time period is terminated when the charge state of the energy storage device as sensed by the voltage sensing input exceeds an upper limit.

3. The driver of claim 1 in which the gate period is determined asynchronously.

4. The driver of claim 1, in which the intelligent controller further comprises a phase-locked loop locked to a frequency of the AC input voltage, and the gate period is synchronously based on the phase-locked loop.

5. The driver of claim 1, further comprising an inductor coupled between the DC output of the rectifier and the input of the current source.

6. The driver of claim 1, in which the intelligent controller further comprises a dimmer control output and the current source further comprises a control input, and the intelligent controller is programmed to determine an amount of dimming that is demanded by a user by determining a fraction of the AC input that is being cut-off by the power source and sending a control command on the dimmer control output to the control input of the current source to dim the output to the load.

7. The driver of claim 1, further comprising an active power factor controller coupled between the DC output of the rectifier and the input of the current source.

8. The driver of claim 1, in which the rectifier is a full-wave rectifier.

9. The driver of claim 1, further comprising a load resistor in series with a test switch having a control input, the resistor and switch being coupled across the DC output of the rectifier, and in which the intelligent controller further comprises a test output coupled to the control input of the test switch, such that the intelligent control can force current from the AC source to be drawn through the rectifier into the load resistor by closing the test switch.

10. The driver of claim 1, further comprising a load resistor in series with a test switch having a control input, the resistor and switch being coupled across the output of the AC source, and in which the intelligent controller further comprises a test output coupled to the control input of the test switch, such that the intelligent control can force current from the AC source to be drawn into the load resistor by closing the test switch.

11. The driver of claim 1 in which the energy storage device is a capacitor.

12. A method of driving a low-power load from an AC source, using a load driver comprising a rectifier coupled to the output from the AC source proving a rectified DC output to an energy storage device for storing energy, a controller programmed to gate the DC output of the rectifier, allowing the DC output to store energy in the energy storage device during a gate period, and a current source taking energy from the energy storage device and supplying power to the load, the method comprising:

opening the gate period on a frequency sufficient for the AC source to operate properly,

closing the gate period at the end of either a minimum gate period chosen to provide a minimum required power draw for operation of the AC source;

or a second gate period, longer than the minimum gate period;

choosing the second gate period during a charge time period starting when a charge state of the energy storage device drops below a lower limit.

13. The method of claim 12, in which the charge time period is terminated when the charge state of the energy storage device exceeds an upper limit.