Dimming control for a switching power supply

• US 9,320,091 B2
• Filed: 10/24/2013
• Issued: 04/19/2016
• Est. Priority Date: 04/20/2010
• Status: Expired due to Fees

• Current Assignee: Power Integrations Incorporated
• Original Assignee: Power Integrations Incorporated
• Inventors: Gaknoki, Yury, Mao, Mingming
• Primary Examiner(s): Behm, Harry
• Application Number:
  US14/062,227
• Publication Number:
  US 20140049241A1
• Time in Patent Office: 908 Days
• Field of Search: 323/300, 323/905, 323237-239, 323241-244, 323/246
• US Class Current: 1/1
• CPC Class Codes: H02M 3/33507 with automatic control of the output voltage or current, e.g. flyback converters H02M3/33561, H02M3/33569 take precedence
• 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 45/385 using flyback topology
• CPC Class Codes: Y02B 20/30 Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]

Abstract

An example controller includes a measurement block and a drive block. The measurement block determines an amount of time that a dimmer circuit, that is coupled to an input of a power supply, disconnects an ac input voltage. The drive block generates a drive signal to control switching of a switch included in the power supply. The drive block operates a closed loop dimming control when the amount of time is less than or equal to a threshold and operates an open loop dimming control when the amount of time is greater than the threshold. The closed loop dimming control includes setting one or more operating conditions of the drive signal in response to a feedback signal that is representative of an output quantity of the power supply. The open loop dimming control includes holding the one or more operating conditions of the drive signal to a value.

Claims

1. A controller for a power supply having a dimmer circuit coupled to an input of the power supply, the controller comprising:

a measurement block to be coupled to receive an input sense signal and to determine an amount of time that the dimmer circuit disconnects an ac input voltage from the input of the power supply based on the input sense signal; and

a drive block coupled to the measurement block and coupled to generate a drive signal to control switching of a switch included in the power supply, wherein the drive block operates a closed loop dimming control in response to an output of the measurement block indicating that the amount of time is less than or equal to a threshold, wherein the closed loop dimming control includes setting one or more operating conditions of the drive signal in response to a feedback signal that is representative of an output quantity of the power supply, and wherein the drive block operates an open loop dimming control in response to the output of the measurement block indicating that the amount of time is greater than the threshold, wherein open loop dimming control includes holding the one or more operating conditions of the drive signal to a value.

2. The controller of claim 1, wherein the one or more operating conditions includes one or more condition selected from the group consisting of switching frequency, switch on-time, switch off-time, and duty cycle.

3. The controller of claim 1, wherein the drive block sets the value of the one or more operating conditions of the drive signal when the amount of time is equal to the threshold, and holds the one or more operating conditions to the value when the amount of time is greater than the threshold.

4. The controller of claim 1, wherein the value is a predetermined value and the drive logic block holds the one or more operating conditions to the predetermined value when the amount of time is greater than the threshold.

5. The controller of claim 1, wherein the input sense signal is a voltage sense signal representative of a dimmer output voltage of the dimmer circuit.

6. The controller of claim 1, wherein the input sense signal is a current sense signal representative of a switch current through the switch.

7. The controller of claim 1, wherein the input sense signal is a voltage sense signal representative of a rectified input voltage of the power supply.

8. The controller of claim 1, wherein the measurement block includes a logic gate coupled to generate the output of the measurement block that is representative of whether the amount of time is greater than the threshold.

9. The controller of claim 1, wherein the measurement block includes a counter coupled to generate the output of the measurement block that is a digital signal representative of the amount of time that dimmer circuit disconnects the ac input voltage from the input of the power supply.

10. A controller for a power supply having a dimmer circuit coupled to an input of the power supply, the controller comprising:

a measurement block to be coupled to receive an input sense signal and to determine an amount of time that the dimmer circuit disconnects an ac input voltage from the input of the power supply based on the input sense signal; and

a drive circuit coupled to the measurement block and coupled to control switching of a switch included in the power supply, wherein the drive circuit controls switching of the switch in response to a feedback signal when an output of the measurement block indicates that the amount of time is less than or equal to a threshold, and wherein the drive circuit controls switching of the switch independent of the feedback signal when the output of the measurement block indicates that the amount of time is greater than the threshold, wherein the feedback signal is representative of an output quantity of the power supply.

11. The controller of claim 10, wherein the drive circuit generates a drive signal to control switching of the switch, and wherein the drive circuit sets one or more operating conditions of the drive signal selected from the group consisting of switching frequency, switch on-time, switch off-time, and duty cycle.

12. The controller of claim 11, wherein the drive circuit sets the one or more operating conditions of the drive signal to a value responsive to the feedback signal in response to the output of the measurement block indicating that the amount of time is equal to the threshold, and wherein the drive circuit holds the one or more operating conditions to the value in response to the output of the measurement block indicating that the amount of time is greater than the threshold.

13. The controller of claim 11, wherein the drive circuit sets the one or more operating conditions of the drive signal to a predetermined value in response to the output of the measurement block indicating that the amount of time is transitioning from less than the threshold to greater than the threshold and wherein the drive circuit holds the one or more operating conditions to the predetermined value in response to the output of the measurement block indicating that the amount of time is greater than the threshold.

14. The controller of claim 10, wherein the input sense signal is a voltage sense signal representative of a dimmer output voltage of the dimmer circuit.

15. The controller of claim 10, wherein the input sense signal is a current sense signal representative of a switch current through the switch.

16. The controller of claim 10, wherein the input sense signal is a voltage sense signal representative of a rectified input voltage of the power supply.

17. The controller of claim 10, wherein the measurement block includes a logic gate coupled to generate the output of the measurement block that is representative of whether the amount of time is greater than the threshold.

18. The controller of claim 10, wherein the measurement block includes a counter coupled to generate the output of the measurement block that is a digital signal representative of the amount of time that dimmer circuit disconnects the ac input voltage from the input of the power supply.

19. A controller for a power supply having a dimmer circuit coupled to an input of the power supply, the controller comprising:

a measurement block to be coupled to receive an input sense signal and to generate a dimming control signal in response thereto, wherein the dimming control signal indicates whether an amount of time that the dimmer circuit disconnects an ac input voltage from the input of the power supply is greater than a threshold; and

a drive circuit coupled to the measurement block and to be coupled to control switching of a switch included in the power supply, wherein the drive circuit controls switching of the switch in response to a feedback signal when the dimming control signal indicates that the amount of time is less than or equal to the threshold, and wherein the drive circuit controls switching of the switch independent of the feedback signal when the dimming control signal indicates that the amount of time is greater than the threshold, wherein the feedback signal is representative of an output quantity of the power supply.

20. The controller of claim 19, wherein the drive circuit comprises:

a feedback reference circuit coupled to receive the feedback signal and a reference signal; and

a drive signal generator coupled to receive the dimming control signal and an output of the feedback reference circuit, wherein the drive signal generator generates the drive signal responsive to the output of the feedback reference circuit when the dimming control signal indicates that the amount of time is less than or equal to the threshold, and wherein the drive signal generator generates the drive signal independent of the output of the feedback reference circuit when the amount of time is greater than the threshold.

21. The controller of claim 20, wherein the drive signal generator comprises:

an integrator coupled to receive the output of the feedback reference circuit and coupled to generate a value representative of the output quantity of the power supply;

a state machine coupled to generate the drive signal and to set one or more operating conditions of the drive signal; and

a dimming control switch coupled between the integrator and the state machine, wherein the dimming control switch is coupled to be open in response to the dimming control signal indicating that the amount of time is greater than the threshold and closed responsive to the dimming control signal indicating that the amount of time is not greater than the phase threshold, and wherein the state machine sets the one or more operating conditions of the drive signal responsive to the value generated by the integrator when the dimming control switch is closed.

22. The controller of claim 21, wherein the drive signal generator further comprises a hold capacitor coupled between the dimming control switch and the state machine to store the value generated by the integrator, wherein the state machine sets the one or more operating conditions of the drive signal responsive to the value stored in the hold capacitor when the dimming control switch is open.

23. The controller of claim 20, wherein the drive signal generator comprises:

an integrator coupled to receive the output of the feedback reference circuit and coupled to generate a value representative of the output quantity of the power supply; and

a state machine coupled to generate the drive signal and to update one or more operating conditions of the drive signal responsive to the value generated by the integrator when the dimming control signal indicates that the amount of time is less than or equal to the threshold, and wherein the state machine does not update the one or more operating conditions and does not respond to the value generated by the integrator when the dimming control signal indicates that the amount of time is greater than the threshold.