Quantization error reduction in constant output current control drivers

• US 9,166,485 B2
• Filed: 03/11/2014
• Issued: 10/20/2015
• Est. Priority Date: 03/11/2013
• Status: Active Grant

• Current Assignee: Signify Holding B.V. (Signify N.V.)
• Original Assignee: Cirrus Logic Incorporated
• Inventors: Maru, Siddharth, He, Zhaohui
• Primary Examiner(s): Le, Tung X
• Application Number:
  US14/203,792
• Publication Number:
  US 20140252990A1
• Time in Patent Office: 588 Days
• Field of Search: 315/209.R, 315/224, 315/225, 315/247, 315/283, 315/287, 315/291, 315/307, 315/308, 315/360
• US Class Current: 1/1
• CPC Class Codes: H02M 1/4258 using a single converter stage both for correction of AC input power factor and generation of a regulated and galvanically isolated DC output voltage H02M1/4241 takes precedence
• CPC Class Codes: H02M 3/156 with automatic control of output voltage or current, e.g. switching regulators
• 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 45/375 using buck topology
• CPC Class Codes: H05B 45/38 using boost topology
• 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]
• CPC Class Codes: Y02B 70/10 Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

Abstract

An electronic system and method includes a controller to control a switching power converter in at least two different modes of operation, a normal mode and an error reduction mode. The controller controls an amount of charge pushed (i.e. delivered) by the switching power converter to a load to reduce a charge quantization error. The charge quantization error represents an amount of charge pushed to the load beyond a target charge amount. The controller determines an amount of charge to be pushed to the load. Based on the amount of charge to be pushed to the load, the controller generates a current control signal that controls a current control switch in the switching power converter. Determination of the control signal depends on whether the controller is operating in normal mode or error reduction mode. The controller attempts to reduce the charge quantization error to avoid power fluctuations.

Claims

1. A method comprising:

operating the switching power converter in a first mode during multiple charge pushing cycles to push a first amount of charge to a load coupled to the switching power converter during a cycle of an input supply voltage to a switching power converter; and

after one or more of the charge pushing cycles and when a remaining amount of charge to be pushed to the load relative to a target amount of charge to be pushed to the load is less than an amount of charge pushed to the load in an immediately preceding charge pushing cycle, operating the switching power converter in an error reduction mode to push a second amount of charge to the load that reduces an error in an amount of charge pushed to the load relative to the target amount that occurs if only the first mode is used to push charge to the load.

2. The method of claim 1 further comprising:

modulating peak current values in the switching power converter during a cycle of the input supply voltage to the switching power converter to push an amount of charge to a load coupled to the switching power converter.

3. The method of claim 1 wherein determining if a remaining amount of charge to be pushed to the load relative to a target amount of charge to be pushed to the load is less than an amount of charge pushed to the load in an immediately preceding charge pushing cycle comprises determining if the remaining amount of charge to be pushed to the load relative to the target amount of charge to be pushed to the load is less than an amount of charge pushed to the load in an immediately preceding charge pushing cycle times a scaling factor.

4. The method of claim 3 wherein the scaling factor is a constant between 0 and 1.

5. The method of claim 1 further comprising:

determining if a remaining amount of charge to be pushed to the load relative to a target amount of charge to be pushed to the load is less than an amount of charge pushed to the load in an immediately preceding charge pushing cycle.

6. The method of claim 1 wherein the load comprises one or more light emitting diodes.

7. The method of claim 1 wherein the switching power converter is a member of a group consisting of a flyback switching power converter, a buck switching power converter, a boost switching power converter, and a boost-buck switching power converter.

8. The method of claim 1 wherein each charge pushing cycle represents a cycle of a current control switch of the switching power converter and the switching power converter includes a transformer to transfer energy to the load, the method further comprising:

determining a target charge to be pushed to the load in accordance with;

Q_TARGET=i_OUT·

Dim·

HLC_PERIOD;

wherein;

Q_TARGET is the target charge to be pushed to the load,

i_OUT is a target current to be pushed to the load,

Dim is a dim level indicated by a dimmer signal, and

HLC_PERIOD is a half line cycle of the input supply voltage provided to the switching power converter;

determining a total amount of charge pushed to the load during the HLC_PERIOD in accordance with;

9. The method of claim 8 wherein i_PEAK(M+y) as a the function of Q_UNPUSHED, Q_PUSHED(M), i_PEAK(n), and T2 comprises:

10. An apparatus comprising:

a controller configured to;

operate a switching power converter in a first mode during multiple charge pushing cycles to push a first amount of charge to a load coupled to the switching power converter during a cycle of an input supply voltage to the switching power converter; and

after one or more of the charge pushing cycles and when a remaining amount of charge to be pushed to the load relative to a target amount of charge to be pushed to the load is less than an amount of charge pushed to the load in an immediately preceding charge pushing cycle, operate the switching power converter in an error reduction mode to push a second amount of charge to the load that reduces an error in an amount of charged pushed to the load relative to the target amount that occurs if only the first mode is used to push charge to the load.

11. The apparatus of claim 10 wherein the controller is further configured to modulate peak current values in a switching power converter during a cycle of an input supply voltage to the switching power converter to push an amount of charge to a load coupled to the switching power converter, wherein modulating the peak current values during the cycle of an input supply voltage.

12. The apparatus of claim 10 wherein to determine if a remaining amount of charge to be pushed to the load relative to a target amount of charge to be pushed to the load is less than an amount of charge pushed to the load in an immediately preceding charge pushing cycle, the controller is further configured to determine if the remaining amount of charge to be pushed to the load relative to the target amount of charge to be pushed to the load is less than an amount of charge pushed to the load in an immediately preceding charge pushing cycle times a scaling factor.

13. The apparatus of claim 12 wherein the scaling factor is a constant between 0 and 1.

14. The apparatus of claim 10 wherein the control is further configured to:

determine if a remaining amount of charge to be pushed to the load relative to a target amount of charge to be pushed to the load is less than an amount of charge pushed to the load in an immediately preceding charge pushing cycle.

15. The apparatus of claim 10 wherein the load comprises one or more light emitting diodes.

16. The apparatus of claim 10 wherein the switching power converter is a member of a group consisting of a flyback switching power converter, a buck switching power converter, a boost switching power converter, and a boost-buck switching power converter.

17. The apparatus of claim 10 wherein each charge pushing cycle represents a cycle of a current control switch of the switching power converter, the switching power converter includes a transformer to transfer energy to the load, and the controller is further configured to:

determine a target charge to be pushed to the load in accordance with;

Q_TARGET=i_OUT·

Dim·

HLC_PERIOD;

wherein;

Q_TARGET is the target charge to be pushed to the load,

i_OUT is a target current to be pushed to the load,

Dim is a dim level indicated by a dimmer signal, and

HLC_PERIOD is a half line cycle of the input supply voltage provided to the switching power converter;

determine a total amount of charge pushed to the load during the HLC_PERIOD in accordance with;

18. The apparatus of claim 17 wherein i_PEAK(M+y) as a the function of Q_UNPUSHED, Q_PUSHED(M), i_PEAK(M), and T2 comprises:

19. An apparatus comprising:

a switching power converter;

a load, coupled to the switching power converter;

a controller, coupled to the switching power converter, wherein the controller is configured to;

operate the switching power converter in a first mode during multiple charge pushing cycles to push a first amount of charge to the load coupled to the switching power converter during a cycle of an input supply voltage to the switching power converter; and

after one or more of the charge pushing cycles and when a remaining amount of charge to be pushed to the load relative to a target amount of charge to be pushed to the load is less than an amount of charge pushed to the load in an immediately preceding charge pushing cycle, operate the switching power converter in an error reduction mode to push a second amount of charge to the load that reduces an error in an amount of charge pushed to the load relative to the target amount that occurs if only the first mode is used to push charge to the load.

20. The apparatus of claim 19 wherein the load comprises one or more light emitting diodes.