DIMMING EDGE DETECTION FOR POWER CONVERTER

• US 20150303812A1
• Filed: 04/22/2014
• Published: 10/22/2015
• Est. Priority Date: 04/22/2014
• Status: Active Grant

• Current Assignee: Power Integrations Incorporated
• Original Assignee: Power Integrations Incorporated
• Inventors: Mao, Mingming, Pregitzer, Ricardo Luis Janezic, Pastore, Tiziano, Zhang, Michael Yue
• Granted Patent: US 9,369,048 B2
• Time in Patent Office: Days
• 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: H02M 3/33515 with digital control
• CPC Class Codes: H02M 5/293 using semiconductor devices only
• 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

A controller for a power converter includes an edge detection circuit and a drive circuit. The edge detection circuit includes a comparator, a count module, and an edge checking module. The comparator is coupled to output a compare signal in response to comparing an input sense signal and a count signal. The input sense signal is representative of an input voltage of the power converter. The count module is coupled to adjust the count signal to track the input sense signal in response to receiving the compare signal. The edge checking module is coupled to output at least one edge signal in response to the compare signal. The drive circuit is coupled to output a drive signal in response to the at least one edge signal. The drive signal is for controlling a switch coupled to regulate an output of the power converter.

Claims

1. A controller for a power converter, the controller comprising:

an edge detection circuit including;

a comparator coupled to output a compare signal in response to comparing an input sense signal and a count signal, wherein the comparator gives the compare signal a first state when the input sense signal is below the count signal and gives the compare signal a second state when the input sense signal is above the count signal, the input sense signal representative of an input voltage of the power converter;

a count module coupled to adjust the count signal to track the input sense signal in response to receiving the compare signal; and

an edge checking module coupled to output at least one edge signal in response to the compare signal not changing between the first and the second state for a given time period; and

a drive circuit coupled to output a drive signal in response to the at least one edge signal, wherein the drive signal is for controlling a switch coupled to regulate an output of the power converter.

2. The controller of claim 1, wherein the count module decreases the count signal when the compare signal has the first state, and wherein the count module increases the count signal when the compare signal has the second state.

3. The controller of claim 1, wherein the edge checking module includes a trailing edge block coupled to output a trailing edge signal when the compare signal is at the first state for at least the given time period, the at least one edge signal including the trailing edge signal.

4. The controller of claim 3, wherein the trailing edge block includes:

a first counter coupled to output a first counter output in response to the compare signal, wherein the first counter output is periodically incremented when the compare signal is at the first state, and wherein the first counter output is reset when the compare signal changes from the first state to the second state; and

a first digital comparator coupled to assert the trailing edge signal when the first counter output reaches a given threshold representative of the given time period, wherein the given threshold is an integer.

5. The controller of claim 1, wherein the edge checking module includes a leading edge block coupled to output a leading edge signal when the compare signal is at the second state for at least the given time period, the at least one edge signal including the leading edge signal.

6. The controller of claim 5, wherein the leading edge block includes:

a second counter coupled to output a second counter output in response to the compare signal, wherein the second counter output is periodically incremented when the compare signal is at the second state, and wherein the second counter output is reset when the compare signal changes from the second state to the first state; and

a second digital comparator coupled to assert the leading edge signal when the second counter output reaches a given threshold representative of the given time period, wherein the given threshold is an integer.

7. The controller of claim 1 further comprising an oscillator coupled to generate a system clock, wherein the count module and the edge checking module are coupled to receive the system clock, and wherein the count module adjusts the count signal in response to the system clock.

8. The controller of claim 7, wherein the given time period is ten cycles of the system clock.

9. The controller of claim 1, wherein the count module includes a counter coupled to output a digital word of N length in response to the compare signal, the count module further including a digital-to-analog converter (“

DAC”

) coupled to output the count signal in response to the digital word, wherein the count signal is an analog signal.

10. The controller of claim 1, wherein the controller and the switch are included in an integrated circuit.

11. The controller of claim 1, wherein the edge checking module includes:

a register coupled to receive the compare signal and to store L number of values of the compare signal and output the L number of values;

a decoder coupled to receive the L number of stored values and determine a total number of the L number of values which are substantially equal to the first state; and

a comparator coupled to receive the total number and to assert a trailing edge signal when the total number reaches a lower threshold.

12. The controller of claim 1, wherein the edge checking module includes:

a register coupled to receive the compare signal and to store L number of values of the compare signal and output the L number of values;

a decoder coupled to receive the L number of stored values and determine a total number of the L number of values which are substantially equal to the second state; and

a comparator coupled to receive the total number and to assert a leading edge signal when the total number reaches an upper threshold.

13. A method of operating a controller of a power converter, the method comprising:

receiving an input sense signal;

generating a compare signal based on a comparison of the input sense signal and a count signal;

adjusting the count signal to track the input sense signal, wherein the adjusting is based on the compare signal; and

outputting at least one edge signal in response to the compare signal not changing states for a given time period, wherein a switch coupled to regulate an output of the power converter is responsive to the at least one edge signal.

14. The method of claim 13, wherein the compare signal has a first state when the input sense signal is below the count signal, and wherein the compare signal has a second state when the input sense signal is above the count signal, and further wherein said adjusting the count signal includes decreasing the count signal when the compare signal has a first state and increasing the count signal when the compare signal has a second state.

15. The method of claim 14, wherein a trailing edge signal is outputted when the compare signal is at the first state for at least the given time period, the at least one edge signal including the trailing edge signal, and wherein outputting the trailing edge signal indicates that a leading edge dimmer is providing the input sense signal.

16. The method of claim 14, wherein a leading edge signal is outputted when the compare signal is at the second state for at least the given time period, the at least one edge signal including the leading edge signal, and wherein outputting the leading edge signal indicates that a trailing edge dimmer is providing the input sense signal.

17. The method of claim 13, wherein the given time period is an integer number of cycles of a clock.

18. A switched mode power converter comprising:

a switch;

an energy transfer element coupled to the switch and coupled to receive an input sense signal; and

a controller coupled to the switch to regulate an output of the switched mode power converter in response to a dimming signal, wherein the controller includes;

an edge detection circuit including;

a comparator coupled to output a compare signal in response to comparing the dimming signal and a count signal, wherein the comparator gives the compare signal a first state when the dimming signal is below the count signal and gives the compare signal a second state when the dimming signal is above the count signal, the dimming signal representative of an input voltage of the switched mode power converter;

a count module coupled to adjust the count signal to track the dimming signal in response to receiving the compare signal; and

an edge checking module coupled to output at least one edge signal in response to the compare signal not changing between the first and the second state for a given time period; and

a drive circuit coupled to output a drive signal in response to the at least one edge signal, wherein the drive signal is for controlling a switch coupled to regulate an output of the switched mode power converter.

19. The switched mode power converter of claim 18, wherein the count module decreases the count signal when the compare signal has the first state, and wherein the count module increases the count signal when the compare signal has the second state.

20. The switched mode power converter of claim 18, wherein the edge checking module includes a trailing edge block coupled to output a trailing edge signal when the compare signal is at the first state for the given time period, the at least one edge signal including the trailing edge signal.

21. The switched mode power converter of claim 18, wherein the edge checking module includes a leading edge block coupled to output a leading edge signal when the compare signal is at the second state for the given time period, the at least one edge signal including the leading edge signal.

22. The switched mode power converter of claim 18, wherein the edge checking module includes:

a register coupled to receive the compare signal and to store L number of values of the compare signal and output the L number of values;

a decoder coupled to receive the L number of stored values and determine a total number of the L number of values which are substantially equal to the first state; and

a comparator coupled to receive the total number and to assert a trailing edge signal when the total number reaches a lower threshold.

23. The switched mode power converter of claim 18, wherein the edge checking module includes:

a register coupled to receive the compare signal and to store L number of values of the compare signal and output the L number of values;

a decoder coupled to receive the L number of stored values and determine a total number of the L number of values which are substantially equal to the second state; and

a comparator coupled to receive the total number and to assert a leading edge signal when the total number reaches an upper threshold.