Methods and apparatus for switching regulator control

• US 20070229001A1
• Filed: 04/03/2006
• Published: 10/04/2007
• Est. Priority Date: 04/03/2006
• Status: Active Grant

• Current Assignee: Allegro Microsystems Incorporated (Sanken Electric Company Limited)
• Original Assignee: Allegro Microsystems Incorporated (Sanken Electric Company Limited)
• Inventors: Christie, Robert, Togneri, Aldo, McIntosh, James
• Granted Patent: US 7,649,325 B2
• Time in Patent Office: Days
• US Class Current: 315/307
• CPC Class Codes: H02M 3/156 with automatic control of output voltage or current, e.g. switching regulators
• CPC Class Codes: H05B 45/10 Controlling the intensity of the light
• CPC Class Codes: H05B 45/3725 Switched mode power supply [SMPS]
• CPC Class Codes: H05B 45/38 using boost 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 circuit includes a capacitive element for coupling across a load element to be energized by a DC signal, a first sense element to monitor an instantaneous sum of currents through the load element and the capacitive element, a switching element to control current through the first sense element, a second sense element coupled to the switching element to sense current through the switching element, an energy storage element coupled to the switching element, a unidirectional current flow element allowing current flow to the load element, and a converter circuit to control the switching element, wherein the converter circuit regulates to the current level monitored across the first sense element, and wherein a converter regulation loop includes a dominant pole to average the current sensed through the first sense element.

Claims

1. A circuit, comprising;

a capacitive element for coupling across a load element to be energized by a DC signal;

a first sense element to monitor an instantaneous sum of currents through the load element and the capacitive element;

a switching element to control current through the first sense element;

a second sense element coupled to the switching element to sense current through the switching element;

an energy storage element coupled to the switching element,

a unidirectional current flow element allowing current flow to the load element; and

a converter circuit to control the switching element;

wherein the converter circuit regulates to the current level monitored across the first sense element, and wherein a converter regulation loop includes a dominant pole to average the current sensed through the first sense element.

2. The circuit according to claim 1, wherein the load element includes an LED stack.

3. The circuit according to claim 1, wherein the capacitive element contains a further impedance element coupled in series with the capacitive element.

4. The circuit according to claim 1, wherein the unidirectional current flow element includes a diode.

5. The circuit according to claim 1, wherein the energy storage element includes an inductor.

6. The circuit according to claim 5, wherein the inductor has a first end coupled to the switching element and a second end coupled to an input voltage signal.

7. The circuit according to claim 1, wherein the converter circuit comprises switch current terminals coupled across the second sense element.

8. The circuit according to claim 7, wherein the converter circuit further includes an inner loop coupled to the switch current terminals to control an average energy storage element current by a peak switch current on a cycle-by-cycle basis.

9. The circuit according to claim 1, further including a second capacitive element coupled in parallel with the first sense element to filter average the current detected by the first sense element.

10. A circuit, comprising:

an LED stack;

a capacitor coupled across the LED stack;

a first current sensing resistor coupled in series with the LED stack and the capacitor to detect an instantaneous sum of currents through the LED stack and the capacitor;

a blocking diode having an anode and a cathode, the cathode being coupled to the LED stack and the capacitor;

an inductor having a first end and a second end, the first end being coupled to the anode of the blocking diode and the second end being coupled to an input voltage signal;

a switching element coupled to the inductor and blocking diode anode, wherein the switching element controls the current through the first current sensing resistor;

a second current sensing resistor coupled to the switching element; and

a converter circuit to control the switching element;

wherein the converter regulates to the current level monitored across the first current sensing resistor.

11. The circuit according to claim 10, wherein the converter circuit includes first and second terminals coupled across the first current sensing resistor;

third and fourth terminals coupled across the second current sensing resistor; and

a fifth terminal coupled to the switching element to control current to the LED stack.

12. The circuit according to claim 11, further including a sixth terminal to receive a modulation signal.

13. The circuit according to claim 12, further including an eighth terminal to receive a current level selection signal.

14. The circuit according to claim 11, further including an outer loop coupled to the first and second terminals and an inner loop coupled to the third and fourth terminals.

15. A method, comprising:

providing a load;

coupling an impedance element across the load;

coupling a first sense element to the load to monitor an instantaneous sum of currents through the load and the impedance element;

providing a switching element to control a current through the first sense element;

coupling a second sense element to the switching element to sense a current through the switching element;

coupling a unidirectional current flow element to the switching element to allow current flow to the load;

coupling a converter circuit to the switching element to control the switching element; and

coupling an energy storage element to switching element.

16. The method according to claim 15, wherein a converter regulation loop includes a dominant pole to average the current sensed through the first element.

17. The method according to claim 15, wherein the converter circuit further includes an inner loop coupled to the switch current terminals to control an average inductor current by a peak switch current on a cycle-by-cycle basis.

18. The method according to claim 15, further including coupling a second capacitive element in parallel with the first sense element to filter average the current detected by the first sense element.