Circuits and Methods for Controlling a Switching Regulator based on a Derived Input Current

• US 20090195230A1
• Filed: 02/05/2008
• Published: 08/06/2009
• Est. Priority Date: 02/05/2008
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Summit Microelectronics, Incorporated (Qualcomm, Inc.)
• Inventors: Adkins, Kenneth C., Kaplish, Anurag
• Granted Patent: US 8,476,890 B2
• Time in Patent Office: Days
• US Class Current: 323/282
• CPC Class Codes: H02M 1/0009 Devices or circuits for detecting current in a converter
• CPC Class Codes: H02M 1/0022 the disturbance parameters being input voltage fluctuations
• CPC Class Codes: H02M 3/156 with automatic control of output voltage or current, e.g. switching regulators

Abstract

In one embodiment the present invention includes a method of controlling a switching regulator based on a derived input current. In one embodiment, an output current of said switching regulator is detected and used to generate a first voltage or current signal corresponding to the output current. Additionally, a switching signal of said switching regulator is detected and used to generate a second voltage or current signal corresponding to the switching signal. The resulting signals may be combined to produce a voltage or current signal corresponding to an input current of said switching regulator. The switching signal may be modified based on the derived voltage or current signal and used to control the system.

Claims

1. A method of controlling a switching regulator comprising:

detecting an output current of said switching regulator;

generating a first voltage or current signal corresponding to the output current;

detecting a switching signal of said switching regulator;

generating a second voltage or current signal corresponding to the switching signal;

combining the first and second signals to produce a third voltage or current signal corresponding to an input current of said switching regulator; and

modifying the switching signal based on the third voltage or current signal.

2. The method of claim 1 wherein the third signal is a voltage, the method further comprising comparing the third voltage signal to a reference voltage.

3. The method of claim 2 wherein the reference is a voltage generated at the output of a digital-to-analog converter.

4. The method of claim 1 wherein the first voltage or current signal is linearly related to the output current and wherein the second voltage or current signal is linearly related to the duty cycle.

5. The method of claim 4 wherein generating the second voltage or current signal comprises filtering the switching signal.

6. The method of claim 1 wherein combining the first and second signals comprises combining the first and second signals in a multiplier circuit.

7. The method of claim 6 further comprising generating a fourth voltage or current signal corresponding to a reference voltage and combining an output of the multiplier circuit with the fourth voltage or current signal in a divider circuit.

8. The method of claim 1 further comprising programming a digital-to-analog converter to generate a programmed voltage or current value corresponding to an input current value and controlling the switching regulator using the third voltage or current signal if the third voltage or current signal is above a programmed voltage or current value.

9. The method of claim 1 further comprising:

coupling the output current to a battery, wherein the voltage on the battery is less than the voltage at the input of the switching regulator, and wherein the input current to the switching regulator is less than the output current; and

reducing the output current as the voltage on the battery increases such that the input current is held constant.

10. A apparatus comprising:

a switching regulator, the switching regulator generating a switching signal;

an output current sense circuit coupled to receive an output current of the switching regulator, and in accordance therewith, generate a first voltage or current signal corresponding to the output current of the switching regulator;

a duty cycle measurement circuit coupled to receive the switching signal, and in accordance therewith, generate a second voltage or current signal corresponding to the duty cycle of the switching signal; and

a control circuit coupled to receive the first and second signals and combine the first and second signals to produce a third voltage or current signal corresponding to an input current of said switching regulator,

wherein the third voltage or current signal is coupled to a control terminal of the switching regulator to modify the switching signal.

11. The method of claim 10 wherein the control circuit comprises a multiplier circuit.

12. The method of claim 11 wherein the output current sense circuit generates a first current or voltage that is proportional to the output current and the duty cycle measurement circuit generates a second current or voltage that is proportional related to the duty cycle, and wherein the multiplier circuit multiplies the first and second currents or voltages to generate a third current that is proportional to the input current.

13. The method of claim 12 further comprising resistor divider having an input coupled to the reference voltage and an intermediate node coupled to an input of a voltage to current converter, and wherein the voltage to current converter generates a fourth current proportional to the reference voltage, and wherein a divider circuit receives the third current and fourth current and generates a fifth current that is proportional to the input current but not proportional to the reference voltage.

14. The method of claim 10 wherein the duty cycle measurement circuit comprises a filter.

15. The method of claim 14 wherein duty cycle measurement circuit comprises a voltage to current converter coupled to the output of the filter.

16. The method of claim 10 further comprising a digital to analog converter coupled to a differential amplifier to program the maximum output current from the switching regulator, wherein an output of the differential amplifier is coupled to a control input of the switching regulator to adjust the switching signal.

17. The method of claim 16 wherein the digital to analog converter is coupled through a first resistor to an output of the output current sense circuit and to an input of the differential amplifier.

18. The method of claim 16 wherein the digital to analog converter is coupled to a first input of the differential amplifier and an output of the output current sense circuit is coupled to a second input of the differential amplifier.

19. The method of claim 10 further comprising a digital to analog converter coupled through a resistor to an output of the control circuit and an input of a differential amplifier to program the maximum input current to the switching regulator, wherein an output of the differential amplifier is coupled to a control input of the switching regulator to adjust the switching signal.

20. The method of claim 10 further comprising a digital to analog converter coupled to a first input of a differential amplifier to program the maximum input current to the switching regulator, wherein a second input of the differential amplifier is coupled to an output of the control circuit to receive a voltage corresponding to the third signal, and wherein an output of the differential amplifier is coupled to a control input of the switching regulator to adjust the switching signal.

21. A apparatus comprising:

a switching regulator, the switching regulator generating a switching signal;

means for sensing an output current of the switching regulator and for generating a first voltage or current signal corresponding to the output current of the switching regulator; and

means for determining the duty cycle of the switching signal coupled to receive the switching signal and for generating a second voltage or current signal corresponding to the duty cycle of the switching signal;

means for combining the first and second signals to produce a third voltage or current signal corresponding to an input current of said switching regulator.

22. The apparatus of claim 21 further comprising means for modifying the duty cycle of the switching regulator based on the third signal.

23. The apparatus of claim 21 further comprising means for changing a control voltage for determine the minimum value of the third signal required to control the switching regulator.

24. The apparatus of claim 21 further comprising means for eliminating the influence of the reference voltage on the third signal corresponding to an input current of said switching regulator.

25. The apparatus of claim 21 further comprising:

a battery, wherein the voltage on the battery is less than the voltage at the input of the switching regulator, and wherein the input current to the switching regulator is less than the output current; and

means for reducing the output current as the voltage on the battery increases such that the input current is held constant.