Inductor over-current protection using a volt-second value representing an input voltage to a switching power converter

• US 9,178,415 B1
• Filed: 03/31/2010
• Issued: 11/03/2015
• Est. Priority Date: 10/15/2009
• Status: Active Grant

• Current Assignee: Cirrus Logic Incorporated
• Original Assignee: Cirrus Logic Incorporated
• Inventors: Kost, Michael A., Melanson, John L., Singh, Rahul, Sood, Mohit, He, Zhaohui
• Primary Examiner(s): Zhang, Jue
• Assistant Examiner(s): Jackson, Lakaisha
• Application Number:
  US12/751,949
• Time in Patent Office: 2,043 Days
• Field of Search: 323/222, 323/223, 323/224, 323/287
• US Class Current: 1/1
• CPC Class Codes: H02M 1/0009 Devices or circuits for detecting current in a converter
• CPC Class Codes: H02M 1/32 Means for protecting converters other than automatic disconnection
• CPC Class Codes: H02M 3/156 with automatic control of output voltage or current, e.g. switching regulators
• CPC Class Codes: H02M 3/157 with digital control

Abstract

A power control system includes a switching power converter and a controller. The controller is configured to detect an over-current condition of an inductor current in the switching power converter using at least one non-inductor-current signal. In at least one embodiment, the switching power converter does not have a resistor or resistor network to sense the inductor current. In at least one embodiment, the controller indirectly determines a state of the inductor current using at least one non-inductor-current signal. Potentially damaging inductor current values that are, for example, greater than a normal maximum value or at a value that causes a discontinuous conduction mode system to operate in continuous conduction mode represent exemplary inductor over-current conditions addressed by one embodiment of the power control system.

Claims

1. An apparatus comprising:

a controller, wherein the controller is configured to;

detect an over-current condition of an inductor current in a switching power converter using a volt-second value that is representative of an input voltage to the switching power converter and a comparison of the volt-second value to a predetermined threshold value;

accumulate samples of an input voltage signal received by the controller to determine the volt-second value; and

determine if an increase in an accumulation of input voltage signal values compared to the predetermined threshold value indicates the over-current condition; and

during an inductor flyback time, decrement the accumulation of input signal values from an accumulation of link voltage signal samples minus input voltage signal samples taken during the inductor flyback time to determine if the switching power converter is operating in discontinuous conduction mode, wherein a link voltage signal received by the controller represents a link voltage of the switching power converter.

2. The apparatus of claim 1 further comprising:

the switching power converter, coupled to the controller, wherein the switching power converter includes a reference terminal, an input terminal to receive an input voltage, an inductor coupled to the input terminal, a power regulation switch coupled between the inductor and the reference terminal, a capacitor coupled to the switch, the inductor, and the reference terminal, and an output terminal coupled to the capacitor to provide a link voltage.

3. The apparatus of claim 2 wherein the predetermined threshold value is a predetermined threshold volt-second value and to detect the over-current condition of the inductor current the controller is further configured to measure an accumulation of an input voltage to the switching power converter in volt-second terms and compare the accumulation of the input voltage to a predetermined threshold volt-second value to determine when the over-current condition of the inductor current exists.

4. The apparatus of claim 1 wherein the predetermined threshold value represents a predetermined over-current threshold, the over-current condition occurs when the inductor current reaches the predetermined over-current threshold, and the controller is further configured to protect the switching power converter from the inductor current if a value of the inductor current exceeds the over-current threshold.

5. The apparatus of claim 4 wherein the controller is further configured to protect the switching power converter if the over-current condition occurs by stopping current flow into an inductor if the over-current condition occurs.

6. The apparatus of claim 4 wherein the controller is further configured to (i) stop current flow into an inductor if the over-current condition occurs, (ii) detect operation of the switching power converter in continuous conduction mode and to prevent the inductor from increasing energy storage until after the switching power converter exits continuous conduction mode, and (iii) restart current flow into the inductor when the switching power converter enters discontinuous conduction mode.

7. The apparatus of claim 1 wherein the controller is further configured to detect operation of the switching power converter in continuous conduction mode and to prevent an inductor from increasing energy storage until after the switching power converter exits continuous conduction mode.

8. The apparatus of claim 1 wherein the controller comprises:

a processor;

a memory, coupled to the processor, wherein the memory includes code stored therein and executable by the processor to detect the over-current condition and to protect the switching power converter from inductor current if the over-current condition is detected.

9. The apparatus of claim 1 wherein the controller further comprises an over-current protection module, and the over-current protection module includes:

terminals to receive an input voltage signal and a link voltage signal, wherein the input voltage signal represents the input voltage to the switching power converter and the link voltage signal represents an output voltage of the switching power converter;

an accumulator to accumulate sample values of the input voltage signal during an ON time of a power regulation switch of the switching power converter; and

circuitry to;

determine if an accumulation of the input voltage signal sample values reach an over-current threshold;

turn the power regulation switch OFF if the accumulation of the input voltage signal sample values reaches the over-current threshold;

decrement the accumulation of the input voltage signal sample values by an accumulation of samples of the link voltage signal minus an accumulation of input voltage signal samples taken after the power regulation switch is turned OFF to determine if the switching power converter is operating in continuous conduction mode;

prevent the power regulation switch from conducting if the switching power converter is operating in continuous conduction mode; and

cause the power regulation switch to conduct after the circuit detects the switching power converter exiting continuous conduction mode.

10. The apparatus of claim 1 wherein the controller further comprises an over-current protection module, and the over-current protection module includes:

terminals to receive an input voltage signal and a link voltage signal, wherein the input voltage signal represents the input voltage to the switching power converter and the link voltage signal represents an output voltage of the switching power converter;

a first accumulator to accumulate sample values of the input voltage signal during an ON time of a power regulation switch of the switching power converter;

first circuitry to;

determine if an accumulation of the input voltage signal sample values reach an over-current threshold;

turn the power regulation switch OFF if the accumulation of the input voltage signal sample values reaches the over-current threshold;

a second accumulator to accumulate previous values of the accumulation value and sampled differences between the input voltage signal and the link voltage signal to determine if the switching power converter is operating in continuous conduction mode during an OFF time of a power regulation switch of the switching power converter;

second circuitry to;

determine if the switching power converter is operating in continuous conduction mode;

prevent the power regulation switch from conducting if the switching power converter is operating in continuous conduction mode; and

cause the power regulation switch to conduct after the circuit detects the switching power converter exiting continuous conduction mode.

11. The apparatus of claim 1 wherein the switching power converter is a boost-type switching power converter.

12. The apparatus of claim 1 wherein the controller is further configured to provide power factor correction to the switching power converter.

13. The apparatus of claim 1 wherein the predetermined threshold value is a predetermined threshold volt-second value and to detect the over-current condition of the inductor current the controller is further configured to measure an accumulation of the input voltage to the switching power converter in volt-second terms and compare the accumulation of the input voltage to the predetermined threshold volt-second value to determine when the over-current condition of the inductor current exists.

14. A method comprising:

detecting an over-current condition of an inductor current in a switching power converter using a volt-second value that is representative of an input voltage to the switching power converter and a comparison of the volt-second value to a predetermined threshold value;

accumulating a line input voltage to the switching power converter during a period of time when the inductor current is increasing and determine from an accumulation of the line input voltage if the inductor current has reached the over-current condition, wherein the input voltage to the switching power converter is the line input voltage; and

after the period of time when the inductor current is increasing, accumulating a link voltage minus a final line input voltage accumulation value to determine if the switching power converter is operating in discontinuous conduction mode, wherein the final line input voltage accumulation value is the final value of the accumulation of the line input voltage prior to a period of time when the inductor current is decreasing.

15. The method of claim 14 further comprising:

determining if an increase in inductor current associated with an inductor of the switching power converter indicates the over-current condition.

16. The method of claim 14 further comprising providing power factor correction to the switching power converter.

17. The method of claim 14 wherein the predetermined threshold value is a predetermined threshold volt-second value and detecting an over-current condition of an inductor current comprises:

measuring an accumulation of an input voltage to the switching power converter in volt-second terms; and

comparing the accumulation of the input voltage to a predetermined threshold volt-second value to determine when the over-current condition of the inductor current exists.

18. The method of claim 14 wherein the predetermined threshold value is a predetermined over-current threshold, and the over-current condition occurs when the inductor current reaches the predetermined over-current threshold, the method further comprising:

protecting the switching power converter from the inductor current if a value of the inductor current exceeds the over-current threshold.

19. The method of claim 18 further comprising:

protecting the switching power converter if the over-current condition occurs by stopping current flow into an inductor if the over-current condition occurs.

20. The method of claim 18 further comprising:

detecting operation of the switching power converter in continuous conduction mode and to prevent an inductor from increasing energy storage until after the switching power converter exits continuous conduction mode.

21. The method of claim 18 further comprising:

stopping current flow into the inductor if the over-current condition occurs;

detecting operation of the switching power converter in continuous conduction mode and to prevent an inductor from increasing energy storage until after the switching power converter exits continuous conduction mode; and

restarting current flow into the inductor when the switching power converter enters discontinuous conduction mode.

22. The method of claim 14 wherein an input voltage signal represents the input voltage to the switching power converter and a link voltage signal represents an output voltage of the switching power converter, the method further comprising:

accumulating the input voltage signal during an ON time of a power regulation switch of the switching power converter;

determining if an accumulation value of the input voltage signal reaches an over-current threshold;

turning the power regulation switch OFF if the accumulation value of the input voltage signal reaches the over-current threshold;

decrementing sampled differences between the input voltage signal and the link voltage signal from a final accumulation value of the input signal to determine if the switching power converter is operating in continuous conduction mode;

preventing the power regulation switch from conducting if the switching power converter is operating in continuous conduction mode; and

causing the power regulation switch to conduct after the circuit detects the switching power converter exiting continuous conduction mode.

23. The method of claim 14 wherein the switching power converter is a boost-type switching power converter.

24. A method comprising:

detecting an over-current condition of an inductor current in a switching power converter using a volt-second value that is representative of an input voltage to the switching power converter and a comparison of the volt-second value to a predetermined threshold value, wherein an input voltage signal represents the input voltage to the switching power converter and a link voltage signal represents an output voltage of the switching power converter;

accumulating the input voltage signal during an ON time of a power regulation switch of the switching power converter;

determining if an accumulation value of the input voltage signal reaches an over-current threshold;

turning the power regulation switch OFF if the accumulation value of the input voltage signal reaches the over-current threshold;

accumulating previous values of the accumulation value and sampled differences between the input voltage signal and the link voltage signal to determine if the switching power converter is operating in continuous conduction mode;

preventing the power regulation switch from conducting if the switching power converter is operating in continuous conduction mode; and

causing the power regulation switch to conduct after the circuit detects the switching power converter exiting continuous conduction mode.