Load current measurement

• US 10,447,142 B1
• Filed: 12/20/2018
• Issued: 10/15/2019
• Est. Priority Date: 12/20/2018
• Status: Active Grant

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Menezes, Vinod Joseph, RR, Manikandan, Chauhan, Rajat, Singhal, Vipul Kumar, Mehendale, Mahesh Madhukar, Tsai, Kaichien
• Primary Examiner(s): Nash, Gary A
• Application Number:
  US16/227,314
• Time in Patent Office: 299 Days
• Field of Search: 323271, 323274, 323277, 323284, 323285, 323288, 323290
• CPC Class Codes: G01R 19/0092 measuring current only all subgroups of G01R19/00 take precedence
• CPC Class Codes: G01R 19/16538 in AC or DC supplies G01R19/16519 and G01R19/16528 take precedence
• CPC Class Codes: G01R 31/40 Testing power supplies testing photovoltaic devices H02S50/10
• CPC Class Codes: G05F 1/462 as a function of the requirements of the load, e.g. delay, temperature, specific voltage/current characteristic
• CPC Class Codes: G05F 1/573 with overcurrent detector
• CPC Class Codes: G05F 1/575 characterised by the feedback circuit
• CPC Class Codes: G05F 3/247 producing a voltage or current as a predetermined function of the supply voltage
• CPC Class Codes: H02M 1/0009 Devices or circuits for detecting current in a converter
• CPC Class Codes: H02M 3/1582 Buck-boost converters H02M3/1584 takes precedence

Abstract

A switch-mode power supply includes a DC-DC converter and metering circuitry that is coupled to the DC-DC converter. The metering circuitry includes scaling circuitry, a current source, a capacitor, switching circuitry, and a comparator. The scaling circuitry is configured to generate a reference current scaled to be a predetermined fraction of a peak current flowing in an inductor of the DC-DC converter. The current source is configured to output a first current that is one-half of the reference current. The capacitor is coupled to the current source. The switching circuitry is configured to switchably connect the current source to the capacitor. The comparator is coupled to the capacitor. The comparator is configured to generate a signal indicating that a voltage across the capacitor exceeds a threshold voltage.

Claims

1. A switch-mode power supply, comprising:

a DC-DC converter; and

metering circuitry coupled to the DC-DC converter, the metering circuitry comprising;

scaling circuitry configured to generate a reference current scaled to be a predetermined fraction of a peak current flowing in an inductor of the DC-DC converter;

a current source configured to output a first current that is one-half of the reference current;

a capacitor coupled to the current source;

switching circuitry configured to switchably connect the current source to the capacitor; and

a comparator coupled to the capacitor, the comparator configured to generate a signal indicating that a voltage across the capacitor exceeds a threshold voltage.

2. The switch-mode power supply of claim 1, wherein the current source is a first current source, and the metering circuitry further comprises:

a second current source configured to output a second current that is one-half of the reference current;

wherein the switching circuitry is configured to switchably connect the first current source and the second current source to the capacitor.

3. The switch-mode power supply of claim 2, wherein the switching circuitry is configured to switchably connect only the first current source to the capacitor based on the DC-DC converter operating in buck mode or boost mode.

4. The switch-mode power supply of claim 2, wherein the switching circuitry is configured to switchably connect the first current source and the second current source to the capacitor based on the DC-DC converter operating in buck-boost mode.

5. The switch-mode power supply of claim 2, wherein the switching circuitry is configured to, based on the DC-DC converter operating in buck mode, connect the first current source to the capacitor for a time interval starting at a time that the DC-DC converter initiates charging of the inductor and ending at a time that the inductor is discharged.

6. The switch-mode power supply of claim 2, wherein the switching circuitry is configured to, based on the DC-DC converter operating in boost mode, connect the first current source to the capacitor for a time interval starting at a time that the peak current is flowing in inductor and ending at a time that the inductor is discharged.

7. The switch-mode power supply of claim 2, wherein the switching circuitry is configured to, based on the DC-DC converter operating in buck-boost mode:

connect the first current source and the second current source to the capacitor for a time interval starting at a time that the peak current is flowing in inductor and ending at a time that charging of the inductor is discontinued; and

connect only the first current source to the capacitor for a time interval starting at the time that charging of the inductor is discontinued and ending at a time that the inductor is discharged.

8. The switch-mode power supply of claim 1, further comprising a processor coupled to the comparator, the processor configured to determine, based time between output pulses of the comparator, an amount of current flowing to a load circuit coupled to the DC-DC converter.

9. The switch-mode power supply of claim 1, wherein the switching circuitry is configured to discharge the capacitor responsive to an output of the comparator indicating that a voltage across the capacitor exceeds the threshold voltage.

10. A load current metering circuit, comprising:

scaling circuitry configured to generate a reference current scaled to be a predetermined fraction of a peak current flowing in an inductor of a DC-DC converter;

a current source configured to output a current that is one-half of the reference current;

a capacitor coupled to the current source;

switching circuitry coupled to the capacitor, the switching circuitry configured to control flow of current from the current source to the capacitor; and

a comparator coupled to the capacitor, the comparator configured to generate a signal indicating that a voltage across the capacitor exceeds a threshold voltage.

11. The load current metering circuit of claim 10, wherein the current source is a first current source, and the load current metering circuit further comprises:

a second current source configured to output a second current that is one-half of the reference current;

wherein the switching circuitry is configured to control flow of current from the second current source to the capacitor.

12. The load current metering circuit of claim 11, wherein the switching circuitry is configured to, based on the DC-DC converter operating in buck mode, switchably connect the first current source to the capacitor for a time interval starting at a time that the DC-DC converter initiates charging of an inductor and ending at a time that the inductor is discharged.

13. The load current metering circuit of claim 11, wherein the switching circuitry is configured to, based on the DC-DC converter operating in boost mode, connect the first current source to the capacitor for a time interval starting at a time that the peak current is flowing in inductor and ending at a time that the inductor is discharged.

14. The load current metering circuit of claim 11, wherein the switching circuitry is configured to, based on the DC-DC converter operating in buck-boost mode:

connect the first current source and the second current source to the capacitor for a time interval starting at a time that the peak current is flowing in inductor and ending at a time that charging of the inductor is discontinued; and

connect only the first current source to the capacitor for a time interval starting at a time that charging of the inductor is discontinued and ending at a time that the inductor is discharged.

15. The load current metering circuit of claim 11, wherein the switching circuitry is configured to, based on the DC-DC converter operating in buck-boost mode:

route the first current and the second current to the capacitor for a time interval starting at a time that the peak current is flowing in inductor and ending at a time that charging of the inductor is discontinued; and

route only the first current to the capacitor for a time interval starting at a time that charging of the inductor is discontinued and ending at a time that the inductor is discharged.

16. The load current metering circuit of claim 10, wherein the switching circuitry is configured to discharge the capacitor responsive to an output of the comparator indicating that a voltage across the capacitor exceeds the threshold voltage.

17. A load current metering circuit, comprising:

a current mirror configured to produce a reference current that is a predetermined fraction of a peak current flowing in an inductor of a DC-DC converter;

a first current source configured to output a first current that is one-half of the reference current;

a second current source configured to output a second current that is one-half of the reference current;

switching circuitry coupled to the first current source and the second current source, and configured to switchably control the first current and the second current;

a capacitor coupled to the switching circuitry, and configured to be charged by the first current and the second current; and

a comparator coupled to the capacitor, the comparator configured to generate a signal indicating that a voltage across the capacitor exceeds a threshold voltage.

18. The load current metering circuit of claim 17, wherein the switching circuitry is configured to, based on the DC-DC converter operating in buck mode, route the first current to the capacitor for a time interval starting at a time that the DC-DC converter initiates charging of an inductor and ending at a time that the inductor is discharged.

19. The load current metering circuit of claim 17, wherein the switching circuitry is configured to, based on the DC-DC converter operating in boost mode, route the first current to the capacitor for a time interval starting at a time that the peak current is flowing in inductor and ending at a time that the inductor is discharged.

20. The load current metering circuit of claim 17, wherein the switching circuitry is configured to discharge the capacitor responsive to an output of the comparator indicating that a voltage across the capacitor exceeds the threshold voltage.