# US 9,882,485 B2 · Current metering for transitioning between operating modes in switching regulators

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- Number: US 9,882,485 B2
- Document ID: US9882485B2
- Status: Granted
- Kind: B2
- Application number: 15/396,612
- Filed: 2016-12-31
- Published: 2017-04-20
- Granted: 2018-01-30
- Earliest claimed: 2015-03-20
- Assignees: Active-Semi, Inc.
- Applicants: Active-Semi, Inc.
- Inventors: Narasimhan Trichy; James Allen Kohout
- Web page: https://patentgrep.com/patent/US9882485B2

## CPC

- H02M 3/158: including plural semiconductor devices as final control devices for a single load
- H02M 1/08: Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters
- H02M 1/0035: {using burst mode control}
- Y02B 70/10: Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes
- H02M: APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF (transformers H01F; dynamo-electric converters H02K47/00; controlling transformers, reactors or choke coils, control or regulation of electric motors, generators or dynamo-electric converters H02P)
- Y02B: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS

## Abstract

Current metering for transitioning to low power operation in switching regulators is disclosed. In an exemplary embodiment, a method is provided that includes generating pulse width modulated charging cycles that enable current to flow to an inductor to adjust an output voltage, and detecting a skipped charging cycle. The method also includes determining whether a number of charging cycles are skipped over a time interval that begins when the skipped charging cycle is detected. The method also includes transitioning to a low power operating mode if it determined that the number of charging cycles have been skipped over the selected time interval. During the low power operating mode pulse frequency modulated charging cycles are generated that enable the current to flow to the inductor to generate the output voltage.

## Claims

### Claim 1

A method comprising:
generating pulse width modulated (PWM) charging cycles and a first minimum on-time signal, wherein the generated PWM charging cycles enable current to flow to an inductor thereby adjusting an output voltage, and wherein the first minimum on-time signal is based on a ratio of an input voltage to the output voltage utilizing a first factor K1;
detecting a skipped charging cycle;
determining whether a selected number of charging cycles is skipped over a selected time interval that begins when the skipped charging cycle is detected;
transitioning to a low power operating mode if it is determined that the selected number of charging cycles is skipped over the selected time interval, wherein a second minimum on-time signal is generated during the low power operating mode, wherein the second minimum on-time signal is based on the ratio of the input voltage to the output voltage utilizing a second factor K2, and wherein the second minimum on-time signal is different from the first minimum on-time signal; and
setting a pulse width of a high side charging signal to be equal to a minimum on-time in the low power operating mode, wherein the minimum on-time is determined from the second minimum on-time signal.

### Claim 2 (depends on 1)

The method of claim 1, wherein the generating of the PWM charging cycles further comprises synchronizing the PWM charging cycles with a clock frequency.

### Claim 3 (depends on 1)

The method of claim 1, wherein the generating of the PWM charging cycles further comprises adjusting the pulse width of the high side charging signal to maintain the output voltage within a selected range.

### Claim 4 (depends on 3)

The method of claim 3, further comprising:
adjusting the pulse width of the high side charging signal to be no less than another minimum on-time determined from the first minimum on-time signal when not in the low power operating mode.

### Claim 5 (depends on 1)

The method of claim 1, wherein the determining of whether the selected number of charging cycles is skipped over the selected time interval further comprises setting the selected number of charging cycles to be 16.

### Claim 6 (depends on 1)

The method of claim 1, wherein the determining of whether the selected number of charging cycles is skipped over the selected time interval further comprises setting the selected time interval to be between 15 and 120 charging cycles.

### Claim 7 (depends on 1)

The method of claim 1, wherein the transitioning to the low power operating mode further comprises:
enabling a burst of pulse frequency modulated (PFM) charging cycles that enable current to flow to the inductor to increase the output voltage if it is determined that the output voltage is less than or equal to a nominal voltage level; and
disabling the burst of the pulse frequency modulated (PFM) charging cycles if it is determined that the output voltage is greater than the nominal voltage level plus a voltage margin.

### Claim 8 (depends on 7)

The method of claim 7, wherein the transitioning to the low power operating mode further comprises skipping the pulse frequency modulated (PFM) charging cycles if it is determined that the output voltage is not less than or equal to the nominal voltage level.

### Claim 9 (depends on 1)

The method of claim 1, further comprising:
transitioning out of the low power operating mode and return to the generating of the PWM charging cycles if it is determined that the output voltage is less than or equal to an undervoltage level.

### Claim 10

An apparatus comprising:
a pulse timer that is used to generate charging cycles in accordance with a first operating mode or a second operating mode, wherein the charging cycles enable current to flow to an inductor to adjust an output voltage;
a minimum on-time generator that generates a first minimum on-time in the first operating mode and a second minimum on-time in the second operating mode, wherein the first minimum on-time is based on a ratio of an input voltage to the output voltage utilizing a first factor K1, wherein the second minimum on-time is based on the ratio of the input voltage to the output voltage utilizing a second factor K2, and wherein the first factor K1 and the second factor K2 are not the same; and
a mode controller that detects a skipped charging cycle and determines whether a selected number of charging cycles is skipped over a selected time interval that begins when the skipped charging cycle is detected, and wherein the mode controller transitions the apparatus from the first operating mode to the second operating mode if the mode controller determined that the selected number of charging cycles is skipped over the selected time interval.

### Claim 11 (depends on 10)

The apparatus of claim 10, wherein the pulse timer adjusts a pulse width of a high side charging signal to maintain the output voltage within a selected range.

### Claim 12 (depends on 10)

The apparatus of claim 10, wherein the mode controller sets the selected number of charging cycles to be 16.

### Claim 13 (depends on 10)

The apparatus of claim 10, wherein the mode controller sets the selected time interval to be between 15 and 120 charging cycles.

### Claim 14 (depends on 10)

The apparatus of claim 10, further comprising:
a cycle skipper that skips the charging cycles in the second operating mode if it is determined that the output voltage is not less than or equal to a nominal voltage level.

### Claim 15 (depends on 10)

The apparatus of claim 10, wherein in the second operating mode, the pulse timer enables a burst of pulse frequency modulated (PFM) charging cycles that enable current to flow to the inductor to increase the output voltage if it is determined that the output voltage is less than or equal to a nominal voltage level, and disables the burst of the pulse frequency modulated (PFM) charging cycles if it is determined that the output voltage is greater than the nominal voltage level plus a voltage margin.

### Claim 16 (depends on 10)

The apparatus of claim 10, wherein the mode controller transitions the apparatus from the second operating mode to the first operating mode if it is determined that the output voltage is less than or equal to an undervoltage level.

### Claim 17

A switching regulator, wherein the switching regulator converts an input voltage to an output voltage, wherein the switching regulator generates an inductor current that flows through an inductor, wherein the switching regulator is operable in a first mode and in a second mode, and wherein the switching regulator comprises:
a minimum on-time generator, wherein in the first mode, the minimum on-time generator generates a first minimum on-time that is determined using a first factor K1 and a ratio of the input voltage and the output voltage, wherein in the second mode, the minimum on-time generator generates a second minimum on-time that is determined using a second factor K2 and the ratio of the input voltage and the output voltage, wherein the switching regulator switches from the first mode to the second mode in response to determining that an on-time of the switching regulator is less than the first minimum on-time, and wherein the first factor K1 and second factor K2 are different; and
a mode controller that detects a skipped charging cycle and determines whether a selected number of charging cycles is skipped over a selected time interval that begins when the skipped charging cycle is detected, and wherein the mode controller transitions the switching regulator from the first mode to the second mode if the mode controller determined that the selected number of charging cycles is skipped over the selected time interval.