# US 12,009,823 B2 · Pulse width modulation method

> Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt

- Number: US 12,009,823 B2
- Document ID: US12009823B2
- Status: Granted
- Kind: B2
- Application number: 18/049,611
- Filed: 2022-10-25
- Published: 2023-06-15
- Granted: 2024-06-11
- Earliest claimed: 2021-12-14
- Assignees: Richtek Technology Corporation
- Applicants: Richtek Technology Corporation
- Inventors: Yi-Kuang Chen
- Web page: https://patentgrep.com/patent/US12009823B2

## CPC

- H03K 3/017: Adjustment of width or dutycycle of pulses (pulse width modulation H03K7/08 {; to maintain energy constant H03K3/015})
- H03K 7/08: Duration or width modulation {; Duty cycle modulation}
- H03K 3/023: by the use of differential amplifiers or comparators, with internal or external positive feedback
- H03K: PULSE TECHNIQUE (measuring pulse characteristics G01R; modulating sinusoidal oscillations with pulses H03C; transmission of digital information H04L; discriminator circuits detecting phase difference between two signals by counting or integrating cycles of oscillation H03D3/04; automatic control, starting, synchronisation or stabilisation of generators of electronic oscillations or pulses where the type of generator is irrelevant or unspecified H03L; coding, decoding or code conversion, in general H03M)

## Abstract

A pulse width modulation (PWM) method for converting an input signal into an output PWM signal includes the following steps: generating a first linear periodic wave and a second linear periodic wave which are triangle waves or sawtooth waves, wherein the amplitude of the first linear periodic wave is greater than the amplitude of the second linear periodic wave; determining whether the level of the input signal is lower than a light load threshold; when the level of the input signal is lower than the light load threshold, generating the output PWM signal according to a comparison between the input signal and the second linear periodic wave; and when the level of the input signal is higher than the light load threshold, generating the output PWM signal according to a comparison between the input signal and the first linear periodic wave.

## Claims

### Claim 1

A pulse width modulation (PWM) method, which is configured to convert an input signal into a corresponding output PWM signal, the PWM method comprising:
generating a first linear periodic wave and a second linear periodic wave, wherein an amplitude of the first linear periodic wave is greater than an amplitude of the second linear periodic wave, wherein each of the first linear periodic wave and the second linear periodic wave is a triangular wave or a sawtooth wave;
determining whether a level of the input signal is less than a light load threshold,
when the level of the input signal is less than the light load threshold, generating the output PWM signal according to a comparison between the input signal and the second linear periodic wave; and
when the level of the input signal is greater than the light load threshold, generating the output PWM signal according to a comparison between the input signal and the first linear periodic wave;
wherein there is a common mode non-zero offset between a common mode level of the second linear periodic wave and a common mode level of the input signal, so that a root mean square (RMS) power of the output PWM signal when the level of the input signal is less than the light load threshold is less than a RMS power of the output PWM signal when the common mode offset is zero.

### Claim 2 (depends on 1)

The PWM method of claim 1, further comprising:
comparing the input signal with the first linear periodic wave to generate a first relay PWM signal, and comparing the input signal with the second linear periodic wave to generate a second relay PWM signal;
when the level of the input signal is less than the light load threshold, generating the output PWM signal according to the second relay PWM signal; and
when the level of the input signal is greater than the light load threshold, generating the output PWM signal according to the first relay PWM signal.

### Claim 3 (depends on 1)

The PWM method of claim 1, further comprising:
when the level of the input signal is greater than the light load threshold, selecting the first linear periodic wave as a selected linear periodic wave;
when the level of the input signal is less than the light load threshold, selecting the second linear periodic wave as the selected linear periodic wave; and
comparing the input signal with the selected linear periodic wave to generate a selection PWM signal, and generating the output PWM signal according to the selection PWM signal.

### Claim 4 (depends on 1)

The PWM method of claim 1, wherein when a value of the input signal is zero, a duty cycle of the output PWM signal is not 50%.

### Claim 5 (depends on 1)

The PWM method of claim 1, wherein a frequency of the second linear periodic wave is X times a frequency of the first linear periodic wave, wherein X is a rational number greater than or equal to one.

### Claim 6 (depends on 5)

The PWM method of claim 5, wherein X is a non-integer greater than one.

### Claim 7 (depends on 1)

The PWM method of claim 1, wherein a predetermined phase difference other than zero exists between the first linear periodic wave and the second linear periodic wave.

### Claim 8 (depends on 7)

The PWM method of claim 7, wherein the predetermined phase difference is a product of 2n multiplied by a rational number.

### Claim 9 (depends on 1)

The PWM method of claim 1, wherein the amplitude of the first linear periodic wave is Y times the amplitude of the second linear periodic wave, wherein Y is a non-integer greater than one.

### Claim 10 (depends on 1)

The PWM method of claim 1, wherein the amplitude of the output PWM signal while the level of the input signal is greater than the light load threshold is greater than the amplitude of the output PWM signal while the level of the input signal is less than the light load threshold.

### Claim 11 (depends on 10)

The PWM method of claim 10, wherein the PWM method is configured to control a power stage circuit to generate the output PWM signal, wherein the power stage circuit comprises a plurality of switches, and the plurality of switches comprises a first switch, a second switch, and a third switch, the first switch being coupled between a light load supply voltage and a switching node; the second switch being coupled between a heavy load supply voltage and the switching node; and the third switch being coupled between the switching node and a ground potential, wherein the heavy load supply voltage is greater than the light load supply voltage; wherein:
when the level of the input signal is less than the light load threshold, the power stage circuit controls the first switch and the third switch to periodically switch complementarily to generate the output PWM signal at the switching node according to the comparison between the input signal and the second linear periodic wave, wherein the output PWM signal is switched between the light load supply voltage and the ground potential; and
when the level of the input signal is greater than the light load threshold, the power stage circuit controls the second switch and the third switch to periodically switch complementarily to generate the output PWM signal at the switching node according to according to the comparison between the input signal and the first linear periodic wave, wherein the output PWM signal is switched between the heavy load supply voltage and the ground potential.

### Claim 12 (depends on 1)

The PWM method of claim 1, wherein the amplitude of the output PWM signal while the level of the input signal is greater than the light load threshold is Z times the amplitude of the output PWM signal while the level of the input signal is less than the light load threshold, wherein Z is a non-integer greater than one.

### Claim 13 (depends on 1)

The PWM method of claim 1, wherein the step of determining whether the level of the input signal is less than the light load threshold comprises:
comparing an offset linear periodic wave with the input signal to generate an offset PWM signal, wherein the offset linear periodic wave is obtained by superimposing the first linear periodic wave with a common mode offset that is not zero, the common mode offset that is not zero is relevant to the light load threshold; and
according to an operation period of the offset linear periodic wave, periodically determining whether an in-phase sub-signal of the offset PWM signal and an inverted-phase sub-signal of the offset PWM signal both have a pulse in a previous operation period, and determining whether the level of the input signal is less than the light load threshold;
wherein the in-phase sub-signal of the input signal and the inverted-phase sub-signal of the input signal are complementary to each other, the in-phase sub-signal of the offset PWM signal being obtained by comparing the offset linear periodic wave with the in-phase sub-signal of the input signal, and the inverted-phase sub-signal of the offset PWM signal being obtained by comparing the offset linear periodic wave with the inverted-phase sub-signal of the input signal.