# US 2017/0288552 A1 · Power converter and method of entering skip at a fixed output power in a light load condition independent of magnetizing inductance

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- Number: US 2017/0288552 A1
- Document ID: US20170288552A1
- Status: Published application
- Kind: A1
- Application number: 15/227,822
- Filed: 2016-08-03
- Published: 2017-10-05
- Earliest claimed: 2016-03-29
- Assignees: Semiconductor Componenents Industries, LLC
- Applicants: Semiconductor Components Industries, LLC
- Inventors: Ajay Karthik HARI; Bryan Wayne MCCOY
- Web page: https://patentgrep.com/patent/US20170288552A1

## CPC

- H02M 3/33507: {with automatic control of the output voltage or current, e.g. flyback converters (H02M3/33561, H02M3/33569 take precedence)}
- H02M 1/0009: {Devices or circuits for detecting current in a converter}
- H02M 1/0035: {using burst mode control}
- H02M 1/08: Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters
- 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

A power converter has a power transistor and inductor coupled in a conduction path with the power transistor. A switching frequency of the power transistor is reduced during a light load condition. A pulse width of a drive signal to the power transistor is controlled to select a current through the inductor and power transistor corresponding to the switching frequency to maintain a fixed output power of the power converter, and further to vary the current through the inductor and power transistor to maintain the fixed output power of the power converter over a range of switching frequencies. A first number of pulses of the drive signal to the power transistor during a first time period sets the fixed output power of the power converter. No pulses of the drive signal are provided during a second time period after the first time period.

## Claims

### Claim 1

A method of maintaining a fixed output power during a light load condition in a power converter, comprising:
providing a power device;
reducing a switching frequency of the power device during the light load condition; and
controlling a pulse width of a drive signal to the power device to vary a current through the power device to maintain the fixed output power of the power converter over a range of switching frequencies.

### Claim 2 (depends on 1)

The method of claim 1, further including measuring a value of the current through the power device to control the pulse width of the drive signal to the power device.

### Claim 3 (depends on 1)

The method of claim 1, further including:
providing a first number of pulses of the drive signal to the power device during a first time period to set the fixed output power of the power converter; and
providing no pulses of the drive signal during a second time period after the first time period.

### Claim 4 (depends on 3)

The method of claim 3, further including:
providing a second number of pulses of the drive signal to the power device during a third time period after the second time period to set the fixed output power of the power converter, wherein the second number of pulses is different from the first number of pulses; and
providing no pulses of the drive signal during a fourth time period after the third time period.

### Claim 5 (depends on 1)

The method of claim 1, further including:
setting the switching frequency of the power device to different values in response to different loads on the power converter; and
varying the current through the power device to maintain the fixed output power of the power converter for the different values of the switching frequency.

### Claim 6 (depends on 1)

The method of claim 1, wherein the current through the power device varies with the switching frequency.

### Claim 7

A method of maintaining a fixed output power during a light load condition in a power converter, comprising:
providing a semiconductor device;
reducing a switching frequency of the semiconductor device during the light load condition; and
controlling a pulse width of a drive signal to the semiconductor device to select a current through the semiconductor device corresponding to the switching frequency to maintain the fixed output power of the power converter.

### Claim 8 (depends on 7)

The method of claim 7, further including controlling the pulse width of the drive signal to the transistor to vary the current through the semiconductor device to enter a fixed power delivery point at the same output power over a range of switching frequencies.

### Claim 9 (depends on 7)

The method of claim 7, further including measuring a value of the current through the semiconductor device to control the pulse width of the drive signal to the semiconductor device.

### Claim 10 (depends on 7)

The method of claim 7, further including:
providing a first number of pulses of the drive signal to the semiconductor device during a first time period to set the fixed output power of the power converter; and
providing no pulses of the drive signal during a second time period after the first time period.

### Claim 11 (depends on 10)

The method of claim 10, further including:
providing a second number of pulses of the drive signal to the semiconductor device during a third time period after the second time period to set the fixed output power of the power converter, wherein the second number of pulses is different from the first number of pulses; and
providing no pulses of the drive signal during a fourth time period after the third time period.

### Claim 12 (depends on 7)

The method of claim 7, further including:
setting the switching frequency of the device to different values in response to different loads on the power converter; and
varying the current through the semiconductor device to maintain the fixed output power of the power converter for the different values of the switching frequency.

### Claim 13 (depends on 7)

The method of claim 7, wherein the current through the semiconductor device varies with the switching frequency.

### Claim 14

A power converter having a fixed output power during a light load condition, comprising:
a semiconductor device;
means for reducing a switching frequency of the semiconductor device during the light load condition; and
means for controlling a pulse width of a drive signal to the semiconductor device to select a current through the semiconductor device corresponding to the switching frequency to maintain the fixed output power of the power converter.

### Claim 15 (depends on 14)

The power converter of claim 14, further including means for controlling the pulse width of the drive signal to the semiconductor device to vary the current through the semiconductor device to maintain the fixed output power of the power converter over a range of switching frequencies and hence a range of primary inductances.

### Claim 16 (depends on 14)

The power converter of claim 14, further including means for measuring a value of the current through the semiconductor device to control the pulse width of the drive signal to the device.

### Claim 17 (depends on 14)

The power converter of claim 14, further including means for providing a first number of pulses of the drive signal to the semiconductor device during a first time period to set the fixed output power of the power converter, and providing no pulses of the drive signal during a second time period after the first time period.

### Claim 18 (depends on 17)

The power converter of claim 17, further including means for providing a second number of pulses of the drive signal to the semiconductor device during a third time period after the second time period to set the fixed output power of the power converter, wherein the second number of pulses is different from the first number of pulses, and providing no pulses of the drive signal during a fourth time period after the third time period.

### Claim 19 (depends on 14)

The power converter of claim 14, further including:
means for setting the switching frequency of the semiconductor device to different values in response to different loads on the power converter; and
means for varying the current through the semiconductor device to maintain the fixed output power of the power converter for the different values of the switching frequency.

### Claim 20 (depends on 14)

The power converter of claim 14, wherein the current through the semiconductor device varies with the switching frequency.