POWER CONVERTER AND METHOD OF ENTERING SKIP AT A FIXED OUTPUT POWER IN A LIGHT LOAD CONDITION INDEPENDENT OF MAGNETIZING INDUCTANCE

• US 20170288552A1
• Filed: 08/03/2016
• Published: 10/05/2017
• Est. Priority Date: 03/29/2016
• Status: Active Grant

• Current Assignee: Semiconductor Components Industries LLC (ON Semiconductor Corporation)
• Original Assignee: Semiconductor Components Industries LLC (ON Semiconductor Corporation)
• Inventors: HARI, Ajay Karthik, MCCOY, Bryan Wayne
• Granted Patent: US 10,050,536 B2
• Time in Patent Office: Days
• CPC Class Codes: H02M 1/0009 Devices or circuits for detecting current in a converter
• CPC Class Codes: H02M 1/0035 using burst mode control
• CPC Class Codes: H02M 1/08 Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters
• CPC Class Codes: H02M 3/33507 with automatic control of the output voltage or current, e.g. flyback converters H02M3/33561, H02M3/33569 take precedence
• CPC Class Codes: 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

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

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.

2. 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.

3. 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.

4. 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.

5. 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.

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

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.

8. 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.

9. 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.

10. 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.

11. 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.

12. 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.

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

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.

15. 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.

16. 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.

17. 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.

18. 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.

19. 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.

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