BURST MODE CONTROLLER AND METHOD

• US 20110267024A1
• Filed: 04/27/2011
• Published: 11/03/2011
• Est. Priority Date: 04/28/2010
• Status: Active Grant

• Current Assignee: NXP B.V. (NXP Semiconductors NV)
• Original Assignee: NXP B.V. (NXP Semiconductors NV)
• Inventors: Halberstadt, Hans
• Granted Patent: US 8,519,688 B2
• Time in Patent Office: Days
• US Class Current: 323/304
• CPC Class Codes: H02M 1/0032 Control circuits allowing low power mode operation, e.g. in standby mode
• CPC Class Codes: H02M 3/156 with automatic control of output voltage or current, e.g. switching regulators
• 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 method for controlling burst mode operation of a switched mode power supply (SMPS) is disclosed. The method comprises:

• • a) receiving a control input signal indicating the start of a current burst period;
  • b) responding to the indication of the start of the current burst period by generating a signal representing the elapsed time during the current burst period and by starting a burst of operation of the SMPS;
  • c) calculating a value for a signal representing a desired duration of the burst of operation of the SMPS in the current burst period from a signal representing the duration of a burst of operation of the SMPS in a preceding burst period, a signal representing the duration of the preceding burst period and a signal representing the desired duration of the current burst period; and
  • d) comparing the signal representing the elapsed time during the current burst period with the signal representing the desired duration of the burst of operation of the SMPS in the current burst period and ceasing the burst of operation of the SMPS if the elapsed time since the start of the current burst period is greater than or equal to the desired duration of the burst of operation of the SMPS in the current burst period.

Claims

1. A method for controlling burst mode operation of a switched mode power supply—

(SMPS), in which a burst period comprises a burst of operation of the SMPS during which the SMPS is generating power at a first, higher level, the SMPS generating power at a second, lower level during the remainder of the burst period, the method comprising;

a) receiving a control input signal indicating the start of a current burst period;

b) starting a burst of operation of the SMPS and measuring the elapsed time during the current burst period;

c) calculating a desired duration of the burst of operation of the SMPS in the current burst period from;

i) the duration of a burst of operation of the SMPS in a preceding burst period;

ii) the duration of the preceding burst period; and

iii) the desired duration of the current burst period;

and

d) comparing the elapsed time during the current burst period with the desired duration calculated in step (c) and ceasing the burst of operation of the SMPS if the elapsed time during the current burst period is greater than or equal to the desired duration calculated in step (c).

2. A method according to claim 1, wherein the control input signal is received when the value of a regulated parameter crosses a threshold value.

3. A method according to claim 1, wherein the elapsed time during the current burst period is measured by generating a signal proportional to the elapsed time since the start of the current burst period.

4. A method according to claim 1, wherein the desired duration calculated in step (c) is equal to the product of the duration of the burst of operation of the SMPS in the preceding burst period with the ratio of the desired duration of the current burst period to the duration of the preceding burst period.

5. A method according to claim 1, wherein the desired duration calculated in step (c) is equal to the sum of the duration of the burst of operation of the SMPS in the preceding burst period and the product of a weighting coefficient with the difference between the desired duration of the burst period and the duration of the preceding burst period.

6. A method according to claim 1, wherein step (b) further comprises sampling a signal representing the duration of the preceding burst period and retaining the sampled signal for use in step (c).

7. A method according to claim 1, further comprising sampling the value of the desired duration calculated in step (c) and retaining the sampled value for use in the comparison of step (d).

8. A method according to claim 1, further comprising modifying the value of the desired duration calculated in step (c) by application of a predefined filter function.

9. A method according to claim 8, wherein the predefined filter function multiplies the desired duration calculated in step (c) by a filter coefficient and adds to this the product of one minus the filter coefficient with the duration of the burst of operation of the SMPS in the preceding burst period.

10. A method according to claim 1, wherein the desired duration calculated in step (c) is constrained between maximum and minimum values.

13. A controller for controlling burst mode operation of a switched mode power supply (SMPS) comprising a circuit adapted to perform the method of claim 1.

11. A controller for controlling burst mode operation of a switched mode power supply—

(SMPS) in which a burst period comprises a burst of operation of the SMPS during which the SMPS is generating power at a first, higher level, the SMPS generating power at a second, lower level during the remainder of the burst period, the controller comprising;

a) a first comparator for receiving a control input signal indicating the start of the current burst period and comparing it with a reference voltage, the output of the first comparator being adapted to switch from a first logic level to a second logic level when the control input signal crosses the reference voltage;

b) a timer adapted to respond to the switch from the first logic level to the second logic level at the output of the first comparator by measuring the elapsed time during the current burst period;

c) a calculation unit adapted to monitor;

i) the duration of a burst of operation of the SMPS in the preceding burst period;

ii) the duration of the preceding burst period; and

iii) the desired duration of the current burst period;

and to calculate a desired duration of the burst of operation of the SMPS in the current burst period from the monitored values; and

d) a first circuit adapted to respond to the switch from the first logic level to the second logic level at the output of the first comparator by starting the burst of operation of the SMPS and to compare the elapsed time during the current burst period with the desired duration calculated in step (c), ceasing the burst of operation of the SMPS if the elapsed time during the current burst period is greater than or equal to the desired duration calculated in step (c).

12. A controller according to claim 11, further comprising a filter unit adapted to modify the value of the desired duration calculated in step by application of a predefined filter function.

14. A switched mode power supply comprising a controller according to claim 11.

15. A switched mode power supply according to claim 14, further comprising circuitry for controlling the output power generated by a converter stage (102) of the switched mode power supply, wherein the circuitry is adapted to control the output power to the higher of a first value derived from a regulated parameter and a second value, which is predetermined to represent a minimum output power, during a burst of operation of the SMPS.