Burst mode controller and method
First Claim
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 start of a current burst period;
b) starting a burst of operation of the SMPS and measuring an 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).
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Abstract
Consistent with an example embodiment, there is method and a controller for controlling burst mode operation of a switched mode power supply (SMPS). It also relates to switched mode power supplies comprising such a controller. One way to increase the efficiency of a switched mode power supply is to operate it at a power level close to the optimum efficiency point for a brief period, followed by a period where the power supply is not switching during which no energy is wasted. This type of operation is known as “burst mode” and results in high efficiency at low power levels.
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Citations
13 Claims
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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:
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a) receiving a control input signal indicating start of a current burst period; b) starting a burst of operation of the SMPS and measuring an 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). - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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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 a remainder of the burst period, the controller comprising:
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a) a first comparator for receiving a control input signal indicating start of a current burst period and comparing it with a reference voltage, an 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 responding 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 monitoring; 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
to calculate a desired duration of the burst of operation of the SMPS in the current burst period from the monitored values; andd) a first circuit responding 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). - View Dependent Claims (12)
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13. A switch mode power supply comprising:
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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 a remainder of the burst period, the controller comprising; a) a first comparator for receiving a control input signal indicating start of a current burst period and comparing it with a reference voltage, an 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 responding 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 monitoring; i) the duration of a burst of operation of the SMPS in a preceding burst period; 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; andd) a first circuit responding 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); and circuitry for controlling the output power generated by a converter stage 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.
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Specification