Pulse-frequency modulation constant on-time with peak-current servo
AssigneeDialog Semiconductor (UK) Limited
InventorMark Childs
Life of this patent
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Abstract
The disclosure describes a DC-DC switching converter providing a peak-current servo, employing a pulse-frequency modulation (PFM) control signal and a constant on-time. A Buck, Boost, Buck-Boost, or similar switching converter that supports PFM mode is required, using a fixed on-time scheme for PFM. A final value of the coil current is sampled, and the sampled value of the coil current is compared to a target value for the coil current, to establish whether it is greater or less than the target value. The on-time of the high side device is adjusted to bring the final value of the coil current closer to the target value, using an adaptive coil current measurement.
Claims26
A DC-DC switching power converter, comprising:
- a high-side and a low-side device, configured to be connected to a node of said DC-DC switching power converter;
- a sampling circuit configured to sample a first voltage at said node when said high side device is turned off, and a second voltage proportional to a reference voltage;
- a comparator to compare said first and said second voltages;
- a counter having an output configured to change based on an output of said comparator;
- and
- a timer configured to adjust an on-time of said high-side device based on said counter output;
- wherein said counter is configured in a loop, to adjust said on-time of said high side device, such that a peak current of subsequent cycles is configured to converge on said reference current.
A DC-DC switching power converter, comprising:
- a high-side and a low-side device, configured to be connected to a node of said DC-DC switching power converter;
- a first sampling circuit configured to sample a total pulse duration for an on-time of both said high-side and said low-side devices;
- a second sampling circuit to sample a clock period;
- a comparator to compare said total pulse duration and said clock period;
- a counter having an output configured to change based on an output of said comparator;
- and
- a timer configured to adjust said total pulse duration based on said counter output.
A method for operating a DC-DC switching converter with a peak-current servo, having a pulse-frequency modulation (PFM) mode, comprising the steps of:
- operating said switching converter using a controlled on-time scheme for said PFM mode, wherein said switching converter comprises high and low side devices, connected to a node of said DC-DC switching converter;
- sampling a first voltage at said node when said high side device is turned off and a second voltage, proportional to a reference voltage;
- comparing said first and second voltages;
- changing a counter value based on said comparing of said first and second voltages;
- and
- adjusting the on-time of said high side device based on said counter value such that a peak current of subsequent cycles converges on a reference current.
Dependencies are inferred from the claim text.