Current mode control arrangement with load dependent ramp signal added to sensed current waveform
AssigneeAmerican Telephone and Telegraph Company, AT&T Bell Labs
InventorJames H. Murdock
Life of this patent
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Abstract
A switching converter in which current mode voltage regulation is implemented includes circuitry to add ramp compensation to the sensed current signal at light load and reduce or disable this ramp signal compensation at heavy load. This load dependent ramp signal improves the stability of operation of the converter and maintains its inherent current limit performance over a wide range of loading. An alternative connection allows for disabling the current sense signal and hence, transforming the current mode to voltage mode control under light load.
Claims9
A switching power converter circuit, comprising
- an input for accepting a source of electrical energy,
- an output for coupling to a load to be energized,
- a power switch for controlling power flow from the input to the output,
- means for periodically enabling the power switch,
- means for supplying a control threshold voltage,
- means for sensing a current flow through the power switch and providing a proportionate current feedback signal,
- means for generating a ramp signal,
- means for summing the ramp signal with the current feedback signal,
- means responsive to a magnitude of the current feedback signal for controlling a magnitude of the ramp signal applied to the means for summing whereby the magnitude of the ramp signal is high when the current feedback signal is low in magnitude and the magnitude of the ramp signal is low when the current feedback signal is high in magnitude, and
- means responsive to an output of the means for summing for disabling the power switch when the output of the means for summing attains a control threshold voltage.
A converter circuit comprising;
- an input and an output,
- a power switch periodically enabled to interconnect the input and the output,
- means for regulating a voltage level at the output including,
- means for generating a current control signal proportionate to a difference between a voltage regulation value and the voltage level at the output,
- means for sensing a current in the power switch and producing a current feedback signal proportionate to current flow in the power switch, a ramp waveform source,
- means for controlling a magnitude of the ramp waveform in response to a magnitude of the current feedback signal,
- means for summing the ramp waveform with the current feedback signal,
- and means for comparing an output of the means for summing with the current control signal and disabling the power switch when the output of the means for summing achieves equality with the current control signal.
Dependencies are inferred from the claim text.