Buck-boost converter with dual-mode control for battery charging
AssigneeAT&T Bell Laboratories
InventorRichard C. Ray
Life of this patent
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Abstract
A voltage controlled flyback converter used as a battery charging circuit avoids the power dissipation of the more conventional series-type regulator-type charging circuits but cannot be readily utilized because of the high gain in the feedback loop due to the battery voltage, which causes instabilities therein when it is operated in a continuous current mode. These instabilities are avoided in a flyback converter used for battery charging by using current control techniques to control current on the primary side of the converter during high-rate battery charging. During low-rate charging, normal voltage feedback from an output current sensing resistor is used as long as the converter operates in a discontinuous mode.
Claims11
A battery charging circuit comprising
- a flyback converter circuit including input means for accepting a source of energy and output means for accepting a battery to be charged,
- charging control means for regulating charging of the battery including
- a high-rate charge control providing a constant current for charging the battery and regulated by sensing a first current in a power switching device of the converter circuit,
- a low-rate charge control providing a second current lower in value than the first current and which is controlled by a voltage responsive to a voltage level at the output means, and
- means for selecting when the low-rate charge control is active in response to a voltage level at the output means.
A converter circuit for supplying charge to a battery comprising
- input means for accepting a DC voltage,
- output means for accepting a battery to be charged,
- a power switch for regulating power flow from the input means to the output means,
- first means for controlling the power switch in response to a current level in the power switch,
- second means for controlling the power switch in response to a current level at the output means, and
- third means for operatively enabling the power switch to be controlled by one of the first and second means in response to a voltage level at the output means.
Dependencies are inferred from the claim text.