| 摘要 |
A switch mode converter uses the bootstrap capacitor 30 to operate all the way to 100% duty cycle by adding only a very small amount of low-area extra circuitry. The additional circuitry includes a charge pump 40 and a duty cycle detect device 42. When the duty cycle detect device 42 detects that the converter is attempting to operate in 100% duty cycle, the charge pump 40 provides additional charge to the bootstrap capacitor 30 to ensure that the 100% duty cycle is maintained. Performance into dropout (when the input supply is actually lower than the desired output) is improved. A significant advantage in some applications (notably battery operation) is provided.
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