| 摘要 |
<p>A battery charging system (10) includes an efficient switch mode power supply (14), multiple linear current limiters (20, 22, 24; 122, 123, 124), and a feedback circuit (28) to allow the switch mode power supply (14) to operate at the minimum voltage necessary to operate a power load and charge batteries (20B, 22B, 24B). Furthermore, the switch mode power supply (14) is capable of producing the maximum power required by the system (10), such as when tthe battery charger is used in conjunction with operation of an electronic device with peak load demands such as when a hard disk is accessed in a portable computer. Two control mechanisms are found in the battery charging system. The first mechanism is an input used to control the switch mode power supply output voltage from an external source. In one embodiment, this is done by referencing a first voltage to that internal to the switch mode power supply (14). The second mechanim is to limit the current within the switch mode power supply (14) not controlled by an external source. This current-limiting feature is linear and is set at an absolute limit point. Each limiter (20, 22, 24; 122, 123, 124) supplies charge current to a battery (20B, 22B, 24B), which charge current is monitored and compared to a reference voltage from a reference voltage source (132) with the resulting error voltage used to control the output of a series pass controller, such as a transistor (Q3, Q5, Q7).</p> |
