| 摘要 |
A battery pack (10) has a charge measurement circuit (12) for estimating the state of charge during use. The charge measurement circuit (12) includes a sense resistor (24), amplifier (26), at least one oscillator (28), counter (30), and a communications circuit (32). The battery pack powers a host device (16), which has a limited number of modes of operation, each mode requiring a different current level. The number of oscillators (28) equals the number of modes of operation of the host device (16). As current is drawn from the battery cells (18), the sense resistor (24) and amplifier (26) act to convert the current to a voltage level. The voltage level is fed to each oscillator (28) present. Each oscillator (28) provides a clock signal at a frequency corresponding to one mode of operation of the host device, and is activated when the voltage level is within a preselected range. The clock signal is fed to a counter (30), which counts at a rate determined by the frequency of the active oscillator (28). The host device (16) can request the current count value from communications circuit (30) to estimate the state of charge of the battery cells (18).
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