| 摘要 |
PROBLEM TO BE SOLVED: To provide a charging circuit for a portable electronic apparatus, particularly for a wireless telephone and a cell-type telephone, whose charging end can be most properly detected even if a power is supplied from a battery while the battery is re-charged. SOLUTION: The estimated value D(n) of the 1st differential of a battery voltage V(n) which is sampled at a timing (n) (step 13) is calculated by a formula: D(n)= V(n)-V(n-16)}+ V(n-1)-V(n-17)}+ V(n-2)-V(n-18)}+... + V(n-15)-V(n-31)} (step 14). The values V(i) are stored in a memory beforehand. A determination parameter P(n) is calculated by a formula: P(n) =λD(n-1)+(1-λ)D(n) whereinλ=0.5-1 (step 15). If P(n) is negative (step 17), the charging of a battery is discontinued (step 18).
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