| 摘要 |
PROBLEM TO BE SOLVED: To convert a digital PCM data stream into a PWM signal with small calculation quantity by checking the difference between the values at the intersection of extrapolated lines and at sample points on both the sides of the intersection, multiplying the value of the difference by an empirically determined multiplier and adding the result to an estimated value. SOLUTION: A sampler 202 executes an algorithm for approximating natural samples, such as samples used for PWM. The sampler 202 converts an up- sampled pulse-code modulated data stream of a set of samples into digital PWM data. An intersection with a sawtooth slanting part of an analog signal is approximated by extrapolating or projecting a straight line between two adjacent sample points other than a sample point, and an estimated value of the intersection is generated. Then the difference between the values at the intersection of the extrapolated lines and at sample points on both the sides of the intersection is checked and multiplied by the empirically determined multiplier, and the result is added to estimated value.
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