Digital-to-analog converter and digital-to-analog converting method
AssigneeMatsushita Electric Industrial Co., Ltd.
InventorMasahiro Moriya
Life of this patent
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Abstract
In a digital-to-analog converter comprising a pulse-width modulation signal generator for generating a pulse-width modulation signal by pulse-width modulating an actual set value with a count value, and a low-pass filter for removing a high frequency component of the pulse-width modulation signal so as to output an analog signal, a difference between a current target digital value and a previous target digital value are multiplied by a coefficient determined from a time constant of the low-pass filter and a cycle of the target set value, and the multiplied value is added to the previous target set value so as to calculate the actual set value.
Claims13
A digital-to-analog converter that decreases response delay caused by a filter time constant, comprising:
- a counter that repeatedly counts a predetermined count value;
- a modulating section that compares one of a count value output from said counter and a reversed count value in which upper bits and lower bits of said count value are reversed with an actual set value corresponding to a target digital value, said modulating section comprising a comparator, and generating one of a pulse-width modulation signal and pulse-density modulation signal;
- a low-pass filter that removes a high frequency component of one of said pulse-width modulation signal and said pulse-density modulation signal output from said modulating section to generate an analog signal;
- and
- a set value calculator for multiplying a difference between a current target digital value and a previous target digital value by a coefficient determined from a time constant of the low-pass filter and an update cycle of said target digital value, and adding a result of the multiplication to the previous target digital value to calculate said actual set value, whenever said target digital value is updated,
- wherein the coefficient cancels a decrease in a substantial variation of said target digital value, caused by the low-pass filter time constant.
A digital-to-analog converting method for pulse-width modulating a target digital value to convert to an analog value, while decreasing response delay caused by a filter time constant, comprising:
- counting a predetermined count value repeatedly;
- modulating an actual set value corresponding to a target digital value, using one of said count value and a reversed count value in which upper bits and lower bits of said count value are reversed, and thereby generating one of a pulse-width modulation signal and a pulse-density modulation signal;
- multiplying a difference between a current target digital value and a previous target digital value by a coefficient which is determined from the time constant of a low-pass filter and an update cycle of said target digital value the coefficient canceling a decrease in a substantial variation in said target digital value, caused by the low-pass filter time constant;
- and
- adding a value of the multiplication to the previous target digital value to calculate said actual set value.
Dependencies are inferred from the claim text.