Pulse width modulation driving circuit for a cross coil meter
AssigneeRohm Co., Ltd.
InventorHiroshi Murase
Life of this patent
Estimating the term…
Abstract
A meter drive apparatus using a counter for counting reference clocks and a comparator for comparing the output value of the counter and the data indicating a directive target of a meter. The output of the comparator is supplied to steering logic where the sign of a current flowing a drive coil of the meter is determined. When supplying the counted value of the counter to the comparator, parallel bits indicating the counted value are cyclically changed. The output of the comparator is PWM-modulated to drive the meter. The effective frequency of PWM waveform is increased, compared to the direct PWM modulation based on the data indicating the directive target of the meter. With this meter drive apparatus, the frequency of the reference clocks may be relatively low.
Claims18
A meter drive apparatus equipped with means for generating first parallel data indicating a directive value of a meter, said apparatus comprising:
- (a) a counter for counting reference clocks to generate second parallel data;
- (b) means for cyclically bit-shifting the second parallel data to generate third parallel data;
- (c) a comparator for comparing the first parallel data with the third parallel to output a binary output according to the result of comparison;
- and
- (d) means for controlling the directive of the meter based on the output of said comparator.
A meter drive apparatus equipped with means for generating a sine first parallel data indicating a current to be supplied to a sine coil of a cross-coil meter and means for generating cosine first parallel data indicating a current to be supplied to a cosine coil of the cross-coil meter, said apparatus comprising:
- (a) a counter for counting reference clocks to generate second parallel data;
- (b) means for cyclically bit-shifting the second parallel data to generate third parallel data;
- (c) a sine comparator for comparing the sine first parallel data with the third parallel data to output a binary output according to the result of comparison;
- (d) a cosine comparator for comparing the cosine first parallel data with the third parallel data to output a binary output according to the result of comparison;
- and
- (e) means for controlling the directive of the cross-coil meter based on the outputs of said sine comparator and said cosine comparator.
A meter apparatus equipped with a meter and means for generating first parallel data indicating an directive value of the meter, said meter apparatus comprising:
- (a) a counter for counting reference clocks to generate second parallel data;
- (b) means for cyclically bit-shifting the second parallel data to generate third parallel data;
- (c) a comparator for comparing the first parallel data with the third parallel data and for outputting a binary output according to the result of comparison;
- and
- (d) means for controlling the directive of said meter based on the output of said comparator.
Dependencies are inferred from the claim text.