PWM control circuit and PWM control method
View Patent ↗The PWM control circuit includes a polarity determination unit, a full wave rectification unit, an adjustment unit that generates an adjusted waveform signal by adjusting waveform of the full wave rectification signal, and a carrier signal generating unit that generates a fixed frequency carrier signal. The PWM control circuit further includes a comparator that generates an original PWM signal by comparing the adjusted waveform signal and the carrier signal, and a PWM waveform shaping unit that generates a first PWM signal for the positive polarity section and a second PWM signal for the negative polarity section, by shaping the original PWM signal according to the polarity signal.
1. A PWM control circuit that generates PWM signals based on an analog sensor output from a sensor provided in a device to be controlled, comprising:
a polarity determination unit that generates a polarity signal based on positive polarity sections and negative polarity sections of the analog sensor output;
a full wave rectification unit that generates a full wave rectification signal by doing full rectification of the analog sensor output;
an adjustment unit that generates an adjusted waveform signal based on waveform of the full wave rectification signal; and
a PWM waveform shaping unit that generates a first PWM signal for the positive polarity section and a second PWM signal for the negative polarity section, based on the polarity signal and the adjusted waveform signal,
wherein the adjusted waveform signal includes a part of the full wave rectification signal and excludes the other part of the full wave rectification signal.
2. The PWM control circuit in accordance with claim 1 , wherein
when a position at which the polarity of the analog sensor output is reversed is defined as a (n−1)π phase point where n is an integer of at least one, said part of the full wave rectification signal includes a (2n−1)π/2 phase point of the full wave rectification signal.
3. The PWM control circuit in accordance with claim 1 , wherein the PWM waveform shaping unit includes:
a carrier signal generating unit that generates a fixed frequency carrier signal; and
a comparator that generates an original PWM signal by comparing the adjusted waveform signal and the carrier signal.
4. The PWM control circuit in accordance with claim 1 , wherein
when a position at which the polarity of the analog sensor output is reversed is defined as a (n−1)π phase point where n is an integer of at least one, the valid signal interval setting unit outputs the full wave rectification signal in a symmetrical output section whose center is at a (2n−1)π/2 phase point, and does not output the full wave rectification signal in a symmetrical non-output section whose center is at the (n−1)π phase point.
5. The PWM control circuit in accordance with claim 1 , wherein the adjustment unit includes:
an offset/gain adjustment unit that adjusts offset and gain of the full wave rectification signal.
6. A method of generating PWM signals based on an analog sensor output from a sensor provided in a device to be controlled, comprising:
(a) generating a polarity signal based on positive polarity sections and negative polarity sections of the analog sensor output;
(b) generating a full wave rectification signal by doing full rectification of the analog sensor output;
(c) generating an adjusted waveform signal based on waveform of the full wave rectification signal; and
(d) generating a first PWM signal for the positive polarity section and a second PWM signal for the negative polarity section, based on the polarity signal and the adjusted waveform signal,
wherein the adjusted waveform signal includes a part of the full wave rectification signal and excludes the other part of the full wave rectification signal.
7. The method according to claim 6 , wherein the step (d) includes:
generating a fixed frequency carrier signal; and
generating an original PWM signal by comparing the adjusted waveform signal and the carrier signal.
8. The method in accordance with claim 6 , wherein
when a position at which the polarity of the analog sensor output is reversed is defined as a (n−1)π phase point where n is an integer of at least one, said part of the full wave rectification signal includes a (2n−1)π/2 phase point of the full wave rectification signal.
9. The method in accordance with claim 7 , wherein
when a position at which the polarity of the analog sensor output is reversed is defined as a (n−1)π phase point where n is an integer of at least one, said part of the full wave rectification signal includes a (2n−1)π/2 phase point of the full wave rectification signal.
10. A PWM control circuit that generates PWM signals based on an analog sensor output from a sensor provided in a device to be controlled, comprising:
a polarity determination unit that generates a polarity signal based on positive polarity sections and negative polarity sections of the analog sensor output;
a full wave rectification unit that generates a full wave rectification signal by doing full rectification of the analog sensor output;
an adjustment unit that generates an adjusted waveform signal based on waveform of the full wave rectification signal; and
a PWM waveform shaping unit that generates a first PWM signal for the positive polarity section and a second PWM signal for the negative polarity section, based on the polarity signal and the adjusted waveform signal,
wherein the adjusted waveform signal includes only a part of the full wave rectification signal.
11. The PWM control circuit in accordance with claim 10 , wherein
when a position at which the polarity of the analog sensor output is reversed is defined as a (n−1)π phase point where n is an integer of at least one, said part of the full wave rectification signal includes a (2n−1)π/2 phase point of the full wave rectification signal.
12. The PWM control circuit in accordance with claim 10 , wherein the PWM waveform shaping unit includes:
a carrier signal generating unit that generates a fixed frequency carrier signal; and
a comparator that generates an original PWM signal by comparing the adjusted waveform signal and the carrier signal.
13. The PWM control circuit in accordance with claim 10 , wherein
when a position at which the polarity of the analog sensor output is reversed is defined as a (n−1)π phase point where n is an integer of at least one, the valid signal interval setting unit outputs the full wave rectification signal in a symmetrical output section whose center is at a (2n−1)π/2 phase point, and does not output the full wave rectification signal in a symmetrical non-output section whose center is at the (n−1)π phase point.
14. The PWM control circuit in accordance with claim 10 , wherein the adjustment unit includes:
an offset/gain adjustment unit that adjusts offset and gain of the full wave rectification signal.