1. A motor drive unit for use with a DC power source, the motor drive unit comprising:
a plurality of inverter circuits configured to convert DC power of the DC power source to AC power;
a current detector configured to detect an output current of at least one of the plurality of inverter circuits, the current detector including a plurality of shunt transistors connected respectively to the emitter terminals of a lower arm transistor of the at least one inverter circuit, and a level shift circuit connected to the plurality of shunt resistors, the level shift circuit configured to shift current signals of the plurality of shunt resistors or perform an amplification after level shifting of the plurality of shunt resistors; and
a controller configured to perform PWM control of the plurality of inverter circuits,
to synchronize a PWM period of the plurality of inverter circuits, and to drive a plurality of motors respectively at once by means of the plurality of inverter circuits.
2. The motor drive unit according to claim 1, wherein the controller performs control in such a way that the PWM period of the plurality of inverter circuits may be identical.
3. The motor drive unit according to claim 1, wherein the controller performs control in such a way that a ratio of PWM period of the plurality of inverter circuits may be an integral multiple.
4. The motor drive unit according to claim 1, wherein the controller comprises an AD converter for performing AD conversion of an output signal of the current detector, and a plurality of PWM controllers for performing PWM control of the plurality of inverter circuits respectively, the AD converter performing AD conversion in synchronization with the PWM period.
5. The motor drive unit according to claim 4, wherein the PWM controller comprises a carrier signal generator, an output voltage setting section, and a comparator, and performs AD conversion by synchronizing a period of the carrier signal generator.
6. The motor drive unit according to claim 4, wherein the AD converter performs AD conversion at once or alternately in synchronization with the PWM period of the plurality of PWM controllers.
7. The motor drive unit according to claim 1, wherein the controller performs at least one of a vector control and a Sensorless sinusoidal wave drive of at least one inverter circuit among the plurality of inverter circuits.
8. A motor drive unit for use with a DC power source, the motor drive unit comprising:
a DC power source;
a plurality of inverter circuits configured to convert DC power of the DC power source to AC power;
a current detector configured to detect an output current of the plurality of inverter circuits; and
a controller configured to (1) perform PWM control of the plurality of inverter circuits, (2) synchronize a PWM period of the plurality of inverter circuits, (3) drive a plurality of motors respectively at once by means of the plurality of inverter circuits and (4) sample the output current detected by each respective one of the plurality of inverter circuits during different synchronized PWM periods.
9. A motor drive unit for use with a DC power source, the motor drive unit comprising:
a plurality of inverter circuits configured to convert DC power of the DC power source to AC power;
a current detector configured to detect an output current of at least one of the plurality of inverter circuits; and
a controller configured to generate a respective PWM signal to drive each of the plurality of inverter circuits, periods of each of the PWM signals being integer multiples of each other.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. A photonic crystal waveguide comprising:
a core formed of a photonic crystal having periodicity in a first direction and propagating an electromagnetic wave in a second direction perpendicular to the first direction, the core comprising a photonic band structure having a Brillouin zone boundary and a photonic band thereon comprising a propagation mode in which the electromagnetic wave is propagated a homogeneous medium cladding having a refractive index a ns; and
the core further comprising a side face parallel to the first direction, the side face in contact with the homogeneous medium cladding, the side face satisfying the condition:
\u03bb0ns>a\u03bb(\u03bb24+a2)0.5
where \u03bb0 denotes a wavelength of the electromagnetic wave in a vacuum, a denotes a period of the photonic crystal, and \u03bb denotes a period of the wave propagated through the core in the second direction perpendicular to the first direction.
2. The photonic crystal waveguide according to claim 1, further comprising a confinement cladding formed of at least one of a homogeneous material or a photonic crystal having periodicity in at least the first direction and arranged on a surface of the core perpendicular to the first direction to prevent the electromagnetic wave propagated through the core from leaking out of the surface.
3. The photonic crystal waveguide according to claim 1 wherein a width 2L of the core in a direction perpendicular to a longitudinal direction of the waveguide is in a range of:
s\u03bb2 cos \u03c60\u22662L<(s+1)\u03bb2 cos \u03c60
when a propagation angle \u03c6 of the electromagnetic wave satisfying:
\u03bb0ns\u2212a(\u03bbcos \u03c6){(\u03bb2 cos \u03c6)2+a2}0.5=0
is in the range of 0<\u03c6<90\xb0, the value in the range defined as a maximum value \u03c60 of propagation angles at which the electromagnetic wave is confined by the side face, and a phase shift amount is s\u03c0 when the wave propagated through the core is reflected by the side face at the maximum value \u03c60 of the propagation angle, and s is in a range of 0\u2266s\u22661.
4. The photonic crystal waveguide according to claim 1 wherein a phase shift amount is s\u03c0 when the wave propagated through the core in the second direction perpendicular to the first direction is perpendicularly incident on the side face and reflected thereby, s is in the range 0\u2266s\u22661, and the conditions:
\u03bb0ns\u22122a>0 and
s\u03bb2\u22662L
are satisfied.
5. The photonic crystal waveguide according to claim 4, wherein a width 2L of the core in a direction perpendicular a longitudinal direction of the wave guide is in a range of:
s\u03bb2\u22662L<(s+1)\u03bb2.
6. The photonic crystal waveguide according to claim 1 further comprising a confinement cladding layer formed of a photonic crystal having periodicity in at least the first direction and formed of the same materials as the core, arranged on a surface of the core, and wherein a photonic bandgap is formed by the confinement cladding layer in the first direction confining the propagation mode in the first direction of the core, while making radiation modes similar to the propagation mode.
7. The photonic crystal waveguide according to claim 1 further comprising a phase modulating device on an end face of the core, such that a periodic structure thereof is exposed, the phase modulating device operable for coupling the wave propagated through the core to an external plane wave.
8. The photonic crystal waveguide according to claim 7, wherein when n denotes a refractive index of an external medium and \u03bb0 denotes a wavelength of an external plane wave in a vacuum, the phase modulating device using the end face of the core parallel to the first direction as an external coupling face, such that the phase modulating device couples, in the coupling face, plane waves having an incident angle \u03b8 in the first direction represented by the formula:
n\xb7sin \u03b8\xb7(a\u03bb0)=0.5
to the end face.
9. The photonic crystal waveguide according to claim 7, wherein when n denotes a refractive index of an external medium and \u03bb0 denotes a wavelength of an external plane wave in a vacuum, the phase modulating device using the end face of the core parallel to the first direction as an external coupling face, and, in the coupling face, causes two planes having the same phase and having incident angles \xb1\u03b8 in the first direction represented by the formula:
n\xb7sin \u03b8\xb7(a\u03bb0)=0.5
to interfere with each other to couple them to the end face.
10. The photonic crystal waveguide according to claim 7, wherein
the phase modulating device is a phase grating arranged proximate an incident surface, which is an end face of the core parallel to the one direction, and has a period in the same direction as the photonic crystal forming the core that is twice the period of the photonic crystal; and
the phase grating couples the external plane wave to the electromagnetic wave propagated through the core.
11. The photonic crystal waveguide according to claim 7, wherein the phase modulating device is a phase grating arranged proximate the end face of the core parallel to the first direction, and has the same period in the same direction as the photonic crystal forming the core; and
at least one of an incident angle or exit angle \u03b8 of an external plane wave coupled to the electromagnetic wave propagated through the core by the phase grating satisfies the formula:
n\xb7sin \u03b8\xb7(a\u03bb0)=0.5
where n denotes a refractive index of an external medium, and \u03bb0 denotes a wavelength of the external plane wave in vacuum.
12. The photonic crystal waveguide according to claim 7, wherein the phase modulating device is a phase grating arranged proximate the end face of the core parallel to the first direction, and has a period in the same direction as the photonic crystal forming the core that is twice the period of the photonic crystal; and
an incident angle or exit angle \u03b8 of the external plane wave coupled to the wave propagated through the core by the phase grating satisfies the formula:
n\xb7sin \u03b8\xb7(a\u03bb0)=0.5
where n denotes a refractive index of an external medium, and \u03bb0 denotes a wavelength of the external plane wave in a vacuum.
13. The photonic crystal waveguide according to claim 7, wherein the core comprises a slant end face inclined with respect to the first direction and the phase modulating device directly couples the external plane wave to the slant end face of the core.
14. The photonic crystal waveguide according to claim 13, further comprising at least one of one of a prism or mirror arranged proximate the slant end face of the core to change an incoming direction or an outgoing direction of the external plane wave.
15. The photonic crystal waveguide according to claim 14, wherein the incoming direction or outgoing direction of the external plane wave is matched with a propagation direction in the core formed by the photonic crystal.
16. The photonic crystal waveguide according to claim 14, wherein the incoming direction or outgoing direction of the external plane wave is perpendicular to a propagation direction in the core formed by the photonic crystal.
17. The photonic crystal waveguide according to claim 14, comprising a prism having a refractive index of 3 or more.
18. The photonic crystal waveguide according to claim 14, further comprising a diffraction grating arranged proximate the slant end face.
19. The photonic crystal waveguide according to claim 18, wherein the incoming direction or the outgoing direction of the external plane wave coupled to the wave propagated through the core by the diffraction grating is matched with a propagation direction in the core formed of the photonic crystal.
20. The photonic crystal waveguide according to claim 1, wherein a width of the core perpendicular to a longitudinal direction of the waveguide is tapered.
21. A photonic crystal waveguide comprising:
a core formed of a photonic crystal having periodicity in a first direction and propagating an electromagnetic wave in a second direction perpendicular to the first direction, the core comprising a photonic band structure having a Brillouin zone center line and a high-order photonic band thereon comprising a propagation mode in which the electromagnetic wave is propagated a homogeneous medium cladding having a refractive index ns; and
the core comprising a side face parallel to the first direction in contact with the homogeneous medium cladding the side face satisfying the condition:
\u03bb0ns\u2212\u03bb>0
where \u03bb0 denotes a wavelength of the electromagnetic wave in vacuum, a denotes a period of the photonic crystal, and \u03bb denotes a period of the wave propagated through the core in the second direction perpendicular to the first direction.
22. The photonic crystal waveguide according to claim 21, further comprising a confinement cladding, formed at least one of a homogeneous material or a photonic crystal having periodicity in at least the first direction, and arranged on a surface of the core perpendicular to the first direction for preventing the electromagnetic wave propagated through the core from leaking out of the surface.
23. The photonic crystal waveguide according to claim 21 wherein width 2L of the core in a direction perpendicular to a longitudinal direction of the waveguide is in a range of:
s\u03bb2 cos \u03c60 23 2L<(s+1)\u03bb2 cos \u03c60
with a propagation angle \u03c6 of the electromagnetic wave satisfying:
\u03bb0ns\u2212\u03bbcos \u03c6=0
and being in a range of 0<\u03c6<90\xb0, with a value in this range being defined as a maximum value \u03c60 of propagation angles at which the electromagnetic wave is confined by the side face; and
wherein a phase shift amount is s\u03c0 when the wave propagated through the core is reflected by the side face at the maximum value \u03c60 of the propagation angle, and s being in the range 0\u2266s\u22661.
24. The photonic crystal waveguide according to claim 21 further comprising
a confinement cladding layer, which is formed of a photonic crystal having a periodicity in at least the first direction, is formed of the same materials as the core and is arranged on a surface of the core, and
a photonic bandgap formed by the confinement cladding layer confining the propagation mode in the first direction of the core, while making radiation modes similar to the propagation mode.
25. The photonic crystal waveguide according to claim 21 further comprising:
a phase modulating device on an end face of the core where a periodic structure thereof is exposed, the phase modulating device operable for coupling the electromagnetic wave propagated through the core to an external plane wave.
26. The photonic crystal waveguide according to claim 25, wherein when n denotes a refractive index of an external medium and \u03bb0 denotes a wavelength of the external plane wave in a vacuum, the phase modulating device using the end face of the core parallel to the first direction as an external coupling face, and, in the coupling face, causes two plane waves having the same phase and having an incident angle \xb1\u03b8 in the first direction that is represented by the formula:
n\xb7sin \u03b8\xb7(a\u03bb0)=1.0
to interfere with each other to couple them to the end face.
27. The photonic crystal waveguide according to claim 25, wherein when n denotes a refractive index of an external medium, and \u03bb0 denotes a wavelength of the external plane wave in a vacuum, the phase modulating device using the end face of the core parallel to the first direction as an external coupling face, and, in the coupling face, causes two plane waves having the same phase and having an incident angle \xb1\u03b8 in the first direction that is represented by the formula:
n\xb7sin \u03b8\xb7(a\u03bb0)=1.0
and the plane wave with \u03b8=0 to interfere simultaneously to couple them to the end face.
28. The photonic crystal waveguide according to claim 25, wherein:
the phase modulating device is a phase grating arranged proximate an incident surface, and has a same period in a same direction as the photonic crystal forming the core; and
the phase grating couples the external plane wave to the electromagnetic wave propagated through the core.
29. The photonic crystal waveguide according to claim 21 wherein a width of the core perpendicular to a longitudinal direction of the waveguide is tapered.
30. An optical device for use as a directional coupler, the optical device comprising two waveguides formed to be bent proximate each other in a coupling region having a predetermined coupling length, in which each of the two waveguides is formed of a photonic crystal waveguide, with each photonic crystal waveguide comprising:
a core formed of a photonic crystal having periodicity in a first direction and which propagates an electromagnetic wave in a second direction perpendicular to the first direction, the core comprising a photonic band structure having a Brillouin zone boundary and a photonic band present thereon comprising a propagation mode in which the electromagnetic wave is propagated;
a homogeneous medium cladding having a refractive index ns; and
the core comprising a side face parallel to the first direction in contact with the homogeneous medium cladding, the side face satisfying the condition:
\u03bb0ns>a\u03bb(\u03bb24+a2)0.5
where \u03bb0 denotes a wavelength of the electromagnetic wave in a vacuum, a denotes a period of the photonic crystal, and \u03bb denotes a period of the wave propagated trough the core in the second direction perpendicular to the first direction.
31. An optical device for use as a Mach Zehnder optical switch, the optical device comprising a first single linear waveguide, two branched waveguides branched from the first single liner waveguide, and a second single linear waveguide formed by merging the two branched waveguides, in which each of the waveguides is formed by a photonic crystal waveguide comprising:
a core formed of a photonic crystal having periodicity in a first direction and which propagates an electromagnetic wave in a second direction perpendicular to the first direction, the core comprising a photonic band structure having a Brillouin zone boundary and a photonic band present thereon comprising a propagation mode in which the electromagnetic wave is propagated;
a homogeneous medium cladding having a refractive index ns; and
the core comprising a side face parallel to the first direction in contact with the homogeneous medium cladding, the side face satisfying the condition:
\u03bb0ns>a\u03bb(\u03bb24+a2)0.5
where \u03bb0 denotes a wavelength of the electromagnetic wave in a vacuum, a denotes a period of the photonic crystal, and \u03bb denotes a period of the wave propagated through the core in the second direction perpendicular to the first direction.
32. An optical device for use as an optical delay line, the optical device comprising a linear waveguide and a single waveguide having a delay portion, wherein each of the waveguides and the delay portion are formed of a photonic crystal waveguide comprising:
a core formed of a photonic crystal having periodicity in a first direction and which propagates electromagnetic wave in a second direction perpendicular to the first direction, the core comprising a photonic band structure having a Brillouin zone boundary and a photonic band present thereon comprising a propagation mode in which the electromagnetic wave is propagated;
a homogeneous medium cladding having a refractive index ns; and
the core comprising a side face parallel to the first direction in contact with the homogeneous medium cladding, the side face satisfying the condition:
\u03bb0ns>a\u03bb(\u03bb24+a2)0.5
where \u03bb0 denotes wavelength of the electromagnetic wave in a vacuum, a denotes a period of the photonic crystal, and \u03bb denotes a period of the wave propagated through the core in the second direction perpendicular to the first direction.
33. An optical device for use as a dispersion control device, the optical device comprising a waveguide formed of a photonic crystal waveguide comprising:
a core formed of a photonic crystal having periodicity in a first direction and which propagates electromagnetic wave in a second direction perpendicular to the first direction, the core comprising a photonic band structure having a Brillouin zone boundary and a photonic band present thereon comprising a propagation mode in which the electromagnetic wave is propagated;
a homogeneous medium cladding having a refractive index ns; and
the core comprising a side face parallel to the first direction in contact with the homogeneous medium cladding, the side face satisfying the condition:
\u03bb0ns>a\u03bb(\u03bb24+a2)0.5
where \u03bb0 denotes a wavelength of the electromagnetic wave in a vacuum, a denotes a period of the photonic crystal, and \u03bb denotes a period of the wave propagated through the core in the second direction perpendicular to the first direction, wherein propagated light having a large dispersion condition is propagated through the waveguide.
34. An optical device comprising:
a photonic crystal waveguide comprising:
a core formed of a photonic crystal having periodicity in a first direction and which propagates electromagnetic wave in a second direction perpendicular to the first direction, the core comprising a photonic band structure having a Brillouin zone boundary and a photonic band present thereon comprising a propagation mode in which the electromagnetic wave is propagated;
a homogeneous medium cladding having a refractive index ns; and
the core comprising a side face parallel to the first direction in contact with the homogeneous medium cladding, the side face satisfying the condition:
\u03bb0ns>a\u03bb(\u03bb24+a2)0.5
where \u03bb0 denotes a wavelength of the electromagnetic wave in a vacuum, a denotes the period of a photonic crystal, and \u03bb denotes a period of the wave propagated through the core in the second direction perpendicular to the first direction, the core comprising a material having nonlinear characteristics; and
the waveguide comprising two surfaces and the optical device further comprising two electrodes arranged on the two surfaces of the waveguide in the first direction.
35. The optical device of claim 34, further comprising a modulator for changing a voltage or an electric current applied to the two electrodes.
36. An optical device comprising:
a photonic crystal waveguide comprising:
a core formed of a photonic crystal having periodicity in a first direction and which propagates an electromagnetic wave in a second direction perpendicular to the first direction, the core comprising a photonic band structure having a Brillouin zone boundary and a photonic band present thereon comprising a propagation mode in which the electromagnetic wave is propagated;
a homogeneous medium cladding having a refractive index ns; and
the core comprising a side face parallel to the first direction in contact with the homogeneous medium cladding, the side face satisfying the condition:
\u03bb0ns>a\u03bb(\u03bb24+a2)0.5
where \u03bb0 denotes a wavelength of the electromagnetic wave in a vacuum, a denotes a period of the photonic crystal, and \u03bb denotes a period of the wave propagated through the core in the second direction perpendicular to the first direction, wherein the cladding is confined imperfectly to generate refracted light from the core.