Circuit to improve motor phase current reconstruction via DC link
View Patent ↗Apparatus for reconstructing the phase currents of a multiphase load driven by a multiphase inverter fed by a DC link and controlled by a PWM controller, the apparatus including a sensor in the DC link, first and second sampling arrangements for sampling the current in the DC link by obtaining an output from said sensor, the first sampling arrangement obtaining a first sample of the current in the DC link during a first time period corresponding to a first switching pattern of said multiphase inverter and storing said first sample; the second sampling arrangement obtaining a second sample of the current in the DC link during a second time period after said first time period and corresponding to a second switching pattern of said multiphase inverter and storing said second sample; an A/D converter for converting said first sample to a digital signal during a time period after said first time period and for converting said second sample to a digital signal during a following third time period.
1. Apparatus for reconstructing the phase currents of a multiphase load driven by a multiphase inverter fed by a DC link and controlled by a PWM controller, the apparatus comprising:
a sensor in the DC link;
first and second sampling arrangements for sampling the current in the DC link by obtaining an output from said sensor,
the first sampling arrangement obtaining a first sample of the current in the DC link during a first time period corresponding to a first switching pattern of said multiphase inverter and storing said first sample;
the second sampling arrangement obtaining a second sample of the current in the DC link during a second time period after said first time period and corresponding to a second switching pattern of said multiphase inverter and storing said second sample;
an A/D converter for converting said first sample to a digital signal during a time period after said first time period and for converting said second sample to a digital signal during a following third time period.
2. The apparatus of claim 1 , wherein the first and second sampling arrangement comprises sample and hold circuits.
3. The apparatus of claim 1 , wherein the sampling arrangements operate such that during a time period, the sampling arrangement samples the current in the DC link for that time period and the A/D converter converts the sample to a digital value for a previous time period.
4. The apparatus of claim 1 , wherein the inverter is three-phase modulated.
5. The apparatus of claim 4 , wherein the sampling arrangements sample sequentially such that the first sampling arrangement samples, then the second sampling arrangement samples twice followed by the first sampling arrangement in a PWM period.
6. The apparatus of claim 1 , wherein the inverter is two-phase modulated.
7. The apparatus of claim 6 , wherein the sampling arrangements sample sequentially such that the first sampling arrangement samples, then the second sampling arrangement samples followed again by the first sampling arrangement in a PWM period.
8. The apparatus of claim 1 , further comprising a multiplexer circuit disposed between said first and second sampling arrangements and said A/D converter.
9. The apparatus of claim 1 , further comprising a multiplexer circuit coupled to said sensor, said first and second sampling arrangements being provided with an output from said multiplexer and providing outputs to said A/D converter.
10. The apparatus of claim 1 , wherein the sensor comprises a resistor in the DC link.
11. The apparatus of claim 1 , wherein the sensor comprises a Hall effect sensor.
12. The apparatus of claim 1 , wherein the A/D converter converts the first sample to a digital signal during the second time period.
13. The apparatus of claim 1 , wherein the A/D converter converts the second sample to a digital signal during the third time period.
14. The apparatus of claim 2 , wherein the sample and hold circuits each comprise a switch and a storage capacitor.