EP0602977A2
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Method and apparatus for operating polyphase DC motors using a PWM chopping signal in zero crossing determination
Assignee: STMicroelectronics lnc USA
•
Filing: 1993-12-16
•
Granted: —
•
Expires: 2013-12-16
Abstract
Abstract A circuit for operating a polyphase dc motor has a plurality of driving coils has a circuit that provides instantaneous drive currents to selected ones of the driving coils in a each of a plurality of predetermined commutation sequences. Circuitry for detecting zero crossings of a back emf voltage of the coils is connected into a floating state during each of the predetermined commutation sequences to produce a back emf detection signal for timing changes among the predetermined commutation sequences. Circuitry controls the drive currents to the selected driving coils to be turned on and off, and circuitry delays the zero crossing detection for a predetermined time after the drive currents are turned-off. In a preferred embodiment, the circuitry for controlling the drive currents to the selected driving coils to be turned on and off comprises circuitry for generating a chop signal when the current in the active coils exceeds a predetermined threshold, and more particularly comprises PWM circuitry. A method for operating a polyphase dc motor having a plurality of driving coils is presented. According to the method, drive current supplied to the driving coils is chopped to control the maximum current delivered thereto by turning the drive current on and off. Zero crossings of a back emf voltage of the driving coils that are connected into a floating state are detected for producing a commutation signal, and the detection of zero crossings is inhibited for a predetermined time after the drive current is turned off during the chopping step to avoid detecting a false zero crossing. The chopping is performed as a part of a PWM operation.
Inventors
- 👤 Francesco Carobolante
- 👤 Scott W. Cameron
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-31 05:09
CPC Classifications
H; H02; H02P; H02P6/00; H02P6/14; H02P6/16; H02P6/18; H02P6/182
Claims Analysis
Total Claims: 20
Claim 1
Independent Claim
113 words
A circuit for operating a polyphase dc motor having a plurality of driving coils, comprising: a circuit to provide instantaneous drive currents to selected ones of said driving coils in a each of a plurality of predetermined commutation sequences; circuitry for detecting zero crossings of a back emf voltage of the coils connected into a floating state during each of said predetermined commutation sequences to produce a back emf detection signal for timing changes among said predetermined commutation sequences; circuitry for controlling the drive currents to said selected driving coils to be turned on and off; and circuitry for delaying zero crossing detection for a predetermined time after the drive currents are turned-off.
Claim 2
Dependent Claim
42 words
The circuit of claim 1 wherein said circuitry for controlling the drive currents to said selected driving coils to be turned on and off comprises circuitry for generating a chop signal when the current in said active coils exceeds a predetermined threshold.
Claim 3
Dependent Claim
27 words
The circuit of claim 2 wherein said circuitry for controlling the drive currents to said selected driving coils to be turned on and off comprises PWM circuitry.
Claim 4
Dependent Claim
33 words
The circuit of claim 2 wherein said circuitry for delaying zero crossing detection comprises circuitry for controlling a back emf sampling time to allow sampling at time of minimum back emf induced noise.
Claim 5
Dependent Claim
60 words
The circuit of claim 4 wherein said circuitry for delaying zero crossing detection comprises circuitry for controlling a back emf sampling time to allow sampling only between times when the drive current circuitry controls the drive current to be turned on and when the circuit to provide instantaneous drive currents to selected ones of said driving coils actually applies current.
Claim 6
Dependent Claim
39 words
The circuit of claim 4 wherein said circuitry for delaying zero crossing detection further comprises a flip-flop that is clocked by the circuitry for controlling the drive currents to said selected driving coils to be turned on and off.
Claim 7
Dependent Claim
197 words
A circuit for operating a sensorless polyphase dc motor having a plurality of driving coils, comprising: a commutation sequencer for producing signals in each of a plurality of commutation sequences to identify which of said driving coils are to be active to receive instantaneous drive currents and which are to be connected into a floating state; drive circuitry for connecting said coils to receive the instantaneous drive currents and into the floating state in accordance with the signals from said commutation sequencer; circuitry for detecting zero crossings of a back emf voltage of the coils connected into the floating states to produce a back emf detection signal; circuitry responsive to the back emf detection signal for producing a delayed signal to increment the commutation sequencer to a next commutation sequence; circuitry for generating a chop signal when the current in said active coils exceeds a predetermined threshold; circuitry for turning the drive currents supplied to the selected active coils on and off to modulate the drive currents in accordance with said chop signal; circuitry for delaying a detection of a next zero crossing for a predetermined time after the drive currents are turned-off by said chop signal.
Claim 8
Dependent Claim
23 words
The circuit of claim 7 wherein said drive circuitry is a triple - ½ - H - bridge, and comprises FET power transistors.
Claim 9
Dependent Claim
49 words
The circuit of claim 7 wherein said circuitry for detecting zero crossings of a back emf voltage comprises a comparator switchably connected to each coil when it is connected in a floating state operable to produce an output when the voltage on the floating coil crosses a reference voltage.
Claim 10
Dependent Claim
40 words
The circuit of claim 7 wherein said circuitry for turning the drive currents supplied to the selected active coils on and off comprises circuitry for generating a chop signal when the current in said active coils exceeds a predetermined threshold.
Claim 11
Dependent Claim
25 words
The circuit of claim 10 wherein said circuitry for turning the drive currents supplied to the selected active coils on and off comprises PWM circuitry.
Claim 12
Dependent Claim
42 words
The circuit of claim 7 wherein said circuitry for delaying a detection of a next zero crossing comprises circuitry for controlling a back emf sampling time to allow sampling at time when minimum back emf induced noise exists on the floating coil.
Claim 13
Dependent Claim
72 words
The circuit of claim 12 wherein said circuitry for delaying a detection of a next zero crossing comprises circuitry for controlling a back emf sampling time to allow sampling only between times when the circuitry for turning the drive currents supplied to the selected active coils on and off controls the drive current to be turned on and when the drive circuitry actually connects said coils to receive the instantaneous drive currents.
Claim 14
Dependent Claim
43 words
The circuit of claim 13 wherein said circuitry for delaying a detection of a next zero crossing further comprises a flip-flop that is clocked by the circuitry for controlling the drive currents to said selected driving coils to be turned on and off.
Claim 15
Dependent Claim
24 words
The circuit of claim 6 or claim 14 wherein said flip-flop is connected to receive an output of said circuitry for detecting zero crossings.
Claim 16
Dependent Claim
20 words
The circuit of claim 1 or claim 7 wherein the polyphase dc motor is a sensorless, brushless polyphase dc motor.
Claim 17
Independent Claim
91 words
A method for operating a polyphase dc motor having a plurality of driving coils, comprising: chopping drive current supplied to said driving coils to control the maximum current delivered thereto by turning the drive current on and off; detecting zero crossings of a back emf voltage of said driving coils that are connected into a floating state for producing a commutation signal; and inhibiting the detection of zero crossings for a predetermined time after the drive current is turned off during said chopping step to avoid detecting a false zero crossing.
Claim 18
Dependent Claim
17 words
The method of claim 17 wherein said chopping is performed as a part of a PWM operation.
Claim 19
Dependent Claim
22 words
The circuit of claim 18 wherein said inhibiting is performed for a time sufficient to allow PWM induced noise to be minimum.
Claim 20
Dependent Claim
48 words
The circuit of claim 18 wherein said inhibiting is performed to allow sampling only between times when the drive current circuitry controls the drive current to be turned on and when the circuit to provide instantaneous drive currents to selected ones of said driving coils actually applies current.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
Maintenance schedule is calculated for granted US utility patents.