EP0735662A2
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
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Filing: 1993-12-16
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Granted: —
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Expires: 2013-12-16
Abstract
Abstract A method and a circuit for operating a polyphase dc motor having a plurality of driving coils are presented. According to them, 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
2026-11-08 01:34
CPC Classifications
H; H02; H02P; H02P6/00; H02P6/14; H02P6/16; H02P6/18; H02P6/182
Claims Analysis
Total Claims: 11
Claim 1
Independent 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 2
Dependent Claim
62 words
A circuit as claimed in claim 1 wherein said motor is operable in a non-PWM operating mode and in a PWM mode, said circuitry for turning the drive currents on and off is operable in the PWM mode and said delaying circuitry is operable in the PWM mode, said delaying circuitry being disabled from delaying such detection in the non-PWM operating mode.
Claim 3
Dependent Claim
25 words
The circuit of claims 1 or 2, wherein said drive circuitry is a triple - ½ - H - bridge, and comprises FET power transistors.
Claim 4
Dependent Claim
51 words
The circuit of claims 1 or 2, 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 5
Dependent Claim
42 words
The circuit of claims 1 or 2, 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 6
Dependent Claim
25 words
The circuit of claim 5, wherein said circuitry for turning the drive currents supplied to the selected active coils on and off comprises PWM circuitry.
Claim 7
Dependent Claim
44 words
The circuit of claims 1 or 2, 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 8
Dependent Claim
72 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 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 9
Dependent Claim
43 words
The circuit of claim 8, 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 10
Dependent Claim
21 words
The circuit of claim 9, wherein said flip-flop is connected to receive an output of said circuitry for detecting zero crossings.
Claim 11
Dependent Claim
19 words
The circuit of claims 1 or 2, wherein the polyphase dc motor is a sensorless, brushless polyphase dc motor.
References Cited (Backward Citations)
No citation records indexed.
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