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US 5,859,520 AGranted
Control of a brushless motor
AssigneeSGS-Thomson Microelectronics S.A.
InventorsJean-Marie Bourgeois, Jean-Marie Charreton, Pierre Guillemin, Bruno Maurice
Life of this patent
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Abstract
The invention provides a method for controlling a brushless motor, with windings connected in star (`wye`) formation, including the steps of periodically applying a supply voltage between first and second windings, detecting the presence of a current in a third winding, and an instant of cessation of that current, monitoring the value of a back emf induced in the third winding and detecting a zero crossing point of the back emf, timing a predetermined delay from the zero crossing point, and after the end of the delay, applying the supply voltage to other windings. The invention also provides a method for use with motors having windings connected in delta formation.
Claims24
A method for controlling a brushless motor having a plurality of windings, each having a first end connected to a common node and each having a second end connectable to supply voltages, comprising the steps of:
- a) applying an upper supply voltage to said second end of each of a first subset of said windings, applying a lower supply voltage to said second end of each of a second subset of said windings, said second end of at least one winding being disconnected from said supply voltages and comprising a disconnected winding, said supply voltage applied to at least one of said first and said second subsets being periodically interrupted;
- b) detecting a current in said disconnected winding and detecting an instant of cessation of said current in said disconnected winding;
- c) monitoring a value of back emf voltage induced in said disconnected winding, said monitoring beginning at said instant of cessation of said current in said disconnected winding;
- d) detecting a zero crossing point of said back emf voltage with respect to one of said upper and said lower supply voltages;
- e) timing a predetermined delay from said zero crossing point detected;
- and
- f) removing said supply voltages from said second ends of said first and said second subsets of said windings at the end of said predetermined delay, then applying said upper supply voltage to said second end of each of a third subset of windings, applying said lower supply voltage to said second end of each of a fourth subset of windings, said second end of at least one winding remaining unconnected to said supply voltages.
4 more elements
A method for controlling a brushless motor having a plurality of windings, each having a first end and a second end connected in delta formation with a plurality of nodes connectable to supply voltages including the steps of:
- a) applying an upper supply voltage to each of a first subset of said nodes, applying a lower supply voltage to each of a second subset of said nodes, at least one of said nodes being disconnected from said supply voltages comprising a disconnected node, said application of said supply voltage to at least one of said first and said second subsets of nodes being periodically interrupted;
- b) detecting a voltage at said disconnected node, said voltage caused by a new equilibrium of currents in said windings;
- c) monitoring a value of a back emf voltage induced in said windings and present at said disconnected node beginning at the instant of said new equilibrium of currents in said windings;
- d) detecting a zero crossing point of said back emf voltage with respect to one of said upper and said lower supply voltages;
- e) timing a predetermined delay from said zero crossing point detected;
- and
- f) removing said supply voltages from said first and second subsets of said nodes at the end of said predetermined delay, applying said upper supply voltage to a third subset of said nodes, applying said lower supply voltage to a fourth subset of said nodes, at least one of said nodes being disconnected from said supply voltages.
4 more elements
A circuit for controlling a brushless permanent magnet motor comprising:
- a plurality of windings, each of said windings having a first end connected at a common node and each of said windings having a second end connectable directly to supply voltages by switches, said second end connected to an upper supply voltage or connected to a lower supply voltage or disconnected from said supply voltages;
- clamping circuitry connectable with said second ends, said clamping circuitry producing a clamped voltage, said clamped voltage representing a voltage across an associated winding;
- a comparator receiving said clamped voltage on one input and a reference voltage on another input, said comparator result indicating polarity of a back emf voltage in said associated winding;
- and
- a latch providing control signals for the circuit, an input of said latch enabled by an enable signal, an output of said latch comprising a back emf voltage detection signal,
- wherein said clamping circuitry and said comparator are duplicated for each of said windings, each of said comparators having an output signal connected to an input of a multiplexer, said multiplexer having an output signal connected to an input of said latch, wherein said multiplexer is connected to select a chosen one of inverted and non-inverted versions of said output signal of each of said comparators, said selected version of said output signal used as said multiplexer output.
3 more elements
A circuit for controlling a brushless permanent magnet motor comprising:
- a plurality of windings, each of said windings having a first end connected at a common node and each of said windings having a second end connectable directly to supply voltages by switches, said second end connected to an upper supply voltage or connected to a lower supply voltage or disconnected from said supply voltages;
- clamping circuitry connectable with said second ends, said clamping circuitry producing a clamped voltage, said clamped voltage representing a voltage across an associated winding;
- a comparator receiving said clamped voltage on one input and a reference voltage on another input, said comparator result indicating polarity of a back emf voltage in said associated winding;
- and
- a latch providing control signals for the circuit, an input of said latch enabled by an enable signal, an output of said latch comprising a back emf voltage detection signal,
- wherein switching circuitry is provided to periodically interrupt at least one of said upper and said lower supply voltages, said enable signal synchronized to said periodic interruption.
3 more elements
A circuit for controlling a brushless permanent magnet motor comprising:
- a plurality of windings, each of said windings having a first end connected at a common node and each of said windings having a second end connectable directly to supply voltages by switches, said second end connected to an upper supply voltage or connected to a lower supply voltage or disconnected from said supply voltages;
- clamping circuitry connectable with said second ends, said clamping circuitry producing a clamped voltage, said clamped voltage representing a voltage across an associated winding;
- a comparator receiving said clamped voltage on one input and a reference voltage on another input, said comparator result indicating polarity of a back emf voltage in said associated winding;
- a latch providing control signals for the circuit, an input of said latch enabled by an enable signal, an output of said latch comprising a back emf voltage detection signal;
- and
- timer circuitry, said timer circuitry timing a predetermined delay period, said delay period beginning at a selected transition of contents of said latch, and at the end of said delay period, removing said supply voltages from certain windings and applying said supply voltages to further windings.
3 more elements
A circuit for controlling a brushless motor by measuring a back emf voltage comprising:
- a plurality of windings, each of said windings having a first end connected at a common node and each of said windings having a second end connectable directly to supply voltages by switches, said second end connected to an upper supply voltage or connected to a lower supply voltage or disconnected from said supply voltages;
- a single circuit detecting an end of a de-energizing period and detecting a zero crossing point of a back emf voltage to be detected, said circuit monitoring the back emf voltage generated by a rotor in each winding during a time between said end of said de-energizing period and said zero crossing point, said monitoring of back emf using an entire value of said back emf, said measurement of back emf performed during off periods of pulse width modulation control of a voltage supplied to each of said windings, said back emf voltage detected used to determine a position of a rotor to efficiently transition from one step to a next step when switching windings in said motor.
A circuit for controlling a brushless permanent magnet motor comprising:
- a plurality of windings, each of said windings having a first end connected at a common node and each of said windings having a second end connectable directly to supply voltages by switches, said second end connected to an upper supply voltage or connected to a lower supply voltage or disconnected from said supply voltages;
- clamping circuitry connectable with said second ends, said clamping circuitry producing a clamped voltage, said clamped voltage representing a voltage across an associated winding;
- means for measuring actual back emf voltage connected to said clamping circuitry;
- and
- a latch providing control signals for the circuit, an input of said latch enabled by an enable signal, an output of said latch comprising a back emf voltage detection signal, said latch being connected to an output of said means for measuring actual back emf voltage,
- wherein a multiplexer is connected to select a chosen one of inverted and non-inverted versions of an output signal of said means for measuring actual back emf voltage, the selected version of said output signal used as said multiplexer output.
3 more elements
A circuit for controlling a brushless permanent magnet motor comprising:
- a plurality of windings, each of said windings having a first end connected at a common node and each of said windings having a second end connectable directly to supply voltages by switches, said second end connected to an upper supply voltage or connected to a lower supply voltage or disconnected from said supply voltages;
- clamping circuitry connectable with said second ends, said clamping circuitry producing a clamped voltage, said clamped voltage representing a voltage across an associated winding;
- means for measuring actual back emf voltage connected to said clamping circuitry;
- and
- a latch providing control signals for the circuit, an input of said latch enabled by an enable signal, an output of said latch comprising a back emf voltage detection signal said latch being connected to an output of said means for measuring actual back emf voltage,
- wherein switching circuitry is provided to periodically interrupt at least one of said upper and said lower supply voltages, said enable signal synchronized to said periodic interruption.
3 more elements
Dependencies are inferred from the claim text.