Motor control device and electric power steering system
A motor control device with which both high-accuracy current detection and improvement in voltage utilization factor are achieved is provided. When an ON time of any one of low potential side switching elements corresponding to respective phases in a driving circuit is shorter than a detection time of a current value, a microcomputer estimates a phase current value of a current undetectable phase based on current values of two phases other than the current undetectable phase corresponding to the said FET. Then, at the time of current detection using the blind correction, during current detection for two phases, other than the current undetectable phase, based on which the blind correction is performed, motor control signals for maintaining switching states of a switching arm corresponding to the current undetectable phase are output.
1. A motor control device, comprising:
a control signal output device that generates and outputs motor control signals; and
a driving circuit that outputs three-phase driving electric power based on the motor control signals, wherein
the driving circuit is formed by connecting switching arms, the switching arms formed by serially connecting pairs of switching elements that are turned ON or OFF based on the motor control signals, in correspondence with respective phases, in parallel with one another,
each of the switching arms respectively have current sensors that detect phase current values of the respective phases corresponding to the switching arms at low potential sides thereof,
the control signal output device generates the motor control signals based on phase current values of the respective phases, detected at a time at which all low potential side switching elements of the respective switching arms are turned ON,
when an ON time of any one of the low potential side switching elements is shorter than the detection time, the control signal output device estimates a phase current value of a currently undetectable phase based on the phase current values of the respective phases, each of the respective phases are phases other than the currently undetectable phase, and
at the time of detection of the respective phases, motor control signals corresponding to the currently undetectable phase are output, and
the motor control signals corresponding to the currently undetectable phase are motor control signals that cause the driving circuit to: (i) keep ON a high potential side switching element of the pair of switching elements and (ii) keep OFF a low potential side switching element of the pair of switching elements.
2. The motor control device according to claim 1 , wherein
the control signal output device executes current feedback control based on detected phase current values of the respective phases to thereby compute voltage command values of the respective phases,
the control signal output device generates the motor control signals based on a comparison between duty command values corresponding to the respective voltage command values and a triangular wave, and
the motor control signals for maintaining switching states of the switching arm corresponding to the currently undetectable phase are output by shifting the duty command values of the respective phases toward a high potential side such that the duty command value of the current undetectable phase becomes a value at which the high potential side switching element corresponding to the current undetectable phase is kept ON.
3. The motor control device according to claim 1 , wherein the control signal output device generates the motor control signals in order to perform pseudo third harmonic superimposed sinusoidal wave conduction.
4. The motor control device according to claim 2 , wherein the control signal output device generates the motor control signals in order to perform pseudo third harmonic superimposed sinusoidal wave conduction.
5. The motor control device according to claim 1 , wherein the control signal output device generates the motor control signals in order to perform sinusoidal wave conduction.
6. The motor control device according to claim 2 , wherein the control signal output device generates the motor control signals in order to perform sinusoidal wave conduction.
7. A method of providing motor control signals, comprising:
detecting, by each current sensor of a plurality of switching arms of a driving circuit, phase current values of respective phases corresponding to the switching arms at low potential sides thereof;
generating, by a control signal output device, motor control signals based on phase current values of the respective phases, detected at a time at which all low potential side switching elements of the switching arms are turned ON;
when an ON time of any one of low potential side switching elements of the switching arms is shorter than the detection time, estimating, by the control signal output device, a phase current value of a currently undetectable phase based on the phase current values of the respective phases, each of the respective phases are phases other than the currently undetectable phase; and
outputting, by the control signal output device at the time of detection of the respective phases, motor control signals corresponding to the currently undetectable phase;
wherein the motor control signals corresponding to the currently undetectable phase are motor control signals that cause the driving circuit to: (i) keep ON a high potential side switching element of the pair of switching elements and (ii) keep OFF a low potential side switching element of the pair of switching elements.