US 7,023,157 B2Granted

Stepping motor drive device and method

AssigneeMatsushita Electric Industrial Co., Ltd.

InventorsShingo Fukamizu, Katsuhiro Onishi

Life of this patent

Estimating the term…

Loading patent…

Abstract

The reference signal generation unit 110a integrates, in the integration circuit 3, a staircase signal generated by the staircase generation unit 2, and thereby generates a reference signal VCTA whose signal level changes continuously over time, and which represents a limit value for the supply current. According to the control of the PWM control unit 120a, the bridge rectification circuit 130a maintains the coil supply current at the limit value, using a current chopper method. Additionally, when the current supply is stopped, the bridge rectification circuit 130a performs synchronous rectification, where the transistors 10 and 12 are brought into conduction, and a regenerative current is circulated in a closed circuit formed with the coil 19a. When the reference signal VCTA decreases relatively fast, the synchronous rectification prohibition unit 115a prohibits one of the transistors 10 and 12 from being brought into conduction when the current supply is stopped.

Claims18

Dependent claims

A stepping motor drive device comprising:

a supply current measurement unit operable to measure a supply current supplied to a coil of a stepping motor;
a reference signal generation unit operable to generate a reference signal whose signal level changes continuously over time and which represents a limit value for the supply current;
a chopper unit operable to pass the supply current in a conducting state through thereof and stop the supply current in a non-conducting state;
a PWM control unit operable to (i) bring the chopper unit into the conducting state in a predetermined cycle, and (ii) when in each cycle the measured supply current exceeds the limit value, bring the chopper unit into the non-conducting state;
a synchronous rectification unit operable to form, in a conducting state, a closed circuit together with the coil;
a synchronous rectification control unit operable to bring, during a time period when the chopper unit is in the non-conducting state, the synchronous rectification unit into the conducting state so as to make a regenerative current from the coil circulate in the closed circuit;
and
a synchronous rectification prohibition unit operable to prohibit, for at least a portion of a time period during which the limit value is decreasing, the synchronous rectification control unit from bringing the synchronous rectification unit into the conducting state.

5 more elements

A stepping motor drive method for a drive device having a synchronous rectification unit which forms, in a conducting state, a closed circuit together with a coil included in a stepping motor, the stepping motor drive method comprising the steps of:

(a) measuring a supply current to the coil;
(b) generating a reference signal whose signal level changes continuously over time and which represents a limit value for the supply current;
(c) starting the supply current to flow to the coil in a predetermined cycle and stopping the supply current when in each cycle the measured supply current exceeds the limit value;
(d) bringing the synchronous rectification unit into a conducting state while the supply current is stopped so as to make a regenerative current from the coil circulate in the closed circuit;
and
(e) prohibiting the synchronous rectification unit, for at least a portion of a time period during which the limit value is decreasing, from being brought into the conducting state in the step (d).

3 more elements

Dependencies are inferred from the claim text.