Granted Patent B2

US 8,278,852 · App. 12/649,146 · Granted Oct 2, 2012

Abstract

Claims (14)

1. A motor driving circuit comprising:

a first transistor on a power source side and a second transistor on a ground side connected in series;

a third transistor on the power source side and a fourth transistor on the ground side connected in series;

a drive control circuit configured to control a energization state of a motor coil so as to be a driving state where either one group of a group of the first and fourth transistors and a group of the second and third transistors is on and the other group is off, or so as to be a regeneration state where the first and third transistors are off and the second and fourth transistors are on, the motor coil connected to a connection point of the first and second transistors and a connection point of the third and fourth transistors;

a set current detection circuit configured to detect whether an amount of current flowing through the motor coil has reached a set level;

an overcurrent detection circuit comprising first, second, third, and fourth comparators coupled respectively to the first, second, third, and fourth transistors, each comparator configured to compare a voltage drop across the respective transistor to a respective reference voltage to detect an overcurrent state where an amount of current flowing through any of the first to fourth transistors is over a predetermined amount of current; and

an overcurrent protection circuit configured to output a regeneration instruction signal for shifting the energization state to the regeneration state in a case where the overcurrent state does not occur and output a drive stop signal for stopping driving the motor coil in a case where the overcurrent state occurs, when the amount of current flowing through the motor coil has reached the set level in the driving state,

the drive control circuit shifting the energization state to the regeneration state to be maintained for a predetermined time period and thereafter returning the energization state to the driving state when the regeneration instruction signal is output, and turning off the first to fourth transistors when the drive stop signal is output.

2. The motor driving circuit of claim 1 , wherein

the overcurrent protection circuit outputs the drive stop signal when the overcurrent state has been maintained for a predetermined time period.

3. The motor driving circuit of claim 1 , wherein

the overcurrent protection circuit includes:

a minimum time count circuit configured to count to measure a minimum time period from a start of the driving state to a shift to the regeneration state; and

a control signal output circuit configured to output the regeneration instruction signal or the drive stop signal based on detection results of the set current detection circuit and the overcurrent detection circuit, after the minimum time period has been measured by counting.

Assignments (9)