Load driving circuit

• US 20100014196A1
• Filed: 07/07/2009
• Published: 01/21/2010
• Est. Priority Date: 07/17/2008
• Status: Active Grant

• Current Assignee: Renesas Electronics Corporation
• Original Assignee: NEC Electronics Corporation (Renesas Electronics Corporation)
• Inventors: Oku, Koichiro
• Granted Patent: US 8,264,280 B2
• Time in Patent Office: Days
• US Class Current: 361/33
• CPC Class Codes: H02H 7/0844 Fail safe control, e.g. by comparing control signal and controlled current, isolating motor on commutation error

Abstract

Detection accuracy of a short circuit state in a load driving circuit is improved thereby operation efficiency of a motor may be enhanced. A gate control circuit 25 turns off NMOS transistors Q1 and Q4, turns on an NMOS transistor Q3, and turns on and off an NMOS transistor Q2 intermittently so as to control rotation of a motor 10. A detection circuit 30a detects a voltage Va at a connection node a between the NMOS transistor Q2 and the motor 10 a predetermined time after the NMOS transistor Q2 is turned on. A control circuit 20 turns off the NMOS transistor Q2 so as to cut off a current from a power supply to the motor 10 if the voltage Va at the connection node a is within a range in which the motor 10 is determined to be short-circuited.

Claims

1. A load driving circuit, comprising:

a switching device for intermittently connecting an inductive load to a power source;

a detection circuit for detecting a voltage at a connection node between the switching device and the inductive load a predetermined time after the switching device connects the inductive load to the power source; and

a control circuit for controlling the switching device so as to cut off power supply to the inductive load in accordance with the detected voltage at the connection node.

2. A load driving circuit according to claim 1, wherein the control circuit controls the switching device so as to cut off the power supply to the inductive load when the voltage at the connection node is within a range in which the inductive load is determined to be short-circuited.

3. A load driving circuit according to claim 1, wherein the detection circuit includes a comparator circuit for comparing the voltage at the connection node with a predetermined voltage, so as to detect the voltage at the connection node based on a comparison result of the comparator circuit.

4. A load driving circuit according to claim 3, further comprising a charging and discharging circuit including a capacitor element,

wherein, after the switching device connects the inductive load to the power source so that a charging and discharging of the capacitor element is started, the comparator circuit compares the voltage at the connection node with a voltage at a charging and discharging end of the capacitor element as the predetermined voltage.

5. A load driving circuit according to claim 4, wherein the charging and discharging circuit further includes a constant current circuit so as to perform the charging and discharging of the capacitor element with a current from the constant current circuit.

6. A load driving circuit according to claim 4, wherein the charging and discharging circuit further includes a resistor element so as to perform the charging and discharging of the capacitor element with a current from the power supply via the resistor element.

7. A load driving circuit according to claim 1, wherein:

the load includes a motor; and

the detection circuit and the control circuit constitute a part of a motor driving device.