Load drive control apparatus with performances of power-consumption reduction and overheat protection

• US 20040201938A1
• Filed: 04/11/2003
• Published: 10/14/2004
• Est. Priority Date: 04/12/2002
• Status: Active Grant

• Current Assignee: DENSO Corporation
• Original Assignee: DENSO Corporation
• Inventors: Watanabe, Hideo, ito, Makoto
• Granted Patent: US 7,088,565 B2
• Time in Patent Office: Days
• US Class Current: 361/103
• CPC Class Codes: H03K 17/0822 in field-effect transistor switches
• CPC Class Codes: H03K 2017/0806 against excessive temperature
• CPC Class Codes: H03K 2217/0036 Means reducing energy consumption

Abstract

A load drive control apparatus comprises a drive control circuit and a mode switchover circuit. The drive control circuit, which operates under a driving power, for driving/controlling a load on a control signal. The drive/control of the load includes an overheat protection control with a hysteresis characteristic carried out on a temperature of a component of the drive control circuit and/or the load. The overheat protection control involves a drive-limiting operation to stop a drive of the load. The mode switchover circuit switches over the drive control circuit between a normal mode and a stand-by mode responsively to the control signal. The stand-by mode is less in driving power consumption than the normal mode. The stop of the drive of the load is maintained during the drive-limiting operation whatever the control signal indicates, as long as the temperature is higher than a lower limit of the hysteresis characteristic.

Claims

1. An apparatus (1, 60) for driving and controlling a load (4), comprising:

a drive control circuit (8, 61), which operates under a driving power, for driving and controlling the load on the basis of a control signal, the drive and control of the load including an overheat protection control with a hysteresis characteristic carried out on the basis of a temperature of at least one of a component placed in the drive control circuit and the load, the overheat protection control involving a drive-limiting operation carried out to stop a drive of the load when an overheat state is detected based on the temperature, the hysteresis characteristic having an upper temperature and a lower temperature; and

a mode switchover circuit (6) for switching over the drive and control of the drive control circuit between a normal mode and a stand-by mode in response to the control signal, the stand-by mode being less in consumption of the driving power than the normal mode,

wherein either the drive control circuit or the mode switchover circuit has means for maintaining the stop of the drive of the load during the drive-limiting operation whatever the control signal indicates, as long as the temperature is higher than the lower limit.

2. The apparatus (1) according to claim 1, wherein the mode switchover circuit includes, as the maintaining means, means configured to prohibit a transition from the normal mode to the stand-by mode during the drive-limiting operation.

3. The apparatus according to claim 2, wherein the normal mode is a mode allowing the driving power to be supplied to the load and the stand-by mode is a mode allowing the driving power to be stopped from being supplied to the load.

4. The apparatus according to claim 3, further comprising a power supply circuit (7) for supplying the driving power to the drive control circuit,

wherein the mode switchover circuit is configured to allow the power supply circuit to mutually switch over the drive and control of the drive control circuit between the normal mode and the stand-by mode in response to the control signal.

5. The apparatus according to claim 4, wherein the drive control circuit has an overheat protection processor (18) for performing the overheat protection control that starts the drive-limiting operation responsively to a condition that the temperature reaches the upper limit (T1) and ends the drive-limiting operation responsively to another condition that the temperature is equal to or lower than the lower limit (T2;

T2<

T1)).

6. The apparatus according to claim 4, wherein the drive control circuit includes a temperature sensor (17) to detect the temperature at the component of the drive control circuit.

7. The apparatus according to claim 6, wherein the drive control circuit includes a drive circuit (10) in which switching elements (11 to 16) is provided, as the component of the drive control circuit, to output current to the load and a control circuit (9) for enabling an on/off control to be performed at the drive circuit for driving and controlling the load and performing the overheat protection control.

8. The apparatus according to either of claims 4, wherein the mode switchover circuit includes

a capacitor (27);

a charge/discharge switchover circuit (23) configured to allow the capacitor to be charged or discharged selectively in response to a switchover-control signal;

a switchover-signal production circuit (21, 22) configured to supply the control signal as the switchover-control signal during a period of time during which the drive-limiting operation is not carried out and to supply a charge-operation signal to command a charge of the capacitor during another period of time during which the drive-limiting operation is carried out; and

a power-supply control circuit (28, 29) configured to control the power supply circuit into a power-supplied state thereof in cases where a terminal voltage of the capacitor is equal to or higher than a predetermined switchover level and to control the power supply circuit into a power-stopped state thereof in cases where the terminal voltage of the capacitor is lower than the predetermined switchover level.

9. The apparatus according to either of claims 4, wherein the mode switchover circuit includes

a capacitor (27);

a charge/discharge switching-over circuit (23) configured to allow the capacitor to be charged or discharged selectively in response to a switchover-control signal; and

a power-supply control circuit (21, 22, 28, 29) configured to selectively control the power supply circuit into a power-supplied state or a power-stopped state thereof in accordance with a terminal voltage of the capacitor, a switchover to the power-supplied state being prohibited during a period of time during which the overheat-protecting operation is carried out.

10. The apparatus (1) according to claim 1, wherein the drive control circuit (8) includes, as the maintaining means, means for starting the overheat protection control that involves the drive-limiting operation in response to a condition that the temperature reaches the upper limit (T1), for determining whether or not the temperature is over a middle limit (T3) responsively to an issue of the control signal indicating the drive of the load, and for prohibiting the drive of the load until the temperature becomes equal to or smaller than the lower limit (T2;

T2<

T3<

T1), in cases where the determination reveals that the temperature is still over the middle limit.

11. The apparatus (60) according to claim 1, wherein the drive control circuit (61) includes, as the maintaining means,

means for memorizing information indicative a temperature rise when the temperature reaches the upper limit,

means for determining whether or not the information has been memorized in response to an issue of the control signal indicating the drive of the load;

and

means for prohibiting the drive of the load until the temperature becomes equal to or smaller than the lower limit, in cases where the determination reveals that the information has been memorized.

12. The apparatus according to claim 11, wherein the drive control circuit is made of a low-power-consumption type of circuit manufactured through a CMOS (complementary metal-oxide semiconductor) process.

13. The apparatus (60) according to claim 1, wherein the drive control circuit (61) includes, as the maintaining means,

means for actuating a timer to count a predetermined period of time when the temperature reaches the upper limit,

means for determining whether or not the timer has been actuated in response to an issue of the control signal indicating the drive of the load;

and

means for prohibiting the drive of the load until the temperature becomes equal to or smaller than the lower limit, in cases where the determination reveals that the timer has been actuated.

14. The apparatus according to claim 13, wherein the drive control circuit is made of a low-power-consumption type of circuit manufactured through a CMOS (complementary metal-oxide semiconductor) process.