JP2000069786A - Load drive control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a load drive control device which makes it possible to take measures for overvoltage without increase in cost. SOLUTION: When an overvoltage detection circuit 29 detects that an overvoltage has been applied to a power supply terminal 27, the overvoltage detection circuit outputs an overvoltage detection signal. If an overvoltage detection signal is output when a standby circuit 28 is in standby mode, the standby circuit goes into normal mode and supplies a drive control circuit 24 with power VBL for driving. The control circuit 39 in the drive control circuit 24 outputs a gate signal with a duty ratio of 100% to a drive circuit 40 to run a brushless motor 21 to consume the energy of the overvoltage.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a load drive control device provided with a drive control circuit for controlling the drive of a load based on predetermined drive conditions.

[0002]

2. Description of the Related Art For example, an ECU (E) which drives and controls a blower motor and a cooling fan motor used in an air conditioner (air conditioner) mounted on an automobile as a load.
For electronic control units, there is a demand to minimize unnecessary power consumption during periods when the operation of the motor is stopped. In order to meet such a demand, there is a configuration in which switching between a normal mode and a standby mode for reducing power consumption is performed based on a predetermined input condition.

FIG. 7 shows an example of the configuration. The ECU 1
Power supply circuit 2, drive control circuit 3, and standby circuit 4
The driving of the motor 5 is controlled by the fan 6.
Is to be rotated. Power is supplied from the vehicle battery 7 to the power supply circuit 2 and the standby circuit 4 via the diode 8.

[0004] The relay 9 provides a mode switching signal to the standby circuit 4 and the power supply circuit 2 in accordance with the operating state of the air conditioner.
The other end is connected to the cathode of the diode 8 via the diode 10 and to the ground via the diode 11 for protecting the battery 7 from reverse polarity connection. A power zener diode 12 is connected between the cathodes of the diodes 8 and 10 and the ground.

When the operation of the air conditioner is stopped and the relay 9 is open, the standby circuit 4 does not supply the driving power from the battery 7 to the main circuit section in the power supply circuit 2. Thus, the standby mode for reducing power consumption is set, and when the operation of the air conditioner is started and the relay 9 is closed, the mode is switched to the normal mode for supplying the main power to the main circuit unit. Then, the supply of drive power from the power supply circuit 2 to the drive control circuit 3 is started, and the drive control circuit 3 controls the drive of the motor 4 to rotate the fan 6.

[0006]

The power Zener diode 12 is provided to protect the power supply circuit 2 and the standby circuit 4 by clamping an overvoltage generated by a load dump or the like. However,
The power Zener diode 12 is an expensive component,
A device with an increased withstand voltage as a countermeasure for overvoltage is more expensive, and thus has a problem of increasing the product price.

[0007] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a load drive control device capable of taking measures against overvoltage without increasing the cost.

[0008]

According to the load drive control device of the first aspect, when an overvoltage detection signal is output from the overvoltage detection circuit during the standby mode, the mode switching means switches to the normal mode. This causes the power supply circuit to start supplying drive power to the drive control circuit. Since the drive control circuit drives the load under the substantially maximum output condition for a predetermined time, the energy of the overvoltage applied to the power supply terminal is consumed within a short time.

Therefore, the power supply circuit and the drive control circuit can be protected from overvoltage without using a power Zener diode. Since the overvoltage detection circuit can be integrally formed as an IC together with the standby circuit, the power supply circuit, and the like, a configuration for dealing with overvoltage can be realized at a low price.

According to the second aspect of the present invention, the mode switching means is configured to perform the mode switching based on a control signal for controlling the drive of the load. Without giving an ignition switch ON / OFF signal to the drive control circuit.
Since the switching between the normal mode and the standby mode can be performed, the whole can be configured at a lower price.

According to the load drive control device of the third aspect, the drive control circuit includes: a load as a brushless motor;
The brushless motor is driven and controlled based on a position detection signal output by a rotation position detection unit that detects a rotation position of the rotor. That is, when the mode shifts from the standby mode to the normal mode due to the detection of the overvoltage, the drive control circuit refers to the position detection signal output by the rotational position detection means to determine the brushless state according to the position of the rotor. It is possible to determine which phase of the motor is appropriate to start energizing from the coil corresponding to the phase. Therefore, no burden is placed on the brushless motor when starting up, so that the life can be extended.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a blower motor of an air conditioner (car air conditioner) mounted on an automobile will be described below with reference to FIGS. FIG. 4 is a functional block diagram showing an electrical configuration. In FIG. 4, for example, a fan 22 of a car air conditioner is attached to a rotating shaft of a motor (load) 21 composed of a brushless motor.
The fan 22 is arranged inside the front of the automobile, and is driven to rotate by the motor 21 to blow air cooled by an evaporator (not shown) into the vehicle interior.

On the rotor of the motor 21, hall ICs (rotational position detecting means) 23a, 23b and 23c for detecting a rotational position are arranged, and position detecting signals VHa, VHb and VHc are generated according to the rotational position of the rotor. The signal is output to the drive control circuit 24. Then, the drive control circuit 24
Drives the motor 21 by PWM based on the position detection signals VHa, VHb and VHc.

The drive control circuit 24 is supplied with a drive power supply VBL from a power supply circuit 26 using a vehicle battery 25 as a main power supply VB. The power supply circuit 26 is directly connected to the battery 25 via a power supply terminal 27 without a switch such as a relay. A drive command signal (control signal) for designating the number of rotations of the motor 21 is externally provided to a drive control circuit 24 and a standby circuit (mode switching means) 28.

The standby circuit 28 outputs a mode switching signal to the power supply circuit 26 in accordance with the drive command value of the motor 21 indicated by the supplied drive command signal. In response to the mode switching signal, the power supply circuit 26 switches between a normal mode in which the drive power supply VBL is supplied to the drive control circuit 24 and a standby mode in which the supply is stopped to reduce power consumption. It has become. Here, the standby mode is a mode in which the current supplied from the battery 25 shown in FIG. 4 and consumed by the drive control circuit 24 and the power supply circuit 26 is much smaller than that in the normal mode. , The current consumption is 1 mA or less.

The input terminal of the overvoltage detection circuit 29 is connected to the power supply terminal 27. The overvoltage detection circuit 29 outputs an overvoltage detection signal to the standby circuit 28 and the drive control circuit 24 when detecting that an overvoltage is applied to the power supply terminal 27 by, for example, a load dump.

The standby circuit 28 outputs a mode switching signal to the power supply circuit 26 so as to immediately shift to the normal mode when an overvoltage detection signal is given in the standby mode. Further, when an overvoltage detection signal is given, the drive control circuit 24 drives the motor 21 with the duty ratio of the PWM signal set to 100%.

FIG. 1 shows the electrical configuration of the standby circuit 28 in more detail. In FIG. 1, the battery 25 is connected to the I0 / VREF generation circuit 30 of the standby circuit 28. I0 / VREF generation circuit 30
Generates a constant current I0 and a reference voltage VREF from a power supply supplied from the battery 25, and supplies the constant current I0 and the reference voltage VREF to each part of the standby circuit 28 as appropriate.

The reference voltage VREF output from the I0 / VREF generating circuit 30 is supplied to a non-inverting input terminal of a first comparator 31. The inverting input terminal of the first comparator 31 is connected to a signal terminal Si from outside. A drive command signal is provided via the control unit. The output terminal of the first comparator 31 is provided to the charge / discharge switching circuit 32 as a switching control signal. The first comparator 31 functions as a buffer for shaping the waveform of a drive command signal that causes dullness when transmitted via a signal line.

Here, the drive command signal is a signal for designating the number of revolutions of the motor 21 by, for example, a low-level duty ratio of a pulse signal (see FIG. 5), and specifically, a duty signal of several hundreds to several kHz. It is. When the duty ratio becomes equal to or more than 20% (drive start condition), the drive control circuit 24 starts driving the motor 21 to control the rotation speed.

The charge / discharge switching circuit 32 includes a charging circuit 33,
It comprises a discharging circuit 34 and a switching control circuit 35. The switching control circuit 35 represented by the symbol of the changeover switch responds to the switching control signal output from the first comparator 31 by connecting the other end (the output terminal 35a) of the capacitor 36 whose one end is connected to the ground. One end of the charging circuit 33 or the discharging circuit 34 (input terminal 35b
Alternatively, switching is performed so as to connect to 35c). Incidentally, the switching control circuit 35 is actually constituted by a transistor or the like.

The other ends of the charge and discharge circuits 33 and 34 are connected to the battery 25 and the ground, respectively.
The ratio of the charge / discharge current to the capacitor 36 is set in advance so as to be substantially equal to the duty ratio of the drive command signal corresponding to the threshold value (mode switching threshold value) for switching between the normal mode and the standby mode. Is set.

For example, when the duty ratio of the drive command signal corresponding to the mode switching threshold is 5%, when the charging circuit 33 is connected to the capacitor 36 via the switching control circuit 35 (31b → 31a). , Condenser 36
Is set to 290 μA, and the discharging circuit 34 switches the switching control circuit 35 (31
When connected to the capacitor 36 via c → 31a), the current value for discharging the charge charged in the capacitor 36 to the ground is set to 10 μA. That is, charge / discharge current ratio (discharge current value / charge current value + discharge current value) = 10 /
(290 + 10) = 5%.

The output terminal 35a of the switching control circuit 35
The non-inverting input terminal of the second comparator 37 is connected to the inverting input terminal of the second comparator 37.
The reference voltage VREF output from the / VREF generation circuit 30 is applied. The output terminal of the second comparator 37 is connected to the negative logic input terminal of the negative logic output OR gate 38, and the output signal of the second comparator 37 becomes the mode switching signal.

The negative logic output terminal of the OR gate 38 is
The power supply circuit 26 is connected to a control signal terminal represented by a symbol of an on / off switch, and supplies a mode switching signal to the power supply circuit 26. Then, as described above, the power supply circuit 26 switches between the normal mode in which the drive power supply VBL from the battery 25 is supplied to the drive control circuit 24 and the standby mode in which the supply is stopped in response to the mode switching signal. Is what you do.

The drive control circuit 24 includes a control circuit 39 and a drive circuit 40. The drive circuit 40 is an n-channel power MOSFET (hereinafter simply referred to as an FET).
41 to 46 are constituted by inverters formed by three-phase bridge connection. A freewheel diode (not shown) is connected (or integrally formed as an element) between the source and the drain of each of the FETs 41 to 46.

The positive bus 40p of the drive circuit 40 is directly connected to the battery 25. The power supply terminal VP of the control circuit 39 is connected to the power supply terminal of the power supply circuit 26, and the negative bus 40n of the drive circuit 40 is connected to the ground. The control circuit 39 includes a control power supply circuit (not shown), and generates a control power supply of, for example, about 5 V from a drive power supply VBL of, for example, about 14 V supplied from the power supply circuit 26. It is supplied to the internal circuit.

The signal input terminal S of the control circuit 39 is connected to the output terminal of the first comparator 31. The position detection signals VHa, VHb and VHc output from the Hall ICs 23a, 23b and 23c are provided to the control circuit 39. In the motor 21, three-phase stator coils 21a, 21b and 21c are connected in a Δ-connection, and output terminals 40a, 40b and 40c of a drive circuit 40 are connected to the coils 21a, 21b and 21c.

Between the power supply terminal 27 and the ground,
The series circuit of the Zener diode 47 and the resistors 48a and 48b is connected. The common connection point of the resistors 48a and 48b is connected to the non-inverting input terminal of the third comparator 49. The non-inverting input terminal of the first comparator 31 is connected to a series circuit of the resistors 50a and 50b and n
The pn-type transistor 51 is connected to the ground via the collector-emitter of the pn-type transistor 51. The common connection point of the resistors 50a and 50b is connected to the inverting input terminal of the third comparator 49.

The output terminal of the third comparator 49 is connected to the base of the transistor 51 and to the power supply terminal 27 via the resistor 52.
The input terminal of the OR gate 38 and the input terminal FL of the full load command signal of the control circuit 39 are connected. A circuit centered on the third comparator 49 is the overvoltage detection circuit 2
9. The third comparator 49 outputs the Zener diode 47, the resistors 48a and 48b, and the 50a and 50b so as to output a high-level overvoltage detection signal when the voltage level applied to the power supply terminal 27 exceeds, for example, 30V. A constant has been set.

FIG. 2 is a functional block diagram showing the internal configuration of the control circuit 39. The logic pattern generator 53 is supplied with position detection signals VHa, VHb and VHc output from the Hall ICs 23a, 23b and 23c, and the logic pattern generator 53 receives the position detection signals VHa, VHb and VHb. By logically synthesizing VHc, gate signals La +, Lb +, Lc + and La−, Lb−, Lc− to be applied to the gates of the FETs 41 to 46 of the drive circuit 40 are generated and output.

The PWM generation unit 54 has a P
For example, a triangular wave signal of a predetermined frequency serving as a carrier of the WM signal is generated. In addition, the PWM generation unit 54 detects, for example, a duty (that is, a rotation speed command value of the motor 21) of the drive command signal externally supplied via the first comparator 31, and outputs a command signal having a level corresponding to the duty. S ′ is generated, and the integrated value of the deviation from the current rotational speed obtained from the Hall ICs 23a to 23c is compared with the level of the triangular wave signal. Then, for example, a PWM signal is generated in which the pulse width increases as the level of the deviation integral value increases.

The PWM signal output from the PWM generator 54 is supplied to one input terminal of an OR gate 55, and the output terminal of the OR gate 55 is connected to the AND gate 5
6a, 56b and 56c are connected to one input terminal. The other input terminal of the OR gate 55 is supplied with an overvoltage detection signal FL output from the overvoltage detection circuit 29.

The gate signals La +, Lb +, and Lc + output from the logic pattern generation unit 53 are not
The gate signals La−, Lb−, Lc− are supplied to AND gates 56 a, 56
b, 56c, and the gate signal LA from the output terminals of AND gates 56a, 56b, 56c.
, LB-, and LC- are applied to the gates of the FETs 44 to 46. That is, the gate signals LA-, L
B− and LC− are output as the logical product of the gate signals La−, Lb− and Lc− and the PWM signal output from the PWM generator 54. The power supply circuit 23, the standby circuit 28, and the overvoltage detection circuit 29 are integrally formed as an IC.

Next, the operation of the present embodiment will be described with reference to FIGS. For example, as shown in the section A of FIG. 6, the drive command signal is not output as an initial state (low level duty ratio 0%), the rotation of the motor 21 is stopped, and the level of the mode switching signal is low. Has become. Accordingly, the power supply circuit 26 stops supplying the driving power supply VBL from the battery 25 and is in the standby mode (see FIG. 6C).

From this state, it is assumed that the operation of the car air conditioner is started, a predetermined amount of air is blown by the fan 22, and the rotation speed of the motor 21 is designated by a drive command signal having a duty ratio of about 60% (FIG. 6, FIG. 6). Section B). When the level of the drive command signal is lower than the reference voltage VREF (3.75 V), the second comparator 37 outputs a low level signal.
When the voltage is higher than the reference voltage VREF, a switching control signal having a high level is output to the switching control circuit 35.

The switching control circuit 35 connects the capacitor 36 to the charging circuit 33 and the discharging circuit 34 according to the low and high levels of the switching control signal. Then, as shown in FIG. 6B, the capacitor 36 is charged with a current of 290 μA when the switching control signal is at a low level, and the charged charge becomes 1 when the switching control signal is at a high level.
Discharged at a current of 0 μA.

Here, the duty ratio of the drive command signal is 5
%, (Charge current value) × (charge time: low level period) = (discharge current value) × (discharge time: high level period), so that the terminal voltage of the capacitor 36 does not change from the initial value. Then, the duty ratio of the drive command signal is 5%.
Is exceeded, (left side)> (right side) in the above equation, the charge amount exceeds the discharge amount, and the terminal voltage of the capacitor 36 rises from the initial value. In this case, as the duty ratio is smaller (that is, the rotation speed command value for the motor 21 is lower), the transition from “standby to normal” is delayed, and the duty ratio is larger (that is, the rotation speed command value for the motor 21 is higher). The transition from "standby to normal" becomes faster as the distance increases.

Therefore, as shown in FIG. 6 (b), the terminal voltage of the capacitor 36 rises from 0V, and the reference voltage VREF
Is exceeded, the second comparator 37 sets the output signal to low level. Then, the power supply circuit 26 outputs the battery 2
5, the drive power supply VBL is supplied to the drive control circuit 24, and the mode shifts from the standby mode to the normal mode (section B → C in FIG. 6).

As described above, by charging / discharging the capacitor 36 in accordance with the duty ratio of the drive command signal and performing mode switching based on the terminal voltage level, when an impulse noise is applied to the drive command signal, , The noise level can be smoothed, and a configuration with good noise resistance can be obtained.

On the other hand, when the operation of the car air conditioner is stopped from the state of the normal mode and the duty ratio of the drive command signal falls below 5%, the capacitor 36 is discharged via the discharge circuit 34, and the terminal voltage of the capacitor 36 becomes the first voltage. When the voltage falls below the threshold value (reference voltage VREF) of the second comparator 37, the second comparator 37 sets the switching control signal to low level. Then, the power supply circuit 26 shifts from the normal mode to the standby mode, and stops supplying the drive power supply VBL to the drive control circuit 24 (FIG. 6, section D → E).

Further, once the mode shifts to the normal mode, the reference voltage VREF given by the I0 / VREF generation circuit 30 is slightly lowered in order to provide hysteresis when the mode shifts to the standby mode. (See FIGS. 6B and 6C). Therefore, as shown in the section D, even if the duty ratio of the drive command signal is suddenly set to 0%, the state does not immediately shift from “normal to standby”.

Next, an operation centering on the drive control circuit 24 and the overvoltage detection circuit 29 will be described. The control circuit 39 of the drive control circuit 24 is supplied with the drive power supply VBL in the normal mode, and when the fan 22 is rotated via the motor 21, the position detection signals VHa and VHb output by the Hall ICs 23a to 23c and VHc (Fig. 3
(See (a) to (c)).
And the gate signals La + to L
c- is generated (see FIGS. 3D to 3F). La + = / VHa.VHc, La- = VHa. / VHc Lb + = VHa. / VHb, Lb-= / VHa.VHb Lc + = VHb. / VHc, Lc + = / VHb.VHc where "/" indicates negative logic. Show. The negative side gate signals La− to Lc− are output from the PWM
The logical product of the WM signal and the WM signal (see FIG. 3G) is obtained, and is output as PWM-modulated gate signals LA- to LC-, as shown in FIGS.

Then, as shown in FIGS. 3 (d) to 3 (f), the directions in which the coils 21a to 21c of the motor 21 are energized by the driving circuit 40 are: U → V,: U → W, : V → W,: V → U,: W → U,: W → V, so that the voltage vector rotates by 60 degrees, and the motor 21 is driven to rotate.

In the state where the driving of the motor 21 is controlled as described above, the connection portion of the power supply line from the battery 25 is disconnected for some reason, and the load on the alternator is rapidly reduced, so that a positive surge voltage (for example, 70 V degree)
Is applied to the power supply terminal 27 (load dump).

Then, the Zener diode 47 of the overvoltage detection circuit 29 becomes conductive, and the divided voltage applied to the non-inverting input terminal of the third comparator 49 becomes larger than the reference voltage VREF applied to the inverting input terminal. And the output terminal of the third comparator 49 becomes high level, and the overvoltage detection signal is output.

The overvoltage detection signal is supplied to the drive control circuit 24
Is given as a full load command FL (see FIG. 3 (h)),
Since a high-level signal is supplied to the input terminal of the OR gate 55, the gate signals LA- to LC- are output as 100% duty signals irrespective of the PWM signal.
Then, since the motor 21 is driven to rotate at high speed under the maximum output condition, the energy of the surge voltage applied to the power supply terminal 27 is rapidly consumed.

In the process of consuming the energy of the surge voltage, the voltage level applied to the power supply terminal 27 gradually decreases. At this time, the transistor 51 is turned on by the output terminal of the third comparator 49 becoming high level, and the level of the reference voltage VREF applied to the inverting input terminal is divided by the resistors 50a and 50b. Is done.

Therefore, once a surge voltage is applied to the power supply terminal 27, the energy is consumed and the overvoltage detection signal (full load command FL) is applied until the applied voltage level drops below 30V and drops to about 25V, for example. ) Continues to be output. In the case of a load dump, it takes about 100 ms to 200 ms until energy of the surge voltage is substantially consumed.

Here, it is assumed that the same surge voltage as described above is applied to the power supply terminal 27 while the operation of the air conditioner is stopped and the air conditioner is in the standby mode. In this case, the drive power supply VBL is not supplied from the power supply circuit 26 to the drive control circuit 24, but when the overvoltage detection signal is output, the OR provided on the output side of the second comparator 37 is provided. When the input terminal of the gate 38 goes high, a mode switching signal is output to the power supply circuit 26.

Then, the supply of the drive power supply VBL to the drive control circuit 24 is started immediately. Then, even when the motor 21 stops rotating, the logic pattern generation unit 53 outputs the position detection signals VHa to VHc output from the Hall ICs 23a to 23c according to the rotational position of the rotor at that time. Logic synthesis is performed to generate and output appropriate gate signals La + to Lc-.

Also in this case, the negative gate signals La- through L-
c- is output as the gate signals LA- to LC- of 100% duty in accordance with the full load command FL regardless of the PWM signal output from the PWM generation unit 54, so that the motor 21 rotates at high speed under the maximum driving condition. When driven, the energy of the surge voltage is rapidly consumed.

As described above, according to this embodiment, when the level of the drive command signal for designating the rotation speed of the motor 21 by the duty ratio of the pulse signal falls below the reference voltage VREF, the standby circuit 28 is switched to the charge / discharge switching circuit 32. Is set to discharge the capacitor 36 when the voltage exceeds the reference voltage VREF. When the terminal voltage of the capacitor 36 falls below the reference voltage VREF, the power supply circuit 26 is charged.
Then, the supply of the drive power supply VBL to the drive control circuit 24 is stopped to shift from the normal mode to the standby mode.

The overvoltage detection circuit 29 outputs an overvoltage detection signal when detecting that an overvoltage has been applied to the power supply terminal 27, and the standby circuit 28 normally operates when the overvoltage detection signal is output during the standby mode. In the mode, the control circuit 39 of the drive control circuit 24 outputs a gate signal having a duty ratio of 100% to the drive circuit 40 to rotate the motor 21.

Therefore, in the standby mode and in a state where the drive power supply VBL is not supplied to the drive control circuit 24, the power supply terminal 2 is supplied due to a load dump or the like.
Even if an overvoltage is applied to 7, the normal mode is immediately shifted to and the motor 21 is rotated under the maximum driving condition, so that the energy of the overvoltage can be consumed within a short time.
Since the overvoltage detection circuit 29 can be integrally formed as an IC together with the power supply circuit 23 and the standby circuit 28, the overvoltage detection circuit 29 can overvoltage the power supply circuit 23 and the drive control circuit 24 without using an external power zener diode. , And a configuration for dealing with overvoltage can be realized at low cost.

The drive control circuit 24 is provided with a Hall IC 2
By referring to the position detection signals VHa to VHc output by 3a to 23c, the motor 2
Since it is possible to determine which of the coils 21a to 21c should be energized to start energizing, it is possible to extend the life of the motor 21 without putting a burden on starting the motor 21. it can.

Further, the standby circuit 28 can determine the drive condition (rotation speed) of the motor 21 specified by the drive command signal and shift to the standby mode. There is no need to use a relay or the signal of an ignition switch to stop the supply, and the power consumption can be reduced without increasing the cost by increasing the number of components and the number of input signals.

The present invention is not limited to the embodiment described above and shown in the drawings, and the following modifications or extensions are possible. When the duty ratio of the drive start condition in the control signal is 20%, the duty ratio of the mode switching threshold is not limited to 5%, and may be set to, for example, 3% or 10%. . In addition, 20%
May be set. The drive command signal is not limited to the signal for specifying the rotation speed of the motor 21 by changing the duty ratio of the pulse signal, but may be a signal for specifying the rotation speed by changing the signal level. Even when such a drive command signal is externally supplied, the standby circuit 28 in the first embodiment can be applied as it is by appropriately adjusting the level of the reference voltage VREF. For example, when the signal level of the drive command signal is the reference voltage VRE
When the mode switching threshold given by F is exceeded, the first
The capacitor 36 is continuously charged by the output signal of the comparator 31, and the terminal voltage increases,
The mode switching signal is output from the second comparator 3 so as to shift from “standby to normal”. Conversely, when the signal level of the drive command signal falls below the mode switching threshold, the capacitor 36 is continuously discharged, so that the mode switching is performed so that the terminal voltage falls and the mode shifts from "normal to standby". A signal is output.

Further, the mode switching means is connected to the battery 25.
By referring to the terminal voltage VB, when the terminal voltage VB decreases to some extent in accordance with the use state of the battery 25, the transition timing from "standby to normal" is further delayed, and "normal to standby" It is preferable to adjust the level of the reference voltage VREF so that the timing of transition to "" becomes earlier. With this configuration, it is possible to suppress the power consumption of the battery 25 and prolong the usable time. The mode switching means is not limited to the standby circuit 28, and may be, for example, one that performs mode switching with reference to ON / OFF of an ignition switch. The rotational position detecting means is not limited to the Hall ICs 23a to 23c, and may be, for example, a means for detecting a zero cross point of an induced voltage waveform generated in the coils 21a to 21c of the motor 21.

The position detection signal referred to by the PWM generation unit 54 is not limited to VHa but may be VHb or VHc. The switching element constituting the drive circuit is FET4
The number is not limited to 1 to 46, and may be a bipolar transistor or an IGBT. When the capacity of the motor 21 is small, the driving power supply VBL may be supplied to the driving circuit 40 via the power supply circuit 23. The motor 21 is not limited to Δ connection, but may be Y connection. The load is not limited to the motor 21.

[Brief description of the drawings]

FIG. 1 is an electrical configuration diagram according to an embodiment of the present invention.

FIG. 2 is a diagram showing a detailed electrical configuration of a control circuit.

FIG. 3 is a timing chart when a control circuit drives a brushless motor.

FIG. 4 is a functional block diagram showing the entire electrical configuration.

FIG. 5 is a diagram showing a relationship between a pulse duty ratio of a drive command signal and a rotation speed of a motor.

FIG. 6 is a diagram showing a drive command signal and a signal waveform of each part of a standby circuit.

FIG. 7 is a diagram corresponding to FIG.

[Explanation of symbols]

21 is a brushless motor (load), 22 is a fan, 23
a, 23b and 23c are Hall ICs (rotational position detecting means), 24 is a drive control circuit, 25 is a battery (main power supply), 26 is a power supply circuit, 28 is a standby circuit (mode switching means), 29 is an overvoltage detecting circuit , 40 indicate a drive circuit, and 41 to 46 indicate power MOSFETs (switching elements).

Claims (3)

[Claims] 1. A drive control circuit for performing drive control of a load based on a predetermined drive condition, a power supply circuit for supplying a drive power to the drive control circuit, and a power supply for the drive by the power supply circuit Mode switching means for switching between a normal mode and a standby mode for reducing power consumption by controlling the supply; and detecting that an overvoltage has been applied to a power supply terminal to which the power supply for driving is supplied. An overvoltage detection circuit that outputs a detection signal, wherein the mode switching means is configured to shift to the normal mode when an overvoltage detection signal is output from the overvoltage detection circuit during the standby mode. When an overvoltage detection signal is output from the overvoltage detection circuit, the drive control circuit drives the load under a substantially maximum output condition for a predetermined time. Load drive control apparatus characterized by being configured urchin. 2. The apparatus according to claim 1, wherein said mode switching means is configured to perform mode switching based on a control signal for performing drive control of said load.
The load drive control device as described in the above. 3. The load control device according to claim 1, wherein the load is a brushless motor, and the load control device includes a rotational position detecting unit that detects a rotational position of a rotor constituting the brushless motor and outputs a position detection signal. 3. The load drive control device according to claim 1, wherein the drive control of the brushless motor is performed based on a position detection signal output from a position detection unit.