JPH11136854A - Overcurrent protection circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To cut down largely the chip area occupied by an overcurrent protection circuit, by applying independently of each other the overcurrent protections obtained from the one overcurrent protection circuit to the outputs for the respective loads of many channels. SOLUTION: For example, when the outputs of motor driving circuits 3 of channels CH1, CH3 are brought into overcurrent states, making high-levels first the outputs of OR circuits 11 of the channels CH1, CH3 and starting the oscillation of an oscillating circuit 12, the output of a comparator 15 is made to be a low-level and only flip-flops 16 of the channels CH1, CH3 are set to open only AND gate circuits 17 of the channels CH1, CH3. Therefore, an overcurrent controlling signal outputted from a comparator 13 synchronously with the oscillation of the oscillating circuit 12 is inputted only to controlling circuits 2 of the channels CHI, CH3 to apply overcurrent controls only to the motor driving circuits 3 of the channels CH1, CH3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an overcurrent protection circuit for overcurrent protection of a multi-channel type motor driver IC or solenoid driver IC.

[0002]

2. Description of the Related Art Conventionally, a motor driver IC or a solenoid driver IC has an overcurrent protection circuit for protecting a driver IC, a motor, a relay and the like when an overcurrent flows to a load. FIG. 3 is a circuit diagram showing a configuration example of a conventional bidirectional motor driver (IC). The control circuit 2 rotates the motor M by controlling the motor drive circuit 3 to control the output current to the motor M.
When the motor M operates normally with a normal output current as shown in FIG. 4, the oscillation circuit 12 of the overcurrent protection circuit 1 stops operating.

However, if the output current increases for some reason and becomes an overcurrent, this is detected and the OR circuit 1 is detected.
1 becomes high level, the oscillation circuit 12 starts to charge as shown in FIG. 4, its oscillation voltage rises, and this voltage is input to the + terminal of the comparator 13.

On the other hand, to the minus terminal of the comparator 13, a divided voltage VTH-H of V0 by the resistors R1, R2, R3 is applied. Therefore, when the oscillation voltage applied to the + terminal of the comparator 13 exceeds VTH-H, the output voltage of the comparator 13 is inverted to a high level. As a result, the control circuit 2 controls the motor drive circuit 3 to make the output current to the motor M zero as shown in FIG. At the same time, the transistor 14 is turned on to drop the resistance R2 to the ground level, so that the negative terminal of the comparator 13 is applied with the divided voltage VTH-L of V0 by the resistances R1 and R2.

Next, when the output current to the motor M becomes zero, the output of the OR circuit 11 becomes low level, so that the oscillation circuit 12 starts discharging and the oscillation voltage drops. When the oscillation voltage becomes VTH-L, the output voltage of the comparator 13 is inverted to a low level. Thus, the control circuit 2 controls the motor drive circuit 3 to supply an output current to the motor M. At the same time, the transistor 14 is turned off, and the negative terminal of the comparator 13 includes resistors R1, R2,
A divided voltage VTH-H of V0 by R3 is applied.

Similarly, in the overcurrent mode, the on / off of the output current to the motor M is repeated in synchronization with the oscillation voltage of the oscillation circuit 12, so that the IC constituting the motor drive circuit 3 and the supply output to the motor M are reduced. Because it is suppressed, the IC and the motor M are not broken.

By the way, in recent years, the number of channels has increased,
A multi-channel driver as shown in FIG. 5, which can drive two or more motors and solenoids with one IC, has been developed. However, these multi-channel driver ICs also require the overcurrent protection circuit 1. In this case, for example, channel C
If overcurrent protection is applied to all channels just because an overcurrent flows in H1, the motors M of CH2, CH3, and H4 stop, so that overcurrent protection cannot be applied to all channels. Therefore, overcurrent protection must be performed independently for each channel, and an overcurrent protection circuit 1 similar to that shown in FIG. 3 is provided for each channel.

However, in this case, the overcurrent protection circuit 1
In this case, four circuits are required, and the semiconductor chip area occupied by these circuits 1 becomes enormous. If the semiconductor chip cannot be accommodated, one overcurrent protection circuit is provided for CH1 and CH2, and one overcurrent protection circuit is provided for CH3 and CH4. A configuration in which a protection circuit is provided is also employed. But,
Even with such a configuration, if an overcurrent flows through CH1,
Since the overcurrent protection circuit common to the small channel sections of CH1 and CH2 operates, the power supplied to the motor M of the normal CH2 is suppressed, and the problem that the motor M stops is inevitable.

[0009]

In the multi-channel type (4-channel type) bidirectional motor driver shown in FIG. 5, if an overcurrent protection circuit 1 is provided for each channel,
There has been a problem that the semiconductor chip area occupied by the plurality of overcurrent protection circuits 1 becomes enormous. In some cases, the semiconductor chip may not fit. Therefore, the number of overcurrent protection circuits is reduced by dividing the four channels into, for example, two channels of small channel sections and providing an overcurrent protection circuit at a rate of one for each of these small channel sections. In this case, when an overcurrent flows in one channel of the small channel section, the supply power to the motor of another normal channel in the small channel section is suppressed, and the motor stops. There was a problem that would.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and an object of the present invention is to provide overcurrent protection by a single overcurrent protection control circuit for output to each load of multiple channels. Each channel can be multiplied independently,
Accordingly, an object of the present invention is to provide an overcurrent protection circuit that can significantly reduce the area of the semiconductor chip occupied by the overcurrent protection circuit.

[0011]

In order to achieve the above object, a feature of the first invention is that when an overcurrent of the output of a multi-channel driver for supplying an output to a multi-channel load is detected, the output is reduced. The overcurrent protection circuit for performing the overcurrent control for reducing the power supply includes a selection means for selectively performing the overcurrent control only on the channel whose output is overcurrent.

According to the first aspect, one overcurrent protection circuit is provided for the multi-channel driver. When this one overcurrent protection circuit detects overcurrent of the driver output of a certain channel and starts overcurrent control, this overcurrent control is performed only for the channel that has become overcurrent by the selection circuit. Works to reduce only the output of this channel driver. Thus, the output of the driver of the channel whose output is normal is not subjected to the overcurrent control, and the normal output state is maintained.

According to a second aspect of the present invention, the selection means includes: holding means for holding overcurrent information indicating that the output of its own channel is in an overcurrent state; and this holding means holds the overcurrent information. And a gate means for inputting an overcurrent control signal output from the overcurrent protection circuit to a control circuit for controlling a driver of the own channel by opening the circuit during each of the channels. .

According to the second aspect, the gate means opens the gate during a period in which the holding means holds overcurrent information indicating that the output of its own channel is in an overcurrent state. Then, the overcurrent control signal output from the overcurrent protection circuit is input to a control circuit that controls the driver of the own channel, and the overcurrent control for the output of the driver of the own channel is performed.

When the output of its own channel returns from the overcurrent state to the normal output state, the selection means of the third aspect of the invention clears the overcurrent information held in the holding means, and clears the overcurrent information. Close means.

According to the third aspect, the gate means clears the overcurrent information held in the holding means when the output of its own channel returns from the overcurrent state to the normal output state. , Close. This allows
In the subsequent normal output state, the overcurrent control signal output from the overcurrent protection circuit is blocked by the opening of the gate means, and is not input to the driver control circuit of its own channel.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram showing a configuration of an overcurrent protection circuit according to one embodiment of the present invention. This example is an example in which the overcurrent protection circuit of the present invention is applied to a multi-channel bidirectional motor driver. However, the same parts as those in the conventional example will be described using the same reference numerals. There are four channels of the bidirectional motor driver of this example, channel 1 (CH1) to channel 4 (CH4), and one overcurrent protection circuit 10 common to these channels is provided. The configuration of each channel is the same, and the control circuit 2 controls the motor drive circuit 3 to control the output current of the motor M. The motor drive circuit 3 outputs a current to the motor M to rotate the motor M. When the output current of the motor drive circuit 3 becomes an overcurrent, the output signal of the OR circuit 11 changes from a low level to a high level, and the output signal becomes a flip-flop (F / F) 16 and the overcurrent protection circuit 1. Is input to the oscillation circuit 12. The flip-flop 16 holds overcurrent information indicating whether or not the motor drive circuit 3 of the channel to which it belongs is in an overcurrent state.
D) Open and close 17. An overcurrent control signal of the overcurrent protection circuit 10 is input to the control circuit 2 through the AND circuit 17.

The OR circuit 11, flip-flop 16, and AND circuit 17 are provided in four sets corresponding to the channels among the components of the overcurrent protection circuit 10, but the remaining circuits for performing the overcurrent protection control are provided for all the channels. This circuit is common, and this circuit occupies most of the area occupied by the semiconductor chip.

Next, the operation of this embodiment will be described with reference to the timing chart of FIG. For example, when the motor M of the channel 1 is operating with a normal output current as shown in FIGS. 2A and 2B, the oscillation circuit 12 of the overcurrent protection circuit 10 stops operating. However, if the output current of the motor drive circuit 3 of the channel 1 increases for some reason and becomes an overcurrent, this is detected and the output of the OR circuit 11 of the channel 1 becomes high as shown in FIG. Become a level. As a result, the oscillation circuit 12 starts charging as shown in FIG. 2B, the oscillation voltage of the oscillation circuit 12 rises, and this voltage is input to the + terminal of the comparator 13 and the − terminal of the comparator 15.

On the other hand, a minus terminal of the comparator 13 is provided with a divided voltage VTH-H1 of V0 by resistors R1, R2 and R3.
Is applied, and the + terminal of the comparator 15 has a resistor R
4. A divided voltage VTH-L2 of V0 by R5 is applied. When the output of the OR circuit 11 becomes high level, the flip-flop 16 of the channel 1 can be set.

As a result, the oscillation output of the oscillation circuit 12 becomes V
When TH-L2 is exceeded, the output of the comparator 15 becomes as shown in FIG.
Inverting from high level to low level as shown in (E),
As a result, the flip-flop 16 of the channel 1 is set, the output thereof is set to the high level as shown in FIG. 2 (F), and the AND circuit 17 of the channel 1 is opened.

Thereafter, the oscillation voltage applied to the + terminal of the comparator 13 becomes VT as shown in FIG.
When H-H1 is exceeded, the output voltage of the comparator 13 is inverted to a high level as shown in FIG. 2D, and this output voltage is passed through the AND circuit 17 of the channel 1 as shown in FIG. 1 to the control circuit 2.

Thus, the control circuit 2 of the channel 1 controls the motor drive circuit 3 of the channel 1 so that the motor M
The output current to is set to zero as shown in FIG. At the same time, the transistor 14 is turned on, and the resistance R
2 to the ground level, the minus terminal of the comparator 13 has a divided voltage VTH-L of V0 by resistors R1 and R2.
1 is applied.

Next, when the output current to the motor M becomes zero, no overcurrent is detected, the output of the OR circuit 11 of the channel 1 becomes low level, the oscillation circuit 12 starts discharging, and the oscillation voltage drops. I do. This oscillation voltage is VTH
At −L1, the output voltage of the comparator 13 is inverted to a low level as shown in FIG. This allows
The control circuit 2 controls the motor drive circuit 3 so that the control circuit 2 shown in FIG.
The output current is supplied to the motor M as shown in FIG. At the same time, the transistor 14 is turned off, and a divided voltage VTH-H1 of V0 by the resistors R1, R2, and R3 is applied to the minus terminal of the comparator 13.

In the overcurrent mode, the same applies to FIG.
(B) As shown in (A), the on / off of the output current to the motor M of the channel 1 is repeated in synchronization with the oscillation voltage of the oscillation circuit 12, and the IC and the motor M constituting the motor drive circuit 3 of the channel 1 are repeated. The output of supply to is suppressed.

Further, at this time, if the output current of the motor drive circuit 3 of the other channel is not an overcurrent, the flip-flop 16 of the other channel is reset and the AND circuit 17 of the other channel is closed. The output voltage (overcurrent control signal) of the comparator 13 of the overcurrent protection circuit 10 is not input to the control circuit 2 of another channel,
Overcurrent control is not performed on the motor drive circuits 3 of the other channels.

Thereafter, as shown in FIG. 2A, when the output of the motor drive circuit 3 of the channel 1 returns from the overcurrent state and becomes normal, the oscillation circuit 12 charges and discharges as shown in FIG. 2B. And the output voltage becomes VTH-L2 or less. As a result, the output of the comparator 15 changes from the low level to the high level, the flip-flop 16 of the channel 1 is reset, and the output is changed to the low level as shown in FIG. Is closed. Thereafter, the outputs of the motor drive circuits 3 of all channels become normal, and the motor M is driven.

The above operation has been described for the case where the output of the motor drive circuit 3 of the channel 1 is in an overcurrent state. For example, when the output of the motor drive circuit 3 of the channels 1 and 3 is in an overcurrent state. Is channel 1,
The flip-flop 16 of the channel 3 is set, the AND circuits 17 of the channels 1 and 3 are opened, and the overcurrent control of the overcurrent protection circuit 1 is performed on the motor drive circuit 3 of the channels 1 and 3.

According to the present embodiment, the overcurrent protection circuit 1
When the output of any one or more of the motor drive circuits 3 in the four-channel motor drive circuit 3 is in an overcurrent state, 0 is transmitted to the motor drive circuit 3 through the control circuit 2 of the channel in which the overcurrent has occurred. Since the overcurrent control can be performed only for the motor M, the problem that the motor drive circuit 3 of the normal channel receives the overcurrent control and the motor M to which the normal output current is supplied is stopped is eliminated. it can. In addition, since overcurrent control for all channels can be performed with only one overcurrent protection circuit for a four-channel bidirectional motor driver, this overcurrent protection circuit (particularly a circuit that performs overcurrent protection control). Part) 1
The semiconductor chip area occupied by zeros can be greatly reduced, and the multi-channel motor driver IC can be miniaturized, and its manufacture can be made easy and inexpensive.

The same effect can be obtained by applying the present invention to a multi-channel type high-side and low-side solenoid driver and a lamp driver other than the bidirectional motor driver.

[0031]

As described above in detail, according to the overcurrent protection circuit of the present invention, the overcurrent protection by one overcurrent protection control circuit is performed for each output of each load of the multichannel for each channel. It can be applied independently, which can greatly reduce the semiconductor chip area occupied by the overcurrent protection circuit.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a configuration of an overcurrent protection circuit according to one embodiment of the present invention.

FIG. 2 is a timing chart showing an operation example of the overcurrent protection circuit shown in FIG.

FIG. 3 is a circuit diagram showing a configuration example of a conventional overcurrent protection circuit.

FIG. 4 is a timing chart illustrating an operation example of the overcurrent protection circuit illustrated in FIG. 3;

FIG. 5 is a circuit diagram showing a conventional example of an overcurrent protection circuit of a multi-channel (four-channel) bidirectional motor driver.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Overcurrent protection circuit 2 Control circuit 3 Motor drive circuit 10 Overcurrent protection circuit 11 OR circuit 12 Oscillation circuit 13, 15 Comparator 14 Transistor 16 Flip-flop 17 AND circuit

Claims (3)

[Claims] When an overcurrent of the output of a multi-channel driver that supplies an output to a multi-channel load is detected,
An overcurrent protection circuit that performs overcurrent control for reducing the output, further comprising a selection unit configured to selectively perform the overcurrent control only on a channel whose output is overcurrent. Overcurrent protection circuit. 2. The information processing apparatus according to claim 1, wherein said selection means holds overcurrent information indicating that an output of its own channel is in an overcurrent state, and said selection means holds an open circuit while said holding means holds said overcurrent information. A gate circuit for inputting an overcurrent control signal output from the overcurrent protection circuit to a control circuit for controlling a driver of the own channel, for each of the channels. The overcurrent protection circuit as described. 3. The selection means clears the overcurrent information held in the holding means and closes the gate means when the output of its own channel returns from the overcurrent state to the normal output state. 3. The overcurrent protection circuit according to claim 2, wherein: