WO2005067134A1

WO2005067134A1 - Power transistor protecting circuit of motor drive circuit, motor drive circuit, and semiconductor device

Info

Publication number: WO2005067134A1
Application number: PCT/JP2005/000118
Authority: WO
Inventors: Mitsuaki Daio; Daiki Yanagishima
Original assignee: Rohm Co., Ltd
Priority date: 2004-01-09
Filing date: 2005-01-07
Publication date: 2005-07-21
Also published as: JPWO2005067134A1; CN1938935A; TW200534564A; KR20060115913A

Abstract

A power transistor protecting circuit of a motor drive circuit, a motor drive circuit, or a semiconductor device, wherein when a breaking of wire exists between the output terminal of a power transistor and another end of an exciting coil of a motor, the power transistor can be prevented from being broken. There are included a terminal open detection circuit, a breaking-of-wire detection circuit and a drive halting circuit. While a power transistor is in an operation of outputting a drive current, it is determined whether there exists an open condition between a terminal, or a line connected thereto, of each exciting coil whose output terminal is not connected to the terminal open detection circuit and an output terminal, or a line connected thereto, which corresponds to each exciting coil. A breaking of wire is detected by detecting an open condition after detecting no open condition.

Description

Specification

Power transistor protection circuit of motor drive circuit, motor drive circuit and semiconductor device

Technical field

The present invention relates to a power transistor protection circuit for a motor drive circuit, a motor drive circuit, and a semiconductor device, and more particularly, to an output terminal of a power transistor and a motor in a stepper motor driver driven by a bipolar (half-wave) drive. The present invention relates to a power transistor protection circuit for a motor drive circuit capable of preventing a power transistor from being destroyed when a disconnection is made between the power transistor and an exciting coil.

Background art

[0002] A bipolar drive stepping motor driver (pulse motor driver) is a one-phase drive,

By sequentially exciting the stator side of the motor by one-phase-two-phase drive or two-phase drive, the protruding rotor is rotated by a predetermined rotation angle.

The driver that supplies the drive current for exciting each stator has a power transistor (output transistor) corresponding to each phase in series with the coil (excitation coil) connected to the power supply line and wound on the stator. Is provided in each. When the power transistor provided for each phase is turned ON / OFF at a predetermined timing, the stator is sequentially excited and the stepping motor is driven.

When the power transistor of a certain phase is turned on, the drive current sequentially increases during the ON period due to a transient phenomenon of a predetermined time constant determined by the inductance of the exciting coil of the phase and the impedance of the power transistor and the like!]. In order to limit this increase to a predetermined value, the power transistor is turned on and turned off after a predetermined period, so that the power transistor is controlled so that no overcurrent flows. Therefore, each phase of the power transistor is normally driven by shobbing with a logic value pulse of "H" (HIGH level) and "L" (LOW level) to be ONZOFF.

[0003] As one of such pulse drive controls, a chopper-controlled three-phase motor driver in which an ON period is set and controlled by a timer circuit and a protection circuit for its IGBT power transistor are known. (Patent Document 1).

Patent Document 1: JP-A-11-112313

Disclosure of the invention

Problems to be solved by the invention

[0004] The above-described power transistor protection circuit generally includes an overcurrent protection circuit and a current limiting circuit. However, if the motor drive driver is integrated into an IC, the output terminal is connected to the terminal of the motor's excitation coil, so connection failure between the output terminal and the motor is likely to occur. In addition, motors and other devices have a rotor, which can cause disconnection of the excitation coil.In motor drive circuits, etc., one of the output terminals of the power transistor may momentarily open due to noise or driving conditions. Therefore, if an attempt is made to detect a disconnection by detecting the open state of the terminal, erroneous detection is likely to occur, which affects the driving operation of the motor drive circuit, and is not practical. Therefore, no protection circuit has been found for this kind of disconnection.

In the stepping motor driver, the motor continues to be driven even if one of the output terminals has a poor connection or the exciting coil is disconnected. At this time, since no back electromotive force is generated in the exciting coil connected to the open terminal, the current flowing to the other exciting coils increases by that amount, and the motor continues to be driven in an overloaded state as a whole driver. Is performed. As a result, the power transistor is destroyed, and the IC itself is destroyed. An object of the present invention is to solve such a problem of the prior art, and to reduce the output terminal force of the power transistor. An object of the present invention is to provide a power transistor protection circuit for a motor drive circuit, a motor drive circuit, or a semiconductor device that can prevent a power transistor from being destroyed when there is a disconnection up to the other end of a coil. Means for solving the problem

[0005] In order to achieve the above object, the configuration of the power transistor protection circuit, the motor drive circuit, or the semiconductor device of the motor drive circuit according to the first invention provides a drive current to an excitation coil of the motor via an output terminal. Output power transistor to multiple excitation coils In the power transistor protection circuit of the motor drive circuit having a plurality of correspondingly,

It includes a terminal open detection circuit, a disconnection detection circuit, and a drive stop circuit. Then, the terminal open detection circuit is configured such that the other terminal of each excitation coil that is not connected to the output terminal is connected to the other terminal, and the excitation coil having one of the deviations from the other line and the other terminal. There are output terminals that are connected! Are provided between one of the lines to which this output terminal is connected and one of the other lines, and are provided corresponding to a plurality of power transistors, respectively. It is to detect whether or not the force is open between either one and the other during the output operation of

The disconnection detection circuit detects that there is no open state between one of the terminals and one of the other terminals, and then detects any of the disconnection states by detecting that it is open. Things,

The drive stop circuit stops the drive operation of the motor drive circuit when the disconnection state is detected by the disconnection detection circuit.

Further, in the second invention, in the terminal open detection circuit, when the power transistor performs the output operation of the drive current, the open state between! /, One of the shifts and! /, And Or to detect the connection state,

The disconnection state is detected when the disconnection detection circuit detects the open state a plurality of times in response to the detection of either the open state or the connection state by the terminal open detection circuit.

The invention's effect

As described above, according to the first invention, when the power transistor is performing the output operation of the drive current, the terminal open detection circuit is not connected to the output terminal and the other terminal of each excitation coil or the other terminal is connected thereto. And the output terminal corresponding to each exciting coil or the output terminal connected to each of the exciting coils is connected to detect whether or not the open line (or the other) is open. Further, as disconnection detection, it is detected that the terminal open detection circuit is not in the open state, and thereafter, it is detected that the terminal is open. As described above, in the first invention, the power transistor detects that the terminals are not in an open state in advance, and then detects that the terminals are in an open state by the power transistor. Each time it is performed, it detects a change in the force that is not open and the force that becomes open. Further, the first invention is based on the condition that the terminals are not in an open state and that the terminals are in an open state. Detect whether or not.

On the other hand, in the second invention, when the power transistor is performing the drive current output operation, the terminal open detection circuit has an open state between one, one of the shifts and one, and the other one of the shifts. To detect any of Then, as the disconnection detection, the disconnection state is detected when the open state is detected a plurality of times in response to the detection of either the open state or the connection state by the terminal open detection circuit.

In the above-described detection, it is a matter of course that the connection state is set to the open state when the connection state is not established, and the connection state is set to the connection state when the connection state is not established.

By judging the disconnection state under these plural conditions, erroneous detection of the disconnection is eliminated, and the disconnection can be reliably detected without affecting the driving operation of the motor drive circuit. Therefore, the driving operation of the motor drive circuit can be stopped when the wire is disconnected.

The power transistor also detects that the power transistor is always in the open state or the open state when the drive transistor is outputting the drive current. At this time, the drive current is flowing through the coil of the motor. It is hardly affected by instantaneous noise and changes in driving conditions. In particular, if the open / closed state is detected near the voltage value corresponding to the drive current limit current value, it is less affected by instantaneous noise and instantaneous open state. Can be detected.

As a result, the output terminal force of the power transistor can be immediately detected when there is a disconnection between the other end of the excitation coil of the motor, so that the power transistor can be prevented from being destroyed.

BEST MODE FOR CARRYING OUT THE INVENTION

FIG. 1 is a block diagram of a bipolar drive stepping motor driver according to an embodiment to which a power transistor protection circuit of a motor drive circuit according to the present invention is applied, and FIG. 6 is a timing chart of the operation of the transistor protection circuit.

In FIG. 1, reference numeral 10 denotes a bipolar driving stepping motor driver IC having four excitation coils. In this, single-phase drive circuits la, lb, lc, Id are provided, and the excitation terminals 11a, l ib, 11c, 11 d of the stepping motor 11 are connected to the respective output terminals 2a, 2b, 2c, 2d. Each is connected.

These excitation coils 11a, lib, 11c, lid are connected to a power supply line 13 of a power supply (battery) 12, and receive power supply therefrom. A flywheel diode D is connected in parallel to each of the excitation coils 11a, lib, 11c, lid.

In addition, the power supply 12 supplies power to the voltage regulator circuit (REG) 2 inside the IC via the terminal 2e, and a predetermined voltage, for example, 3 V, which is stabilized to the internal power supply line + VDD via REG2. Is transmitted to various internal circuits.

Since the single-phase drive circuits la, lb, lc, and Id are each composed of the same circuit, the details are shown only in the single-phase drive circuit la. Hereinafter, the single-phase drive circuit la will be described, and the description of the single-phase drive circuits lb, lc, Id will be omitted because they are the same.

Describing the single-phase drive circuit la, it comprises an N-channel MOSFET power transistor 3, a power transistor protection circuit 4, a current limiting circuit 5, and a reference voltage generating circuit 6. Note that, for convenience of explanation, the current limiting circuit 5 of each single-phase drive circuit is outside the dotted frame of the single-phase drive circuit la.

The power transistor 3 has a drain connected to the output terminal 2a, and outputs an excitation current to the output terminal 2a. The source side of the power transistor 3 is connected via a terminal 2f to an output current detecting resistor Rs attached outside the IC, and is grounded via this. The output current of the output terminal 2a is a current sinking from the exciting coil 11a to the output terminal 2a.

The lower transistor protection circuit 4 includes a terminal open detection circuit 4a for detecting an open state between the power supply line 12a of the battery 12 and the output terminal 2a, and a disconnection detection circuit 4b.

The terminal open detection circuit 4a detects that the terminals are open by detecting the voltage between the output terminal 2a and the terminal (the other terminal) on the power supply line 13 side of the exciting coil 11a. There is a resistor divider circuit 44, a resistor divider circuit 45, and a comparator Data 46. The resistance voltage dividing circuit 44 is connected between the output terminal 2a and the ground GND, and has the resistances Rl and R2. The resistor voltage dividing circuit 45 includes resistors R3 and R4, one of which is connected to the power supply line 13 via the terminal 2i and the other of which is connected to the ground GND.

The (+) input of the comparator 46 is connected to the connection point of the resistor of the resistance voltage dividing circuit 44 and receives the divided voltage Va at the connection point. The (1) input is connected to the connection point of the resistance of the resistance voltage dividing circuit 45 and receives the divided voltage Vb at the connection point. Here, when the output of the power transistor 3 is generated and reaches a predetermined drive current value, Va> Vb because the output terminal 2a has a voltage value corresponding to this current value. At this time, the output of the comparator 46 changes from “H” to “L”. That is, the comparator 46 generates an “L” significant output detection pulse indicating that an output current is generated when the output is “L” (see FIG. 2D). This output detection pulse is a detection signal output by the terminal open detection circuit 4a to indicate that the output terminal 2a is connected to the other terminal of the exciting coil 11a. Conversely, this output detection pulse indicates that these pins are not open. Therefore, when this output detection pulse is not generated while the power transistor 3 is performing the drive current output operation, these terminals are in the open state.

Here, as shown in FIG. 2 (d), the voltage of the divided voltage Vb is set to a voltage value close to the limit current value of the drive current (5% to 20% lower). As described above, when the power transistor 3 is performing the output operation of the drive current, it is detected whether the output terminal 2a is in the open state, and when the drive current is close to the voltage value corresponding to the limited current value, If the terminal detects whether or not the terminal is in the open state, the drive current continues to flow through the motor coil, and the detection of the terminal open state is less likely to be affected by noise or instantaneous open state due to the relationship. .

The disconnection detection circuit 4b also has a comparator 4c and an octal counter 4d, and the octal counter 4d also receives the clock CLK transmitted via the terminal 2h. The (+) input of the comparator 4c receives the comparison reference voltage VR from the reference voltage generation circuit 6 provided commonly to the single-phase drive circuits la, lb, lc, and Id. The detection voltage signal is received from the circuit 4a. The output of the comparator 4c is connected to the reset terminal R of the octal counter 4d. Note that the reference voltage generation circuit 6 is supplied with the power by laser trimming or the like. Pressure adjustment is possible. By this voltage adjustment, the voltage VR is set so that each of the comparators 4c of the single-phase drive circuits la, lb, lc, Id generates a reset signal.

The reset signal changes from “H” to “L” of the comparator 46, and when the comparator 4c changes to “H” next, the falling trigger signal when the comparator 4c falls from “H” to “L” is generated. Used.

The disconnection detection circuit 4b receives the detection voltage signal from the terminal open detection circuit 4a, and detects the disconnection by counting the clock CLK with the octal counter 4d that the open state continues for a certain period of time. That is, the disconnection detection signal is generated when the octal counter 4d finishes counting (counting up to 8 or more). As a result, a disconnection detection signal is generated during a period when the power transistor 3 is not performing a drive current output operation. Thus, the disconnection detection signal does not need to be affected by noise during the operation of the power transistor 3.

By the way, the period TG of the gate drive pulse for driving the power transistor 3 is TG <8 × T, and T is the period of the clock CLK. Here, the period TG is set to, for example, a period of about 6 counts (6 × T) of the octal counter 4d!

The comparator 4c generates an "H" output pulse (reset pulse) and resets the octal counter 4d only when the comparator 46 generates an "L" output detection pulse. As a result, the octal counter 4d starts counting from "0". Since the next gate drive pulse is generated before 8 XT, an output current of the power transistor 3 is generated. As long as this occurs, octal counter 4d will continue to be reset. As a result, the 8-counter counter 4d does not generate an 8-count end signal.

Here, when the terminal force of the excitation coil 11a on the side of the power supply line 13 is disconnected between the connection terminal 2a and the connection terminal 2a, the divided voltage of the resistance voltage dividing circuit 44 becomes the ground GND potential, and the output generated by the comparator 46 is generated. Even if a gate drive pulse is generated, the detection pulse remains at “H” when no output current is generated in the power transistor 3 (see the second half waveform of FIG. 4E). Therefore, the output pulse (reset pulse) of the comparator 4c remains "L", and the octal counter 4d is not reset by the output pulse of the comparator 4c. . As a result, when the output current of the power transistor 3 is not generated, an eight count end signal of the octal counter 4d is generated. This 8 count end signal is used as a disconnection detection signal.

Reference numeral 41 denotes a drive stop signal generation circuit, which comprises an OR gate 42 and a latch circuit 43. Then, the latch circuit 43 receives the 8-count end signal "H" of the final stage of the octal counter 4d of the single-phase drive circuits la, lb, lc, Id via the OR gate 42 as a disconnection detection signal. As a result, the latch circuit 43 receives the 8 count end signal “H” at “1” and latches the logical sum signal of the exciting coils 11a-1 Id according to the clock CLK.

When the disconnection detection signal (“1”) is latched, the latch circuit 43 applies this “1” to the phase excitation signal generation circuit 9 as a drive stop signal SP. Thereby, the phase excitation signal generation circuit 9 stops its operation. When the reset signal “1” is input to the reset terminal R of the latch circuit 43 via the terminal RS, the value of the latch circuit 43 is cleared to “0”. In the initial state, the latch circuit 43 is set to “0” by the reset signal.

Therefore, when a disconnection occurs between the terminal coil of the excitation coil 11a on the power supply line 13 side and the connection terminal 2a, an octal counter 4d generates an 8 count end signal ("H") as a disconnection detection signal. As a result, "1" is latched in the latch circuit 43, and the operation of the phase excitation signal generation circuit 9 stops. As a result, the stepping motor driver IC 10, especially the power transistor 3, does not need to be destroyed.

By the way, as the disconnection detection signal, an overflow signal or a carry signal of the octal counter 4d may be used.

The current limiting circuit 5 includes a comparator 5a and a reference voltage generating circuit 5b. The (+) input terminal of the comparator 5a is connected to the terminal 2f, the reference voltage generation circuit 5b is provided outside the IC, and is connected to the (1) input terminal of the comparator 5a via the terminal 2g, and the reference voltage VREF To the (1) input terminal. Assuming that the terminal voltage (voltage at terminal 2f) of the output current detection resistor Rs is Vs, the drive current (output current) of the power transistor 3 increases, and the output current that causes the voltage Vs to exceed the reference voltage VREF When the voltage is generated in the transistor 3, in other words, when the output current reaches the specified value, the comparator 5a generates the detection noise S. This detection pulse S is output to the pulsing pulse generation circuit 7 to output “H”. Turns the shoving pulse P OFF ("H" to "L") and drives the OFF timer circuit 8. As a result, the power transistor 3 is turned off (the operation is described later).

The stop time of the tibbing pulse P (the period of “L”) is counted by the OFF timer circuit 8 for setting the OFF time, and after a fixed period of time, for example, 15 seconds, the tibbing pulse P changes from “L” to “H”. " The shoving pulse P is a pulse that becomes “H” for a selected period in a range of, for example, about 30 μsec to 50 μsec. That is, the chubbing pulse P is generated as a chubbing pulse when the norm of “H” becomes “L” in response to the detection pulse S and becomes “H” after a predetermined time.

As a result, when the terminal voltage Vs of the resistor Rs exceeds the voltage VREF, the current limiting circuit 5 stops the driving current and limits the output current of the power transistor 3. In this regard, the current limiting circuit 5 is provided to also serve as an overcurrent protection circuit of the motor drive circuit.

[0012] In the steady state, the shoving pulse P of "H" is sent to the phase excitation signal generation circuit 9, and for example, in the phase excitation signal generation circuit 9, the gate drive pulse of the single-phase drive circuit la is output by an AND gate. "H" and AND logic are taken and output to the gate of the power transistor 3 (see FIGS. 2 (a) and 2 (b)). Therefore, in the power transistor 3, a pulsing pulse (corresponding to the pulsing pulse P) that cuts off the transistor 3 at a predetermined frequency during the “H” of the gate drive pulse is generated from the phase excitation signal generation circuit 9. Will be. When the chopping pulse P is "L", the gate drive pulse becomes "L", the power transistor 3 is turned off, and the drive current for the exciting coil 1 la of the stepping motor 11 stops. Here, a flywheel diode D is provided in parallel with each exciting coil! /, So that the current flowing through each exciting coil 11a, llb, 11c, lid is determined by the pulsing pulse P being "L". During the OFF period, the current flows through the flywheel diode D. It is an average current determined by the relationship between the ON period and the OFF period by the shoving pulse P.

[0013] Here, the chabbing pulse generation circuit 7 and the OFF timer circuit 8 are provided in common with the single-phase drive circuits la, lb, lc, and Id. 1A, lb, lc, and Id excitation pulse drive is generated for each excitation pulse P The signal is sent to the phase excitation signal generation circuit 9.

The phase excitation signal generation circuit 9 drives the gates of the power transistors 3 of the single-phase drive circuits la, lb, lc, and Id according to single-phase drive, one-phase to two-phase drive, two-phase drive, and the like for each excitation coil. This circuit generates pulses at a predetermined timing and generates "H" and "L" gate drive pulses. Further, the "H" period of each gate pulse is shoved by each shoving pulse P to limit the drive current. Note that the cycle of the shoving pulse P is smaller than the cycle of the clock CLK.

FIG. 2 is a timing chart of the operation of the power transistor protection circuit 4.

FIG. 2A shows a gate drive pulse of the single-phase drive circuit la, and during this period of “H”, the power transistor 3 is driven by shoving. FIG. 2 (b) shows the shobbing pulse P. During the "H" period, a driving current flows through the exciting coil 11a of the stepping motor 11, so that the output voltage Vout of the output terminal 2a becomes , Figure 2 (It looks like this.

Here, it is assumed that the power transistor 3 of the single-phase drive circuit la generates an output current in accordance with the gate drive pulse in FIG. In this case, the comparator 46 changes from “H” to “L” when the divided voltage Va obtained by dividing the voltage according to the voltage of the output terminal 2a exceeds the divided voltage Vb (see FIG. 2 (d)). As shown in FIG. 2 (e), according to the voltage Vout of the output terminal 2a in FIG. 2 (c), the output pulse becomes "H", "L", "H", " It becomes an output detection pulse of L ". Since the cycle of the chopping panel P is smaller than the clock CLK, the comparator 4c generates an “H” output (reset pulse) in accordance with the output pulse of the output detection pulse “L” of the comparator 46. To reset the octal counter 4d. As a result, the latch circuit 43 remains at the initial value “0”, and the phase excitation signal generation circuit 9 continues to operate without generating the drive stop signal SP.

[0015] The last output detection pulse of "L" of the comparator 46 generated at this time is generated in accordance with the chopping norse P in FIG. Then, the "L" output detection pulse of the comparator 46 which is generated next corresponds to the first shoving pulse P after the next gate drive pulse is generated. At this time, the generation period of the output detection pulse of “L” of the comparator 46 is shorter than the period 8 XT during which the octal counter 4d counts for eight clocks. Therefore, the terminal force of the excitation coil 11a on the side of the power supply line 13 is also connected. As long as there is no disconnection up to the terminal 2a, the drive stop signal SP for the phase excitation signal generation circuit 9 is not generated from the latch circuit 43. Note that the count period of the octal counter 4d only needs to be longer than the last output detection pulse power and the first output detection pulse.

On the other hand, when there is a disconnection between the excitation coil 1 la of the power supply line 13 and the connection terminal 2 a due to a poor connection with the stepping motor 11 or the like, the power transistor 3 of the single-phase drive circuit la is switched in accordance with the gate drive pulse. Does not generate an output current even if is driven. Therefore, as shown in the latter half of FIG. 2 (c), the voltage Vout of the output terminal 2a does not occur. Therefore, the divided voltage Va becomes Va = 0V.

As a result, Va <Vb, and the output detection pulse generated from the comparator 46 remains “H”. Thus, the octal counter 4d counts the clock CLK without being reset. Therefore, when the next output current does not occur, the output detection pulse of "L" is not generated from the comparator 46, so that the octal counter 4d generates the 8 count end signal ("H"), which is output. This is latched as "1" in the power latch circuit 43 through the OR gate 42. As a result, the operation of the phase excitation signal generation circuit 9 stops, so that the stepping motor driver IC 10 does not need to be destroyed.

In this case, the 8 count end signal (disconnection detection signal) from the octal counter 4d is longer than the period during which the comparator 46 generates more than one "L" output detection pulse in the period during which the next output current is generated. It is preferred that Therefore, here, the period up to the end of 8 counts of the octal counter 4d is a value longer than the generation cycle of each gate drive pulse in each of the single-phase drive circuits la, lb, lc, and Id. Is set to As a result, it is possible to detect that the terminal open state continues for one cycle or more of the gate drive pulse.

The OR gate 42 receives the 8 count end signal (disconnection detection signal) obtained by the final stage of the octal counter 4d of the single-phase drive circuits la, lb, lc, and Id by a logical sum. The operation of the phase excitation signal generation circuit 9 is stopped even when the 8 count end signal (disconnection detection signal) is generated in the octal counter 4d of lb, lc, or Id.

[0017] In the above embodiment, from the reset of the octal counter 4d to the end of counting of the octal counter 4d Is 8 XT, and the period TG of the gate drive pulse is 6 XT. Therefore, if the detection signal indicating the connection state of the terminal open detection circuit 4a is not generated once, it is determined that the terminal open detection signal has been generated and the disconnection detection circuit 4b determines that the connection is broken.

However, in the present invention, for example, the octal counter 4d can be a 13-ary counter or a counter that counts more. In this case, if the detection signal indicating the connection state of the terminal open detection circuit 4a does not occur continuously more than once, it is assumed that the terminal open detection signal has been continuously generated more than once, and at this time, the disconnection detection circuit is first generated. 4b determines that the wire is broken. This makes it possible to more reliably determine the disconnection.

In other words, according to the present invention, the disconnection determination may be made such that the period from the reset of the counter 4d to the end of the count exceeds twice the period TG of the gate drive pulse.

Note that the disconnection detection circuit 4b may determine that a disconnection has occurred when the terminal open detection signal is not detected continuously but is detected a plurality of times.

By the way, in the embodiment, the comparator 5a is provided in each of the single-phase drive circuits la, lb, lc, and Id, but the comparator 5a is provided in common to a plurality of single-phase drive circuits. You may. In this case, for example, each of the comparators 5a of the single-phase drive circuits la and lb and each of the comparators 5a of the single-phase drive circuits lc and Id share a detection resistor Rs for the output current value. Two can be used in total. Further, in the embodiment, the comparator 5 is one having two (+) input terminals. The internal circuit of the comparator 5 may be composed of two comparators in parallel. This may also use a comparator with two (+) input terminals and two (1) input terminals.

Further, in the embodiment, the disconnection detection signal is used as the count end signal of the n-ary counter, but the present invention does not need to use the count end signal of the counter. The disconnection detection signal according to the present invention is provided if the detection signal of the terminal open detection circuit is received and the output of the drive current at the time of receiving the signal is later than the period until the output of the next drive current generated. Good. Further, the power transistor Tr of the embodiment is a MOSFET transistor. Of course, this may be a bipolar transistor.

Furthermore, in the embodiment, the motor drive circuit of the stepper motor driver IC of the bipolar drive is described. However, the output circuit of the power transistor is used as the drive circuit of the push-pull operation, and the bipolar drive (positive phase It is needless to say that the present invention may be applied to a stepping motor driver IC having the opposite phase of double-wave drive).

Industrial applicability

As described above, in the embodiment, if the power transistor 3 that controls the power transistor 3 to be turned off via the tibbing pulse generation circuit 7 and the OFF timer circuit 8 is configured to be turned off, The shoving pulse generation circuit 7 and the OFF timer circuit 8 are not necessarily required for the present invention.

Further, in the embodiment, any drive circuit having a current limiting circuit that limits the drive current by turning off the power transistor at a specified current value described in the stepping motor driver IC is used. Even if there is, this invention can be applied. Brief Description of Drawings

FIG. 1 is a block diagram of a bipolar drive stepping motor driver according to an embodiment to which a power transistor protection circuit of a motor drive circuit according to the present invention is applied.

FIG. 2 is a timing chart of the operation of the power transistor protection circuit.

Explanation of symbols

[0021] la, lb, lc, Id… single-phase drive circuit,

2a, 2b, 2c, 2d ... output terminals,

3 channel MOSFET power transistor,

4… Power transistor protection circuit 4a… Terminal open detection circuit

4b… Disconnection detection circuit, 4c, 46 ··· Comparator,

4 (1 ····· octal counter, 5… current limiting circuit,

5a… Comparator, 6… Reference voltage generation circuit,

7 ... Chiobbing pulse generation circuit, 8 ~ OFF timer circuit,

9… Phase excitation signal generation circuit ···· Stepping motor dry IC

a, lib, 11c, lid… excitation coil,

······· Power supply, 13… Clock generation circuit, 14… Clock generation circuit… Driving stop signal generation circuit, 42 ··· OR gate, ··· Latch circuit,

... resistance, D ... flywheel diode.

Claims

The scope of the claims

[1] In the power transistor protection circuit in a motor drive circuit having a plurality of power transistors for outputting a drive current to an exciting coil of a motor via an output terminal in correspondence with the plurality of exciting coils,

A terminal open detection circuit, a disconnection detection circuit, and a drive stop circuit are provided,

The terminal open detection circuit may be configured to determine whether the other terminal of each of the exciting coils not connected to the output terminal is connected to the other terminal and the other terminal is connected to the other terminal. The output terminal is connected to the excitation coil having the following. The output terminal is connected to a line to which the output terminal is connected and the other of the output terminal and a corresponding one of the plurality of power transistors. The power transistor is provided to output the drive current, and when the power transistor is turned on, the power transistor detects whether or not the force is in an open state between one of the shifts and the other.

The disconnection detection circuit detects a disconnection state by detecting that the terminal open detection circuit is not in an open state between one of the terminals and the other of the force and the open state thereafter. To detect,

The drive stop circuit is a power transistor protection circuit that stops a drive operation of the motor drive circuit when a disconnection state is detected by the disconnection detection circuit.

[2] The terminal open detection circuit generates one of a detection signal indicating that one of the terminals is in an open state and the other is in an open state. A plurality of the disconnection detection circuits are provided corresponding to each of the plurality of power transistors, and each of the disconnection detection circuits is connected to the terminal open detection circuit provided for the corresponding power transistor. 2. The power transistor protection circuit according to claim 1, wherein a disconnection state is determined when the open state is detected after the non-open state is detected after receiving the detection signal.

[3] The terminal open detection circuit detects a voltage between one of the ones and the other one, and the detection signal detects the connection state as not being in the open state. 3. The power transistor protection circuit according to claim 2, wherein:

[4] The disconnection detection signal indicates that the power transistor performs the output operation of the drive current. 4. The power transistor protection circuit according to claim 3, wherein the power transistor protection circuit is generated after the output operation of the drive current is completed when the detection signal is not received at the time of V.

[5] Each of the disconnection detection circuits has a counter that counts a clock having a period T by n (n is an integer of 2 or more), and the counter is reset in response to the detection signal. The disconnection detection signal is an n-count end signal of the counter, which is longer than a period from the output of the drive current having a period until the end of the n-count to the output of the drive current to be generated next. 4. The power transistor protection circuit according to 4.

6. The power transistor protection circuit according to claim 4, wherein the disconnection detection signal is generated by not receiving the detection signal a plurality of times.

[7] Each of the terminal open detection circuits has a first comparator for comparing a voltage between one of the terminals and the other, and generates the detection signal as a detection pulse by the first comparator. 6. Each of the disconnection detecting circuits has a second comparator for comparing the detection pulse with a predetermined reference voltage, and generates a signal for resetting the counter in accordance with an output of the second comparator. The described power transistor protection circuit.

[8] The drive stop circuit includes an OR gate and a latch circuit, receives each of the disconnection detection signals obtained from each of the disconnection detection circuits by the OR gate, latches the signal in the latch circuit, and outputs the output of the latch circuit. 7. The power transistor protection circuit according to claim 6, wherein a signal for driving the power transistor is stopped in response to the condition.

[9] The power transistor generates a drive current that also sinks the output terminal force as an output current, the other terminal is connected to a power supply line, and one of the voltages is a voltage of the power supply line 1 is a voltage divided by the resistor voltage dividing circuit, the voltage value of which is close to the voltage value at the time when the drive current is limited, and the other voltage is the voltage of the output terminal. 8. The current limiting circuit according to claim 7, wherein the voltage is a voltage obtained by dividing a voltage by a second resistor voltage dividing circuit.

[10] In the power transistor protection circuit of the motor drive circuit having a plurality of power transistors for outputting a drive current to the excitation coil of the motor via the output terminal corresponding to the plurality of excitation coils, A terminal open detection circuit, a disconnection detection circuit, and a drive stop circuit, wherein the terminal open detection circuit connects the other terminal of each of the excitation coils not connected to the output terminal to the other terminal. Then, the excitation coil having one of the terminals and the other terminal is connected to the output line, and the output terminal is connected to the line to which the output terminal is connected. And the power transistor is provided in correspondence with a plurality of the power transistors, and the power transistor performs an output operation of the drive current. Between the open state and the connected state during

The disconnection detection circuit detects a disconnection state when the open state is detected a plurality of times in response to detection of either the open state or the connection state by the terminal open detection circuit,

11. The power transistor protection circuit according to claim 10, wherein the disconnection detection circuit sets the disconnection state by being continuously in the open state a plurality of times.

[12] A motor drive circuit in which the motor drive circuit having the power transistor protection circuit according to any one of claims 11 to 11 is formed into an IC, and a motor is driven by the output current of the power transistor.

13. The motor drive circuit according to claim 12, wherein the motor is a stepping motor.

[14] A semiconductor device in which the motor drive circuit according to claim 12 or 13 is integrated into an IC.