JPH0488897A - Motor driving circuit - Google Patents

Abstract

PURPOSE:To turn OFF a driving transistor when a load for disturbing the rotation of a motor is applied and to reduce power consumption by providing a flip-flop, a setter, a controller, a charging/discharging circuit, a second comparator, an invalidating circuit, a resetter, and a varying circuit. CONSTITUTION:If a load for disturbing the rotation of a motor is applied, the terminal voltage Vf of a detecting resistor Rf is raised. When the voltage Rf of the resistor Rf becomes equal to a reference voltage VT1 at a time t0, a set/reset signal of a flip-flop 4 becomes 'L', and control transistors Q16, Q26, Q36 are turned ON. That is, the bases of drive transistors Q13, Q23, Q33 are grounded, and drivers 1U, 1V, 1W are not operated, and the voltage VRf of the resistor Rf becomes zero. Simultaneously, since a transistor Q52 is turned OFF, a capacitor C is started to be charged through a transistor Q49.

Description

[Detailed description of the invention] (b) Industrial application fields The present invention relates to a motor drive circuit.

(b) Prior Art FIG. 3 is a circuit diagram of a main part of a conventional motor drive circuit.

In FIG. 3, the drive circuit (ltJ) flV) (I
W) supplies drive current to the drive coils U, , V, and W. In the drive circuit flU) flV) (IW), logic signals 5Lll, SO2, SVI,
5V21 Sv+, SW2 are drive coils U, V, W
It is set to "H" (high level) or rLJ (low level) depending on the state in which drive current is supplied to rLJ. In the drive circuit (IU), the drive transistor QzQ+□ is Darlington-connected and operates by being supplied with the logic signal $υ1. Drive transistor Q 13Q
14Q +s is Darlington connected, logic signal 5
L11! It operates by being supplied with The control transistor Q+e is connected between the base of the drive transistor Q13 and the ground, and is connected between the base of the drive transistor Q13 and the ground.
Controls the operation of 4Q1. Furthermore, the drive circuit (,IU)
(IVI (IW) is the same circuit, so the drive circuit (lVj
(Description of tel is omitted. The detection resistor R, is connected between the common emitter of the drive transistors Q , , Q 25Q, 5 and the ground, and the detection resistor R,
IS, Q 22Q 25. This detects the drive current of Q32Qss. That is, as will be described later, when a load is applied to prevent the motor from rotating, the detection resistor R
, and when no load is applied to prevent the rotation of the motor, the terminal voltage of the detection resistor R7 is .

becomes small.

The comparison circuit (2) compares the terminal voltage of the detection resistor R, and the reference voltage A, and compares the terminal voltage of the detection resistor R,
This controls the drive current of Q36. Comparison circuit (2
), the transistor Q 1Q 2 Q s Q
- and the current source 101 are differential circuits, and the detection resistor R1
The terminal voltage VRj of is compared with the reference voltage ■,1.

Transistor QsQs is a current mirror circuit and operates according to the collector current of transistor Q2. Transistor Q7 operates according to the difference current between the collector currents of transistors Q4Qe. Transistor Q is
Connected between constant voltage VA2 and ground, current source ID2
It operates according to the difference current between the supply current of Q7 and the collector current of transistor Q7. That is, control transistor Q+eQ
2sQas operates according to the difference current between the constant current generated by the constant voltage VA2 and the collector current of the transistor Q8. It is assumed that in the normal driving state of the motor, the terminal voltage V□ of the detection resistor Rr is set to be smaller than the reference voltage vT1.

The above drive circuit (IU) (IV) (IW), detection resistor R9, and comparison circuit (2) form a loop to limit the maximum drive current of the motor and protect the motor drive circuit. It is.

For example, when a load is applied to prevent the motor from rotating, another negative feedback loop (not shown) operates according to the terminal voltage of the detection resistor Rr, so the drive transistor Q1
□Q 1a, Q 22Q 25. The drive current of Q3□Q0 becomes large in order not to disturb the rotation of the motor, and the terminal voltage VR+ of the detection resistor Rr also becomes small.

Therefore, the transistor Q IQ 2 Q 3Q- is in an equilibrium state when the terminal voltage 1 of the detection resistor R2 becomes equal to the reference voltage 2A, that is, the drive transistor Q
12Q 1s, Q 2□Q 2a, Q 32Q 3
The maximum drive current of No. 5 is limited to the value at the time when the terminal voltage (2) + t- of the detection resistor R2 becomes equal to the reference voltage (2) A1, thereby protecting the motor drive circuit.

(c) Problems to be Solved by the Invention However, since the method limits the maximum drive current of the motor, there is a problem in that the power consumption increases.

Therefore, the present invention makes it possible to reduce power consumption by turning off the drive transistor when a load that prevents the rotation of the motor is applied, and furthermore, when the drive transistor is turned on and a through current flows, the comparison signal of the comparison circuit is The purpose of the present invention is to provide a motor drive circuit that can disable the

(d) Means for Solving the Problems The present invention has been made to solve the above problems, and includes a detection resistor for detecting the drive current of a drive transistor for driving a motor, and a detection resistor for detecting the drive current of a drive transistor for driving a motor. A motor drive circuit comprising: a first comparison circuit that compares a detection signal obtained by the detection signal with a first reference signal; and a control transistor that turns off the drive transistor based on the comparison signal of the first comparison circuit. , a flip-flop circuit, and the first
a control circuit that turns on and off the control transistor based on a set reset signal of the flip-flop circuit; and a set of the flip-flop circuits. a charging/discharging circuit that charges and discharges the charge of a capacitor based on a reset signal; a second comparison circuit that compares a charging/discharging signal from the charging/discharging circuit with a second reference signal; and the second comparison circuit. an invalidation circuit that invalidates the comparison signal of the first comparison circuit based on the comparison signal of the second comparison circuit; and a reset circuit that resets the flip-flop circuit based on the comparison signal of the second comparison circuit.
a variable circuit that varies the second reference signal to a first level or a second level based on a comparison signal of the second comparison circuit, wherein the second reference signal is at the first level. The comparison signal of the first comparison circuit is disabled during the period during which the first comparison signal is held at the second level, thereby preventing malfunction of the first comparison circuit.

(E) Function According to the present invention, when a load is applied to prevent rotation of the motor, the drive transistor is turned off and power consumption is reduced. Further, when the drive transistor is turned on and a through current flows, the comparison signal of the comparison circuit becomes invalid, thereby preventing the comparison circuit from malfunctioning.

(f) Example The details of the present invention will be specifically explained with reference to the drawings.

FIG. 1 is a circuit diagram showing one embodiment of the motor drive circuit of the present invention, which is assumed to be integrated on one chip. Note that the same elements in FIGS. 1 and 2 are given the same reference numerals.

In FIG. 1, the first comparison circuit (3) includes a detection resistor R
The terminal voltage VBI of t and the reference voltage V T 1 are compared. It is assumed that in the normal driving state of the motor, the terminal voltage VFII of the detection resistor Rt is set to be smaller than the reference voltage (2).

The flip-flop circuit (4) is a set/reset type. In the flip-flop circuit (4), the transistor Q4□Q43 is connected in series between the power supply voltage VOO and the base of the transistor Q40, and sets the initial state of the flip-flop circuit (4). transistor Q6
．． (cent circuit) is current source I. It operates according to the difference current between the supply current of Q2 and the collector current of transistor Q7,
This is to set the flip-flop circuit (4).

The control circuit (5) controls the control transistor Q+e based on the cent reset signal of the flip-flop circuit (4).
It controls the operation of Q zaQ as. In the control circuit (5), the transistor Q44 is operated by being supplied with the set/reset signal of the flip-flop circuit (4). Transistor Qas is connected between a constant voltage V,2 and ground, and operates according to the difference current between the supply current of current source 103 and the collector current of transistor Q44. That is, the control transistor Q+aQzeQ3s is controlled when the center reset signal of the flip-flop circuit (4) is rH.
It is turned off when the voltage is "J" and turned on when the cent reset signal of the flip-flop circuit (4) is "L".

The charging/discharging circuit (6) charges and discharges the charge of the externally connected capacitor C based on the set/reset signal of the flip-flop circuit (4). Charge/discharge circuit (6
), transistor Q46 operates according to the difference current between the supply current of current source ID3 and the collector current of transistor Q44. Transistor Q4? operates by applying a constant voltage VtS. In addition, transistor Q4
The collector current of □ becomes a constant current due to the externally connected resistor R1. Transistor Q4aQ-sQa.

is a current mirror circuit, and transistor Q4? It operates with a collector current of . Transistor Q s +
Q a 2 is a current mirror circuit, which operates according to the difference current between the collector currents of the transistor Q48QSO. That is, when the set reset signal of the flip-flop circuit (4) is "H", the capacitor C and the transistor Qa
e forms a discharge loop and flip-flop circuit (4)
When the set/reset signal of is "L", capacitor C and transistor Q4G form a charging loop.

The second comparison circuit (7) detects the terminal voltage of the capacitor C (■).

and reference voltage V75 are compared.

In the second comparison circuit (7), transistors Q, 3Q
54Q s5Q sa and current source I. 5 is a differential circuit, in which the terminal voltage o of the capacitor C and the reference voltage VT6
Compare with. Transistor Qs7Qsa is a current mirror circuit and operates according to the collector current of transistor Qsa. Transistor Qso operates according to the difference current between the collector currents of transistors QS4Q58. That is, transistor Q. does not operate when the terminal voltage of capacitor C (■c) is lower than the reference voltage Vy6, and the terminal voltage of capacitor C (■). It will operate when the reference voltage is smaller than 5. Transistors qa, f (ineffective circuit) are connected to the supply current of current source ID4 and transistor Q. The first comparator circuit (
This invalidates the comparison result of 3). The transistor Q, 2 (reset circuit) operates according to the difference current between the supply current of the current source 104 and the collector current of the transistor Qso, and resets the flip-flop circuit (4).

The variable circuit (8) is for varying the reference voltage (1). In the variable circuit (8), resistor R4Rs is connected in series between constant voltage V74 and ground, and resistor R6 is connected between the base of transistor Qss and ground. The transistor Qas operates according to the difference current between the current supplied from the current source D4 and the current flowing through the collector of the transistor Qao, and connects the resistor R5R in parallel. That is, the reference voltage V75 changes depending on the operating state of the transistor QI13 and has hysteresis. It should be noted that the comparison result of the first comparison circuit (3) is at least equal to the drive circuit (IU
) (It/) (IW) The resistance value of the resistor R4RsRo is set so that it is ineffective only during the generation period of the through current of (IW).

The operation of FIG. 1 will be described below based on the waveform diagram of FIG. 2.

First, when no load is applied to prevent the rotation of one motor, the terminal voltage V R+ of the detection resistor R is the reference voltage VT,
Since it becomes smaller, the cent reset signal of the flip-flop circuit (4) becomes "H", and the control transistor Q1
．． aQ 26Q 38 is turned off. That is, the drive circuit in FIG. 3 (tl) tlV) (lW+ is the drive coil U
, W are operated depending on the state in which the drive current is supplied to them. At this time, transistor Q52 turns on, so the charge on capacitor C increases to transistor Q! It is in a state where it is discharged through 2. Therefore, since the transistor Qsa is turned off, the transistor Q83 is turned off, and the reference voltage V is equal to the value obtained by dividing the resistor R4Rs by BOF+F.

Next, when a load is applied to prevent the rotation of the motor, the terminal voltage VIH of the detection resistor R1 becomes large. and,
At time t0, when the terminal voltage ■□ of the detection resistor R7 becomes equal to the reference voltage ■A, the flip-flop circuit (4
) becomes "off", and the control transistor Q teQ 26Q sa turns on. That is, the base of the drive transistor Q teQ 23Q 33 is grounded, the drive circuit (IU) (IV) (IJ) stops operating, and the terminal voltage V p (of the detection resistor R7 becomes zero. At the same time, the transistor Q5□ To turn off, capacitor C starts to be charged via transistor Q49. Then, at time t1, when terminal voltage V0 of capacitor C becomes equal to reference voltage V75°1, transistor Qss turns on, so transistor Q e
1 is turned on, and the comparison result of the first comparison circuit (3) becomes invalid. At the same time, the cent reset signal of the flip-flop circuit (4) becomes "H", and the drive circuit (IU) (IV
) (IW) is a working transistor Q 52
turns on, and the charge in capacitor C begins to be discharged via transistor Q52. At the same time, the transistor Qa3 turns on, and the reference voltage Va becomes the value Vtaos (<V?!0FF) obtained by dividing the resistor R4RsRe. However, any drive transistor Q +6Q 26Q 3
Since s turns on instantly, the corresponding drive circuit (IU) (IV
) Drive transistor Q in (17) 12Q2□Q3
The emitter potential of □ drops instantaneously to approximately ground potential, but its base potential cannot drop instantly due to the parasitic capacitance between its base and the emitter, and the potential difference between its base and emitter is not sufficient to turn it on. Become. In other words, the drive transistor Q +2Q +s, Q 22Q 25
．． A through current (large current) momentarily flows through Q3□Qss, and the terminal voltage ■1 of the detection resistor Rt is extremely low (> V T
l). Therefore, the first comparison circuit (3) provides the same comparison result (erroneous signal) as when a load is applied to prevent the rotation of the motor, but this comparison result is invalidated by the transistor Q e +. Therefore, malfunction by the first comparator circuit (3) is prevented. Then, at time t2, when the terminal voltage VC of the capacitor C becomes equal to the reference voltage V5°, the transistor Qs
Since a is turned off, the transistor Q e + is turned off, and the comparison result of the first comparison circuit (3) is canceled and supplied to the transistor Q5. That is, the first comparison circuit (3
) is invalidated only at times t, .about.t2 determined by the hysteresis of the reference voltage (T). At the same time, the transistor Q63 is turned off, and the reference voltage VTB becomes the value V, which is obtained by dividing the voltage of the resistor R4Rs, again by 5°□. Then, when the terminal voltage V0 of the capacitor C finishes being discharged through the transistor Q52, the circuit of FIG. 1 reaches the time t. It will return to its previous state.

Note that if a load to prevent rotation of the motor is applied again after that, the above operation will be repeated.

From the above, when a load is applied to prevent the motor from rotating, the drive transistor Q +sQ 21iQ ss is turned off, that is, the drive circuit flU) (IV,) (1'W) does not operate, and therefore the power consumption is small. becomes. Furthermore, when the drive transistor Q + sQ 25Q ss is turned on instantaneously and a through current flows, the comparison result of the first comparator circuit (3) becomes invalid only in the time delay band determined by the hysteresis of the reference voltage (a). , malfunction by the first comparator circuit (3) is prevented.

(g) Effects of the Invention According to the present invention, when a load is applied to prevent the rotation of the motor, the drive transistor can be turned off to reduce power consumption, and furthermore, the drive transistor is turned on and a through current flows. At this time, advantages such as the ability to invalidate the comparison signal of the first comparison circuit to prevent malfunction by the comparison circuit can be obtained.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram showing one embodiment of the present invention, and Fig. 2 is a circuit diagram showing an embodiment of the present invention.
FIG. 3 is a waveform diagram showing the state shown in the figure, and FIG. 3 is a circuit diagram showing a conventional circuit. [2! i:1 (3)・・First comparator circuit, (4)・Flip-flop circuit, (5)・・Control circuit, (6)・・Charge/discharge circuit, (7)・Second comparator circuit, (8 )...variable circuit, Q
+2Q 15Q 22Q 25Q 32Q 35...
Drive transistor, Q 16Q 26Q 38...Control transistor, R. Detection resistor, C... Capacitor.

Claims (1)

[Claims] (1) A detection resistor that detects a drive current of a drive transistor for driving a motor, a first comparison circuit that compares a detection signal from the detection resistor with a first reference signal, and the first comparison circuit. a control transistor that turns off the drive transistor based on a comparison signal of the first comparison circuit; a flip-flop circuit; and a control transistor that sets the flip-flop circuit based on the comparison signal of the first comparison circuit. a set circuit; a control circuit that turns on and off the control transistor based on a set reset signal of the flip-flop circuit; and a charge/discharge circuit that charges and discharges a capacitor based on the set reset signal of the flip-flop circuit. , a second comparison circuit that compares the charge/discharge signal from the charge/discharge circuit with a second reference signal, and invalidates the comparison signal of the first comparison circuit based on the comparison signal of the second comparison circuit. a reset circuit that resets the flip-flop circuit based on the comparison signal of the second comparison circuit; and a reset circuit that resets the second reference signal based on the comparison signal of the second comparison circuit. a variable circuit that varies from the first level to the second level, and during a period when the second reference signal is held from the first level to the second level, the comparison signal of the first comparison circuit A motor drive circuit characterized in that the first comparator circuit is disabled to prevent malfunctions caused by the first comparison circuit.