JPS63117682A - Integrated motor drive circuit - Google Patents

Abstract

PURPOSE:To increase a motor driving voltage by composing a current mirror circuit of a power transistor and a small signal transistor, and obtaining a control signal by a current detecting resistor connected in series with the small signal transistor. CONSTITUTION:A current monitoring small signal transistor QS1 is connected in parallel with the emitter and the base of a power transistor QP1, and the collector of the transistor QS1 is connected to the cathode of a current detecting resistor R1. When a voltage across the R1 becomes larger than a reference voltage Vref of a comparator C1, it operates to limit a current of the output (a) of a signal controller C2 by the output C1out of the comparator C1. Thus, a current flowing to the base, the collector of the transistor Q1 and a load current flowing through the base, the collector of the transistor QP1 are both limited.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an integrated motor drive circuit, and particularly to a current limiting circuit for a motor drive IC.

[Conventional technology]

3 and 4 respectively show examples of conventional motor drive circuits. FIG. 3 shows an example of the circuit when the motor is rotated in one direction by the power transistor Qp, and FIG. t, Qps and QPIl QP
An example of a circuit in which the motor is rotated in both forward and reverse directions using I is shown.

In FIG. 3, QPI has its collector connected to load L1, and its base connected to predriver transistor Q,
is connected to the collector of R, and its emitter is connected to the current detection resistor R
This is a power transistor connected to 1. Further, one input of C1 is connected to the anode side of the resistor R,
The other input is a voltage comparator connected to a reference voltage V, . Ct is an operation mode control circuit whose output a is connected to the base of the predriver Q.

The circuit of FIG. 4 is also almost the same as that of FIG. 3, and the block corresponding to predriver 01 is composed of transistors Q8, Q, and the collectors of these transistors are connected to power transistors Q, 2, . It is connected to the base of Q and 3. The load L1 is a power transistor apt.

(QP3) emitter and transistor Q P S ,
(Q P 4) is connected between the collectors. The current limiting resistor R2 and comparator C1 are connected to the resistor RI+ in Figure 3.
This is similar to the case of comparator CI.

Next, the operation will be explained.

In the circuit shown in Fig. 3, the power transistor QPI
The conduction and non-conduction of are controlled by the control circuit C2. When the output of the circuit C2 is "low", the base current of the predriver 01 flows, and its collector drives the power transistor Q□, which becomes conductive, and the load current □ is supplied to the load L1. A current amplified by the base current 3 of the power transistor QPI flows through the load, but IL increases and IL
The voltage determined by I is the reference voltage of the comparator C1. , the comparator C1 operates, and its output C1out controls the internal circuit of the signal control circuit C2 so that the circuit C! output current,
That is, the predriver Q1 is operated so that its base current does not flow any further. In other words, a current limiting operation is performed for the load current rL.

Also, in the circuit shown in FIG. 4, the same operation as the circuit shown in FIG. When the signal is "high", the transistors Q, , QPt and QPS are conductive, and the load current IL flows through the transistors QFZ and Q□, and when the signal a is "low" and the signal S is "high", the transistor Q , , QP3 and QP4 are conductive, and the load current {circle around (2)} flows through the transistors QP, ,Q, .R2 in FIG. 4 means a current detection resistor, and the voltage of ILXR, is v, . 7 or more, the control circuit C2 receives the voltage of the resistor R and operates to prevent the load current IL from flowing any further, as in the case of FIG. 3 above.

[Problem that the invention seeks to solve]

As shown in FIGS. 3 and 4, in the conventional motor drive circuit, the current detection resistor R,
Or R2 is load L1 and power transistor QP
+ (In the case of Figure 4, QPI, QP5 or QP
3, Q p 4 ), so when the electric voltage VCC is kept constant, there is a drawback that the maximum value of the motor drive voltage applied to the load L+ is limited. That is, the voltage drop of RXIL is not supplied to the motor, which is a major drawback when considering motor drive at low voltage.

The present invention was made in order to eliminate the above-mentioned drawbacks, and an object of the present invention is to obtain an integrated circuit motor drive circuit that can apply all voltages excluding the residual voltage of the power transistor from the power supply voltage to the motor. .

[Means for solving problems]

The integrated motor drive circuit according to the present invention connects a small signal transistor in parallel with a power transistor to form a current mirror circuit, connects a current detection resistor in series with the small signal transistor, and detects the motor drive current based on the motor drive current. ←The voltage is supplied to the control circuit of the power transistor.

[Effect]

In the present invention, a current mirror circuit is configured by a power transistor and a small signal transistor, and a control signal is obtained by a current detection resistor connected in series with the small signal transistor, so that the residual voltage of the power transistor is determined from the power supply voltage. All voltages except for can be applied to the motor load as the motor drive voltage.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIGS. 1 and 2 respectively show the first embodiment of the present invention. An integrated motor drive circuit according to a second embodiment is shown, with FIG. 1 showing a circuit example corresponding to the conventional circuit shown in FIG. 3 above, and FIG. 2 showing an example of a circuit corresponding to the conventional circuit shown in FIG. 4 above.

In the figure, power transistor Q1. The connections of the predriver Q and the signal control circuit C2 are the same as the conventional circuit shown in Fig. 3, and the power transistors QPZ and QP:
I, Q,, QPSI predriver Q2゜Q
3 and the signal control circuit C2 are the same as in the conventional circuit shown in FIG. In FIG. 1, a small signal transistor Qs for current monitoring is connected in parallel with the emitter and base of the power transistor QPl, and the collector of the small signal transistor Q31 is connected to the cathode side of the t-liquid detection resistor R. .

The cathode of the resistor R1 is connected to one input of the comparator C3, and the anode side is connected to the power supply voltage VCC. Further, a reference voltage source Vl@g is connected between the other input of the comparator CI and the power supply voltage VCC, and its output C3°□ is connected to the signal control circuit Ct. Other connections are similar to those in the circuit shown in FIG.

Next, the operation will be explained.

In the circuit shown in FIG. 1, a power transistor QP,
and current monitor transistor Q! I is integrated on the same chip, and each base-emitter junction area 3e
(qs+), 313 (QPI) is 5e(Qi
l) The pattern is designed to be −1/n S e (QPI). Normally, the collector current of transistors on the same chip flows in proportion to the junction area, so the collector current ICI of Qil is Ic+-1/n-I L "i, where IL is the load current.
t). Since this collector current flows to the detection resistor R2, the voltage across R1 is Vat"Ic+XR+-1/n'RIIL GX:
Ii, ... (2) When this voltage ■□ becomes larger than the reference voltage Vraf of the comparator C1, the output of the comparator CI is inverted, and the output C2 of the circuit C,
This acts to limit the current of the output a of the signal control circuit Ct, and the current flowing through the base and collector of the transistor Q and the load current flowing via the base and collector of the transistor QP are both limited by the conduction of the comparator C1. limited by the current determined at the time.

The same is true in the case of the circuit shown in FIG. Since each transistor is set to be proportional to the load current of QP4 or Q□, a current proportional to the load current ■1 flows through the detection resistor R2, and the voltage across it is
. is thicker than the reference voltage of comparator C1 as in the case of FIG.
By ゜□, the output signal a of the signal control circuit Ct.

b (when Q P z , Q P S 4 is on), or the output signals a, , b, (when QP 3, Q, 4 are on) are limited, thereby limiting the motor drive current, that is, the load current.

In this way, according to this embodiment, the power transistor and the small signal transistor whose junction areas are in a constant ratio are integrated on the same chip, and the current proportional to the load current of the small signal transistor is detected. Regardless of the circuit voltage (voltage drop) required for the current detection circuit, the power supply voltage can be effectively used as the load drive voltage.

Note that the present invention applies to the first and second steps shown in FIGS. 1 and 2 above.
The present invention can be widely applied not only to the embodiment circuit, but also to two-phase and three-phase plugless motor drive circuits, relay drive circuits, etc. at low power supply voltages.

〔Effect of the invention〕

As described above, according to the integrated circuit motor drive circuit according to the present invention, a current mirror circuit is configured by a power transistor and a small signal transistor, and a control signal is generated by a current detection resistor connected in series with the small signal transistor. Therefore, the voltage applied to drive the motor can be effectively increased with the same power supply, and the number of turns of the motor coil can be simplified to reduce the cost and downsize the motor, which has great advantages.

[Brief explanation of the drawing]

FIGS. 1 and 2 respectively show the first embodiment of the present invention. A third circuit diagram showing an integrated circuit motor drive circuit according to a second embodiment.
1 and 4 are diagrams showing examples of conventional circuits corresponding to the circuits shown in FIGS. 1 and 2, respectively. Q□～Q2. ...Drive power transistor, Q1~Q
3... Predrive transistor, Q, 1 to Q, 3
...Small signal transistor for current monitor, R,,R. ...Current detection resistor, C, ...Comparator, C2...Signal control circuit. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Scope of Claims] 1) An integrated motor drive circuit having a power transistor that supplies a drive current to a motor load, and a circuit that controls the power transistor based on the drive current, the emitter of the power transistor; a small signal transistor connected in parallel with the base and forming a current mirror circuit together with the power transistor; and a current detection resistor connected in series with the small signal transistor for supplying a voltage based on the drive current to the control circuit. An integrated motor drive circuit comprising: