JPS62201088A - Bias circuit of hall element - Google Patents

Abstract

PURPOSE:To optimize the bias value of a differential amplifier and to increase and compensate current of a Hall element at high temperature, whose sensitivity is usually decreased at high temperature, by connecting a diode in series to the Hall element. CONSTITUTION:A timing signal for commutation is obtained by a Hall element 16 for detecting a magnetic field, and each phase of a stator coil is alternately turned ON or OFF thereby a rotational torque is generated. A diode 30 is connected to the negative side of an input electrode of the Hall element 16. Output electrode of the Hall element 16 is connected to each base of transistors to constitute a differential amplifier 20. Since the diode 30 is connected in series, operation limit voltage of the differential amplifier 20 is lowered.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a bias circuit for a Hall element used in, for example, a brushless motor.

(Prior Art) In recent years, with the spread of ultra-compact and thin headphone stereos, compact integrated video cameras, etc., there has been a demand for compact, low-cost motors. In the ultimate form, a flat brushless motor becomes essential, but under the conventional concept, a loss of 1-increase was unavoidable.

The simplification and cost reduction of the brushless motor system can be seen in, for example, US Pat.・There is a Tanabata that has been devised to W to to cleverly prevent the occurrence of a dead center where the torque becomes zero. However, even though the Hall element is 11[iil], a complicated electronic circuit is still provided separately to control the motor, and it has not reached the point where it can compete with brushed motors in terms of cost.

FIG. 6 shows an example of such a conventional brushless motor system, in which a stator body 11 is equipped with three sets of two-phase stator coils 12, six in total. Further, a Hall element 13 for position detection is also attached to the stator main body 11. Such a stator body 11
is connected to the stator coil 1 via seven wires 14.
It is electrically connected to the electronic circuit board 15 on which the second drive circuit is configured.

The breakdown of the seven wires 14 is as follows:
2 for current supply to the Hall element 13,
There are two for the Hall voltage detection signal. Mounted on the electronic circuit board 15 are a motor control circuit circuit 16, a semi-fixed resistor 17 for speed adjustment, and several chip components 18, which constitute the drive circuit for the stator coil 12. The chip components 18 are chip power transistors, resistors, capacitors, etc.In addition, 19 in the figure
is a leader line for supplying the 'R source. Further, although not particularly illustrated, for example, 6
A WfG rotor magnet is provided at the pole.

In a brushless motor having such a configuration, a commutation timing signal is obtained by the Hall element 13 for detecting a magnetic field, and rotational torque is obtained by alternately turning on and off each phase of the stator coil 12. The Hall element 13 for detecting the magnetic field is made of germanium (Ge), silicon (Si), indium antimonide (InSb), indium arsenide (InAs), etc., and as in the above-mentioned configuration, the stator coil 12 It was installed separately from the drive circuit.

As described above, the conventional brushless motor system was quite complex and had a considerable difference in cost compared to conventional brushed motors, making it difficult to adopt it in popular sets such as the one mentioned above. .

Further, since the electronic circuit section required the area of the substrate 15, it was difficult to miniaturize the device.

The Hall element 1 in such a brushless motor
The bias circuit No. 3 was, for example, as shown in FIG. That is, the output electrode of the Hall element 13 was connected to the bases of the transistors with common emitters constituting the differential amplifier 20. However, in such a circuit, as shown by the solid line in FIG. 8, the base bias voltage changes linearly toward the origin in proportion to Vcc, so that the voltage corresponding to the VOE of the differential amplifier 20 Then, the transistor of the differential amplifier 20 becomes inoperable. This voltage is relatively high; in this illustrated circuit, 2V
s E = 1.4V or more. In other words, such a conventional Hall element bias circuit has an IB low voltage (
1-1.5V) was not suitable for use.

Furthermore, compensation for temperature characteristics was not sufficient.

(Problems to be Solved by the Invention) The present invention has been made in view of the above points.
The present invention provides a bias circuit for a Hall element that lowers the operating limit voltage of an amplifier with a Hall voltage output of 1 to 1,5 V to the maximum, and also compensates for the temperature characteristics of the Hall element.

[Structure of the invention] (Means and effects for solving the problem) That is, in the bias circuit for a Hall element according to the present invention,
By placing a diode in series with the Hall element,
In addition to optimizing the bias of the differential amplifier, the current of the Hall element, whose sensitivity decreases at high temperatures, is increased at high temperatures to compensate.

(Example) An example of the present invention will be described below with reference to the drawings. 1st
The figure shows the circuit configuration, and a diode 30 is connected in series to the negative side (lower side in the figure) of the input current of the Hall element 13. The output electrode of the Hall element is an NPN whose emitters constituting the differential amplifier 20 are commonly connected.
Connected to each base of the transistor.

When the diodes 30 are connected in series in this way.

The base bias voltage is shown by the solid line in Figure 2,
That is, the operating limit voltage is lowered, and the transistors of the differential amplifier 20 operate up to around 2VBE=0.9V.

Incidentally, when the differential amplifier 20 is of the PNP type, the diode 30 is naturally placed on the positive side (upper side in the figure).

Furthermore, FIG. 3 is a diagram showing the temperature characteristics of sensitivity when the Hall cable 13 is placed on a silicon chip, for example. , -0.6%/' When the C1 specific resistance is 0.6 Ωcm (indicated by the solid line in the figure), it has a temperature characteristic of -0.56%/°C, that is, the sensitivity decreases as the temperature increases. By biasing such a Hall probe 13 through a diode as in the configuration described above, compensation for temperature characteristics becomes possible.

In this case, naturally there will be a deviation in compensation depending on the value of Vcc.

Qualitatively, from Figure 3, with a change of +50°C, there is a sensitivity fluctuation at a ratio of 117/85 = 1.3765.

(2) With a change of 50°C, the VF of diode 30 is
It fluctuates by 100111V.

Therefore, Vcc-(VF-ΔVF) 117Vcc-VF
85,', 32V F + 85ΔVp-32Vcc,
', Vc = Vp + (85/32)ΔVp
= 0.7+ (85,-'32) x O,1= 0
．． 9G (3V Therefore, in such a configuration, when Vcc = 1v,
Complete temperature characteristic compensation is achieved. In other words, it is preferable that the condition be satisfied near the reduced voltage limit where the Hall voltage output is minimum and exposed to the most severe conditions. In addition,
When the voltage is increased, the Hall output becomes sufficiently large, so it seems that there is no problem with some temperature characteristics.

In this way, by connecting the diode 30 in series with the Hall element 13, the bias of the differential amplifier 20 can be optimized, and the sensitivity of the Hall element 13, which decreases in sensitivity at high temperatures, can be reduced.
It is possible to compensate by increasing the current at high temperatures.

FIG. 4 is a diagram showing an internal equivalent circuit of the integrated circuit 31 including such a bias circuit for the Hall element. In the figure, 1
Reference numeral 3 denotes the above-mentioned Hall element formed in the integrated circuit, and 30 indicates the above-mentioned diode which serves both to optimize the bias of the transistor and to compensate for the temperature characteristics of the Hall element.

Further, 32 is a high gain 1q amplifier including a positive feedback circuit as disclosed in Japanese Patent Publication No. 53-17029, which amplifies the Hall voltage. 33 is a relay amplifier that further amplifies the Hall voltage, but here it is already in switching operation. The operating current 1 is determined by the output of voltage comparator 34.

35, 3G is a power transistor, and stator coil 12. , 122 are driven alternately. 37 is a constant current power supply section. This is a feedback type constant current circuit, and its value is determined by the thermal voltage and resistance caused by the difference (ratio) in current density of the transistors.

This constant current circuit 37 is designed to ensure that the operation starts.
Contains starter circuit.

The voltage comparator 34 compares the potential difference between the base QN pressure (point 38) from the reference voltage generator and a point 39 that generates a voltage proportional to the induced voltage from the stator coils 121 and 122, and determines whether the potential difference is A feedback circuit is formed so that the value becomes zero. The semi-fixed resistor 17 for speed adjustment and the smoothing capacitor Biai are connected to the point 39 outside the integrated circuit 31.

Further, 40 is an induced voltage detection section of the stator coils 121 and 122. During the period when the stator coils 121 and 122 are driven by the power transistors 35 and 36, they are off, and the stator coils 121 and 122 are turned off.
When no current is flowing through the current, a current proportional to the induced voltage is derived and supplied to the point 39.

The capacitor 182 is for limiting the frequency characteristics of the speed control loop to suppress oscillation. This is an external component that may not necessarily be required depending on the loop gain setting.

Transistor 41 has a thermal shutdown function. Chip temperature can be detected with a simple configuration of just one element. That is, the voltage applied between the pace emitters is a voltage proportional to the thermal voltage VT, and has a temperature characteristic of about +0.4%/°C. Also, since the VBE of the transistor has a temperature characteristic of about -2 mV/'C1, that is, about -0.3%/'C, 0.4+0.3=0.7%/ ℃ is used to detect which temperature gradient, and the temperature detection sensitivity is high.

The detection point to which the base is connected uses the voltage across the emitter resistor of the starter circuit of the constant current source mentioned above, so the number of elements can be reduced without disturbing the stage performance of the starter circuit, which is cut off except during startup. can.

By adopting such a circuit configuration, an integrated circuit circuit with fewer external components can be constructed.

Since FIG. 5 does not show the configuration of a brushless motor using such an integrated circuit 31, the stator body 11 includes two-phase stator coils 1 in which every other winding is connected in series.
2 has been it. Further, a printed circuit board 15 is integrally provided on the stator main body 11. The above-mentioned integrated circuit 31 enclosed in a flat package is mounted on this substrate 15. This integrated circuit 31 includes
As mentioned above, a Hall sensor is built in, and the chip is mounted on the substrate 15 so as to be at exactly the electrical angle position required for commutation. The lead frame of this integrated circuit 31 is made of a non-magnetic material so as not to generate torque unevenness. The board 15 also includes a semi-fixed resistor 17 for speed adjustment and an external chip capacitor 1.
8 is also installed. Note that 19 in the figure is a lead wire for power supply and grounding.

Also, facing the stator coil 12, as shown in FIG.
As shown in FIG. 2, a rotor magnet 51 magnetized into six poles is provided. This rotor magnet 51 is
Part of the special magnetization is applied to avoid the 1-lux dead center, but since the principle is based on U.S. Pat. No. 4,211,963 et al., it will not be discussed here. In addition, the same figure (
b) The middle 52 is a back plate configured to rotate together with the rotor 51, and is made of a material with high transmittance.

If the M source is supplied from the lead wire 19 to the brushless motor having such a configuration, the speed adjustment semi-fixed resistor 1
The motor rotates at the speed set by 1.

That is, by using an integrated circuit incorporating a Hall element bias circuit according to the present invention, the motor can be made ultra-small;
The product is thinner and more cost-effective, making it comparable in cost to the combination of a conventional brushed motor and electronic governor.

[Effects of the Invention] As detailed above, according to the present invention, ultra-low voltage (1 to
It is possible to lower the operational limit voltage of the amplifier with a Hall voltage output of 1.5 V to the maximum, and also compensate for the temperature characteristics of the Hall element.

[Brief explanation of drawings]

FIG. 1 is a circuit configuration diagram showing an embodiment of a bias circuit for a Hall element according to the present invention, and FIG. 2 is a diagram for explaining the operating limit voltage of a transistor of a differential amplifier using a bias circuit for a Hall element according to the present invention. Figure 3 is a diagram for explaining the temperature characteristics of sensitivity of the Hall element, Figure 4 is a specific internal equivalent circuit diagram of an integrated circuit to which the Hall element bias circuit of the present invention is applied, and Figure 5 is a diagram for explaining the temperature characteristics of sensitivity of the Hall element. 4 shows the configuration of a brushless motor using the integrated circuit of FIG. 4, (a) is a plan view, (b) is a side view, FIG. 6 is a diagram showing a conventional brushless motor, and FIG. 7 is a diagram of a conventional brushless motor. FIG. 8 is a diagram showing the operating limit voltage of a transistor of a differential amplifier using a conventional Hall element bias circuit. 13... Hall element, 20... Differential amplifier 30
···diode. Applicant's representative Patent attorney Takehiko Suzue Figure 2 Circumference 1 degree Ta ('C) Figure 3 Figure 5 Disclosure Figure 6

Claims (1)

[Claims] A Hall element bias circuit characterized in that at least one diode is connected in series to the input electrode of a Hall element connected to the base of each transistor of a differential amplifier having a transistor whose Hall voltage output electrode has a common emitter. .