JPH02230807A - Hall element detection signal amplifier circuit - Google Patents

Abstract

PURPOSE:To improve the driving characteristic of a motor by outputting a current in response to a voltage of a Hall element detection signal inputted to a differential amplifier circuit from the collector of a 3rd transistor(TR). CONSTITUTION:A current I1 flows to a collector of a transistor(TR) Q5 in response to a voltage inputted between bases of TRs Q5, Q6. Let a base-emitter voltage of TRs Q1-Q3 be Vf, then a voltage Vf is applied between the collector and emitter of TRs Q2 because the collector and the base of the TR Q2 are connected respectively. Since the emitter-base voltage of the TR Q3 is Vf and the base of the TR Q3 is connected to the collector of the TR Q1, a voltage 2Vf is applied to the TR Q1. Since the voltage is nearly constant (Vf and 2Vf) regardless of the circuit of the next stage through which a current 12 flows, the Early's effect is not caused, and the ratio of the I1 to I2 is accurately 1:1 when the emitter area ratio of the TRs Q1, Q2 is 1:1. Thus, the drive characteristic of the motor is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application This invention relates to a circuit that amplifies a detection signal of a Hall element that detects the position of a magnetic pole of a DC motor.

(bl Conventional Technology) Generally, a circuit that controls a DC motor includes an amplifier circuit that amplifies a rotor magnetic pole detection signal generated by a Hall element, a waveform synthesis circuit that synthesizes a predetermined drive waveform from the amplified magnetic pole detection signal, and a waveform synthesis circuit that synthesizes a predetermined drive waveform from the amplified magnetic pole detection signal. It consists of a drive circuit that drives the stator coil based on the following.

FIG. 3 shows an example of a conventional amplifier circuit that amplifies the detection signal of the Hall element. In FIG. 3, Q7 and Q8 are each PNP type transistors, and their bases and emitters are commonly connected, and the base and collector of Q7 are connected. Further, a current source is connected to the collector of Q8. A current mirror circuit is configured by Q7 and Q8. Both Q5 and Q6 are NPN
type transistors whose emitters are commonly connected to a current source. Transistors Q5 and Q6
A detection signal of the Hall element is inputted between the bases of , from human input terminals INI and IN2. These transistors Q5 and Q6 constitute a differential amplifier circuit.

With this circuit configuration, the input terminals INI-IN2
A current corresponding to the voltage input between them flows as a collector current of Q7, and if the current mirror ratio is 1:1, a collector current of the same value flows through Q8, and this is output to the output terminal OUT.

(C) Problems to be Solved by the Invention However, in the conventional Hall element detection signal amplification circuit shown in FIG. 3, an offset may occur in the output. In other words, since the base and collector of transistor Q7 on the input side of the current mirror circuit are connected, the collector-emitter voltage is fixed at the base-emitter voltage and does not fluctuate greatly, but the output side Regarding the transistor Q8, the voltage applied between its collector and emitter varies greatly depending on the circuit connected to the subsequent stage. Therefore, if the voltage applied between the collector and emitter of Q8 is not equal to the voltage applied between the collector and emitter of 07, the collector current of Q7 and Q8 will change due to the Early effect.
A difference occurs in the collector current of , and an offset occurs in the output current 1o. In particular, in the case of a PNP transistor, it is provided on a semiconductor substrate as a so-called lateral PNP transistor, and h0. Due to its poor characteristics, its influence is large.
Also, since the base current of Q8 flows to the Q5 side, even if the emitter area ratio of Q7 and Q8 is 1:1, the output current I
o decreases by the base current of Q8. Especially the lateral P
In the case of NP-type transistors, the current amplification factor hfa is low, so the error becomes large. 4 and 5 show the influence of offset on input/output characteristics. FIG. 4 shows that when a sine wave voltage signal Vin, which is a detection signal of the Hall element, is input between the input terminals,
An example is shown in which the output current to is offset in ten directions. Moreover, FIG. 5 represents this in terms of DC.

For example, in the case of a three-phase DC motor, three Hall elements are arranged, a magnetic pole detection signal is generated for each phase by the amplifier circuit shown in Figure 3, and the coil drive waveform is generated from the magnetic pole detection signal for the three phases. However, if the amplified signal of the Hall element detection signal contains an offset, the effect will appear on the motor drive signal after synthesis, causing problems such as torque fluctuations (ripples) or reductions. there were.

SUMMARY OF THE INVENTION An object of the present invention is to provide a Hall element detection signal amplification circuit that amplifies an input electromotive voltage signal of a Hall element without offset and outputs it to a subsequent stage to improve motor drive characteristics.

(d) Means for Solving the Problems The Hall element detection signal amplification circuit of the present invention uses first to third transistors of PNP type, and connects between the bases and emitters of the first and second transistors, respectively. A common connection is made, the base and collector of the second transistor are connected, the emitter of the third transistor is connected to the collector of the second transistor, and the base of the third transistor is connected to the collector of the first transistor. and a differential amplifier circuit consisting of at least two transistors, in which the collector of one transistor is connected to the collector of the first transistor, and the collector of the other transistor is connected to a power supply. The third transistor is configured in a semiconductor integrated circuit, and is characterized in that the collector of the third transistor outputs a current corresponding to the voltage of the Hall element detection signal input to the differential amplifier circuit.

(e) Operation An example of the structure of this invention is shown in FIG. In Figure 1, Q1
Q3 are the first to third transistors of the PNP type according to the present invention, and Q5 and Q6 constitute the differential amplifier circuit according to the present invention. Because of this circuit configuration, current I1 flows through the collector of Q5 in response to the voltage input between the bases of Q5 and Q6. Here, if the base-emitter voltage in the transistors Q1 to Q3 is Vf, Vf is applied between the collector and emitter of Q2 because the collector and base of Q2 are connected. Further, the emitter-base voltage of Q3 is Vf, and since the base of Q3 is connected to the collector of Q1, 2Vf is applied to Q1. Since the collector-emitter voltages of Q1 and Q2 are approximated (■f and 2Vf) L and constant regardless of the next stage circuit through which I2 flows, they are hardly affected by the aforementioned Early effect, and Ql and Q2 If the emitter area ratio of is 1:1, the ratio of 1 and 12 will also be exactly 1:1.

Also, the base current of Q3 flows as part of I1,
The base current of Q1 is drawn by Q3. Therefore Q
The error due to the base current of 3 flowing to the Il side is approximately Q
The current amplification factor is reduced to 1/3.

Therefore, the current 2 is outputted without any offset from the current I1 flowing in accordance with the electromotive voltage of the Hall element.

(f) Embodiment FIG. 2 shows a circuit diagram of a Hall element detection signal amplification circuit which is an embodiment of the present invention. Transistor Q as shown in the figure
By connecting the bases and emitters of transistors Q1 and Q2 in common, connecting the base and collector of Q2, connecting the emitter of transistor Q3 to the collector of Q2, and connecting the base of Q3 to the collector of Q1, the current can be established. It constitutes a mirror circuit. In addition, the emifters of transistors Q5 and Q6 are commonly connected, and the current source 1
and connect the collector of Q5 to the collector of Q1,
The collector of Q6 is connected to the power supply. These two transistors Q5 and Q6 constitute a differential amplifier circuit. Further, a current source 2 is connected to the collector of the transistor Q3. Here, the current source circuit is configured such that the current flowing through the current source 1 is twice the current flowing through the current source 2.

A Hall element 3 is connected between two input terminals INI and IN2, and a collector current I1 flows through Q5 according to the input voltage Vin. This causes base current to flow through Q3,
The base potentials of Q1 and Q2 are pulled. Since the emitter-base potentials of Q1 and Q2 are equal, the current I
A current equal to 1 flows through Q2 and Q3, and a current IO is output from the output terminal OUT. At this time, the voltage applied between the collector and emitter of Q2 is equal to the emitter-base voltage Vf, and the voltage applied between the collector and emitter of Q1 is 2'' and is constant, so the output terminal O
Regardless of the circuit configuration of the waveform synthesis circuit connected to the UT, it is hardly affected by the Early effect. In addition, as mentioned above, the pace current of Q3 is extremely small,
Output current due to base current of 3 flowing to ■1 side■
The amount of current decrease at 0 becomes extremely small. On the other hand, since the two transistors Q5 and Q6 constituting the differential amplifier circuit are arranged close to each other on the semiconductor substrate, characteristics such as current amplification factor can be made the same. As a result, the current 1 corresponding to the electromotive voltage of the Hall element 3 is directly output to the next stage waveform synthesis circuit as the output current 1o without any offset.

(Effects of the Invention As described above, according to the present invention, the offset caused by the current mirror circuit connected to the differential amplifier circuit is removed, so the waveform synthesis circuit synthesizes an appropriate driving waveform signal, and the motor Rotation characteristics are improved.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an example of the configuration of the present invention. FIG. 2 is a circuit diagram of a Hall element detection signal amplification circuit according to an embodiment of the present invention. FIG. 3 is a circuit diagram of a conventional Hall element detection signal amplification circuit. FIGS. 4 and 5 are diagrams showing examples of offsets caused by conventional circuits. Q1 to Q3 - first to third transistors, (Q5+Q6
) 1 differential amplifier circuit, 3 1 Hall element.

Claims (1)

[Claims] (1) Using first to third transistors of PNP type, the bases and emitters of the first and second transistors are connected in common, the base and collector of the second transistor are connected, and the a current mirror circuit consisting of at least two transistors, in which the emitter of a third transistor is connected to the collector of the second transistor, and the base of the third transistor is connected to the collector of the first transistor; A differential amplifier circuit having a collector connected to the collector of the first transistor and a collector of the other transistor connected to a power supply is configured in a single semiconductor integrated circuit, and a hole input to the differential amplifier circuit is configured. A Hall element detection signal amplification circuit that causes a collector of a third transistor to output a current according to a voltage of an element detection signal.