JPH02230806A - Amplifier circuit for hall element detection signal - Google Patents

Abstract

PURPOSE:To improve the driving characteristic of a motor by amplifying an inputted start voltage signal of a Hall element in the state without any offset and amplifying the signal to the post-stage. CONSTITUTION:A current 11 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-Q4 be Vf, then a voltage Vf is applied between the collector and emitter of TRs Q2, Q3 respectively because the collector and the base of the TRs Q2, Q3 are connected respectively. Since the emitter-base voltage of the TR Q4 is Vf and a voltage 2Vf is applied between the collector of the TR Q3 and the emitter of the TR Q1, a voltage vf is applied between the collector and the emitter of the TR Q1 finally. Since the voltage is constant regardless of the circuit of the next stage through which a current I2 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 (Al Industrial Field of Application) The present invention relates to a circuit for amplifying a detection signal of a Hall element for detecting the position of a magnetic pole of a DC motor.

(b) Prior art In general, 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 the like. It consists of a drive circuit that drives the stator coil based on the waveform.

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 the input terminals INI and IN2. These transistors Q5 and Q6 constitute a differential amplifier circuit.

With this circuit configuration, a current corresponding to the voltage input between the input terminals INI and IN2 flows as the collector current of Q7, and if the current mirror ratio is 1=1, the collector current of the same value flows to Q8, and this It 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 the transistor Q7 on the input side of the current mirror circuit are connected, the voltage between the collector and emitter is fixed at the voltage between the base and emitter and does not vary greatly. Regarding 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 Q7, the collector current of Q7 and Q8
A difference occurs in the collector current of , and an offset occurs in the output current Io. 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
o decreases by the base current of Q8. Especially the lateral P
In the case of an NP type transistor, the current amplification factor 1'lfa is low, so the error becomes large.

4 and 5 show the influence of offset on input/output characteristics. FIG. 4 shows an example in which an offset is applied to the output current 1o in ten directions when a substantially sinusoidal voltage signal Vin, which is a detection signal of the Hall element, is input between the input terminals. 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 7}, the effect will appear on the motor drive signal after synthesis, resulting in, for example, fluctuations (ripples) or reductions in torque. There was a problem.

An object of the present invention is to provide a Hall element detection signal amplification circuit that amplifies a manually input electromotive voltage signal of a Hall element without offset and outputs it to a subsequent stage, thereby improving the drive characteristics of a motor.

(Means for Solving Problem d1) The Hall element detection signal amplification circuit of the present invention uses first to fourth transistors of PNP type, and has a common connection between the bases and emitters of the first and second transistors. The bases of the third and fourth transistors are connected in common, and the bases of the second and third transistors are connected in common.
a current mirror circuit consisting of at least two transistors, with the collectors of the first and second transistors connected to the emitters of the third and fourth transistors; A differential amplifier circuit connected to a collector of the third transistor and a collector of the other transistor connected to a power supply is configured in a single semiconductor integrated circuit, and a Hall element that is input to the differential amplifier circuit is detected. It is characterized in that a current corresponding to the voltage of the signal is output from the collector of the fourth transistor.

(e) Operation An example of the structure of this invention is shown in FIG. In Figure 1, Q1
Q4 are the first to fourth 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 1 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 Q4 is Vf, since the collector bases of Q2 and Q3 are connected, Vf is applied between the collector emitters of Q2 and Q3, respectively. Also Q
Since the emitter-base voltage of Q4 is Vf, and 2Vf is applied between the collector of Q3 and the emitter of Q1, Vf is also applied between the collector and emitter of Q1.

Since this voltage is constant regardless of the next stage circuit through which ■2 flows, it is not affected by the early effect mentioned above, and Q
If the emitter area ratio of 1 and 02 is 1:1, I1 and 12
The ratio is also exactly 1=1.

Also, the base current of Q4 flows as part of ■1, but
The base current of Q1 is drawn by Q4. Therefore Q
The error due to the base current of 4 flowing to the ■1 side is approximately Q
The current amplification factor is reduced to 1/4.

Therefore, the current 2 is output without 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
The bases and emitters of transistors Q3 and Q2 are commonly connected, the bases and collectors of transistors Q2 and Q3 are connected, and the collectors of Q1 and Q2 are connected to the collectors of Q3 and Q4. By connecting each to the emitter, a current mirror circuit is constructed. Also, the emitters of transistors Q5 and Q6 are commonly connected and connected to current source 1, the collector of Q5 is connected to the collector of Q3, and the emitters of transistors Q6
collector 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 Q4. 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 Q4,
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 I flows through Q2 and Q4, and a current 1o is output from the output terminal OUT. At this time, the voltage applied between the collector emitters of 01 to Q3 is equal to the emitter-base voltage Vf and is constant, so the output terminal OUT
It is not affected by the Early effect regardless of the circuit configuration of the waveform synthesis circuit connected to the circuit. Further, as described above, the base current of Q4 is extremely small, and the amount of current decrease in the output current to due to the base current of Q4 flowing to the Il side is extremely small. On the other hand, since the Z 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 uniform. As a result, the current If corresponding to the electromotive voltage of the Hall element 3 is changed to the output current I without any offset.
It is output as O to the next stage waveform synthesis circuit.

(g) Effects of the Invention As described above, according to the present invention, since the offset caused by the current mirror circuit connected to the differential amplifier circuit is removed, an appropriate driving waveform signal is synthesized by the waveform synthesis circuit, and the motor The rotational characteristics of 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 Q4 - first to fourth transistors, (Q5+Q6
) -Differential amplifier circuit, 3-Hall element.

Claims (1)

[Claims] (1) Using the first to fourth transistors of PNP type, the bases and emitters of the first and second transistors are commonly connected, and the bases of the third and fourth transistors are commonly connected. , a current mirror circuit configured by connecting the bases and collectors of the second and third transistors, respectively, and connecting the collectors of the first and second transistors to the emitters of the third and fourth transistors, respectively; a differential amplifier circuit consisting of two transistors, the collector of one transistor being connected to the collector of the third transistor, and the collector of the other transistor being connected to a power supply, in a single semiconductor integrated circuit; A Hall element detection signal amplification circuit that causes a collector of a fourth transistor to output a current according to a voltage of a Hall element detection signal input to the differential amplifier circuit.