JPS60229694A - Current switching circuit - Google Patents

Abstract

PURPOSE:To suitably switch a current with a simple circuit by generating a base control signal of a transistor for switching the current by an amplified controlled in the gain and the output operating range by a current proportional to an input current amount. CONSTITUTION:After the output of a Hall element is amplified by a differential amplifier which has transistors 5, 6 inputting the output of the Hall element, a transistor 18 and a resistor 20, it is supplied to the bases of transistors 2, 3 which form a switch circuit. A current source of the differential amplifier, i.e., the current amount of a current source which has the transistor 18 and the resistor 20 is varies proportionally to the current amount input to the transistors 2, 3. When thus constructed, the amplitude of a switching signal input to the bases is varied proportionally to the current supplied to the common emitter of the transistors 2, 3 which form a switch circuit.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a current switching circuit, and particularly to a current switching circuit suitable for the case where the amount of current is varied.

[Background of the invention]

A current switching circuit is generally operated by connecting several semiconductor switches in parallel and switching them at desired timing.

Here, an example of a conventional current switching circuit will be described with reference to FIG. 1, taking a brushless motor drive circuit as an example. In the figure, 1 is an X current source whose current amount can be controlled, 2 is a transistor for switching the current source 1, 4 is a current amount, and 5 to 8 are transistors. -10 is a resistor, 11@12 is a stator coil, 13 is a rotor magnet, 14 is a Hall element that detects the rotational phase of the rotor magnet 130, and 15.16 is a voltage source.

The current flowing through the stator coils 11 and 12 exerts a rotational force on the rotor magnet 15, and the phase of this rotation is detected by the Hall element 14. The output of this Hall element 14 is connected to the current source 4, the transistors 5 and 6, and the collector resistor? After being amplified by a differential amplifier consisting of -10, it is applied to the bases of current switching transistors 2 and 5.

This causes the current of current source 1 to flow through transistor 2 or 3.
The current is supplied to the stator coil 12 or 11 as a pacemi current of the transistor 8 or 7 through the transistor 8 or 7, and the current is amplified by the transistor 8 or 7. In this way, by switching the current flowing through the stator coils 11 and 12 at appropriate timing, the stator coils 11 and 12 continue to rotate in one direction.

FIG. 2 shows operating waveforms of the main parts of the circuit shown in FIG. 1. The waveform (→, -) indicates the output waveform of the Hall element 14,
This is input to the bases of transistors 5 and 6 forming a differential amplifier. on the waveform).

) shows the output waveform of this differential amplifier, and one terminal of the collector resistor 9 and 10 and the current switching transistor 2.
3 shows the waveform at the connection point of pace input. The current of current source 1 is supplied to the base of transistor 8 or 7 via transistor 2 or 3 by this switching control signal (c), and the collector current has a waveform of (e) or (f).
becomes.

Here, in general, by controlling the amount of current from the current source 1, the amount of current flowing through the stator coil 11812 is varied to control the rotational speed of the rotor magnet. Like this,
In many cases, the amount of current of the current source 1 is varied, and the amount of current flowing through the switching circuit transistors 2 and 6 is varied. At this time, as shown in Figure 1, if a constant amplitude base control signal is always input to change the amount of current flowing through transistors 2 and 3, the maximum current value will change. It is necessary to input a large-amplitude base control signal so that the switching circuit can operate satisfactorily. However, when designed in this way, there is a problem that the switching gain becomes too large in a region where the amount of current is relatively small. This has caused problems such as oscillation and the need for large capacitors at both ends of the stator coils 11 and 12.

[Purpose of the invention]

An object of the present invention is to eliminate the above-mentioned drawbacks of the prior art, and to automatically set the optimum base control signal amplitude of the switching transistor according to changes in the amount of input current using a relatively simple circuit configuration. To provide a current switching circuit capable of realizing current switching with the minimum necessary gain.

[Summary of the invention]

In order to achieve the above object, the present invention provides means for generating a base control signal for a tR cut transistor by an amplifier whose gain and output operating range are controlled by a current proportional to the amount of input current. .

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIGS. 3 to 8. Figure 31 shows the general characteristics of a differential amplifier. FIG. 3 shows a part of FIG. 1, and the same parts are indicated by the same symbols. In the same figure, the input/output characteristics (V
an, Iout) are expressed as shown in FIG. In the same figure, the input voltage Vin of the differential amplifier is plotted on the horizontal axis,
The output current 10μt is plotted on the vertical axis, and the collector voltage of one transistor 2 or 3 @1. shows.

General VcIc is expressed by the following formula.

'c+ = 16/(1-*-'?) 9: to the amount of charge of the child: Boltzmann's constant T: absolute temperature Here, k T/q is approximately 26rlLV, and from the above equation, the current of Icl is converted to the current of IO. To make it about 1/10, main=
Approximately 60 mV is required. Therefore, when the transistors 2 and 3 constituting the differential amplifier are used as a switch circuit, when the current value I0 of the current source 1 is controlled and changed, the necessary switching input signal CFin) also changes. In other words, the transistor 2- used as a switch circuit
If the current value in the off state of 3 is set to 1 μA or less, for example, at lo-100 μA, “z n #12
0 mF' or more is required, and at 1o = = 1 mA, V = 180 mV or more is required.In this way, when configuring a differential switch circuit with transistors, its input!
It is desirable to control the control input C'in) of the switch circuit in proportion to the flow rate.

Hereinafter, specific embodiments of the present invention will be described with reference to FIGS. 5 and 6. The same parts as in FIGS. 1 and 6 are indicated by the same symbols. 17 and 18 are transistors, 19 and 20 are resistors, 21
indicates a variable current. Here, transistor 17 and resistor 1
The nine-fist variable lightning source 21 constitutes the current source 1. Further, the transistor 18 and the resistor 20 constitute a current source 4. The mid-winter component operates in the same manner as the conventional circuit shown in FIG. That is, the output of the Hall element 14 is amplified by a differential amplifier composed of a transistor 5 @ 6 and a transistor 18 ◆ a resistor 20 which inputs the output of the Hall element 14 , and then the transistors 2 and 3 forming the switch circuit are amplified.
supply to the base of In the embodiment of the present invention, the voltage fM of this differential amplifier (consisting of 18 transistors and 20 Φ resistors) is
The current of −! 4 transistors 2 forming a switch circuit
Input to ψ3! The flow rate (collector of transistor 17! sweat amount) K is configured to vary on one side.

That is, the bases of the transistors 17 and 18 are connected in common and controlled by the f'l source 21. With this configuration, the transistor 2 constituting the switch circuit
- The amplitude of the switching signal input to its base changes proportionally to the N Rt K supplied to the common emitter of the three. This is because the amount of ti of the transistor 18 changes in proportion to the change in the current flowing through the transistor 17, and as a result,
The signal amplitude produced at the resistors 9 and 10 also changes proportionally.

FIG. 6 shows the main waveforms of FIG. 5. When the variable power supply 21 changes as shown in waveform (1), the output waveform of the Hall element 14 +
21. +31, the pace input waveform of transistors 2 and 3 forming the switch circuit is waveform (4), 151
As shown in FIG. 2, the current amount increases in proportion to the amount of current flowing through the transistors 17 and 18 caused by changes in the variable power supply 21. In this way, the motor control current supplied from the transistor 17 is stably switched by the transistors 2 and 3 forming the switch circuit, and becomes the base potential of the transistor 7 and 8. As a result, the current flowing through the coils 11 and 12 has a waveform of +61, ff+.

Another embodiment of the present invention is shown in FIG. 7e and FIG. 8.

The figure shows the 8El of the present invention applied to a three-phase motor drive circuit. In the same figure, 22 to 24 are rotor magnets,
25 to 27 are stator coils, 28 are bias power supplies, 29 to 53 are transistors, 54 to 56 are resistors, 57 is a transistor, and 56 is a variable resistor.

Here, the Hall elements 22 to 24 are connected to the rotor magnet 13.
at a position where magnetic flux can be detected and each output waveform is 1
They are arranged in a relationship that causes a phase shift of 20 degrees. That is, the output waveform of one side of each Hall element becomes the waveform shown in FIG. 8 +2), (31, (41).Of course,
The other output waveform is the inverse of these waveforms. Transistors 41 to A3.4 with these inputs
4 to 46, and input to a differential amplifier composed of 47 to d9. Next, the transistor A that constituted this differential amplifier
The collector resistors 1 to 43 degrees 44 to 4547 to 49 are connected to each other and supplied to collector resistors 54 to 56, respectively.

Here, the voltage waveform generated at each resistor 54 to 56 is the waveform +51. (61, (as shown in 71. Also,
The voltage amplitude generated here is the transistor 43, 46, 49
It is proportional to the amount of current flowing through the So, this waveform +51
, (6+, +71 as inputs) A current proportional to the current (collector current of transistor 51) supplied to the common emitter of transistors 38 to 40 constituting the 3-differential switch circuit that constitutes the input is extracted as the collector current of transistor 52, By configuring a current mirror circuit between the diode-connected transistor 50 and the transistors 43 and 46φ49, a switching signal having an amplitude proportional to the amount of current flowing through the differential switch circuit, which is the main focus of the present invention, can be input to the base. Furthermore, this amount of current can be controlled by controlling the variable resistor 58 to supply the diode m[
This is achieved by controlling the current flowing through the transistor 53 and configuring a current mirror circuit between this transistor 53 and the transistors 51 and 52. The current switched by the 5 differential switch circuits (transistors 58 to 40) in this way is amplified by the power transistors 32 to 34, and the stator coils 25 to 27 for driving the motor are amplified by the power transistors 32 to 34.
The sink current will be . On the other hand, transistors '55-37
Similarly, the fc3 differential switch circuit configured by the transistor 50 and the transistor 57 switches and outputs the undercurrent supplied via the current mirror circuit configured by the transistor 50 and the transistor 57.
After current is amplified by transistors 29 to 31, it becomes a source current for stator coils 25 to 27 for driving the motor. In this way, the current waveform flowing through the transistors 52 to 34 becomes a six-phase waveform shown in waveform (8)K in FIG. 8, and the combined current is controlled by the variable resistor 58. or more t′(,
In a three-differential switch circuit, similarly, a switching signal having an amplitude proportional to the amount of current flowing through its common emitter can be supplied as a pace input to each transistor.

Although the present embodiment has been described with respect to a motor drive circuit, it goes without saying that the present invention can be widely applied to a circuit that controls the amount of current flowing through a differential switch circuit constructed using similar semiconductor elements.

As described above, according to the present invention, there is no need to increase the gain unnecessarily during the power switching transition flowing through each stator coil, and at the same time, there is no need to increase the gain unnecessarily. , 4 Excessive current 7f: Sufficient cutoff even when it is necessary to flow [Effects of the invention] According to the present invention, in proportion to the amount of current flowing to the common emitter of a plurality of transistors constituting a differential switch circuit,
Disconnection signal 1b input to the pace of each transistor
Since the width can be changed, the switch circuit can always be operated with the minimum necessary switching signal amplitude, and at the same time, a sufficient switching effect can be obtained even with excessive input current.

[Brief explanation of drawings]

Figure 1 is a circuit diagram 1m showing an example of a conventional motor drive circuit.
The second factor is the main waveform factor in Fig. 1, Fig. 3 is a circuit diagram of a general tracking amplifier, Fig. A4 is a characteristic diagram showing the characteristics of Fig. 3, and Fig. 5
The figure is a circuit diagram showing one embodiment of the present invention, the sixth factor is the main fBe type diagram of FIG. 5, the seventh factor is a circuit diagram showing another embodiment of the present invention, and FIG. The main waveform part is shown. 1... Current source 2-5... Transistor 5116.
・Transistor 940...Resistor 17/18...Transistor 19620...Resistor 21...Variable Source Patent Attorney Akio Takahashi 1st Ward? figure

Claims (1)

[Claims] A plurality of transistor groups to which a signal current is supplied, whose emitters are connected to each other, and whose respective collectors serve as output terminals, and a control signal generator that generates a control signal to be input to the bases of the transistor groups. What is claimed is: 1. A current switching circuit comprising: a current switching circuit that controls the output amplitude of a control signal generator in proportion to the amount of signal current;