JPH01144388A - Driving circuit of brushless motor - Google Patents

Abstract

PURPOSE:To drive efficiently by placing a saturation reducing means of an output transistor between input and output transistors and providing a current reducing means. CONSTITUTION:A driving circuit of a brushless motor is such that bases of input transistors (Tr1, Tr2) are connected to an input terminal Au, and that emitters of Tr3-Tr4 of a current reducing means E reducing current are respectively connected between emitters of Tr1 and Tr2. A series connection of a resistor R1, diodes D1-D3, and a resistor R2 is formed as a saturation reducing means S to reduce the saturation voltage of output Tr5-Tr6. The current equivalent to three phase portions of U-W is simultaneously turned ON and OFF by turning simultaneously ON and OFF Tr7-Tr8 for current cutting-off in case of power OFF. In addition, a Tr9 of a current mirror circuit K1 is connected to a collector of the Tr1. Accordingly, an input waveform as the output can be taken out as it is by the means S to the saturation voltage of output Tr5-Tr6.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a drive circuit for a brushless motor constructed of circuits such as transistors.

[Prior art]

In a separate application, the present applicant proposed a brushless motor drive circuit representing one phase as shown in FIG. In this drive circuit, a waveform synthesized from the Hall element output for 1200 current conduction is input to the input terminal A, and this waveform is applied to the input transistor 'Trl.
, Tr2, and drive the final stage transistors Trs, Trs, and a drive coil is connected to the output terminal B. In the above circuit configuration, the input waveform is taken out as an output as it is, and the emitters of the input transistors Trt and Trz are respectively connected to the output transistor T.
The input transistor Tr is connected to the diodes D1 and D2 of the saturation reduction means S for reducing the saturation voltage of rs and Trs.
1. The transistor is configured to cancel the base-emitter voltage VBE of Tr 2, reduce the output waveform VCE saturation of the output transistor, and drive efficiently.

However, the resistor R1 connected in series with the saturation reduction means S,
A current sufficient to drive the input transistors Tr1 and Tr2 must flow through the die A-Dt, 02 and the resistor R2. For example, in a three-phase drive, three phases are required, and the total current value is The disadvantage is that it becomes large.

[Purpose of the invention]

In view of the above-mentioned drawbacks, the present invention improves the base-emitter voltage V6E of the input transistor that distributes the input into the upper and lower parts by 1-1/
The purpose of the present invention is to propose a brushless motor drive circuit that reduces the drive current of the input transistor while maintaining the function of the brushless motor.

[Structure of the invention]

The present invention includes an input transistor that inputs a Hall element signal, and a drive coil of a motor that receives the output of the input transistor. I] an output transistor, a saturation reduction means located between the input transistor and the output transistor, for canceling the base-emitter voltage VBE of the input transistor to reduce the saturation voltage of the output transistor; The present invention further comprises a current reducing means connected between the reducing means and the input transistor to reduce the drive current of the input transistor.

〔Example〕

The present invention will be explained below with reference to illustrated embodiments. To explain the U-th phase of the three-phase drive of the brushless motor drive circuit, in Fig. 1, when the base of the input transistor Tz is connected to the input terminal Aμ, the base of the input transistor Trz is connected to the input terminal Au. has been done. Input transistor T
Between the emitters of r+ and Tr2, there are transistors Tr3 and T of current reduction means E for reducing the drive current of Tr1 and Tr2.
The emitters of r4 are connected to each other. The base of Tra is connected to the midpoint between diode D3 and resistor R2, and the collector is connected to ground. The base and collector of Tra are connected across resistor R1.

Resistor R1 and diodes D1, D2, D3, resistor R2
The series connection of the output transistors Trs and Tr6 is saturation reduction means S for reducing the saturation voltage of Trs and Tra for efficient driving by reducing the output waveform VCE saturation of the output transistors Trs and Tr6, and the diode D1 is the transistor Tr4 of the current reduction means E. Base-emitter voltage V BE
For cancellation, diode D2 is input transistor Tr
The diode D3 is for canceling the base-emitter voltage VBE of input transistor Tr1.

An output terminal Bu is connected to the midpoint between the diodes D2 and D3, and one end of the drive coil 1 is connected to the output terminal Bu. Resistor R1 is connected to V via transistor Tr7.
On the cc side terminal, the resistor R2 is connected to the GND terminal via the transistor Tra.

Further, the transistors Try and Trs are transistor switches for cutting current when the power is turned off.

By turning on and off Tr7 and Tra at the same time,
U, V, W (7) 3 phase current 1.1mON, OF
F I can do it.

One transistor Tr! is connected to the collector of the input transistor Tl-1 in a current mirror circuit. The base is connected. The collector of TrI+ has an output transistor Tr.
The base of s is connected. The collector of Trs is connected to the Vcc (Ill terminal) via a resistor R5. The emitter of Trs is connected to the output terminal Bu.

The base of the second transistor Trm is connected to the collector of the input transistor Tr2 in a current mirror circuit. The base of transistor Tr 11 of 3 is connected to the collector of Tr +m in a current mirror circuit. The base of the output transistor Tr s is connected to the collector of Tr n. Tra emitter Ga G
Connected to the ND terminal.

The operation of the drive circuit of the brushless motor described above is based on the input terminal A.
A voltage waveform synthesized from the Hall element signal for 1200 energization is input to u.

When a voltage of 2 V BE + R2·12 or higher is applied, the transistor Tr 1 is turned on, and the current amplified by the current mirror circuit Tr 1 drives the output transistor Trs.

Also, Vcc-R1・I 1-VBE=V8E+R2・1
When a voltage of 2 or less is applied, the transistor Tr2 is turned on, and the current amplified by the current mirror circuit 1<2, K3 drives the output transistor Tr6.

Resistor R1% Diode D1, D2, D3, Resistor R2
, the operation of transistors Tr3 and Tr4 is as follows: ■When transistor Tr1 is ON, Tr3 draws current; ■When transistor Tr2 is ON, Trt supplies current; in both cases, Tr1 , 1 of the current required by Tl-2
/ hfe (Tr3 hfe, Tri hfe
) only needs to flow as the base current of TraTr4.

That is, the drive currents of the input transistors 'rr 1 and Tr 2 are reduced by the current reducing means E.

In addition, by adding transistors Tr3 and Tr4, ■ base-emitter voltage vB of transistors Trz and Tr4
The cancellation of ε is ensured by the diodes D1 and D2, and the cancellation of the base-emitter voltage Vs+ of the input transistor Tr1 is guaranteed by the diode D3, respectively, and the saturation reduction means S is used to reduce the saturation voltage of the output transistors Trs and Tra. The input waveform can be output as is. Therefore, the input waveform is directly output as the output waveform, so it is efficiently driven.

To prevent simultaneous ON of input transistors Try and Tr2, ■Tz-Tr3-D 3-8 point output (potential), V
ln (input voltage) -VBE (D3) -VBE
(Trt >+VBE (D2) = (Vin-V
BE) Items in parentheses above indicate the relevant diodes, transistors, etc. Further, (V In −V BE ) indicates the potential at point a.

■At point a horn → D 2 → D 1 → Tra-Tr2, (V In-VBE) + 2 VIE-VBE=V
In other words, the emitter potential of the input transistor Trz becomes V In, and simultaneous ON of Trl and Tr2 can be prevented.

Furthermore, the output terminal Bu and the input transistor Trt, the emitter of Tr2 are connected to the transistor Tra, Trt and the diode D.
1, D2, and D3, a feedback effect from the output is obtained, which has the effect of preventing °spike noise at the output end.

In FIG. 1, ■ and W represent the V-th phase and the W-th phase, and the circuit configuration is the same as that of the U-th phase, with input transistors, output transistors, current mirror circuits, etc. being omitted. The input to the input terminal Ay is output to the output terminal F3v, and the input to the input terminal Aw is output to the output terminal Bw. In addition, by making the saturation reduction means S, which cancels the base-emitter voltage VBE of the input transistor of each phase and reduces the saturation voltage of the output transistor, common to the V side and the GND side, the current cut transistor Tr7,
Only two Tres are required, and the number of elements can be reduced.

A control signal is input from the outside to the bases of transistors Tr7 and rr8, and Tr7. The input transistors Tr t and Tr 2 are connected by using Trs as a current source and making it proportional to the control signal current.
can supply current to.

〔Effect of the invention〕

As described above, the present invention provides saturation reduction means for canceling the base-emitter voltage VBE of the input transistor and reducing the saturation voltage of the output transistor, by locating the saturation reduction means between the input transistor and the output transistor. 9ii) A current reduction means that can reduce the V CE saturation of the output transistor and drive it efficiently without impairing the far effect, and reduce the drive current of the input transistor between the saturation reduction means and the input transistor. By connecting the above, it is possible to provide a brushless motor drive circuit that has effects beyond practical use, such as being able to reduce the drive current value of the input transistor.

[Brief explanation of the drawing]

FIG. 1 shows an embodiment of the present invention, FIG. 1 is a drive circuit diagram of a brushless motor, and FIG. 2 is a drive circuit diagram of a brushless motor proposed by the applicant in a separate application. 1... Drive coil, Tz, Trz... Input transistor, rr5, Tr8... Output transistor, E...
・Current reduction means, S... Saturation reduction means, V BE...
・Base Emitter II! l voltage. Applicant Sankyo Seiki Seisakusho Co., Ltd.

Claims (1)

[Claims] An input transistor that inputs a Hall element signal, an output transistor that receives the output of the input transistor and drives the motor drive coil, and an output transistor that is located between the input transistor and the output transistor, and is located between the base and emitter of the input transistor. a saturation reduction means for canceling the voltage VBE to reduce the saturation voltage of the output transistor;
A drive circuit for a brushless motor, comprising: a current reduction means connected between the saturation reduction means and the input transistor to reduce the drive current of the input transistor.