JPS6155358B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a forward/reverse drive circuit for a brushless motor, and is particularly suitable for use in a two-phase switching type brushless motor.

DC commutator motors used in electronic devices can be driven in forward and reverse directions by changing the polarity of the power source. Furthermore, in a brushless motor in which a field magnet is disposed on the rotor side and an excitation coil is disposed on the stator side, the direction of the switching drive current flowing through the excitation coil is reversed to rotate the motor in forward and reverse directions.

Figure 1 shows a conventionally well-known forward/reverse drive circuit for such a brushless motor, which is described in Japanese Patent Publication No. 52-27328, and is applied to a two-phase switching drive brushless motor, and also has a power reversal switch. It is composed of semiconductor switches.

In Fig. 1, when switch S ₁ is connected to the negative side of power supply Vs, transistors Q ₅ ,
Q ₈ is on, line a is positive, line b
becomes a negative power level. An operating current flows through the Hall element H from line a through a diode D ₅ and resistors R ₃ and R ₄ , and a return current of the Hall element flows through a diode D ₈ to line b. The Zener diode ZD is a Hall element H.
This is to make the applied voltage constant.

The + and - outputs of the Hall element H are transistors
It is supplied to the bases of Q ₂ and Q ₄ , and these transistors are turned on alternately at 180 degrees in electrical angle. Therefore, a switching drive current flows from line a through diodes D ₁ and D ₃ to coils L ₁ and L ₂ , respectively, and this drive current flows from the emitters of transistors Q ₂ and Q ₄ to line b via resistor R ₂ . flows to Note that the resistor R ₂ is a common emitter resistor for operating the transistors Q ₂ and Q ₄ as a differential switching circuit.

When the motor is reversed, the switch _S1 is connected to the positive side of the power supply Vs, so transistors _Q6 and _Q7 are turned on, respectively, and line a becomes negative and line b becomes positive power supply level. The operating current of the Hall element H is the diode D ₆ and the resistor
It flows through R ₃ , R ₄ , the Hall element, and the diode D ₇ to line a. Since the + and - outputs of the Hall element H turn on the transistors Q ₁ and Q ₃ alternately,
A switching drive current flows from line b through diodes D ₂ and D ₄ to coils L ₁ and L ₂ in the opposite direction to the normal rotation, and this drive current flows through the transistor
Line a from the emitters of Q ₁ and Q ₂ through resistor R ₁
flows to

The conventional motor drive circuit shown in FIG. 1 has the following drawbacks.

(A) At least four
Two power transistors _Q5 to _Q8 are required.

(B) Four diodes D ₅ to _{D 8} (bridge circuit) are required to keep the direction of current flowing through the Hall element H constant.

(C) In order to allow current to flow from the plus side line a or b to the coils _{L 1 and} L ₂ to which switching transistors Q 1 to Q ₄ are connected at both ends, a current capacity comparable to that of the transistors Q ₁ to _{Q 4} is required. power diodes D ₁ to _{D 4} are required.

That is, since the configurations of items (A) to (C) above are always required, the circuit configuration becomes complicated, resulting in high cost and reduced operational reliability. Furthermore, (D) the current flowing through coil L ₂ (or L ₁ ) is, for example, transistor Q ₅ → diode D ₃ → coil L ₂
→Transistor Q ₄ →Resistor R ₂ →Transistor Q ₃
, the collector-emitter saturation voltage VCEsat of three power transistors Q ₅ , Q ₄ , Q ₈ and the diode D ₃
There is a forward voltage drop of , and efficiency is degraded due to these voltage losses.

It has the following drawbacks.

The present invention provides a brushless motor drive circuit that eliminates these drawbacks.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 is a motor drive circuit diagram showing one embodiment of the present invention. Note that the same parts as in FIG. 1 are given the same reference numerals.

In the embodiment shown in FIG. 2, the power lines a and b are fixed to positive and negative, respectively, and the polarity is not reversed as in FIG. 1. One end of each of the coils L ₁ and L ₂ is commonly connected, and this common connection point is switched and connected to line a (+) and line b (-) by transistors Q ₅ and Q ₆ , thereby The current direction of the coils L ₁ and L ₂ is reversed to rotate the motor forward and reverse. Therefore, the power supply switching circuit is extremely simplified and only requires two power transistors Q ₅ and Q ₅ .

Note that this power source switching circuit can be replaced by a switch _S1 , and the movable contact terminal of the switch _S1 may be connected to the common connection point of the coils _L1 and _L2 . Note that when the power switching circuit shown in Figure 1 is configured with mechanical contact switches, one set of movable contacts (two systems) and two
The structure of the switch shown in FIG. 2 is also simplified in this case since it must be constructed of a double-throw switch (so-called reversing switch) having a set of fixed contacts.

The other ends A and B of the coils L ₁ and L ₂ are connected to a negative power supply line b via diodes D ₁₅ and D ₂₁ and transistors Q ₂ and Q ₄ , respectively.
A switching current in the forward rotation direction is caused to flow through the coils L ₁ and L ₂ by Q ₂ and Q ₄ . Also, coils L ₁ , L ₂
Terminals A and B of are connected to the positive power supply line a through diodes D ₁₄ and D ₂₀ and transistors Q ₁ and Q ₃ , respectively.
The transistors Q ₁ and Q ₃ cause switching currents of opposite rotation to flow through the coils L ₁ and L ₂ .

Note that the diodes D ₁₄ , D ₁₅ , D ₂₀ , and D ₂₁ are activated when the back electromotive force induced in the non-energized coil L ₁ or L ₂ is applied to the drive transistors Q ₁ to _{Q 4} . This is to prevent the transistor from being reversely conductive, and is unnecessary in principle. For example, when transistor Q ₂ is turned on during normal rotation and drive current is flowing through coil L ₁ , the flux linkage of the other coil L ₂ causes terminal B of L ₂ to have a voltage higher than the power supply voltage. A back electromotive force is generated. If the diode D ₂₀ is not inserted between the terminal B of the coil L ₃ and the collector of the transistor Q ₃ , the back electromotive force at the terminal B causes the transistor Q ₃ to conduct, and current also flows through the coil L ₂ . This current generates torque in the opposite direction to the rotational direction, so the motor is braked and the output torque is reduced. Therefore, by inserting the diode _D20 , reverse conduction of the transistor _Q3 can be prevented, and the output torque of the motor does not decrease. Diodes D ₁₄ , D ₁₅ , and D ₂₁ are also inserted for the same purpose.

The motor low position detecting means of this embodiment is composed of a photointerrupter consisting of a light emitting diode _D22 and a phototransistor _Q10 . The rotational position of the rotor is detected by blocking light. Since the polarities of the power lines a and b are not reversed in forward and reverse directions, a bridge circuit of diodes D ₅ to _{D 8} as shown in Figure 1 is used to always energize the light emitting diode D ₂₂ and phototransistor Q ₁₀ in one direction. is not necessary. Further, even if the rotor position detecting means is constituted by a Hall element as shown in FIG. 3, a diode bridge circuit is similarly unnecessary. Note that the light emitting diode D ₂₂ has a resistor R ₃
A constant voltage is supplied via a resistor _R4 from a constant voltage circuit consisting of a Zener diode ZD and a Zener diode ZD.

The drive transistors Q ₁ and Q ₂ are driven by the switching signals of the collector and emitter outputs of the FET transistor Q ₁₀ , and the transistors Q ₃ and Q ₄
are driven by opposite phase switching signals obtained from the collectors of transistors _Q1 and _Q2 , respectively.
That is, the base of transistor Q ₁ is connected to diode D ₁₀
and the collector of the phototransistor _Q10 via the resistor _R5 , and the base of the transistor _Q2 is connected to the emitter of the phototransistor _Q10 via the diode _D13 . Furthermore, the base of transistor Q ₃ is connected to diode D ₁₆ and resistor R ₆
Similarly _{, the base of transistor Q 4 is} connected to the collector of transistor Q ₂ via diode D ₁₉ and resistor R ₇ .

Transistors Q ₁ and Q ₂ are cut off during forward rotation, and transistors Q ₂ and Q ₄ are cut off during reverse rotation.
A control line c is provided connected to the common connection point of the coils L ₁ , L ₂ to cut off the transistors Q ₁ , Q ₃ or Q, respectively, depending on the positive or negative voltage level of this control line c. ₂ and _Q4 are cut off. That is, a diode is connected between the cathodes of the diodes D ₁₀ and D ₁₆ at the bases of the transistors Q ₁ and Q ₃ and the control line c.
D ₁₁ and D ₁₇ are connected together, and diodes D ₁₂ and D ₁₈ are connected between the respective anodes of diodes D ₁₃ and D ₁₉ at the bases of transistors Q ₂ and Q ₄ and the control line c. Note that the diodes D ₁₀ , D ₁₁ and D ₁₆ , D ₁₇
The circuit surrounded by the dotted line in FIG. ₂ , which consists of diodes D ₁₂ , _{D 13 and}
The circuit surrounded by the dotted line consisting of D ₁₆ and D ₁₉ can be replaced with positive logic AND gates G ₃ and G ₄ .

During forward rotation, control line c is approximately at the power supply voltage Vs
, the diodes D ₁₁ and D ₁₇ are turned on, respectively, and the high level cathode voltage turns off the diodes D ₁₀ and D ₁₆ , cutting off the transistors Q ₁ and Q ₃ . In addition, at the time of reversal, the control line c becomes low level (ground potential), so the diodes D ₁₂ and D ₁₈ are turned on, respectively.
Its low level anode voltage causes the diode to
D ₁₃ and D ₁₉ are turned off, and transistors Q ₂ and Q ₄ are cut off.

Next, the operation of the motor drive circuit shown in FIG. 2 will be explained. For forward rotation, connect switch _S1 to the negative side. This causes current to flow through resistors R ₈ and R ₉ , forward biasing transistor Q ₅ and turning it on. Therefore, a positive power supply voltage Vs is supplied to the common connection point of the coils L ₁ and L ₂ . This causes the control line c to go high and transistors Q ₁ and Q ₃ to be cut off as described above. Furthermore, since the diodes D ₁₂ and D ₁₈ connected to the control line c are off, the emitter output of the phototransistor Q ₁₀ also turns on and off the transistor Q ₂ , and a negative phase signal is generated at the collector of the transistor Q _{2 .} However, transistor Q ₄ is turned on in opposite phase to Q ₂ .
It will be turned off. As a result, the motor is rotated in the normal direction.

Next, when switch S ₁ is connected to the + side, resistance R ₁₁
A base current flows through the transistor Q ₇ through the low resistor R 10 , turning on the transistor Q ₇ , and a base current flows through the low resistance R ₁₀ and the transistor Q ₇ to the transistor Q ₆ , turning on the transistor Q ₆ . Therefore, the common connection point of coils L ₁ and L ₂ becomes a negative power supply level (ground potential). This causes control line c to go low, turning on diodes D ₁₂ and D ₁₈ and cutting off transistors Q ₂ and Q ₄ . Furthermore, since the diodes D ₁₁ and D ₁₇ connected to the control line c are off, the collector output of the phototransistor Q ₁₀ also turns on and off the transistor Q ₁ .
Furthermore, the transistor Q ₃ is turned on and off in a phase opposite to that of Q ₁ by a reverse phase signal generated at the collector of the transistor Q ₁ . As a result, a switching current is applied to the coils L ₁ and L ₂ in a direction opposite to that during normal rotation, and the motor is reversed.

In the circuit shown in Figure 2, for example, during normal rotation, the coil L ₂
When energized, current flows through the path of transistor Q ₅ → coil L ₂ , diode D ₂₁ , and transistor Q ₄ , so the voltage loss is absorbed by the transistor.
The collector-emitter saturation voltage V _CE sat of Q ₅ and Q ₄ is 2 times, and the forward voltage drop of diode D ₂₁ is 1.
Since it is the sum of the individual components, the voltage loss is smaller than that of the drive circuit shown in FIG. 1, and the efficiency of the drive circuit is therefore improved.

Figure 3 shows an example of using a Hall element H as a rotor position detection element, and the positive output of the Hall element H is connected to a resistor.
It is supplied to the transistor _Q11 via _R12 , and the collector output and emitter output of this transistor _Q11 drive the transistors _Q1 and _Q2 . Further, the negative output of the Hall element H is supplied to the transistor _Q12 via the resistor _R13 , and the collector output and emitter output of this transistor _Q12 are used to connect the transistors _Q3 and _Q4.
is driving.

Figure 4 shows the transistors Q ₁ , Q ₃ , Q ₂ ,
As mentioned above, the base drive circuit of Q ₄ is composed of negative logic AND gates G ₁ , G ₂ and positive logic AND gates G ₃ , G _{4 .}
, respectively.

FIG. 5 shows an example in which the present invention is applied to a three-phase unidirectional switching type brushless motor. The three-phase coils L ₁ , L ₂ , and L ₃ are sequentially energized at an electrical angle of 120°. For this reason, a third phase (coil L ₃ ) drive circuit is provided in addition to the drive circuit shown in FIG. 2. In addition, the rotor position is detected using light emitting diodes for each phase.
D ₂₂ , D ₂₃ , D ₂₄ and phototransistor Q ₁₀ ,
This is done using a photo interrupter consisting of Q ₁₃ and Q ₁₄ , respectively.

Generally, in a three-phase one-way switching current-carrying type brushless motor as shown in FIG. 5, forward and reverse driving is performed by reversing the output phase of a position detection element such as a Hall element. However, when the position detection element is constituted by a photointerrupter as shown in FIG. 5, it is not easy to invert the output phase, and the circuit configuration becomes complicated. However, by configuring as shown in FIG. 5, the motor can be rotated in the forward and reverse directions with a relatively simple circuit without reversing the output phase of the photointerrupter.

As described above, the present invention switches and connects the common connection point of the coils of each phase to the positive and negative sides of the power supply in forward and reverse rotation, and connects the other end of each coil to the positive and negative sides of the power supply. Only one of the first and second switching drive circuits connected between the switching drive circuits is operated to apply a drive current in the forward or reverse direction to the coil, thereby causing the motor to rotate forward or reverse. Therefore, the configuration is such that only the polarity of the power supply supplied to the common connection point of the coils of each phase is reversed, without reversing the polarity of the power supply line to which the first and second switching drive circuits are connected. , the configuration of the forward rotation/reverse rotation switching means is simplified. Further, a diode bridge circuit (diodes D ₅ to D ₈ in FIG. 1) for fixing the polarity of the power supplied to the detection element for detecting the rotational position of the rotor in one direction is also unnecessary. Furthermore, since one of the first and second switching drive circuits is controlled to be inactive in response to forward and reverse rotation, a power diode (D ₁ in Figure 1) that bypasses these switching drive circuits is used. ~ _D4 ) becomes unnecessary.

[Brief explanation of the drawing]

FIG. 1 is a forward/reverse drive circuit diagram of a conventionally known brushless motor, FIG. 2 is a forward/reverse drive circuit diagram of a two-phase switching type brushless motor showing an embodiment of the present invention, and FIGS. 3 to 4 Each figure is a motor forward/reverse drive circuit diagram showing a modification of FIG. 2, and FIG. 5 is a motor forward/reverse drive circuit diagram showing an embodiment applied to a three-phase switching type brushless motor.
In addition, in the symbols used in the drawings, _S1 ...Selector switch, a...Positive power line, b...Minus power line, c...Control line, _L1 , _L2 ...Coil, Q1~ _{Q 4} ...transistor, Vs...power supply.

Claims (1)

[Claims] 1. A changeover switch means for switching and connecting the common connection point of the coils of each phase to the positive side and negative side of the power source, and between the other end of the coil of each phase and the positive side and negative side of the power source, respectively. first and second switching drive circuits that are connected to the rotor position detection signal and turn on and off according to the rotor position detection signal to flow drive currents in the forward and reverse directions to the coils, and a common connection point of the coils of each phase. Depending on the potential, the first
and a control means for disabling one of the second switching drive circuits, and the motor is rotated forward or reverse by switching the changeover switch means.