JPH05292786A - Driving system for dc brushless motor - Google Patents

Abstract

PURPOSE:To obviate the necessity of conventionally required high power switching element and resistor for converting the output from a PWM circuit to high potential side by disposing a switching element on the low potential side of a DC power supply. CONSTITUTION:A PWM controller K generates a pulse output having width corresponding to the level of torque command signal. The pulse output drives a switching element S3 to turn the voltage of a DC power supply E ON/OFF and the voltage is smoothed through a coil L and a capacitor C to be applied on transistors Q1-Q6 connected complementally. On the other hand, a motor drive control circuit DR receives an output from a rotor position detector RT and produces an output for controlling the transistors Q1-Q6 through a photocoupler PC. Since the switching element S3 is disposed on the low potential side of the DC power supply E, conventionally required high power resistor and high speed switching element can be obviated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brushless DC motor drive system.

[0002]

2. Description of the Related Art A conventional drive system for a brushless DC motor is such that a voltage from a DC power source E is supplied to a resistor R as shown in FIG.
₁ and R ₂ is applied to the switching element S ₁ composed of transistors when the load resistance, controlled by the output of the pulse width modulation circuit (PWM controller) K of the switching element S ₁ is the torque command signal is supplied, the resistance R ₁ Switch element S consisting of a transistor controlled by the potential at the connection point of R and R _2.
2 is driven to supply the output of the switch element S ₂ to the smoothing circuit H including the coil L, the capacitor C and the flywheel diode D, and the output voltage of the smoothing circuit H is used as the power supply voltage.

On the other hand, transistors Q ₁ and Q ₂ connected in a complementary manner to apply a voltage to the U-phase stator coil of the brushless DC motor M, and transistors Q ₃ and Q connected in the same manner to apply a voltage to the V-phase stator coil. ₄ , applying the power supply voltage to the transistors Q ₅ and Q ₆ which are similarly connected and apply a voltage to the W-phase stator coil,
Transistors Q ₇ , Q ₈ controlled by the output of a motor drive control circuit DR, which is, for example, a μPC1246C (manufactured by NEC), which receives the output of the rotor position detector RT of the brushless DC motor M and controls the drive of the brushless DC motor M , Q ₉ outputs produce transistors Q ₁ , Q ₃ ,
Controls Q _5, was configured to control the transistor Q _2, Q _4, Q ₆ by the output of the motor drive control circuit DR.

[0004]

However, since the switch element S ₂ is on the high potential side of the DC power source E as described above, the switch element S ₁ for converting the output of the PWM controller K to the high potential side. There was a problem that required. In general, the switching element S ₁ is required to have a high-speed switching operation, and therefore, there are restrictions on the switch elements that can be used, and a large control current is passed for the high-speed operation, so that the resistance R ₁ and There is also a problem that the current flowing through R ₂ is large and the power loss is large.

It is an object of the present invention to provide a brushless DC motor drive system having a simple structure and improved switching efficiency.

[0006]

A brushless DC motor drive system according to the present invention includes a pulse width modulation circuit for receiving a torque designation signal and outputting a pulse having a pulse width corresponding to the torque designation signal level, and a low DC power supply. Connected to the potential side,
In addition, the switch element driven by the output of the pulse width modulation circuit, the smoothing circuit connected between the switch element and the high potential side of the DC power supply, and the voltage of the smoothing circuit are supplied as the power supply voltage. And a transistor for switching and controlling a stator coil that is driven based on the output of the received motor drive control circuit and to which a power supply voltage is applied.

Further, a photocoupler driven based on the output of the motor drive control circuit and driving a transistor for switching and controlling the voltage application to the stator coil may be provided.

[0008]

According to the brushless DC motor drive system of the present invention, upon receiving the torque command signal, the pulse width modulation circuit outputs a pulse output having a pulse width corresponding to the torque command signal level, and the pulse output drives the switch element. Then, the voltage of the DC power supply is turned on and off, smoothed by the smoothing circuit, the transistor is driven based on the output of the motor drive control circuit that receives the output of the rotor position detector, and the power supply voltage is applied. The brushless DC motor is rotationally controlled so as to generate a torque corresponding to the torque command signal level. Here, since the switch element is provided on the low potential side of the DC power supply, the switch element and the resistor which have been conventionally required for converting the output of the pulse width modulation circuit to the high potential side are unnecessary.

When a photocoupler is provided, the transistor is drive-controlled via the photocoupler.

[0010]

EXAMPLES The present invention will be described below with reference to examples. FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention.

In this embodiment, a flywheel diode D is used.
A smoothing circuit H constituted by a coil L and a capacitor C connected in parallel with a diode D is connected to the high potential side of the DC power source E, and a switching element S is provided between the low potential side of the DC power source E and the smoothing circuit H. ₃ connect consists receives torque command signal, for example MyuPC1094 (manufactured by NEC) PW
The output of the M controller K controls ON / OFF of the switch element S ₃ .

Using the output voltage of the smoothing circuit H, that is, the voltage applied to the capacitor C as the power supply voltage, the transistors Q ₁ and Q ₂ and the transistor Q _{3 are} connected in a complementary manner.
And Q _4, is applied to the transistors Q ₅ and Q _6, controls the transistor Q ₁ to Q ₆ by the photo-coupler PC which is driven by the output of the motor drive control circuit DR.

As shown in FIG. 2, the photocoupler PC is a photodiode PD ₁ driven by the output of the motor drive control circuit DR which receives the output of the rotor position detector RT.
And -PD _6, photodiode PD ₁ and the phototransistor PT ₁ ~PT ₆ for driving the transistor Q ₁ to Q ₆ receives light from -PD _6, the phototransistor from the voltage V _M applied to the brushless DC motor M Zener diode ZD ₁ for generating a power supply voltage applied to PD _{1 to} PD ₃ ,
The power supply circuit includes a Zener diode ZD ₂ for generating a power supply voltage applied to the phototransistors PD _{4 to} PD ₆ and a resistor R ₃ . The power supply circuit has a voltage V _M
When there is a large fluctuation, a constant current circuit may be used.

In the present embodiment constructed as described above,
In response to the torque command signal level, the PWM controller K generates a pulse output having a pulse width corresponding to the torque command signal level, and this pulse output drives the switch element S ₃ to turn on / off the voltage of the DC power supply E. , Q is smoothed by the coil L and the capacitor C, and the complementary connection of the transistors Q ₁ and Q ₂ , the transistor Q
It is applied as a power supply voltage to ₃ and Q ₄ , and transistors Q ₅ and Q ₆ .

On the other hand, by the output of the motor drive control circuit DR which receives the output of the rotor position detector RT, the transistors Q ₁ and Q ₂ , the transistors Q ₃ and Q ₄ , the transistors Q ₅ and Q ₆ are passed through the photocoupler PC. Is controlled so that the brushless DC motor M is rotationally controlled to generate a torque corresponding to the torque command signal level. This is similar to the conventional case.

In this case, since the switch element S ₃ is provided on the low potential side of the DC power source E, the high power resistors R ₁ and R ₂ required conventionally and the switch element S ₁ required to be turned on and off at high speed are provided. It becomes unnecessary.

Furthermore, the switch element S _{3 is connected} to the DC power source E.
The high potential side of the DC power source E is applied to one end of the stator of the brushless DC motor M through the transistor Q ₁ , Q ₃ or Q ₅ as in the present embodiment.
The low potential side of the DC power supply E controlled by the switch element S ₃ is applied to the other end of the stator of the brushless DC motor M.

However, since the rotor position detector RT and the motor drive control circuit DR are constructed on the basis of the low potential side of the DC power source E, the voltage on the other end side of the stator of the brushless DC motor, which fluctuates greatly, is greatly changed. the it is difficult to control directly by the output of the transistor Q _2, Q ₄ and Q ₆ a motor drive control circuit DR for switching. For example, as shown in FIG. 3, transistors Q _{10 to} Q ₁₅
Required to drive transistors Q ₂ , Q ₄ and Q ₆ .

However, by driving the transistors Q _{1 to} Q ₆ by the output of the motor drive control circuit DR via the photocoupler PC as shown in FIGS. 1 and 2, the transistors Q _{7 to} Q ₁₅ are unnecessary. , transistors for switching the supply voltage to the stator coil U, V and W are finished by the transistor Q ₁ to Q _6, never circuit configuration becomes complicated.

[0020]

As described above, according to the brushless DC motor drive system of the present invention, since the switch element is provided on the low potential side of the DC power supply, the output of the pulse width modulation circuit is converted to the high potential side. This has the effect of eliminating the need for high-power switch elements and resistors that have been conventionally required.

When the transistor for switching and controlling the stator coil to which the power supply voltage is applied is drive-controlled through the photocoupler, the number of transistors is small and the circuit configuration is simple. ..

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention.

FIG. 2 is a block diagram showing a photocoupler portion in one embodiment of the present invention.

FIG. 3 is a circuit diagram for explaining the operation of one embodiment of the present invention.

FIG. 4 is a block diagram showing a configuration of a conventional example.

[Explanation of symbols]

E DC power supply S ₃ switch element K PWM controller H smoothing circuit M brushless DC motor RT rotor position detector DR motor drive control circuit PC photo coupler U, V, W stator coil Q _{1 to} Q ₆ transistor

Claims (2)

[Claims] 1. A pulse width modulation circuit which receives a torque designation signal and outputs a pulse having a pulse width corresponding to a torque designation signal level, and a pulse width modulation circuit which is connected to a low potential side of a DC power supply and which outputs the pulse width modulation circuit. Motor drive control that receives the output of the rotor position detector, the switch element that is driven, the smoothing circuit that is connected between the switch element and the high potential side of the DC power supply, and the voltage of the smoothing circuit that is supplied as the power supply voltage. A brushless DC motor drive method comprising: a switch that controls switching of a stator coil that is driven based on the output of a circuit and to which a power supply voltage is applied. 2. The brushless DC motor drive system according to claim 1, further comprising a photocoupler driven based on the output of the motor drive control circuit and driving a switch for switching control of voltage application to the stator coil. A brushless DC motor drive method characterized in that