JP4228057B2 - DC brushless motor drive circuit with snubber circuit - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a drive circuit for a DC brushless motor, and particularly has a regenerative circuit in a configuration of two-phase half-wave drive, and is configured to absorb regenerative energy by a kickback voltage absorbing power amplifier.
[0002]
[Prior art]
FIG. 3 shows an example of a driving circuit including a regenerative circuit of a DC brushless motor that is conventionally driven by a two-phase half-wave drive. In the illustrated circuit, the output of the magnetic detector 20 is converted into a two-phase half-wave energization signal by the driving IC 21, and the two energization power amplifiers 3 are alternately turned on and off by the two-phase half-wave energization signal 21. The current is supplied to the winding 1 by repeating the above, and the rotor is rotated in a predetermined direction by repeating the interruption. In FIG. 3, only one set of the winding 1 and the energizing power amplifier 3 is shown to avoid complication.
When the energizing power amplifier 3 is turned off, since the winding 1 is an inductive load, a steep voltage called a kickback voltage is generated at the collector of the energizing power amplifier 3. Since this voltage may exceed the rated voltage of the energizing power amplifier 3 and be damaged, it is necessary to add a regenerative circuit called a snubber circuit that suppresses and absorbs this voltage.
In a small motor, as shown in FIG. 3, it is a general configuration that a Zener diode 2 is inserted as a regenerative circuit between the collector and emitter of the energizing power amplifier 3. In this method, the kickback voltage is kept below the sum of the Zener voltages of the Zener diode 2, so that the energizing power amplifier 3 is prevented from being damaged.
At that time, the Zener diode 2 generates heat because it absorbs the energy of the kickback voltage.
[0003]
[Patent Literature]
A similar example is disclosed in Japanese Patent Laid-Open No. 05-292725.
[0004]
[Problems to be solved by the invention]
However, in recent years, there has been a strong demand for a small and large-capacity output for the motor drive circuit, and a large capacity of the control elements constituting the power amplifier and the regenerative circuit for energization is required. Largely restricted.
In the prior art, the number of Zener diode elements corresponds to the energy of the kickback voltage and is usually proportional to the power of the motor, and thus increases.
However, in a small motor, the component mounting area is limited, and the Zener diode has a great influence on the mounting area. Therefore, it is difficult to increase the number of Zener diodes more than the current state.
Accordingly, it is an object of the present invention to obtain a DC brushless motor drive circuit including a snubber circuit including an inexpensive regenerative circuit capable of realizing a small and large capacity output while suppressing an increase in mounting area.
[0005]
[Means for Solving the Problems]
A regenerative circuit according to the present invention is controlled by a circuit for detecting a kickback voltage between the collector and emitter of a power amplifier for energization, a comparison circuit for comparing the output of the detection circuit with a reference voltage, and an output of the comparison circuit. A power amplifier for regeneration, and a current of the power amplifier for regeneration is passed in proportion to the kickback voltage to suppress the kickback voltage to be equal to the voltage of the detection circuit.
[0006]
In the present invention, a regenerative power amplifier having a capacity corresponding to a current that has absorbed the energy of the kickback voltage with a plurality of Zener diodes is used, and the kickback voltage is detected with one Zener diode. Compared with a comparison circuit, and controls the regenerative power amplifier by the output of the comparison circuit to try to absorb the energy of the kickback voltage. The mounting area is reduced and the structure is inexpensive.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
[0008]
FIG. 1 shows a block diagram of a snubber circuit according to the present invention. The detection unit 4 and the control unit 7 are arranged at both ends of the energization power amplifier 3 that controls supply / cut-off of the energization of the winding 1, and the output of the detection unit 4 and the output of the reference unit 6 are compared by the comparison unit 5. The control unit 7 is controlled by the output of the comparison unit 5. When the energizing power amplifier 3 is turned off, the kickback voltage generated at the collector thereof is detected by the detection unit 4, and the detection voltage is compared with the voltage preset by the reference unit 6 by the comparison unit 5. And the output of the comparison unit 5 is sent to the control unit 7 as an input. The control unit 7 controls the output according to the input, and feeds back the output as the input of the detection unit 4.
Therefore, with the above configuration, it is possible to have a function of holding the kickback voltage at a certain value corresponding to the voltage preset by the reference unit 6, so that the regenerative circuit is realized.
[0009]
An example of a specific circuit is shown in FIG. In the figure, 1 is a winding, 3 is a power amplifier for energization, 8, 9 and 10 are resistors, 11 is a Zener diode, and 12 is a regenerative transistor.
A series circuit of a resistor 8 and a Zener diode 11 and a series circuit of a transistor 12 and a resistor 10 are connected between a collector and an emitter of the energizing power amplifier 3, respectively, and a series circuit of the resistor 8 and the Zener diode 11 is connected. The connection point is connected to the base of the regenerative transistor 12 via the resistor 9.
[0010]
In the circuit shown in FIG. 2, a kickback voltage is generated at the collector terminal of the energizing power amplifier 3, and when the kickback voltage exceeds the operating voltage of the Zener diode 11, a current flows through the Zener diode 11 via the resistor 8. At this time, the terminal of the Zener diode 11 is held at a constant voltage. When the voltage is input to the base of the regenerative transistor 12 via the resistor 9, the regenerative transistor 12 is energized and a collector current flows. At this time, a voltage is generated between the collector and emitter of the regenerative transistor 12 and across the resistor 10. This voltage is fed back to the Zener diode 11 through the resistor 8 again, so that the kickback voltage is held at a value corresponding to the voltage of the Zener diode 11.
Further, the energy of the kickback voltage is consumed by the regeneration transistor 12 and the resistor 10. From the above, this circuit configuration functions as a snubber circuit.
[0011]
In the illustrated circuit configuration, only one Zener diode 11 may be provided. Even if the regenerative transistor 12 is provided, the mounting area in the configuration of the present invention is smaller than that of the conventional configuration including a plurality of Zener diodes, and there is a margin. Therefore, since it is possible to provide a power amplifier for energization control with a larger capacity, it is possible to cope with a motor with a higher output.
[0012]
【The invention's effect】
Since the drive circuit of the DC brushless motor provided with the snubber circuit according to the present invention has the above-described configuration, the mounting area of the control element is smaller than that of the conventional configuration, and there is a margin for the allowable mounting area. The output can be realized at low cost.
[Brief description of the drawings]
FIG. 1 is a block diagram of a snubber circuit provided in a drive circuit for a DC brushless motor according to the present invention.
FIG. 2 is an actual circuit diagram of a snubber circuit provided in a drive circuit of a DC brushless motor according to the present invention.
FIG. 3 is an example of a driving circuit including a snubber circuit that is conventionally implemented to implement the present invention;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Winding 2 Zener diode 3 Energizing power amplifier 4 Detection part 5 Comparison part 6 Reference part 7 Control part 8, 9, 10 Resistance 11 Zener diode 12 Regenerative transistor 20 Magnetic detector 21 Driving IC

Claims (1)

A stator including a two-phase stator winding, a rotor including a permanent magnet having N and S magnetic poles which are rotatably supported by the stator via a gap, and detects the magnetic pole position of the rotor , A driving IC that converts the output signal of the magnetic detector into a two-phase half-wave energizing signal, and energizing power that amplifies the output of the driving IC and energizes the two-phase stator winding A drive circuit for a DC brushless motor having an amplifier and a regenerative circuit that absorbs a kickback voltage generated at the end of energization by the energization power amplifier, and rotating the rotor in a predetermined direction;
A series circuit of a resistor and a Zener diode and a series circuit of a kickback voltage absorbing power amplifier and a resistor are connected between a collector and an emitter of the energizing power amplifier, respectively, and a connection point of the series circuit of the resistor and the Zener diode; A drive circuit for a DC brushless motor comprising a snubber circuit, comprising: a regeneration circuit formed by connecting a base of a power amplifier for the regeneration circuit via a resistor.

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