JPS6292790A - Drive circuit for motor - Google Patents

Abstract

PURPOSE:To absorb surge voltage generated on the changeover of phase positively by transmitting surge voltage over a coil for drive having another phase through a resistor inserted between one terminals for coils for drive having two phase. CONSTITUTION:A resistor 16 is inserted between terminals on the sides connected to power transistor terminals for coils 3, 4 for drive having two phase. Surge energy generated in the coil for drive having one phase, such as the coil 3 for drive is transmitted over the drive coil 4 side having the other phase through the resistor 16, Zener currents flowing by surge voltage are made to flow as the base currents of a power transistor 5 on the side where surge voltage is generated, and the collector potential of the power transistor 5 is brought near to Zener voltage.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a motor drive circuit for a DC brushless motor driven by two-phase drive coils.

[Prior Art] A motor drive circuit in a DC brushless motor driven by a rotating magnetic field formed by a conventional two-phase drive coil has a configuration as shown in FIG. 4, for example.

In the figure, (1) is the power supply, (2) is the GND, and D)
, (4) are motor drive coils, (5) and (6) are power transistors, (7), (8), <9),
(10) and (II) are diodes for backflow prevention, 12) are Zener diodes, (+3) and (+4>
is the gate signal. Note that the gate signals (13), (1
The timing chart for 4) is shown in Figure 2.

The conventional motor drive circuit is configured as described above, and when the gate signals (13) and (14) are supplied to the bases of power 1 to transistors (5) and (6) at the timing shown in FIG. Accordingly, the motor drive coil (3), (
4) A voltage is applied across the terminal.

Then, current alternately flows through the drive coils (3) and (4) to form a rotating magnetic field and rotate the DC brushless motor.

[Problems to be Solved by the Invention] In the conventional motor drive circuit as described above, the structure is such that the surge voltage generated by the inductance load at the time of phase switching does not rise above the Zener voltage. When the drive coils (3) and (4) of the other phase shift from ON to OFF state, the drive coils (3>, (4) of the other phase
) voltage drops to near GND (2). As a result, the Zener current of the other phase power transistors (5), (6)
) leaks from the base of the power transistors (5) and (6) to the collector side, and does not flow to the bases of the power transistors (5) and (6), which should be operating.As a result, the collector potential rises, and eventually the power transistors (5) and (6) There is a problem in that the breakdown voltage is exceeded, leading to destruction of the power transistors (5) and (6), or malfunction of the motor drive circuit.

As a circuit to absorb the above-mentioned surge voltage, for example, a method of installing a series circuit (snubber circuit) of a resistor and a capacitor in parallel with the drive coil has often been used, but since it is necessary to install it for each phase, the number of components is reduced. This includes problems such as increasing the number of files and taking up space.

This invention was made to solve the above-mentioned problems, so it is possible to reliably absorb the surge voltage that occurs when switching the phase of the motor's drive coil, and also to save space. The purpose is to obtain a motor drive circuit.

[Means for Solving the Problems] The motor drive circuit according to the present invention includes a resistor inserted between the terminals of the two-phase drive coil on the side connected to the power transistor terminal, and surge voltage is reduced through the resistor. is sent to the drive coil of the other phase.

[Function] In this invention, the surge energy generated in the drive coil of one phase is sent to the drive coil of the other phase via a resistor, and the Zener current flowing due to the surge voltage is transferred to the drive coil of the other phase. It is possible to ensure that the base current of the power transistor flows, and the collector potential of the power transistor can be made close to the Zener voltage.

[Embodiments of the invention] Hereinafter, one embodiment of the present invention will be described based on the drawings.

In Figure 1, (1) is the power supply, (2) is the GND, and (3)
, (4) are motor drive coils, (5) and (6) are power transistors, respectively, (7), (δ), (9),
(10), (II) are diodes for backflow prevention, (12) are Zener diodes, (+3), (14)
> is that data 1- signal. As mentioned above, the motor drive circuit in the DC brushless motor driven by the two-phase drive coils D) and (4) also converts the surge voltage into the Zener voltage using the Zener diode (12) shown in FIG. 4 as a conventional example. The two-phase drive coils (3) and (4) are of a configuration that does not allow the rise to rise above
The configuration is characterized in that a resistor (16>) is inserted between the terminals connected to the terminals of the power transistors (5) and (6).

That is, when the gate signals (+3) and (14) that drive the power transistors (5) and (6) are supplied to the bases of the power transistors (5) and (6) at the timing shown in FIG. motor drive coil D),
A voltage shown in FIG. 3 is applied to both ends of (4), and current alternately flows through the driving coils D) and <4), forming a rotating magnetic field that rotates the motor.

When the drive coils (3) and (4) switch from the ON state to the OFF state, a surge voltage is generated due to the inductance load. For example, when the drive coil (4) switches from ON to OFF, Diode (8)
, (9) , Zener diode (12), resistor (15
), GND through the diode (11), respectively.
(2>) At that time, the surge voltage flows as a Zener current, but due to the resistor (16) inserted between the drive coils (3) and (4), the potential of the drive coil (3) that does not generate surge voltage The potential increases due to the current flowing through the resistor (16), and the Zener current leaks, so it does not flow through the base and collector of the power transistor <5> on the side that is not generating the surge voltage.Therefore, the surge voltage becomes higher than the Zener voltage. If so, current flows to the base of the power transistor (6), and the power transistor (6)
) flows, the collector potential drops, and the base current stops flowing, turning off the power transistor (6).
state, and the collector potential rises again. Then, the base current flows again, the collector current of the power transistor (6) flows again, and the collector potential drops, and the collector potential is maintained at the Zener potential at the time of the surge voltage generation. As is clear, the motor drive circuit of the present invention converts the surge voltage generated during phase switching of the drive coils into the power that supplies current to the two-phase drive coils in a DC brushless motor driven by two-phase drive coils. The Zener diode connected to the base side of the transistor prevents the voltage from rising above the Zener voltage, and a resistor is inserted between the terminals of the drive coil connected to the terminals of the power transistor, and the surge voltage generated is transferred to the resistor. Since the surge voltage is sent to the driving coil of the other phase that is not generating the surge voltage through the circuit, it reliably absorbs the surge voltage that occurs when switching the phase of the driving coil, preventing damage to the power transistor or malfunction of the circuit. In addition to being able to prevent this as much as possible, the structure is simple and does not require space, so space saving can be realized.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a motor drive circuit showing an embodiment of the present invention, FIG. 2 is a timing chart of a gate signal, FIG. 3 is a timing chart showing a voltage waveform of a drive coil corresponding to a gate signal, and FIG. FIG. 4 is a circuit diagram showing a conventional Mori drive circuit. In the figure, 1) is a power supply, (3) and (4) are drive coils, (5) and (6) are power transistors, (12) is a Zener diode, and (
16) is resistance. Note that the same reference numerals in the figures indicate the same or equivalent parts. Agent Masuo Oiwa (and 2 others) Figure 1 Figure 2: Figure 1

Claims (1)

[Claims] In a DC brushless motor driven by a two-phase drive coil, the surge voltage that occurs when the drive coil changes phase is converted into Zener voltage by a Zener diode connected to the base side of the power transistor that supplies current to the two-phase drive coil. In this configuration, a resistor is inserted between the terminals of the driving coil connected to the terminals of the power transistor, and the generated surge voltage is passed through the resistor to drive the other phase that does not generate the surge voltage. A motor drive circuit characterized in that the power is sent to a coil for use.