JPH02246790A - Motor driving device - Google Patents

Abstract

PURPOSE:To protect a drive transistor from breakdown and to reduce vibration and noise by modulating and suppressing drive current, through a triangular wave signal, with such timing as the drive transistor is turned ON or OFF when driving state is switched. CONSTITUTION:When a motor is started, switches(Sw) 7a, 7b, 7c are connected with a starting circuit 1 to turn drive TRs 4a, 4b, 4c sequentially ON so as to rotate a rotor. Then, a drive state switching circuit 3 is operated in some way, and drive current is modulated and suppressed by the output from a triangular wave oscillator 10 when the Sw 7a, 7b, 7c are switched to a position signal generating circuit 2. Since drive current is modified and suppressed by a drive current command 11 based on the waveform of a triangular wave output (a) when drive state is switched, currents, shown by (i), (j), (k), flow through stator windings 5a, 5b, 5c thus suppressing transient variation of voltage due to the inductance of stator winding, when the active phase is switched, and suppressing jumping of collector potential of the drive Tr.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a motor drive device that has drive state switching between startup and steady rotation.

(Prior Art) Conventionally, when driving a brushless motor without using a special position detection element such as a Hall element to obtain a rotational position signal for switching the energization phase of the stator winding, the It is often done to separate the drive state during steady rotation and the drive state during steady rotation (see JP-A-61-150694).

FIG. 3 shows a block diagram of a conventional example. In the figure, 1 is a starting circuit, 2 is a position signal generation circuit, 3 is a drive state switching circuit,
4a, 4b, 4c are drive transistors, 5a,
5b, 5c are stator windings, 6 is a drive current circuit, 7a, 7
b, 7c are switches, 8a.

8b and 8c are capacitors, and 9a, 9b, and 9c are resistors.

At startup, the switches 7a, 7b, 7c are connected to the startup circuit 1, and the startup circuit 1 connects the drive transistor 4.
a, 4b, and 4c are sequentially turned on, and the rotor t rotates. When the drive state switching circuit 3 operates in some way, the switches 7a and 7b are activated.

7c is switched to the position signal generating circuit 2, and the drive transistors 4a, 4b, 4c are turned on in sequence by the 1 position signal, and the rotor continues to rotate. Therefore.

When the drive state switching circuit 3 operates and the drive transistor that has been turned on by the startup circuit 1 turns off, a high voltage appears between the emitter and collector of the drive transistor due to a sudden change in current, damaging the drive transistor. There is a risk that

To suppress this spike voltage, capacitors 8a, 8b, 8e and resistors 9a, 9b are used as shown in FIG.

9c is connected to the stator winding, and when the drive transistor is turned from on to off, the capacitor absorbs the spike voltage generated by the stator winding. In addition,
The resistor is provided to prevent resonance caused by the inductance of the stator winding and the capacitance of the capacitor.

(Problem to be Solved by the Invention) According to such conventional methods, in order to prevent damage to the drive transistor, resistors and capacitors must be attached to each stator winding, which reduces the number of external parts. The disadvantage was that it increased. Moreover, when adopting the configuration shown in FIG. 3, a capacitor with an extremely large capacitance was often required.

Furthermore, since the phase of the stator winding is abruptly switched, there is a problem in that the drive current changes rapidly, causing vibrations and electromagnetic noise.

(Means for Solving the Problems) In order to solve the above problems, the present invention suppresses the drive current by using a triangular wave oscillator output at the timing when the drive state switching circuit operates and one energized phase is switched when switching the drive state. It is something.

(Function) According to the present invention, the triangular wave signal is used to modulate and suppress the drive current at the timing when the drive transistor turns on or off when switching the drive state, so the change in the current flowing through the stator winding becomes smooth. , spike voltages generated in the stator windings are suppressed.

This prevents damage to the drive transistor, and also reduces vibration and electromagnetic noise.

(Example) FIG. 1 is a block diagram showing an embodiment of the present invention.

In FIG. 1, IO is a triangular wave oscillator, 11 is a drive current command, 12 is a pulse signal generator, 13 is a logic circuit, and 14
a and 14b are outputs of the drive state switching circuit, and explanations of the same symbols as in FIG. 3 will be omitted.

At startup, the switches 7a, 7b, 7c are connected to the startup circuit 1, and the startup circuit 1 connects the drive transistor 4.
a, 4b, and 4c are sequentially turned on, and the rotor rotates. Then, the drive state switching circuit 3 works in some way, and the switches 7a, 7b, 7c switch to the position signal generation circuit 2.
When switching to , the drive current is modulated and suppressed by the output of the triangular wave oscillator 10.

FIG. 2 is a waveform diagram of essential parts of the embodiment shown in FIG. 1.

A case is shown in which the drive transistor 4a changes from on to off and the drive transistor 4b changes from off to on when switching the drive state. That is, FIG. 2(a) shows the output waveform of the triangular wave oscillator 10, and FIG. 2(b) shows the output waveform of the pulse signal generator 12. FIGS. 2(0) and 2(d) show the waveforms of the outputs 14a and 14b of the drive state switching circuit 3, respectively, and are synchronized with the output (b) of the pulse signal generator 12. Figure 2(d)
The H portion of the waveform represents the state in which the switches 7a, 7b, and 7c are connected to the starting circuit 1, and the L portion represents the state where the switches 7a, 7b, and 7c are connected to the starting circuit 1.

7b and 7c are connected to the position signal generation circuit 2. FIG. 2Ce) is the output of the logic circuit 13, which is obtained by logically processing the waveforms of (b) and (c). FIGS. 2(f), (g), and (h) are base input waveforms of drive transistors 4a, 4b, and 4c, respectively. Therefore, when switching the drive state, the drive current command 11 modulates and suppresses the drive current circuit 6 using the waveform of the triangular wave output (a) in the H portion of the waveform (8), so that the stator winding 5a , 5b, and 5c are shown in Figure 2 (iL (, iL
The current shown in (k) flows. That is, this suppresses a transient voltage change due to the inductance of the stator winding that occurs when switching the energization phase, and suppresses a jump in the collector potential of the drive transistor.

(Effect of the present invention) As described above, according to the present invention, it is possible to suppress the spike voltage caused by the inductance of the stator winding without attaching a capacitor or resistor to the stator winding. . Furthermore, the change in drive current becomes smooth when switching drive states.

Vibration and electromagnetic noise are also suppressed.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a motor drive device showing an embodiment of the present invention, FIG. 2 is a waveform diagram of main parts for explaining FIG. 1,
FIG. 3 is a block diagram showing a conventional example. 1... Starting circuit, 2... Position signal generation circuit. 3... Drive state switching circuit, 4a, 4b, 4c.
- Drive transistor, 5a, 5b, 5c... Stator winding, 6... Drive current circuit, 7a. 7b, 7cm switch, 8a, 8b, 8c・=
Capacitor, 9a, 9b, 9c...Resistor. 10... Triangular wave oscillator, 11... Drive current command,
12...Pulse signal generator, 13...Logic circuit. Patent Applicant Matsushita Electric Industrial Co., Ltd. Figure 2°°ゝPa''''"°Go?. 田10FK222. (°)"4077)5&'"9hi 13
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Claims (1)

[Claims] a starting circuit that sequentially energizes the stator windings, a position signal generation circuit, a drive state switching circuit that switches the drive state of the stator winding, a triangular wave oscillator that generates a triangular wave signal, and an output of the triangular wave oscillator. comprising a pulse signal generator that synchronously generates pulse signals, and a logic circuit whose inputs are the output of the pulse signal generator and the output of the drive state switching circuit,
When switching the drive state from the starting circuit to the position signal generation circuit by the output of the drive state switching circuit, the stator winding drive current is suppressed using the output of the triangular wave oscillator and the output of the logic circuit. Motor drive device.