JPH02151294A - Motor driving device - Google Patents

Abstract

PURPOSE:To guarantee the safety of a motor drive itself by coupling latch means with set and reset terminals utilizing the output of an oscillator as a reset signal to motor current limiting means, calculating a logic product of the output and the output of a comparator for determining the duty of a motor winding, and coupling it to a power amplifier. CONSTITUTION:A motor current is detected and amplified by a current detector 5. When the voltage arrives at a preset current limiting level VCL, the output of a current limiting comparator 6 is switched as b. In this case, a RS type flip-flop 10 is set by the output of the current limiting comparator 6, a power amplifier 1 is cut OFF as shown in Fig. 2c through an AND gate 8, and the motor current is reduced. Since the oscillation frequency of an oscillator 4 is set to approx. 10-100kHz to become much higher frequency than a time constant of the inductance component Lm and the resistance component Rm of the motor, the period of the operation of limiting the current the release thereof becomes the same as the oscillation frequency of the oscillator 4.

Description

[Detailed Description of the Invention] Field of Application of T Tojo The present invention is a motor drive device that uses a semiconductor integrated circuit to obtain high output and large current, and has a current limit that also guarantees the safety of the device. It is related to.

2. Description of the Related Art Conventionally, this type of current-limited motor drive device has had a configuration as shown in FIG.

In Fig. 3, 1 is a power amplifier, 2 is a comparator, 3 is an error amplifier, 4 is an oscillator, 5 is a current detector, 6 is a hysteresis comparator for current limiting, 7 is a torque command input terminal, and 8 is an AND circuit. , 9 is the motor winding, RC5 is the current detection resistor, R@IR (+Rcf is the gain setting resistor of the error amplifier 3, and Dl or D2 is the flywheel diode that circulates the motor current.Here, we will simply refer to the one-phase motor. This is assumed to be the case.

FIG. 4 shows the relationship between the torque command signal and the voltage of each part when the motor is rotating, and FIG. 5 shows the relationship between the motor current and the voltage of each part when the current is limited.

Dl or D2 is D when the power amplifier 11 is a current sink type.
1, and D2 when it is a current source type, which is an appropriate arrangement for the power amplifier 1.

Hereinafter, a case where a triangular wave oscillator is used as the oscillator 4 will be explained using FIGS. 4 and 5.

First, in order to rotate the motor, torque command input terminal 7
Then, a torque command signal is applied as shown in FIG. 4(a). Then, a motor current is generated as shown in FIG. 4(a), which is amplified by the current detector 5 to obtain an output voltage proportional to the motor current. The error between this voltage and the torque command signal is the shaded area in FIG. 4(a). This error is amplified by the error amplifier 3 to obtain an error voltage as shown in FIG. 4(b). This error voltage and the oscillator 4 shown in FIG.
Compare the amplitude voltage of the triangular wave oscillation with the comparator 2,
The comparator output shown in FIG. 4(d) is obtained.

This comparator output is power amplified by a power amplifier 1 and causes current to flow through the motor windings. The control is based on a so-called pulse width in which the motor windings are energized at the higher level "H" of the comparator output in Figure 4, and the motor windings are de-energized at the lower level "L". A modulation (hereinafter abbreviated as PWM) method is performed to control the motor current.

Here, when the motor current exceeds a certain current value IMCH as shown in FIG. The voltage becomes higher than the level VCt, and the hysteresis comparator 6 outputs a signal as shown in FIG. 5(b). With this signal, Fig. 5 (C)
The power amplifier 1 is cut off and the motor current is reduced as shown in FIG.

When the motor current falls below a certain current value IMCL, the hysteresis comparator 6 outputs a signal that causes the power amplifier 1 to operate again, thereby limiting the motor current so that the motor current begins to flow.

Problems to be Solved by the Invention In such a conventional configuration, the operation and release of the current limit depend on the inductance component of the motor winding.

It is uniquely determined by the resistance component R1 and the hysteresis width ΔvcL of the hysteresis comparator 6.

This is due to the inductance component of the motor windings.

A delay occurs in the motor current due to the resistance component R6, and as shown in FIG. 5(a), the hysteresis comparator 6 repeats energization and de-energization within the hysteresis width ΔVCt.

If the cycle of this repetition is tct, then tCL=1△Vct-Rm/Lm...
``(1) However, k obtains the relational expression of the proportional constant equation 1.

This repetitive frequency component becomes unnecessary radiation to the outside through the motor windings, and adversely affects the surroundings of the motor drive device.

The present invention solves these problems, and enables the remoter to be driven with high output and large current, which makes it possible to easily take measures against the above-mentioned unnecessary radiation, and also ensures the safety of the device itself. A motor drive device with current limitation is provided.

Means for Solving the Problem In order to solve this problem, the present invention provides a set and reset terminal material latching means that utilizes the output of an oscillator as a reset signal to limit the motor current to a preset level. The output is ANDed with the output of a comparator that determines the duty of the motor windings, and the result is coupled to a power amplifier.

Effect: With this configuration, when the motor current increases, the output of the current limiting means for limiting the motor current to a preset level is set by the 5 latch means, and even if the output of the power amplifier is cut off, the oscillator oscillates. Since the latch means is reset by the frequency, the release of the current limit is synchronized with the oscillation frequency of the oscillator.

Embodiment FIG. 1 is a circuit diagram of a motor drive device with current limitation according to an embodiment of the present invention. Here, a simple single-phase motor example is shown.

In FIG. 1, ■ is a power amplifier, 2 is a comparator, 3 is an error amplifier, 4 is an oscillator, 5 is a current detector, 6 is a current limit comparator, 7 is a torque command input terminal, 8 is an AND circuit, 9 is a motor winding, 10 is an R3 type flip-flop circuit as an example of a latch means for set and reset terminal materials, RC3 is a current detection resistor, Ran Rr+Rcr is a gain setting resistor of the error amplifier 3, vcL is a current limit level, vM is the motor voltage, and Dl or D2 is a flywheel diode that circulates the motor current.

FIG. 2 shows the relationship between the motor current and the voltage at each part when the current is limited.

Dl or D2 is arranged appropriately for the power amplifier 1, such as Dl when the power amplifier 1 is a current sink type, and D2 when the power amplifier 1 is a current source type. The operation of current limiting when a triangular wave oscillator is used as the oscillator 4 will be explained below with reference to FIG.

The process is the same as the conventional example until the torque command is input and the motor rotates, but when the torque command reaches the maximum and the motor is energized at full duty, the motor current will be the resistance component of the motor winding R, / the inductance of the motor winding. The current gradually increases due to the time constant of the component. This situation is shown in FIG. 2(a).

This motor current is detected by a current detector 5.

amplified. When the voltage reaches a preset current limit level vcL, the output of the current limit comparator 6 is switched as shown in FIG. 2(b).

The current value at this time is I 1icH in FIG. 2. At this time, R
The 8-type flip-flop circuit 10 is set, and the power amplifier 1 is cut off through the AND circuit 8 as shown in FIG. 2(C), and the motor current is reduced. At this time, the output of the current limiting comparator is switched to operate the output of the power amplifier 1 again as shown in FIG. 2(b), but the previous cutoff signal is latched by the R3 type flip-flop circuit 10. Therefore, the power amplifier 1 continues to remain in the cut-off state.

Next, when the R5 type flip-flop is reset at a certain timing during the recording of the triangular wave oscillation of the oscillator 4, the previous cut-off state is reset, so that the power amplifier 1 returns to the operating state. FIG. 2(d) shows the case where the reset is performed at the voltage with the highest triangular wave amplitude. Therefore, the power amplifier 1 of FIG. 2(c) is
) indicates that the device is in the operating state again at the voltage with the highest triangular wave amplitude.

The above operation occurs repeatedly, but usually the oscillator 4
The oscillation frequency of is set to about 10KHz to 100KHz, and the inductance component L of the motor and the resistance component RI1
Since the frequency is much higher than the time constant of 1, the period of operation and release of the current limit becomes the same as the oscillation frequency of the oscillator 4.

Effects of the Invention As described above, according to the present invention, the cycle of current limiting operation and release is the same as the oscillation frequency of the oscillator 4, and this frequency component can be set arbitrarily.

In addition, the reference frequency of PWM is set to a frequency that does not have an adverse effect on surrounding devices, etc., and measures are taken to prevent unnecessary radiation at that frequency, so additional measures against unnecessary radiation are required to limit the current. It will never be.

Furthermore, since the current limiting comparator does not need to have hysteresis, it can be realized with a simple circuit.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram of a motor drive device with current limitation according to an embodiment of the present invention, and Fig. 3 is a circuit diagram of a conventional current control device.
Power amplifier, 2... Comparator, 3... Error amplifier, 4... Oscillator, 5... Current detector, 6... Hiss comparator for current limit,
7... Torque command input terminal, 8... AND circuit, 9... Latch means with set and reset terminals. Name of agent: Patent attorney Shigetaka Awano and one other person

Claims (1)

[Claims] It has a comparator that amplifies the error between the torque command signal and the signal that detects the motor current, compares the error voltage with the voltage of the oscillator, and determines the energization duty of the motor windings, and sets the motor current in advance. The output of the current limiting means is connected to a set terminal of a latch means having set and reset terminals, and the reset terminal of the latch means is connected to the output of the oscillator. combining the outputs, connecting the AND of the output of the latching means and the output of the comparator to a power amplifier, controlling the motor current, and synchronizing the limitation of the current with the oscillation frequency of the oscillator; A motor drive device featuring: