JPS5812593A - Holding current generating circuit for pulse motor - Google Patents

Abstract

PURPOSE:To eliminate the vibrating noise of a pulse motor by selecting one of two types of pulses exceeding audible frequency in response to the level of a current flowing through a circuit and applying it as a switching pulse, thereby maintaining the effective current value flowing through the circuit constant. CONSTITUTION:An oscillator 11 generates two types of pulses (a), (b) of duty ratio exceeding the audible frequency. The pulses (a), (b) are selected by a selector 12, and are outputted as a switching pulse (d). The current flowing through a circuit is smoothed and detected by an integration circuit 13, the output of the integration circuit 13 is applied to level detectors 14, 15, which compares the output with the set value. The selector 12 is controlled by the output signals of the detectors 14, 15 to select any of the pulses (a), (b). The duty ratio of the pulses (a), (b) is alternately selected by the selector 12 for the pulses (a), (b), thereby maintaining the effective current value flowing through the circuit constant.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a circuit for generating a Hall current supplied to a coil of a pulse motor when the rotor of a pulse motor is held in a stopped state. ) Unlike the hold current and the pulse current given when the pulse motor rotates, the hold current can be treated as a direct current with a constant value, so if the hold current is reduced by 1.1 using the same power supply as when supplying the pulse current, then Excessive current flows through the coil, causing it to burn out. Therefore, in the drive circuit of the pulse motor, there is a hold 1 in order to generate a predetermined holding torque within the current rated value of the pulse motor.
An E-flow light cow circuit is provided.

Conventionally employed hold current generating circuits include a switching circuit shown in FIG. 1, a circuit using a separate power supply shown in FIG. 2, and a circuit for dropping the power supply voltage shown in FIG. 3. Here, 1 is the coil of the pulse motor, 2.3
is a pnp type switching transistor, 4 and 5 are n
A pn type switching transistor, Vcc is a power supply voltage for driving a pulse motor which is connected to the circuit, and A and A are control signals. Here, A and 1 are mutually inverted control signals, and for example, A has a level of
When a control signal of about 100 volts is given to A, switching transistors 3 and 4 are turned on, switching transistors 2 and 5 are turned off, and the drive 1F current flows from right to left in coil 71zl. Become.

The switching type shown in FIG. 1 detects the current flowing through the coil/I/1 due to the voltage drop caused by the resistor 6, and compares this voltage drop with the set voltage Vo by a level detector 7. The switching transistor 2 or 3 is turned on and off by the AND signal of the output signal of the output signal and the control signal A or A, and when the bulge motor is temporarily stopped, a pulsating DC current I as shown in FIG. 1(b) is used as a hold current. It is designed to be supplied to coil 1. The switching frequency of transistors 2 and 3 at this time must be set to 2 to 3 kilohertz to prevent oscillation of the circuit. However, such a pulsating current I causes a pulse motor! When the motor core and rotor vibrate, it is impossible to avoid vibrations, but since the pulsating frequency is within the audible frequency range of 2 to 3 kilohertz, it is held in place by such a circuit. The circuit that uses the voltage drop across the resistor 8 shown in Figure 3 holds the pulse Tanabata with a completely smooth direct current, so it cannot be used as a switching device. Although it does not produce a harsh sound, the one shown in the second diagram requires a separate power supply voltage Vll for holding in addition to the power supply voltage Vcc used when rotating the pulse motor, and the one shown in the third diagram In the circuit, the power loss due to the resistor 8 is significant.

In addition, in these circuits, 1α changes in the current flowing through coil 1 due to variations in equipment or changes in resistance due to heat generation, etc., and there is a possibility that the hold current will be insufficient and it will not be possible to guarantee the stopped state of rotation r. Sometimes. In addition,
Reference numeral 9a in FIG. 1 is an AND circuit, 9b is an inverting and amplifying transistor, and 10 in FIGS. 2 and 3 is a switching transinutor for switching the circuit between a drive state and a bold state.

The present invention provides a hold current generating circuit that does not have the drawbacks described above (1), that is, it does not generate harsh vibration noise, does not require an expensive separate power supply, and does not require a wasteful 'r[ The purpose of this invention is to provide a hold current generating circuit that can maintain a constant holding torque without consuming power and without being affected by variations in equipment characteristics or heat generation.

FIG. 4 shows an embodiment of the halt current generation circuit according to the present invention, in which 1 to 6, 9a, and 9b are the devices described above, 11 is an oscillating 3g, 1ll) rectifier,
13 is an integration circuit consisting of a resistor R and a capacitor C, 14.15 is a level detector, Vcc and A, A are the aforementioned power supply voltage and control signal, v-1 and v2 are voltage setting values,
vl is given its upper value, and v2 is given its lower value. Incidentally, the signal states in portions a, b, c, and d of FIG. 4 are shown in FIG.

Hatsu 1 Tatsuki 11 is Hafi in the order of 2 gods with different duty ratios.
Pulses a and b are constantly output, and these pulses a and b have a frequency that exceeds the audible range, for example, a frequency of 20 volts and 1 volt. The selector 12 has the function of selecting one of these two pulses a and b and applying it to the AND circuit 9a. Level detectors g14 and 15 select which of the pulses a and b. is controlled by the output signal of On the wood flow side, level detection 14)1
When the output signal is emitted from the level detector 15, the selector 12 selects the pulse b, and when the output signal is emitted from the level detector 15, the selector 12 selects the pulse a and sends the pulse to the AND circuit 9a. configured to give.

The integrating circuit 13 handles the pulsating circuit current due to the on/off of the switching transistors 2 and 3, which is 20 in the above example.
It is constituted by an R C smoothing circuit having a time constant sufficient to smooth the kilohertz pulsation component, and therefore, by the operation of the selector 12, the AND circuit Q a K
When the pulse to be learned is converted from pulse a to pulse b, the Lll force voltage C of the integrating circuit 13 drops smoothly due to the decrease in the duty ratio. - When converted from to a, the output voltage C of the integrating circuit 13 rises smoothly. Pulse a must have a duty ratio sufficient to cause the circuit to generate a current with a value such that the average voltage drop across resistor 6 is greater than the set voltage V+; It must have a duty ratio that causes the circuit to generate a current of such value that the voltage drop is less than the set voltage v2. If necessary, provide an appropriate regulator in the oscillator 11 so that the duty ratio of pulses a and b can be adjusted.Compare the output voltage of the level detection Rg14.15u-integrator circuit 13 with the set voltages v1 and v2. When they match, an output signal is given to the selector 12'.

]-4 In the circuit configured as described above, it is assumed that the selector 12 is now selecting pulse a. At this time, the output voltage of the integrating circuit 13 increases smoothly by ]2, and soon its voltage value reaches vl, at that time the level detector 14 issues an output signal, and the selector 12
vs a K < /lz Z b is applied to the AND circuit 9a. Then, the value of the current flowing through the circuit decreases by the difference in the unity ratio between pulse a and pulse b, and the output voltage t1 of the integrating circuit 13 decreases smoothly. When this voltage 1)11 reaches a set value v2, the level detector 15 issues an output signal, and the selector 12 selects pulse a instead of pulse b, increasing the value of the current flowing through the circuit. The increase in this current value is the output of the integrating circuit 13 "1".
By raising the F pressure again smoothly and periodically repeating the operations described in -, the current value flowing through the circuit is controlled to a constant value. In this case, the pulsating frequency of the current flowing through the circuit is below the audible range, so there is no risk of noise even if the motor core or rotor vibrates, and the current flowing through the circuit is set to 0fiV+, V2. Since the current value is controlled, the current Yf+ flowing through the circuit does not change due to device variations or heat generation. Furthermore, since the current value is controlled by switching, there is no need for a separate power supply and there is no need for wasted power consumption. In addition, if there is a possibility that the level detectors 14 and 15 may oscillate, these detectors 14 and 15
This oscillation can be avoided by using a material having hysteresis characteristics.

As is clear from the description of the embodiments above, the hold current generation circuit for a pulse motor of the present invention is a field current generation circuit that turns the circuit on and off using switching pulses to generate a hold current of a desired value. An oscillator 11 that generates two types of pulses a and b with a duty ratio exceeding the frequency, and a - of these two types of pulses a and b.
A selector 12 selects y and d as switching pulses y and d.
, an integrating circuit 13 for smoothing and detecting the current flowing through the circuit, and a level detector 14.15 for comparing the output of the integrating circuit 13 with a set value. 15 of 141 The selector 12 is controlled by the power signal to select either of the two types of pulses a and b, and the selector 12 alternately selects the two types of pulses a and b. By doing this, the duty ratio of the two types of pulses a and b is determined so that the effective value -1;, Mt Ill'4 flowing through the circuit is maintained constant. The pulse motor does not generate harsh (5V) noise, does not require an expensive separate power supply, does not consume unnecessary power, and is free from variations in device characteristics and heat generation. It is possible to obtain a hold current generation circuit that can maintain a constant holding torque of a snipulse motor.

[Brief explanation of the drawing]

1 to 3 are diagrams illustrating a conventional hold current generation circuit for a pulse motor, FIG. 4 is a diagram illustrating an embodiment of the hold current generation circuit of the present invention, and FIG. FIG. 3 is a diagram showing the state of signals in each part of the circuit over time. In the figure, 1 is the coil of the pulse motor, 2, 3, 4, 5 are switching transistors, 6 is a resistor for detecting electric current Mt,
9a is an AND circuit, 9b is an inverting amplifier rjJIll transistor, 11 is an oscillator, 12 is a selector 1, 13 is an integrating circuit, 14.15 is a level detector, Vcc is an IF voltage, A, A are control signals, VI ld I-force setting fi'f, V2 is the downward setting. Agent Patent Attorney Fuki Nishi Figure 1 Figure 4 Figure 5 V2

Claims (1)

[Claims] (1) A hold current generation circuit for a pulse motor that turns the circuit on and off using switching pulses to generate a hold current of a desired value, and includes an oscillator that generates two types of pulses with different duty ratios exceeding an audible frequency; It has a selector that selects - of the type of pulse as a switching pulse, an integrating circuit that detects the current flowing through the circuit by smoothing it, and a level detector that compares the output of this integrating circuit with a set value. The output signal of this level detector controls the Ail selector to select one of the 2gff class pulses, and this selector alternately selects the two types of pulses to control the effective voltage flowing through the circuit. A hold current generation circuit for a pulse motor, characterized in that a duty ratio of each of the two types of pulses is determined so that the current is maintained constant.