JPS6240077A - Control circuit for speed of motor - Google Patents

Abstract

PURPOSE:To prevent an overshoot by mounting a starting circuit charging a capacitor for holding a sample for a sample holding circuit for a fixed time immediately after the power switch is turned ON. CONSTITUTION:A sample-reset pulse generating circuit 2 generates sample pulses and reset pulses in response to trapezoidal waves from a trapezoidal wave circuit 1. When a power supply is closed, trapezoidal waves from a trapezoidal wave circuit 11 are interrupted by the ON of a transistor Q43 until the voltage of a capacitor CRS reaches reference voltage. The charging voltage of a capacitor CT for a sawtooth wave generating circuit 3 is elevated, the transistor Q43 is turned OFF, and trapezoidal waves are inputted to a sample- reset pulse generator 2a from the trapezoidal wave circuit 11. Accordingly, a motor M is started smoothly without an overshoot from the number of revolution already set.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a motor speed control circuit that performs feedback control based on a signal from a detection element that detects the rotational speed of a DC motor.

[Background Art J As shown in Figure 2, the rotation speed of the motor is detected and a sawtooth wave is generated using a timing pulse, and the sawtooth wave voltage is sampled and held using the timing pulse, and the sampled and held voltage is compared with a reference. In the case of speed control in which the motor is feedback-controlled by comparing the voltage with the triangular wave voltage, immediately after the voltage is turned on, the capacitors for generating the sawtooth wave are not charged. Therefore, even if a hold pulse, which is a timing pulse, is generated and the sawtooth wave voltage is sampled and held, the voltage will not be proportional to the motor rotation speed, and the pulse will not be output from the output circuit that controls the switching circuit that drives the motor. Since this is not generated, the motor will not start.

As a countermeasure for this problem, a method conventionally used as a motor starting circuit is to forcibly charge zero sample and hold capacitors using an external power source for a certain period of time after the power is turned on.

However, in this case, there is a problem in that the charging time varies due to variations in components. If the charging time is short, the sample and hold capacitor 0 will not rise to the required voltage and will not start. Furthermore, if the charging time is too long, the motor cannot be controlled and when started, it does not start rotating smoothly from a low rotation speed, and the waiting rotation speed for startup overshoots and the motor rotates at a high speed.

[Object of the Invention] The present invention has been provided in view of the above-mentioned points, and it is an object of the present invention to provide a speed control circuit for a motor that can smoothly start and control the speed from a low rotation speed. .

[Disclosure 1 of the Invention An embodiment of the present invention will be described below with reference to the drawings. FIG. 2 shows a block diagram of the speed control circuit, and FIG. 3 shows its time chart.

A speed detection circuit 1 that outputs a signal proportional to the rotational speed of the motor includes a frequency generator FG, an operational amplifier OP, resistors R, , R, and the like.

The sample/reset pulse generation circuit 2, which is a timing pulse generation circuit that generates timing pulses such as sample pulses and reset pulses, is composed of a trapezoidal wave circuit 11 that generates a trapezoidal wave, a hysteresis pulse generator 2&, etc. A trapezoidal wave circuit 11 that inputs a trapezoidal wave to the generator 2a includes a constant current source 1, a capacitor CR, and the like. A sawtooth wave generation circuit 3 that generates a sawtooth wave by the reset pulse of the sample/reset pulse generator 2a includes a constant current source I2 and a capacitor CT.
A sample/reset pulse generator 2a
The sample and hold circuit 4 that samples and holds the sawtooth wave voltage using the sample pulse of is a buffer 4 a y
It is composed of 4 b s Fundensa CH, etc.

The speed variable circuit 7 that sets an appropriate speed is composed of a resistor Rx, a volume VR, a buffer T7a, etc., and its output is input to an error amplifier 12 and compared with the output from the sample and hold circuit 4, and the difference is inverted and amplified. Ru. moreover,
The output of the error amplifier 12 is compared with the reference triangular wave from the reference triangular wave generating circuit 5 by a comparator 13, and when the output of the comparator 13 is at H level, the output circuit 8 is driven. Then, the output of the output circuit 8 turns on the power MO9FET 14 that constitutes the switching circuit to drive the motor M.The power source is the battery B, and the voltage is boosted by the external pressure circuit 10 and supplied to the motor M. has been done.

The F-V conversion circuit that performs F-V conversion on the speed signal of the motor M is formed by the sawtooth wave generation circuit 3 and the sample hold circuit 4.

The operation will be explained to the dog using Figure $2 and Figure @3. Note that (a) to (j) in Figure 3 show the waveforms at points a to j in Figure 2. A speed signal proportional to the rotation speed of the motor M is outputted by a frequency generator FG, and the outputted speed signal is amplified by Rp/Rs times by an operational amplifier ○P1. The output of the operational amplifier OP as shown in FIG. 3(a) is input to the hysteresis comparator ○P2, and the third
As shown in Figure (b), a square wave pulse with a frequency proportional to the rotation speed is obtained. This square wave causes the trapezoidal wave circuit 11 of the sample/reset pulse generation circuit 2 to generate a trapezoidal wave as shown in FIG. 3(c). The rise of this trapezoidal wave is compared with the reference voltage Vl+V2tV from the reference voltage generation circuit 6, and the sample pulse (tjSa diagram (beak,
)) and the timing at which the reset pulse (FIG. 3(d)) is generated is determined. On the other hand, in the sawtooth wave generation circuit 3, the capacitor CT is charged by the constant current source I2, and as shown in FIG.
), when a reset pulse occurs, the 6-sample hold circuit 4 discharges the charge stored in the capacitor 0 and generates a sawtooth wave as shown in the figure. Hold capacitor CH
By charging or discharging, the sawtooth wave voltage at that time is sampled and held. Therefore, a DC signal proportional to the rotational speed as shown in FIG. 3(g) is outputted to the sample hold circuit 4.

In the error amplifier 12, the difference between the voltage set by the speed variable circuit 7 and the output voltage Vo of the sample hold circuit 4 is set as R.
^/ The output is inverted and amplified by RN times, and the output is compared with the reference triangular wave of the reference triangular wave generation circuit 5 by the comparator 13 as shown in Fig. 3 (h), and a square wave is generated as shown in Fig. 3 <i>. It has gained. This square wave is outputted through the output circuit 8 to obtain a date voltage as shown in FIG. 2(j), and the power supply to the DC motor M is controlled by PWM using the power MO3F''ET14. The lock protection circuit 9 has the following function: When an overload is applied to the motor M, the rotation speed of the motor M decreases.

Therefore, the output frequency of the frequency generator FG becomes smaller and the output voltage of the sample and hold circuit 4 becomes higher.

This voltage is detected by a voltage divided by resistors R, I and RL2 and a comparator 15, and when the rotation speed falls below a set value, the output pulse is cut off and the motor M is stopped.

Next, the operation immediately after the power switch is turned on, that is, immediately after the power is turned on, will be described. When the power is turned on, the capacitor CR of the sample/reset pulse generation circuit 2 begins to be charged. A sample pulse is generated at the rising edge. However, at this time, since the capacitor CT of the sawtooth wave generating circuit 3 is also being charged, the sample and hold voltage is also low. Therefore, the voltage inverted and amplified by the error amplifier 12 is large and has a higher level than the reference triangular wave, and the date signal of the power MO3FET 14 is not output, so the motor M will not start.

Therefore, as a specific embodiment of the present invention, as shown in FIG. 1, the output of the comparator 13, that is, the transistor Q
43 is connected to the trapezoidal wave output terminal of the sample/reset pulse generation circuit 2. Furthermore, Figure 1,
FIGS. 4 and 5 are specific circuit diagrams in which each circuit is constructed using an IC. When the power is turned on, the voltage of the capacitor cRg is applied to the resistor R14fR15 through the resistor R1j.
Transistor Q until the voltage is divided by 1R16
43 turns on, the trapezoidal wave from the trapezoidal wave circuit 11 is blocked. Therefore, since the trapezoidal wave is not input to the sample/reset pulse generator 2t, no sample pulse is generated from the sample/reset pulse generator 2a, and the capacitor CT of the sawtooth wave generation circuit 3
is charged and the charging voltage is 4+ people.
By turning off the transistor Q43, a trapezoidal wave is input from the trapezoidal wave circuit 11 to the sample/reset pulse generator 2a. Therefore, a sample pulse is also output from the sample/reset pulse generator 2a, and the increased sawtooth wave voltage is sampled and held in the sample and hold circuit 4. Therefore, when this sampled and held voltage is inverted and amplified by the error amplifier 12, it becomes lower than the reference triangular wave voltage, the output of the comparator 13 becomes H level, the date signal of the FET 14 is output, and the motor M is started. With this configuration, when the power switch is turned on, the motor M starts smoothly without overshooting the set rotation speed.

By the way, in order to quickly discharge the charge of the capacitor CR5 for setting the startup time if the power switch is turned on and off quickly (repeatedly), the emitter of the PNP transistor Qzs is connected to the capacitor CR5, and the transistor Q211
The collectors of each are connected to ground, and the bases are connected to the power line.

Therefore, capacitor CR5 is connected to transistor Q2 so that the terminal voltage of terminal R8 changes by (Vcc Vsa).
, and quickly responds to power changes.

Therefore, even if the power switch chattering or the power switch is repeatedly turned on and off quickly, the motor M can be started smoothly from the set rotation speed.

Next, a second example will be described. In Figure 4,
When the power is turned on, the value of the inverting input of the comparator 17 becomes lower than the value of the non-inverting input due to the charging darkness of the capacitor CT, and the output of the comparator 17 becomes H level. Next, when setting the R87 lip 70 knob 18 manually, the power supply voltage S immediately after the power is turned on is due to a delay in the power supply voltage Vcc. . The voltage divided by the resistors R, , R, becomes lower than the threshold value of 7 rips and 70 lobes 18. On the other hand, as for the reset signal, since the output of the comparator 17 is at the H level, the output Q of the 7-lip 70-tube 18 is at the L level. Therefore, the transistor Q17 is turned on, and by turning on the transistor Q17, a constant current is drawn in to charge the capacitor C of the trapezoidal wave circuit 11, so a trapezoidal wave is not generated and the sample Φ is sampled from the reset pulse generator 2a. No pulse is generated. Next, when the power supply voltage becomes stable, the human power S for setting the 7-lip 70-tube 18 becomes higher than the threshold φ value and becomes H level. *The capacitor 0 of the sawtooth wave generating circuit 3 has been charged, and the resistors R,,R,
When the voltage becomes higher than the voltage obtained by dividing the power supply voltage, the output of the comparator 17 becomes L level. Therefore, 7 ritsu 1
The 70 tube 18 output becomes H level, and the transistor Q
When +t is turned off, a trapezoidal wave is generated and input to the sample/reset pulse generator 2a, and the sample/reset pulse generator 2a generates a sample pulse. Therefore, by sampling and holding the sufficiently high voltage of capacitor CT in capacitor CH,
A date signal for starting motor M is output. Motor M
rotates, 0 capacitors are discharged, and the reset human power R of 7 lip 70 knob 18 is H, and ζ1l-1-f? -1-
JJm-, L1→iC'N 11+--an-7r1J
Since there are s number of transistors, the output of the 7-lip 70-tube 18 remains at the H level, and the transistor Q+7 remains off. In this way, by configuring the comparator 17.7 lip 70 tube 18, transistor QIT, etc., when the power switch is turned on, the rotation speed can be started smoothly from the set rotation speed without overshooting.

FIG. 5 shows the third embodiment. First, when the power is turned on,
Capacitor CR5 is charged with a time constant determined by resistor RI3 and capacitor cRs. That voltage and resistance Rl 41
The voltage determined by R+srR+e is compared by the comparator 13 of the starting circuit 16, and when the terminal voltage of the terminal R8 is lower than the terminal voltage of the terminal SB, a sample pulse is generated by the output of the starting circuit 16. Therefore, the output voltage of the sample and hold circuit 4 becomes the same voltage as the sawtooth wave voltage, and when the capacitor 0 is charged, the output of the sample and hold circuit 4 becomes high, and the voltage inverted and amplified by the error amplifier 12 becomes the reference voltage. The signal becomes lower than the triangular wave, the output of the comparator 13 becomes H level, the date signal of the FET 14 is output, and the motor M is started. Further, if there is chattering or the like in the switch when the power is turned on, the power supply voltage will not be supplied to the motor M even if a starting pulse is generated, so the motor M will not start. Therefore, the open reset circuit 19 at startup
The comparator 20 compares the reference voltage in the circuit with the voltage obtained by dividing the power supply voltage Vcc by resistors R8 and R5,
If the power supply voltage falls below the set voltage due to titering or other causes, the start-up time setting capacitor CR5 is discharged via transistor Q27, and the required start-up time is set after the power supply voltage stabilizes at the set voltage. sample pulses are generated. Therefore, when the power switch is turned on, the motor M starts smoothly without overshooting the set rotation speed. Also,
Even if the switch chattering or the switch is repeatedly turned on and off quickly, the motor M starts smoothly from the set rotation speed.

[Effect of the Invention 1] As described above, the present invention includes a speed detection circuit that outputs a signal proportional to the rotation speed of the motor, a timing pulse generation circuit that generates a timing pulse based on the speed signal from the speed detection circuit, and a timing pulse. F-V converts the motor speed signal using the timing pulse of the generation circuit
A conversion circuit, a comparison circuit that compares the F-V converted signal from the F-V conversion circuit with a predetermined reference triangular wave, and a switching circuit that supplies driving power to the motor using the output of the comparison circuit, The F-V conversion circuit that converts the motor speed signal into F-V is combined with the sawtooth wave generation circuit that generates a sawtooth wave using the timing pulse of the timing pulse generation circuit, and the timing pulse of the timing pulse generation circuit. In a motor speed control circuit consisting of a sample and hold circuit and a sawtooth wave voltage at that time,
Since it is equipped with a startup circuit that charges the sample-hold capacitor of the sample-and-hold circuit for a certain period of time immediately after the power switch is turned on, the sample-and-hold capacitor of the sample-and-hold circuit is charged for a certain period of time immediately after the power switch is turned on. By charging the capacitor, the sawtooth wave voltage can be sampled and held at the charging voltage of the capacitor, and therefore the motor can be started smoothly without overshooting the set rotation speed.

[Brief explanation of drawings]

FIG. 1 shows l! of one embodiment of the present invention. Figure 2 is a block diagram of the speed control circuit of the same as above, Figure 3 is a time chart of the same as above, Figure 4 is a specific circuit diagram of the main part of the second embodiment of the same, and Figure 5 is a block diagram of the same as above. It is a specific circuit diagram of the main part of the @3 embodiment. 1 is a speed detection circuit, 2 is a sample/reset pulse generation circuit, 3 is a sawtooth wave generation circuit, 4 is a sample hold circuit, 5 is a reference triangular wave generation circuit, 6 is a reference voltage generation circuit,
8 is an output circuit, 6 is a starting circuit, and M is a motor.

Claims (6)

[Claims] (1) A speed detection circuit that outputs a signal proportional to the motor rotation speed, a timing pulse generation circuit that generates timing pulses based on the speed signal from the speed detection circuit, and a timing pulse generation circuit that uses the timing pulses of the timing pulse generation circuit to detect the motor. An F-V conversion circuit that converts the speed signal to F-V,
It is equipped with a comparison circuit that compares the F-V converted signal from the V conversion circuit with a predetermined reference triangular wave, and a switching circuit that supplies drive power to the motor using the output of the comparison circuit. A sawtooth wave generation circuit generates a sawtooth wave using the timing pulse of the timing pulse generation circuit, and the voltage of the sawtooth wave at that time is sampled using the timing pulse of the timing pulse generation circuit. A motor speed control circuit comprising a hold circuit and a motor speed control circuit, further comprising a startup circuit that charges a sample hold capacitor of the sample hold circuit for a certain period of time immediately after turning on a power switch. circuit. (2) Speed of the motor according to claim 1, characterized in that it is provided with a startup circuit that charges a sample and hold capacitor that delays the generation of sample pulses for a certain period of time immediately after the power switch is turned on. control circuit. (3) Set the time to delay the charging of the sample and hold capacitor using the CR timer, connect the emitter of a PNP transistor to the capacitor of the CR timer, connect the base to the power supply fin, and connect the ground to the collector, respectively.
3. The motor speed control circuit according to claim 2, wherein the capacitor discharges as the power supply voltage decreases, and the voltage of the capacitor decreases at the same speed as the power supply voltage decreases. (4) The motor according to claim 1, characterized in that the motor startup time is set by comparing the sawtooth wave voltage and the set voltage to delay the charging of the sample and hold capacitor. speed control circuit. (5) The motor speed control circuit according to claim 1, wherein the sample pulse is generated for a certain period of time immediately after the power switch is turned on. (6) The motor speed control circuit according to claim 5, wherein when the power supply voltage falls below a set value, the time during which sample pulses are generated is reset.