JPH07170784A - Pulse width modulation driver - Google Patents

Abstract

PURPOSE:To prevent the heat generation of switching devices and a servo motor by performing PWM control with a highest possible frequency. CONSTITUTION:Heat generated in each switching device 1-4 of a FOR/REV motor control circuit is detected by a temperature sensor 11, and from a frequency converter circuit 17 in accordance with this detected temperature a reference clock signal of its frequency is generated. Receiving this reference clock signal, a pulse width modulated signal of a frequency according to the reference clock signal and having a constant duty ratio is supplied to each switching device 1-4 from a pulse generator circuit 18. Consequently, each switching device 1-4 is turned on or off, and current is supplied to a servo motor 5 to drive it.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a forward / reverse rotation motor control circuit for driving a servo motor or the like used in a robot. Each switching element of the forward / reverse rotation motor control circuit is turned on / off by a pulse width modulation signal. And a pulse width modulation driving device for driving a servo motor.

[0002]

2. Description of the Related Art FIG. 5 is a block diagram of a forward / reverse rotation motor control circuit applied to drive a servomotor of a robot or the like. MO
The switching elements 1, 2 and 3, 4 such as SFETs are respectively connected in series, and the circuits formed by these switching elements 1, 2, 3 and 4 are connected in parallel. In addition, recovery diodes d1 to d4 are formed in the switching elements 1 to 4, respectively. A servo motor 5 is connected to the connection points of the switching elements 1 and 2 and the connection points of 3 and 4. A power supply Vs is connected to each switching element 1 and 3, and each switching element 2 and 4 is connected to the ground.

With such a configuration, the pulse width modulation (PWM) signals cw and ccw shown in FIG. 6 generated by the pulse generating circuit are supplied to the switching elements 1 to 4, respectively.
When the PWM signals cw and ccw are supplied, the switching elements 1 to 4 are turned on during the high level period and turned off during the low level period. Therefore, the switching elements 1 and 4 are simultaneously turned on by the PWM signal cw, the current i1 flows through the servo motor 5, and the PWM signal c
The switching elements 2 and 3 are simultaneously turned on by cw, and a current i2 flows through the servo motor 5. However, the servo motor 5 is driven by the difference between the currents i1 and i2.

By the way, in the above circuit, each PWM signal c
When the frequencies of w and ccw become low, the OFF period of each switching element 1 to 4 becomes long, and as a result, each switching element 1 to 4 increases loss and generates heat.

On the other hand, when the frequency of each PWM signal cw, ccw becomes high, the loss of each switching element 1 to 4 can be reduced and heat generation can be suppressed, but on the other hand, the power consumption of the servo motor 5 increases, The servo motor 5 generates heat.

When increasing the frequencies of the PWM signals cw and ccw, there is a limit due to the recovery period of the recovery diodes d1 to d4. For example, when the switching elements 1 and 4 are turned off, the current i1 flows through the recovery diodes d1 and d4 to be recovered.
When the OFF period of each switching element 1, 4 becomes shorter than the recovery period of each recovery diode d1, d4, the current i1 is not recovered, and as a result, each switching element 1, 4 generates heat.

[0007]

As described above, each PWM is
When the frequencies of the signals cw and ccw decrease, the switching elements 1 to 4 generate heat, and when the frequencies of the PWM signals cw and ccw increase, the servo motor 5 generates heat.

Therefore, an object of the present invention is to provide a pulse width modulation driving device which can perform PWM control at a frequency as high as possible and can prevent heat generation of a switching element and a servomotor.

[0009]

According to a first aspect of the present invention, each pulse width modulation signal is supplied to each switching element of a forward / reverse rotation motor control circuit in which each switching element is bridge-connected and a servomotor is connected to an intermediate point thereof. In a pulse width modulation drive device for driving a servo motor by a temperature sensor, a temperature sensor that detects the heat generation amount of each switching element, a frequency conversion circuit that generates a reference clock signal of a frequency according to the detection result from the temperature sensor, A pulse width modulation driving device, which is provided with a pulse width modulation circuit that generates a pulse width modulation signal having a frequency corresponding to a reference clock signal from the frequency conversion circuit and a constant duty ratio, and a pulse width modulation driving device.

According to the second aspect of the present invention, the servo motor is driven by supplying each pulse width modulation signal to each switching element of the forward / reverse rotation motor control circuit in which each switching element is bridge-connected and the servo motor is connected to the intermediate point thereof. In a pulse width modulation drive device, a temperature sensor that detects the amount of heat generated by each switching element, a reference signal generation circuit that generates a reference signal, and the detection result of the temperature sensor and the reference signal from the reference signal generation circuit are compared. A comparison circuit, a frequency conversion circuit that generates a reference clock signal having a frequency according to the comparison result of this comparison circuit, and a pulse that has a constant duty ratio and a frequency according to the reference clock signal from this frequency conversion circuit. A pulse width modulation driving device, which includes a pulse width generation circuit for generating a width modulation signal, and which is intended to achieve the above object.

According to the third aspect of the present invention, the servo motor is driven by supplying each pulse width modulation signal to each switching element of the forward / reverse rotation motor control circuit in which each switching element is bridge-connected and the servo motor is connected to the intermediate point thereof. In a pulse width modulation drive device, a temperature sensor that detects the amount of heat generated by each switching element, a reference signal generation circuit that generates a reference signal, and the detection result of the temperature sensor and the reference signal from the reference signal generation circuit are compared. A comparison circuit, a reference oscillating circuit that oscillates a clock signal of a reference frequency, a reference clock signal from the reference oscillating circuit, and outputs a divided clock signal and outputs the reference clock signal as it is. A frequency conversion circuit that selects a frequency-divided clock signal or a reference clock signal based on the comparison result of the frequency division circuit and the frequency comparison circuit; And a pulse width generation circuit for generating a pulse width modulation signal having a frequency corresponding to a clock signal selected by the frequency conversion circuit and having a constant duty ratio. is there.

According to a fourth aspect of the present invention, the frequency conversion circuit lowers the frequency of the reference clock signal when the detection result of the temperature sensor decreases, and increases the frequency of the reference clock signal when the detection result increases. Is.

[0013]

According to the first aspect, the heat generation amount of each switching element in the forward / reverse rotation motor control circuit is detected by the temperature sensor, and the frequency conversion circuit generates the reference clock signal of that frequency in accordance with the detected temperature. Upon receiving this reference clock signal, the pulse generation circuit supplies a pulse width modulation signal having a frequency corresponding to the reference clock signal and a constant duty ratio to each switching element. As a result, each switching element is turned on / off to supply current to the servo motor, and the servo motor is driven.

According to the present invention, the detection result of the temperature sensor is compared with the reference signal from the reference signal generating circuit, and the reference clock signal having the frequency corresponding to the comparison result is generated.
Then, the pulse width modulation circuit generates a pulse width modulation signal having a frequency corresponding to the reference clock signal and a constant duty ratio.

According to the present invention, the detection result of the temperature sensor is compared with the reference signal from the reference signal generating circuit, and the reference clock signal is divided to output a divided clock signal and the reference clock signal is generated. Output as is. And
Based on the comparison result, the divided clock signal or the reference clock signal is selected, and a pulse width modulation signal having a frequency corresponding to the selected clock signal and a constant duty ratio is generated.

In this case, according to the fourth aspect, the frequency conversion circuit lowers the frequency of the reference clock signal when the detection result of the temperature sensor decreases, and changes the frequency of the reference clock signal when the detection result increases. It is rising.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to the drawings. The same parts as those in FIG. 5 are designated by the same reference numerals, and detailed description thereof will be omitted. FIG. 1 is a configuration diagram of a pulse width modulation drive circuit. The switching elements 1 to 4 are attached to the heat dissipation plate 10. The external appearance of the switching element 1 is shown in duplicate for the sake of clarity.

The heat radiating plate 10 includes a switching element 1
A temperature sensor 11 is provided to detect the amount of heat generated by. The temperature sensor 11 has a resistance value that changes according to the temperature, and is connected to the detection circuit 12. The detection circuit 12 has a function of converting the temperature signal v into a temperature signal v having a voltage level corresponding to a resistance change of the temperature sensor 11.

A detection circuit 12 and a reference voltage circuit 14 which is a reference signal generation circuit are connected to the comparator 13. The comparator 13 compares the temperature signal v with the reference voltage signal vo from the reference voltage circuit 14, and outputs the comparison result, v <vo or v> vo.

On the other hand, a reference oscillator circuit 1 including a crystal oscillator
5 is provided, and a reference clock signal of frequency f is output from the reference oscillation circuit 15. A frequency divider 16 having a frequency division ratio n is connected to the reference oscillation circuit 15. The frequency divider 16 receives the reference clock signal, outputs the reference clock signal as it is without dividing it, and obtains a divided output obtained by dividing the reference clock signal by a division ratio n. There is.

Further, the frequency conversion circuit 17 receives the comparison result of the comparator 13 which is a comparison circuit, and when v <vo, selects and outputs the reference clock signal of the frequency f among the divided outputs of the frequency divider 16. Also, it has a function of selectively outputting the divided output of the reference clock signal when v> vo.

The pulse generation circuit 18 is the frequency conversion circuit 1
It has a function of receiving the reference clock signal selected by 7 and outputting the PWM signals cw and ccw according to the frequency of the reference clock signal and having a constant duty ratio. Each of the switching elements 1 to 4 is connected to the pulse generating circuit 18, of which the PWM signal cw is supplied to each of the switching elements 1 and 4, and the PWM signal ccw is supplied to each of the switching elements 2 and 3. There is.

Next, the operation of the apparatus configured as described above will be described. The reference oscillating circuit 15 outputs a reference clock signal having a frequency f, and the frequency divider 16 outputs the reference clock signal and each frequency-divided signal divided by n.

On the other hand, the temperature sensor 11 shows a resistance value according to the temperature of the heat sink 10, and the detection circuit 12 converts the resistance value of the temperature sensor 11 into a temperature signal v of a voltage level and outputs it.

The comparator 13 compares the temperature signal v with the reference voltage signal vo from the reference voltage circuit 14,
As a result of this comparison, v <vo or v> vo is sent to the frequency conversion circuit 17.

The frequency conversion circuit 17 receives the comparison result of the comparator 13 and outputs the temperature signal v as the reference voltage signal vo.
If the voltage level is lower than (v <vo), the frequency divider 16
The reference clock signal of frequency f is selected from the divided output of and is sent to the pulse generation circuit 18.

When the pulse generating circuit 18 receives the reference clock signal of the frequency f, it outputs the PWM signals cw and ccw shown in FIGS. 2A and 2B based on the reference clock signal. Thus, of these PWM signals cw, ccw, the PWM signal cw is supplied to the switching elements 1 and 4, and the PWM signal ccw is supplied to the switching elements 2 and 3. When the PWM signals cw and ccw are supplied, the switching elements 1 to 4 are turned on during the high level period and turned off during the low level period. Therefore,
The switching elements 1 and 4 are simultaneously turned on by the PWM signal cw, and a current i1 flows through the servo motor 5 to cause PW.
The switching elements 2 and 3 are simultaneously turned on by the M signal ccw, and a current i2 flows through the servo motor 5. However, due to the difference between these currents i1 and i2, the servomotor 5
Drive.

When the switching elements 1 to 4 generate heat, the temperature of the heat sink 10 rises, and the temperature signal v becomes higher than the voltage level of the reference voltage signal vo, the comparator 13 outputs the comparison result v> vo as a frequency. It is sent to the conversion circuit 17.

In this case, the frequency conversion circuit 17 includes the frequency divider 1
Among the outputs of 6, the reference clock signal is divided by the division ratio n, and the divided output, for example, the divided output by 2 is selected and sent to the pulse generation circuit 18.

Upon receiving the divided reference clock signal, the pulse generation circuit 18 outputs the PWM signals cw and ccw shown in FIGS. 2C and 2D based on the reference clock signal. These PWM signals cw and ccw are the same as those in FIG.
The frequencies of the PWM signals cw and ccw shown in (a) and (b) are doubled, and the duty ratio is constant. Thus, of these PWM signals cw, ccw, the PWM signal cw is supplied to the switching elements 1 and 4, the PWM signal ccw is supplied to the switching elements 2 and 3, and the servo motor 5 is driven.

When the switching elements 1 to 4 generate heat in this manner, the frequencies of the PWM signals cw and ccw are increased and the duty ratio is changed to be constant. Therefore, the efficiency is constant and the heat generation of the servomotor 5 is prevented.

As described above, in the first embodiment, the heat generation amount of each of the switching elements 1 to 4 is detected by the temperature sensor 11, and the frequency of the reference clock signal sent to the pulse generating circuit 18 is changed according to the detected temperature. So each P
The changes of the WM signals cw and ccw are relatively the same, and the duty ratio is constant and does not change. Therefore, it is possible to prevent the switching elements 1 to 4 and the servo motor 5 from generating heat, and the PWM control can be performed at high speed.

Next, the second embodiment of the present invention will be described with reference to FIG. The detection circuit 12 is connected to the pulse generation circuit 18 via a V / F (voltage / frequency) converter 20 as a frequency conversion circuit. The V / F converter 20 has a function of converting the temperature signal v from the detection circuit 12 into a reference clock signal having a frequency corresponding to the voltage level and sending the reference clock signal to the pulse generation circuit 18.

With such a configuration, the temperature signal v corresponding to the temperature of the radiator plate 10 to which the switching elements 1 to 4 are attached is sent to the V / F converter 20. Here, if the temperature of the heat sink 10 rises and the voltage level of the temperature signal v rises, the V / F converter 20 sends out a reference clock signal having a frequency higher by the increased voltage of the temperature signal v. If the voltage level of the temperature signal v becomes low, V /
The F converter 20 sends out a reference clock signal having a frequency lowered by the lowered voltage.

The pulse generating circuit 18 outputs the PWM signals cw and ccw having a constant duty ratio according to the frequency of the reference clock signal from the V / F converter 20. As described above, in the second embodiment, since the reference clock signal having the frequency corresponding to the heat generation amount of each of the switching elements 1 to 4 is sent to the pulse generating circuit 18, each PWM is similar to the first embodiment. The changes in the signals cw and ccw are relatively the same, and the duty ratio can be constant.
It is possible to prevent the switching elements 1 to 4 and the servomotor 5 from generating heat, and to perform PWM control at high speed.

Next, a third embodiment of the present invention will be described with reference to FIG. The reference oscillator circuit 15 is connected to a frequency divider 21 that obtains each frequency-divided output of 1 / n times. Further, a selector 22 as a frequency conversion circuit is connected between the comparator 13 and the pulse generation circuit 18. The selector 22 selectively outputs each divided output (reference clock signal) of the frequency divider 21 according to the comparison result of the comparator 13 which is a comparison circuit. When the comparison result of the comparator 13 is v <vo. Selects and outputs a low-frequency reference clock signal from each divided output, and the comparison result is v> vo
In this case, it has a function of selectively outputting a high-frequency reference clock signal of each divided output.

With such a configuration, when the amount of heat generated by each of the switching elements 1 to 4 is small and the comparison result of the comparator 13 is v <vo, the selector 22 outputs the reference clock signal of the lower frequency among the divided outputs. Select and output. Further, if the amount of heat generated by each of the switching elements 1 to 4 increases and the comparison result of the comparator 13 is v> vo, the selector 22
Selects and outputs a high-frequency reference clock signal of each divided output.

Therefore, it goes without saying that the same effects as those of the above-mentioned respective embodiments can be obtained. The present invention is not limited to the above-mentioned embodiments, and may be modified within the scope of the invention. For example, each switching element 1 to 4 is M
The transistor is not limited to the OSFET and may be another transistor. or,
The temperature sensor 11 may be a thermistor, a thermocouple, a resistance thermometer, or the like.

Further, the reference voltage signal vo supplied to the comparator 13 may be plural, and the frequency division outputs may be plural to change the frequency of each PWM signal cw, ccw to plural.

In addition, the frequency conversion circuit 17 or the selector 22
As the reference frequency to be sent to, the frequency of the reference clock signal of frequency f (5 MHz) is set to 2 by PLLIC or the like.
A plurality of doubled, tripled ...

[0041]

As described above in detail, according to the present invention, P
It is possible to provide a pulse width modulation driving device that can perform WM control at a frequency as high as possible and can prevent heat generation of a switching element and a servo motor.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a first embodiment of a pulse width modulation driving device according to the present invention.

FIG. 2 is a waveform diagram showing a frequency change of a PWM signal in the same device.

FIG. 3 is a configuration diagram showing a second embodiment of the device of the present invention.

FIG. 4 is a configuration diagram showing a third embodiment of the device of the present invention.

FIG. 5 is a configuration diagram of a forward / reverse rotation motor control circuit.

FIG. 6 is a waveform diagram of a PWM signal supplied to the circuit.

[Explanation of symbols]

1 to 4 ... Switching element, 5 ... Servo motor, 10 ...
Heat sink, 11 ... Temperature sensor, 12 ... Detection circuit, 13 ... Comparator, 14 ... Reference voltage circuit, 15 ... Reference oscillation circuit, 16, 21 ... Divider, 17 ... Frequency conversion circuit, 18
... pulse generator circuit, 20 ... V / F converter, 22 ... selector.

Claims (4)

[Claims] 1. A pulse width modulation for driving the servo motor by supplying each pulse width modulation signal to each switching element of a forward / reverse rotation motor control circuit in which each switching element is bridge-connected and a servo motor is connected at an intermediate point thereof. In the driving device, a temperature sensor that detects the heat generation amount of each of the switching elements, a frequency conversion circuit that generates a reference clock signal having a frequency according to the detection result from the temperature sensor, and a reference clock signal from the frequency conversion circuit. And a pulse width generation circuit for generating the pulse width modulation signal having a constant duty ratio and a pulse width modulation circuit. 2. A pulse width modulation for driving the servo motor by supplying each pulse width modulation signal to each switching element of a forward / reverse rotation motor control circuit in which each switching element is bridge-connected and a servo motor is connected at an intermediate point thereof. In the drive device, a temperature sensor that detects the amount of heat generated by each of the switching elements, a reference signal generation circuit that generates a reference signal, and a detection result of the temperature sensor and a reference signal from the reference signal generation circuit are compared. A comparison circuit, a frequency conversion circuit that generates a reference clock signal having a frequency corresponding to a comparison result in the comparison circuit, and a frequency that corresponds to the reference clock signal from the frequency conversion circuit and a constant duty ratio. A pulse width modulation drive device, comprising: a pulse width generation circuit for generating a pulse width modulation signal. 3. A pulse width modulation for driving the servo motor by supplying each pulse width modulation signal to each switching element of a forward / reverse rotation motor control circuit in which each switching element is bridge-connected and a servo motor is connected at an intermediate point thereof. In the drive device, a temperature sensor that detects the amount of heat generated by each of the switching elements, a reference signal generation circuit that generates a reference signal, and a detection result of the temperature sensor and a reference signal from the reference signal generation circuit are compared. Comparing circuit, a reference oscillating circuit that oscillates a clock signal having a reference frequency, a reference clock signal from the reference oscillating circuit is frequency-divided to output a divided clock signal, and the reference clock signal is output as it is. Frequency that selects the divided clock signal or the reference clock signal based on the comparison result of the divider circuit and the comparison circuit A pulse width modulation circuit for generating the pulse width modulation signal having a constant duty ratio and a frequency corresponding to the clock signal selected by the frequency conversion circuit. Drive. 4. The frequency conversion circuit lowers the frequency of the reference clock signal when the detection result of the temperature sensor decreases, and increases the frequency of the reference clock signal when the detection result increases. The pulse width modulation driving device according to item 1, 2 or 3.