JP2529097B2 - Encoder power supply device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circular power supply device having an encoder and an encoder power supply circuit, and in particular, the encoder and the encoder power supply circuit are used separately. The present invention relates to an encoder power supply device that operates. 2. Description of the Related Art In recent years, with the development of semiconductor devices, speed control of rotating electric machines has become popular. In particular, vector control capable of controlling an induction motor as much as a DC motor and control of a DC brushless motor having a magnet rotor are widely performed. These speed controls require an encoder that detects the actual speed or position (rotation angle) of the rotating machine (JP-A-54-104517). The encoder is attached to a rotating machine and comprises a code plate fixed to a rotary shaft and a detecting section for detecting the code of the code plate. The controller supplies power to the encoder, receives a detection signal from the encoder, compares it with a command signal, and controls the rotating machine. By the way, there are cases where the rotating machine and the controller are used relatively distant from each other. In such a case, the connection wire connecting the encoder and the controller becomes long, and the voltage drop due to the resistance of this connection wire also becomes large. That is, the voltage drop is determined by the product of the current flowing through the connection line and the resistance of the connection line. Therefore, as the connecting line becomes longer, the resistance also increases and the voltage drop increases. If the voltage applied to the encoder is lower than the desired terminal voltage, the detection accuracy will decrease and the signal level transmitted to the controller will also decrease. Therefore,
The controller may not be able to receive an accurate signal, which may result in failure to accurately control the rotating machine. Therefore, when the conventional encoder and controller are used separately, the thickness of the connecting line that connects them is increased to reduce the voltage drop, or the resistance is calculated based on the length of the connecting line to calculate the voltage drop. Then, the supply voltage of the controller was added for that amount and supplied to the encoder. However, the former has a drawback that the price of the connecting line is high, and the latter is troublesome to calculate the voltage drop. SUMMARY OF THE INVENTION In view of the above drawbacks, the present invention is to provide an encoder power supply device having an encoder power supply circuit capable of easily applying a voltage desired by the encoder. The present invention provides an encoder power supply circuit comprising an encoder power supply circuit and an encoder which receives power from the encoder power supply circuit through a power supply line and detects the speed or position of a rotating shaft. In the device, a voltage signal line for feeding back the positive side terminal voltage and the negative side terminal voltage of the encoder from the encoder to the encoder power supply circuit side is provided, and the encoder power supply circuit is an encoder fed back from the voltage signal line. Means for obtaining a voltage drop amount of the positive side supply line and the negative side supply line of the power supply line from the positive side terminal voltage and the negative side terminal voltage, a preset reference voltage, and the obtained voltage drop amount. The encoder so that the terminal voltage of the encoder becomes a desired terminal voltage based on the reference voltage A means for correcting the output voltage of the power supply circuit is provided. The positive side terminal voltage and the negative side terminal voltage of the encoder are fed back from the encoder to the encoder power supply circuit side, and the positive side terminal voltage and the negative side terminal voltage of the fed-back encoder are used to supply the power source. The voltage drop of the positive supply line and the negative supply line of the supply line is obtained. The output voltage of the encoder power supply circuit is corrected so that the terminal voltage of the encoder becomes a desired terminal voltage based on the obtained voltage drop and the reference voltage. An embodiment of the present invention will be described below with reference to FIGS. 1 to 4. FIG. 1 is a schematic configuration diagram of an encoder power supply device. Here, 1 is a controller, 2 is an encoder, 3 is a motor to which the encoder 2 is attached, 4 is an encoder cable for connecting the controller 1 and the encoder 2, and 5 is a main cable for supplying power from the controller 1 to the motor 3. FIG. 2 is a schematic diagram for explaining the controller 1 and the encoder 2 in more detail. The controller 1 includes an encoder power supply circuit 6, a receiver circuit 7 that receives a detection signal from the encoder 2, and a motor drive circuit (not shown) that controls the motor 3 at a variable speed based on the signal from the receiver circuit 7. . The encoder 2 includes a code plate (not shown) fixed to the rotary shaft of the motor 3, a signal generation circuit 8 for detecting the code of this code plate, and a driver circuit 9 for receiving the signal of the signal generation circuit 8 and sending it to the controller 1. The encoder cable 4 includes a power supply line 40 for supplying power from the encoder power supply circuit 6 to the signal generating circuit 8 and the driver circuit 9 of the encoder 2, and a code signal line 41 for sending a signal from the driver circuit 9 to the receiver circuit 7. Have and. The arrows shown on the power supply line 40 and the code signal line 41 indicate the direction of signals, not the direction of current. Further, a detailed description will be given with reference to FIG. The encoder power supply circuit 6 comprises a rectifying circuit 10 for converting an AC power supply into a DC power supply, a smoothing capacitor C1 and a voltage adjusting means R. In the voltage adjusting means R, 11 is a switching regulator IC, C2, C3 and C4 are capacitors, and R is a capacitor.
1, R2, R3, R4, R5, R6, R7, R8, R9 are resistors,
VR1 is a variable resistor, D1 is a unidirectional element, Q1 and Q2 are self-extinguishing elements such as transistors, and L1 is an inductance. Next, the operation of the encoder power supply circuit 6 will be described. The DC voltage rectified by the rectifier circuit 10 is smoothed by the smoothing capacitor C1 and the Vcc terminal of the IC 11 and G
It is applied to the ND terminal. The output of the IC 11 is output from the Vref terminal, and the voltage is divided by the variable resistors VR1, R3, and R4. Between resistor R3 and resistor 4 and N.V. It is connected to the INV terminal. The output voltage of the encoder power supply circuit 6 is divided by the resistors R5 and R6 and input to the INV terminal. On the other hand, the resistor R1 and the capacitor C3 are connected in parallel to form an oscillation circuit, and the reference is generated.
This reference wave corresponds to the voltage of the INV terminal described above, INV
Transistor Q is compared with the value subtracted from the terminal voltage
1. Turn on and off Q2. This control will be described with reference to FIG. The horizontal axis represents time t, and the vertical axis represents voltage E. Here, the reference wave is W, INV terminal and N.V. The voltage difference from the INV terminal is V
In this case, the transistors Q1 and Q2 are controlled to be turned on in the range P-P in which the value of the reference wave W is lower than the voltage difference V. Now, when the controller 1 and the encoder 2 are separated and fixed, and the voltage drop of the power supply line 40 is large,
By adjusting the variable resistor VR1, the voltage difference V can be lowered to the voltage difference V0 and the output voltage of the encoder power supply circuit 6 can be increased. Therefore, these desired voltages can be applied to the encoder signal generator 8 and the driver circuit 9. The adjustment of the variable resistor VR1 is performed based on the voltage indicator 12 which displays the terminal voltage PVf of the encoder signal generator 8 and the driver circuit 9. This voltage indicator 1
2 is located on the encoder power supply circuit 6 side, and is connected to the encoder signal generator 8 and the driver circuit 9 by the voltage signal line 42. Here, since the voltmeter 12 is generally composed of a high resistance, the current flowing through the voltage signal line 42 is much smaller than the current flowing through the power supply line 40. Therefore, there is almost no voltage drop due to the voltage signal line 42, and the voltage indicator 12 can display a value substantially equal to the voltage PVf value of the encoder signal generator 8 and the driver circuit 9. The voltage signal line 42 may be arranged in the same cable as the power supply line 40 and the code signal line 41, or may be a cable different from the power supply line 40. As described above, according to this embodiment,
The voltage signal line 42 and the voltage indicator 12 are provided so that the terminal voltage PVf of the encoder signal generator 8 and the driver circuit 9 can be detected on the controller 1 side.
Since the output voltage of the encoder power supply circuit 6 is adjusted based on the display value of 2, even if the controller 1 and the encoder 2 are located apart from each other and the voltage drop of the power supply line 40 is large, the terminal of the encoder 2 can be easily The voltage PVf can be adjusted to a desired value. Therefore, the voltage drop of the power supply line 40 can be calculated and the desired voltage can be simply and accurately applied to the signal generation circuit 8 and the driver circuit 9 of the encoder 2 without increasing the size of the power supply line 40. Can be applied. Another embodiment of the present invention will be described with reference to FIG. A voltage signal line 42A for feeding back the voltage on the encoder 2 side to the controller 1 side is provided, and a resistor R5 is connected in series to this voltage signal line 42A. The terminal voltage PVf on the encoder 2 side is divided by the resistor R5 and the resistor R6,
It is input to the INV terminal of IC11. With such a structure, if the output voltage PV of the encoder power supply circuit 6 is first adjusted by the variable resistor VR1 so that the desired voltage PVf can be applied to the encoder 2, it is possible to change the ambient temperature. Accordingly, the output voltage PV of the encoder power supply circuit 6 can be automatically corrected even if the voltage drop of the encoder cable 4 changes. Further, since one voltage signal line 42A can be used, if another one line 42B is used in parallel with the negative side line 40B of the power supply line 40, the voltage drop can be further reduced. Another embodiment of the present invention will be described with reference to FIG. Here, 13 and 14 are voltage drop detection circuits for detecting the voltage drop of the power supply line 40, OP1, OP2, and O.
P3 and OP4 are differential amplifiers. The voltage signal lines 42A and 42B are the encoder 2
Terminal voltage PV of the signal generation circuit 8 and the driver circuit 9
The f1 and EGf1 are fed back to the controller 1 side. On the controller 1 side, the voltage signal line 42A is connected to the voltage drop detection circuit 13, and the voltage signal line 42B is connected to the voltage detection circuit 14. The voltage detection circuit 13 has a differential amplifier OP2 and calculates the difference between the voltage level of the P terminal of the encoder power supply circuit 6 and the terminal voltage PVf1 on the encoder 2 side, that is, the voltage drop of the power supply line 40A. To detect. Similarly, the voltage detection circuit 14 has a differential amplifier OP3, and the encoder 2
The difference between the side terminal voltage EGf1 and the ground of the encoder power supply circuit 6, that is, the voltage drop of the voltage supply line 40B is detected. The differential amplifier OP1 inverts a value obtained by dividing the output voltage PV of the encoder power supply circuit 6 by the resistors R26 and R27 and outputs the inverted voltage. Next, these differential amplifiers OP1 and OP
2, Add the output of OP3. Here, the operational amplifier OP1
The output of the operational amplifiers OP2 and OP3, that is, the voltage drop of the power supply lines 40A and 40B is subtracted from the output of. This signal is inverted by the operational amplifier OP4 and input to the INV terminal of the switching regulator IC11. This IN
The input signal of the V terminal is a value obtained by subtracting the voltage drop of the power supply lines 40A and 40B from the output voltage PV of the encoder power supply circuit 6, that is, a signal corresponding to the terminal voltage PVf1 of the encoder 2. If the inputs to the operational amplifiers OP1, OP2 and OP3 are set to + and-terminals opposite to those shown in the figure, the operational amplifier OP4 for inverting the sum of these outputs may be unnecessary. With such a configuration, the output voltage PV of the encoder power supply circuit 6 can be adjusted based on the voltage signal corresponding to the terminal voltage PVf of the encoder 2, so that the desired voltage can be accurately supplied to the encoder 2. Can be applied. According to the present invention, the encoder power supply circuit is provided with a voltage signal line for feeding back the positive side terminal voltage and the negative side terminal voltage of the encoder from the encoder to the encoder power supply circuit side. The voltage drop amount of the positive side supply line and the negative side supply line of the power supply line is obtained from the positive side terminal voltage and the negative side terminal voltage of the encoder fed back from the signal line, and the preset reference voltage and the obtained Since the output voltage of the encoder power supply circuit is corrected so that the terminal voltage of the encoder becomes a desired terminal voltage based on the voltage drop and the reference voltage, the positive side supply line and the negative side supply of the power supply line are supplied. Both voltage drops on the line can be compensated and the encoder will be applied with the desired voltage regardless of the distance between the controller and the encoder. You. Therefore, the detection accuracy of the encoder is improved,
It has the effect of improving reliability. Further, it is not necessary to calculate the voltage drop of the power supply line between the controller and the encoder each time, and the man-hour can be reduced.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram of an encoder power supply device of the present invention. FIG. 2 is a schematic diagram illustrating a configuration of a main part of FIG. FIG. 3 is a circuit diagram of an encoder power supply device showing an embodiment of the present invention. FIG. 4 is a time chart explaining the operation of FIG. FIG. 5 is a circuit diagram of an encoder power supply device showing another embodiment of the present invention. FIG. 6 is a circuit diagram of an encoder power supply device showing still another embodiment of the present invention. [Explanation of Codes] 1 ... Controller, 2 ... Encoder, 3 ... Motor,
4 ... Encoder cable, 5 ... Main cable, 6 ...
Encoder power supply circuit, 7 ... Receiver circuit, 8 ... Signal generating circuit, 9 ... Driver circuit, 40, 40A,
40B ... Power supply line, 42, 42A, 42B ... Voltage signal line, PVf ... Encoder terminal voltage, PV ... Encoder power supply circuit output voltage.

   ────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Sadayuki Igarashi               7-1, 1-1 Higashi Narashino, Narashino City, Chiba Prefecture                 Hitachi Keiyo Engineering Co., Ltd.               Within                (56) References Japanese Patent Publication Sho 52-18895 (JP, B1)

Claims (1)

(57) [Claims] An encoder power supply device comprising: an encoder power supply circuit; and an encoder that receives power from the encoder power supply circuit through a power supply line to detect the speed or position of a rotating shaft. A voltage signal line for feeding back the side terminal voltage and the negative side terminal voltage from the encoder to the encoder power supply circuit side is provided, and the encoder power supply circuit includes a positive side terminal voltage and a negative side voltage of the encoder fed back from the voltage signal line. Means for obtaining the voltage drop amount of the positive side supply line and the negative side supply line of the power supply line from the side terminal voltage, a preset reference voltage, and the encoder based on the obtained voltage drop amount and the reference voltage Correct the output voltage of the encoder power supply circuit so that the terminal voltage of the encoder becomes the desired terminal voltage. Encoder power supply apparatus characterized by comprising means that.