JP2008136296A - Power supply unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power supply unit capable of detecting an abnormal state in a series circuit of a switching element and a discharging resistor connected in between DC power source lines, without causing increase in cost. <P>SOLUTION: When a voltage between the DC power source lines 12a, 12b is attempting to increase, exceeding an upper limit value of 380V, an FET 17 of an overvoltage protective portion 6 carries out switching operation to supply power to the discharging resistor 5; and when a state where on-duty in the switching operation of the FET 17 exceeds a preset threshold of 3.7% continues for a predetermined period of time, a control device 7 determines that the state is abnormal. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  In the present invention, when a series circuit of a switching element and a discharge resistor is connected between a pair of DC power supply lines for supplying DC power to a load, and the voltage between the pair of DC power supply lines becomes equal to or higher than the upper limit voltage. The present invention relates to a power supply apparatus provided with a discharge control means for conducting a switching element.

Some power supply devices that supply DC power to a load are configured to perform overvoltage protection when the power supply voltage rises above an upper limit. For example, in a power supply device that supplies power to a motor or the like, when the voltage between power supply lines rises due to regenerative power generated when the motor decelerates, the switching element inserted between the power supply lines is turned on, and this switching element is connected in series. The voltage between the power supply lines is reduced by consuming regenerative power by the connected discharging resistor (see, for example, Patent Documents 1 and 2).
JP-A-6-15590 JP 10-193293 A

  When the voltage is lowered as described above, the electric power consumed by the discharging resistor becomes thermal energy, which raises the temperature of the resistor itself and its surroundings. For example, when the discharging resistor is always energized due to a short circuit failure of the switching element, the generated heat becomes high temperature, which may adversely affect peripheral components or the resistor itself may melt. As a method for solving this problem, it is conceivable to arrange a thermal switch or use a discharge resistor with a fuse. However, since the parts corresponding to the high temperature environment as described above are relatively expensive, there is a problem that adding these parts increases the manufacturing cost of the apparatus.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a power supply capable of detecting an abnormal state in a series circuit of a switching element and a discharging resistor connected between DC power supply lines without causing an increase in cost. To provide an apparatus.

  According to the power supply device of the first aspect, the discharge control means turns on the switching element when the detected voltage becomes equal to or higher than the upper limit value, and turns off when the detected voltage falls below the upper limit value. Therefore, when the voltage between the DC power supply lines tends to rise beyond the upper limit value, the discharge control means repeats the above operation to energize the discharge resistor, so that the on / off operation of the switching element has a certain duty ratio. It will be a thing. The abnormality determination means performs an abnormality determination process when the on-duty detected based on the on / off state of the switching element exceeds a preset threshold value. As the on-duty increases, that is, the energization time to the discharge resistor increases, the temperature of the discharge resistor increases. Therefore, if the on-duty of the switching element is monitored, an abnormal temperature increase of the discharge resistor can be detected. .

  According to the power supply device of the second aspect, when the state where the on-duty of the switching element is equal to or greater than the threshold value continues for a time set according to the on-duty, it is determined as abnormal. The temperature of the discharge resistor rises during the on period of the switching element and becomes substantially constant or falls during the off period. Therefore, if the time for determining an abnormality is set according to the on-duty, the abnormality can be detected according to the degree of temperature rise of the discharge resistor.

  According to the third aspect of the present invention, the on / off state of the switching element is detected at regular intervals, the counting means counts up or down according to the on / off state, and the count value becomes a predetermined value. It will be judged as abnormal. As described above, since the temperature of the discharging resistor changes according to the ON / OFF period of the switching element, if the count value is increased or decreased according to the temperature change and reaches a predetermined value corresponding to the abnormality detection level, The temperature rise of the discharge resistor can be detected by the counting means.

  According to the power supply device of the fourth aspect, the switching element counts up in the on state, counts down in the off state, and the addition value of the upcount is set to a multiple of the subtraction value of the downcount. The increase / decrease of the integrated value of the count can be set in detail according to the degree of increase.

  According to the power supply device according to claim 5, since the setting magnification of the addition value of the upcount is set according to the threshold value of the on-duty, the count value of one on-off period from the stage when the on-duty reaches the threshold value The total of will rise. Therefore, if the energization is continued in a state where the on-duty of the switching element slightly exceeds the threshold value, the integrated value of the count increases, so that an increase in the temperature of the discharge resistor can be detected.

  According to the power supply device of the sixth aspect, the diagnosis unit performs functional diagnosis of the element depending on whether or not the terminal voltage of the discharging resistor changes when the switching element is turned on. That is, if the switching element becomes conductive, a voltage drop occurs between the terminals of the discharging resistor, and therefore the terminal voltage of the discharging resistor does not change as expected even if the diagnostic means controls the conducting of the switching element. It can be determined that the switching element has failed.

Hereinafter, an embodiment in which the present invention is applied to a power supply apparatus that supplies power to a motor of a robot will be described with reference to the drawings.
FIG. 1 shows an electrical configuration of the power supply apparatus. The power supply device 1 rectifies and smoothes the power supplied from, for example, a three-phase 200 V commercial AC power supply 2 and supplies it to the industrial robot 3 as a load, and the output of the DC power supply circuit 4 When the voltage exceeds the upper limit value, an overvoltage protection unit (corresponding to a discharge control means) 6 that discharges by the discharge resistor 5 and lowers its output voltage, and a control unit (ON / OFF) that detects an abnormal state in the overvoltage protection unit 6 Off detection means, abnormality determination means, counting means, and diagnosis means) 7. In this embodiment, the output voltage of the DC power supply circuit 4 is about 280 V during normal operation, and the upper limit is set to 380 V, for example.

  The DC power supply circuit 4 includes a full-wave rectifier circuit 8 and a smoothing capacitor 9, and R, S, and T phase outputs of the AC power supply 2 are connected to a switch 10 and AC power supply lines 11r and 11s. , 11t and connected to the input side of the full-wave rectifier circuit 8. The DC power output from the full-wave rectifier circuit 8 is supplied to the robot 3 via DC power supply lines 12a and 12b, and a smoothing capacitor 9 is connected between the DC power supply lines 12a and 12b. The full-wave rectifier circuit 8 has a known configuration in which six rectifier elements are connected in a three-phase bridge shape.

  The overvoltage protection unit 6 includes voltage dividing resistors 13 and 14, a comparator 15, an OR gate 16, a discharging resistor 5, an N-channel MOSFET (hereinafter simply referred to as FET) 17, and voltage dividing resistors 18 and 19. The voltage dividing resistors 13 and 14 are connected in series between the DC power supply lines 12 a and 12 b, and the common connection point (voltage dividing point) is connected to the non-inverting input terminal of the comparator 15. The reference potential Vs is applied to the inverting input terminal of the comparator 15, and the output terminal is connected to one input terminal of the OR gate 16. A gate signal Sg from the control unit 7 is given to the other input terminal of the OR gate 16.

  In this embodiment, the voltage detection means 20 is constituted by the voltage dividing resistors 13 and 14 and the comparator 15. Further, the resistance values of the voltage dividing resistors 13 and 14 are set such that the voltage at the voltage dividing point becomes larger than the reference potential Vs when the voltage between the DC power supply lines 12a and 12b becomes equal to or higher than the upper limit value (380V).

  In addition, a series circuit of the discharge resistor 5 and the FET 17 is connected between the DC power supply lines 12a and 12b. The output terminal of the OR gate 16 described above is connected to the gate of the FET 17. A series circuit of voltage dividing resistors 18 and 19 is connected between the drain of the FET 17 and the power supply line 12b, and the potential at the common connection point (voltage dividing point) is output to the control unit 7 as a voltage signal Va. Has been. The resistance values of the voltage dividing resistors 18 and 19 are set so that the voltage signal Va is substantially at the power supply voltage level (H level) of the control unit 7 when the FET 17 is in the OFF state.

  The control unit 7 is mainly composed of a microcomputer having a CPU 7a, an A / D converter 7b, and the like. The voltage signal Va is input from the overvoltage protection unit 6 to the control unit 7, and the voltage signal Va is converted into a digital value by the A / D converter 7b. The CPU 7a performs this conversion data for a predetermined period. In the example, sampling is performed every 1 ms. Based on this data, the CPU 7a detects an abnormal temperature in the discharging resistor 5 and performs a function diagnosis of the FET 17 (see the description of the action described later).

  The control unit 7 normally sets the gate signal Sg to the L level, and sets the gate signal Sg to the H level when performing functional diagnosis of the FET 17. That is, the control unit 7 is configured to control the FET 17 to be in an on state and perform a function diagnosis thereof. And the control part 7 will output the abnormal temperature detection signal Sa and the failure detection signal Sb, respectively, with respect to the engine board (not shown) which drive-controls the motor of the robot 3, if the abnormality and the failure mentioned above are detected.

Next, the operation of the above configuration will be described with reference to FIGS.
The temperature of the discharge resistor 5 increases as the period during which the FET 17 is turned on and energized (on duty) is longer. In this embodiment, it is assumed that when the FET 17 continues the switching operation with the on-duty exceeding the threshold value, the temperature of the discharge resistor 5 gradually increases and finally reaches an abnormal level. The CPU 7a detects that a temperature abnormality has occurred by detecting the state. In the present embodiment, the on-duty threshold value is 3.7%.

  FIG. 2 shows the contents of the above-described control of the CPU 7a, and the abnormal temperature detection processing in the discharging resistor 5 will be described along the flowchart of FIG. The CPU 7a performs initial setting such as resetting the count value (cnt) in step S1. In step S2, the process waits for 1 ms, which is the sampling interval, and proceeds to step S3 and subsequent steps after 1 ms.

  Normally, the voltage between the DC power supply lines 12a and 12b is about 280V, and the FET 17 is turned off. As a result, the voltage signal Va is at the H level (“NO” in step S3), so the process proceeds to step S5 and the count value is decremented (cnt = cnt−1). However, when cnt = 0, the value is maintained. In subsequent step S6, it is confirmed whether or not the count value is equal to or higher than the abnormal temperature detection value A: “62000”. Since the count value at this time is “0” (“NO”), the process returns to step S2.

  After that, step S2 and subsequent steps are executed in the same manner as described above. However, since the FET 17 is normally off, the voltage signal Va is always at the H level and the count value does not increase at all. Therefore, the count value does not exceed the abnormality detection value “62000” and does not proceed from step S6 to step S7, so that the abnormal temperature detection signal Sa is not output.

  On the other hand, when the motor 3 (not shown) is decelerated in the robot 3, the voltage between the DC power supply lines 12a and 12b rises due to the regenerative power generated by the motor. When this voltage exceeds the upper limit value of 380 V, the FET 17 is turned on, and regenerative power is consumed by the discharging resistor 5. When the voltage decreases and becomes less than 380 V, the FET 17 is turned off and the voltage increases again. Therefore, while the deceleration operation is continued, the above operation is repeated in the overvoltage protection unit 6, and the switching operation of the FET 17 is accompanied by a certain duty ratio.

In this case, since the voltage signal Va is at the L level during the ON period of the FET 17 (“YES” in step S3), the count value increases by the addition value B: “26” while repeating steps S2 to S6 (cnt = cnt + 26). On the other hand, since the voltage signal Va becomes H level during the OFF period of the FET 17 (“NO” in step S3), the count value decreases by the subtraction value C: “1” by repeating steps S2 to S6 (cnt = cnt -1). Therefore, the time T required for the count value to reach the abnormal temperature detection value A is calculated from the on period Ton, the off period Toff, the addition value B, and the subtraction value C by the following formula when the sampling interval is 1 ms. Is done.
T = A / (Ton × B−Toff × C) [ms]

  For example, when the on-duty of the FET 17 is 6% (off-duty = 94%), the count value becomes “62000” after 100 seconds (“YES” in step S6). That is, when the on-duty state of 6% continues for 100 seconds, the CPU 7a determines that the discharging resistor 5 has reached the abnormal temperature, and outputs the abnormal temperature detection signal Sa to the engine board (step S7). Exit. Then, for example, the engine board stops the driving of the motor by a driving circuit such as an inverter, and performs an abnormality process such as lighting an LED that notifies the abnormality.

  Further, for example, if the abnormality between the robot 3 and the voltage between the DC power supply lines 12a and 12b continues to rise rapidly due to some abnormality, the on-duty of the FET 17 becomes an extremely large value, for example, 100%. Therefore, the discharge resistor 5 is always energized, and the temperature of the discharge resistor 5 rises rapidly. Thus, when the on-duty becomes 100% (off-duty = 0%), if the state continues for about 2.3 seconds, the count value becomes “62000” or more (“YES” in step S6), It is determined that the discharge resistor 5 has reached the abnormal temperature in a very short time, and the abnormal temperature detection signal Sa is output (step S7).

  In this embodiment, the abnormal temperature detection value A, the addition value B, and the subtraction value C are 1 on / off when the discharging resistor 5 is energized based on the on-duty exceeding the threshold value 3.7%. The total count value for the period is set to increase. Therefore, when the on-duty of the FET 17 during the discharge operation of the regenerative power is 3.7% or less, that is, when the energization period to the discharge resistor 5 is short and the temperature rise of the discharge resistor 5 is small, the count is performed. Since the value does not reach “62000” (“NO” in step S6), the abnormal temperature detection signal Sa is not output without proceeding to step S7 as in the case of the normal operation described above.

Next, the function diagnosis process of the FET 17 will be described with reference to the flowchart showing the control contents of the CPU 7a shown in FIG. Note that this function diagnosis processing is performed before the power supply device 1 is normally operated, for example.
In step T1, the CPU 7a outputs an H level gate signal Sg, and controls the FET 17 to be in an ON state. In step T2, it is confirmed whether or not the level of the voltage signal Va is H level. At this time, if the FET 17 is functioning normally, the voltage signal Va becomes L level (“NO”), and the process is terminated. On the other hand, when the voltage signal Va is at the H level (“YES”), it is determined that the FET 17 has an open failure, the process proceeds to step T3, the failure detection signal Sb is output to the engine board, and the process is terminated. .

According to the present embodiment described above, the following effects can be obtained.
In the power supply device 1, when the voltage between the DC power supply lines 12 a and 12 b tends to increase beyond the upper limit value of 380 V, the FET 17 of the overvoltage protection unit 6 performs a switching operation to energize the discharge resistor 5, and the control unit 7 Is determined as abnormal when the on-duty in the switching operation of the FET 17 exceeds a preset threshold value of 3.7% for a predetermined time or longer.

  Specifically, the CPU 7a samples the voltage signal Va every 1 ms, counts up when the voltage signal Va is L level, and counts down when the voltage signal Va is H level. And CPU7a determines the temperature abnormality of the resistance 5 for discharge based on the integrated value of the said count operation | movement. That is, an up / down count is performed according to the temperature rise of the discharge resistor 5 during the ON period of the FET 17 and the temperature fall (or substantially constant) during the OFF period, and this count value is equal to or higher than the abnormal temperature detection value A. Since it is determined that a temperature abnormality has occurred, the occurrence of a temperature abnormality in the discharge resistor 5 can be detected according to the degree of increase. Therefore, when the temperature of the discharge resistor 5 rises abnormally due to a short-circuit failure of the FET 17 or an abnormality on the robot 3 side that is a load, it is possible to prevent adverse effects on peripheral parts and fusing of the discharge resistor 5. it can.

Further, the count-up addition value B is set to “26”, and the count-down subtraction value C is set to “1”. In this case, for example, when the FET 17 performs a switching operation with an on-duty (off-duty = 96.3%) corresponding to a threshold value and energizes the discharging resistor 5 for a period of 1000 milliseconds, The total count value per period is “−1” as shown in the following formula and does not increase.
26 × 37−963 = −1
When the FET 17 performs a switching operation with an on-duty of 3.8% exceeding the threshold value of 3.7%, the total count value of the period increases, and a temperature abnormality of the discharge resistor 5 is detected. can do.

  Further, the CPU 7a controls the FET 17 to be in an ON state before performing the normal operation, and performs the function diagnosis of the FET 17 based on the voltage signal Va corresponding to the terminal voltage of the discharging resistor 5. It is possible to prevent an excessive temperature rise of the discharge resistor 5 due to the above.

The present invention is not limited to the embodiments described above and shown in the drawings, and the following modifications or expansions are possible.
The sampling interval of the voltage signal Va, the on-duty threshold value, the abnormal temperature detection value A, the addition value B, and the subtraction value C can be appropriately changed according to the temperature of the discharge resistor 5 that is determined to be abnormal.
The count value may be decreased during the ON period of the FET 17 and the count value may be increased during the OFF period. In this case, the initial value of the count value is set to the detection value A, and the count value becomes “0”. An abnormal temperature may be detected.
When the CPU 7a detects that the on-duty of the FET 17 exceeds the threshold value, the CPU 7a may perform control so as to immediately determine that there is an abnormality.
The function of the voltage detection means 20 may be realized by, for example, microcomputer software of the control unit 7.

Instead of the A / D converter 7b, an on-duty in the switching operation of the FET 17 may be detected or a function diagnosis may be performed using a comparator. Alternatively, a differential amplifier may be connected to both ends of the discharging resistor 5 and detection may be performed based on the output.
A P channel MOSFET may be connected to the DC power supply line 12a side (power supply side) as a switching element.
You may apply to what uses the alternating current power supply of single phase 200V or 100V.
The power supply device 1 is not limited to supplying power to an industrial robot, but may be one that supplies power to other electric and electronic devices.

1 is an electrical configuration diagram of a power supply device according to an embodiment of the present invention. Flow chart showing control contents related to abnormal temperature detection processing of discharging resistor Flowchart showing control contents related to FET function diagnosis processing

Explanation of symbols

  In the drawings, 1 is a power supply device, 2 is an AC power supply, 4 is a DC power supply circuit, 5 is a discharge resistor, 6 is an overvoltage protection unit (discharge control unit), 7 is a control unit (on / off detection unit, abnormality determination unit). , Counting means, diagnostic means), 12a and 12b are DC power supply lines, 17 is an N-channel MOSFET (switching element), and 20 is voltage detection means.

Claims (6)

A DC power supply circuit that rectifies the power supplied from the AC power supply and converts it to DC, a pair of DC power supply lines that supply the DC power to the load, voltage detection means that detects a voltage between the DC power supply lines, A series circuit of a switching element and a discharge resistor connected between the pair of DC power supply lines, and a discharge control means for conducting the switching element when a voltage detected by the voltage detection means exceeds an upper limit voltage. In the power supply provided,
An on / off detection means for detecting an on / off state of the switching element;
A power supply apparatus comprising: an abnormality determination unit configured to perform an abnormality determination process when an on-duty of the switching element detected via the on / off detection unit exceeds a preset threshold value.   The abnormality determining means determines that an abnormality occurs when a state in which the on-duty of the switching element is equal to or greater than the threshold value continues for a time set according to the on-duty. The power supply device according to 1. The on / off detection means detects the on / off state of the switching element at regular intervals,
The abnormality determining unit includes a counting unit that counts up or counts down according to an on / off state that is detected every fixed period.
3. The power supply device according to claim 2, wherein when the count value by the counting means reaches a predetermined value set in advance, it is determined that there is an abnormality.   4. The power supply device according to claim 3, wherein the counting means counts up in the on state and counts down in the off state, and sets the addition value of the up count to a multiple of the subtraction value of the down count.   The power supply apparatus according to claim 4, wherein a setting magnification of the addition value is set based on the on-duty threshold value. A DC power supply circuit that rectifies the power supplied from the AC power supply and converts it to DC, a pair of DC power supply lines that supply the DC power to the load, voltage detection means that detects a voltage between the DC power supply lines, A series circuit of a switching element and a discharge resistor connected between the pair of DC power supply lines, and a discharge control means for conducting the switching element when a voltage detected by the voltage detection means exceeds an upper limit voltage. In the power supply provided,
Comprising diagnostic means for diagnosing the function of the switching element;
The diagnosis means is configured to be able to control conduction of the switching element, and performs diagnosis according to whether or not the terminal voltage of the discharging resistor has changed when the switching element is turned on. apparatus.

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