JP2010108130A - Switching device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a switching device for obtaining high reliability. <P>SOLUTION: When all switches SW1 to SW4 are put in an ON status, and the ON resistance values of all the switches SW1 to SW4 are normal, current (Irb1) and current (Irb2) are matched. Meanwhile, when the abnormality of the ON resistance value of the switch SW2 is generated, the current (Irb1) shows a value corresponding to the synthetic resistance value of the switch SW1 and the switch SW2, and the current (Irb2) shows a value corresponding to the synthetic resistance value of the switch SW3 and the switch SW4. Thus, it is possible to sufficiently increase the ratio of those currents, and to easily detect the increase of the ON resistance value. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a switching device capable of selecting on / off of a power supply for a load by switching a switch.

In the field of process automation, devices for switching power on / off are used for field devices such as electromagnetic valves. Since such a device requires high reliability (for example, IEC61508), a function for diagnosing its own state is required.
JP 2005-44074 A

  However, since it is a precondition to maintain the power on / off state at the time of self-diagnosis, the internal switch cannot be freely turned on / off, and it is difficult to perform a complete self-diagnosis. . For example, in the self-diagnosis while the normal output state is off, there is a problem that it cannot be diagnosed whether or not the output state can be turned on.

  An object of the present invention is to provide a switching device that can obtain high reliability.

The switching device of the present invention is a switching device capable of selecting an on / off state of a power supply with respect to a load by switching the switch, and is formed between the power supply and the load, and includes a circuit network including a plurality of switches in the circuit, Control means for independently controlling each of the plurality of switches included in the circuit network; and current monitoring means for monitoring a current of a circuit in the circuit network, wherein the control means turns on a power supply to the load. A control for sequentially switching the states of the plurality of switches under the condition of maintaining the / off state is executed, and the current monitoring means monitors the current when the control is executed.
According to this switching device, since the current at the time of control execution is monitored by the current monitoring means, it is possible to detect an abnormality of the switching device with high accuracy while maintaining the state of the power supply with respect to the load.

  The current monitoring means may monitor the current flowing in each of the switching circuits connected in parallel in the circuit network and having the switch inserted therein.

  The power source may be an AC power source, and the current monitoring unit may monitor an effective value of the current.

  The power source may be an AC power source, and the current monitoring unit may monitor an instantaneous value of the current acquired in accordance with a cycle of the AC power source.

  The current monitoring unit may monitor the current value by comparing the instantaneous value of the current current with the instantaneous value of the current acquired by an integral multiple of the cycle of the AC power supply.

  According to the switching device of the present invention, since the current at the time of control execution is monitored by the current monitoring means, it is possible to detect an abnormality of the switching device with high accuracy while maintaining the state of the power supply with respect to the load.

  Hereinafter, embodiments of a switching device according to the present invention will be described.

  Hereinafter, the switching device according to the first embodiment will be described with reference to FIGS.

  FIG. 1A is a diagram illustrating a circuit configuration of the switching device according to the first embodiment, and FIG. 1B is a diagram illustrating a configuration of a switch.

  As shown to Fig.1 (a), the switching apparatus of a present Example is comprised using four switches SW1-SW4. As shown in FIG. 1B, the switch SW1 is configured by combining N-type field effect transistors (MOSFETs) Q11 and Q12. The switches SW2 to SW4 are configured similarly. The switches SW1 to SW4 can be controlled independently of each other by the control circuit 4.

  As shown in FIG. 1 (a), in the switching device of this embodiment, two switches (switch SW1 and switch SW2) that can be independently controlled on / off are an AC power source 1 having an effective voltage value of 100 V, a load 2 and the like. Are connected in series, and the midpoints of the resistors (R1, R2) of the same resistance value connected in series so as to divide the AC voltage V of the AC power supply 1 are connected to the midpoints of the switches SW1 and SW2. Has been. The voltage at the midpoint (Vrb1) is monitored by the voltage monitoring circuit 3.

  Similarly, two switches (switch SW3 and switch SW4) that can be controlled on / off independently are connected in series between the AC power source 1 and the load 2 so that the AC voltage V of the AC power source 1 is divided. The midpoint of the resistors (R3, R4) having the same resistance value connected in series is connected to the midpoint of the switch SW3 and the switch SW4. The voltage at the midpoint (Vrb2) is monitored by the voltage monitoring circuit 3.

  The resistance values of the resistors R1 to R4 are normally high resistance values that do not affect the load 2 in the off state.

  As shown in FIG. 1A, a current detector CT1 is provided in a switching circuit in which switches SW1 and SW2 are connected in series, and a current detector CT2 is provided in a switching circuit in which switches SW3 and SW4 are connected in series. Each is provided. The current values (Irb1, Irb2) of the respective switching circuits are monitored by the current monitoring circuit 5.

  The monitoring result in the voltage monitoring circuit 3 is given to the control circuit 4, and the control circuit 4 performs diagnosis on the four switches SW1 to SW4 based on the monitoring result.

  FIG. 2 is a diagram showing the relationship between the state of each switch during normal operation and the monitored voltage.

  When the normal output state is on, the switches SW1 to SW4 are sequentially switched to the states (states 4, 8, 12 to 16) in which the “output state” is on in FIG. 2, and the effective voltages (Vrb1 and Vrb2 at that time) ) Can be confirmed to have the correct voltage value shown in FIG.

  Similarly, when the normal output state is OFF, the switches SW1 to SW4 are sequentially switched to the states (states 1 to 3, 5 to 7, and 9 to 11) in which the “output state” is OFF in FIG. By confirming that the effective voltages (Vrb1 and Vrb2) are the correct voltage values shown in FIG. 2, the soundness of each switch can be self-diagnosed.

  FIG. 3 shows effective voltages (Vrb1 and Vrb2) that are detected when any one of the transistors constituting the switch SW1 or the switch SW2 is turned on (failed to be fixed on). For example, the upper stage of “State 1” shows a state in which one of the transistors Q11 and Q12 constituting the switch SW1 is on-failed, and “↓” indicates that the transistor Q11 is on-failed and passes through a parasitic diode of the transistor Q12. This means that current flows. “↑” means that the transistor Q12 is turned on and a current flows through the parasitic diode of the transistor Q11.

  As shown in FIG. 3, when an on failure occurs in the transistor, an effective voltage (Vrb1) different from that in the normal state shown in FIG. 2 is detected, so that the occurrence of the failure can be detected.

  Similarly, when an on failure occurs in the switch SW3 or the switch SW4, the occurrence of the failure can be detected based on the effective voltage (Vrb2).

  If any of the switches SW1 to SW4 has an off-failure (failure stuck to the off-state), the state corresponds to one of the state groups shown in FIG. 2, and is based on the effective voltage (Vrb1, Vrb2). An off-fault is detected. For example, when the switch SW4 has an off failure, the effective voltages (Vrb1 and Vrb2) are the same as the “state 1” in FIG. 2 when the state of each switch is “state 2”. For this reason, it is possible to detect an OFF failure of the switch SW4 based on the effective voltage.

  As described above, in the switching device of this embodiment, the switch group can perform self-diagnosis while maintaining the output state regardless of whether the normal output state is on or off. It is possible to perform maintenance such as. Further, diagnosis by superimposing pulses on the power supply can be made unnecessary, and disturbance to the load can be prevented.

  However, it is difficult to detect a failure in which the resistance values of the switches SW1 to SW4 increase when the switch is on only by monitoring the voltage. The monitoring of the current values (Irb1, Irb2) is intended to detect a failure of the switches SW1 to SW4 in such a mode that the resistance value increases.

  FIG. 4 shows the voltages (Vrb1, Vrb2) and currents that are monitored when a failure occurs in a mode in which the resistance value of the switches is large when all the switches SW1 to SW4 are on (“state 16” in FIG. 2). (Irb1, Irb2) is shown.

  In the example of FIG. 4, the voltage (Vrb1, Vrb2) and current (Irb1, Irb2) detected when the on-resistance value of the switches SW1 to SW4 in a normal state is 0.2Ω and the impedance of the load 2 is 100Ω or 500Ω. ).

  Here, for example, even when the on-resistance value of the switch SW2 shows an abnormal value of 1Ω which is five times the normal state, the change in the voltage (Vrb1, Vrb2) is very small, and the on-resistance value abnormality is detected. I can't.

  Further, in the monitoring of only the voltages (Vrb1, Vrb2), if one of the switches has failed before the self-diagnosis is performed, an unintended output state is caused by the on / off switching operation of the switches SW1 to SW4 during the self-diagnosis. There is a problem of becoming. For example, in the example of FIG. 4, even when the on-resistance value of the switch SW2 is infinite, the self-diagnosis is performed starting from the state in which all the switches SW1 to SW4 are on (“state 16” in FIG. 2). In this state, the abnormality of the switch SW2 cannot be detected based on the voltages (Vrb1, Vrb2). The diagnosis is started from this state, and when the switch SW3 and the switch SW4 are turned off, the output state is unintentionally turned off.

  On the other hand, based on the current (Irb1, Irb2), an increase in the on-resistance value of the switch can be easily detected.

  As shown in FIG. 4, when all the switches SW1 to SW4 are turned on (“state 16” in FIG. 2), if the on resistance values of all the switches SW1 to SW4 are normal, the current (Irb1) The current (Irb2) matches. On the other hand, when an abnormality occurs in the on-resistance value of the switch SW2, the current (Irb1) corresponds to the combined resistance value of the switches SW1 and SW2, and the current (Irb2) corresponds to the combined resistance value of the switches SW3 and SW4. Since the values to be shown are respectively shown, the ratio of these currents becomes sufficiently large, and an increase in the on-resistance value can be easily detected. For example, when the on-resistance value of the switch SW2 is 1Ω, the current ratio (Irb2 / Irb1) is tripled regardless of the impedance of the load 2. Therefore, an abnormality in the resistance value of the switch is easily detected.

  Further, by executing abnormality detection based on such currents (Irb1, Irb2) before executing the self-diagnosis by switching the switches SW1 to SW4, it is possible to prevent an unintended output state from occurring.

  The number of switches in series and the number in parallel are not limited to two, and may be three or more. The power source may be a DC power source.

  Hereinafter, the switching device according to the second embodiment will be described with reference to FIG.

  FIG. 5 is a diagram illustrating a circuit configuration of the switching device according to the second embodiment. The same components as those in the first embodiment are denoted by the same reference numerals.

  As shown in FIG. 5, the switching device of the present embodiment is configured by using four switches SW1 to SW4, as in the first embodiment. The switch SW1 is configured by combining N-type field effect transistors (MOSFETs) Q11 and Q12. The switches SW2 to SW4 are configured similarly. The switches SW1 to SW4 can be controlled independently of each other by the control circuit 4.

  As shown in FIG. 1, in the switching device of this embodiment, two switches (switch SW1 and switch SW2) that can be independently controlled on / off are provided between an AC power supply 1 having an effective voltage value of 100 V and a load 2. The midpoints of the resistors (R1, R2) of the same resistance value connected in series and connected in series so as to divide the AC voltage V of the AC power supply 1 are connected to the midpoint of the switch SW1 and the switch SW2. . The voltage at the midpoint (Vrb1) is monitored by the voltage monitoring circuit 31.

  Similarly, two switches (switch SW3 and switch SW4) that can be controlled on / off independently are connected in series between the AC power source 1 and the load 2 so that the AC voltage V of the AC power source 1 is divided. The midpoint of the resistors (R3, R4) having the same resistance value connected in series is connected to the midpoint of the switch SW3 and the switch SW4. The voltage at the midpoint (Vrb2) is monitored by the voltage monitoring circuit 31.

  The resistance values of the resistors R1 to R4 are normally high resistance values that do not affect the load 2 in the off state.

  As shown in FIG. 5, in the switching device of the present embodiment, the current (Irb) flowing through the load 2 is measured by the current detector CT, and the measured current value is monitored by the current monitoring unit 51. The current monitoring unit 51 is connected to a rotary buffer 52 that sequentially stores measured current values.

  The monitoring result in the voltage monitoring circuit 31 is given to the control unit 41, and the control unit 41 controls the four switches SW1 to SW4 independently based on the monitoring result. Self-diagnosis based on the voltage monitored via the voltage monitoring circuit 31 is executed in the same procedure as in the first embodiment.

  Next, the current monitoring operation in the current monitoring unit 51 will be described.

  In the switching device of the first embodiment, the effective value of the current is monitored. However, in order to measure the effective value, it is necessary to detect and calculate the potential of at least one cycle of the AC power supply. When the frequency of the power supply 1 is 50 Hz, the cycle is 20 ms, and when it is 60 Hz, the cycle is 16.66 ms. In addition, when the same diagnostic operation is applied to both 50 Hz and 60 Hz as the frequency of the power supply 1, it takes 100 ms as a time to obtain a diagnostic result. Therefore, a response time is required until the diagnosis result is reflected in the operation, and an unintended output state may occur.

  On the other hand, in the switching device of the present embodiment, the occurrence of an abnormality or the occurrence of an unintended output state can be immediately detected by synchronizing the diagnosis operation in the current monitoring unit 51 with the change in the power supply voltage.

  FIG. 6 is a flowchart showing the operation of the current monitoring unit 51, and FIG. 7 is a diagram showing a write operation to the rotary buffer 52. Here, a case where the frequency of the power supply is 50 Hz and the size of the rotary buffer 52 is made to correspond to data for 20 ms will be described.

  Steps S <b> 1 to S <b> 2 in FIG. 6 indicate the startup process in the current monitoring unit 51. This process is executed after power-on and subsequent reset release, and generates a trigger at the period of the fixed-cycle timer. Timer interrupt processing is executed by this trigger.

  In step S1 of FIG. 6, the fixed period timer is started. Subsequently, in step S2, the process of generating a trigger is repeated after the timer expires. As a result, the trigger is repeatedly generated with the period of the fixed period timer. The cycle of the fixed cycle timer is a time that is a divisor of an integral multiple of the power cycle (time corresponding to 1/16 of the power cycle in the example of FIG. 7), and the rotary buffer 52 has an integral multiple of the power cycle. The AD (analog / digital) conversion result of the current measurement value sampled by a divisor of is stored.

  Steps S11 to S17 in FIG. 6 show timer interrupt processing in the current monitoring unit 51 executed in response to the trigger.

  In step S11 of FIG. 6, AD conversion is performed on the current value measured by the current detector CT.

  Next, in step S12, the reference destination data in the rotary buffer 52 is read with reference to the write pointer.

  Next, in step S13, the data obtained in step S11 is compared with the data read in step S12, and it is determined whether or not the difference between the two is within a predetermined range. Here, the size of the rotary buffer 52 corresponds to 20 ms worth of data and corresponds to one cycle of the AC power supply. For this reason, the reference destination data at the position indicated by the write pointer is data for one cycle before, and if no abnormality has occurred during that period, the data should match. In the example of FIG. 7, the buffer area of the rotary buffer 52 is divided into 16, and data (AD0, AD1, AD2,... AD16) is written every 1/16 period. Each buffer area is sequentially overwritten with data shifted in timing by one period.

  If the determination in step S13 is affirmed, the process proceeds to step S14. If the determination is negative, the process proceeds to step S15.

  In step S14, the error counter is cleared and the process proceeds to step S16. On the other hand, in step S14, the error counter is incremented and the process proceeds to step S16.

  In step S16, the data obtained in step S11 is stored (overwritten) in the buffer pointed to by the write pointer.

  In step S17, the write pointer is updated to the next buffer, and the process returns from the interrupt process.

  As described above, while the data before one cycle does not match the current data (there is a difference of a predetermined range or more), the error counter is incremented, and the consecutive number of mismatches is presented as the error count number. . The error counter number is given to the control unit 41 in real time, and when the error count number exceeds a predetermined value, it is determined that there is an abnormality and a predetermined process is executed.

  It should be noted that the responsiveness of the process to the occurrence of abnormality can be adjusted by the error count number determined to be abnormal. In addition, erroneous detection of an abnormality can be prevented.

  In addition, by making the size of the rotary buffer correspond to data by AD conversion for 100 ms, data for 6 cycles of 50 Hz or 5 cycles of 60 Hz can be stored, so that the power cycle is 50 Hz or 60 Hz. This can be done without switching firmware. In this case, it is not a comparison with the data of the previous cycle, but the instantaneous value of the current obtained by multiplying the instantaneous value of the current current by an integral multiple (5 or 6 times) of the cycle of the AC power supply (5 cycles). It is compared with the data of the previous or 6 cycles).

  As described above, according to the switching device of the present embodiment, the occurrence of abnormality can be detected immediately. In addition, the responsiveness and sensitivity of the abnormality determination can be optimized by adjusting the abnormality determination condition by the error count threshold value or the like.

  FIG. 8 is a diagram illustrating a configuration example in which two current detectors are provided.

  In the example of FIG. 8, the current (Irb1) of the switching circuit including the switches SW1 and SW2 is detected by the current detector CT1, and the current (Irb2) of the switching circuit including the switches SW3 and SW4 is detected by the current detector CT2. And supplied to the current monitoring unit 51A. The current monitoring unit 51A stores the current flowing through the load 2, that is, the sum of the current (Irb1) and the current (Irb2) in the rotary buffer 52, and the current sum of the current (Irb1) and the current (Irb2) and the rotary buffer The data stored in 52 is compared.

  In the case of the configuration shown in FIG. 8 as well, the occurrence of an abnormality can be detected quickly as in the configuration shown in FIG.

As described above, according to the switching device of the present invention, since the current at the time of control execution is monitored by the current monitoring means, the abnormality of the switching device can be detected with high accuracy while maintaining the state of the power supply with respect to the load. Reliability can be obtained.
Further, since the instantaneous value of the current acquired in accordance with the cycle of the AC power supply is monitored, abnormality detection can be performed immediately.

  The scope of application of the present invention is not limited to the above embodiment. The present invention can be widely applied to switching devices capable of selecting on / off of a power supply for a load by switching a switch.

It is a figure which shows the structure of the switching apparatus of Example 1, (a) is a figure which shows the circuit structure of a switching apparatus, (b) is a figure which shows the structure of a switch. The figure which shows the relationship between the state of each switch at the time of normal operation | movement, and the voltage monitored. The figure which shows the effective voltage (Vrb1 and Vrb2) detected at the time of an ON failure. The figure which shows the voltage (Vrb1, Vrb2) and electric current (Irb1, Irb2) monitored at the time of the failure in the mode where the resistance value of a switch becomes large. FIG. 6 is a diagram illustrating a circuit configuration of a switching device according to a second embodiment. The flowchart which shows operation | movement of a current monitoring part. The figure which shows write-in operation to a rotary buffer. The figure which shows the structural example which provided two electric current detectors.

Explanation of symbols

1 Power supply 2 Load 4 Control circuit (control means)
5 Current monitoring circuit (current monitoring means)
41 Control unit (control means)
51 Current monitoring unit (current monitoring means)

Claims (5)

In a switching device capable of selecting an on / off state of a power supply for a load by switching a switch,
A network formed between a power source and a load and including a plurality of switches in the circuit;
Control means for independently controlling the plurality of switches included in the circuit network;
Current monitoring means for monitoring a current in a circuit in the network;
With
The control means executes control for sequentially switching the states of the plurality of switches under the condition of maintaining the on / off state of the power supply with respect to the load, and the current monitoring means monitors the current when the control is executed. A switching device characterized by: 2. The switching device according to claim 1, wherein the current monitoring unit monitors a current flowing in each of the switching circuits in which the switches are inserted and connected in parallel in the circuit network. The switching device according to claim 1, wherein the power source is an AC power source, and the current monitoring unit monitors an effective value of the current. 3. The switching device according to claim 1, wherein the power source is an AC power source, and the current monitoring unit monitors an instantaneous value of a current acquired in accordance with a cycle of the AC power source. The current monitoring unit monitors the current value by comparing the instantaneous value of the current current with the instantaneous value of the current acquired by an integer multiple of the period of the AC power supply. The switching device according to claim 4.

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