JP4043626B2 - Load drive circuit - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention provides a load constituted by connecting in series a normal cut-off switch that directly turns ON / OFF a load current supplied to a load and an emergency cut-off switch that forcibly cuts off the load current when the normal cut-off switch is ON. The present invention relates to a drive circuit.
[0002]
[Prior art]
  For example, when driving and controlling machine moving parts,WorkIn view of the safety of the user, etc., the ability to be stopped when it should be stopped is regarded as important and a redundant configuration is adopted. For example, when the energization of the machine movable part is controlled, two switches are interposed in series with the energization circuit, and even if an ON failure occurs in one switch, the energization path can be forcibly cut off by the other switch. A load driving circuit using such a series double system configuration is known, for example, from International Publication WO98 / 10452.
[0003]
  Figure9Shows an example of a conventional load driving circuit having such a series double system configuration.
  Figure9In FIG. 2, the operation contacts (turned ON during excitation) 2a and 3a of the electromagnetic relays 2 and 3 are interposed in series in the energization circuit 1 of the load (not shown). As the electromagnetic relays 2 and 3, forcible operation type electromagnetic relays having return contacts 2b and 3b in which ON / OFF operations are complementary to each other are used. When the load drive signal is input, the relay control circuit 4 outputs an output (an AC signal) on condition that the return contacts 2b and 3b are ON (referred to as back check by confirming that the operation contacts 2a and 3a are OFF). And a sequence circuit 5 having a self-holding function for self-holding the output and an on-delay function for turning on / off the output of the self-holding circuit. A relay drive circuit 6 including an AC amplifier 6A, a transformer 6B, a rectifier circuit 6C, and an off-delay circuit 6D that directly receives a self-holding output as a 1 system is provided to drive the electromagnetic relay 2 and an on-delay as a 2 system. A semiconductor switch circuit 7 that receives the output and drives the electromagnetic relay 3 is provided.
[0004]
Therefore, at the start of load energization, the first system operation contact 2a is turned on and then the second system operation contact 3a is turned on. At the end of load energization, the second system operation contact 3a is turned off and then the first system operation is performed. The contact 2a is turned off.
[0005]
  The relationship between the load drive signal IN, the ON / OFF operation of the operation contacts 2a and 3a, and the load current I is shown in FIG.10become that way.
  In other words, the 1 system operating contact 2a does not cut off the load current directly,forThe two-system operating contact 3a has a function of a cutoff switch, and has a function of a normal cutoff switch that directly controls the cutoff / energization of the load current. In this circuit, whether the semiconductor switch OFF function is normal can be confirmed by intermittently turning off the semiconductor switch in a time period that does not affect the load operation during load energization.
[0006]
  In addition, as another conventional example,11As shown in FIG. 4, the common cut-off switch side is constituted by a parallel double system by a parallel circuit of two operating contacts 3a and 3a ', and the electromagnetic relays 3 and 3' are driven by the semiconductor switch circuits 7 and 7 ', respectively. And figure12As shown in the time chart, the two electromagnetic relays 3 and 3 'are alternately turned on and off during the load energization. In the drawing, 3b 'indicates a return contact of the electromagnetic relay 3'.
[0007]
  In this circuit, the normal confirmation of the OFF function of the electromagnetic relay on the side of the normal cut-off switch can be confirmed by repeating the ON / OFF operation of the return contact of each electromagnetic relay while the load is energized. The figure9The same parts as those in FIG.
[0008]
[Problems to be solved by the invention]
However, the above-described conventional load driving circuit requires a fail-safe off-delay circuit or on-delay circuit to guarantee the operation sequence of the first and second systems, and the configuration of the relay control circuit is complicated. . In addition, since the transformer coupling is used for driving the electromagnetic relay, there is a problem that the circuit becomes large when the output is large.
[0009]
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a load driving circuit that can be simplified and downsized in circuit configuration and that has high reliability.
[0010]
[Means for Solving the Problems]
  For this reason, in claim 1 of the present invention, the load power supply circuit is provided with a normal cut-off switch and an emergency cut-off switch in series, and the emergency cut-off switch and the normal cut-off switch are turned on in this order when a load drive signal is input. In a load drive circuit configured to drive and supply power to the load, and to stop the power supply of the load by driving OFF in the order of the normal cut-off switch and the emergency cut-off switch when the load drive signal is stopped. 1 operation contact and 2nd operation contactA first return contact that performs ON / OFF operation in a complementary relationship with the first operation contact, and a second return contact that performs ON / OFF operation in a complementary relationship with the second operation contact,An electromagnetic relay having a configuration in which a distance between the movable contact and the fixed contact of the first operation contact is shorter than a distance between the movable contact and the fixed contact of the second operation contact is provided, and the first operation contact of the electromagnetic relay is used as the emergency cutoff switch. And the second operating contact as the normal cut-off switch,Provided with the condition that both the first and second return contacts are ON, relay control means for outputting a relay drive signal in response to the input of the load drive signal is provided, and the relay control means is connected to the first trigger terminal. A self-holding circuit for inputting a trigger signal when both the second return contact and the second return contact are ON, inputting the load drive signal to a hold terminal to generate an output, and holding the trigger signal by the output; A relay drive circuit for generating the relay drive signal via a transformer coupling based on an outputThe configuration.
[0011]
  In such a configuration,negativeWhen the load driving signal is input, the electromagnetic relay is excited. In this case, the first operation contact with a short distance between the movable contact and the fixed contact is turned on first, and then the second operation contact is turned on. When the load drive signal is stopped and the electromagnetic relay is de-energized, the second operation contact is turned off first, and then the first operation contact is turned off.Further, when both the first and second return contacts of the electromagnetic relay are ON, that is, when the OFF function of the first and second operation contacts is normal, the electromagnetic relay is excited by the input of the load drive signal. It becomes like this. Furthermore, since the electromagnetic relay is driven using an AC signal by transformer coupling, a fail-safe relay driving circuit is obtained.
[0015]
  In the invention of claim 2, the load power supply circuit is provided with a normal cut-off switch and an emergency cut-off switch in series, and when the load drive signal is input, the emergency cut-off switch and the normal cut-off switch are turned on in this order to load In the load drive circuit configured to stop the power supply of the load by driving OFF in the order of the normal cut-off switch and the emergency cut-off switch when the load drive signal is stopped, A second operating contact; a first return contact that operates ON / OFF in a complementary relationship with the first operating contact; and a second return contact that performs ON / OFF operation in a complementary relationship with the second operating contact; A plurality of electromagnetic relays having a configuration in which the distance between the movable contact and the fixed contact of the first operating contact is shorter than the distance between the movable contact and the fixed contact of the second operating contact are provided, and each first operating contact of these electromagnetic relays is cut off for emergency use. The The relay drive signal is output by the input of the load drive signal on the condition that each of the second operation contacts is the normal cutoff switch and both the first and second return contacts are ON. Relay control means,The relay control meansTheA self-holding circuit that receives a trigger signal when the first and second return contacts are both turned on to the trigger terminal, generates an output when the load drive signal is input to the hold terminal, and self-holds the trigger signal with the output. And a plurality of semiconductor switch circuits that are provided for each of the plurality of electromagnetic relays and output a relay drive signal to each corresponding electromagnetic relay based on the output of the self-holding circuit.
[0016]
In such a configuration, the load energization control becomes a multi-system configuration, and the function of interrupting the energization of the load is not lost unless an ON failure occurs in all the semiconductor switch circuits.
[0017]
  Claim3Then, each of the semiconductor switch circuits is connected in series with the electromagnetic relay, and is turned on / off by turning on / off of a pulse signal input based on the output of the self-holding circuit, thereby energizing / cutting off the current to the load electromagnetic relay. A relay energizing semiconductor switch for controlling the relay, and a relay short-circuiting semiconductor switch that is connected in parallel to the electromagnetic relay and that is turned ON / OFF by the ON / OFF of the pulse signal to short-circuit both ends of the electromagnetic relay. When the semiconductor switch for energization is in an ON failure, the energization path of the electromagnetic relay is interrupted due to the occurrence of an overcurrent, and a failure detection function is provided that generates a failure detection output when a circuit failure occurs.
[0018]
In such a configuration, when the relay energizing semiconductor switch fails, an overcurrent flows when the relay short-circuiting semiconductor switch is turned on, and the energizing path of the relay is interrupted. Further, when a circuit failure occurs, the failure detection function can detect the failure.
[0019]
  Claim4Then, each said semiconductor switch circuit is provided with two each of the said semiconductor switches for relay energization and the semiconductor switch for relay short circuit, the series circuit of each semiconductor switch for one relay energization and relay short circuit, and for the other relay energization And a series circuit of each semiconductor switch for relay short circuit are connected in parallel between the power supply terminal and the ground terminal to form a bridge circuit, and the semiconductor switches of each series circuit are connected to each other to interpose an electromagnetic relay. In addition, a photocoupler for detecting a circuit failure is provided in parallel with the electromagnetic relay.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of a load driving circuit of the present invention will be described with reference to the drawings.
FIG. 1 is a configuration diagram of a first embodiment of a load driving circuit according to the present invention.
[0021]
In FIG. 1, the load drive circuit of this embodiment outputs a relay drive signal when a load drive signal IN is input on condition that two return contacts b1 and b2 of an electromagnetic relay 20 to be described later are both in an ON state. A relay control circuit 10 is provided as a relay control means.
[0022]
  The relay control circuit 10 includes the return contactb1, b2When both are ON, the operation confirmation contacts a1 and a2 OFF confirmation signal (power supply voltage V_CC) Is input to the trigger terminal T as a trigger signal, and when the load drive signal IN is input to the hold terminal H, an AC output is generated, and this AC output is fed back to the trigger terminal T to self-hold the trigger signal. 11 and a relay drive circuit 12 that outputs a relay drive signal that excites the electromagnetic relay 20 via a transformer coupling based on the AC output of the self-holding circuit 11. As the self-holding circuit, a fail-safe circuit known in International Publication WO94 / 23303, International Publication WO94 / 23496, etc. using a fail-safe AND operation oscillator can be used.
[0023]
  The relay drive circuit 12 amplifies the AC output of the self-holding circuit 11.circuit12A and AC amplification input to the primary sidecircuitA transformer 12B that transmits the amplified output of 12A to the secondary side, and a rectifier circuit 12C that rectifies the AC output of the transformer 12B and outputs a relay drive signal to the electromagnetic relay 20 are provided.
[0024]
Two operation contacts a1 and a2 of the electromagnetic relay 20 are configured to be interposed in series in a load power supply circuit 14 for supplying power to a load (not shown).
In FIG. 2, the contact structure of the electromagnetic relay 20 of this embodiment is shown.
[0025]
In FIG. 2, the electromagnetic relay 20 of this embodiment is turned on / off in a complementary relationship with the two first and second operation contacts a1 and a2 and the first and second operation contacts a1 and a2, respectively. First and second return contacts b1 and b2 that perform an OFF operation are provided.
[0026]
The first and second operation contacts a1 and a2 include movable contacts a11 and a21 and fixed contacts a12 and a22, respectively. The first and second return contacts b1 and b2 are movable contacts b11 and a11, respectively. b21 and fixed contacts b12 and b22.
[0027]
The movable contacts a11, a21, b11, b21 move in the right direction in the figure (in the direction of the arrow in the figure) when excited, and move in the direction opposite to the arrow direction due to, for example, the elastic return force of the spring during non-excitation. The movable insulating plate 21 that returns to the original position is fixed as shown in the figure via a flexible support member. The fixed contacts a12, a22, b12, b22 are fixed to the fixed insulating plate 22 facing the movable insulating plate 21 through a flexible support member as shown in the figure. The return force of the movable insulating plate 21 may be set to a force that can secure the separation distance x1 of the first operating contact a1 even if the second operating contact a2 is welded.
[0028]
The distance x1 between the movable contact a11 and the fixed contact a12 of the first operating contact a1 and the distance x2 between the movable contact a21 and the fixed contact a22 of the second operating contact a2 are shorter than the distance x2 (x1 <x2). Is set.
[0029]
Therefore, as shown in FIG. 3, in the electromagnetic relay 20 of the present embodiment, the second operation contact a2 is turned on after the first operation contact a1 is turned on as the electromagnetic force is increased at the time of excitation, and at the time of non-excitation. Conversely, the first operation contact a1 is turned off after the second operation contact a2 is turned off as the electromagnetic force decreases. Here, the first operation contact a1 has a function of an emergency cut-off switch for interrupting the load power supply circuit 14 in an emergency, and the second operation contact a2 is used for interrupting the current of the load power supply circuit 14 at a normal time. It has a function of a cutoff switch.
[0030]
  Next, the operation of the circuit of the first embodiment will be described.
  If the first and second operation contacts a1 and a2 of the electromagnetic relay 20 are normally in the OFF state at the start of power supply to the load, the first and second return contacts b1 and b2 are in the ON state and the power supply voltage V_CCIs input to the trigger terminal T of the self-holding circuit 11 of the relay control circuit 10. In this state, when the load drive signal IN is input to the hold terminal H, an AC output is generated from the self-holding circuit 11, and the AC amplification of the relay drive circuit 6 is performed.Circuit 12A,Trance12BAnd rectifier circuit12CThus, the electromagnetic relay 20 is excited. As a result, the first operation contact a1 is turned on, and then the second operation contact a2 is turned on, the load power supply circuit 14 is closed and power is supplied to the load. When the first operation contact a1 is turned on, the return contact b1 is turned off, but the self-holding function of the self-holding circuit 11 continues the output of the self-holding circuit 11 and energization of the load continues.
[0031]
When the load drive signal IN stops, the output of the self-holding circuit 11 stops and the electromagnetic relay 20 is de-excited. As a result, the second operation contact a2 is turned off first to stop the power feeding of the load, and then the first operation contact a1 is turned off. If the first and second operation contacts a1 and a2 are normally turned off, the first and second return contacts b1 and b2 are turned on, and the OFF confirmation signals of the first and second operation contacts a1 and a2 are self-holding circuit 11. To the next trigger power supply operation.
[0032]
When a welding failure occurs in the second operation contact a2, the first operation contact a1 is turned off by stopping the load drive signal IN, and the power supply to the load can be stopped. In the next power feeding operation, the second return contact b2 is not turned ON and a relay OFF confirmation signal is not generated, so that no relay drive signal is generated from the relay control circuit 10 and power is not supplied to the load.
[0033]
According to this configuration, it is not necessary to use an off-delay circuit, an on-delay circuit, or the like as in the prior art, and the configuration of the relay control circuit can be simplified. Moreover, since it is set as the structure which drives the electromagnetic relay 20 using an alternating current signal by a transformer coupling, it becomes fail safe signal processing and safety | security does not fall.
[0034]
FIG. 4 is a configuration diagram of the second embodiment of the present invention.
In FIG. 4, the load drive circuit according to the present embodiment is configured such that the operation contacts a1A, a2A and a1B, a2B of the two electromagnetic relays 20A, 20B having the structure described in the first embodiment are connected to the load power supply circuit 14 in series. Disguise. The return contacts b1A, b2A and b1B, b2B of the electromagnetic relays 20A, 20B are also connected to the power supply voltage V_CCThe terminal and the trigger terminal T of the self-holding circuit 31 of the relay control circuit 30 are connected in series. The relay control circuit 30 of the present embodiment includes a semiconductor switch that drives the electromagnetic relay 20A by the output of the output control circuit 31 having the self-holding circuit shown in FIG. 1 and the output control circuit 31 based on the output of the self-holding circuit. The circuit 32 and the semiconductor switch circuit 33 that drives the electromagnetic relay 20B based on the output of the output control circuit 31 are also provided.
[0035]
FIG. 5 shows an example of the semiconductor switch circuits 32 and 33. The semiconductor switch circuits 32 and 33 have the same configuration.
In FIG. 5, the power supply voltage V_CCA fuse F, resistors R1, R2, and an NPN transistor Q1 are sequentially connected in series between the terminal and the GND terminal. A series circuit of a PNP transistor Q2 and an NPN transistor Q3 is connected in parallel to the series circuit of the resistors R1, R2 and the NPN transistor Q1. The intermediate point between the resistors R1 and R2 is connected to the base of the transistor Q2, and the collector terminal of the transistor Q1 is connected to the base of the transistor Q3. A capacitor C is connected between the collector terminals of the transistors Q2 and Q3 via a resistor. In parallel with the transistor Q3, the electromagnetic relay 20A is connected in the semiconductor switch circuit 32, and the electromagnetic relay 20B is connected in the semiconductor switch circuit 33. Here, the transistor Q2 has a function of a relay energizing semiconductor switch, and the transistor Q3 has a function of a relay short-circuiting semiconductor switch.
[0036]
In the semiconductor switch circuits 32 and 33, when an input signal having a pulse waveform as shown in FIG. 5 is input to the base of the transistor Q1, the transistor Q1 is turned on, the transistor Q2 is turned on, and the transistor Q3 is turned off. The relay is energized. When the input signal changes from ON to OFF, the transistor Q1 is turned OFF, the transistor Q2 is turned OFF, the transistor Q3 is turned ON, and the electromagnetic relay is de-energized. The OFF time of the input signal is set sufficiently short so that the operation contacts a1A, a2A and a1B, a2B of the electromagnetic relays 20A, 20B can be maintained in the ON state.
[0037]
According to the semiconductor switch circuits 32 and 33, when a short circuit (ON side) failure occurs in the transistor Q2, the transistor Q3 is turned on when the input signal is turned off, the power supply voltage terminal and the GND terminal are short-circuited, and an overcurrent is generated. By flowing, the fuse F is blown, and the output of the semiconductor switch circuit is stopped. Even if the fuse F is not blown, an AC signal is generated at the point V1 in FIG. 5 when the transistor Q2 is short-circuited. Therefore, by rectifying the AC signal via the AC coupling by the capacitor C and extracting the output, the transistor It is possible to detect a short-circuit fault in Q2. The capacitor C serves as a circuit failure detection function. When a disconnection (OFF side) failure occurs in the transistor Q2, the charging time constant of the failure detection capacitor C becomes longer, and the amplitude of the AC output signal decreases.
[0038]
Next, the operation will be described.
When the electromagnetic relays 20A and 20B are normal, an input signal having a pulse waveform intermittently turned off as shown in FIG. 5 is generated from the output control circuit 31 based on the output of the self-holding circuit by the input of the load drive signal IN. . By this input signal, a relay drive signal is generated from each of the semiconductor switch circuits 32 and 33, and each of the electromagnetic relays 20A and 20B is driven. In this case, the first operation contacts a 1A and a 1B of the electromagnetic relays 20A and 20B are turned on, and then the second operation contacts a 2A and a 2B are turned on and a load current flows through the load power supply circuit 14. When the load drive signal IN stops, the second operation contacts a 2A and a 2B are turned OFF to stop the power feeding of the load, and then the first operation contacts a 1A and a 1B are turned OFF.
[0039]
According to such a configuration, even when an output ON failure (failure in which output continues to occur) occurs in either one of the semiconductor switch circuits 32 and 33, if the load drive signal IN stops, the normal-side semiconductor switch circuit As a result, the electromagnetic relay is driven to stop feeding the load. That is, the two electromagnetic relays 20A and 20B constitute a series double system to form a redundant configuration. As a result, safety can be ensured even if a semiconductor switch circuit is used without using transformer coupling, and the load drive circuit can be easily downsized.
[0040]
However, in the configuration of the semiconductor switch circuit of FIG. 5, when a short circuit failure occurs in the transistor Q1, the ON state of the transistor Q2 and the OFF state of the transistor Q3 continue regardless of the presence or absence of an input signal, and the relay drive signal blocking ability Is lost and the electromagnetic relay continues to be excited. Therefore, when the short circuit failure of the transistor Q1 occurs in both the semiconductor switch circuits 32 and 33, it becomes impossible to cut off the power supply of the load.
[0041]
FIG. 6 shows another configuration example of the semiconductor switch circuit. In addition, the same code | symbol is attached | subjected to the same element as FIG.
In FIG. 6, a voltage doubler rectifier circuit including capacitors C1 and C2 and diodes D1 and D2 is provided between the resistor R3 and the collector of the transistor Q1 and the base of the transistor Q2, and the output terminal V2 of the voltage doubler rectifier circuit is provided. (A connection point between the diode D2 and the capacitor C2) is connected to the base of the transistor Q2. In the transistor Q2, the voltage at the output terminal V2 is the power supply voltage V._CCWhen it is larger, it is turned off and the power supply voltage V_CCTurns on when: Also, resistors R4 and R5 that divide the output voltage of the output terminal V2 are provided, and this voltage dividing point is connected to the base of the transistor Q3. The resistors R4 and R5 have an output voltage at the output terminal V2 of the power supply voltage V._CCWhen it is higher, the transistor Q3 is turned on and the power supply voltage V_CCThe resistance value is set so that the transistor Q3 is turned off at the following times. The electromagnetic relays 20A and 20B are connected in parallel to the transistor Q2 and connected in series to the transistor Q3. Accordingly, in the semiconductor switch circuits 32 'and 33', the transistor Q2 has a function of a relay short-circuiting semiconductor switch, and the transistor Q3 has a function of a relay energizing semiconductor switch.
[0042]
As shown in FIG. 6, the semiconductor switch circuits 32 'and 33' use a high-frequency signal that is intermittently turned OFF as an input signal. The relationship between this input signal and the output voltage at the output terminal V2 is shown in FIG.
[0043]
In such a configuration, during the period when the high-frequency signal is ON, the power supply voltage V_CCA higher voltage doubled rectified output is generated at the output terminal V2. At this time, the transistor Q2 is turned off, the transistor Q3 is turned on, and the electromagnetic relays 20A and 20B are excited. During the period when the high frequency signal is OFF, the voltage at the output terminal V2 is the power supply voltage V_CCIn the following, the transistor Q2 is turned on, the transistor Q3 is turned off, and the electromagnetic relays 20A and 20B are de-excited.
[0044]
According to the configuration of the semiconductor switch circuits 32 'and 33', when a short circuit (ON side) failure occurs in the transistor Q1, the power supply voltage V is applied to the output terminal V2._CCHigher potentials cannot be generated. Accordingly, the transistor Q3 is not turned on and the electromagnetic relays 20A and 20B are de-energized, so that a relay drive signal continues to be generated due to a short circuit (ON side) failure in the transistor Q1 as in the semiconductor switch circuits 32 and 33 in FIG. The problem can be solved.
[0045]
In the circuit configuration of FIG. 6, when a disconnection (OFF side) failure occurs in the transistor Q2, the charge charged in the circuit failure detection capacitor C is discharged via the electromagnetic relays 20A and 20B. Therefore, the amplitude of the AC output signal decreases.
[0046]
By the way, the configuration of the semiconductor switch circuit of FIG. 5 and FIG. 6 includes a relay energizing semiconductor switch (transistor Q2 in FIG. 5, transistor Q3 in FIG. 6) and a relay shorting semiconductor switch (transistor Q3 in FIG. 5, transistor in FIG. Q2) is provided, and when a short circuit failure occurs in the relay energization semiconductor switch, the fuse F is blown by turning on the relay short circuit semiconductor switch, and the electromagnetic relay is de-energized. The disconnection (OFF side) failure of the relay short-circuiting semiconductor switch means the loss of this function, and the short-circuiting (ON side) failure of the relay energizing semiconductor switch in the situation where the OFF-side failure has occurred in the relay short-circuiting semiconductor switch. If this occurs, the electromagnetic relay continues to be excited and the power supply to the load cannot be stopped. For this reason, detection of an OFF-side failure of the relay short-circuit semiconductor switch is extremely important.
[0047]
FIG. 8 shows a configuration example of a semiconductor switch circuit that further reliably detects the OFF-side failure of the relay short-circuiting semiconductor switch. The same elements as those in FIGS. 5 and 6 are denoted by the same reference numerals.
[0048]
In FIG. 8, the semiconductor switch circuits 32 "and 33" constitute a bridge circuit with four transistors Q2, Q2 ', Q3 and Q3'. A series circuit of a diode D and an electromagnetic relay 20A (or 20B) is connected between the collector connection point of the transistors Q2 and Q3 'and the emitter connection point of the transistors Q3 and Q2'. In addition, a series circuit of a resistor and a photocoupler PC is connected in parallel to this series circuit.
[0049]
When transistors Q2 and Q2 'are turned on and current flows in the direction of the arrow in the figure, the electromagnetic relay is energized, and when transistors Q3 and Q3' are turned on and current flows in the direction opposite to the arrow in the figure, a photocoupler The light projecting element of the PC is turned on and an output is generated from the light receiving element. Therefore, the transistors Q2 and Q2 'have a function of a relay energizing semiconductor switch, and the transistors Q3 and Q3' have a function of a relay short-circuiting semiconductor switch. Transistors Q2, Q2 'and transistors Q3, Q3' are turned ON / OFF in a complementary relationship. As the switching circuit 40 for turning on / off the transistors Q2, Q2 ', Q3, and Q3', the circuit surrounded by the one-dot chain line in FIG. 5 is used in this embodiment, but the circuit surrounded by the one-dot chain line in FIG. It is also possible to use it.
[0050]
  Even if the diode D is short-circuited,2The movable insulating plate 21 is shown in the figure.2It is configured to move in the direction opposite to the arrow direction of FIG.
  In the semiconductor switch circuits 32 ″ and 33 ″, when the input signal having the pulse waveform shown in FIG. 5 is input, the transistors Q2 and Q2 ′ are turned on and the transistors Q3 and Q3 ′ are turned off during the ON period of the input signal. Is excited. During the OFF period of the input signal, the transistors Q2 and Q2 'are turned off, the transistors Q3 and Q3' are turned on, and the electromagnetic relay is de-energized. At this time, a current flows through the photocoupler PC and an output is generated from the light receiving element. This operation is repeated in synchronization with ON / OFF of the input signal.
[0051]
When the semiconductor switch circuits 32 ″ and 33 ″ having such a configuration operate normally, an AC signal is generated on the light receiving side of the photocoupler PC. If an ON-side failure occurs in one of the relay energizing transistors Q2 and Q2 ', if the relay short-circuiting transistors Q3 and Q3' are normal, the fuse F is blown (at this time, the photocoupler PC is disconnected). Does not generate an AC signal). If an OFF-side failure occurs in one of the relay short-circuit transistors Q3 and Q3 ', the photocoupler PC is not energized and no AC signal is generated. Therefore, the circuit failure of the semiconductor switch circuits 32 ″ and 33 ″ can be reliably detected by monitoring the output of the photocoupler PC.
[0052]
【The invention's effect】
As described above, according to the first aspect of the present invention, the off-delay circuit and the on-delay circuit are not required, and the configuration of the load driving circuit can be simplified.
[0053]
  AlsoSince the electromagnetic relay drive signal is not generated when the operation contact of the electromagnetic relay is not in the OFF state, the safety is high.
[0054]
  Furthermore, since the relay drive signal is generated by using the transformer coupling, the fail-safe configuration is achieved and the safety is high.
  Claim2-4According to the invention, since the electromagnetic relay has a double system configuration and the semiconductor switch circuit is used instead of the transformer coupling, safety can be ensured and the load driving circuit can be downsized.
[Brief description of the drawings]
FIG. 1 is a circuit configuration diagram of a first embodiment of the present invention.
FIG. 2 is a view showing a contact structure of the electromagnetic relay according to the embodiment.
3 is an ON / OFF characteristic diagram of the electromagnetic relay of FIG.
FIG. 4 is a circuit configuration diagram of a second embodiment of the present invention.
5 is a configuration diagram of the semiconductor switch circuit of FIG. 4;
FIG. 6 is another configuration diagram of the semiconductor switch circuit.
7 is a diagram showing the relationship between the input signal of FIG. 6 and the output voltage of the voltage doubler rectifier circuit.
FIG. 8 is still another configuration diagram of the semiconductor switch circuit.
FIG. 9 is a circuit configuration diagram showing an example of a conventional load driving circuit.
10 is a time chart of the relay operation contact operation of FIG. 9;
FIG. 11 is a circuit configuration diagram showing another example of a conventional load driving circuit.
12 is a time chart of the relay operation contact operation of FIG.
[Explanation of symbols]
10, 30 Relay control circuit
11 Self-holding circuit
12 Relay drive circuit
20, 20A, 20B Electromagnetic relay
31 Output control circuit
32, 32 ', 32 ", 33, 33', 33" Semiconductor switch circuit
a1, a2, a1A, a2A, a1B, a2B
b1, b2, b1A, b2A, b1B, b2B Return contact

Claims (4)

In the load power supply circuit, a normal cut-off switch and an emergency cut-off switch are connected in series. When the load drive signal is input, the emergency cut-off switch and the normal cut-off switch are turned on in this order to supply power to the load. In the load driving circuit configured to stop the power supply of the load by driving OFF in the order of the emergency cutoff switch and the emergency cutoff switch by stopping the signal,
A first operating contact and a second operating contact that are turned on at the time of excitation, a first return contact that operates ON / OFF in a complementary relationship with the first operating contact, and an ON / OFF in a complementary relationship with the second operating contact. and a second return contacts for operation, the distance between the movable contact and the fixed contact of the first operation contacts provided an electromagnetic relay of shorter configuration than the distance between the movable contact and the fixed contact of the second operating contact, wherein the said electromagnetic relay second The load drive signal is input on condition that one operation contact is the emergency cut-off switch, the second operation contact is the normal cut-off switch, and both the first and second return contacts are ON. And a relay control means for outputting a relay drive signal at the time when the first and second return contacts are both turned on at the trigger terminal, and the load drive signal at the hold terminal. A self-holding circuit for self-holding the trigger signal input to generate an output in the output, the configuration and a relay driving circuit for generating the relay drive signal via transformer coupling on the basis of the output of said self hold circuit A load driving circuit characterized by that. In the load power supply circuit, a normal cut-off switch and an emergency cut-off switch are connected in series. When the load drive signal is input, the emergency cut-off switch and the normal cut-off switch are turned on in this order to supply power to the load. In the load driving circuit configured to stop the power supply of the load by driving OFF in the order of the emergency cutoff switch and the emergency cutoff switch by stopping the signal,
A first operating contact and a second operating contact that are turned on at the time of excitation, a first return contact that operates ON / OFF in a complementary relationship with the first operating contact, and an ON / OFF in a complementary relationship with the second operating contact. A plurality of electromagnetic relays having a configuration in which the distance between the movable contact of the first operation contact and the fixed contact is shorter than the distance between the movable contact of the second operation contact and the fixed contact. The load drive signal is provided on the condition that each first operation contact is the emergency cut-off switch, each second operation contact is the normal cut-off switch, and both the first and second return contacts are ON. a relay control means for outputting a relay driving signal at the input of the relay control unit, a trigger signal is input when said first and second return contacts are both turned oN trigger pin, driving the load to the hold terminal A self-holding circuit that generates an output when a signal is input and self-holds a trigger signal by the output, and a relay to each electromagnetic relay corresponding to each of the plurality of electromagnetic relays based on the output of the self-holding circuit A load drive circuit comprising a plurality of semiconductor switch circuits each outputting a drive signal. Each of the semiconductor switch circuits is connected in series with the electromagnetic relay and is turned on / off by turning on / off a pulse signal input based on the output of the self-holding circuit to control current supply / cutoff to the load electromagnetic relay. A relay energizing semiconductor switch, and a relay short-circuiting semiconductor switch that is connected in parallel to the electromagnetic relay and short-circuits both ends of the electromagnetic relay by the ON / OFF operation of the pulse signal. 3. The load drive circuit according to claim 2 , wherein the load drive circuit has a failure detection function for interrupting the energization path of the electromagnetic relay due to the occurrence of an overcurrent when the semiconductor switch is in an ON failure, and generating a failure detection output in the event of a circuit failure. Each of the semiconductor switch circuits has two semiconductor switches for relay energization and two semiconductor switches for relay short-circuiting, one series of semiconductor switches for relay energization and one for relay short-circuit, and the other for relay energization and relay A series circuit of each semiconductor switch for short-circuiting is connected in parallel between the power supply terminal and the ground terminal to form a bridge circuit, and between the semiconductor switches of each series circuit is connected with an electromagnetic relay, 4. The load drive circuit according to claim 3 , wherein a photocoupler for detecting a circuit failure is provided in parallel with the electromagnetic relay.

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