JP6344086B2 - Control device - Google Patents

Description

  The present invention relates to a control device, and more particularly, to a power supply voltage abnormality process in a control device using a plurality of power supply voltages.

  Japanese Patent Application Laid-Open No. 4-276564 (Patent Document 1) and Japanese Patent Application Laid-Open No. 2002-82139 (Patent Document 2) describe a power supply voltage monitoring device in an apparatus using a plurality of power supply voltages.

  Patent Document 1 describes a configuration of a monitoring circuit for monitoring an abnormality in another power supply voltage using one power supply voltage among a plurality of power supply voltages. In particular, Patent Document 1 discloses a configuration in which an abnormality of another power supply voltage is detected by inputting divided voltages having different voltage dividing ratios of the one power supply voltage to two comparators, respectively.

  Patent Document 2 discloses a circuit configuration in which the same negative voltage is input to input terminals having different polarities for two comparators.

JP-A-4-276564 JP 2002-82139 A

  In a control device that uses a plurality of power supply voltages, particularly when the power supply voltage of a microcomputer for controlling a load varies, load control may be affected.

  In general, for a microcomputer, an operation guarantee voltage range of a power supply voltage is preset as a specification value. However, depending on the fluctuation level of the power supply voltage, even if the power supply voltage falls outside the guaranteed operating voltage range, the microcomputer does not always stop operating. During such an operation, there is a concern that the operation of the load is different from the normal operation due to the control by the microcomputer under the varied power supply voltage.

  The present invention has been made to solve such a problem, and an object of the present invention is to reliably control a microcomputer when a power supply voltage of the microcomputer is abnormal in a control device using a plurality of power supply voltages. It is to provide a power supply configuration for stopping.

  A control device according to the present invention includes a microcomputer for controlling a load, first and second power supply wirings, a voltage adjustment circuit, an abnormality detection circuit, and a voltage reduction circuit. The first power supply line transmits the first power supply voltage. The voltage adjustment circuit steps down the first power supply voltage of the first power supply wiring to generate a second power supply voltage. The second power supply wiring supplies the second power supply voltage generated by the voltage adjustment circuit to the microcomputer. The abnormality detection circuit detects an abnormality of the second power supply voltage based on a comparison between a voltage that changes according to the first power supply voltage and a voltage that changes according to the second power supply voltage. The voltage drop circuit is configured to operate without processing by the microcomputer when the abnormality detection circuit detects an abnormality in the second power supply voltage. The voltage lowering circuit lowers the second power supply voltage to a voltage region where the microcomputer becomes inoperable by lowering the voltage of the first power supply wiring input to the voltage adjusting circuit during operation.

  According to the above control device, when the abnormality of the second power supply voltage, which is the operating power supply of the microcomputer, is detected by the abnormality detection circuit, the voltage adjustment is performed by operating the voltage reduction circuit without processing by the microcomputer. The first power supply voltage input to the circuit is reduced. As a result, the second power supply voltage output from the voltage adjustment circuit can be lowered to a voltage region where the microcomputer cannot operate. Therefore, when the second power supply voltage is abnormal, the operation of the microcomputer can be reliably stopped through a decrease in the first power supply voltage. In particular, since the voltage drop circuit can be operated without processing by the microcomputer, the second power source is used to surely stop the operation of the microcomputer even if the operation of the microcomputer is unstable. The voltage can be lowered.

  Preferably, the control device further includes a power conversion circuit. The power conversion circuit is configured to convert a voltage from an external power supply into a first power supply voltage and output the first power supply wiring. The voltage reduction circuit is disposed between the power conversion circuit and the first power supply wiring, and cuts off a current path between the power conversion circuit and the first power supply wiring during operation, while being inactive. And a first power supply wiring are configured to form a current path.

  In this way, when the second power supply voltage is abnormal, the voltage supply from the power conversion circuit can be cut off without being accompanied by processing by the microcomputer. As a result, by reducing the voltage input to the voltage adjustment circuit from the first power supply wiring, it is possible to reliably reduce the second power supply voltage and stop the operation of the microcomputer.

  Preferably, the control device further includes a power conversion circuit. The power conversion circuit is configured to execute a power conversion operation of converting a voltage from an external power supply into a first power supply voltage and outputting the first power supply voltage to the first power supply wiring. The voltage reduction circuit is configured to stop the power conversion operation by the power conversion circuit during operation.

  In this way, when the second power supply voltage is abnormal, the output of the first power supply voltage by the power conversion circuit can be stopped without being accompanied by processing by the microcomputer. As a result, the second power supply voltage can be reduced through a reduction in the voltage input from the first power supply wiring to the voltage adjustment circuit, so that an additional circuit for cutting off the voltage supply is not arranged. The operation of the microcomputer can be surely stopped when the second power supply voltage is abnormal.

  Alternatively, preferably, the control device further includes a power conversion circuit. The power conversion circuit is configured to execute a power conversion operation of converting a voltage from an external power supply into a first power supply voltage and outputting the first power supply voltage to the first power supply wiring. The power conversion circuit includes a control circuit for controlling the output voltage from the power conversion circuit based on the feedback signal of the first power supply voltage. The voltage reduction circuit converts the feedback signal input to the control circuit so as to reduce the output voltage of the power conversion circuit during operation.

  In this case, when the second power supply voltage is abnormal, the output voltage of the power conversion circuit is changed by converting the feedback signal for controlling the first power supply voltage by the power conversion circuit without processing by the microcomputer. Can be lowered. As a result, the voltage input from the first power supply wiring to the voltage adjustment circuit can be reduced, so that the second power supply voltage can be reduced without providing an additional circuit for cutting off the voltage supply. .

  Alternatively, preferably, the control device further includes a power conversion circuit. The power conversion circuit is configured to execute a power conversion operation of converting a voltage from an external power supply into a first power supply voltage and outputting the first power supply voltage to the first power supply wiring. The power conversion circuit includes a control circuit for controlling the output voltage from the power conversion circuit based on the feedback signal of the first power supply voltage. The control circuit has a function of stopping the power conversion operation when an overcurrent occurs in the circuit. The voltage reduction circuit converts the feedback signal input to the control circuit so as to generate an overcurrent in the power conversion circuit when operating.

  In this way, when the second power supply voltage is abnormal, by converting the feedback signal for controlling the first power supply voltage so that the voltage rising operation is continued without involving processing by the microcomputer, The power conversion circuit can be stopped by the occurrence of an overcurrent. As a result, the second power supply voltage can be reduced by reducing the voltage input to the voltage adjustment circuit from the first power supply wiring. As a result, it is possible to reliably stop the operation of the microcomputer when the second power supply voltage is abnormal without arranging an additional circuit for cutting off the voltage supply.

  Preferably, the control device further includes a booster circuit and a power conversion circuit. The step-up circuit converts an AC voltage from an external power source into a DC voltage and outputs it. The boosting circuit has a boosting function for generating a DC voltage higher than the amplitude of the AC voltage. The power conversion circuit is configured to perform a power conversion operation that converts the output voltage of the booster circuit into a first power supply voltage and outputs the first power supply voltage to the first power supply wiring. The booster circuit is configured to output a first voltage when the boosting function is turned on, and to output a second voltage lower than the first voltage when the boosting function is turned off. The power conversion circuit has a function of stopping the power conversion operation when an overcurrent occurs in the circuit. The voltage lowering circuit is configured to turn off the boosting function of the boosting circuit during operation.

  With this configuration, in the control device having the booster circuit, when the second power supply voltage is abnormal, the booster in the booster circuit is stopped without causing the microcomputer to process the power conversion circuit. Can be stopped by the occurrence of As a result, the second power supply voltage can be lowered by lowering the voltage input to the voltage adjustment circuit from the first power supply wiring. Thus, the operation of the microcomputer can be reliably stopped when the second power supply voltage is abnormal without arranging an additional circuit for cutting off the voltage supply.

  Preferably, the control device further includes a fuse element inserted and connected to the first power supply wiring. The voltage lowering circuit operates so as to allow the fusing current of the fuse element to flow through the fuse element during operation.

  In this way, when the second power supply voltage is abnormal, it is possible to cut off the voltage supply from the first power supply wiring to the voltage adjustment circuit by fusing the fuse element without any processing by the microcomputer. . As a result, since the second power supply voltage output from the voltage adjustment circuit can be lowered, the operation of the microcomputer can be stopped more reliably when the second power supply voltage is abnormal.

  According to the present invention, in a control device that uses a plurality of power supply voltages, when the power supply voltage of the microcomputer is abnormal, the microcomputer can be reliably stopped without being accompanied by processing by the microcomputer.

It is a circuit diagram for demonstrating schematic structure of the control apparatus according to Embodiment 1 of this invention. It is a schematic circuit diagram for demonstrating the structure of the control apparatus according to this Embodiment 2. FIG. It is a schematic circuit diagram for demonstrating the structure of the control apparatus according to this Embodiment 3. FIG. It is a schematic circuit diagram for demonstrating the structure of the control apparatus according to the modification of this Embodiment 3. FIG. It is a schematic circuit diagram for demonstrating the structure of the control apparatus according to this Embodiment 4. FIG. It is a circuit diagram for demonstrating the structure of the principal part of the control apparatus according to Embodiment 5 of this invention. It is a circuit diagram for demonstrating the structure of the principal part of the control apparatus according to the modification of Embodiment 5 of this invention.

  Embodiments of the present invention will be described below in detail with reference to the drawings. In the following description, the same or corresponding parts in the drawings are denoted by the same reference numerals, and the description thereof will not be repeated in principle.

[Embodiment 1]
FIG. 1 is a circuit diagram for illustrating a schematic configuration of a control device according to the first embodiment of the present invention.

  Referring to FIG. 1, control device 1 a according to the first embodiment includes a power conversion circuit 2, a voltage regulator 40, a voltage cutoff circuit 50, and a microcomputer 300. The control device 1a controls a load (not shown) by the microcomputer 300. As shown in FIG. 1, the control device 1a can be mounted separately on a power supply board and a control board. When mounting separately on both boards, electrical contact between the power supply board and the control board can be secured by a connector (not shown).

  The power conversion circuit 2 includes a diode bridge 12, smoothing capacitors 14 and 24, a transistor 15, a transformer 20, and a diode D1. The diode bridge 12 is electrically connected to the external power supply 10 via a not-shown outlet or the like. The external power supply 10 is typically a commercial system power supply of 100 VAC to 200 VAC.

  The diode bridge 12 rectifies the AC voltage from the external power supply 10. The smoothing capacitor 14 smoothes the voltage rectified by the diode bridge 12. As a result, the smoothing capacitor 14 holds a DC voltage (for example, about 140 V) corresponding to the amplitude of the AC voltage from the external power supply 10.

  The transistor 15 is periodically turned on / off to convert the DC voltage held in the smoothing capacitor 14 into a pulsed AC voltage. The AC voltage generated by the transistor 15 is applied to the primary winding 21 of the transformer 20.

  The secondary side winding 23 outputs an AC voltage having the same frequency as the AC voltage of the primary side winding 21 whose amplitude is converted in accordance with the turn ratio of the primary side winding 21 and the secondary side winding 23. By transmitting the AC voltage switched by the transistor 15 through the transformer 20, the transformer 20 can be reduced in size.

  The AC voltage output to the secondary winding 23 is converted into a DC voltage Vs between the power supply wiring 100 and the ground wiring 120 by the diode D1 and the smoothing capacitor 24. Hereinafter, the DC voltage Vs is also referred to as a power supply voltage Vs. The power supply voltage Vs is controlled to about 15V, for example. The power supply voltage Vs can be controlled by adjusting the effective value of the AC voltage input to the primary winding 21 by the on / off control of the transistor 15.

  The power supply wiring 100 for supplying the power supply voltage Vs is connected to the power supply wiring 110 via the voltage cutoff circuit 50. As will be described later, the voltage cutoff circuit 50 is directly controlled by the detection signal Fvc from the voltage abnormality detection circuit 400 to be activated or deactivated. The voltage abnormality detection circuit 400 can be mounted on either the power supply board or the control board. When the voltage abnormality detection circuit 400 is mounted on the control board, the detection signal Fvc can be transmitted to the voltage cutoff circuit 50 on the power supply board via a connector (not shown).

  Further, the ground wiring 120 (ground voltage GND) is electrically common between the secondary winding 23 of the power supply board and the control board. On the other hand, the ground wiring 19 (ground voltage GND #) of the circuit group connected to the primary winding 21 is electrically insulated from the ground wiring 120.

  When the voltage cutoff circuit 50 is not in operation (normal time), the power supply wirings 100 and 110 are electrically connected by turning on the transistor 53. Thereby, the power supply voltage Vs is transmitted by the power supply wiring 110. That is, the power supply voltage Vs is supplied as a power supply voltage to the elements or circuits of the control device 1a by the power supply wirings 100 and 110.

  On the other hand, when the voltage cutoff circuit 50 operates, the power supply wirings 100 and 110 are electrically disconnected by turning off the transistor 53. At this time, the supply of the power supply voltage Vs to the power supply wiring 110 is stopped.

  In the control board, the power supply wiring 110 is connected to the input (IN) node of the voltage regulator 40 via the current limiting resistor R0. The voltage regulator 40 steps down the DC voltage at the input (IN) node and outputs the power supply voltage Vcc from the output (OUT) node. Power supply voltage Vcc is controlled to, for example, 5 V by voltage regulator 40. An output (OUT) node of the voltage regulator 40 is connected to the power supply wiring 200. The power supply wiring 200 supplies the power supply voltage Vcc to the circuits or elements of the control device 1a including the microcomputer 300. Although not shown, smoothing capacitors are arranged between the power supply wiring 110 and the ground wiring 120 and between the power supply wiring 200 and the ground wiring 120.

  As described above, the power supply voltage Vs corresponds to the “first power supply voltage”, and the power supply wiring 110 corresponds to the “first power supply wiring”. The power supply voltage Vcc supplied to the microcomputer 300 corresponds to the “second power supply voltage”, and the power supply wiring 200 corresponds to the “second power supply wiring”. Further, the voltage cutoff circuit 50 corresponds to an aspect of a “voltage drop circuit”.

  Here, consider the control of a load (not shown) by the microcomputer 300 when the power supply voltage Vcc fluctuates. For example, in the configuration of FIG. 1, when the input / output nodes of the voltage regulator 40 are short-circuited, the power supply voltage Vcc that is the power supply of the microcomputer 300 increases.

  Generally, for the microcomputer 300, the operation guarantee voltage range of the power supply voltage is preset as a specification value. Therefore, when the power supply voltage Vcc is out of the guaranteed operating voltage range, the microcomputer 300 stops its operation, and the operation of the load is also stopped.

  However, even if the power supply voltage Vcc falls outside the operation guaranteed voltage range, the microcomputer 300 does not always stop operating. In such a case, the control of the load by the microcomputer 300 may be affected by fluctuations in the power supply voltage Vcc.

  Therefore, it is necessary to provide a monitoring function for detecting an abnormality in the power supply voltage Vcc. Therefore, the control device 1a further includes a voltage abnormality detection circuit 400. The voltage abnormality detection circuit 400 includes a voltage dividing circuit 410 and a comparator 430. The voltage abnormality detection circuit 400 corresponds to an “abnormality detection circuit”.

  The voltage dividing circuit 410 includes resistance elements Ra and Rb connected in series between the power supply wiring 110 and the ground wiring 120. When the electric resistance values of the resistance elements Ra and Rb are also expressed by Ra and Rb, the voltage dividing ratio Dk (Vdv / Vs) by the voltage dividing circuit 410 is expressed by Dk = Ra / (Ra + Rb).

  A divided voltage Vdv (Vdv = Vs × Dk) by the voltage dividing circuit 410 is input to the comparator 430 via the resistance element Rc. On the other hand, the other input terminal of the comparator 430 is connected to the power supply wiring 200 via the resistance element Rd. Further, the comparator 430 is connected to the power supply wiring 110 and the ground wiring 120 and operates by the power supply voltage Vs.

  As a result, the comparator 430 compares the divided voltage Vdv and the power supply voltage Vcc, and outputs a detection signal Fvc based on the voltage comparison result. The detection signal Fvc is set to either a logic high level (hereinafter also referred to as “H level”) or a logic low level (hereinafter also referred to as “L level”). The H level of the detection signal Fvc is the power supply voltage Vs, and the L level is the ground voltage GND.

  Comparator 430 sets detection signal Fvc to the H level when Vcc> Vdv. On the other hand, when Vcc <Vdv, comparator 430 sets detection signal Fvc to the L level. For example, the detection signal Fvc is set to H level when the power supply voltage Vcc rises above a predetermined determination voltage Vt (Vt = Vdv) according to the resistance values of the resistance elements Ra and Rb.

  Thus, voltage abnormality detection circuit 400 sets detection signal Fvc to the H level when it detects an abnormality in power supply voltage Vcc (hereinafter also simply referred to as “Vcc abnormality”). On the other hand, when no Vcc abnormality is detected, detection signal Fvc is maintained at the L level.

  In the following, a configuration for detecting a Vcc abnormality when the power supply voltage Vcc rises (Vcc> Vt) as in the voltage abnormality detection circuit 400 of FIG. 1 will be exemplified. However, contrary to this example, the detection signal Fvc may be set to the H level when the power supply voltage Vcc drops below the determination voltage. Alternatively, by providing a plurality of comparators 430, when the power supply voltage Vcc rises or falls from a certain range, the detection signal Fvc is set to H level to detect a Vcc abnormality. In control device 1 a according to the first embodiment, detection signal Fvc from voltage abnormality detection circuit 400 is input to voltage cutoff circuit 50.

Next, the configuration and operation of the voltage cutoff circuit 50 will be described.
The voltage cutoff circuit 50 includes a thyristor 51, transistors 52 and 53, and resistance elements 55 to 58.

  P-type transistor 53 is electrically connected between power supply wirings 100 and 110. The gate (control electrode) of transistor 53 is connected to node N2. Resistance element 58 is connected between power supply line 100 and node N2.

  N-type transistor 52 is connected between nodes N2 and N3. The gate (control electrode) of transistor 52 is connected to node N1. Resistance element 55 is connected between power supply line 100 and node N1, and resistance element 56 is connected between nodes N1 and N3. Resistance element 57 is connected between ground line 120 and node N3.

  Thyristor 51 is connected between node N1 and ground wiring 120 as a forward direction from node N1 to ground wiring 120. A detection signal Fvc from the voltage abnormality detection circuit 400 is input to the gate of the thyristor 51.

  When the Vcc abnormality is not detected, the detection signal Fvc is maintained at the L level, so that the voltage cutoff circuit 50 is inactivated. When the voltage cut-off circuit 50 is not operated, the thyristor 51 is kept off. At this time, the resistance values of the resistance elements 55 to 57 are designed so that the transistor 52 is turned on. Further, the resistance values of the resistance elements 57 and 58 are designed such that when the transistor 52 is turned on, the voltage at the node N2 (the gate of the transistor 53) drops from the power supply voltage Vs beyond the threshold voltage. Thus, the transistor 53 is turned on in response to the transistor 52 being turned on, so that a current path is formed between the power supply wirings 100 and 110. As a result, the power supply voltage Vs is supplied to the power supply wiring 110 of the control board.

  The voltage regulator 40 steps down the power supply voltage Vs supplied to the power supply wiring 110 and controls the power supply voltage Vcc of the microcomputer 300 to a predetermined voltage level (for example, about 5 V) when the voltage cutoff circuit 50 is not in operation. be able to.

  On the other hand, when a Vcc abnormality is detected and the detection signal Fvc is set to the H level, the voltage cutoff circuit 50 is activated and the thyristor 51 is turned on. The resistance value of the resistance element 55 is designed so that the voltage at the node N1 becomes a voltage for turning off the transistor 52 when the thyristor 51 is on. Thereby, the thyristor 51 is turned on and the transistor 52 is turned off. Accordingly, the node N2 is connected to the power supply wiring 100 (power supply voltage Vs) via the resistance element 58, so that the transistor 53 is turned off.

  As a result, when the voltage cutoff circuit 50 is operated, that is, when a Vcc abnormality is detected, the transistor 53 is turned off in response to the thyristor 51 being turned on and the transistor 52 being turned off, so that the current path between the power supply wirings 100 and 110 is changed. Blocked. Thereby, the supply of the power supply voltage Vs to the power supply wiring 110 of the control board is stopped.

  Once turned on, the thyristor 51 remains on until the passing current becomes zero. Therefore, once the detection signal Fvc is set to the H level, the thyristor 51 is maintained in the ON state until the power supply voltage Vs decreases, and the current path cut off by the transistor 53 is maintained.

  Therefore, when the Vcc abnormality is detected by the voltage abnormality detection circuit 400, the voltage supply to the power supply wiring 110 is stopped by the operation of the voltage cutoff circuit 50. As a result, the input voltage from the power supply wiring 110 to the voltage regulator 40 decreases, so the power supply voltage Vcc output from the voltage regulator 40 decreases. Finally, the output voltage of the voltage regulator 40 becomes 0 (ground voltage GND), so that the power supply voltage Vcc can be lowered to 0 (ground voltage GND). That is, the voltage cutoff circuit 50 operates so as to lower the power supply voltage Vs through a decrease in the power supply voltage Vs.

  As described above, according to the control device 1a according to the first embodiment, when the voltage abnormality detection circuit 400 detects the Vcc abnormality, the voltage cutoff circuit 50 is operated according to the detection signal Fvc without being processed by the microcomputer 300. By doing so, the supply of the power supply voltage Vs from the power supply wiring 100 to the power supply wiring 110 can be cut off. As a result, by reducing the voltage of the power supply wiring 110, the power supply voltage Vcc is lowered to a voltage region where the microcomputer 300 cannot operate, so that the operation of the microcomputer 300 can be stopped reliably.

  In particular, since the operation of lowering the power supply voltage Vcc can be started without being accompanied by processing by the microcomputer 300, the operation of the microcomputer 300 can be performed even if the operation of the microcomputer 300 becomes unstable due to runaway or the like. It can be stopped reliably.

[Embodiment 2]
In the following, a variation of the power supply configuration for reducing the power supply voltage Vcc to the voltage range in which the microcomputer 300 cannot operate when the abnormality of the power supply voltage Vcc is detected as described in the first embodiment will be described.

  FIG. 2 is a schematic circuit diagram for illustrating the configuration of the control device according to the second embodiment.

  2 is compared with FIG. 1, the control device 1b according to the second embodiment is different from the control device 1a according to the first embodiment in the configuration on the power supply board side. Specifically, in the secondary winding 23 of the transformer 20, the arrangement of the voltage cutoff circuit 50 shown in FIG. 1 is omitted. In the configuration in which the voltage cutoff circuit 50 is not disposed, it is not necessary to distinguish between the power supply wirings 100 and 110 in FIG. Therefore, in the following, it is assumed that the power conversion circuit 2 supplies the power supply voltage Vs to the power supply wiring 110.

  Further, in the control device 1b, a voltage reduction circuit 70 for reducing the power supply voltage Vs through the reduction of the power supply voltage Vs according to the detection signal Fvc is arranged instead of the voltage cutoff circuit 50.

  In FIG. 2, a configuration for controlling on / off of the transistor 15, which is omitted in FIG. 1, is described for the power conversion circuit 2. First, this configuration will be described.

  The transformer 20 is further provided with a primary winding 22. An AC voltage having the same frequency as the AC voltage of the primary side winding 21 whose amplitude is converted according to the turn ratio of the primary side windings 21 and 22 is output to the primary side winding 22. Between the primary windings 21 and 22, the ground wiring 19 (ground voltage GND #) is common. The AC voltage output to the primary winding 22 is converted into a DC voltage Vd between the power supply wiring 65 and the ground wiring 19 by the diode D2 and the smoothing capacitor 62. The DC voltage Vd is used as a power supply voltage of a control IC (integrated circuit) for controlling the power conversion operation of the power conversion circuit 2 by turning on / off the transistor 15.

  The control IC 60 generates a control signal for controlling on / off of the transistor 15 in order to control the power supply voltage Vs. This control signal is input to the gate of the transistor 15.

  For example, the control IC 60 controls on / off of the transistor 15 so as to increase the effective value of the AC voltage input to the primary winding 21 when the power supply voltage Vs falls below a target value (for example, 15 V). . On the other hand, the control IC 60 controls on / off of the transistor 15 so as to decrease the effective value of the AC voltage input to the primary winding 21 when the power supply voltage Vs rises above a target value (for example, 15 V). To do. For example, in the periodic on / off control for generating an alternating voltage by the transistor 15, the effective value of the alternating voltage can be increased or decreased by increasing or decreasing the width of the on period.

  A current detection resistor 16 for detecting the passing current of the transistor 15 is connected between the transistor 15 and the ground wiring 19. The control IC 60 can detect the passing current of the transistor 15 based on the voltage drop amount in the current detection resistor 16.

  Further, the control IC 60 has a latch terminal 61. When a predetermined voltage or higher is applied to the latch terminal 61, the control IC 60 stops the switching operation of the transistor 15. That is, the transistor 15 is kept off. Once a voltage equal to or higher than a predetermined voltage is applied to the latch terminal 61, the control IC 60 continues the operation of maintaining the transistor 15 off by the latch function until it is reset due to a decrease in the power supply voltage Vd. It is configured.

  When the transistor 15 is maintained in the OFF state, the DC voltage held by the smoothing capacitor 14 is applied to the primary side winding 21. As a result, no voltage is generated in the primary side winding 22 and the secondary side winding 23. Therefore, the power conversion by the power conversion circuit 2 is stopped, and the generation of the power supply voltage Vs is stopped.

  Similar to the voltage cut-off circuit 50, the voltage drop circuit 70 operates without any processing by the microcomputer 300 in response to the detection signal Fvc from the voltage abnormality detection circuit 400. The voltage drop circuit 70 includes a transistor 71, a resistance element 72, and a photocoupler 75. The photocoupler 75 includes a photodiode 75a that emits light when a current flows and a phototransistor 75b that is turned on in response to light emission of the photodiode 75a.

  The resistance element 72, the photodiode 75a, and the transistor 71 are connected in series between the power supply wiring 110 and the ground wiring 120. The detection signal Fvc is input to the base (control electrode) of the transistor 71. The phototransistor 75 b is connected between the power supply wiring 65 and the latch terminal 61.

  When the detection signal Fvc is at L level (when Vcc is normal), the transistor 71 is turned off, so that no current flows through the photodiode 75a, so that the phototransistor 75b is maintained in the off state. For this reason, since the latch terminal 61 is electrically disconnected from the power supply wiring 65, the latch function is not turned on. Therefore, the transistor 15 is controlled to be turned on / off so as to control the power supply voltage Vs to a target value.

  On the other hand, when a Vcc abnormality is detected and detection signal Fvc is set to H level, voltage drop circuit 70 is activated. When the voltage drop circuit 70 is activated, the transistor 71 is turned on, so that a current flows through the photodiode 75a. Therefore, the phototransistor 75b is turned on in response to the light emission of the photodiode 75a. The latch terminal 61 is electrically connected to the power supply wiring 65 to apply a voltage higher than a predetermined voltage.

  Thereby, the latch function of the control IC 60 is turned on, and the operation of maintaining the transistor 15 in the off state, that is, the operation of stopping the power conversion in the power conversion circuit 2 is continuously executed. As a result, since the generation of the power supply voltage Vs by the power conversion circuit 2 is stopped, the input voltage from the power supply wiring 110 to the voltage regulator 40 is reduced, and thus the power supply voltage Vcc output from the voltage regulator 40 is reduced. Finally, the power supply voltage Vcc can be lowered to a voltage region where the microcomputer 300 cannot operate.

  As described above, in control device 1b according to the second embodiment, voltage conversion circuit 70 is operated according to detection signal Fvc from voltage abnormality detection circuit 400, and power conversion for power supply wiring 110 is performed by the latch function of control IC 60. The supply of the power supply voltage Vs from the circuit 2 can be stopped. As a result, as in the first embodiment, by reducing the voltage of the power supply wiring 110 in accordance with the detection signal Fvc, the power is supplied to a voltage region where the microcomputer 300 becomes inoperable without being processed by the microcomputer 300. The voltage Vcc can be reduced. That is, the operation of the microcomputer 300 can be stopped reliably.

  In the control device 1b according to the second embodiment, the arrangement of the voltage drop circuit 70 having a smaller number of components than the voltage cutoff circuit 50 (FIG. 1) causes the Vcc abnormality to occur as in the control device 1a according to the first embodiment. Since the operation of the microcomputer 300 can be surely stopped at the time of detection, it is advantageous in terms of downsizing the apparatus.

[Embodiment 3]
FIG. 3 is a circuit diagram for illustrating a schematic configuration of a control device according to the third embodiment of the present invention.

  3 and 2, control device 1c according to the third embodiment includes a voltage reduction circuit 90 instead of voltage reduction circuit 70, as compared with control device 1b according to the second embodiment. Further, the power conversion circuit 2 has a detailed configuration for controlling the power supply voltage Vs by turning on and off the transistor 15, which is not shown in FIG. Specifically, a Vs detection circuit 80 connected to the control input terminal 63 of the control IC 60 is shown.

  The Vs detection circuit 80 includes a shunt regulator 82, resistance elements 83 and 84, and a photocoupler 85. The photocoupler 85 includes a photodiode 85a that emits light when a current flows and a phototransistor 85b that is turned on in response to light emission of the photodiode 85a.

  Resistance elements 83 and 84 are connected in series between power supply wiring 110 and ground wiring 120. A divided voltage of the power supply voltage Vs by the resistance elements 83 and 84 is input to the reference (R) terminal of the shunt regulator 82. The photodiode 85 a is connected in series with the shunt regulator 82 between the power supply wiring 110 and the ground wiring 120.

  On the control IC 60 side, the phototransistor 85 b of the photocoupler 85 is connected in series with the resistance element 64 between the power supply wiring 65 and the ground wiring 19. The resistance element 64 is connected between the control input terminal 63 of the control IC 60 and the ground wiring 19. The control IC 60 can detect on / off of the phototransistor 85 b based on the voltage of the control input terminal 63.

  In the Vs detection circuit 80, when the voltage of the power supply wiring 110 (power supply voltage Vs) rises above the reference, a current is generated between the cathode (K) terminal and the anode (A) terminal by the shunt regulator 82. Accordingly, the phototransistor 85b is turned on when the photodiode 85a emits light.

  On the other hand, when the voltage of the power supply wiring 110 (power supply voltage Vs) is lower than the reference, no current is generated between the cathode (K) terminal and the anode (A) terminal of the shunt regulator 82. Therefore, the photodiode 85a does not emit light, and the phototransistor 85b is turned on. As described above, by the operation of the Vs detection circuit 80, the control input terminal 63 is supplied with the H level voltage (Vd) when Vs increases, and with the L level voltage (GND #) when Vs decreases. As described above, the Vs detection circuit 80 has a function of inputting the feedback signal of the power supply voltage Vs to the control IC 60.

  When the L level voltage is input to the control input terminal 63, the control IC 60 controls the on / off of the transistor 15 so as to increase the effective value of the AC voltage input to the primary winding 21. On the other hand, when the H level voltage is input to the control input terminal 63, the on / off of the transistor 15 is controlled so as to reduce the effective value of the AC voltage input to the primary winding 21. In this way, the control IC 60 can perform feedback control of the power supply voltage Vs by on / off control of the transistor 15. That is, the power conversion circuit 2 controls the power supply voltage Vs based on the feedback signal from the Vs detection circuit 80.

  The feedback control of the power supply voltage Vs by the control IC 60 using the Vs detection circuit 80 is not directly related to the control operation at the time of detecting the Vcc abnormality, and thus the description thereof is omitted in the first and second embodiments. The control device according to the embodiment also has the same configuration.

  The voltage abnormality detection circuit 400 further includes a latch circuit 440 for holding the detection signal Fvc from the comparator 430 as compared with the configuration of FIGS. 1 and 2. Latch circuit 440 is configured to maintain detection signal Fvc at the H level when detection signal Fvc changes from the L level to the H level. The holding operation by the latch circuit 440 is continued until the power supply voltage Vs decreases.

  The voltage drop circuit 90 operates according to the detection signal Fvc from the voltage abnormality detection circuit 400. The voltage reduction circuit 90 includes an N-type transistor 92 and a resistance element 94. The transistor 92 is connected between the cathode (K) terminal and the anode (A) terminal of the shunt regulator 82.

  The detection signal Fvc that has passed through the latch circuit 440 is input to the gate (control electrode) of the transistor 92. The resistance element 94 pulls down the gate (control electrode) of the transistor 92 to the ground voltage GND.

  When power supply voltage Vcc is normal (when Vcc abnormality does not occur), detection signal Fvc is set to L level, and transistor 92 is turned off. Therefore, the Vs detection circuit 80 operates to generate the feedback signal for controlling the power supply voltage Vs to the target value as described above.

  On the other hand, when Vcc abnormality occurs, the detection signal Fvc is set to the H level, so that the transistor 92 is turned on. As a result, the cathode (K) terminal and the anode (A) terminal of the shunt regulator 82 are short-circuited, so that a current continues to flow through the photodiode 85a.

  Accordingly, since the phototransistor 85b is also continuously turned on, an H level voltage indicating an increase in the power supply voltage Vs is continuously applied to the control input terminal 63 of the control IC 60 as a feedback signal from the Vs detection circuit 80. Entered. As a result, the transistor 15 is controlled to maintain the effective value of the AC voltage input to the primary winding 21 at the minimum value in terms of control. At this time, the power supply voltage Vs drops to about 2 to 3 V, for example, with respect to 15 V at normal time.

  As a result, the input voltage from the power supply wiring 110 to the voltage regulator 40 decreases, so the power supply voltage Vcc output from the voltage regulator 40 decreases. As a result, the power supply voltage Vcc can be lowered to a voltage region where the microcomputer 300 cannot operate.

  Thus, in control device 1c according to the third embodiment, voltage drop circuit 90 is operated in accordance with detection signal Fvc that has passed through latch circuit 440 to convert the feedback signal from Vs detection circuit 80 to control IC 60. As a result, the power supply voltage Vs supplied by the power conversion circuit 2 can be lowered to the minimum level for control. As a result, in the same manner as in the first embodiment, the power supply voltage Vcc is reduced to a voltage region where the microcomputer 300 becomes inoperable without being processed by the microcomputer 300 in accordance with the detection signal Fvc from the voltage abnormality detection circuit 400. Can be reduced. That is, the operation of the microcomputer 300 can be stopped reliably.

[Modification of Embodiment 3]
FIG. 4 is a circuit diagram for illustrating a schematic configuration of a control device according to a modification of the third embodiment of the present invention.

  Referring to FIGS. 4 and 3, control device 1 d according to the modification of the third embodiment replaces voltage drop circuit 90 (FIG. 3) with a voltage drop as compared with control device 1 c according to the third embodiment. Circuit 90 # is arranged. The configuration of other parts of the control device 1d is the same as that of the control device 1c shown in FIG. That is, also in the control device 1e, the voltage abnormality detection circuit 400 is configured to include the latch circuit 440.

  Voltage drop circuit 90 # operates in response to detection signal Fvc from voltage abnormality detection circuit 400, similarly to voltage drop circuit 90. Voltage reduction circuit 90 # includes an N-type transistor 92 and a resistance element 94. The transistor 92 is connected between the reference (R) terminal and the anode (A) terminal of the shunt regulator 82. The resistance element 94 pulls down the gate (control electrode) of the transistor 92 to the ground voltage GND, similarly to the voltage drop circuit 90 (FIG. 3).

  Voltage drop circuit 90 # short-circuits the reference (R) terminal and anode (A) terminal of shunt regulator 82 by turning on transistor 92 when detection signal Fvc is set to H level when Vcc abnormality occurs. As a result, the shunt regulator 82 detects that the input voltage of the reference (R) terminal has dropped, so that no current is generated between the cathode (K) terminal and the anode (A) terminal.

  For this reason, a state in which no current flows through the photodiode 85a is maintained, so that the phototransistor 85b is also continuously turned off. As a result, an L level voltage indicating a decrease in the power supply voltage Vs is continuously input as a feedback signal from the Vs detection circuit 80 to the control input terminal 63 of the control IC 60. As a result, the transistor 15 continues to be controlled so as to increase the effective value of the AC voltage input to the primary side winding 21.

  Normally, the control IC 60 is provided with a safety function that automatically detects the occurrence of an overcurrent or an excessively high temperature of an element in the power conversion circuit 2 and automatically stops the operation of the power conversion circuit 2. Therefore, in control device 1d according to the third modification of the third embodiment, when detection signal Fvc is set to H level when a Vcc abnormality occurs, control operation for increasing power supply voltage Vs is forcibly continued. As a result, an overcurrent or an excessively high temperature occurs in the power conversion circuit 2. Thereby, the power conversion by the power conversion circuit 2 is stopped by operating the existing safety function by the control IC 60.

  As a result, since the generation of the power supply voltage Vs by the power conversion circuit 2 is stopped, the input voltage to the voltage regulator 40 is lowered, so that the power supply voltage Vcc output from the voltage regulator 40 is lowered. Finally, the power supply voltage Vcc can be lowered to a voltage region where the microcomputer 300 cannot operate.

  Thus, in control device 1d according to the modification of the third embodiment, similarly to control device 1c according to the third embodiment, detection signal Fvc from voltage abnormality detection circuit 400 is not accompanied by processing by microcomputer 300. By operating voltage reduction circuit 90 # accordingly, power supply voltage Vcc can be reduced to a voltage region where microcomputer 300 cannot operate.

[Embodiment 4]
In the fourth embodiment, a power supply configuration for reducing the power supply voltage Vcc when a Vcc abnormality is detected in a control device having a configuration provided with a booster circuit will be described.

FIG. 5 is a circuit configuration diagram of the control device according to the fourth embodiment of the present invention.
Referring to FIG. 5, control device 1 e according to the fourth embodiment includes a booster circuit 500. The booster circuit 500 is configured to supply a high-voltage load 600 with a DC voltage Vdc higher than a DC voltage corresponding to the amplitude of the AC voltage of the external power supply 10. For example, when the AC voltage amplitude of the external power supply 10 is about 140V, the booster circuit 500 generates a DC voltage of about Vdc = 280V, so that the operating power of the high voltage load 600 is supplied.

  In control device 1e according to the fourth embodiment, booster circuit 500 is arranged between external power supply 10 and power conversion circuit 2 having the same configuration as in the first to third embodiments. Therefore, not the output voltage of the diode bridge 12 but the DC voltage Vdc output from the booster circuit 500 is input to the power conversion circuit 2. Similarly to the first to third embodiments, power conversion circuit 2 performs DC / AC conversion (transistor 15) and AC / DC conversion (diode D1 and smoothing capacitor 24) on DC voltage Vdc output from booster circuit 500. A power supply voltage Vs is supplied. The configuration for converting power supply voltage Vs into power supply voltage Vcc supplied to microcomputer 300 is the same as in the first to third embodiments and their modifications.

Next, the configuration and operation of the booster circuit 500 will be described.
The booster circuit 500 includes a power supply wiring 501, a smoothing capacitor 502, a reactor 506, a diode 508, a transistor 510, a current detection resistor 512, a smoothing capacitor 515, and a control IC 550. The operation power of the control IC 550 is supplied from the power supply wiring 65 in common with the control IC 60.

  The power supply wiring 501 receives the AC voltage rectified by the diode bridge 12. Smoothing capacitor 502 is connected between power supply wiring 401 and ground wiring 19. That is, smoothing capacitor 502 holds a DC voltage (for example, about 140 V) corresponding to the amplitude of the AC voltage of external power supply 10.

  Reactor 506 and diode 508 are connected in series between power supply lines 501 and 520. Transistor 510 is connected in series with current detection resistor 512 between a connection node of reactor 506 and diode 508 and ground wiring 19. The current detection resistor 512 is connected between the input terminal of the control IC 550 and the ground wiring 19. The control IC 550 can detect the passing current of the transistor 510 based on the voltage of the input terminal, that is, the voltage drop amount of the current detection resistor 512.

  By periodically providing an ON period and an OFF period of the transistor 510, a function of a so-called boost chopper circuit is realized, and a DC voltage higher than the voltage of the power supply wiring 501 can be generated in the power supply wiring 520.

  In the step-up chopper circuit, the transistor 510 is periodically turned on / off (switched), and the DC voltage Vdc output to the power supply wiring 520 is controlled by controlling the time ratio (duty ratio) of the on period with respect to the switching cycle. Can do. In booster circuit 500, the power factor can be increased by controlling the current waveform of reactor 506 to a current having the same frequency and the same phase as the output voltage (full-wave rectified voltage) from diode bridge 12. In this case, the DC voltage Vdc can be controlled by controlling the current peak value of the full-wave rectified waveform. As described above, the booster circuit 500 controls the boosted DC voltage Vdc to the target voltage (for example, 280 V) by the on / off control of the transistor 510 by the control IC 550 when the boost function is on.

  On the other hand, since the transistor 510 is kept off when the boosting function is off, the DC voltage Vdc is equivalent to the DC voltage held in the smoothing capacitor 502. That is, when the boosting function is off, the power supply voltage Vdc is lower than when the boosting function is on.

  On / off of the boost function in the boost circuit 500 is controlled by a boost stop signal Sbs from the microcomputer 300. The boost stop signal Sbs is transmitted to the control IC 550 via the photocoupler 560. The photocoupler 560 includes a photodiode 560a and a phototransistor 560b. The photodiode 560 a is connected in series with the N-type transistor 570 between the power supply wiring 110 and the ground wiring 120. A boost stop signal Sbs from the microcomputer 300 is input to the base (control electrode) of the transistor 570.

  The microcomputer 300 sets the boost stop signal Sbs to the H level when the boost function of the boost circuit 500 is turned off. For example, during the standby operation (standby mode) of the device on which control device 1e is mounted, boost stop signal Sbs is set to the H level. Normally, the boost stop signal Sbs is set to L level.

  When the boost stop signal Sbs is at the L level, the transistor 570 is turned off, so that no current flows through the photodiode 560a, and the phototransistor 560b is turned off. As a result, the voltage at input terminal 552 of control IC 550 rises from ground voltage GND #. In response to this, the control IC 550 turns on the boost function of the boost circuit 500.

  On the other hand, when the boost stop signal Sbs is set to the H level, the transistor 570 is turned on, so that the phototransistor 560b is turned on in response to the current flowing through the photodiode 560a. As a result, the ground voltage GND # is input to the input terminal 552 of the control IC 550 through the ground wiring 19. In response to this, the control IC 550 turns off the boosting function of the boosting circuit 500.

  Further, the control device 1e is provided with a voltage lowering circuit 91 that operates in response to the detection signal Fvc from the voltage abnormality detection circuit 400. The voltage reduction circuit 91 includes an N-type transistor 580 connected in parallel to the transistor 570 between the power supply wiring 110 and the ground wiring 120. The detection signal Fvc is input to the base (control electrode) of the transistor 580. Also in the control device 1e, the voltage abnormality detection circuit 400 is configured to include the latch circuit 440.

  When voltage abnormality detection circuit 400 detects Vcc abnormality, transistor 580 is turned on by setting detection signal Fvc to H level. That is, when the voltage drop circuit 91 operates, the ground voltage GND # is input to the input terminal 552 of the control IC 550 through the ground wiring 19 in the same manner as when the boost stop signal Sbs is set to the H level. Thereby, the boosting function of booster circuit 500 can be turned off when Vcc abnormality is detected.

  When the boosting function of the booster circuit 500 is turned off and the DC voltage Vdc corresponding to the input voltage of the power conversion circuit 2 decreases, the current value required to supply the same power increases, so that the current Ic flowing through the transistor 15 Increase. For example, when the power supply voltage Vdc drops from 280V to 140V, Ic increases about twice.

  As a result, the control IC 60 of the power conversion circuit 2 detects an overcurrent of the current Ic passing through the transistor 15 and stops the power conversion operation. As a result, since the generation of the power supply voltage Vs by the power conversion circuit 2 is stopped, the input voltage from the power supply wiring 110 to the voltage regulator 40 is reduced, and thus the power supply voltage Vcc output from the voltage regulator 40 is reduced. Finally, the power supply voltage Vcc can be lowered to a voltage region where the microcomputer 300 cannot operate.

  Note that when the boost stop signal Sbs is set to the H level during the standby operation, the power consumption in the control device 1e is small. For this reason, even if the power supply voltage Vdc decreases, the current Ic does not increase to the overcurrent detection level, and the power conversion operation by the power conversion circuit 2 is continued.

  Thus, in control device 1e according to the fourth embodiment, in the configuration provided with the booster circuit, when the Vcc abnormality is detected, the boosting function of booster circuit 500 is stopped according to detection signal Fvc from voltage abnormality detection circuit 400. Thus, the power supply voltage Vcc can be lowered to a voltage region where the microcomputer 300 becomes inoperable without being accompanied by processing by the microcomputer 300.

  6 illustrates the configuration in which the transistor 580 that is turned on in response to the detection signal Fvc is disposed separately from the transistor 570 that is turned on in response to the boost stop signal Sbs. However, the boost stop signal Sbs and the detection signal Fvc If the circuit configuration is such that a logical sum (OR) signal is input to the base (control electrode) of the transistor 570, the arrangement of the transistor 580 can be omitted. As described above, in the control device 1e according to the fourth embodiment, in the configuration including the booster circuit, the circuit elements to be added are suppressed, and the power supply voltage is increased to the voltage region where the microcomputer 300 cannot operate when the Vcc abnormality is detected. Vcc can be lowered.

[Embodiment 5]
In the fifth embodiment, a circuit configuration for reliably reducing the power supply voltage Vcc using a fuse element will be described.

  FIG. 6 is a circuit diagram illustrating a configuration of a main part of the control device according to the fifth embodiment of the present invention. FIG. 6 shows a configuration downstream of the power supply wiring 110 connected to the secondary winding 23 of the transformer 20. In the control device according to the fifth embodiment, the configuration for supplying power supply voltage Vs to power supply wiring 110 is arbitrary. For example, the power supply voltage Vs can be supplied by the power conversion circuit 2 (or the power converter 2 and the booster circuit 500) similar to those shown in FIGS.

  Referring to FIG. 6, in the control device according to the fifth embodiment, fuse element FS is inserted and connected to power supply wiring 110. That is, the power supply voltage Vs output to the power supply wiring 110 by the power conversion circuit 2 is supplied to the input (N) node of the voltage regulator 40 via the fuse element FS.

  Furthermore, in the control device according to the fifth embodiment, an energization circuit 350 for fusing fuse element FS is arranged. The energization circuit 350 includes resistance elements Rf0 to Rf2 and an npn transistor Qf1.

  Resistance elements Rf1 and Rf2 are connected in series to power supply line 200 and ground line 120 to form a voltage dividing circuit for power supply voltage Vcc. Resistance element Rf0 and transistor Qf1 are connected in series with respect to fuse element FS between power supply wiring 110 and ground wiring 120.

  Transistor Qf1 is formed of an npn transistor. A divided voltage of the power supply voltage Vcc by the resistance elements Rf1 and Rf2 is input to the base (control electrode) of the transistor Qf1. Therefore, transistor Qf1 is turned on as power supply voltage Vcc rises.

  When the transistor Qf1 is turned on, an energization path from the power supply wiring 110 to the ground wiring 120 through the fuse element FS is formed. The electrical resistance of the resistance element Rf0 is designed so that the amount of current in the current-carrying path is at a level sufficient to blow the fuse element FS.

  Therefore, according to the energization circuit 350 shown in FIG. 6, when the power supply voltage Vcc rises above a predetermined voltage, the Vcc abnormality can be detected and the fuse element FS can be blown. This predetermined voltage can be adjusted by the voltage division ratio by the resistance elements Rf1 and Rf2. As described above, the energization circuit 350 is configured to have the functions of the “voltage abnormality detection circuit” and the “voltage drop circuit”.

  In the control device in the fifth embodiment, when power supply voltage Vcc rises above a predetermined voltage, energization circuit 350 detects Vcc abnormality and blows fuse element FS. As a result, the supply voltage of the power supply voltage Vs is cut off, so that the input voltage from the power supply wiring 110 to the voltage regulator 40 is lowered, so that the power supply voltage Vcc output from the voltage regulator 40 is lowered. Eventually, the power supply voltage Vcc can be lowered to a voltage region where the microcomputer 300 cannot operate. In particular, the operation of the microcomputer 300 can be surely stopped when the Vcc abnormality is detected by melting the fuse element without processing by the microcomputer 300.

[Modification of Embodiment 5]
FIG. 7 is a circuit diagram showing a configuration of a main part of the control device according to the modification of the fifth embodiment of the present invention.

  7 is compared with FIG. 6, in the modification of the fifth embodiment, a configuration for fusing fuse element FS when power supply voltage Vcc decreases will be described.

  In the modification of the fifth embodiment, an energization circuit 350 # is provided instead of the energization circuit 350, as compared with the configuration shown in FIG. The fuse element FS is inserted and connected to the power supply wiring 110 as in the configuration of FIG.

  Energization circuit 350 # includes transistors Qf1 and Qf2 and resistance elements Rf1 to Rf6. Resistance element Rf0 and npn-type transistor Qf1 are connected in series with fuse element FS between power supply wiring 110 and ground wiring 120, as in the configuration of FIG.

  Resistance elements Rf1 and Rf2 are connected in series to power supply line 200 and ground line 120, and output a divided voltage of power supply voltage Vcc to node Nb. This divided voltage is input to the base (control electrode) of the pnp transistor Qf2 via the resistance element Rf5.

  Resistance elements Rf3 and Rf4 are connected in series to power supply wiring 110 and ground wiring 120, and output a reference voltage Vs obtained by dividing power supply voltage Vcc to node Na. Transistor Qf2 is formed of a pnp transistor, and is connected between node Na and resistance element Ra.

  The pnp transistor Qf2 is turned on when the divided voltage of the power supply voltage Vcc decreases with respect to the reference voltage Vs. When the npn transistor Qf1 is turned on in response to the pnp transistor Qf2 being turned on, an energization path for blowing the fuse element FS is formed.

  Therefore, energization circuit 350 # can blow fuse element FS when power supply voltage Vcc drops below a predetermined voltage. This predetermined voltage can be adjusted by the voltage dividing ratio by the resistance elements Rf1 and Rf2 and the reference voltage Vs. Thus, energization circuit 350 # is also configured to have both the functions of “voltage abnormality detection circuit” and “voltage drop circuit”.

  In the control device in the modification of the fifth embodiment, when power supply voltage Vcc drops below a predetermined voltage, energization circuit 350 # detects Vcc abnormality and blows fuse element FS. As a result, the power supply voltage Vcc can be reliably lowered to a voltage region where the microcomputer 300 becomes inoperable when Vcc is abnormal (decreased) without being accompanied by processing by the microcomputer 300.

  If energization circuits 350 and 350 # are configured to be connected in parallel to fuse element FS, Vcc abnormality is detected corresponding to both increase and decrease of power supply voltage Vcc, and fuse element FS is blown. Thus, the operation of the microcomputer 300 can be surely stopped.

  In the first to fourth embodiments, the configuration for detecting the Vcc abnormality is not limited to the configuration of the illustrated voltage abnormality detection circuit 400, and the abnormality (increase and / or decrease) in the power supply voltage Vcc. Any configuration can be applied as long as it can be detected.

  In addition, if the control device according to the present embodiment is a control device that uses a plurality of power supply voltages, the microcomputer is not limited to a load controlled by the control device, and the microcomputer is adapted to the power supply voltage abnormality. It is possible to apply a power supply configuration for surely stopping.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  1a, 1b, 1c, 1d, 1e Control device, 2 Power conversion circuit, 10 External power supply, 12 Diode bridge, 14, 24, 62, 502, 515 Smoothing capacitor, 15, 52, 53, 71, 92 Transistor, 16, 412, 512 Current detection resistor, 19, 120, 190 Ground wiring, 20 transformer, 21, 22 Primary side winding, 23 Secondary side winding, 40 Voltage regulator, 50 Voltage cutoff circuit, 51 Thyristor, 55-58, 64 , 72, 83, 84, 94 resistance element, 60 control IC (power conversion circuit), 61 latch terminal, 63 control input terminal, 65, 100, 110, 200, 401, 501, 520 power supply wiring, 70, 90, 91 Voltage drop circuit, 75, 85, 560 photocoupler, 75a, 85a, 560a photodiode, 7 b, 85b, 560b Phototransistor, 80 Vs detection circuit, 82 shunt regulator, 300 microcomputer, 350, 350 # energization circuit, 400 voltage abnormality detection circuit, 410 voltage divider circuit, 430 comparator, 440 latch circuit, 500 booster circuit, 506 reactor, 508 diode (boost circuit), 510 transistor (boost circuit), 550 control IC (boost circuit), 552 input terminal, 570, 580 transistor (for boost function stop), 600 high voltage load, D1, D2 diode (power) Conversion circuit), FS fuse element, Fvc detection signal, GND, GND # ground voltage, N1-N3, Na, Nb node, Qf1, Qf2 transistor (conduction circuit), R0 current limiting resistor, Ra, Rb, Rc, Rd resistance Elementary (Voltage abnormality detection circuit), Rf0~Rf6 resistive element (conducting circuit), Sbs boost stop signal, Vcc, Vd, Vdc, Vs the power supply voltage, Vd, Vdc DC voltage, Vdv divided voltage.

Claims (7)

A microcomputer for controlling the load;
A first power supply wiring for transmitting a first power supply voltage;
A voltage adjustment circuit for generating a second power supply voltage by stepping down the first power supply voltage of the first power supply wiring;
A second power supply wiring for supplying the second power supply voltage generated by the voltage adjustment circuit to the microcomputer;
An abnormality detection circuit for detecting an abnormality of the second power supply voltage based on a comparison between a voltage that changes according to the first power supply voltage and a voltage that changes according to the second power supply voltage;
A voltage drop circuit configured to operate without processing by the microcomputer when the abnormality detection circuit detects an abnormality in the second power supply voltage; and
The voltage reduction circuit reduces the second power supply voltage to a voltage range where the microcomputer becomes inoperable by reducing the voltage of the first power supply wiring input to the voltage adjustment circuit during operation. Let the control device. A power conversion circuit for converting a voltage from an external power supply into the first power supply voltage and outputting the first power supply voltage to the first power supply wiring;
The voltage drop circuit is disposed between the power conversion circuit and the first power supply wiring, and cuts off a current path between the power conversion circuit and the first power supply wiring during operation. The control device according to claim 1, wherein the control device is configured to form a current path between the power conversion circuit and the first power supply wiring in operation. A power conversion circuit for performing a power conversion operation for converting a voltage from an external power supply into the first power supply voltage and outputting the converted voltage to the first power supply wiring;
The control device according to claim 1, wherein the voltage reduction circuit is configured to stop the power conversion operation by the power conversion circuit when activated. A power conversion circuit for performing a power conversion operation for converting a voltage from an external power supply into the first power supply voltage and outputting the converted voltage to the first power supply wiring;
The power conversion circuit includes:
A control circuit for controlling an output voltage from the power conversion circuit based on a feedback signal of the first power supply voltage;
The control device according to claim 1, wherein the voltage reduction circuit converts the feedback signal input to the control circuit so as to reduce an output voltage of the power conversion circuit during operation. A power conversion circuit for performing a power conversion operation for converting a voltage from an external power supply into the first power supply voltage and outputting the converted voltage to the first power supply wiring;
A control circuit for controlling an output voltage from the power conversion circuit based on a feedback signal of the first power supply voltage;
The control circuit has a function of stopping the power conversion operation when an overcurrent occurs in the circuit,
The control device according to claim 1, wherein the voltage reduction circuit converts the feedback signal input to the control circuit so as to generate an overcurrent in the power conversion circuit when operating. A step-up circuit having a step-up function for generating a DC voltage higher than the amplitude of the AC voltage, for converting an AC voltage from an external power source into a DC voltage and outputting the DC voltage;
A power conversion circuit for performing a power conversion operation for converting the output voltage of the booster circuit into the first power supply voltage and outputting the converted voltage to the first power supply wiring;
The booster circuit is configured to output a first voltage when the booster function is turned on, and to output a second voltage lower than the first voltage when the booster function is turned off. And
The power conversion circuit has a function of stopping the power conversion operation when an overcurrent occurs in the circuit,
The control device according to claim 1, wherein the voltage drop circuit is configured to turn off the boosting function of the boosting circuit when activated. A fuse element inserted and connected to the first power supply wiring;
2. The control device according to claim 1, wherein the voltage reduction circuit operates so as to allow a fusing current of the fuse element to flow through the fuse element during operation.

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