JP6372189B2 - 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 unit, and a voltage drop 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 unit detects an abnormality in the second power supply voltage based on a comparison between a voltage according to the first power supply voltage and a voltage according to the second power supply voltage. The voltage reduction circuit lowers the voltage of the first power supply wiring input to the voltage adjustment circuit during operation in accordance with a command from the microcomputer, whereby the second power supply reaches a voltage range where the microcomputer becomes inoperable. Reduce voltage. The microcomputer activates the voltage drop circuit when the abnormality detection unit detects an abnormality in the second power supply voltage.

  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 unit, the microcomputer operates the voltage drop circuit and is input to the voltage adjustment circuit. The first power supply voltage is lowered. 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, by configuring the voltage reduction circuit to operate in response to a command from the microcomputer, the timing at which the abnormality of the second power supply voltage occurs in the microcomputer (for example, the built-in nonvolatile memory) The circuit state at the timing can be stored. Thereby, information useful for failure analysis can be collected.

  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 supplied from the first power supply wiring to the voltage adjustment circuit is reduced by cutting off the voltage supply from the power conversion circuit, so that the second The operation of the microcomputer can be stopped by reliably reducing the power supply voltage.

  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, by stopping the output of the first power supply voltage by the power conversion circuit, the voltage input from the first power supply wiring to the voltage adjustment circuit is reduced. The second power supply voltage can be lowered. 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.

  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 way, when the second power supply voltage is abnormal, the voltage input from the first power supply wiring to the voltage adjustment circuit is reduced by converting the feedback signal for controlling the first power supply voltage by the power conversion circuit. By doing so, the second power supply voltage can be lowered without providing an additional circuit for cutting off the voltage supply. Furthermore, if the conversion of the feedback signal is stopped, the normal control of the first power supply voltage by the power conversion circuit can be restored. Therefore, when the abnormality of the second power supply voltage is temporary, the control by the microcomputer automatically Recovery is possible.

  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, the feedback signal for controlling the first power supply voltage is converted so that the voltage rising operation is continued, so that the power conversion circuit is Can be stopped. 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.

  In this manner, in the control device having the booster circuit, when the second power supply voltage is abnormal, the booster in the booster circuit is stopped to stop the power conversion circuit due to the occurrence of an overcurrent. 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.

  According to the present invention, in the control device using a plurality of power supply voltages, the microcomputer can be reliably stopped when the power supply voltage of the microcomputer is abnormal.

It is a circuit diagram for demonstrating schematic structure of the control apparatus according to Embodiment 1 of this invention. FIG. 11 is a schematic circuit diagram for illustrating detection of a Vcc abnormality according to a modification of the first embodiment. FIG. 3 is a conceptual diagram for explaining the influence of Vcc abnormality on the operation of the A / D conversion circuit shown in FIG. 2. It is a conceptual diagram for demonstrating the determination method at the time of utilizing the voltage dividing circuit for power saving mode detection for the structure for Vcc abnormality detection shown in FIG. FIG. 5 is a circuit diagram for explaining a modification of the Vcc detection configuration shown in FIG. 2. FIG. 6 is a conceptual diagram for explaining determination for Vcc abnormality detection in the Vcc detection configuration shown in FIG. 5. It is a circuit diagram for demonstrating schematic structure of the control apparatus according to Embodiment 2 of this invention. It is a circuit diagram for demonstrating schematic structure of the control apparatus according to Embodiment 3 of this invention. It is a circuit diagram for demonstrating schematic structure of the control apparatus according to the modification of Embodiment 3 of this invention. It is a circuit diagram for demonstrating schematic structure of the control apparatus according to Embodiment 4 of this invention. It is a flowchart for demonstrating operation | movement at the time of Vcc abnormality detection of the control apparatus according to Embodiment 4 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 microcomputer 300 normally has a built-in nonvolatile memory capable of holding stored contents even when the power is stopped.

  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 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 activated or deactivated in accordance with a command (control signal Sct) from the microcomputer 300. The control signal Sct can also be transmitted from the microcomputer 300 on the control board 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 disposed between the power supply wiring 110 and the ground wiring 120 and between the power supply wiring 200 and the ground wiring 120, respectively.

  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 one aspect of the “abnormality detection unit”.

  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 200 and the ground wiring 120 and operates by the power supply voltage Vcc.

  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 Vcc, 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.

  When detection signal Fvc from voltage abnormality detection circuit 400 is set to H level, microcomputer 300 detects an abnormality in power supply voltage Vcc (hereinafter also simply referred to as “Vcc abnormality”). On the other hand, microcomputer 300 recognizes that power supply voltage Vcc is normal when detection signal Fvc is at L level. That is, no Vcc abnormality is detected.

  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 Vcc abnormality may be detected when the power supply voltage Vcc drops below the determination voltage. Alternatively, by providing a plurality of comparators 430, it is possible to adopt a configuration in which a Vcc abnormality is detected when the power supply voltage Vcc rises or falls from a certain range.

  When the microcomputer 300 detects a Vcc abnormality, it sets the control signal Sct for turning on the lowering operation of the power supply voltage Vcc to the H level. On the other hand, control signal Sct is maintained at the L level when no Vcc abnormality is detected. In control device 1 a according to the first embodiment, control signal Sct 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 control signal Sct from the microcomputer 300 is input to the gate of the thyristor 51.

  When the Vcc abnormality is not detected, the control signal Sct 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 the Vcc abnormality is detected and the control signal Sct 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 control signal Sct is set to the H level, the thyristor 51 is maintained in the ON state until the power supply voltage Vs decreases, and the interruption of the current path by the transistor 53 is maintained.

  Therefore, when the Vcc abnormality is detected by the microcomputer 300, the voltage supply to the power supply wiring 110 is stopped by the operation of the voltage cutoff circuit 50, so that 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). In other words, the voltage cutoff circuit 50 operates so as to reduce the power supply voltage Vs through the reduction of the power supply voltage Vs in accordance with the control signal Sct.

  Thus, according to control device 1a according to the first embodiment, when microcomputer 300 detects a Vcc abnormality, power supply wiring is activated by operating voltage cutoff circuit 50 in accordance with control signal Sct from microcomputer 300. By reducing the voltage 110, the power supply voltage Vcc can be lowered to a voltage region where the microcomputer 300 becomes inoperable. As a result, the operation of the microcomputer 300 can be reliably stopped when the Vcc abnormality is detected.

  In addition, since the operation for lowering the power supply voltage Vcc is started in accordance with a control signal from the microcomputer 300, the nonvolatile memory built in the microcomputer 300 has a timing when the Vcc abnormality occurs and the timing concerned. It is possible to store the circuit state at Therefore, the operation of the microcomputer 300 can be stopped reliably by reducing the power supply voltage Vcc, and information useful for failure analysis can be collected.

[Modification of Embodiment 1]
In the first embodiment, the configuration in which the voltage abnormality detection circuit 400 is provided as an external circuit of the microcomputer 300 is exemplified. On the other hand, it is also possible to detect a Vcc abnormality based on an analog / digital conversion (A / D conversion) value of the power supply voltage Vcc in the microcomputer 300. In the modification of the first embodiment, a variation for detecting a Vcc abnormality by software processing in the microcomputer 300 will be described.

  FIG. 2 is a schematic circuit diagram for explaining detection of a Vcc abnormality according to the modification of the first embodiment.

  Referring to FIG. 2, voltage dividing circuit 410 is configured similarly to FIG. 1, and outputs a divided voltage Vdv obtained by dividing power supply voltage Vs to node N0. The voltage dividing ratio Dk in the voltage dividing circuit 410 is the same as that in FIG. 1, and the divided voltage Vdv is expressed by Vdv = Vs × Dk.

  The output node N0 of the voltage dividing circuit 410 is electrically connected to the input terminal 310 of the microcomputer 300 via the resistance element Rc. A diode Dp for protecting the input terminal 310 from a voltage exceeding the power supply voltage Vcc is connected between the input terminal 310 and the power supply wiring 200.

  The microcomputer 300 has an A / D converter 320. The A / D converter 320 converts the input voltage (divided voltage Vdv) to the input terminal 310 into a digital value Dv. The digital value Dv is obtained by quantizing the divided voltage Vdv in 2 n stages using an n-bit signal (n: plural).

  A / D converter 320 receives reference voltage Vref according to power supply voltage Vcc. The reference voltage Vref is generated from the power supply voltage Vcc inside the microcomputer 300. For this reason, when the power supply voltage Vcc rises or falls, the reference voltage Vref also rises or falls accordingly.

The CPU (Central Processing Unit) 330 has a control process for detecting fluctuations in the power supply voltage Vcc based on the digital value Dv from the A / D (analog / digital) converter 320. The CPU 330 outputs a control signal Sct (FIG. 1) according to the determination result based on the digital value Dv.

  FIG. 3 is a conceptual diagram for explaining the influence of Vcc abnormality on the operation of the A / D converter 320. Hereinafter, an example in which the A / D converter 320 generates the digital value Dv using an 8-bit signal (n = 8) will be described (n = 8).

  Referring to FIG. 3, A / D converter 320 quantizes input divided voltage Vdv by decomposing a voltage range from ground voltage GND to reference voltage Vref into 256 stages. Therefore, the minimum value Dmin = 0 of the digital value Dv and the maximum value Dmax = 255.

  The right side of FIG. 3 shows an A / D conversion operation when the power supply voltage Vcc is normal. When the power supply voltage Vcc is normal, it is assumed that Dv = Dv1 is converted according to the divided voltage Vdv (Vdv = Vs × Dk).

  On the other hand, the left side of FIG. 3 shows an A / D conversion operation when the power supply voltage Vcc increases due to the occurrence of a short circuit between input and output in the voltage regulator 40 (hereinafter also referred to as “when Vcc increases”). . When the power supply voltage Vcc increases, the A / D conversion reference voltage Vref also increases accordingly. As a result, the voltage range corresponding to Dmin to Dmax is expanded. As a result, the input voltage corresponding to Dv = Dv1 increases. Specifically, it is understood that the input voltage (analog voltage) corresponding to the digital value Dv increases according to the increase rate of the power supply voltage Vcc.

  On the other hand, even if a short circuit between input and output occurs in the voltage regulator 40, the power supply voltage Vs does not change. For this reason, even when Vcc rises, the divided voltage Vdv of the voltage dividing circuit 410 does not change from when Vcc is normal. On the other hand, since the reference voltage Vref is increased, the digital value Dv obtained by A / D converting the divided voltage Vdv is reduced to Dv = Dv2.

  Therefore, it is possible to detect an increase in the power supply voltage Vcc in response to the digital value Dv decreasing from Dv1 exceeding the determination value Dth.

  Although illustration is omitted, when the power supply voltage Vcc decreases, the digital value Dv obtained by A / D converting the divided voltage Vdv increases from Dv1 when Vcc is normal. Therefore, it is possible to detect a decrease in the power supply voltage Vcc in accordance with an increase in the digital value Dv.

  Here, an operation when the power supply voltage Vcc of the power supply wiring 200 is input to the A / D converter 320 and the power supply voltage Vcc is directly monitored will be considered as a comparative example. In this case, as the power supply voltage Vcc increases, the input voltage to the A / D converter 320 increases and the reference voltage Vref for A / D conversion also increases. As a result, since the ratio of the input voltage (Vcc) to the reference voltage Vref does not change, the digital value Dv output from the A / D converter 320 does not substantially change. Therefore, it is difficult to detect an abnormality in the power supply voltage Vcc based on the digital value Dv.

  On the other hand, according to the Vcc abnormality detection configuration shown in FIG. 2, the A / D converter 320 generates a divided voltage Vdv of the power supply voltage Vs that is stable even when the power supply voltage Vcc is abnormal, and the power supply voltage Vcc. A comparison result with the reference voltage Vref that changes accordingly can be obtained. That is, by comparing the power supply voltages Vs and Vcc through A / D conversion, it is possible to detect the fluctuation of the power supply voltage Vcc when the power supply voltage Vs is stable.

Next, an arrangement example of the voltage dividing circuit 410 necessary for detecting the Vcc abnormality will be described.
In the control device 1a, it is common to apply a power saving mode in order to reduce power consumption during standby. In the power saving mode, the power supply voltage Vs is lowered. For example, the power supply voltage Vs is reduced from 15V to 9V in the power saving mode. For this reason, the microcomputer 300 needs to monitor the power supply voltage Vs in order to confirm whether or not the power saving mode is applied. Therefore, the voltage dividing circuit 410 (FIG. 2) for detecting the Vcc abnormality can be arranged also for the power saving mode detection.

  FIG. 4 is a conceptual diagram for explaining a determination method when the voltage dividing circuit for detecting the power saving mode is used for Vcc abnormality detection.

  Referring to FIG. 4, in the power saving mode, the digital value Dv of the A / D converter 320 decreases as the power supply voltage Vs decreases. Therefore, the determination value Dt1 for detecting the power saving mode can be set in correspondence with the divided voltage Vdv in the power supply voltage Vs in the power saving mode. When the digital value Dv obtained by A / D converting the divided voltage Vdv is smaller than the determination value Dt1, the microcomputer 300 can detect a decrease in the power supply voltage Vs due to application of the power saving mode.

  On the other hand, since the power supply voltage Vs is controlled to 15 V during normal times (when the power saving mode is not applied), the digital value Dv is a value in the range where the determination value Dt1 is also high. Further, using a reference voltage Vref corresponding to a normal value (standard value) of the power supply voltage Vcc, a digital value (Dv1 in FIG. 3) when the power supply voltage Vs (15V) is A / D converted is included. The range of Dv ≦ Dt3 can be the normal Vcc range.

  In other words, using Dt2 and Dt3 as determination values, when Dt1 <Dv <Dt2, an increase in the power supply voltage Vcc is detected, while a decrease in the power supply voltage Vcc is detected when Dv> Dt3. it can. The determination values Dt1 to Dt3 can be adjusted by the voltage dividing ratio Dk by the voltage dividing circuit 410.

  The microcomputer 300 detects a Vcc abnormality when Dt1 <Dv <Dt2 or Dv> Dt3, and sets the control signal Sct to the H level. On the other hand, when Dt2 ≦ Dv ≦ Dt3, the control signal Sct is set to L level (Vcc abnormality non-detection).

Next, a modified example of the Vcc abnormality detection configuration shown in FIG. 2 will be further described.
FIG. 5 is a circuit diagram for explaining a modification of the Vcc detection configuration shown in FIG.

  5 is compared with FIG. 2, in the circuit configuration of FIG. 5, the voltage dividing circuit 410 is connected between the wiring 115 and the ground wiring 120 instead of the power supply wiring 100. That is, the voltage dividing circuit 410 divides the input voltage of the voltage regulator 40.

  The output node N0 of the voltage dividing circuit 410 is connected to the input terminal 310 of the microcomputer 300 via the resistance element Rc, similarly to the configuration of FIG. The configuration of other parts is the same as that in FIG. 2 including the arrangement of the diode Dp (not shown) and the configuration in the microcomputer 300.

  According to the circuit configuration of FIG. 5, when the input / output of the voltage regulator 40 is short-circuited, the power supply voltage Vcc rises to a level equivalent to the voltage of the wiring 115. On the other hand, the reference voltage Vref of the A / D converter 320 also increases according to the voltage of the wiring 115. For this reason, the digital value Dv output from the A / D converter 320 is a value according to the voltage dividing ratio Dk in the voltage dividing circuit 410.

  FIG. 6 is a conceptual diagram for explaining determination for short circuit detection in the Vcc abnormality detection configuration shown in FIG.

  Referring to FIG. 6, when the input / output of voltage regulator 40 is short-circuited, digital value Dv from A / D converter 320 approaches a constant value D * determined by voltage division ratio Dk. For example, when Vref = Vcc, D * = Dmax × Dk.

  On the other hand, when the short circuit between the input and output of the voltage regulator 40 does not occur, the power supply voltage Vs and the reference voltage Vref are greatly different (Vs> Vref). It is understood that it rises above D *.

  Therefore, in the circuit configuration of FIG. 5, when the digital value Dv falls within the range of the determination values Dta to Dtb, it is possible to detect a Vcc abnormality due to a short circuit between the input and output of the voltage regulator 40. . Determination values Dta and Dtb are determined in advance in correspondence with a voltage range including a constant value D * corresponding to a constant voltage according to the voltage division ratio Dk. As a result, there is an advantage that it is easy to set a determination value for detecting a short circuit between the input and output of the voltage regulator 40.

  In the modification of the first embodiment (FIGS. 2 and 5), the function of the “abnormality detection unit” for detecting the Vcc abnormality by the voltage dividing circuit 410, the A / D converter 320, and the determination processing in the CPU 430. Is realized.

[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. Also in the following embodiments, the control signal Sct by the microcomputer 300 can be generated in the same manner as in the first embodiment or its modification.

  FIG. 7 is a schematic circuit diagram for illustrating the configuration of the control device according to the second embodiment.

  Compared with FIG. 1 in FIG. 7, 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 Vcc through the reduction of the power supply voltage Vs in accordance with the control signal Sct is disposed instead of the voltage cutoff circuit 50.

  In FIG. 7, 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 contrary, 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 the target value. 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.

  The voltage drop circuit 70 operates in response to the control signal Sct from the microcomputer 300, similarly to the voltage cutoff circuit 50. 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. A control signal Sct 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 control signal Sct 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.

  In contrast, when a Vcc abnormality is detected and control signal Sct is set to H level, voltage drop circuit 70 operates. 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. For this reason, the latch terminal 61 is applied with a voltage of a predetermined level or higher by being electrically connected to the power supply wiring 65.

  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, the generation of the power supply voltage Vs by the power conversion circuit 2 is stopped, so that the power supply voltage Vs and the power supply voltage Vcc continue to decrease, and finally the voltage region where the microcomputer 300 becomes inoperable is reached. The power supply voltage Vcc can be reduced.

  Thus, in control device 1b according to the second embodiment, voltage conversion circuit 2 for power supply wiring 110 is operated by the latch function of control IC 60 by operating voltage reduction circuit 70 in accordance with control signal Sct from microcomputer 300. The supply of the power supply voltage Vs from can be stopped. As a result, as in the first embodiment, the power supply voltage Vcc can be lowered to a voltage region where the microcomputer 300 cannot operate by reducing the voltage of the power supply wiring 110 in accordance with the control signal Sct. 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]
In the third embodiment, a configuration of a control device that has an automatic return function when the Vcc abnormality is temporary will be described.

  FIG. 8 is a circuit diagram for illustrating a schematic configuration of a control device according to the third embodiment of the present invention.

  Comparing FIG. 8 with FIG. 7, control device 1 c according to the third embodiment includes a voltage reduction circuit 90 instead of voltage reduction circuit 70 as compared with control device 1 b 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 drop circuit 90 operates in response to the control signal Sct from the microcomputer 300, similarly to the voltage drop circuit 70. 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.

  A control signal Sct set to H level when a Vcc abnormality is detected is input from the microcomputer 300 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, control signal Sct 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.

  In contrast, when Vcc abnormality occurs, the control signal Sct is set to the H level, whereby 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 during the H level period of the control signal Sct, the power supply voltage Vs rises as a feedback signal from the Vs detection circuit 80 to the control input terminal 63 of the control IC 60. Is continuously input. 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 the power supply voltage Vs decreases, the output voltage of the voltage regulator 40 also decreases, so the power supply voltage Vcc also decreases. Thereby, 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 control signal Sct from microcomputer 300 to convert the feedback signal from Vs detection circuit 80 to control IC 60. Thus, the power supply voltage Vs supplied by the power conversion circuit 2 can be lowered to the minimum level in terms of control. As a result, as in the first embodiment, the power supply voltage Vcc can be lowered to a voltage region where the microcomputer 300 becomes inoperable in accordance with the control signal Sct. That is, the operation of the microcomputer 300 can be stopped reliably.

  Further, in the control device 1c shown in FIG. 8, the Vcc abnormality is temporary. For example, when the detection signal Fvc changes to H level and returns to L level within a predetermined time, When the computer 300 returns the control signal Sct from the H level to the L level, the power supply voltages Vs and Vcc can be automatically restored. The predetermined time needs to be set with a margin so as to be shorter than the time normally required until the power supply voltage Vcc decreases corresponding to the operation of the voltage reduction circuit 90. On the other hand, when the detection signal Fvc does not change from the H level to the L level within the predetermined time, the microcomputer 300 detects even if the detection signal Fvc changes to the L level in accordance with the decrease in the power supply voltage Vcc. The signal Fvc is held at the H level.

  When the control signal Sct is returned to the L level, the shunt regulator 82 receives the divided voltage of the power supply voltage Vs by the resistance elements 83 and 84 again at the reference (R) terminal. Thereby, the Vs detection circuit 80 can input the feedback signal for controlling the power supply voltage Vs to the control IC 60 again.

  Therefore, control device 1c according to the third embodiment does not require the arrangement of voltage cutoff circuit 50 as in the first embodiment. In addition, when Vcc abnormality is temporary, control signal Sct By returning to the L level, the power supply voltage Vs and the power supply voltage Vcc can be automatically restored.

[Modification of Embodiment 3]
FIG. 9 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.

  9 and 8, control device 1d according to the modification of the third embodiment replaces voltage drop circuit 90 (FIG. 8) with a voltage drop as compared with control device 1c 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.

  Voltage drop circuit 90 # operates in response to control signal Sct from microcomputer 300, 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. 8).

  Voltage control circuit 90 # short-circuits the reference (R) terminal and anode (A) terminal of shunt regulator 82 by turning on transistor 92 when control signal Sct 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, if the control signal Sct is maintained at the H level when the Vcc abnormality occurs, the control operation for increasing the 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, the generation of the power supply voltage Vs by the power conversion circuit 2 is stopped, so that the power supply voltage Vs and the power supply voltage Vcc continue to decrease, and finally the voltage region where the microcomputer 300 becomes inoperable is reached. The power supply voltage Vcc can be reduced.

  Thus, in control device 1d according to the modification of the third embodiment, similarly to control device 1c according to the third embodiment, voltage reduction circuit 90 # is operated in accordance with control signal Sct, and Vs detection circuit 80 is operated. By converting the feedback signal from the control IC 60 to the control IC 60, the power supply voltage Vcc can be lowered to a voltage region where the microcomputer 300 cannot operate.

  Also in the control device 1d, the control signal Sct can be set similarly to the control device 1c. In other words, when the Vcc abnormality is temporary, for example, when the detection signal Fvc returns to the L level within a predetermined time after the detection signal Fvc changes to the H level, the microcomputer 300 controls the control signal Sct. By returning from H level to L level, the power supply voltages Vs and Vcc can be automatically restored.

[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. 10 is a circuit configuration diagram of the control device according to the fourth embodiment of the present invention.
Referring to FIG. 10, 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 particular, the DC voltage Vdc output to the power supply wiring 520 can be controlled by periodically turning on / off (switching) the transistor 510 and controlling the time ratio (duty ratio) of the ON period with respect to the switching period.

  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 flowing through the reactor 506. 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.

  Furthermore, the control device 1e is provided with a voltage drop circuit 91 that operates according to the control signal Sct. 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. A control signal Sct from the microcomputer 300 is input to the base (control electrode) of the transistor 580. In control device 1e as well, control signal Sct can be set similarly to control device 1c according to the third embodiment. In other words, when the Vcc abnormality is temporary, for example, when the detection signal Fvc returns to the L level within a predetermined time after the detection signal Fvc changes to the H level, the microcomputer 300 controls the control signal Sct. Can be returned to the L level.

  Therefore, when microcomputer 300 detects a Vcc abnormality, transistor 580 is turned on by setting control signal Sct to the 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.

  FIG. 11 shows a flowchart for illustrating the operation at the time of Vcc abnormality detection of control device 1e according to the fourth embodiment of the present invention.

  Referring to FIG. 11, when microcomputer 300 detects a Vcc abnormality (when YES in S100), microcomputer 300 sets control signal Sct to H level and operates voltage reduction circuit 91 to increase the voltage of booster circuit 500. The function is turned off (S110).

  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 (S120). For example, when the power supply voltage Vdc drops from 280V to 140V, Ic increases about twice.

  Accordingly, the control IC 60 of the power conversion circuit 2 detects Ic> Ith (Ith: reference value), thereby detecting an overcurrent and stopping the power conversion operation (S130). As a result, generation of the power supply voltage Vs by the power conversion circuit 2 is stopped, so that the power supply voltage Vs and the power supply voltage Vcc continue to decrease. As a result, 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 from the power supply wirings 110 and 200 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.

  As described above, in the control device 1e according to the fourth embodiment, in the configuration including the booster circuit, when the Vcc abnormality is detected, the booster function of the booster circuit is stopped to supply power to the voltage region where the microcomputer 300 cannot operate. The voltage Vcc can be reduced.

  10 illustrates a configuration in which the transistor 580 that is turned on in response to the control signal Sct is disposed separately from the transistor 570 that is turned on in response to the boost stop signal Sbs. The arrangement of the transistor 580 can be omitted if the transistor is turned on / off according to the logical sum (OR) signal of the control signal Sct. As described above, control device 1e according to the fourth embodiment realizes a power supply configuration for reducing power supply voltage Vcc when Vcc abnormality is detected while suppressing additional circuit elements in a configuration including a booster circuit. be able to.

  Note that the configuration for detecting a Vcc abnormality is not particularly limited through the first to fourth embodiments, and any configuration is possible as long as the microcomputer 300 can detect an abnormality (increase or decrease) in the power supply voltage Vcc. The configuration can be applied. That is, the Vcc abnormality may be detected by an external circuit of the microcomputer 300 as in the configuration of FIG. 1, and the Vcc abnormality is detected by combining the processing by the microcomputer 300 as in the configuration of FIG. 2 or FIG. Also good.

  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, 22, 24, 62, 502, 515 Smoothing capacitor, 15, 52, 53, 71, 92, 470 , 510, 570, 580 transistor, 16, 412, 512 current detection resistor, 19, 120 ground wiring, 20 transformer, 21, 22 primary winding, 23 secondary winding, 40 voltage regulator, 50 voltage cutoff circuit, 51 Thyristor, 55 to 58, 64, 72, 83, 84, 94, Ra to Rd Resistive element, 60 Control IC, 61 Latch terminal, 63 Control input terminal, 65, 100, 110, 200, 401, 501, 520 Power supply Wiring, 70, 90, 90 #, 91 Voltage drop circuit, 75, 85, 560 Photocoupler, 75a, 85 , 560a Photodiode, 75b, 85b, 560b Phototransistor, 80 Vs detection circuit, 82 shunt regulator, 115 wiring, 300 microcomputer, 310,552 input terminal, 320 A / D converter, 400 voltage abnormality detection circuit, 410 minutes Voltage circuit, 430 comparator, 500 boost circuit, 506 reactor, 508 diode (boost circuit), 510 transistor (boost circuit), 550 control IC (boost circuit), 570, 580 transistor (for boost function stop), 600 high voltage load, D1, D2 diode (power conversion circuit), Dk voltage division ratio, Dmax maximum value, Dt1 to Dt3, Dta, Dtb, Dth judgment value, Dv digital value, Fvc detection signal, GND, GND # ground voltage, N0 to N3 No , R0 current limiting resistor, Sbs boost stop signal, Sct control signal (at Vcc abnormality detection), Vcc, Vd, Vdc, Vs the power supply voltage, Vdv divided voltage, Vref reference voltage, Vt determination voltage.

Claims (1)

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 unit for detecting an abnormality of the second power supply voltage based on a comparison between a voltage according to the first power supply voltage and a voltage according to the second power supply voltage;
When operating in accordance with a command from the microcomputer, the voltage of the first power supply wiring input to the voltage adjustment circuit is reduced to reduce the second power supply to a voltage range where the microcomputer becomes inoperable. A voltage drop circuit for reducing the voltage,
The microcomputer activates the voltage drop circuit when the abnormality detection unit detects an abnormality in the second power supply voltage ,
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 , wherein the voltage drop circuit is configured to turn off the boost function of the boost circuit when activated .

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