JP2011024294A - Control circuit of power conversion circuit and power conversion equipment including the control circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a DC/DC converter device capable of prohibiting a step-up operation of a DC/DC converter circuit by appropriately determining malfunction of voltage sensors even during connection of DC power supplies having varying output voltages. <P>SOLUTION: A control circuit 4 generates a PWM signal, and controls the step-up operation of the DC/DC converter circuit 1 by the PWM signal. The control circuit 4 includes a malfunction determination section 46 for determining whether malfunction has occurred in a circuit including an input-voltage sensor, an output-voltage sensor, and a power-conversion circuit based on a difference between an input voltage of the DC/DC converter circuit 1 detected by an input-voltage sensor 2 and an output voltage of the DC/DC converter circuit 1 detected by an output-voltage sensor 3, an operation/stop determination section 41 for prohibiting the step-up operation of the DC/DC converter circuit 1 when the malfunction occurs, an operation/stop change section 42, and a gate block section 45. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a control circuit for a power conversion circuit, a power conversion device including the control circuit, a program for realizing the control circuit, and a recording medium on which the program is recorded.

  2. Description of the Related Art Conventionally, a DC / DC converter device that boosts a DC voltage input from a DC power source such as a solar cell, controls the voltage to a constant voltage, and outputs it to a load has been developed.

  In the DC / DC converter device, an output voltage is detected by an output voltage sensor provided on the output side, and the detected output voltage is controlled to be a target voltage. The DC / DC converter device is provided with means for stopping the operation when the detected output voltage becomes an abnormal voltage so that an overvoltage is not output to the load.

  In order to determine whether to stop the operation based on the voltage detected by the output voltage sensor, it is assumed that the output voltage sensor is normal. That is, when the output voltage sensor is abnormal, the detected output voltage does not indicate the correct voltage. Therefore, even if the voltage is normally output from the DC / DC converter device, the output voltage is determined to be abnormal and the operation is started. May be stopped. Conversely, even if the output voltage of the DC / DC converter device is abnormal, the operation is continued without being determined as abnormal, and an overvoltage may be output to the load. Further, since the DC / DC converter device performs control so that the output voltage becomes the target voltage, the output voltage of the DC / DC converter device reaches the target voltage when the output voltage sensor is abnormal. In some cases, the output voltage is controlled to increase. In this case, an overvoltage is output to the load.

  In Patent Document 1 (Japanese Patent Application Laid-Open No. 8-116664), a range of the time change characteristic of the output voltage when the DC / DC converter device is normally activated (hereinafter referred to as “normal range”) is stored in advance. A DC / DC converter device is described that determines that there is an abnormality when the detected change in the output voltage with time deviates from the normal range and stops the operation. In this DC / DC converter device, the time change of the output voltage deviates from the normal range even when the voltage sensor is abnormal, so that not only the abnormality of the DC / DC converter device but also the abnormality of the voltage sensor can be detected.

JP-A-8-116664

  However, since this DC / DC converter device is based on the assumption that a constant voltage is input from a DC power source, when a DC power source such as a solar cell whose output voltage varies due to variations in solar radiation intensity is connected, It cannot be applied. That is, when the input DC voltage fluctuates, the output voltage also fluctuates due to the control delay, so that even if the DC / DC converter device is operating normally, the output voltage deviates from the normal range. In some cases, a malfunction of stopping the operation may occur. Therefore, in this DC / DC converter device, it is necessary to change the normal range according to the fluctuation of the output voltage of the DC power supply based on the fluctuation of the solar radiation intensity, but the fluctuation of the solar radiation intensity is irregular, Cannot be determined. Such a problem occurs not only when the solar battery is used but also when a DC power source having a factor that the output voltage fluctuates is used.

  The present invention has been conceived under the above-described circumstances, and is a DC / DC that can appropriately determine abnormality of a voltage sensor even when a DC power source whose output voltage varies is connected. The object is to provide a DC converter device.

  In order to solve the above problems, the present invention takes the following technical means.

  The control circuit provided by the first aspect of the present invention is a control circuit that generates a PWM signal and controls a power conversion operation of the power conversion circuit based on the PWM signal, the power detected by an input voltage sensor. Whether an abnormality has occurred in the circuit including the input voltage sensor, the output voltage sensor, and the power conversion circuit based on the difference between the input voltage of the conversion circuit and the output voltage of the power conversion circuit detected by the output voltage sensor An abnormality determining means for determining whether or not, and a control prohibiting means for prohibiting a power conversion operation of the power conversion circuit when the abnormality occurs.

  According to this configuration, occurrence of an abnormality is determined based on the difference between the detected input voltage and output voltage, and if an abnormality occurs, the power conversion operation of the power conversion circuit is prohibited. Thereby, when the input voltage sensor or the output voltage sensor is abnormal, it is possible to prevent the overvoltage from being output to the load by starting the power conversion circuit or continuing the operation.

  Further, since the abnormality determination is performed by comparing the detected input voltage with the output voltage, even if a DC power supply whose output voltage fluctuates is connected and the input voltage of the power conversion circuit fluctuates, Can be determined appropriately.

  In a preferred embodiment of the present invention, the control prohibiting unit prohibits the power conversion operation of the power conversion circuit by stopping the generation operation of the PWM signal generating unit that generates the PWM signal.

  In a preferred embodiment of the present invention, the control prohibiting unit stops the output of the PWM signal from the PWM signal generating unit that generates the PWM signal to the power conversion circuit, thereby performing the power conversion operation of the power conversion circuit. Is prohibited.

  In a preferred embodiment of the present invention, the abnormality determining means includes an input / output voltage difference calculating means for calculating an input / output voltage difference by subtracting the output voltage from the input voltage, and the input / output voltage difference is a predetermined voltage. Determining means for determining whether or not the difference is greater than, and determining means for determining that the abnormality has occurred when the input / output voltage difference is greater than the predetermined voltage difference.

  According to this configuration, an abnormality is determined when the input / output voltage difference is larger than the predetermined voltage difference. Since the input voltage of the power conversion circuit should be equal to or lower than the output voltage, if the detected input voltage is larger than the detected output voltage, it is considered that the output voltage sensor or the like is abnormal. Therefore, when the input / output voltage difference is larger than the predetermined voltage difference of zero or more, it can be determined that there is an abnormality. In addition, by comparing the input / output voltage difference with the predetermined voltage difference, it is possible to suppress erroneous detection of abnormality due to detection errors of the input voltage sensor and the output voltage sensor.

  In a preferred embodiment of the present invention, the abnormality determining means calculates a theoretical output voltage calculating means for calculating a theoretical output voltage obtained by a predetermined arithmetic expression using the input voltage and the period and on-time of the PWM signal. And a second discriminating unit that discriminates whether or not an absolute value of a difference between the theoretical output voltage and the output voltage is larger than a predetermined threshold value, wherein the judging unit has the input / output voltage difference It is determined that the abnormality has occurred when either the case where the voltage difference is greater than the predetermined voltage difference or the case where the absolute value is greater than the predetermined threshold value.

  According to this configuration, even when the theoretical output voltage and the output voltage are separated by the predetermined threshold or more, it is determined as abnormal. Since the theoretical output voltage and the output voltage should be close to each other, it is considered that there is an abnormality when the theoretical output voltage is more than the predetermined threshold. Therefore, it can be determined that there is an abnormality when the theoretical output voltage and the output voltage are separated from each other by the predetermined threshold or more. The on-time of the PWM signal is a duration of the on-state of the PWM signal (a state in which the switching element of the power conversion circuit to which the PWM signal is input is turned on).

  In a preferred embodiment of the present invention, the abnormality determining means calculates a theoretical output voltage calculating means for calculating a theoretical output voltage obtained by a predetermined arithmetic expression using the input voltage and the period and on-time of the PWM signal. And when the absolute value of the difference between the theoretical output voltage and the output voltage exceeds a predetermined threshold, timing is started, and when the absolute value is less than or equal to the threshold, timing means for stopping the timing, and the timing Second determination means for determining whether or not the time counted by the means has reached a predetermined duration, wherein the determination means has a larger input / output voltage difference than the predetermined voltage difference. When the time measured by the time measuring means reaches the predetermined duration, it is determined that the abnormality has occurred.

  According to this configuration, the duration of the state where the theoretical output voltage and the output voltage are separated from each other by the predetermined threshold or more is counted, and it is determined that there is an abnormality when the predetermined duration is reached. Accordingly, it is possible to suppress erroneous detection of abnormality due to fluctuations in the input voltage or output voltage of the power conversion circuit.

  In a preferred embodiment of the present invention, the power conversion circuit is a DC / DC converter circuit.

  In a preferred embodiment of the present invention, the power conversion circuit includes an rectifying element, a switching element connected in reverse parallel to the rectifying element, and a capacitor connected in parallel to the output terminal. It is a converter circuit.

  A power conversion device provided by the second aspect of the present invention includes the power conversion circuit and a control circuit provided by the first aspect of the present invention.

  The program provided by the third aspect of the present invention causes a computer to function as a control circuit provided by the first aspect of the present invention.

  The recording medium provided by the fourth aspect of the present invention is a computer-readable recording medium that records the program provided by the third aspect of the present invention.

  Other features and advantages of the present invention will become more apparent from the detailed description given below with reference to the accompanying drawings.

It is a figure for demonstrating the DC / DC converter apparatus which concerns on 1st Embodiment of this invention. FIG. 2 is a circuit diagram illustrating a circuit configuration of a DC / DC converter, an input voltage sensor, and an output voltage sensor in the DC / DC converter device illustrated in FIG. 1 by an equivalent circuit of main circuit elements. It is a flowchart for demonstrating the process of a driving | operation / stop determination part. It is a flowchart for demonstrating the process of an abnormality determination part. It is a figure for demonstrating the AC / DC converter apparatus which concerns on 2nd Embodiment of this invention. It is a figure for demonstrating the internal structure of an AC / DC converter circuit.

  Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings, taking as an example the case where a control circuit according to the present invention is used in a DC / DC converter device.

  FIG. 1 is a diagram for explaining a DC / DC converter device according to a first embodiment of the present invention. FIG. 2 is a circuit diagram showing the circuit configuration of the DC / DC converter circuit 1, the input voltage sensor 2, and the output voltage sensor 3 in the DC / DC converter apparatus A by an equivalent circuit of main circuit elements.

  The DC / DC converter device A boosts the DC voltage input from the DC power supply B, controls it to a constant voltage, and outputs it to the load C. The DC power source B outputs a DC voltage to the DC / DC converter device A, and includes, for example, a solar battery. A solar cell generates direct-current power by converting solar energy into electrical energy. The DC power supply B outputs the generated DC power to the DC / DC converter device A. Note that the DC power source B is not limited to one that generates DC power from a solar cell. For example, the DC power source B may be a fuel cell, a storage battery, an electric double layer capacitor, a lithium ion battery, or AC power generated by a diesel engine generator, a micro gas turbine generator, a wind turbine generator, or the like. It may be a device that converts to DC power and outputs it.

  As shown in FIG. 1, the DC / DC converter device A includes a DC / DC converter circuit 1, an input voltage sensor 2, an output voltage sensor 3, and a control circuit 4.

  The input voltage sensor 2 detects an input voltage input from the DC power source B to the DC / DC converter circuit 1. The input voltage Vi detected by the input voltage sensor 2 is output to the control circuit 4 as an input voltage signal. The output voltage sensor 3 detects an output voltage output from the DC / DC converter circuit 1 to the load C. The output voltage Vo detected by the output voltage sensor 3 is output to the control circuit 4 as an output voltage signal.

  The DC / DC converter circuit 1 is a so-called step-up converter circuit that boosts the input voltage input from the DC power source B to a preset voltage and outputs the boosted voltage to the load C. A DC / DC converter circuit 1 in FIG. 2 shows a circuit configuration of the DC / DC converter circuit 1 in the present embodiment. As shown in FIG. 2, the DC / DC converter circuit 1 includes a transistor S1 as a switching element, a reactor L1, a diode D1, and a capacitor C1. The switching element is not limited to a transistor, and may be an IGBT, a MOSFET, a GTO, or the like. In the DC / DC converter circuit 1, a reactor L1 and a diode D1 are connected in series between an input terminal and an output terminal, a transistor S1 is connected in parallel at the connection point, and a capacitor C1 is connected in parallel on the output terminal side. It has a connected configuration. The circuit configuration of the DC / DC converter circuit 1 is not limited to this, and any known boost converter may be used.

  The transistor S1 is turned on when a base voltage is applied during an on period in which the PWM signal input from the control circuit 4 is on (eg, high level), and the PWM signal is off (eg, low). When the base voltage is not applied during the off period, the level is turned off. That is, on and off are switched by the input PWM signal. During the period when the transistor S1 is on, the electric power input from the DC power source B is accumulated as electromagnetic energy in the reactor L1. When the transistor S1 is off, the electromagnetic energy accumulated in the reactor L1 is released through the diode D1. At this time, the reactor voltage due to the released electromagnetic energy is superimposed on the DC voltage Vi input from the DC power source B. By switching the transistor S1 on and off, accumulation of electromagnetic energy in the reactor L1 and release of electromagnetic energy from the reactor L1 are alternately repeated.

Since the electromagnetic energy accumulated in the reactor L1 and the electromagnetic energy released from the reactor L1 are equal, the theoretical output voltage Vo ′ of the DC / DC converter circuit 1 is the input voltage Vi, and the period of the PWM signal. T, where Ton is the duration of the on state (hereinafter referred to as “on time”),

Vo '= Vi / {1- (Ton / T)} (1)

It can be calculated by the following equation. Since (Ton / T) is a value from “0” to “1”, the theoretical output voltage Vo ′ is a voltage equal to or higher than the input voltage Vi, and is a voltage obtained by boosting the input voltage input from the DC power supply B. It becomes.

  When the PWM signal is not input from the control circuit 4 (that is, the input signal is always off), the transistor S1 is always off. In this case, the DC / DC converter circuit 1 is stopped and does not perform the boosting operation. The fact that the PWM signal is not inputted can be considered that the PWM signal whose on-time Ton is “0” is inputted. Therefore, in the above equation (1), when Ton = 0, Vo ′ = Vi, and the theoretical output voltage Vo ′ coincides with the input voltage Vi.

The control circuit 4 controls the DC / DC converter circuit 1 so that the output voltage of the DC / DC converter circuit 1 becomes an output voltage setting value Vo ^* (a voltage value set in advance as a voltage output to the load C). For generating a PWM signal. The control circuit 4 receives the input voltage signal Vi and the output voltage signal Vo from the input voltage sensor 2 and the output voltage sensor 3, respectively, and outputs the generated PWM signal to the DC / DC converter circuit 1. The control circuit 4 has a configuration for detecting an abnormality in the output voltage sensor 3 and the like and stopping the output of the PWM signal.

  The control circuit 4 includes an operation / stop determination unit 41, an operation / stop switching unit 42, a voltage control unit 43, a PWM signal generation unit 44, a gate block unit 45, and an abnormality determination unit 46.

The operation / stop determination unit 41 determines whether to operate or stop the DC / DC converter circuit 1. The operation / stop determination unit 41 starts from the input voltage signal Vi output from the input voltage sensor 2 with a starting voltage setting value Vi ^* (in order to start the DC / DC converter circuit 1 when the input voltage exceeds this value). The difference voltage signal ΔVi obtained by subtracting the set voltage value) and the abnormality determination signal from the abnormality determination unit 46 are input, and the operation / stop signal is output to the operation / stop switching unit 42. In the present embodiment, the abnormality determination unit 46 outputs a low level signal as an abnormality determination signal while determining that there is no abnormality, and outputs a high level signal (abnormality when it is determined that there is an abnormality). The detection signal is switched and output, but the present invention is not limited to this. For example, a detection pulse may be output when it is determined that there is an abnormality. In this embodiment, the operation signal is a high level signal and the stop signal is a low level signal, but the present invention is not limited to this.

FIG. 3 is a flowchart for explaining the processing of the operation / stop determination unit 41. First, it is determined whether or not the differential voltage signal ΔVi is greater than “0”, that is, whether or not the input voltage Vi exceeds the starting voltage setting value Vi ^* (S1). When the differential voltage signal ΔVi is larger than “0” (S1: YES), it is determined whether or not the abnormality determination signal is an abnormality detection signal indicating that there is an abnormality (S2). When the abnormality determination signal is not an abnormality detection signal (S2: NO), an operation signal is output to the operation / stop switching unit 42 (S3).

  When the differential voltage signal ΔVi is “0” or less at step S1 (S1: NO), or when the abnormality determination signal is an abnormality detection signal at step S2 (S2: YES), the stop signal is the operation / stop switching unit 42. (S4).

That is, the operation / stop determination unit 41 outputs an operation signal when the input voltage Vi exceeds the start voltage set value Vi ^* , but the abnormality determination unit 46 determines that an abnormality has occurred and an abnormality detection signal is input. Sometimes, the operation signal is switched to a stop signal. The operation / stop determination unit 41 outputs a stop signal regardless of the abnormality determination signal when the input voltage Vi is equal to or less than the start voltage set value Vi ^* .

The operation / stop switching unit 42 switches the target value of the output voltage of the DC / DC converter circuit 1 in accordance with the operation / stop signal input from the operation / stop determination unit 41, so that the DC / DC converter circuit 1 Switching between operation and stop. When the signal input from the operation / stop determination unit 41 is switched from the stop signal to the operation signal, the operation / stop switching unit 42 changes the target value from “0” to the preset output voltage setting value Vo ^* . Switch. The control circuit 4 generates and outputs a PWM signal for setting the output voltage to the output voltage set value Vo ^* . As a result, the DC / DC converter circuit 1 is activated and enters an operating state. While the operation signal is input from the operation / stop determination unit 41, the operation state of the DC / DC converter circuit 1 continues.

On the other hand, when the signal input from the operation / stop determination unit 41 is switched from the operation signal to the stop signal, the operation / stop switching unit 42 switches the target value from the output voltage setting value Vo ^* to “0”. The control circuit 4 starts control of the output voltage so that the output voltage becomes “0”, and generates and outputs a PWM signal. The output voltage decreases according to the response speed of the output voltage control, and the ON time of the PWM signal also gradually decreases. Eventually, the ON time of the PWM signal becomes “0”, and the output voltage matches the input voltage. That is, the PWM signal is always turned off (the PWM signal is stopped), and the DC / DC converter circuit 1 is stopped. While the stop signal is input from the operation / stop determination unit 41, the stop state of the DC / DC converter circuit 1 continues.

The operation / stop switching unit 42 switches the target value between the output voltage set value Vo ^* and “0”, and gradually switches between the operation state and the stop state of the DC / DC converter circuit 1, thereby switching suddenly. The inconvenience caused by this is avoided. Further, when the gate block unit 45 shuts off the PWM signal, if the target value of the output voltage is left as the output voltage set value Vo ^* , the voltage control unit 43 outputs the output voltage that has been lowered due to the shutoff of the PWM signal. In order to maintain the voltage setting value Vo ^* , the command value to the PWM signal generation unit 44 is continuously increased. When the gate block unit 45 releases the cutoff of the PWM signal in this state, a PWM signal corresponding to the command value in the increased state is supplied to the DC / DC converter circuit 1 and the output voltage jumps. appear. Therefore, the operation / stop switching unit 42 switches the target value in accordance with the interruption and release of the PWM signal by the gate block unit 45.

  The voltage control unit 43 is for feedback control of the output voltage of the DC / DC converter circuit 1 to a target value. The voltage control unit 43 receives a deviation between the output voltage signal Vo output from the output voltage sensor 3 and the target value output from the operation / stop switching unit 42, and a correction value for setting the deviation to “0”. Is output to the PWM signal generation unit 44 as a command value signal.

  The PWM signal generation unit 44 generates and outputs a PWM signal based on the command value signal input from the voltage control unit 43 and the generated carrier signal. The carrier signal is generated as a triangular wave signal having a predetermined frequency. For example, the PWM signal generation unit 44 generates, as a PWM signal, a pulse signal that becomes a high level when the command value signal is larger than the carrier signal and becomes a low level when the command value signal is smaller than the carrier signal.

  The gate block unit 45 blocks the PWM signal input from the PWM signal generation unit 44 to the DC / DC converter circuit 1 based on the signal input from the abnormality determination unit 46. When the gate block signal is not input from the abnormality determination unit 46, the gate block unit 45 outputs the PWM signal input from the PWM signal generation unit 44 to the DC / DC converter circuit 1 as it is. On the other hand, when a gate block signal is input from the abnormality determination unit 46, a signal that is always off is output to the DC / DC converter circuit 1 instead of the PWM signal input from the PWM signal generation unit 44. In the present embodiment, the abnormality determination unit 46 outputs a low level signal to the gate block unit 45 while determining that there is no abnormality, and if it determines that there is an abnormality, the high level signal (gate Block signal) is output, but the present invention is not limited to this.

  The abnormality determination unit 46 determines abnormality of the output voltage sensor 3 and the like. When it is determined that the output voltage sensor 3 or the like is abnormal, the abnormality determination unit 46 outputs a gate block signal to the gate block unit 45 and outputs an abnormality detection signal to the operation / stop determination unit 41.

  Before the DC / DC converter circuit 1 is started (when it is in a stopped state), the abnormality determination unit 46 converts the input voltage signal Vi input from the input voltage sensor 2 and the output voltage signal Vo input from the output voltage sensor 3. Based on this, the abnormality of the output voltage sensor 3 or the like is determined.

As shown in FIG. 2, the DC / DC converter circuit 1 has a configuration in which a diode D1 is connected between an input terminal and an output terminal. The anode terminal of the diode D1 is connected to the input terminal via the reactor L1, and the cathode terminal is connected to the output terminal. Since the diode D1 allows current to flow only from the anode side to the cathode side, when the PWM signal is not input and the transistor S1 continues to be off, the anode side voltage (input voltage) is the cathode side voltage (output voltage). ) It will not be higher. Accordingly, the input voltage Vi detected by the input voltage sensor 2 and the output voltage Vo detected by the output voltage sensor 3 should satisfy the relationship Vi ≦ Vo. Therefore,

Vi−Vo> 0 (2)

If the condition is satisfied, it is considered that the output voltage sensor 3 or the like is abnormal.

  However, detection errors may occur in each sensor. Therefore, when an abnormality is determined based on the above equation (2), there is a possibility that the abnormality is erroneously determined due to a detection error even if the detection value of each sensor is normal. In this embodiment, in order to prevent the DC / DC converter circuit 1 from being stopped due to erroneous detection of an abnormality, the abnormality is determined in consideration of the maximum detection error value of each sensor.

If the detection error of the input voltage sensor 2 is ± ΔVi, the actual input voltage is any value from Vi−ΔVi to Vi + ΔVi, and if the detection error of the output voltage sensor 3 is ± ΔVo, the actual output voltage is The value is any value from Vo−ΔVo to Vo + ΔVo. In order to completely eliminate the erroneous determination of abnormality due to the detection error, the determination condition is that the minimum value (Vi−ΔVi) that the actual input voltage can take is larger than the maximum value (Vo + ΔVo) that the actual output voltage can take. There is a need to. Therefore,

(Vi−ΔVi) − (Vo + ΔVo)> 0
That is,
Vi−Vo> ΔVi + ΔVo (3)

It is necessary to determine whether or not the abnormality is satisfied.

The abnormality determination unit 46 is configured such that the input voltage Vi detected by the input voltage sensor 2 and the output voltage Vo detected by the output voltage sensor 3 are

Vi−Vo> Vref1 (0 ≦ Vref1 ≦ ΔVi + ΔVo) (4)

When the state that satisfies the condition continues for a predetermined time (for example, several milliseconds), it is determined that the output voltage sensor 3 or the like is abnormal. If Vref1 is too small, the possibility of erroneous detection is increased, but if it is too large, the accuracy of determination is deteriorated. In this embodiment, Vref1 is a value of several percent of the input rated voltage, but is not limited to this. When the detection error of each sensor can be ignored, the above equation (2) may be used as a reference equation for determination.

  Further, in this embodiment, in order to eliminate erroneous determination due to instantaneously satisfying the above equation (4) when the input voltage varies or when the output voltage varies due to load variation, the above ( Although the condition of the state of the expression (4) is continued for a predetermined time, it may be determined that there is an abnormality immediately when the expression (4) is satisfied.

  After the DC / DC converter circuit 1 is activated (in the operating state), the abnormality determination unit 46 receives the input voltage signal Vi input from the input voltage sensor 2, the output voltage signal Vo input from the output voltage sensor 3, Based on the PWM signal input from the gate block unit 45, an abnormality in the output voltage sensor 3 or the like is determined.

When the DC / DC converter circuit 1 is in an operating state, a PWM signal is input to the abnormality determination unit 46. The abnormality determination unit 46 measures the period T and the on time Ton of the PWM signal, and calculates the theoretical output voltage Vo ′ from the input voltage Vi detected by the input voltage sensor 2 according to the above equation (1). calculate. The calculated theoretical output voltage Vo ′ and the output voltage Vo detected by the output voltage sensor 3 are

| Vo-Vo '|> Vref2 (5)

When the state satisfying the condition continues for a predetermined time (for example, several seconds), the output voltage Vo detected by the output voltage sensor 3 is greatly different from the theoretical output voltage Vo ′. It is determined that any of the sensor 2, the output voltage sensor 3, and the control circuit 4 is abnormal. Note that Vref2 is a threshold value set in advance, and in the present embodiment, the value is several percent of the input rated voltage, but is not limited thereto.

  Further, in this embodiment, in order to eliminate erroneous determination due to instantaneously satisfying the above equation (5) when the input voltage varies or when the output voltage varies due to load variation, Although the condition of the state of the equation (5) is continued for a predetermined time, it may be determined that there is an abnormality immediately when the equation (5) is satisfied.

  FIG. 4 is a flowchart for explaining the processing of the abnormality determination unit 46.

  First, it is determined whether or not the DC / DC converter circuit 1 is in an operating state, that is, whether or not the signal input from the gate block unit to the abnormality determination unit 46 is a PWM signal (whether or not there is an ON period). (S11). When it is determined that the input signal is not a PWM signal and the DC / DC converter circuit 1 is in a stopped state (S11: NO), it is determined whether or not the above equation (4) is satisfied (S12).

  If the above equation (4) is satisfied (S12: YES), it is determined whether or not the predetermined time has elapsed for the duration of the state (S13). If the predetermined time has not elapsed (S13: NO), the process returns to step S12. If the predetermined time has elapsed (S13: YES), it is determined that there is an abnormality, a gate block signal is output to the gate block unit 45, and an abnormality detection signal is output to the operation / stop determination unit 41 (S14). Processing is terminated.

  In step S12, when the above equation (4) is not satisfied (S12: NO), the process returns to step S11. At this time, the counter of the time during which the state satisfying the above equation (4) is continued is reset to zero.

  In step S11, when it is determined that the input signal is a PWM signal and the DC / DC converter circuit 1 is in an operating state (S11: YES), the PWM signal cycle T and on-time Ton are measured. The theoretical output voltage Vo ′ is calculated by the above equation (1) (S15). Next, it is determined whether or not the above equation (5) is satisfied (S16).

  When the above equation (5) is satisfied (S16: YES), it is determined whether or not the predetermined time has elapsed for the duration of the state (S17). If the predetermined time has not elapsed (S17: NO), the process returns to step S15. When the predetermined time has elapsed (S17: YES), it is determined that there is an abnormality, a gate block signal is output to the gate block unit 45, and an abnormality detection signal is output to the operation / stop determination unit 41 (S14). Processing is terminated.

  In step S16, when the above equation (5) is not satisfied (S16: NO), the process returns to step S11. At this time, the counter of the time during which the state satisfying the above expression (5) is continued is reset to zero.

  In the present embodiment, the abnormality determination unit 46 performs abnormality determination in the stopped state of the DC / DC converter circuit 1 and abnormality determination in the operating state. However, the present invention is not limited to this. Only the determination may be performed. Since the DC / DC converter circuit 1 is a step-up converter circuit, the relationship of Vi ≦ Vo should be established even in the operating state. Therefore, regardless of whether the DC / DC converter circuit 1 is in the operating state or in the stopped state, only the abnormality determination in the stopped state (abnormality determination using the above equation (4)) may be performed.

  In addition, the abnormality determination unit 46 outputs both the gate block signal and the abnormality detection signal when it is determined as abnormal, but the present invention is not limited to this, and only one of the signals may be output. .

  The control circuit 4 may be realized as an analog circuit or a digital circuit. Further, the processing performed by each unit may be designed by a program, and the computer may function as the control circuit 4 by executing the program. The program may be recorded on a recording medium and read by a computer.

  Next, the operation of the control circuit 4 will be described.

When the input voltage Vi detected by the input voltage sensor 2 is equal to or lower than the start voltage setting value Vi ^{* in} the stop state of the DC / DC converter circuit 1, the operation / stop determination unit 41 sends a stop signal to the operation / stop switching unit 42. Output (in FIG. 3, S1: NO to S4). Since the operation / stop switching unit 42 keeps the target value “0”, the PWM signal generation unit 44 outputs a signal that the off period continues. Therefore, the DC / DC converter circuit 1 continues to be stopped.

At this time, the abnormality determination unit 46 performs abnormality determination using the above equation (4) (S12 and S13 in FIG. 4). When it is determined that there is an abnormality, a gate block signal is output to the gate block unit 45, and an abnormality detection signal is output to the operation / stop determination unit 41 (S14). Therefore, even when the input voltage from the DC power supply B increases and the input voltage Vi detected by the input voltage sensor 2 exceeds the starting voltage setting value Vi ^* (S1: YES in FIG. 3), the operation / stop determination is made. The unit 41 outputs a stop signal to the operation / stop switching unit 42 (in FIG. 3, S2: YES to S4). In addition, the gate block unit 45 blocks the output of the PWM signal. Thereby, starting of the DC / DC converter circuit 1 is prevented.

When the abnormality determination unit 46 does not determine that there is an abnormality, when the input voltage Vi exceeds the starting voltage set value Vi ^* , the operation / stop determination unit 41 outputs an operation signal to the operation / stop switching unit 42 (in FIG. 3, S2 : S3 from NO. When the operation / stop switching unit 42 switches the target value to the output voltage setting value Vo ^* , the PWM signal generation unit 44 outputs the PWM signal to the DC / DC converter circuit 1. As a result, the DC / DC converter circuit 1 is activated and enters an operating state.

  In the operating state of the DC / DC converter circuit 1, the abnormality determination unit 46 performs abnormality determination by the above equation (5) (S16 and S17 in FIG. 4). When it is determined that there is an abnormality, a gate block signal is output to the gate block unit 45, and an abnormality detection signal is output to the operation / stop determination unit 41 (S14). As a result, the operation / stop determination unit 41 outputs a stop signal to the operation / stop switching unit 42 (in FIG. 3, S2: YES to S4). Since the operation / stop switching unit 42 switches the target value to “0” and the voltage control unit 43 starts control to set the output voltage to “0”, the on period of the PWM signal output from the PWM signal generation unit 44 Is gradually shortened and becomes a signal in which the off period continues. Further, the PWM signal output from the PWM signal generation unit 44 is blocked by the gate block unit 45, and thus is not output to the DC / DC converter circuit 1. Therefore, the DC / DC converter circuit 1 is stopped.

If the abnormality determination unit 46 does not determine that there is an abnormality, the operation signal output from the operation / stop determination unit 41 is continued (in FIG. 3, S2: S3 from NO), and the PWM signal is output, so the DC / DC converter circuit 1 continues the driving state. On the other hand, when the input voltage from the DC power source B decreases and the input voltage Vi detected by the input voltage sensor 2 becomes equal to or less than the starting voltage set value Vi ^* , the operation / stop determination unit 41 operates / stops the switching unit 42. A stop signal is output to (in FIG. 3, S1: NO to S4). When the operation / stop switching unit 42 switches the target value to “0”, the voltage control unit 43 starts control to set the output voltage to “0”. Is gradually shortened and becomes a signal in which the off period continues. Thereby, the DC / DC converter circuit 1 shifts from the operating state to the stopped state.

  Next, the operation of the control circuit 4 will be described.

  In the present embodiment, abnormality determination of the voltage sensor is performed while the DC / DC converter circuit 1 is stopped, and activation is blocked when it is determined as abnormal. Therefore, it is possible to prevent the overvoltage from being output to the load when the DC / DC converter circuit 1 is activated when there is an abnormality in the voltage sensor.

  Further, the abnormality determination of the voltage sensor when the DC / DC converter circuit 1 is stopped is performed by comparing the input voltage and the output voltage of the DC / DC converter circuit 1, so that the DC power source B whose output voltage varies is connected. Thus, even when the input voltage of the DC / DC converter circuit 1 fluctuates, the abnormality can be appropriately determined.

  In addition, the detection condition of the sensor is considered in the determination condition formula for determining the abnormality of the voltage sensor, and the condition for determining that the state corresponding to the determination condition expression continues for a predetermined time is determined to be abnormal. Judgment can be reduced.

  In the present embodiment, the abnormality determination is performed even in the operation state of the DC / DC converter circuit 1, and the operation is stopped when it is determined as abnormal. Therefore, when there is an abnormality, it is possible to prevent the overvoltage from being output to the load by continuing the operation of the DC / DC converter circuit 1.

  Further, the abnormality determination in the operating state of the DC / DC converter circuit 1 is performed using the input voltage of the DC / DC converter circuit 1, so that the DC power source B whose output voltage varies is connected to the DC / DC converter. Even when the input voltage of the circuit 1 fluctuates, the abnormality can be determined appropriately.

  Moreover, in the abnormality determination in the driving state, since it is a condition for determining that the state corresponding to the determination conditional expression continues for a predetermined time as an abnormality, erroneous determination of abnormality can be reduced.

  In the first embodiment, the case where the control circuit according to the present invention is used in a DC / DC converter device has been described. However, the present invention is not limited to this. The abnormality determination method before activation in the control circuit according to the present invention (abnormality determination method using the above equation (4)) can also be used for a power conversion device such as an AC / DC converter device.

  FIG. 5 is a diagram for explaining an AC / DC converter device according to a second embodiment of the present invention. In the figure, the same or similar elements as those in the DC / DC converter apparatus A shown in FIG.

  The AC / DC converter device A ′ is connected to an AC power supply B ′ instead of the DC power supply B, has an AC / DC converter circuit 5 instead of the DC / DC converter circuit 1, and has an input side. It differs from the DC / DC converter device A in that the filter circuit 6 is provided. The internal configuration of the control circuit 4 is the same as that of the control circuit 4 of FIG.

  The filter circuit 6 removes harmonic components due to switching output from the AC / DC converter circuit 5. The filter circuit 6 includes a low-pass filter including a reactor and a capacitor, and allows only the fundamental wave component to pass therethrough and prevents the harmonic component from flowing out to the AC power supply B ′. The configuration of the filter circuit 6 is not limited to this, and any known filter circuit for removing high frequency components and harmonic components may be used. The AC / DC converter 5 converts the AC voltage input from the AC power supply B ′ into a preset DC voltage and outputs it to the load C.

  FIG. 6 is a diagram for explaining an example of the internal configuration of the AC / DC converter circuit 5.

  As shown in FIG. 6, the AC / DC converter circuit 5 includes a diode bridge configured by four diodes D2 as rectifying elements, and a capacitor C2 connected in parallel thereto. A transistor S2 as a switching element is connected in antiparallel to each diode D2 of the diode bridge. The switching element is not limited to a transistor, and may be an IGBT, a MOSFET, a GTO, or the like. Further, the diode bridge is a diode bridge constituted by six diodes D2 when the input AC power supply B 'is a three-phase AC.

  The AC / DC converter circuit 5 converts the AC voltage input from the AC power supply B 'into a DC voltage using a diode bridge, and smoothes and outputs the DC voltage using the capacitor C2. The AC / DC converter circuit 5 adjusts the output voltage by switching the transistor S2 on and off in accordance with the PWM signal input from the control circuit 4.

  Since the PWM signal is not input when the AC / DC converter circuit 5 is stopped, the transistor S2 is always turned off. At this time, the voltage output from the diode bridge is only a rectified input AC voltage. Further, since the capacitor C2 is connected in parallel, the output voltage supplied to the load C does not become smaller than the voltage output from the diode bridge. Therefore, the output voltage supplied to the load C does not become smaller than the input voltage input from the AC power supply B ′. Accordingly, the input voltage Vi detected by the input voltage sensor 2 and the output voltage Vo detected by the output voltage sensor 3 should satisfy the relationship Vi ≦ Vo. Therefore, abnormality of the output voltage sensor 3 etc. can be determined using the above equation (4).

  Therefore, also in the present embodiment, when the AC / DC converter circuit 5 is in a stopped state, an abnormality determination of the voltage sensor or the like is performed, and if it is determined to be abnormal, activation is prevented, so that the same as in the first embodiment The effect of can be produced.

  Although the second embodiment has been described with respect to an AC / DC converter circuit using a diode bridge, the present invention is not limited to this. The present invention can be applied to any AC / DC converter circuit that includes a rectifying element and performs PWM control of a switching element connected in antiparallel to the rectifying element. Moreover, it is not limited to a full-wave rectifier circuit, and may be a half-wave rectifier circuit.

  The control circuit of the power conversion circuit according to the present invention and the power conversion device including the control circuit are not limited to the above-described embodiments. The specific configuration of each part of the control circuit of the power conversion circuit according to the present invention and the power conversion device including the control circuit can be varied in design in various ways.

A DC / DC converter device A 'AC / DC converter device B DC power supply B' AC power supply C Load 1 DC / DC converter circuit 2 Input voltage sensor 3 Output voltage sensor 4 Control circuit 41 Operation / stop judgment unit (control prohibition means)
42 Operation / stop switching part (control prohibition means)
43 Voltage control unit 44 PWM signal generation unit 45 Gate block unit (control prohibition means)
46 Abnormality determination unit (abnormality determination means, input / output voltage difference calculation means, determination means, determination means, theoretical output voltage calculation means, second determination means, timing means)
5 AC / DC converter circuit 6 Filter circuit

Claims (11)

A control circuit that generates a PWM signal and controls the power conversion operation of the power conversion circuit by the PWM signal,
Based on the difference between the input voltage of the power conversion circuit detected by the input voltage sensor and the output voltage of the power conversion circuit detected by the output voltage sensor, the input voltage sensor, the output voltage sensor, and the power conversion circuit An abnormality determining means for determining whether or not an abnormality has occurred in a circuit including:
When the abnormality occurs, control prohibiting means for prohibiting the power conversion operation of the power conversion circuit;
A control circuit for a power conversion circuit, comprising:   The control circuit according to claim 1, wherein the control prohibiting unit prohibits a power conversion operation of the power conversion circuit by stopping a generating operation of the PWM signal generating unit that generates the PWM signal.   2. The power control circuit according to claim 1, wherein the control prohibiting unit prohibits a power conversion operation of the power conversion circuit by stopping output of a PWM signal from the PWM signal generating unit that generates the PWM signal to the power conversion circuit. Control circuit. The abnormality determining means includes
An input / output voltage difference calculating means for calculating an input / output voltage difference by subtracting the output voltage from the input voltage;
Discriminating means for discriminating whether or not the input / output voltage difference is larger than a predetermined voltage difference;
Determining means for determining that the abnormality has occurred when the input / output voltage difference is greater than the predetermined voltage difference;
The control circuit according to claim 1, comprising: The abnormality determining means includes
Theoretical output voltage calculation means for calculating a theoretical output voltage obtained by a predetermined arithmetic expression using the input voltage and the period and on-time of the PWM signal;
Second discriminating means for discriminating whether or not an absolute value of a difference between the theoretical output voltage and the output voltage is larger than a predetermined threshold;
The determination unit determines that the abnormality has occurred when either the input / output voltage difference is greater than the predetermined voltage difference or the absolute value is greater than the predetermined threshold.
The control circuit according to claim 4. The abnormality determining means includes
Theoretical output voltage calculation means for calculating a theoretical output voltage obtained by a predetermined arithmetic expression using the input voltage and the period and on-time of the PWM signal;
When the absolute value of the difference between the theoretical output voltage and the output voltage exceeds a predetermined threshold, timing is started, and when the absolute value is equal to or less than the threshold, timing means for stopping the timing;
A second determining means for determining whether or not a time measured by the time measuring means has reached a predetermined duration; and
The determination means is that the abnormality has occurred when either the input / output voltage difference is greater than the predetermined voltage difference or the time measured by the time measuring means reaches the predetermined duration. judge,
The control circuit according to claim 4.   The control circuit according to claim 1, wherein the power conversion circuit is a DC / DC converter circuit.   5. The AC / DC converter circuit includes: a rectifying element; a switching element connected in antiparallel to the rectifying element; and a capacitor connected in parallel to an output terminal. The control circuit according to any one of the above.   The power converter device provided with the said power converter circuit and the control circuit in any one of Claim 1 thru | or 8.   The program for functioning a computer as a control circuit in any one of Claim 1 thru | or 8.   The computer-readable recording medium which recorded the program of Claim 10.

Images