Method for determining the connection status of a power supply and a heating resistor.

Abstract

The present invention provides a power supply device that allows for easy determination of the connection status of a heating resistor before reducing the pressure inside an airtight container. [Solution] The power supply unit 1A has a power conversion circuit 3A having a modulation circuit 4 that modulates a first power which is DC power and converts it into a second power, and a rectifier and smoothing circuit 5 that converts the second power into a third power which is DC power, a heating resistor 61 to which the third power is supplied, a modulation control circuit 7A that outputs modulation circuit drive signals Sg1 to Sg4 that control the modulation circuit 4, and a current detection signal S that detects the magnitude of the load current If supplied by the power conversion circuit 3A to the heating resistor 61. If The modulation control circuit 7A comprises a load current detection unit 8 that generates a current detection signal S If Based on this, the drive frequencies of the modulation circuit drive signals Sg1 to Sg4 are controlled so that the magnitude of the load current If approaches the target value of the load current If. The modulation control circuit 7A determines the electrical connection state between the power conversion circuit 3A and the heating resistor 61 based on the drive frequency.

Description

Technical Field

[0001] The present invention relates to a power supply device and a method for determining the connection state of a heating resistor.

Background Art

[0002] The device described in Patent Document 1 includes a buck-boost circuit that boosts and buck-boosts the voltage supplied to a filament, and predicts the remaining life of the filament using the measured value of the current flowing through the low-voltage side of the buck-boost circuit. For example, in the device described in Patent Document 1, the time derivative of the current flowing through the low-voltage side is obtained, and the difference between the current value at the current time and the current value at the end-of-life point is divided by the obtained time derivative to calculate the remaining time until the end-of-life point.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] A power supply device that supplies power to a heating resistor such as a filament is known. A heating resistor such as a filament is housed in, for example, a cylindrical airtight container and used in a reduced-pressure atmosphere. Therefore, when using the heating resistor, time is required to reduce the pressure inside the airtight container. On the other hand, between the heating resistor and the power supply circuit, poor contact between terminals or disconnection may occur. If such disconnection or poor contact is found when starting the operation of the heating resistor by reducing the pressure inside the airtight container, after operations such as correcting the contact state between the terminals or replacing the heating resistor, it is necessary to reduce the pressure inside the airtight container again. Reducing the pressure inside the airtight container may take several hours, and repeating the pressure reduction inside the airtight container is a factor that reduces work efficiency.

[0005] The present invention aims to provide a power supply device and a method for determining the connection status of a heating resistor, which can easily determine the connection status of a heating resistor before reducing the pressure inside an airtight container. [Means for solving the problem]

[0006] [1] A power supply device relating to one aspect of the present disclosure comprises a power supply unit, a power conversion circuit, a heating resistor module, a modulation control circuit, and a load current detection unit. The power supply unit outputs a first power, which is DC power. The power conversion circuit has a modulation circuit that modulates the first power and converts it into a second power, and a rectifier and smoothing circuit that converts the second power into a third power, which is DC power. The heating resistor module has a heating resistor to which the third power is supplied, and an airtight container that holds the heating resistor in a reduced-pressure atmosphere. The modulation control circuit is connected to the modulation circuit and outputs a modulation circuit drive signal to control the modulation circuit. The load current detection unit detects the magnitude of the load current supplied by the power conversion circuit to the heating resistor, which is the magnitude of the load current due to the third power or the magnitude of the current that fluctuates with the load current, and generates a first current detection signal. The modulation control circuit has a parameter control unit and a connection state determination unit. Based on the first current detection signal, the parameter control unit controls the modulation parameters of the modulation circuit drive signal so that the magnitude of the load current approaches the target value of the load current. The connection state determination unit determines the electrical connection state between the power conversion circuit and the heating resistor based on the modulation parameters.

[0007] In the power supply unit described in [1] above, the parameter control unit feedback-controls the modulation parameters of the modulation circuit drive signal so that the magnitude of the load current approaches the target value of the load current. The modulation parameters are, for example, the frequency in frequency modulation or the duty cycle in PWM modulation. In this case, if there is poor contact between the terminals or a break in the wire between the heating resistor and the power conversion circuit, the load current will not flow, but the modulation parameters are set to extreme values ​​in an attempt to make the load current flow. Therefore, the electrical connection state between the power conversion circuit and the heating resistor can be determined based on the modulation parameters. This makes it possible to easily determine the connection state of the heating resistor before depressurizing the airtight container, eliminating the need to repeatedly depressurize the airtight container and improving work efficiency.

[0008] [2] In the power supply device described in [1] above, the modulation circuit may further include a switching circuit and a resonant circuit. The switching circuit is connected to the power supply unit and converts the first power supplied from the power supply unit into AC power as the second power. The resonant circuit is connected between the switching circuit and the rectifier-smoothing circuit and steps up or down the AC voltage due to the AC power. The parameter control unit controls the drive frequency of the switching circuit as a modulation parameter. The connection state determination unit determines the connection state based on whether or not the drive frequency has reached a threshold. The impedance of the resonant circuit included in the power conversion circuit decreases, for example, as the drive frequency approaches the resonant frequency of the resonant circuit. That is, the impedance of the resonant circuit changes with the drive frequency, and consequently the impedance of the heating resistor changes with the drive frequency. However, if a contact problem or disconnection occurs between the terminals or between the heating resistor and the power conversion circuit, the impedance of the heating resistor becomes equivalent to infinite, and the drive frequency drops to an extreme value. Therefore, the electrical connection state between the heating resistor and the power conversion circuit can be determined based on whether or not the drive frequency has reached a threshold.

[0009] [3] The power supply unit described in [1] or [2] above may further include an anode positioned opposite the heating resistor as the cathode, to which thermionic electrons emitted from the heating resistor converge, and a second current detection unit that detects the magnitude of the current flowing between the cathode and the anode and generates a second current detection signal. The parameter control unit may have a first operating mode and a second operating mode. In the first operating mode, the parameter control unit controls the modulation parameters based on the second current detection signal so that the magnitude of the current flowing between the cathode and the anode approaches a target value of the current. In the second operating mode, the parameter control unit controls the modulation parameters regardless of the second current detection signal. With this power supply unit, in the first operating mode, the magnitude of the current flowing between the cathode and the anode can be appropriately controlled when the heating resistor module is in operation. In the second operating mode, for example, before the heating resistor module is in operation, the modulation parameters can be controlled without controlling the current flowing between the cathode and the anode, making it possible to accurately determine the electrical connection state between the heating resistor and the power conversion circuit.

[0010] [4] A power supply device relating to one aspect of the present disclosure includes a power supply unit, a power conversion circuit, a heating resistor module, a modulation control circuit, Receiving circuit, The power supply unit also includes a connection status determination unit. The power supply unit outputs a first power, which is DC power. The power conversion circuit includes a modulation circuit, a transformer, and a rectifier / smoothing circuit. The modulation circuit modulates the first power and converts it into a second power. The primary winding of the transformer is connected to the modulation circuit. The rectifier / smoothing circuit is connected to the first secondary winding of the transformer and converts the second power into a third power, which is DC power. The heating resistor module includes a heating resistor to which the third power is supplied and an airtight container that holds the heating resistor in a reduced-pressure atmosphere. The modulation control circuit is connected to the modulation circuit and outputs a modulation circuit drive signal to control the modulation circuit. The receiving circuit is connected to the second secondary winding of the transformer. The connection status determination unit , electric The electrical connection state between the power conversion circuit and the heating resistor is determined. The modulation control circuit drives the modulation circuit and generates a connection confirmation signal via a transformer. Receiving circuitThe signal transmission to be transmitted is performed before the power transmission, in which the second power generated by driving the modulation circuit is transmitted to the rectifier and smoothing circuit via the transformer. The connection status determination unit receives a connection confirmation signal from the modulation control circuit. Receiving circuit The connection status is determined based on whether or not the destination was successfully reached.

[0011] In the power supply unit described in [4] above, the modulation control circuit drives the modulation circuit and generates a connection confirmation signal via a transformer. Receiving circuit The signal transmission to be transmitted ,strange This is performed before power transmission, which involves driving the control circuit to generate a second power and transmitting it to the rectifier-smoothing circuit via a transformer. If poor contact or a break in the terminals occurs between the heating resistor and the power conversion circuit, the output terminal of the rectifier-smoothing circuit becomes open, making power transmission impossible. Furthermore, the time waveform of the connection confirmation signal in signal transmission is also distorted, and the connection confirmation signal is lost. Receiving circuit It will no longer reach that point. Therefore, the connection confirmation signal generated by the modulation control circuit will Receiving circuit Based on whether or not a certain threshold has been reached, the electrical connection state between the power conversion circuit and the heating resistor can be determined. This makes it possible to easily determine the connection state of the heating resistor before depressurizing the airtight container, eliminating the need to repeatedly depressurize the airtight container and improving work efficiency.

[0012] [5] In any of the power supply devices described in [1] to [4] above, the airtight container may further have a first connection terminal connected to a rectifier-smoothing circuit that outputs a third power. The heating resistor may further have a second connection terminal connected to the heating resistor and capable of contacting the first connection terminal, and may be configured to be detachable from the airtight container. In such a configuration, if the heating resistor module is not properly mounted to the airtight container, the contact between the first connection terminal and the second connection terminal will be insufficient. In any of the power supply devices described in [1] to [4] above, in such cases, the insufficient connection can be easily detected before the airtight container is depressurized.

[0013] [6] A method for determining the connection state of a heating resistor according to one aspect of the present disclosure is a method for determining the connection state of a heating resistor using a power supply unit. The power supply unit comprises a power supply unit, a power conversion circuit, a heating resistor module, a modulation control circuit, and a load current detection unit. The power supply unit outputs a first power, which is DC power. The power conversion circuit has a modulation circuit that modulates the first power and converts it into a second power, and a rectifier and smoothing circuit that converts the second power into a third power, which is DC power. The heating resistor module comprises a heating resistor to which the third power is supplied, and an airtight container that holds the heating resistor in a reduced-pressure atmosphere. The modulation control circuit is connected to the modulation circuit and outputs a modulation circuit drive signal to control the modulation circuit. The load current detection unit detects the magnitude of the load current supplied to the heating resistor by the power conversion circuit, which is the magnitude of the load current due to the third power or the magnitude of the current that fluctuates with the load current, and generates a first current detection signal. This method comprises the steps of: controlling the modulation parameters of a modulation circuit drive signal based on a first current detection signal so that the magnitude of the load current approaches a target value of the load current; and determining the electrical connection state between a power conversion circuit and a heating resistor based on the modulation parameters.

[0014] In the connection state determination method described in [6] above, the parameter control unit feedback controls the modulation parameters of the modulation circuit drive signal so that the magnitude of the load current approaches the target value of the load current. At this time, if there is poor contact between terminals or a break in the wire between the heating resistor and the power conversion circuit, the load current will not flow, but the modulation parameters will be set to extreme values ​​in an attempt to make the load current flow. Therefore, the electrical connection state between the power conversion circuit and the heating resistor can be determined based on the modulation parameters. This makes it possible to easily determine the connection state of the heating resistor before depressurizing the airtight container, eliminating the need to repeatedly depressurize the airtight container and improving work efficiency.

[0015] [7] A method for determining the connection state of a heating resistor according to one aspect of the present disclosure is a method for determining the connection state of a heating resistor using a power supply unit. The power supply unit includes a power supply unit, a power conversion circuit, a heating resistor module, a modulation control circuit, and Receiving circuitThe power supply unit outputs a first power, which is DC power. The power conversion circuit has a modulation circuit that modulates the first power and converts it into a second power, a transformer whose primary winding is connected to the modulation circuit, and a rectifier and smoothing circuit connected to the first secondary winding of the transformer that converts the second power into a third power, which is DC power. The heating resistor module has a heating resistor to which the third power is supplied, and an airtight container that holds the heating resistor in a reduced-pressure atmosphere. The modulation control circuit is connected to the modulation circuit and outputs a modulation circuit drive signal to control the modulation circuit. Receiving circuit This is connected to the second secondary winding of the transformer. In this method, the connection confirmation signal generated by driving the modulation circuit is transmitted through the transformer. Receiving circuit The steps include transmitting a signal to be transmitted and receiving a connection confirmation signal from the modulation control circuit. Receiving circuit The system includes the steps of determining the electrical connection state between the power conversion circuit and the heating resistor based on whether or not the current state has been reached successfully, and, if the connection state is normal, performing power transmission by driving the modulation circuit to transmit the second power generated to the rectifier and smoothing circuit via a transformer.

[0016] The connection status determination method described in [7] above involves, before the step of power transmission in which the second power generated by driving the modulation circuit is transmitted to the rectifier and smoothing circuit via a transformer, a connection confirmation signal generated by driving the modulation circuit is transmitted via a transformer. Receiving circuit The system includes a step of transmitting a signal to be transmitted. If poor contact or a break in the connection occurs between the heating resistor and the power conversion circuit, the output terminal of the rectifier and smoothing circuit becomes open. As a result, not only does power transmission become impossible in the power transmission step, but the time waveform of the connection confirmation signal is also distorted in the signal transmission step, and the connection confirmation signal is lost. Receiving circuit It will no longer reach that point. Therefore, the connection confirmation signal generated by the modulation control circuit will Receiving circuit Based on whether or not a certain threshold has been reached, the electrical connection state between the power conversion circuit and the heating resistor can be determined. This makes it possible to easily determine the connection state of the heating resistor before depressurizing the airtight container, eliminating the need to repeatedly depressurize the airtight container and improving work efficiency. [Effects of the Invention]

[0017] According to the present invention, it is possible to provide a power supply device that can easily determine the connection state of a heating resistor before reducing the pressure inside an airtight container, and a method for determining the connection state of a heating resistor. [Brief explanation of the drawing]

[0018] [Figure 1] Figure 1 is a schematic diagram of the circuit diagram of a power supply device according to the first embodiment of this disclosure. [Figure 2] Figure 2 is a schematic diagram showing the structure of the heating resistance module provided in the pressure reducing tube. [Figure 3] Figure 3 is a block diagram showing an example of the internal configuration of an inverter control circuit. [Figure 4] Figure 4 is a graph showing an example of the frequency characteristics of the gain of a power conversion circuit including a heating resistor. [Figure 5] Figure 5 is a flowchart showing an example of a method for determining the electrical connection state between a heating resistor and a power conversion circuit. [Figure 6] Figure 6 is a graph showing the time evolution of various values ​​in the second operating mode. [Figure 7] Figure 7 is a graph showing the time evolution of various values ​​when the heating resistor and the power conversion circuit are properly connected. [Figure 8] Figure 8 is a graph showing the time evolution of various values ​​when the connection between the heating resistor and the power conversion circuit is abnormal. [Figure 9] Figure 9 is a circuit diagram showing the configuration of the power supply device according to the second embodiment. [Figure 10] Figure 10 shows an example of the time waveform of the voltage output from the inverter. [Figure 11] Figure 11 is a graph showing the time waveform of the connection confirmation signal. [Figure 12] Figure 12 is a flowchart showing an example of a method for determining the electrical connection state between a heating resistor and a power conversion circuit. [Figure 13] Figure 13 is a circuit diagram showing the configuration of the power supply device according to the first modified example. [Figure 14] Figure 14 is a circuit diagram showing the configuration of the power supply unit according to the second modified example. [Figure 15] Figure 15 is a circuit diagram showing the configuration of the power supply device according to the third modified example. [Figure 16] Figure 16 is a circuit diagram showing the configuration of the power supply unit according to the fourth modified example. [Figure 17] Figure 17 is a circuit diagram showing the configuration of the power supply device according to the fifth modified example. [Modes for carrying out the invention]

[0019] Hereinafter, preferred embodiments of a power supply device and a method for determining the connection state of a heating resistor according to one embodiment of this disclosure will be described in detail with reference to the drawings.

[0020] [First Embodiment] Figure 1 is a schematic diagram of the circuit of a power supply unit 1A according to the first embodiment of the present disclosure. The power supply unit 1A is a power supply unit for supplying power to a heating resistor 61 which is a load, and for raising the temperature of the heating resistor 61. The heating resistor 61 constitutes the cathode (filament) of the pressure reducing tube 6. The pressure reducing tube 6 is, for example, a vacuum tube. The pressure reducing tube 6 is, for example, an X-ray tube or an electron beam tube.

[0021] The power supply unit 1A comprises a power supply unit 2, a power conversion circuit 3A, a pressure reducing tube 6, an inverter control circuit 7A, a load current detection unit 8, and a tube current detection unit 9.

[0022] The power supply unit 2 outputs a first power, which is DC power. The power supply unit 2 functions as an AC / DC converter that converts AC power generated in the AC power source AP into the first power, which is DC power. The power supply unit 2 is a power supply circuit that supplies the first power to the inverter 4 included in the power conversion circuit 3A. The power supply unit 2 is, for example, a switching type AC / DC converter. In that case, the power supply unit 2 may have a switching element (not shown).

[0023] The power supply unit 2 receives a tube current instruction signal S that indicates a target value for the magnitude of the tube current Iout flowing through the pressure reducing tube 6. ISET (Second current instruction signal) is input. Tube current instruction signal S ISET This can be set arbitrarily by the user, for example. Power supply unit 2 operates in feedforward control. Power supply unit 2 receives, for example, a tube current instruction signal S. ISET The magnitude of the first power may be varied according to the magnitude of the tube current instruction signal S. As an example, the power supply unit 2 receives the tube current instruction signal S. ISET Depending on the magnitude, the frequency or duty cycle of the signal driving the switching element may be varied.

[0024] The power supply unit 2 has a function to limit the magnitude of the first power within a predetermined range. Internally, for example, an upper limit value for the magnitude of the first power is set in the power supply unit 2, and the power supply unit 2 limits the magnitude of the first power so as not to exceed this upper limit value. The upper limit value may be a value less than or equal to the rated power of the semiconductor switch included in the switching circuit 41 connected downstream of the power supply unit 2.

[0025] The power conversion circuit 3A supplies a third power, which is a DC power greater than the magnitude of the first power, to the heating resistor 61. As a result, the power conversion circuit 3A supplies a load current If, due to the third power, to the heating resistor 61. The power conversion circuit 3A includes an inverter 4 and a rectifier / smoothing circuit 5. The inverter 4 is the modulation circuit in this embodiment. The inverter 4 converts the first power, which is DC power, into a second power, which is AC power, and supplies the second power to the rectifier / smoothing circuit 5. The inverter 4 includes a switching circuit 41 and a resonant circuit 42.

[0026] The switching circuit 41 converts a first power, which is DC power, into a second power, which is AC power. The switching circuit 41 includes semiconductor switches S1 to S4. In the example in Figure 1, the semiconductor switches S1 to S4 are composed of MOSFETs. The semiconductor switches S1 to S4 may also be composed of, for example, insulated gate bipolar transistors (IGBTs). Each of the semiconductor switches S1 to S4 includes a control terminal, a first current terminal, and a second current terminal. The control terminal corresponds to the gate terminal of the MOSFET, the first current terminal corresponds to the drain terminal of the MOSFET, and the second current terminal corresponds to the source terminal of the MOSFET. In the example in Figure 1, the switching circuit 41 includes a configuration in which two leg circuits 411 and 412 are connected in parallel. Leg circuit 411 is a circuit in which the second current terminal of semiconductor switch S1 and the first current terminal of semiconductor switch S2 are connected. The REG circuit 412 is a circuit in which the second current terminal of semiconductor switch S3 and the first current terminal of semiconductor switch S4 are connected.

[0027] The switching circuit 41 further includes power terminals 41a and 41b connected to the power supply unit 2, control terminals 41c to 41f connected to the inverter control circuit 7A, and output terminals 41g and 41h connected to the subsequent resonant circuit 42. Power terminal 41a is connected to the first current terminals of semiconductor switches S1 and S3, i.e., the high side of the switching circuit. Power terminal 41b is connected to the second current terminals of semiconductor switches S2 and S4, i.e., the low side of the switching circuit 41. First power is supplied to the switching circuit 41 from the power supply unit 2 via power terminals 41a and 41b, respectively.

[0028] Each of the control terminals 41c to 41f is a control terminal for the respective semiconductor switches S1 to S4. The inverter drive signals Sg1 to Sg4, described later, are output from the inverter control circuit 7A to the control terminals 41c to 41f. Output terminal 41g is located at the point between semiconductor switch S1 and semiconductor switch S2, and output terminal 41h is located at the point between semiconductor switch S3 and semiconductor switch S4. The resonant circuit 42 is connected to output terminals 41g and 41h.

[0029] In the example shown in Figure 1, the switching circuit 41 can operate as a full-bridge circuit. The inverter control circuit 7A changes the polarity of the voltage supplied to the resonant circuit 42 by, for example, alternately switching semiconductor switches S1 to S4. As a result, the switching circuit 41 converts the first power, which is DC power, into the second power, which is AC power.

[0030] The resonant circuit 42 steps up or down the AC voltage supplied by the AC power from the switching circuit 41 at the resonant frequency. The resonant circuit 42 is connected between the switching circuit 41 and the rectifier / smoothing circuit 5. The resonant circuit 42 includes a transformer TR1 which includes a primary winding N1 and a secondary winding N2 isolated from the primary winding N1, and a resistor R1 and a resonant capacitor Cr connected between one end N1a of the primary winding N1 of the transformer TR1 and the output terminal 41g of the inverter 4. The resonant capacitor Cr is connected in series with the resistor R1. The resonant capacitor Cr is connected in series with the primary winding N1. The resistor R1 functions, for example, as a DC resistor on the primary winding N1 side of the resonant circuit 42. The secondary winding N2 of the transformer TR1 is connected to a heating resistor 61, which is a load, via the rectifier / smoothing circuit 5.

[0031] The transformer TR1 contains several parasitic components. The transformer TR1 includes a resonant inductance Lr (parasitic inductance) and an excitation inductance Lp. The resonant inductance Lr is the leakage inductance of the transformer TR1. The resonant inductance Lr exists in the primary winding N1 so as to be connected in series with the resonant capacitor Cr. The excitation inductance Lp exists so as to be connected in parallel with the primary winding N1. The resonant circuit 42 is a series resonant circuit (LLC resonant circuit) composed of the resonant capacitor Cr, the resonant inductance Lr, and the excitation inductance Lp. The resonant frequency f1 of the resonant circuit 42 is expressed, for example, by equation (1). f1=1 / 2×π×SQRT(Lr×Cr)…(1) In equation (1), SQRT represents the square root. As shown in equation (1), at the resonant frequency f1, the resonant inductance Lr is dominant over the excitation inductance Lp, so the resonant frequency f1 is determined based on the resonant capacitor Cr and the resonant inductance Lr.

[0032] The resonant circuit 42 steps up or down the AC voltage supplied by the second power from the switching circuit 41 at the resonant frequency. The resonant circuit 42 then supplies the stepped-up or stepped-down second power to the rectifier and smoothing circuit 5.

[0033] The rectifier-smoothing circuit 5 converts the second power supplied from the resonant circuit 42 into a third power, which is DC power. The magnitude of the third power is greater than the magnitude of the first power. The rectifier-smoothing circuit 5 includes a rectifier circuit 51 and a smoothing circuit 52. The rectifier circuit 51 is connected to the resonant circuit 42 via a resistor R2. The resistor R2 is connected between one end N2a of the secondary winding N2 and the rectifier circuit 51. The rectifier circuit 51 is, for example, a circuit composed of four diodes connected in a bridge configuration. The smoothing circuit 52 includes, for example, at least one smoothing capacitor. The smoothing circuit 52 may also be composed of a group of capacitors connected in series with each other. The AC voltage from the second power, which has been stepped up or stepped down in the resonant circuit 42, is converted into a DC voltage by being rectified in the rectifier circuit 51 and smoothed in the smoothing circuit 52. The rectifier-smoothing circuit 5 then supplies the DC power corresponding to the converted DC voltage as the third power to the heating resistor 61. As a result, the heating resistor 61 is supplied with a load current If from the third power source.

[0034] Figure 2 is a schematic diagram showing the structure of the heating resistor module 60 provided in the pressure reducing tube 6. As shown in Figure 2, the heating resistor module 60 has a heating resistor 61 and an airtight container 63. The heating resistor 61 is supported by a support 65. The heating resistor 61 and the support 65 are placed inside the airtight container 63. The airtight container 63 is, for example, a cylindrical body with both ends closed, and holds the heating resistor 61 in a reduced pressure atmosphere (e.g., vacuum). The support 65 is configured to be detachable from the airtight container 63. The airtight container 63 has a plurality of connection terminals 631 (first connection terminals) inside it that are connected to the rectifier and smoothing circuit 5 and output third power. The heating resistor 61 has a plurality of connection terminals 64 (second connection terminals) attached to the support 65. One of the plurality of connection terminals 64 is connected to one end of the heating resistor 61, and another of the plurality of connection terminals 64 is connected to the other end of the heating resistor 61. Multiple connection terminals 64 are located on one end of the support 65, and multiple connection terminals of the airtight container 63 6It is possible to contact 31. Each of the multiple connection terminals 64 contacts each of the multiple connection terminals 631 when the heating resistor 61 and support 65 are inserted into the airtight container 63. In addition, the lid 632 of the airtight container 63 presses the support 65 from the opposite side of the multiple connection terminals 64. As a result, the heating resistor 61 is electrically connected to the power conversion circuit 3A via the connection terminals 64 and 631. The connection terminals 64 separate from the connection terminals 631 when the heating resistor 61 and support 65 are removed from the airtight container 63.

[0035] In the heating resistor module 60, a load current If is supplied to the heating resistor 61, causing the heating resistor 61 to generate heat. As a result, thermionic electrons B are emitted from the heating resistor 61. Meanwhile, a high voltage generated by an external high-voltage power supply Vc from the power supply unit 1A is applied between the heating resistor 61 and the anode 62 (see Figure 1). Thermionic electrons B emitted from the heating resistor 61 move from the heating resistor 61 through a window 633 provided in the side wall of the airtight container 63 to the anode 62 due to the potential difference between the anode 62 and the heating resistor 61, and converge at the anode 62. As a result, a tube current Iout flows through the pressure reducing tube 6 as shown in Figure 1.

[0036] Refer to Figure 1 again. The inverter control circuit 7A is the modulation control circuit in this embodiment. The inverter control circuit 7A outputs inverter drive signals (modulation circuit drive signals) Sg1 to Sg4 to the inverter 4 to control the inverter 4. The inverter control circuit 7A is connected to the inverter 4. In the example in Figure 1, the inverter control circuit 7A includes four output terminals, each output terminal being connected to the control terminals 41c to 41f of the switching circuit. The inverter drive signal Sg1 is output to the semiconductor switch S1. The inverter drive signal Sg2 is output to the semiconductor switch S2. The inverter drive signal Sg3 is output to the semiconductor switch S3. The inverter drive signal Sg4 is output to the semiconductor switch S4.

[0037] The load current detection unit 8 detects the magnitude of the load current If or the magnitude of the current that fluctuates with the load current If. The input terminal of the load current detection unit 8 is connected, for example, between the switching circuit 41 and the resonant circuit 42. In the example in Figure 1, the input terminal of the load current detection unit 8 is connected to the node between the output terminal 41h and the other end N1b of the primary winding N1 of the transformer TR1. The output terminal of the load current detection unit 8 is connected to the inverter control circuit 7A. In the example in Figure 1, the load current detection unit 8 detects the magnitude of the primary side current that fluctuates with the load current If on the primary winding N1 side of the transformer TR1 (the primary side of the inverter 4). Alternatively, the load current detection unit 8 may detect the load current If on the secondary winding N2 side of the transformer TR1 (the secondary side of the inverter 4). In this case, the input terminal of the load current detection unit 8 may be connected, for example, between the other end N2b of the secondary winding N2 of the transformer TR1 and the rectifier and smoothing circuit 5.

[0038] The load current detection unit 8 is the first current detection unit in this embodiment. The load current detection unit 8 receives a load current detection signal S that indicates the magnitude of the load current If or the magnitude of the current that fluctuates with the load current If. If Generates the (first current detection signal). Load current detection signal S If This is, for example, a voltage signal. The load current detection unit 8 may include a current transformer and a shunt resistor. In this case, the load current detection unit 8 reduces the magnitude of the load current If or the magnitude of the current that fluctuates with the load current If using the current transformer, and then measures the load current If or the current that fluctuates with the load current If. shunt By converting it to voltage using a resistor, the load current detection signal S is generated. If The load current detection unit 8 generates a load current detection signal S. If Any configuration that can generate this is sufficient, and it is not limited to the above configuration.

[0039] The tube current detection unit 9 is the second current detection unit in the present embodiment. The tube current detection unit 9 detects the magnitude of the tube current Iout. The input terminal of the tube current detection unit 9 is connected to the anode 62 of the decompression tube 6. The output terminal of the tube current detection unit 9 is connected to the inverter control circuit 7A. The tube current detection unit 9 generates a tube current detection signal S IOUT (the second current detection signal). The tube current detection signal S IOUT is, for example, a voltage signal. Similar to the load current detection unit 8, the tube current detection unit 9 may include a current transformer and a shunt resistor, or may include a configuration other than the current transformer and the shunt resistor.

[0040] FIG. 3 is a block diagram showing an example of the internal configuration of the inverter control circuit 7A. The inverter control circuit 7A has a parameter control unit 70 and a connection state determination unit 74. The parameter control unit 70 includes a control element 71, a control element 72, a frequency control unit 73, and a switch 75. The control elements 71 and 72 are, for example, operational amplifiers. The control element 71 includes an input terminal 71a, an input terminal 71b, and an output terminal 71c. The control element 72 includes an input terminal 72a, an input terminal 72b, and an output terminal 72c. The switch 75 is a two-input one-output switch having input terminals 75a and 75b and an output terminal 75c. The switch 75 may be a mechanical switch or a semiconductor switch such as a transistor. The output terminal 71c of the control element 71 is connected to one input terminal 75b of the switch 75. The output terminal 75c of the switch 75 is connected to the input terminal 72b of the control element 72. The output terminal 72c of the control element 72 is connected to the input terminal of the frequency control unit 73. One of the plurality of output terminals of the frequency control unit 73 is connected to the input terminal of the connection state determination unit 74. In the following description, the state where the output terminal 75c of the switch 75 is connected to the input terminal 75b is referred to as the first operation mode, and the state where the output terminal 75c of the switch 75 is connected to the input terminal 75a is referred to as the second operation mode.

[0041] The tube current detection signal S is applied to the input terminal 71aIOUT The following is input. Input terminal 71b receives a tube current instruction signal S, which indicates the target value of the magnitude of the tube current Iout. ISET The following is input. The control element 71 receives the tube current detection signal S from the output terminal 71c. IOUT and tube current indicator signal S ISET It outputs a signal corresponding to the difference with the tube current detection signal S. The control element 71 outputs a signal corresponding to the difference with the tube current detection signal S. IOUT The tube current indicator signal S ISET If it is greater than this, the magnitude of the output signal is reduced, and the tube current detection signal S IOUT The tube current indicator signal S ISET If it is smaller than this, the magnitude of the output signal is increased. Through this operation, the control element 71 controls the tube current instruction signal S ISET and tube current detection signal S IOUT Based on this, the tube current indicator signal S is the target value of the magnitude of the tube current Iout. ISET The output signal is controlled so that the tube current Iout approaches the target value.

[0042] In the first operating mode, the output signal from the control element 71 passes through the switch 75 and the load current instruction signal S Ifdr This is input to the control element 72. Also, the tube current instruction signal S is input to the input terminal 75a of the switch 75. ISET The following is input. In the second operating mode, the tube current indicator signal S ISET The load current instruction signal S Ifdr This is input to the control element 72.

[0043] Input terminal 72a receives the load current detection signal S from the load current detection unit 8. If The following is input. Input terminal 72b receives a load current instruction signal S, which indicates the target value of the magnitude of the load current If. Ifdr The input is received. The control element 72 receives the load current detection signal S from the output terminal 72c. If and load current instruction signal S Ifdr The signal corresponding to the difference is the frequency indication signal S freq The signal is output to the frequency control unit 73. The control element 72 receives the load current detection signal S. If The load current instruction signal S Ifdr If it is greater than, the frequency indication signal S freqThe size of the load current detection signal S is reduced. If The load current instruction signal S Ifdr If it is smaller than, the frequency indication signal S freq The magnitude of is increased. Through this operation, the control element 72 receives the load current instruction signal S. Ifdr and load current detection signal S If Based on this, the load current instruction signal S is the target value of the magnitude of the load current If. Ifdr The frequency indicator signal S is sent so that the load current If approaches the specified value. freq Control.

[0044] The frequency control unit 73 controls the drive frequency, which is the frequency of the inverter drive signals Sg1 to Sg4, so that the magnitude of the load current If approaches the target value of the load current If. The drive frequency is a modulation parameter in this embodiment. The input terminal of the frequency control unit 73 receives the frequency instruction signal S freq The following is input. The frequency control unit 73 receives the frequency instruction signal S freq The drive frequency is variably controlled according to the magnitude of the signal. The frequency control unit 73 may include, for example, a VCO (voltage-controlled oscillator). In this case, the frequency control unit 73 controls the frequency instruction signal S freq As the magnitude increases, the drive frequency is increased, and the frequency instruction signal S freq If the size decreases, the driving frequency can be reduced.

[0045] The frequency control unit 73 includes four output terminals as output terminals of the inverter control circuit 7A, and each output terminal is connected to the control terminals 41c to 41f of the switching circuit, respectively. The frequency control unit 73 may also have a function to adjust the timing of the output of the inverter drive signals Sg1 to Sg4. This may cause the semiconductor switches S1 to S4 to switch alternately.

[0046] The frequency control unit 73 varies the drive frequency, which changes the magnitude of the AC power output from the switching circuit 41. For example, as the drive frequency approaches the resonant frequency f1 of the resonant circuit 42, the magnitude of the load current If increases. As a result, the magnitude of the AC power output from the switching circuit 41 increases. With this configuration, the control element 72 receives a load current instruction signal S, where the load current If is the target value of the magnitude of the load current If. Ifdr The frequency indicator signal S approaches freq Control.

[0047] With the above configuration, in the first operating mode, the parameter control unit 70 receives the tube current detection signal S IOUT Based on this, the drive frequency is controlled so that the magnitude of the tube current Iout approaches the target value of the tube current Iout. In addition, in the first operating mode, the parameter control unit 70 receives the load current detection signal S If Based on this, the drive frequencies of the inverter drive signals Sg1 to Sg4 are controlled so that the magnitude of the load current If approaches the target value of the load current If. In addition, in the second operating mode, the parameter control unit 70 controls the tube current detection signal S IOUT Regardless, the tube current indicator signal S ISET and load current detection signal S If Based on this, the drive frequencies of the inverter drive signals Sg1 to Sg4 are controlled so that the magnitude of the load current If approaches the target value of the load current If.

[0048] The connection status determination unit 74 determines the electrical connection status between the power conversion circuit 3A and the heating resistor 61 based on the drive frequencies of the inverter drive signals Sg1 to Sg4. Between the heating resistor 61 and the power conversion circuit 3A, poor contact or disconnection may occur between connection terminals 64 and 631. In that case, the load current If does not flow, but the drive frequency is set to an extreme value in order to allow the load current If to flow. Therefore, the electrical connection status between the power conversion circuit 3A and the heating resistor 61 can be determined based on the drive frequencies of the inverter drive signals Sg1 to Sg4. In this embodiment, the connection status determination unit 74 determines the connection status based on whether or not the drive frequency has reached a threshold. If the connection status is abnormal, the connection status determination unit 74 outputs a connection abnormality signal Se.

[0049] Figure 4 is a graph showing an example of the frequency characteristics of the gain of the power conversion circuit 3A, including the heating resistor 61. In Figure 4, the horizontal axis represents the driving frequency, and the vertical axis represents the gain. The gain is, for example, the ratio of the third power to the first power. As shown in Figure 4, the gain of the power conversion circuit 3A changes with the change in driving frequency. The gain of the power conversion circuit 3A is, for example, largest at the resonant frequency f1.

[0050] Here, if a poor connection or disconnection occurs between connection terminals 64 and 631 between the heating resistor 61 and the power conversion circuit 3A, the load current If will stop flowing. However, the frequency control unit 73, through a feedback circuit including the control element 72, attempts to increase the gain of the power conversion circuit 3A to allow the load current If to flow. As a result, the drive frequency shifts from the initial frequency fa to a lower frequency and reaches the lower limit of the movable range (for example, the resonant frequency f1) (arrow A in the figure). If a threshold is set in advance near the lower limit of the movable range, the connection state determination unit 74 can determine the electrical connection state between the heating resistor 61 and the power conversion circuit 3A based on whether or not the drive frequency has reached that threshold.

[0051] Figure 5 is a flowchart showing an example of a method for determining the electrical connection state between the heating resistor 61 and the power conversion circuit 3A using the power supply device 1A described above. This method comprises steps ST11 and ST12. First, in step ST11, the frequency control unit 73 controls the drive frequencies of the inverter drive signals Sg1 to Sg4 so that the magnitude of the load current If approaches the target value of the load current If. The frequency control unit 73 controls the frequency instruction signal S freq The drive frequency is variably controlled according to the magnitude of the load. Next, in step ST12, the connection state determination unit 74 determines the electrical connection state between the heating resistor 61 and the power conversion circuit 3A based on the drive frequencies of the inverter drive signals Sg1 to Sg4. The connection state determination unit 74 determines the connection state based on extreme changes in the drive frequency, for example, whether or not the drive frequency has reached a threshold. If the connection state is normal, the inside of the airtight container 63 is depressurized, a load current If flows through the heating resistor 61, and the depressurizing tube 6 is operated.

[0052] The effects obtained by the power supply unit 1A and connection status determination method of this embodiment, as described above, will now be explained. In the power supply unit 1A, the parameter control unit 70 feedback controls the drive frequencies of the inverter drive signals Sg1 to Sg4 so that the magnitude of the load current If approaches the target value of the load current If. As mentioned above, if there is poor contact between the terminals or a break in the wire between the heating resistor 61 and the power conversion circuit 3A, the load current If will not flow. However, the drive frequencies of the inverter drive signals Sg1 to Sg4 are set to extreme values ​​in an attempt to make the load current If flow. Therefore, the connection status determination unit 74 can determine the electrical connection status between the power conversion circuit 3A and the heating resistor 61 based on the drive frequencies of the inverter drive signals Sg1 to Sg4. As a result, it is possible to easily determine the connection status of the heating resistor 61 before depressurizing the airtight container 63, eliminating the need to repeatedly depressurize the airtight container 63 and improving work efficiency.

[0053] As in this embodiment, the inverter 4 may include a switching circuit 41 and a resonant circuit 42. The switching circuit 41 is connected to the power supply unit 2 and converts the first power supplied from the power supply unit 2 into AC power as the second power. The resonant circuit 42 is connected between the switching circuit 41 and the rectifier and smoothing circuit 5 and steps up or down the AC voltage due to the AC power. The parameter control unit 70 controls the drive frequency of the switching circuit 41. The connection state determination unit 74 determines the connection state based on whether or not the drive frequency has reached a threshold. The impedance of the resonant circuit 42 included in the inverter 4 decreases, for example, as the drive frequency approaches the resonant frequency of the resonant circuit 42. That is, the impedance of the resonant circuit 42 changes with the drive frequency, and consequently the impedance of the heating resistor 61 changes with the drive frequency. However, if a contact problem or disconnection occurs between the terminals of the heating resistor 61 and the power conversion circuit 3A, the impedance of the heating resistor 61 becomes equivalent to infinite, and the drive frequency drops to an extreme value. Therefore, the electrical connection state between the heating resistor 61 and the power conversion circuit 3A can be determined based on whether or not the driving frequency has reached a threshold.

[0054] As in this embodiment, the airtight container 63 may have a connection terminal 631 connected to the rectifier and smoothing circuit 5 to output a third power. The heating resistor 61 may have a connection terminal 64 that can contact the connection terminal 631 and be configured to be detachable from the airtight container 63. In such a configuration, if the heating resistor 61 (heating resistor module 60 in this embodiment) is not properly mounted to the airtight container 63, the contact between the connection terminal 631 and the connection terminal 64 will be insufficient. With the power supply 1A, in such cases, the insufficient connection can be easily detected before the airtight container 63 is depressurized.

[0055] As in this embodiment, the power supply unit 1A is positioned opposite the heating resistor 61 which acts as the cathode, and detects the magnitude of the tube current Iout flowing between the cathode (heating resistor 61) and the anode 62 to which thermionic electrons emitted from the heating resistor 61 converge, thereby generating a tube current detection signal S IOUTThe parameter control unit 70 may also include a tube current detection unit 9 that generates a tube current detection signal S. IOUT Based on this, the drive frequency is controlled so that the magnitude of the tube current Iout approaches the target value of the tube current Iout. In the second operating mode, the parameter control unit 70 controls the tube current detection signal S IOUT Regardless of this, the drive frequency is controlled. With this power supply 1A, in the first operating mode, the magnitude of the tube current Iout can be appropriately controlled when the heating resistor module 60 is operating, i.e., when the pressure reducing tube 6 is operating. Furthermore, in the second operating mode, for example, before the pressure reducing tube 6 is operating (before the heating resistor module 60 is operating), the drive frequency can be controlled without controlling the tube current Iout, and the electrical connection state between the heating resistor 61 and the power conversion circuit 3A can be accurately determined. Note that since this is before the operation of the pressure reducing tube 6, the load current instruction signal S in the second operating mode is not controlled. Ifdr (Tube current instruction signal S ISET ) can be a small value that only allows a small load current If to flow.

[0056] Figure 6 is a graph showing the time evolution of various values ​​in the second operating mode. In Figure 6, line G1 represents the load current instruction signal S. Ifdr Line G2 shows the output voltage from inverter 4 (50V / div), line G3 shows the drive frequency of inverter 4 (200kHz / div), line G4 shows the primary current of transformer TR1 (1A / div), line G5 shows the voltage value of the third power supplied to heating resistor 61 (100V / div), line G6 shows the connection abnormality signal Se (5V / div) output from connection status determination unit 74, and line G7 shows the tube current Iout (1mA / div).

[0057] As shown by line G1, first at timing t1, the load current instruction signal S IfdrThe inverter starts up. Subsequently, as the drive frequency (line G3) of the inverter 4 decreases, the output voltage (line G2) from the inverter 4 increases, and the primary current (line G4) of the transformer TR1 increases. At this point, if there is poor contact between the terminals or an open circuit between the heating resistor 61 and the power conversion circuit 3A, the drive frequency (line G3) continues to decrease due to feedback control in the parameter control unit 70, and the primary current of the transformer TR1 continues to increase. When the drive frequency (line G3) reaches a predetermined threshold (timing t2 in the figure), the connection status determination unit 74 determines that there is a connection abnormality and outputs a connection abnormality signal Se.

[0058] Figure 7 is a graph showing the time variation of various values ​​when the heating resistor 61 and the power conversion circuit 3A are properly connected. Figure 8 is a graph showing the time variation of various values ​​when the connection between the heating resistor 61 and the power conversion circuit 3A is abnormal (poor contact, open circuit, etc.). In Figures 7 and 8, line G8 represents the output voltage (25V / div) from the output terminal 41g of the inverter 4, line G9 represents the output voltage (25V / div) from the output terminal 41h of the inverter 4, and line G10 represents the primary side current of the transformer TR1 (20A / div in Figure 7, 2A / div in Figure 8).

[0059] When the connection between the heating resistor 61 and the power conversion circuit 3A is normal, as shown in Figure 7, the primary current of the transformer TR1 becomes a resonant current waveform with a fundamental period that does not contain harmonic components. The driving frequency is, for example, 112.7 kHz, which is within the control range. The amplitude of the primary current of the transformer TR1 is, for example, about 14.6 A. In contrast, when the connection between the heating resistor 61 and the power conversion circuit 3A is abnormal, as shown in Figure 8, the primary current of the transformer TR1 becomes a high-frequency resonant current waveform. Therefore, the driving frequency becomes a small value, for example, 92.5 kHz, in order to suppress high-frequency resonance, which is the minimum value within the control range. The amplitude of the primary current of the transformer TR1 becomes small, for example, about 1.2 A. Thus, when the connection between the heating resistor 61 and the power conversion circuit 3A is abnormal, the driving frequency becomes extremely small. The connection state determination unit 74 of this embodiment uses this difference in driving frequency to determine the connection state between the heating resistor 61 and the power conversion circuit 3A.

[0060] [Second Embodiment] Figure 9 is a circuit diagram showing the configuration of the power supply unit 1B according to the second embodiment. The power supply unit 1B includes a power conversion circuit 3B instead of the power conversion circuit 3A of the first embodiment. Also, the power supply unit 1B includes an inverter control circuit 7B instead of the inverter control circuit 7A of the first embodiment. The other components of the power supply unit 1B, excluding the power conversion circuit 3B and the inverter control circuit 7B, are the same as those of the power conversion circuit 3A of the first embodiment. In addition to the same configuration as the power conversion circuit 3A of the first embodiment, the power conversion circuit 3B further includes a transformer TR2, a waveform shaping circuit 11, and a control circuit 12.

[0061] The inverter control circuit 7B of this embodiment differs from the inverter control circuit 7A of the first embodiment in the following respects, and is otherwise identical to the inverter control circuit 7A of the first embodiment. The inverter control circuit 7B performs both power transmission, which transmits the second power generated by driving the inverter 4 to the rectifier and smoothing circuit 5 via transformers TR1 and TR2, and signal transmission, which transmits the control signal Sc generated by driving the inverter 4 to the control circuit 12 via transformers TR1 and TR2. Between the inverter control circuit 7B and the control circuit 12, the control signal Sc is transmitted, for example, by UART (Universal Asynchronous Receiver / Transmitter) communication, with the inverter control circuit 7B as the master and the control circuit 12 as the slave.

[0062] Figure 10 shows an example of a time waveform of the voltage output from the inverter 4. This time waveform D1 includes a first period T1 and a second period T2. The inverter control circuit 7B performs power transmission during the first period T1. During power transmission, the inverter control circuit 7B drives the switching circuit 41 to generate a periodic square wave V1. The frequency of the square wave V1 is, for example, in the range of 100kHz to 150kHz. In the second period T2, which is separate from the first period T1, the inverter control circuit 7B performs signal transmission of a control signal Sc. During signal transmission, the inverter control circuit 7B drives the switching circuit 41 to generate a control signal Sc, which is a periodic square wave. The frequency of the control signal Sc is greater than the frequency of the square wave V1, for example, 1MHz or more. The power transmission by the square wave V1 and the signal transmission of the control signal Sc are performed in a time-separated state from each other.

[0063] The time waveform D1 includes a third period T3 between the first period T1 and the second period T2. The first period T1 follows the second period T2 again. The third period T3 is a period for consuming the power remaining in the power transmission path through power transmission. This removes ringing components on the power transmission path. In other words, the third period T3 is a stabilization period. Power consumption in the third period T3 is performed, for example, by a dummy resistor.

[0064] Refer to Figure 9 again. The ends of the primary winding L1 of transformer TR2 are connected to the ends of the secondary winding N2 of transformer TR1, respectively, and are connected to the resonant circuit 42 of inverter 4 via transformer TR1. The rectifier and smoothing circuit 5 is connected to the first secondary winding L2 of transformer TR2 via resistor R2. In the power transmission described above, the second power, which is AC power output from inverter 4, is supplied to the rectifier and smoothing circuit 5 through transformers TR1 and TR2.

[0065] In this embodiment, the control signal Sc is also used as a connection confirmation signal to check the electrical connection status between the power conversion circuit 3B and the heating resistor 61. That is, the connection status confirmation signal S is used with the inverter control circuit 7B. CS The input is received, and the connection status confirmation signal S CS Based on, or connection status confirmation signal S CS The control signal Sc is generated by the inverter control circuit 7B so as to include the following. The waveform shaping circuit 11 is connected to the second secondary winding L3 of the transformer TR2. In the signal transmission described above, the waveform shaping circuit 11 receives the control signal Sc from the inverter 4 via transformers TR1 and TR2, improves the distortion of the control signal Sc, and then transmits the control signal Sc to the control circuit 12. The waveform shaping circuit 11 is, for example, a low-pass filter having a cutoff frequency higher than the signal transmission bandwidth, and removes harmonic components of the control signal Sc that do not contribute to the transmitted signal.

[0066] The control circuit 12 is connected to the waveform shaping circuit 11, and via the waveform shaping circuit 11, it is connected to the second secondary winding L3 of the transformer TR2. In the signal transmission described above, the control circuit 12 receives the control signal Sc and transmits a signal Sd indicating that it has received the control signal Sc. The control circuit 12 operates on the secondary side, i.e., the high-voltage side, of the transformer TR1 based on the control signal Sc. The control circuit 12 may, for example, control various circuits on the high-voltage side, or control the pressure reducing tube 6 (for example, control of the cathode voltage and grid voltage). The control circuit 12 may also include a digital circuit.

[0067] The power supply unit 1B further includes a signal transmission inverter 91, a transformer TR3, a waveform shaping circuit 11a, and a connection state determination unit 12a. The input terminal of the signal transmission inverter 91 is connected to the control circuit 12. One output terminal of the signal transmission inverter 91 is connected to one end of the secondary winding N2 via a resonant capacitor Cr1. The other output terminal of the signal transmission inverter 91 is connected to the other end of the secondary winding N2. One end of the primary winding L4 of the transformer TR3 is connected to one end N1a of the primary winding N1, and the other end of the primary winding L4 is connected to the other end N1b of the primary winding N1. The waveform shaping circuit 11a is connected to the secondary winding L5 of the transformer TR3. In the signal transmission described above, the waveform shaping circuit 11a receives a signal Sd from the control circuit 12 via the signal transmission inverter 91, transformer TR1, and transformer TR3, improves the distortion of the signal Sd, and then transmits the signal Sd to the connection state determination unit 12a. The waveform shaping circuit 11a is, for example, a low-pass filter having a cutoff frequency higher than the signal transmission bandwidth, which removes harmonic components of the signal Sd that do not contribute to the transmitted signal.

[0068] The connection state determination unit 12a is connected to the waveform shaping circuit 11a and, via the waveform shaping circuit 11a, is connected to the secondary winding L5 of the transformer TR3. The connection state determination unit 12a receives the signal Sd in the signal transmission described above. The connection state determination unit 12a determines the electrical connection state between the power conversion circuit 3B and the heating resistor 61. Unlike the connection state determination unit 74 of the first embodiment, the connection state determination unit 12a determines the electrical connection state between the power conversion circuit 3B and the heating resistor 61 based on whether or not the control signal Sc generated by the inverter control circuit 7B has reached the control circuit 12 (i.e., whether or not the signal Sd has reached the connection state determination unit 12a).

[0069] Figure 11(a) is a graph showing the time waveform of the original data of the control signal Sc input to the inverter control circuit 7B. Figure 11(b) is a graph showing the time waveform of the control signal Sc output from the power conversion circuit 3B and received by the waveform shaping circuit 11, when the electrical connection between the power conversion circuit 3B and the heating resistor 61 is abnormal. If poor contact or a break in the terminals occurs between the heating resistor 61 and the power conversion circuit 3B, the output terminal of the rectifier smoothing circuit 5 becomes open, disrupting the matching conditions and generating reflected waves. This not only makes power transmission impossible, but also, as shown in Figure 11(b), the time waveform of the control signal Sc in signal transmission is distorted. As a result, the control signal Sc becomes undecipherable by the control circuit 12 and does not reach the control circuit 12 normally. In this case, the control circuit 12 does not transmit the signal Sd. Therefore, the connection state determination unit 12a can determine the electrical connection state between the power conversion circuit 3B and the heating resistor 61 based on whether or not the control signal Sc generated by the inverter control circuit 7B has reached the control circuit 12 normally (i.e., whether or not the signal Sd has reached the connection state determination unit 12a).

[0070] Figure 12 is a flowchart illustrating an example of a method for determining the electrical connection state between the heating resistor 61 and the power conversion circuit 3B using the power supply device 1B described above. The inverter control circuit 7B may operate according to this method. This method comprises steps ST21 to ST23. First, in step ST21, the inverter control circuit 7B transmits a control signal Sc by controlling the inverter 4. At this time, the control signal Sc may be a dummy signal used solely for determining the connection state. When the control signal Sc reaches the control circuit 12, the control circuit 12 transmits a signal Sd. Next, in step ST22, the electrical connection state between the heating resistor 61 and the power conversion circuit 3B is determined based on whether or not the control signal Sc generated by the inverter control circuit 7B reached the control circuit 12 (in other words, based on whether or not the signal Sd generated by the control circuit 12 reached the connection state determination unit 12a). The connection state determination unit 12a outputs a connection abnormality signal if the connection state is abnormal. If the connection state is normal, the inside of the airtight container 63 is depressurized. Next, in step ST23, the inverter control circuit 7B controls the inverter 4 to transmit power. Specifically, it flows the load current If through the heating resistor 61 and operates the pressure reducing tube 6.

[0071] The effects obtained by the power supply unit 1B of this embodiment, as described above, will now be explained. In the power supply unit 1B, the inverter control circuit 7B transmits a control signal Sc (connection confirmation signal) generated by driving the inverter 4 to the control circuit 12 via transformers TR1 and TR2, before transmitting the second power generated by driving the inverter 4 to the rectifier and smoothing circuit 5 via transformers TR1 and TR2. Then, based on whether or not the control signal Sc from the inverter control circuit 7B has reached the control circuit 12 successfully, the electrical connection state between the power conversion circuit 3B and the heating resistor 61 is determined. As a result, the connection state of the heating resistor 61 can be easily determined before depressurizing the airtight container 63, eliminating the need to repeatedly depressurize the airtight container 63 and improving work efficiency.

[0072] [First variation] Figure 13 is a circuit diagram showing the configuration of the power supply unit 1C according to the first modified example. The power supply unit 1C differs from the second embodiment in the following respects, and is otherwise identical to the second embodiment. The transformer TR2 of the power supply unit 1C does not have a secondary winding L2 (see Figure 9). The secondary winding N2 of the transformer TR1 is connected to the rectifier circuit 51 without going through the transformer TR2. The power supply unit 1C of this modified example can obtain the same effects as the power supply unit 1B according to the second embodiment.

[0073] [Second variation] Figure 14 is a circuit diagram showing the configuration of a power supply unit 1D according to a second modified example. In addition to the configuration of the second embodiment, the power supply unit 1D includes a control unit 81, a light-emitting element 82, a light-receiving element 83, a control unit 84, a light-receiving element 85, a light-emitting element 86, an optical fiber FB1, and an optical fiber FB2. The control unit 81, the light-emitting element 82, and the light-receiving element 83 are located on the low-voltage side. The control unit 84, the light-receiving element 85, and the light-emitting element 86 are located on the high-voltage side.

[0074] The control unit 81 communicates optically with the control unit 84. Specifically, the control unit 81 outputs an electrical first transmission signal. This first transmission signal is converted into a first optical signal SP1 by the light-emitting element 82, and the first optical signal SP1 propagates through the optical fiber FB1 to the photodetector 85, where it is converted back into an electrical first transmission signal. This first transmission signal is received by the control unit 84. The control unit 84 also outputs an electrical second transmission signal. This second transmission signal is converted into a second optical signal SP2 by the light-emitting element 86, and the second optical signal SP2 propagates through the optical fiber FB2 to the photodetector 83, where it is converted back into an electrical second transmission signal. This second transmission signal is received by the control unit 81.

[0075] The control unit 81 is connected to the inverter control circuit 7B, and the inverter control circuit 7B receives a connection status confirmation signal S. CS The control unit 84 is connected to the control circuit 12 and provides a connection status confirmation signal S to the inverter control circuit 7B. CSWhen the control unit 81 is notified by the first optical signal SP1 that the control signal Sc has been provided, the control unit 12 checks whether or not it has received the control signal Sc. The control unit 81 is connected to the connection status determination unit 12a, and when the control unit 84 is notified by the second optical signal SP2 that it has received the control signal Sc, the control unit 81 checks whether or not it has received the signal Sd in the connection status determination unit 12a. Thus, according to this modified example, the control units 81 and 84 each check whether or not the control signal Sc has been received in the control unit 12 and whether or not the signal Sd has been received in the connection status determination unit 12a, respectively, so that the connection status of the heating resistor 61 can be determined more accurately. In addition, when a connection failure of the heating resistor 61 is detected, the control signal Sc can be easily retransmitted and the connection status can be re-determined.

[0076] [Third variation] Figure 15 is a circuit diagram showing the configuration of the power supply unit 1E according to the third modified example. The power supply unit 1E differs from the second modified example in the following respects, and is otherwise identical to the second modified example. The transformer TR2 of the power supply unit 1E does not have a secondary winding L2 (see Figure 14). Furthermore, the secondary winding N2 of the transformer TR1 is connected to the rectifier circuit 51 without going through the transformer TR2. With the power supply unit 1E of this modified example, the same effects as the power supply unit 1D according to the second modified example can be obtained.

[0077] [Fourth variation] Figure 16 is a circuit diagram showing the configuration of the power supply unit 1F according to the fourth modified example. The power supply unit 1F has a configuration that is the same as the second modified example, but without the transformer TR3, the waveform shaping circuit 11a, and the connection status determination unit 12a. In this modified example, the control circuit 12 transmits the signal Sd to the control unit 84 instead of the connection status determination unit 12a. The control unit 84 outputs the signal Sd to the light-emitting element 86. The signal Sd is converted into an optical signal by the light-emitting element 86, and the optical signal of signal Sd propagates through the optical fiber FB2. The optical signal that reaches the photodetector 83 is converted back into an electrical signal Sd. This signal Sd is received by the control unit 81. Even in this modified example, the connection status of the heating resistor 61 can be determined more accurately.

[0078] [Fifth variation] Figure 17 is a circuit diagram showing the configuration of the power supply unit 1G according to the fifth modification. The power supply unit 1G differs from the fourth modification in the following respects, and is otherwise identical to the fourth modification. The transformer TR2 of the power supply unit 1G does not have a secondary winding L2 (see Figure 16). The secondary winding N2 of the transformer TR1 is connected to the rectifier circuit 51 without going through the transformer TR2. With the power supply unit 1G of this modification, the same effects as the power supply unit 1F according to the fourth modification can be obtained.

[0079] While embodiments of this disclosure have been described above, this disclosure is not necessarily limited to the embodiments described above, and various modifications are possible without departing from its essence. For example, in the above embodiments, X-ray tubes and electron beam tubes are given as examples of pressure reducing tubes, but pressure reducing tubes are not limited to these.

[0080] In the first embodiment, the inverter control circuit 7A includes a connection status determination unit 74, but the connection status determination unit may be provided outside the inverter control circuit. Furthermore, the power supply unit may notify the user that the connection status is abnormal if the connection status determination unit determines that the connection status is abnormal. For example, the power supply unit may display a message indicating that the connection status is abnormal on a display.

[0081] Furthermore, the power supply device of the above embodiment includes an inverter 4 as a modulation circuit and an inverter control circuit 7A or 7B as a modulation control circuit, with AC power output from the inverter 4 as second power. The modulation circuit and modulation control circuit are not limited to these. The modulation circuit may, for example, output PWM-modulated power as second power, and the modulation control circuit may output a modulation circuit drive signal for PWM modulation to the modulation circuit. In that case, the duty cycle of the PWM modulation corresponds to the modulation parameter. The connection state determination unit then determines the electrical connection state between the power conversion circuit and the heating resistor based on whether or not the duty cycle has reached a certain threshold. [Explanation of Symbols]

[0082] 1A, 1B, 1C, 1D, 1E, 1F, 1G... Power supply unit, 2... Power supply unit, 3A, 3B... Power conversion circuit, 4... Inverter, 5... Rectifier and smoothing circuit, 6... Pressure reducing tube, 7A, 7B... Inverter control circuit, 8... Load current detection unit, 9... Tube current detection unit, 11... Waveform shaping circuit, 11a... Waveform shaping circuit, 12... Control circuit, 12a... Connection status determination unit 、4 1…Switching circuit, 41a,41b…Power terminals, 41c~41f…Control terminals, 41g,41h…Output terminals, 42…Resonant circuit, 51…Rectifier circuit, 52…Smoothing circuit, 60…Heating resistor module, 61…Heating resistor, 62…Anode, 63…Hermetry container, 64…Connection terminal (second connection terminal), 65…Support, 70…Parameter control unit, 71,72…Control elements, 71a,71b,72a,72b…Input terminals, 71c,72c…Output terminals, 73…Frequency control unit, 74…Connection status determination unit, 75…Switch, 75a,75b…Input terminals, 75c…Output terminals, 81,84…Control 82,86…Light-emitting element, 83,85…Photodetector, 91…Inverter for signal transmission, 411,412…Reg circuit, 631…Connection terminal (first connection terminal), 632…Lid, 633…Window, AP…AC power supply, B…Thermionic element, Cr,Cr1…Resonant capacitor, D1…Time waveform, fa…Initial frequency, f1…Resonant frequency, FB1,FB2…Optical fiber, If…Load current, Iout…Tube current, L1,N1…Primary winding, L2,L3,N2…Secondary winding, Lp…Excitation inductance, Lr…Resonant inductance, N1a,N2a…One end, N1b,N2b…Other end, R1,R2…Resistor, S freq ...frequency indication signal, S If ...Load current detection signal, S Ifdr ...Load current indication signal, S IOUT ...tube current detection signal, S ISET ...tube current instruction signal, Sc...control signal, Sd...signal, S1~S4...semiconductor switch, S CS ...Connection status confirmation signal, Se...Connection abnormality signal, Sg1~Sg4...Inverter drive signal, SP1...First optical signal, SP2...Second optical signal, t1, t2...Timing, T1...First period, T2...Second period, T3...Third period, TR1, TR2 TR3 ...Transformer, V1...square wave, Vc...high voltage power supply

Claims

1. A power supply unit that outputs a first power which is DC power, A power conversion circuit having a modulation circuit that modulates the first power and converts it into a second power, and a rectifier and smoothing circuit that converts the second power into a third power which is DC power, A heating resistor module having a heating resistor to which the aforementioned third power is supplied, and an airtight container for holding the heating resistor in a reduced-pressure atmosphere, A modulation control circuit connected to the modulation circuit and outputting a modulation circuit drive signal to control the modulation circuit, The power conversion circuit includes a first current detection unit that detects the magnitude of the load current supplied to the heating resistor by the third power or the magnitude of a current that fluctuates together with the load current, and generates a first current detection signal. The modulation control circuit is A parameter control unit controls the modulation parameters of the modulation circuit drive signal so that the magnitude of the load current approaches the target value of the load current, based on the first current detection signal. The system includes a connection state determination unit that determines the electrical connection state between the power conversion circuit and the heating resistor based on the modulation parameters, The modulation circuit described above is A switching circuit connected to the power supply unit, which converts the first power supplied from the power supply unit into AC power as the second power, The circuit further comprises a resonant circuit connected between the switching circuit and the rectifier / smoothing circuit, which steps up or down the AC voltage generated by the AC power, The parameter control unit controls the drive frequency of the switching circuit as the modulation parameter. The connection status determination unit determines the connection status based on whether or not the drive frequency has reached a threshold, and is a power supply device.

2. A power supply unit that outputs a first power which is DC power, A power conversion circuit having a modulation circuit that modulates the first power and converts it into a second power, and a rectifier and smoothing circuit that converts the second power into a third power which is DC power, A heating resistor module having a heating resistor to which the aforementioned third power is supplied, and an airtight container for holding the heating resistor in a reduced-pressure atmosphere, A modulation control circuit connected to the modulation circuit and outputting a modulation circuit drive signal to control the modulation circuit, The power conversion circuit supplies a load current to the heating resistor, and a first current detection unit detects the magnitude of the load current due to the third power or the magnitude of a current that fluctuates with the load current to generate a first current detection signal. An anode is positioned opposite the heating resistor, which acts as the cathode, and the thermionic electrons emitted from the heating resistor converge thereto, The system includes a second current detection unit that detects the magnitude of the current flowing between the cathode and the anode and generates a second current detection signal, The modulation control circuit is A parameter control unit controls the modulation parameters of the modulation circuit drive signal so that the magnitude of the load current approaches the target value of the load current, based on the first current detection signal. The system includes a connection state determination unit that determines the electrical connection state between the power conversion circuit and the heating resistor based on the modulation parameters, The parameter control unit has a first operating mode and a second operating mode, In the first operating mode, the parameter control unit controls the modulation parameters based on the second current detection signal so that the magnitude of the current flowing between the cathode and the anode approaches the target value of the current. In the second operating mode, the parameter control unit controls the modulation parameter regardless of the second current detection signal.

3. A power supply unit that outputs a first power which is DC power, A power conversion circuit having a modulation circuit that modulates the first power and converts it into a second power, a transformer whose primary winding is connected to the modulation circuit, and a rectifier and smoothing circuit connected to the first secondary winding of the transformer that converts the second power into a third power which is DC power, A heating resistor module having a heating resistor to which the aforementioned third power is supplied, and an airtight container for holding the heating resistor in a reduced-pressure atmosphere, A modulation control circuit connected to the modulation circuit and outputting a modulation circuit drive signal to control the modulation circuit, A receiving circuit connected to the second secondary winding of the transformer, The system includes a connection state determination unit that determines the electrical connection state between the power conversion circuit and the heating resistor, The modulation control circuit performs a signal transmission, which involves transmitting a connection confirmation signal generated by driving the modulation circuit to the receiving circuit via the transformer, before the power transmission, which involves transmitting the second power generated by driving the modulation circuit to the rectifier-smoothing circuit via the transformer. The connection status determination unit determines the connection status based on whether or not the connection confirmation signal from the modulation control circuit has successfully reached the receiving circuit.

4. The airtight container has a first connection terminal that is connected to the rectifier and smoothing circuit and outputs the third power, The power supply device according to any one of claims 1 to 3, wherein the heating resistor has a second connection terminal that can contact the first connection terminal and is configured to be detachably attached to the airtight container.

5. A method for determining the connection status of a heating resistor using a power supply device, The aforementioned power supply device is A power supply unit that outputs a first power which is DC power, A power conversion circuit having a modulation circuit that modulates the first power and converts it into a second power, and a rectifier and smoothing circuit that converts the second power into a third power which is DC power, A heating resistor module having a heating resistor to which the aforementioned third power is supplied, and an airtight container for holding the heating resistor in a reduced-pressure atmosphere, A modulation control circuit connected to the modulation circuit and outputting a modulation circuit drive signal to control the modulation circuit, The power conversion circuit includes a first current detection unit that detects the magnitude of the load current supplied to the heating resistor by the third power or the magnitude of a current that fluctuates together with the load current, and generates a first current detection signal. The aforementioned method, The steps include controlling the modulation parameters of the modulation circuit drive signal based on the first current detection signal so that the magnitude of the load current approaches the target value of the load current, The system includes the step of determining the electrical connection state between the power conversion circuit and the heating resistor based on the modulation parameters, The modulation circuit described above is A switching circuit connected to the power supply unit, which converts the first power supplied from the power supply unit into AC power as the second power, The circuit further comprises a resonant circuit connected between the switching circuit and the rectifier / smoothing circuit, which steps up or down the AC voltage generated by the AC power, In the step of controlling the modulation parameter, the drive frequency of the switching circuit is controlled as the modulation parameter. A method for determining the connection state of a heating resistor, wherein the step of determining the connection state is to determine the connection state based on whether or not the drive frequency has reached a threshold.

6. A method for determining the connection status of a heating resistor using a power supply device, The aforementioned power supply device is A power supply unit that outputs a first power which is DC power, A power conversion circuit having a modulation circuit that modulates the first power and converts it into a second power, and a rectifier and smoothing circuit that converts the second power into a third power which is DC power, A heating resistor module having a heating resistor to which the aforementioned third power is supplied, and an airtight container for holding the heating resistor in a reduced-pressure atmosphere, A modulation control circuit connected to the modulation circuit and outputting a modulation circuit drive signal to control the modulation circuit, The power conversion circuit supplies a load current to the heating resistor, and a first current detection unit detects the magnitude of the load current due to the third power or the magnitude of a current that fluctuates with the load current to generate a first current detection signal. An anode is positioned opposite the heating resistor, which acts as the cathode, and the thermionic electrons emitted from the heating resistor converge thereto, The system includes a second current detection unit that detects the magnitude of the current flowing between the cathode and the anode and generates a second current detection signal, The aforementioned method, The steps include controlling the modulation parameters of the modulation circuit drive signal based on the first current detection signal so that the magnitude of the load current approaches the target value of the load current, The system includes the step of determining the electrical connection state between the power conversion circuit and the heating resistor based on the modulation parameters, The step of controlling the modulation parameters includes a first operating mode and a second operating mode. In the first operating mode, the modulation parameters are controlled based on the second current detection signal so that the magnitude of the current flowing between the cathode and the anode approaches a target value of the current. A method for determining the connection state of a heating resistor, which controls the modulation parameter regardless of the second current detection signal in the second operating mode.

7. A method for determining the connection status of a heating resistor using a power supply device, The aforementioned power supply device is A power supply unit that outputs a first power which is DC power, A power conversion circuit having a modulation circuit that modulates the first power and converts it into a second power, a transformer whose primary winding is connected to the modulation circuit, and a rectifier and smoothing circuit connected to the first secondary winding of the transformer that converts the second power into a third power which is DC power, A heating resistor module having a heating resistor to which the aforementioned third power is supplied, and an airtight container for holding the heating resistor in a reduced-pressure atmosphere, A modulation control circuit connected to the modulation circuit and outputting a modulation circuit drive signal to control the modulation circuit, The receiving circuit is connected to the second secondary winding of the transformer, The aforementioned method, The steps include: performing signal transmission by driving the modulation circuit and transmitting the connection confirmation signal generated to the receiving circuit via the transformer; The steps include determining the electrical connection state between the power conversion circuit and the heating resistor based on whether the connection confirmation signal from the modulation control circuit has successfully reached the receiving circuit, If the connection state is normal, the power transmission step involves driving the modulation circuit to generate the second power and transmitting it to the rectifier and smoothing circuit via the transformer. A method for determining the connection state of a heating resistor, comprising:

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