Power supply unit and power control method for heating resistor

Abstract

The present invention provides a power supply device that enables control of the load current of a thermal resistance element so as to stably change the tube current toward a set value. [Solution] The power supply unit 1A includes a tube current detection unit 9, a power adjustment unit 10, and an instruction signal generation unit 11A. The power adjustment unit 10 generates a load current instruction signal S Ifdr The heating resistor 61 is supplied with power of a corresponding magnitude. The tube current detection unit 9 detects the magnitude of the tube current Iout and signals a tube current detection signal S IOUT The instruction signal generation unit 11A receives the set value of the tube current Iout and generates the tube current detection signal S so that the magnitude of the tube current Iout approaches the set value. IOUT Based on the load current instruction signal S Ifdr The instruction signal generation unit 11A generates the tube current detection signal S. IOUT From load current instruction signal S Ifdr The gain generated is variable. The smaller the set value, the smaller the gain. The smaller the difference between the magnitude of the tube current Iout and the set value, the smaller the gain.

Description

[Technical Field]

[0001] This disclosure relates to a power supply device and a method for controlling the power of a heating resistor. [Background technology]

[0002] Power supply devices equipped with an inverter and a control circuit for controlling the inverter are known. Power supply devices can be applied to devices that have a heating resistor (filament) as a cathode and an anode inside a vacuum tube, such as an X-ray generator or an electron beam generator. The X-ray generator described in Patent Document 1 emits thermionic electrons from the filament by passing an electric current through the filament to heat it, and focuses these thermionic electrons onto a target at the anode. The power supply device in the X-ray generator described in Patent Document 1 is equipped with a tube current control circuit to stably drive the X-ray tube. The tube current control circuit controls the current supplied to the filament so that the tube current flowing between the anode and cathode of the X-ray tube approaches a predetermined set value. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2010-49974 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] In a power supply unit used in a device equipped with a heating resistor inside a pressure reducing tube, the magnitude of the load current supplied to the heating resistor is controlled when the tube current setting is changed. At this time, it is desirable for the tube current to change stably toward the setting value. However, since the change in tube current depends on the temperature change of the heating resistor, there is a large lag in the change of tube current in response to a change in the tube current setting value. Therefore, overshoot is likely to occur, and there is a problem in that it is not easy to control the load current of the heating resistor in order to change the tube current stably toward the setting value.

[0005] This disclosure describes a method for stably changing the tube current toward a set value. Canada The objective is to provide a power supply device that enables control of the load current of a thermal resistance element, and a method for controlling the power of a thermal resistance element. [Means for solving the problem]

[0006] [1] A power supply device relating to one aspect of the present disclosure supplies power to a heating resistor of a pressure reducing tube, which comprises a heating resistor as a cathode and an anode positioned opposite the heating resistor and upon which thermionic electrons emitted from the heating resistor converge. The power supply device comprises a power adjustment unit, a tube current detection unit, and an instruction signal generation unit. The power adjustment unit supplies power to the heating resistor in an amount corresponding to a load current instruction signal for instructing the magnitude of the load current flowing through the heating resistor. The tube current detection unit detects the magnitude of the tube current flowing between the heating resistor and the anode, or the magnitude of a current that fluctuates with the tube current, and generates a tube current detection signal. The instruction signal generation unit receives a set value for the tube current as input and generates a load current instruction signal based on the tube current detection signal so that the magnitude of the tube current approaches the set value. The instruction signal generation unit is configured such that the gain when generating the load current instruction signal from the tube current detection signal is variable. The smaller the set value, the smaller the gain. The smaller the difference between the magnitude of the tube current and the set value, the smaller the gain.

[0007] In the power supply unit described in [1] above, a feedback loop is formed by a tube current detection unit, an instruction signal generation unit, and a power adjustment unit. The gain of this feedback loop, that is, the gain when the instruction signal generation unit generates a load current instruction signal from the tube current detection signal, decreases as the set value of the tube current decreases, and also decreases as the difference between the magnitude of the tube current and the set value decreases. As a result, immediately after the operation of the pressure reducing tube or immediately after the set value is changed, when the magnitude of the tube current is far from the set value, the gain of the feedback loop increases, allowing the tube current to change rapidly. Then, as the magnitude of the tube current approaches the set value, the gain of the feedback loop decreases, allowing the tube current to converge stably to the set value. Therefore, the power supply unit described in [1] above improves the slowness of the change in tube current and allows the tube current to change stably toward the set value. Canada The load current of the thermal resistance material can be controlled.

[0008] [2] In the power supply device described in [1] above, the power adjustment unit may include a power supply unit, a power conversion circuit, and a modulation control circuit. The power supply unit outputs a first power, which is DC power. The power conversion circuit includes a modulation circuit that modulates the first power to convert it into a second power, and a rectifier and smoothing circuit that converts the second power to a third power, which is DC power, and supplies the third power to the heating resistor as the power. The modulation control circuit is connected to the modulation circuit and outputs a modulation circuit drive signal to control the modulation circuit. The modulation control circuit controls the modulation parameters of the modulation circuit drive signal so that the magnitude of the load current flowing through the heating resistor approaches the magnitude of the load current indicated by the load current instruction signal. By having such a configuration, for example, the power adjustment unit can supply power to the heating resistor in a magnitude corresponding to the load current instruction signal.

[0009] [3] In the power supply device described in [1] above, the power adjustment unit may include a power supply unit and a power conversion circuit. The power supply unit outputs a first power which is DC power, and is configured such that the magnitude of the first power is variable. The power conversion circuit includes a modulation circuit that modulates the first power to convert it into a second power, and a rectifier and smoothing circuit that converts the second power into a third power which is DC power, and supplies the third power as the power to the heating resistor. The power supply unit controls the magnitude of the first power so that the magnitude of the load current flowing through the heating resistor approaches the magnitude of the load current indicated by the load current instruction signal. By providing the power adjustment unit with such a configuration, for example, it is possible to supply power to the heating resistor with a magnitude corresponding to the load current instruction signal.

[0010] [4] A power control method for a heating resistor according to one aspect of the present disclosure is a method for controlling the power supplied to a heating resistor of a pressure reducing tube, which comprises a heating resistor as a cathode and an anode positioned opposite the heating resistor and upon which thermionic electrons emitted from the heating resistor converge. The method comprises a tube current detection step, an instruction signal generation step, and a power adjustment step. In the tube current detection step, the magnitude of the tube current flowing between the heating resistor and the anode, or the magnitude of a current that fluctuates with the tube current, is detected and a tube current detection signal is generated. In the instruction signal generation step, a set value for the tube current is input, and a load current instruction signal is generated based on the tube current detection signal to instruct the magnitude of the load current flowing through the heating resistor so that the magnitude of the tube current approaches the set value. In the power adjustment step, the power supplied to the heating resistor is controlled to a magnitude corresponding to the load current instruction signal. In the instruction signal generation step, the gain when generating the load current instruction signal from the tube current detection signal is made variable. The gain is reduced as the set value is smaller, and the gain is reduced as the difference between the magnitude of the tube current and the set value is smaller.

[0011] In the power control method described in [4] above, a feedback loop is formed by a tube current detection step, an instruction signal generation step, and a power adjustment step. The gain of this feedback loop, that is, the gain when generating a load current instruction signal from the tube current detection signal in the instruction signal generation step, decreases as the set value of the tube current decreases, and also decreases as the difference between the magnitude of the tube current and the set value decreases. This power control method improves the slowness of the change in tube current, similar to the power supply device described in [1] above, and allows the tube current to change stably toward the set value. Canada The load current of the thermal resistance material can be controlled. [Effects of the Invention]

[0012] According to this disclosure, the tube current is stably changed toward a set value. Canada This invention provides a power supply device that enables control of the load current of a thermal resistor, and a method for controlling the power of a thermal resistor. [Brief explanation of the drawing]

[0013] [Figure 1] Figure 1 is a schematic diagram of the power supply device circuit according to the first embodiment. [Figure 2] Figure 2 is a block diagram showing an example of the internal configuration of the inverter control circuit and the instruction signal generation unit. [Figure 3] Figure 3 is a diagram illustrating an example of gain adjustment according to the magnitude of the tube current indicator signal. [Figure 4] Figure 4 is a graph plotting the relationship between the set value based on the tube current instruction signal and the gain weight. [Figure 5] Figure 5 is a diagram illustrating an example of gain adjustment based on the difference between the tube current detection signal and the tube current instruction signal. [Figure 6] Figure 6 is a graph showing the time evolution of the gain of the control element. [Figure 7] Figure 7 is a diagram showing an example of the optimal gradient for the set value. [Figure 8] Figure 8 is a simplified block diagram showing the control system. [Figure 9]Figure 9 is a graph showing the time evolution of various values ​​in the power supply unit. [Figure 10] Figure 10 is a graph showing the time variation of the tube current. [Figure 11] Figure 11 is a flowchart showing an example of a method for controlling the power supplied to a heating resistor. [Figure 12] Figure 12 is a graph showing an example of the time variation of load current and tube current. [Figure 13] Figure 13 is a schematic diagram of the power supply device circuit according to the second embodiment. [Modes for carrying out the invention]

[0014] Specific examples of this disclosure will be described below with reference to the drawings. However, this disclosure is not limited to these examples, and is intended to include all modifications within the meaning and scope of the claims as indicated by the claims. In the following description, identical elements in the drawings will be denoted by the same reference numerals, and redundant descriptions will be omitted.

[0015] (First Embodiment) Figure 1 is a schematic diagram of the circuit of a power supply 1A according to the first embodiment of this disclosure. The power supply 1A is a power supply for supplying power to a heating resistor 61, which is a load, and raising the temperature of the heating resistor 61. The heating resistor 61 constitutes the cathode (filament) of a pressure reducing tube 6. Inside the pressure reducing tube 6, an anode 62 is further provided, which is positioned opposite the heating resistor 61. 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. When a load current If is supplied to the heating resistor 61, the heating resistor 61 generates heat. As a result, thermionic electrons B are emitted from the heating resistor 61. On the other hand, a high voltage generated by a high-voltage power supply Vc outside the power supply 1A is applied between the heating resistor 61 and the anode 62. Thermionic electrons B emitted from the heating resistor 61 move from the heating resistor 61 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.

[0016] The power supply unit 1A includes a power adjustment unit 10. The power adjustment unit 10 provides a load current instruction signal S for indicating the magnitude of the load current If flowing through the heating resistor 61. Ifdr The power adjustment unit 10 supplies power to the heating resistor 61 in an amount corresponding to (described later). The power adjustment unit 10 includes a power supply unit 2 and a power conversion circuit 3.

[0017] 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 3. 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).

[0018] The power supply unit 2 receives a tube current instruction signal S that indicates the set value of the tube current Iout flowing through the pressure reducing tube 6. ISET The following is input: Tube current indicator 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 of the signal driving the switching element may be varied.

[0019] 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.

[0020] The power conversion circuit 3 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 3 supplies a load current If, due to the third power, to the heating resistor 61. The power conversion circuit 3 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.

[0021] 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.

[0022] 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.

[0023] Each of the control terminals 41c to 41f is a control terminal for the respective semiconductor switches S1 to S4. Inverter drive signals Sg1 to Sg4 are output from the inverter control circuit 7A to the control terminals 41c to 41f. Output terminal 41g is located between semiconductor switches S1 and S2, and output terminal 41h is located between semiconductor switches S3 and S4. The resonant circuit 42 is connected to output terminals 41g and 41h.

[0024] 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.

[0025] 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 TR, which has 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 TR 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 TR is connected to the heating resistor 61, which is the load, via the rectifier / smoothing circuit 5.

[0026] The transformer TR contains several parasitic components. The transformer TR includes a resonant inductance Lr (parasitic inductance) and an excitation inductance Lp. The resonant inductance Lr is the leakage inductance of the transformer TR. 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 fr of the resonant circuit 42 is expressed, for example, by equation (1). fr=1 / 2×π×SQRT(Lr×Cr)…(1) In equation (1), SQRT represents the square root. As shown in equation (1), at the resonant frequency fr, the resonant inductance Lr is dominant over the excitation inductance Lp, so the resonant frequency fr is determined based on the resonant capacitor Cr and the resonant inductance Lr.

[0027] 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.

[0028] 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.

[0029] The power supply unit 1A of this embodiment further comprises an inverter control circuit 7A, a load current detection unit 8, a tube current detection unit 9, and an instruction signal generation unit 11A. 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, respectively. 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.

[0030] The load current detection unit 8 detects the magnitude of the load current If or the magnitude of a current that varies together 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 resonance circuit 42. In the example of FIG. 1, the input terminal of the load current detection unit 8 is connected to a node between the output terminal 41h and the other end N1b of the primary winding N1 of the transformer TR. The output terminal of the load current detection unit 8 is connected to the inverter control circuit 7A. In the example of FIG. 1, the load current detection unit 8 detects the magnitude of the primary side current that varies together with the load current If on the primary winding N1 side of the transformer TR (primary side of the inverter 4). Note that the load current detection unit 8 may detect the load current If on the secondary winding N2 side of the transformer TR (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 TR and the rectifying and smoothing circuit 5.

[0031] The load current detection unit 8 generates a load current detection signal S that indicates the magnitude of the load current If or the magnitude of a current that varies together with the load current If. If If The load current detection signal S 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 a current that varies together with the load current If by the current transformer, and then converts the load current If or the current that varies together with the load current If into a voltage by the resistor, thereby generating the load current detection signal S. shunt If

[0032] The tube current detection unit 9 detects the magnitude of the tube current Iout or the magnitude of a current that varies together with the tube current Iout. The input terminal of the tube current detection unit 9 is connected to the anode 62 of the step-down 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 that indicates the magnitude of the tube current Iout or the magnitude of a current that varies together with the tube current Iout. IOUT IOUTThis is, for example, a voltage signal. The tube current detection unit 9 may include a current transformer and a shunt resistor, or it may include components other than a current transformer and a shunt resistor.

[0033] The instruction signal generation unit 11A outputs a tube current instruction signal S that indicates the set value of the tube current Iout. ISET The following is input. The instruction signal generation unit 11A generates a tube current instruction signal S ISET The tube current detection signal S should be adjusted so that the magnitude of the tube current Iout approaches the set value indicated by the signal. IOUT Based on the load current instruction signal S Ifdr The inverter control circuit 7A generates the load current instruction signal S. Ifdr The drive frequencies (modulation parameters) of the inverter drive signals Sg1 to Sg4 are controlled so that the magnitude of the load current If flowing through the heating resistor 61 approaches the magnitude of the load current If indicated by the inverter.

[0034] Figure 2 is a block diagram showing an example of the internal configuration of the inverter control circuit 7A and the instruction signal generation unit 11A. The inverter control circuit 7A includes a control element 72 and a frequency control unit 73. The instruction signal generation unit 11A includes a control element 71. 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 output terminal 71c of the control element 71 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.

[0035] The input terminal 71a of the control element 71 receives the tube current detection signal S. IOUT The following is input. Input terminal 71b receives a tube current indicator signal S, which indicates the set value 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 A load current instruction signal S has a magnitude obtained by multiplying the difference by the gain. Ifdr The control element 71 outputs the tube current detection signal S. IOUTThe tube current indicator signal S ISET If it is greater than, the load current instruction signal S Ifdr The size is reduced, and the tube current detection signal S IOUT The tube current indicator signal S ISET If it is smaller than, the load current instruction signal S Ifdr The magnitude of is increased. Through this operation, the control element 71 receives the tube current instruction signal S. ISET and tube current detection signal S IOUT Based on this, the tube current indicator signal S ISET Load current instruction signal S approaches the tube current Iout. Ifdr Generates.

[0036] Input terminal 72a receives the load current detection signal S from the load current detection unit 8. If The load current instruction signal S is input to input terminal 72b. 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 freq The 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 set value for 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.

[0037] 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 set 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.

[0038] 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 respective control terminals 41c to 41f of the switching circuit. The frequency control unit 73 may also have a function to adjust the timing of the output of inverter drive signals Sg1 to Sg4. This may cause the semiconductor switches S1 to S4 to switch alternately.

[0039] 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 fr 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 set value for the magnitude of the load current If. Ifdr The frequency indicator signal S approaches freq Control.

[0040] Here, the instruction signal generation unit 11A generates the tube current detection signal S IOUT From load current instruction signal S Ifdr The gain when generating the signal, i.e., the gain of the control element 71, is configured to be variable. The gain of the control element 71 is set to the set value of the tube current Iout (tube current instruction signal SISET The gain of the control element 71 automatically changes so that it becomes smaller as the value of the tube current Iout decreases. IOUT and tube current indicator signal S ISET It automatically changes so that the smaller the difference from the current, the smaller it becomes. In other words, the control element 71 controls the tube current instruction signal S. ISET The gain is adjusted according to the magnitude of the signal, and this adjusted gain is used to detect the tube current S. IOUT and tube current indicator signal S ISET Further adjustments are made according to the difference. The instruction signal generation unit 11A generates the tube current instruction signal S ISET , and tube current detection signal S IOUT and tube current indicator signal S ISET The system may further include a memory unit that stores the difference between the two values ​​and the corresponding relationship between multiple gains.

[0041] Figure 3 shows the tube current indicator signal S. ISET This diagram shows an example of gain adjustment according to the magnitude of the signal. Figure 3 shows the tube current indicator signal S. ISET The set values ​​from 10V to 100V and examples of gain weights corresponding to each set value are shown. Figure 4 also shows the tube current indicator signal S ISET This is a graph plotting the relationship between the set value and the gain weight. Figure 4 shows a line L11 connecting multiple plots and its approximation curve L12, and Figure 3 also shows the numerical values ​​corresponding to this approximation curve L12. In this embodiment, the tube current instruction signal S ISET The gain weight is increased in a quadratic manner (where n is an integer greater than or equal to 2) in response to an increase in the set value. In the examples shown in Figures 3 and 4, the gain weight increases in proportion to the square of the set value.

[0042] Figures 5(a) and (b) show the tube current detection signal S IOUT and tube current indicator signal S ISET This is a diagram showing an example of gain adjustment according to the difference. Figure 5 shows the tube current detection signal S. IOUT and tube current indicator signal S ISETThe difference is shown as the percentage of the value not reached from the set value. The under-value in the table corresponds to the difference between the magnitude of the tube current Iout and the set value of the tube current Iout, and is equal to the value obtained by multiplying the set value by the under-value percentage. Figure 5(a) shows the case when the set value is 100V, and Figure 5(b) shows the case when the set value is 40V. The number of steps for changing the gain, i.e., the number of threshold divisions, is 4 in both cases. In Figure 5, the gain division value is calculated by the following formula. Gain division value = (base) A However, A = number of threshold divisions - threshold number The gain of the control element 71 is obtained by dividing the gain weight by the gain division value. That is, when the gain weight is B and the gain division value is C, the gain D of the control element 71 is calculated as D = B / C. In the illustrated example, the base value is set to 2, but the base value may be any value greater than or equal to 2.

[0043] The line L21 shown in Figure 6(a) represents the time variation of the gain of the control element 71, corresponding to Figure 5(a). The line L22 shown in Figure 6(b) represents the time variation of the gain of the control element 71, corresponding to Figure 5(b). Referring to Figures 6(a) and (b), it can be seen that in (a), the threshold number changes from 4 to 3 and the gain decreases at approximately 1000 seconds, and in (b), at approximately 3400 seconds, and then the gain decreases stepwise until the threshold number becomes 0. Figures 6(a) and (b) also show the time variation L23 and L24 of the setpoint until the original setpoint (100V and 40V, respectively) is reached. The setpoint is controlled to increase proportionally to time with a certain gradient until the original setpoint is reached. Figure 7 is a diagram showing an example of the optimal gradient of the setpoint. The gradient of the setpoint is set so that the time until the original setpoint is reached is greater than or equal to the response time of the heating resistor 61. Furthermore, the gradient of the set value is set to increase as the original set value increases.

[0044] Figure 8 is a simplified block diagram showing the control system of this embodiment. In Figure 8, block B1 represents the gain of the instruction signal generation unit 11A, block B2 represents the control target including the inverter 4, rectifier and smoothing circuit 5, pressure reducing tube 6, and inverter control circuit 7A, and block B3 represents the feedback system including the tube current detection unit 9. As shown in Figure 8, the control system of this embodiment constitutes a PI control system, and the instruction signal generation unit 11A controls the coefficient K i The integral element B11 includes the coefficient K p It has a linear element B12 that includes the coefficient K. i and K p Both are considered to be dynamically variable.

[0045] Figure 9 is a graph showing the time variation of various values ​​in the power supply unit 1A of this embodiment. In Figure 9, line G1 represents the tube current indicator signal S ISET The line G2 shows the gain of the control element 71 (10 / div), the line G3 shows the load current If (5A / div), and the line G4 shows the tube current Iout (20mA / div).

[0046] As shown in Figure 9, the tube current indicator signal S ISET As the temperature rises to a certain set value (timing t1), the gain of the control element 71 gradually increases. During period P1 in the figure, the temperature of the heating resistor 61 is low and no tube current Iout flows, so the tube current detection signal S IOUT and tube current indicator signal S ISET The difference is large. Therefore, the instruction signal generation unit 11A has a proportional gain (coefficient K). p ) and integral gain (coefficient K i Both of the following are gradually increased. Therefore, the gain of the control element 71 gradually increases. Note that an upper limit is set for the load current If, so even during period P1, the load current If will not exceed a certain upper limit.

[0047] During period P2 following period P1, the temperature of the heating resistor 61 rises and the tube current Iout gradually increases. At this time, the tube current detection signal S IOUT and tube current indicator signal S ISETAs the difference gradually decreases, the gain of the control element 71 also gradually decreases. This suppresses the overshoot of the tube current Iout. If an overshoot occurs in the tube current Iout, the integral gain (coefficient K) i The overshoot may be reduced by increasing the rate of change of (for example, by 10 times). In period P3 after period P2, it is determined that the tube current Iout has stabilized at the set value, and the gain of the control element 71 is kept constant.

[0048] Figure 10 is a graph showing the time variation (10mA / div) of the tube current Iout. In Figure 10, lines G11 to G15 represent the cases where the set values ​​of the tube current Iout are 10mA, 20mA, 30mA, 40mA, and 50mA, respectively. As shown in Figure 10, it can be seen that with the power supply device 1A of this embodiment, the tube current Iout converges to the set value at approximately the same timing and in approximately the same amount of time, regardless of the magnitude of the set value of the tube current Iout.

[0049] Figure 11 is a flowchart showing an example of a method for controlling the power supplied to the heating resistor 61 using the power supply device 1A described above. This method comprises a tube current detection step ST1, an instruction signal generation step ST2, and a power adjustment step ST3. In the tube current detection step ST1, the magnitude of the tube current Iout flowing between the heating resistor 61 and the anode 62, or the magnitude of the current that fluctuates with the tube current Iout, is detected, and a tube current detection signal S IOUT In the instruction signal generation step ST2, the set value of the tube current Iout is input, and the tube current detection signal S is generated so that the magnitude of the tube current Iout approaches the set value. IOUT Based on this, a load current instruction signal S is used to indicate the magnitude of the load current If flowing through the heating resistor 61. Ifdr In the instruction signal generation step ST2, the tube current detection signal S is generated. IOUT From load current instruction signal S IfdrMake the gain variable when generating. Then, the smaller the set value of the tube current Iout, the smaller the gain, and the smaller the difference between the magnitude of the tube current Iout and the set value of the tube current Iout, the smaller the gain. In the power adjustment step ST3, the power (third power) supplied to the heating resistor 61 is controlled to a magnitude corresponding to the load current instruction signal S Ifdr according to. Thereafter, the tube current detection step ST1, the instruction signal generation step ST2, and the power adjustment step ST3 are repeated.

[0050] The effects obtained by the power control method of the power supply device 1A and the heating resistor 61 of the present embodiment described above will be described together with the problems of the conventional power supply device and power control method. Generally, in a power supply device applied to a device provided with a heating resistor 61 in a decompression tube 6, when the set value of the tube current Iout is changed, the magnitude of the load current If supplied to the heating resistor 61 is controlled. Conventionally, as a control method for the load current If, there is a method of measuring the temperature of the heating resistor 61 and controlling the load current If so that the temperature of the heating resistor 61 approaches the target temperature. However, this method has the following problems. FIG. 12 is a graph showing an example of the time change of the load current If and the tube current Iout in this method. As shown in FIG. 12, while the load current If rises in an extremely short time, the time required for the rise of the tube current Iout is extremely long. This phenomenon is due to the fact that the temperature change of the heating resistor 61 is significantly slower than the change of the load current If.

[0051] In response to this problem, a method of measuring the magnitude of the tube current Iout and controlling the load current If so that the tube current Iout approaches the set value can be considered. However, since the change in the tube current Iout depends on the temperature change of the heating resistor 61, the delay in the change of the tube current Iout with respect to the change in the set value of the tube current Iout is still large. Therefore, there is a problem that overshoot is likely to occur and it is not easy to control the load current If so that the tube current Iout changes stably toward the set value.

[0052] In response to this problem, in the present embodiment, the tube current detection unit 9 (tube current detection step ST1 ), instruction signal generation unit 11A (instruction signal generation step ST 2 ), and power adjustment unit 10 (power adjustment step ST 3 A feedback loop is formed by this. The gain of this feedback loop, i.e., the tube current detection signal S in the instruction signal generation unit 11A, is used. IOUT From load current instruction signal S Ifdr The gain when generating the feedback loop decreases as the set value of the tube current Iout decreases, and also decreases as the difference between the magnitude of the tube current Iout and the set value decreases. As a result, immediately after the operation of the pressure reducing tube 6 or immediately after the set value is changed, when the magnitude of the tube current Iout is far from the set value, the gain of the feedback loop increases, allowing the tube current Iout to change rapidly. Then, as the magnitude of the tube current Iout approaches the set value, the gain of the feedback loop decreases, allowing the tube current Iout to stably converge to the set value. For example, referring to line G4 in Figure 9, it can be seen that the tube current Iout converges stably in a short time of about 2 ms. Thus, according to this embodiment, the slowness of the change in tube current Iout is improved, and the tube current Iout can be stably changed toward the set value. Canada The load current If of the thermal resistance can be controlled.

[0053] As in this embodiment, the power adjustment unit 10 may include a power supply unit 2, a power conversion circuit 3, and an inverter control circuit 7A. The power supply unit 2 outputs a first power, which is DC power. The power conversion circuit 3 includes an inverter 4 that modulates the first 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, and supplies the third power as the power to the heating resistor 61. The inverter control circuit 7A is connected to the inverter 4 and outputs inverter drive signals Sg1 to Sg4 to control the inverter 4. The inverter control circuit 7A outputs a load current instruction signal S Ifdr The drive frequencies of the inverter drive signals Sg1 to Sg4 are controlled so that the magnitude of the load current If flowing through the heating resistor 61 approaches the magnitude of the load current If indicated by the power adjustment unit 10.Ifdr Power of a magnitude corresponding thereto can be supplied to the heating resistor 61.

[0054] (Second Embodiment) FIG. 13 is a schematic diagram of a circuit of a power supply device 1B according to a second embodiment of the present disclosure. The power supply device 1 B is a power supply device for supplying power to a heating resistor 61 serving as a load and increasing the temperature of the heating resistor 61. The configuration of the pressure reducing tube 6 including the heating resistor 61 is the same as that of the first embodiment. Further, the power supply device 1B includes a tube current detection unit 9 and a power adjustment unit 10. The configurations of the tube current detection unit 9 and the power adjustment unit 10 are the same as those of the first embodiment. The power supply device 1B includes an inverter control circuit 7B instead of the inverter control circuit 7A of the first embodiment. The configuration of the inverter control circuit 7B is the same as that of the inverter control circuit 7A except that it does not include a control element 72 (see FIG. 2).

[0055] The power supply device 1B includes an instruction signal generation unit 11B instead of the instruction signal generation unit 11A of the first embodiment. A tube current instruction signal S ISET indicating a set value of the tube current Iout and a tube current detection signal S IOUT are input to the instruction signal generation unit 11B. The instruction signal generation unit 11B generates a load current instruction signal S ISET based on the tube current detection signal S IOUT so that the magnitude of the tube current Iout approaches the set value indicated by the tube current instruction signal S Ifdr .

[0056] Specifically, the instruction signal generation unit 11B includes a control element 74. The control element 74 is, for example, an operational amplifier. The control element 74 includes an input terminal 74a, an input terminal 74b, and an output terminal 74c. The output terminal 74c of the control element 74 is connected to the power supply unit 2. The tube current detection signal S IOUT is input to the input terminal 74a of the control element 74. A tube current instruction signal S ISET indicating a set value of the tube current Iout is input to the input terminal 74b. The control element 74 outputs, from the output terminal 74c, the tube current detection signal S IOUT and the tube current instruction signal S ISETA load current instruction signal S has a magnitude obtained by multiplying the difference by the gain. Ifdr The control element 74 outputs the tube current detection signal S. IOUT The tube current indicator signal S ISET If it is greater than, the load current instruction signal S Ifdr The size is reduced, and the tube current detection signal S IOUT The tube current indicator signal S ISET If it is smaller than, the load current instruction signal S Ifdr The magnitude of is increased. Through this operation, the control element 74 receives the tube current instruction signal S. ISET and tube current detection signal S IOUT Based on this, the tube current indicator signal S ISET Load current instruction signal S approaches the tube current Iout. Ifdr Generates.

[0057] Load current indication signal S Ifdr This is input to the power supply unit 2. The power supply unit 2 is configured so that the magnitude of the first power output is variable. The power supply unit 2 receives the load current instruction signal S Ifdr The magnitude of the first power is controlled so that the magnitude of the load current If flowing through the heating resistor 61 approaches the magnitude of the load current If indicated by the power supply unit 2. If the power supply unit 2 is a switching type AC / DC converter, the power supply unit 2 may make the magnitude of the first power variable by changing the drive frequency or duty cycle of the switching element.

[0058] The instruction signal generation unit 11B generates the tube current detection signal S IOUT From load current instruction signal S Ifdr The gain when generating the signal, i.e., the gain of the control element 74, is configured to be variable. The gain of the control element 74 is set to the set value of the tube current Iout (tube current instruction signal S ISET The gain of the control element 74 automatically changes so that it becomes smaller as the value of the tube current Iout decreases. In addition, the gain of the control element 74 is the difference between the magnitude of the tube current Iout and the set value of the tube current Iout, i.e., the tube current detection signal S IOUT and tube current indicator signal S ISET It automatically changes so that the smaller the difference, the smaller it becomes. In other words, the control element 74 controls the tube current instruction signal SISET The gain is adjusted according to the magnitude of the signal, and this adjusted gain is used to detect the tube current S. IOUT and tube current indicator signal S ISET Further adjustments are made according to the difference. The instruction signal generation unit 11B generates the tube current instruction signal S ISET , and tube current detection signal S IOUT and tube current indicator signal S ISET The system may further include a memory unit that stores the difference between the given value and the corresponding relationship between multiple gains. The specific gain setting examples are the same as in the first embodiment.

[0059] According to this embodiment, the same effects as in the above embodiment can be obtained. Furthermore, by having the power adjustment unit 10 and the instruction signal generation unit 11B configured as in this embodiment, for example, the load current instruction signal S Ifdr A corresponding amount of power can be supplied to the heating resistor 61.

[0060] As shown in Figure 13, an adder 12 is provided between the instruction signal generation unit 11B and the power supply unit 2, and the adder 12 generates the load current instruction signal S Ifdr Preheat signal S PRE The preheat signal S may be added. PRE This signal is used to increase the temperature of the heating resistor 61 by increasing the load current If when the heating resistor 61 is cold (for example, before the pressure reducing tube 6 starts operating).

[0061] The power supply device and the power control method for the heating resistor according to this disclosure are not limited to the embodiments described above, and various other modifications are possible. For example, the configuration of the power adjustment unit is not limited to the configuration of each embodiment above, as long as it can supply power to the heating resistor in an amount corresponding to the load current instruction signal. The configuration of the tube current detection unit is not limited to the configuration of each embodiment above, as long as it can detect the magnitude of the tube current or the magnitude of the current that fluctuates with the tube current. The instruction signal generation unit is not limited to the configuration of each embodiment above, as long as it can generate a load current instruction signal so that the magnitude of the tube current approaches a set value. The gain of the instruction signal generation unit is not limited to the specific examples of each embodiment above, as long as it is small as the set value of the tube current is small and as long as the difference between the magnitude of the tube current and the set value of the tube current is small.

[0062] 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 a 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 a second power, and the modulation control circuit may output a modulation circuit drive signal for PWM modulation to the modulation circuit. [Explanation of Symbols]

[0063] 1A, 1B... Power supply unit, 2... Power supply unit, 3... 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, 10... Power adjustment unit, 11A, 11B... Instruction signal generation unit, 12... Adder, 41... Switching circuit, 41a, 41b... Power terminals, 41c~41f... Control terminals, 41g, 41h... Output terminals, 42... Resonant circuit, 51... Rectifier circuit, 52... Smoothing circuit, 61... Heating resistor, 62... Anode, 71, 72, 74... Control elements, 71a, 71b, 72a, 72b, 74a, 74b... Input terminals, 71c, 72c, 74c... Output terminals, 73... Frequency control unit 、411,412…Reg circuit, AP…AC power supply, B…Thermionic, B1,B2,B3…Block, B11…Integrating element, B12…Linear element, Cr…Resonant capacitor, If…Load current, Iout…Tube current, Lp…Excitation inductance, Lr…Resonant inductance, N1…Primary winding, N2…Secondary winding, N1a,N2a…One end, N1b,N2b…Other end, P1,P2,P3…Period, 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, S PRE ...Preheat signal, S1~S4...Semiconductor switch, Sg1~Sg4...Inverter drive signal, ST1...Tube current detection step, ST2...Indicator signal generation step, ST3...Power adjustment step, TR...Transformer, Vc...High voltage power supply.

Claims

1. A power supply device for supplying power to a heating resistor of a pressure reducing tube, the heating resistor comprising a heating resistor as a cathode and an anode positioned opposite the heating resistor, to which thermionic electrons emitted from the heating resistor converge, A power adjustment unit supplies power to the heating resistor in a magnitude corresponding to a load current instruction signal for instructing the magnitude of the load current flowing through the heating resistor, A tube current detection unit detects the magnitude of the tube current flowing between the heating resistor and the anode, or the magnitude of a current that fluctuates with the tube current, and generates a tube current detection signal. An instruction signal generation unit inputs the set value of the tube current and generates the load current instruction signal based on the tube current detection signal so that the magnitude of the tube current approaches the set value, Equipped with, The instruction signal generation unit is configured such that the gain when generating the load current instruction signal from the tube current detection signal is variable. A power supply device wherein the gain is smaller the smaller the setting value, and the gain is smaller the smaller the difference between the magnitude of the tube current and the setting value.

2. The power adjustment unit 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, and supplies the third power as the power to the heating resistor, The modulation control circuit is connected to the modulation circuit and outputs a modulation circuit drive signal to control the modulation circuit, The power supply device according to claim 1, wherein the modulation control circuit controls the modulation parameters of the modulation circuit drive signal so that the magnitude of the load current flowing through the heating resistor approaches the magnitude of the load current indicated by the load current instruction signal.

3. The power adjustment unit is A power supply unit that outputs a first power which is DC power, and is configured such that the magnitude of the first power is variable, The power conversion circuit includes 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, and supplies the third power as the power to the heating resistor, The power supply unit controls the magnitude of the first power so that the magnitude of the load current flowing through the heating resistor approaches the magnitude of the load current indicated by the load current instruction signal, as described in claim 1.

4. A method for controlling the power supplied to a heating resistor of a pressure reducing tube, which comprises a heating resistor as a cathode and an anode positioned opposite the heating resistor, where thermionic electrons emitted from the heating resistor converge, A tube current detection step involves detecting the magnitude of the tube current flowing between the heating resistor and the anode, or the magnitude of a current that fluctuates with the tube current, and generating a tube current detection signal. A signal generation step involves inputting a set value for the tube current and generating a load current instruction signal based on the tube current detection signal to instruct the magnitude of the load current flowing through the heating resistor so that the magnitude of the tube current approaches the set value. A power adjustment step that controls the power supplied to the heating resistor to a magnitude corresponding to the load current instruction signal, Equipped with, In the instruction signal generation step, the gain when generating the load current instruction signal from the tube current detection signal is made variable. A power control method for a heating resistor, wherein the gain is reduced as the set value becomes smaller, and the gain is reduced as the difference between the magnitude of the tube current and the set value becomes smaller.

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