Power transmission circuit

Abstract

A power transmission circuit 1 connected to a circuit for boosting the voltage from a low potential side to a high potential side: performs, in a first period, power transmission for transmitting, to a rectifier circuit 16 via a first transformer 14 and a second transformer 15, a high voltage-side voltage generated by a low voltage-side control circuit 12 driving a low voltage side inverter circuit 13; and performs, in a second period different from the first period, a first signal transmission for transmitting, to the high voltage-side control circuit 18 via the first transformer 14 and the second transformer 15, a first signal generated by the low voltage-side control circuit 12 driving the low voltage-side inverter circuit 13.

Description

Power Transmission Circuit

[0001] The present disclosure relates to power transfer circuits.

[0002] High-voltage power supplies that generate high voltages of the order of several hundred kilovolts use a power transmission circuit that transmits power from the low-voltage side to a power supply element mounted on a board on the high-voltage side and transmits instruction signals to a control element mounted on the high-voltage side (see, for example, Patent Document 1). In the power transmission circuit disclosed in Patent Document 1, in addition to transmitting power, an ON / OFF signal is transmitted to the high-voltage side by a transmission switch provided on the low-voltage side.

[0003] JP 2008-41318 A

[0004] The frequency of the transmitted power is, for example, several hundred kHz, and the frequency of the transmitted signal is higher than the power frequency, for example, several MHz. Therefore, when transmitting power and signals simultaneously, a filter must be provided on the high-voltage side to separate them. In high-voltage power supplies, to ensure the dielectric strength between the low-voltage side and the high-voltage side, a method of impregnating a portion of the high-voltage power supply with insulating oil or a method of coating a portion of the high-voltage power supply with insulating resin is sometimes adopted. However, in these cases, the characteristics of the filter change in the insulating oil or insulating resin, which may result in inaccurate reception of the signal on the high-voltage side.

[0005] An object of the present disclosure is to provide a power transmission circuit that can accurately transmit power and signals from a low potential side to a high potential side.

[0006] A power transmission circuit according to one aspect of the present disclosure is [1] "a power transmission circuit connected to a circuit that boosts a voltage from a low potential side to a high potential side, the power transmission circuit including: a first transformer that is an isolation transformer including a low-voltage side winding that is a primary winding connected to the low potential side, and a high-voltage side winding that is a secondary winding connected to the high potential side; a low-voltage side inverter circuit having an output terminal connected to the low-voltage side winding; a low-voltage side control circuit that is connected to an input terminal of the low-voltage side inverter circuit and drives the low-voltage side inverter circuit; a second transformer including a primary winding, a first secondary winding, and a second secondary winding, the primary winding being connected to the high-voltage side winding; a rectifier circuit connected to the secondary winding, and a high-voltage side control circuit connected to the second secondary winding and operating based on a first signal, wherein the low-voltage side control circuit drives the low-voltage side inverter circuit to generate a high-voltage side voltage, and the high-voltage side voltage is transmitted to the rectifier circuit via the first transformer and the second transformer in a first period, and the low-voltage side control circuit drives the low-voltage side inverter circuit to generate a first signal, and the low-voltage side control circuit transmits the first signal to the high-voltage side control circuit via the first transformer and the second transformer in a second period different from the first period.

[0007] In the power transmission circuit described in [1] above, power can be transmitted from the low-voltage side to the high-voltage side by transmitting the voltage generated by the low-voltage side inverter circuit as the high-voltage side voltage through the first transformer. Furthermore, a first signal can be transmitted from the low-voltage side to the high-voltage side by transmitting a first signal through the same first transformer as the power transmission. Power transmission occurs during a first period, and first signal transmission occurs during a second period. That is, the high-voltage side voltage transmitted through the power transmission and the first signal transmitted through the first signal transmission are transmitted in a time-separated state. This eliminates the need for a filter to separate the high-voltage side voltage and the first signal, allowing the high-voltage side control circuit on the high-voltage side to accurately receive the first signal even in insulating oil and insulating resin. Furthermore, by transmitting the high-voltage side voltage to a rectifier circuit connected to the first secondary winding, the high-voltage side voltage can be rectified to generate a power supply voltage to be supplied to, for example, a power supply element arranged on the high-voltage side. In addition, by providing a second transformer between the first transformer and the rectifier circuit and high-voltage side control circuit, it is possible to prevent unexpected common impedance from being formed between the first transformer and the rectifier circuit and high-voltage side control circuit.

[0008] A power transmission circuit according to one aspect of the present disclosure may be [2] "the power transmission circuit according to [1], wherein a waveform shaping circuit that improves distortion of the first signal is connected between the second secondary winding and the high-voltage side control circuit." In this case, a waveform shaping circuit that improves distortion of the first signal is connected between the second secondary winding and the high-voltage side control circuit. This improves distortion of the first signal before the first signal is input to the high-voltage side control circuit, allowing the high-voltage side control circuit to receive the first signal more accurately.

[0009] A power transmission circuit according to one aspect of the present disclosure may be [3] "the power transmission circuit according to [1] or [2], further including a high-voltage side inverter circuit having an output terminal connected between the high-voltage side winding of the first transformer and the primary winding of the second transformer and an input terminal connected to the high-voltage side control circuit, wherein the low-voltage side control circuit performs an operation separate from driving the low-voltage side inverter circuit based on a second signal, and the high-voltage side control circuit drives the high-voltage side inverter circuit to generate a second signal, and transmits the second signal to the low-voltage side control circuit via the first transformer during a third period separate from the first period and the second period." In this case, the second signal can be transmitted from the high-potential side to the low-potential side by transmitting the second signal via a first transformer that is common to power transmission and first signal transmission. This allows bidirectional signal transmission between the low-potential side and the high-potential side in addition to the first signal transmission. Furthermore, since the second signal is transmitted during the third period, it is transmitted in a state separated in time from the high-voltage side voltage and the first signal, which allows the low-voltage side control circuit on the low-potential side to accurately receive the second signal even in insulating oil and insulating resin.

[0010] A power transmission circuit according to one aspect of the present disclosure may be [4] "the power transmission circuit according to any one of [1] to [3], wherein the first transformer is a loosely coupled transformer." In this case, for example, the leakage inductance is increased compared to a tightly coupled transformer, and in defining the resonant frequency, the leakage inductance becomes dominant compared to the excitation inductance in a region where the load resistance value is sufficiently small relative to the reactance value of the excitation inductance at the resonant frequency, making it easier to define the resonant frequency. This makes it easier to set the frequency of the voltage transmitted by power transmission and the frequency of the first signal based on the resonant frequency.

[0011] A power transmission circuit according to one aspect of the present disclosure may be [5] "the power transmission circuit according to any one of [1] to [4], further comprising: a second low-voltage side control circuit provided on the low-voltage side and generating the first signal separately from the low-voltage side control circuit; a light-emitting element connected to the second low-voltage side control circuit; an optical fiber including an input end optically coupled to the light-emitting element and arranged to connect the low-voltage side and the high-voltage side; a photodetector element optically coupled to an output end of the optical fiber on the high-voltage side; an output terminal connected to the high-voltage side control circuit; and an amplifier including a pair of input terminals, one of which is connected to the photodetector element and the other of which is connected to a reference potential on the high-voltage side." In this case, the first signal generated by the second low-voltage side control circuit is electro-optically converted by the light-emitting element and transmitted from the low-voltage side to the high-voltage side by the optical fiber. The transmitted first signal is photoelectrically converted by the photodetector element on the high-voltage side, amplified by an amplifier, and output to the high-voltage side control circuit. The other of the pair of input terminals of the amplifier is connected to a high-potential reference potential, and the output terminal is connected to a high-voltage side control circuit. The reference potential of the high-voltage side control circuit is the same as the high-potential side reference potential. This allows the amplifier to transmit a first signal within the high-potential side region. With the above configuration, by securing a signal transmission route separate from the first transformer and the second transformer, it is possible to deal with, for example, cases where the transmission volume is insufficient using only the first signal transmission.

[0012] A power transmission circuit according to one aspect of the present disclosure is [6] "a power transmission circuit connected to a circuit that boosts a voltage from a low potential side to a high potential side, the power transmission circuit including: a first transformer that is an isolation transformer including a low-voltage side winding that is a primary winding connected to the low potential side; and a high-voltage side winding that is a secondary winding connected to the high potential side; a low-voltage side inverter circuit having an output terminal connected to the low-voltage side winding; a low-voltage side control circuit that is connected to an input terminal of the low-voltage side inverter circuit and drives the low-voltage side inverter circuit; a rectifier circuit connected to the high-voltage side winding; a first DC converter including an input terminal and an output terminal, the input terminal being connected to the rectifier circuit; and a second DC converter that is connected to the output terminal. and a second DC converter connected to the first transformer, the second transformer, the rectifier circuit, and the first DC converter, and operating based on a first signal, wherein the low-voltage side control circuit drives the low-voltage side inverter circuit to generate a high-voltage side voltage, and the high-voltage side voltage is transmitted to the second DC converter via the first transformer, the rectifier circuit, and the first DC converter, during a first period, and the low-voltage side control circuit drives the low-voltage side inverter circuit to generate a first signal, and the low-voltage side control circuit drives the low-voltage side inverter circuit to generate a first signal, and the low-voltage side control circuit transmits the first signal to the second DC converter via the first transformer, the rectifier circuit, and the first DC converter, during a second period different from the first period.

[0013] In the power transmission circuit described in [6] above, the high-voltage-side voltage transmitted by power transmission and the first signal transmitted by first signal transmission are also transmitted in a time-separated state. This eliminates the need for a filter to separate the high-voltage-side voltage and the first signal, allowing the high-voltage-side control circuit on the high-potential side to accurately receive the first signal even in insulating oil or insulating resin. Furthermore, by transmitting the high-voltage-side voltage to a rectifier circuit connected to the first secondary winding, the high-voltage-side voltage can be rectified to generate a power supply voltage to be supplied to, for example, a power supply element arranged on the high-potential side.

[0014] According to the present disclosure, power and signals can be transmitted accurately from the low potential side to the high potential side.

[0015] 5(a) shows an example of the operation of the low-voltage side inverter circuit in a first period in the case of a full-bridge circuit. FIG. 5(b) shows an example of the operation of the low-voltage side inverter circuit in a third period in the case of a full-bridge circuit. FIG. 5(a) shows an example of the operation of the low-voltage side inverter circuit in the first and second periods in the case of a half-bridge circuit. FIG. 5(b) shows an example of the operation of the low-voltage side inverter circuit in a third period ...a) shows an example of the operation of the low-voltage side inverter circuit in the first and second periods in the case of a half-bridge circuit. FIG. 5(b) shows an example of the operation of the low-voltage side inverter circuit in a third period in the case of a half-bridge circuit. FIG. 5(a) is a block diagram of a high-voltage power supply including a power transmission circuit according to a first modification. FIG. 5(b) is a diagram showing an example of the transmission waveform transmitted in the power transmission circuit according to the first modification. FIG. 8(a) is a block diagram of a power transmission circuit according to a second modification. FIG. 8(b) is a block diagram of a power transmission circuit according to a third modification. FIG. 8(c) is a block diagram of a power transmission circuit according to a fourth modification. FIG. 8(d) is a block diagram of a power transmission circuit according to a fifth modification.

[0016] Hereinafter, a preferred embodiment of a power transmission circuit according to an embodiment of the present disclosure will be described in detail with reference to the drawings.

[0017] FIG. 1 is a block diagram of a high-voltage power supply 10 including a power transmission circuit 1 according to one aspect of the present disclosure. The high-voltage power supply 10 is applicable to devices that use an input voltage of several hundred kV, such as X-ray tubes and electron beam irradiation devices. In this embodiment, the high-voltage power supply 10 is described as being applied to an X-ray tube XL. The high-voltage power supply 10 includes a power transmission circuit 1, a high-voltage generation circuit 3, a detection circuit 4, a cathode power supply 51, a filament power supply 52, and a grid power supply 53. The X-ray tube XL includes a cathode electrode CE, a filament FE, and a grid electrode GE. The filament FE generates heat when current is applied. The cathode electrode CE is heated by the filament FE and emits electrons. The grid electrode GE adjusts the amount of electrons emitted from the cathode electrode CE by forming an electric field between the grid electrode GE and the cathode electrode CE.

[0018] The high-voltage generation circuit 3 generates a high voltage to be supplied to the X-ray tube XL. The high-voltage generation circuit 3 includes an inverter 31, an output transformer 32, and a Cockcroft-Walton circuit 33. The inverter 31 is a circuit configured with multiple transistors. The inverter 31 may be a bridge circuit or a push-pull circuit. In the case of a bridge circuit, the inverter 31 is, for example, a half-bridge circuit in which the source terminal of a high-side FET and the drain terminal of a low-side FET are connected to each other. The inverter 31 converts an input DC voltage into an AC voltage. The output transformer 32 includes a primary winding 32a and a secondary winding 32b. The primary winding 32a is connected to the inverter 31. The output transformer 32 is a functional unit that boosts the AC voltage generated by the inverter 31 in accordance with the turns ratio of the primary winding 32a and the secondary winding 32b. The input of the Cockcroft-Walton circuit 33 is connected to the secondary winding 32b. The output of the Cockcroft-Walton circuit 33 is connected to the X-ray tube XL. The Cockcroft-Walton circuit 33 generates a DC voltage by boosting and rectifying the AC voltage output from the output transformer 32. The Cockcroft-Walton circuit 33 boosts and rectifies the AC voltage output from the output transformer 32 to several hundred kV and supplies it to the X-ray tube XL.

[0019] In the high-voltage generating circuit 3, the inverter 31 and the primary winding 32a of the output transformer 32 are arranged in a low-potential side region 6, which has a first reference potential G1 as its reference potential. For example, the low-potential side region 6 includes a wiring board having the first reference potential G1 as its reference potential, and the inverter 31 and the output transformer 32 are mounted on the wiring board. The first reference potential G1 is, for example, 0 V. Meanwhile, the output of the Cockcroft-Walton circuit 33 is connected to the X-ray tube XL and defines the reference potential of a high-potential side region 7, which has a second reference potential G2 as its reference potential. The second reference potential G2 is, for example, several hundred kV. The high-potential side region 7 includes, for example, a wiring board having the second reference potential G2 as its reference potential. In the high-voltage power supply 10, in order to ensure the dielectric strength voltage between the low-potential side region 6 and the high-potential side region 7, a means for impregnating a part of the high-voltage power supply 10 with insulating oil, or a means for coating or molding a part of the high-voltage power supply 10 with insulating resin may be employed.

[0020] The detection circuit 4 detects the current supplied to the X-ray tube XL and outputs an indicator voltage Va based on the detection result to the power transmission circuit 1. The detection circuit 4 includes a detection resistor R1 and an error amplifier 45. The error amplifier 45 includes a pair of input terminals 45a and 45b and an output terminal 45c. One input terminal 45a is connected to a node between the secondary winding 32b and the input of the Cockcroft-Walton circuit 33. The detection resistor R1 is connected between the one input terminal 45a and a first reference potential G1. The detection resistor R1 detects the magnitude of the current supplied to the Cockcroft-Walton circuit 33 and converts it into a detection voltage Vb. In other words, the detection circuit 4 detects the magnitude of the current supplied to the X-ray tube XL by detecting the current supplied to the Cockcroft-Walton circuit 33. The detection voltage Vb is input to one input terminal 45a. An externally input set voltage Vc is input to the other input terminal 45b. The set voltage Vc is a voltage that indicates a set value of the current supplied to the X-ray tube XL. The error amplifier 45 outputs to the power transmission circuit 1 an instruction voltage Va obtained by amplifying the difference between the detected voltage Vb and the set voltage Vc.

[0021] The power transmission circuit 1 transmits power from the low-potential side area 6 to the cathode power supply 51, filament power supply 52, and grid power supply 53 arranged in the high-potential side area 7, and also transmits instruction signals for controlling the output of the cathode power supply 51, filament power supply 52, and grid power supply 53. The power transmission circuit 1 has an AD converter 11, a low-voltage side control circuit 12, a low-voltage side inverter circuit 13, a first transformer 14, a second transformer 15, a rectifier circuit 16, a waveform shaping circuit 17, a high-voltage side control circuit 18, and a DA converter 19. The AD converter 11, the low-voltage side control circuit 12, the low-voltage side inverter circuit 13, and the primary winding 14a of the first transformer 14 are arranged in the low-potential side area 6. The secondary winding 14 b of the first transformer 14 , the second transformer 15 , the rectifier circuit 16 , the waveform shaping circuit 17 , the high-voltage side control circuit 18 , and the DA converter 19 are arranged in the high-potential side area 7 .

[0022] In the power transmission circuit 1, power transmission and first signal transmission are performed between the low-voltage side region 6 and the high-voltage side region 7. In the power transmission circuit 1, the first signal transmission is performed by, for example, UART (Universal Asynchronous Receiver / Transmitter) communication, with the low-voltage side control circuit 12 acting as the master side and the high-voltage side control circuit 18 acting as the slave side. FIG. 2 shows an example of a transmission waveform transmitted by the power transmission and the first signal transmission. The transmission waveform D1 includes a first period T1 and a second period T2. The low-voltage side control circuit 12 performs power transmission during the first period T1. In the power transmission, the low-voltage side control circuit 12 drives the low-voltage side inverter circuit 13 to generate a high-voltage side voltage V1, which is then transmitted to the rectifier circuit 16 via a first transformer 14 and a second transformer 15. High-voltage side voltage V1 is a high-frequency voltage whose magnitude periodically changes between a low level and a high level, and the frequency of high-voltage side voltage V1 is, for example, 100 kHz. Low-voltage side control circuit 12 performs first signal transmission during a second period T2 separate from first period T1. During the first signal transmission, low-voltage side control circuit 12 transmits first signal S1 via low-voltage side inverter circuit 13, first transformer 14, and second transformer 15. First signal S1 is a signal used by high-voltage side control circuit 18 to control the output of cathode power supply 51, filament power supply 52, and grid power supply 53. First signal S1 is a high-frequency voltage whose magnitude changes between a low level and a high level according to the transmission waveform, and the frequency of first signal S1 is higher than the frequency of high-voltage side voltage V1, and is, for example, 1 MHz. The high-voltage-side voltage V1 transmitted by power transmission and the first signal S1 transmitted by first signal transmission are transmitted in a time-separated manner. In other words, in the power transmission circuit 1, the high-voltage-side voltage V1 and the first signal S1 are transmitted by a time division multiplexing (TDM) method.

[0023] In the power transmission circuit 1, the low-voltage side control circuit 12, the low-voltage side inverter circuit 13, the first transformer 14, the second transformer 15, and the rectifier circuit 16 configure a power transmission path 8. First, the configuration of the power transmission path 8 will be described.

[0024] Output terminal 12b of low-voltage side control circuit 12 is connected to the input terminal of low-voltage side inverter circuit 13. Low-voltage side control circuit 12 is, for example, an FPGA (Field-Programmable Gate Array). Low-voltage side inverter circuit 13 is a bridge circuit, such as a half-bridge circuit, configured with multiple transistors. Low-voltage side control circuit 12 drives low-voltage side inverter circuit 13 at a frequency of, for example, 100 kHz to generate high-voltage side voltage V1.

[0025] The first transformer 14 includes a primary winding 14a and a secondary winding 14b. The primary winding 14a is disposed in the low-potential side region 6, and therefore can be referred to as a low-voltage side winding. The secondary winding 14b is disposed in the high-potential side region 7, and therefore can be referred to as a high-voltage side winding. The first transformer 14 is an isolation transformer that insulates the low-potential side region 6 from the high-potential side region 7. The primary winding 14a is connected to the output terminal of the low-voltage side inverter circuit 13. A series resonance capacitor Cs is connected between one end of the primary winding 14a and the output of the low-voltage side inverter circuit 13.

[0026] 3A is a circuit diagram that schematically illustrates the parasitic components that exist between the primary winding 14a and the low-voltage side inverter circuit 13. As shown in FIG. 3A, the leakage inductance La of the first transformer 14 is connected in series with the series resonance capacitor Cs. The excitation inductance Lp of the first transformer 14 is connected in parallel with the primary winding 14a. The series resonance capacitor Cs, the leakage inductance La, and the excitation inductance Lp form a series resonance circuit RC (LLC resonance circuit). In FIG. 3A, a load resistance R is connected in parallel with the excitation inductance Lp. Ｌ is connected.

[0027] The first transformer 14 is a loosely coupled transformer. Compared to a tightly coupled transformer, a loosely coupled transformer has a lower coupling coefficient between the primary winding 14a and the secondary winding 14b, and therefore the magnitude of the leakage inductance La is larger. Two resonant frequencies are defined in the series resonant circuit RC. The resonant frequency f ０ is the resonance frequency determined by the excitation inductance Lp, the leakage inductance La, and the series resonance capacitor Cs. １ is the resonant frequency determined by the leakage inductance La and the series resonant capacitor Cs. The resonant frequency f of the series resonant circuit RC １ is expressed by the formula (1). １ = 1 / 2 × π × SQRT(La × Cs) (1) In equation (1), SQRT represents a square root. As shown in equation (1), the resonant frequency f １ In this case, the leakage inductance La becomes dominant compared to the excitation inductance Lp, so the resonant frequency f １ is determined based on the series resonance capacitor Cs and the leakage inductance La. １ In this case, the resonant frequency f １ The reactance value of the exciting inductance Lp at the load resistance R Ｌ In this region, the magnitude of the load resistance R Ｌ The magnitude of 2πf is set based on equation (2). １ Lp>>R Ｌ ...(2) When equation (2) is satisfied, series resonance is established between the series resonance capacitor Cs and the excitation inductance Lp, and highly efficient power transmission is achieved.

[0028] 3B is a diagram showing the frequency characteristics of the series resonant circuit RC. The horizontal axis of FIG. 3B represents the drive frequency (Hz), and the vertical axis represents the magnitude of the output voltage of the series resonant circuit RC as a relative output. In this embodiment, the resonant frequency f １The frequency of the first signal S1 is set based on the frequency characteristic shown in FIG. 3B so that the magnitude of the output of the first signal S1 is, for example, 1 / 10 of the magnitude of the output of the high-voltage side voltage V1.

[0029] Referring again to FIG. 1 , the second transformer 15 includes a primary winding 15a, a first secondary winding 15b, and a second secondary winding 15c. The primary winding 15a is connected to the secondary winding 14b of the first transformer 14. The first secondary winding 15b is connected to the input terminal of the rectifier circuit 16. The second secondary winding 15c is connected to the input terminal of the waveform shaping circuit 17. The second transformer 15 prevents unexpected common impedance from being formed between the first transformer 14 and the rectifier circuit 16 and high-voltage side control circuit 18. In power transmission, the high-voltage side voltage V1 is transmitted from the primary winding 15a to the first secondary winding 15b and then to the rectifier circuit 16.

[0030] Rectifier circuit 16 generates power supply voltage Vcc, which is a DC voltage, from high-voltage side voltage V1 transmitted from second transformer 15. Rectifier circuit 16 includes, for example, a rectifier diode and a smoothing capacitor. High-voltage side voltage V1 is rectified by the rectifier diode and smoothed by the smoothing capacitor, thereby being converted into power supply voltage Vcc. Power supply voltage Vcc serves as a power supply voltage for driving elements arranged on high-potential side region 7 (e.g., cathode power supply 51, filament power supply 52, grid power supply 53, and high-voltage side control circuit 18).

[0031] Next, the configuration of the first signal transmission path 9 will be described, focusing on differences from the power transmission path 8. Of the power transmission circuit 1, the AD converter 11, low-voltage side control circuit 12, low-voltage side inverter circuit 13, first transformer 14, second transformer 15, waveform shaping circuit 17, high-voltage side control circuit 18, and DA converter 19 configure the first signal transmission path 9.

[0032] The input of the AD converter 11 is connected to the output terminal 45c of the error amplifier 45. The AD converter 11 converts the indication voltage Va from an analog signal to a digital signal.

[0033] Input terminal 12a of low-voltage side control circuit 12 is connected to the output terminal of AD converter 11. When low-voltage side control circuit 12 receives a digital signal of instruction voltage Va from AD converter 11, it generates first signal S1. Low-voltage side control circuit 12 drives low-voltage side inverter circuit 13 at a frequency (e.g., 1 MHz) different from that used during power transmission, and transmits first signal S1 to first transformer 14. First signal S1 is then transmitted from primary winding 14a to secondary winding 14b of first transformer 14, thereby being transmitted from low potential side region 6 to high potential side region 7. In other words, transmission of high-voltage side voltage V1 from low potential side region 6 to high potential side region 7 (power transmission) and transmission of first signal S1 from low potential side region 6 to high potential side region 7 (first signal transmission) are performed via the common first transformer 14.

[0034] The first signal S1 has, for example, one cycle as one value. The number of bits of this value is, for example, 8 bits, and the magnitude varies between 00000000 and 11111111. For example, the high level of the first signal S1 represents '1', and the low level represents '0'. The low-voltage side control circuit 12 sets each value of the first signal S1 between 0000 and 1111 based on the magnitude of the instruction voltage Va.

[0035] A termination resistor R2 is provided in parallel with the primary winding 15a between the secondary winding 14b of the first transformer 14 and the primary winding 15a of the second transformer 15. The termination resistor R2 is provided to suppress reflection of the first signal S1. In the first signal transmission, the first signal S1 is transmitted from the primary winding 15a to the second secondary winding 15c and then to the waveform shaping circuit 17 after reflection is suppressed by the termination resistor R2. Furthermore, instead of the termination resistor R2, a CR circuit in which the termination resistor R2 and a capacitor are connected in series may be provided in parallel with the primary winding 15a. When a CR circuit is provided in parallel with the primary winding 15a, AC termination can be achieved when the magnitude of the first signal S1 changes while maintaining the waveform quality of the first signal S1.

[0036] The input terminal of the waveform shaping circuit 17 is connected to the second secondary winding 15c of the second transformer 15. The waveform shaping circuit 17 reduces distortion in the first signal S1 and transmits the first signal S1 to the high-voltage side control circuit 18. The waveform shaping circuit 17 is, for example, a low-pass filter with a cutoff frequency higher than the signal transmission band, and removes harmonic components of the first signal S1 that do not contribute to the transmission signal. The input terminal of the waveform shaping circuit 17 is connected to the power supply voltage Vcc generated by the rectifier circuit 16. The amplitude of the voltage generated in the second secondary winding 15c varies depending on the load condition of the rectifier circuit 16. The input terminal of the waveform shaping circuit 17 is configured as a differential circuit with the power supply voltage Vcc as the reference. This allows the waveform shaping circuit 17 to stably receive the first signal S1 regardless of the load condition.

[0037] A first input terminal 18a of the high-voltage side control circuit 18 is connected to the output end of the waveform shaping circuit 17. Based on the distortion-reduced first signal S1, the high-voltage side control circuit 18 generates a cathode control signal Sc for controlling the cathode power supply 51, a filament control signal Sf for controlling the filament power supply 52, and a grid control signal Sg for controlling the grid power supply 53. The cathode control signal Sc, the filament control signal Sf, and the grid control signal Sg are, for example, the input voltages of the power supplies 51-53. The high-voltage side control circuit 18 may control the input voltages of the power supplies 51-53 to control the values ​​of the output voltages from the power supplies 51-53. The high-voltage side control circuit 18 generates the cathode control signal Sc, the filament control signal Sf, and the grid control signal Sg based on the values ​​of the first signal S1. In other words, the high-voltage side control circuit 18 performs serial / parallel conversion of the first signal S1 into the cathode control signal Sc, the filament control signal Sf, and the grid control signal Sg. For example, the first value of the first signal S1 may correspond to the cathode control signal Sc, the second value may correspond to the filament control signal Sf, and the third value may correspond to the grid control signal Sg. The magnitudes of the cathode control signal Sc, the filament control signal Sf, and the grid control signal Sg may be set based on a lookup table associated with each value of the first signal S1.

[0038] Input terminal 19a of DA converter 19 is connected to first output terminal 18b of high-voltage side control circuit 18. DA converter 19 includes first output terminal 19b, second output terminal 19c, and third output terminal 19d. First output terminal 19b is connected to input terminal 51a of cathode power supply 51. Second output terminal 19c is connected to input terminal 52a of filament power supply 52. ​​Third output terminal 19d is connected to input terminal 53a of grid power supply 53. DA converter 19 converts the cathode control signal Sc input from high-voltage side control circuit 18 into an analog signal and outputs it from first output terminal 19b to cathode power supply 51. DA converter 19 converts the filament control signal Sf input from high-voltage side control circuit 18 into an analog signal and outputs it from second output terminal 19c to filament power supply 52. The DA converter 19 converts the grid control signal Sg input from the high-voltage side control circuit 18 into an analog signal, and outputs it to the grid power supply 53 from the third output terminal 19d.

[0039] A first output terminal 51b of the cathode power supply 51 is connected to the cathode electrode CE of the X-ray tube XL. The cathode power supply 51 supplies an output voltage controlled by the high-voltage side control circuit 18 to the cathode electrode CE. A first output terminal 52b of the filament power supply 52 is connected to the filament FE of the X-ray tube XL. The filament power supply 52 supplies an output voltage controlled by the high-voltage side control circuit 18 to the filament FE. A first output terminal 53b of the grid power supply 53 is connected to the grid electrode GE of the X-ray tube XL. The grid power supply 53 supplies an output voltage controlled by the high-voltage side control circuit 18 to the grid electrode GE.

[0040] Referring again to FIG. 2 , transmission waveform D1 transmitted from low-voltage side control circuit 12 to high-voltage side control circuit 18 includes a third period T3 between a first period T1 and a second period T2. In transmission waveform D1, the second period T2 is followed again by the first period T1. The third period T3 is a period for consuming power remaining in power transmission path 8 due to power transmission. This eliminates ringing components on power transmission path 8. In other words, the third period T3 is a stable period. Power consumption during the third period T3 is performed, for example, by a dummy resistor. A circuit in which a dummy resistor and a switch element are connected in series may be provided between first secondary winding 15b of second transformer 15 and second reference potential G2. After the first period T1 ends, a signal to turn on the switch element may be transmitted from low-voltage side control circuit 12 or high-voltage side control circuit 18.

[0041] Alternatively, power consumption during the third period T3 may be achieved, for example, by forming a short circuit network in the low-voltage side inverter circuit 13. FIG. 4 is a diagram illustrating an example of the operation of the low-voltage side inverter circuit 13. As shown in FIG. 4, the low-voltage side inverter circuit 13 may be configured as a full-bridge circuit using transistors TR1 to TR4. Each of transistors TR1 to TR4 includes a first current terminal and a second current terminal. FIG. 4(a) shows an example of the operation of the low-voltage side inverter circuit 13 during the first period T1 in the case of a full-bridge circuit. During the first period T1, periods in which transistors TR1 and TR4 are simultaneously turned ON and periods in which transistors TR2 and TR3 are simultaneously turned ON alternately. During the periods in which transistors TR1 and TR4 are simultaneously turned ON, the inverter current I Ｆ１ flows from the second current terminal TR1b of the transistor TR1 through the primary winding 14a to the first current terminal TR4a of the transistor TR4. Ｆ１ flows from the second current terminal TR4b of the transistor TR4 to the first reference potential G1. During the period when the transistors TR2 and TR3 are simultaneously turned on, the inverter current I Ｆ２flows from the second current terminal TR3b of the transistor TR3 through the primary winding 14a to the first current terminal TR2a of the transistor TR2. Ｆ２ flows from the second current terminal TR2b of the transistor TR2 to the first reference potential G1.

[0042] 4B shows an example of the operation of the low-voltage side inverter circuit 13 in the third period T3 in the case of a full-bridge circuit. In the third period T3, for example, the transistors TR2 and TR4 are turned on simultaneously, forming a short circuit network. The inverter current I Ｆ３ flows from the second current terminal TR2b of the transistor TR2 to the second current terminal TR4b of the transistor TR4 via the first reference potential G1. Ｆ３ flows from the first current terminal TR4a of the transistor TR4 through the primary winding 14a to the first current terminal TR2a of the transistor TR2. The formation of such a short circuit network facilitates the consumption of the resonant energy accumulated during the first period T1. This suppresses waveform distortion at the start of the second period T2, enabling stable communication.

[0043] As shown in FIG. 5, the low-voltage side inverter circuit 13 may be configured as a half-bridge circuit using transistors TR1 to TR4. Each of transistors TR1 to TR4 includes a first current terminal and a second current terminal. FIG. 5(a) shows an example of the operation of the low-voltage side inverter circuit 13 in the first period T1 and the second period T2 in the case of a half-bridge circuit. During the first period T1, a period in which transistor TR1 is ON and a period in which transistor TR2 is ON are alternately repeated for power transmission. During the second period T2, a period in which transistor TR3 is ON and a period in which transistor TR4 is ON are alternately repeated for signal transmission. During the period in which the period in which transistor TR1 is ON and the period in which transistor TR2 is ON are alternately repeated, the inverter current I Ｆ１The inverter current I flows from the second current terminal TR1b of the transistor TR1 through the primary winding 14a to the first reference potential G1. During the period when the transistor TR3 is ON and the period when the transistor TR4 is ON are alternately repeated, the inverter current I Ｆ２ flows from the second current terminal TR3b of the transistor TR3 through the primary winding 14a to the first reference potential G1. A damping resistor DR1 may be connected between the second current terminal TR3b of the transistor TR3 and the primary winding 14a. Connecting the damping resistor DR1 reduces high-frequency components while maintaining the waveform quality of the first signal S1, which can contribute to noise suppression.

[0044] 5B shows an example of the operation of the low-voltage side inverter circuit 13 in the third period T3 in the case of a half-bridge circuit. In the third period T3, for example, the transistors TR2 and TR4 are turned on, forming a short circuit network including the damping resistor DR1. The inverter current I Ｆ３ flows from the second current terminal TR4b of the transistor TR4 to the first reference potential G1. The formation of a short circuit network including the damping resistor DR1, which is a power consumption element, facilitates the dissipation of the resonance energy accumulated during the first period T1. This suppresses waveform distortion at the start of the second period T2, enabling stable communication.

[0045] As low-voltage side control circuit 12 transmits transmission waveform D1, power transmission in first period T1, power consumption in third period T3, and first signal transmission in second period T2 are repeated in the order of first period T1, third period T3, and second period T2. Low-voltage side control circuit 12, which is the master, and high-voltage side control circuit 18, which is the slave, have the function of synchronizing with each of first period T1, second period T2, and third period T3. The synchronization function is, for example, a function of detecting the start of each of first period T1, second period T2, and third period T3 using counters included in low-voltage side control circuit 12 and high-voltage side control circuit 18.

[0046] Low-voltage side control circuit 12 may switch between a first mode and a second mode in response to an external input. In the first mode, low-voltage side control circuit 12 repeatedly performs power transmission in a first period T1, power consumption in a third period T3, and first signal transmission in a second period T2, in the order of the first period T1, the third period T3, and the second period T2. In the second mode, low-voltage side control circuit 12 normally repeatedly performs only power transmission in the first period T1. At a predetermined timing, low-voltage side control circuit 12 sequentially performs power transmission in the first period T1, power consumption in the third period T3, and first signal transmission in the second period T2, only once during one transmission. [Operation and Effects]

[0047] In the power transmission circuit 1, power can be transmitted from the low-voltage side region 6 to the high-voltage side region 7 by transmitting the voltage generated by the low-voltage side inverter circuit 13 as the high-voltage side voltage V1 via the first transformer 14. Furthermore, first signal transmission can be performed from the low-voltage side region 6 to the high-voltage side region 7 by transmitting the first signal S1 via the first transformer 14 shared with the power transmission. The power transmission is performed during the first period T1, and the first signal transmission is performed during the second period T2. In other words, the high-voltage side voltage V1 transmitted by the power transmission and the first signal S1 transmitted by the first signal transmission are transmitted in a time-separated state. This eliminates the need for a filter to separate the high-voltage side voltage V1 and the first signal S1, and therefore the high-voltage side control circuit 18 can accurately receive the first signal S1 on the high-voltage side, even in insulating oil and insulating resin. Furthermore, by transmitting high-voltage side voltage V1 to rectifier circuit 16 connected to first secondary winding 15b, high-voltage side voltage V1 is rectified to generate power supply voltage Vcc, which is supplied to power supply elements such as power supplies 51-53 arranged in high-potential side region 7 and to circuits operating in high-potential side region 7. In addition, by providing second transformer 15 between first transformer 14 and rectifier circuit 16 / high-voltage side control circuit 18, it is possible to prevent unexpected common impedance from being formed between first transformer 14 and rectifier circuit 16 / high-voltage side control circuit 18.

[0048] Waveform shaping circuit 17, which improves distortion of first signal S1, is connected between second secondary winding 15c and high-voltage side control circuit 18. In this case, by improving the distortion of first signal S1 before first signal S1 is input to high-voltage side control circuit 18, high-voltage side control circuit 18 can receive first signal S1 more accurately.

[0049] The first transformer 14 is a loosely coupled transformer. In this case, the leakage inductance La increases compared to a tightly coupled transformer. This increases the resonant frequency f ０ In defining the above, in the region where the load resistance value is sufficiently small relative to the reactance value of the excitation inductance at the resonance frequency, the leakage inductance La becomes dominant compared to the excitation inductance Lp, and the resonance frequency f ０ Therefore, the resonant frequency f ０ Based on this, it is possible to easily set the frequency of the voltage transmitted by the power transmission and the frequency of the first signal S1.

[0050] Although the embodiments of the present disclosure have been described above, the present disclosure is not necessarily limited to the above-described embodiments, and various modifications are possible without departing from the spirit of the present disclosure.

[0051] FIG. 6 is a block diagram of a high-voltage power supply 10A according to a first modification. Only differences from the high-voltage power supply 10 according to the embodiment will be described. The high-voltage power supply 10A includes a power transmission circuit 1A instead of the power transmission circuit 1. In the power transmission circuit 1A, in addition to power transmission and first signal transmission, a second signal transmission is performed from the high-voltage side control circuit 18 to the low-voltage side control circuit 12. In addition to the configuration of the power transmission circuit 1, the power transmission circuit 1A also includes a second DA converter 21, a second waveform shaping circuit 22, a third transformer 23, a high-voltage side inverter circuit 24, and a second AD converter 25. The second DA converter 21, the second waveform shaping circuit 22, and the third transformer 23 are arranged in the low-potential side region 6. The high-voltage side inverter circuit 24 and the second AD converter 25 are arranged in the high-potential side region 7. In the power transmission circuit 1A, similarly to the power transmission circuit 1, a termination resistor R2 is provided in parallel with the primary winding 15a of the second transformer 15. Alternatively, a CR circuit in which the termination resistor R2 and a capacitor are connected in series may be provided in parallel with the primary winding 15a.

[0052] The second signal S2 transmitted in the second signal transmission is, for example, a digital signal representing the detected values ​​of the output voltages of the cathode power supply 51, the filament power supply 52, and the grid power supply 53. The frequency of the second signal S2 is greater than the frequency of the high-voltage side voltage V1, for example, 1 MHz. Like the first signal S1, the second signal S2 has, for example, one value per cycle. The number of bits of each value is, for example, 8 bits, and the magnitude varies between 00000000 and 11111111. The low-voltage side control circuit 12 performs an operation other than driving the low-voltage side inverter circuit 13 based on the second signal S2. For example, the detected values ​​of the output voltages of the cathode power supply 51, the filament power supply 52, and the grid power supply 53 are output to the outside via the second DA converter 21.

[0053] The configuration of second signal transmission path 20 that performs second signal transmission will be described below, focusing on differences from first signal transmission path 9. Of the power transmission circuit 1A, second AD converter 25, high-voltage side control circuit 18, high-voltage side inverter circuit 24, first transformer 14, third transformer 23, second waveform shaping circuit 22, low-voltage side control circuit 12, and second DA converter 21 configure second signal transmission path 20.

[0054] The second AD converter 25 includes a first input terminal 25a, a second input terminal 25b, and a third input terminal 25c. The first input terminal 25a is connected to the second output terminal 51c of the cathode power supply 51. The second input terminal 25b is connected to the second output terminal 52c of the filament power supply 52. ​​The third input terminal 25c is connected to the second output terminal 53c of the grid power supply 53. The second AD converter 25 converts the output voltage of the cathode power supply 51 into a digital signal and outputs the digital signal from the output terminal 25d to the high-voltage side control circuit 18. The second AD converter 25 converts the output voltage of the filament power supply 52 into a digital signal and outputs the digital signal from the output terminal 25d to the high-voltage side control circuit 18. The second AD converter 25 converts the output voltage of the grid power supply 53 into a digital signal and outputs the digital signal from the output terminal 25d to the high-voltage side control circuit 18.

[0055] A digital signal of the output voltage of cathode power supply 51, a digital signal of the output voltage of filament power supply 52, and a digital signal of the output voltage of grid power supply 53 are input to second input terminal 18c of high-voltage side control circuit 18. High-voltage side control circuit 18 generates second signal S2 by arranging each digital signal in time series. In other words, high-voltage side control circuit 18 performs parallel / serial conversion on the digital signals of the output voltage of cathode power supply 51, the output voltage of filament power supply 52, and the output voltage of grid power supply 53 to generate second signal S2. High-voltage side control circuit 18 outputs second signal S2 from second output terminal 18d to high-voltage side inverter circuit 24.

[0056] The input terminal of high-voltage side inverter circuit 24 is connected to second output terminal 18d of high-voltage side control circuit 18. The output terminal of high-voltage side inverter circuit 24 is connected to secondary winding 14b of first transformer 14. High-voltage side control circuit 18 drives high-voltage side inverter circuit 24 at a frequency of, for example, 1 MHz, and transmits second signal S2 to first transformer 14. A series resonance capacitor Cs2 is connected between the output terminal of high-voltage side inverter circuit 24 and secondary winding 14b. The resonance frequency f of series resonance circuit RC is １ can be calculated including the value of the series resonance capacitor Cs2. A damping resistor may be connected between the series resonance capacitor Cs2 and the high-voltage side inverter circuit 24. Connecting the damping resistor leads to a reduction in high-frequency components while maintaining the waveform quality of the second signal S2, which can contribute to noise suppression.

[0057] The second signal S2 is transmitted from the secondary winding 14b to the primary winding 14a of the first transformer 14, and is thereby transmitted from the high potential side region 7 to the low potential side region 6. In other words, the second signal transmission is performed via the first transformer 14, which is also used for the first signal transmission and power transmission.

[0058] The secondary winding 23b of the third transformer 23 is connected to the primary winding 14a of the first transformer 14. The primary winding 23a of the third transformer 23 is connected to the input terminal of the second waveform shaping circuit 22. The second signal S2 is transmitted from the secondary winding 23b to the primary winding 23a of the third transformer 23. The third transformer 23 can prevent an unexpected common impedance from being formed between the first transformer 14 and the second waveform shaping circuit 22.

[0059] The input terminal of the second waveform shaping circuit 22 is connected to the primary winding 23a of the third transformer 23. The second waveform shaping circuit 22 improves distortion of the second signal S2 and transmits the second signal S2 to the low-voltage side control circuit 12. The second waveform shaping circuit 22 is, for example, a low-pass filter having a cutoff frequency higher than the signal transmission band, and removes harmonic components of the second signal S2 that do not contribute to the transmission signal.

[0060] Second input terminal 12c of low-voltage side control circuit 12 is connected to the output end of second waveform shaping circuit 22. Low-voltage side control circuit 12 extracts a digital signal of the output voltage of cathode power supply 51, a digital signal of the output voltage of filament power supply 52, and a digital signal of the output voltage of grid power supply 53 from second signal S2 with reduced distortion, and outputs them to second DA converter 21.

[0061] The input terminal of second DA converter 21 is connected to second output terminal 12d of low-voltage side control circuit 12. Second DA converter 21 converts the digital signal of the output voltage of cathode power supply 51, the digital signal of the output voltage of filament power supply 52, and the digital signal of the output voltage of grid power supply 53 into analog signals, respectively, and outputs them to the outside of high-voltage power supply 10A. The output of second DA converter 21 fluctuates depending on the magnitude of the digital signal of the output voltage of cathode power supply 51, the digital signal of the output voltage of filament power supply 52, and the digital signal of the output voltage of grid power supply 53. For this reason, it can be considered that low-voltage side control circuit 12 controls the output of second DA converter 21 with second signal S2.

[0062] 7 is a diagram showing an example of a transmission waveform transmitted in the power transmission circuit 1A. In the power transmission circuit 1A, a second transmission waveform D2 is transmitted from the low-voltage side control circuit 12 to the high-voltage side control circuit 18. The second transmission waveform D2 includes a fourth period T4 after the second period T2. While the low-voltage side control circuit 12 transmits the second transmission waveform D2 to the high-voltage side control circuit 18, it does not transmit power or signals during the fourth period T4. In the power transmission circuit 1A, a third transmission waveform D3 is transmitted from the high-voltage side control circuit 18 to the low-voltage side control circuit 12. The third transmission waveform D3 is included in the fourth period T4. Low-voltage side control circuit 12 transmits second transmission waveform D2 to high-voltage side control circuit 18, thereby performing power transmission in the first period T1, power consumption in the third period T3, and first signal transmission in the second period T2, in the order of first period T1, third period T3, and second period T2. Thereafter, high-voltage side control circuit 18 transmits third transmission waveform D3 to low-voltage side control circuit 12, thereby performing second signal transmission in the fourth period T4. As a result, in power transmission circuit 1A, power transmission in the first period T1, power consumption in the third period T3, first signal transmission in the second period T2, and second signal transmission in the fourth period T4 are repeated in the order of first period T1, third period T3, second period T2, and fourth period T4.

[0063] In power transmission circuit 1A, low-voltage side control circuit 12 and high-voltage side control circuit 18 may also switch between a first mode and a second mode in response to an external input. In the first mode, low-voltage side control circuit 12 and high-voltage side control circuit 18 repeatedly perform power transmission in a first period T1, power consumption in a third period T3, first signal transmission in a second period T2, and second signal transmission in a fourth period T4, in the order of first period T1, third period T3, second period T2, and fourth period. In the second mode, low-voltage side control circuit 12 normally repeatedly performs power transmission only in the first period T1. At a predetermined timing, the low-voltage side control circuit 12 and the high-voltage side control circuit 18 perform power transmission, power consumption, first signal transmission, and second signal transmission only once during one transmission, in the order of a first period T1, a third period T3, a second period T2, and a fourth period T4.

[0064] In the power transmission circuit 1A described above, the second signal S2 can be transmitted from the high potential side region 7 to the low potential side region 6 by transmitting the second signal S2 via the first transformer 14, which is also used for power transmission and first signal transmission. This allows signal transmission in both directions between the low potential side region 6 and the high potential side region 7, in addition to the first signal transmission. Furthermore, since the second signal S2 is transmitted during the fourth period T4, it is transmitted in a state separated in time from the high potential side voltage V1 and the first signal S1. This allows the low voltage side control circuit 12 to accurately receive the second signal S2 in the low potential side region 6, even in insulating oil and insulating resin. [Second Modification and Third Modification]

[0065] FIG. 8A is a block diagram of a power transmission circuit 1B according to a second modification. Note that FIG. 8 omits the illustration of the power supplies 51-53, the X-ray tube XL, the high-voltage generation circuit 3, and the detection circuit 4. The terminal for inputting a voltage from the outside is designated VoltageInput, and the terminal for outputting a voltage to the outside is designated VoltageOutput. The power transmission circuit 1B differs from the power transmission circuit 1 in that it includes a first low-voltage inverter circuit 13A and a second low-voltage inverter circuit 13B instead of the low-voltage inverter circuit 13. In the power transmission circuit 1, a common low-voltage inverter circuit 13 is driven in power transmission and first signal transmission. In contrast, in the power transmission circuit 1B, the first low-voltage inverter circuit 13A is driven at, for example, 100 kHz in power transmission. In the first signal transmission, the second low-voltage side inverter circuit 13B is driven at a frequency higher than the drive frequency of the first low-voltage side inverter circuit 13A, for example, 1 MHz. In the example of FIG. 8(a), a damping resistor R3 is provided between the output terminal of the second low-voltage side inverter circuit 13B and the primary winding 14a of the first transformer 14. The damping resistor R3 suppresses vibration of the first signal S1. FIG. 8(b) is a block diagram of a power transmission circuit 1C according to a third modification. The power transmission circuit 1C differs from the power transmission circuit 1A only in that the power transmission circuit 1C includes a first low-voltage side inverter circuit 13A and a second low-voltage side inverter circuit 13B instead of the low-voltage side inverter circuit 13. In the power transmission circuit 1C, the first low-voltage side inverter circuit 13A is driven at, for example, 100 kHz. In the second signal transmission, the second low-voltage side inverter circuit 13B is driven at a frequency, for example, 1 MHz, higher than the drive frequency of the first low-voltage side inverter circuit 13A. Similarly to the power transmission circuit 1, the power transmission circuits 1B and 1C may also have a termination resistor R2 connected in parallel with the primary winding of the second transformer 15. Alternatively, a CR circuit in which the termination resistor R2 and a capacitor are connected in series may be provided in parallel with the primary winding of the second transformer 15. Also, similar to the power transmission circuit 1A, the power transmission circuit 1C may also have a damping resistor connected between the series resonant capacitor Cs2 and the high-voltage side inverter circuit 24. [Fourth Modification]

[0066] In the power transmission circuits of the above-described embodiments and modifications, a new signal transmission path may be added in addition to the first signal transmission path 9 and the second signal transmission path 20. Fig. 9 is a block diagram of a power transmission circuit 1D according to a fourth modification. The power transmission circuit 1D differs from the power transmission circuit 1A only in that it includes a third signal transmission path 30 and a fourth signal transmission path 40.

[0067] The third signal transmission path 30 includes a second low-voltage side control circuit 26, a light-emitting element 27, an optical fiber 28, a photodiode (photodetector element) 29, a PD drive circuit 44, and an amplifier 34. The second low-voltage side control circuit 26 and the light-emitting element 27 are provided in the low potential side region 6. The photodiode 29, the PD drive circuit 44, and the amplifier 34 are provided in the high potential side region 7.

[0068] In the power transmission circuit 1D, the second transformer 15 defines, in the high potential side region 7, a second high potential side region 71 which is a floating region, and a third high potential side region 72 which has the second reference potential G2 as its reference potential.

[0069] The input terminal of second low-voltage side control circuit 26 is connected to the output terminal of AD converter 11. Second low-voltage side control circuit 26 generates first signal S1 separately from low-voltage side control circuit 12. Light-emitting element 27 is connected to the output terminal of second low-voltage side control circuit 26. Light-emitting element 27 converts first signal S1 into optical energy. The input terminal of optical fiber 28 is optically coupled to light-emitting element 27. Optical fiber 28 is arranged in parallel with first transformer 14 and is arranged to connect low potential side region 6 and high potential side region 7. The first signal S1 converted into optical energy is transmitted from low potential side region 6 to high potential side region 7 by optical fiber 28.

[0070] The photodiode 29 is optically coupled to the output end of the optical fiber 28 in the second high-potential side region 71. The first signal S1 transmitted by the optical fiber 28 is photoelectrically converted by the photodiode 29 in the third high-potential side region 72. The PD drive circuit 44 transmits the first signal S1 photoelectrically converted by the photodiode 29 to the amplifier 34.

[0071] Amplifier 34 includes a pair of input terminals 34a, 34b and an output terminal 34c. One input terminal 34a is connected to photodiode 29 via PD drive circuit 44. The other input terminal 34b is connected to second reference potential G2. Output terminal 34c is connected to high-voltage side control circuit 18. Amplifier 34 amplifies first signal S1 and outputs first signal S1 to high-voltage side control circuit 18. First signal S1 is transmitted from second low-voltage side control circuit 26 to high-voltage side control circuit 18 via third signal transmission path 30 described above.

[0072] The fourth signal transmission path 40 includes a second low-voltage side control circuit 26, a photodiode 35, an optical fiber 36, a light-emitting element 37, an LED drive circuit 38, and an amplifier 39. The second low-voltage side control circuit 26 and the photodiode 35 are provided in the low potential side area 6. The light-emitting element 37, the LED drive circuit 38, and the amplifier 39 are provided in the high potential side area 7.

[0073] One input terminal 39a of amplifier 39 is connected to high-voltage side control circuit 18. The other input terminal 39b is connected to second reference potential G2. Output terminal 39c is connected to light-emitting element 37 via LED drive circuit 38. Amplifier 39 amplifies second signal S2 and outputs second signal S2 to light-emitting element 37 via LED drive circuit 38. Light-emitting element 37 is optically coupled to an input end of optical fiber 36 in third high-potential side region 72. An output end of optical fiber 36 is optically coupled to photodiode 35 in low-potential side region 6. Photodiode 35 is connected to second low-voltage side control circuit 26. Second signal S2 converted into optical energy by light-emitting element 37 is transmitted from high-potential side region 7 to low-potential side region 6 via optical fiber 36. Second signal S2 transmitted via optical fiber 36 is photoelectrically converted by photodiode 35 and output to second low-voltage side control circuit 26. The second signal S2 is transmitted from the high-voltage side control circuit 18 to the second low-voltage side control circuit 26 via the fourth signal transmission path 40 described above.

[0074] In the power transmission circuit 1D described above, the first signal S1 generated by the second low-voltage side control circuit 26 is electro-optically converted by the light-emitting element 37 and transmitted from the low-potential side region 6 to the high-potential side region 7 via the optical fiber 36. The transmitted first signal S1 is photoelectrically converted by the photodetector element in the high-potential side region 7, amplified by the amplifier 34, and output to the high-voltage side control circuit 18. The other input terminal 34b of the amplifier 34 is connected to the second reference potential G2, and the output terminal 34c is connected to the high-voltage side control circuit 18. The reference potential of the high-voltage side control circuit 18 is the same as the second reference potential G2. This allows the amplifier 34 to transmit the first signal S1 within the third high-potential side region 72, which has the second reference potential G2 as its reference potential. With the above configuration, by securing a signal transmission route separate from the first transformer 14 and the second transformer 15, it is possible to deal with, for example, a situation in which the transmission amount is insufficient using only the first signal transmission. In the power transmission circuit 1D, similarly to the power transmission circuit 1A, a damping resistor may be connected between the series resonant capacitor Cs2 and the high-voltage side inverter circuit 24. [Fifth Modification]

[0075] The third signal transmission path 30 and the fourth signal transmission path 40 described in the fourth modification may be applied to other circuits. Fig. 10 is a block diagram of a power transmission circuit 1E according to a fifth modification. In addition to the third signal transmission path 30 and the fourth signal transmission path 40, the power transmission circuit 1E includes a low-voltage side control circuit 12, a low-voltage side inverter circuit 13, a first transformer 14, a rectifier circuit 16A, an isolated DC-DC converter 50 (first DC converter), a non-isolated DC-DC module 42 (second DC converter), and a second high-voltage side control circuit 43. The power transmission circuit 1E includes an isolated DC-DC converter 50 instead of the second transformer 15. The isolated DC-DC converter 50 includes an input terminal 50a and an output terminal 50b, and the input terminal 50a and the output terminal 50b are insulated from each other. The rectifier circuit 16A is provided between the secondary winding 14b of the first transformer 14 and the input terminal 50a of the isolated DC-DC converter 50. In the power transmission circuit 1E, the amplifier 34 is an isolated amplifier in which input terminals 34a, 34b are isolated from the output terminal 34c. Similarly, the amplifier 39 is an isolated amplifier in which input terminals 39a, 39b are isolated from the output terminal 39c.

[0076] In the power transmission circuit 1E, for example, the high-voltage side voltage V1 may be rectified in the rectifier circuit 16A, and the magnitude of the DC voltage may be converted in the isolated DC-DC converter 50, after which the rectified voltage may be utilized as the power supply voltage for the non-isolated DC-DC module 42. The power supply voltage for the amplifier 34 may be supplied from Vcc generated by the rectifier circuit 16A. The power supply voltage for the amplifier 39 may be supplied from the output terminal 50b of the isolated DC-DC converter 50.

[0077] The isolated DC-DC converter 50 separates the second reference potential G2 into a third reference potential G21 and a fourth reference potential G22 in the high-potential region 7. An input terminal 50a of the isolated DC-DC converter 50 is connected to the third reference potential G21. An output terminal 50b of the isolated DC-DC converter 50 is connected to the first input terminal 42a of the non-isolated DC-DC module 42. An output terminal 50b of the isolated DC-DC converter 50 is connected to the fourth reference potential G22.

[0078] In the power transmission circuit 1E, the low-voltage side control circuit 12, the low-voltage side inverter circuit 13, the first transformer 14, the rectifier circuit 16A, the isolated DC-DC converter 50, and the non-insulated DC-DC module 42 constitute a first signal transmission path 9. The non-insulated DC-DC module 42 is disposed in a third high-potential side area 72. The non-insulated DC-DC module 42 receives a first signal S1 from the isolated DC-DC converter 50. The non-insulated DC-DC module 42 supplies an internally generated output voltage to the X-ray tube XL. In the example of FIG. 10 , surge absorbers Z are provided between each terminal of the non-insulated DC-DC module 42 and between each terminal and a fourth reference potential G22. The surge absorbers Z, for example, improve the surge withstand voltage of the non-insulated DC-DC module 42.

[0079] In the power transmission circuit 1E, the low-voltage side control circuit 12, the low-voltage side inverter circuit 13, the first transformer 14, and the second high-voltage side control circuit 43 constitute a fifth signal transmission path 60. The second high-voltage side control circuit 43 is disposed in a second high-potential side area 71. A first terminal 43a of the second high-voltage side control circuit 43 is connected to the secondary winding 14b of the first transformer 14. A second terminal 43b of the second high-voltage side control circuit 43 is connected to the PD drive circuit 44 and the LED drive circuit 38. The second high-voltage side control circuit 43 may supply, for example, power supply voltages to the PD drive circuit 44 and the LED drive circuit 38. Although not shown in FIG. 10 , the fifth signal transmission path 60 may transmit, for example, a signal from the low-voltage side control circuit 12 to the second high-voltage side control circuit 43, for use by the second high-voltage side control circuit 43 to calibrate the amplifiers 34 and 39. Alternatively, in fifth signal transmission path 60 , second high-voltage side control circuit 43 may detect a fault state of amplifiers 34 , 39 and transmit the detected signal to low-voltage side control circuit 12 .

[0080] In the power transmission circuit 1E, the amplifiers 34 and 39 are arranged to straddle the second high potential side region 71 and the third high potential side region 72. The output terminal 34c of the amplifier 34 is connected to the second input terminal 42b of the non-insulated DCDC module 42 in the third high potential side region 72. One input terminal 39a of the amplifier 39 is connected to the output terminal 42c of the non-insulated DCDC module 42 in the third high potential side region 72. The other input terminal 39b of the amplifier 39 is connected to a fourth reference potential G22.

[0081] The amplifier 34 transmits the first signal S1 transmitted by the third signal transmission path 30 from the second high potential side area 71 to the third high potential side area 72. The first signal S1 generated by the second low voltage side control circuit 26 is transmitted from the low potential side area 6 to the second high potential side area 71 by the optical fiber 28. The first signal S1 is photoelectrically converted by the photodiode 29 in the second high potential side area 71. The PD drive circuit 44 transmits the first signal S1 photoelectrically converted by the photodiode 29 to the amplifier 34. The amplifier 34 transmits the first signal S1 from the second high potential side area 71 to the third high potential side area 72 and outputs it to the non-isolated DCDC module 42.

[0082] The amplifier 39 transmits the second signal S2 input from the non-insulated DCDC module 42 from the third high potential side area 72 to the second high potential side area 71. The second signal S2 is transmitted from the second high potential side area 71 to the low potential side area 6 by the optical fiber 36. The second signal S2 is photoelectrically converted by the photodiode 35 and output to the second low voltage side control circuit 26.

[0083] In the power transmission circuit 1E of this modification, power is transmitted from the low potential side region 6 to the high potential side region 7 by transmitting the voltage generated by the low voltage side inverter circuit 13 as the high voltage side voltage V1 via the first transformer 14. In addition, a first signal S1 is transmitted from the low potential side region 6 to the high potential side region 7 via the first transformer 14 that is also used for power transmission, thereby performing a first signal transmission from the low potential side region 6 to the high potential side region 7. The power transmission is performed in the first period T1, and the first signal transmission is performed in the second period T2. This eliminates the need to provide a filter to separate the high voltage side voltage V1 and the first signal S1, and therefore the second high voltage side control circuit 43 can accurately receive the first signal S1 in the high potential side region 7 even in insulating oil and insulating resin.

[0084] The power transmission circuit according to the present invention is not limited to the above-described embodiments and examples of each modification, but is defined by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims.

[0085] In the above embodiment, the waveform shaping circuit 17 is connected between the second secondary winding 15c and the high-voltage side control circuit 18, but it is possible to omit the waveform shaping circuit 17 as necessary. Furthermore, in the above embodiment, the first transformer 14 is a loosely coupled transformer, but the first transformer 14 may be an isolation transformer other than a loosely coupled transformer.

[0086] DESCRIPTION OF SYMBOLS 1, 1A, 1B, 1C, 1D, 1E...power transmission circuit, 12...low-voltage side control circuit, 13...low-voltage side inverter circuit, 14...first transformer, 15...second transformer, 14a...primary winding (low-voltage side winding) of first transformer, 14b...secondary winding (high-voltage side winding) of first transformer, 15a...primary winding of second transformer, 15b...first secondary winding of second transformer, 15c...second secondary winding of second transformer, 16, 16A...rectifier circuit, 17...waveform shaping circuit, 18...high-voltage side control circuit, 24...high-voltage side inverter circuit, 27, 37...light-emitting element element, 28, 36...optical fiber, 29...photodiode (light detection element), 34, 39...amplifier, 42...non-insulated DCDC module (second DC converter), 50...insulated DCDC converter (first DC converter), 6...low potential side region (low potential side), 7...high potential side region (high potential side), G1...first reference potential, G2...second reference potential, G21...third reference potential, G22...fourth reference potential, S1...first signal, S2...second signal, T1...first period, T2...second period, T4...fourth period (third period), V1...high voltage side voltage.

Claims

1. A power transmission circuit connected to a circuit that boosts voltage from a low potential side to a high potential side, comprising: a first transformer that is an isolated transformer including a low-voltage side winding that is a primary winding connected to the low potential side, and a high-voltage side winding that is a secondary winding connected to the high potential side; a low-voltage side inverter circuit having an output terminal connected to the low-voltage side winding; a low-voltage side control circuit connected to an input terminal of the low-voltage side inverter circuit and driving the low-voltage side inverter circuit; a second transformer including a primary winding, a first secondary winding, and a second secondary winding, the primary winding being connected to the high-voltage side winding; a rectifier circuit connected to the first secondary winding; and a high-voltage side control circuit connected to the second secondary winding and operating based on a first signal; wherein the low-voltage side control circuit drives the low-voltage side inverter circuit to generate a high-voltage side voltage, and the high-voltage side voltage is transmitted to the rectifier circuit via the first transformer and the second transformer during a first period; a first signal transmission, in which the first signal generated by the low-voltage side control circuit driving the low-voltage side inverter circuit is transmitted to the high-voltage side control circuit via the first transformer and the second transformer, during a second period separate from the first period.

2. The power transmission circuit according to claim 1, wherein a waveform shaping circuit for improving distortion of the first signal is connected between the second secondary winding and the high-voltage side control circuit.

3. The power transmission circuit according to claim 1 or 2, further comprising a high-voltage side inverter circuit whose output terminal is connected between the high-voltage side winding of the first transformer and the primary winding of the second transformer and whose input terminal is connected to the high-voltage side control circuit, wherein the low-voltage side control circuit performs an operation separate from driving the low-voltage side inverter circuit based on a second signal, and wherein the high-voltage side control circuit drives the high-voltage side inverter circuit to generate the second signal, and transmits the second signal to the low-voltage side control circuit via the first transformer during a third period separate from the first period and the second period.

4. A power transmission circuit according to any one of claims 1 to 3, wherein the first transformer is a loosely coupled transformer.

5. The power transmission circuit according to any one of claims 1 to 4, further comprising: a second low-voltage side control circuit provided on the low-potential side and generating the first signal separately from the low-voltage side control circuit; a light-emitting element connected to the second low-voltage side control circuit; an optical fiber including an input end optically coupled to the light-emitting element and arranged to connect the low-potential side and the high-potential side; a photodetector element optically coupled to an output end of the optical fiber on the high-potential side; and an amplifier including an output terminal connected to the high-voltage side control circuit and a pair of input terminals, one of which is connected to the photodetector element and the other of which is connected to a reference potential on the high-potential side.

6. A power transmission circuit connected to a circuit that boosts voltage from a low potential side to a high potential side, comprising: a first transformer that is an isolated transformer including a low-voltage side winding that is a primary winding connected to the low potential side, and a high-voltage side winding that is a secondary winding connected to the high potential side; a low-voltage side inverter circuit having an output terminal connected to the low-voltage side winding; a low-voltage side control circuit that is connected to the input terminal of the low-voltage side inverter circuit and drives the low-voltage side inverter circuit; a rectifier circuit connected to the high-voltage side winding; a first DC converter that has input terminals and output terminals and has the input terminal connected to the rectifier circuit; and a second DC converter that is connected to the output terminal and operates based on a first signal; and during a first period, power transmission is performed in which the high-voltage side voltage generated by the low-voltage side control circuit driving the low-voltage side inverter circuit is transmitted to the second DC converter via the first transformer, the rectifier circuit, and the first DC converter. a first signal transmission, in which the first signal generated by the low-voltage side control circuit driving the low-voltage side inverter circuit is transmitted to the second DC converter via the first transformer, the rectifier circuit, and the first DC converter, during a second period separate from the first period.

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