阅读说明：本技术 电源装置和磁共振成像系统 (Power supply device and magnetic resonance imaging system ) 是由 杜述 李文明 汪坚敏 佟瞳 于 2018-05-31 设计创作，主要内容包括：本发明公开了一种电源装置和磁共振成像系统,装置包括电源端模块和负载端模块；电源端模块包括电源单元和参考电压拉低单元；负载端模块包括：电压比较器,其输入端与负载供电端连接,用于将负载供电端的实际电压和额定电压进行比较；参考电压拉低单元包括：计数器,其输出端与数模转换器的输入端一一连接,用于在实际电压低于额定电压时进行计数,在实际电压等于额定电压时保持计数结果不变,并输出计数结果对应的数字信号；数模转换器,其输出端与反相器的输入端连接,用于将数字信号转换为正模拟电压；反相器,其输出端与电源单元的输出电压参考端连接,用于将模拟电压反相为负模拟电压。本发明能够补偿电源和负载供电端之间线缆上的压降损失。(The invention discloses a power supply device and a magnetic resonance imaging system, wherein the device comprises a power supply end module and a load end module; the power end module comprises a power unit and a reference voltage pull-down unit; the load end module includes: the input end of the voltage comparator is connected with the load power supply end and is used for comparing the actual voltage of the load power supply end with the rated voltage; the reference voltage pull-down unit includes: the output ends of the counters are connected with the input ends of the digital-to-analog converters one by one and are used for counting when the actual voltage is lower than the rated voltage, keeping the counting result unchanged when the actual voltage is equal to the rated voltage and outputting digital signals corresponding to the counting result; the output end of the digital-to-analog converter is connected with the input end of the inverter and is used for converting the digital signal into positive analog voltage; and the output end of the phase inverter is connected with the output voltage reference end of the power supply unit and is used for inverting the analog voltage into a negative analog voltage. The invention can compensate the voltage drop loss on the cable between the power supply and the power supply end of the load.)

1. a power supply device, comprising:

A power supply unit, the output end of which is connected with the load power supply end (G1) and is used for supplying power to the load;

A voltage comparator (21) having an input connected to a load supply terminal (G1) for comparing an actual voltage of the load supply terminal (G1) with a rated voltage;

The reference voltage pull-down unit (12) comprises a counter (1222), a digital-to-analog converter (1221) and an inverter (121), when the voltage comparator judges that the actual voltage is lower than the rated voltage, the counter is used for counting, the digital signal which is obtained by the counter and represents a counting result is converted into a corresponding analog voltage by the digital-to-analog converter, the analog voltage is inverted by the inverter, and the inverted analog voltage is provided for an output voltage reference end of the power supply unit.

2. The power supply device according to claim 1,

the output end of the digital-to-analog converter (1221) is connected with the input end of the inverter (121) and is used for converting the digital signal into a corresponding positive analog voltage, and the larger the digital signal is, the larger the positive analog voltage is;

The output terminal of the inverter (121) is connected to an output voltage reference terminal (Ref1) of the power supply unit for inverting the analog voltage to a negative analog voltage.

3. The power supply apparatus according to claim 1, wherein the voltage comparator (21) has a negative input terminal connected to the load supply terminal (G1), and a positive input terminal to which the rated voltage is input, and is configured to compare voltages of the positive and negative input terminals and output a first level when the voltage of the negative input terminal is lower than that of the positive input terminal, and output a second level otherwise.

4. the power supply device according to claim 1,

The power supply unit and the reference voltage pull-down unit are positioned on a power supply end module (1) on the power supply end side of the magnetic resonance imaging system, and the voltage comparator (21) is positioned on a load end module (2) on the load end side of the magnetic resonance imaging system.

5. the power supply device according to claim 4, wherein the load side module (2) further comprises:

And a first programmable logic controller (22), the input end of which is connected with the output end of the voltage comparator (21), the output end of which is connected with the reference voltage pull-down unit (12), and the first programmable logic controller is used for outputting a first signal capable of controlling the counter (1222) to count when receiving the first level and outputting a second signal capable of controlling the counter (1222) to keep the counting result unchanged when receiving the second level.

6. The power supply device according to claim 5, wherein the first signal includes a trigger signal and a first control signal, and the second signal includes a second control signal; said first programmable logic controller (22) including a first output (Out22-1) for outputting said trigger signal and a second output (Out22-2) for outputting said first control signal and said second control signal; the first output (Out22-1) is connected to an input of the counter (1222);

The reference voltage pull-down unit (12) further comprises:

A second programmable logic controller (1223) comprising a first input terminal (In1223-1) connected to the second output terminal (Out22-2), an output terminal of which is connected to the enable terminal (EN2) of the counter (1222) and the enable terminal (EN1) of the digital-to-analog converter (1221), for enabling the enable terminal (EN2) of the counter (1222) and the enable terminal (EN1) of the digital-to-analog converter (1221) to be In an enable state when receiving the first control signal, and for enabling the enable terminal (EN2) of the counter (1222) and the enable terminal (EN1) of the digital-to-analog converter (1221) to be In a lock state when receiving the second control signal.

7. The power supply arrangement according to claim 6, wherein the first programmable logic controller (22) further comprises a third output (Out22-3) for outputting a synchronization signal, and wherein the second programmable logic controller (1223) further comprises a second input (In1223-2) connected to the third output (Out 22-3).

8. The power supply arrangement according to claim 1, wherein the digital-to-analog converter (1221) is configured to perform a digital-to-analog conversion according to a first formula, the first formula comprising:

V_o＝0.01X(D₀+2D₁+4D₂+…+2^(n-1)D_n-1)

wherein D ₀ -D _n-1 are digital signals output by the counter (1222), V _o is a positive analog voltage output by the digital-to-analog converter (1221), and n is the number of input ends of the digital-to-analog converter (1221).

9. The power supply device according to claim 1, wherein the inverter (121) comprises an operational amplifier (1211), a feedback resistor (Rf), and a ground resistor (R4), wherein:

The positive input end of the operational amplifier (1211) is connected to the ground end through the ground resistor (R4), the negative input end of the operational amplifier (1211) is connected to the output end of the digital-to-analog converter (1221), the feedback resistor (Rf) is connected between the negative input end and the output end of the operational amplifier (1211), and the output end of the operational amplifier (1211) is coupled to the output voltage reference end (Ref 1).

10. The power supply arrangement according to claim 9, characterized in that a first resistor (R1) is connected between the output voltage reference terminal (Ref1) of the power supply unit and the output terminal (Out11) of the power supply unit; the inverter (121) further comprises a second resistor (R2) and/or a third resistor (R3), the second resistor (R2) being arranged between the output voltage reference terminal (Ref1) and the output terminal of the operational amplifier; the third resistor (R3) is disposed between the negative input of the operational amplifier and the output of the digital-to-analog converter (1221).

11. The power supply device according to any one of claims 1 to 10, wherein the load supply terminal (G1) is a power supply input terminal of a preamplifier in a magnetic resonance imaging system.

12. A magnetic resonance imaging system comprising a preamplifier and power supply means for supplying power to said preamplifier, said power supply means being as claimed in claim 11.

Technical Field

The invention relates to the technical field of nuclear magnetic resonance, in particular to a power supply device and a magnetic resonance imaging system.

Background

in a magnetic resonance imaging system, there is typically a dedicated power supply unit module that supplies power to various components in the system, such as the preamplifier (abbreviated LNA) of the receive coil. The power supply unit modules are typically distributed in cabinets outside the magnetic resonance examination room, or on the magnet side or other locations of the equipment room. In any case, a relatively long cable runs from the power supply unit module supplying power to the LNA. When the coil normally works, the total current of the LNA of the high-receiving-channel coil cannot be ignored, and due to the loss of the cable, the total current of the LNA can generate voltage drop on the cable, so that the power supply voltage of the LNA can not reach the rated voltage of the device, and the performance of the LNA is further influenced, for example, the noise factor of the LNA can be deteriorated.

disclosure of Invention

In view of the above, the present invention provides a power supply apparatus and a magnetic resonance imaging system, which can compensate for voltage drop loss on a cable between a power supply unit and a power supply terminal of a load, and ensure normal operation of the load.

In a first aspect, the present invention provides a power supply apparatus comprising: the power supply unit is connected with the load power supply end and used for supplying power to a load; the input end of the voltage comparator is connected with the load power supply end and is used for comparing the actual voltage of the load power supply end with the rated voltage; the reference voltage pull-down unit comprises a counter, a digital-to-analog converter and an inverter, when the voltage comparator judges that the actual voltage is lower than the rated voltage, the counter is used for counting, the digital-to-analog converter is used for converting a digital signal which is obtained by the counter and represents a counting result into corresponding analog voltage, the inverter is used for inverting the analog voltage, and the inverted analog voltage is provided for the reference end of the power supply unit.

in some embodiments, the voltage comparator, the negative input terminal of which is connected to the load supply terminal, and the positive input terminal of which inputs the rated voltage, is specifically configured to compare the voltages of the positive input terminal and the negative input terminal thereof, and output a first level when the voltage of the negative input terminal thereof is lower than the voltage of the positive input terminal thereof, and otherwise output a second level.

in some embodiments, the load side module further comprises: and the input end of the first programmable logic controller is connected with the output end of the voltage comparator, the output end of the first programmable logic controller is connected with the reference voltage pull-down unit, and the first programmable logic controller is used for outputting a first signal capable of controlling the counter to count when receiving the first level and outputting a second signal capable of controlling the counter to keep the counting result unchanged when receiving the second level.

In some embodiments, the first signal comprises a trigger signal and a first control signal, and the second signal comprises a second control signal; the first programmable logic controller comprises a first output end used for outputting the trigger signal and a second output end used for outputting the first control signal and the second control signal; the first output end is connected with the input end of the counter; the reference voltage pull-down unit further includes: and the second programmable logic controller comprises a first input end connected with the second output end, wherein the output end of the first programmable logic controller is connected with the enabling end of the counter and the enabling end of the digital-to-analog converter, and is used for enabling the enabling end of the counter and the enabling end of the digital-to-analog converter to be in an enabling state when the first control signal is received and enabling the enabling end of the counter and the enabling end of the digital-to-analog converter to be in a locking state when the second control signal is received.

In some embodiments, the first programmable logic controller further comprises a third output for outputting a synchronization signal, and the second programmable logic controller further comprises a second input connected to the third output.

in some embodiments, the digital-to-analog converter is configured to perform digital-to-analog conversion according to a first formula, the first formula comprising:

V_o＝0.01X(D₀+2D₁+4D₂+…+2^(n-1)D_n-1)

In the formula, D ₀ to D _n-1 are digital signals output by the counter, V _o is a positive analog voltage output by the digital-to-analog converter, and n is the number of input ends of the digital-to-analog converter.

in some embodiments, the inverter comprises an operational amplifier, a feedback resistor, and a ground resistor, wherein: the positive input end of the operational amplifier is connected with the grounding end through the grounding resistor, the negative input end of the operational amplifier is connected with the output end of the digital-to-analog converter, the feedback resistor is connected between the negative input end and the output end of the operational amplifier, and the output end of the operational amplifier is coupled with the output voltage reference end.

in some embodiments, a first resistor is connected between an output voltage reference terminal of the power supply unit and an output terminal of the power supply unit; the inverter further comprises a second resistor and/or a third resistor, wherein the second resistor is arranged between the output voltage reference end and the output end of the operational amplifier; the third resistor is arranged between the negative input end of the operational amplifier and the output end of the digital-to-analog converter.

in some embodiments, the load power supply terminal is a power supply input terminal of a preamplifier in the magnetic resonance imaging system.

in a second aspect, the present invention provides a magnetic resonance imaging system, comprising a preamplifier and a power supply device for supplying power to the preamplifier, wherein the power supply device is the above power supply device.

in summary, when the voltage of the load power supply end is lower than the rated voltage, the load end module outputs the trigger signal and the first control signal to the reference voltage pull-down unit, and when the reference voltage pull-down unit receives the trigger signal and the first control signal, the reference voltage pull-down unit outputs a gradually decreasing negative voltage, so that the voltage of the reference voltage is gradually decreased, and further the voltage of the load power supply end is gradually raised, thereby compensating the voltage drop loss on a cable between the power supply device and the load power supply end, avoiding the situation that the voltage of the load power supply end cannot reach the rated voltage, and further ensuring the normal operation of the load.

drawings

the foregoing and other features and advantages of the invention will become more apparent to those skilled in the art to which the invention relates upon consideration of the following detailed description of a preferred embodiment of the invention with reference to the accompanying drawings, in which:

FIG. 1 is a schematic diagram of a power supply apparatus according to an embodiment of the present invention;

Fig. 2 is a waveform diagram of the trigger signal and the output voltage of the digital-to-analog converter according to an embodiment of the present invention.

Wherein the reference numbers are as follows:

Detailed Description

In order to more clearly understand the technical features, objects and effects of the present invention, embodiments of the present invention will now be described with reference to the accompanying drawings, in which the same reference numerals indicate the same or structurally similar but functionally identical elements.

"exemplary" means "serving as an example, instance, or illustration" herein, and any illustration, embodiment, or steps described as "exemplary" herein should not be construed as a preferred or advantageous alternative.

For the sake of simplicity, the drawings only schematically show the parts relevant to the present invention, and they do not represent the actual structure as a product. In addition, for simplicity and clarity of understanding, only one of the components having the same structure or function is schematically illustrated or labeled in some of the drawings.

The invention provides a power supply device, also called a power supply unit processing device, which can be used for supplying power to each component in a magnetic resonance imaging system, such as a preamplifier (LNA for short) in a coil, and can also be applied to other fields or systems for supplying power.

As shown in fig. 1, the apparatus includes a power source terminal module 1 and a load terminal module 2; the power end module 1 comprises a power supply unit and a reference voltage pull-down unit 12, the reference voltage pull-down unit 12 comprises a counter 1222, a digital-to-analog converter 1221 and an inverter, the inverter is the inverting subunit 121, and the counter 1222 and the digital-to-analog converter 1221 form a voltage generating subunit 122; the load side module 2 comprises a voltage comparator 21, wherein:

the input end of the voltage comparator 21 is connected with a load power supply end G1 and is used for comparing the actual voltage of the load power supply end G1 with the rated voltage;

The counter 1222, the output end of which is connected to the input ends d 1-dn of the digital-to-analog converter 1221 one by one, and is configured to count when the actual voltage is lower than the rated voltage, keep the count result unchanged when the actual voltage is equal to the rated voltage, and output a digital signal corresponding to the count result;

The output end of the digital-to-analog converter 1221 is connected to the input end of the inverter, and is configured to convert the digital signal into a corresponding positive analog voltage, where the larger the digital signal is, the larger the positive analog voltage is;

The output end of the inverter 121 is connected to the output voltage reference end Ref1 of the power supply unit, and is used for inverting the analog voltage into a negative analog voltage;

the output end of the power supply unit is connected with the load power supply end G1 and is used for supplying power to a load.

It is understood that the power supply unit may comprise a DC-DC converter 11, an output terminal of the power supply unit, i.e. an output terminal Out11 of the DC-DC converter 11, and an output voltage reference terminal of the power supply unit, i.e. an output voltage reference terminal Ref1 of the DC-DC converter 11.

it will be appreciated that the DC-DC converter 11 converts the DC voltage received at its own input, for example, converts the received high voltage to a usable low voltage, and then outputs the low voltage through its own output. In general, the output voltage reference terminal Ref1 of the output voltage of the DC-DC converter 11 is grounded, i.e. the reference voltage is 0, while the output voltage reference terminal Ref1 is connected to the reference voltage pull-down unit 12 in this application, when the actual voltage of the reference voltage pull-down unit 12 at the load supply terminal G1 is lower than the rated voltage, the negative analog voltage is output and gradually decreases, so the voltage of the output voltage reference terminal Ref1 is negative and gradually decreases, and thus the voltage value of the load supply terminal G1 is gradually pulled up. And when the reference voltage pull-down unit 12 keeps the output negative analog voltage constant when the actual voltage at the load supply terminal is equal to the rated voltage, the voltage at the output voltage load terminal is kept constant, so that the voltage at the load supply terminal G1 is kept at a higher voltage value.

It is understood that, in a device or port where no reference voltage is specifically mentioned, the reference voltage is 0, for example, the reference voltage of the load supply terminal G1 is 0. Since the output terminal Out11 of the DC-DC converter 11, the load supply terminal G1 and the actual voltage input terminal of the voltage comparator 21 are connected, the connection point can be referred to as a first node J1. Since the load supply terminal G1 (the reference voltage of which is 0) is connected to the first node J1, the voltage of the load supply terminal G1 is the voltage of the first node J1, and since the first node J1 is connected to the output terminal of the DC-DC converter 11, the voltage of the first node J1 is the voltage of the output terminal of the DC-DC converter 11 with respect to the output voltage reference terminal Ref1 thereof, that is, the voltage of the load supply terminal G1 is the voltage of the output terminal of the DC-DC converter 11 with respect to the output voltage reference terminal Ref1 thereof.

The operation principle of the power supply device is briefly described as follows:

when the voltage comparator 21 in the load power supply terminal G1 compares the actual voltage at the load power supply terminal G1 with the rated voltage, and when the reference voltage pull-down unit 12 knows that the actual voltage is lower than the rated voltage, the counter 1222 therein will start counting to generate a digital signal, then the digital-to-analog converter 1221 will convert the digital signal into a negative analog voltage, the inverter 121 will invert the negative analog voltage into a positive analog voltage, since the larger the count, the larger the digital signal, the larger the positive analog voltage, and the smaller the negative analog voltage, since the output terminal of the inverter 121 is connected to the output terminal of the power supply unit, the smaller the reference voltage of the power supply unit is, and further the voltage at the load power supply terminal G1 will gradually increase. When the actual voltage of the load supply terminal G1 increases to the rated voltage, the counter 1222 stops counting, so the digital signal remains unchanged, and therefore the positive analog voltage obtained by the digital-to-analog converter 1221 remains unchanged, and the negative analog voltage obtained by the inverter 121 remains unchanged, and therefore the reference voltage of the output voltage reference terminal Ref1 remains unchanged, thereby maintaining the voltage of the load supply terminal G1 at the rated voltage.

In the voltage device provided by the invention, the voltage comparator 21 compares the actual voltage of the load power supply end G1 with the rated voltage, then when the actual voltage is lower than the rated voltage, the counter 1222 starts counting to generate a digital signal, the digital-to-analog converter 1221 converts the digital signal into a positive analog voltage, the inverter 121 inverts the positive analog voltage into a negative analog voltage, thereby reducing the reference voltage of the output voltage reference end and further raising the voltage of the load power supply end G1. When the actual voltage is equal to the rated voltage, the results of the counter 1222, the digital-to-analog converter 1221 and the inverter 121 are all kept unchanged, so that the voltage of the load supply terminal G1 is kept at the rated voltage. Therefore, the invention can compensate the voltage drop loss on the cable between the power supply unit and the load power supply end G1, avoid the situation that the voltage of the load power supply end G1 cannot reach the rated voltage, and further ensure the normal operation of the load.

In some embodiments, the voltage comparator 21 has a negative input terminal connected to the load supply terminal G1, and a positive input terminal to which the rated voltage is inputted, and is specifically configured to compare voltages of the positive and negative input terminals and output a first level when the voltage of the negative input terminal is lower than that of the positive input terminal, and otherwise output a second level. For example, the actual voltage value of the load supply terminal G1 received by the negative input terminal and the nominal voltage value received by the positive input terminal are compared by the voltage comparator 21, when the actual voltage value is lower than the nominal voltage value, the voltage comparator 21 outputs a first level (e.g., 1), and when the actual voltage value is equal to the nominal voltage value, the voltage comparator 21 outputs a second level (e.g., 0).

In some embodiments, the load side module 2 further comprises:

A first programmable logic controller 22, whose input terminal is connected to the output terminal of the voltage comparator 21 and output terminal is connected to the reference voltage pull-down unit 12, for outputting a first signal capable of controlling the counter 1222 to count when receiving the first level, and outputting a second signal capable of controlling the counter 1222 to keep the count result unchanged when receiving the second level.

In practice, the logic in the first programmable logic controller 22 may be pre-programmed to output a first signal when receiving a first level and a second signal when receiving a second level. Here, the load side module 2 includes the voltage comparator 21 and the first programmable logic controller 22, and since the logic in the first programmable logic controller 22 can be set by programming in advance, the number of devices can be saved, and the circuit can be simplified.

wherein the first signal may include a trigger signal and a first control signal, and the second signal may include a second control signal; the trigger signal is used to trigger the counter 1222 to count, the first control signal is used to control the enable terminals of the counter 1222 and the digital-to-analog converter 1221 to be in the enable state, and the second control signal can be used to control the enable terminals of the counter 1222 and the digital-to-analog converter 1221 to be in the disable state.

Correspondingly, the first programmable logic controller 22 includes a first output terminal Out22-1 for outputting the trigger signal and a second output terminal Out22-2 for outputting the first control signal and the second control signal; the first output Out22-1 is connected to an input of the counter 1222; the first output terminal Out22-1 of the first programmable logic controller 22 is used for outputting the trigger signal, and the second output terminal Out22-2 is used for outputting the first control signal and the second control signal.

The reference voltage pull-down unit 12 further includes a second programmable logic controller 1223, the second programmable logic controller 1223 includes a first input terminal In1223-1 connected to the second output terminal Out22-2, an output terminal thereof is connected to the enable terminal EN2 of the counter and the enable terminal EN1 of the digital-to-analog converter, and is configured to enable the enable terminal EN2 of the counter 1222 and the enable terminal EN1 of the digital-to-analog converter 1221 to be In an enable state when receiving the first control signal, and enable the enable terminal EN2 of the counter 1222 and the enable terminal EN1 of the digital-to-analog converter 1221 to be In a lock state when receiving the second control signal.

It can be understood that when the enable terminal EN2 of the counter 1222 is in the enable state, the counter 1222 can count, and when the enable terminal EN2 is in the disable state, the counting is stopped, and the counting result is not changed. The enable terminal EN1 of the digital-to-analog converter 1221 is enabled to perform digital-to-analog conversion, and is disabled to stop performing digital-to-analog conversion.

It is understood that the counter 1222, the second programmable logic controller 1223 and the digital-to-analog converter 1221 constitute the voltage generating subunit 122, and the inverter constitutes the inverting subunit 121. The voltage generation subunit 122 and the inverting subunit 121 are connected in sequence to form the reference voltage pull-down unit 12, wherein the voltage generation subunit 122 is responsible for generating a gradually increasing positive voltage, and the inverting subunit 121 is responsible for inverting the gradually increasing positive voltage to obtain a gradually decreasing negative voltage.

In practical applications, the counter 1222 may be a 4-bit counter, and there may be 16 counting results in one counting period, and the dac 1221 may generate 16 positive analog voltages according to the 16 counting results. When the counter 1222 is a 4-bit counter, the number of output terminals may be 4, or 4 or more, and since the input terminals d1 through dn of the digital-to-analog converter 1221 are connected to the output terminal of the counter 1222, the number of input terminals of the digital-to-analog converter 1221 may be 4, or 4 or more, for example, 8.

In practical applications, the digital-to-analog converter 1221 may perform digital-to-analog conversion according to a first formula, where the first formula includes:

V_o＝0.01X(D₀+2D₁+4D₂+…+2^(n-1)D_n-1)

Where D ₀ to D _n-1 represent digital signals output by the counter 1222, V _o represents analog voltages output by the digital-to-analog converter 1221, and n represents the number of input terminals of the digital-to-analog converter 1221.

for example, when the count result is 0001, the digital-to-analog conversion result is 0.16, and when the count result is 0010, the digital-to-analog conversion result is 0.32, and it is seen that the more the count is, the larger the analog voltage obtained by the digital-to-analog conversion is.

In addition, the first programmable logic controller 22 further includes a third output terminal Out22-3 for outputting a synchronization signal, and the second programmable logic controller 1223 further includes a second input terminal In1223-2 connected to the third output terminal Out22-3, the second input terminal In1223-2 being connected to a third output terminal Out 22-3. When the first programmable logic controller 22 receives the first level, it also sends a synchronization signal to the second programmable logic controller 1223 to synchronize the first programmable logic controller 22 and the second programmable logic controller 1223. The counter 1222 in the reference voltage pull-down unit 12 counts a number of times each time the load side module 2 issues a trigger signal.

Here, by means of program control, the voltage of the load power supply terminal G1 is raised until the voltage of the load power supply terminal G1 reaches the rated voltage, so that the integrated circuit is convenient for being integrated with other digital function modules, a complex analog feedback circuit is avoided, the implementation is easy, and by means of program control, the design of the circuit is more flexible.

In some embodiments, the inverter 121 includes an operational amplifier 1211, a feedback resistor Rf, and a ground resistor R4, wherein: the positive input terminal of the operational amplifier 1211 is connected to the ground terminal through the ground resistor R4, the negative input terminal of the operational amplifier 1211 is connected to the output terminal of the digital-to-analog converter 1221, the feedback resistor Rf is connected between the negative input terminal and the output terminal of the operational amplifier 1211, and the output terminal of the operational amplifier 1211 is coupled to the output voltage reference terminal Ref 1.

Here, the inverter 121 includes an operational amplifier 1211, a feedback resistor Rf and a ground resistor R4, and in order to further facilitate the adjustment of the reference voltage, a first resistor R1, a second resistor R2 and a third resistor R3 may be further provided, that is, the inverter 121 further includes a first resistor R1, a second resistor R2 and/or a third resistor R3, the first resistor R1 is provided between an output voltage reference terminal Ref1 of the power supply unit and an output terminal Out11 of the power supply unit, and the second resistor R2 is provided between the output voltage reference terminal Ref1 and an output terminal of the operational amplifier 1211; the third resistor R3 is disposed between the negative input terminal of the operational amplifier 1211 and the output terminal of the digital-to-analog converter 1221.

with the addition of the second resistor R2 and the third resistor R3, the relationship among the output voltage V _o of the digital-to-analog converter 1221, the reference voltage V _Ref1 of the output voltage reference terminal Ref1, and the voltage V _c of the load power supply terminal G1 can be expressed as:

Wherein, R1 is a first resistor, R2 is a second resistor, R2 is a third resistor, and Rf is a feedback resistor.

In practical applications, by adjusting the above resistors, the relationship between the voltage V _c of the load power supply terminal G1 and the output voltage V _o of the digital-to-analog converter 1221 can be satisfied, where V _c is 7.2+ V _o.

As shown in table 1 below, in a counting period, after the counter 1222 receives a rising edge sent by the first programmable logic controller 22, i.e. the trigger signal, it counts a number of times, i.e. the counting result is increased by 1, the digital signals received by 8 input terminals of the digital-to-analog converter 1221 correspond to the counting result of the counter 1222, the digital-to-analog converter 1221 performs digital-to-analog conversion according to the received digital signals, and obtains an analog voltage, as shown in fig. 2, as the counting result increases, the value of the analog voltage gradually increases, and as the analog voltage increases by 0.16 every time the counting is performed, in fig. 2, the rectangular wave is the trigger signal, and the step wave is the analog voltage gradually increases, since the relationship between the voltage V _c of the load supply terminal G1 and the output voltage V _o of the digital-to-analog converter 1221, V _c is 7.2+ V _o, so that the voltage V _c, i.e. V _out of the load supply terminal G1, starts to step-up from 7.2V, and this process can also be seen from table 1, until the sixteenth clock signal.

TABLE 1 data correspondence table

In table 1 above, the last column is an actual voltage value obtained by measuring the voltage at the load power supply terminal G1, and the difference between the actual voltage value and the theoretical voltage value is small and can be ignored.

It can be understood that when the power supply apparatus in the present application is applied to a preamplifier of a magnetic resonance imaging system, the load power supply terminal G1 is a power supply input terminal of the preamplifier of the magnetic resonance imaging system.

The present application further provides a magnetic resonance imaging system comprising a preamplifier and power supply means for powering said preamplifier. The power supply device is the power supply device.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.