Power supply and medical system

A power supply can be driven in parallel in a master-slave arrangement using fewer wires. Each power supply includes: input terminals; output terminals; a master terminal; a slave terminal; a switching power supply that switches an inputted voltage and executes one of a constant-voltage operation that outputs a DC voltage of a target voltage value and a constant-current operation that outputs a DC current of a target current value; an indicative voltage generator that generates a current detection signal indicating the current outputted from the output terminals, superimposes a bias voltage (>a threshold voltage), and outputs to the master terminal; and an operation switcher that compares a voltage applied to the slave terminal and the threshold voltage and outputs, based on the result, a control signal for switching to the constant-voltage operation or the constant-current operation, to the switching power supply.

FIELD OF THE INVENTION

The present invention relates to a power supply capable of operating in a master-slave arrangement when used in numbers, and to a medical system equipped with this power supply.

DESCRIPTION OF THE RELATED ART

As one example of this type of power supply, a power supply that has already been developed by the present applicant is known (see “RKE SERIES” introduced on the homepage of TDK Lambda Co., Ltd. at the Internet URL (found on Mar. 7, 2019)

“https://product.tdk.com/info/ja/catalog/datasheets/rke_j.pdf”). As depicted inFIG. 7, this power supply is equipped with alternating current (AC) input terminals (these AC input terminals are not depicted), a + direct current (DC) output terminal, a −DC output terminal, a common signal terminal −COM, a reference output voltage terminal REF, a variable output voltage terminal RV, and a current balance terminal CB. As a configuration where + and − DC output terminals of a plurality of these power supplies are connected to a common load and driven to operate in parallel, it becomes possible to select one of a configuration (or “first configuration”) capable of equalizing the output current of each power supply by connecting the respective current balance terminals CB and the respective common signal terminals −COM of the power supplies together, and a configuration (or “second configuration” or so-called “master-slave parallel driving”) where, in addition to the connections in the first configuration, the reference output voltage terminal REF of one power supply selected as a master out of the power supplies is connected to the variable output voltage terminals RV of all of the power supplies (including the master) so that the output voltage of  other power supplies (or “slaves”) can be made to follow the output voltage of the master by merely changing the output voltage of the master while equalizing the output currents of the respective power supplies.

SUMMARY OF THE INVENTION

However, when a plurality of the power supplies described above are driven in parallel in a master-slave arrangement to supply power to a single load, as described above it is necessary to connect the respective current balance terminals CB together and the respective common signal terminals −COM of the power supplies together, and to also connect the reference output voltage terminal REF of the power supply as the master to the variable output voltage terminals RV of all the power supplies. Since the number of wires is large, there is the problem to be solved of the burden of wiring the power supplies together.

The present invention was conceived in view of the problem described above and has a principal object of providing a power supply that enables a plurality of power supplies to be driven in parallel in a master-slave arrangement with fewer wires and a medical system equipped with this power supply.

To achieve the stated object, a power supply according to the present invention comprises: a pair of input terminals into which an input voltage is inputted; a pair of output terminals; a master terminal; a slave terminal; a switching power supply that includes a switch that switches a direct current (DC) input voltage, which has been generated based on the input voltage, and is configured to switch between and execute a constant-voltage operation that generates a DC voltage of a set target voltage value base on the input voltage and outputs to the output terminals and a constant-current  operation that generates a DC current of a set target current value based on the input voltage and outputs to the output terminals; an indicative voltage generator that generates a current indicating voltage whose voltage value changes in proportion to a current value of a current outputted from the switching power supply to a periphery via the output terminals, superimposes a bias voltage with a predetermined voltage value, which exceeds a predetermined voltage threshold value, onto the current indicating voltage, and outputs from the master terminal to the periphery as an operation indicating voltage; and an operation switcher that compares an applied voltage value of an applied voltage, which is applied from the periphery to the slave terminal, and the threshold voltage value, outputs a control signal for switching to the constant-voltage operation to the switching power supply when the applied voltage value is below the threshold voltage value, and outputs a control signal for switching to the constant-current operation, which sets a current value in proportion to a difference in voltage value between the applied voltage value and the bias voltage as the set target current value, to the switching power supply when the applied voltage value is above the threshold voltage value.

In this way, with this power supply, it is possible to connect a plurality of power supplies in a master-slave arrangement to construct a power supply system. As the connecting tasks (wiring tasks) when power is to be supplied (outputted) to a common load, it is sufficient, as connection tasks aside from a task of connecting the input terminals of the power supplies to an input line and a task of connecting the output terminals of the power supplies to the load (that is, as connection tasks required to produce the master-slave arrangement), to merely perform a task of connecting the master terminal of the power supply set as the master to the slave terminals of the remaining power supplies with  wires. Therefore, it is possible to complete the connecting tasks to produce the master-slave arrangement with fewer wires.

In the power supply according to the present invention, in an execution state of the constant-current operation, the switching power supply calculates a control variable by applying a control variable, which reflects fluctuations in a voltage of the output terminals, to a control variable that reflects a difference between a present current value of the DC current and the set target current value, and controls an on-duty of the switch based on the calculated control variable.

Accordingly, with the power supply described above, when the power supply is operating as a slave, the switching power supply is capable of starting an operation based on a control variable that reflects fluctuations in the voltage of the output terminals (that is, an operation that increases or decreases the current value of the DC current of that power supply in keeping with the fluctuations in the present voltage value of the DC voltage of that power supply) ahead of an operation based on a control variable that reflects a difference between the present current value of the DC current and the set target current value (an operation that increases or decreases the current value of the DC current of that power supply in concert with a master power supply). By doing so, even when the present voltage value of the DC output voltage has suddenly fluctuated, a power supply that operates as a slave is capable of increasing and decreasing the current value of the DC current outputted from that power supply so as to favorably follow the sudden fluctuations, which means that the plurality of power supplies connected in the master-slave arrangement are capable as a whole of restoring the present voltage value of the DC voltage to the target voltage value in a short time and maintaining the set target voltage value thereafter.

A medical system according to the present invention comprises: a plurality of one of the power supplies described above that each further include: a primary-side rectifier/smoother that is connected via a pair of power supply lines to the pair of input terminals and rectifies and smoothes an alternating current (AC) input voltage, which is inputted as the input voltage via the pair of input terminals and the pair of power supply lines, from an input line connected to the pair of input terminals, and outputs as the DC input voltage to the switching power supply; and a fuse or a breaker interposed on the pair of power supply lines, and are each configured with the switching power supply as an isolation converter that includes an isolation transformer, wherein the output terminals of the plurality of power supplies are connected in parallel and one power supply out of the plurality of power supplies as set as a master power supply and the master terminal of the master power supply is connected to the slave terminals of every remaining power supply; and a medical appliance that is connected to the output terminals that are connected in parallel and operates based on the DC voltage from the power supplies.

Accordingly, with the medical system described above, by using a configuration in which each power supply includes an isolation transformer with reinforced insulation and that further includes a fuse or a breaker on the pair of power supply lines, it is possible to meet medical standards in units of the power supplies alone. This means that it is possible to realize a configuration that is capable of achieving medical standards without interposing an isolation transformer or a fuse (or a breaker) outside each power supply (in more detail, on the input line connected to each power supply). Also, according to the medical system, by including the power supplies, it is possible to achieve the same effects as when the power supply system is  constructed by connecting the plurality of power supplies described above in the master-slave arrangement.

A medical system according to the present invention comprises: a plurality of one of the power supplies described above that each further include a primary-side rectifier/smoother that is connected via a pair of power supply lines to the pair of input terminals and rectifies and smoothes an AC input voltage, which is inputted as the input voltage via the pair of input terminals and the pair of power supply lines, from an input line connected to the pair of input terminals, and outputs as the DC input voltage to the switching power supply, and are each configured with the switching power supply as an isolation converter that includes an isolation transformer, wherein the output terminals of the pluralit of power supplies are connected in parallel and one power supply out of the plurality of power supplies is set as a master power supply and the master terminal of the master power supply is connected to the slave terminals of every remaining power supply; a fuse or a breaker interposed on the input line; and a medical appliance that is connected to the output terminals that are connected in parallel and operates based on the DC voltage from the power supplies.

According to the medical system, where each power supply includes the isolation transformer that has reinforced insulation, it is possible to realize a configuration capable of meeting medical standards by merely interposing the fuse (or the breaker) outside each power supply (in more detail, on the input lines (the L-phase line and N-phase line) connected to each power supply). Also, according to the medical system, by including the power supplies, it is possible to achieve the same effects as when the power supply system is constructed by connecting the plurality of power supplies described above in the master-slave arrangement.

A medical system according to the present invention comprises: a plurality of one of the power supplies described above that each further include: a primary-side rectifier/smoother that is connected via a pair of power supply lines to the pair of input terminals and rectifies and smoothes an AC input voltage, which is inputted as the input voltage via the pair of input terminals and the pair of power supply lines, from an input line connected to the pair of input terminals, and outputs as the DC input voltage to the switching power supply; and a first fuse or a first breaker interposed on one power supply line out of the pair of power supply lines, and are each configured with the switching power supply as an isolation converter that includes an isolation transformer, wherein the output terminals of the plurality of power supplies are connected in parallel and one power supply out of the plurality of power supplies is set as a master power supply and the master terminal of the master power supply is connected to the slave terminals of every remaining power supply; a second fuse or a second breaker interposed on the input line connected via the input terminal to another power supply line out of the pair of power supply lines; and a medical appliance that is connected to the output terminal s that are connected in parallel and operates based on the DC voltage from the power supplies.

According to the medical system, where each power supply includes the isolation transformer that has reinforced insulation, since each power supply internally further includes the first fuse or the first breaker interposed on one power supply line, by merely interposing the second fuse (or the second breaker) outside each power supply (in more detail, on the input line connected to the other power supply line out of the input lines connected to each power supply), it is possible to realize a configuration capable of meeting medical standards. Also, according to the medical system, by including the power supplies described above, it is possible to  achieve the same effects as when the power supply system is constructed by connecting the plurality of power supplies described above in the master-slave arrangement.

In this way, according to the present invention, it is possible to connect a plurality of power supplies in a master-slave arrangement to construct a power supply system. As the connecting tasks required to produce the master-slave arrangement out of the connecting tasks (wiring tasks) when power is to be supplied (outputted) to a common load, it is sufficient to merely perform a task of connecting the master terminal of the power supply set as the master to the slave terminals of the remaining power supplies with wires. Therefore, it is possible to complete the connecting tasks to produce the master-slave arrangement with fewer wires.

It should be noted that the disclosure of the present invention relates to the contents of Japanese Patent Application No. 2019-055905 that was filed on Mar. 25, 2019, the entire contents of which are herein incorporated by reference.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of a power supply and a medical system will now be described with reference to the attached drawings.

First, the configuration of a power supply1as an example of a power supply according to the present invention will be described with reference toFIG. 1. As one example, the power supply1includes a pair of input terminals2aand2b,a primary-side rectifier/smoother3, a pair of output terminals4aand4b,a master terminal5(indicated as “MST” in the drawing), a slave terminal6(indicated as “SLV” in the drawing), a switching power supply7, an indicative voltage generator8, and an operation switcher9. The power supply1also includes a common signal terminal10(indicated as “−COM” inFIG. 1) connected to a part (the ground G for the indicative voltage generator8, the operation switcher9, and the like) that is a reference potential for an  operation indicating voltage vent, described later, outputted from the master terminal5and an applied voltage Vslv, described later, applied to the slave terminal6.

The pair of input terminals2aand2bare connected to an input line (not illustrated) outside the power supply1. An AC input voltage Vac is inputted into this pair of input terminals2aand2bas an input voltage that is being supplied to the input line. The primary-side rectifier/smoother3is connected to the pair of input terminals2aand2bvia a pair of power supply lines11and12, rectifies and smoothes the AC input voltage Vac inputted via the pair of input terminals2aand2band the pair of power supply lines11and12, and outputs a DC input voltage Vi.

The switching power supply7includes, as one example, a converter21and a controller22. In more detail, the converter21includes, as one example, a switch31with one or two or more switching elements (switches)31a,an isolation transformer32with a primary winding32aand a secondary winding32b,and a secondary-side rectifier/smoother33and is configured as an isolation converter.

Although not illustrated, the switch31is configured using any known circuit configuration, such as a single-ended forward configuration, a push-pull configuration, a half-bridge configuration, and a full-bridge configuration, and includes an appropriate number of switching elements31afor the selected circuit configuration. Due to the switching elements31abeing driven by a drive signal Sd outputted from the controller22, the switch31intermittently applies the DC input voltage Vi to the primary winding32aof the isolation transformer32(in more detail, by performing on-off operations with an on-duty set by the pulse width of the drive signal Sd).

The isolation transformer32generates an induced voltage in the secondary winding32bwhen the DC input voltage Vi is intermittently applied by the switch31to the primary winding32a. The secondary-side rectifier/smoother33rectifies and smoothes the induced voltage to convert to a DC voltage (DC output voltage) Vo, and outputs the voltage across the pair of output terminals4aand4bvia a pair of output lines13and14.

The converter21includes a voltage detector34that detects the DC output voltage Vo and outputs a voltage detection signal Svo whose voltage value changes in proportion to the voltage value of the DC output voltage Vo and a current detector35that detects an output current (DC current) Io flowing on the pair of output lines13and14and outputs a current detection signal Sio whose voltage value changes in proportion to the current value of the DC current Io.

The controller22generates and outputs the drive signal Sd for the switch31for controlling the on-duty of the switching elements31a,based on the voltage detection signal Svo and the current detection signal Sio outputted from the converter21, a reference voltage Vvr indicating a target voltage value Vtg for the DC output voltage Vo, a reference voltage Vir indicating a target current value Itg for the DC current Io, and a control signal Smd (a signal indicating constant-voltage operation or constant-current operation) outputted from the operation switcher9. The reference voltage Vir is calculated by the controller22subtracting a bias voltage Vb (with a voltage value Vb1), described later, from an applied voltage Vslv (with a voltage value Vslv1) applied from the periphery to the slave terminal6as described later, and has a voltage value of (Vslv1−Vb1).

As one example, as depicted inFIG. 2, the controller22includes a first error calculator41, a second error calculator42, a constant voltage calculator43, a first constant current calculator44, a second constant current calculator45, an adder46, and a drive signal generator47.

In the controller22, the first error calculator41calculates a difference between the voltage value (or “present voltage value”) of the DC output voltage Vo indicated by the voltage detection signal Svo and the target voltage value Vtg indicated by the reference voltage Vvr, and outputs a first error signal Ver1indicating this difference. The second error calculator42calculates a difference between the current value (the present current value) of the DC current Io indicated by the current detection signal Sio and the target current value Itg indicated by the reference voltage Vir, and outputs a second error signal Ver2indicating this difference.

As one example in the present embodiment, the constant voltage calculator43is composed of a PID (Proportional-Integral-Differential) calculator, inputs the first error signal Ver1, performs a PID operation on the first error signal Ver1, and outputs a control variable (or “constant-voltage control variable”) Apv for a constant-voltage operation (that is, for when a constant-voltage operation is being executed).

As one example in the present embodiment, the first constant current calculator44is composed of a PI (Proportional-Integral) calculator, inputs the second error signal Ver2, performs a PI calculation on the second error signal Ver2, and outputs a main control variable (or “first constant-current control variable”) Api1for a constant-current operation. As one example in the present embodiment, the second constant current calculator45is  composed of a PD (Proportional-Differential) calculator, inputs the first error signal Ver1, performs a PD calculation on the first error signal Ver1, and outputs a sub control variable (or “second constant-current control variable”) Api2for a constant-current operation. The adder46functions together with the first constant current calculator44and the second constant current calculator45to form a constant current calculator as a whole, adds the main control variable Api1and the sub control variable Api2, and outputs a final control variable (constant current control variable) Api for a constant-current operation.

In other words, the first constant current calculator44, the second constant current calculator45, and the adder46calculate and output the control variable (the constant current control variable) Api produced by applying (adding) a control variable (the sub control variable Api2) that reflects fluctuations (that is, the difference between the voltage value of the DC output voltage Vo and the target voltage value Vtg) in the voltage across the output. terminals4aand4b(that is, the DC output voltage Vo) to the control variable (the main control variable Api1) that reflects the difference between the present current value of the DC current Io and the target current value Itg.

The drive signal generator47inputs the constant-voltage control variable Apv, the constant-current control variable Api, and the control signal Smd, and generates and outputs the drive signal Sd for controlling the on-duty of the switching elements31afor the switch31based on the control variable (the constant-voltage control variable Apv during a constant-voltage operation and the constant-current control variable Api during a constant-current operation) corresponding to the operation (constant-voltage operation or constant-current operation) indicated by the control signal Smd.

With the configuration described above, when the control signal Smd outputted from the operation switcher9indicates a constant-voltage operation, the controller22outputs the drive signal Sd generated based on the constant-voltage control variable Apv to the converter21and controls the on-duty of the switching elements31a, thereby the switching power supply7constructed of the converter21and the controller22executes the constant-voltage operation that sets the present voltage value of the DC output voltage Vo at the target voltage value Vtg. Also, when the control signal Smd outputted from the operation switcher9indicates a constant-current operation, the controller22outputs the drive signal Sd generated based on the constant-current control variable Api to the converter21and controls the on-duty of the switching elements31a, thereby the switching power supply7executes the constant-current operation that sets the present current value of the DC current Io at the target current value Itg.

The indicative voltage generator8generates a current indicating voltage whose voltage value changes in proportion to the current value of the DC current IO outputted from the switching power supply unit7via the output terminals4aand4bto the periphery. In the present embodiment, as described above, since the current detection signal Sio outputted from the switching power supply7is a voltage signal whose voltage value (hereinafter, referred to as the “voltage value Vsio” for ease of explanation) changes in proportion to the current value of the DC current Io, the indicative voltage generator8uses the current detection signal Sio as this current indicating voltage. The indicative voltage generator8also generates a bias voltage Vb of a predetermined voltage value Vb1which exceeds a predetermined threshold voltage value Vth (that is, Vb1>Vth>0). The indicative voltage generator8generates the operation indicating voltage Vcnt  by superimposing the bias voltage Vb (with the voltage value Vb1) on the current detection signal Sio (with the voltage value Vsio) as the current indicating voltage. By doing so, the voltage value of the operation indicating voltage Vcnt is set to (Vb1+Vsio).

The indicative voltage generator8outputs the operation indicating voltage Vcnt from the master terminal5to the periphery. With the power supply1according to the present embodiment, when a plurality of power supplies are connected in a master-slave arrangement, as described later, the master terminal5of one power supply1operated as a master is connected to the slave terminals6of all other power supplies1operated as slaves. This means that the operation indicating voltage Vcnt is applied as the applied voltage Vslv to the slave terminals6of all the other power supplies1as slaves. In addition, the power supply1is configured so that when the master terminal5of another power supply1is not connected to the slave terminal6, the voltage of the slave terminal6is set at a voltage value that is below the threshold voltage value Vth (for example, zero volts).

The operation switcher9compares the applied voltage value Vslv1of the applied voltage Vslv that is applied from the periphery to the slave terminal with the threshold voltage value Vth, and when the applied voltage value Vslv1is equal to or below the threshold voltage value Vth (as described above, when the master terminal5of another power supply1is not connected to the slave terminal6, that is, when the power supply1is a master), outputs a control signal Smd for indicating a constant-voltage operation (that is, switching to a constant-voltage operation) to (the controller22of) the switching power supply7. On the other hand, when the applied voltage value Vslv1is above the threshold voltage value Vth (as described above, when the master terminal5of another power supply1is connected to the slave terminal6, that is, when the power supply1is a slave), the operation switcher9outputs a control signal Smd for indicating a constant-current operation (that is, switching to a constant-current operation) to (the controller22of) the switching power supply7.

Next, as depicted inFIG. 3, an example of a power supply system PSS that has a plurality of the power supplies1(in the present embodiment, three power supplies11,12, and13) connected in parallel in a master-slave arrangement to a single load LD to supply power will be used to describe the operation of the power supplies11,12, and13(hereinafter collectively referred to as the “power supplies1” when no distinction is made between them).

In the power supply system PSS, the output terminals4aand4bof the power supplies11,12, and13are connected in parallel, one (the power supply11) out of the power supplies11,12and13is set as the master power supply, and the master terminal5of the master power supply (the power supply11) is connected by wires to the slave terminals6of all of the remaining power supplies12and13(the slave power supplies). Note that the slave terminal6of the power supply11and the master terminals5of the power supplies12and13are left unconnected. The common signal terminals10of the power supplies11,12and13are connected to each other by wires. By doing so, the ground G of the power supplies11,12, and13is set at the same potential. Note that although not illustrated, in place of the common signal terminal10, when the low potential-side output terminal4bout of the output terminals4aand4bis used as the ground of the indicative voltage generator8, the operation switcher9, and the like, it is possible to omit the connecting of the common signal terminals10. The input terminals2aand2bof the power supplies11,12and13are connected in parallel and the AC input voltage Vac is inputted from a shared input line. It is also assumed that the reference  voltages Vvr of the power supplies11,12, and13(that is, voltages indicating the target voltage value Vtg for the DC output voltage Vo) are all set at the same voltage. The load LD is an electronic appliance (for example, a medical appliance) or the like that operates based on power from the power supplies11,12, and13(that is, power calculated from the DC output voltage Vo and a total current (3×Io) for the DC currents Io from the power supplies11,12, and13).

When the AC input voltage Vac is inputted from the input terminals2aand2b,the primary-side rectifier/smoother3of each of the power supplies11,12, and13rectifies and smoothes the AC input voltage Vac and outputs the DC input voltage Vi to the switching power supply7.

Here, at the power supply11that functions as the master, since the slave terminal6is unconnected and no voltage is applied from the periphery, the applied voltage Vslv (with the voltage value Vslv1) is a voltage value (in the present embodiment, zero volts) that is below the threshold voltage value Vth. The operation switcher9compares the applied voltage value Vslv1(zero volts) of the applied voltage Vslv with the threshold voltage value Vth (>0) and since the applied voltage value Vslv1is equal to or below the threshold voltage value Vth, outputs a control signal Smd for indicating the constant-voltage operation to the switching power supply7.

Since the control signal Smd outputted from the operation switcher9indicates the constant-voltage operation, the controller22of the switching power supply7outputs a drive signal Sd generated based on the constant-voltage control variable Apv to the converter21and controls the on-duty of the switching elements31ato execute a constant-voltage operation that sets the present  voltage value of the DC output voltage Vo at the target voltage value Vtg. In a constant-voltage operation, when the present voltage value of the DC output voltage Vo falls below the target voltage value Vtg due for example to fluctuations in the load LD, the switching power supply7executes control that increases the on-duty of the switching elements31ato increase the current value of the DC current Io and restore the present voltage value of the DC output voltage Vo to the target voltage value Vtg. On the other hand, when the present voltage value of the DC output voltage Vo exceeds the target voltage value Vtg, the switching power supply7executes control that decreases the on-duty of the switching elements31ato decrease the current value of the DC current Io and restore the present voltage value of the DC output voltage Vo to the target voltage value Vtg.

The indicative voltage generator8uses the current detection signal Sio (that is, a signal whose voltage value changes in proportion to the current value of the DC current Io) outputted from the converter21of the switching power supply7as the current indicating voltage, and superimposes the bias voltage Vb (with a voltage value Vb1) on the current detection signal Sio (with the voltage value Vsio) to generate the operation indicating voltage Vcnt (with the voltage value Vb1+Vsio) that is outputted to the master terminal5. By doing so, the operation indicating voltage Vcnt (with the voltage value Vb1+Vsio) is applied to the slave terminals6of the other power supplies12and13connected by wiring to the master terminal5.

At the other power supplies12and13the operation indicating voltage Vcnt (with the voltage value Vb1+Vsio) is applied to the slave terminals6as the applied voltage Vslv (with the voltage value Vslv1=Vb1+Vsio). Here, since the voltage value Vb1of the bias voltage Vb exceeds the threshold voltage value Vth,  the applied voltage Vslv also has a voltage value that exceeds the threshold voltage value Vth. The operation switcher9compares the applied voltage value Vslv1of the applied voltage Vslv and the threshold voltage value Vth and since the applied voltage value Vslv1exceeds the threshold voltage value Vth, outputs the control signal Smd for indicating the constant-current operation to the switching power supply.

Since the control signal Smd outputted from the operation switcher9indicates the constant-current operation, the controller22of the switching power supply7outputs a drive signal Sd generated based on the constant-current control variable Api to the converter21to control the on-duty of the switching elements31aand thereby execute a constant-current operation that sets the present current value of the DC current Io at the target current value Itg.

As described above, the constant-current control variable Api is a control variable calculated by applying (adding) a control variable (the sub control variable Api2) that reflects fluctuations (that is, the difference between the voltage value of the DC output voltage Vo and the target voltage value Vtg) in the DC output voltage Vo to a control variable (the main control variable Api1) that reflects the difference between the present current value of the DC current to and the target current value Itg.

Here, in a normal state where the voltage value (or “present voltage value”) of the DC output voltage Vo outputted from the power supplies11,12and13connected in parallel to the load LD is being kept at the target voltage value Vtg, the first error signal Ver1outputted from the first error calculator41is zero and for this reason, the sub control variable Api2outputted by the second constant current calculator45is also zero. Accordingly,  the constant-current control variable Api is a control variable (the main control variable Api1) in keeping with only the difference between the present current value of the DC current Io and the target current value Itg.

Since the main control variable Api1is a control variable calculated and outputted by the first constant current calculator44based on the second error signal Ver2outputted from the second error calculator42(that is, the difference between the current value (the present current value) of the DC current Io indicated by the current detection signal Sio and the target current value Itg indicated by the reference voltage Vir), the main control variable Api1is a control variable for setting the current value (the present current value) of the DC current Io at the target current value Itg indicated by the reference voltage Vir. Since the reference voltage Vir is a voltage calculated by subtracting the bias voltage Vb (with the voltage value Vb1) from the applied voltage Vslv (with the voltage value Vslv1) applied to the slave terminal6and the applied voltage Vslv (with the voltage value Vslv1) is the operation indicating voltage Vcnt (with the voltage value Vb1+Vsio), the voltage value of the reference voltage Vir the voltage value Vsio, that is, a voltage value that indicates the present current value of the DC current Io at the power supply11.

By doing so, during a normal state where the voltage value (the present voltage value) of the DC output voltage Vo outputted from the power supplies11,12, and13is stable at the target voltage value Vtg, at the power supplies12and13, the controller22of the switching power supply7outputs a drive signal Sd generated based on the constant-current control variable Api composed of only the main control variable Api1to the converter21to control the on-duty of the switching elements31aand thereby execute a constant-current operation where the present current  value of the DC current Io is set at the target current value Itg indicated by the reference voltage Vir (that is, the present current value of the DC current to at the power supply11). Accordingly, the present current values of the DC currents Io outputted from the power supplies12and13are kept equal to the present current value of the DC current Io at the power supply11, so that power with the DC output voltage Vo at the target voltage value Vtg and a DC current (3×Io) whose current value is three times the present current value of the DC current Io at the power supply11is supplied to the load LD.

On the other hand, in a state where the voltage value (the present voltage value) of the DC output voltage Vo outputted from the power supplies11,12, and13has fluctuated from the target voltage value Vtg, the first error signal Ver1outputted from the first error calculator41becomes a voltage value (≠zero volts) in keeping with the difference between the voltage value (the present voltage value) of the DC output voltage Vo and the target voltage value Vtg, and due to this, the sub control variable Api2outputted by the second constant current calculator45also becomes a control variable (≠zero) in keeping with the difference between the voltage value (the present voltage value) of the DC output voltage Vo and the target voltage value Vtg. Accordingly, the constant-current control variable Api is a control variable calculated by adding the sub control variable Api2to a control variable (the main control variable Api1) in keeping with the difference between the present current value of the DC current to and the target current value Itg, that is, a control variable produced by applying (adding) a control variable (the sub control variable Api2) that reflects fluctuations in the DC output voltage Vo (that is, the difference between the voltage value of the DC output voltage Vo and the target voltage value Vtg) to a control variable (the main control variable Api1) that reflects the difference between the present  current value of the DC current Io and the target current value Itg.

As described above, this main control variable Api1is a control variable for setting the current value (the present current value) of the DC current Io at the target current value Itg indicated by the reference voltage Vir (the present current value of the DC current Io at the power supply11). Also, as described above, with the power supply11, the switching power supply7executes a constant-voltage operation, whereby the current value of the DC current Io is increased when the present voltage value of the DC output voltage Vo has fallen below the target voltage value Vtg due for example to a fluctuation in the load LD, or the current value of the DC current Io is decreased when the present voltage value of the DC output voltage Vo has exceeded the target voltage value Vtg due for example to a fluctuation in the load LD, to thereby restore the present voltage value of the DC output voltage Vo to the target voltage value Vt. This means that even with a configuration where the switching power supplies7of the power supplies12and13execute a constant-current operation where the sub control variable Api2is not applied (added) to the main control variable Api1that constructs the constant-current control variable Api (that is, a constant-current operation based on the constant-current control variable Api composed of only the main control variable Api1), since it is possible for the power supplies12and13to operate in concert with the power supply11to increase or decrease the current value of the respective DC currents Io, it is possible for these power supplies to operate in concert with the power supply11and keep the present voltage value of the DC output voltage Vo at the target voltage value Vtg.

However, the power supply1according to the present embodiment uses a configuration where the first error signal Ver1(a signal indicating the difference between the voltage value (the present voltage value) of the DC output voltage Vo and the target voltage value Vtg) from the first error calculator41that is used in the constant-voltage operation is calculated at the second constant current calculator45as the sub control variable (or “second constant-current control variable”) Api2for a constant-current operation and is added (applied) to the main control variable Api1to generate the constant-current control variable Api. Accordingly, at the power supplies12and13, the switching power supplies7are capable of starting an operation based on the sub control variable Api2(that is, an operation that detects fluctuations with respect to the target voltage value Vtg in the present voltage value of the DC output voltage Vo of that power supply1and increases or decreases the current value of the DC current Io of that power supply1in keeping with the detected fluctuations) ahead of an operation based on the main control variable Api1(an operation that increases or decreases the current value of the DC current Io of that power supply1in concert with the power supply11). By doing so, even when the present voltage value of the DC output voltage Vo has suddenly fluctuated, the power supplies12and13are capable of increasing and decreasing the current value of the DC current Io outputted from that power supply1so as to favorably follow the sudden fluctuations, which means that the power supplies11,12, and13as a whole are capable of restoring the present voltage value of the DC output voltage Vo to the target voltage value Vtg in a short time and maintaining the target voltage value Vtg thereafter.

By operating in this way, even when the power value of the power required at the load LD suddenly falls (that is, when the load becomes lighter) or suddenly rises (that is, when the load becomes heavier) from the normal power value, the power supplies11,12, and13that are connected in a master-slave arrangement are  capable as a whole of generating power with a DC output voltage Vo at the target voltage value Vtg and respective DC currents Io whose current value is ⅓ of the current value required by the load LD and supplying (outputting) this power to the load LD.

In this way, with the power supply1, it is possible to connect a plurality of power supplies (in the example described above, the three power supplies11,12, and13) in a master-slave arrangement to construct a power supply system PSS. As the connecting tasks (wiring tasks) when power is to be supplied (outputted) to a common load LD, it is sufficient, as connection tasks aside from a task or connecting the input terminals2aand2bof the power supplies11,12, and13to an input line and a task of connecting the output terminals4aand4bof the power supplies11,12, and13to the load LD (that is, as connection tasks required to produce the master-slave arrangement), to merely perform a task of connecting the common signal terminals10of the power supplies11,12, and13together and a task of connecting the master terminal5of the power supply (the power supply11) set as the master to the slave terminals6of the remaining power supplies12and13(the slave power supplies) with wires.

Accordingly, by using the power supply1, compared to a case where the conventional power supplies described above are connected in a master-slave arrangement to construct a power supply system (where the connecting tasks required to produce a master-slave arrangement include connecting tasks of connecting the current balance terminals CB together and the common signal terminals −COM together for all the power supplies and connecting the reference output voltage terminal REF of the power supply set as the master to the variable output voltage terminals RV of all of the power supplies), it is possible to complete the connecting tasks to produce the master-slave arrangement and thereby construct the  power supply system PSS with fewer wires. This means that according to the power supply1, it is possible to reduce the burden of connecting tasks for constructing the power supply system PSS (that is, it is possible to reduce the time required by connecting tasks).

Also, with the power supply1, when executing a constant-current operation, the switching power supply7calculates the final control variable (the control variable Api) for a constant-current operation by applying (adding) a control variable (the sub control variable Api2) that reflects fluctuations in the voltage (the DC output voltage Vo) at the output terminals4aand4bof that power supply1to a control variable (the main control variable Api1) that reflects the difference between the present current value of the DC current to outputted by that power supply1and the target current value Itg and controls the on-duty of the switching elements31abased on this calculated control variable Api.

This means that with the power supply1, at a power supply1operating as a slave (in the example described above, the power supplies12and13that execute a constant-current operation), the switching power supply7is capable of starting an operation based on the sub control variable Api2(that is, an operation that detects fluctuations with respect to the target voltage value Vtg in the present voltage value of the DC output voltage Vo of that power supply1and increases or decreases the current value of the DC current Io of that power supply1in keeping with the detected fluctuations) ahead of an operation based on the main control variable Api1(an operation that increases or decreases the current value of the DC current Io of an individual power supply1in concert with the power supply11). By doing so, even when the present voltage value of the DC output voltage Vo has suddenly  fluctuated, a power supply1that operates as a slave (the power supplies12and13) is capable of increasing and decreasing the current value of the DC current Io outputted from that power supply1so as to favorably follow the sudden fluctuations, which means that the plurality of power supplies1connected in the master-slave arrangement are capable as a whole of restoring the present voltage value of the DC output voltage Vo to the target voltage value Vtg in a short time and maintaining the target voltage value Vtg thereafter.

Note that when sudden fluctuations do not occur for the load LD, there are cases where a power supply1operating as a slave may use a control variable (the main control variable Api1) that reflects the difference between the present current value of the DC current Io of that power supply1as a slave and the target current value Itg (that is, the present current value of the DC current Io of the power supply1as a master indicated by the voltage value Vsio included in the operation indicating voltage Vcnt applied from the power supply1as the master to the slave terminal6) as the final control variable Api for a constant-current operation. In such cases, in the configuration of the controller22depicted inFIG. 2, the second constant current calculator45and the adder46may be omitted to produce a configuration that sets only the main control variable Api1outputted by the first constant current calculator44as the control variable Api.

In this way, a power supply system with the power supply1that is configured so that a plurality of power supplies1can be connected in parallel in a master-slave arrangement and supply power to a single load LD (in the example described above, the power supply system PSS composed of the three power supplies11,12and13) is capable of being used in a medical system where the load LD is a medical appliance.

A medical system MES1equipped with the power supply system PSS will now be described with reference toFIG. 4for an example configuration equipped with a power supply system PSS composed of the three power supplies11,12, and13as depicted inFIG. 3. Note that it is assumed here that the isolation transformer32of each of the power supplies1(the power supplies11,12, and13inFIG. 4) is sufficiently isolated to meet medical standards (that is, the isolation transformers32have reinforced insulation). It is further assumed that a medical appliance is connected as the load LD and that an FG line for grounding is connected to a housing H of each power supply1. Note also that the controller22, the indicative voltage generator8, and the operation switcher9of each power supply1have been omitted from the drawings and the configuration for connecting the common signal terminals10of the power supplies1together has also been omitted from the drawings.

In this system, each power supply1operates by inputting the AC input voltage Vac as an input voltage supplied across input lines (an L-phase line and an N-phase line) via the pair of input terminals2aand2b.To do so, as described above, the power supply1internally includes the primary-side rectifier/smoother3connected via the pair of power supply lines11and12to the pair of input terminals2aand2b,and is configured so that the primary-side rectifier/smoother3rectifies and smoothes the AC input voltage Vac inputted via the input lines L and N, the pair of input terminals2aand2b,and the pair of power supply lines11and12to generate the DC input voltage Vi, which is outputted to the converter21of the switching power supply7. The power supply1also internally includes a fuse71(or a breaker) that is interposed on the pair of power supply lines11and12.

According to the medical system MES1equipped with the power  supply system PSS (a power supply system composed of a plurality of power supplies1connected in parallel in a master-slave arrangement), each power supply1is equipped with the isolation transformer32that has reinforced insulation and the fuse71as described above and is configured so as to be capable of meeting medical standards by itself. This means that it is possible to realize a configuration capable of meeting medical standards without an isolation transformer and a fuse (or a breaker) being provided outside each power supply1(in more detail, on the input lines (the L-phase line and N-phase line) connected to the power supply1). Also, according to the medical system MES1, by including the power supply system PSS, it is possible to achieve the same effects as when the power supply system PSS is constructed using the power supply1described above.

Also, although in the medical system MES1described above, each power supply1internally includes the fuse71(or the breaker), it is also possible to configure a medical system using power supplies1that do not internally include the fuse71(or the breaker). A medical system MES2that uses this configuration will now be described with reference toFIG. 5. Note that configurations that are the same as the medical system MES1described above have been assigned the same reference numerals and duplicated description is omitted, with the following description instead focusing on configurations that differ to the medical system MES1.

As depicted inFIG. 5, in this medical system MES2, the fuse71(or the breaker) is interposed on the input lines (the L-phase line and the N-phase line) connected to the input terminals2aand2bof each power supply1. With this configuration, the AC input voltage Vac supplied across the input lines (the L-phase line and the N-phase line) is inputted into the input terminals2aand2bof each power supply1via the fuse71(or the breaker) provided for  each power supply1.

According to the medical system MES2equipped with the power supply system PSS (a power supply system constructed by connecting a plurality of power supplies1in parallel in a master-slave arrangement), since each power supply1includes the isolation transformer32that has reinforced insulation as described above, it is possible to realize a configuration capable of meeting medical standards by merely interposing the fuse71(or the breaker) outside each power supply1(in more detail, on the input lines (the L-phase line and N-phase line) connected to each power supply1). Also, according to the medical system MES2, by including the power supply system PSS, it is possible to achieve the same effects as when the power supply system PSS is constructed using the power supply1described above.

Although the medical systems MES1and MES2described above are configured with the fuse71(or the breaker) interposed only one of inside and outside each power supply1, it is also possible to use a configuration where a fuse71(or a breaker) is interposed both inside and outside each power supply1. A medical system MES3that uses this configuration will now be described with reference toFIG. 6. Note that configurations that are the same as the medical systems MES1and MES2described above have been assigned the same reference numerals and duplicated description is omitted, with the following description instead focusing on configurations that differ to the medical systems MES1and MES2.

In the medical system MES3, each power supply1internally includes a fuse711as a first fuse (or a breaker as a first breaker) that is interposed on one power supply line (as one example in the present embodiment, the power supply line12) out of the pair of power supply lines11and12. Additionally, a fuse712as a second fuse (or a breaker as a second breaker) is disposed outside each power supply1in a state where the fuse712is interposed on an input line (in the present embodiment, the L-phase line) connected via an input terminal (in the present embodiment, the input terminal2a) to the other power supply line (as one example in the present embodiment, the power supply line11) out of the pair of power supply lines11and12. Note that although not illustrated, it is also possible to use a configuration where the fuse711as the first fuse (or a breaker as the first breaker) is interposed on the power supply line11and corresponding to this, the fuse712as the second fuse (or a breaker as the second breaker) as interposed on the N-phase line.

According to the medical system MES3equipped with the power supply system PSS (a power supply system constructed by connecting a plurality of power supplies1in parallel in a master-slave arrangement), since each power supply1internally includes the isolation transformer32that has reinforced insulation as described above and the fuse711(or a breaker) interposed on one power supply line (the power supply line11or the power supply line12), by merely interposing the other fuse712(or a breaker) outside each power supply1(in more detail, on the input line (the L-phase line or the N-phase line) connected to the other power supply line out of the input lines (the L-phase line and the N-phase line) connected to each power supply1), it is possible to realize a configuration capable of meeting medical standards. Also, according to the medical system MES3, by including the power supply system PSS, it is possible to achieve the same effects as when the power supply system PSS is constructed of the power supply1described above.