JP2023168161A - Power source and test board - Google Patents

Abstract

To provide a power source and a test board which supply stable electric power to keep a voltage drop within an allowable range even when the current consumption of a load increases rapidly.SOLUTION: A power source 600 is provided with: a switching element 105 connected between a positive potential and a power supply output terminal 102; a control circuit 420 for controlling the switching element so that an output voltage of the power supply output terminal approaches a target voltage; a capacitor 150 connected in parallel with a device under test (DUT) 145 which is a load to the power supply output terminal; and a current source 660 connected in parallel with a capacitor to the power supply output terminal and allowing current to flow from the power supply output terminal regardless of an on/off state of the switching element.SELECTED DRAWING: Figure 6

Description

TECHNICAL FIELD The present invention relates to a device with a power supply and a test board.

A power supply is connected to the load and supplies power to the load. In order to supply stable power supply to the load, the power supply is required to suppress the voltage drop within an allowable range even when the current consumption of the load increases rapidly.

In a first aspect of the present invention, a switching element connected between a positive potential and a power supply output terminal, a control circuit that controls the switching element so as to bring an output voltage of the power supply output terminal close to a target voltage, and a power supply A capacitor is connected in parallel with the load to the output terminal, and a current source is connected in parallel with the capacitor to the power supply output terminal and causes current to flow out from the power supply output terminal regardless of the on/off state of the switching element. Provides a device that includes:

In the above device, the current source may cause current to maintain the switching element in the saturation region to flow out from the power supply output terminal in a state where no current flows through the load.

In any of the above devices, the current source may include a resistor connected between the power supply output terminal and ground potential.

In any of the above devices, the current source may be a constant current source that causes a current of a predetermined magnitude to flow out from the power output terminal.

In any of the above devices, the current source may drain from the power output terminal no more than 10%, or no more than 5% of the maximum current supplied from the power output terminal to the load.

In any of the above devices, the current source may drain a current from the power output terminal that is 0.0275% or more or 0.055% or more of the maximum current that is supplied from the power supply output terminal to the load.

Any of the above devices includes a power supply unit that includes a switching element and a control circuit and outputs power from a power output terminal, and a capacitor and a device under test that is removably connected to the power supply unit. The test board may include a test board having a device mounting section to be mounted.

A second aspect of the present invention includes a switching element connected between a positive potential and a power supply output terminal, and a control circuit that controls the switching element so that the output voltage of the power supply output terminal approaches a target voltage. A device mounting part that is detachably connected to the power supply unit and has a device under test mounted thereon, a capacitor connected in parallel with the device under test to the power output terminal, and a capacitor connected in parallel to the power output terminal with the device under test. To provide a test board including a current source that causes current to flow out from a power output terminal regardless of the on/off state of a switching element.

In the above test board, the current source may cause current to maintain the switching element in the saturation region to flow out from the power output terminal in a state where no current flows through the device under test.

In any of the test boards described above, the current source may include a resistor connected between the power supply output terminal and ground potential.

In any of the above test boards, the current source may be a constant current source that causes a predetermined amount of current to flow out from the power output terminal.

In any of the test boards described above, the current source may drain from the power output terminal no more than 10% or no more than 5% of the maximum current supplied from the power output terminal to the device under test.

In any of the above test boards, the current source may cause a current to flow from the power output terminal that is 0.0275% or more or 0.055% or more of the maximum current supplied from the power output terminal to the device under test.

Note that the above summary of the invention does not list all the features of the invention. Furthermore, subcombinations of these features may also constitute inventions.

The configuration of a device 10 according to a first comparative example is shown. The configuration of a pseudo load circuit 200 used to measure fluctuations in power supply voltage is shown. 7 is a graph showing fluctuations in power supply voltage in the device 10 according to the first comparative example. The configuration of a device 400 according to a second comparative example is shown. 7 is a graph showing fluctuations in power supply voltage in a device 400 according to a second comparative example. The configuration of a device 600 according to this embodiment is shown. It is a graph showing fluctuations in power supply voltage in the device 600 according to the present embodiment. It is a graph showing the relationship between bypass capacitor capacity and voltage drop in the device 600 according to the present embodiment. It is a graph showing the relationship between the magnitude of the resistance used as the current source 660 and the voltage drop in the device 600 according to the present embodiment. It is a graph showing the fluctuation of the power supply voltage when the output voltage of the power supply unit 402 is 3.3V in the device 600 according to the present embodiment. The configuration of a constant current source 1100 as an example of the current source 660 according to this embodiment is shown.

Hereinafter, the present invention will be described through embodiments of the invention, but the following embodiments do not limit the invention according to the claims. Furthermore, not all combinations of features described in the embodiments are essential to the solution of the invention.

FIG. 1 shows the configuration of an apparatus 10 according to a first comparative example. The device 10 is a test device as an example of a device having a power source. The apparatus 10 includes a power supply unit 20, a test board 30, and a test unit 40.

The power supply unit 20 outputs power from the power output terminal 102 . The power supply unit 20 is connected to an upstream power supply such as an AC-DC converter, and outputs an output voltage of a predetermined magnitude from the power supply output terminal 102 using power from the upstream power supply.

Power supply unit 20 includes switching element 105, switching element 110, and control circuit 120. The switching element 105 is a semiconductor switching element such as a MOSFET (metal oxide semiconductor field effect transistor). The switching element 105 has a first main terminal, a second main terminal (for example, a drain and a source), and a control terminal (for example, a gate) that controls the connection state between the first main terminal and the second main terminal. The main terminals of the switching element 105 are connected between the positive potential of a more upstream power supply and the power supply output terminal 102 .

The switching element 110, like the switching element 105, is a semiconductor switching element such as a MOSFET. The main terminals of the switching element 105 are connected between the negative potential (also referred to as "ground potential") of a power supply located further upstream and the power supply output terminal 102 .

Control circuit 120 controls switching element 105 and switching element 110 so that the output voltage of power supply output terminal 102 approaches the target voltage. Control circuit 120 includes a voltage source 125, an operational amplifier 130, and a bias control circuit 135. Voltage source 125 is a constant voltage source that outputs a target voltage.

The operational amplifier 130 outputs a signal according to the difference between the output voltage of the power output terminal 102 fed back from the test board 30 and the target voltage output by the voltage source 125. The operational amplifier 130 may output a signal proportional to the difference obtained by subtracting the output voltage of the power supply output terminal 102 from the target voltage.

Bias control circuit 135 controls switching element 105 and switching element 110 according to a signal from operational amplifier 130. The bias control circuit 135 turns on the switching element 105 (or increases the current flowing between the main terminals of the switching element 105) when the difference obtained by subtracting the output voltage of the power supply output terminal 102 from the target voltage is positive. 110 is turned off (or the current flowing between the main terminals of the switching element 110 is reduced), a current flows from the positive potential to the power supply output terminal 102, and the output voltage of the power supply output terminal 102 is increased. The bias control circuit 135 turns off the switching element 105 (or reduces the current flowing between the main terminals of the switching element 105) when the difference obtained by subtracting the output voltage of the power supply output terminal 102 from the target voltage is negative, and turns off the switching element 110. is turned on (or the current flowing between the main terminals of the switching element 110 is increased), the current flows out from the power supply output terminal 102 to a negative potential, and the output voltage of the power supply output terminal 102 is lowered. Thereby, the control circuit 120 brings the output voltage of the power supply output terminal 102 closer to the target voltage, and brings the output voltage within a predetermined error range from the target voltage.

The test board 30 is detachably connected to the power supply unit 20 and the test unit 40. Note that the test board 30 may be a burn-in board for a burn-in test of a device under test (DUT) 145 mounted on the test board 30, or may be a test board for a functional test of the DUT 145. The test board 30 includes a device mounting section 140 and a capacitor 150.

The device mounting section 140 is, for example, an IC socket or the like, and mounts the DUT 145 thereon and electrically connects each terminal of the DUT 145 to each wiring of the test board 30. DUT 145 is an example of a load that consumes power from the power source. The device mounting section 140 electrically connects the power input terminal of the DUT 145 to the power output terminal 102 via the power wiring of the test board 30. Further, the device mounting section 140 electrically connects one or more signal input/output terminals of the DUT 145 to one or more test terminals 170 via signal wiring of the test board 30.

Capacitor 150 is connected in parallel with DUT 145 to power output terminal 102 . Capacitor 150 is also referred to as a "bypass capacitor." Capacitor 150 is provided closer to DUT 145 than power supply unit 20 . Capacitor 150 supplies accumulated charge to DUT 145 in response to an increase in power consumption of DUT 145. Thereby, the capacitor 150 absorbs instantaneous fluctuations in the power consumption of the DUT 145 and stabilizes the output voltage of the power supply output terminal 102. Switching element 105, switching element 110, and control circuit 120 in power supply unit 20, and capacitor 150 in test board 30 function as a power source that supplies power to DUT 145.

The test unit 40 is detachably connected to the test board 30. The test board 30 has a test circuit 180. Test circuit 180 is electrically connected to signal input/output terminals of DUT 145 via one or more test terminals 170. The test circuit 180 tests the operation of the DUT 145. The test circuit 180 determines the quality of the DUT 145 by supplying a test signal (test signal) to the DUT 145 and determining whether a response signal output by the DUT 145 in response to the test signal matches an expected value. You may do so.

FIG. 2 shows the configuration of a pseudo load circuit 200 used to measure fluctuations in power supply voltage. The pseudo load circuit 200 includes a switching element 210 and a resistor 220 that are electrically connected in series between the power supply output terminal 102 and the ground potential. When a pulse waveform is input to the control terminal, the switching element 210 turns on the main terminals at the rising edge of the pulse waveform, and turns off the main terminals at the falling edge of the pulse waveform. When the switching element 210 is turned on, the resistor 220 causes a pulse current having a magnitude equal to the voltage at the power output terminal 102 divided by the resistance value of the resistor 220 to flow.

FIG. 3 is a graph showing fluctuations in power supply voltage in the device 10 according to the first comparative example. In the graph of this figure, the horizontal axis represents the passage of time, and the vertical axis represents the power supply voltage (output voltage of the power supply output terminal 102). The graph in this figure shows simulation results of power supply voltage fluctuations when the pseudo load circuit 200 is used as the load, the load current is 20 A, and the capacitance of the capacitor 150 is 500 μF, 800 μF, and 1000 μF.

In the example shown in the figure, the power supply unit 20 outputs a rated output voltage of 2.7V to the power supply output terminal 102. When the switching element 210 in the pseudo load circuit 200 is turned on at time 5.00 ms, a voltage drop of 585 mV is observed when the capacitance of the capacitor 150 is 500 μF, 526 mV when the capacitance is 800 μF, and 496 mV when the capacitance is 1000 μF. . In this way, when using the power supply having the configuration shown in the power supply unit 20 of FIG. 1, instantaneous voltage drops can be suppressed by increasing the capacity of the capacitor 150.

FIG. 4 shows the configuration of a device 400 according to a second comparative example. Device 400 is a modification of device 10 shown in FIG. Components in the device 400 that are given the same reference numerals as those in the device 10 in FIG. 1 have the same functions and configurations as the corresponding components in the device 10, and therefore descriptions thereof will be omitted below except for the differences.

The device 400 according to the second comparative example includes a power supply unit 402 instead of the power supply unit 20. Power supply unit 402 includes switching element 105 and control circuit 420. Switching element 105 is similar to switching element 105 in FIG. The second comparative example does not include the switching element 110 of FIG. 1. As a result, the power supply unit 402 is turned on and off according to the comparison result between the output voltage of the power output terminal 102 fed back from the test board 30 and the target voltage, and when turned on, the power supply unit 402 is selectively connected to a negative potential (ground potential). ) does not have a switching element that causes current to flow out.

Control circuit 420 controls switching element 105 so that the output voltage of power supply output terminal 102 approaches the target voltage. In the second comparative example, when the output voltage of the power supply output terminal 102 falls below the target voltage, the control circuit 420 turns on the switching element 105 (or increases the current flowing between the main terminals of the switching element 105). , increases the output voltage of the power output terminal 102. On the other hand, when the output voltage of the power supply output terminal 102 becomes higher than the target voltage, the control circuit 420 turns off the switching element 105 and waits for the output voltage of the power supply output terminal 102 to decrease. Thereby, the control circuit 420 brings the output voltage of the power supply output terminal 102 closer to the target voltage, and brings the output voltage within a predetermined error range from the target voltage.

Control circuit 420 includes a voltage source 125 and an operational amplifier 130. Voltage source 125 and operational amplifier 130 are similar to voltage source 125 and operational amplifier 130 of FIG.

FIG. 5 is a graph showing fluctuations in power supply voltage in the device 400 according to the second comparative example. In the graph of this figure, the horizontal axis represents the passage of time, and the vertical axis represents the power supply voltage (output voltage of the power supply output terminal 102). The graph in this figure shows simulation results of fluctuations in power supply voltage when the pseudo load circuit 200 is used as the load, the load current is 20 A, and the capacitance of the capacitor 150 is 500 μF, 800 μF, and 1000 μF.

In the example shown in the figure, the power supply unit 402 outputs a rated output voltage of 3.3V to the power supply output terminal 102. When the switching element 210 in the pseudo load circuit 200 is turned on at time 6.00 ms, a voltage drop of 670 mV is seen when the capacitance of the capacitor 150 is 500 μF, 821 mV when it is 800 μF, and 904 mV when it is 1000 μF. . As described above, when using the power supply having the configuration shown in the power supply unit 402 of FIG. 4, even if the capacity of the capacitor 150 is increased, it may not always be possible to suppress the instantaneous voltage drop.

The power supply shown in the power supply unit 402 of FIG. 4 outputs a discharge current (current flowing from a positive potential to the capacitor 150 and DUT 145 via the switching element 105), but it outputs a sink current (current flowing from the capacitor 150 and DUT 145 to the switching element 110). does not provide a current (toward a negative potential) through the Therefore, when the current consumption of the DUT 145 becomes approximately 0, the switching element 105 may be turned off for a long period of time, and the drain current of the switching element 105 may be 0 A for a long period of time. As a result, the switching element 105 is in a deep cutoff region.

Thereafter, when the current consumption of the DUT 145 increases, the control circuit 420 supplies a gate drive current to the switching element 105 in order to turn the switching element 105 on. At this time, since the control circuit 420 needs to charge the gate-source capacitance of the switching element 105, turn-on of the switching element 105 is delayed during the time required to charge the charge. Further, the control circuit 420 is a feedback circuit that operates according to the feedback of the output voltage of the power supply output terminal 102, and a delay occurs due to a response delay depending on the frequency band, a delay time of the operational amplifier 130, etc. If the current consumption of the DUT 145 suddenly increases from 0, the control circuit 420 will cause the gate-source voltage of the switching element 105 to increase due to factors such as a delay in detecting the initial output voltage fluctuation if the capacitor 150 has a large capacity. is delayed. As a result, it takes time to switch the switching element 105 from the deep cut-off region through the saturation region to the linear region, and the voltage drop may become rather large.

FIG. 6 shows the configuration of a device 600 according to this embodiment. Device 600 is a modification of device 400 shown in FIG. Components in device 600 that are given the same reference numerals as those in device 400 in FIG. 4 have the same functions and configurations as device 400, and therefore explanations will be omitted below except for the differences.

The apparatus 600 includes a power supply unit 402, a test board 602, and a test unit 40. Power supply unit 402 and test unit 40 are similar to apparatus 400 of FIG. The test board 602 has a configuration in which a current source 660 is added to the test board 30 in FIG.

Current source 660 is connected in parallel with capacitor 150 to power output terminal 102 . Current source 660 causes current to flow out from power supply output terminal 102 regardless of the on/off state of switching element 105. Current source 660 is also referred to as a "bleeder resistor," and the current flowing through current source 660 is also referred to as a "bleeder current."

Thereby, the power supply unit 402 controls the switching element 105 to flow a drain current corresponding to the current flowing out from the current source 660 even when the current consumption of the DUT 145 is 0. As a result, the switching element 105 does not enter the deep cut-off region state even when the current consumption of the DUT 145 is zero. Therefore, even if the current consumption of DUT 145 suddenly increases, power supply unit 402 can increase the drain current of switching element 105 in a short time.

The current source 660 may be configured to cause a current that maintains the switching element 105 in the saturation region to flow out from the power output terminal 102 in a state where no current flows through the load such as the DUT 145. Further, the current source 660 may constantly cause the bleeder current (>0) to flow out from the power output terminal 102 regardless of whether the switching element 105 is turned on or off.

FIG. 7 is a graph showing fluctuations in power supply voltage in the device 600 according to this embodiment. In the graph of this figure, the horizontal axis shows the passage of time, and the vertical axis shows the power supply voltage (output voltage of the power supply output terminal 102). In the graph of this figure, a pseudo load circuit 200 is used as a load. In the example shown in the figure, it is assumed that the pseudo load circuit 200 causes a load current of 20 A to flow when the switching element 210 is on. Further, the capacitance of the capacitor 150 is set to 200 μF.

This diagram shows the cases when the current IB flowing through the current source 660 is 0 (“No IB”), when the current IB is small (“IB Small”, IB = 11 mA), and when the current IB is medium (“IB Medium”). , IB=110 mA), and when the current IB is large (“IB large”, IB=1.1 A), simulation results of power supply voltage fluctuation are shown.

In the example shown in the figure, when the current IB is 0, a voltage drop of 1.12V occurs. On the other hand, as the current IB increases from IB small to IB medium to IB large, the voltage drop decreases to 0.35V, 0.29V, and 0.23V.

FIG. 8 is a graph showing the relationship between bypass capacitor capacity and voltage drop in the device 600 according to this embodiment. In the graph of this figure, the horizontal axis is the capacitance of the capacitor 150 (capacitance of the bypass capacitor), and the vertical axis is the voltage drop in the output voltage of the power supply output terminal 102. The graph in this figure shows the power supply with the configuration shown in Figure 1 (also indicated as "power supply A"), the power supply with the configuration shown in Figure 4 (also indicated as "power supply B"), and the current The simulation results of the voltage drop when the load current is 10A and 20A are shown for each of the three types of power supplies, including the power supply with a power supply of .1A.

As shown in this graph, in the case of power supply B, increasing the capacitance of capacitor 150 increases the voltage drop. However, in the power supply B in which the current source 660 is added to the test board 602 side, the voltage drop can be made smaller than in the power supply A.

FIG. 9 is a graph showing the relationship between the magnitude of the resistance used as the current source 660 and the voltage drop in the device 600 according to this embodiment. In the example shown in the figure, current source 660 has a configuration including a resistor connected between power output terminal 102 and ground potential. The current source 660 may be configured only with such a bleeder resistor, and in this case, the current source 660 flows a bleeder current having a magnitude obtained by dividing the output voltage of the power supply output terminal 102 by the resistance value of the bleeder resistor. In the graph of this figure, a pseudo load circuit 200 is used as a load. In the example shown in the figure, it is assumed that the pseudo load circuit 200 causes a load current of 20 A to flow when the switching element 210 is on.

This figure shows simulation results of voltage drops when the capacitance of the capacitor 150 is 200 μF, 300 μF, 400 μF, and 500 μF. In this figure, the output voltage rating is 3.3V, so when the bleeder resistances are 3Ω, 30Ω, and 300Ω, the bleeder currents are 1.1A, 110mA, and 11mA. As shown in this figure, the device 600 can effectively reduce the voltage drop in a range where the bleeder resistance is 300Ω or more compared to a range where the bleeder resistance is less than 300Ω. In the device 600, when the size of the bleeder resistance is in the range of 300Ω or more, the power supply fluctuation characteristics are not significantly improved even if the resistance value is decreased and the bleeder current is increased. Therefore, the current source 660 may be configured to cause a current of 0.055% (11 mA/20A) or more or 0.0275% or more of the maximum current supplied from the power output terminal 102 to the DUT 145 to flow out from the power output terminal 102. .

Further, it is sufficient for the current source 660 to cause a current that is 10% or less of the maximum current supplied from the power output terminal 102 to the DUT 145 to flow out from the power output terminal 102. The current source 660 may cause a current of 5% or less of the maximum current to flow out of the power supply output terminal 102.

FIG. 10 is a graph showing fluctuations in the power supply voltage when the output voltage of the power supply unit 402 is 3.3V in the device 600 according to this embodiment. In the graph of this figure, the horizontal axis represents the passage of time, and the vertical axis represents the power supply voltage (output voltage of the power supply output terminal 102). The graph in this figure shows cases where the pseudo load circuit 200 is used as the load, the load current is 20A, the capacitance of the capacitor 150 is 200μF, and the resistance values of the bleeder resistor used as the current source 660 are 3Ω, 30Ω, and 300Ω. , shows the simulation results of power supply voltage fluctuation. As shown in this figure, when the output voltage of the power supply unit 402 is 3.3V, the voltage drop can be suppressed to within 0.3V by setting the resistance value of the bleeder resistor to about 3Ω.

FIG. 11 shows the configuration of a constant current source 1100 as an example of the current source 660 according to this embodiment. The current source 660 may be a constant current source that causes a predetermined amount of current to flow out from the power output terminal 102, as shown in the figure.

Constant current source 1100 includes a Zener diode 1110, a resistor 1120, a switching element 1130, and a resistor 1140. Zener diode 1110 and resistor 1120 are connected in series between power supply output terminal 102 and ground potential. The Zener diode 1110 has its anode side connected to the ground potential and its cathode side connected to the resistor 1120. The Zener diode 1110 makes the voltage on the cathode side a constant voltage obtained by adding the Zener voltage to the voltage on the anode side. Resistor 1120 absorbs the difference between the output voltage of power supply output terminal 102 and the voltage on the cathode side of Zener diode 1110.

Switching element 1130 and resistor 1140 are connected in series between power supply output terminal 102 and ground potential. The switching element 1130 has a control terminal connected between the resistor 1120 and the Zener diode 1110, and subtracts a gate-source voltage drop predetermined by the characteristics of the switching element 1130 from the constant voltage on the cathode side of the Zener diode 1110. outputs the source voltage. The resistor 1140 passes a constant current having a magnitude equal to the source voltage divided by the resistance value.

According to the device 600 described above, even when using the power supply unit 402 that does not have the switching element 110 that operates complementary to the switching element 105 and causes current to flow out from the power output terminal 102, the voltage drop in the output voltage can be reduced. It is possible to realize a power supply that can sufficiently suppress the In the apparatus 600 that uses such a power source to test the DUT 145, even when the power is turned on to the DUT 145 at the start of a test and a large current of power is instantaneously started to be supplied, the voltage drop in the output voltage can be sufficiently suppressed. It becomes possible to do so.

Such a power supply can be used for purposes other than testing the DUT 145. Even when the device 600 is applied to a purpose other than testing the DUT 145, the device 600 can increase the drain current flowing through the switching element 105 during a short response time in response to a sudden increase in the current consumption of the load. , the voltage drop in the output voltage of the power supply output terminal 102 can be reduced.

Although the present invention has been described above using the embodiments, the technical scope of the present invention is not limited to the range described in the above embodiments. It will be apparent to those skilled in the art that various changes or improvements can be made to the embodiments described above. It is clear from the claims that such modifications or improvements may be included within the technical scope of the present invention.

The order of execution of each process, such as the operation, procedure, step, and stage in the apparatus, system, program, and method shown in the claims, specification, and drawings, is specifically defined as "before" or "before". It should be noted that they can be implemented in any order unless the output of the previous process is used in the subsequent process. Even if the claims, specifications, and operational flows in the drawings are explained using "first," "next," etc. for convenience, this does not mean that it is essential to carry out the operations in this order. It's not a thing.

10 device, 20 power supply unit, 30 test board, 40 test unit, 102 power output terminal, 105 switching element, 110 switching element, 120 control circuit, 125 voltage source, 130 operational amplifier, 135 bias control circuit, 140 device mounting section, 145 DUT, 150 capacitor, 170 test terminal, 180 test circuit, 200 pseudo load circuit, 210 switching element, 220 resistor, 400 device, 402 power supply unit, 420 control circuit, 600 device, 602 test board, 660 current source, 1100 constant current Source, 1110 Zener diode, 1120 Resistor, 1130 Switching element, 1140 Resistor

Claims (8)

a switching element connected between the positive potential and the power output terminal;
a control circuit that controls the switching element so that the output voltage of the power supply output terminal approaches a target voltage;
a capacitor connected in parallel with a load to the power output terminal;
A device comprising: a current source connected in parallel with the capacitor to the power supply output terminal and causing a current to flow out from the power supply output terminal regardless of the on/off state of the switching element. 2. The device according to claim 1, wherein the current source causes a current that maintains the switching element in a saturation region to flow out from the power supply output terminal in a state where no current flows through the load. 3. The apparatus of claim 2, wherein the current source includes a resistor connected between the power supply output terminal and ground potential. 3. The device according to claim 2, wherein the current source is a constant current source that causes a predetermined amount of current to flow out from the power output terminal. 3. The apparatus of claim 2, wherein the current source causes a current to flow out of the power output terminal that is 10% or less of a maximum current supplied from the power output terminal to the load. 3. The apparatus according to claim 2, wherein the current source causes a current that is 0.055% or more of a maximum current supplied from the power output terminal to flow from the power output terminal to the load. a power supply unit that includes the switching element and the control circuit and outputs power from the power output terminal;
The apparatus according to claim 1, further comprising: a test board that is detachably connected to the power supply unit and has a device mounting section on which the capacitor and the device under test serving as the load are mounted. Detachably connected to a power supply unit having a switching element connected between a positive potential and a power output terminal, and a control circuit that controls the switching element so that the output voltage of the power output terminal approaches a target voltage. ,
a device mounting section for mounting the device under test;
a capacitor connected in parallel with the device under test to the power output terminal;
A test board comprising: a current source connected in parallel with the capacitor to the power output terminal and causing a current to flow out from the power output terminal regardless of the on/off state of the switching element.

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