JP2000316275A - Power supply equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable stable power control with high precision, independently of nonlineality of a load and existence of negative resistance which a discharge tube generally has. SOLUTION: A power converter is equipped with a power converting part for controlling output power by pulse width modulation(PWM) for controlling a switching element 3 on the basis of a power command 12 from a DC power source 1, 2. In a power supply equipment which supplies electric power to a load 9 by the power converter, means 11, 19 and means 20, 21 are installed. The means 11, 19 obtain instantaneous power on the output side of the switching element 3, every sampling period from the product of an input voltage and an input current of the power converting part of the power converter, and obtain an integrated value by integrating the instantaneous power. The means 20, 21 turn on the switching element 3 at the initial point of the sampling period, and turn off the element 3 when the integrated value reaches an aimed power value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply device for supplying power to a load such as a laser flash tube or a laser diode at a high speed, and more particularly to a load non-linearity and a negative load generally included in a discharge tube. TECHNICAL FIELD The present invention relates to a power supply device capable of performing stable and high-precision power control irrespective of the presence or absence of a resistance.

[0002]

2. Description of the Related Art Conventionally, a power supply device for supplying power to a load such as a laser flash tube or a laser diode at a high speed has been widely used.

[0003] Hereinafter, as a representative example of this type of power supply device, a technique disclosed in "Patent No. 2658900 [pulse power supply device]" will be described.

FIG. 11 is a block diagram showing an example of a circuit configuration of a conventional pulse power supply device.

In FIG. 11, a capacitor 2 is charged from a charging power source 1 and a switching element (hereinafter, referred to as an IGBT) 3 is turned on and off, so that a power conversion unit including a reactor 4, a diode 5, and a filter capacitor 7 is provided. The output power of a certain step-down chopper circuit is controlled, and power is supplied to a flash tube 9 via a diode 8 for reverse blocking.

[0006] The current of the reactor 4 is detected by a current detector 6 as I, and the voltage of the flash tube 9 is determined by a voltage detector 10.
, V is obtained, and the product of I and V is obtained by the multiplier ₁₁ to obtain the load power V11.

[0007] the power command P ^* 12 and the load power V _11, compared with the hysteresis comparator 13 PW
By outputting the M signal and turning on / off the IGBT 3 via the drive circuit 14, the power supplied to the flash tube 9 is controlled.

A simmer circuit for flowing a simmer current is constituted by the DC power supply 15 and the resistor 16.

FIG. 12 is a diagram showing operation waveforms of the pulse power supply device of FIG.

As shown in FIG. 12, the power command P ^* 12 is controlled by the hysteresis of the hysteresis comparator 13 to turn on and off the IGBT 3 between the widths of + ΔP and −ΔP, so-called delta modulation. The load power is controlled in a so-called manner.

[0011]

However, while the pulse power supply device using the above-described control method has a simple circuit configuration and is easy to control, it has the following problems.

(A) The switching frequency of the IGBT 3 changes. That is, when the load voltage is 1/2 of the voltage of the capacitor 2, the switching frequency of the IGBT 3 is the highest, and as the capacitor 2 discharges and decreases, the IGBT 3
The switching frequency of BT3 decreases. Therefore, I
Since the maximum frequency is limited in order to ensure the reliability of the GBT 3, the inductance of the reactor 4 is relatively large, and the response of power control is slow.

(B) In the range where the switching frequency of the IGBT 3 is lowered, the power response is also slow.

(C) When the switching frequency of the IGBT 3 decreases, the noise of the reactor 4 increases.

(D) Since the ripple power is controlled to be constant, when the switching frequency of the IGBT 3 decreases, it is necessary to design the capacitance of the capacitor 7 to be large to reduce the ripple power, and as a result, the responsiveness is reduced. descend.

(E) By connecting the capacitor 7, if the diode 8 is not connected so that simmer power does not flow into the capacitor 7 from the resistor 16, the capacitor 7
Then, a phenomenon in which no simmer current flows due to the negative resistance characteristic of the flash tube 9 occurs.

An object of the present invention is to perform power control while controlling the switching frequency of the IGBT at a constant level, to omit a filter capacitor and a reverse blocking diode, to provide a load non-linearity and a discharge tube. It is an object of the present invention to provide a power supply device capable of performing power control stably and with high accuracy irrespective of the presence or absence of a negative resistance generally included in the power supply device.

[0018]

In order to achieve the above object, according to the first aspect of the present invention, the output power is controlled by pulse width modulation (PWM) control of a switching element from a DC power supply based on a power command. In a power supply device that supplies power to a load by a power conversion device having a power conversion unit to be controlled, a switching element output side is obtained from a product of an input voltage and an input current of a power conversion unit of the power conversion device at each sampling cycle. And a means for integrating the instantaneous power to obtain an integral value to obtain an integral value, and a means for turning on the switching element at the beginning of the sampling period and turning off the switching element when the integral value reaches the target power value. ing.

Therefore, in the power supply device according to the first aspect of the present invention, the switching element of the power conversion unit of the power conversion device is turned on at the beginning of the sampling period, and the integrated value of the instantaneous power on the switching element output side is set to the target power value. By turning off the switching element when the power reaches the limit, the power supplied to the load can be controlled stably and with high accuracy.

According to the second aspect of the present invention, the first aspect is provided.
In the power supply device of the invention, the power conversion device is constituted by a plurality of power conversion units, and the switching elements of the plurality of power conversion units are sequentially controlled at equal intervals by a sampling cycle.

Therefore, in the power supply apparatus according to the second aspect of the present invention, the switching elements of the plurality of power conversion units are sequentially turned on at equal intervals, whereby the operation can be performed so as to cancel the ripple of the power.

According to a third aspect of the present invention, in the power supply device according to the first aspect of the present invention, the integrated value or the target power value is corrected by adding a dither signal gradually increasing or decreasing in synchronization with the sampling cycle. Means are added.

Therefore, in the power supply device according to the third aspect of the present invention, by adding a dither signal that gradually increases or decreases in synchronization with the sampling period to the integrated value or the target power value, the power integration amount is small. However, the switching element can be turned off in synchronization with the sampling period.

Further, in the invention of claim 4, according to the above-mentioned claim 3,
In the power supply device according to the invention, a dither correction signal proportional to the PWM modulation rate is added to the target power value.

Therefore, in the power supply apparatus according to the fourth aspect of the present invention, the power error due to the dither signal is reduced by adding the dither compensation signal proportional to the PWM modulation rate to the target power value, and the accuracy of power control is reduced. Can be improved.

Further, according to a fifth aspect of the present invention, in the power supply device according to the first aspect of the present invention, an advance means for outputting a target power value by inputting a power command is added.

Therefore, in the power supply apparatus according to the fifth aspect of the present invention, a part of the power conversion section (chopper circuit) of the power conversion apparatus is obtained by advancing the magnitude / phase of the power command to obtain the target power value. High-speed response can be achieved by compensating for the delay caused by the reactor.

[0028] On the other hand, according to the invention of claim 6, a power converter having a power converter for controlling output power by performing pulse width modulation (PWM) control of a switching element from a DC power supply based on a power command, In a power supply device that supplies power to a load, a product of an output voltage and an output current of a power conversion unit of the power conversion device or a product of an input voltage and an input current of the power conversion unit of the power conversion device for each sampling cycle. And a means for turning on the switching element at the beginning of the sampling period and turning off the switching element when the instantaneous power value reaches the target power value.

Therefore, in the power supply device according to the present invention, the switching element of the power conversion unit of the power conversion device is turned on at the beginning of the sampling period, and the output power or the input power of the power conversion unit of the power conversion device is reduced. By turning off the switching element when the instantaneous value reaches the target power value, control of the power supplied to the load can be performed stably and with high accuracy.

[0030] In the invention of claim 7, according to claim 6,
In the power supply device of the invention, the power conversion device is constituted by a plurality of power conversion units, and the switching elements of the plurality of power conversion units are sequentially controlled at equal intervals by a sampling cycle.

Therefore, in the power supply device according to the seventh aspect of the invention, the switching elements of the plurality of power conversion sections are sequentially turned on at equal intervals, whereby the operation can be performed so as to cancel the ripple of power.

Further, according to the invention of claim 8, in the power supply device of the invention of claim 6, the instantaneous power value or the target power value is corrected by adding a dither signal gradually increasing or decreasing in synchronization with the sampling cycle. The means to do it is added.

Therefore, in the power supply apparatus according to the eighth aspect of the present invention, the instantaneous power change rate is low by adding a dither signal that gradually increases or decreases in synchronization with the sampling period to the instantaneous power value or the target power value. In this case, the switching element can be turned off in synchronization with the sampling period.

According to the ninth aspect of the present invention, the above-mentioned eighth aspect is provided.
In the power supply device according to the invention, a dither correction signal proportional to the PWM modulation rate is added to the target power value.

Therefore, in the power supply apparatus according to the ninth aspect of the present invention, the power error due to the dither signal is reduced by adding the dither compensation signal proportional to the PWM modulation rate to the target power value, and the power control accuracy is improved. Can be improved.

According to a tenth aspect of the present invention, in the power supply device according to the first or sixth aspect, a means for turning off the switching element when a current flowing through the switching element reaches a set value or more is added. are doing.

Therefore, in the power supply device according to the tenth aspect of the present invention, the switching element is turned off when the value of the current flowing through the switching element reaches a set value or more, so that the switching element current does not exceed the set value. This can prevent the switching element from being broken.

[0038]

Embodiments of the present invention will be described below in detail with reference to the drawings.

(First Embodiment) FIG. 1 is a block diagram showing an example of a circuit configuration of a power supply device according to the present embodiment. The same parts as those in FIG. The description is omitted, and only different portions are described here.

In FIG. 1, the IGBT 3A, the reactor 4A, the diode 5A,
And a step-down chopper circuit of group A, which is a power conversion unit including the current detector 6A, and a step-down chopper circuit of group B, which is a power conversion unit including the IGBT 3B, the reactor 4B, the diode 5B, and the current detector 6B. Then, a current is supplied to the flash tube 9 as a load.

[0041] and V ₁₀ detects the voltage of the capacitor 2 by the voltage detector 10, the output I _A and V ₁₀ from the current detector 6A
The instantaneous power V _11A is obtained by calculating the product of
The output V _11A from the multiplier 11A integrated and an integrator 19A obtains the integrated value V _19A.

The oscillator 17 outputs a frequency for determining the sampling period, the distributor 18 outputs reset A and reset B signals alternately output, and the integrator 19A is reset by the reset A at the rise of the reset signal.

[0043] outputs the target power value V ₃₀ through the circuit 30 proceeds from the power command P ^* _12, with the above-described integrated value V _19A and the target power value V ₃₀ is compared by the comparator 20A, is input to the flip-flop 21A . Flip-flop 21A
Are reset at the rising edge of the reset A signal and set by the output from the comparator 20A. The output from the flip-flop 21A is supplied to the IGBT via the drive circuit 14A.
3A is PWM-controlled.

[0044] determined by multiplier 11B the product of the output V ₁₀ from the output I _B and the voltage detector 10 from the current detector 6B, the target output which is integrated by the integrator 19B are reset its output a reset B compared with the power value V ₃₀ and a comparator 20B, a flip-flop 2 is reset by the reset B
1B is set, and the IGBT 3B is PWM-controlled by the output from the flip-flop 21B via the drive circuit 14B.

Next, the operation of the power supply apparatus of the present embodiment configured as described above will be described with reference to FIG.

At time t ₀ , when the IGBT 3 is turned on, the current I starts to increase, and the voltage V _D across the diode 5 starts.
Is the voltage V _c of the capacitor 2. Therefore, instantaneous power V _D · I (= V _c · I) is injected into reactor 4 and load 9.

The value ∫V _c obtained by integrating the instantaneous power V _c · I
I, as shown in FIG. _2D , V _D.
I becomes an integrated value, which is the power input to the step-down chopper circuit.

[0048] by comparing the integral value ∫V _c · I and the current command P ^*, at time t ₁ the integral value ∫V _c · I matches the current command P ^* when turning off the switching element 3, diode 5 Becomes zero, and the energy stored in the reactor 4 flows out to the flash tube 9 as a load during the time t _{1 to} t ₂ , and the current decreases from I ₁ to I ₂ .

Assuming that the inductance of the reactor 4 is L,

(Equation 1)

This means that the energy has been released during this time.

The injection energy between time t ₀ and t ₁ is ∫
V _D · I,

(Equation 2)

Is the same as

(Equation 3)

Increases even when the IGBT 3 is turned off.

Although the integration in FIG. 2D may use ΔV _D · I, since V _c is detected for controlling the voltage of the capacitor 2, it is better to use ΔV _c · I. It is economical.

At time t ₂ , the reset signal resets the integrated value ΔV _c · I. The flip-flop (F / F) in FIG. 1 is also reset by the reset signal, and P ^* = ∫V
_{Since the} flip-flop F / F is set at the time of _c · I, the output of the flip-flop (F / F) is as shown in FIG. 2 (f). By switching the IGBT 3 with this signal, the input to the step-down chopper is made. Energy to be controlled.

[0056] At steady state, the energy stored in the reactor 4 at between t ₀ ~t _1, since being released to the load between t ₁ ~t _2, power response is within one cycle. The transient, it is necessary to extra store current change of the flash tube 9 is loaded in the reactor 4, in order to compensate for the lag of the control, power command P ^* 1 by the leading circuit 30 1
By giving the extra amount of change by 2 in advance, a high-speed power control response can be achieved.

In FIG. 1, two sets of the circuit shown in FIG. 2 are incorporated and controlled so as to operate at the timing shown in FIG. 3, that is, sequentially at equal intervals according to the sampling period.

[0058] That is, the reset A reset B are input at equal intervals alternately, the current I _A and I _B is to have a 180 degree phase difference, the flip-flop 21A, 21B is I
GBT3A, by switching 3B alternately, as shown in FIG. 3, when the duty is 50% of the switching, the load current I _A + I _B is extremely small wave ripple. When the duty is not 50%, the ripple slightly increases.

Although FIG. 1 shows a case where the power converter is constituted by two sets of chopper circuits, the present invention is not limited to this.
Even if the power converter is composed of more than one set of chopper circuits, the ripple becomes zero at a specific duty on the same principle.

Furthermore, a single set of chopper circuits can be used, and when it is desired to reduce the ripple, the ripple is absorbed by a capacitor 7 as shown in FIG. Supply power. Since the diode 8 is necessary for stably supplying the simmer power, it is unnecessary when the load is a laser diode.

As described above, in the power supply device of the present embodiment, the IGBTs 3A and 3B of the chopper circuits, which are power conversion units, are turned on at the beginning of the sampling period, and the IGB
Since the IGBTs 3A and 3B are turned off when the integrated value of the instantaneous power on the output side of the T3A and 3B reaches the target power value, the control of the power supplied to the flash tube 9 as a load is performed.
It is possible to perform stably and highly accurately in a state where the ripple is extremely small.

Further, the capacitor 7, which was conventionally required,
Since the diode 8 is not required, efficient power conversion can be performed.

(Second Embodiment) In the first embodiment, when the power control range is extremely wide, FIG.
Since the output from the integrator 19A (FIG. 2D) gradually rises, (f) (F / F output) is caused by noise or the like.
May vary.

Therefore, in the case where the control is performed to a very small power, as shown in the block diagram of FIG.
The waveform (g) of the dither circuit 23A synchronized with the signal is added to the output from the integrator 19A by the adding circuit 22A and compared by the comparator 20A. Since the output from the flip-flop 21A is a PWM signal, an output V ₂₄ proportional to the modulation rate is obtained by the modulation rate detection circuit 24 including the PWM signal output from the flip-flop 21B, and the power command P ^* _{12 is set} to V By adding ₂₄ , a decrease in power control accuracy due to the dither signal is compensated for.

FIG. 5 mainly shows a block diagram of the chopper circuit on the A side of the control circuit in FIG. 1, and the same applies to the B side.

Next, the operation of the power supply device of the present embodiment configured as described above will be described.

When the power value is small, ΔV _{c in} FIG.
· I _A, since a gentle slope as shown in FIG,
When the comparison is performed by the comparator 20A, the output of the flip-flop 21A due to noise or the like, that is, the PWM of FIG.
The pulse width of the waveform becomes unstable.

[0068] Thus, synchronized with the reset A shown in FIG. 5 (e) to (g) the dither signal, by adding the ∫V _c · I _A in FIG. 5 (d), substantially equal to force the PWM by dither It becomes a pulse and becomes stable.

Now, when the PWM waveform is as shown in FIG. 5 (h), the magnitude of H in the dither waveform becomes an error in power control, and the modulation rate of PWM is proportional to H. By controlling the power based on a new reference obtained by adding the modulation rate V ₂₄ detected by the detection circuit 24 to the power command P ^* by the addition circuit 25, accurate power control can be stably performed.

As described above, in the power supply apparatus according to the present embodiment, the dither compensation signal proportional to the PWM modulation rate is added to the target power value, so that the power error caused by the dither signal is reduced. It is possible to improve the accuracy of power control.

(Third Embodiment) FIG. 6 is a block diagram showing an example of a circuit configuration of a power supply device according to the present embodiment. The same parts as those in FIGS. 1 and 5 are denoted by the same reference numerals. Is shown.

[0072] In FIG. 6, detects the voltage of the flash tube 9 by the voltage detector 10 obtains the instantaneous power by multiplying by the current I _A and the multiplier 11A, the dither circuit is synchronized with the reset signal A 2
The 3A dither signal and the value obtained by adding the instantaneous power and the dither signal by the adder 22A are compared by the comparator 20A, and the PWM signal for turning on the IGBT 3A at the reset A is output by the flip-flop 21A. Flip-flop 2 to turn off IGBT 3A
1A is set to be a PWM signal, and the IGBT 3A is PWM-controlled by the drive circuit 14A.

Similarly, the driving of the IGBT 3B is controlled by the current I _B
And the output from the voltage detector 10 are multiplied by a multiplier 11B to obtain instantaneous power. The sum of the output from the dither circuit 23B synchronized with the reset B signal is obtained by an adder 22B and compared by a comparator 20B. The reset circuit 21B resets by the reset B signal, obtains the PWM signal to be set by the output from the comparator 20B, and
Drives the IGBT 3B.

Here, the difference between the reset B signal and the reset A signal is 180 degrees in phase, so that the ripple of the flash tube 9 is canceled out.

The correction of the error due to the addition of the dither signal is performed by outputting the output proportional to the modulation rate by the modulation rate detection circuit 24 from the PWM signal as in the case of FIG.
By adding to the power command P ^* 12 by the adder 25,
It is possible to perform accurate power control.

Further, since the outputs from the multipliers 11A and 11B are the instantaneous electric power injected into the flash tube 9, the IGB
The instantaneous power is increased by turning on the T3A and the IGBT 3B alternately, and when the instantaneous power reaches the target power value, the instantaneous power is controlled by alternately turning off the IGBTs 3A and 3B.

(Fourth Embodiment) FIG. 7 is a block diagram showing an example of a circuit configuration of a power supply device according to the present embodiment. The same parts as those in FIG. The description is omitted, and only different portions are described here.

That is, as shown in FIG. 7, the power supply device of the present embodiment converts the voltage of the capacitor 2 into AC by the inverter bridge 29 and rectifies the output by the rectifier 33 through the transformer 32, as shown in FIG. The electric power smoothed by the reactor 34 is supplied to the flash tube 9.

The primary current of the transformer 32 is detected by the current detector 6, the current rectified by the rectifier circuit 31 and the capacitor 2
Is multiplied by the multiplier 11 with the voltage detected by the voltage detector 10 to obtain the instantaneous power, and further integrated by the integration circuit 19 to obtain the primary-side input power of the transformer 32.

The other circuits are the same as those in FIG. 1. When the input power matches the target power value, the inverter bridge 29 is turned off.

Since V in FIG. 7 is the primary voltage of the transformer 32 and I is the primary current, ∫VI = ∫V _c · I becomes
Since it is the same as ΔV _c · I in FIG. 2, it can be applied even when the transformer 32 in FIG. 7 is used according to the same principle as in FIG.

The output from the transformer 32 is connected to the rectifier 34
In rectifying detects an output current from the reactor 34 by the current detector 35, and V ₃₆ by detecting the voltage across the flash tube 9 by the voltage detector 36, the product of the output I ₃₅ from current detector 35 the output power value V ₃₇ obtained in multiplication circuit 37, by replacing the multiplier 11A of FIG. 6, it is also possible to control the input power of the flash tube 9 directly. This situation is shown in FIG.
₃₆ , I ₃₅ , and PWM, respectively.

As described above, in the power supply device according to the present embodiment, the IGBTs 3A and 3B of the chopper circuit as the power converter are turned on at the beginning of the sampling period, and the instantaneous input power of the chopper circuit as the power converter is changed. When the value reaches the target power value, the IGBTs 3A and 3B are turned off, so that the power supplied to the flash tube 9 as a load can be controlled stably and with high precision with extremely little ripple. Becomes

(Fifth Embodiment) In each of the above embodiments, the case where the chopper circuit as the power conversion unit is of the step-down chopper type is described. but in the case of the step-up chopper type, such as a block diagram in FIG. 8, for example, the V ₁₀ detects the input voltage of the chopper circuit by the voltage detector 10 to detect the current of the reactor 4 by the current detector 6 an input power of the chopper circuit calculated by the multiplier 11 the product of the I and V _10, by replacing the multiplier 11A of FIG. 6, the input-side power controller, indirectly can do load power control Becomes

(Sixth Embodiment) As shown in the block diagram of FIG. 9, the detection side integrates a current I with an integrator 19A.
Divider 4 the power command P ^* 12 at voltage V _c of the capacitor 2
Even if the current command is converted to a current command corresponding to the power command by dividing by 0, and these are compared by the comparator 20, the same effect can be naturally obtained as in the case described above.

(Seventh Embodiment) When the above-described current control is performed, a condition exceeding the current rating of the IGBT also occurs, and the reliability of the IGBT is reduced.

[0087] Therefore, when such a situation occurs, as shown in the block diagram in FIG. 10, it detects the overcurrent level detector 41 which receives the current I _A, OR circuits 4
By incorporating a sequence in which the IGBT is turned off by either the output of the comparator 20 or the level detector 41, the IGBT current is controlled so as not to exceed a set value, thereby preventing the IGBT from being destroyed and improving reliability. Can be improved.

[0088]

As described above, according to the power supply apparatus of the present invention, the power of the load is controlled at a high speed and at an instantaneous value in each sampling cycle, so that the load non-linearity and Power control can be performed stably and with high accuracy regardless of the presence or absence of a negative resistance generally included in a discharge tube.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a first embodiment of a power supply device according to the present invention.

FIG. 2 is a block diagram and a waveform diagram for explaining an operation in the power supply device according to the first embodiment.

FIG. 3 is a waveform chart for explaining the operation of the power supply device according to the first embodiment.

FIG. 4 is a block diagram showing a modified example of the first embodiment of the power supply device according to the present invention.

FIG. 5 is a block diagram and a waveform diagram showing a second embodiment of the power supply device according to the present invention.

FIG. 6 is a block diagram showing a third embodiment of the power supply device according to the present invention.

FIG. 7 is a block diagram and a waveform diagram showing a fourth embodiment of the power supply device according to the present invention.

FIG. 8 is a block diagram and a waveform diagram showing a fifth embodiment of the power supply device according to the present invention.

FIG. 9 is a block diagram showing a sixth embodiment of the power supply device according to the present invention.

FIG. 10 is a block diagram showing a seventh embodiment of the power supply device according to the present invention.

FIG. 11 is a block diagram showing a circuit configuration example of a conventional pulse power supply device.

FIG. 12 is a waveform chart for explaining the operation of the pulse power supply device of FIG. 11;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Charging power supply, 2 ... Capacitor, 3 ... IGBT, 4 ... Reactor, 5 ... Diode, 6 ... Current detector, 7 ... Capacitor, 8 ... Diode, 9 ... Flash tube, 10 ... Voltage detector, 11 ... Multiplier , 12 power command, 13 hysteresis comparator, 14 drive circuit, 15 DC power supply, 16 resistor, 17 oscillator, 18 distributor, 19 integrator, 20 comparator, 21 flip-flop, 22 ... Addition circuit, 23 dither circuit, 24 modulation rate detection circuit, 25 addition circuit, 29 inverter bridge, 30 advance circuit, 31 rectifier circuit, 32 transformer, 33 diode, 34 reactor Current detector, 36: voltage detector, 37: multiplication circuit, 40: divider, 41: level detector, 42: OR circuit.

Claims (10)

[Claims] 1. A power supply for supplying power to a load from a DC power supply by a power conversion device including a power conversion unit that controls output power by performing pulse width modulation (PWM) control of a switching element based on a power command. In the supply device, for each sampling period, the instantaneous power on the output side of the switching element is obtained from the product of the input voltage and the input current of the power conversion unit of the power conversion device, and the integrated value is obtained by integrating the instantaneous power. Means for turning on the switching element at the beginning of the sampling period and turning off the switching element when the integrated value reaches a target power value. 2. The power supply device according to claim 1, wherein the power conversion device includes a plurality of power conversion units, and switching elements of the plurality of power conversion units are sequentially spaced at equal intervals by the sampling period. A power supply device characterized in that the power supply device is controlled by: 3. The power supply device according to claim 1, further comprising a means for adding a dither signal that increases or decreases gradually in synchronization with the sampling period to the integrated value or the target power value to correct the integrated value or the target power value. A power supply device comprising: 4. The power supply device according to claim 3, wherein a dither correction signal proportional to the PWM modulation rate is added to the target power value. 5. The power supply device according to claim 1, further comprising an advance means for outputting the target power value by inputting the power command. 6. A power supply for supplying power to a load from a DC power supply by a power conversion device including a power conversion unit that controls output power by performing pulse width modulation (PWM) control on a switching element based on a power command. In the supply device, for each sampling period, an instantaneous power value is obtained from a product of an output voltage and an output current of a power conversion unit of the power conversion device or a product of an input voltage and an input current of the power conversion unit of the power conversion device. A power supply device, comprising: a means for determining; and a means for turning on the switching element at the beginning of the sampling period and turning off the switching element when the instantaneous power value reaches a target power value. 7. The power supply device according to claim 6, wherein the power conversion device includes a plurality of power conversion units, and switching elements of the plurality of power conversion units are sequentially arranged at regular intervals according to the sampling period. A power supply device characterized in that the power supply device is controlled by: 8. The power supply device according to claim 6, further comprising: a means for correcting the instantaneous power value or the target power value by adding a dither signal gradually increasing or decreasing in synchronization with the sampling cycle. A power supply device characterized by comprising: 9. The power supply device according to claim 8, wherein a dither correction signal proportional to the PWM modulation rate is added to the target power value. 10. The power supply device according to claim 1, further comprising means for turning off the switching element when a current flowing through the switching element reaches a set value or more. Power supply device.