JP2002064973A - Stabilized dc power supply apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a stabilized DC power supply apparatus which can expand the range of a voltage which can be outputted and control the voltage with higher precision. SOLUTION: A plurality of stages of step-down converter units, which have respectively two transistors 111 (121) and 112 (122) turned on and turned off complementarily and low-pass filters connected to the transistors, are connected to each other. The on-duties of the switching operations of the converter units of the respective stages are mutually adjusted between the plurality of the converter units by a control unit 200. With such a constitution, the power supply control can be practiced in a highly efficient state.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a step-down DC-D
The present invention relates to a stabilized DC power supply device having a C converter.

[0002]

2. Description of the Related Art Japanese Unexamined Patent Publication No. Hei 8-266039 discloses a DC stabilized power supply device which enables efficient and stable operation.

The stabilized DC power supply described in this publication can open and close a flywheel diode and a switching element of a conventionally known step-down DC-DC converter in a complementary manner, and can pass current in both directions. As a switching element, and the bleeder circuit is deleted. Further, this DC stabilized power supply device changes the ON (ON) duty of the switching element, that is, the time ratio of the ON time (open time) to one cycle of the switching element (generally called a “duty coefficient”). , The output voltage can be changed.

[0004]

However, each switching element requires a predetermined rise time from the off state (closed state) to the on state (open state), and each switching element requires a certain rise time from the on state to the off state. A certain standing time is required. In particular, the DC stabilized power supply of the type described in the above publication has a configuration in which two switching elements are opened and closed in a complementary manner, so that the two switching elements are simultaneously turned on to avoid a short circuit. , Dead time is often set. As a result, due to the set dead time, the range in which the on-duty of the switching element can be changed is limited, and the range of the voltage that can be output increases. Further, even when a voltage can be output, the accuracy of the output voltage value is low. In particular, since the minimum value of the ON time of the switching element is limited to about the dead time value, it is difficult to reduce the voltage to an extremely small voltage value.

Further, according to the stabilized DC power supply described in the above publication, when the output voltage is determined, the on-duty of the switching element is uniquely determined. Therefore, there is a problem that the on-duty at which power supply control can be performed in a highly efficient state cannot be appropriately selected, and high-efficiency control in consideration of power loss cannot be performed.

Further, according to the stabilized DC power supply described in the above-mentioned publication, power loss of the switching element cannot be managed. Specifically, when the performance of the switching element temporarily deteriorates due to continuous use of the DC stabilized power supply for a long time, and the power loss temporarily increases,
It is not possible to take measures to reduce the load on the temporarily degraded switching element, and if the power output is continued as it is, the switching element may be damaged or its life may be shortened. Therefore, it is necessary to stop using the DC stabilized power supply and protect the switching element.

[0007] The present invention has been made to solve the above-mentioned problems of the prior art.

SUMMARY OF THE INVENTION It is an object of the present invention to expand the range of voltages that can be stepped down and the range of voltages that can be output.
An object of the present invention is to provide a stabilized DC power supply device whose output voltage is controlled with high accuracy.

Another object of the present invention is to operate a switching element in a region where power loss is small,
An object is to provide a highly efficient DC stabilized power supply device with reduced power loss.

Further, another object of the present invention is to reduce the load on the degraded switching element when the performance of the switching element is temporarily degraded and the power loss is increased. Depending on the change in characteristics,
An object of the present invention is to provide a stabilized DC power supply that can always achieve the highest efficiency.

[0011]

Means for achieving the above object are constituted as follows. (1) A stabilized DC power supply according to the present invention includes a step-down DC having two switching means which are opened and closed complementarily and a low-pass filter connected to the two switching means.
-A DC stabilized power supply device having a DC converter unit, wherein the DC-DC converter unit is connected in a plurality of stages, and an open time or a closed period for one cycle of switching means of each stage of the DC-DC converter unit. It is characterized by having a control unit for mutually adjusting the time ratio among the plurality of DC-DC converter units. (2) The control unit mutually adjusts the ratio among the plurality of DC-DC converters so that the power loss in each stage of the DC-DC converters is equalized among the plurality of DC-DC converters. I do. (3) The DC stabilized power supply further includes all DC-
Determining means for determining whether or not the sum of the power losses obtained by adding the power losses in the DC converter unit has increased over time; and the control unit has determined that the sum has increased. In this case, the ratio is mutually adjusted among the plurality of DC-DC converter units. (4) The control unit mutually adjusts the ratio among the plurality of DC-DC converter units so as to minimize the sum of the power losses obtained by adding the power losses in all the DC-DC converter units. . (5) The control unit sets the ratio to a plurality of D so as to make the output voltage of the stabilized DC power supply device equal to the reference voltage.
Mutual adjustment is made between the C-DC converter units. (6) The switching means includes a bipolar or field effect transistor.

[0012]

According to the first aspect of the present invention, there are provided a plurality of step-down DC-DC converters each having two switching means which are opened and closed complementarily and a low-pass filter connected to the two switching means. Are connected in stages,
The ratio of the open time or the close time to one cycle can be calculated using multiple DC
Since the DC converters are mutually adjusted, the range of the voltage that can be stepped down can be expanded and the range of the voltage that can be output can be expanded, and the output voltage can be controlled with high accuracy.

According to the second aspect of the present invention, the D
The power loss in the C-DC converter section is reduced by a plurality of DC-DC
Since the ratio is adjusted so as to be equal between the converter units, excessive power loss is prevented from occurring in one converter unit, and the switching means of each converter unit can operate in a highly efficient state. As a result,
Highly efficient power control in consideration of power loss can be realized.

According to the third aspect of the present invention, when it is determined that the total power loss has increased with the passage of time, the ratio is adjusted. If the performance of some switching means temporarily deteriorates due to use and the power loss temporarily increases, the load on the switching element whose performance has temporarily deteriorated can be reduced. The highest efficiency can always be realized even when the characteristic of the above-mentioned characteristic changes with time.

According to the fourth aspect of the present invention, the ratio is adjusted so as to minimize the sum of the power losses obtained by adding the power losses in all the DC-DC converter sections. Even if the characteristics change over time, the power loss can always be suppressed.

According to the fifth aspect of the present invention, the ratio is adjusted so that the output voltage of the stabilized DC power supply becomes equal to the reference voltage, so that the reference voltage can be set in a wide range. In addition, the accuracy in matching the output voltage with the set reference voltage is improved.

According to the sixth aspect of the present invention, since the switching means includes a bipolar or field effect transistor, the power loss of the semiconductor switching element which is easily damaged by heat or the like can be made uniform among the elements, and the switching loss can be reduced. A DC stabilized power supply that is highly efficient and whose output voltage is controlled with high precision by preventing the burden of Can be realized.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a stabilized DC power supply according to the present invention will be described in detail with reference to the drawings.

FIG. 1 is a schematic configuration diagram showing a circuit configuration of a stabilized DC power supply according to the present embodiment.

The stabilized DC power supply 1 according to this embodiment includes a power supply main body 100 and a control unit 200.

The power supply body 100 is a unit that actually functions as a DC-DC converter, and performs various switching operations (chopping operations). On the other hand, the control unit 200 detects a current value and a voltage value at a predetermined position of the power supply main body 100, and controls a switching operation of the power supply main body according to the detected current value and voltage value.

The power supply body 100 includes a transistor 111
(Q1), a transistor 112 (Q2), a choke coil 113 (L1), a capacitor 114 (C2), and a first-stage converter unit including diodes 115 and 116. Here, the choke coil 113
(L1) and the capacitor 114 (C2) function as a low-pass filter.

The first stage converter section is configured as follows.

The transistor 111 (Q1) is connected to the low-pass filters (L1, C2). The output terminal of the transistor 111 (Q1) and a low-pass filter (L
1, C2) at the common connection point with the input terminal.
2 (Q2) is connected to the input terminal. On the other hand, the output terminal of the transistor 112 (Q2) is connected to a common line. Here, the transistor 111 (Q1) and the transistor 112 (Q2) are opened and closed complementarily, that is, turned on and off.

As in the first stage converter section, a transistor 121 (Q3), a transistor 122 (Q4),
Choke coil 123 (L2), capacitor 124 (C
3), the diodes 125 and 126 constitute a second-stage converter section.

The output terminal of the first-stage converter unit, that is, the output terminal of the low-pass filter, and the input terminal of the second-stage converter unit are connected.

Therefore, the input voltage V1 is equal to the first voltage V1.
After being stepped down by the converter unit of the stage,
The voltage is stepped down and output by the converter unit at the stage. In addition, as the transistors 111, 112, 121, and 122 functioning as switching means, either a bipolar transistor or a field-effect transistor can be used. Preferably, a MOSFET and a bipolar transistor are combined to form one chip. It is desirable to use IGBTs.

The power supply body 100 includes current sensors 117 and 127 for detecting input currents A1 and A2 to the first-stage and second-stage converters, and a second-stage converter. A current sensor 128 for detecting an output current A3 output from the power supply is provided. The input power supply 13 connected to the first-stage converter section
A power supply capacitor 131 is connected to 0 (V1).

Next, the stabilized DC power supply 1 corresponding to the present embodiment configured as described above, in particular, the power supply body 100
Will be described.

FIG. 2 is a waveform diagram showing the switching operation of two transistors which are opened and closed complementarily.

Hereinafter, assuming that the time during which the transistor 111 (Q1) is in the on state, that is, the open state, is the on time (open time) ton1 and the time of one cycle is T, the on duty D1 of the transistor 111 (Q1) is (Duty coefficient) is defined as the ratio of the open time to the time T of one cycle (cycle), ton1 / T. Similarly, the on-duty D2 of the transistor 112 (Q2) is ton2
/ T, the on-duties D3 and D4 of the transistor 121 (Q3) and the transistor 122 (Q4).
Are defined as ton3 / T and ton4 / T, respectively.

The first-stage converter section reduces the input voltage V1 to V2. The stepped-down voltage V2 is given by the following equation.

V2 during power running is given by equation (1).

V2 = (ton1 / T) × V1 = D1 × V1 (1) V2 at the time of regeneration is given by equation (2).

V2 = {T / (T-ton2)} × V1 = {1 / (1-D2)} × V1 (2) The powering means the second stage from the first stage converter. This is a state in which current flows out to the converter section side, and conversely, regeneration is a state in which current flows into the first-stage converter section from the second-stage converter side. As shown in the equations (1) and (2), the on-duties D1 and D2
, The output voltage V2 of the first-stage converter section is determined.

Here, also in the present embodiment, the range in which each on-duty can be adjusted is limited by considering the dead time tdead, ie, the rise time and the fall time.

FIG. 3 is an enlarged view showing a portion X in the waveform diagram of FIG.

Considering the rise and fall times of the transistors 111 (Q1) and 112 (Q2), the transistors 111 (Q1) and 1
A dead time tdead is defined in order to prevent occurrence of a state where 12 (Q2) is simultaneously turned on. Therefore, the range in which the on-duties D1 and D2 can be adjusted is limited, and as a result, the value of V2 is limited. For example, since ton1 ≦ T−2 · tdead, V2 is V2 ≦ {(T−2 · tdead) / T} × V1
Subject to the restriction.

The second-stage converter section reduces the voltage V2 input from the first-stage converter section to V3. Also in this case, the output voltage V3 is obtained by the above equation (1) and (2)
Similar to the equation, it is given by the following equation.

V3 during power running is given by equation (3).

V3 = (ton3 / T) × V2 = D3 × V2 (3) V3 at the time of regeneration is given by equation (4).

V3 = {T / (T-ton4)} × V2 = {1 / (1-D4)} × V2 (4) Therefore, by using the equations (1) to (4),
The relationship between the input voltage V1 and the output voltage V3 finally input to the power supply body 100 is given by the following equations (5) and (6).

V3 = D1 × D3 × V1 (during power running) (5) V3 = V1 / {(1-D2) (1-D4)} (during regeneration) (6) As described above, according to the present embodiment, According to the DC stabilized power supply device, since the step-down operation is performed in a plurality of stages, the amount of step-down per stage can be reduced, and the range in which the step-down operation is possible is widened. Specifically, even when the voltage is reduced to a very small voltage value, the output voltage is less likely to be limited due to the dead time tdead and the like, and the finally output voltage V
3 can be improved in accuracy.

Further, according to the stabilized DC power supply of the present embodiment, when the output voltage is determined, the ON duty of the switching element is not uniquely determined. That is, a predetermined voltage can be output by freely combining the on-duty D1 and the on-duty D3, and by freely combining the on-duty D2 and the on-duty D4. Therefore, as will be described later, by appropriately adjusting and distributing the on-duties D1 to D4, it is possible to perform high-efficiency control in consideration of the power loss.

Next, a description will be given of a control unit 200 for mutually adjusting the on-duty of the switching element in each converter section among a plurality of converter sections.

FIG. 4 is a schematic configuration diagram of the control unit.

The CPU 201 controls each component of the stabilized DC power supply 1.

The RAM 202 temporarily stores current values and voltage values input to and output from the converter units of each stage included in the power supply main unit 100, and values of power and power loss calculated by the CPU 201. Also, a reference voltage value set by an operation unit (not shown), that is, an instruction value of an output voltage of the stabilized DC power supply device can be stored.

The ROM 203 stores various control programs and the like.

The input interface 204 includes an input voltage V1 and an input current A1,
Further, it is an input interface for taking in the input voltage V2, the input current A2, the output voltage V3, and the output current A3 of the second-stage converter section.

The A / D converter 205 converts various types of analog data input through the input interface 204 into digital data. The data converted into digital data is subjected to various types of arithmetic processing by the CPU 201. Further, based on the calculation processing result, the transistor 111 (Q1) and the transistor 112 (Q
1), transistor 121 (Q3), transistor 12
2 (Q4) on-duty D1, D2, D
3, and D4 are mutually coordinated among the plurality of converter sections.

The PWM output unit 206 controls each of the transistors 111 and 11 in accordance with the adjusted on-duty.
2, 121 and 122 are output. Note that the PWM output unit 206 is a unit that controls the output voltage of the DC stabilized power supply device 1 by adjusting the pulse width of the drive signal in accordance with each on-duty. In other words, the PWM ( This is a unit that performs control using pulse width modulation.

FIG. 5 is a flowchart showing the processing contents of the control unit of the stabilized DC power supply according to this embodiment.

In step S 100, the input voltage V 1 to the first-stage converter, the input voltage V 2 of the second-stage converter, and the output voltage V 3 are obtained through the input interface 204. For example, the voltage of each corresponding portion is divided and taken into the input interface 204, and the taken voltage value is subjected to analog / digital conversion and temporarily stored in the RAM 202.

As an initial setting, each on-duty is set so as to satisfy the relations of D1 = D3 and D2 = D4. That is, the transistor 111 (Q1) of the first-stage converter and the transistor 121 of the second-stage converter corresponding to this transistor
(Q3) and the on-duty is set to be equal between the transistor 112 (Q2) and the transistor 122 (Q4) of the second-stage converter unit corresponding to this transistor. Is set to

In step S101, it is determined whether or not the preset reference voltage VREF is equal to the output voltage of the second stage, that is, the output voltage V3 of the stabilized DC power supply. When the reference voltage VREF is different from the output voltage V3 (S101: NO), fine adjustment of the on-duties D3 and D4 is performed as the process of step S102.
On the other hand, when the reference voltage VREF is equal to the output voltage V3 (S101: YES), the process proceeds to step S103.

In step S103, the input current A1 to the first-stage converter section, the input current A2 and the output current A3 to the second-stage converter section are detected by the current sensors 117, 127, and 128, respectively. The data is input to the input interface 204.

In step S104, the power supplied to a predetermined portion of the stabilized DC power supply is calculated. The supplied power is calculated by multiplying the voltage value obtained in step S100 by the current value obtained in step S103. Specifically, power P1 supplied to the first-stage converter, power P2 supplied to the second-stage converter, and power supplied to the load connected to the second-stage converter are provided. Power P3 is P1 = V
It is calculated by the formula of 1 × A1, P2 = V2 × A2, P3 = V3 × A3.

In step S105, the power loss L1 in the first-stage converter and the power loss L2 in the second-stage converter are calculated. Specifically, L1 is
It is calculated by calculating the difference between the power P1 and the power P2 (L1 = P1−P2), and L2 is the power P2 and the power P
3 (L2 = P
2-P3).

In step S106, according to the calculated power losses L1 and L2, the on-duties D1, D2, D3 and D4 of the transistors 111, 112, 121 and 122 included in the converters of the respective stages are reduced by a plurality of converters. Is adjusted and distributed. Based on the adjusted on-duty, each transistor 111 (Q1), transistor 112 (Q2), transistor 121 (Q3),
A drive signal for controlling ON / OFF of the transistor 122 (Q4), that is, opening and closing, is output from the PWM output unit 206.

FIG. 6 is a flowchart showing the contents of the processing related to the adjustment of each on-duty, and shows the contents of a subroutine corresponding to step S106 in FIG. Note that the process shown in FIG. 6 is a process of mutually adjusting each on-duty between the plurality of converter units so that the power loss in the converter units at each stage is equalized among the plurality of DC-DC converter units. It is.

In step S200, it is determined whether the first-stage power loss L1 is equal to the second-stage power loss L2. If L1 and L2 are equal (S200: YE
S) Since there is no need to adjust each on-duty, the return processing is performed as it is.

In step S201, it is determined whether or not the vehicle is running. During power running (S201: YE
S), and proceed to step S202. On the other hand, if it is not during power running, that is, if it is during regeneration (S201: NO), the process proceeds to step S205. Note that the equation indicating the relationship between the power supply voltage and each on-duty is different between the powering operation and the regenerative operation, so that the determination process in step S201 is performed.

In step S202, that is, in the case of power running, the first-stage power loss L1 and the second-stage power loss L2 are compared. As a result of the comparison, when the power loss L2 of the second stage is larger than the power loss L1 of the first stage, that is, when L1 <L2 (S202:
YES), the process proceeds to step S203, and if the second-stage power loss L1 is larger than the first-stage power loss L2, that is, if L1> L2 (S202: NO),
Proceed to step S204.

The comparison between L1 and L2 can be made directly as shown in the present embodiment.
It is also possible to make an indirect comparison by determining a larger value of L2 as Lmax and determining whether Lmax matches L1 or L2.

In step S203, since the power loss L1 of the first-stage converter is smaller than the power loss L2 of the second-stage converter, a process for increasing the first-stage power loss L1 is performed. Also, with this process,
A process for reducing the power loss L2 in the second stage is performed.

Specifically, the output voltage V2 from the first-stage converter section is increased (V2 = V2 + α), and the value V2 / V obtained by dividing the first-stage output voltage V2 by the input voltage V1 is obtained.
The process of increasing 1 is performed. This processing is performed based on an experimental result that the loss in each converter section is proportional to the output power and proportional to the value obtained by dividing the output voltage by the input voltage.

As is apparent from the above equation (1), the value given by V2 / V1 can be increased by increasing the on-duty D1 of the transistor 111 which is the first-stage switching element. . Further, since the output voltage V3 of the stabilized DC power supply 1 is kept constant, the on-duty D1 needs to be reduced as a result of the on-duty D1 increasing. Specifically, the minute value β (where β> 0) is added to the value of the on-duty D1 (D1 = D1 + β), and the minute value β is subtracted from the on-duty D3 (D3 = D3-β).

In step S204, since the power loss L1 of the first stage converter is larger than the power loss L2 of the second stage converter, conversely, the first stage power loss L1
Is performed. With this processing, the second
A process of increasing the power loss L3 in the stage is performed. Specifically, the output voltage V2 from the first-stage converter section is reduced (V2 = V2-α), and the first-stage output voltage V2
A process is performed to reduce V2 / V1, which is the ratio between the input voltage V1 and the input voltage V1. Therefore, a process of reducing the on-duty D1 (D1 = D1-β) and increasing the on-duty D3 (D3 = D3 + β) is performed.

On the other hand, in step S205, the power loss L1 of the first stage and the power loss L2 of the second stage are compared as a process in the case of regeneration. If L1 <L2 (step S205: YES), the process proceeds to step S206, while if L1> L2 (step S20).
6: NO), and proceeds to step S207.

In step S206, the output voltage V2 from the first-stage converter is increased to increase L2 (V2 = V2 + α). In this case, the above (2)
As is clear from the equation, a process of reducing the on-duty D2 (D2 = D2-β) and increasing the on-duty D4 (D4 = D4 + β) is performed. .

In step S207, the output voltage V2 from the first-stage converter is reduced to reduce L2 (V2 = V2-α). In this case, the above (2)
As is apparent from the equation, the on-duty D2 is increased (D2 = D2 + β), and the on-duty D4 is decreased (D4 = D4-β).

By successively repeating the processes shown in FIGS. 5 and 6, the switching elements of the converter units in each stage are turned on so that the power loss in the converter units in each stage is equalized among the plurality of converter units. The duty is adjusted. Note that when equalizing the power loss in the converter units in each stage among the plurality of DC-DC converter units, it may not be possible to exactly equalize the power losses due to measurement errors. Therefore, the case where the power loss in the converter unit of each stage is equal includes the case where each power loss does not differ more than the error range of the device.

Therefore, according to the processing shown in FIG. 6, it is possible to prevent excessive power loss from occurring in one converter section and to equalize the power loss in all converter sections. Thus, each converter section can operate in a highly efficient state. As a result, high-efficiency power control considering power loss is realized.

FIG. 7 is a flowchart showing another processing content relating to the adjustment of each on-duty, and shows the content of a subroutine corresponding to step S106 in FIG.

The process shown in FIG. 7 is a case in which each on-duty is adjusted only when the sum of the power losses in all the converters increases with the passage of time. As a case where the total power loss increases with the passage of time, there may be a case where the performance of some switching elements temporarily deteriorates.

In step S300, the total sum Lnow of the power loss in all converter units is calculated. More specifically, L1 and L2 are added to the total power loss Lnow (Lnow = L1 + L2).

In step S301, the previously calculated R
The total power Lold temporarily stored in the AM 203 or the like is compared with the current total power loss Lnow newly calculated in step S301. Lnow <Lold
In the case of (S302: YES), in step S303, the value of Lnow calculated this time is updated as a new Lold, and the return processing is performed as it is (step S303). On the other hand, when Lold <Lnow (S30
2: NO), in step S304, the currently calculated L
The value of now is updated as a new Lold, and step S30
Go to 5.

As described above, by comparing the total sum Lold of the previously calculated power loss with the total sum Lnow of the newly calculated power loss, it is possible to determine whether the power loss has increased with time. Is determined. As a result of the determination, only when the sum increases, the on-duty of the switching element such as the transistor included in the converter unit of each stage is adjusted.

The processing in steps S305 to S312 is the same as the processing in steps S200 to S207 described with reference to FIG. 6, and a description thereof will be omitted.

As described above, the processing shown in FIG. 7 is limited to the case where the performance of some switching elements is temporarily deteriorated due to long-time use and the power loss is temporarily increased. In this case, the on-duty can be adjusted to take measures to reduce the load on the temporarily deteriorated switching element.

In the above description, as an example of a process for adjusting each of the on-duties D1, D2, D3, and D4, each of the switching units is set so that the power loss in each converter unit is made equal among the plurality of converter units. Although the process of adjusting the on-duty of the control has been described, the present invention is not limited to this. For example, it is also possible to adjust each on-duty so as to minimize the total power loss in all converter units. In this case, each on-duty D
1, D2, D3, and D4 are sequentially changed in small amounts, the total power loss at that time is sequentially calculated, and a combination of on-duties D1 to D4 that minimizes the total power loss is determined.

Further, in the above description, the converter unit is 2
Although the case where the stages are connected is shown, the present invention is not limited to this. The converter units may be connected in three or more stages.

Although the case where a transistor is used as the switching means of each DC-DC converter section has been described, the present invention is not limited to this. Further, it is apparent that the ratio of the off time (close time) to one cycle of the switching means may be adjusted instead of adjusting the on-duty.

The embodiments described above are not described to limit the present invention, and various modifications can be made by those skilled in the art without departing from the technical concept of the present invention.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram illustrating a circuit configuration of a stabilized DC power supply device according to an embodiment.

FIG. 2 is a waveform diagram showing switching operations of two transistors that are opened and closed in a complementary manner.

3 is an enlarged view showing the waveform diagram of FIG. 2 in an enlarged manner.

FIG. 4 is a schematic configuration diagram of a control unit provided in a stabilized DC power supply device according to the present embodiment.

FIG. 5 is a flowchart illustrating processing performed by a control unit provided in the stabilized DC power supply device according to the present embodiment.

FIG. 6 is a flowchart illustrating the content of an on-duty adjustment process.

FIG. 7 is a flowchart showing another processing content relating to adjustment of each on-duty.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... DC stabilized power supply device 100 ... Power supply main body 111 ... Transistor (Q1) 112 ... Transistor (Q2) 113 ... Choke coil (L1) 114 ... Conductor (C2) 115 ... Diode 116 ... Diode 117 current sensor (I1), 121 transistor (Q3), 122 transistor (Q4), 123 choke coil (L2), 124 conductor (C3), 125 diode, 126 diode, 127 current sensor ( I2), 128: current sensor (I3), 130: power supply, 200: control unit, 201: CPU, 202: RAM, 203: ROM, 204: input interface, 205: A / D converter, 206: PWM output unit.

Claims (6)

[Claims] 1. A DC stabilized power supply device comprising a step-down DC-DC converter unit having two switching means that are opened and closed in a complementary manner and a low-pass filter connected to the two switching means, A plurality of DC-DC converters are connected, and the ratio of the open time or the closed time to one cycle of the switching means of each DC-DC converter is mutually adjusted between the plurality of DC-DC converters. A stabilized DC power supply device comprising a control unit. 2. The control unit according to claim 1, wherein the control unit controls the ratio between the plurality of DC-DC converters so that power loss in each stage of the DC-DC converter is equalized among the plurality of DC-DC converters. 2. The method according to claim 1, wherein
4. The stabilized DC power supply device according to item 1. 3. The control unit further comprising: a determination unit configured to determine whether a sum of power losses obtained by adding power losses in all the DC-DC converter units increases as time passes. 3. The stabilized DC power supply device according to claim 1, wherein, when it is determined that the sum has increased, the ratio is mutually adjusted among a plurality of DC-DC converter units. 4. The control unit according to claim 1, wherein the control unit determines the ratio between the plurality of DC-DC converter units so as to minimize the sum of the power loss obtained by adding the power losses in all the DC-DC converter units. The stabilized DC power supply device according to claim 1, wherein adjustment is performed. 5. The controller according to claim 1, wherein the controller mutually adjusts the ratio between the plurality of DC-DC converters so that an output voltage of the stabilized DC power supply becomes equal to a reference voltage. Item 5. The stabilized DC power supply according to any one of Items 1 to 4. 6. The stabilized DC power supply according to claim 1, wherein the switching unit includes a bipolar or field effect transistor.