WO2018074169A1

WO2018074169A1 - Power supply system

Info

Publication number: WO2018074169A1
Application number: PCT/JP2017/035128
Authority: WO
Inventors: 西田　映雄
Original assignee: 株式会社村田製作所
Priority date: 2016-10-20
Filing date: 2017-09-28
Publication date: 2018-04-26

Abstract

In the present invention, by means of control signals output from each converter (10A – 10C) a target voltage, which is a target value for the output voltage of one of the three converters, is set to Vout1, and a target voltage for the other two converters is set to Vout2 (<Vout1). The period for which the target voltage is set to Vout1 is equal for each converter. Thus, a reduction in loss during a light load can be suppressed and variation among the converters with respect to temperature increases and stress on components can be reduced by means of a simple control.

Description

Power system

The present invention relates to a power supply system in which a plurality of converters are connected in parallel.

Conventionally, a power supply system having a redundant configuration in which a plurality of converters having the same configuration are connected in parallel is known. In such a power supply system, the output power of each converter is generally set to approximately the same value so that there is no bias in temperature rise and stress on components among a plurality of converters. . For example, Japanese Patent Laying-Open No. 2015-53808 (Patent Document 1) discloses a control method in which output currents of a plurality of rectifier units connected in parallel are made uniform.

In general, when a light load is applied to a converter, the effect of fixed loss such as a control circuit (IC (Integrated Circuit)) included in the converter increases and efficiency decreases. Therefore, if power is supplied uniformly from all the converters at the time of light load, the output current from each converter becomes too small and the loss in each converter becomes large.

Therefore, Japanese Patent Laying-Open No. 2015-53807 (Patent Document 2) describes some components of a slave converter in a power supply device including a master converter and a slave converter when the output current of the master converter is less than a threshold value. A technique is disclosed in which the slave converter is operated when the output current of the master converter exceeds a threshold value after being stopped. This suppresses an increase in converter loss during light load.

Specifically, the control circuit of the slave converter receives a signal indicating the magnitude of the output current of the master converter, and switches the slave converter to either the sleep state or the operating state based on the signal. Further, the control circuit of the slave converter controls on / off of each component in the slave converter according to whether the slave converter is in the sleep state or the operating state.

Japanese Patent Laid-Open No. 2015-53808 Japanese Patent Laying-Open No. 2015-53807

However, in the power supply device disclosed in Patent Document 2, the components that operate in the slave converter differ depending on whether the slave converter is in a dormant state or in an operating state. Therefore, the control circuit of the slave converter performs arithmetic processing according to the operating component depending on whether it is in the sleep state or the operation state. As a result, there arises a problem that the calculation function of the control circuit becomes complicated.

Further, in the power supply device disclosed in Patent Document 2, while the master converter is operating, a period in which the slave converter is idle occurs. As a result, there also arises a problem that the temperature rise and the stress on the components are uneven between the converters.

The present invention has been made in order to solve the above-described problem. In a power supply system in which a plurality of converters are connected in parallel, a simple control suppresses a decrease in loss at light load and the conversion between converters. An object of the present invention is to provide a power supply system that can reduce temperature rise and stress bias on parts.

A power supply system according to an aspect of the present invention is a power supply system including N converters (N is an integer of 2 or more), and N converters connected in parallel. Each of the N converters includes a power converter that converts an input voltage into an output voltage, a first controller that controls the power converter so that the output voltage of the power converter becomes a target value, And a setting unit for setting a target value in the first control unit. The power supply system further controls the setting unit of each of the N converters to set the target value in the m converters (1 ≦ m <N) of the N converters to the first voltage, and the rest A second control unit is provided for causing the target value in the Nm range to be a second voltage lower than the first voltage. The second control unit controls each setting unit of the N converters so that the period during which the setting unit sets the first voltage as the target value is equalized in the N converters.

Preferably, when the output current of the power conversion unit is less than the threshold value, the first control unit controls the power conversion unit so that the output voltage becomes a target value, and the output current of the power conversion unit reaches the threshold value. In this case, the power conversion unit is controlled so that the output voltage becomes lower than the target value.

Preferably, the first control unit controls the power conversion unit so that the output voltage becomes a target value when the output current of the power conversion unit is 0, and the output is performed as the output current of the power conversion unit increases. The power converter is controlled so that the voltage drops from the target value.

Preferably, each of the N converters further includes a detection unit that detects an output current of the power conversion unit, a first threshold value, and a second threshold value that is lower than the first threshold value. And a hysteresis comparator for outputting either the signal or the second signal. The hysteresis comparator outputs the first signal when the detection value detected by the detection unit exceeds the first threshold when the second signal is output, and outputs the first signal. When the detected value becomes less than the second threshold value, the second signal is output. The second control unit controls the setting unit of each of the N converters so that the output signal of any one of the hysteresis comparators of the N converters changes from the second signal to the first signal. Controls the setting unit of each of the N converters so that the target value in the N converters is set to the first voltage and enters the second mode, and one of the hysteresis comparators of the N converters When the output signal changes from the first signal to the second signal, the target value in the m converters of the N converters is set to the first voltage, and the target value in the remaining N−m converters is changed to the first value. 2 voltage.

Preferably, the power conversion unit is a switching regulator including a switching element. When the target value is set to the second voltage, the first control unit sets the number of times of switching per unit time of the switching element, compared to the case where the target value is set to the first voltage. Reduce.

According to the present invention, by simple control, it is possible to suppress a decrease in loss at light load, and to reduce temperature rise between converters and stress bias on components.

It is a block diagram which shows the structure of the power supply system which concerns on Embodiment 1 of this invention. An example of the timing chart of the input / output control signal and the target voltage in each converter included in the power supply system is shown. It is a figure which shows an example of the circuit structure of a power converter. It is a graph for demonstrating the relationship between an output voltage and output current in case a power converter performs constant current drooping operation. It is a graph for demonstrating the relationship between an output voltage and an output current in case a power converter performs constant power drooping operation. 6 is a graph for explaining a relationship between an output voltage and an output current in the power supply system according to the second embodiment. FIG. 6 is a circuit block diagram illustrating a configuration of a converter included in a power supply system according to a third embodiment. 10 is a timing chart illustrating an example of a relationship among an output current, a mode signal, a control signal, and a target voltage in each converter according to Embodiment 3.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and description thereof will not be repeated.

<Embodiment 1>
FIG. 1 is a block diagram showing a configuration of a power supply system 1 according to Embodiment 1 of the present invention. As shown in FIG. 1, the power supply system 1 includes input terminals P1 and P2 to which input power is applied, converters 10A to 10C, and output terminals P3 and P4 connected to a load. Converters 10A-10C are connected in parallel between input terminals P1, P2 and output terminals P3, P4. Converters 10A to 10C have the same configuration, and each is also referred to as converter 10.

Converters 10A to 10C convert input power applied between input terminals P1 and P2, and output the converted power between output terminals P3 and P4. Converters 10A to 10C have the same configuration. Converters 10A to 10C include input terminals P11, P12, and P13, output terminals P14, P15, and P16, power converter 11, target voltage setting unit 12, controller 13, control signal output unit 14, and diode D1. Including.

The input terminals P11 and P12 are connected to the input terminals P1 and P2, respectively. The output terminals P14 and P15 are connected to the output terminals P3 and P4, respectively.

The power converter 11 converts the power received by the input terminals P11 and P12 and outputs the converted power. The power conversion unit 11 is a switching regulator including a switching element such as a power MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor).

The diode D1 has an anode connected to one of the output side terminal pairs of the power conversion unit 11 and a cathode connected to the output terminal P14. The diode D1 prevents reverse current flow when the anode side potential is less than the potential of the output terminal P14, and the power output from the power converter 11 when the anode side potential is equal to or higher than the potential of the output terminal P14. Is supplied to the output terminal P14. The diode D1 functions as a so-called OR connection diode.

The controller 13 controls on and off of the switching element of the power conversion unit 11 so that the output voltage output from the power conversion unit 11 approaches the target voltage. That is, the controller 13 functions as a control unit (first control unit) that controls the power conversion unit 11 so that the output voltage of the power conversion unit 11 becomes the target voltage.

When the voltage between the output terminals P14 and P15 is higher than the target voltage, no current is supplied to the output, so the output current of the power converter 11 is zero. As shown in FIG. 1, since the output terminals P14 of the converters 10A to 10C are connected to each other and the output terminals P15 of the converters 10A to 10C are connected to each other, the output terminals P14 and P15 are connected to the respective converters 10A to 10A. The maximum voltage output from 10C is applied. Therefore, when the target voltage is lower than the voltage output from the other converter 10, the output current of the power converter 11 is zero.

The target voltage setting unit 12 sets a target voltage in the controller 13 based on a control signal received by the input terminal P13. The target voltage setting unit 12 uses either Vout1 (for example, 12.05V) that is the first voltage or Vout2 (for example, 11.95V) that is the second voltage lower than Vout1 as the target voltage. Set.

Specifically, the target voltage setting unit 12 changes the target voltage from Vout2 to Vout1 when the control signal changes from the low level to the high level, and changes the predetermined value after the control signal changes from the high level to the low level. When the first holding time (for example, about 10 seconds) elapses, the target voltage is changed from Vout1 to Vout2.

The control signal output unit 14 generates a signal obtained by delaying the control signal input to the input terminal P13 by a predetermined delay time (for example, about 10 seconds), and outputs the generated signal from the output terminal P16 as a control signal. . That is, the control signal output unit 14 changes the control signal output from the output terminal P16 from the low level to the high level after a predetermined delay time has elapsed since the control signal input to the input terminal P13 changes from the low level to the high level. After a predetermined delay time has elapsed since the control signal input to the input terminal P13 changes from the high level to the low level, the control signal output from the output terminal P16 is switched from the high level to the low level.

As shown in FIG. 1, output terminal P16 of converter 10A is connected to input terminal P13 of converter 10B, output terminal P16 of converter 10B is connected to input terminal P13 of converter 10C, and output terminal P16 of converter 10C is connected to the converter. It is connected to the input terminal P13 of 10A. In other words, converters 10A to 10C are connected in a ring shape, and converter 10 delays the control signal received from previous-stage converter 10 to subsequent-stage converter 10 by a predetermined delay time and outputs the delayed signal. Only the control signal output unit 14 of the converter 10C is set to output a high-level control signal (hereinafter referred to as a pulse signal) having a predetermined pulse width to the output terminal P16 at the time of startup. Thus, the pulse signals are input with a predetermined delay time shifted in the order of converter 10A, converter 10B, converter 10C, converter 10A,.

FIG. 2 shows an example of a timing chart of the input / output control signals and the target voltage set by the target voltage setting unit 12 in each converter 10. In FIG. 2, the first stage, which is the uppermost stage, shows the control signal In (A) received by the input terminal P13 of the converter 10A (that is, the control signal Out (C) output from the output terminal P16 of the converter 10C). The second stage shows the control signal In (B) received by the input terminal P13 of the converter 10B (that is, the control signal Out (A) output from the output terminal P16 of the converter 10A), and the third stage shows the converter 10C. The control signal In (C) received by the input terminal P13 (that is, the control signal Out (B) output from the output terminal P16 of the converter 10B) is shown. The fourth stage shows the target voltage in the converter 10A, the fifth stage shows the target voltage in the converter 10B, and the sixth stage shows the target voltage in the converter 10C.

In the example shown in FIG. 2, the target voltage setting unit 12 holds the target voltage at Vout1 after the control signal changes from the high level to the low level, and the control signal output unit 14 is connected from the input terminal P13. The delay time Td from when the pulse signal is received until the pulse signal is output from the output terminal P16, and the pulse width W of the control signal are:
Tk = Td-W
It is set to satisfy.

Note that the pulse width W is a short time compared to the first holding time Tk and the delay time Td.

As shown in FIG. 2, when a pulse signal is input to the input terminal P13 of the converter 10A, the target voltage setting unit 12 of the converter 10A switches the target voltage from Vout2 to Vout1, and receives the pulse signal before receiving the pulse signal. After maintaining the target voltage at Vout1 for one holding time Tk (for example, about 10 seconds), the target voltage is switched from Vout1 to Vout2.

The control signal output unit 14 of the converter 10A delays the pulse signal input to the input terminal P13 by the delay time Td and outputs it from the output terminal P16. In the example shown in FIG. 2, since Td = Tk + W is set, the target voltage setting unit 12 of the converter 10B has the input terminal P13 at the timing when the target voltage setting unit 12 of the converter 10A switches the target voltage from Vout1 to Vout2. The target voltage is switched from Vout2 to Vout1. The target voltage setting unit 12 of the converter 10B switches the target voltage from Vout1 to Vout2 after maintaining the target voltage at Vout1 for the first holding time Tk after receiving the pulse signal.

Similarly, the control signal output unit 14 of the converter 10B delays the pulse signal input to the input terminal P13 by the delay time Td and outputs it from the output terminal P16. The target voltage setting unit 12 of the converter 10C receives the pulse signal from the input terminal P13 at the timing when the target voltage setting unit 12 of the converter 10B switches the target voltage from Vout1 to Vout2, and switches the target voltage from Vout2 to Vout1. The target voltage setting unit 12 of the converter 10C switches the target voltage from Vout1 to Vout2 after maintaining the target voltage Vout1 for the first holding time Tk after receiving the pulse signal.

In this way, the target voltage setting units 12 of the remaining two converters 10 remain in the period during which the target voltage setting unit 12 of one converter 10 among the three converters 10A to 10C sets the target voltage to Vout1. The target voltage is set to Vout2. The controller 13 controls the power converter 11 so that the output voltage of the power converter 11 approaches the target voltage. Therefore, during the period when the target voltage of converter 10A is set to Vout1, the target voltage (Vout2) of

converters

10B and 10C is lower than the voltage between output terminals P14 and P15. As a result, the output currents of

converters

10B and 10C are 0, and power is not supplied from output terminals P14 and P15. Similarly, during the period in which the target voltage of converter 10B or converter 10C is set to Vout1, converter 10 in which the target voltage is set to Vout2 does not supply power from output terminals P14 and P15.

Each control signal output unit 14 included in each converter 10A to 10C controls a target voltage setting unit 12 of each of converters 10A to 10C, thereby achieving a target voltage in one of the three converters 10A to 10C. Function as a control unit (second control unit) that sets Vout1 to Vout2 that is lower than Vout1. As a result, the converter 10 that supplies power is one unit among the converters 10A to 10C, and the converter 10 that supplies power is compared to the case where power is supplied by three units of the converters 10A to 10C. The output power increases. As a result, it is possible to suppress a reduction in loss due to the influence of fixed loss even at light loads without requiring complicated calculation processing.

In addition, since the period during which power is supplied (that is, the period during which the target voltage is set to Vout1) is uniform for each converter 10A to 10C, the amount of heat generated in converters 10A to 10C and the bias of stress on components are suppressed. Can do.

FIG. 3 is a diagram illustrating an example of a circuit configuration of the power conversion unit 11. As shown in FIG. 3, the power conversion unit 11 includes, for example, switching elements Q1, Q2, rectifying elements SR1, SR2, capacitors C11, C12, C13, coils L1, L2, a transformer T1, and a smoothing This is an LLC resonance type DC-DC converter having a capacitor C14.

Switching elements Q1, Q2, capacitors C11, C12, and coil L1 convert a DC voltage input between input terminals P11, P12 into an AC voltage, and the converted AC voltage is applied to the primary winding of transformer T1. Entered.

The AC voltage generated in the secondary winding of the transformer T1 is rectified and smoothed by the rectifying elements SR1 and SR2, the capacitor C13, the coil L2, and the smoothing capacitor C14. As a result, a DC voltage is output to the output terminals P14 and P15. In FIG. 3, MOSFETs are used as rectifying elements SR1 and SR2 by functioning as diodes.

In the example illustrated in FIG. 3, the power conversion unit 11 that converts the DC voltage input to the input terminals P <b> 11 and P <b> 12 into a different DC voltage is illustrated, but the circuit configuration of the power conversion unit 11 is limited to FIG. 3. It is not a thing. For example, the power conversion unit 11 may include a circuit configuration that steps down or boosts a DC voltage obtained by rectifying the AC voltage input to the input terminals P11 and P12.

Next, the operation when the power consumed in the load connected to the output terminals P3 and P4 increases will be described.

As shown in FIG. 2, the power supply system 1 has a configuration (redundant configuration) in which power can be supplied to the load even from only a part of the plurality of converters 10A to 10C. Therefore, when the power consumed in the load connected to the output terminals P3 and P4 is relatively light (small) (hereinafter referred to as light load), the power is obtained only from the converter 10 whose target voltage is set to Vout1. The rating of each converter 10 is set so that can be supplied. When the load is light, as shown in FIG. 2, the power supply system 1 can change the power consumed by the load by sequentially switching the converter 10 whose target voltage is set to Vout1 (that is, the converter 10 that supplies power to the load). Can be supplied.

When the power consumed by the load increases beyond the rated range (hereinafter referred to as overload), the controllers 13 of the converters 10A to 10C perform a protective operation. Specifically, when the output current of the power conversion unit 11 reaches the threshold value Ith0, the controller 13 fixes the output current to the threshold value Ith0 and performs a constant current drooping operation for reducing the output voltage as a protective operation.

FIG. 4 shows the relationship (solid line) between the output voltage and the output current in the power converter 11 of the converter 10 in which the target voltage is set to Vout1 when the constant current drooping operation is performed as a protection operation, and the target voltage is set to Vout2. It is a graph which shows the relationship (one-dot chain line) of the output voltage and output current in the power converter 11 of the converter 10 to be set. In the following description, the case where the target voltage of converter 10A is set to Vout1 and the target voltages of

converters

10B and 10C are set to Vout2 will be described as an example. However, the same applies when the target voltage of

converters

10B and 10C is set to Vout1.

FIG. 4A shows the operating point A1 of the converter 10A, the operating point B1 of the converter 10B, and the operating point C1 of the converter 10C when the power consumed by the load is within the rated range of the converter 10. An example is shown. In this case, power converter 11 of converter 10A outputs Vout1 that is the target voltage, and outputs current Ia consumed by the load (current value corresponding to operating point A1). On the other hand, since the output voltage (Vout1) from the converter 10A is applied between the output terminals P14 and P15 of the

converters

10B and 10C, the

converters

10B and 10C are applied between the output terminals P14 and P15 rather than the target voltage. The voltage increases. Therefore, the output currents of

converters

10B and 10C are 0 (current values corresponding to operating points B1 and C1 are 0). Thus, when the power consumed by the load is within the rated range of converter 10,

converters

10B and 10C do not supply power to the load.

FIG. 4B shows the operating point A2 of the converter 10A, the operating point B2 of the converter 10B, and the operating point of the converter 10C when the power consumed by the load exceeds the rated range of one converter 10. An example with C2 is shown. When the output current of converter 10A reaches threshold value Ith0, in converter 10A, controller 13 switches the operation of power converter 11 from the constant voltage operation to the constant current drooping operation. When the output voltage of the converter 10A decreases to Vout2 (operation point A2), the voltage between the output terminals P14 and P15 becomes the same as the target voltage in the

converters

10B and 10C, so the output current of the power converter 11 increases. Power is supplied from the power converter 11 to the load. When the output current of power conversion unit 11 in each of

converters

10B and 10C is Ib = {current consumed by load (load current) −Ith0} / 2 (operation points B2 and C2), outputs from converters 10A to 10C The sum of the currents matches the load current and this state is maintained.

Thus, at the time of heavy load, power is also supplied from the

converters

10B and 10C whose target voltage is set to Vout2, and power can be stably supplied to the load. That is,

converters

10B and 10C in which the target voltage is set to Vout2 do not supply power when the output current of converter 10A in which the target voltage is set to Vout1 does not reach threshold value Ith0, but are not substantially operating. If the converter 10A alone cannot supply the power consumed by the load, the power can be supplied.

When the output current of the converter 10A reaches the threshold value Ith0, the

converters

10B and 10C can immediately supply power.

In the example shown in FIG. 4, the controller 13 of the converters 10A to 10C controls the power conversion unit 11 so as to perform a constant current drooping operation as a protective operation. However, when the output current of the power conversion unit 11 reaches the threshold value Ith0, the controller 13 may control the power conversion unit 11 so that the constant power drooping operation is performed as a protection operation instead of the constant current drooping operation. The constant power drooping operation is an operation for lowering the output voltage in accordance with the increase in the output current so that the product of the output current and the output voltage is constant.

FIG. 5 shows the relationship (solid line) between the output voltage and the output current in the power conversion unit 11 of the converter 10 in which the target voltage is set to Vout1 when the constant power drooping operation is performed as a protection operation, and the target voltage is set to Vout2. It is a graph which shows the relationship (one-dot chain line) of the output voltage and output current in the power converter 11 of the converter 10 to be set. In the following description, the case where the target voltage of converter 10A is set to Vout1 and the target voltages of

converters

10B and 10C is set to Vout1.

FIG. 5A shows the operating point A1 of the converter 10A, the operating point B1 of the converter 10B, and the operating point C1 of the converter 10C when the power consumed by the load is within the rated range of the converter 10. An example is shown. In this case, as in FIG. 4A, the power conversion unit 11 of the converter 10A outputs the target voltage Vout1, and outputs the current Ia required for the load (current value corresponding to the operating point A1). To do. In

converters

10B and 10C, the voltage applied between output terminals P14 and P15 is higher than the target voltage. Therefore, in

converters

10B and 10C, the output current of power converter 11 is 0 (the current value corresponding to operating points B1 and C1 is 0). Thus, when the power consumed by the load is within the rated range of converter 10,

converters

10B and 10C do not supply power to the load.

FIG. 5B shows the operating point A3 of the converter 10A, the operating point B3 of the converter 10B, and the operating point C3 of the converter 10C when the power consumed by the load exceeds the rating of one converter 10. An example is shown. When the output current of converter 10A reaches threshold value Ith0, in converter 10A, controller 13 switches the operation of power converter 11 from the constant voltage operation to the constant power drooping operation. When the output voltage of the converter 10A decreases to Vout1 (operation point A3), the voltage between the output terminals P14 and P15 becomes the same as the target voltage in the

converters

10B and 10C, so the output current of the power converter 11 increases. Power is supplied from the power converter 11 to the load. Here, when the output current at the operating point A3 is Ic, the output current of the power conversion unit 11 in each of the

converters

10B and 10C is Id = {current required for the load (load current) −Ic} / 2. (Operation points B3, C3), the sum of the output currents from the converters 10A to 10C matches the load current, and this state is maintained. Thus, at the time of heavy load, power is also supplied from the converter 10 whose target voltage is set to Vout2, and power can be stably supplied to the load.

<Embodiment 2>
A power supply system according to Embodiment 2 of the present invention will be described below. In the first embodiment, the controller 13 controls the power conversion unit 11 so that the output voltage becomes the target voltage when the protection operation is not executed (that is, when the output current does not reach the threshold value Ith0). On the other hand, in the second embodiment, when the protection operation is not performed, the controller 13 controls the power conversion unit 11 so that the voltage-current characteristic (droop characteristic) becomes smaller as the output current becomes larger. To do.

The controller 13 controls the power conversion unit 11 so that the output voltage becomes the target voltage when the output current of the power conversion unit 11 is 0, and the output voltage becomes the target as the output current of the power conversion unit 11 increases. The power conversion unit 11 is controlled so as to decrease from the voltage. Specifically, the controller 13 detects the output current of the power converter 11 and generates a droop correction value ΔV proportional to the output current. The controller 13 controls the power converter 11 to output a voltage obtained by subtracting the droop correction value ΔV from the target voltage set by the target voltage setting unit 12.

FIG. 6 shows the relationship (solid line) between the output voltage and the output current in the power converter 11 of the converter 10 in which the target voltage is set to Vout1, and the output in the power converter 11 of the converter 10 in which the target voltage is set to Vout2. It is a graph which shows the relationship (one-dot chain line) of a voltage and an output current. In the following description, the case where the target voltage of converter 10A is set to Vout1 and the target voltages of

converters

10B and 10C is set to Vout1.

As shown in FIG. 6, in the converter 10A, the output voltage is Vout1 when the output current is 0, but the output voltage decreases as the output current increases. Similarly, in

converters

10B and 10C, the output voltage is Vout2 when the output current is 0, but the output voltage decreases as the output current increases.

FIG. 6A shows the operating point A4 of the converter 10A, the operating point B4 of the converter 10B when the power consumed by the load is relatively small within the rated range of the converter 10 (at the time of light load), An example with the operating point C4 of the converter 10C is shown. In the example shown in FIG. 6A, the converter 10A is a voltage corresponding to the current Ie consumed by the load (current value corresponding to the operating point A1), and is the target voltage Vout1 of the

converters

10B and 10C. Output higher voltage. Therefore, in

converters

10B and 10C, the output current of power conversion unit 11 is 0 (current values corresponding to operating points B4 and C4 are 0). Thus, at the time of light load,

converters

10B and 10C do not supply power to the load.

FIG. 6B shows the operating point A5 of the converter 10A, the operating point B5 of the converter 10B when the power consumed by the load is relatively large within the rated range of the converter 10 (during heavy load), An example with the operating point C5 of the converter 10C is shown.

In the example shown in FIG. 6B, the output voltage of the converter 10A is lower than Vout2, which is the target voltage of the

converters

10B and 10C, due to the droop characteristic (operation point A5). In

converters

10B and 10C, since the voltage between output terminals P14 and P15 is smaller than the target voltage, power converter 11 increases the output current and supplies power to the load. At this time, also in

converters

10B and 10C, the output voltage decreases as the output current increases due to the droop characteristic. When the output voltages of

converters

10B and 10C coincide with the output voltage of converter 10A and the sum of the output currents of converters 10A to 10C coincides with the current consumed by the load, the operations of converters 10A to 10C are stabilized. That is, if the output current at the operating point A5 is If, the output current of the power converter 11 in each of the

converters

10B and 10C is Ig = {current required for the load (load current) −If} / 2 ( The sum of output currents from the operating points B5, C5) and the converters 10A to 10C coincides with the load current, and this state is maintained.

Thus, according to the second embodiment,

converters

10B and 10C can supply power to the load before the protection operation is performed in converter 10A in which the target voltage is set to Vout1. . When the output current reaches the threshold value Ith0, the efficiency of the power conversion unit 11 decreases due to the influence of a loss (conduction loss) proportional to the square of the output current. Therefore, in the second embodiment, the efficiency of converter 10 when the power consumed by the load is increased can be improved as compared with the first embodiment.

<Embodiment 3>
The power supply system according to the third embodiment is a modification of the first or second embodiment described above, in which a part of target voltages of a plurality of converters is Vout1, and the remaining target voltage is Vout2. Apart from the control method described in (hereinafter referred to as light load mode), there is a normal mode in which the set voltage of each converter is the same value, and depending on the output current of any of the converters, Switch normal mode.

FIG. 7 is a circuit block diagram showing the configuration of each converter 20A to 20C included in the power supply system according to the third embodiment. The power supply system according to Embodiment 3 includes converters 20A to 20C shown in FIG. 7 instead of converters 10A to 10C shown in FIG.

As shown in FIG. 7, converters 20A to 20C have a target voltage setting unit 22 and a control signal output instead of target voltage setting unit 12 and control signal output unit 14 as compared with converters 10A to 10C shown in FIG. And the output current detection circuit 15 and the hysteresis comparator 16 are further provided.

The output current detection circuit 15 is a circuit that detects a current between one of the output side terminal pairs of the power conversion unit 11 and the output terminal P15. The output current detection circuit 15 includes a resistor connected between one of the output side terminal pairs of the power converter 11 and the output terminal P15, and a differential amplifier that amplifies the voltage drop of the resistor. The output current detection circuit 15 outputs a voltage Vdet that is proportional to the output current of the power converter 11. That is, the voltage Vdet is a detection value indicating the output current of the power conversion unit 11.

The hysteresis comparator 16 compares the voltage Vdet output from the output current detection circuit 15 with a threshold value, and according to the magnitude relationship, the output signal (hereinafter referred to as a mode signal) is either high level or low level. Switch to. The hysteresis comparator 16 has two threshold values, a threshold value Vth1 and a threshold value Vth2 (<threshold value Vth1). When the mode signal is at a low level, the mode signal is switched to a high level when the voltage Vdet exceeds the threshold value Vth1. When the signal is at the high level, the mode signal is switched to the low level when the voltage Vdet becomes less than the threshold value Vth2.

The hysteresis comparator 16 is a non-inverting hysteresis comparator that includes a comparator 17, a resistor R1, and a resistor R2, and a fixed voltage is applied to the inverting terminal of the comparator 17.

The resistor R2 is connected between the non-inverting terminal of the comparator 17 and the output current detection circuit 15, and the voltage Vdet is applied to the non-inverting terminal of the comparator 17 via the resistor R2. A fixed voltage Vref is applied to the inverting terminal of the comparator 17. A resistor R1 is connected between the output terminal and the non-inverting terminal of the comparator 17 to provide positive feedback. The difference between the threshold value Vth1 and the threshold value Vth2 of the hysteresis comparator 16 is determined based on the resistance values of the resistors R1 and R2 and the fixed voltage Vref.

The target voltage setting unit 22 receives a control signal from the input terminal P13 and also receives a mode signal from the hysteresis comparator 16, and sets a target voltage based on the received control signal and mode signal.

When the mode signal output from the hysteresis comparator 16 is at a low level, the target voltage setting unit 22 changes the target voltage from Vout2 to Vout1 when the control signal changes from a low level to a high level. The target voltage is changed from Vout1 to Vout2 when a predetermined first holding time (for example, about 10 seconds) elapses after changing from the high level to the low level.

However, if the target voltage is set to Vout2 when the control signal changes from the high level to the low level, the target voltage setting unit 22 changes the target voltage to Vout1, and then changes to a predetermined first holding time (for example, The target voltage is changed from Vout1 to Vout2 after about 10 seconds).

The target voltage setting unit 22 sets the target voltage to Vout1 when the mode signal output from the hysteresis comparator 16 is at a high level.

The target voltage setting unit 22 changes the target voltage from Vout1 to Vout2 when the mode signal output from the hysteresis comparator 16 changes from high level to low level when the control signal is at high level. Thereafter, the target voltage setting unit 22 performs an operation when the mode signal output from the hysteresis comparator 16 is at a low level.

When the mode signal output from the hysteresis comparator 16 is at a low level, the control signal output unit 24 generates a signal obtained by delaying the control signal received from the input terminal P13 by a predetermined delay time (for example, about 10 seconds). Then, the generated signal is output from the output terminal P16 as a control signal.

The control signal output unit 24 outputs a high-level control signal from the output terminal P16 when the mode signal output from the hysteresis comparator 16 is at a high level. When the mode signal output from the hysteresis comparator 16 changes from the high level to the low level, the control signal output unit 24 also changes the control signal output from the output terminal P16 from the high level to the low level.

As in the first embodiment, only the control signal output unit 14 of the converter 10C is set to output a high-level control signal (hereinafter referred to as a pulse signal) having a predetermined pulse width to the output terminal P16 at the time of startup. Yes.

Further, each control signal output unit 24 of converters 10A to 10C is set to output a pulse signal to output terminal P16 at the pulse signal start timing. The pulse signal start timing is defined as a predetermined delay time from timing X (for example, for example, when timing X is the timing at which the control signal first changes from high level to low level after the mode signal has changed from high level to low level) This is the timing when about 10 seconds have elapsed.

FIG. 8 is a timing chart showing an example of the relationship among the output current, the mode signal, the control signal, and the target voltage of each of the converters 20A to 20C according to the third embodiment.

In FIG. 8, the first stage, which is the uppermost stage, shows the total output current of the converters 20A to 20C. The total current corresponds to the current consumed by the load. The second to fourth stages indicate output currents of the converters 20A to 20C. The fifth to seventh stages show mode signals output from the hysteresis comparator 16 in each of the converters 20A to 20C. The eighth stage shows the control signal In (A) received by the input terminal P13 of the converter 20A (that is, the control signal Out (C) output from the output terminal P16 of the converter 20C), and the ninth stage shows the converter 20B. The control signal In (B) received by the input terminal P13 (that is, the control signal Out (A) output from the output terminal P16 of the converter 20A) is shown, and the 10th stage shows the control signal In received by the input terminal P13 of the converter 20C. (C) (that is, the control signal Out (B) output from the output terminal P16 of the converter 20B) is shown. The eleventh to thirteenth stages indicate target voltages in the respective converters 20A to 20C.

In FIG. 8, during the period from time t0 to t1, the mode signal output from the hysteresis comparator 16 of all the converters 20A to 20C is at a low level. Therefore, during this period, as in the first embodiment, the power supply system sets the target voltage of one of the converters 20A to 20C to Vout1, the target voltage of the remaining converter 20 to Vout2, and the target voltage to Vout1. The set converter 20 operates in a light load mode in which the converter 20 is sequentially switched every predetermined time. In the example shown in FIG. 7, the target voltage is set to Vout1 in the order of converter 20A, converter 20B, and converter 20C.

Next, it is assumed that the output current of the converter 20C reaches Ith1 at time t1 when the target voltage of the converter 20C is set to Vout1. Here, Ith1 is a current value corresponding to the threshold value Vth1 of the hysteresis comparator 16. Ith2 is a current value corresponding to the threshold value Vth2 of the hysteresis comparator 16. At this time, the mode signal output from the hysteresis comparator 16 of the converter 20C is switched from the low level to the high level. Thereby, in converter 20C, target voltage setting unit 22 maintains the target voltage at Vout1, and control signal output unit 24 switches the control signal output to converter 20A from the low level to the high level. Thereafter, the control signal output unit 24 of the converter 20C also maintains the output control signal Out (C) at the high level while the mode signal from the hysteresis comparator 16 is maintained at the high level.

When the control signal Out (C) output from the converter 20C changes from the low level to the high level, the target voltage setting unit 22 of the converter 20A that receives the control signal Out (C) switches the target voltage to Vout1. As a result, converter 20A also begins to supply power to the load. As a result, the output current of converter 20C decreases. However, in the converter 20C, since the mode signal output from the hysteresis comparator 16 is switched to the high level, the threshold value of the hysteresis comparator 16 is changed to the threshold value Vth2. Therefore, when the amount of decrease in the output current of converter 20C is smaller than the difference between threshold value Vth1 and threshold value Vth2, hysteresis comparator 16 of converter 20C continues to output a high-level mode signal.

Next, at time t2 when a predetermined delay time has elapsed from time t1, the control signal output unit 24 of the converter 20A switches the control signal Out (A) output to the converter 20B from the low level to the high level.

When the control signal Out (A) from the converter 20A changes from the low level to the high level, the target voltage setting unit 22 of the converter 20B that receives the control signal Out (A) switches the target voltage to Vout1. Thus, converter 20B also supplies power to the load. As a result, the power supply system is in a normal mode in which the current supplied to the load is shared by converters 20A to 20C.

At this time, in the converter 20C, the output current decreases, but both the mode signals output from the hysteresis comparator 16 are switched to the high level, and the threshold value of the hysteresis comparator 16 is changed to the threshold value Vth2. Therefore, as long as the output current of converter 20C does not become less than Ith2 (current value corresponding to threshold value Vth2), hysteresis comparator 16 of converter 20C continues to output a high-level mode signal. On the other hand, in

converters

20A and 20B, since the output current does not reach Ith1, hysteresis comparator 16 continues to output a low-level mode signal.

Next, at time t3 when a predetermined delay time has elapsed from time t2, the control signal output unit 24 of the converter 20B switches the control signal Out (B) output to the converter 20C from the low level to the high level.

At this time, in the converter 20C, the mode signal from the hysteresis comparator 16 is already at the high level, so the target voltage setting unit 22 sets the target voltage regardless of the change in the control signal Out (B) from the converter 20B. Continue to set to Vout1.

In this way, the normal mode in which the target voltage is set to Vout1 is switched in all the converters 20A to 20C. Thereafter, the current consumed by the load decreases, and in the converter 20C, the mode signal output from the hysteresis comparator 16 is at a high level until the output current becomes less than Ith2 (current value corresponding to the threshold value Vth2). Normal mode is maintained until the signal changes from low to low.

In the example shown in FIG. 8, at time t4, the output current of the converter 20C becomes less than Ith2, and the mode signal output from the hysteresis comparator 16 changes from high level to low level. Thereby, target voltage setting unit 22 of converter 20C lowers the target voltage to Vout2. As a result, in converter 20C, the target voltage is lower than the voltage between output terminals P14 and P15, and the output current of power conversion unit 11 becomes zero. As a result, the power supply from converter 20C to the load becomes zero, and the output current from

converters

20A and 20B increases.

Further, at time t4, the control signal output unit 24 of the converter 20C receives the fact that the mode signal output from the hysteresis comparator 16 has changed to low level, and outputs the control signal Out (C) output to the converter 20A to low level. Switch to.

Next, at time t5 when a predetermined first holding time has elapsed from time t4 when control signal Out (C) was switched to the low level, target voltage setting unit 22 of converter 20A changes the target voltage from Vout1 to Vout2. .

In the example shown in FIG. 8, the delay time and the first holding time are set to be the same. Therefore, at time t5, the control signal output unit 24 of the converter 20A switches the control signal Out (A) output to the converter 20B from the high level to the low level.

Next, at time t6 when a predetermined first holding time has elapsed from time t5 when control signal Out (A) is switched to the low level, target voltage setting unit 22 of converter 20B changes the target voltage from Vout1 to Vout2. . Further, since the delay time and the first holding time are set to be the same, at time t6, the control signal output unit 24 of the converter 20B changes the control signal Out (B) output to the converter 20C from the high level to the low level. Switch.

The target voltage setting unit 22 of the converter 20C sets the target voltage to Vout2 at the timing (time t6) when the control signal Out (B) changes from the high level to the low level. Therefore, target voltage setting unit 22 of converter 20C changes the target voltage to Vout1 at time t6, and then changes the target voltage from Vout1 to Vout2 at time t7 when a predetermined first holding time has elapsed.

Here, at time t6, the timing at which the control signal In (C) (= control signal OUT (B)) first changes from the high level to the low level after the mode signal changes from the high level to the low level in the converter 20C. X. Since the delay time and the first holding time are set to be the same, time t7 is a timing when a predetermined delay time has elapsed from timing X (time t6). Therefore, control signal output unit 24 of converter 20C determines that time t7 is the pulse signal start timing, and outputs the pulse signal to output terminal P16.

As shown in FIG. 8, from time t5, the power supply system is switched to the light load mode in which the target voltage of only one of the converters 20A to 20C is set to Vout1.

As described above, according to the third embodiment, in any of converters 20A to 20C, when output current exceeds Ith1 (that is, voltage Vdet output from output current detection circuit 15 exceeds threshold value Vth1). ), The target voltages of all the converters 20A to 20C are unified to Vout1.

As a result, during heavy loads where the power to be supplied to the load has increased, all of the converters 20A to 20C can share the power consumed by the load, and only one converter 20 can supply the power consumed by the load. Compared to the case, the output current of the converter 20 can be reduced. As a result, it is possible to suppress a decrease in efficiency due to conduction loss accompanying an increase in output current.

Further, when the output current of the converter 20 (converter 20C in the example shown in FIG. 8) whose mode signal output from the hysteresis comparator 16 is high level is less than Ith2 (that is, output from the output current detection circuit 15). When the voltage Vdet is less than the threshold value Vth2, the power supply system enters a light load mode in which one target voltage of the converters 20A to 20C is set to Vout1, and the target voltage of the remaining converter 20 is set to Vout2. Can be switched.

This makes it possible to increase the output current of the converter 20 that supplies power to the load, as compared to the case where the power consumed by the load is shared by all the converters 20 at a light load. As a result, it is possible to suppress a decrease in efficiency due to a fixed loss accompanying a decrease in output current.

Furthermore, since the converters 20 whose target voltage is set to Vout1 are sequentially switched every predetermined delay time, the amount of heat generated by each converter 20 can be made uniform, and the stress on the components of each converter 20 can be made uniform. can do.

<Embodiment 4>
In the first to third embodiments, in the converter in which the target voltage is set to Vout2, the voltage between the output terminals P14 and P15 is higher than the voltage output from the power conversion unit 11. At this time, due to the diode D1, the power converter 11 cannot flow current to the output terminals P14 and P15. Therefore, the controller 13 controls the power conversion unit 11 so that the output current becomes zero. That is, the power conversion unit 11 does not supply power. However, even in this case, the switching elements Q1 and Q2 (see FIG. 3) of the power conversion unit 11 are switched according to the switching frequency, and a switching loss occurs.

In the power supply system according to the fourth embodiment, when the target voltage is set to Vout2, the controller 13 is a unit in the switching elements Q1 and Q2 of the power conversion unit 11 than when the target voltage is set to Vout1. Reduce the number of switching operations per hour. Thereby, the switching loss in the converter that does not contribute to the power supply to the load can be reduced.

As a method for reducing the number of times of switching per unit time in the switching elements Q1 and Q2, a known technique can be used.

For example, when the controller 13 performs PFM (Pulse Frequency Modulation) control on the power conversion unit 11, the controller 13 may perform intermittent oscillation by thinning out a predetermined number of pulses.

Further, when PWM (Pulse Width Modulation) control is performed on the power conversion unit 11, the controller 13 oscillates while switching the switching elements Q1 and Q2 and stops the oscillation that keeps the switching elements Q1 and Q2 off. You may perform burst control which repeats a period alternately.

Further, the controller 13 may perform hysteresis control based on the output voltage of the power conversion unit 11. Specifically, the controller 13 sets the voltage slightly higher than Vout1 as the upper limit value, sets the voltage slightly lower than Vout1 as the lower limit value, and when the output voltage of the power converter 11 exceeds the upper limit value, the switching element Q1 , Q2 are kept off, and switching of the switching element Q1 is started when the output voltage of the power converter 11 becomes less than the lower limit value.

<Modification>
In the above description, the power supply system includes three converters, one of which is set to Vout1, and the other two are set to Vout2. However, the number of converters is not limited to this. Further, the number of target voltages set to Vout1 is not limited to one. For example, the power supply system may include five converters, of which three target voltages may be set to Vout1, and the remaining two may be set to Vout2. That is, the target voltage for m converters (1 ≦ m <N) of N converters may be Vout1, and the target voltage for the remaining N−m converters may be Vout2.

In the above description, each converter has the control

signal output units

14 and 24 that output the control signal to the target

voltage setting units

12 and 22 of the converter including the input terminal P13 connected to the output terminal P16 of the converter. Included. However, the power supply system may include a control signal output unit that outputs a control signal to each of the converters 10 and 20 outside the converters 10 and 20 instead of the control

signal output units

14 and 24. In this case, the control signal output unit may output a low level control signal to the

converters

10B and 10C, for example, while outputting a high level control signal to the converter 10A.

The embodiment disclosed this time is an example, and is not limited to the above contents. The scope of the present invention is defined by the terms of the claims, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

1 power system, 10 (10A to 10C), 20 (20A to 20C) converter, 11 power conversion unit, 12, 22 target voltage setting unit, 13 controller, 14, 24 control signal output unit, 15 output current detection circuit, 16 Hysteresis comparator, 17 operational amplifier, Q1, Q2 switching element.

Claims

A power supply system including N converters (N is an integer of 2 or more), wherein the N converters are connected in parallel,
Each of the N converters is
A power converter that converts input voltage to output voltage;
A first control unit for controlling the power conversion unit such that the output voltage of the power conversion unit becomes a target value;
A setting unit for setting the target value in the first control unit,
The power supply system further includes:
By controlling the setting unit of each of the N converters, the target value in m (1 ≦ m <N) of the N converters is set to the first voltage, and the remaining N− a second control unit for causing the target value in m units to be a second voltage lower than the first voltage;
The second control unit controls the setting unit of each of the N converters so that a period during which the setting unit sets the first voltage as the target value is equalized in the N converters. Let the power system.
When the output current of the power conversion unit is less than a threshold, the first control unit controls the power conversion unit so that the output voltage becomes the target value, and the output current of the power conversion unit is The power supply system according to claim 1, wherein when the threshold value is reached, the power conversion unit is controlled so that an output voltage is lower than the target value.
The first control unit controls the power conversion unit so that an output voltage becomes the target value when an output current of the power conversion unit is 0, and an increase in the output current of the power conversion unit The power supply system according to claim 1, wherein the power conversion unit is controlled so that an output voltage decreases from the target value.
Each of the N converters further includes:
A detection unit for detecting an output current of the power conversion unit;
A hysteresis comparator having a first threshold and a second threshold lower than the first threshold, and outputting a first signal or a second signal;
The hysteresis comparator outputs the first signal when the detection value detected by the detection unit exceeds the first threshold when outputting the second signal, and outputs the first signal. When the detection value falls below the second threshold when outputting, the second signal is output,
The second control unit controls the setting unit of each of the N converters so that an output signal of the hysteresis comparator of each of the N converters is changed from the second signal to the first signal. The target value in the N converters is set to the first voltage, and the output signal of any one of the hysteresis comparators in the N converters is changed from the first signal to the first signal. In the case of changing to the second signal, the target value in the m converters of the N converters is set to the first voltage, and the target value in the remaining N−m converters is set to the second voltage. The power supply system according to any one of claims 1 to 3.
The power conversion unit is a switching regulator including a switching element,
When the target value is set to the second voltage, the first control unit is configured so that the unit time of the switching element is greater than the case where the target value is set to the first voltage. The power supply system according to any one of claims 1 to 4, wherein the number of times of per-switching is reduced.