JPH04275022A - Method of starting dc power supply system - Google Patents

Abstract

PURPOSE:To avoid a rush current and start without fail a supply side converter to which a plurality of load side converters are cascade-connected to constitute a DC power supply system. CONSTITUTION:Load side converters 31-3n are cascade-connected to a supply side converter 2 and DC powers are supplied to respective loads 41-4n from the respective load side converters 31-3n, A soft-start circuit 5 which elevates an output gradually to a rated value is attached to the supply side converter 2. On the other hand, start-delaying circuits 61-6n, which start the load side converters 31-3n after delay times longer than the soft-start period are attached to the respective load side converters 31-3n to suppress rush currents, etc., produced at the time of start. By eliminating a common part for the load side converters 31-3n, the system can be controlled easily and the reliability can be improved.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a method for starting a DC power supply system that is configured by connecting a plurality of converters in series to one converter and supplies DC power to loads such as communication equipment. be.

0002

2. Description of the Related Art Power supply systems that supply DC power to communication equipment use converters for DC voltage conversion, and a plurality of converters are often connected in series. Such a conventional DC power supply system is shown in FIG. In the conventional example shown in FIG. 5, the input terminal of the power supply side converter 2 is connected to the output terminal of the DC power supply 1, and the output terminal of the power supply side converter 2 is connected to the output terminal of the power supply side converter 2.
3n input terminals are connected. Load side converter 31
Inrush current suppression circuits 71 to 7n are connected to inrush current suppression circuits 71 to 7n, respectively, and a sequential startup control circuit 8 is commonly connected to all load side converters 31 to 3n. Load side converter 31
Loads 41-4n are connected to the output terminals 41-3n, respectively.

In order to prevent the switching elements of the power supply converter 2 from being destroyed due to excessive current flowing in the power supply converter 2 compared to the rated value in the event of a load short-circuit, etc., a drooping region is set in which the output current is controlled to be constant. has been established. On the other hand, since the load side converters 31 to 3n perform constant voltage control on their outputs, the load side converters 31 to 3n can be seen as constant power loads when viewed from the input terminals. Therefore, when the number of load converters 31 to 3n corresponding to the rated load is connected to the power supply converter 2, when the input voltage is low such as during startup, a current higher than the rated output current of the power supply converter 2 flows. Since the power supply converter 2 operates in the drooping region, the output voltage cannot rise to the rated value and cannot be started.

[0004] Therefore, in order to prevent this inability to start, two measures have been taken in conventional cascade-connected converters. The first is the inrush current suppression circuit 7 to suppress the peak value of the inrush current flowing to the input filter capacitors of the load side converters 31 to 3n when the power supply side converter 2 is started.
1 to 7n are added to the load side converters 31 to 3n. The second is a sequential start-up control circuit 8 that starts up the load-side converters 31 to 3n one by one in order to prevent the overcurrent flowing through the power-supplying converter 2 from exceeding the rated output current when the power-supplying converter 2 is started. is added in common.

FIGS. 6(A), 6(B), and 6(C) show the starting characteristics of the conventional power supply side converter 2. (A) shows the output of the power feeding side converter 2 during power feeding at startup, and (B) shows the output current waveform at that time. (C) shows a startup locus drawn as a Lissajous waveform, with the vertical axis representing the output voltage of the power feeding converter 2 and the horizontal axis representing the output current of the power feeding converter 2. From (C), in the conventional example, charging currents suppressed by inrush current suppressing circuits 71 to 7n flow to the input filter capacitors of load side converters 31 to 3n at startup ((1) to (2)). After that, the input filter capacitors of the load side converters 31 to 3n are charged (
(2) to (3)), and the sequential startup control circuit 8 sequentially starts the load side converters 31 to 3n ((4) to (5)).
, settles at an equilibrium point (6). In the conventional example, the above startup method was used.

[0006]

[Problem to be Solved by the Invention] However, in the method of starting up a DC power supply system according to the above-mentioned conventional technology,
The control by the inrush current suppression circuits 71 to 7n and the startup control by the startup control circuit 8 must be performed sequentially for each load side converter 31 to 3n, which has the disadvantage that the control becomes complicated. In addition, in such a startup method, the sequential startup circuit 8 becomes a common part of the system, and if the sequential startup circuit 8 stops operating or malfunctions due to a failure, for example, it may not be possible to suppress the inrush current. There is a risk that the power supply side converter 2 may become unable to start, or that any of the load side converters 31 to 3n may become unable to start, which is a drawback that affects the reliability of the DC power supply system.

The present invention has been made to solve the above-mentioned problems, and its purpose is to solve the problems described above. When starting the converter,
It is an object of the present invention to provide a method for starting a DC power supply system that is simple and does not reduce reliability, for reliably starting a power supply side converter.

[0008]

[Means for Solving the Problems] In order to achieve the above object, in the method for starting a DC power supply system of the present invention, a DC power supply is provided in which a plurality of load side converters are connected in cascade to one power supply side converter. In the system, the power supply side converter is provided with a soft start function that gradually increases the output voltage after the input voltage is applied, and the load side converter is started after a certain time Td delay after the input voltage is applied. Equipped with a startup delay function that performs
First, the process of soft-starting the power supply side converter and gradually increasing its output voltage, and second, the process of applying the output voltage of the power supply side converter as an input voltage and then setting the constant voltage to be longer than the soft start period. The method is characterized in that it has a step of starting the load-side converter after a delay of time Td.

[0009]

[Operation] In the starting method of the DC power supply system of the present invention, when starting the power supply side converter, the soft start function of the power supply side converter is used to gradually increase the output voltage of the power supply side converter to the rated value, and the output voltage of the power supply side converter is gradually increased to the rated value. Gradually charge input filter capacitors, etc. As a result, the rush current flowing through the input filter capacitor and the like of the load-side converter can be suppressed. Furthermore, by setting the start delay time Td of the start delay function of the load side converter to be longer than the soft start period of the power supply side converter, the load side converter is started after the output voltage of the power supply side converter reaches the rated value, and the power supply side To start the load-side converter without causing an output current exceeding the rated value to flow through the converter. This simplifies the start-up control of the load-side converter by controlling only the individual start-up delay, and eliminates a control unit that is common to each load-side converter, thereby improving reliability.

0010

Embodiments Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram of a DC power supply system showing one embodiment of the present invention. In this example, PWM
The case where a (pulse width modulation) controlled converter is used will be explained as an example. As the component parts in the figure, 1 is a DC power supply,
2 is a power supply side converter, 31 to 3n are load side converters, 41 to 4n are loads, 5 is a soft start circuit, 61 to 3n are load side converters, 41 to 4n are loads, 5 is a soft start circuit, 61 to
6n indicates a start-up delay circuit.

In the connection configuration of each of these components, the input terminal of the power supply converter 2 is connected to the output terminal of the DC power supply 1, and the power supply converter 2 is connected to a soft start circuit 5, which is the main part of this embodiment. is connected. The input terminals of a plurality of load side converters 31 to 3n are connected to the output terminal of the power supply side converter 2. In addition, start delay circuits 61 to 6n, which are another main part, are connected to the load side converters 31 to 3n, respectively, and loads 41 to 4n are connected to the output terminals of the load side converters 31 to 3n, respectively.
is connected. The power supply side converter 2 functions as a constant voltage source in a steady state, and has a function of performing droop control when the rated current is exceeded.

First, the configuration of the soft start circuit 5, which is the main part of this embodiment, is shown in the schematic diagram of the power supply side converter 2 in FIG.

The power supply side converter 2 has a switching element 22 connected in series to the primary side of a high frequency transformer 21 and connected to input terminals 231 and 232, and an output rectifying element 24 and an output smoothing element on the secondary side. choke coils 25 are connected in series to the output terminals 261, 262,
An input filter capacitor 27 is provided between the input terminals 231 and 232, an output smoothing capacitor 28 is provided between the output terminals 261 and 262, and an output flywheel element 29 is provided between both ends of the transformer 21 and the output rectifying element 24. Each is connected and configured.

The soft start circuit 5 includes a power supply side PWM circuit (hereinafter referred to as a PWM circuit) 51 and a power supply side start circuit (hereinafter referred to as a PWM circuit).
(starting circuit) 52. One input of the soft start circuit 5 (the input of the PWM circuit 51) is connected to the power supply side converter 2.
The other input of the PWM circuit 51 is connected to the output of the starting circuit 52. The output of PWM circuit 51 is connected to switching element 22 of power supply converter 2 . The power supply side converter 2 is activated by the PWM circuit 5 by the soft start circuit 5 at startup.
Gradually widen the pulse width of step 1 to raise the output voltage to the rated value. That is, the rise characteristics of the output voltage of the power supply side converter 2 at the time of startup can be changed by the constant of the soft start circuit 5.

Next, the start-up delay circuit, which is another important part, will be explained with reference to the schematic diagram of the load-side converter 3 shown in FIG.

The load side converter 3 is also basically constructed in the same manner as the power supply side converter. That is, a switching element 32 is connected in series to the primary side of a high frequency transformer 31 and connected to input terminals 331 and 332, and the second
On the next side, an output rectifying element 34 and an output smoothing choke coil 35 are connected in series to output terminals 361 and 362, and an input filter capacitor 37 is connected between input terminals 331 and 332, and an input filter capacitor 37 is connected between output terminals 361 and 362. The output smoothing capacitor 38 is connected to the transformer 31 and the output rectifying element 34.
An output flywheel element 39 is connected between both ends of the output flywheel.

A circuit for controlling such a load-side converter 3 is a load-side control circuit 9 having a load-side drive circuit 91. The start-up delay circuit 6 is included in this control circuit 9. The input of the load-side control circuit 9 (input of the start-up delay circuit 6) is connected to the input terminal 331 of the load-side converter 3,
The output terminal of the start-up delay circuit 6 is connected to the input terminal of the load-side drive circuit 91. The output terminal of the load side drive circuit 91 is connected to the switching element 32 of the load side converter 3. The start-up delay circuit 6 has a function of outputting a start-up signal to the load-side drive circuit 91 after a certain period of time Td has elapsed since the input voltage was applied. Therefore, by changing the constant of the startup delay circuit 6, the startup delay time Td can be changed. Here, this startup delay time Td is set longer than the soft start period determined by the soft start circuit 5 of the power supply side converter 2 described above.

The operation and effects of one embodiment configured as above will be described.

FIGS. 4A, 4B, and 4C are diagrams showing the startup characteristics of the power supply converter 2 for explaining the operation of this embodiment. 1 shows the startup characteristics of the power supply side converter 2 when the load side converters 31 to 3n are connected in cascade as shown in FIG. (A) and (B) are the output voltage waveform and output current waveform of the power supply side converter 2 at startup, respectively. (C
) shows the startup locus of the power feeding converter 2 with the output voltage of the power feeding converter 2 on the vertical axis and the output current of the power feeding converter 2 on the horizontal axis.

In the startup method of this embodiment, first, the output voltage of the power supply side converter 2 is gradually increased to the rated value by the soft start function during startup by the soft start circuit 5, and the input filters of the load side converters 31 to 3n are Charge the capacitor 37 ((1) to (3)). Since the startup delay time Td of the load side converters 31 to 3n is set longer than the soft start period Ts by the soft start function, the output current of the power supply side converter 2 is maintained at zero ((4) to (5) )). Thereafter, the load-side converters 31 to 3n are started at the rated input voltage by the start-up delay circuit 6 (5), so an output current exceeding the rated value does not flow to the power supply converter 2 ((5) to (6) ))
, power supply side converter 2 and load side converters 31 to 3
The startup of n is completed (7).

As described above, by providing the power supply side converter 2 with a soft start function and gradually increasing the output voltage to the rated value, an excessive rush current flows to the input filter capacitor 37 of the load side converters 31 to 3n. prevent Thereby, it is possible to prevent the power feeding side converter 2 from being unable to start due to droop control. Furthermore, the startup delay time Td of the startup delay circuit 6 of the load side converters 31 to 3n
By setting Ts longer than the soft start period Ts of the power supply converter 2, the power supply converter 2 can be started without flowing an output current exceeding the rated value.

Comparing the present embodiment shown in FIG. 1 with the conventional example shown in FIG. Individual load-side converters 31 to 3n
The inrush current suppression circuits 71 to 7n that were added to the circuits become unnecessary. Furthermore, in this embodiment, in order to prevent the output current exceeding the rated value from flowing through the power supply side converter 2, the load side converters 31 to
Sequential startup control circuit 8 that started 3n one by one
can be deleted, the load-side converter 3 can be easily controlled, there is no common control section, and reliable startup is possible, and the reliability of the DC power supply system can be improved.

In the above embodiment, the case where a PWM control type converter is used has been described, but the present invention can be applied to other types of converters other than PWM control type converters. As described above, the present invention can be applied in various ways and can take various embodiments in accordance with the gist thereof.

[0025]

Effects of the Invention As is clear from the above explanation, according to the method for starting a DC power supply system of the present invention, a soft start function is added to the power supply side converter, a start delay function is added to the load side converter, and the start delay is By setting the time longer than the soft start period, inrush current to the input filter capacitor of the load side converter can be suppressed, and an output current exceeding the rated value can be prevented from flowing to the power supply side converter. Therefore, the conventional inrush current control circuit and the sequential activation control circuit of the common part can be eliminated, and it is possible to provide a simpler and more reliable activation method than the conventional activation method.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a DC power supply system showing an embodiment of the present invention.

[Figure 2] Schematic diagram of the power supply side converter in the above embodiment

[Figure 3] Schematic diagram of the load-side converter in the above embodiment

[Figure 4] (A), (B), and (C) are diagrams showing the startup characteristics of the power supply side converter of the above example.

[Figure 5] Block diagram of a conventional DC power supply system

[
Figure 6: (A), (B), and (C) are diagrams showing the startup characteristics of the power supply side converter of the above conventional example.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1...DC power supply, 2...Power supply side converter, 3...Load side converter, 4...Load, 5...Soft start circuit, 6...Start delay circuit, 9...Load side control circuit, 22...Switching element of power supply side converter, 32 ...Switching element of load side converter, 51...Power supply side PWM circuit, 52...Power supply side starting circuit, 91...Load side drive circuit.

Claims (1)

[Claims] Claim 1: In a DC power supply system in which a plurality of load side converters are connected in series to one power supply side converter, the power supply side converter has a soft start function that gradually increases the output voltage after application of an input voltage. The load-side converter is equipped with a start-up delay function that starts the load-side converter after a certain period of time Td after the input voltage is applied, and first, the power supply-side converter is soft-started to gradually increase its output voltage. and then a step of starting the load-side converter after applying the output voltage of the power supply-side converter as an input voltage and delaying the fixed time Td set longer than the soft-start period. A method of starting up a distinctive DC power supply system.