JP2004328893A - Power supply device and its operation method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To supply a stable and almost constant power supply voltage to a CPU or the like by suppressing output voltage fluctuations when a load is suddenly changed without depending on a multi-phase system. <P>SOLUTION: The power supply device is constituted as follows: An almost constant DC output voltage is supplied to the load via an output capacitor by converting the DC input voltage with a first converter in the switching system. A second converter in a series regulator system is connected between DC input/output terminals on the positive side of the first converter. The power supply device keeps the DC output voltage almost constant by sharing a load current with both converters when the load current fluctuates. The first converter is constituted of a step-down chopper 10 composed of a main switching element 11 and a synchronous rectification element 12, which are mutually connected in series between DC input terminals P1, N1, and a reactor 13 which is connected between the mutual connection point of both elements 11, 12 and an output terminal P2. The second converter is constituted of a switching element 61 connected in series between the input/output terminals P1, P2. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a power supply device for a load of an information device or the like in which current consumption changes abruptly, such as a CPU, and more particularly to a power supply device capable of controlling an output voltage at a high speed and substantially constant even when a load suddenly changes, and a method of operating the same. Things.
[0002]
[Prior art]
FIG. 4 is a circuit diagram (FIG. 4A) showing a power supply device for an information device such as a CPU and an operation explanatory diagram (FIG. 4B). This circuit is described in Non-Patent Document 1 described later.
[0003]
In FIG. 4A, P1 and N1 are DC input terminals connected to a DC power supply (not shown). An input capacitor 40 is connected between these input terminals P1 and N1, and an input capacitor is connected between the input terminals P1 and N1. In parallel with 40, step-down choppers 10, 20, and 30 having the same configuration are connected. Each step-down chopper, for example, the step-down chopper 10 includes a main switching element 11 such as an n-channel MOSFET and a synchronous rectifying element 12 connected in series with each other at both ends of an input capacitor 40, and a reactor 13 having one end connected to their interconnection point. It consists of In the other step-down choppers 20, 30, reference numerals 21 and 31 denote main switching elements, reference numerals 22 and 32 denote synchronous rectification elements, and reference numerals 23 and 33 denote reactors.
[0004]
The other end of each of the reactors 13, 23, 33 and the sources of the synchronous rectifiers 12, 22, 32 are collectively connected to the DC output terminals P2, N2, respectively, between the output terminals P2, N2. Is connected to an output capacitor 50.
Although not shown, a CPU or the like as a load is connected in parallel between the DC output terminals P2 and N2.
[0005]
Next, the operation of FIG. 4A will be described with reference to FIG. Since the operations of the step-down choppers 10, 20, and 30 are the same, the step-down chopper 10 will be described here as an example.
When the main switching element 11 of the step-down chopper 10 is turned on, the energy stored in the capacitor 40 moves to the capacitor 50 via the reactor 13 through the path of the capacitor 40 → the main switching element 11 → the reactor 13 → the capacitor 50. Next, when the main switching element 11 is turned off, the energy stored in the reactor 13 moves to the capacitor 50 through a path of the reactor 13 → the capacitor 50 → the synchronous rectification element 12. Also, at this time, turning on the synchronous rectifier 12 reduces the on-voltage of the synchronous rectifier 12.
[0006]
The step-down chopper 10 adjusts the DC output voltage across the capacitor 50 by adjusting the on / off ratio of the main switching element 11 and the synchronous rectifier element 12, and the other step-down choppers 20 and 30 operate similarly.
Further, the step-down choppers 10, 20, and 30 are operated in three multiplexes by shifting the phases of turning on the main switching elements 11, 21, and 31 by 120 degrees as shown in FIG. 4B. This is called a multi-phase method.
By employing such a multi-phase method, the output voltage fluctuation of the power supply device can be reduced even for a load that fluctuates rapidly such as a CPU.
[0007]
FIG. 5 shows the case where power is supplied to the step load in the case where the step-down chopper has one phase (FIG. 5A) and the case where the step-down chopper has three phases as shown in FIG. 4A (FIG. 5B). It shows the output voltage and the current of each part. Here, “ΔI = 30 A” described in the titles of FIGS. 5A and 5B means a change width of the reactor current (load current). In the three phases of FIG. The change width ΔI of the load current as the total value of the reactor current is 30A.
The three-phase operation reduces the output voltage fluctuation ΔV from about 0.15 V to about 0.11 V, and reduces the settling time Δt from about 11 μs to about 4 μs, indicating that the output voltage is stabilized in a short time.
[0008]
Further, although the circuit configuration is different from that of FIG. 4, a switching power supply that suppresses pulsation of an input current waveform by switching a plurality of transistors connected in parallel to a DC power supply while sequentially shifting the phase by a predetermined electrical angle. An apparatus is described in Patent Document 1.
[0009]
[Non-patent document 1]
Hiroto Terashi, "Design Method of Computer Power Supply", Densei Lambda Co., Ltd., Distribution Materials for 2002 Switching Power Supply Symposium, D3-3-1 to 22, 2002 [Patent Document 1]
JP-A-10-127050 ([0012], [0013], [0024], FIG. 2 etc.)
[0010]
[Problems to be solved by the invention]
The voltage fluctuation range allowable as the power supply voltage of the load of the CPU or the like is 1.3V ± 0.5V at present, but it is required to be 1.3V ± 0.2V in the future. For example, Don Wood, Ted It is described in "Trends in Power Distribution Interconnect Technologies" by DiBene (2002 IBM Power Technology Symposium, 2002), and it is required that the voltage fluctuation range be reduced to half or less of the current level.
[0011]
As can be seen from the three-phase operation waveforms in FIG. 5B, even if the phase is changed from one phase to three phases by multiplexing, the voltage fluctuation width is reduced only by about 25% from about 0.15 V to about 0.11 V. In order to reduce voltage fluctuation by half by multiplexing, the number of phases must be further increased. For this reason, the conventional multi-phase method has a problem in that the number of parts increases, the apparatus becomes expensive, and the apparatus becomes large.
Further, a load such as a CPU fluctuates a load current with a magnitude of about several kA / μs, and a voltage drop of several V occurs even when a parasitic inductance due to wiring or the like is 1 nH (wiring length is about 1 mm). When the size of the apparatus is increased by connecting the choppers in parallel, there is a problem that even if the number of phases is increased, the effect becomes ineffective at a certain number of phases.
[0012]
Accordingly, the present invention provides a power supply device and a method of operating the power supply device, in which a fluctuation in output voltage at the time of a sudden load change is promptly suppressed, and a stable power supply voltage is supplied to a load such as a CPU without depending on the multi-phase method. It is what we are going to offer.
[0013]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, a power supply device according to claim 1 converts a DC input voltage by a first converter of a switching system and supplies a substantially constant DC output voltage to a load via an output capacitor. , A second converter of a series regulator type is connected between the positive DC input terminal and the positive DC output terminal of the first converter, and when the load current fluctuates, the first and second converters are connected. The load current is shared by the device, and the DC output voltage is kept almost constant.
[0014]
According to a second aspect of the present invention, in the power supply device according to the first aspect, the first conversion device includes a main switching element and a synchronous rectification element connected in series between a pair of DC input terminals. A step-down chopper comprising a reactor connected between an interconnection point of the elements of the above and a positive-side DC output terminal, and the second converter is provided with a positive-side DC input terminal of the step-down chopper and a positive-side DC output It is composed of switching elements connected in series between the terminals.
[0015]
As a method for operating the power supply device according to the first or second aspect, as described in the third aspect, in a steady state where the load current is substantially constant, the first converter supplies power to the load, When the power supply changes, power corresponding to the fluctuation is supplied from the second converter to the load.
In this case, the output voltage command value of the second converter is set to be lower than the output voltage command value of the first converter, as described in claim 4. As described above, it is desirable to detect the deviation between the output voltage command value of the first converter and the output voltage, and to operate the second converter so as to eliminate this deviation.
[0016]
At present, the operating frequency of the switching power supply is 250 kHz to 1 MHz as shown in the above-mentioned Non-Patent Document 1. The high frequency characteristic of the switching type step-down chopper is less than 1/2 of the switching frequency, and even if this type of step-down chopper is made into two phases or three phases, it can only have a response speed of at most 1 to 3/2 or less of the switching frequency. No. However, the operating frequency of the series regulator is the frequency characteristic of the constituent switching elements. Therefore, if an element capable of high-speed switching such as a MOSFET is used, high-speed operation up to a frequency characteristic of several tens of MHz or more is possible. The series regulator is a type of linear regulator, and is widely known as a power stabilizing device that operates like an automatic variable resistor in order to always keep a voltage supplied to a load constant.
That is, in the power supply device according to the first and second aspects, the second conversion device of the series regulator system is operated and the output capacitor is charged by the output current so as to compensate for the output voltage fluctuation at the time of a sudden change in load. Thereby, the fluctuation of the output voltage is quickly suppressed.
[0017]
According to the operation method described in claims 3 to 5, the series converter type second converter does not operate in the steady state, and the power conversion efficiency is lower than the switching type first converter, for example, of the step-down chopper. Since it is determined by the conversion efficiency, higher efficiency can be achieved.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows a circuit configuration of the present embodiment, and the same components as those in FIG. 4A are denoted by the same reference numerals.
[0019]
In FIG. 1, a step-down chopper 10, which is a switching type first converter, is connected to both ends of an input capacitor 40 between the DC input terminals P1 and N1, as in FIG. It is composed of a series circuit of a main switching element 11 and a synchronous rectification element 12 composed of an n-channel MOSFET, and a reactor 13 having one end connected to an interconnection point between the elements 11 and 12. An output capacitor 50 is connected between the other end of the reactor 13 and the source of the synchronous rectifier 12, and both ends are DC output terminals P2 and N2 of the power supply device.
Although not shown, a load such as a CPU is connected to the DC output terminals P2 and N2.
[0020]
In this embodiment, a switching element 61 such as an n-channel MOSFET constituting a series regulator is connected in series as a second converter between the positive DC input terminal P1 and the DC output terminal P2. Specifically, the drain of the switching element 61 is connected to the DC input terminal P1, and the source is connected to the DC output terminal P2.
[0021]
When the output voltage command value of the step-down chopper 10 is set as an output voltage command value V ₀ ^* as a power supply device by a control circuit (not shown), the output voltage command value V ₀₂ ^* of the series regulator by the switching element 61 is set to For example, it is set to a value lower than V ₀ ^* by about 0.05 V.
[0022]
Next, the operation of this embodiment will be described.
FIG. 2A is an operation waveform diagram when the load current is constant and steady, and FIG. 2B is an operation waveform diagram when the load current suddenly changes in a step-like manner from the no-load state.
First, in the steady state, the output voltage of the power supply device is maintained at the command value V ₀ ^* by the output current of the step-down chopper 10, so that the switching element 61 of the series regulator is turned off as shown in FIG. The control is performed so as not to occur. Therefore, the conversion efficiency of the power supply device is the conversion efficiency of the switching step-down chopper 10.
[0023]
As shown in FIG. 2B, when the load current changes stepwise from the no-load state, the voltage of the output capacitor 50 decreases, and the output voltage command value V ₀ ^{* of the} step-down chopper 10 decreases. an attempt to compensate for minute electric power output voltage V ₀ decreases, the oN period of the main switching element 11 is operated to increase. However, since the output current of the step-down chopper 10 does not rise sharply due to the control delay of the step-down chopper 10 and the reactor 13, the output current is a first-order lag current having ripples as shown in FIG. As a result, the output capacitor 50 is further discharged, so that the output voltage of the power supply device becomes lower than the command value V ₀ ^* .
[0024]
When the output voltage V ₀ reaches the output voltage command value V ₀₂ ^* of the series regulator, the switching element 61 of the series regulator is turned on, so that the capacitor 50 is charged through the path of the capacitor 40 → the switching element 61 → the capacitor 50. Electric current flows. Here, the series regulator operates with the frequency characteristics of the MOSFET that is the constituent switching element, and thus can obtain a high-speed response characteristic of several tens of MHz or more.
[0025]
By the operation of the series regulator, the output voltage V ₀ of the power supply device is maintained at the output voltage command value V ₀₂ ^* of the series regulator. Eventually, the current of the step-down chopper 10 reaches the required load current, and the voltage of the capacitor 50 reaches the output voltage command value V ₀ ^* of the step-down chopper 10. As a result, the output current of the series regulator becomes zero, and thereafter, the operation becomes the same as in the steady state in FIG. 2A, and the conversion efficiency of the switching step-down chopper 10 can be obtained.
[0026]
As described above, according to the present embodiment, by setting the output voltage command value V ₀₂ ^* of the series regulator to a value slightly lower than the output voltage command value V ₀ ^* of the step-down chopper 10, the power supply When the output voltage of the power supply temporarily drops, the series regulator operates to share the supply power corresponding to the voltage fluctuation. As a result, the output voltage V ₀ of the power supply device is maintained at the output voltage command value V ₀₂ ^* , and thereafter, the output voltage V ₀ quickly recovers to the output voltage command value V ₀ ^* of the step-down chopper 10. Significant fluctuations in the output voltage can be suppressed.
[0027]
Next, FIG. 3 is an operation waveform diagram in a case where a series regulator is operated so as to detect a deviation of the output voltage V ₀ of the power supply device (a change from the output voltage command value V ₀ ^* ) and compensate for the deviation. It is.
In this case, the output voltage command value V ₀₂ ^* of the series regulator is set substantially equal to the output voltage command value V ₀ ^* of the step-down chopper 10, and the output voltage V ₀ is slightly smaller than the output voltage command value V ₀₂ ^{* of the} series regulator. However, when a deviation occurs due to a decrease, control is performed to turn on the switching element 61 of the series regulator to eliminate the deviation.
[0028]
Since the steady-state variation of the output voltage V ₀ is hardly generated, the output current of the series regulator as shown in FIG. 3 (a) is substantially zero, the overall operation is the same as FIG. 2 (a).
Then, by detecting the deviation (V 0 _* ^-V ₀₎ of the output voltage V ₀ load change occurs as shown in FIG. 3 (b) decreases, the control circuit is the output voltage command value V ₀ ^* The The switching element 61 of the series regulator is quickly turned on so as to eliminate the deviation, and the capacitor 50 is charged through the path of the capacitor 40 → the switching element 61 → the capacitor 50.
[0029]
At this time, similarly to FIG. 2B, the step-down chopper 10 operates to increase the ON period of the main switching element 11 in an attempt to supplement the power corresponding to the decrease in the output voltage V _0. Current gradually increases while having ripples, and eventually reaches a value required as a load current.
As a result, the output voltage V ₀ stops decreasing, and the output current of the series regulator becomes zero. Thereafter, the operation becomes the same as in the normal state.
[0030]
As shown in FIG. 2 and FIG. 3 described above, the series regulator is controlled so as not to operate when the load current is almost constant, and when the output voltage V ₀ decreases due to a sudden change in the load, the output voltage command value V ₀₂ ^* , the series regulator can be operated almost simultaneously with the step-down chopper as shown in FIG. 2, or the series regulator can be operated in advance as shown in FIG. When the load suddenly changes, the load current is shared by the step-down chopper and the series regulator to suppress the fluctuation of the output voltage at an early stage, so that a stable DC voltage can be supplied to the load.
[0031]
【The invention's effect】
As described above, according to the present invention, by using only two circuits of the first converter such as the switching step-down chopper and the second converter of the series regulator type, the output when the load changes abruptly is obtained. Voltage fluctuation can be suppressed at an early stage, and the number of components is reduced as compared with a conventional multi-phase power supply device, so that the size and cost of the device can be reduced.
In addition, a high conversion efficiency equivalent to that of a switching step-down chopper can be obtained in a steady state, and a high-speed response equivalent to a case where only a series regulator is used can be obtained during a load change.
[Brief description of the drawings]
FIG. 1 is a circuit diagram showing an embodiment of the present invention.
FIG. 2 is an operation waveform diagram of the embodiment of FIG.
FIG. 3 is an operation waveform diagram of the embodiment of FIG.
FIG. 4 is a circuit diagram and an operation explanatory diagram showing a conventional technique.
FIG. 5 is an operation waveform diagram when the step-down chopper has one phase and three phases.
[Explanation of symbols]
10: Step-down chopper 11: Main switching element 12: Synchronous rectifying element 13: Reactor 40: Input capacitor 50: Output capacitor 61: Switching element (series regulator)
P1, N1: DC input terminal P2, N2: DC output terminal

Claims (5)

In a power supply device for converting a DC input voltage by a first converter of a switching system and supplying a substantially constant DC output voltage to a load via an output capacitor,
A second converter of a series regulator type is connected between the positive DC input terminal and the positive DC output terminal of the first converter, and when the load current fluctuates, the first and second converters A power supply device sharing a load current and keeping a DC output voltage substantially constant. The power supply device according to claim 1,
A first switching device, a main switching element and a synchronous rectifying element connected in series between a pair of DC input terminals, and a reactor connected between an interconnection point of these elements and a positive DC output terminal. Composed of a step-down chopper consisting of
A power supply device, wherein the second converter is constituted by a switching element connected in series between a positive DC input terminal and a positive DC output terminal of the step-down chopper. The power supply device according to claim 1 or 2,
In a steady state where the load current is almost constant, power is supplied to the load by the first converter, and when the load current fluctuates, power corresponding to the fluctuation is supplied from the second converter to the load. How to operate the power supply. The method for operating a power supply device according to claim 3,
An operation method of a power supply device, wherein an output voltage command value of a second converter is set lower than an output voltage command value of a first converter. The method for operating a power supply device according to claim 3,
A method of operating a power supply device, comprising: detecting a deviation between an output voltage command value and an output voltage of a first converter, and operating a second converter to eliminate the deviation.

Images