1267720 九、發明說明： ^ 【發明所屬之技術領域】 本發明係關於一種用於並聯式電源供應器的電流 分配（current sharing)技術，並且更特別的是本發明 係關於一種用於並聯式電源供應器中，具有電流限制功 能的主動下降電流分配電路（active droop current sharing circuit) 〇 _ 【先前技術】 交換式電源供應器通常係作用為用來輸送電力以 滿足電子系統的需求的基本電力供應單元。例如，直流 -直流轉換器通常係設計為將一直流電壓準位轉換成一 個或數個不同的直流電壓準位以符合一系列的規格要 求。 在實際運作時，當提供電力給一電子系統同時考慮 到負載能力時，兩台或多台直流—直流轉換器會並聯連 • 接以組成一並聯式電源供應系統。並聯式電源供應系統 了以長:供南階的几餘也力（high-level redundancy)給 需要電力以高連續性（high continuity)及高可靠度 (high reliability)來分布的特殊應用。 理論上’並聯式電源供應系統係設定為平均分配負 载電流。也就是說，在一並聯式電源供應系統中的每個 並馬卩式笔源供應裔係设定為提供總負載電流的一個大 約相等的比例給一共同負載(common l〇ad)。然而在許 多實際應用中，並聯式電源供應器經常會遭遇到其個別 1267720 ^出電，因為諸如溫度係數、老化與輸出阻抗差異等因 _文艾口此使得並聯式電源供應器之間的精確電漭 匹配相對而言變的難以達成。 爪1267720 IX. Description of the Invention: ^ Technical Field of the Invention The present invention relates to a current sharing technique for a parallel power supply, and more particularly to a parallel power supply. Active droop current sharing circuit with current limiting function in the supplier 〇_ [Prior Art] The switching power supply usually functions as a basic power supply for transmitting power to meet the needs of the electronic system. unit. For example, DC-DC converters are typically designed to convert a DC voltage level to one or several different DC voltage levels to meet a range of specifications. In actual operation, when power is supplied to an electronic system while considering the load capacity, two or more DC-DC converters are connected in parallel to form a parallel power supply system. The parallel power supply system has a long range: high-level redundancy for the south is required for special applications where power is distributed with high continuity and high reliability. In theory, the parallel power supply system is set to distribute the load current evenly. That is, each of the parallel-type power supply systems in a parallel power supply system is set to provide a substantially equal ratio of the total load current to a common load (common). However, in many practical applications, the parallel power supply often encounters its individual 1267720 ^ power supply, because the temperature coefficient, the aging and the output impedance difference, etc., make the precision between the parallel power supplies. EDonkey matching is relatively difficult to achieve. claw
Sharing Unique) 文個電源轉換器平均分配負載電流，仍有可 化.供Λ11發出突發性的變 衡。由並聯式電負載電流分配可能會產生不平 會降低並聯式電所引起的負載電流不平均分配 換器使用同步整：::應糸統的效能與可靠度。當電源轉 回授特性而_=^個問題會因為這些電路的固有 缠换成特重要。在某些情況下，具有比其他 出電壓的一電源轉換器會自其他的 :巧換錢入電流，藉此進一步降低電源電路的效 :坆個'及入宅成（sink current)通常是取決於電源轉 換器之間的電壓差1及其輸出阻抗。 、在缺少強制電流分配的情形下，以並聯方式設置的 電源轉換1§通常會被設定在—限流模式（eurrent iimit mode)下運作’其係禁止輸出電流超過一個特定值。在 此種情形下，具有較高輸出電壓及/或具有較低阻抗的 轉換為經常會提供最大的容許電流（maximum allowed current) ’而具有較低輸出電壓及/或具有較高阻抗的 轉換器會以相當低的輪出電流或是沒有輸出電流的方 式閒士或者更糟粒的是，自其他負載繁重的轉換器汲 )電流：因此限流的電源轉換器的效率會變的相當低， 亚且閒置（汲入）的電源轉換器的效率實際上為零，其是 因為沒入轉換II並未傳送電源，但是卻在消耗電源。因 7 126772〇 此，有效的電流分配將會逐漸改善並聯式電源供應系統 的整體效率。 數種完成電流分配設置的技術已經提出。其中一種 最常用的電流分配技術係利用以電子化的方式加入輸 出電壓下降（output voltage droop)為輪出電流的函數 的做法，藉此使得輸出電壓可以透過與電流的函數關係 向下調整。以電壓下降的角度來補償負載電流分配的技 術通常稱為下降電流分配（droop current sharing)， I 其中每個並聯式電源供應器的輸出電壓係取決於其輸 出電流。在此種情形下，每個並聯式電源供應器設置個 別的電流分配腳位（current sharing pin)且並聯連接 於背板（backplane)上，使得並聯式電源供應器得以分 予其負載電流的复。當一台並聯式電源供應器的輸出 電流增加時，其輸出電壓會略為下降來強迫其他並聯式 ㊄源供應器負擔更多的負載電流。若是在已知的負載下 所有的並聯式電源供應器都調整至相同的電壓且具有 相同的電壓對電流斜率（voltage versus current I sI〇pe)，它們會以高準確率的方式來分擔負載。利用這 種電流分配系統，便可在不需要一個互連匯流排 (interconnection bus)的條件下實現一個自動電流分 配機制。 在大部分的直流電源供應器中，能夠提供一個固定 的直流電壓是較為理想的。因此在一直流電源供應器中 普遍需要一個回授電路來維持一個固定的直流電壓。在 一並聯式電源供應系統中，每個並聯式電源供應器使用 實際的電流回授信號來調整其輸出電壓參考值而使得 8 1267720 所有的並聯式電源供應器共同分配負載電流。在這種方 法中，大部分的直流電源供應器會提供一個過電流保護 功能（overcurrent protection function)來根據輸出 電壓對輸出電流關係限制輸出電流於一最大額定值 (maximum rated value)内 ° 圖一顯示具兩主動下降電流分配（active droop current sharing)與過電流保護功能（overcurTent protection function)的傳統並聯式電源供應器。在圖 一中，一直流-直流轉換器100係於一背板（未顯示）上 並聯連接以提供一個或是多個預定電壓準位給一個共 同負載101，並且與其他的並聯式電源供應器分擔一部 分的總負載電流。主動下降電流分配電路110包含一電 流感測電阻（current sensing resistor)Rs，其位於直 流-直流轉換器100的輸出端與共同負載101之間，用 以產生與輸出電流成正比的一電壓，使得直流-直流轉 換器100的實際輸出電壓相等於直流-直流轉換器1〇〇 的名義輸出電壓（nominal output voltage)減去電流感 測電阻Rs兩端的壓降（voltage drop)的值。此外，一 電流分配放大器（current sharing amplifierM 11係設 置於電流感測電阻Rs與耦接至直流-直流轉換器loo的 一開關控制器103之間。該電流分配放大器111係將名 義輸出電壓與經由一分壓器（voltage divider) 112所得 到的部分輸出電壓（fractional output voltage)的差 異放大，並且將代表由並聯式電源供應器所提供的輸出 電流之放大差異值（amplified difference value)輸 出。該放大差異值會送至開關控制器103使得開關控制 器103能夠微調直流-直流轉換器100的開關電晶體電 1267720Sharing Unique) The average load current of the power converters is still available. The supply 11 provides a sudden change. The parallel current load current distribution may cause unevenness. It will reduce the uneven distribution of load current caused by the parallel type. The converter uses synchronous whole::: The efficiency and reliability of the system. When the power is turned back to the characterization, _=^ problems are inherently important because of the inherent tangling of these circuits. In some cases, a power converter with a different output voltage will be used to exchange current into the current, thereby further reducing the effectiveness of the power circuit: the 'sink current' and the sink current usually depend on The voltage difference between the power converters is 1 and its output impedance. In the absence of forced current distribution, the power conversion 1 § set in parallel is usually set to operate in the eurrent iimit mode, which prohibits the output current from exceeding a certain value. In this case, a converter with a higher output voltage and/or a lower impedance will often provide a maximum allowable current and a converter with a lower output voltage and/or higher impedance. Will be a relatively low turn-off current or no output current in the way of a slash or worse, from other heavy-duty converters 汲) current: so the efficiency of the current-limited power converter will become quite low, The efficiency of a sub-active (intrusive) power converter is virtually zero because it does not transmit power and does not transmit power, but consumes power. For 7 126772, effective current distribution will gradually improve the overall efficiency of the parallel power supply system. Several techniques for completing current distribution settings have been proposed. One of the most common current distribution techniques utilizes the electronically added output voltage droop as a function of the wheel current, thereby allowing the output voltage to be adjusted downward as a function of current. The technique of compensating for load current distribution at a voltage drop angle is commonly referred to as droop current sharing, where the output voltage of each of the parallel power supplies is dependent on its output current. In this case, each parallel power supply is provided with a separate current sharing pin and connected in parallel to the backplane, so that the parallel power supply can be divided into its load current. . When the output current of a parallel power supply increases, its output voltage drops slightly to force other parallel five-source supplies to carry more load current. If all parallel power supplies are tuned to the same voltage and have the same voltage versus current I sI〇pe under known loads, they will share the load with high accuracy. With this current distribution system, an automatic current distribution mechanism can be implemented without the need for an interconnect bus. In most DC power supplies, it is desirable to be able to provide a fixed DC voltage. Therefore, a feedback circuit is generally required in a DC power supply to maintain a fixed DC voltage. In a parallel power supply system, each parallel power supply uses an actual current feedback signal to adjust its output voltage reference so that all of the parallel power supplies of the 8 1267720 share the load current. In this method, most DC power supplies provide an overcurrent protection function to limit the output current to a maximum rated value based on the output voltage. A conventional parallel power supply with two active droop current sharing and overcurTent protection functions is shown. In FIG. 1, the DC-DC converter 100 is connected in parallel on a backplane (not shown) to provide one or more predetermined voltage levels to a common load 101, and to other parallel power supplies. Share a portion of the total load current. The active falling current distribution circuit 110 includes a current sensing resistor Rs between the output of the DC-DC converter 100 and the common load 101 for generating a voltage proportional to the output current. The actual output voltage of the DC-DC converter 100 is equal to the nominal output voltage of the DC-DC converter 1 减 minus the value of the voltage drop across the current sense resistor Rs. In addition, a current sharing amplifier (current sharing amplifier M 11 is disposed between the current sensing resistor Rs and a switch controller 103 coupled to the DC-DC converter loo. The current distribution amplifier 111 is configured to pass the nominal output voltage The difference in fractional output voltage obtained by a voltage divider 112 is amplified and will represent an amplified difference value output of the output current provided by the parallel power supply. The amplification difference value is sent to the switch controller 103 so that the switch controller 103 can finely adjust the switching transistor power 1267720 of the DC-DC converter 100.
Gyele) ’藉此調整每個並 式輪出電壓，並且藉由延長由每個並聯 :後;ί i fa 口開關控制器10 3所發出的開關控制信號 外，一過電流偵測電路120係耦接於直流-直流 轉換姦100的輸出端與開關控制器1〇3之間。該過電流 偵測電路120包含一誤差操作電路（err〇r 〇p"erati⑽Gyele) 'This adjusts each of the parallel wheel-out voltages, and by extending the switch control signal from each of the parallel: rear; ί i fa port switch controllers 10 3 , an overcurrent detection circuit 120 The output is coupled between the output of the DC-DC converter 100 and the switch controller 1〇3. The overcurrent detection circuit 120 includes an error operation circuit (err〇r 〇p"erati(10)
c,ircUit)i21，用以比較名義輸出電壓與實際輸出電壓 並且根據輸出電壓產生一電流回授信號。該電流回授信 號會送至一誤差放大器丨22的反向輸入端。該誤差放大 器122會將該電流回授信號放大成為一誤差電壓信號， 其代表電流回授信號與一第一參考信號Vrefl之間的差 異。該誤差電壓信號會耦合至開關控制器1〇3以補償直 流一直流轉換器10 0的輸出電壓的變化。此外，該誤差 龟壓·號作用為一電流命令信號（current command signal)，其使得開關控制器103能夠因應該誤差電壓 信號來監視並控制直流-直流轉換器1〇〇的輸出電流， 使得開關控制器103的電流感測輸入（current sense input)能夠立即啟動來限制直流-直流轉換器100的輸 出電流避免超過其最大額定值。若直流-直流轉換器1〇〇 的輸出電流超過其最大額定值’開關控制器10 3會停止 傳送提供給直流-直流轉換器100的開關電晶體電路的 開i控制信號，並且關閉直流-直流轉換器1〇〇的開關 運作以避免損害。 另外’並聯式電源供應器10 0包含一過電流保護狀 1267720c, ircUit) i21, for comparing the nominal output voltage with the actual output voltage and generating a current feedback signal based on the output voltage. The current feedback signal is sent to the inverting input of an error amplifier 丨22. The error amplifier 122 amplifies the current feedback signal into an error voltage signal representative of the difference between the current feedback signal and a first reference signal Vref1. The error voltage signal is coupled to the switch controller 1〇3 to compensate for variations in the output voltage of the DC-DC converter 100. In addition, the error turtle pressure number acts as a current command signal, which enables the switch controller 103 to monitor and control the output current of the DC-DC converter 1〇〇 in response to the error voltage signal, so that the switch The current sense input of the controller 103 can be immediately activated to limit the output current of the DC-DC converter 100 from exceeding its maximum rating. If the output current of the DC-DC converter 1〇〇 exceeds its maximum rating, the switch controller 103 stops transmitting the ON control signal supplied to the switching transistor circuit of the DC-DC converter 100, and turns off the DC- The switching of the DC converter 1〇〇 operates to avoid damage. In addition, the parallel power supply 10 0 includes an overcurrent protection 1267720
態信號產生器（OCP status signal generator)130。該 過電流保護狀態信號產生器130包含一過電流保護比較 器（OCP comparator)131，用以比較直流-直流轉換器100 的名義輸出電壓與一第二參考信號Vref2之間的差異， 以便判斷是否有過電流的狀況發生。若判斷有過電流的 狀況發生，過電流保護比較器131會產生一過電流保護 狀態信號（OCP status signal)且傳送該過電流保護狀 Ί"L號給一内部處理電路（housekeeping circuit，未顯 不），以警告在並聯式電源供應系統内部的其他電路有 過電流狀況發生於並聯式電源供應器中。 、疼;、、'、圃 w丨矛观亚聯式冤源供應器能夠在數個並 ，式電源供應器中提供電流分配並提供過電流保護能 =，習知亚聯式電源供應器會遭遇到—些主要的不利條 μ ΐ :—般而言傳統並聯式電源供應器的電流分配 二大二，限制。再者，傳統並聯式電源供應器會加 ㈣二於主動下降電流分配電路與過電流 上缺應器將會體積過大且在電路設計 的體積增1ϋ的提出係為了將並聯式電源供應器 較大…聯式電源供應器的電路結物 【發明内容】 簡而言之，本發·明提供一種結人且、六 的主動下降電流分享雷跋& % ^ ，、有包抓限制功能 ，电丨l刀予電路的並聯式電源供應器。 根據本發明的-較佳實施例，該主動下降電流分享 11 1267720 電路包含一電流感測器（current sensor)，其位於一電 源轉換器的輪出端與一共同負載之間，用以產生一感測 輸出笔壓；一電流感測放大器（current sensing amplifier)，耦接至該電流感測器，用以將該感測輸出 電麼放大以產生一電流回授信號，一起始準位產生器 (threshold level generator)，用以設定一起始準位 為相等於與該電源轉換器的最大容許輸出電流相對應 的電壓準位，並且於當該電流回授信號的電壓準位大於 該起始準位時，傳導一電流；以及一開關控制器，其耦 接至該電源轉換器與該起始準位產生器，用以因應該電 流回授信號調整該電源轉換器的輸出電壓，並且藉由感 測流經該起始準位產生器的電流，限制電源轉換器的輸 出電流不得超過最大容許輸出電流。 【實施方式】 圖二圖例顯示根據本發明的一較佳實施例之結合 電流限制功能的主動下降電流分享電路的並聯式電源 供應器。 圖二的並聯式電源供應器包含一直流-直流轉換器 200,其設定提供一個預定的電壓準位給一共同負載201 並且與其他並聯式電源供應器的分擔一部分的總負載 電流。此外，圖二的並聯式電源供應器包含一主動下降 電流分配電路（active droop current sharing circuit)202，其耦合於直流-直流轉換器200與共同負 载201之間。該主動下降電流分配電路202包含一電流 感測電阻（current sensing resistor)203，其與共同 12 1267720 負載201串聯來產生正比於輸出電流的一電壓，使 ， 流-直流轉換器200的實際輸出電壓相等於直流〜直济〔轉 換器200的名義輸出電壓減去電流感測電阻203上的$ 降。此外，一電流感測放大器（current senSing amplifier)204耦接於該電流感測電阻203，並且具^有 一非反向輸入端（non-inverting input terrainal)|馬4妾 至名義輸出電壓以及一反向輸入端（inverting inpu1： terminal)耦接至透過分壓器222所得到的部分輪出電 壓。電流感測放大器204係用來將該電流感測電陡 φ 上所產生的感測電壓（sensed voltage)給放大以便產生 放大感測輸出電壓（amplified sensed 〇utput voltage)，其代表由並聯式電源供應器所提供的輪出電 流。特別是，由電流感測放大器204所提供的放大感二 輸出電壓作用為一電流回授信號，其使得開關控制[界 206能夠減少直流—直流轉換器200的開關電晶體電& (未顯示）的任務週期（duty cycle)，並且藉此減少並聯 式電源供應器的輸出電壓，以便在當並聯式電源供應界 的輸出電流超過所要求的負載電流配額時，在數個並聯 式電源供應裔之間達成適當的電流平衡。 電流感測放大器204進一步|馬接至一起始準位產生 菇（threshold level generator)205，其係耦接於該電 流感測放大器204與該開關控制器206之間。根據本實 施例，該起始準位產生器205通常係由一齊納二極體 (zener diode)所完成。該齊納二極體2〇5係用來設定 一起始準位，例如，齊納二極體的崩潰電壓（breakd〇wn voltage)，用以作為限制直流-直流轉換器2〇〇的的輸 出笔/’iL起過最大額定值的標準（criteri〇n)。例如，齊 13 1267720 ^ 【圖式簡單說明】 圖一係為傳統並聯式電源供應器的電路圖；以及 圖二係為顯示根據本發明的一較佳實施例的並聯 式電源供應器的電路圖。 【主要元件符號說明】 100,200直流-直流轉換器 101,201共同負載 • 1〇3,206開關控制器 110習知技術的主動下降電流分配電路 111電流分配放大 112,222分壓器 120習知技術的過電流偵測電路 ' 121誤差操作電路 122誤差放大器 130過電流保護狀態信號產生器 131,207過電流保護比較器 φ 202本發明的主動下降電流分配電路 203電流感測電阻 204電流感測放大器 205起始準位產生器 15OCP status signal generator 130. The overcurrent protection state signal generator 130 includes an overcurrent protection comparator (OCP comparator) 131 for comparing the difference between the nominal output voltage of the DC-DC converter 100 and a second reference signal Vref2 to determine whether An overcurrent condition has occurred. If it is determined that an overcurrent condition occurs, the overcurrent protection comparator 131 generates an overcurrent protection status signal (OCP status signal) and transmits the overcurrent protection condition quot"L number to an internal processing circuit (housekeeping circuit, not shown) No) to warn that other circuits inside the parallel power supply system have overcurrent conditions that occur in the parallel power supply. ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, Encountered - some major disadvantages μ ΐ : - Generally speaking, the current distribution of the traditional parallel power supply is two and two, limited. Furthermore, the conventional parallel power supply will add (four) two to the active descent current distribution circuit and the overcurrent on the reducer will be too large and the volume of the circuit design is increased by one 为了 in order to make the parallel power supply larger ...the circuit of the power supply of the joint power supply [invention] In a nutshell, the present invention provides a human-like and six-fold active falling current sharing Thunder & % ^ , with a packet-restricting function,丨l knife to the parallel power supply of the circuit. According to a preferred embodiment of the present invention, the active falling current sharing 11 1267720 circuit includes a current sensor located between the wheel end of a power converter and a common load to generate a current sensor Sensing the output pen pressure; a current sensing amplifier coupled to the current sensor for amplifying the sensing output to generate a current feedback signal, a starting level generator (threshold level generator), configured to set a starting level equal to a voltage level corresponding to a maximum allowable output current of the power converter, and when the voltage level of the current feedback signal is greater than the starting level a bit current, conducting a current; and a switch controller coupled to the power converter and the start level generator for adjusting the output voltage of the power converter according to the current feedback signal, and by Sensing the current flowing through the starting level generator limits the output current of the power converter to not exceed the maximum allowable output current. [Embodiment] FIG. 2 illustrates a parallel power supply of an active falling current sharing circuit incorporating a current limiting function in accordance with a preferred embodiment of the present invention. The parallel power supply of Figure 2 includes a DC-DC converter 200 that is configured to provide a predetermined voltage level to a common load 201 and share a portion of the total load current with other parallel power supplies. In addition, the parallel power supply of FIG. 2 includes an active droop current sharing circuit 202 coupled between the DC-DC converter 200 and the common load 201. The active falling current distribution circuit 202 includes a current sensing resistor 203 that is coupled in series with the common 12 1267720 load 201 to generate a voltage proportional to the output current such that the actual output voltage of the stream-to-DC converter 200 The phase is equal to DC ~ 直济 [the nominal output voltage of the converter 200 minus the $ drop on the current sense resistor 203. In addition, a current sense amplifier (current senSing amplifier) 204 is coupled to the current sense resistor 203 and has a non-inverting input terrain (Ma- 4) to a nominal output voltage and a reverse The input terminal (inverting inpu1: terminal) is coupled to a partial turn-off voltage obtained by the voltage divider 222. The current sense amplifier 204 is configured to amplify the sensed voltage generated on the current sense electrical steepness φ to generate an amplified sensed output voltage (amplified sensed 〇put voltage), which is represented by a parallel power supply The output current provided by the supplier. In particular, the amplified sense output voltage provided by the current sense amplifier 204 acts as a current feedback signal that enables the switch control [Boundary 206 can reduce the switching transistor power of the DC-DC converter 200 & (not shown) a duty cycle, and thereby reducing the output voltage of the parallel power supply so that when the output current of the parallel power supply supply exceeds the required load current quota, in several parallel power supply A proper current balance is achieved. The current sense amplifier 204 is further coupled to a threshold level generator 205 coupled between the electrical influenza amplifier 204 and the switch controller 206. According to this embodiment, the starting level generator 205 is typically implemented by a Zener diode. The Zener diode 2〇5 is used to set an initial level, for example, the breakdown voltage of the Zener diode, which is used as an output limiting the DC-DC converter 2〇〇. Pen/'iL has exceeded the maximum rating (criteri〇n). For example, Figure 13 is a circuit diagram of a conventional parallel power supply; and Figure 2 is a circuit diagram showing a parallel power supply in accordance with a preferred embodiment of the present invention. [Main component symbol description] 100,200 DC-DC converter 101,201 common load • 1〇3,206 switch controller 110 Active drop current distribution circuit of the prior art 111 Current distribution amplification 112,222 voltage divider 120 Conventional overcurrent detection circuit ' 121 error operation circuit 122 error amplifier 130 over current protection state signal generator 131, 207 over current protection comparator φ 202 active falling current distribution circuit 203 of the present invention current sense resistor 204 current sense amplifier 205 start level generator 15