JP2007336635A - Regenerative synchronous rectification circuit - Google Patents
Regenerative synchronous rectification circuit Download PDFInfo
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- JP2007336635A JP2007336635A JP2006163193A JP2006163193A JP2007336635A JP 2007336635 A JP2007336635 A JP 2007336635A JP 2006163193 A JP2006163193 A JP 2006163193A JP 2006163193 A JP2006163193 A JP 2006163193A JP 2007336635 A JP2007336635 A JP 2007336635A
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- synchronous rectification
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Abstract
Description
本発明はスイッチング電源装置に関し、より具体的には同期整流回路に関する。 The present invention relates to a switching power supply device, and more particularly to a synchronous rectifier circuit.
従来方式の1例として図2に示した同期整流回路が有る。 As an example of the conventional system, there is a synchronous rectifier circuit shown in FIG.
図2において誤差増幅器U1からの信号によりQ2のオン時間を制御してMOSFET Q1のオン、オフを制御している。出力端子OUT+、OUT−の電圧が低い時はQ1をオフすることができず、N3巻線の電圧がQ1のスレッショルド電圧に下がるまではQ1はオンを続け、N2巻線から入力に回生電流が流れてしまう。
従来の回路では同期整流素子を的確にコントロールするには複雑な回路が必要となり、また、同期整流素子駆動の為に補助巻線が必要であった。 In the conventional circuit, a complicated circuit is required to accurately control the synchronous rectifier element, and an auxiliary winding is required for driving the synchronous rectifier element.
請求項1の発明は誤差増幅素子をトランスの2次巻線と同期整流素子との間に接続する事により、励磁エネルギー放出時間は同期整流MOSFETを確実にオンにし、励磁エネルギー放出時間の末期には出力端子電圧がそのまま誤差増幅素子に与えられる為、負荷が軽くて出力端子電圧が高い時は、励磁エネルギー放出後も同期整流MOSFETをオンさせたままとなる。その結果余分なエネルギーは1次側に回生し、出力端子電圧は高精度に制御される。また、1次側にフィードバックするフォトカプラは不要となる。 According to the first aspect of the present invention, by connecting the error amplifying element between the secondary winding of the transformer and the synchronous rectifying element, the excitation energy release time can be surely turned on the synchronous rectification MOSFET, and at the end of the excitation energy release time. Since the output terminal voltage is directly applied to the error amplifying element, when the load is light and the output terminal voltage is high, the synchronous rectification MOSFET remains on even after the excitation energy is released. As a result, excess energy is regenerated to the primary side, and the output terminal voltage is controlled with high accuracy. Further, a photocoupler that feeds back to the primary side is not necessary.
請求項2の発明はトランスの2次巻線の負電圧を利用し、同期整流素子の駆動電圧を確保する事により、補助巻線が不要となる。
The invention of
少ない部品点数で同期整流および出力電圧制御ができるので経済的効果が大きい。 Since synchronous rectification and output voltage control can be performed with a small number of parts, the economic effect is great.
本発明の実施では充分にオン抵抗の低い、かつ入力容量の少ない同期整流用MOSFETを選ぶ事が肝要である。 In implementing the present invention, it is important to select a synchronous rectification MOSFET having a sufficiently low on-resistance and a small input capacitance.
図1のQ3が主スイッチ素子である。Q4によって一定時間オン、オフする。 Q3 in FIG. 1 is a main switch element. Turns on and off for a certain time by Q4.
トランスの2次巻線N2からはR3,R4を通じて誤差増幅器U1に電圧が与えられる。 A voltage is applied from the secondary winding N2 of the transformer to the error amplifier U1 through R3 and R4.
トランスの2次巻線N2のドットマーク側がプラスの間。つまり2次側にエネルギーの放出が行われていない間は、D1からC2を通じて同期整流素子駆動用の電圧が充電される。 The dot mark side of the secondary winding N2 of the transformer is between plus. In other words, the voltage for driving the synchronous rectifier element is charged through D1 to C2 while energy is not released to the secondary side.
誤差増幅器U1の出力はR2を通じてQ5を制御、およびD2を通じてQ2を制御する。つまり2次巻線N2の電圧が設定値以上であればQ5をオン、Q2をオフして、同期整流素子Q1のオンを継続する。 The output of error amplifier U1 controls Q5 through R2 and Q2 through D2. That is, if the voltage of the secondary winding N2 is equal to or higher than the set value, Q5 is turned on, Q2 is turned off, and the synchronous rectifier element Q1 is kept on.
定格負荷では2次巻線N2からのエネルギー放出が完了するとQ5がオフ、Q2がオンになり、ゲート電荷が引き抜かれてQ1がオフになり、トランスのNB巻線に発生する電圧で主スイッチ素子Q3がオンになる。これは従来のフライバックコンバーターと同じである。 When the energy release from the secondary winding N2 is completed at the rated load, Q5 is turned off, Q2 is turned on, the gate charge is extracted, Q1 is turned off, and the voltage generated in the NB winding of the transformer is the main switch element. Q3 turns on. This is the same as a conventional flyback converter.
負荷が軽い場合は2次巻線N2からのエネルギー放出が終わった時点でも出力端子電圧が高くなる。この場合、設定電圧になるまで誤差増幅素子U1はQ5をオンし続け、Q1もオンし続ける。結果、出力からトランスの2次巻線N2に電流が逆流し、1次巻線N1を通して入力側に余分なエネルギーが回生される。 When the load is light, the output terminal voltage becomes high even when the energy emission from the secondary winding N2 is finished. In this case, the error amplifying element U1 keeps turning on Q5 and Q1 keeps on until the set voltage is reached. As a result, current flows backward from the output to the secondary winding N2 of the transformer, and excess energy is regenerated to the input side through the primary winding N1.
同期整流用MOSFETのQ1に充分オン抵抗の低い物を選べば、N2巻線からのエネルギー放出末期の電圧は出力端子電圧に等しい。故に高精度な出力電圧の制御が可能であり、フォトカプラなどによる1次側へのフィードバックは不要になる。 If the Q1 of the synchronous rectification MOSFET is selected to have a sufficiently low on-resistance, the voltage at the end of energy emission from the N2 winding is equal to the output terminal voltage. Therefore, it is possible to control the output voltage with high accuracy, and feedback to the primary side by a photocoupler or the like is not necessary.
負荷が定格出力を越えて重くなった場合、誤差増幅器U1は出力を停止するので、同期整流素子が働かなくなり、効率が低下するという問題が発生する。 When the load becomes heavier than the rated output, the error amplifier U1 stops the output, so that the synchronous rectifier does not work and the efficiency is lowered.
R3と並列に置かれたC1により2次巻線N2の電圧が低い時でも、ある一定時間、強制的にU1を駆動させる事により、2次巻線N2の電流が多い間だけ同期整流素子を駆動する事ができ、効率低下をある程度防止できる。 Even when the voltage of the secondary winding N2 is low due to C1 placed in parallel with R3, the synchronous rectifying element is only activated while the current of the secondary winding N2 is large by forcibly driving U1 for a certain period of time. It can be driven and efficiency reduction can be prevented to some extent.
V1 電圧源
OUT+、OUT− 出力端子
Q3 主スイッチ素子
Q1 同期整流素子
U1 誤差増幅素子
T1 トランス
N1 1次巻線
N2 2次巻線
N3 補助巻線
NB ベース巻線
Q2、Q4、Q5 スイッチ素子
R1、R2、R3、R4、R5 抵抗
C1、C2 コンデンサ
D1、D2 ダイオード
V1 Voltage source OUT +, OUT− Output terminal Q3 Main switch element Q1 Synchronous rectifier element U1 Error amplifying element T1 Transformer N1 Primary winding N2 Secondary winding N3 Auxiliary winding NB Base windings Q2, Q4, Q5 Switch element R1, R2, R3, R4, R5 Resistor C1, C2 Capacitor D1, D2 Diode
Claims (2)
2. The synchronous rectification switching device according to claim 1, wherein a diode and a capacitor are connected in series to the transformer secondary winding to ensure a driving voltage of the synchronous rectification element.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
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JP2006163193A JP2007336635A (en) | 2006-06-13 | 2006-06-13 | Regenerative synchronous rectification circuit |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
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JP2006163193A JP2007336635A (en) | 2006-06-13 | 2006-06-13 | Regenerative synchronous rectification circuit |
Publications (1)
Publication Number | Publication Date |
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JP2007336635A true JP2007336635A (en) | 2007-12-27 |
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JP2006163193A Pending JP2007336635A (en) | 2006-06-13 | 2006-06-13 | Regenerative synchronous rectification circuit |
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2006
- 2006-06-13 JP JP2006163193A patent/JP2007336635A/en active Pending
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