CN101132150B - Flyback power converter with synchronous rectifier - Google Patents
Flyback power converter with synchronous rectifier Download PDFInfo
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- CN101132150B CN101132150B CN2006101150923A CN200610115092A CN101132150B CN 101132150 B CN101132150 B CN 101132150B CN 2006101150923 A CN2006101150923 A CN 2006101150923A CN 200610115092 A CN200610115092 A CN 200610115092A CN 101132150 B CN101132150 B CN 101132150B
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- switch
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Abstract
This invention discloses a back-speed type power source switching device having synchronous rectifier. Said rectifier comprises a synchronous switch; a current transformer, series connecting the drainend of the synchronous witch and the output end; and a secondary side synchronous rectifier driver, connecting the grid end of the synchronous switch. And also, the shunt resistance is parallel conne cting the current transformer, providing a by pass of the secondary side current for said current transformer so, reducing the current passing through the current transformer. This invention enhances the efficiency of the integral transformer with prolonging its service life.
Description
Technical field
The present invention relates to a kind of flyback power converter, relate in particular to a kind of flyback power converter with synchronous rectifier, wherein synchronous rectifier has the current transformer that is used for activating the synchronous rectification operation, and the shunt resistance in parallel with this current transformer.
Background technology
Fig. 1 shows a kind of known flyback power converter (flyback converter) with synchronous rectification (synchronous rectification function).As shown in Figure 1, flyback transformer (flybacktransformer) TF has an elementary winding (primary winding) Np
11, the one end is coupled to a rectification input direct voltage (rectified input DC voltage) Vin, and the other end is coupled to the drain electrode end (drain terminal) of the main switch MS that is made up of MOS transistor.One primary side switch circuit (primaryswitch circuit) 11 is coupled to the gate terminal (gate terminal) of main switch MS, and it is set at and sends the switch switching of pulse signal (pulse signals) with control main switch MS.When main switch MS conducting (turnon), elementary winding Np
11Can receive an input current I from input
1, so that with store energy in elementary winding Np
11In.At the same time, formed and be connected to second subprime winding (secondary winding) N of flyback transformer TF by MOS transistor
S12Synchro switch (synchronous switch) SS can be by being connected to the first secondary winding N
S11Secondary side synchronous rectifier driver (secondary
Synchronous rectification driver) 13 and end (turn off).Then, when main switch MS by the time, synchro switch SS can be by secondary side synchronous rectifier driver 13 and conducting, makes elementary winding Np
11Stored energy is sent to the primary side (secondary side) of flyback transformer TF, thus at second subprime winding N
S12Both sides induce the alternating voltage of a high frequency, and cause secondary side current (secondary current) I
2Synchro switch SS flows through.At this, secondary side synchronous rectifier driver 13 is by the first secondary winding N
S11The driving voltage that is provided drives, and the first secondary winding N
S11With second subprime winding N
S12Be connected to each other.Secondary side synchronous rectifier driver 13 is set at primary side switch circuit 11 synchro switches to be switched, so synchro switch SS can be used as rectifier (rectifier).Utilize the repeat switch of synchro switch SS to switch second subprime winding N
S12The high-frequency ac voltage of both sides just rectifiable becomes the direct voltage wanted.This direct voltage of wanting can carry out Filtering Processing and produce an output dc voltage Vout via an output capacitance Cout, to offer a load (not shown).
In addition, flyback power converter shown in Figure 1 also comprises a current transformer (currenttransformer) 14, is series between the drain electrode end and output of synchro switch SS.Current transformer 14 has an elementary winding 15 and a level winding 16, and it has sizable turn ratio (being about 1: 100).As secondary side current I
2When flowing through elementary winding 15, secondary winding 16 can produce an output signal that is directly proportional with the electric current of the elementary winding 15 of flowing through.This output signal can be sent to secondary side synchronous rectifier driver 13, makes thus as the second subprime winding N that flows through of the electric current with correct polarity
S12During with synchro switch SS, secondary side synchronous rectifier driver 13 is driven synchro switch SS and is activated the synchronous rectification operation.Flyback power converter shown in Figure 1 also comprises a feedback control circuit (feedback control circuit) 12, be coupled between output and the primary side switch circuit 11, it is set at the variation of the output voltage that detects flyback power converter and produces an error signal according to the result who detects, and makes primary side switch circuit 11 be fixed on the predetermined level according to the output voltage of this error signal with flyback power converter thus.
As everyone knows, current transformer 14 is a kind of magnetic elements.When current transformer 14 during, just can produce sizable power loss (power loss) because the transformer heating at conduction current.The power loss relevant with current transformer 14 comprises copper loss (copper loss), iron loss (iron loss), eddy current loss (eddy current loss) and magnetic hysteresis loss (hysteresis loss).These power losss can reduce the efficient of current transformer 14 and reduce the insulation characterisitic of current transformer 14, and then make the life-span of current transformer 14 shorten and cause the whole efficiency of flyback power converter to improve.
Summary of the invention
The object of the present invention is to provide a kind of flyback power converter with synchronous rectifier, it can reduce the power loss of current transformer.
According to preferred embodiment of the present invention, a kind of power supply changeover device with synchronous rectifier, for example flyback power converter comprises a transformer, has primary side and primary side; One main switch is coupled to this primary side; And a synchronous rectification circuit, be coupled to the primary side of this transformer, wherein this circuit of synchronous rectification comprises: a synchronous switch, directly and the primary side of this transformer couple; One synchronous rectifier driver is coupled to the control input end of this synchro switch, switches to finish the synchronous rectification operation in order to the switch of controlling this synchro switch; One current transformer is series between this synchro switch and the output, when being forward current in order to the electric current when this current transformer of flowing through, sending and controls signal to this synchronous rectifier driver to activate the synchronous rectification operation; And a shunt resistance, in parallel with this current transformer, in order to the electric current of a current bypass to this current transformer of flowing through to be provided.More specifically, the resistance value of this shunt resistance is much smaller than the resistance value of this current transformer.
Aforesaid power supply changeover device, wherein this current transformer sends this control signal via its secondary winding.
Aforesaid power supply changeover device, this shunt resistance is in parallel with the elementary winding of this current transformer.
Aforesaid power supply changeover device, this synchronous rectifier driver is connected to this Secondary winding of transformer.
Aforesaid power supply changeover device also comprises an output capacitance, is connected between this current transformer and the output.
Aforesaid power supply changeover device, wherein this transformer has one first secondary winding and a second subprime winding.Aforesaid power supply changeover device wherein also comprises a primary side switch circuit, is coupled to the control input end of this main switch, switches in order to the switch of controlling this main switch;
Aforesaid power supply changeover device, also comprise a feedback control circuit, be coupled between output and this primary side switch circuit, change and produce an error signal in order to the output voltage that detects this power supply changeover device, make this primary side switch circuit be fixed on the predetermined value thus according to the output voltage of this error signal with this power supply changeover device according to the result who detects.
Therefore flyback power converter with synchronous rectifier of the present invention can reduce the caused power loss of current transformer, and improves the whole efficiency of flyback power converter and can prolong life-span of current transformer.
Advantage of the present invention and feature can cooperate following Reference numeral to describe in detail by following embodiment, with the understanding that obtains more deeply.
Description of drawings
Fig. 1 shows a kind of known flyback power converter with synchronous rectification; And
Fig. 2 shows the flyback power converter with synchronous rectification according to preferred embodiment of the present invention.
Wherein, description of reference numerals is as follows:
TF: flyback transformer
Np
11: the elementary winding of flyback transformer
N
S11, N
S12: the flyback Secondary winding of transformer
MS: main switch
11: the primary side switch circuit
SS: synchro switch
13; Secondary side synchronous rectifier driver
14: current transformer
15: the elementary winding of current transformer
16: the secondary winding of current transformer
Cout: output capacitance
12: feedback control circuit
Np
21: the elementary winding of flyback transformer
N
S21, N
S22: the flyback Secondary winding of transformer
21: the primary side switch circuit
23: secondary side synchronous rectifier driver
24: current transformer
25: the elementary winding of current transformer
26: the secondary winding of current transformer
20: shunt resistance
22: feedback control circuit
Embodiment
The preferred embodiment that embodies feature of the present invention and advantage will be described in detail in the explanation of back.Be understood that the present invention can have various variations on different schemes, they do not depart from the scope of the present invention, and explanation wherein and the icon usefulness that should explain in itself, rather than in order to restriction the present invention.
Fig. 2 shows the flyback power converter with synchronous rectification according to preferred embodiment of the present invention.It is noted that in everywhere of the present invention the components identical numbering is pointed to components identical.As shown in Figure 2, a flyback transformer TF has an elementary winding Np
21, the one end is coupled to a rectification input direct voltage Vin, and the other end is coupled to the drain electrode end of main switch MS.Primary side switch circuit 21 is coupled to the gate terminal of main switch MS, and it is set at and sends the switch switching of pulse signal with control main switch MS.When main switch MS conducting, elementary winding Np
21Can receive input current I from input
1, so that rectification input direct voltage Vin is stored in elementary winding Np
21In.At the same time, formed and be connected to the second subprime winding N of flyback transformer TF by MOS transistor
S22Synchro switch SS can be by being connected to the first secondary winding N
S21Secondary side synchronous rectifier driver 23 and end.Then, when main switch MS by the time, synchro switch SS can be by secondary side synchronous rectifier driver 23 and conducting, makes elementary winding Np
21Stored energy is sent to the primary side of flyback transformer TF, thus at second subprime winding Ns
22Both sides induce the alternating voltage of a high frequency, and cause secondary side current 1
2Synchro switch SS flows through.At this, secondary side synchronous rectifier driver 23 is by the first secondary winding N
S21The driving voltage that is provided drives, and the first secondary winding N
S21With second subprime winding N
S22Be connected.Secondary side synchronous rectifier driver 23 is set at primary side switch circuit 21 synchro switches to be switched, so synchro switch SS can be used as rectifier.Utilize the repeat switch of synchro switch SS to switch second subprime winding N
S22The high-frequency ac voltage of both sides just rectifiable becomes the direct voltage wanted.This direct voltage of wanting can carry out Filtering Processing and produce an output dc voltage Vout via an output capacitance Cout, to offer a load (not shown).
In addition, flyback power converter shown in Figure 2 also comprises a current transformer 24, is series between the drain electrode end and output of synchro switch SS.Current transformer 24 has elementary winding 25 and secondary winding 26, and it has sizable turn ratio (being about 1: 100).As secondary side current I
2When flowing through elementary winding 25, secondary winding 26 can produce an output signal that is directly proportional with the electric current of the elementary winding 25 of flowing through.This output signal can be sent to secondary side synchronous rectifier driver 23, makes thus as the second subprime winding N that flows through of the electric current with correct polarity
S22During with synchro switch SS, secondary side synchronous rectifier driver 23 is driven synchro switch SS and is activated the synchronous rectification operation.Flyback power converter shown in Figure 2 also comprises a feedback control circuit 22, be coupled between output and the primary side switch circuit 21, it is set at the variation of the output voltage that detects flyback power converter and produces an error signal according to the result who detects, and makes primary side switch circuit 21 be fixed on the predetermined level according to the output voltage of this error signal with flyback power converter thus.
In addition, flyback power converter of the present invention also comprises a shunt resistance (shuntresistor) 20, and it is set in parallel with current transformer 24.Shunt resistance 20 is for having the circuit element of low-resistance value, and its effect provides the usefulness to the current bypass of the current transformer 12 of flowing through.When synchro switch SS conducting, secondary side current I
2Just can respond to and generate and flow through synchro switch SS and current transformer 24.At this moment, because the resistance value of shunt resistance 20 is much smaller than the resistance value of current transformer 24, most secondary side current I
2Can flow through shunt resistance 20 and a fraction of secondary side current I is only arranged
2The current transformer 24 of can flowing through.Therefore, the aforementioned power loss that is caused owing to transformer characteristic just can effectively reduce, and makes the whole efficiency of flyback power converter be greatly improved, and has further prolonged the life-span of current transformer 24.It should be noted that when selecting the resistance value of shunt resistance 20 its value and secondary side current I
2Current value be inversely proportional to, just as secondary side current I
2Current value when big more, the resistance value of shunt resistance 20 must be more little.
In sum, the present invention proposes a kind of flyback power converter with synchronous rectifier, synchronous rectifier wherein comprises a current transformer, whether in order to the flow through secondary side current of current transformer of detection is forward current (forward current), and when current transformer detects secondary side current and is a forward current, send a control signal and drive synchro switch, activate the synchronous rectification operation thus so that secondary side synchronous rectifier driver is sent gate drive signal.In addition, a shunt resistance is in parallel with current transformer, and it reduces the caused power loss of current transformer thus in order to the secondary side current bypass of the current transformer of will flowing through, and therefore improves the whole efficiency of flyback power converter.
The present invention can make various equivalences, modification and variation by those of ordinary skills, and it does not all break away from the protection range of claims.
Claims (11)
1. power supply changeover device with synchronous rectifier, it comprises:
One transformer has primary side and primary side; And
One synchronous rectification circuit is coupled to the primary side of this transformer, and it comprises:
One synchronous switch, primary side direct and this transformer couples;
One synchronous rectifier driver is coupled to the control input end of this synchro switch, switches to finish the synchronous rectification operation in order to the switch of controlling this synchro switch;
One current transformer is series between this synchro switch and the output, when being forward current in order to the electric current when this current transformer of flowing through, sending and controls signal to this synchronous rectifier driver to activate the synchronous rectification operation; And
One shunt resistance, in parallel with this current transformer, in order to the electric current of current bypass to this current transformer of flowing through to be provided.
2. power supply changeover device according to claim 1, it is a flyback power converter.
3. power supply changeover device according to claim 1, wherein the resistance value of this shunt resistance is less than the resistance value of this current transformer.
4. power supply changeover device according to claim 1 also comprises a main switch, is coupled to the primary side of this transformer.
5. power supply changeover device according to claim 4 also comprises a primary side switch circuit, is coupled to the control input end of this main switch, switches in order to the switch of controlling this main switch.
6. power supply changeover device according to claim 5, also comprise a feedback control circuit, be coupled between output and this primary side switch circuit, change and produce an error signal in order to the output voltage that detects this power supply changeover device, make this primary side switch circuit be fixed on the predetermined value thus according to the output voltage of this error signal with this power supply changeover device according to the result who detects.
7. power supply changeover device according to claim 1, wherein this current transformer sends this control signal via its secondary winding.
8. power supply changeover device according to claim 1, wherein this shunt resistance is in parallel with the elementary winding of this current transformer.
9. power supply changeover device according to claim 1, wherein this synchronous rectifier driver is connected to this Secondary winding of transformer.
10. power supply changeover device according to claim 1 also comprises an output capacitance, is connected between this current transformer and the output.
11. power supply changeover device according to claim 1, wherein this transformer has one first secondary winding and a second subprime winding.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2006101150923A CN101132150B (en) | 2006-08-24 | 2006-08-24 | Flyback power converter with synchronous rectifier |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2006101150923A CN101132150B (en) | 2006-08-24 | 2006-08-24 | Flyback power converter with synchronous rectifier |
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| Publication Number | Publication Date |
|---|---|
| CN101132150A CN101132150A (en) | 2008-02-27 |
| CN101132150B true CN101132150B (en) | 2010-09-15 |
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|---|---|---|---|
| CN2006101150923A Active CN101132150B (en) | 2006-08-24 | 2006-08-24 | Flyback power converter with synchronous rectifier |
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Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101997413B (en) * | 2009-08-12 | 2014-03-05 | 台达电子工业股份有限公司 | Power supply converter with synchronous rectifier and control method for synchronous rectifier |
| CN104167942A (en) * | 2014-08-21 | 2014-11-26 | 中国兵器工业集团第二一四研究所苏州研发中心 | Synchronous rectifying device of isolated flyback type high power supply |
| US10027235B2 (en) * | 2016-02-02 | 2018-07-17 | Fairchild Semiconductor Corporation | Self-tuning adaptive dead time control for continuous conduction mode and discontinuous conduction mode operation of a flyback converter |
| CN111049391A (en) * | 2019-12-24 | 2020-04-21 | 普联国际有限公司 | Off-line flyback converter and power supply equipment |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1731660A (en) * | 2004-08-04 | 2006-02-08 | 丰昱科技股份有限公司 | Synchronization vibration-damping circuit of holding flyback exchange power convertor as basal structure |
-
2006
- 2006-08-24 CN CN2006101150923A patent/CN101132150B/en active Active
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1731660A (en) * | 2004-08-04 | 2006-02-08 | 丰昱科技股份有限公司 | Synchronization vibration-damping circuit of holding flyback exchange power convertor as basal structure |
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| CN101132150A (en) | 2008-02-27 |
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