CN101997413A - Power supply converter with synchronous rectifier and control method for synchronous rectifier - Google Patents

Power supply converter with synchronous rectifier and control method for synchronous rectifier Download PDF

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Publication number
CN101997413A
CN101997413A CN2009101667469A CN200910166746A CN101997413A CN 101997413 A CN101997413 A CN 101997413A CN 2009101667469 A CN2009101667469 A CN 2009101667469A CN 200910166746 A CN200910166746 A CN 200910166746A CN 101997413 A CN101997413 A CN 101997413A
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China
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circuit
switch element
synchronous rectifier
resistance
synchronous
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CN101997413B (en
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李晗
刘钢
陈警
章进法
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Delta Optoelectronics Inc
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Delta Optoelectronics Inc
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    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
    • Y02B70/10—Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

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Abstract

The invention discloses a power supply converter with a synchronous rectifier and a control method for the synchronous rectifier. The power supply converter comprises a switching circuit, a transformer, a main control circuit, the synchronous rectifier, a current transformer and a synchronous rectifying control circuit, wherein the transformer is provided with a primary winding and a secondary winding, and the primary winding is connected with the switching circuit; the main control circuit is connected with the switching circuit to control the operation of the switching circuit; the synchronous rectifier is connected in series with the secondary winding; the current transformer is connected in series with the synchronous rectifier and outputs a detection signal according to the current flowing through the synchronous rectifier; the synchronous rectifying control circuit is connected with the control end of the synchronous rectifier, the current transformer and the control end of the switching circuit to receive the detection signal and a main control signal and used for controlling the operation of the synchronous rectifier; and when the main control circuit controls the switching circuit to be conducted, the synchronous rectifying control circuit controls the synchronous rectifier to be conducted, and the synchronous rectifying control circuit controls stoppage of the synchronous rectifier according to the detection signal. The synchronous rectifier is not easily burnt, and the integral efficiency is relatively promoted.

Description

Control method with power supply changeover device and synchronous rectifier of synchronous rectifier
Technical field
The present invention relates to a kind of power supply changeover device, relate in particular to a kind of power supply changeover device of the deadline that current transformer removes to detect synchronous rectifier and control method of synchronous rectifier utilized with synchronous rectifier.
Background technology
In various power supply changeover devices (power converter circuit), for example resonant mode power supply changeover device etc. can have commutation circuit, transformer and rectifier diode usually.Wherein commutation circuit is connected with the elementary winding of transformer, and it is subjected to the control of a control circuit and carries out conducting or end.Transformer then receives electric energy by the primary side winding, and carries out conducting or during the switching that ends in commutation circuit, and the mode of the utilization of power electromagnetic induction of elementary winding is sent to Secondary winding of transformer.Then be connected as for rectifier diode, become a direct current voltage, use to offer load in order to the ac voltage rectifier that the secondary winding induction is generated with Secondary winding of transformer.
Yet because the forward conduction voltage drop of rectifier diode can make rectifier diode produce sizable conducting loss, therefore the synchronous rectifier of being made up of transistor has replaced rectifier diode gradually and has been applied in the power supply changeover device.Compared to the power supply changeover device framework of tradition use rectifier diode, the power supply changeover device that uses synchronous rectifier to carry out rectification just can reduce power loss.
Really can make power supply changeover device reduce power loss though use synchronous rectifier to carry out rectification, yet because synchronous rectifier is made up of transistor, so synchronous rectifier need accurately be controlled to the switching carrying out conducting or end.The control mode of synchronous rectifier is directly by the conducting of a control integrated circuit (control integrated circuit) control synchronous rectifier at present, in addition, the drain electrode of control integrated circuit meeting sample-synchronous rectifier and the voltage difference between the source electrode two ends, and then calculate the electric current that flows through synchronous rectifier, control synchronous rectifier whereby and end.
Yet the control mode of above-mentioned synchronous rectifier can be influenced by the leakage inductance on the circuit of power supply changeover device, make the control integrated circuit accurately drain electrode of sample-synchronous rectifier and the voltage difference between the source electrode two ends, and then cause control integrated circuit can't control the action of synchronous rectifier accurately, for example control integrated circuit may be controlled synchronous rectifier and ends in advance, thus, synchronous rectifier just burns easily, and the whole efficiency of power supply changeover device is comparatively not good yet.
Therefore, how to develop the control method that a kind of utilization that improves above-mentioned known technology defective has the power supply changeover device and the synchronous rectifier of synchronous rectifier, real in pressing for the problem of solution at present.
Summary of the invention
Main purpose of the present invention is to provide a kind of control method of power supply changeover device and synchronous rectifier of tool synchronous rectifier, to solve known power supply changeover device because of directly utilizing the action of control integrated circuit control synchronous rectifier, so when control integrated circuit is influenced by leakage inductance on the circuit of known power supply changeover device, can can't control accurately the action of synchronous rectifier, cause having defectives such as synchronous rectifier may burn and the whole efficiency of known power supply changeover device is not good.
For reaching above-mentioned purpose, of the present invention one than the broad sense execution mode for a kind of power supply changeover device is provided, it comprises commutation circuit, receives input voltage; Transformer has elementary winding and secondary winding, and elementary winding is total to contact with the power output end and first of commutation circuit and is connected; Main control circuit is connected in the control end of commutation circuit, controls the commutation circuit operation in order to produce at least one main control signal, makes the energy selectivity ground of input voltage be sent to elementary winding via commutation circuit; At least one synchronous rectifier is total to contact with Secondary winding of transformer and second and is connected in series; At least one current transformer is connected in series with synchronous rectifier, in order to the output detection signal according to flowing through the electric current of synchronous rectifier; And at least one synchronous commutating control circuit, being connected with the control end of control end, current transformer and the commutation circuit of synchronous rectifier, it receives corresponding detection signal and corresponding main control signal, and the operation of control synchronous rectifier; Wherein when the conducting of master control circuit controls commutation circuit, the conducting of synchronous commutating control circuit control synchronous rectifier, and synchronous commutating control circuit is controlled synchronous rectifier according to detection signal and is ended.
For reaching above-mentioned purpose, of the present invention another than the broad sense execution mode for a kind of control method of synchronous rectifier is provided, at least one synchronous rectifier in order to the control power supply changeover device, wherein power supply changeover device also comprises commutation circuit, main control circuit, transformer, at least one current transformer and at least one synchronous commutating control circuit, commutation circuit is connected with the elementary winding of transformer, main control circuit is connected with the commutation circuit control end, current transformer and synchronous rectifier are connected in series with Secondary winding of transformer, the control end of synchronous commutating control circuit commutation circuit is connected with the control end of synchronous rectifying controller, the synchronous commutating control circuit control method comprises, make transformer carry out the conversion of energy: (a) to produce main control signal to commutation circuit and this synchronous commutating control circuit, make the commutation circuit action and make the energy selectivity ground of input voltage be sent to this transformer via commutation circuit by main control circuit; (b) synchronous commutating control circuit is according to the conducting of main control signal control synchronous rectifier; (c) current transformer detects synchronous rectifier and transmits detection signal and give this synchronous commutating control circuit; And (d) synchronous commutating control circuit is controlled synchronous rectifier and is ended according to detection signal.
The invention provides a kind of control method of power supply changeover device and synchronous rectifier of tool synchronous rectifier, it detects the situation of the electric current tool reverse circulated that flows through synchronous rectifier fast by current transformer, make that synchronous commutating control circuit can be immediately and control synchronous rectifier accurately and end, so synchronous rectifier of the present invention just is difficult for burning, and the whole efficiency of power supply changeover device of the present invention also promotes relatively.
Description of drawings
Fig. 1: it is the circuit block diagram of the power supply changeover device of preferred embodiment of the present invention.
Fig. 2: it is the detailed circuit structural representation of first synchronous commutating control circuit shown in Figure 1.
Fig. 3: it is electric current, voltage and the sequential view of power supply changeover device shown in Figure 1.
Fig. 4: it is that another of comparison circuit shown in Figure 2 changes example.
Fig. 5: it is that one of start-up circuit shown in Figure 2 changes example.
Fig. 6: it is the electrical block diagram of first synchronous commutating control circuit of another preferred embodiment of the present invention.
Fig. 7: it is the present invention's electrical block diagram of first synchronous commutating control circuit of a preferred embodiment again.
Fig. 8: its be reset circuit shown in Figure 5 one change example again.
Fig. 9: it is the control method flow chart of first synchronous rectifier shown in Figure 1.
Figure 10: it is the substep of step S93 shown in Figure 9.
Description of reference numerals in the above-mentioned accompanying drawing is as follows:
1: power supply changeover device
11: commutation circuit
12: main control circuit
13a～13b: the first～the second synchronous commutating control circuit
14a～14b: the first～the second synchronous rectifier
15: resonant circuit
16: filter circuit
20: start-up circuit
201: totem-pote circuit
21: comparison circuit
210: comparing unit
50: holding circuit
51: reset circuit
311: voltage source
OP: comparator
CT 1～CT 2: the first～the second current transformer
COM 1～COM 2: the first～the second is total to contact
S 1～S 2: the first～the second main control signal
S 3～S 4: the first～the second synchronous rectification control signal
I D1～I D2: the first～the second electric current
Q 1～Q 2: the first～the second main switch element
Q 3, Q 6, Q 7: first～the 3rd auxiliary switch element
Q 4, Q 5, Q 8: first～the 3rd reset circuit switch element
Q 1a, Q 2a, Q 3a, Q 4a, Q 5a, Q 8a: the first conduction of current end
Q 1b, Q 2b, Q 3b, Q 4b, Q 5b, Q 8b: the second conduction of current end
T: transformer
N p: elementary winding
N s: secondary winding
R 1: start-up circuit resistance
R 2: comparison circuit resistance
R 3, R 4: the first～the second holding circuit resistance
R 5, R 8: the first～the second reset circuit resistance
R 6～R 7: the first～the second comparing unit resistance
D 1～D 2: the first～the second diode
V T1～V T2: the first～the second detection signal
B 1: the NPN bipolar junction transistor
B 2: the PNP bipolar junction transistor
T 1～T 4: the time
V In: input voltage
V CC: boost voltage
V o: output voltage
V Ref: reference voltage
L o: load
D Sc: Schottky diode
C: keep electric capacity
C s: power supply electric capacity
C f: filter capacitor
C R1, C R2: the first～the second resonant capacitance
L r: resonant inductance
L m: magnetizing inductance
The process step of the control method of S90～93: the first isochronous controller
S930: setting up procedure
S931: comparison step
S932: keep step
S933: reset process
Embodiment
Some exemplary embodiments that embody feature of the present invention and advantage will be described in detail in the explanation of back segment.Be understood that the present invention can have various variations on different modes, it does not depart from the scope of the present invention, and explanation wherein and the accompanying drawing usefulness that ought explain in itself, but not in order to restriction the present invention.
See also Fig. 1, it is the circuit block diagram of the power supply changeover device of preferred embodiment of the present invention.As shown in Figure 1, the power supply changeover device 1 of present embodiment is connected in a load L o, it is in order to an input voltage V InBe converted to an output voltage V o, to supply with load L oUse.This power supply changeover device 1 comprises one and switches circuit 11, a transformer T, a main control circuit 12, a resonant circuit 15, a filter circuit 16, at least one synchronous commutating control circuit, the first synchronous commutating control circuit 13a for example shown in Figure 1 and the second synchronous commutating control circuit 13b, at least one synchronous rectifier, the first synchronous rectifier 14a for example shown in Figure 1 and the second synchronous rectifier 14b, and at least one current transformer, the first current transformer CT for example shown in Figure 1 1And the second current transformer CT 2
Commutation circuit 11 receives input voltage V In, and commutation circuit 11 can be but is not limited to by the first main switch element Q 1And the second main switch element Q 2Constitute the first main switch element Q wherein 1The first conduction of current end Q 1aWith the second main switch element Q 2The second conduction of current end Q 2bConnect, and the second main switch element Q 2The first conduction of current end Q 2aWith the first common contact COM 1Connect.And the first main switch element Q in the present embodiment, 1And the second main switch element Q 2Staggered carry out conducting or end.
Resonant circuit 15 is connected in the elementary winding N of commutation circuit 11 and transformer T pBetween.In the present embodiment, resonant circuit 15 comprises at least one resonant capacitance, the first resonant capacitance C for example shown in Figure 1 R1And the second resonant capacitance C R2, and a resonant inductance L r, the first resonant capacitance C wherein R1An end and the first main switch element Q 1The second conduction of current end Q 1bConnect the first resonant capacitance C R1The other end then with the second resonant capacitance C R2An end connect and the second resonant capacitance C R2The other end then with the second main switch element Q 2The first conduction of current end Q 2aReach first and be total to contact COM 1Connect.Resonant inductance L rAn end be connected in the first main switch element Q 1The first conduction of current end Q 1aAnd the second main switch element Q 2The second conduction of current end Q 2bBetween, resonant inductance L rThe other end then with the elementary winding N of transformer T pConnect.
Transformer T has elementary winding N pAnd secondary winding N s, wherein elementary winding N pAn end and the power output end of commutation circuit 11, the i.e. first main switch element Q 1The first conduction of current end Q 1aAnd the second main switch element Q 2The second conduction of current end Q 2bConnect elementary winding N pThe other end then be connected in the first contact COM altogether 1, and the secondary winding N of transformer T sHave centre cap and be connected in load L oIn addition, in the present embodiment, elementary winding N pCan be but be not limited to comprise the equivalence a magnetizing inductance L m, it is connected in parallel in elementary winding N p, in order to the elementary winding N of equivalence pDuring operation to the inductance characteristic of the excitatory generation of transformer T.
Filter circuit 16 and load L oParallel connection, it is in order to sending load L to oElectric energy filtering, and in the present embodiment, filter circuit 16 can be but is not limited to by filter capacitor C fConstitute this filter capacitor C fAn end be connected in the secondary winding N of transformer T sCentre cap and load L oBetween, the other end then is total to contact COM with second 2Connect.
Main control circuit 12 is connected with the control end of commutation circuit 11, i.e. the main control circuit 12 and the first main switch element Q 1The control end and the second main switch element Q 2Control end connect, main control circuit 12 is in order to produce one first main control signal S respectively 1And one second main control signal S 2To the first main switch element Q 1The control end and the second main switch element Q 2Control end, with respectively by the first main control signal S 1And the second main control signal S 2And control the first main switch element Q 1And the second main switch element Q 2Operation, make input voltage V InEnergy optionally be sent to the elementary winding N of transformer T via this commutation circuit 11 p, thus, the secondary winding N of transformer T sJust can produce the induction alternating voltage because of electromagnetic induction.
The first synchronous rectifier 14a is serially connected with the secondary winding N of transformer T sAn end and second contact COM altogether 2Between, the two or two synchronous rectifier 14b then is serially connected with secondary winding N sThe other end and the second contact COM 2Between, the first synchronous rectifier 14a and the second synchronous rectifier 14b are in order to the secondary winding N with transformer T sThe induction ac voltage rectifier that is produced becomes direct voltage.
The first current transformer CT 1And the second current transformer CT 2Be serially connected with the secondary winding N of transformer T respectively sTwo ends, and the first current transformer CT 1More be total to contact COM with the first synchronous commutating control circuit 13a and second 2Connect the second current transformer CT 2Then more be total to contact COM with the second synchronous commutating control circuit 13b and second 2Connect the first current transformer CT 1Flow through first electric current I of the first synchronous rectifier 14a in order to basis D1And export the first detection signal V T1, the second current transformer CT 2Then flow through second electric current I of the second synchronous rectifier 14b in order to basis D2And export the second detection signal V T2
The control end of the first synchronous commutating control circuit 13a and the first synchronous rectifier 14a and the first current transformer CT 1Connect, and then receive the first detection signal V T1, and the first synchronous commutating control circuit 13a more with the first main switch element Q 1Control end connect and receive main control circuit 12 and export to the first main switch element Q 1The first main control signal S 1, the first synchronous commutating control circuit 13a is in order to the foundation first main control signal S 1And the first detection signal V T1And export one first synchronous rectification control signal S 3To the control end of the first synchronous rectifier 14a, carry out conducting or end to control the first synchronous rectifier 14a.And the control end of the second synchronous commutating control circuit 13b and the second synchronous rectifier 14b and the second current transformer CT 2Connect, and then receive the second detection signal V T2, and the second synchronous commutating control circuit 13b more with the second main switch element Q 2Control end connect and receive main control circuit 12 and export to the second main switch element Q 2The second main control signal S 2, the second synchronous commutating control circuit 13b is in order to the foundation second main control signal S 2And the second detection signal V T2And export one second synchronous rectification control signal S 4To the control end of the second synchronous rectifier 14b, carry out conducting or end to control the second synchronous rectifier 14b.
In the present embodiment, when main control circuit 12 by the first main control signal S 1And the first main switch element Q of control commutation circuit 11 1During conducting, the first synchronous commutating control circuit 13a is also according to the first main control signal S 1And control the first synchronous rectifier 14a conducting, and the first synchronous commutating control circuit 13a is more according to the first current transformer CT 1The first detection signal V of output T1End and control the first synchronous rectifier 14a.Similarly, when main control circuit 12 by the second main control signal S 2And the second main switch element Q of control commutation circuit 11 2During conducting, the second synchronous commutating control circuit 13b is also according to the second main control signal S 2And control the second synchronous rectifier 14b conducting, and the second synchronous commutating control circuit 13b is more according to the second current transformer CT 2The second detection signal V of output T2End and control the second synchronous rectifier 14b.
Below internal circuit configuration and the annexation of the first synchronous commutating control circuit 13a will be described with Fig. 2.In addition,, therefore will in Fig. 1 and Fig. 2, indicate identical English symbol, interconnect to represent it because the partial circuit element has interconnective relation among Fig. 1 and Fig. 2.
See also Fig. 2, it is the detailed circuit structural representation of first synchronous commutating control circuit shown in Figure 1.As shown in the figure, first synchronous commutating control circuit, 1 3a mainly comprises a start-up circuit 20 and a comparison circuit 21, wherein the first main switch element Q of the input of start-up circuit 20 and commutation circuit 11 1Control end connect and receive the first main control signal S that is exported by main control circuit 12 1, the output of start-up circuit 20 then is connected with the control end of the first synchronous rectifier 14a, and this start-up circuit 20 is according to the first main control signal S 1And export one first synchronous rectification control signal S 3To the control end of the first synchronous rectifier 14a, therefore work as main control circuit 12 by the first main control signal S 1And control the first main switch element Q 1During conducting, start-up circuit 20 is also according to the first main control signal S 1And the first synchronous rectification control signal S of output enable (enable) level 3To the control end of the first synchronous rectifier 14a, to drive the first synchronous rectifier 14a conducting.In addition, start-up circuit 20 more can be in the first synchronous rectification control signal S 3Voltage level when being dragged down, prevent the first main control signal S 1Voltage level along with the first synchronous rectification control signal S 3Voltage level dragged down and dragged down.The comparison circuit 21 and the first current transformer CT 1, the control end of the first synchronous rectifier 14a and start-up circuit 20 output connect, it receives the first current transformer CT 1The first detection signal V that is exported T1, and as the first detection signal V T1During greater than the reference voltage in the comparison circuit 21, start-up circuit 20 is exported to the first synchronous rectification control signal S of the control end of the first synchronous rectifier 14a 3Voltage level drag down, make the synchronous rectification control signal S that wins 3Be forbidden energy (disable) level, and then drive the first synchronous rectifier 14a and end.
In the above-described embodiments, start-up circuit 20 mainly comprises a start-up circuit resistance R 1, this start-up circuit resistance R 1An end and the first main switch element Q 1Control end connect the start-up circuit resistance R 1The other end then be connected with the control end of the first synchronous rectifier 14a, as the first detection signal V T1Value greater than the value of the reference voltage of comparison circuit 21, make the first synchronous rectification control signal S of comparison circuit 21 with start-up circuit 20 outputs 3Voltage level when dragging down, start-up circuit 20 just can pass through the start-up circuit resistance R 1And prevent the first main control signal S 1Level along with the first synchronous rectification control signal S 3Voltage level dragged down and dragged down.Comparison circuit 21 comprises a comparison circuit resistance R 2, a comparing unit 210 and one first diode D 1, comparison circuit resistance R wherein 2An end and the first current transformer CT 1Connect and receive the first detection signal V T1, the comparison circuit resistance R 2The other end be connected with the input of comparing unit 210, so the input of comparing unit 210 is just through the comparison circuit resistance R 2And receive the first detection signal V T1So comparing unit 210 is just according to the first detection signal V T1Value whether carry out conducting or end greater than the value of the conducting voltage of comparing unit 210 itself.The output of comparing unit 210 is connected with the output of start-up circuit 20, the control end of the first synchronous rectifier 14a, and the earth terminal of comparing unit 210 and second is contact COM altogether 2Be connected, as the first detection signal V T1Value when making comparing unit 210 conductings greater than the value of the conducting voltage of comparing unit 210, the first synchronous rectification control signal S 3Voltage level just can be compared circuit 21 and drag down, and then drive the first synchronous rectifier 14a and end.Hence one can see that, and the conducting voltage of comparing unit 210 promptly is set at comparison circuit 21 and is used for and the first detection signal V T1The reference voltage of comparing.
In the present embodiment, comparing unit 210 can be but is not limited to by the first auxiliary switch element Q 3Realize, so the first auxiliary switch element Q 3Conducting voltage be comparison circuit 21 and be used for and the first detection signal V T1The reference voltage of comparing.And the first auxiliary switch element Q 3Control end through the input of comparing unit 210 and with the comparison circuit resistance R 2The other end connect, and receive the first detection signal V T1, the first auxiliary switch element Q 3The second conduction of current end Q 3bThrough the output of comparing unit 210 and with the start-up circuit resistance R of start-up circuit 20 1The other end and the control end of the first synchronous rectifier 14a connect and the first auxiliary switch element Q 3The first conduction of current end Q 3aThrough the earth terminal of comparing unit 210 and with the second contact COM altogether 2Connect.The cathode terminal of the first diode D1 is connected in the comparison circuit resistance R 2The other end and the first auxiliary switch element Q 3Control end between, and the first diode D 1Anode tap then with the second contact COM altogether 2Connect the first diode D 1Effect with clamper is in order to clamp down on the first auxiliary switch element Q 3The control end and the first conduction of current end Q 3aBetween voltage, prevent the first detection signal V T1When negative value, reverse current is excessive and with the first auxiliary switch element Q 3Burn.
In the present embodiment, the internal circuit configuration of the second synchronous commutating control circuit 13b is similar in appearance to the internal circuit configuration of the first synchronous commutating control circuit 13a, and the internal circuit element of the second synchronous commutating control circuit 13b and the second main switch element Q 2, the second current transformer CT 2And second annexation between the synchronous rectifier 14b also similar in appearance to the internal circuit element and the first main switch element Q of the first synchronous commutating control circuit 13a 1, the first current transformer CT 1And first the annexation between the synchronous rectifier 14a, so the following internal circuit configuration that will repeat no more the second synchronous commutating control circuit 13b and with the second main switch element Q 2, the second current transformer CT 2And second the annexation between the synchronous rectifier 14b, also repeating no more the various possibility execution modes of second synchronous commutating control circuit, 1 3b, is that example is come exemplary illustrated technology of the present invention and various possible execution mode with the first synchronous commutating control circuit 13a all only.
In the above-described embodiments, the first main switch element Q 1, the second main switch element Q 2, the first auxiliary switch element Q 3, the first synchronous rectifier 14a and the second synchronous rectifier 14b can be mos field effect transistor (MOSFET) and constitute, but not as limit, and the first main switch element Q 1, the second main switch element Q 2, the first auxiliary switch element Q 3, the first synchronous rectifier 14a and the second synchronous rectifier 14b more can adopt N type or P-type mos field-effect transistor according to the side circuit demand.
The operation logic of power supply changeover device of the present invention below will be described.See also Fig. 3, and cooperate Fig. 1 and Fig. 2, wherein Fig. 3 is electric current, voltage and the sequential view of power supply changeover device shown in Figure 1.As shown in Figure 3, when for example in time T 1The time, main control circuit 12 can be output as the first main control signal S that enables level 1The first main switch element Q to commutation circuit 11 1Control end, make the main switch element Q that wins 1The beginning conducting is so the first synchronous commutating control circuit 13a is just according to the first main control signal S 1And be output as the first synchronous rectification control signal S that enables level 3To the control end of the first synchronous rectifier 14a, and then control the first synchronous rectifier 14a conducting, thus, flow through first electric current I of the first synchronous rectifier 14a D1Just begin to rise, therefore the first current transformer CT 1The first detection signal V that is exported T1Just corresponding to first electric current I D1And be negative value.In addition, owing to the first synchronous rectifier 14a is made of mos field effect transistor, so first electric current I D1In time T 1Just can begin to rise by zero because of the body diode (body diode) of the first synchronous rectifier 14a before.
When the time T that arrives through after a while 2The time, at this moment, flow through first electric current I of the first synchronous rectifier 14a D1Dropped to zero and be about to change and flowed to the first current transformer CT 1The first detection signal V that is exported T1Just can corresponding first electric current I D1Changed course and by negative value change on the occasion of, and form a pulse (pulse), this moment the first detection signal V T1The comparison circuit resistance R of meeting in comparison circuit 21 2And be sent to the first auxiliary switch element Q 3Control end, and in the first detection signal V T1Value greater than the first auxiliary switch element Q 3Turn-on voltage the time drive the first auxiliary switch element Q 3Conducting, thus, comparison circuit 21 just can be with the first synchronous rectification control signal S 3Voltage level drag down, make the synchronous rectification control signal S that wins 3The first synchronous rectifier 14a changes into the forbidden energy level by enabling level, so just can end.As from the foregoing, when first electric current I that flows through the first synchronous rectifier 14a of the present invention D1When being about to reverse circulated, the first current transformer CT 1Just can detect this situation fast, and notify the first synchronous commutating control circuit 13a with testing result, make the synchronous commutating control circuit 13a that wins control the ground first synchronous rectifier 14a immediately and end.
See also Fig. 4 and cooperate Fig. 3, wherein Fig. 4 is that another of comparison circuit shown in Figure 2 changes example.As shown in Figure 4, the comparison circuit 21 of present embodiment only has the comparison circuit resistance R compared to comparison circuit shown in Figure 2 21 2And comparing unit 210, and in the present embodiment, comparing unit 210 changes by a comparator OP and a voltage source 311 and is constituted.Wherein, comparison circuit resistance R 2An end and the first current transformer CT 1Connect and receive the first detection signal V T1, the comparison circuit resistance R 2The other end then through the input of comparing unit 210 and be connected with the inverting input of comparator OP, voltage source 311 is serially connected with between the earth terminal of the non-inverting input of comparator OP and comparing unit 210, and through the earth terminal of comparing unit 210 and with the second contact COM altogether 2Connect, it is in order to provide a reference voltage V RefTo the non-inverting input of comparator OP, as for the output of comparator OP then through the output of comparing unit 210 and with the start-up circuit resistance R of start-up circuit 20 1The other end and the control end of the first synchronous rectifier 14a connect, comparator OP is in order to the first detection signal V relatively T1And reference voltage V Ref, and in the first detection signal V T1Value greater than reference voltage V RefValue the time, in output export a low voltage level signal and with the first synchronous rectification control signal S of start-up circuit 20 output 3Voltage level drag down, make the synchronous rectification control signal S that wins 3Be the forbidden energy level, and then drive the first synchronous rectifier 14a and end.
Therefore as shown in Figure 3, when for example in time T 1The time, the first synchronous rectifier 14a is received as the first synchronous rectification control signal S that enables level 3And present conducting state, and work as through after a while feasible first electric current I that flows through the first synchronous rectifier 14a D1When beginning descends gradually, the first current transformer CT 1The first detection signal V that is exported T1Just can begin accordingly to rise gradually, and as the first detection signal V T1Value in fact greater than reference voltage V RefValue, for example in time T 2The time, comparator OP just can export a low level signal and with the first synchronous rectification control signal S of start-up circuit 20 output 3Voltage level drag down, make the synchronous rectification control signal S that wins 3Change the forbidden energy level into, thus, just can drive the first synchronous rectifier 14a and end.So utilize the first synchronous commutating control circuit 13a of the comparison circuit 211 of present embodiment equally can be according to the first current transformer CT 1Testing result and the instant control ground first synchronous rectifier 14a ends.
As for the second main switch element Q 2, the second current transformer CT 2, the second synchronous commutating control circuit 13b and the second synchronous rectifier 14b manner of execution all respectively with the first main switch element Q 1, the first current transformer CT 1, the first synchronous commutating control circuit 13a and the first synchronous rectifier 14a manner of execution similar, so repeat no more in this.
Because having, current transformer can detect the characteristic that electric current changes rapidly, so power supply changeover device of the present invention 1 is by the first current transformer CT 1And the second current transformer CT 2Just can detect first electric current I that flows through the first synchronous rectifier 14a respectively fast D1And second electric current I of the second synchronous rectifier 14b D2The situation that the tool reverse circulated is arranged, make win synchronous commutating control circuit 13a and the second synchronous commutating control circuit 13b can be immediately and control the first synchronous rectifier 14a accurately and the second synchronous rectifier 14b ends, thus, the first synchronous rectifier 14a and the second synchronous rectifier 14b just are difficult for burning, and the whole efficiency of power supply changeover device of the present invention 1 also promotes relatively.
Below will further specify other possible execution mode of the first synchronous commutating control circuit 13a of the present invention and the second synchronous commutating control circuit 13b.And since the second synchronous commutating control circuit 13a similar to circuit structure and the annexation of the first synchronous commutating control circuit 13b, so below be that example is come exemplary illustrated only with the first synchronous commutating control circuit 13a.In addition,, therefore will indicate identical English symbol, interconnect to represent it in Fig. 1 and following diagram because partial circuit element in the following drawings and the partial circuit element of Fig. 1 have interconnective relation.
In certain embodiments, driving force for the internal circuit of strengthening power supply changeover device 1, as shown in Figure 5, the start-up circuit 20 of the first synchronous commutating control circuit 13a also comprises a totem (totem pole) circuit 201, this totem-pote circuit 201 is connected in the control end of this commutation circuit 11, i.e. the first main switch element Q 1Control end and the start-up circuit resistance R of start-up circuit 20 1Between, and comprise a NPN bipolar junction transistor B 1An and PNP bipolar junction transistor B 2, NPN bipolar junction transistor B wherein 1Base stage and PNP bipolar junction transistor B 2The base stage and the first main switch element Q 1Control end connect NPN bipolar junction transistor B 1Collector electrode receive a boost voltage V Cc, NPN bipolar junction transistor B 1Emitter and the start-up circuit resistance R of start-up circuit 20 1Connect PNP bipolar junction transistor B 2Emitter be connected in NPN bipolar junction transistor B 1Emitter and start-up circuit resistance R 1Between, PNP bipolar junction transistor B 2Collector electrode and second contact COM altogether 2Connect.In the present embodiment, NPN bipolar junction transistor B 1And PNP bipolar junction transistor B 2Be subjected to the first main control signal S respectively 1Control and carry out conducting or end, and then make totem-pote circuit 201 can strengthen the driving force of the internal circuit of power supply changeover device 1.Certainly, totem-pote circuit 201 is not limited to be used in the start-up circuit 20 of the first synchronous commutating control circuit 13a shown in Figure 5, also applicable in above-mentioned other embodiment or the start-up circuit of first synchronous commutating control circuit of the embodiment of the following stated.
In other embodiments, when the first synchronous rectifier 14a ends,, cause the first current transformer CT because the stray capacitance that the leakage inductance on the circuit of power supply changeover device 1 and the first synchronous rectifier 14a are had may be vibrated 1The first detection signal V that is exported T1Also and then continue change, make synchronous rectifier 1 4a that wins can carry out repeatedly conducting or by and can't be maintained at the state that ends, so, can be provided with one and keep (hold) circuit 50 in the comparison circuit 21 of first synchronous rectification shown in Figure 2 control 13a and form as shown in Figure 6 circuit structure for fear of above-mentioned possible situation.This holding circuit 50 is connected in the comparison circuit resistance R 2And between the control end of comparing unit 210, this holding circuit 50 is in order to through the comparison circuit resistance R 2Receive the first detection signal V T1, and make the first detection signal V T1Change into by negative value on the occasion of and a special time is kept in the pulse that forms.Therefore as shown in Figure 3, when in time T 2, and flow through first electric current I of the first synchronous rectifier 14a D1By desire the reverse circulated and the first detection signal V on the occasion of dropping to zero T1By negative value change on the occasion of and when forming a pulse, holding circuit 50 just can be with the first detection signal V T1Pulse condition and level keep a special time, thus, the first synchronous rectifier 14a is just corresponding to the first detection signal V T1And keep cut-off state in this special time,, the first synchronous rectifier 14a can't be maintained at the situation of cut-off state so just not being subjected to the influence of the stray capacitance vibration that the leakage inductance on the circuit of power supply changeover device 1 and the first synchronous rectifier 14a had.
In the above-described embodiments, holding circuit 50 can comprise one second diode D 2, one keep capacitor C, one first holding circuit resistance R 3And one second holding circuit resistance R 4, the second diode D wherein 2Anode tap and the comparison circuit resistance R of comparison circuit 21 2The other end and the first diode D 1Cathode terminal connect the second diode D 2The cathode terminal and the first holding circuit resistance R 3An end and an end of keeping capacitor C connect the first holding circuit resistance R 3The other end and the first auxiliary switch element Q 3The control end and the second holding circuit resistance R 4An end connect the second holding circuit resistance R 4The other end and the other end of keeping capacitor C then with the second contact COM altogether 2Connect, and in the present embodiment, the second holding circuit resistance R 4Resistance value can be but be not limited to greater than the first holding circuit resistance R 3Resistance value.
Below the manner of execution of holding circuit 50 that rough explanation is shown in Figure 6.See also Fig. 3 and Fig. 6, when in time T 2, and flow through first electric current I of the first synchronous rectifier 14a D1By on the occasion of dropping to zero and when desiring reverse circulated, the first current transformer CT 1The first detection signal V T1Just can by negative value change on the occasion of and form a pulse, and through the comparison circuit resistance R 2And the second diode D 2And to keeping the capacitor C charging.And the stray capacitance that the leakage inductance on the circuit of power supply changeover device 1 and the first synchronous rectifier 14a are had vibration causes the first current transformer CT 1The first detection signal V that is exported T1When and then continuing change, when for example dropping to zero, the first detection signal V T1Just can stop keeping the capacitor C charging, at this moment, because the first holding circuit resistance R 3And the second holding circuit resistance R 4Impedance relationship, keep on the capacitor C and just can't discharge, make the voltage keep capacitor C can continue to be maintained at a high level state, so the first auxiliary switch element Q 3Still can be maintained at the state of conducting, thus, the first synchronous rectifier 14a just can not be subjected to the influence of the stray capacitance vibration that the leakage inductance on the circuit of power supply changeover device 1 and the first synchronous rectifier 14a had and be maintained at the state that ends constantly.
In addition, because holding circuit 50 can make the synchronous rectifier 14a that wins be maintained at cut-off state, so in order to make the first synchronous rectifier 14a in the first main switch element Q 1Next switch periods in can normally change conducting state into by cut-off state, rather than maintain cut-off state always, in some embodiment, as shown in Figure 6, the first synchronous commutating control circuit 13a has more a reset circuit 51 corresponding to holding circuit 50, this reset circuit 51 and the output of this holding circuit 50 and the first main switch element Q of commutation circuit 11 1Control end be connected, in order to the holding circuit 50 that resets, make the synchronous rectifier 14 of winning in the first main switch element Q 1Next switch periods in can normally change conducting state into by cut-off state.
Reset circuit 51 can comprise one first reset circuit switch element Q 4, one second reset circuit switch element Q 5And one first reset circuit resistance R 5, the first reset circuit switch element Q wherein 4Control end and the first main switch element Q of commutation circuit 11 1Control end connect and receive the first main control signal S that is exported by main control circuit 12 1, the first reset circuit switch element Q 4The first conduction of current end Q 4aBe connected in second and meet end COM altogether 2, the first reset circuit switch element Q 4The second conduction of current end Q 4bWith the first reset circuit resistance R 5An end and the second reset circuit switch element Q 5Control end connect the second reset circuit switch element Q 5The first conduction of current end Q 5aWith the second common contact COM 2Connect the second reset circuit switch element Q 5The second conduction of current end Q 5bThe first auxiliary switch element Q with comparison circuit 21 3Control end, the first holding circuit resistance R 3The other end and the second holding circuit resistance R 4An end connect the first reset circuit resistance R 5The other end then receive auxiliary voltage source V CCIn addition, in certain embodiments, the first reset circuit switch element Q 4And the second reset circuit switch element Q 5Can be but be not limited to and constituted by mos field effect transistor, and the first reset circuit switch element Q 4And the second reset circuit switch element Q 5More can adopt N type or P-type mos field-effect transistor according to the circuit actual demand.
Below the manner of execution of reset circuit 51 that rough explanation is shown in Figure 6.See also Fig. 3 and Fig. 6, when in time T 1To time T 2The time, the first main control signal S 1Maintain and enable level, and the first detection signal V T1Can be by negative value become on the occasion of and form a pulse, and this pulse meeting because of holding circuit 50 by time T 2Begin to keep a special time.As the T time of advent 3The time, the first main control signal S 1Just can become the forbidden energy level by enabling level, at this moment the first reset circuit switch element Q 4Can be corresponding to the first main control signal S 1And ending, so boost voltage V CCJust can be through the first reset circuit resistance R 5And drive the second reset circuit switch element Q 5Conducting, therefore keeping capacitor C just can pass through the second reset circuit switch element Q 5Conducting electric energy is given out light, thus, the first auxiliary switch element Q 3Just can end, promptly holding circuit 50 circuit 51 that is reset resets, so when in time T 4And the first main control signal S 1Become once more when enabling level by the forbidden energy level, start-up circuit 20 just can be according to the first main control signal S 1And the first synchronous rectification control signal S of output enable level 3To the control end of the first synchronous rectifier 14a, so the first synchronous rectifier 14a just can be in the first main switch element Q 1Next switch periods in normally walk around and become conducting state by cut-off state.
See also Fig. 7, it is the present invention's electrical block diagram of first synchronous commutating control circuit of a preferred embodiment again.As shown in the figure, the partial circuit structure of first synchronous commutating control circuit of present embodiment and Fig. 6 the partial circuit structural similarity of synchronous commutating control circuit, and the element representative structure and the functional similarity of same tag, so element characteristics, manner of execution repeat no more in this.Compare with Fig. 6, the comparing unit 210 in the comparison circuit 21 of present embodiment changes by one second auxiliary switch element Q 6, one the 3rd auxiliary switch element Q 7, one first comparing unit resistance R 6And one second comparing unit resistance R 7Constitute, comparing unit 210 and holding circuit 50 just can constitute an interlock circuit whereby.The second auxiliary switch element Q wherein 6Can be but be not limited to the PNP bipolar junction transistor, and the second auxiliary switch element Q 6The base stage and the second comparing unit resistance R 7An end and the 3rd auxiliary switch element Q 7Collector electrode connect, and be connected the second auxiliary switch element Q with the control end of the first synchronous rectifier 14a and the output of start-up circuit 20 through the output of comparing unit 210 6The emitter and the first comparing unit resistance R 6An end connect the second auxiliary switch element Q 6Collector electrode through the input of comparing unit 210 and the output of holding circuit 50, the i.e. first holding circuit resistance R 3The other end and the second holding circuit resistance R 4An end connect the 3rd auxiliary switch element Q 7Can be but be not limited to the NPN bipolar junction transistor, and the 3rd auxiliary switch element Q 7Base stage through the input of comparing unit 210 and the output of holding circuit 50, the i.e. first holding circuit resistance R 3The other end and the second holding circuit resistance R 4An end connect the 3rd auxiliary switch element Q 7The collector electrode and the second comparing unit resistance R 7An end and the second auxiliary switch element Q 6Base stage connect, and be connected the 3rd auxiliary switch element Q with the control end of the first synchronous rectifier 14a through the output of comparing unit 210 7Emitter through the earth terminal of comparing unit 210 and with the second contact COM altogether 2Connect the first comparing unit resistance R 6The other end and the second comparing unit resistance R 7The other end be connected to each other and receive boost voltage V CC
In addition, compare with Fig. 6, the capacitor C of keeping of the holding circuit 50 of present embodiment changes and the second holding circuit resistance R 4Parallel connection, and keep an end and the first holding circuit resistance R of capacitor C 3The other end, the second holding circuit resistance R 4An end and the input of comparing unit 210 connect, the other end of keeping capacitor C then with the second holding circuit resistance R 4The other end and second contact COM altogether 2Connect, and the holding circuit 50 of present embodiment can reach the identical effect of holding circuit 50 as shown in Figure 6 equally.
Below the manner of execution of synchronous commutating control circuit 13a that rough explanation is shown in Figure 7.See also Fig. 3 and Fig. 7, when for example in time T 1The time, the first synchronous rectifier 14a is received as the first synchronous rectification control signal S that enables level 3And present conducting state, and work as through after a while feasible first electric current I that flows through the first synchronous rectifier 14a D1When beginning descends gradually, the first current transformer CT 1The first detection signal V that is exported T1Just can begin accordingly to rise gradually, and as the first detection signal V T1Value in fact greater than the 3rd auxiliary switch element Q 7Conducting voltage the time, for example in time T 2The time,, the 3rd auxiliary switch element Q 7Just can conducting, the second auxiliary switch element Q at this moment 6Base stage can be dragged down, cause the second auxiliary switch element Q 6Conducting, therefore the 3rd auxiliary switch element Q 7Base stage just can be through the first comparing unit resistance R 6And reception boost voltage V CC, cause the 3rd auxiliary switch element Q 7Maintain the state of conducting, make the synchronous rectification control signal S that wins 3Dragged down, and since the effect of holding circuit 50, the first synchronous rectification control signal S 3What just can continue is dragged down, and causes the first synchronous rectifier 14a can not be subjected to the influence of the stray capacitance vibration that the leakage inductance on the circuit of power supply changeover device 1 and the first synchronous rectifier 14a had and is maintained at the state that ends constantly.As from the foregoing, comparison circuit 21 can be at the first detection signal V T1Greater than the 3rd auxiliary switch element Q 7Conducting voltage the time with the first synchronous control signal S 3Drag down, so the 3rd auxiliary switch element Q 7Conducting voltage be comparison circuit 21 and be used for and the first detection signal V T1The reference voltage of comparing.
In certain embodiments, holding circuit 50 shown in Figure 7 also can be applicable in as shown in Figure 4 the comparison circuit 21 and forms as shown in Figure 8 circuit structure.In described embodiment, holding circuit 50 is connected in the comparison circuit resistance R 2And between comparing unit 210 inputs.
Certainly, in other embodiments, the first comparing unit resistance R 6And the second comparing unit resistance R 7Be not limited to receive boost voltage V as shown in Figure 7 Cc, in other embodiments, the first comparing unit resistance R 6And the second comparing unit resistance R 7The other end also can change control end with commutation circuit 11, the i.e. first main switch element Q 1Control end connect and receive the first main control signal S 1, and this execution mode can make holding circuit 50 reach identical effect equally.In addition, in certain embodiments, holding circuit 50 more can be but is not limited to and is made of a rest-set flip-flop.
Certainly, the circuit structure of reset circuit inside also is not limited to execution mode as shown in Figure 6, also can have as Fig. 7 to difference variation shown in Figure 8.See also Fig. 7, in the present embodiment, reset circuit 51 is by a Schottky diode D ScConstitute this Schottky diode D ScThe cathode terminal and the first main switch element Q 1Control end connect and receive the first main control signal S 1, Schottky diode D ScThe anode tap and the first holding circuit resistance R 3And the second holding circuit resistance R 4Connect.And as the first main control signal S 1During for the forbidden energy level, reset circuit 51 just can pass through Schottky diode D ScAnd the holding circuit 50 that resets makes and keeps capacitor C the electric energy that stores is given out light.
See also Fig. 8, its be reset circuit shown in Figure 6 one change example again.As shown in the figure, in the present embodiment, reset circuit 51 comprises one second reset circuit resistance R 8And the 3rd reset circuit switch element Q 8, the second reset circuit resistance R wherein 8An end and the control end of commutation circuit 11, the i.e. first main switch element Q 1Control end connect and receive the first main control signal S 1, the second reset circuit resistance R 8The other end and the 3rd reset circuit switch element Q 8Control end connect.The 3rd reset circuit switch element Q 8Can be a P-type mos field-effect transistor and constitute, but not as limit, also can be PNP dipole field-effect transistor and constitute, the 3rd reset circuit switch element Q 8The first conduction of current end Q 8aWith the second common contact COM 2Connect the 3rd reset circuit switch element Q 8The second conduction of current end Q 8bWith the first holding circuit resistance R 3The other end and the second holding circuit resistance R 4An end connect.Therefore by above-mentioned circuit structure, reset circuit 51 is in the first main control signal S 1During for the forbidden energy level, the holding circuit 50 that just can reset makes and keeps capacitor C the electric energy that stores is given out light.
Certainly, in other embodiments, an end of the second reset circuit resistance R 8 can change another control end with commutation circuit 11, i.e. the second main switch element Q 2Control end connect and receive the second main control signal S 2, and the 3rd reset circuit switch element Q 8Then need change a N type metal oxide semiconductor field-effect transistor accordingly into and constitute, and this execution mode also can make reset circuit 51 reach identical effect.
Certainly, but comparison circuit 21 shown in Figure 2, comparison circuit 21 shown in Figure 4 and comparison circuit 21 mutual alternative shown in Figure 7, but comparing unit 210 shown in Figure 2 and comparing unit 210 mutual alternative shown in Figure 5, but holding circuit 50 shown in Figure 6 and Fig. 7 and holding circuit 50 mutual alternative shown in Figure 8, but reset circuit 51 mutual alternative of the reset circuit 51 of Fig. 6, the reset circuit 51 of Fig. 7 and Fig. 8, but not as limit.
Below will further specify the process step of the control method of first synchronous rectifier shown in Figure 1.See also Fig. 9, and cooperate Fig. 2, wherein Fig. 9 is the control method flow chart of the first synchronous rectifier 14a shown in Figure 1.As shown in Figure 9, at first, shown in step S90, produce the first main control signal S by main control circuit 12 1 Give commutation circuit 11 and this first synchronous commutating control circuit 13a, make commutation circuit 11 actions and order about the conversion that transformer T carries out energy.Then, shown in step S91, transmit the first detection signal V by current transformer CT T1Give the first synchronous commutating control circuit 13a.Then, shown in step S92, according to the first main control signal S 1Make the synchronous commutating control circuit 13a that wins control the first synchronous rectifier 14a conducting.At last, shown in step S93, according to the first detection signal V T1End and make the synchronous commutating control circuit 13a that wins control the first synchronous rectifier 14a.
In addition, in certain embodiments, as shown in figure 10, have more four sub-steps in the step S93, be setting up procedure S930, comparison step S93 1 in regular turn, keep step S932 and reset process S932.At first, carry out setting up procedure S930, promptly receive the first main control signal S by start-up circuit 20 1, and according to the first main control signal S 1And export one first synchronous rectification control signal S 3To the control end of the first synchronous rectifier 14a, and prevent the first main control signal S 1Voltage level along with the first synchronous rectification control signal S 3Voltage level dragged down and dragged down.Then, compare step S931, promptly pass through comparing unit 210 detection signal V tCompare with reference voltage, to work as detection signal V tLevel during greater than the level of reference voltage, order about the first synchronous rectifier 14a and end.Then, keep step S932, promptly make detection signal V by holding circuit 50 tChange into by negative value on the occasion of and a special time is kept in the pulse that forms.At last, carry out reset process S933, promptly, make the first synchronous rectifier 14a in the next switch periods of commutation circuit 11, can normally change conducting state into by cut-off state by reset circuit 51 holding circuit 50 that resets.
And the control method of the second synchronous rectifier 14b shown in Figure 1 is similar in appearance to the first synchronous rectifier 14a, so repeat no more in this.Because power supply changeover device 1 of the present invention is by the first current transformer CT 1And the second current transformer CT 2Can be immediately and control the first synchronous rectifier 14a accurately and the second synchronous rectifier 14b ends, so the first synchronous rectifier 14a and the second synchronous rectifier 14b just are difficult for burning, and the whole efficiency of power supply changeover device of the present invention 1 also promotes relatively.
In sum, the invention provides a kind of control method of power supply changeover device and synchronous rectifier of tool synchronous rectifier, it detects the situation of the electric current tool reverse circulated that flows through synchronous rectifier fast by current transformer, make that synchronous commutating control circuit can be immediately and control synchronous rectifier accurately and end, so synchronous rectifier of the present invention just is difficult for burning, and the whole efficiency of power supply changeover device of the present invention also promotes relatively.The present invention must appoint and executes that the craftsman thinks and be to modify as all by haveing the knack of those of ordinary skills, does not so take off the scope as the desire protection of attached claim institute.

Claims (21)

1. power supply changeover device, it comprises:
One switches circuit, receives an input voltage;
One transformer has an elementary winding and a level winding, and this elementary winding is total to contact with the power output end and one first of this commutation circuit and is connected;
One main control circuit is connected at least one control end of this commutation circuit, controls this commutation circuit operation in order to produce at least one main control signal, makes the energy selectivity ground of this input voltage be sent to this elementary winding via this commutation circuit;
At least one synchronous rectifier is total to contact with this secondary winding and one second of this transformer and is connected in series;
At least one current transformer is connected in series with this synchronous rectifier, in order to export a detection signal according to the electric current that flows through this synchronous rectifier; And
At least one synchronous commutating control circuit, be connected with this control end of control end, this current transformer and this commutation circuit of this synchronous rectifier, it receives this corresponding detection signal and this corresponding main control signal, and exports a synchronous rectification control signal and control this synchronous rectifier operation;
Wherein when this commutation circuit conducting of this master control circuit controls, this synchronous commutating control circuit is controlled this synchronous rectifier conducting, and this synchronous commutating control circuit is controlled this synchronous rectifier according to this detection signal and ended.
2. power supply changeover device as claimed in claim 1, wherein this synchronous commutating control circuit also comprises the comparison circuit with a comparison circuit resistance and a comparing unit, wherein an end of comparison circuit resistance is connected with this current transformer and receives this detection signal, and the other end of this comparison circuit resistance is connected with the input of this comparing unit, the output of this comparing unit is connected with the control end of this synchronous rectifier, this comparison circuit is in order to when the level of this detection signal during greater than the level of a reference voltage, the level of this synchronous rectification control signal dragged down be the forbidden energy level, end to order about this synchronous rectifier.
3. power supply changeover device as claimed in claim 2, wherein this comparing unit comprises:
One comparator, the reverse input end of this comparator be through the input of this comparing unit and be connected with the other end of this comparison circuit resistance, and the output of this comparator is through the output of this comparing unit and be connected with the control end of this synchronous rectifier; And
One voltage source is serially connected with between the earth terminal of the non-inverting input of this comparator and this comparing unit, and through the earth terminal of this comparison circuit and with this second altogether contact be connected, in order to this reference voltage to be provided.
4. power supply changeover device as claimed in claim 2, wherein this comparing unit comprises:
One first auxiliary switch element, the control end of this first auxiliary switch element is through the input of this comparing unit and be connected with the other end of this comparison circuit resistance, one first conduction of current end of this first auxiliary switch element is connected with this second common contact through the earth terminal of this comparing unit, one second conduction of current end of this first auxiliary switch element is through the output of comparing unit and be connected with the control end of this synchronous rectifier, and the conducting voltage of this first auxiliary switch element is this reference voltage.
5. power supply changeover device as claimed in claim 2, wherein this comparing unit comprises:
One second auxiliary switch element, this second auxiliary switch element base stage through the output of this comparing unit and be connected with the control end of this synchronous rectifier, the collector electrode of this second auxiliary switch element is through the input of this comparing unit and be connected with the other end of this comparison circuit resistance;
One the 3rd auxiliary switch element, the base stage of the 3rd auxiliary switch element is connected with the other end of this comparison circuit resistance and the collector electrode of this second auxiliary switch element, the collector electrode of the 3rd auxiliary switch element is connected with the control end of this synchronous rectifier through the output of this comparing unit, the emitter of the 3rd auxiliary switch element through the earth terminal of this comparing unit with this second altogether contact be connected;
One first comparing unit resistance, an end of this first comparing unit resistance is connected with the emitter of second auxiliary switch element, and the other end of this first comparing unit resistance is connected with this control end of this commutation circuit and receives this main control signal; And
One second comparing unit resistance, one end of this second comparing unit resistance is connected with the collector electrode of the base stage of this two auxiliary switch element, the 3rd auxiliary switch element and the control end of this synchronous rectifier, and the other end of this second comparing unit resistance is connected with this control end of this commutation circuit and receives this main control signal;
Wherein, the conducting voltage of the 3rd auxiliary switch element is this reference voltage.
6. power supply changeover device as claimed in claim 2, wherein this comparing unit comprises:
One second auxiliary switch element, this second auxiliary switch element base stage through the output of this comparing unit and be connected with the control end of this synchronous rectifier, the collector electrode of this second auxiliary switch element is through the input of this comparing unit and be connected with the other end of this comparison circuit resistance;
One the 3rd auxiliary switch element, the base stage of the 3rd auxiliary switch element is connected with the other end of this comparison circuit resistance and the collector electrode of this second auxiliary switch element, the collector electrode of the 3rd auxiliary switch element is connected with the control end of this synchronous rectifier through the output of this comparing unit, the emitter of the 3rd auxiliary switch element through the earth terminal of this comparing unit with this second altogether contact be connected;
One first comparing unit resistance, an end of this first comparing unit resistance is connected with the emitter of this second auxiliary switch element, and the other end of this first comparing unit resistance receives a boost voltage; And
One second comparing unit resistance, one end of this second comparing unit resistance is connected with the collector electrode of the base stage of this two auxiliary switch element, the 3rd auxiliary switch element and the control end of this synchronous rectifier, and the other end of this second comparing unit resistance is connected with the other end of this first comparing unit resistance and receives this boost voltage;
Wherein, the conducting voltage of the 3rd auxiliary switch element is this reference voltage.
7. power supply changeover device as claimed in claim 6, wherein this synchronous commutating control circuit also comprises and keeps circuit, this holding circuit is connected with this comparison circuit resistance and receives this detection signal, with so that this detection signal change into by negative value on the occasion of and a special time is kept in the pulse that forms.
8. power supply changeover device as claimed in claim 7, wherein this holding circuit comprises:
One second diode, the anode tap of this second diode is connected with the other end of this start-up circuit resistance;
One first holding circuit resistance, the cathode terminal of this second diode of an end of this first holding circuit resistance connects;
One keeps electric capacity, and this end of keeping electric capacity is connected with the other end of this first holding circuit resistance, and this other end of keeping electric capacity is connected with this second common contact;
One second holding circuit resistance is kept electric capacity with this and is connect, and an end of this second holding circuit resistance is connected with the other end of this first holding circuit resistance, this second holding circuit resistance other end with this second altogether contact be connected.
9. power supply changeover device as claimed in claim 7, wherein this holding circuit comprises:
One second diode, the anode tap of this second diode is connected with the other end of this comparison circuit resistance;
One keeps electric capacity, and this end of keeping electric capacity is connected with the cathode terminal of this second diode, and this other end of keeping electric capacity is connected with this second common contact;
One first holding circuit resistance, an end of this first holding circuit resistance is connected with this end of keeping electric capacity; And
One second holding circuit resistance, an end of this second holding circuit resistance is connected with the other end of this first holding circuit resistance, and the other end of this second holding circuit resistance is connected with this second common contact.
10. power supply changeover device as claimed in claim 9, wherein this synchronous commutating control circuit also comprises a reset circuit, be connected with the output of this holding circuit, in order to this holding circuit that resets, make this synchronous rectifier in the next switch periods of this commutation circuit, can normally change conducting state into by cut-off state.
11. power supply changeover device as claimed in claim 10, wherein this reset circuit comprises:
One first reset circuit switch element, the control end of this first reset circuit switch element are connected with this control end of this commutation circuit and receive this main control signal, and one first conduction of current end of this first reset circuit switch element second connects end altogether and is connected with this;
One second reset circuit switch element, the control end of this second reset circuit switch element is connected with one second conduction of current end of this first reset circuit switch element, one first conduction of current end of this second reset circuit switch element is connected with this second common contact, and one second conduction of current end of this second reset circuit is connected with the output of this holding circuit; And
One first reset circuit resistance, an end of this first reset circuit resistance is connected with this first conduction of current end of this first reset circuit switch element, and the other end of this first reset circuit resistance receives this auxiliary voltage source.
12. power supply changeover device as claimed in claim 10, wherein this reset circuit comprises:
One second reset circuit resistance, an end of this second reset circuit resistance are connected with this control end of this commutation circuit and receive this main control signal; And
One the 3rd reset circuit switch element, the control end of the 3rd reset circuit switch element is connected with the other end of this second reset circuit resistance, one first conduction of current end of the 3rd reset circuit switch element is connected with this second common contact, one second conduction of current end of the 3rd reset circuit switch element is connected with the output of this holding circuit, and the 3rd reset circuit switch element is a P-type mos field-effect transistor.
13. power supply changeover device as claimed in claim 10, wherein this reset circuit comprises:
One second reset circuit resistance, an end of this second reset circuit resistance connects and this corresponding main control signal of reception with another this control end of this commutation circuit; And
One the 3rd reset circuit switch element, the control end of the 3rd reset circuit switch element is connected with the other end of this second reset circuit resistance, one first conduction of current end of the 3rd reset circuit switch element is connected with this second common contact, one second conduction of current end of the 3rd reset circuit switch element is connected with the output of this holding circuit, and the 3rd reset circuit switch element is a N type metal oxide semiconductor field-effect transistor.
14. as the arbitrary described power supply changeover device of claim 2-13, wherein this synchronous commutating control circuit also comprises a start-up circuit, be connected with the control end of this commutation circuit and the control end of this synchronous rectifier, in order to receive this main control signal and to export the control end that this synchronous rectification controls signal to this synchronous rectifier according to this main control signal, and when the voltage level of this synchronous rectification control signal was dragged down, the voltage level that prevents this main control signal was along with the voltage level of this synchronous rectification control signal is dragged down and dragged down.
15. power supply changeover device as claimed in claim 14, wherein this start-up circuit comprises a start-up circuit resistance.
16. power supply changeover device as claimed in claim 15, wherein this start-up circuit also comprises a totem-pote circuit, and this totem-pote circuit is connected between the control end and this start-up circuit resistance of this commutation circuit, in order to strengthen the driving force of this power supply changeover device.
17. the control method of a synchronous rectifier, in order to control at least one synchronous rectifier of a power supply changeover device, wherein this power supply changeover device also comprises a switching circuit, one main control circuit, one transformer, at least one current transformer and at least one synchronous commutating control circuit, this commutation circuit is connected with an elementary winding of this transformer, this main control circuit is connected with the control end of this commutation circuit, this current transformer and this synchronous rectifier system are connected in series with a level winding of this transformer, this synchronous commutating control circuit is connected with the control end of this commutation circuit and the control end of this synchronous rectifying controller, and this synchronous commutating control circuit control method comprises:
(a) produce a main control signal to this commutation circuit and this synchronous commutating control circuit by this main control circuit, make this commutation circuit action and make the energy selectivity ground of an input voltage be sent to this transformer via this commutation circuit;
(b) this synchronous commutating control circuit is controlled this synchronous rectifier conducting according to this main control signal;
(c) this current transformer detects this synchronous rectifier and transmits a detection signal and give this synchronous commutating control circuit; And
(d) this synchronous commutating control circuit is controlled this synchronous rectifier and is ended according to this detection signal.
18. the control method of synchronous rectifier as claimed in claim 17, wherein step (d) also comprises comparison step, system compares this detection signal and a reference voltage by a comparing unit, with when the level of this detection signal during, order about this synchronous rectifier and end greater than the level of this reference voltage.
19. the control method of synchronous rectifier as claimed in claim 18, wherein step (d) also comprises and keeps step, is to keep circuit by one to make this detection signal keep a special time being changed on the occasion of the pulse that forms by negative value.
20. the control method of synchronous rectifier as claimed in claim 19, wherein step (d) also comprises reset process, by a reset circuit this holding circuit that resets, make this synchronous rectifier in the next switch periods of this commutation circuit, can normally change conducting state into by cut-off state.
21. control method as the arbitrary described synchronous rectifier of claim 17-20, wherein step (d) also comprises setting up procedure, receive a main control signal of this main control circuit output by a start-up circuit, and export the control end that a synchronous rectification controls signal to this synchronous rectifier according to this main control signal, and the voltage level that prevents this main control signal is dragged down and is dragged down along with the voltage level of this synchronous rectification control signal.
CN200910166746.9A 2009-08-12 2009-08-12 Power supply converter with synchronous rectifier and control method for synchronous rectifier Expired - Fee Related CN101997413B (en)

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