CN101997413B - 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
CN101997413B
CN101997413B CN200910166746.9A CN200910166746A CN101997413B CN 101997413 B CN101997413 B CN 101997413B CN 200910166746 A CN200910166746 A CN 200910166746A CN 101997413 B CN101997413 B CN 101997413B
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circuit
switch element
synchronous
resistance
synchronous rectifier
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CN101997413A (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

The control method with power supply changeover device and the 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 with synchronous rectifier of the deadline that current transformer removes to detect synchronous rectifier and control method of synchronous rectifier utilized.
Background technology
In various power supply changeover devices (power converter circuit), such as resonant mode power supply changeover device etc., conventionally can there is commutation circuit, transformer and rectifier diode.Wherein commutation circuit is connected with the armature winding of transformer, and it is subject to the control of a control circuit and carries out conducting or cut-off.Transformer receives electric energy by primary side winding, and when commutation circuit is carried out the switching of conducting or cut-off, the mode of the utilization of power electromagnetic induction of armature winding is sent to the secondary winding of transformer.As for rectifier diode, be connected with the secondary winding of transformer, in order to the ac voltage rectifier that secondary winding induction is generated, become a direct voltage, to offer load, use.
Yet because the forward conduction voltage drop of rectifier diode can make rectifier diode produce sizable conducting loss, the synchronous rectifier being therefore comprised of transistor has replaced rectifier diode gradually and has been applied in power supply changeover device.The power supply changeover device framework that uses rectifier diode compared to tradition, the power supply changeover device that carries out rectification with synchronous rectifier just can reduce power loss.
Although use synchronous rectifier to carry out rectification, really can make power supply changeover device reduce power loss, yet because synchronous rectifier is comprised of transistor, so synchronous rectifier need to accurately be controlled to carry out the switching of conducting or cut-off.The control mode of synchronous rectifier is directly by a control integration circuit (control integrated circuit), to control synchronous rectifier conducting at present, in addition, the drain electrode of control integration circuit meeting sample-synchronous rectifier and the voltage difference between source electrode two ends, and then calculate the electric current that flows through synchronous rectifier, control whereby synchronous rectifier cut-off.
Yet the control mode of above-mentioned synchronous rectifier can be affected by the leakage inductance on the circuit of power supply changeover device, make control integration the circuit accurately drain electrode of sample-synchronous rectifier and the voltage difference between source electrode two ends, and then cause control integration circuit cannot control accurately the action of synchronous rectifier, for example control integration circuit may be controlled synchronous rectifier and ends in advance, thus, synchronous rectifier just easily burns, 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 defect has power supply changeover device and the synchronous rectifier of synchronous rectifier, real is current problem in the urgent need to address.
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 directly utilizing control integration circuit to control the action of synchronous rectifier, therefore when control integration circuit is affected by leakage inductance on the circuit of known power supply changeover device, can cannot control accurately the action of synchronous rectifier, cause having the defects 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 compared with broad sense execution mode for a kind of power supply changeover device is provided, it comprises commutation circuit, receives input voltage; Transformer, has armature winding and secondary winding, and armature 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 commutation circuit operation in order to produce at least one main control signal, make input voltage energy selectivity via commutation circuit, be sent to armature winding; At least one synchronous rectifier, is total to contact with the secondary winding and second of transformer 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 controls synchronous rectifier operation; Wherein, when the conducting of master control circuit controls commutation circuit, synchronous commutating control circuit is controlled synchronous rectifier conducting, and synchronous commutating control circuit is controlled synchronous rectifier cut-off according to detection signal.
For reaching above-mentioned purpose, of the present invention another compared with broad sense execution mode for a kind of control method of synchronous rectifier is provided, in order to control at least one synchronous rectifier of 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 armature winding of transformer, main control circuit is connected with commutation circuit control end, current transformer and synchronous rectifier are connected in series with the secondary winding of transformer, the control end of synchronous commutating control circuit commutation circuit is connected with the control end of synchronous rectifying controller, synchronous commutating control circuit control method comprises, make transformer carry out the conversion of energy: (a) by main control circuit, to produce main control signal to commutation circuit and this synchronous commutating control circuit, make commutation circuit action and make input voltage energy selectivity via commutation circuit, be sent to this transformer, (b) synchronous commutating control circuit is controlled synchronous rectifier conducting according to main control signal, (c) current transformer detects synchronous rectifier and transmits detection signal to this synchronous commutating control circuit, and (d) synchronous commutating control circuit is controlled synchronous rectifier cut-off 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 the synchronous commutating control circuit can be immediately and control accurately synchronous rectifier cut-off, so synchronous rectifier of the present invention is just difficult for burning, and the whole efficiency of power supply changeover device of the present invention also promotes relatively.
Accompanying drawing explanation
Fig. 1: the circuit block diagram of its power supply changeover device that is preferred embodiment of the present invention.
Fig. 2: it is the detailed circuit structural representation of the first synchronous commutating control circuit shown in Fig. 1.
Fig. 3: it is electric current, voltage and the sequential view of the power supply changeover device shown in Fig. 1.
Fig. 4: it is another variation example of the comparison circuit shown in Fig. 2.
Fig. 5: it is that one of the start-up circuit shown in Fig. 2 changes example.
Fig. 6: the electrical block diagram of its first synchronous commutating control circuit that is another preferred embodiment of the present invention.
Fig. 7: it is the present invention's electrical block diagram of the first synchronous commutating control circuit of a preferred embodiment again.
Fig. 8: it is a variation example again of the reset circuit shown in Fig. 5.
Fig. 9: it is the control method flow chart of the first synchronous rectifier shown in Fig. 1.
Figure 10: it is the sub-step of the step S93 shown in Fig. 9.
Description of reference numerals in 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: the first～three auxiliary switch element
Q 4, Q 5, Q 8: the first～three reset circuit switch element
Q 1a, Q 2a, Q 3a, Q 4a, Q 5a, Q 8a: the first electric current conduction terminals
Q 1b, Q 2b, Q 3b, Q 4b, Q 5b, Q 8b: the second electric current conduction terminals
T: transformer
N p: armature 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: NPN bipolar junction transistor
B 2: 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: maintain 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
S90～93: the process step of the control method of the first isochronous controller
S930: setting up procedure
S931: comparison step
S932: maintain step
S933: reset process
Embodiment
Some exemplary embodiments that embody feature & benefits of the present invention will describe in detail in the explanation of back segment.Be understood that the present invention can have various variations in different modes, it does not depart from the scope of the present invention, and explanation wherein and the accompanying drawing use that ought explain in itself, but not in order to limit the present invention.
Refer to Fig. 1, the circuit block diagram of its power supply changeover device that is preferred embodiment of the present invention.As shown in Figure 1, the power supply changeover device 1 of the present embodiment is connected in a load L o, it is in order to by an input voltage V inbe converted to an output voltage V o, with supply load L ouse.This power supply changeover device 1 comprises a commutation 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 as shown in Figure 1 of example and the second synchronous commutating control circuit 13b, at least one synchronous rectifier, example the first synchronous rectifier 14a and the second synchronous rectifier 14b as shown in Figure 1, and at least one current transformer, example the first current transformer CT as 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 be not limited to by the first main switch element Q 1and the second main switch element Q 2institute forms, wherein the first main switch element Q 1the first electric current conduction terminals Q 1awith the second main switch element Q 2the second electric current conduction terminals Q 2bconnect, and the second main switch element Q 2the first electric current conduction terminals 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 cut-off.
Resonant circuit 15 is connected in the armature winding N of commutation circuit 11 and transformer T pbetween.In the present embodiment, resonant circuit 15 comprises at least one resonant capacitance, example the first resonant capacitance C as shown in Figure 1 r1and the second resonant capacitance C r2, and a resonant inductance L r, the first resonant capacitance C wherein r1one end and the first main switch element Q 1the second electric current conduction terminals Q 1bconnect the first resonant capacitance C r1the other end with the second resonant capacitance C r2one end connect, and the second resonant capacitance C r2the other end with the second main switch element Q 2the first electric current conduction terminals Q 2aand the first contact COM altogether 1connect.Resonant inductance L rone end be connected in the first main switch element Q 1the first electric current conduction terminals Q 1aand the second main switch element Q 2the second electric current conduction terminals Q 2bbetween, resonant inductance L rthe other end with the armature winding N of transformer T pconnect.
Transformer T has armature winding N pand secondary winding N s, armature winding N wherein pone end and the power output end of commutation circuit 11, i.e. the first main switch element Q 1the first electric current conduction terminals Q 1aand the second main switch element Q 2the second electric current conduction terminals Q 2bconnect armature winding N pthe other end be connected in the first contact COM altogether 1, and the secondary winding N of transformer T sthere is centre cap and be connected in load L o.In addition, in the present embodiment, armature winding N pcan be but be not limited to comprise an equivalent magnetizing inductance L m, it is connected in parallel in armature winding N p, in order to equivalent armature winding N pinductance characteristic to the excitatory generation of transformer T during operation.
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 finstitute forms, this filter capacitor C fone end be connected in the secondary winding N of transformer T scentre cap and load L obetween, the other end is total to contact COM with second 2connect.
Main control circuit 12 is connected with the control end of commutation circuit 11, i.e. main control circuit 12 and the first main switch element Q 1control end and the second main switch element Q 2control end connect, main control circuit 12 is in order to produce respectively one first main control signal S 1and one second main control signal S 2to the first main switch element Q 1control 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 via this commutation circuit 11, be sent to the armature winding N of transformer T p, thus, the secondary winding N of transformer T sjust can produce induction alternating voltage because of electromagnetic induction.
The first synchronous rectifier 14a is serially connected with the secondary winding N of transformer T sone end and second contact COM altogether 2between, the two or two synchronous rectifier 14b is serially connected with the other end and the second contact COM of secondary winding Ns 2between, the first synchronous rectifier 14a and the second synchronous rectifier 14b are in order to by the secondary winding N of transformer T sthe induction ac voltage rectifier producing becomes direct voltage.
The first current transformer CT 1and the second current transformer CT 2be serially connected with respectively the secondary winding N of transformer T 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 2more be total to contact COM with the second synchronous commutating control circuit 13b and second 2connect the first current transformer CT 1in order to basis, flow through the first electric current I of the first synchronous rectifier 14a d1and export the first detection signal V t1, the second current transformer CT 2in order to basis, flow through the second electric current I of the second synchronous rectifier 14b 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 foundation the 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, to control the first synchronous rectifier 14a, carry out conducting or cut-off.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 foundation the 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, to control the second synchronous rectifier 14b, carry out conducting or cut-off.
In the present embodiment, when main control circuit 12 is 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 t1and control the first synchronous rectifier 14a, end.Similarly, when main control circuit 12 is 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 t2and control the second synchronous rectifier 14b, end.
To internal circuit configuration and the annexation of the first synchronous commutating control circuit 13a be described with Fig. 2 below.In addition,, because partial circuit element in Fig. 1 and Fig. 2 has interconnective relation, therefore identical English symbol will be indicated in Fig. 1 and Fig. 2, to represent that it interconnects.
Refer to Fig. 2, it is the detailed circuit structural representation of the first synchronous commutating control circuit shown in Fig. 1.As shown in the figure, the first synchronous commutating control circuit 13a 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 being exported by main control circuit 12 1, the output of start-up circuit 20 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 when main control circuit 12 is 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 while 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.Comparison circuit 21 and the first current transformer CT 1, the control end of the first synchronous rectifier 14a and the output of start-up circuit 20 connect, it receives the first current transformer CT 1the the first detection signal V exporting t1, and as the first detection signal V t1while being greater than the reference voltage in 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 first synchronous rectification control signal S 3for forbidden energy (disable) level, and then drive the first synchronous rectifier 14a cut-off.
In the above-described embodiments, start-up circuit 20 mainly comprises a start-up circuit resistance R 1, this start-up circuit resistance R 1one end and the first main switch element Q 1control end connect, start-up circuit resistance R 1the other end be connected with the control end of the first synchronous rectifier 14a, as the first detection signal V t1value be greater than the value of the reference voltage of comparison circuit 21, make comparison circuit 21 by the first synchronous rectification control signal S of start-up circuit 20 outputs 3voltage level while dragging down, start-up circuit 20 just can pass through 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 2one end and the first current transformer CT 1connect and receive the first detection signal V t1, comparison circuit resistance R 2the other end be connected with the input of comparing unit 210, therefore the input of comparing unit 210 is just through 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 be greater than comparing unit 210 itself conducting voltage value and carry out conducting or cut-off.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 be greater than comparing unit 210 conducting voltage value and while making comparing unit 210 conducting, 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 cut-off.Hence one can see that, and the conducting voltage of comparing unit 210 is set as 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 3institute realizes, therefore 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 comparison circuit resistance R 2the other end connect, and receive the first detection signal V t1, the first auxiliary switch element Q 3the second electric current conduction terminals 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 electric current conduction terminals 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 comparison circuit resistance R 2the other end and the first auxiliary switch element Q 3control end between, and the first diode D 1anode tap with the second contact COM altogether 2connect the first diode D 1there is the effect of clamper, in order to clamp down on the first auxiliary switch element Q 3control end and the first electric current conduction terminals Q 3abetween voltage, prevent the first detection signal V t1when negative value, reverse current is excessive and by 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 synchronous rectifier 14b also similar in appearance to 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 annexation between synchronous rectifier 14a, therefore below by repeat no more the second synchronous commutating control circuit 13b internal circuit configuration and with the second main switch element Q 2, the second current transformer CT 2and second annexation between synchronous rectifier 14b, also repeating no more the various of the second synchronous commutating control circuit 13b may execution mode, and the first synchronous commutating control circuit 13a of only take comes exemplary illustrated technology of the present invention and various possible execution mode as example.
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 form, 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 side circuit demand.
Below by the operation logic of explanation power supply changeover device of the present invention.Refer to Fig. 3, and coordinate Fig. 1 and Fig. 2, wherein Fig. 3 is electric current, voltage and the sequential view of the power supply changeover device shown in Fig. 1.As shown in Figure 3, when for example in time T 1time, 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 first main switch element Q 1start conducting, therefore 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 the first electric current I of the first synchronous rectifier 14a d1just start to rise, therefore the first current transformer CT 1the the first detection signal V exporting t1just corresponding to the first electric current I d1and be negative value.In addition, because the first synchronous rectifier 14a is consisted of mos field effect transistor, so the first electric current I d1in time T 1just can by zero, start to rise because of the body diode (body diode) of the first synchronous rectifier 14a before.
When the time T that arrives through after a while 2time, now, flow through the first electric current I of the first synchronous rectifier 14a d1dropped to zero and be about to change and flow to, the first current transformer CT 1the the first detection signal V exporting t1just can corresponding the first electric current I d1changed course and by negative value change on the occasion of, and form a pulse (pulse), now 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 be greater than the first auxiliary switch element Q 3turn-on voltage time drive the first auxiliary switch element Q 3conducting, thus, comparison circuit 21 just can be by the first synchronous rectification control signal S 3voltage level drag down, make the first synchronous rectification control signal S 3the first synchronous rectifier 14a by enabling level, changes into forbidden energy level, so just can end.As from the foregoing, when flowing through the first electric current I of the first synchronous rectifier 14a of the present invention d1while being about to reverse circulated, the first current transformer CT 1just this situation can be detected fast, and notify the first synchronous commutating control circuit 13a by testing result, make the first synchronous commutating control circuit 13a immediately control ground the first synchronous rectifier 14a cut-off.
Refer to Fig. 4 and coordinate Fig. 3, wherein Fig. 4 is another variation example of the comparison circuit shown in Fig. 2.As shown in Figure 4, the comparison circuit 21 of the present embodiment, compared to the comparison circuit 21 shown in Fig. 2, only has comparison circuit resistance R 2and comparing unit 210, and in the present embodiment, comparing unit 210 changes by comparator OP and a voltage source 311 and is formed.Wherein, comparison circuit resistance R 2one end and the first current transformer CT 1connect and receive the first detection signal V t1, comparison circuit resistance R 2the other end 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 non-inverting input of comparator OP and the earth terminal of 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 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 be greater than reference voltage V refvalue time, in output export a low voltage level signal and by the first synchronous rectification control signal S of start-up circuit 20 output 3voltage level drag down, make the first synchronous rectification control signal S 3for forbidden energy level, and then drive the first synchronous rectifier 14a cut-off.
Therefore as shown in Figure 3, when for example in time T 1time, the first synchronous rectifier 14a is received as the first synchronous rectification control signal S that enables level 3and present conducting state, and when through after a while, make to flow through the first electric current I of the first synchronous rectifier 14a d1while starting to decline gradually, the first current transformer CT 1the the first detection signal V exporting t1just can start accordingly to rise gradually, and as the first detection signal V t1value be greater than in fact reference voltage V refvalue, for example, in time T 2time, comparator OP just can export a low level signal and by the first synchronous rectification control signal S of start-up circuit 20 output 3voltage level drag down, make the first synchronous rectification control signal S 3change forbidden energy level into, thus, just can drive the first synchronous rectifier 14a cut-off.So utilize the first synchronous commutating control circuit 13a of the comparison circuit 211 of the present embodiment equally can be according to the first current transformer CT 1testing result and instant control ground the first synchronous rectifier 14a cut-off.
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, therefore repeat no more in this.
Because current transformer has the characteristic that can detect rapidly curent change, 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 fast respectively the first electric current I that flows through the first synchronous rectifier 14a d1and the second electric current I of the second synchronous rectifier 14b d2the situation that has tool reverse circulated, make the first synchronous commutating control circuit 13a and the second synchronous commutating control circuit 13b can be immediately and control accurately the first synchronous rectifier 14a and the second synchronous rectifier 14b cut-off, thus, the first synchronous rectifier 14a and the second synchronous rectifier 14b are just difficult for burning, and the whole efficiency of power supply changeover device of the present invention 1 also promotes relatively.
Other possible execution mode of the first synchronous commutating control circuit 13a of the present invention and the second synchronous commutating control circuit 13b will be further illustrated below.And because the second synchronous commutating control circuit 13a is similar to circuit structure and the annexation of the first synchronous commutating control circuit 13b, therefore only take below the first synchronous commutating control circuit 13a, carry out exemplary illustrated as example.In addition,, because the partial circuit element of the partial circuit element in the following drawings and Fig. 1 has interconnective relation, therefore will indicate identical English symbol in Fig. 1 and following diagram, to represent that it interconnects.
In certain embodiments, in order to strengthen the driving force of the internal circuit of 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 2base 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 subject to respectively the first main control signal S 1control and carry out conducting or cut-off, 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 in the start-up circuit 20 that need be used in the first synchronous commutating control circuit 13a shown in Fig. 5, also applicable in above-mentioned other embodiment or the start-up circuit of the first synchronous commutating control circuit of the embodiment of the following stated.
In other embodiments, when first synchronous rectifier 14a when cut-off, because the stray capacitance that the leakage inductance on the circuit of power supply changeover device 1 and the first synchronous rectifier 14a have may be vibrated, cause the first current transformer CT 1the the first detection signal V exporting t1also and then continue change, make the first synchronous rectifier 14a repeatedly to carry out conducting or cut-off and cannot be maintained at the state of cut-off, so for fear of above-mentioned possible situation, can arrange one and maintain (hold) circuit 50 and control in the comparison circuit 21 of 13a and form circuit structure as shown in Figure 6 in the first synchronous rectification shown in Fig. 2.This holding circuit 50 is connected in comparison circuit resistance R 2and between the control end of comparing unit 210, this holding circuit 50 is in order to through comparison circuit resistance R 2receive the first detection signal V t1, and make the first detection signal V t1the pulse forming being changed on the occasion of by negative value maintains a special time.Therefore as shown in Figure 3, when in time T 2, and flow through the first electric current I of the first synchronous rectifier 14a d1by on the occasion of dropping to zero and want reverse circulated and the first detection signal V t1when being changed on the occasion of and being formed a pulse by negative value, holding circuit 50 just can be by the first detection signal V t1pulse condition and level maintain a special time, thus, the first synchronous rectifier 14a is just corresponding to the first detection signal V t1and maintain cut-off state in this special time, so not just being subject to the impact of the stray capacitance vibration that leakage inductance on the circuit of power supply changeover device 1 and the first synchronous rectifier 14a have, the first synchronous rectifier 14a cannot be maintained at the situation of cut-off state.
In the above-described embodiments, holding circuit 50 can comprise one second diode D 2, one maintain 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 2cathode terminal and the first holding circuit resistance R 3one end and the one end that maintains capacitor C connect, the first holding circuit resistance R 3the other end and the first auxiliary switch element Q 3control end and the second holding circuit resistance R 4one end connect, the second holding circuit resistance R 4the other end and the other end that maintains capacitor C 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 be greater than the first holding circuit resistance R 3resistance value.
Below by the manner of execution of the holding circuit 50 shown in rough key diagram 6.Refer to Fig. 3 and Fig. 6, when in time T 2, and flow through the first electric current I of the first synchronous rectifier 14a d1by on the occasion of dropping to zero and while wanting reverse circulated, the first current transformer CT 1the first detection signal V t1just can change on the occasion of and form a pulse by negative value, and through comparison circuit resistance R 2and the second diode D 2and to maintaining capacitor C charging.And leakage inductance on the circuit of power supply changeover device 1 is vibrated with the stray capacitance that the first synchronous rectifier 14a has, cause the first current transformer CT 1the the first detection signal V exporting t1while and then continuing change, for example, while dropping to zero, the first detection signal V t1just can stop maintaining capacitor C charging, now, due to the first holding circuit resistance R 3and the second holding circuit resistance R 4impedance relationship, maintain in capacitor C and just cannot discharge, make the voltage that maintains capacitor C can continue to be maintained at a high level state, therefore 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 subject to the impact of the stray capacitance vibration that leakage inductance on the circuit of power supply changeover device 1 and the first synchronous rectifier 14a have and be maintained at constantly the state of cut-off.
In addition, because can making the first synchronous rectifier 14a, holding circuit 50 is 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 by cut-off state, change conducting state into, 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 first synchronous rectifier 14 in the first main switch element Q 1next switch periods in can normally by cut-off state, change conducting state into.
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 being exported by main control circuit 12 1, the first reset circuit switch element Q 4the first electric current conduction terminals Q 4abe connected in second and meet altogether end COM 2, the first reset circuit switch element Q 4the second electric current conduction terminals Q 4bwith the first reset circuit resistance R 5one end and the second reset circuit switch element Q 5control end connect, the second reset circuit switch element Q 5the first electric current conduction terminals Q 5awith the second common contact COM 2connect the second reset circuit switch element Q 5the second electric current conduction terminals 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 4one end connect, the first reset circuit resistance R 5the other end receive auxiliary voltage source V cC.In 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 formed 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 circuit actual demand.
Below by the manner of execution of the reset circuit 51 shown in rough key diagram 6.Refer to Fig. 3 and Fig. 6, when in time T 1to time T 2time, the first main control signal S 1maintain and enable level, and the first detection signal V t1can become on the occasion of and form a pulse from negative value, and this pulse meeting is because holding circuit 50 is by time T 2start to maintain a special time.As the T time of advent 3time, the first main control signal S 1just can become forbidden energy level from enabling level, now 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 maintaining 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, be reset circuit 51 of holding circuit 50 resets, so when in time T 4and the first main control signal S 1from forbidden energy level, again become while enabling 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, therefore the first synchronous rectifier 14a just can be in the first main switch element Q 1next switch periods in normally from cut-off state, walk around and become conducting state.
Refer to Fig. 7, it is the present invention's electrical block diagram of the first synchronous commutating control circuit of a preferred embodiment again.As shown in the figure, the part circuit structure of first synchronous commutating control circuit of the present embodiment and Fig. 6 the part circuit structure of synchronous commutating control circuit similar, and element representative structure and the functional similarity of same tag, therefore element characteristics, manner of execution repeat no more in this.Compare with Fig. 6, the comparing unit 210 in the comparison circuit 21 of the 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 7institute forms, and comparing unit 210 and holding circuit 50 just can form an interlock circuit whereby.The second auxiliary switch element Q wherein 6can be but be not limited to PNP bipolar junction transistor, and the second auxiliary switch element Q 6base stage and the second comparing unit resistance R 7one 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 6emitter and the first comparing unit resistance R 6one end connect, the second auxiliary switch element Q 6collector electrode through the input of comparing unit 210 and the output of holding circuit 50, i.e. the first holding circuit resistance R 3the other end and the second holding circuit resistance R 4one end connect, the 3rd auxiliary switch element Q 7can be but be not limited to 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, i.e. the first holding circuit resistance R 3the other end and the second holding circuit resistance R 4one end connect, the 3rd auxiliary switch element Q 7collector electrode and the second comparing unit resistance R 7one 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 that maintains of the holding circuit 50 of the present embodiment changes and the second holding circuit resistance R 4parallel connection, and maintain one end and the first holding circuit resistance R of capacitor C 3the other end, the second holding circuit resistance R 4one end and the input of comparing unit 210 connect, the other end that maintains capacitor C with the second holding circuit resistance R 4the other end and second contact COM altogether 2connect, and the holding circuit 50 of the present embodiment can reach the identical effect of holding circuit 50 as shown in Figure 6 equally.
Below by the manner of execution of the synchronous commutating control circuit 13a shown in rough key diagram 7.Refer to Fig. 3 and Fig. 7, when for example in time T 1time, the first synchronous rectifier 14a is received as the first synchronous rectification control signal S that enables level 3and present conducting state, and when through after a while, make to flow through the first electric current I of the first synchronous rectifier 14a d1while starting to decline gradually, the first current transformer CT 1the the first detection signal V exporting t1just can start accordingly to rise gradually, and as the first detection signal V t1value be greater than in fact the 3rd auxiliary switch element Q 7conducting voltage time, for example, in time T 2time,, the 3rd auxiliary switch element Q 7just can conducting, now the second auxiliary switch element Q 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 first synchronous rectification control signal S 3dragged down, and due to 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 subject to the impact of the stray capacitance vibration that leakage inductance on the circuit of power supply changeover device 1 and the first synchronous rectifier 14a have and is maintained at constantly the state of cut-off.As from the foregoing, comparison circuit 21 can be at the first detection signal V t1be greater than the 3rd auxiliary switch element Q 7conducting voltage time by 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, the holding circuit shown in Fig. 7 50 also can be applicable in comparison circuit 21 as shown in Figure 4 and forms circuit structure as shown in Figure 8.In described embodiment, holding circuit 50 is connected in 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 and receive as shown in Figure 7 boost voltage V cc, in other embodiments, the first comparing unit resistance R 6and the second comparing unit resistance R 7the other end also can change the control end with commutation circuit 11, i.e. the 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 consisted of a rest-set flip-flop.
Certainly, the circuit structure of reset circuit inside is also not limited to execution mode as shown in Figure 6, and the difference that also can have as shown in Fig. 7 to Fig. 8 changes.Refer to Fig. 7, in the present embodiment, reset circuit 51 is by a Schottky diode D scinstitute forms, this Schottky diode D sccathode terminal and the first main switch element Q 1control end connect and receive the first main control signal S 1, Schottky diode D scanode 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 forbidden energy level, reset circuit 51 just can pass through Schottky diode D scand reset holding circuit 50 makes to maintain capacitor C the electric energy of storage is given out light.
Refer to Fig. 8, it is a variation example again of the reset circuit shown in Fig. 6.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 8one end and the control end of commutation circuit 11, i.e. the 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 form, but not as limit, also can be PNP dipole field-effect transistor and form, the 3rd reset circuit switch element Q 8the first electric current conduction terminals Q 8awith the second common contact COM 2connect the 3rd reset circuit switch element Q 8the second electric current conduction terminals Q 8bwith the first holding circuit resistance R 3the other end and the second holding circuit resistance R 4one end connect.Therefore by above-mentioned circuit structure, reset circuit 51 is in the first main control signal S 1during for forbidden energy level, the holding circuit 50 that just can reset, makes to maintain capacitor C the electric energy of storage is given out light.
Certainly, in other embodiments, one 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 8need to change into accordingly a N-type mos field effect transistor and form, and this execution mode also can make reset circuit 51 reach identical effect.
Certainly, comparison circuit 21 shown in comparison circuit 21 shown in comparison circuit 21 shown in Fig. 2, Fig. 4 and Fig. 7 can be replaced mutually, comparing unit 210 shown in comparing unit 210 shown in Fig. 2 and Fig. 5 can be replaced mutually, holding circuit 50 shown in holding circuit 50 shown in Fig. 6 and Fig. 7 and Fig. 8 can be replaced mutually, the reset circuit 51 of the reset circuit 51 of Fig. 6, the reset circuit 51 of Fig. 7 and Fig. 8 can be replaced mutually, but not as limit.
The process step of the control method of the first synchronous rectifier shown in Fig. 1 will be further illustrated below.Refer to Fig. 9, and coordinate Fig. 2, wherein Fig. 9 is the control method flow chart of the first synchronous rectifier 14a shown in Fig. 1.As shown in Figure 9, first, as shown in step S90, by main control circuit 12, produce the first main control signal S 1give 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,, as shown in step S91, by current transformer CT, transmit the first detection signal V t1give the first synchronous commutating control circuit 13a.Then, as shown in step S92, according to the first main control signal S 1make the first synchronous commutating control circuit 13a control the first synchronous rectifier 14a conducting.Finally, as shown in step S93, according to the first detection signal V t1and make the first synchronous commutating control circuit 13a control the first synchronous rectifier 14a cut-off.
In addition, in certain embodiments, as shown in figure 10, in step S93, have more four sub-steps, be sequentially setting up procedure S930, comparison step S931, maintain step S932 and reset process S932.First, carry out setting up procedure S930, by start-up circuit 20, receive the first main control signal S 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, pass through comparing unit 210 by detection signal V tcompare with reference voltage, to work as detection signal V tlevel while being greater than the level of reference voltage, order about the first synchronous rectifier 14a cut-off.Then, maintain step S932, by holding circuit 50, make detection signal V tthe pulse forming being changed on the occasion of by negative value maintains a special time.Finally, carry out reset process S933,, by reset circuit 51 reset holding circuits 50, make the first synchronous rectifier 14a can normally by cut-off state, change conducting state in the next switch periods of commutation circuit 11.
And the control method of the second synchronous rectifier 14b shown in Fig. 1 is similar in appearance to the first synchronous rectifier 14a, therefore 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 accurately the first synchronous rectifier 14a and the second synchronous rectifier 14b cut-off, so the first synchronous rectifier 14a and the second synchronous rectifier 14b are just 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 the synchronous commutating control circuit can be immediately and control accurately synchronous rectifier cut-off, so synchronous rectifier of the present invention is just 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 craftsman thinks and be to modify as all by haveing the knack of those of ordinary skills, so scopes of de-as attached claim institute wish protection.

Claims (21)

1. a power supply changeover device, it comprises:
One commutation circuit, receives an input voltage;
One transformer, has an armature winding and a secondary winding, and this armature 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, make this input voltage energy selectivity via this commutation circuit, be sent to this armature winding;
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 cut-off according to this detection signal.
2. power supply changeover device as claimed in claim 1, wherein this synchronous commutating control circuit also comprises a comparison circuit with a comparison circuit resistance and a comparing unit, wherein one 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 and the input of this comparing unit are connected, the output of this comparing unit is connected with the control end of this synchronous rectifier, when this comparison circuit is greater than the level of a reference voltage in order to the level when this detection signal, the level of this synchronous rectification control signal is dragged down as forbidden energy level, to order about this synchronous rectifier cut-off.
3. power supply changeover device as claimed in claim 2, wherein this comparing unit comprises:
One comparator, the reverse input end of this comparator is 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 non-inverting input of this comparator and the earth terminal of 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 electric current conduction terminals of this first auxiliary switch element is connected with this second common contact through the earth terminal of this comparing unit, one second electric current conduction terminals 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 the 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, one end of this first comparing unit resistance is connected with the emitter of the 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 base stage of this second auxiliary switch element, the 3rd collector electrode of 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 the 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, one 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 base stage of this second auxiliary switch element, the 3rd collector electrode of 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 a holding circuit, this holding circuit is connected with this comparison circuit resistance and receives this detection signal, uses so that the pulse that this detection signal forms being changed on the occasion of by negative value maintains a special time.
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 comparison circuit resistance;
One first holding circuit resistance, the cathode terminal of this second diode of one end of this first holding circuit resistance connects;
One maintains electric capacity, and this one end that maintains electric capacity is connected with the other end of this first holding circuit resistance, and this other end that maintains electric capacity is connected with this second common contact;
One second holding circuit resistance, maintains electric capacity and connects with this, and one 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 maintains electric capacity, and this one end that maintains electric capacity is connected with the cathode terminal of this second diode, and this other end that maintains electric capacity is connected with this second common contact;
One first holding circuit resistance, one end of this first holding circuit resistance is connected with one end that this maintains electric capacity; And
One second holding circuit resistance, one 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 can normally by cut-off state, change conducting state in the next switch periods of this commutation circuit.
11. power supply changeover devices 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 is connected with this control end of this commutation circuit and receives this main control signal, and one first electric current conduction terminals of this first reset circuit switch element second connects altogether end 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 electric current conduction terminals of this first reset circuit switch element, one first electric current conduction terminals of this second reset circuit switch element is connected with this second common contact, and one second electric current conduction terminals of this second reset circuit switch element is connected with the output of this holding circuit; And
One first reset circuit resistance, one end of this first reset circuit resistance is connected with this first electric current conduction terminals of this first reset circuit switch element, and the other end of this first reset circuit resistance receives this boost voltage.
12. power supply changeover devices as claimed in claim 10, wherein this reset circuit comprises:
One second reset circuit resistance, one end of this second reset circuit resistance is connected with this control end of this commutation circuit and receives 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 electric current conduction terminals of the 3rd reset circuit switch element is connected with this second common contact, one second electric current conduction terminals 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 devices as claimed in claim 10, wherein this reset circuit comprises:
One second reset circuit resistance, one end of this second reset circuit resistance connects and this main control signal corresponding to 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 electric current conduction terminals of the 3rd reset circuit switch element is connected with this second common contact, one second electric current conduction terminals 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 mos field effect transistor.
14. power supply changeover devices as described in as arbitrary in 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 according to this main control signal the control end that this synchronous rectification controls signal to this synchronous rectifier, and when the voltage level of this synchronous rectification control signal is dragged down, the voltage level that prevents this main control signal is along with the voltage level of this synchronous rectification control signal is dragged down and dragged down.
15. power supply changeover devices as claimed in claim 14, wherein this start-up circuit comprises a start-up circuit resistance.
16. power supply changeover devices 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.
The control method of 17. 1 kinds of synchronous rectifiers, in order to control at least one synchronous rectifier of a power supply changeover device, wherein this power supply changeover device also comprises a commutation 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 armature 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 secondary 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, this synchronous commutating control circuit control method comprises:
(a) by this main control circuit, produce a main control signal and give this commutation circuit and this synchronous commutating control circuit, make this commutation circuit action and make an input voltage energy selectivity via this commutation circuit, be sent to this transformer;
(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 to this synchronous commutating control circuit; And
(d) this synchronous commutating control circuit is controlled this synchronous rectifier cut-off according to this detection signal.
The control method of 18. synchronous rectifiers 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, while being greater than the level of this reference voltage with the level when this detection signal, order about this synchronous rectifier cut-off.
The control method of 19. synchronous rectifiers as claimed in claim 18, wherein step (d) also comprises and maintains step, is to make this detection signal changed on the occasion of the pulse forming and maintained a special time by negative value by a holding circuit.
The control method of 20. synchronous rectifiers 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 can normally by cut-off state, change conducting state in the next switch periods of this commutation circuit.
The control method of 21. synchronous rectifiers as described in as arbitrary in claim 17-20, wherein step (d) also comprises setting up procedure, by a start-up circuit, receive a main control signal of this main control circuit output, and export according to this main control signal the control end that a synchronous rectification controls signal to this synchronous rectifier, and the voltage level that prevents this main control signal is along with the voltage level of this synchronous rectification control signal is dragged down and dragged down.
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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CN105099230B (en) 2014-04-16 2018-07-31 华为技术有限公司 Controlled resonant converter and its synchronous rectification translation circuit
CN106993359A (en) * 2016-01-21 2017-07-28 金宝橱有限公司 Can Synchronization Control concatenation light fixture
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