CN103066825A - Power supply power off method and power supply - Google Patents
Power supply power off method and power supply Download PDFInfo
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- CN103066825A CN103066825A CN2012105584999A CN201210558499A CN103066825A CN 103066825 A CN103066825 A CN 103066825A CN 2012105584999 A CN2012105584999 A CN 2012105584999A CN 201210558499 A CN201210558499 A CN 201210558499A CN 103066825 A CN103066825 A CN 103066825A
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- former limit
- transformer
- main switch
- switch
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
- H02M1/36—Means for starting or stopping converters
Abstract
The invention discloses a power supply power off method. The power supply power off method comprises the following steps: receiving a power off signal, changing the turn-on time of a primary side main switch of a transformer, or changing the switch on and off frequency of the primary side main switch, detecting the voltage-second product of the primary side input voltage or a control value corresponding to the voltage-second product on the subsidiary side of the transformer in the turn-on time, or detecting the switch on and off frequency of the primary side main switch on the subsidiary side of the transformer, controlling the switching on or off of a synchronous rectifier of the subsidiary side of the transformer according to the voltage-second product or the corresponding control value or the switch on and off frequency of the primary side main switch. When the power supply power off method and power supply are adopted, self-oscillation can be effectively avoided in a power off process, extra circuit elements need not to be added, and a circuit is small in area, simple in structure, and low in cost.
Description
Technical field
The present invention relates to field of power supplies, relate in particular to a kind of power supply closedown method and power supply.
Background technology
Than the asynchronous rectification of diode significant odds for effectiveness is arranged at low-voltage, high-current field synchronous rectification, therefore in Switching Power Supply, use very extensive.But at former edge-impulse width modulated (Pulse WidthModulation, when PWM) control is applied in the isolated DC power supply, the driving signal demand of secondary synchronous rectification circuit is delivered to secondary from former limit, after the shutdown of former frontier juncture machine control unit, secondary synchronous rectification circuit has just lost control.The isolated DC power supply is when using the secondary synchronous rectification, and the electric current in the outputting inductance can be two-way, and the outputting inductance electric current can become negative sense when underloading.If the DC-isolation power supply is in when shutdown, the synchronously driven shutoff of secondary is not controlled, and then uncontrollable self-oscillation occurs circuit easily behind the machine of former frontier juncture, thereby has increased circuit element stress.The self-oscillation meeting continues the long period in some cases, even can be sustained, and impact plays machine next time.Fig. 1 is the oscillogram before and after the existing normal shock active clamp DC converter secondary continued flow tube shutdown.As shown in Figure 1, when the t=550 microsecond, the power supply shutdown, the waveform after the shutdown is very intensive, just because of the circuit of synchronous rectification in the power supply self-oscillation has occured.
For self-oscillatory problem occurs circuit of synchronous rectification after solving shutdown, usually make at the synchronously driven shutoff control loop of secondary in the prior art and use up occasionally driving transformer and transmit off signal from former limit.Fig. 2 is the existing schematic diagram that utilizes the shutdown of optocoupler control circuit, and as shown in Figure 2, after off signal passed to the secondary control circuit by optocoupler or other isolating device, the secondary control circuit was turned off circuit of synchronous rectification.But, no matter be to transmit off signal with optocoupler or other isolating device, in circuit, all need the extra circuits element.And because optocoupler or other isolating device will satisfy the requirement of safety creepage distance, the element area is larger.These have all increased volume and the cost of circuit.In addition, the shutdown of at present common former limit PWM shutdown control unit all is at random constantly, that is to say that shutdown can occur in any time in the switch periods constantly, so, even transmit the time of delay of off signal is short to and can ignores with optocoupler or other isolating device, electric current during the underloading shutdown in the secondary outputting inductance still may be reverse, thus secondary synchro switch pipe overvoltage even avalanche breakdown when causing shutting down.
Summary of the invention
Embodiment of the invention technical problem to be solved is, a kind of power supply closedown method and power supply are provided.Can when shutdown, effectively avoid self-oscillation.
First aspect, the embodiment of the invention provide a kind of power supply closedown method, can comprise: receive off signal, change the ON time of the former limit main switch of transformer; Secondary at transformer detects voltagesecond product or controlling value corresponding to described voltagesecond product of former limit input voltage in described ON time; Control the shutoff of synchronous rectifier of the secondary of described transformer according to described voltagesecond product or controlling value corresponding to described voltagesecond product, to realize the power supply shutdown.
Second aspect, the embodiment of the invention provide another kind of power supply closedown method, can comprise: receive off signal, change the switching frequency (or switch periods) of the former limit main switch of transformer; Detect the switching frequency (or switch periods) of described former limit main switch at the secondary of transformer; Shutoff according to the synchronous rectifier of the secondary of the described transformer of the switching frequency (or switch periods) of described former limit main switch control.
The third aspect, the embodiment of the invention provide a kind of power supply, can comprise: the shutdown control unit, be used for receiving off signal, and change the ON time of the former limit main switch of transformer; The controlling value acquiring unit is used for detecting voltagesecond product or controlling value corresponding to described voltagesecond product of former limit input voltage in described ON time at the secondary of transformer; The secondary control unit is used for controlling according to described voltagesecond product or controlling value corresponding to described voltagesecond product the turn-on and turn-off of synchronous rectifier of the secondary of described transformer.
Fourth aspect, the embodiment of the invention provide another kind of power supply, can comprise: the shutdown control unit, be used for receiving off signal, and change the switching frequency (or switch periods) of the former limit main switch of transformer; Frequency detecting unit (or cycle detection unit) is for the switching frequency (or switch periods) that detects described former limit main switch at the secondary of transformer; The secondary control unit is used for the shutoff according to the synchronous rectifier of the secondary of the described transformer of switching frequency (or switch periods) control of described former limit main switch.
As seen the power supply closedown method and the power supply that provide of the embodiment of the invention by receiving off signal, changes the ON time of the former limit main switch of transformer, or changes the switching frequency of former limit main switch; Secondary at transformer detects voltagesecond product or controlling value corresponding to described voltagesecond product of former limit input voltage in described ON time, or the switching frequency of former limit main switch; According to described voltagesecond product or controlling value corresponding to described voltagesecond product, or the switching frequency of former limit main switch, control the shutoff of synchronous rectifier of the secondary of described transformer, can adjust to the state that is conducive to shut down most to switching circuit, then remove to turn-off the circuit of synchronous rectification of former limit circuit and secondary according to predetermined optimum shutdown sequential, thereby reach the purpose of effectively avoid shutting down vibration and shutdown stress.Need not increases new circuit element, thereby has saved volume and the cost of circuit, and simple in structure, cost is low, has also improved the reliability and stability of power supply simultaneously.
Description of drawings
In order to be illustrated more clearly in the embodiment of the invention or technical scheme of the prior art, the below will do to introduce simply to the accompanying drawing of required use in embodiment or the description of the Prior Art, apparently, accompanying drawing in the following describes only is some embodiments of the present invention, for those of ordinary skills, under the prerequisite of not paying creative work, can also obtain according to these accompanying drawings other accompanying drawing.
Fig. 1 is the oscillogram before and after the existing normal shock active clamp DC converter secondary continued flow tube shutdown;
Fig. 2 is the existing schematic diagram that utilizes the shutdown of optocoupler control circuit;
Fig. 3 is the schematic flow sheet of the power supply closedown method that provides of the embodiment of the invention;
Fig. 4 a is the schematic flow sheet of another power supply closedown method of providing of the embodiment of the invention;
Fig. 4 b is the again schematic flow sheet of a power supply closedown method that the embodiment of the invention provides;
Fig. 5 is the again schematic flow sheet of a power supply closedown method that the embodiment of the invention provides;
Fig. 6 is the logical construction schematic diagram of the power supply that provides of the embodiment of the invention;
Fig. 7 is a kind of circuit diagram of shutdown control unit in the embodiment of the invention power supply;
Fig. 8 is the logical construction schematic diagram of another power supply of providing of the embodiment of the invention;
Fig. 9 is the logical construction schematic diagram of the again power supply that provides of the embodiment of the invention;
Figure 10 is the logical construction schematic diagram of the again power supply that provides of the embodiment of the invention;
Figure 11 is the signal timing diagram of explanation power supply shown in Figure 10;
Figure 12 is the logical construction schematic diagram of the again power supply that provides of the embodiment of the invention;
Figure 13 is the again flow chart of a power supply closedown method that provides of the embodiment of the invention.
Embodiment
Below in conjunction with the accompanying drawing in the embodiment of the invention, the technical scheme in the embodiment of the invention is clearly and completely described, obviously, described embodiment only is the present invention's part embodiment, rather than whole embodiment.Based on the embodiment among the present invention, those of ordinary skills belong to the scope of protection of the invention not making the every other embodiment that obtains under the creative work prerequisite.
At this, what also need to illustrate a bit is, for fear of having blured the present invention because of unnecessary details, only show in the accompanying drawings with according to the closely-related apparatus structure of the solution of the present invention, and omitted other details little with relation of the present invention.
See also Fig. 3, the method flow schematic diagram of a kind of power supply closedown method that provides for the embodiment of the invention, this power supply closedown method can be applied to the self-powered synchronous rectified power.As shown in the figure, the method comprises:
S101, reception off signal, the ON time of the former limit main switch of change transformer.
Alternatively, the switch periods of former limit main switch can change also and can not change.
S102, detect voltagesecond product or controlling value corresponding to described voltagesecond product of former limit input voltage in described ON time at the secondary of transformer.
Alternatively, the controlling value of the correspondence of described voltagesecond product can be magnitude of voltage, also can be current value.
Particularly, select voltagesecond product as detected parameters to be herein because according to the input voltage of secondary and ON time can be very easy obtain the voltagesecond product parameter, circuit structure is simple, calculate and judge convenient.Certainly, the isoparametric value of frequency, cycle, pulsewidth that timer conter detects pwm signal also can be set with as the reference conditions that judge whether to shut down in circuit.
S103, control the shutoff of synchronous rectifier of the secondary of described transformer according to described voltagesecond product or controlling value corresponding to described voltagesecond product.
As seen, the power supply closedown method that the embodiment of the invention provides is by changing the ON time of former limit main switch, the voltagesecond product of the input voltage that the change secondary detects, thereby, switching circuit is adjusted to the state that is conducive to shut down most, then remove to turn-off the circuit of synchronous rectification of former limit circuit and secondary according to predetermined optimum shutdown sequential, thereby reach the purpose of eliminating shutdown vibration and shutdown stress.Need not increases new circuit element, has saved volume and the cost of circuit.
See also Fig. 4 a, the schematic flow sheet of the power supply closedown method that provides for the embodiment of the invention.In the present embodiment, said method comprising the steps of:
S201 receives off signal, shortens the ON time of the former limit main switch of transformer.
Particularly, the mode of ON time that the former limit main switch of following several shortening transformers is arranged, but be not limited to following several mode: at least one switch periods before the former limit main switch that can shorten transformer turn-offs, the ON time that shortens the switch after the switch periods is less than the ON time that shortens the switch before the switch periods.Chopped pulse width in also can at least one switch periods before the former limit of transformer main switch turn-offs.At least one switch periods before the former limit main switch that can also shorten transformer turn-offs, and select in the switch periods that is shortened one or more, chopped pulse width in described one or more switch periods that are shortened.
Preferably, can be in last cycle before former limit main switch turn-offs the chopped pulse width.Specific implementation is the high level of chopped pulse, to realize shortening last ON time before switch turn-offs.The pulse here can be pwm pulse.
Need to prove that the time of various parameter changes can finish in the moment that former limit main switch turn-offs, but measured with switch periods herein, when being beneficial to subsequent detection take the cycle as unit the statistics detected value.
S202 detects voltagesecond product or controlling value corresponding to described voltagesecond product of former limit input voltage in described ON time at the secondary of transformer.
The controlling value of the correspondence of voltagesecond product can be magnitude of voltage, also can be current value.
Particularly, select voltagesecond product as detected parameters to be herein because according to the input voltage of secondary and ON time can be very easy obtain the voltagesecond product parameter, circuit structure is simple, calculate and judge convenient.Certainly, the isoparametric value of frequency, cycle, pulsewidth that timer conter detects pwm signal also can be set with as the reference conditions that judge whether to shut down in circuit.
S203 when described voltagesecond product or controlling value corresponding to described voltagesecond product are less than or equal to preset value, turn-offs the synchronous rectifier of secondary.
Particularly, when preset value herein can not shut down with reference to power supply, the stable state voltagesecond product during the circuit normal operation arranged, and usually can this preset value be set less than the stable state voltagesecond product according to the change trend of switch periods and/or pulse duration.
See also Fig. 4 b, the schematic flow sheet of the power supply closedown method that provides for the embodiment of the invention.In the present embodiment, said method comprising the steps of:
S301 receives off signal, lengthens the ON time of the former limit main switch of transformer;
Concrete, the mode of ON time that the former limit main switch of following several lengthening transformers is arranged, but be not limited to following several mode: at least one switch periods before the former limit main switch that can lengthen transformer turn-offs, the ON time that lengthens the switch after the switch periods is greater than the ON time that lengthens the switch before the switch periods; Perhaps, add long pulse width at least one switch periods before the former limit of transformer main switch turn-offs; Perhaps, the former limit main switch that lengthens transformer turn-offs at least one front switch periods, selects one or more switch periods from least one switch periods that is lengthened out, and adds long pulse width in described one or more switch periods that are lengthened out.
Preferably, can add long pulse width in last cycle before former limit main switch turn-offs.Specific implementation is the high level that adds long pulse, to realize prolonging last ON time before switch turn-offs.The pulse here can be pwm pulse.
Need to prove that the time of various parameter changes can finish in the moment that former limit main switch turn-offs, but measured with switch periods herein, when being beneficial to subsequent detection take the cycle as unit the statistics detected value.
S302 detects voltagesecond product or controlling value corresponding to described voltagesecond product of former limit input voltage in described ON time at the secondary of transformer;
S303 when controlling value corresponding to described voltagesecond product or described voltagesecond product during more than or equal to preset value, turn-offs the synchronous rectifier of secondary.
Particularly, herein preset value correspondingly can be set to greater than the stable state voltagesecond product.
As seen, the power supply closedown method that the embodiment of the invention provides is by utilizing the transmission path of the original pwm signal of circuit or other signal, before shutdown, send one group from former limit and be different from shutdown pulse under the normal operating condition to secondary, so that secondary circuit detection and Identification, simultaneously, utilize the special shutdown pulse of this group, can adjust to the state that is conducive to shut down most to switching circuit, then remove to turn-off the circuit of synchronous rectification of former limit circuit and secondary according to predetermined optimum shutdown sequential, thereby reach the purpose of eliminating shutdown vibration and shutdown stress.Need not increases new circuit element, thereby has saved volume and the cost of circuit.Comprehensively consisted of diversified pattern and change switch periods and/or change pulse duration, can change separately a certain parameter and also can change simultaneously two parameters, the pulse that the shutdown pulse that only need to guarantee to send on former limit is different under the normal operating condition gets final product.
See also Fig. 5, the embodiment of the invention also provides a kind of power supply closedown method, and the method comprises:
S401, reception off signal, the switching frequency of the former limit main switch of change transformer.
The ON time of switch can prolong, and also can remain unchanged, and also can shorten, and this embodiment of the invention is not construed as limiting.
S402, detect the switching frequency of described former limit main switch at the secondary of transformer;
S403, control the shutoff of synchronous rectifier of the secondary of described transformer according to the switching frequency of described former limit main switch.
Under a kind of implementation, improve the switching frequency of the former limit main switch of transformer behind the reception off signal.Secondary is preserved the preset value of a switching frequency, and this preset value can be set to slightly higher than the switching frequency of power supply under normal condition.Secondary sense switch frequency compares this switching frequency and described preset value, when this switching frequency that detects is greater than or equal to this preset value, turn-offs the synchronous rectifier of secondary.
Under another kind of implementation, reduce the switching frequency of the former limit main switch of transformer behind the reception off signal.Secondary is preserved the preset value of a switching frequency, and this preset value can be set to slightly lower than the switching frequency of power supply under normal condition.After the secondary sense switch frequency, this switching frequency and described preset value are compared, when this switching frequency that detects is less than or equal to preset value, turn-off the synchronous rectifier of secondary.
Certainly, it will be appreciated by persons skilled in the art that changing switching frequency is equal to the change switch periods in fact.The implementation in sense switch frequency or sense switch cycle all is those skilled in the art's general knowledge, does not repeat them here.In addition, the technical scheme of the change ON time that the embodiment of the invention provides can realize simultaneously with the technical scheme that changes switching frequency, as long as at secondary corresponding detection mode and preset value are set, just can reach identical purpose.
See also Fig. 6, be a kind of circuit diagram of embodiment of the invention power supply.Shown in Figure 6 is the semibridge system rectification circuit.It will be appreciated by those skilled in the art that this only is exemplary, and unrestricted the present invention, the present invention also can use full-bridge type rectification circuit or streaming rectification circuit doubly.In the present embodiment circuit, power supply comprises:
Under a kind of implementation, shutdown control unit 101 is used for the ON time of the former limit main switch of shortening transformer.
Particularly, following several implementation is arranged: the former limit main switch that shortens transformer turn-offs front at least one switch periods; Perhaps, chopped pulse width at least one switch periods before the former limit of transformer main switch turn-offs; Perhaps, at least one switch periods before the former limit main switch that shortens transformer turn-offs, and select in the switch periods that is shortened one or more, chopped pulse width in described one or more switch periods that are shortened.
Under another kind of implementation, shutdown control unit 101 is used for the ON time of the former limit main switch of lengthening transformer.
Particularly, following several implementation is arranged: the former limit main switch that lengthens transformer turn-offs at least one front switch periods; Perhaps, add long pulse width at least one switch periods before the former limit of transformer main switch turn-offs; Perhaps, the former limit main switch that lengthens transformer turn-offs at least one front switch periods, selects one or more switch periods from least one switch periods that is lengthened out, and adds long pulse width in described one or more switch periods that are lengthened out.
Controlling value acquiring unit 102, described controlling value acquiring unit are configured to obtain voltagesecond product or the voltagesecond product corresponding controlling value of former limit input voltage in described ON time with described transformer;
Under a kind of implementation, controlling value acquiring unit 102 detects the corresponding controlling value of the former voltagesecond product of limit input voltage vin s in described ON time at transformer TX1 secondary; Under other implementation, the isoparametric value of frequency, cycle, pulsewidth that timer conter detects pwm signal can be set with as the reference conditions that judge whether to shut down in circuit.
Under a kind of implementation, when described voltagesecond product or controlling value corresponding to described voltagesecond product are less than or equal to preset value, turn-off the synchronous rectifier of secondary, to realize the power supply shutdown.
For example, the former limit main switch Q1 that shutdown control unit 101 shortens transformer TX1 turn-offs at least one front switch periods, the described voltagesecond product that controlling value acquiring unit 102 detects or controlling value corresponding to described voltagesecond product are less than or equal to preset value, secondary control unit 103 is closed the circuit of synchronous rectification of secondary at this moment, finishes shutdown.
Again for example, when the former limit main switch Q1 of shutdown control unit 101 lengthening transformer TX1 turn-offs at least one front switch periods, controlling value corresponding to the described voltagesecond product that controlling value acquiring unit 102 detects or described voltagesecond product is more than or equal to preset value, secondary control unit 103 is closed the circuit of synchronous rectification of secondary at this moment, finishes shutdown.
As shown in Figure 6, this power circuit also comprises: modulation signal generator 104, transformer TX1, former limit main switch Q1, the first secondary-side switch Q2, the second secondary-side switch Q3 and LC filter; Switch Q1, Q2 and Q3 can be metal-oxide-semiconductor or other active switch.
Described modulation signal generator 104 is electrically connected with described shutdown control unit 101, is used for former limit input voltage vin is modulated; Wherein, modulation signal generator 104 can be the pulse width modulating signal generator, also can be the pulse frequency modulated signal generator.
Described shutdown control unit 101 is electrically connected with described former limit main switch Q1; Described former limit main switch Q1 is used for controlling the closed circuit of former limit circuit loop and opening circuit.
Described former limit main switch Q1 one end connects former limit Input voltage terminal Vin, other end ground connection by the primary coil P1 of described transformer TX1;
Described controlling value acquiring unit 102 is connected between secondary voltage input Vins and the described secondary control unit;
Described secondary control unit 103 links to each other with described the first secondary-side switch Q2 and the second secondary-side switch Q3;
Described the first secondary-side switch Q2 and the second secondary-side switch Q3 link to each other with described LC filter;
Wherein, described former limit main switch Q1, the first secondary-side switch Q2 and the second secondary-side switch Q3 are isolated gate FET.Certainly, also can be other suitable switching devices.
In the present embodiment, preferably, adopt isolated gate FET to describe as switch.
As shown in Figure 6, the LC filter circuit comprises an outputting inductance L1 and a filter capacitor C1.The termination secondary voltage input Vins of outputting inductance L1, another termination output voltage terminal Vo, output voltage terminal Vo is by filter capacitor C1 ground connection.The source ground of former limit main switch Q1, grid connect shutdown control unit 101, and drain electrode meets original edge voltage input Vin by primary coil P1.The source ground of the first secondary-side switch Q2, grid connect secondary control unit 103, and drain electrode meets secondary Input voltage terminal Vins by secondary coil S1.The source ground of the second secondary-side switch Q3, grid connect secondary control unit 103, and drain electrode meets output voltage terminal Vo by outputting inductance L1.
When needs shut down, shutdown control unit 101 received off signal, and changed switch periods and/or change pulse duration at least one cycle before the former limit main switch Q1 of transformer TX1 turn-offs as required.Here, we select the chopped pulse width to describe.Because shortened pulse duration, therefore the ON time Ton of former limit main switch Q1 will shorten.In the ON time Ton that shortens, former limit input voltage vin continues to induce secondary input voltage vin s at secondary, controlling value acquiring unit 102 receives secondary input voltage vin s, and calculate the voltagesecond product in ON time Ton with secondary input voltage vin s, namely calculate and the voltagesecond product of the proportional former limit of secondary input voltage vin s input voltage vin in this ON time Ton.Controlling value acquiring unit 102 can directly judge according to voltagesecond product, also can carry out corresponding calculating and voltagesecond product controlling value one to one according to voltagesecond product.In the present embodiment, the controlling value acquiring unit 102 outputs controlling value Vvs corresponding with the former limit voltagesecond product of input voltage vin in ON time Ton., need to prove that this controlling value Vvs can be magnitude of voltage as shown in Figure 6 herein, certainly, according to the design needs of circuit, this controlling value also can be current value.Therefore in the present embodiment, because shutdown control unit 101 has shortened pulse duration, the ON time Ton of former limit main switch Q1 reduces, so the voltagesecond product of secondary input voltage vin s in ON time Ton reduce, and then corresponding controlling value Vvs reduces.Secondary control unit 103 detects controlling value Vvs, when voltagesecond product is less than or equal to preset value, its corresponding controlling value also is less than or equal to certain preset value, trigger secondary control unit 103 and send control command with the first secondary-side switch Q2 and the second secondary-side switch Q3 shutoff, thereby so that the loop open circuit of circuit of synchronous rectification, power supply thoroughly shuts down.
Need to prove, when power supply in when normal operation, the former limit voltagesecond product of input voltage vin in ON time Ton keeps a fixed value substantially, this fixed value and output voltage V o are proportional.Voltagesecond product when in the present embodiment, power supply being worked becomes the stable state voltagesecond product.When described preset value is set, can arrange according to the stable state voltagesecond product.In the present embodiment, it is less than the corresponding controlling value of stable state voltagesecond product preset value can be set.When power supply works, off signal is not sent on former limit, the loop of 101 pairs of former limits of shutdown control unit circuit is inoperative, the ON time of former limit main switch Q1 keeps normal condition, at this moment, the former limit voltagesecond product of input voltage vin in ON time Ton is the stable state voltagesecond product, and the controlling value that at this moment secondary control unit 103 detects is larger than preset value, normally controls the closed circuit of circuit of synchronous rectification loop or opens circuit.In the time will shutting down to power supply, off signal is sent on former limit, the shutdown control unit receives off signal, the chopped pulse width, the ON time Ton of former limit main switch Q1 dwindles, thereby the voltagesecond product of former limit input voltage vin in this ON time Ton is reduced to less than preset value, so secondary control unit 103 no longer carries out normal control operation to circuit of synchronous rectification, the first secondary-side switch Q2 is controlled in instruction and the second secondary-side switch Q3 turn-offs but directly send, so that circuit of synchronous rectification opens circuit, power supply thoroughly shuts down.
Accordingly, when shortening switch periods (namely increasing switching frequency) or shortening simultaneously switch periods and pulse duration, situation as mentioned above;
When prolonging switch periods or prolonging simultaneously switch periods and pulse duration, the ON time Ton of former limit main switch Q1 will prolong, the voltagesecond product of secondary input voltage vin s in ON time Ton increases, controlling value Vvs increases, when voltagesecond product during more than or equal to preset value secondary control unit 103 send that the first secondary-side switch Q2 is controlled in instruction and the second secondary-side switch Q3 turn-offs, so that circuit of synchronous rectification opens circuit, power supply thoroughly shuts down.At this moment, preset value is larger than the controlling value corresponding with the stable state voltagesecond product.When power supply works, off signal is not sent on former limit, 101 pairs of former limits of shutdown control unit circuit loop is inoperative, the ON time Ton of main switch Q1 keeps normal condition, at this moment the voltagesecond product of former limit input voltage vin in ON time Ton is the stable state voltagesecond product, the controlling value that at this moment secondary control unit 103 detects is less than predetermined value, normally controls the closed circuit of circuit of synchronous rectification loop or opens circuit.As mentioned above, in the time will shutting down to power supply, off signal is sent on former limit, the shutdown control unit is in response to off signal, and deliberately the ON time with main switch increases, thereby the voltagesecond product of former limit input voltage in this ON time increases, controlling value Vvs increases to larger than predetermined value, so the secondary control unit no longer carries out normal control operation to circuit of synchronous rectification, but give an order circuit of synchronous rectification is opened circuit, power supply thoroughly shuts down.
Certainly, also may exist two parameters of switch periods and pulse duration to change opposite situation, at this time only need to determine which parameter dominate gets final product, concrete control procedure is seen foregoing description, repeats no more.
By power supply provided by the invention, the self-oscillation that produces in the time of can effectively avoiding power cutoff, and need not to add new circuit element, so circuit area is little, simple in structure, cost is low, has also improved the reliability and stability of power supply simultaneously.
See also Fig. 7, be a kind of circuit diagram of shutdown control unit in the embodiment of the invention power supply.
The transmission method of this pass provided by the invention machine information is in the realization of PWM controller, and the analog PWM control of digital P WM control ratio has more simple advantage.In digital P WM control, because pwm pulse width and cycle information before the shutdown all are known, and can be stored in the controller, so can work out out easily the shutdown pulse train of complicated optimization.In analog PWM control, realize with analog circuit the shutdown pulse train of complicated optimization, then difficulty is relatively large, so will simplify and optimize shutdown pulse train as far as possible.
In the present embodiment, described shutdown control unit comprises RC series circuit, weber clamper comparator Volt-Second Clam and shutdown pulse comparator Shutdown Pulse PWM.
Described RC series circuit is connected between former limit Input voltage terminal Vin and the ground;
The in-phase input end of described weber clamper comparator Volt-Second Clam and shutdown pulse comparator Shutdown PulsePWM is connected between the resistance R vsc and capacitor C vsc of described RC circuit jointly by weber clamper pin VSCLAMP, and the threshold value of described weber clamper comparator Volt-Second Clam and shutdown pulse comparator Shutdown Pulse PWM is different.
On former limit PWM shutdown control unit, can adopt an external RC circuit to receive on the input voltage VIN of former limit, produce the ramp voltage that a slope is proportional to former limit input voltage VIN at the weber clamper pin VSCLAMP of shutdown control unit.During the circuit normal operation, the peak value of this ramp voltage is fed control loop or weber clamper comparator Volt-Second Clam is controlled on the lower level, this ramp voltage of last cycle in the needs shutdown is allowed to rise to a higher level, produces the shutdown broad pulse that a voltagesecond product strengthens by shutdown pulse comparator Shutdown Pulse PWM.
As shown in Figure 7, the threshold value of the pulse comparator Shutdown Pulse PWM that shuts down this moment is 3V, and the threshold value of weber clamper comparator Volt-Second Clam is 2.5V.Ramp voltage when normal operation on the VSCLAMP pin is by weber clamper comparator Volt-Second Clam restriction, and general crest voltage is operated in about 1.5V-2V.Last lengthens the shutdown pulse and is produced by the pulse comparator Shutdown Pulse PWM that shuts down, and the shutdown pulse duration that then produces is 1.5-2 times of the normal operation pulse.The shutdown pulse duration might be longer than a normal switch cycles.The length of the shutdown broad pulse that last voltagesecond product strengthens can't help control loop and weber clamp circuit determine, but determined after relatively through shutdown pulse comparator Shutdown Pulse PWM and 3V threshold level by the voltage of weber clamper pin VSCLAMP.
Certainly, the detection of secondary controlling value acquiring unit also can be based on equally voltagesecond product and detect principle, just can realize with a simple RC circuit and a voltage comparator.
Need to prove that principle of the present invention comprises DC/DC, AC/DC, DC/AC, the class isolated converters such as AC/AC applicable to the pass machine information transmission of striding isolating interface in all isolation class power supplys.
Certainly, principle of the present invention is applicable to PWM shutdown control unit too at secondary, closes machine information to the application on former limit from the secondary transmission; And principle of the present invention is applicable to analog control and digital control.It is more convenient for realizing optimum shutdown pwm pulse sequence with digital control in essence.
See also Fig. 8, execute the circuit diagram of another power supply that example provides for the present invention.
In the present embodiment, specifically illustrated another form of implementation of shutdown control unit 101.Shutdown control unit 101 comprises control switch 1011, driver element 1012, charge/discharge unit 1013, comparator 1014 and logical block 1015.Control switch 1011 is connected between the input of the output of modulation signal generator 104 and driver element 1012, and closed or disconnect in response to the control signal that comes from logical block 1015.Driver element 1012 is configured to receive via control switch 1011 modulation signal of modulation signal generator 104, and the output modulation signal is to the control terminal of former limit main switch Q1.Charge/discharge unit 1013 is connected between the control terminal and ground of former limit main switch Q1, is used for charging according to the ON time of former limit main switch Q1, and the output valve corresponding with the charging result flowed to comparator 1014.Comparator 1014 is configured to receive the output valve of charge/discharge unit 1013, output valve and reference value are compared, and on the one hand comparative result is exported to the work that modulation signal generator 104 is controlled modulation signal generator 104, so that in the output valve of charge/discharge unit 1013 during greater than reference value, turn-off modulation signal generator 104, on the other hand comparative result is exported to logical block 1015.Logical block 1015 is configured to according to off signal, the output of comparator 1014, and the signal of the input of driver element 1012 is exported control signal, so that show when wanting power cutoff at off signal, disconnect control switch 1011, and so that when disconnecting control switch 1011, has high level on the input of driver element 1012, in order to charge/discharge unit 1013 is charged, and in the output valve of charge/discharge unit 1013 during greater than reference value, connect control switch 1011, so that have low level on the input of driver element 1012, in order to turn-off former limit main switch.Hence one can see that, in the time will shutting down to power supply, off signal is sent on former limit, shutdown control unit 101 is in response to off signal, control switch 1011 is disconnected, charge/discharge unit 1013 is charged, and so that the charging interval at this moment longer than the charging interval under the power supply normal condition, when with output valve corresponding to charging result during greater than reference value, control switch 1011 is connected, at this moment the modulation signal that the input of driver element 1012 is turned off pulls into low level, and former limit main switch Q1 is turned off, thereby the ON time Ton of main switch Q1 increases.According to an example of the present invention, reference value Vref can be set according to the design parameter of circuit, so that the output valve that charge-discharge circuit 1013 is exported when power supply works is less than reference value Vref, and the output valve that charge-discharge circuit 1013 is exported when power supply will shut down can be greater than reference value Vref.As mentioned above, in the time will shutting down to power supply, off signal is sent on former limit, shutdown control unit 101 deliberately increases the ON time of main switch by charge/discharge unit 1013 in response to off signal, thereby the voltagesecond product of former limit input voltage in this ON time increases, controlling value Vvs increases to larger than predetermined value, so the secondary control unit no longer carries out normal control operation to circuit of synchronous rectification, but give an order circuit of synchronous rectification is opened circuit, power supply thoroughly shuts down.
Similarly, by the power supply according to the embodiment of the invention, power cutoff is avoided self-oscillation effectively, and owing to need not to use the optocoupler device, so area is little, saves cost, simple in structure, easy for installation.
Among the embodiment shown in Figure 9, specifically illustrated controlling value acquiring unit 102 and can comprise charging circuit 1021 and discharge circuit 1022.Discharge circuit 1022 discharges to charging circuit 1021 when the ON time of main switching control begins, charging circuit 1021 charges in ON time Ton afterwards, and magnitude of voltage that will be corresponding with the charging result when ON time Ton finishes is as described controlling value Vvs.Therefore, controlling value acquiring unit 102 obtains the controlling value Vvs corresponding to the integrated value of time with input voltage vin s, and exports controlling value Vvs to secondary control unit 103.The power supply shutdown principle of present embodiment and the power supply shutdown principle of embodiment noted earlier are basic identical, do not repeat them here.
Among the embodiment shown in Figure 10, specifically illustrated a form of implementation of shutdown control unit and controlling value acquiring unit.In the present embodiment, modulation signal generator 104 is PWM modulation signal generators, but it will be appreciated by those skilled in the art that, according to different application demands, also can use PFM (Pulse frequency modulation in the present embodiment,, pulse frequency modulated) and modulation signal generator.Shutdown control unit 101 comprise the charge-discharge circuit that consisted of by resistance R 3 and capacitor C4 and diode, comparator U2, with door U1, control switch k1 and driver element U4, wherein R3 and C4 are connected between the control terminal and ground of former limit main switch Q1, and D1 is connected across the R3 two ends, is used for C4 is discharged.During the power supply normal operation, off signal is low level, and then with door U1 output low level, control switch k1 is closed, and pwm signal is transferred into driver element to drive former limit main switch Q1 by switch k1.When off signal is high level, and when PWM modulation signal and U2 also are high level, then with door U1 output high level, control switch k1 disconnects, and the input of driver element U4 keeps high level, and output also keeps high level, until being charged to, the voltage of C4 is higher than Vref, comparator U2 is inverted to low level, then with door again output low level, switch k1 is closed.Simultaneously, because comparator U2 is inverted to low level, quit work by this change notification PWM modulation signal generator, thereby the PWM modulation signal becomes low level, the input of driver element U4 is pulled into low level by the PWM modulation signal, and former limit main switch Q1 is turned off.The time constant that how long prolongs by charge-discharge circuit R3C4 from the off signal ON time Ton. that namely is extended during this period of time that to be high level turn-off to former limit main switch Q1 determines.Diode D1 is used for discharging to capacitor C4.Capacitor C4 is is ceaselessly discharged and recharged, and can form the sawtooth waveforms of one-period.During normal operation, the amplitude of sawtooth waveforms is not high, and amplitude just can significantly increase during shutdown.
In the present embodiment, charging circuit 1021 in the controlling value acquiring unit 102 comprises the first capacitor C2 and first resistance R 1 of series connection, and discharge circuit 1022 comprises the second capacitor C3 and second resistance R 2 of series connection, the branch circuit parallel connection at the branch road at C3 and R2 place and R1 and C2 place, and C3 and R2 are connected on the control end of switch Q4, switch Q4 is connected across the C2 two ends, when being used for conducting C2 is discharged.
In the present embodiment, during the ON time Ton of PWM modulation signal, secondary winding S1 induces one and the proportional secondary input voltage vin of former limit input voltage vin s, when voltage Vins is in rising edge, the differential circuit that forms by capacitor C 3 and resistance R 2 is to very narrow pulsed drive of switch Q4, Q4 is opened in a flash, the electric charge of the first capacitor C2 is bled off, voltage is moved 0V to.Give the first capacitor C2 charging by the first resistance R 1 during ON time Ton, Ton does not recharge when finishing, and this moment, the size of voltage Vvs of the first capacitor C2 namely represented Vin at the integration to the time of Ton period, was called for short voltagesecond product.By the time next ON time Ton,, the controlling value acquiring unit 402 again charging of again discharging so goes round and begins again.When power supply worked, Vin was that voltagesecond product keeps a fixed value substantially at the integration to the time of Ton period, and when shutdown, because ON time Ton is deliberately enlarged markedly, then voltagesecond product also enlarges markedly, controlling value Vvs enlarges markedly.Secondary control unit 103 detects after the Vvs that enlarges markedly, switch Q2 and Q3 on the shutoff circuit of synchronous rectification of giving an order, and power supply thoroughly shuts down, and has prevented that electric current from pouring in down a chimney, and suppressed self-oscillation.In the present embodiment, two of secondary control unit 103 drive the input of signal (be used for driving switch Q2 and Q3) from secondary winding S2 and the S3 of transformer.
Figure 11 is the signal timing diagram of explanation self-powered synchronous rectified power shown in Figure 10.
Figure 11 shows the sequential chart of the controlling value Vvs that the voltage Vg2 of control terminal of the switch Q2 of circuit of synchronous rectification of voltage Vg1, secondary of the control terminal of main switching control Q1 and Q3 and Vg3 and controlling value acquiring unit 102 export.Referring to Figure 11, last ON time Ton of former limit main switch Q1 (Vg1 is last period of high level) is longer than the ON time of front, and this is because when shutdown shutdown control unit 101 increases ON time Ton in response to off signal.As can be seen from Figure 11, in the ON time Ton that increases, the controlling value Vvs of controlling value acquiring unit 102 outputs is increased to larger than the controlling value Vvs under the normal condition, surpasses predetermined value.At the ON time Ton that increases (namely, Vg1 is last period of high level) afterwards, Vg1 becomes 0, thereby main switch Q1 turn-offs, and controlling value Vvs is above predetermined value, so secondary control unit 103 detects the Vvs that enlarges markedly, the level of the control terminal of switch Q2 on the circuit of synchronous rectification and Q3 is turn-offed in the control of giving an order, switch Q2 and Q3 are turn-offed, and power supply thoroughly shuts down, and the self-oscillation phenomenon do not occur.
In the scheme of the embodiment of the invention, off signal can comprise when being not limited to because the off signal that the action triggers such as remote power-off, overcurrent protection, overvoltage protection, overheat protector, under-voltage protection produce.
See also Figure 12, for the embodiment of the invention also provides another kind of power supply, this power supply comprises:
The ON time of switch can prolong, and also can remain unchanged, and also can shorten, and this embodiment of the invention is not construed as limiting.
Under a kind of implementation, the shutdown control unit 11 concrete switching frequencies that are used for the former limit main switch of raising transformer; Secondary control unit 13 specifically is used for: when the switching frequency of described former limit main switch is greater than or equal to preset value, turn-off the synchronous rectifier of secondary.
Under another kind of implementation, shutdown control unit 11 specifically is used for: the switching frequency that reduces the former limit main switch of transformer; Secondary control unit 13 specifically is used for: when the switching frequency of described former limit main switch is less than or equal to preset value, turn-off the synchronous rectifier of secondary.
Specific implementation can be with reference to the embodiment of the method for correspondence.It will be appreciated by persons skilled in the art that changing switching frequency is equal to the change switch periods in fact.The implementation in sense switch frequency or sense switch cycle all is those skilled in the art's general knowledge, and namely frequency detecting unit 12 also can be used as to do cycle detection, and correspondingly, preset value is set to the value of the switch periods under the corresponding power normal condition.The means of frequency detecting and cycle detection are varied, and those skilled in the art can select according to demand voluntarily.
Figure 13 is the flow chart of the method that the self-device synchronous rectification power supply is shut down according to an embodiment of the invention.
Referring to Figure 13, in the time will shutting down to the self-device synchronous rectification power supply, carry out shutdown according to following steps.
At step S11, off signal is sent on former limit, increases last ON time of former limit main switch on former limit; At step S12, detect the voltagesecond product of former limit input voltage in described ON time at secondary; At step S13, when described voltagesecond product during more than or equal to predetermined value, then close the circuit of synchronous rectification of secondary, so that described power supply is shut down.
By the description of above-described embodiment, the present invention has the following advantages:
Utilize the transmission path of the original pwm signal of circuit or other signal, before shutdown, send one group from former limit and be different from shutdown pulse under the normal operating condition to secondary, perhaps change the frequency of former limit switching tube, so that secondary circuit detection and Identification, thereby realize switching circuit is adjusted to the state that is conducive to shut down most, then remove to turn-off the circuit of synchronous rectification of former limit circuit and secondary according to predetermined optimum shutdown sequential, thereby reach the purpose of eliminating shutdown vibration and shutdown stress.Need not increases new circuit element, thereby has saved volume and the cost of circuit, simple in structure, cost is low, has also improved the reliability and stability of power supply simultaneously.Comprehensively consisted of diversified pattern and change switching frequency and change pulse duration, can change separately a certain parameter and also can change simultaneously two parameters, only need to guarantee that this parameter that relevant parameter (such as voltagesecond product or switch periods etc.) that secondary detects is different under the normal operating condition gets final product.
One of ordinary skill in the art will appreciate that all or part of flow process that realizes in above-described embodiment method, to come the relevant hardware of instruction to finish by computer program, described program can be stored in the computer read/write memory medium, this program can comprise the flow process such as the embodiment of above-mentioned each side method when carrying out.Wherein, described storage medium can be magnetic disc, CD, read-only store-memory body (Read-Only Memory, ROM) or store-memory body (Random Access Memory, RAM) etc. at random.
Above disclosed is preferred embodiment of the present invention only, certainly can not limit with this interest field of the present invention, and the equivalent variations of therefore doing according to claim of the present invention still belongs to the scope that the present invention is contained.
Claims (23)
1. a power supply closedown method is characterized in that, described method comprises:
Receive off signal, change the ON time of the former limit main switch of transformer;
Secondary at transformer detects voltagesecond product or controlling value corresponding to described voltagesecond product of former limit input voltage in described ON time;
Control the shutoff of synchronous rectifier of the secondary of described transformer according to described voltagesecond product or controlling value corresponding to described voltagesecond product.
2. method according to claim 1 is characterized in that, described reception off signal, and the ON time of the former limit main switch of change transformer specifically comprises:
Receive off signal, lengthen the ON time of the former limit main switch of transformer;
The shutoff of the synchronous rectifier of the described secondary of controlling described transformer according to described voltagesecond product or controlling value corresponding to described voltagesecond product specifically comprises:
When controlling value corresponding to described voltagesecond product or described voltagesecond product during more than or equal to preset value, turn-off the synchronous rectifier of secondary.
3. method according to claim 2 is characterized in that, the ON time of the former limit main switch of described lengthening transformer specifically comprises:
The former limit main switch that lengthens transformer turn-offs at least one front switch periods; Perhaps,
Add long pulse width at least one switch periods before the former limit of transformer main switch turn-offs; Perhaps,
The former limit main switch that lengthens transformer turn-offs at least one front switch periods, selects one or more switch periods from least one switch periods that is lengthened out, and adds long pulse width in described one or more switch periods that are lengthened out.
4. method according to claim 1 is characterized in that, described reception off signal, and the ON time of the former limit main switch of change transformer specifically comprises:
Receive off signal, shorten the ON time of the former limit main switch of transformer;
The shutoff of the synchronous rectifier of the described secondary of controlling described transformer according to described voltagesecond product or controlling value corresponding to described voltagesecond product specifically comprises:
When described voltagesecond product or controlling value corresponding to described voltagesecond product are less than or equal to preset value, turn-off the synchronous rectifier of secondary.
5. method as claimed in claim 4 is characterized in that, the ON time of the former limit main switch of described shortening transformer specifically comprises:
The former limit main switch that shortens transformer turn-offs front at least one switch periods; Perhaps,
Chopped pulse width at least one switch periods before the former limit of transformer main switch turn-offs; Perhaps,
At least one switch periods before the former limit main switch that shortens transformer turn-offs, and select in the switch periods that is shortened one or more, chopped pulse width in described one or more switch periods that are shortened.
6. a power supply closedown method is characterized in that, described method comprises:
Receive off signal, change the switching frequency of the former limit main switch of transformer;
Detect the switching frequency of described former limit main switch at the secondary of transformer;
Control the shutoff of synchronous rectifier of the secondary of described transformer according to the switching frequency of described former limit main switch.
7. method according to claim 6 is characterized in that, the switching frequency of the former limit main switch of described change transformer specifically comprises:
Improve the switching frequency of the former limit main switch of transformer;
Described switching frequency according to described former limit main switch is controlled the shutoff of synchronous rectifier of the secondary of described transformer, specifically comprises:
When the switching frequency of described former limit main switch is greater than or equal to preset value, turn-off the synchronous rectifier of secondary.
8. method according to claim 6 is characterized in that, the switching frequency of the former limit main switch of described change transformer specifically comprises:
Reduce the switching frequency of the former limit main switch of transformer;
Described switching frequency according to described former limit main switch is controlled the shutoff of synchronous rectifier of the secondary of described transformer, specifically comprises:
When the switching frequency of described former limit main switch is less than or equal to preset value, turn-off the synchronous rectifier of secondary.
9. a power supply is characterized in that, comprises
The shutdown control unit is used for receiving off signal, changes the ON time of the former limit main switch of transformer;
The controlling value acquiring unit is used for detecting voltagesecond product or controlling value corresponding to described voltagesecond product of former limit input voltage in described ON time at the secondary of transformer;
The secondary control unit is used for controlling according to described voltagesecond product or controlling value corresponding to described voltagesecond product the turn-on and turn-off of synchronous rectifier of the secondary of described transformer.
10. power supply according to claim 9 is characterized in that, described shutdown control unit specifically is used for: receive off signal, lengthen the ON time of the former limit main switch of transformer;
Described secondary control unit specifically is used for: when controlling value corresponding to described voltagesecond product or described voltagesecond product during more than or equal to preset value, turn-off the synchronous rectifier of secondary.
11. power supply according to claim 10 is characterized in that, described shutdown control unit specifically is used for:
Receive off signal, the former limit main switch that lengthens transformer turn-offs at least one front switch periods; Perhaps,
Receive off signal, add long pulse width at least one switch periods before the former limit of transformer main switch turn-offs; Perhaps,
Receive off signal, the former limit main switch that lengthens transformer turn-offs at least one front switch periods, selects one or more switch periods from least one switch periods that is lengthened out, and adds long pulse width in described one or more switch periods that are lengthened out.
12. power supply according to claim 9 is characterized in that, described shutdown control unit specifically is used for: receive off signal, shorten the ON time of the former limit main switch of transformer;
Described secondary control unit specifically is used for: when described voltagesecond product or controlling value corresponding to described voltagesecond product are less than or equal to preset value, turn-off the synchronous rectifier of secondary.
13. power supply according to claim 12 is characterized in that, described shutdown control unit specifically is used for:
Receive off signal, the former limit main switch that shortens transformer turn-offs front at least one switch periods; Perhaps,
Receive off signal, chopped pulse width at least one switch periods before the former limit of transformer main switch turn-offs; Perhaps,
Receive off signal, at least one switch periods before the former limit main switch that shortens transformer turn-offs, and select in the switch periods that is shortened one or more, chopped pulse width in described one or more switch periods that are shortened.
14. power supply according to claim 9 is characterized in that, described shutdown control unit comprises RC series circuit, weber clamper comparator and shutdown pulse comparator;
Described RC series circuit is connected between former limit Input voltage terminal and the ground;
Described weber the clamper comparator and the in-phase input end of shutdown pulse comparator by weber the clamper pin jointly be connected between the resistance and electric capacity of described RC circuit, and described weber the clamper comparator and the threshold value of shutdown pulse comparator different.
15. power supply according to claim 14 is characterized in that, described power supply also comprises: modulation signal generator, transformer, former limit main switch, the first secondary-side switch, the second secondary-side switch and LC filter;
Described modulation signal generator is electrically connected with described shutdown control unit, is used for former limit input voltage is modulated;
Described shutdown control unit is electrically connected with described former limit main switch;
Described former limit main switch one end connects former limit Input voltage terminal, other end ground connection by the primary coil of described transformer;
Described controlling value acquiring unit is connected between secondary voltage input and the described secondary control unit;
Described secondary control unit links to each other with described the first secondary-side switch and the second secondary-side switch;
Described the first secondary-side switch and the second secondary-side switch link to each other with described LC filter.
16. power supply according to claim 9, it is characterized in that, described controlling value acquiring unit is arranged on the secondary of described transformer, receive and the proportional secondary input voltage of described former limit input voltage, and comprise discharge circuit and charging circuit, described charging circuit comprises the first capacitor, when described discharge circuit when described ON time begins with described the first capacitor discharge after, described charging circuit in described ON time to described the first capacitor charging, and when described ON time finishes with the magnitude of voltage on described the first capacitor as described controlling value.
17. power supply according to claim 16 is characterized in that, described secondary control unit is configured to turn-off described synchronous rectifier when described controlling value during more than or equal to predetermined value.
18. power supply according to claim 9 is characterized in that, described shutdown control unit comprises:
Control switch, described control switch are connected between the output of the input of driver element and modulation signal generator, and closed or disconnect in response to control signal;
Driver element, described driver element is configured to receive via described control switch the modulation signal of described modulation signal generator, and the output modulation signal is to the control terminal of described former limit main switch;
Charge/discharge unit, described charge/discharge unit are connected between the control terminal and ground of described former limit main switch, be used for charging according to the ON time of described former limit main switch, and the output valve corresponding with the charging result flowed to comparator;
Comparator, described comparator is configured to receive the output valve of described charge/discharge unit, described output valve and reference value are compared, and on the one hand comparative result is exported to the work that described modulation signal generator is controlled modulation signal generator, so that in the output valve of charge/discharge unit during greater than described reference value, turn-off described modulation signal generator, on the other hand comparative result is exported to logical block;
Logical block, described logical block is configured to according to described off signal, the output of described comparator, and the signal of the input of described driver element is exported control signal, so that show to turn-off described power supply the time at off signal, disconnect control switch, and so that when disconnecting control switch, has high level on the input of driver element, in order to charge/discharge unit is charged, and in the described output valve of described charge/discharge unit during greater than described reference value, connect control switch, so that have low level on the input of driver element, in order to turn-off former limit main switch.
19. power supply according to claim 18 is characterized in that, described logical block is and door.
20. power supply as claimed in claim 18 is characterized in that, described off signal is because remote power-off, overcurrent protection, overvoltage protection, overheat protector, under-voltage protection and the off signal of triggering for generating.
21. a power supply is characterized in that, described power supply comprises:
The shutdown control unit is used for receiving off signal, changes the switching frequency of the former limit main switch of transformer;
Frequency detecting unit is for the switching frequency that detects described former limit main switch at the secondary of transformer;
The secondary control unit is used for controlling according to the switching frequency of described former limit main switch the shutoff of synchronous rectifier of the secondary of described transformer.
22. power supply according to claim 21 is characterized in that, described shutdown control unit specifically is used for: the switching frequency that improves the former limit main switch of transformer;
Described secondary control unit specifically is used for: when the switching frequency of described former limit main switch is greater than or equal to preset value, turn-off the synchronous rectifier of secondary.
23. power supply according to claim 21 is characterized in that, described shutdown control unit specifically is used for: the switching frequency that reduces the former limit main switch of transformer;
Described secondary control unit specifically is used for: when the switching frequency of described former limit main switch is less than or equal to preset value, turn-off the synchronous rectifier of secondary.
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| CN201110432371.3 | 2011-12-21 | ||
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| CN106448586A (en) * | 2016-09-27 | 2017-02-22 | 青岛海信电器股份有限公司 | Liquid crystal apparatus and liquid crystal screen power supply switch control method |
| CN106448586B (en) * | 2016-09-27 | 2019-06-28 | 青岛海信电器股份有限公司 | The method of controlling switch of the power supply of liquid-crystal apparatus and liquid crystal display |
| WO2019042280A1 (en) * | 2017-09-01 | 2019-03-07 | 华为技术有限公司 | Method and device for controlling flyback diode and power supply switching device |
| US10917014B2 (en) | 2017-09-01 | 2021-02-09 | Huawei Technologies Co., Ltd. | Free-wheeling diode control method and apparatus and power switching apparatus |
| CN111052576A (en) * | 2017-09-25 | 2020-04-21 | 华为技术有限公司 | Power supply system with reduced bulk capacitance |
| US10978962B2 (en) | 2017-09-25 | 2021-04-13 | Huawei Technologies Co., Ltd. | Power supply system with reduced bulk capacitance |
| CN111052576B (en) * | 2017-09-25 | 2021-05-18 | 华为技术有限公司 | Power supply system with reduced bulk capacitance |
| CN109193599A (en) * | 2018-11-02 | 2019-01-11 | 李振奎 | A kind of ladder cuts unrestrained arc-suppressing method and extinguisher |
| TWI701895B (en) * | 2020-04-22 | 2020-08-11 | 產晶積體電路股份有限公司 | Time parameter control method |
Also Published As
| Publication number | Publication date |
|---|---|
| CN103066825B (en) | 2016-03-09 |
| CN102437725A (en) | 2012-05-02 |
| CN104319986A (en) | 2015-01-28 |
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