Full-bridge converter mode switch control method and control switching circuit
Technical field
The present invention relates to the DC converting technology, particularly relate to a kind of phase shift and finite both mode switch control method and control switching circuit of full-bridge converter.
Background technology
Along with the development of power electronic technology, with the DC converter be core application of switching power more and more widely, simultaneously, require increasingly high to the efficient of converter.As a kind of DC converter topology, the phase-shifting full-bridge topology can realize the ZVT of switching tube, greatly reduces switching loss, can satisfy user demand preferably.
Shown in Fig. 1~more than 4 kinds of phase whole-bridging circuit schematic diagrams that can realize ZVT.
Wherein, diode D1~D4 is respectively endophyte diode or the external diode of switching tube Q1~Q4, and capacitor C 1~C4 is respectively parasitic capacitance or the external capacitor of Q1~Q4.Lr is a resonant inductance, and it has comprised the leakage inductance of transformer.Lo is an output afterflow inductance.Discharge and recharge for the junction capacitance of switching tube through resonant inductance Lr and afterflow inductance L o, thereby realize switching tube Q1~Q4 ZVT.
In existing practical application, the driving of switching tube is generally provided by special chip, like UCC2875, UCC2895 etc.Be the inside theory diagram of UCC2895 and the sequential chart of output (these contents are incorporated the present invention into) thereof shown in Fig. 5~6:
Wherein, phase shift output signal OUTA, OUTB, OUTC, OUTD difference driving switch pipe Q1, Q2, Q3, Q4.Under the phase-shift control mode, switching tube Q1 and Q2 take turns conducting, each conducting 180 degree angle, and switching tube Q3 and Q4 also are like this.But switching tube Q1 and Q4 be conducting simultaneously not, if the conducting of switching tube Q4 elder generation, and conducting behind the switching tube Q1, both differ an angle, i.e. phase shifting angle, so, switching tube Q3 and Q4 just form leading arm, switching tube Q1 and Q2 composition lagging leg.Through regulating the adjustable size joint output voltage of phase shifting angle.
When load current was big, four switching tubes of full-bridge circuit can be realized soft switch.But when load current less (<50% nominal load current), the electric current in resonant inductance and the afterflow inductance is less, and its energy shortage is with the electric charge on the junction capacitance of taking the switching tube that will open away; Therefore; When this switching tube is opened, just can't realize that no-voltage is open-minded, its switching loss strengthens.Along with further reducing of load current, switching loss further strengthens, especially the switching loss of lagging leg.Near zero load the time, the voltage on the switching tube is near Vin, and the energy on its junction capacitance is:
(wherein, C is capacity or the equivalent capacity of both parallel connections of junction capacitance capacity or the external capacitor of switching tube).When switching tube is opened, in the whole consumption of the energy on the junction capacitance and this switching tube.And in the traditional P WM pattern, the voltage of switching tube is merely Vin/2.Therefore, when underloading, the switching loss of phase shift pattern is four times of PWM pattern.
In sum, present phase whole-bridging circuit can't realize thoroughly that when underloading the no-voltage of switching tube is open-minded, and during especially near zero load, switching loss sharply increases.The increase of switching loss is unfavorable for the heat radiation of switching tube on the one hand; On the other hand, be unfavorable for that converter obtains higher efficient in the loading range of broad.
Summary of the invention
Main purpose of the present invention is exactly the deficiency to prior art, and a kind of mode switch control method and control switching circuit are provided, and can make full-bridge converter obtain more high efficiency.
For realizing above-mentioned purpose, the present invention adopts following technical scheme:
A kind of mode switch control method of full-bridge converter may further comprise the steps:
A. gather the signal of the load weight of the said full-bridge converter of reflection;
B. analyzing said signal and whether belong to the heavy duty signal of the reflection of defining in advance, is then to get into step c, otherwise gets into steps d;
C. controlling said full-bridge converter works under the phase shift pattern;
D. controlling said full-bridge converter works under the finite both pattern.
Preferably, among the step a, the signal of the load weight of the said full-bridge converter of said reflection is a load current signal; Among the step b, the load current that collects gets into steps d during less than 50% nominal load current.
Step b comprises:
B1. said signal is carried out filtering, processing and amplifying;
B2. relatively amplified signal value and preset reference value are if said amplified signal value greater than said fiducial value then get into said step c, otherwise gets into said steps d.
Among the step c, the said control under the said phase shift pattern comprises:
Make in the said full-bridge converter first switching tube on first brachium pontis and second switch pipe take turns the conducting half period; The 3rd switching tube on second brachium pontis and the 4th switching tube take turns the conducting half period; The conducting of the said second switch pipe that the conduction ratio of said the 3rd switching tube is corresponding differs a phase shifting angle, and the conducting of said first switching tube that the conduction ratio of said the 4th switching tube is corresponding also differs a phase shifting angle.
In the steps d, the said control under the said finite both pattern comprises:
Make in the said full-bridge converter first switching tube on first brachium pontis and second switch pipe take turns the conducting half period; The 3rd switching tube and the 4th switching tube on second brachium pontis are worked under the PWM pattern; And said the 3rd switching tube and corresponding said conducting a period of time second switch pipe while, said the 4th switching tube and corresponding said conducting a period of time first switching tube while.
A kind of mode switch control circuit of full-bridge converter comprises:
Acquisition Circuit is used to gather the signal of the load weight of the said full-bridge converter of reflection;
Analysis circuit is used to analyze said signal and whether belongs to the heavy duty signal of the reflection of defining in advance;
Commutation circuit, be used for said analysis circuit provide be as a result the time make said full-bridge converter switch to the work of phase shift pattern, and said analysis circuit provide not as a result the time make said full-bridge converter switch to the work of finite both pattern.
Preferably, said Acquisition Circuit is to gather load current signal, and said analysis circuit is whether to analyze load current greater than 50% nominal load current.
Said analysis circuit comprises:
Filter circuit is used for said signal is carried out Filtering Processing;
Amplifying circuit is used for said signal is carried out processing and amplifying;
Comparison circuit is used for amplified signal value and preset reference value are compared, when said amplified signal value greater than said fiducial value time output high level signal, otherwise output low level signal.
Said full-bridge converter comprises first brachium pontis and second brachium pontis; Said first brachium pontis comprises first switching tube and second switch pipe; Said second brachium pontis comprises the 3rd switching tube and the 4th switching tube; Said first switching tube and said the 4th switching tube are corresponding on ON time, and said second switch pipe and said the 3rd switching tube are corresponding on ON time;
Said commutation circuit comprise first or logical circuit, second or logical circuit, the 3rd with logical circuit and the 4th and logical circuit; Said first or the output of one of the logical circuit said comparison circuit of input termination; Said first or another input termination first drive signal of logical circuit; Said second or the output of one of the logical circuit said comparison circuit of input termination; Said second or another input termination second drive signal of logical circuit; The said the 3rd with the output of one of logical circuit input termination said second or logical circuit; The said the 3rd with another input termination the 3rd drive signal of logical circuit; The said the 4th with the output of one of logical circuit input termination said first or logical circuit, the said the 4th with the moving signal of another input termination 4 wheel driven of logical circuit, said first drive signal and said second drive signal offer first switching tube on first brachium pontis and second switch pipe in the said full-bridge converter respectively; The said the 3rd with logic circuit output signal offer the 3rd switching tube on second brachium pontis in the said full-bridge converter, the said the 4th with logic circuit output signal offer the 4th switching tube on second brachium pontis in the said full-bridge converter.
The said the 3rd is sending to before said the 3rd switching tube earlier through processing and amplifying with logic circuit output signal, the said the 4th with logic circuit output signal before sending to said the 4th switching tube earlier through processing and amplifying.
Beneficial technical effects of the present invention is:
The present invention is according to the mode of operation of the corresponding switching full-bridge converter of load weight of full-bridge converter; When being judged as heavy duty; Full-bridge converter is worked, and under the phase shift pattern when being judged as underload, full-bridge converter is switched to work under the finite both pattern; Thereby when underload, can effectively reduce the switching loss of switching tube, make converter can in wideer loading range, obtain higher efficient.
Description of drawings
Fig. 1~4 are several kinds of phase whole-bridging circuit schematic diagrams that can realize ZVT;
Fig. 5 is the inside theory diagram of chip for driving UCC2895 that is used for the switching tube of phase whole-bridging circuit;
Fig. 6 is the sequential chart of drive signal output that is used for the switching tube of phase whole-bridging circuit;
Fig. 7 is the flow chart of a phase shift of the present invention and an embodiment of finite both method for handover control;
Fig. 8 is the structure chart of a phase shift of the present invention and an embodiment of finite both control switching circuit.
Embodiment
Below combine accompanying drawing that the present invention is further specified through embodiment.
The control model of adjustment full-bridge converter is switched in the present invention according to the load weight situation of full-bridge converter; When load is heavier is that load current is when big; Make full-bridge converter work in conventional phase shift pattern; And when load gentlier be load current hour, make full-bridge circuit work in the finite both pattern.Under the less situation of load current, full-bridge converter can effectively reduce switching loss with the work of finite both pattern, thereby improves overall efficiency.
As shown in Figure 7, in one embodiment, a kind of mode switch control method of full-bridge converter may further comprise the steps:
A. gather the signal of the load weight of the said full-bridge converter of reflection;
B. analyzing said signal and whether belong to the heavy duty signal of the reflection of defining in advance, is then to get into step c, otherwise gets into steps d;
C. controlling said full-bridge converter works under the phase shift pattern;
D. controlling said full-bridge converter works under the finite both pattern.
In a preferred embodiment, among the step a, the signal of the load weight of the said full-bridge converter of said reflection is a load current signal; Among the step b, the load current that collects gets into steps d during less than 50% nominal load current.
In a preferred embodiment, step b comprises:
B1. said signal is carried out filtering, processing and amplifying;
B2. relatively amplified signal value and preset reference value are if said amplified signal value greater than said fiducial value then get into step c, otherwise gets into steps d.
Please refer to Fig. 1-4, the full-bridge converter of a plurality of embodiment comprises first brachium pontis and second brachium pontis, and said first brachium pontis comprises the first switching tube Q1 and second switch pipe Q2, and said second brachium pontis comprises the 3rd switching tube Q3 and the 4th switching tube Q4.As full-bridge circuit, said first switching tube Q1 and said the 4th switching tube Q4 are corresponding on ON time, and said second switch pipe Q2 and said the 3rd switching tube Q3 are corresponding on ON time.
Among the step c, the said control under the phase shift pattern comprises:
Make in the said full-bridge converter the first switching tube Q1 on first brachium pontis and second switch pipe Q2 take turns i.e. 180 degree of conducting half period; The 3rd switching tube Q3 on second brachium pontis and the 4th switching tube Q4 take turns the conducting half period; And the conducting of the conducting of said the 3rd switching tube Q3 and said second switch pipe Q2 differs a phase shifting angle, and the conducting of the conducting of said the 4th switching tube Q4 and the said first switching tube Q1 also differs a phase shifting angle.Be not conducting simultaneously of switching tube Q2 and Q3, switching tube Q1 and Q4 be conducting simultaneously not.If the conducting of switching tube Q4 elder generation and conducting behind the switching tube Q1, both differ a phase shifting angle, and then switching tube Q3 and Q4 just form leading arm, switching tube Q1 and Q2 composition lagging leg.Through regulating the adjustable size joint output voltage of phase shifting angle.When load current was big, four switching tubes of full-bridge converter can be realized soft switch.At this moment, discharge and recharge for the junction capacitance of switching tube, thereby realize switching tube Q1~Q4 ZVT through resonant inductance Lr and afterflow inductance L o.
In the steps d, the said control under the said finite both pattern comprises:
Make in the said full-bridge converter first switching tube on first brachium pontis and second switch pipe take turns the conducting half period; The 3rd switching tube and the 4th switching tube on second brachium pontis are worked under the PWM pattern; And said the 3rd switching tube and corresponding said conducting a period of time second switch pipe while, said the 4th switching tube and corresponding said conducting a period of time first switching tube while.
Please refer to Fig. 1-4; The finite both control mode is to let two switching tubes such as switching tube Q1 and the Q2 of a brachium pontis take turns the conducting half period; The switching tube of another brachium pontis such as switching tube Q3 and Q4 are PWM work, but wherein switching tube Q4 in the just conducting of switching tube Q1 conduction period, but switching tube Q3 is in the just conducting of switching tube Q2 conduction period; Switching tube Q4 and switching tube Q1 be the conducting Ton time simultaneously, and Q3 and Q2 be conducting Ton time while also.Because switching tube Q3 and Q4 work in the PWM pattern when load is light, it compares the switching loss that can reduce switching tube Q3 and Q4 with the phase shift pattern.
Please refer to Fig. 8, according to one embodiment of present invention, a kind of mode switch control circuit of full-bridge converter comprises Acquisition Circuit, analysis circuit and commutation circuit.Wherein, Acquisition Circuit is used to gather the signal of the load weight that reflects said full-bridge converter; Analysis circuit is used to analyze said signal and whether belongs to the heavy duty signal of the reflection of defining in advance; Commutation circuit be used for said analysis circuit provide be as a result the time make said full-bridge converter switch to the work of phase shift pattern, and said analysis circuit provide not as a result the time make said full-bridge converter switch to the work of finite both pattern.The signal of the reflected load weight of Acquisition Circuit collection can be feedback signal and input current signal of load current signal, circuit etc.For gathering load current, whether analysis circuit can provide the result who is or denys greater than 50% nominal load current according to load current.
Said analysis circuit preferably includes filter circuit, amplifying circuit and comparison circuit.Wherein, filter circuit is used for said signal is carried out Filtering Processing; Amplifying circuit is used for said signal is carried out processing and amplifying; Comparison circuit is used for amplified signal value IO and preset reference value Ref are compared, when said amplified signal value greater than said fiducial value time output high level signal, otherwise output low level signal.The control model of full-bridge circuit is confirmed in the output of comparison circuit, if the output high level signal then makes full-bridge circuit work in the phase shift pattern; If the output low level signal then makes full-bridge circuit work in the finite both pattern.
Please refer to Fig. 9; Said commutation circuit preferably include first or logical circuit A, second or logical circuit B, the 3rd with logical circuit C and the 4th with logical circuit D; Said first or the output of one of logical circuit A input termination comparison circuit; Said first or another input termination first drive signal OUTA of logical circuit A; Said second or the output of one of the logical circuit B said comparison circuit of input termination; The said second or another input termination second drive signal OUTB of logical circuit B, the said the 3rd with the input termination said second of logical circuit C or the output of logical circuit B, the said the 3rd with another input termination the 3rd drive signal OUTC of logical circuit C; The said the 4th with the output of one of logical circuit D input termination said first or logical circuit A, the said the 4th with the moving signal OUTD of another input termination 4 wheel driven of logical circuit D.Wherein, Said first drive signal OUTA and the said second drive signal OUTB offer first switching tube Q1 on first brachium pontis and second switch pipe Q2 in the said full-bridge converter respectively; The 3rd exports signal OUTC1 with logical circuit C offers the 3rd switching tube Q3 on second brachium pontis in the said full-bridge converter, and the said the 4th exports signal OUTD1 with logical circuit D offers the 4th switching tube Q4 on second brachium pontis in the full-bridge converter.
More preferably, the said the 3rd with logical circuit C output signal OUTC1 before sending to the 3rd switching tube Q3 earlier through processing and amplifying, the said the 4th with logical circuit D output signal OUTD1 before sending to said the 4th switching tube Q4 earlier through processing and amplifying.
Please refer to Fig. 9, the principle of switching through the commutation circuit implementation pattern is following:
Among the phase shift output OUTA of full-bridge chip, OUTB, OUTC, the OUTD, output OUTA, OUTB be (or after the amplification of overdriving) difference driving switch pipe Q1 and switching tube Q2 directly.And the output OUTC of full-bridge chip, OUTD do following processing respectively: output OUTA, OUTB respectively through first or logical circuit and second or logical circuit carry out exclusive disjunction with the output of circuit relatively, obtain first or logical circuit and second or output signal OUTA1, the OUTB1 of logical circuit; To export again OUTC and signal OUTB1 through the 3rd with logical circuit with after, the signal OUTC1 of generation is used for directly (or after the amplification of overdriving) driving switch pipe Q3; To export OUTD and signal OUTA1 through the 4th with logical circuit with after, the signal OUTD1 of generation is used for directly (or after the amplification of overdriving) driving switch pipe Q4.
Above content is to combine concrete preferred implementation to the further explain that the present invention did, and can not assert that practical implementation of the present invention is confined to these explanations.For the those of ordinary skill of technical field under the present invention, under the prerequisite that does not break away from the present invention's design, can also make some simple deduction or replace, all should be regarded as belonging to protection scope of the present invention.