CN104852560A - Method of optimizing stress equilibrium in switching power supply and switching power supply to which method is applied - Google Patents

Abstract

The invention discloses a method of optimizing stress equilibrium in a switching power supply, which comprises steps: a first diode is used for building an energy matching relationship among a first capacitor, an inductor and a transformer, that is, when a switching tube is conducted, an exciting circuit of the inductor and an exciting circuit of the transformer are separated via the first diode, when the switching tube is cutoff, the inductor and the transformer are connected via the first diode, within a half power frequency cycle, the first capacitor is divided into a charging period and a non-charging period, and when the first capacitor is in the non-charging period, the first diode is in a non-conduction period; the average power when the first capacitor is in the charging period and the average power when the first capacitor is in the discharging period are regarded as the same; and according to the energy matching relationship among the inductor, the first capacitor and the transformer, the principle of conservation of energy is used, and the inductor parameter selection range is calculated by the capacitance value of the first capacitor, the transformer turn ratio and the source-side winding inductance. Compared with the prior art, voltage stress of each element can be balanced, and electromagnetic interference caused by a large voltage change rate can be reduced.

Description

In Switching Power Supply stress equilibrium optimization method and be suitable for the Switching Power Supply of the method

Technical field

The present invention relates to a kind of method for designing of power circuit, particularly a kind of primary side is the optimization method of stress equilibrium in the Switching Power Supply of third-order system (main power exists two magnetic elements and a capacitive element) and is suitable for the Switching Power Supply of the method.

Background technology

Power supply is the various forms of circuit arrangements converted electric energy to needed for power consumption equipment, and it is all power producers by electric workable device.Direct-current switch power supply is a kind of electrical energy changer adopting the switching circuit of Duty ratio control to form, and is widely used in the every field such as life, production, scientific research, military affairs.

What the electric capacity for Switching Power Supply prime was generally chosen is alminium electrolytic condenser, and alminium electrolytic condenser has that cost is low, volume is little, rated insulation voltage advantages of higher and by wide selection.But, because alminium electrolytic condenser adopts the blotting paper being soaked with paste electrolyte to be clipped in winding in the middle of two aluminium foils to form, excessively of a specified duration when stored, after the electrolyte volatilization of its inside, leakage current increases, equivalent series resistance (ESR:Equivalent Series Resistance) also increases thereupon, therefore alminium electrolytic condenser generally only has 2 to three years useful life, and can affect the characteristic of electrolyte in high/low temperature situation, so alminium electrolytic condenser is also very responsive to temperature.

For reducing the pollution of electronic equipment internal Switching Power On Electric Net, International Electrotechnical Commission and some countries and regions are proposed the standards such as IEC1000-3-2 and EN61000-3-2, have made limitation regulation to current harmonics.For meeting Harmonics of Input restriction requirement, the most effective technological means is with regard to Active Power Factor Correction, the circuit (PFC:Power Factor Correction writes a Chinese character in simplified form) of a series of raising power factor that has been born, two-step scheme by the active PFC technology widely adopted at present, these circuit well solve the low problem of power supply PF value, the PF value of circuit can reach more than 0.9, but this adds the complexity of circuit system and control undoubtedly, add cost, and have impact on the conversion efficiency of power supply, particularly in the occasion that power is little, shortcoming is more outstanding.

Current interchange turns all essential in direct current topology has the electrochemical capacitor of a high-voltage large-capacity to carry out low frequency filtering, but this electrochemical capacitor has a series of shortcoming, as: the life-span, property at high and low temperature etc., but also affect the PF value (power factor: Power Factor writes a Chinese character in simplified form) of Switching Power Supply, etc. these all govern the development of Switching Power Supply.

As everyone knows, flyback topologies is the isolated form of Buck-boost circuit, generally be widely used in middle low power occasion, it is simple that it has circuit structure, components and parts are few, be easy to the advantages such as multiple-channel output, Fig. 1 shows traditional flyback topologies circuit, comprises rectifier bridge, input filter capacitor C1, transformer T1, switching tube Q1, the drive circuit of switching tube, output filter capacitor Co, output rectifier diode D1.Input voltage is by after rectifier bridge, high level part and input capacitance C1 positive pole are connected, general title high level part is busbar voltage, low level part is connected with the negative pole of input capacitance C1, general title low level part is ground, converter former limit, busbar voltage is connected with transformer T1 input, transformer T1 input Same Name of Ends drains with switching tube Q1 and is connected, be connected to the source electrode of switching tube Q1 and the former limit of converter, transformer exports Same Name of Ends and is connected with the anode of output diode, output diode negative electrode connects output capacitance positive pole, the output ground of converter is connected with another output of transformer, the electric capacity other end with output be connected.The course of work of circuit is as follows:

When switching tube Q1 conducting, transformer T1 primary current, under the effect of input voltage, linearly rises.Transformer primary voltage senses secondary, and rectifier diode is oppositely ended, and the output voltage of power supply provides supply by output filter capacitor Co.When switching tube Q1 turns off, transformer primary current is forced to turn off, and because inductive current can not suddenly change, therefore produces an induced electromotive force in primary side.According to the law of electromagnetic induction, when secondary induced electromotive force reaches output voltage, secondary commutation diode current flow.The energy that primary inductance stores when switching tube is opened, is coupled to secondary inductance by magnetic core, is then discharged in output capacitance Co by secondary coil.

Known by above-mentioned analysis, the magnetic core of the high frequency transformer of common reverse exciting switching voltage regulator is operated in the first quartile of magnetic hysteresis loop, in switching tube conduction period, a transformer storage power, and between the off period just by the energy transferring that stores in primary coil to secondary, therefore it is transformer, is again energy storage inductor.It should be noted that constant by the sense of current of transformer in this process, stem opens the direct current field intensity that certain air gap can reduce remnant field, raising magnetic core wherein, prevents magnetic core saturated.And so hold air gap and can cause leakage field phenomenon, thus add the leakage inductance of transformer, cause energy loss.The input capacitance capacitance of common circuit of reversed excitation requires very large, inevitably introduces the defect that electrochemical capacitor brings.And the output of power supply is only transmitted by the energy storage of flyback transformer, the former limit DC component of transformer is comparatively large, therefore needs magnetic core to open certain air gap, thus transformer leakage inductance is just very large, and loss is very large.

Current no electrolytic capacitor technology is used for greatly LED and drives lighting field, and LED drive power can not meet the performance requirement of industrial power, industrial load will exceed a lot than LED to the performance requirement of power supply to the performance requirement of power supply, and LED illumination power supply is constant current output, and industrial power requires to export for constant voltage, when inputting steamed bun wave-wave paddy, output voltage has larger fluctuation, and namely converter cannot eliminate so large Hz noise, exports and has larger ripple.Moreover the input range of current no electrolytic capacitor power supply does not reach the requirement of industrial power yet.

Design Switching Power Supply is a process full of contradictions, fish and bear's paw are unable to have both at one and the same time, need the various index of balanced compromise, as the compromise of steady-state behaviour and dynamic property, the compromise of power density and reliability, the compromise of small-signal performance and large-signal performance, design trade-off under high/low temperature, compromise between electrical property and hot property, compromise of critical component etc., certainly otherwise compromise is also had, the compromise of the still critical component that these all compromises are the most basic, can the choosing of some main power devices be related to whole Switching Power Supply and normally work and the performance optimization of Switching Power Supply, the voltage stress that such as main power device bears, current stress and magnetic stress etc.In the design of common Switching Power Supply; as the design of power transformer; first the turn ratio of transformer will be optimized; the turn ratio of transformer is related to the voltage stress of input switch pipe and the voltage stress of output diode; the voltage stress of switching tube is also relevant with the leakage inductance of transformer, therefore wishes that the leakage inductance of transformer is the smaller the better, but realize leakage inductance minimum while; often increase the distributed capacitance between winding, this usually can increase common mode EMI interference and reduce fail safe.In addition, as the compromise of driving force.In order to reduce the switching loss of device for power switching (MOSFET), wish that its switching process is as far as possible short, this drives resistance to realize by reducing gate leve, but while switching speed improves, often increase the common mode EMI of power supply, make EMI properties deteriorate.

Show a kind of brand-new topology of Switching Power Supply at number of patent application " a kind of power circuit " the Chinese patent prospectus that is 201410822779.5, its topological circuit structure as shown in Figure 2.In the circuit topology shown in patent " a kind of power circuit ", there are two perceptual devices in its main loop of power circuit---inductance and transformer, and with a capacitive device.The method for designing of current existing Switching Power Supply topology is not suitable for the brand-new topology in above patent, and the design of rational inductance, electric capacity and transformer can widen the input voltage range of Switching Power Supply, reduces output ripple.

Summary of the invention

The object of this invention is to provide a kind of design balance that can solve two inductive elements and a capacitive element, the basis that power output meets the demands is reduced the capacitance of input stage electric capacity as much as possible, make being designed with theoretical foundation and can following of this new topology, also can reduce the design difficulty of the first electric capacity, inductance, transformer, the more important thing is the voltage stress balancing each components and parts, thus the electromagnetic interference reduced because large voltage change ratio causes, reduce stress to improve the optimization method of stress equilibrium in the Switching Power Supply of overall efficiency.

In order to achieve the above object, the present invention is achieved through the following technical measures:

An optimization method for stress equilibrium in Switching Power Supply, comprises and requires according to the stress of switching tube the transformer turns ratio that calculates in circuit of reversed excitation; Limit, the source winding sensibility reciprocal of transformer in circuit of reversed excitation is calculated according to the first C meter, also comprise the energy match relation being set up the first electric capacity, inductance and transformer by the first diode, namely when switching tube conducting, the energized circuit of inductance and the energized circuit of transformer is separated by the first diode, when switching tube turns off, inductance and transformer is communicated with by the first diode, with in half power frequency period, first electric capacity is divided into charging period and does not charge period, do not charge period at the first electric capacity, that is the first diode not turn on period; And the average power in first capacitor charging period is considered as identical with the average power in first capacitor discharge period; According to the energy match relation of inductance and the first electric capacity and transformer, use conservation of energy principle, calculated the parameter choose scope of inductance by the capacitance of the first electric capacity, transformer turns ratio and limit, source winding sensibility reciprocal.

Preferably, described in, to calculate the relationship of the parameter choose scope of inductance as follows, according to the AC-input voltage value range [Vinmin, Vinmax] of design requirement, according to formula the average voltage calculating the first electric capacity two ends is V _{cdc_ave}; The energy match relation of the first electric capacity set up according to the first diode, inductance and transformer, in half power frequency period, the first electric capacity is divided into charging period and does not charge period, does not charge period at the first electric capacity, that is the first diode not turn on period, according to formula $t=\frac{\mathrm{\π}}{4\mathrm{\πf}}-\frac{\arcsin \left(\frac{V_{\min }}{\sqrt{2}{V}_{\mathrm{in}\min }}\right)}{2\mathrm{\πf}},,E_1=\frac{1}{2}{C}_{\mathrm{DC}}{\left(\sqrt{2}{V}_{\mathrm{in}\min }\right)}^2-\frac{1}{2}{D}_{\mathrm{DC}}{V}_{\min }^2,P_{\mathrm{ave}}=\frac{E_1}{\frac{\mathrm{\π}}{2\mathrm{\πf}}-t_2},$ Draw the average power Pave do not charged period at the first electric capacity; The average power in first capacitor charging period is considered as identical, according to formula E with the average power in first capacitor discharge period ₂=P _ave× t draws the ENERGY E 2 that the first capacitor charging transmits to transformer period; According to formula draw the power P in_c of transformer transmission in half power frequency period; According to formula draw average duty ratio Dave; According to formula calculate the sensibility reciprocal of inductance.

The present invention also provides a kind of Switching Power Supply, and comprise rectifier bridge, the first electric capacity, inductance, circuit of reversed excitation and the second electric capacity, described rectifier bridge has positive output end and negative output terminal, and described first Capacitance parallel connection is between the positive output end and negative output terminal of rectifier bridge, the former limit circuit of described circuit of reversed excitation comprises the former limit winding of transformer, the driver module of the first switching tube and driving the first switching tube, also comprise the first diode and by the clamp circuit of the anode clamper of the first diode at the negative output terminal current potential of rectifier bridge, described clamp circuit, be made up of second switch pipe, the concrete annexation of described switching power circuit is, the positive output end of rectifier bridge is connected with one end of inductance, the other end of inductance is connected with the drain electrode of second switch pipe and the anode of the first diode respectively, the source electrode of second switch pipe is connected with the negative output terminal of rectifier bridge, the negative electrode of the first diode is connected with one end of the second electric capacity and the drain electrode of the first switching tube respectively, and the source electrode of the first switching tube is connected with the Same Name of Ends of former limit winding, and the different name end of former limit winding is connected with the other end of the second electric capacity, the Same Name of Ends of former limit winding is also connected with the negative output terminal of rectifier bridge, second switch pipe Q2 and the first switching tube Q1 uses same driver module, described first diode D1 separates/is communicated with the loop of inductance L 1 and transformer T1, and namely when the first switching tube and the conducting of second switch pipe, inductance forms the energized circuit of inductance through second switch pipe, meanwhile, the former limit winding of the second electric capacity through transformer, the energized circuit of the first switching tube formation transformer, now diode D1 separates the loop of inductance L 1 and transformer T1, when the first switching tube and second switch pipe turn off, first diode is communicated with inductance and transformer, form single current circuit, inductance and transformer to be exported at the energy trasfer that the excitation stage stores, namely set up the energy match relation of the first electric capacity, inductance and transformer by the first diode.

Preferably, the energy match relation of described first electric capacity, inductance and transformer, show as following mathematical relationship, namely the span of the first electric capacity, transformer and inductance estimates value successively by following formula, according to the AC-input voltage value range [Vinmin of design requirement, Vinmax], according to formula the average voltage calculating the first electric capacity two ends is V _{cdc_ave}; The energy match relation of the first electric capacity set up according to the first diode, inductance and transformer, in half power frequency period, the first electric capacity is divided into charging period and does not charge period, does not charge period at the first electric capacity, that is the first diode not turn on period, according to formula $t=\frac{\mathrm{\π}}{4\mathrm{\πf}}-\frac{\arcsin \left(\frac{V_{\min }}{\sqrt{2}{V}_{\mathrm{in}\min }}\right)}{2\mathrm{\πf}},E_1=\frac{1}{2}{C}_{\mathrm{DC}}{\left(\sqrt{2}{V}_{\mathrm{in}\min }\right)}^2-\frac{1}{2}{D}_{\mathrm{DC}}{V}_{\min }^2,$ draw the average power Pave do not charged period at the first electric capacity; The average power in first capacitor charging period is considered as identical, according to formula E with the average power in first capacitor discharge period ₂=P _ave× t, draws the ENERGY E 2 that the first capacitor charging transmits to transformer period; According to formula draw the power P in_c of transformer transmission in half power frequency period; According to formula draw average duty ratio Dave; According to formula calculate the sensibility reciprocal of inductance.

Compared with prior art, the present invention has following beneficial effect:

(1) the sensibility reciprocal span of two the perceptual components and parts reducing Switching Power Supply input capacitance (bus capacitor) capacitance accurately can be drawn by calculating;

(2) carry out device according to calculated parameter value to choose, effectively reduce the probability of happening of start burner part situation;

(3) calculation of parameter of each components and parts is comparatively close with actual conditions, is conveniently optimized other performances such as power-efficients;

(4) effectively can shorten the construction cycle, reduce costs.

Accompanying drawing explanation

Fig. 1 shows traditional flyback topologies circuit;

The simple topology unit signal of Fig. 2 to be number of patent application be Chinese patent of 201410822779.5;

Fig. 3 is the circuit theory diagrams of the Switching Power Supply of first embodiment of the invention;

Fig. 4 is the first electric capacity both end voltage waveform and rectification bridge output end voltage waveform;

Fig. 5 is that the Switching Power Supply of first embodiment of the invention is in conduction period at switching tube Q1, the current direction schematic diagram of circuit;

Fig. 6 is that the Switching Power Supply of first embodiment of the invention is in blocking interval at switching tube Q1, the current direction schematic diagram of circuit;

Fig. 7 is the output ripple oscillogram of the Switching Power Supply of first embodiment of the invention;

Fig. 8 is the circuit theory diagrams of the Switching Power Supply of second embodiment of the invention.

Embodiment

First embodiment

Figure 3 shows that the circuit theory diagrams of first embodiment of the invention Switching Power Supply, a kind of Switching Power Supply, comprise rectifier bridge 101, first electric capacity C1, Boost circuit, the first switching tube Q1, the second electric capacity C _dC, circuit of reversed excitation, Boost circuit comprises inductance L 1, second switch pipe Q2, the first diode D1; Circuit of reversed excitation comprises the first transformer T1, output diode Do (output rectifier diode), the 3rd electric capacity Co (output capacitance).Described rectifier bridge 101 becomes Rectified alternating current AC rectification, and the two ends of the first electric capacity C1 are connected respectively to positive output end and the negative output terminal of rectifier bridge 101; The output voltage of rectifier bridge 101 raises by described Boost circuit, the positive output end of rectifier bridge 101 connects one end of inductance L 1 in Boost circuit, the other end of inductance L 1 is connected to the drain electrode of second switch pipe Q2, and be connected with the anode of the first diode D1, the source electrode of second switch pipe Q2 is connected with the negative output terminal of rectifier bridge 101; The drain electrode of the first switching tube Q1 is connected with the negative electrode of the first diode D1, and with the second electric capacity C _dCone end be connected, the source electrode of the first switching tube Q1 is connected with the negative output terminal of rectifier bridge 101; In described circuit of reversed excitation, the second electric capacity C _dCthe other end be connected with the former limit winding different name end of transformer T1, the former limit Motor Winding Same Name of Ends of transformer T1 is connected with the negative output terminal of rectifier bridge 101, the vice-side winding different name end of transformer T1 is connected with the anode of described output rectifier diode Do, after the negative electrode of described output rectifier diode Do is connected with described output filter capacitor Co positive pole, as the positive pole that power supply exports, the negative pole of described output filter capacitor Co is connected with transformer T1 vice-side winding Same Name of Ends, as the negative pole that power supply exports.

First embodiment of the invention Switching Power Supply operation principle:

Single use text description principle, can allow the art personnel understand difficulty, so, please use principle figure be allow, coordinate signal conventional in electronic engineering to flow to and operation principle of the present invention is described.

Fig. 3 is by above-mentioned technical scheme, the simple topology unit drawn out and component units schematic diagram, a kind of Switching Power Supply, comprise rectifier bridge 101, voltage-multiplying circuit 102, drive circuit 103, circuit of reversed excitation 104, rectifier bridge 101 becomes Rectified alternating current AC rectification, and the waveform of Rectified alternating current as shown in Figure 4; Drive circuit 103 by some characteristics of control circuit simultaneously switch tube Q1 and switching tube Q2 carry out Duty ratio control, that is the public control signal of switching tube Q1 and Q2; Voltage-multiplying circuit 102 comprises diode D1, inductance L 1 and switching tube Q2, is controlled inductance stored energy and is released energy, the energy supposition input voltage of release is sent to the electric capacity C in circuit of reversed excitation 104 by the break-make of switching tube _dCon; Circuit of reversed excitation comprises bus capacitor C _dC, switching tube Q1, transformer, output rectifier diode Do, output filter capacitor.

Assuming that described two switching tubes Q1, Q2 are N-MOS pipe, carry out principle explanation under being all operated in discontinuous mode with the inductance L 1 in voltage-multiplying circuit 102 with the transformer T1 in circuit of reversed excitation, then the operation principle of Switching Power Supply of the present invention one-period is in the steady state:

(1) N-MOS pipe Q1 and Q2 conducting:

As N-MOS pipe Q1 and Q2 conducting, N-MOS pipe Q1 and Q2 is equivalent to a wire, Fig. 5 illustrates the flow direction of now electric current, from the output of rectifier bridge 101 just → the inductance L 1 → voltage-multiplying circuit 102 of voltage-multiplying circuit 102 the output negative pole of switching tube Q2 → get back to rectifier bridge 101, concrete current direction is as shown in dotted line in Fig. 5 301.In addition, the former limit of power supply also has a current circuit, from bus capacitor C _dCthe bus capacitor C of the transformer primary side winding of the N-MOS pipe Q1 → circuit of reversed excitation 104 of positive pole → circuit of reversed excitation 104 → get back to circuit of reversed excitation 104 _dCnegative pole, concrete current direction is as shown in dotted line in Fig. 5 302.Now transformer carries out stored energy, and power supply vice-side winding relies on the electric energy stored in output capacitance Co, and concrete current direction is as shown in dotted line in Fig. 5 303.

In this process, the electric current flowing through inductance L 1 is started from scratch linear rising, and inductance L 1 starts energy storage; Bus capacitor C simultaneously in circuit of reversed excitation _dCby the former limit electric discharge of N-MOS pipe Q1 to transformer T1, the electric current of transformer T1 former limit winding is started from scratch and is linearly risen, the sense of current of transformer T1 former limit winding: flow to former limit different name end from former limit Same Name of Ends, and excitatory and by the former limit winding storage power of transformer T1 to the former limit winding of transformer T1; At this moment the vice-side winding of transformer T1 induces negative lower positive induced voltage, and as symbol logo in Fig. 5, this induced voltage and the turn ratio of transformer T1, former limit winding voltage are relevant, and under this voltage effect, diode Do is reverse-biased, not conducting.

Because the energized circuit of two inductive elements separates, the electric current flowing through each switching device reduces, and therefore can select the switching device that power grade is lower, so just decrease the loss of switching device, improve the efficiency of complete machine power supply.

(2) N-MOS pipe Q1 and Q2 turns off then:

When N-MOS pipe Q1 and Q2 conducting complete, when then turning off rapidly, now N-MOS pipe Q1 and Q2 is equivalent to open circuit, and Fig. 6 illustrates current direction now, from the output of rectifier bridge 101 just → the inductance L 1 → voltage-multiplying circuit 102 of voltage-multiplying circuit 102 diode D1 → circuit of reversed excitation in bus capacitor C _dCthe output negative pole of the transformer primary side winding of → circuit of reversed excitation 104 → get back to rectifier bridge 101, concrete current direction is as shown in dotted line in Fig. 6 304.Now transformer carries out fault offset, the vice-side winding of transformer T1 induces just lower negative induced voltage, electric current from the different name end of transformer T1 vice-side winding flow out → rectifier diode Do through circuit of reversed excitation 104 → to load and output capacitance Co releases energy → gets back to the Same Name of Ends of transformer T1 vice-side winding, concrete current direction is as shown in the dotted line 305 in Fig. 6.

In this process, inductance L 1 in voltage-multiplying circuit 102 is due to current break, induce left negative right positive induced electromotive force, as symbol logo in Fig. 6, therefore can regard the induced electromotive force sum of rectifier bridge 101 output voltage and inductance L 1 as to the bus capacitor C in circuit of reversed excitation 104 _dCwith the former limit charging of transformer T1, now the winding current direction, former limit of transformer T1 is from former limit different name end to Same Name of Ends, therefore the vice-side winding of transformer T1 induces just lower negative induced voltage, as in Fig. 6, symbol represents.

Simultaneously, because transformer T1 stores energy at N-MOS pipe Q1 turn on period, there is provided energy at N-MOS pipe Q1 blocking interval to load, be equivalent to the inductance in voltage-multiplying circuit 102 and the transformer in circuit of reversed excitation 104, at N-MOS pipe Q1 blocking interval simultaneously for load provides energy.

After inductance L 1 with the fault offset of transformer T1, circuit just enters resonance condition, inductance L 1, transformer T1 mainly separate with the resonant tank of the junction capacitance of diode D1 by the switching tube Q2 added, the resonant tank of inductance comprises: the resonant tank on input capacitance C1, inductance L 1 itself and the former limit of switching tube Q2, transformer T1 comprises: switching tube Q1, transformer T1 former limit winding and bus capacitor C _dC.If there is no switching tube Q2, when inductance L 1 resonance in voltage-multiplying circuit 102 is to left positive right negative, and input voltage lower than its induced voltage time, just there is negative pressure in the anode of the diode D1 in voltage-multiplying circuit 102, so diode D1 two ends just occur heavily stressed.After adding switching tube Q2, the anode of the diode D1 in voltage-multiplying circuit 102 will be clamped at zero volt, so would not occur the heavily stressed problem at diode D1 two ends.In other words, in current circuit after inductance L 1 fault offset, clamp circuit by the minimum voltage clamper of diode D1 anode at rectifier bridge negative output terminal current potential, make the voltage stress of diode D1 identical with the voltage stress of switching tube Q1, wherein, the voltage stress of switching tube Q1 refers to the voltage that its drain-source interpolar bears.

Controlling to realize overpower, under the source electrode of N-MOS pipe Q1, sealing in current sampling resistor, sampled signal is sent into drive circuit and control drive singal; In order to realize closed-loop control, sending into drive circuit at output sampling output voltage by feedback circuit, controlling the duty ratio of drive singal.

In Switching Power Supply of the present invention, the Thoughts on Optimized Design of each Primary Component is: first require that (comprise derate application) calculates transformer turns ratio in circuit of reversed excitation according to the stress of switching tube, then calculate limit, the source winding sensibility reciprocal of transformer in circuit of reversed excitation according to the first C meter, then calculate the parameter choose scope of inductance and the first electric capacity according to the conservation of energy.Wherein the turn ratio of transformer is identical with the computational methods of common flyback with the computational methods of limit, transformer source sensibility reciprocal, and limit, calculating transformer source sensibility reciprocal needs the voltage ripple of definition first electric capacity, does not repeat them here, the main computational process that inductance in topology is described.

Suppose that the operating frequency of Switching Power Supply is f _s, power frequency period is f, and AC-input voltage scope is [V _inmin, V _inmax], the capacitance C of the first electric capacity _dC, input power is P _in, the first electric capacity is η to the efficiency of transformer transmitting energy, and the minimum voltage at electric capacity two ends is V _min, limit, the transformer source sensibility reciprocal calculated is L _p.Known by the topological circuit of Fig. 2, the duty ratio of power work is only relevant with the voltage at the first electric capacity two ends, and during setting power supply input low pressure, the average duty ratio of Switching Power Supply is D _ave, as shown in Figure 4, in figure, the voltage waveform at the first electric capacity two ends is the first half near sinusoidal ripple to the voltage waveform at the first electric capacity two ends, and the latter half is similar to sawtooth waveforms, and what in this case calculate is conveniently regarded as sawtooth waveforms, and the average voltage at the first electric capacity two ends is V _{cdc_ave}, then have:

$V_{\mathrm{cdc}\_\mathrm{ave}}=\frac{\sqrt{2}{V}_{\mathrm{in}\min }+V_{\min }}{2}---\left(1\right)$

As shown in Figure 4, in half power frequency period, the first electric capacity is divided into charging period and does not charge period voltage waveform after the voltage waveform at the first electric capacity two ends and rectifier bridge, and the time of the first capacitor charging can be expressed as:

$t=\frac{\mathrm{\π}}{4\mathrm{\πf}}-\frac{\arcsin \left(\frac{V_{\min }}{\sqrt{2}{V}_{\mathrm{in}\min }}\right)}{2\mathrm{\πf}}---\left(2\right)$

Therefore, do not charge period at the first electric capacity, that is the first diode not turn on period, the energy that electric capacity transmits to transformer can be expressed as:

$E_1=\frac{1}{2}{C}_{\mathrm{DC}}{\left(\sqrt{2}{V}_{\mathrm{in}\min }\right)}^2-\frac{1}{2}{C}_{\mathrm{DC}}{V}_{\min }^2---\left(3\right)$

The average power of not charging period at the first electric capacity can be drawn:

$P_{\mathrm{ave}}=\frac{E_1}{\frac{\mathrm{\π}}{2\mathrm{\πf}}-t_2}---\left(4\right)$

The average power in first capacitor charging period is considered as identical with the average power in first capacitor discharge period, so can show that the energy that the first capacitor charging transmits to transformer period is:

E ₂＝P _ave×t (5)

In half power frequency period, the power of transformer transmission is:

$P_{\mathrm{in}\_c}=\frac{\frac{1}{\mathrm{\η}}(E_1+E_2)}{\frac{1}{2f}}---\left(6\right)$

Can show that average duty ratio is thus

$D_{\mathrm{ave}}=\sqrt{\frac{2P_{\mathrm{in}\_c}{L}_p{f}_s}{V_{\mathrm{cdc}\_\mathrm{ave}}^2}}---\left(7\right)$

The sensibility reciprocal of inductance is:

$L_1=\frac{D_{\mathrm{ave}}^2{\left(0.9V_{\mathrm{in}\min }\right)}^2}{{(P_{\mathrm{in}}-P_{\mathrm{in}\_c})}^2}---\left(8\right)$

According to the Optimization Design of Switching Power Supply of the present invention, the operating frequency of configuration switch power supply is 65KHz, and power frequency period is 20mS, and AC-input voltage scope is the capacitance 1uF of [85V, 264V], the first electric capacity, and input power is 4W, the first electric capacity C _dCefficiency to transformer transmitting energy is the minimum voltage at the 0.75, first electric capacity two ends is 50V, by the computational methods of common circuit of reversed excitation, show that limit, the source sensibility reciprocal of transformer is 1.5mH, above-mentioned parameter is brought into formula 1---formula 8, just can draw the value of inductance L 1:

$L_1=\frac{D_{\mathrm{ave}}^2{\left(0.9V_{\mathrm{in}\min }\right)}^2}{{(P_{\mathrm{in}}-P_{\mathrm{in}\_c})}^2}=1.03\mathrm{mH}$

In fact the final value of parameter is transformer sensibility reciprocal is 1.5mH, and inductance sensibility reciprocal is 968uH, now low pressure 85VAC input basis on, the minimum voltage of the bus capacitor recorded at about 50V, result of calculation and Theoretical Design result closely similar.Make great progress by commissioning experience and examination parameter before comparing, accomplished the combination of theory and practice.

Warp is 85VAC ~ 264VAC to input service voltage range, output voltage is 15V, power output is having electrochemical capacitor industrial power and adopting the sample of first embodiment of the invention scheme to test of 3W, the output ripple waveform recorded under low pressure input condition as shown in Figure 7, peak-to-peak value, within 100mV, meets industrial power requirement.

Second embodiment

Circuit shown in Fig. 8 is the circuit theory diagrams of the Switching Power Supply of second embodiment of the invention, a kind of Switching Power Supply, is with the difference part of the first embodiment: change the switching tube Q2 in the first embodiment into diode D2, concrete connected mode is expressed as follows:

The secondary of embodiment two is identical with the first embodiment, the rectification circuit on former limit is also identical with circuit of reversed excitation structure, therefore do not repeat them here, difference part---the voltage-multiplying circuit of main both elaborations, in voltage-multiplying circuit, one end of inductance L 1 connects the positive output end of rectifier bridge, in voltage-multiplying circuit, the other end of inductance L 1 connects the negative electrode of the second diode D2, and connect the anode of the first diode D1, the anode of the second diode D2 connects the negative output terminal of rectifier bridge, the negative electrode of the first diode D1 connects the drain electrode of the first switching tube and one end of the second electric capacity CDC, the other end of the second electric capacity CDC is connected with the different name end of transformer primary side winding.

Assuming that components and parts are ideal component in described circuit, under being all operated in discontinuous mode with the inductance L 1 in voltage-multiplying circuit with the transformer T1 in circuit of reversed excitation, carry out principle explanation, then the operation principle of one-period in the steady state:

(1) N-MOS pipe Q1 conducting:

When the Q1 conducting of N-MOS pipe, N-MOS pipe Q1 is equivalent to a wire, now the flow direction of electric current: from the output of rectifier bridge 101 just → the inductance L 1 → voltage-multiplying circuit 103 of voltage-multiplying circuit 103 diode D1 → voltage-multiplying circuit 103 in the output negative pole of switching tube Q1 → get back to rectifier bridge 101.In addition, main primary also has a current circuit, from the negative pole of the transformer T1 former limit winding of the N-MOS pipe Q1 → circuit of reversed excitation 104 of bus capacitor CDC positive pole → circuit of reversed excitation 104 → the get back to bus capacitor CDC of circuit of reversed excitation 104.Now transformer T1 carries out stored energy, and power supply vice-side winding relies on the electric energy stored in output capacitance Co.

In this process, the electric current flowing through inductance L 1 is started from scratch linear rising, and inductance L 1 starts energy storage; Bus capacitor simultaneously in circuit of reversed excitation is discharged to transformer primary side by N-MOS pipe Q1, the electric current of transformer T1 former limit winding is started from scratch and is linearly risen, the sense of current of transformer T1 former limit winding: flow to former limit different name end from former limit Same Name of Ends, and excitatory and by the former limit winding storage power of transformer T1 to the former limit winding of transformer T1; At this moment the vice-side winding of transformer T1 induces negative lower positive induced voltage, and this induced voltage and the turn ratio of transformer T1, former limit winding voltage are relevant, and under this voltage effect, diode Do is reverse-biased, not conducting.

(2) N-MOS pipe Q1 turns off then:

When N-MOS pipe Q1 conducting is complete, when then turning off rapidly, now N-MOS pipe Q1 is equivalent to open circuit, current direction now: from the output of rectifier bridge 101 just → the inductance L 1 → voltage-multiplying circuit 103 of voltage-multiplying circuit 103 diode D1 → circuit of reversed excitation in the output negative pole of transformer primary side winding → get back to rectifier bridge 101 of bus capacitor CDC → circuit of reversed excitation 104.Now transformer T1 carries out fault offset, the vice-side winding of transformer T1 induces just lower negative induced voltage, electric current from the different name end of transformer T1 vice-side winding flow out → rectifier diode Do through circuit of reversed excitation 104 → to load and output capacitance Co releases energy → gets back to the Same Name of Ends of transformer T1 vice-side winding.

In this process, inductance L 1 in voltage-multiplying circuit 103 is due to current break, induce left negative right positive induced electromotive force, therefore the induced electromotive force sum can regarding rectifier bridge 101 output voltage and inductance L 1 as is charged to the former limit of the bus capacitor CDC in circuit of reversed excitation 104 and transformer T1, now the winding current direction, former limit of transformer T1 is from former limit different name end to Same Name of Ends, therefore the vice-side winding of transformer T1 induces just lower negative induced voltage.

Simultaneously, because transformer T1 stores energy at N-MOS pipe Q1 turn on period, energy is provided to load at N-MOS pipe Q1 blocking interval, be equivalent to the inductance L 1 in voltage-multiplying circuit 103 and the transformer T1 in circuit of reversed excitation 104, at N-MOS pipe Q1 blocking interval simultaneously for load provides energy, therefore design standard when transformer T1 and inductance L 1 work independently under all can being less than same power, this is that existing topology cannot be accomplished.After inductance L 1 with the fault offset of transformer T1, circuit just enters resonance condition, the diode D2 added mainly by the anode potential clamper of diode D1 in voltage-multiplying circuit 102 about zero volt, and there will not be negative pressure, therefore the stress of diode D1 is still identical with the stress of N-MOS pipe Q1, there will not be the heavily stressed phenomenon of diode D1.In other words, in current circuit after inductance L 1 fault offset, clamp circuit by the minimum voltage clamper of diode D1 anode at rectifier bridge negative output terminal current potential, make the voltage stress of diode D1 identical with the voltage stress of switching tube Q1, wherein, the voltage stress of switching tube Q1 refers to the voltage that its drain-source interpolar bears.

Account form and all parameters of the second embodiment and the first embodiment are all identical, change the switching tube Q2 in the first embodiment into design that diode D2 does not affect circuit parameter, so the result of calculation of circuit parameter is identical with the first embodiment, do not repeat them here.

Below be only some embodiments of the present invention, it should be pointed out that above-mentioned preferred implementation should not be considered as limitation of the present invention, protection scope of the present invention should be as the criterion with claim limited range.For those skilled in the art, without departing from the spirit and scope of the present invention, can also make some improvements and modifications, these improvements and modifications also should be considered as protection scope of the present invention.

Claims (4)

1. the optimization method of stress equilibrium in Switching Power Supply, comprises and requires according to the stress of switching tube the transformer turns ratio that calculates in circuit of reversed excitation; Calculate limit, the source winding sensibility reciprocal of transformer in circuit of reversed excitation according to the first C meter, it is characterized in that: also comprise

The energy match relation of the first electric capacity, inductance and transformer is set up by the first diode, namely when switching tube conducting, the energized circuit of inductance and the energized circuit of transformer is separated by the first diode, when switching tube turns off, be communicated with inductance and transformer by the first diode, with in half power frequency period, the first electric capacity is divided into charging period and does not charge period, do not charge period at the first electric capacity, that is the first diode not turn on period; And the average power in first capacitor charging period is considered as identical with the average power in first capacitor discharge period;

According to the energy match relation of inductance and the first electric capacity and transformer, use conservation of energy principle, calculated the parameter choose scope of inductance by the capacitance of the first electric capacity, transformer turns ratio and limit, source winding sensibility reciprocal.

2. the optimization method of stress equilibrium in Switching Power Supply according to claim 1, is characterized in that: described in calculate the relationship of the parameter choose scope of inductance as follows,

According to the AC-input voltage value range [Vinmin, Vinmax] of design requirement, according to formula the average voltage calculating the first electric capacity two ends is V _{cdc_ave};

The energy match relation of the first electric capacity set up according to the first diode, inductance and transformer, in half power frequency period, the first electric capacity is divided into charging period and does not charge period, does not charge period at the first electric capacity, that is the first diode not turn on period, according to formula

$t=\frac{\mathrm{\π}}{4\mathrm{\πf}}-\frac{\arcsin \left(\frac{V_{\min }}{\sqrt{2}{V}_{\mathrm{in}\min }}\right)}{2\mathrm{\πf}}$

$E_1=\frac{1}{2}{C}_{\mathrm{DC}}{\left(\sqrt{2}{V}_{\mathrm{in}\min }\right)}^2-\frac{1}{2}{C}_{\mathrm{DC}}{V}_{\min }^2$

$P_{\mathrm{ave}}=\frac{E_1}{\frac{\mathrm{\π}}{2\mathrm{\πf}}-t_2},$

Draw the average power Pave do not charged period at the first electric capacity;

The average power in first capacitor charging period is considered as identical, according to formula E with the average power in first capacitor discharge period ₂=P _ave× t, draws the ENERGY E 2 that the first capacitor charging transmits to transformer period;

According to formula draw the power P in_c of transformer transmission in half power frequency period;

According to formula draw average duty ratio Dave;

According to formula calculate the sensibility reciprocal of inductance.

3. Switching Power Supply, comprise rectifier bridge, the first electric capacity, inductance, circuit of reversed excitation and the second electric capacity, described rectifier bridge has positive output end and negative output terminal, and described first Capacitance parallel connection is between the positive output end and negative output terminal of rectifier bridge; The former limit circuit of described circuit of reversed excitation comprises the former limit winding of transformer, the first switching tube and drives the driver module of the first switching tube, it is characterized in that:

Also comprise the first diode and by the clamp circuit of the anode clamper of the first diode at the negative output terminal current potential of rectifier bridge, described clamp circuit, be made up of second switch pipe, the concrete annexation of described switching power circuit is, the positive output end of rectifier bridge is connected with one end of inductance, the other end of inductance is connected with the drain electrode of second switch pipe and the anode of the first diode respectively, and the source electrode of second switch pipe is connected with the negative output terminal of rectifier bridge; The negative electrode of the first diode is connected with one end of the second electric capacity and the drain electrode of the first switching tube respectively, and the source electrode of the first switching tube is connected with the Same Name of Ends of former limit winding, and the different name end of former limit winding is connected with the other end of the second electric capacity; The Same Name of Ends of former limit winding is also connected with the negative output terminal of rectifier bridge; Second switch pipe Q2 and the first switching tube Q1 uses same driver module;

Described first diode D1 separates/is communicated with the loop of inductance L 1 and transformer T1, namely

When the first switching tube and the conducting of second switch pipe, inductance forms the energized circuit of inductance through second switch pipe; Meanwhile, the former limit winding of the second electric capacity through transformer, the energized circuit of the first switching tube formation transformer, now diode D1 separates the loop of inductance L 1 and transformer T1;

When the first switching tube and second switch pipe turn off, first diode is communicated with inductance and transformer, form single current circuit, inductance and transformer to be exported at the energy trasfer that the excitation stage stores, namely set up the energy match relation of the first electric capacity, inductance and transformer by the first diode.

4. Switching Power Supply according to claim 3, it is characterized in that: the energy match relation of described first electric capacity, inductance and transformer, show as following mathematical relationship, namely the span of the first electric capacity, transformer and inductance estimates value successively by following formula

According to the AC-input voltage value range [Vinmin, Vinmax] of design requirement, according to formula the average voltage calculating the first electric capacity two ends is V _{cdc_ave};

The energy match relation of the first electric capacity set up according to the first diode, inductance and transformer, in half power frequency period, the first electric capacity is divided into charging period and does not charge period, does not charge period at the first electric capacity, that is the first diode not turn on period, according to formula

$t=\frac{\mathrm{\π}}{4\mathrm{\πf}}-\frac{\arcsin \left(\frac{V_{\min }}{\sqrt{2}{V}_{\mathrm{in}\min }}\right)}{2\mathrm{\πf}}$

$E_1=\frac{1}{2}{C}_{\mathrm{DC}}{\left(\sqrt{2}{V}_{\mathrm{in}\min }\right)}^2-\frac{1}{2}{C}_{\mathrm{DC}}{V}_{\min }^2$

$P_{\mathrm{ave}}=\frac{E_1}{\frac{\mathrm{\π}}{2\mathrm{\πf}}-t_2},$

Draw the average power Pave do not charged period at the first electric capacity;

The average power in first capacitor charging period is considered as identical, according to formula E with the average power in first capacitor discharge period ₂=P _ave× t, draws the ENERGY E 2 that the first capacitor charging transmits to transformer period;

According to formula draw the power P in_c of transformer transmission in half power frequency period;

According to formula draw average duty ratio Dave;

According to formula calculate the sensibility reciprocal of inductance.