CN104300503A - Switching mode power supply input voltage range expansion circuit and design method thereof - Google Patents

Abstract

The invention discloses a switching mode power supply input voltage range expansion circuit and a design method of the expansion circuit. The expansion circuit comprises a first voltage expansion circuit connected between a direct current voltage input circuit and a switching mode power supply chip. The direct current voltage input circuit is an alternating current and direct current converting circuit or a direct current voltage source. The switching mode power supply chip is provided with the overvoltage and undervoltage protection end. The positive pole voltage output end of the first voltage expansion circuit is connected with the overvoltage and undervoltage protection end of the switching mode power supply chip. The negative pole voltage output end of the first voltage expansion circuit is connected with the grounded end of the switching mode power supply chip. The invention further discloses the design method of the switching mode power supply input voltage range expansion circuit. According to the expansion circuit and the design method, implementation is convenient, cost is low, the adaptability of a switching mode power supply to a power grid can be improved, the application range of the switching mode power supply is widened, the work reliability of the switching mode power supply can be effectively improved, practicality is high, and application and popularization are convenient.

Description

Switching Power Supply input voltage range expands circuit and method for designing thereof

Technical field

The invention belongs to switch power technology field, be specifically related to a kind of Switching Power Supply input voltage range and expand circuit and method for designing thereof.

Background technology

Along with the develop rapidly of science and technology, the relation of Switching Power Supply and people is day by day close, plays more and more important effect in daily life.In prior art, the overvoltage of Switching Power Supply breaker in middle power supply chip and under-voltage protection scope are general all narrow, such as that common is about 1V ~ 4V, and the overvoltage of switching power source chip and under-voltage protection scope limit Switching Power Supply input voltage range, and, in prior art, generally direct voltage input circuit be connected simple resistant series bleeder circuit between switching power source chip, make the input voltage range of Switching Power Supply can only be 165VAC ~ 265VAC, more weak to the adaptive capacity of electrical network, and the application of Switching Power Supply is restricted, therefore, it is significant that design Switching Power Supply input voltage range expands circuit.

Summary of the invention

Technical problem to be solved by this invention is for above-mentioned deficiency of the prior art, provide a kind of structure simple, realize convenient and cost is low, can strengthen the adaptive capacity of Switching Power On Electric Net, widened the range of application of Switching Power Supply, effectively can improve the Switching Power Supply input voltage range of the reliability of Switching Power Supply work expands circuit.

For solving the problems of the technologies described above, the technical solution used in the present invention is: a kind of Switching Power Supply input voltage range expands circuit, it is characterized in that: comprise the first voltage expanded circuit be connected between direct voltage input circuit and switching power source chip, described direct voltage input circuit is ac-dc converter circuit or direct voltage source, with overvoltage and under-voltage protection end on described switching power source chip, the cathode voltage output of the first voltage expanded circuit connects with the overvoltage of switching power source chip and under-voltage protection end, the cathode voltage output of the first voltage expanded circuit connects with the earth terminal of switching power source chip.

Above-mentioned Switching Power Supply input voltage range expands circuit, it is characterized in that: comprise n the second voltage expanded circuit be connected between the first voltage expanded circuit and switching power source chip, the cathode voltage input of first second voltage expanded circuit connects with the cathode voltage output of the first voltage expanded circuit, the cathode voltage input of first second voltage expanded circuit connects with the cathode voltage output of the first voltage expanded circuit, in two adjacent the second voltage expanded circuits, the cathode voltage input of a rear second voltage expanded circuit connects with the cathode voltage output of previous second voltage expanded circuit, in two adjacent the second voltage expanded circuits, the cathode voltage input of a rear second voltage expanded circuit connects with the cathode voltage output of previous second voltage expanded circuit, an end cathode voltage output for the second voltage expanded circuit connects with the overvoltage of switching power source chip and under-voltage protection end, the cathode voltage output of end the second voltage expanded circuit connects with the earth terminal of switching power source chip, wherein, the value of n is natural number.

Above-mentioned Switching Power Supply input voltage range expands circuit, it is characterized in that: described first voltage expanded circuit is by triode Q ₁and resistance R ₁, R ₂, R ₃, R ₄, R ₅and R ₆composition, described resistance R ₁one end be the cathode voltage input Vi+ of the first voltage expanded circuit and connect with the cathode voltage output of direct voltage input circuit, described resistance R ₁the other end and resistance R ₂one end and resistance R ₅one end connect and be the cathode voltage output of the first voltage expanded circuit, described resistance R ₂the other end and resistance R ₃one end and resistance R ₄one end connect, described resistance R ₅the other end and triode Q ₁base stage and resistance R ₆one end connect, described resistance R ₄the other end and triode Q ₁collector electrode connect, described resistance R ₃the other end and triode Q ₁emitter and resistance R ₆the other end connect, described resistance R ₃the other end be the cathode voltage input Vi-of the first voltage expanded circuit and connect with the cathode voltage output of direct voltage input circuit, described resistance R ₆the other end be the cathode voltage output of the first voltage expanded circuit.

Above-mentioned Switching Power Supply input voltage range expands circuit, it is characterized in that: i-th the second voltage expanded circuit is by triode Q _i+1and resistance R _{3 (i+1)+1}, R _(3i+1)+2and R _{3 (i+1)+3}composition, described resistance R _(3i+1)+2one end be the cathode voltage input of i-th the second voltage expanded circuit, described resistance R _(3i+1)+2the other end and triode Q _i+1base stage and resistance R _{3 (i+1)+3}one end connect, described triode Q _i+1collector electrode and resistance R _{3 (i+1)+1}one end connect, described resistance R _{3 (i+1)+1}the other end be i-th the second voltage expanded circuit cathode voltage output end vo+, described triode Q _i+1the cathode voltage input of transmitting very i-th the second voltage expanded circuit, described resistance R _{3 (i+1)+3}the other end be i-th the second voltage expanded circuit cathode voltage output end vo-; Wherein, the value of i is the natural number of 1 ~ n.

Present invention also offers a kind of method step simple, greatly can simplify Switching Power Supply input voltage range and expand the circuit structure of circuit and the Switching Power Supply input voltage range that can solve the problem widening Switching Power Supply input voltage range at low cost expands the method for designing of circuit, it is characterized in that the method comprises the following steps:

Step one, determine the minimum value V of input voltage _iminwith the maximum V of input voltage _imax;

The resistance R of step 2, selection suitable parameters ₁, resistance R ₂, resistance R ₃, resistance R ₄, resistance R ₅with resistance R ₆, and connect described triode Q ₁and resistance R ₁, resistance R ₂, resistance R ₃, resistance R ₄, resistance R ₅with resistance R ₆, form the first voltage expanded circuit; Detailed process is as follows:

Step 201, according to formula choose resistance R ₃resistance, wherein, V _ominfor the under-voltage protection voltage of switching power source chip, V _omaxfor the overvoltage protection voltage of switching power source chip, I ₁for input voltage is minimum value V _imintime flow through resistance R ₂with resistance R ₃electric current;

Step 202, according to formula choose resistance R ₆resistance, wherein, I ₂for input voltage is minimum value V _imintime flow through resistance R ₅with resistance R ₆electric current;

Step 203, according to formula I ₁(R ₂+ R ₃)=I ₂(R ₅+ R ₆)=U _x1determine resistance R ₂with resistance R ₅value relatable, and according to resistance R ₃with resistance R ₆resistance level choose resistance R ₂resistance and resistance R ₅resistance, wherein, U _x1for input voltage is minimum value V _imintime resistance R ₂with resistance R ₃place branch road and resistance R ₅with resistance R ₆the shunt voltage of place branch road;

Step 204, according to formula determine resistance R ₁minimum resistance R _1min;

Step 205, according to formula $I_3=\frac{V_{o\max }}{V_{o\min }}{I}_1,V_{o\min }\≤I_3\frac{R_3{R}_4}{R_3+R_4}\≤V_{o\max }$ Choose resistance R ₄resistance, wherein, I ₃for input voltage is maximum V _imaxtime flow through resistance R ₂with resistance R ₃electric current;

Step 206, according to formula $R_m=\frac{R_3{R}_4}{R_3+R_4},I_3(R_2+R_m)=I_4(R_5+R_6)=U_{x2}$ Determine electric current I ₄and voltage U _x2, wherein, R _mfor resistance R ₃with resistance R ₄equivalent resistance in parallel, I ₄for input voltage is maximum V _imaxtime flow through resistance R ₅with resistance R ₆electric current, U _x2for input voltage is maximum V _imaxtime resistance R ₂with resistance R ₃place branch road and resistance R ₅with resistance R ₆the shunt voltage of place branch road;

Step 207, according to formula determine resistance R ₁maximum value R _1max, and according to formula R _1min≤ R ₁≤ R _1maxchoose resistance R ₁resistance;

Step 208, by resistance R ₁one end connect with the cathode voltage output of direct voltage input circuit, by resistance R ₁the other end and resistance R ₂one end and resistance R ₅one end connect, by resistance R ₂the other end and resistance R ₃one end and resistance R ₄one end connect, by resistance R ₅the other end and triode Q ₁base stage and resistance R ₆one end connect, by resistance R ₄the other end and triode Q ₁collector electrode connect, by resistance R ₃the other end and triode Q ₁emitter and resistance R ₆the other end connect, by resistance R ₃the other end be connect with the cathode voltage output of direct voltage input circuit;

Step 3, according to formula $\left\{\begin{array}{c}{\tilde{V}}_{i\min }=\frac{(R_{L1}+R_1)(R_2+R_3)}{R_{L1}{R}_3}{V}_{o\min }\\ {\tilde{V}}_{i\max }=\frac{(R_{L1}^{\′}+R_1)(R_2+R_{M1})}{R_{L1}^{\′}{R}_{M1}}{V}_{o\max }\end{array}\right.$ Calculate the actual input voltage minimum value of the first voltage expanded circuit with actual input voltage maximum and judged whether when and time, terminate the design that described Switching Power Supply input voltage range expands circuit; Otherwise, perform step 4; Wherein, resistance R _l1resistance be $R_{L1}=\frac{(R_2+R_3)(R_5+R_6)}{(R_2+R_3)+(R_5+R_6)},$ Resistance resistance be $R_{L1}^{\′}=\frac{(R_2+R_{M1})(R_5+R_6)}{(R_2+R_{M1})+(R_5+R_6)},$ Resistance R _m1resistance be $R_{M1}=\frac{R_3{R}_4}{R_3+R_4};$

Step 4, get n=1, the components and parts of formation the n-th the second voltage expanded circuit are selected according to the component parameter system of selection of the second voltage expanded circuit, connect each components and parts and form the second voltage expanded circuit, and the n-th the second voltage expanded circuits are connected between the first voltage expanded circuit and switching power source chip; Wherein, the component parameter system of selection of i-th the second voltage expanded circuit is:

Step I, according to formula R _{3 (i+1)+1}=a ⁱr ₄choose resistance R _{3 (i+1)+1}resistance, wherein, the value of a is the real number of 2 ~ 3;

Step II, according to formula R _(3i+1)+2=R ₅choose resistance R _(3i+1)+2resistance;

Step III, according to formula choose resistance R _{3 (i+1)+3}resistance, wherein, the value of b is the real number of 2 ~ 3;

Wherein, n is the number of the second voltage expanded circuit 3 and the value of n is natural number, and the value of i is the natural number of 0 ~ n;

Step 5, according to formula $\left\{\begin{array}{c}{\tilde{V}}_{i\min }^{\′}=\frac{(R_{L(n-1)}+R_1)(R_2+R_3)}{R_{L(n-1)}{R}_3}{V}_{o\min }\\ {\tilde{V}}_{i\max }^{\′}=\frac{(R_{L(n+1)}^{\′}+R_1)\left({R_2+R}_{M(n+1)}\right)}{R_{L(n+1)}^{\′}{R}_{M(n+1)}}{V}_{o\max }\end{array}\right.$ Calculate the actual input voltage minimum value that the Switching Power Supply input voltage range be made up of the first voltage expanded circuit and the individual second voltage expanded circuit of n expands circuit with actual input voltage maximum and judged whether and when and time, terminate the design that described Switching Power Supply input voltage range expands circuit; Otherwise, perform step 6; Wherein, resistance R _{l (n+1)}resistance be the value of j is the natural number of 0 ~ n+1; Resistance resistance be $R_{L(n+1)}^{\′}=\frac{(R_2+R_{M(n+1)})\underset{j=1}{\overset{n+1}{\mathrm{\Π}}}(R_{3j+2}+R_{3j+3})}{\underset{j=1}{\overset{n+1}{\mathrm{\Π}}}(R_{3j+2}+R_{3j+3})+(R_2+R_{M(n+1)})\underset{j=1}{\overset{n+1}{\mathrm{\Σ}}}\underset{j=1,j\≠j}{\overset{n+1}{\mathrm{\Π}}}(R_{3j+2}+R_{3j+3})},$ The value of j is the natural number of 1 ~ n+1; Resistance R _{m (n+1)}resistance be $R_{M(n+1)}=\frac{R_3\underset{j=1}{\overset{n+1}{\mathrm{\Π}}}{R}_{3j+1}}{\underset{j=1}{\overset{n+1}{\mathrm{\Π}}}{R}_{3j+1}+R_3\underset{j=1}{\overset{n+1}{\mathrm{\Σ}}}\underset{j=1,j\≠j}{\overset{n+1}{\mathrm{\Π}}}{R}_{3j+1}},$ The value of j is the natural number of 1 ~ n+1;

Step 6, by the value of n increase 1, the components and parts of formation the n-th the second voltage expanded circuit are selected according to the component parameter system of selection of the second voltage expanded circuit, connect each components and parts composition the n-th the second voltage expanded circuit, and the n-th the second voltage expanded circuits are connected between (n-1)th the second voltage expanded circuit and switching power source chip; Return step 5.

The present invention compared with prior art has the following advantages:

1, Switching Power Supply input voltage range of the present invention expands the structure of circuit simply, and realization is convenient and cost is low.

2, the input voltage range of Switching Power Supply can be expanded as 65VAC-800VAC from 165VAC ~ 265VAC by Switching Power Supply input voltage range expansion circuit of the present invention, Switching Power Supply input voltage range of the present invention is expanded circuit to be added in Switching Power Supply, the adaptive capacity of Switching Power On Electric Net can be strengthened, the application of Switching Power Supply can be made unrestricted, widened the range of application of Switching Power Supply.

3, Switching Power Supply input voltage range of the present invention being expanded circuit is added in Switching Power Supply, and when input voltage is in the scope set, it is inoperative that this Switching Power Supply input voltage range expands circuit; And when the maximum of input voltage higher than setting range or the minimum value lower than setting range, this Switching Power Supply input voltage range expands circuit can shutdown switch power supply, Switching Power Supply is played a protective role; When in the scope that input voltage returns to setting, Switching Power Supply can also self-recoverage; Switching Power Supply input voltage range of the present invention expands the reliability that circuit can improve Switching Power Supply work effectively, and the service behaviour avoiding Switching Power Supply is subject to the impact of input voltage range.

4, the method step of the method for designing of Switching Power Supply input voltage range expansion circuit of the present invention is simple, and method for designing have employed the just not numerous mentality of designing of energy letter, when there being the first voltage expanded circuit to satisfy the demand, just do not add the second voltage expanded circuit, when there being a second voltage expanded circuit to satisfy the demand, just do not add multiple second voltage expanded circuit, greatly can simplify the circuit structure that Switching Power Supply input voltage range expands circuit, and the problem widening Switching Power Supply input voltage range can be solved at low cost.

5, of the present invention practical, result of use is good, is convenient to promote the use of.

In sum, the present invention realizes convenient and cost is low, can strengthen the adaptive capacity of Switching Power On Electric Net, widen the range of application of Switching Power Supply, effectively can improve the reliability of Switching Power Supply work, practical, is convenient to promote the use of.

Below by drawings and Examples, technical scheme of the present invention is described in further detail.

Accompanying drawing explanation

Fig. 1 is the schematic block circuit diagram that the embodiment of the present invention 1 breaker in middle power input voltage scope expands circuit.

Fig. 2 is the circuit theory diagrams of the first voltage expanded circuit in the embodiment of the present invention 1.

Fig. 3 is the schematic block circuit diagram that the embodiment of the present invention 2 breaker in middle power input voltage scope expands circuit.

Fig. 4 is the circuit connecting relation schematic diagram of the first voltage expanded circuit and the 1st the second voltage expanded circuit in the embodiment of the present invention 2.

Fig. 5 is the schematic block circuit diagram that the embodiment of the present invention 3 breaker in middle power input voltage scope expands circuit.

Fig. 6 is the circuit connecting relation schematic diagram of the first voltage expanded circuit in the embodiment of the present invention 3, the 1st the second voltage expanded circuit and the 2nd the second voltage expanded circuit.

Fig. 7 is the using state schematic diagram that Switching Power Supply input voltage range of the present invention expands circuit.

Description of reference numerals:

1-direct voltage input circuit; 2-the first voltage expanded circuit; 3-the second voltage expanded circuit;

4-switching power source chip; 5-input voltage range expands circuit;

6-isolated switch transformer; 7-voltage feedback circuit; 8-AC power.

Embodiment

Embodiment 1

As depicted in figs. 1 and 2; Switching Power Supply input voltage range of the present invention expands circuit; comprise the first voltage expanded circuit 2 be connected between direct voltage input circuit 1 and switching power source chip 4; described direct voltage input circuit 1 is ac-dc converter circuit or direct voltage source; with overvoltage and under-voltage protection end on described switching power source chip 4; the cathode voltage output of the first voltage expanded circuit 2 connects with the overvoltage of switching power source chip 4 and under-voltage protection end, and the cathode voltage output of the first voltage expanded circuit 2 connects with the earth terminal of switching power source chip 4.

As shown in Figure 2, in the present embodiment, described first voltage expanded circuit 2 is by triode Q ₁and resistance R ₁, R ₂, R ₃, R ₄, R ₅and R ₆composition, described resistance R ₁one end be the cathode voltage input Vi+ of the first voltage expanded circuit 2 and connect with the cathode voltage output of direct voltage input circuit 1, described resistance R ₁the other end and resistance R ₂one end and resistance R ₅one end connect and be the first voltage expanded circuit 2 cathode voltage output end vo+, described resistance R ₂the other end and resistance R ₃one end and resistance R ₄one end connect, described resistance R ₅the other end and triode Q ₁base stage and resistance R ₆one end connect, described resistance R ₄the other end and triode Q ₁collector electrode connect, described resistance R ₃the other end and triode Q ₁emitter and resistance R ₆the other end connect, described resistance R ₃the other end be the cathode voltage input Vi-of the first voltage expanded circuit 2 and connect with the cathode voltage output of direct voltage input circuit 1, described resistance R ₆the other end be the first voltage expanded circuit 2 cathode voltage output end vo-.

In the present embodiment, the method for designing that Switching Power Supply input voltage range of the present invention expands circuit is:

Step one, determine the minimum value V of input voltage _iminwith the maximum V of input voltage _imax;

In the present embodiment, get V _imin=40V, V _imax=400V;

The resistance R of step 2, selection suitable parameters ₁, resistance R ₂, resistance R ₃, resistance R ₄, resistance R ₅with resistance R ₆, and connect described triode Q ₁and resistance R ₁, resistance R ₂, resistance R ₃, resistance R ₄, resistance R ₅with resistance R ₆, form the first voltage expanded circuit 2; Detailed process is as follows:

Step 201, according to formula choose resistance R ₃resistance, wherein, V _ominfor the under-voltage protection voltage of switching power source chip 4, V _omaxfor the overvoltage protection voltage of switching power source chip 4, I ₁for input voltage is minimum value V _imintime flow through resistance R ₂with resistance R ₃electric current;

In the present embodiment, known V _omin=0.7V, V _omax=3.5V, I ₁=5uA; According to formula calculate: 140K Ω≤R ₃≤ 700K Ω, chooses R ₃=700K Ω;

Step 202, according to formula choose resistance R ₆resistance, wherein, I ₂for input voltage is minimum value V _imintime flow through resistance R ₅with resistance R ₆electric current;

In the present embodiment, known I ₂=4uA, according to formula calculate R ₆=125K Ω, directly can get R in theory ₆=125K Ω, looking for producer to customize resistance value is the resistance R of 125K Ω ₆but, consider that 125K Ω is not conventional resistance, conveniently, get R ₆=120K Ω;

Step 203, according to formula I ₁(R ₂+ R ₃)=I ₂(R ₅+ R ₆)=U _x1determine resistance R ₂with resistance R ₅value relatable, and according to resistance R ₃with resistance R ₆resistance level choose resistance R ₂resistance and resistance R ₅resistance, wherein, U _x1for input voltage is minimum value V _imintime resistance R ₂with resistance R ₃place branch road and resistance R ₅with resistance R ₆the shunt voltage of place branch road;

In the present embodiment, known R ₃=700K Ω, I ₁=5uA, I ₂=4uA, R ₆=120K Ω; According to formula I ₁(R ₂+ R ₃)=I ₂(R ₅+ R ₆)=U _x1the resistance R determined ₂with resistance R ₅value relatable be 4R ₅=5R ₂+ 3000K Ω; Again due to resistance R ₃with resistance R ₆resistance level be K Ω level, therefore get R ₂=1000K Ω, R ₅=2000K Ω; Now, U _x1=8.5V.

Step 204, according to formula determine resistance R ₁minimum resistance R _1min;

In the present embodiment, known V _imin=40V, U _x1=8.5V, I ₁=5uA, I ₂=4uA; According to formula calculate R _1min=3500K Ω;

Step 205, according to formula $I_3=\frac{V_{o\max }}{V_{o\min }}{I}_1,V_{o\min }\≤I_3\frac{R_3{R}_4}{R_3+R_4}\≤V_{o\max }$ Choose resistance R ₄resistance, wherein, I ₃for input voltage is maximum V _imaxtime flow through resistance R ₂with resistance R ₃electric current;

In the present embodiment, known V _omin=0.7V, V _omax=3.5V, I ₁=5uA; According to formula calculate I ₃=25uA, again known R ₃=700K Ω, according to formula calculate $28\mathrm{K\Ω}\≤\frac{{700R}_4}{700+R_4}\≤140\mathrm{K\Ω},$ Choose R ₄=150K Ω;

Step 206, according to formula i ₃(R ₂+ R _m)=I ₄(R ₅+ R ₆)=U _x2determine electric current I ₄and voltage U _x2, wherein, R _mfor resistance R ₃with resistance R ₄equivalent resistance in parallel, I ₄for input voltage is maximum V _imaxtime flow through resistance R ₅with resistance R ₆electric current, U _x2for input voltage is maximum V _imaxtime resistance R ₂with resistance R ₃place branch road and resistance R ₅with resistance R ₆the shunt voltage of place branch road;

In the present embodiment, known R ₃=700K Ω, R ₄=150K Ω; According to formula calculate R _m=124K Ω, again known R ₂=1000K Ω, I ₃=25uA, R ₅=2000K Ω, R ₆=120K Ω; According to formula I ₃(R ₂+ R _m)=I ₄(R ₅+ R ₆)=U _x2calculate U _x2=28V, I ₄=13uA;

Step 207, according to formula determine resistance R ₁maximum value R _1max, and according to formula R _1min≤ R ₁≤ R _1maxchoose resistance R ₁resistance;

In the present embodiment, known V _imax=400V, I ₃=25uA, I ₄=13uA, U _x2=28V; According to formula calculate R _1max=9789K Ω; According to formula R _1min≤ R ₁≤ R _1maxobtain 3500K Ω≤R ₁≤ 9789K Ω, chooses R ₁=9000K Ω;

Step 208, by resistance R ₁one end connect with the cathode voltage output of direct voltage input circuit 1, by resistance R ₁the other end and resistance R ₂one end and resistance R ₅one end connect, by resistance R ₂the other end and resistance R ₃one end and resistance R ₄one end connect, by resistance R ₅the other end and triode Q ₁base stage and resistance R ₆one end connect, by resistance R ₄the other end and triode Q ₁collector electrode connect, by resistance R ₃the other end and triode Q ₁emitter and resistance R ₆the other end connect, by resistance R ₃the other end be connect with the cathode voltage output of direct voltage input circuit 1;

Step 3, according to formula $\left\{\begin{array}{c}{\tilde{V}}_{i\min }=\frac{(R_{L1}+R_1)(R_2+R_3)}{R_{L1}{R}_3}{V}_{o\min }\\ {\tilde{V}}_{i\max }=\frac{(R_{L1}^{\′}+R_1)(R_2+R_{M1})}{R_{L1}^{\′}{R}_{M1}}{V}_{o\max }\end{array}\right.$ Calculate the actual input voltage minimum value of the first voltage expanded circuit 2 with actual input voltage maximum and judged whether and when and time, terminate the design that described Switching Power Supply input voltage range expands circuit; Otherwise, perform step 4; Wherein, resistance R _l1resistance be $R_{L1}=\frac{(R_2+R_3)(R_5+R_6)}{(R_2+R_3)+(R_5+R_6)},$ Resistance resistance be $R_{L1}^{\′}=\frac{(R_2+R_{M1})(R_5+R_6)}{(R_2+R_{M1})+(R_5+R_6)},$ Resistance R _m1resistance be

In the present embodiment, known R ₂=1000K Ω, R ₃=700K Ω, R ₄=150K Ω, R ₅=2000K Ω, R ₆=120K Ω; According to formula calculate R _l1=943K Ω; According to formula $R_{L1}^{\&prime;}=\frac{(R_2+R_{M1})(R_5+R_6)}{(R_2+R_{M1})+(R_5+R_6)},$ Calculate according to formula calculate R _m1=124K Ω; Known V again _omin=0.7V, V _omax=3.5V; According to formula $\left\{\begin{array}{c}{\tilde{V}}_{i\min }=\frac{(R_{L1}+R_1)(R_2+R_3)}{R_{L1}{R}_3}{V}_{o\min }\\ {\tilde{V}}_{i\max }=\frac{(R_{L1}^{\&prime;}+R_1)(R_2+R_{M1})}{R_{L1}^{\&prime;}{R}_{M1}}{V}_{o\max }\end{array}\right.$ Calculate ${\tilde{V}}_{i\min }=18V,{\tilde{V}}_{i\max }=420V;$ Due to 18V<40V and 400V<420V, namely have and therefore the design that described Switching Power Supply input voltage range expands circuit is terminated.

It should be noted that, in order to value and convenience of calculation, the above U _x1, R _m, U _x2, I ₄, R _1max, R _l1, r _m1, with result of calculation all have employed the counting reservation method rounded up.

In the present embodiment, the operation principle that Switching Power Supply input voltage range of the present invention expands circuit is: resistance R ₅with resistance R ₆for triode Q ₁divider resistance, when input voltage is also low than the under-voltage protection voltage of switching power source chip 4, triode Q ₁base voltage be less than triode Q ₁conducting voltage, now, resistance R ₄do not have place in circuit, whole Switching Power Supply input voltage range is expanded circuit and is equivalent to only by resistance R ₂, resistance R ₃, resistance R ₅with resistance R ₆form, resistance R ₂with resistance R ₃after series connection again with the resistance R connected ₅with resistance R ₆parallel connection, and then overall and resistance R ₁series connection; The voltage of the cathode voltage output end vo of the first voltage expanded circuit 2+get is less than the under-voltage protection voltage of switching power source chip 4, and switching power source chip 4 does not work.Along with the rising of input voltage, time on the under-voltage protection voltage that input voltage is elevated to switching power source chip 4, switching power source chip 4 is started working, resistance R ₆dividing potential drop increase, triode Q ₁conducting, along with triode Q ₁the increase of conducting degree finally to saturation conduction, in the process, resistance R ₄access loop gradually, from the cathode voltage output end vo of the first voltage expanded circuit 2+diminish with the equivalent resistance of the cathode voltage output end vo of the first voltage expanded circuit 2-see into, the cathode voltage output end vo of the first voltage expanded circuit 2+to the first voltage expanded circuit 2 cathode voltage output end vo-output voltage relative to the input voltage of the cathode voltage input Vi+ to the cathode voltage input Vi-of the first voltage expanded circuit 2 of the first voltage expanded circuit 2 in slow increase, but the voltage of the cathode voltage output end vo+output of the first voltage expanded circuit 2 is also in the overvoltage protection voltage range of switching power source chip 4, when input voltage continues to raise, due to from the cathode voltage output end vo of the first voltage expanded circuit 2+no longer change with the equivalent resistance of the cathode voltage output end vo of the first voltage expanded circuit 2-see into, the voltage linear that equivalent resistance is got increases, when input voltage reaches the overvoltage protection voltage of switching power source chip 4, switching power source chip 4 quits work.

When in the scope that input voltage is reduced to setting, whether whether self-recoverage will have self-recovering function according to switching power source chip 4 and determine Switching Power Supply.When switching power source chip 4 has self-recovering function, along with the reduction of input voltage, time under the overvoltage protection voltage that input voltage is reduced to switching power source chip 4, switching power source chip 4 is started working, when input voltage continues to reduce, and resistance R ₆on voltage reduce gradually, triode Q ₁base voltage reduce until turn off gradually, resistance R ₄excise from circuit gradually; from the cathode voltage output end vo of the first voltage expanded circuit 2+increase with the equivalent resistance of the cathode voltage output end vo of the first voltage expanded circuit 2-see into; the cathode voltage output end vo of the first voltage expanded circuit 2+to the first voltage expanded circuit 2 cathode voltage output end vo-output voltage in slow reduction; but change less; the voltage of the cathode voltage output end vo+output of the first voltage expanded circuit 2 does not also reach the under-voltage protection point of switching power source chip 4, at this moment resistance R ₄excise from circuit; when input voltage reduces again; from the cathode voltage output end vo of the first voltage expanded circuit 2+substantially constant with the equivalent resistance of the cathode voltage output end vo of the first voltage expanded circuit 2-see into; the voltage linear that equivalent resistance is got reduces; when input voltage reaches the under-voltage protection voltage of switching power source chip 4, switching power source chip 4 quits work.

Embodiment 2

As shown in Figure 3 and Figure 4, the Switching Power Supply input voltage range of the present embodiment expands circuit as different from Example 1: Switching Power Supply input voltage range of the present invention expands circuit, also comprise 1 the second voltage expanded circuit 3 be connected between the first voltage expanded circuit 2 and switching power source chip 4, the cathode voltage input of the second voltage expanded circuit 3 connects with the cathode voltage output of the first voltage expanded circuit 2, the cathode voltage input of the second voltage expanded circuit 3 connects with the cathode voltage output of the first voltage expanded circuit 2, the cathode voltage output of the second voltage expanded circuit 3 connects with the overvoltage of switching power source chip 4 and under-voltage protection end, the cathode voltage output of the second voltage expanded circuit 3 connects with the earth terminal of switching power source chip 4.Second voltage expanded circuit 3 is by triode Q ₂and resistance R ₇, R ₈and R ₉composition, described resistance R ₈one end be the cathode voltage input of the second voltage expanded circuit 3, described resistance R ₈the other end and triode Q ₂base stage and resistance R ₉one end connect, described triode Q ₂collector electrode and resistance R ₇one end connect, described resistance R ₇the other end be the second voltage expanded circuit 3 cathode voltage output end vo+, described triode Q ₂the cathode voltage input of transmitting very the second voltage expanded circuit 3, described resistance R ₉the other end be the second voltage expanded circuit 3 cathode voltage output end vo-.All the other structures are all identical with embodiment 1.

The Switching Power Supply input voltage range of the present embodiment expands the method for designing of circuit as different from Example 1:

In step one, get V _imin=71V, V _imax=710V;

In step 204, according to formula calculate R _1min=6944K Ω;

In step 207, according to formula calculate R _1max=17947K Ω; According to formula R _1min≤ R ₁≤ R _1maxobtain 6944K Ω≤R ₁≤ 17945K Ω, chooses R ₁=9000K Ω;

In step 3, according to formula $\left\{\begin{array}{c}{\tilde{V}}_{i\min }=\frac{(R_{L1}+R_1)(R_2+R_3)}{R_{L1}{R}_3}{V}_{o\min }\\ {\tilde{V}}_{i\max }=\frac{(R_{L1}^{\&prime;}+R_1)(R_2+R_{M1})}{R_{L1}^{\&prime;}{R}_{M1}}{V}_{o\max }\end{array}\right.$ Calculate due to 18V<71V and 710V>420V, namely do not meet and therefore, step 4 is performed;

Step 4, get n=1, the components and parts of formation the 1st the second voltage expanded circuit 3 are selected according to the component parameter system of selection of the second voltage expanded circuit 3, connect each components and parts and form the second voltage expanded circuit 3, and the 1st the second voltage expanded circuit 3 is connected between the first voltage expanded circuit 2 and switching power source chip 4; Wherein, the component parameter system of selection of i-th the second voltage expanded circuit 3 is:

Step I, according to formula R _{3 (i+1)+1}=a ⁱr ₄choose resistance R ₃( _i+1) _{+ 1}resistance, wherein, the value of a is the real number of 2 ~ 3;

In the present embodiment, get i=1, namely according to formula R ₇=aR ₄choose resistance R ₇resistance; Get a=2.6, due to R ₄=150K Ω, therefore R ₇=390K Ω;

Step II, according to formula R _(3i+1)+2=R ₅choose resistance R ( _3i+1) _{+ 2}resistance;

In the present embodiment, get i=1, namely according to formula R ₈=R ₅choose resistance R ₈resistance; Due to R ₅=2000K Ω, therefore R ₈=2000K Ω;

Step III, according to formula choose resistance R _{3 (i+1)+3}resistance, wherein, the value of b is the real number of 2 ~ 3;

In the present embodiment, get i=1, namely according to formula choose resistance R ₉resistance, get b=2.35, due to R ₆=120K Ω, therefore R ₉=51K Ω;

Wherein, n is the number of the second voltage expanded circuit 3 and the value of n is natural number;

Step 5, according to formula $\left\{\begin{array}{c}{\tilde{V}}_{i\min }^{\&prime;}=\frac{(R_{L(n-1)}+R_1)(R_2+R_3)}{R_{L(n-1)}{R}_3}{V}_{o\min }\\ {\tilde{V}}_{i\max }^{\&prime;}=\frac{(R_{L(n+1)}^{\&prime;}+R_1)\left({R_2+R}_{M(n+1)}\right)}{R_{L(n+1)}^{\&prime;}{R}_{M(n+1)}}{V}_{o\max }\end{array}\right.$ Calculate the actual input voltage minimum value that the Switching Power Supply input voltage range be made up of the first voltage expanded circuit 2 and the individual second voltage expanded circuit 3 of n expands circuit with actual input voltage maximum and judged whether and when and time, terminate the design that described Switching Power Supply input voltage range expands circuit; Otherwise, perform step 6; Wherein, resistance R _{l (n+1)}resistance be the value of j is the natural number of 0 ~ n+1; Resistance resistance be $R_{L(n+1)}^{\&prime;}=\frac{(R_2+R_{M(n+1)})\underset{j=1}{\overset{n+1}{\mathrm{\&Pi;}}}(R_{3j+2}+R_{3j+3})}{\underset{j=1}{\overset{n+1}{\mathrm{\&Pi;}}}(R_{3j+2}+R_{3j+3})+(R_2+R_{M(n+1)})\underset{j=1}{\overset{n+1}{\mathrm{\&Sigma;}}}\underset{j=1,j\&NotEqual;j}{\overset{n+1}{\mathrm{\&Pi;}}}(R_{3j+2}+R_{3j+3})},$ The value of j is the natural number of 1 ~ n+1; Resistance R _{m (n+1)}resistance be $R_{M(n+1)}=\frac{R_3\underset{j=1}{\overset{n+1}{\mathrm{\&Pi;}}}{R}_{3j+1}}{\underset{j=1}{\overset{n+1}{\mathrm{\&Pi;}}}{R}_{3j+1}+R_3\underset{j=1}{\overset{n+1}{\mathrm{\&Sigma;}}}\underset{j=1,j\&NotEqual;j}{\overset{n+1}{\mathrm{\&Pi;}}}{R}_{3j+1}},$ The value of j is the natural number of 1 ~ n+1;

In the present embodiment, get n=1, resistance R _l2resistance be namely $R_{L2}=\frac{(R_2+R_3)(R_5+R_6)(R_8+R_9)}{(R_5+R_6)(R_8+R_9)+(R_2+R_3)(R_8+R_9)+(R_2+R_3)(R_5+R_6)},$ I.e. resistance R _l2for resistance R ₂with resistance R ₃after series connection, then with the resistance R connected ₅with resistance R ₆, and the resistance R of series connection ₈with resistance R ₉equivalent resistance in parallel; Calculate R _l2=646K Ω; Resistance R _m2resistance be $R_{M2}=\frac{R_3\underset{j=1}{\overset{2}{\mathrm{\&Pi;}}}{R}_{3j+1}}{\underset{j=1}{\overset{2}{\mathrm{\&Pi;}}}{R}_{3j+1}+R_3\underset{j=1}{\overset{2}{\mathrm{\&Sigma;}}}\underset{j=1,j\&NotEqual;j}{\overset{2}{\mathrm{\&Pi;}}}{R}_{3j+1}},$ Namely $R_{M2}=\frac{R_3{R}_4{R}_7}{R_4{R}_7+R_3{R}_7+R_3{R}_4},$ I.e. resistance R _m2for resistance R ₃, resistance R ₄with resistance R ₇equivalent resistance in parallel, calculates R _m2=94K Ω, resistance resistance be $R_{L2}^{\&prime;}=\frac{(R_2+R_{M2})\underset{j=1}{\overset{2}{\mathrm{\&Pi;}}}(R_{3j+2}+R_{3j+3})}{\underset{j=1}{\mathrm{\&Pi;}}(R_{3j+2}+R_{3j+3})+(R_2+R_{M2})\underset{j=1}{\overset{2}{\mathrm{\&Sigma;}}}\underset{j=1,j\&NotEqual;j}{\mathrm{\&Pi;}}(R_{3j+2}+R_{3j+3})},$ Namely $R_{L2}^{\&prime;}=\frac{(R_2+R_{M2})(R_5+R_6)(R_8+R_9)}{(R_5+R_6)(R_8+R_9)+(R_2+R_{M2})(R_5+R_6)+(R_2+R_{M2})(R_8+R_9)},$ I.e. resistance for resistance R ₂with resistance R _m2after series connection, then with the resistance R connected ₅with resistance R ₆, and the resistance R of series connection ₈with resistance R ₉equivalent resistance in parallel; Calculate according to formula $\left\{\begin{array}{c}{\tilde{V}}_{i\min }^{\&prime;}=\frac{(R_{L2}+R_1)(R_2+R_3)}{R_{L2}{R}_3}{V}_{o\min }\\ {\tilde{V}}_{i\max }^{\&prime;}=\frac{(R_{L2}^{\&prime;}+R_1)\left({R_2+R}_{M2}\right)}{R_{L2}^{\&prime;}{R}_{M2}}{V}_{o\max }\end{array}\right.$ Calculate ${\tilde{V}}_{i\min }^{\&prime;}=25.4V,{\tilde{V}}_{i\max }^{\&prime;}=727V,$ Due to 25.4V<71V and 710V<727V, namely have and therefore the design that described Switching Power Supply input voltage range expands circuit is terminated.

It should be noted that, in order to value and convenience of calculation, the above R _1min, R ₉, R _l2, R _m2with result of calculation all have employed the counting reservation method rounded up.

All the other method steps are all identical with embodiment 1.

In the present embodiment, the operation principle that Switching Power Supply input voltage range of the present invention expands circuit is: in the first voltage expanded circuit 2, resistance R ₅with resistance R ₆for triode Q ₁divider resistance, in the 1st the second voltage expanded circuit 3, resistance R ₈with resistance R ₉for triode Q ₂divider resistance, when input voltage is also low than the under-voltage protection voltage of switching power source chip 4, triode Q ₁base voltage be less than triode Q ₁conducting voltage, triode Q ₂base voltage be less than triode Q ₂conducting voltage, now, resistance R ₄with resistance R ₇all do not have place in circuit, whole Switching Power Supply input voltage range is expanded circuit and is equivalent to only by resistance R ₂, resistance R ₃, resistance R ₅, resistance R ₆, resistance R ₈with resistance R ₉form, resistance R ₂with resistance R ₃after series connection again with the resistance R connected ₅with resistance R ₆, and the resistance R of series connection ₈with resistance R ₉parallel connection, and then overall and resistance R ₁series connection; The voltage of the cathode voltage output end vo of the 1st the second voltage expanded circuit 3+get is less than the under-voltage protection voltage of switching power source chip 4, and switching power source chip 4 does not work.Along with the rising of input voltage, time on the under-voltage protection voltage that input voltage is elevated to switching power source chip 4, switching power source chip 4 is started working, resistance R ₆with resistance R ₉dividing potential drop increase, due to described resistance R ₆resistance value be greater than described resistance R ₉resistance value, therefore resistance R ₆dividing potential drop be greater than resistance R ₉dividing potential drop, triode Q ₁first conducting, along with triode Q ₁the increase of conducting degree finally to saturation conduction, resistance R ₄access loop gradually, from the cathode voltage output end vo of the 1st the second voltage expanded circuit 3+diminish with the equivalent resistance of the cathode voltage output end vo of the 1st the second voltage expanded circuit 3-see into, the voltage that the voltage of the cathode voltage output end vo+output of the 1st the second voltage expanded circuit 3 inputs relative to the cathode voltage input Vi+ of the first voltage expanded circuit 2 to the voltage of the cathode voltage output end vo-output of the 1st the second voltage expanded circuit 3 is very little to the change of the voltage that the cathode voltage input Vi-of the first voltage expanded circuit 2 inputs; In the process, resistance R ₉power on to be pressed with and increased, but still do not reach triode Q ₂conducting voltage, resistance R ₇also do not access loop; Along with the continuation of input voltage raises, triode Q ₂conducting degree increase until saturated gradually, resistance R ₇access loop gradually, from the cathode voltage output end vo of the 1st the second voltage expanded circuit 3+diminish gradually with the equivalent resistance of the cathode voltage output end vo of the 1st the second voltage expanded circuit 3-see into, the voltage of the cathode voltage output end vo+output of the 1st the second voltage expanded circuit 3 is to the voltage of the cathode voltage output end vo-output of the 1st the second voltage expanded circuit 3 in slow increase, but the voltage of the cathode voltage output end vo+output of the 1st the second voltage expanded circuit 3 is also in the overvoltage protection voltage range of switching power source chip 4; When input voltage continues to raise; due to from the cathode voltage output end vo of the 1st the second voltage expanded circuit 3+no longer change with the equivalent resistance of the cathode voltage output end vo of the 1st the second voltage expanded circuit 3-see into; the voltage linear that equivalent resistance is got increases; when input voltage reaches the overvoltage protection voltage of switching power source chip 4, switching power source chip 4 quits work.

When in the scope that input voltage is reduced to setting, whether whether self-recoverage will have self-recovering function according to switching power source chip 4 and determine Switching Power Supply.When switching power source chip 4 has self-recovering function, along with the reduction of input voltage, time under the overvoltage protection voltage that input voltage is reduced to switching power source chip 4, switching power source chip 4 is started working, when input voltage continues to reduce, due to resistance R ₉resistance value be less than resistance R ₆resistance value, therefore triode Q ₂conducting degree reduce gradually, until turn off, to make resistance R ₇excise from circuit, from the cathode voltage output end vo of the 1st the second voltage expanded circuit 3+increase with the equivalent resistance of the cathode voltage output end vo of the 1st the second voltage expanded circuit 3-see into, the voltage that the voltage of the cathode voltage output end vo+output of the 1st the second voltage expanded circuit 3 inputs relative to the cathode voltage input Vi+ of the first voltage expanded circuit 2 to the voltage of the cathode voltage output end vo-output of the 1st the second voltage expanded circuit 3 is very little to the change of the voltage that the cathode voltage input Vi-of the first voltage expanded circuit 2 inputs, when input voltage reduces again, triode Q ₁turn off gradually, resistance R ₄excise from circuit gradually, from the cathode voltage output end vo of the 1st the second voltage expanded circuit 3+again increase with the equivalent resistance of the cathode voltage output end vo of the 1st the second voltage expanded circuit 3-see into, the voltage of the cathode voltage output end vo+output of the 1st the second voltage expanded circuit 3 to the voltage of the cathode voltage output end vo-output of the 1st the second voltage expanded circuit 3 in slow reduction, but change still less, the voltage of the cathode voltage output end vo+output of the 1st the second voltage expanded circuit 3 does not also reach the under-voltage protection point of switching power source chip 4, at this moment resistance R ₄with resistance R ₇excise from circuit, when input voltage reduces again, from the cathode voltage output end vo of the 1st the second voltage expanded circuit 3+substantially constant with the equivalent resistance of the cathode voltage output end vo of the 1st the second voltage expanded circuit 3-see into, the voltage linear that equivalent resistance is got reduces, when input voltage reaches the under-voltage protection voltage of switching power source chip 4, switching power source chip 4 quits work.

Embodiment 3

As shown in Figure 5 and Figure 6, the Switching Power Supply input voltage range of the present embodiment expands circuit as different from Example 2: the quantity of described second voltage expanded circuit 3 is 2, the cathode voltage input of the 1st the second voltage expanded circuit 3 connects with the cathode voltage output of the first voltage expanded circuit 2, the cathode voltage input of the 1st the second voltage expanded circuit 3 connects with the cathode voltage output of the first voltage expanded circuit 2, the cathode voltage input of the 2nd the second voltage expanded circuit 3 connects with the cathode voltage output of the 1st the second voltage expanded circuit 3, the cathode voltage input of the 2nd the second voltage expanded circuit 3 connects with the cathode voltage output of the 1st the second voltage expanded circuit 3, the cathode voltage output of the 2nd the second voltage expanded circuit 3 connects with the overvoltage of switching power source chip 4 and under-voltage protection end, the cathode voltage output of the 2nd the second voltage expanded circuit 3 connects with the earth terminal of switching power source chip 4, 2nd the second voltage expanded circuit 3 is by triode Q ₃and resistance R ₁₀, R ₁₁and R ₁₂composition, described resistance R ₁₁one end be the cathode voltage input of the 2nd the second voltage expanded circuit 3, described resistance R ₁₁the other end and triode Q ₃base stage and resistance R ₁₂one end connect, described triode Q ₃collector electrode and resistance R ₁₀one end connect, described resistance R ₁₀the other end be the 2nd the second voltage expanded circuit 3 cathode voltage output end vo+, described triode Q ₃the cathode voltage input of transmitting very the 2nd the second voltage expanded circuit 3, described resistance R ₁₂the other end be the 2nd the second voltage expanded circuit 3 cathode voltage output end vo-.All the other structures are all identical with embodiment 2.

The Switching Power Supply input voltage range of the present embodiment expands the method for designing of circuit as different from Example 2:

In step one, get V _imin=100V, V _imax=1200V;

In step 204, according to formula calculate R _1min=10167K Ω;

In step 207, according to formula calculate R _1max=30842K Ω; According to formula R _1min≤ R ₁≤ R _1maxobtain 10167K Ω≤R ₁≤ 30842K Ω, chooses R ₁=12000K Ω;

In step 3, according to formula $\left\{\begin{array}{c}{\tilde{V}}_{i\min }=\frac{(R_{L1}+R_1)(R_2+R_3)}{R_{L1}{R}_3}{V}_{o\min }\\ {\tilde{V}}_{i\max }=\frac{(R_{L1}^{\&prime;}+R_1)(R_2+R_{M1})}{R_{L1}^{\&prime;}{R}_{M1}}{V}_{o\max }\end{array}\right.$ Calculate due to 23.3V<100V and 1200V>550V, namely do not meet and therefore, step 4 is performed;

In step 5, according to formula $\left\{\begin{array}{c}{\tilde{V}}_{i\min }^{\&prime;}=\frac{(R_{L2}+R_1)(R_2+R_3)}{R_{L2}{R}_3}{V}_{o\min }\\ {\tilde{V}}_{i\max }^{\&prime;}=\frac{(R_{L2}^{\&prime;}+R_1)\left({R_2+R}_{M2}\right)}{R_{L2}^{\&prime;}{R}_{M2}}{V}_{o\max }\end{array}\right.$ Calculate due to 25.4V<100V and 1200V>956V, namely do not meet and therefore, step 6 is performed;

Step 6, by the value of n increase 1, the components and parts of formation the n-th the second voltage expanded circuit 3 are selected according to the component parameter system of selection of the second voltage expanded circuit 3, connect each components and parts composition the n-th the second voltage expanded circuit 3, and the n-th the second voltage expanded circuits 3 are connected between (n-1)th the second voltage expanded circuit 3 and switching power source chip 4; Return step 5.

Now n=2, the component parameter system of selection of the 2nd the second voltage expanded circuit 3 is:

In step I, get i=2, namely according to formula R ₁₀=a ²r ₄choose resistance R ₁₀resistance; Get a=2.6, due to R ₄=150K Ω, therefore R ₁₀=1014K Ω, directly can get R in theory ₁₀=1014K Ω, looking for producer to customize resistance value is the resistance R of 1014K Ω ₁₀but, consider that 1014K Ω is not conventional resistance, conveniently, get R ₁₀=1000K Ω;

In step II, get i=2, namely according to formula R ₁₁=R ₅choose resistance R ₁₁resistance; Due to R ₅=2000K Ω, therefore R ₁₁=2000K Ω;

In step III, get i=2, namely according to formula choose resistance R ₁₂resistance, get b=2.35, due to R ₆=120K Ω, therefore R ₁₂=22K Ω;

Return step 5 again, get n=2, resistance R _l3resistance be namely $R_{L3}=\frac{(R_2+R_3)(R_5+R_6)(R_8+R_9)\left(R_{11}{+R}_{12}\right)}{(R_5+R_6)(R_8+R_9)(R_{11}+R_{12})+(R_2+R_3)(R_8+R_9)(R_{11}+R_{12})+(R_2+R_3)(R_5+R_6)(R_8+R_9)+(R_2+R_3)(R_5+R_6)(R_8+R_9)},$ I.e. resistance R _l3for resistance R ₂with resistance R ₃after series connection, then with the resistance R connected ₅with resistance R ₆, the resistance R of series connection ₈with resistance R ₉, and the resistance R of series connection ₁₁with resistance R ₁₂equivalent resistance in parallel; Calculate R _l3=490K Ω; Resistance R _m3resistance be namely $R_{M3}=\frac{R_3{R}_4{R}_7{R}_{10}}{R_4{R}_7{R}_{10}+R_3{R}_7{R}_{10}+R_3{R}_4{R}_{10}+R_3{R}_4{R}_7},$ I.e. resistance R _m3for resistance R ₃, resistance R ₄, resistance R ₇with resistance R ₁₀equivalent resistance in parallel, calculates R _m3=86K Ω, resistance resistance be $R_{L3}^{\&prime;}=\frac{(R_2+R_{M3})\underset{j=1}{\overset{3}{\mathrm{\&Pi;}}}(R_{3j+2}+R_{3j+3})}{\underset{j=1}{\mathrm{\&Pi;}}(R_{3j+2}+R_{3j+3})+(R_2+R_{M2})\underset{j=1}{\overset{n+1}{\mathrm{\&Sigma;}}}\underset{j=1,j\&NotEqual;j}{\overset{n+1}{\mathrm{\&Pi;}}}(R_{3j+2}+R_{3j+3})},$ Namely $R_{L3}^{\&prime;}=\frac{(R_2+R_{M3})(R_5+R_6)(R_8+R_9)\left(R_{11}{+R}_{12}\right)}{(R_5+R_6)(R_8+R_9)(R_{11}+R_{12})+(R_2+R_{M3})(R_5+R_6)(R_{11}+R_{12})+(R_2+R_{M3})(R_8+R_9)(R_{11}+R_{12})+(R_2+R_{M3})(R_5+R_6)(R_8+R_9)},$ I.e. resistance for resistance R ₂with resistance R _m3after series connection, then with the resistance R connected ₅with resistance R ₆, the resistance R of series connection ₈with resistance R ₉, and the resistance R of series connection ₁₁with resistance R ₁₂equivalent resistance in parallel; Calculate according to formula $\left\{\begin{array}{c}{\tilde{V}}_{i\min }^{\&prime;}=\frac{(R_{L3}+R_1)(R_2+R_3)}{R_{L3}{R}_3}{V}_{o\min }\\ {\tilde{V}}_{i\max }^{\&prime;}=\frac{(R_{L3}^{\&prime;}+R_1)\left({R_2+R}_{M3}\right)}{R_{L3}^{\&prime;}{R}_{M3}}{V}_{o\max }\end{array}\right.$ Calculate due to 43.3V<100V and 1200V<1289V, namely have and therefore the design that described Switching Power Supply input voltage range expands circuit is terminated.

It should be noted that, in order to value and convenience of calculation, the above R ₁₂, R ₁₂, R _l3, R _m3with result of calculation all have employed the counting reservation method rounded up.

All the other method steps are all identical with embodiment 2.

In the present embodiment, the operation principle that Switching Power Supply input voltage range of the present invention expands circuit is: in the first voltage expanded circuit 2, resistance R ₅with resistance R ₆for triode Q ₁divider resistance, in the 1st the second voltage expanded circuit 3, resistance R ₈with resistance R ₉for triode Q ₂divider resistance, in the 2nd the second voltage expanded circuit 3, resistance R ₁₁with resistance R ₁₂for triode Q ₃divider resistance, when input voltage is also low than the under-voltage protection voltage of switching power source chip 4, triode Q ₁base voltage be less than triode Q ₁conducting voltage, triode Q ₂base voltage be less than triode Q ₂conducting voltage, triode Q ₃base voltage be less than triode Q ₃conducting voltage, now, resistance R ₄, resistance R ₇with resistance R ₁₀all do not have place in circuit, whole Switching Power Supply input voltage range is expanded circuit and is equivalent to only by resistance R ₂, resistance R ₃, resistance R ₅, resistance R ₆, resistance R ₈, resistance R ₉, resistance R ₁₁with resistance R ₁₂form, resistance R ₂with resistance R ₃after series connection again with the resistance R connected ₅with resistance R ₆, the resistance R of series connection ₈with resistance R ₉, and the resistance R of series connection ₁₁with resistance R ₁₂parallel connection, and then overall and resistance R ₁series connection; The voltage of the cathode voltage output end vo of the 2nd the second voltage expanded circuit 3+get is less than the under-voltage protection voltage of switching power source chip 4, and switching power source chip 4 does not work.Along with the rising of input voltage, time on the under-voltage protection voltage that input voltage is elevated to switching power source chip 4, switching power source chip 4 is started working, resistance R ₆, resistance R ₉with resistance R ₁₂dividing potential drop increase, due to described resistance R ₆resistance value be greater than described resistance R ₉resistance value, described resistance R ₉resistance value be greater than described resistance R ₁₂resistance value, therefore resistance R ₆dividing potential drop be greater than resistance R ₉dividing potential drop, resistance R ₉dividing potential drop be greater than resistance R ₁₂dividing potential drop, triode Q ₁first conducting, along with triode Q ₁the increase of conducting degree finally to saturation conduction, resistance R ₄access loop gradually, from the cathode voltage output end vo of the 1st the second voltage expanded circuit 3+diminish with the equivalent resistance of the cathode voltage output end vo of the 1st the second voltage expanded circuit 3-see into, the voltage that the voltage of the cathode voltage output end vo+output of the 1st the second voltage expanded circuit 3 inputs relative to the cathode voltage input Vi+ of the first voltage expanded circuit 2 to the voltage of the cathode voltage output end vo-output of the 1st the second voltage expanded circuit 3 is very little to the change of the voltage that the cathode voltage input Vi-of the first voltage expanded circuit 2 inputs; In the process, resistance R ₉power on to be pressed with and increased, but still do not reach triode Q ₂conducting voltage, resistance R ₇also do not access loop; Along with the continuation of input voltage raises, triode Q ₂conducting degree increase until saturated gradually, resistance R ₇access loop gradually, from the cathode voltage output end vo of the 2nd the second voltage expanded circuit 3+diminish gradually with the equivalent resistance of the cathode voltage output end vo of the 2nd the second voltage expanded circuit 3-see into, the voltage that the voltage of the cathode voltage output end vo+output of the 2nd the second voltage expanded circuit 3 inputs relative to the cathode voltage input Vi+ of the first voltage expanded circuit 2 to the voltage of the cathode voltage output end vo-output of the 2nd the second voltage expanded circuit 3 is very little to the change of the voltage that the cathode voltage input Vi-of the first voltage expanded circuit 2 inputs; In the process, resistance R ₁₂power on to be pressed with and increased, but still do not reach triode Q ₃conducting voltage, resistance R ₁₀also do not access loop; Along with the continuation of input voltage raises, triode Q ₃conducting degree increase until saturated gradually, resistance R ₁₀access loop gradually, from the cathode voltage output end vo of the 2nd the second voltage expanded circuit 3+diminish gradually with the equivalent resistance of the cathode voltage output end vo of the 2nd the second voltage expanded circuit 3-see into, the voltage of the cathode voltage output end vo+output of the 2nd the second voltage expanded circuit 3 is to the voltage of the cathode voltage output end vo-output of the 2nd the second voltage expanded circuit 3 in slow increase, but the voltage of the cathode voltage output end vo+output of the 2nd the second voltage expanded circuit 3 is also in the overvoltage protection voltage range of switching power source chip 4; When input voltage continues to raise; due to from the cathode voltage output end vo of the 2nd the second voltage expanded circuit 3+no longer change with the equivalent resistance of the cathode voltage output end vo of the 2nd the second voltage expanded circuit 3-see into; the voltage linear that equivalent resistance is got increases; when input voltage reaches the overvoltage protection voltage of switching power source chip 4, switching power source chip 4 quits work.

When in the scope that input voltage is reduced to setting, whether whether self-recoverage will have self-recovering function according to switching power source chip 4 and determine Switching Power Supply.When switching power source chip 4 has self-recovering function, along with the reduction of input voltage, time under the overvoltage protection voltage that input voltage is reduced to switching power source chip 4, switching power source chip 4 is started working, when input voltage continues to reduce, due to resistance R ₁₂resistance value be less than resistance R ₉resistance value, therefore triode Q ₃conducting degree reduce gradually, until turn off, to make resistance R ₁₀excise from circuit, from the cathode voltage output end vo of the 2nd the second voltage expanded circuit 3+increase with the equivalent resistance of the cathode voltage output end vo of the 2nd the second voltage expanded circuit 3-see into, the voltage that the voltage of the cathode voltage output end vo+output of the 2nd the second voltage expanded circuit 3 inputs relative to the cathode voltage input Vi+ of the first voltage expanded circuit 2 to the voltage of the cathode voltage output end vo-output of the 2nd the second voltage expanded circuit 3 is very little to the change of the voltage that the cathode voltage input Vi-of the first voltage expanded circuit 2 inputs, when input voltage reduces again, due to resistance R ₉resistance value be less than resistance R ₆resistance value, therefore triode Q ₂conducting degree reduce gradually, until turn off, to make resistance R ₇excise from circuit, from the cathode voltage output end vo of the 2nd the second voltage expanded circuit 3+increase with the equivalent resistance of the cathode voltage output end vo of the 2nd the second voltage expanded circuit 3-see into, the voltage that the voltage of the cathode voltage output end vo+output of the 2nd the second voltage expanded circuit 3 inputs relative to the cathode voltage input Vi+ of the first voltage expanded circuit 2 to the voltage of the cathode voltage output end vo-output of the 1st the second voltage expanded circuit 3 is very little to the change of the voltage that the cathode voltage input Vi-of the first voltage expanded circuit 2 inputs, when input voltage reduces again, triode Q ₁turn off gradually, resistance R ₄excise from circuit gradually, from the cathode voltage output end vo of the 2nd the second voltage expanded circuit 3+again increase with the equivalent resistance of the cathode voltage output end vo of the 2nd the second voltage expanded circuit 3-see into, the voltage of the cathode voltage output end vo+output of the 2nd the second voltage expanded circuit 3 to the voltage of the cathode voltage output end vo-output of the 2nd the second voltage expanded circuit 3 in slow reduction, but change still less, the voltage of the cathode voltage output end vo+output of the 2nd the second voltage expanded circuit 3 does not also reach the under-voltage protection point of switching power source chip 4, at this moment resistance R ₄, resistance R ₇with resistance R ₁₀excise from circuit, when input voltage reduces again, from the cathode voltage output end vo of the 2nd the second voltage expanded circuit 3+substantially constant with the equivalent resistance of the cathode voltage output end vo of the 2nd the second voltage expanded circuit 3-see into, the voltage linear that equivalent resistance is got reduces, when input voltage reaches the under-voltage protection voltage of switching power source chip 4, switching power source chip 4 quits work.

Fig. 7 is the using state schematic diagram of the present invention when being applied in a concrete Switching Power Supply, this Switching Power Supply comprise connect successively direct voltage input circuit 1, input voltage range expand circuit 5, switching power source chip 4 and isolated switch transformer 6, the cathode voltage output of described isolated switch transformer 6 is connected to voltage feedback circuit 7, and the output of described voltage feedback circuit 7 connects with the feedback voltage input of described switching power source chip 4; Wherein, described direct voltage input circuit 1 is by rectifier bridge D ₁with polar capacitor C ₁the ac-dc converter circuit formed, described rectifier bridge D ₁the first AC signal input and the second AC signal input is corresponding respectively connects with two AC signal outputs of AC power 8, described polar capacitor C ₁positive pole and described rectifier bridge D ₁cathode voltage output connect and be the cathode voltage output of direct voltage input circuit 1, described polar capacitor C ₁negative pole and described rectifier bridge D ₁cathode voltage output connect and be the cathode voltage output of direct voltage input circuit 1; Described isolated switch transformer 6 is by switching tube Q ₄, transformer T, rectifier diode D ₂, inductance L and polar capacitor C ₂composition, described switching tube Q ₄grid connect with the drive singal output of switching power source chip 4, described switching tube Q ₄drain electrode connect with one end of the first siding ring of transformer T, described switching tube Q ₄source electrode and described polar capacitor C ₁negative pole connect, the other end of the first siding ring of described transformer T connects with the cathode voltage output of direct voltage input circuit 1, one end of the second siding ring of described transformer T and rectifier diode D ₂positive pole connect, described rectifier diode D ₂negative pole connect with one end of inductance L, the other end of described inductance L and polar capacitor C ₂positive pole connect and be the cathode voltage output V+ of isolated switch transformer 6, the other end of the second siding ring of described transformer T and polar capacitor C ₂negative pole connect and be the cathode voltage output V-of isolated switch transformer 6.

During the work of this Switching Power Supply, input voltage range expands circuit 5 can by polar capacitor C ₁the large voltage transitions of direct current exported becomes the protection of the overvoltage/undervoltage of switching power source chip 4 to hold the small voltage that can identify, and then switching power source chip 4 can judge whether to carry out overvoltage/undervoltage protection.

The above; it is only preferred embodiment of the present invention; not the present invention is imposed any restrictions, every above embodiment is done according to the technology of the present invention essence any simple modification, change and equivalent structure change, all still belong in the protection range of technical solution of the present invention.

Claims (5)

1. a Switching Power Supply input voltage range expands circuit, it is characterized in that: comprise the first voltage expanded circuit (2) be connected between direct voltage input circuit (1) and switching power source chip (4), described direct voltage input circuit (1) is ac-dc converter circuit or direct voltage source, with overvoltage and under-voltage protection end on described switching power source chip (4), the cathode voltage output of the first voltage expanded circuit (2) connects with the overvoltage of switching power source chip (4) and under-voltage protection end, the cathode voltage output of the first voltage expanded circuit (2) connects with the earth terminal of switching power source chip (4).

2. expand circuit according to Switching Power Supply input voltage range according to claim 1, it is characterized in that: comprise n the second voltage expanded circuit (3) be connected between the first voltage expanded circuit (2) and switching power source chip (4), the cathode voltage input of first second voltage expanded circuit (3) connects with the cathode voltage output of the first voltage expanded circuit (2), the cathode voltage input of first second voltage expanded circuit (3) connects with the cathode voltage output of the first voltage expanded circuit (2), in two adjacent the second voltage expanded circuits (3), the cathode voltage input of a rear second voltage expanded circuit (3) connects with the cathode voltage output of previous second voltage expanded circuit (3), in two adjacent the second voltage expanded circuits (3), the cathode voltage input of a rear second voltage expanded circuit (3) connects with the cathode voltage output of previous second voltage expanded circuit (3), an end cathode voltage output for the second voltage expanded circuit (3) connects with the overvoltage of switching power source chip (4) and under-voltage protection end, the cathode voltage output of end the second voltage expanded circuit (3) connects with the earth terminal of switching power source chip (4), wherein, the value of n is natural number.

3. expand circuit according to Switching Power Supply input voltage range according to claim 2, it is characterized in that: described first voltage expanded circuit (2) is by triode Q ₁and resistance R ₁, R ₂, R ₃, R ₄, R ₅and R ₆composition, described resistance R ₁one end be the cathode voltage input Vi+ of the first voltage expanded circuit (2) and connect with the cathode voltage output of direct voltage input circuit (1), described resistance R ₁the other end and resistance R ₂one end and resistance R ₅one end connect and be the cathode voltage output of the first voltage expanded circuit (2), described resistance R ₂the other end and resistance R ₃one end and resistance R ₄one end connect, described resistance R ₅the other end and triode Q ₁base stage and resistance R ₆one end connect, described resistance R ₄the other end and triode Q ₁collector electrode connect, described resistance R ₃the other end and triode Q ₁emitter and resistance R ₆the other end connect, described resistance R ₃the other end be the cathode voltage input Vi-of the first voltage expanded circuit (2) and connect with the cathode voltage output of direct voltage input circuit (1), described resistance R ₆the other end be the cathode voltage output of the first voltage expanded circuit (2).

4. expand circuit according to Switching Power Supply input voltage range according to claim 3, it is characterized in that: i-th the second voltage expanded circuit (3) is by triode Q _i+1and resistance R _{3 (i+1)+1}, R _(3i+1)+2and R _{3 (i+1)+3}composition, described resistance R _(3i+1)+2one end be the cathode voltage input of i-th the second voltage expanded circuit (3), described resistance R _(3i+1)+2the other end and triode Q _i+1base stage and resistance R _{3 (i+1)+3}one end connect, described triode Q _i+1collector electrode and resistance R _{3 (i+1)+1}one end connect, described resistance R _{3 (i+1)+1}the other end be i-th the second voltage expanded circuit (3) cathode voltage output end vo+, described triode Q _i+1the cathode voltage input of transmitting very i-th the second voltage expanded circuit (3), described resistance R _{3 (i+1)+3}the other end be i-th the second voltage expanded circuit (3) cathode voltage output end vo-; Wherein, the value of i is the natural number of 1 ~ n.

5. design Switching Power Supply input voltage range as claimed in claim 4 and expand a method for circuit, it is characterized in that the method comprises the following steps:

Step one, determine the minimum value V of input voltage _iminwith the maximum V of input voltage _imax;

The resistance R of step 2, selection suitable parameters ₁, resistance R ₂, resistance R ₃, resistance R ₄, resistance R ₅with resistance R ₆, and connect described triode Q ₁and resistance R ₁, resistance R ₂, resistance R ₃, resistance R ₄, resistance R ₅with resistance R ₆, form the first voltage expanded circuit (2); Detailed process is as follows:

Step 201, according to formula choose resistance R ₃resistance, wherein, V _ominfor the under-voltage protection voltage of switching power source chip (4), V _omaxfor the overvoltage protection voltage of switching power source chip (4), I ₁for input voltage is minimum value V _imintime flow through resistance R ₂with resistance R ₃electric current;

Step 202, according to formula choose resistance R ₆resistance, wherein, I ₂for input voltage is minimum value V _imintime flow through resistance R ₅with resistance R ₆electric current;

Step 203, according to formula I ₁(R ₂+ R ₃)=I ₂(R ₅+ R ₆)=U _x1determine resistance R ₂with resistance R ₅value relatable, and according to resistance R ₃with resistance R ₆resistance level choose resistance R ₂resistance and resistance R ₅resistance, wherein, U _x1for input voltage is minimum value V _imintime resistance R ₂with resistance R ₃place branch road and resistance R ₅with resistance R ₆the shunt voltage of place branch road;

Step 204, according to formula determine resistance R ₁minimum resistance R _1min;

Step 205, according to formula choose resistance R ₄resistance, wherein, I ₃for input voltage is maximum V _imaxtime flow through resistance R ₂with resistance R ₃electric current;

Step 206, according to formula i ₃(R ₂+ R _m)=I ₄(R ₅+ R ₆)=U _x2determine electric current I ₄and voltage U _x2, wherein, R _mfor resistance R ₃with resistance R ₄equivalent resistance in parallel, I ₄for input voltage is maximum V _imaxtime flow through resistance R ₅with resistance R ₆electric current, U _x2for input voltage is maximum V _imaxtime resistance R ₂with resistance R ₃place branch road and resistance R ₅with resistance R ₆the shunt voltage of place branch road;

Step 207, according to formula determine resistance R ₁maximum value R _1max, and according to formula R _1min≤ R ₁≤ R _1maxchoose resistance R ₁resistance;

Step 208, by resistance R ₁one end connect with the cathode voltage output of direct voltage input circuit (1), by resistance R ₁the other end and resistance R ₂one end and resistance R ₅one end connect, by resistance R ₂the other end and resistance R ₃one end and resistance R ₄one end connect, by resistance R ₅the other end and triode Q ₁base stage and resistance R ₆one end connect, by resistance R ₄the other end and triode Q ₁collector electrode connect, by resistance R ₃the other end and triode Q ₁emitter and resistance R ₆the other end connect, by resistance R ₃the other end be connect with the cathode voltage output of direct voltage input circuit (1);

Step 3, according to formula $\left\{\begin{array}{c}{\tilde{V}}_{i\min }=\frac{(R_{L1}+R_1)(R_2+R_3)}{R_{L1}{R}_3}{V}_{o\min }\\ {\tilde{V}}_{i\max }=\frac{(R_{L1}^{\&prime;}+R_1)(R_2+R_{M1})}{R_{L1}^{\&prime;}{R}_{M1}}{V}_{o\max }\end{array}\right.$ Calculate the actual input voltage minimum value of the first voltage expanded circuit (2) with actual input voltage maximum and judged whether and when and time, terminate the design that described Switching Power Supply input voltage range expands circuit; Otherwise, perform step 4; Wherein, resistance R _l1resistance be $R_{L1}=\frac{(R_2+R_3)(R_5+R_6)}{(R_2+R_3)+(R_5+R_6)},$ Resistance R ' _l1resistance be $R_{L1}^{\&prime;}=\frac{(R_2+R_{M1})(R_5+R_6)}{(R_2+R_{M1})+(R_5+R_6)},$ Resistance R _m1resistance be $R_{M1}=\frac{R_3{R}_4}{R_3+R_4};$

Step 4, get n=1, the components and parts of formation the n-th the second voltage expanded circuit (3) are selected according to the component parameter system of selection of the second voltage expanded circuit (3), connect each components and parts and form the second voltage expanded circuit (3), and the n-th the second voltage expanded circuits (3) are connected between the first voltage expanded circuit (2) and switching power source chip (4); Wherein, the component parameter system of selection of i-th the second voltage expanded circuit (3) is:

Step I, according to formula R _{3 (i+1)+1}=a ⁱr ₄choose resistance R _{3 (i+1)+1}resistance, wherein, the value of a is the real number of 2 ~ 3;

Step II, according to formula R _(3i+1)+2=R ₅choose resistance R _(3i+1)+2resistance;

Step III, according to formula r ₆choose resistance R _{3 (i+1)+3}resistance, wherein, the value of b is the real number of 2 ~ 3;

Wherein, n is the number of the second voltage expanded circuit (3) and the value of n is natural number, and the value of i is the natural number of 0 ~ n;

Step 5, according to formula $\left\{\begin{array}{c}{\tilde{V}}_{i\min }^{\&prime;}=\frac{(R_{L(n+1)}+R_1)(R_2+R_3)}{R_{L(n+1)}{R}_3}{V}_{o\min }\\ {\tilde{V}}_{i\max }^{\&prime;}=\frac{(R_{L(n+1)}^{\&prime;}+R_1)(R_2+R_{M(n+1)})}{R_{L(n+1)}^{\&prime;}{R}_{M(n+1)}}{V}_{o\max }\end{array}\right.$ Calculate the actual input voltage minimum value that the Switching Power Supply input voltage range be made up of the first voltage expanded circuit (2) and the individual second voltage expanded circuit (3) of n expands circuit with actual input voltage maximum and judged whether and when and time, terminate the design that described Switching Power Supply input voltage range expands circuit; Otherwise, perform step 6; Wherein, resistance R _{l (n+1)}resistance be the value of j is the natural number of 0 ~ n+1; Resistance R ' _{l (n+1)}resistance be $R_{L(n+1)}^{\&prime;}=\frac{(R_2+R_{M(n+1)})\underset{j=1}{\overset{n+1}{\mathrm{\&Pi;}}}(R_{3j+2}+R_{3j+3})}{\underset{j=1}{\overset{n+1}{\mathrm{\&Pi;}}}(R_{3j+2}+R_{3j+3})+(R_2+R_{M(n+1)})\underset{j=1}{\overset{n+1}{\mathrm{\&Sigma;}}}\underset{j=1,j\&NotEqual;j}{\overset{n+1}{\mathrm{\&Pi;}}}(R_{3j+2}+R_{3j+3})},$ The value of j is the natural number of 1 ~ n+1; Resistance R _{m (n+1)}resistance be the value of j is the natural number of 1 ~ n+1;

Step 6, by the value of n increase 1, the components and parts of formation the n-th the second voltage expanded circuit (3) are selected according to the component parameter system of selection of the second voltage expanded circuit (3), connect each components and parts composition the n-th the second voltage expanded circuit (3), and the n-th the second voltage expanded circuits (3) are connected between (n-1)th the second voltage expanded circuit (3) and switching power source chip (4); Return step 5.