CN202652086U - Flyback multiplexed output switching power supply - Google Patents

Abstract

The utility model discloses a flyback multiplexed output switching power supply and pertains to the field of electronic technology, which comprises an alternating current input end and a direct current input end. The alternating current input end is sequentially connected with an alternating current input unit, a step-down transformer and a rectifier filter unit; the direct current input end is connected with a redundancy diode; and the output end of the rectifier filter unit, the output end of the redundancy diode and a flyback step-down output unit are connected. The flyback multiplexed output switching power supply disclosed by the utility model is simple in circuit, stable in output voltage, multiple in stage, large in output power and strong in adjustability. The direct current power supply can be from a high voltage switch cabinet or an uninterruptible power supply (UPS). Thus, the output of the power supply can be ensured no matter which input fails, input redundancy of the power supply can be realized and the power supply demand of the control circuit in various fields can be met.

Description

The inverse-excitation type multi-output switch power source

Technical field

The utility model relates to a kind of DC power supply, and especially multi-output switch power source belongs to power supply and electronic technology field.

Background technology

At present, there are the defectives such as power output is less, output voltage is unstable, the output voltage grade is few, adjustability is poor in the multi-output switch power source for the control loop power supply.

The utility model content

For the problems referred to above, the utility model provides a kind of inverse-excitation type multi-output switch power source.

The technical scheme that its technical problem that solves the utility model adopts is: the inverse-excitation type multi-output switch power source comprises ac input end and direct-flow input end; Ac input end connects with AC input cell, step-down transformer and rectification filtering unit successively; Direct-flow input end connects with redundant diode; The output of rectification filtering unit, the output of redundant diode and inverse-excitation type reduced output voltage element connection.

The beneficial effects of the utility model are, circuit is simple, and output accuracy height, output voltage stabilization, grade are many, and power output is large, adjustability is strong.DC power supply can be from high-voltage board or UPS uninterrupted power supply.So just can realize that power supply still can keep output when no matter which input is broken down, realize that the power supply input is redundant.Can satisfy the control loop power demands in a lot of fields.

Description of drawings

Fig. 1 is the utility model theory diagram;

Fig. 2 is the circuit theory diagrams of inverse-excitation type reduced output voltage unit 5 among Fig. 1.

Parts and numbering among the figure:

The 1-AC input cell, 2-step-down transformer, 3-rectification filtering unit, 4-redundant diode, 5-inverse-excitation type reduced output voltage unit.

Embodiment

Below in conjunction with embodiment the utility model is further specified.

Referring to Fig. 1, the inverse-excitation type multi-output switch power source comprises ac input end and direct-flow input end; Ac input end connects with AC input cell 1, step-down transformer 2 and rectification filtering unit 3 successively; Direct-flow input end connects with redundant diode 4; The output of the output of rectification filtering unit 3, redundant diode 4 connects with inverse-excitation type reduced output voltage unit 5.

AC input cell 1 is protection and EMI filtration module, and fuse plays the effect of overcurrent protection, and EMI can suppress power supply and electrical network High-frequency Interference each other.

Step-down transformer 2 is with the input power step-down; Rectification filtering unit 3 is to its rectification, filtering.Improve the quality of DC power supply, increase Systems balanth.

Redundant diode 4 is independent of each other DC power supply and AC power.

Inverse-excitation type reduced output voltage unit 5 is through step-down, again multichannel output, and the output voltage grade has ± 24V, ± 15V, ± 12V, ± 5V, for the outside.

1). operation principle

As shown in Figure 2, IC1 and IC2 are the control chips of two parallel connections, its D and S pin are equivalent to two switch series in parallel on the primary coil of transformer, during D and S connection, input DC power powers up transformer, produce the DYN dynamic while of self-induction when the winding of primary coil has electric current to flow through, produce simultaneously induced electromotive force at the two ends of transformer secondary output coil windings yet, but because the effect of rectifier diode VD5 to VD13 does not produce loop current.Be equivalent to the transformer secondary output open coil, the secondary coil of transformer is equivalent to an inductance.Therefore, the electric current that flows through the transformer winding is exactly the exciting current of transformer, and transformer winding two ends produce self induction electromotive force and can be expressed from the next:

During control IC connects

$e1=L1\frac{\mathrm{di}}{\mathrm{dt}}=\mathrm{Ui}$

Or

$e1=N1\frac{\mathrm{d\φ}}{\mathrm{dt}}=\mathrm{Ui}$

In the following formula, e1 is the self induction electromotive force that transformer N1 winding produces, and L1 is the inductance of transformer N1 winding, and N1 is the number of turn of transformer N1 winding coil winding, and φ is transformer fe magnetic flux in the heart.Following formula is carried out integration can be got:

$i1=\frac{U_i}{L_1}t+i\left(0\right)$

$\mathrm{\φ}=\frac{U_i}{N_1}t+\mathrm{\φ}\left(0\right)$

In the following formula, i1 is the electric current that flows through the transformer winding, and φ is transformer fe magnetic flux in the heart; I1 (0) is the initial current in the transformer, that is: control IC rigidly connects the electric current that logical transient flow is crossed the transformer winding; φ (0) is initial magnetic flux, that is: control IC rigidly connects logical moment transformer fe magnetic flux in the heart.When Switching Power Supply worked in output critical continuous mode current status, the i1 here (0) just in time 0, and φ (0) just in time equals residual flux SBr.IC will turn-off when control, and Switching Power Supply is when working in output current critical continuous mode state, and i1 and φ all reach maximum:

Control IC shutdown moment

$\mathrm{ilm}=\frac{U_i}{L_1}{T}_{\mathrm{on}}$

${\mathrm{\φ}}_m=\frac{U_i}{N_1}{T}_{\mathrm{on}}+S\·\mathrm{Br}=S\·\mathrm{Bm}$

In the following formula, i1m is the maximum current that flows through transformer N1 winding, flows through the electric current of transformer winding before the control IC shutdown moment that is:; φ m is transformer fe maximum magnetic flux in the heart, controls the front transformer fe magnetic flux in the heart of IC shutdown moment that is:, and S is the transformer core magnetic conductive area, and Br is residual magnetic flux density, and Bm is maximum magnetic induction.

When control IC transfers suddenly shutdown moment to by connecting, the current i 1 that flows through transformer is suddenly 0, this means that transformer fe magnetic flux φ in the heart also will produce sudden change, this is impossible, if transformer fe magnetic flux φ in the heart produces sudden change, the primary and secondary wire loop of transformer will produce the back electromotive force of infinite height, back electromotive force can produce infinitely-great electric current again, and electric current can resist the variation of magnetic flux, therefore, transformer fe flux change in the heart is final or will be subject to that electric current in the primary and secondary coil of transformer retrains.

Therefore, at control IC blocking interval, transformer fe magnetic flux φ is in the heart mainly decided by the electric current in the transformer secondary output wire loop, both:

$e2=-L2\frac{{\mathrm{di}}_2}{\mathrm{dt}}=\mathrm{uo}$

Perhaps

$e2=-N2\frac{\mathrm{d\φ}}{\mathrm{dt}}=\mathrm{uo}$

In the following formula, e2 is the electrification kinetic potential that transformer secondary output coil N winding produces, and L2 is the inductance of transformer secondary output coil windings, and N2 is the number of turn of transformer winding coil winding, φ is transformer fe magnetic flux in the heart, and uo is the output voltage of transformer secondary output coil windings.Because the output voltage of the transformer secondary output coil windings of flyback transformer Switching Power Supply all passes through rectifying and wave-filtering, and the time constant of filter capacitor and load resistance is very large, therefore, rectifying and wave-filtering output voltage U o substantially just equals the amplitude Up of uo.

Following formula is carried out integration, and uses uo Uo for it, can try to achieve:

$i2=-\frac{U_o}{L_2}t+i2\left(0\right)$

$\mathrm{\φ}=-\frac{U_o}{N_2}t+\mathrm{\φ}\left(0\right)$

In the formula, i2 is the electric current that flows through the transformer secondary output coil windings, and φ is transformer fe magnetic flux in the heart; I2 (0) is the initial current of transformer secondary output coil windings, and φ (0) is initial magnetic flux.In fact, i2 (0) just in time equals control switch and has just disconnected transient flow and cross the electric current that the electric current of transformer winding is converted the secondary winding loop, that is: i2 (0)=i1m/n; And just in time equaling control switch, φ (0) just disconnected moment transformer fe magnetic flux in the heart, that is: φ (0)=SBm.When control IC will turn-off, i2 and φ all reached minimum value.That is:

$i2x=-\frac{U_o}{L_2}{T}_{\mathrm{off}}+\frac{i_{1m}}{n}$

$\mathrm{\φx}=-\frac{U_o}{N_2}{T}_{\mathrm{off}}+S\·\mathrm{Bm}$

In the following formula,, n is the turn ratio of transformer secondary output coil and primary coil.When Switching Power Supply worked in electric current critical continuous mode operating state, i2x equaled 0, φ x and equals SBr.

The output voltage that comprehensively can get the flyback transformer Switching Power Supply is:

$U_o=\frac{n{U}_i}{1-D}D$

In the following formula, Uo is the output voltage of flyback transformer Switching Power Supply, Ui transformer input voltage, and D is the duty ratio of control IC, n is the turn ratio of transformer secondary output coil and primary coil.

Hence one can see that, the duty of flyback transformer switching power supply by changing control switch recently the by-pass cock power supply output voltage and the charging and discharging currents of energy storage filter capacitor reached burning voltage output.

2). the design of transformer

(1) core type is that the operating frequency that satisfies TOP chip 130kHz is selected manganese-zinc ferrite. the shape of magnetic core (such as EI, EE etc.), and should select as far as possible circular magnetic core to reduce leakage inductance.

(2) maximum duty cycle (Dmax) provides the empty ratio of maximum point by formula (2):

Dmax＝VOR/[VOR+(Vmin-VDS)]

In the formula: VOR---secondary reflection is to elementary reflected voltage, optional 135V

VDS---TOP on state voltage, optional 5V is to 10V

(3) primary self-induction LP can be obtained by formula (3):

LP＝[ηVmin?Dmax]/2POf

In the formula: Po---the output gross power

The switching frequency of f---TOP, f=130kHz

(4) sectional area of wire determines that by the average current that flows through each winding (IAVG), peak current (IP), rms current (IRMS), ripple current (IR) power work is under continuous mode or discontinuous mode.

(5) the one turn voltage value is operated under the anti-sharp state, and the winding output voltage is directly proportional with the one turn voltage value, and determining needs to determine the one turn voltage value before each umber of turn N.

(6) the primary and secondary number of turn transformer of the transformer number of turn can be from selecting the secondary winding number of turn. and be alternating current 220V (± 15%) voltage for input voltage, secondary selection 0.6NPV can meet the demands. according to no-load voltage ratio, determine again primary turns.

3). output rectification filter

Output rectifier and filter is made of rectifier diode and filter capacitor. and the switching loss of output rectifier diode accounts for the sixth of the loss of power, it is the principal element that affects switch power efficiency, comprising: forward conduction loss and reverse recovery loss. forward voltage drop is lower during owing to the Schottky diode conducting, therefore have lower forward conduction loss. in addition, Schottky diode is short reverse recovery time, aspect the ripple in reducing reverse recovery loss and elimination output voltage obvious performance advantage is arranged, therefore select Schottky diode as rectifier diode. choose Schottky diode with reference to maximum peak reverse voltage, the maximum peak reverse voltage of secondary each winding is obtained by following formula:

$V_{\mathrm{XM}}=V_X+\left(\right|V_{\max }\frac{N_X}{N_P})$

In the formula: VXM, VX, NX---maximum peak reverse voltage, output voltage, the umber of turn of the output of X road

NP---primary turns

Vmax---primary input maximum voltage,

$V_{\max }=|=\sqrt{2}{V}_{{\mathrm{AC}}_{\max }}$

To output filter capacitor, ESR (equivalent series resistance) and ripple current are its two important parameters. when electric capacity two ends during less than 35V, ESR is only relevant with the volume of electric capacity. under the enough prerequisite of the bandwidth that guarantees control loop, should select the high and low filter capacitor of appearance value of withstand voltage. and the computing formula of ripple current is:

$I_{\mathrm{RIPPLE}}=\sqrt{I_{\mathrm{SRMS}}^2-I_O^2}$

In the formula: ISRMS---the rms current of each winding output

Io---the rated current of each winding output

If filter effect is undesirable, can be in subordinate connect again a L, C filtering link. rule of thumb, L gets about 3.3u H, and capacitance selection is determined according to the size of secondary output current.

4). feedback circuit

The form of feedback loop determines according to the output voltage precision, " optocoupler+TL431 " that this programme uses can be controlled at the output voltage precision ± 0.2% with interior voltage feedback signal through potential-divider network (the Ref end that R5, R9 introduce TL431 is converted into current feedback signal, through the control end of input TOP after the light-coupled isolation.

Optocoupler is operated in linear condition; if play buffer action. the CTR of optocoupler (current amplification degree) upper limit surpasses 200%; cause easily the TOP223Y overvoltage protection. opposite; if the CTR lower limit is less than 40%; duty ratio D can not reduce with the increase of feedback current; thereby cause overcurrent. therefore, should choose the CTR scope near 100% optocoupler. this programme is selected LTV817A (80%～120%).

It has the following advantages inverse-excitation type AC and DC dual input multi-output switch power source:

1. AC and DC dual input: power supply is exchanged by the input of three-phase 380V control power supply by the AC and DC dual input, and direct current is inputted by 220V.

2. adopt the multiple-stage filtering mode: EMI filtering is adopted in the input of power supply.The High-frequency Interference that can suppress in the AC network also can suppress power supply to the interference of AC power to the interference while of power supply, and the LC filtering mode is adopted in the output of power supply, makes the Voltage-output of power supply more stable.

3.IC chip reliability is high: the control IC chip of power supply is TOP233Y, and peripheral cell is few, and system reliability is high,

4. power output is large: this power acquisition push-pull type, power output is between 50～500W.

Claims (1)

1. an inverse-excitation type multi-output switch power source comprises ac input end and direct-flow input end; It is characterized in that ac input end connects with AC input cell (1), step-down transformer (2) and rectification filtering unit (3) successively; Direct-flow input end connects with redundant diode (4); The output of the output of rectification filtering unit (3), redundant diode (4) connects with inverse-excitation type reduced output voltage unit (5).

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