CN101714820A - Multiplexed output power of low-voltage power supply - Google Patents

Abstract

The invention provides a multiplexed output power of low-voltage power supply. The multiplexed output power comprises a filter circuit, a power conversion circuit, an output rectification high-frequency wave filter circuit, a low dropout voltage regulator, a sampling circuit, a feedback isolation circuit, a control circuit and a self-starting and auxiliary power supply circuit; input voltage is converted into three-path output voltage through the filter circuit, the power conversion circuit, the output rectification high-frequency filter circuit and the low dropout voltage regulator; or the input voltage is connected with the control circuit through the power conversion circuit, the output rectification high-frequency filter circuit, the sampling circuit and the feedback isolation circuit; the self-starting and auxiliary power supply circuit is arranged between the filter circuit and the control circuit; the power conversion circuit is connected with the control circuit through current sampling, and the control circuit generates a driving signal to connect with the power conversion circuit. The invention solves the technical problems of complex design of peripheral circuit and low stability of a traditional modulator, and has the advantages of reasonable design, high practicability, and the like.

Description

Low-voltage power supply multi-path output power

Technical field

A kind of power supply of the present invention is specifically related to a kind of multiple-output electric power of low-voltage power supply.

Background technology

In electronic product, power supply is essential, but in most of distributed power supply systems, low-voltage power supply system, and Switching Power Supply is widely used ambipolar voltage-controlled type pulse width modulator at present, exists shortcomings such as periphery circuit design complexity, stability are low.

Summary of the invention

In order to solve existing modulator periphery circuit design complexity, technical problem that stability is low, the invention provides a kind of multiple-output electric power of low-voltage power supply.

Technical scheme of the present invention is as follows:

The multiple-output electric power of low-voltage power supply provided by the invention comprises filter circuit, circuit for power conversion, the output rectification high-frequency filtration, low-dropout regulator, sample circuit, feedback isolation circuit, control circuit, and self-starting and auxiliary power circuit, described input voltage is through filter circuit, circuit for power conversion, output rectification high-frequency filtration, and low-dropout regulator is converted to three road output voltages; Or input voltage through circuit for power conversion, output rectification high-frequency filtration, sample circuit, the feedback isolation circuit is connected with control circuit; Described self-starting and auxiliary power circuit are arranged between filter circuit and the control circuit; Described circuit for power conversion is connected with control circuit through current sample, and described control circuit produces drive signal and is connected with circuit for power conversion.

Above-mentioned circuit for power conversion is the single-ended forward type translation circuit; A road of described single-ended forward type translation circuit output is closed loop, and other is output as open loop.

Above-mentioned control circuit is elected the current-control type pulse-width modulation circuit of third generation CMOS technology as.

Above-mentioned single-ended forward type translation circuit input voltage is 8V～40VDC, and the output direct current is+5V/3A ± 15V/0.5A ,+10V/0.5A.

Advantage of the present invention is as follows:

1, this power supply is based on the low-voltage power supply multi-path output power that certain unmanned plane model requires development, and the BICOMS current control mode pulse width modulator (PWM) that it uses has remarkable advantages than ambipolar voltage-controlled type.At first, reduced PWM starting current and operating current, simplified circuit design; The second, because the high speed of BICOMS, thereby the time delay that has reduced to turn-off MOSFET has improved the reliability of power supply; The 3rd, because advanced lead-edge-blanking technology has reduced noise sensitivity.The coupling inductance of output employing is simultaneously compared with independent inductance, except that reducing volume, weight, has also improved load dynamic property and intersection adjusting function, has reduced ripple.The performance that this power supply reaches at home and abroad maintains the leading position in the like product.Being widely used at present me develops in supporting airborne, each family computer of missile-borne.It is reasonable in design, practicality is high, be easy to apply.

2, this power supply adopts BICMOS current-control type technology, has simplified the design of circuit greatly, has reduced cost, has improved reliability.Adopt coupling inductance except that reducing volume, weight, improved the load dynamic property and intersected adjusting function.By actual product checking, power source performance is stable, only needs by this power supply method for designing, and the appropriate change parameter can be developed the power supply of various different output voltages,

Description of drawings:

Fig. 1 is a power supply architecture block diagram of the present invention;

Fig. 2 is auxiliary power circuit figure, and wherein (a) is for before simplifying, (b) for after simplifying;

Fig. 3 is current detection circuit figure, wherein is before (a) simplifies, after (b) simplifying;

Fig. 4 is band lead-edge-blanking after-current detection waveform figure;

Fig. 5 is the common magnetic reset circuit diagram of positive activation type converter; Wherein

Fig. 6 is full load pin 6 output square wave figure;

The V of switching tube when Fig. 7 is the main and side road overall loading _DSOscillogram.

Embodiment:

Referring to Fig. 1, the multiple-output electric power of low-voltage power supply provided by the invention, comprise filter circuit, circuit for power conversion, the output rectification high-frequency filtration, low-dropout regulator, sample circuit, the feedback isolation circuit, control circuit, and self-starting and auxiliary power circuit, described filter circuit is through circuit for power conversion, output rectification high-frequency filtration, low-dropout regulator, sample circuit, the feedback isolation circuit is connected with control circuit, or through circuit for power conversion, output rectification high-frequency filtration, sample circuit, the feedback isolation circuit is connected with control circuit; Described self-starting and auxiliary power circuit are arranged between filter circuit and the control circuit; Described circuit for power conversion is connected with control circuit through current sample, and described control circuit is connected with circuit for power conversion after driving.Circuit for power conversion is the single-ended forward type translation circuit, and a road of described single-ended forward type translation circuit output is closed loop, and other is output as open loop.Control circuit is elected the current-control type pulse-width modulation circuit of third generation CMOS technology as.Single-ended forward type translation circuit input voltage is 8V～40VDC, and the output direct current is+5V/3A ± 15V/0.5A ,+10V/0.5A.

Wherein, control circuit is selected current control mode pulse width modulator (PWM) chip---UCC3800 series for use, and this series is further perfect with at present widely-used complete compatibility of UC3842/43 pin and function.Its main feature is: low starting current, operating current; Inner soft start; Self-stabilization Vcc voltage; Lead-edge-blanking; The following complete period of fault condition resets; Reduced conduction delay.

The main effect of circuit for power conversion is to realize power conversion and isolation.The circuit for power conversion of this power supply selects to be fit to the single-ended forward type translation circuit of low-voltage DC supply.Select the advantage of single-ended forward type translation circuit to be: only to adopt a MOS field effect tube switch element, simplified the design of drive circuit and circuit for power conversion; Reduce the cost of product, improved reliability of products; Design of transformer is simple, is easy to processing.

Referring to Fig. 2, simplified the design of start-up circuit and Vcc power supply, common double polar form voltage-controlled type PWM chip needs complicated auxiliary power circuit power supply, usually shown in Fig. 2 (a).Because BICMOS PWM chip has low starting current, when input voltage is higher than 12V, can adopt the RC circuit to realize self-starting, the auxiliary power circuit after the simplification is shown in Fig. 2 (b).

Because the PWM chip internal is stablized Vcc, resistance R ₁Can play the effect of current limliting.This electric current is limited in the 10mA, and resistance is calculated by (1) formula.

R ₁＝(Vin-13.5)/0.01A (1)

In the formula: R ₁It is current-limiting resistance among Fig. 3 (b); Vin is a power input voltage; 13.5V be the operating voltage of PWM chip, i.e. Vcc.

Referring to Fig. 3, the design of current detection circuit has been simplified in the design of chip internal 100ns lead-edge-blanking circuit, need not the RC filter network that current detecting is used, and has improved the antijamming capability of current sample, has eliminated the high order harmonic component interference.Current detection circuit behind the employing BICOMS PWM is shown in Fig. 3 (b).Fig. 4 is the current detecting measured waveform behind the band lead-edge-blanking circuit.

Referring to Fig. 5, in the circuit for power conversion magnetic-reset circuit select for use and design is crucial.Common reset circuit has: (1) magnetic-reset winding [Fig. 5 (a)]; (2) RCD clamp circuit [Fig. 5 (b)]; (3) the lossless clamp circuit of LCD [Fig. 5 (c)]; (4) active-clamp [Fig. 5 (d)].Reset circuit (1) makes the structure complicated of transformer, and switching tube is when turn-offing, and leakage inductance can cause than outage pointing peak, high point.Reset circuit (2) is when power switch pipe conducts energy during to secondary transmission because transformer leakage field energy stored, when switching tube turn-offs on resistance R with this energy consumption.Sort circuit inefficiency, clamping voltage are the twice of input voltage.Reset circuit (3) utilizes inductance, capacitor resonance to come clamp switch pipe shutoff voltage, and clamping voltage is low, and loss ratio RCD clamp circuit is little.Reset circuit (4) is the magnetic reset technology of a kind of suitable high frequency, efficiency operation, and it is made up of an auxiliary switch and a clamping capacitance, is connected in parallel on primary winding two ends.ON time by the control auxiliary switch is carried out magnetic reset, and its shortcoming is circuit complexity, cost height.By comparison, select the lossless clamp circuit of LCD for use to these four kinds of magnetic reset circuit.

The concrete condition of design power transformer is as follows:

1, magnetic core selects for use

The power output that goes out according to the core material Shou Ce Give of producer and the relation of magnetic core size, this power supply is selected GU26 * 16 type magnetic cores, its net sectional area A for use _eBe 0.959cm ²

2, calculate the turn ratio

U ₀＝U ₀₁+U _D+U _L＝5.0+0.5+0.2＝5.7V (2)

In the formula: U ₀Be N ₂Output voltage;

U ₀₁Be 5V main road output voltage;

U _DFor the rectifying tube forward voltage drop, get 0.5V;

U _LFor pressure drop on the inductance, get 0.2V.

$n_{12}=\frac{N_1}{N_2}=\frac{U_{1\min }}{U_{2\min }}=\frac{8}{11.4}=0.7---\left(3\right)$

In the formula: n ₁₂Be the former secondary turn ratio of main road;

U _1minBe the minimum input voltage of power supply;

$U_{2\min }=\frac{U_0}{D_{\max }}=11.4V$ (D _MaxBe maximum duty cycle, get 0.5);

The actual n that gets ₁₂=8: 11.

3, calculate the main road secondary number of turn

$N_2=\frac{U_{2\min }{T}_{\mathrm{on}\max }}{\mathrm{\Δ}{\mathrm{BA}}_e}\×{10}^2=11.89---\left(4\right)$

In the formula: $T_{\mathrm{on}\max }=T_S{D}_{\max }=\frac{D_{\max }}{f_s}=5\mathrm{\μS}$ (f _SFor the power work frequency, select 100KHZ);

Δ B is the magnetic flux increment, selects 500GS;

A _eBe the magnetic core net sectional area.

The actual N that gets ₂=12 circles.

4, calculate the former limit number of turn

N ₁＝N ₂×n ₁₂＝8.7 (5)

The actual N that gets ₁=9 circles.

5, calculate its excess-three bypass secondary number of turn

$N_3=N_4=N_2\×\frac{U_{02}+{U^{\′}}_D+{U^{\′}}_L}{U_0}=33.89---\left(6\right)$

In the formula: U ₀₂For+15V bypass output voltage,

U ' _DFor the rectifying tube forward voltage drop, get 0.9V;

U ' _LFor pressure drop on the inductance, get 0.2V.

The actual N that gets ₃=N ₄=34 circles.

Calculate+10V bypass secondary number of turn N with identical method ₅=24 circles.

During coiling because former limit, main road secondary current is bigger, for reducing leakage inductance, adopts two-wire parallel wound and four line parallel wounds respectively.

As follows to the concrete analysis of output coupling inductance with design:

Concrete condition at the output of this power supply duplex, output inductor should not adopt independent inductance, and should adopt coupling inductance, soon four tunnel output inductor is on a magnetic core, have only+the 5V main circuit is controlled, output characteristic is better, and ± 15V ,+10V three tunnel uses the three terminal regulator voltage stabilizing respectively.

1, coupling inductance is to the influence of power source performance

Adopt coupling inductance to compare, reduced volume and weight, following advantage is arranged aspect electrical property with discrete filter inductance:

A) after the employing coupling inductance, increase the variation item of other several roads inductive currents in each road outputting inductance amount, increased the filter inductance value, reduced output ripple voltage;

B) help improving the dynamic property of power supply.Adopt coupling inductance, the variation of every road voltage to cause and the same variation tendency of other each road output voltages help the control of circuit, guaranteed that also circuit has reasonable dynamic property.

C) load is intersected the influence of adjusting function.Adopt coupling inductance can reduce the output current pulsation, widen the scope of circuit continuous mode, reduce critical continuous current, thereby reduce between interrupted and continuous mode output voltage gap or make load intersect adjusting function to drop on the continuous mode working range, improved the load intersection adjusting function of multiple-output electric power.

2, design and calculating

In conjunction with this multiple-output electric power circuit, core material, the performance of coupling inductance have been carried out analyzing relatively, finally select import magnetic core for use, there is air gap the inside of this material own.

The turn ratio of selecting the number of turn of inductance will satisfy inductance equals the turn ratio of the output winding of main transformer.If the turn ratio of coupling inductance can not guarantee to equate with the turn ratio of transformer, then between each road output voltage, can exist additional electric current to flow, thereby produce very big ripple in its output.In order to reduce leakage inductance, adopted the method for even coiling, in conjunction with the relation of the main power transformer turn ratio, the winding of coupling inductance has 4, be respectively+the 5V output inductor, ± the 15V output inductor ,+the 10V filter inductance, the turn ratio is closed and is: $\frac{N_{15V}}{N_{5V}}=\frac{17}{6},$ $\frac{N_{10V}}{N_{5V}}=2.$

At first determine the output inductor value.

$L=\frac{U_{2\min }-U_D-U_{0\max }}{\mathrm{\Δ}{I}_L}{T}_{\mathrm{on}\max }---\left(7\right)$

In the formula: U _2minBe the secondary coil minimum voltage;

U _DFor the rectifying tube forward voltage drop, get 0.5V;

U _0maxBe maximum output voltage;

Δ I _LBe the electric current changing value of outputting inductance, get output current

10％～30％。

Determine the inductance number of turn according to formula (8) then,

$N_L=\frac{{\mathrm{LI}}_{\mathrm{SP}}}{B_{\mathrm{MAX}}{A}_e}---\left(8\right)$

In the formula: I _SPBe the inductive current peak-peak;

B _MAXBe magnetic circuit magnetic flux density maximum.

Be redistributed to each branch road at last, obtain each coil turn and size according to each road actual current and secondary turns ratio.Actual getting+5V output inductor number of turn is 14 circles, and ± 15V output inductor the number of turn respectively is 40 circles, and+10V output inductor the number of turn is 28 circles, and output loading intersection regulation rate reaches 0.8%, and the ripple voltage value also only is 100mv.

As follows according to the body experimental result:

1) major parameter of circuit design: BICMOS current-control type multiple-output electric power major parameter is: input direct voltage scope: 8V-40VDC; Output dc voltage :+5V/3A, ± 15V/0.5A ,+10V/0.5A; Output gross power: 35W; Operating frequency: 100KHZ.

2) experimental waveform is referring to Fig. 6-Fig. 7,

3) this power supply has reached following technical indicator (± 15V ,+10V survey index after being three terminal regulator):

Load regulation :+5V 0.1%;

+15V 0.1％；

-15V 0.1％；

+10V 0.1％；

Voltage regulation :≤0.1%; Intersect and regulate: 0.8%; Output ripple voltage peak-to-peak value: V _P-P≤ 100mv;

Efficient: 75%; Overall dimension: 103.4mm * 93.5mm * 30.2mm; Also have output overcurrent, short circuit, over-voltage protecting function.

Claims (4)

1. the multiple-output electric power of a low-voltage power supply, comprise filter circuit, circuit for power conversion, output rectification high-frequency filtration, low-dropout regulator, sample circuit, the feedback isolation circuit, control circuit, and self-starting and auxiliary power circuit, described input voltage is through filter circuit, circuit for power conversion, output rectification high-frequency filtration, and low-dropout regulator is converted to three road output voltages; Or input voltage through circuit for power conversion, output rectification high-frequency filtration, sample circuit, the feedback isolation circuit is connected with control circuit; Described self-starting and auxiliary power circuit are arranged between filter circuit and the control circuit; Described circuit for power conversion is connected with control circuit through current sample, and described control circuit produces drive signal and is connected with circuit for power conversion.

2. the multiple-output electric power of low-voltage power supply according to claim 1, it is characterized in that: described circuit for power conversion is the single-ended forward type translation circuit; A road of described single-ended forward type translation circuit output is closed loop, and other is output as open loop.

3. the multiple-output electric power of low-voltage power supply according to claim 1 and 2, it is characterized in that: described control circuit is elected the current-control type pulse-width modulation circuit of third generation CMOS technology as.

4. the multiple-output electric power of low-voltage power supply according to claim 3, it is characterized in that: described single-ended forward type translation circuit input voltage is 8V～40VDC, the output direct current is+5V/3A ± 15V/0.5A ,+10V/0.5A.

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