CN106134508B - A kind of auto-excitation type DC/DC converter with input undervoltage defencive function - Google Patents

Abstract

Have an auto-excitation type DC/DC converter for input undervoltage defencive function, when input voltage is from above freezing while being raised to starting resistor, DC/DC converter starts normally to start and enter steady-working state. In the time that input voltage drops to under-voltage protection point, the input undervoltage protection circuit of DC/DC converter inside changes state, blocks the base stage of power switch transistor, makes DC/DC converter quit work and no longer restart, and realizes input undervoltage defencive function. In the time that input voltage rises to starting resistor again, DC/DC converter restarts. Input undervoltage protection circuit has hysteretic characteristic, and starting resistor is put corresponding voltage higher than under-voltage protection, and to ensure in the time that input voltage declines and be stabilized in under-voltage protection point, DC/DC converter can not be operated in the oscillatory regime of repeated priming. The power supply of input undervoltage protection circuit part is provided by the auxiliary output of DC/DC converter itself, in realizing input undervoltage defencive function, does not affect DC/DC converter and normally starts.

Description

A kind of auto-excitation type DC/DC converter with input undervoltage defencive function

Technical field

The present invention relates to a kind of supply convertor with input undervoltage defencive function.

Background technology

Control and measurement precision, reliability, security and the electromagnetism of spacecraft whole system or each subsystemCompatible in close relations with the overall plan of spacecraft earthed system. In order to realize spacecraft design of ground systemReasonability and validity, receive the DC/DC converter of a power supply buses should realize input and output everyFrom. The common configuration isolation formula of DC/DC converter accessory power supply is realized powering up and is started and isolation, this auxiliary electricalSource is larger on the combination property impact of DC/DC converter.

In addition,, do not possess during lower than the minimum normal working voltage of DC/DC converter at power supply buses voltageThe DC/DC converter of input undervoltage defencive function easily breaks down or output voltage causes load extremelyOperation irregularity. In order to ensure that spacecraft is occurring that under the extreme case of various faults, TT&C system still canNormal work, the key state information that ground flying control centre can Real-time Obtaining spacecraft, so that in timeAdopt an effective measure, fault effects is down to minimum, require the DC/DC converter of key position to fitAnswer the wide region of input voltage to change, and there will not be fault under undervoltage condition, obviously, existingDC/DC converter cannot meet this demand.

Summary of the invention

Technology of the present invention is dealt with problems and is: overcome the deficiencies in the prior art, provide a kind of reliability high,Be applicable to the auto-excitation type DC/DC converter with input undervoltage defencive function that wide-range input voltage changes.

Technical solution of the present invention is: a kind of auto-excitation type DC/DC with input undervoltage defencive functionConverter, comprises input undervoltage protection circuit and self-excitation inverse-excitation type DC/DC converter, and described self-excitation is anti-Swash formula DC/DC converter comprise power transformer T1, power switch transistor V1, Zener diode V6,Clamp diode V7, input current-limiting resistance R1, input storage capacitor C1, divider resistance R2 and R3;The anode of external input voltage after input current-limiting resistance R1, be connected to simultaneously input storage capacitor C1 one end andThe Same Name of Ends of the former limit of power transformer T1 winding, the negative terminal of external input voltage is connected to input energy storage electricity simultaneouslyHold the other end, the anode of clamp diode V7 and the emitter stage of power switch transistor V1 of C1, powerThe different name of the former limit of transformer T1 winding is connected to the colelctor electrode of power switch transistor V1, power switch three utmost pointsThe base stage of pipe V1 is connected to the negative electrode of clamp diode V7 and the negative electrode of Zener diode V6 simultaneously; Power becomesAt least there is secondary winding and a secondary winding of isolating with former limit of not isolating with former limit in depressor T1,One end of the anode of Zener diode V6 and divider resistance R3 is connected to described secondary of not isolating with former limit simultaneouslyThe Same Name of Ends of winding, the other end of divider resistance R3 is connected to the base stage of power switch transistor V1, point piezoelectricityThe two ends of resistance R2 respectively with Same Name of Ends and the power switch transistor V1 of the former limit of power transformer T1 windingBase stage be connected; Described input undervoltage protection circuit obtains sampled voltage from external input voltage, establishes simultaneouslyPut input undervoltage protection voltage, input undervoltage protection circuit is by described sampled voltage and input undervoltage protection voltageCompare, comparative result is as the output of input undervoltage protection circuit and be connected to power switch transistor V1Base stage, control self-excitation inverse-excitation type DC/DC converter work or stop.

Described input undervoltage protection circuit comprises Zener diode V8, protection triode V9, voltage ratioDevice U1A and U2A, resistance R 4～R9; External input voltage is delivered to after resistance R 4 and R5 sampling simultaneouslyVoltage comparator U1A and U2A reverse input end, a termination power transformer T1 of resistance R 6 with formerThe different name end of the secondary winding that limit does not isolate, the other end of resistance R 6 is connected to one end of resistance R 7 with steady simultaneouslyThe negative electrode of pressing diode V8, the other end of resistance R 7 is connected to the input in the same way of voltage comparator U1A simultaneouslyEnd and one end of resistance R 8, the output that the other end of resistance R 8 is connected to voltage comparator U1A simultaneously withThe input in the same way of voltage comparator U2A, the anode of Zener diode V8 connects reference potential; Voltage ratioThe output of device U2A is connected to the base stage of protection triode V9; One end of resistance R 9 is connected to voltage comparatorThe output of U1A, what the other end of resistance R 9 was connected to power transformer T1 simultaneously does not isolate with former limitThe different name end of secondary winding and the power end of voltage comparator U1A; The base stage of triode V9 is also connected to powerThe different name end of the secondary winding of not isolating with former limit of transformer T1, emitter stage connects reference potential, colelctor electrodeAs the output of input undervoltage protection circuit.

Described power switch transistor V1 or protection triode V9 are NPN type triode.

Described voltage comparator U1A and U2A are OC output type.

The present invention's advantage is compared with prior art:

(1) DC/DC converter input undervoltage protection circuit part of the present invention provides power supply by converter selfPower supply, the startup stage powering up, in power supply process of establishing, the duty of input undervoltage protection circuit is notAffect the normal startup of DC/DC converter. In the time that input voltage is reduced to under-voltage protection point, DC/DC becomesParallel operation can make the off position of DC/DC converter reliably working before startup, and can not be operated in repetitionThe oscillatory regime starting, the functional reliability and the security that have improved DC/DC converter, can avoid simultaneouslyIts loaded work piece, at under-voltage power supply state, makes auto-excitation type DC/DC converter applications change at input voltageWide ranges is higher with the occasion reliability that adds power process complexity;

(2) input undervoltage protection circuit of the present invention, by DC/DC converter self power supply, circuit is simple,Secondary power loss is little, does not affect the normal startup of auto-excitation type DC/DC converter;

(3) input undervoltage protection circuit of the present invention has hysteretic characteristic, can ensure to protect in input undervoltageWhen state, DC/DC converter there will not be the situation of vibration;

(4) auto-excitation type DC/DC converter of the present invention, can be by changing the output number of windings of power transformerAmount and the number of turn, realize the output of multichannel isolation or the different voltages of non-isolation;

(5) auto-excitation type DC/DC converter of the present invention has input overcurrent protection circuit (as the resistance in figureDevice R1, is applicable to inverter power hour), when occur inlet highway short trouble time, resistance R 1Fusing, can make DC/DC converter and inlet highway disconnect, thereby ensures the safety of inlet highway. RootAccording to the difference of inlet highway voltage and power output, input overcurrent protection function can be by resistor, fuseOr negative temperature coefficient thermistor is realized;

(6) input of auto-excitation type DC/DC converter of the present invention can add LC input filter circuit,To reduce input current AC compounent, improve electromagnetic compatibility characteristic.

Brief description of the drawings

Fig. 1 is the electric circuit constitute schematic diagram of DC/DC converter of the present invention.

Detailed description of the invention

As shown in Figure 1, there is the auto-excitation type DC/DC converter of input undervoltage defencive function for the present inventionCircuit theory diagrams. In figure, VIN+ and VIN-represent respectively main track and the loop line of DC/DC converter inlet highway.In Fig. 1, express 4 tunnels outputs, comprise do not isolate with input and 2 tunnels taking input loop line as reference potential justNegative output and with 2 positive negative outputs in tunnel of input isolation, respectively with+VP ,-VP ,+VS and-VS represents.

The present invention mainly comprises the work of two parts circuit design, i.e. auto-excitation type DC/DC converter design and defeatedEnter under-voltage protecting circuit design.

One, auto-excitation type DC/DC converter design

Auto-excitation type DC/DC converter is the outer part of dotted line frame in Fig. 1, is single switch flyback circuit topology, workDo at electric current critical continuous conduction mode. In the situation that input voltage is constant, along with power output increases, workIt is constant that dutycycle keeps, and operating frequency reduces; In the situation that output loading is constant, along with input voltage literHeight, work dutycycle reduces, and operating frequency raises.

The feedback winding 3-4 of main power transformer T1 completes the base of output voltage feedback and switching tube V1 simultaneouslyThe utmost point drives. Corresponding negative output-the VP not isolating with input of this winding is directly voltage stabilizing output, output voltageFor negative value, absolute value equals the voltage stabilizing value of voltage-stabiliser tube V6. Winding 4-5, the 6-7 of main power transformer T1With 9-10 corresponding voltage stabilizing output+VP ,+VS indirectly and-VS, it is steady that output voltage equals respectively voltage-stabiliser tube V6The product of pressure value and each winding and the winding 3-4 turn ratio. Winding 1-2, the 3-4 of main power transformer T1,4-5,The number of turn of 6-7 and 9-10 is used respectively N₁、N₂、N₃、N₄And N₅Represent, suppose known input voltage,Gross output, expectation efficiency He Ge road output voltage. Provide the phase of auto-excitation type DC/DC converter belowClose design formula.

When the normal steady operation of converter, switch triode V1 collector voltage V_CEWith input voltage, directRelation between voltage stabilizing output voltage and the main power transformer T1 turn ratio is shown in formula (1),

$V_{CE}=V_{IN}+\left|V_{-P}\right|\·\frac{N_1}{N_2}---\left(1\right)$

In formula: V_IN---input voltage (V);

V_-P---the corresponding output voltage of transformer T1 winding 3-4 (V).

Switch triode V1 work dutycycle D and input voltage, direct voltage stabilizing output voltage and transformer T1Relation between the turn ratio is shown in formula (2), for approximate calculation, and V in formula_ONCan ignore.

$D=\frac{V_{-VP}}{V_{-VP}+(V_{IN}-V_{ON})\·\frac{N_2}{N_1}}---\left(2\right)$

In formula: V_ON---switch triode V1 saturation conduction pressure drop (V).

Converter operating frequency (being switch triode V1 switching frequency) f and input voltage, work dutyRatio, converter gross output, transformer T₁Relation between winding 1-2 inductance value and transducer effciencySee formula (3),

$f=\frac{{(V_{IN}-V_{ON})}^2\·D^2\·\mathrm{\η}}{2P_O\·L_P}---\left(3\right)$

In formula: f---converter operating frequency (Hz);

η---transducer effciency;

P_O---converter gross output (W);

L_P---the inductance value (H) of transformer T1 winding 1-2.

Switch triode V1 colelctor electrode peak point current I_P(being the peak point current of transformer T1 winding 1-2) withRelation between input voltage, operating frequency, work dutycycle and transformer T1 winding 1-2 inductance value is shown inFormula (4),

$I_P=\frac{V_{IN}-V_{ON}}{L_P\·f}\·D---\left(4\right)$

The corresponding output dc voltage V of transformer T1 winding 4-5,6-7 and 9-10_+P、V_-SAnd V_+SWith directlyThe relation connecing between voltage stabilizing output voltage and the transformer T1 turn ratio is shown in respectively formula (5), (6) and (7),

$V_{+P}=\frac{N_3}{N_2}\·\left|V_{-P}\right|---\left(5\right)$

$V_{-S}=\frac{N_4}{N_2}\·V_{-P}---\left(6\right)$

$V_{+S}=\frac{N_5}{N_2}\·\left|V_{-P}\right|---\left(7\right)$

The working inverse voltage V of output commutation diode V2, V3, V4 and V5_S2、V_S3、V_S4And V_S5And the relation between direct voltage stabilizing output voltage and the transformer T1 turn ratio is shown in respectively formula (8), (9), (10)(11),

$V_{S2}=\frac{N_3}{N_2}\·\left|V_{-P}\right|+V_{IN}\frac{N_2}{N_1}---\left(8\right)$

$V_{S3}=\left|V_{-P}\right|+V_{IN}\frac{N_2}{N_1}---\left(9\right)$

$V_{S4}=\frac{N_5}{N_2}\·\left|V_{-P}\right|+V_{IN}\frac{N_2}{N_1}---\left(10\right)$

$V_{S5}=\frac{N_4}{N_2}\·\left|V_{-P}\right|+V_{IN}\frac{N_2}{N_1}---\left(11\right)$

Suppose that the base voltage that switch triode V1 saturation conduction is corresponding is V_BE, the starting resistor of converter V_STARTRelation between (converter start working corresponding minimum input voltage) and resistance R 2 and R3 is shown inFormula (12),

$V_{START}=\frac{R_2+R_3}{R_3}\·V_{BE}---\left(12\right)$

In Fig. 1, resistance R 2 and R3 are used for setting the starting resistor of converter. The effect of resistance R 1 is anti-Only converter short trouble affects the safety of inlet highway. Inductance L 1 and capacitor C 1 are low pass filter, useReduce input ripple current, improve Electro Magnetic Compatibility. Capacitor C 2～C5 is converter output storage capacitor,Be used for ensureing the stability of output voltage and reduce output ripple. V2～V5 is anti exciting converter output rectification twoUtmost point pipe, realizes former limit energy to secondary transmission. V6 is Zener diode, and its effect is defeated for stablizing each roadGo out voltage. Diode V7 inverse parallel between the b of switch triode V1, the e utmost point, can prevent V1 b,The too high backward voltage of e interpolar damages triode V1.

The key point of design process of the present invention is carried out to necessary explanation below.

A. by formula (1) and (4), can determine the voltage and current parameter of switch triode V1, rootAccording to the design feature of converter, determine packing forms, carry out switch triode type selecting;

B. determine transformer efficiency winding 1-2 and the turn ratio of feeding back winding 3-4 by formula (1)

C. according to the operation principle of critical current pattern flyback DC/DC converter, by formula (2)～(7)Carry out the design of power transformer, determine each umber of turn N₁～N₅With former limit power winding 1-2Inductance value L_P(being determined by magnetic core air gap and the power winding 1-2 number of turn);

D. by formula (8) and winding 3-4 power output, can determine the voltage of output commutation diode V3And current parameters, according to the design feature of converter, determine packing forms, export rectification twoUtmost point pipe type selecting. Output commutation diode V2, V4 and V5 determine and the same V3 of type selecting;

E. it is basic identical that other relevant component parameter design and selections and PWM control DC/DC converter," principle of Switching Power Supply and the design " revised edition one that specifically can write referring to Zhang Zhansong, Cai XuansanThe design of Chapter 11 anti exciting converter in book.

Two, input undervoltage protection circuit design

Input undervoltage protection circuit part is the interior part of dotted line frame in Fig. 1, and this part mainly comprises voltage stabilizing two utmost pointsThe components and parts such as pipe V8, protection triode V9, comparator U1A and U2A, mainly realize input voltage inspectionSurvey and input undervoltage defencive function.

Voltage comparator U1A and U2A are by single power supply, and power supply is Transformer Winding 4-5 correspondenceOutput V_+P，V_+PWith V_-PAll taking input loop line as reference potential. Resistor R4 and R5 are to inputting motherLine carries out dividing potential drop, obtains corresponding inlet highway voltage signal V_INS，V_INSSend voltage comparator U1A andThe reverse input end of U2A. V_INSWith input voltage V_INBetween relation (negligible resistance device R1 and inductanceThe impact of device L1) see formula (13),

$V_{INS}=\frac{R_5}{R_4+R_5}\·V_{IN}---\left(13\right)$

The effect of capacitor C6 is to voltage signal V_INSCarry out filtering, avoid the temporary disturbance of input voltageThe action of triggering input undervoltage protection circuit.

The effect of voltage-stabiliser tube V8 is to form and input undervoltage point V_UCorresponding reference voltage V_REF. When input electricityPress V_IN＞V_UTime, the reverse input end voltage of voltage comparator U1A is greater than input terminal voltage in the same way, outputLow level (supposing that output voltage is 0V), also output low level of voltage comparator U2A, protection drives threeUtmost point pipe V9, in cut-off state, does not affect auto-excitation type DC/DC converter and normally works. Now voltage ratioThe V of input terminal voltage in the same way of device U1A_NINSee formula (14),

$V_{NIN}=\frac{R_8}{R_7+R_8}\·V_{REF}---\left(14\right)$

By formula (13) and (14), work as V_INS＝V_NINTime, the corresponding input undervoltage protection of input voltage point,Magnitude of voltage is V_U, itself and V_REFBetween relation see formula (15),

$V_U=\frac{R_4+R_5}{R_5}\·\frac{R_8}{R_7+R_8}\·V_{REF}---\left(15\right)$

As input voltage V_INBe less than V_UTime, the reverse input end voltage of voltage comparator U1A is less than in the same wayInput terminal voltage, voltage comparator U1A exports high level, and voltage comparator U2A also exports high level,Protection drives triode V9 in saturation conduction state, and the base stage of lockout switch triode V1, makes auto-excitation typeDC/DC converter quits work. The now V of input terminal voltage in the same way of voltage comparator U1A_NIUSee formula (16)，

$V_{NIU}=\frac{(R_8+R_9)\·V_{REF}+R_7\·V_{+P}}{R_7+R_8+R_9}---\left(16\right)$

From formula (14) and (16), V_NIN＜V_NIU. By design resistance R₇、R₈And R₉'sResistance parameter, can determine rational return difference signal delta=V_NIU-V_NIN, input voltage return difference Δ V_INWith V_REFAnd V_+PBetween relation see formula (17),

${\mathrm{\ΔV}}_{IN}=\[\frac{(R_8+R_9)\·V_{REF}+R_7\·V_{+P}}{R_7+R_8+R_9}-\frac{R_8}{R_7+R_8}\·V_{REF}\]\·\frac{R_4+R_5}{R_5}---\left(17\right)$

Voltage back diffirence makes under-voltage protection function have hysteretic characteristic, meanwhile, the starting resistor of converter is set V_STARTBe greater than V_U+ΔV_IN, converter can not be vibrated, to ensure input undervoltage at under-voltage protection stateThe reliability of defencive function.

In Fig. 1, resistance R 4 and R5 carry out dividing potential drop to inlet highway, set input undervoltage protection point. Electric capacityC6 plays signal filtering effect. Resistance R 7 and R8 make voltage comparator U1A have hysteretic characteristic, to preventThere is vibration at the input undervoltage protection point place setting. Resistance R 9 and R10 are respectively U1A and U2A'sOutput pull-up resistor, R10 is again the base stage current-limiting resistance of triode V9 simultaneously. Voltage comparator U1A andU2A is OC (open collector) output type, as LM193 etc.

Below the key point of input undervoltage protection circuit design process is described.

A. formula (14) is under the prerequisite that is 0V at hypothesis voltage comparator U1A output low level voltageGo out, should consider the impact of actual low level voltage, V_NINActual value can be a bit larger tham calculated value;

B. reference voltage V_REFPrecision and temperature drift depend on characteristic and the operating point electricity of voltage-stabiliser tube V8Stream;

C. V in formula (16)_NIUWith power supply voltage V_+PRelevant, should consider its input voltage regulation,The impact of load regulation and temperature drift;

D. due to the base emitter voltage V of converter switches triode V1_BERelevant with temperature, by formula (12)Known, starting resistor V_STARTAlso relevant with temperature, therefore should consider that temperature is to starting resistor V_STARTImpact.

The content not being described in detail in description of the present invention belongs to those skilled in the art's known technology.

Claims (4)

1. an auto-excitation type DC/DC converter with input undervoltage defencive function, is characterized in that comprising:Input undervoltage protection circuit and self-excitation inverse-excitation type DC/DC converter, described self-excitation inverse-excitation type DC/DC becomesParallel operation comprises power transformer T1, power switch transistor V1, Zener diode V6, clamp diodeV7, input current-limiting resistance R1, input storage capacitor C1, divider resistance R2 and R3; External input voltageAnode after input current-limiting resistance R1, be connected to one end and the power transformer of input storage capacitor C1 simultaneouslyThe Same Name of Ends of the former limit of T1 winding, the negative terminal of external input voltage is connected to another of input storage capacitor C1 simultaneouslyEnd, the anode of clamp diode V7 and the emitter stage of power switch transistor V1, power transformer T1 is formerThe different name of limit winding is connected to the colelctor electrode of power switch transistor V1, the base stage of power switch transistor V1Be connected to the negative electrode of clamp diode V7 and the negative electrode of Zener diode V6 simultaneously; Power transformer T1 at leastThere is secondary winding and a secondary winding of isolating with former limit of not isolating with former limit, Zener diodeOne end of the anode of V6 and divider resistance R3 is connected to the of the same name of described and secondary winding that former limit does not isolate simultaneouslyEnd, the other end of divider resistance R3 is connected to the base stage of power switch transistor V1, two of divider resistance R2End respectively with the Same Name of Ends of the former limit of power transformer T1 winding and the base stage phase of power switch transistor V1Connect; Described input undervoltage protection circuit obtains sampled voltage from described external input voltage, arranges simultaneouslyInput undervoltage protection voltage, input undervoltage protection circuit enters described sampled voltage and input undervoltage protection voltageRelatively, comparative result is as the output of input undervoltage protection circuit and be connected to power switch transistor V1's for rowBase stage, controls self-excitation inverse-excitation type DC/DC converter work or stops.

2. a kind of auto-excitation type DC/DC with input undervoltage defencive function according to claim 1 becomesParallel operation, is characterized in that: described input undervoltage protection circuit comprises Zener diode V8, protection triodeV9, voltage comparator U1A and U2A, resistance R 4～R9; Described external input voltage is through resistance R 4After sampling with R5, deliver to voltage comparator U1A and U2A reverse input end, a termination of resistance R 6 simultaneouslyThe different name end of the secondary winding of not isolating with former limit of power transformer T1, the other end of resistance R 6 connects simultaneouslyTo one end of resistance R 7 and the negative electrode of Zener diode V8, the other end of resistance R 7 is connected to voltage ratio simultaneouslyCompared with one end of the input in the same way of device U1A and resistance R 8, the other end of resistance R 8 is connected to voltage ratio simultaneouslyCompared with the input in the same way of the output of device U1A and voltage comparator U2A, the anode of Zener diode V8Connect reference potential; The output of voltage comparator U2A is connected to the base stage of protection triode V9; Resistance R 9An end be connected to the output of voltage comparator U1A, the other end of resistance R 9 is connected to power transformer simultaneouslyThe different name end of secondary winding and the power end of voltage comparator U1A of not isolating with former limit of T1; TriodeThe different name end of the secondary winding of not isolating with former limit that the base stage of V9 is also connected to power transformer T1, emitter stageConnect reference potential, colelctor electrode is as the output of input undervoltage protection circuit.

3. a kind of auto-excitation type DC/DC with input undervoltage defencive function according to claim 1 and 2Converter, is characterized in that: described power switch transistor V1 or protection triode V9 are NPNType triode.

4. a kind of auto-excitation type DC/DC with input undervoltage defencive function according to claim 3 becomesParallel operation, is characterized in that: described voltage comparator U1A and U2A are OC output type.