CN201576933U - Circuit capable of restraining instant surge current produced during startup - Google Patents

Abstract

A circuit capable of restraining instant surge current produced during startup comprises a field-effect transistor VT1, a capacitor C 1 and resistors R1, R2 and R3, wherein the capacitor C1 is connected in parallel between the field-effect transistor VT1 and a source electrode, the resistors R1 and R2 are connected in parallel between the power supply at the input end of the circuit and the ground after being connected in series, one end of the resistor R3 is connected with the grid of theVT1, the other end thereof is connected with the resistor R1 and the resistor R2, and the drain electrode of the field-effect transistor VT1 serves as an output end of the circuit. The utility model adopts a P gutter channel MOSFET pipe to replace a thermistor, the on resistance is small and used in a subsystem with higher steady-state current, and the self-consumption is very small; the utility model does not require a drive circuit, the circuit is simple, and the number of devices used in the utility model is small; the utility model can change the charging speed of the capacitor by changing the values of the C1 and the R3, thereby achieving the purpose of controlling the starting time and further determining the time interval of the restart when the subsystem is under a state of power failure; and after the use of the utility model, the numerical value of the surge current drops remarkably, and the inhibition effect is obvious.

Description

A kind of circuit that produces instantaneous surge current when suppressing to start

Technical field

The utility model relates to a kind of circuit that suppresses surge current, is applicable to DC power-supply system, and the inhibition circuit the when subsystem of use primary power source bus produces surge current when powering on belongs to the electroporation field.

Background technology

When the subsystem on being connected on the primary power source bus powers on, follow the initial stage charging of subsystem input filtering electric capacity can produce surge current.This electric current can reach more than ten times of regular event electric current, and input current can calculate with following formula:

$i=U^{-\frac{t}{\mathrm{RC}}}/R---\left(1\right)$

In the formula: U is the primary power source busbar voltage; T is the time; R is the resistance relevant with connecting line with the printed board cabling; C then is the input capacitance of subsystem.When initial state is in conducting (t=0), I=U/R.Because R is very little, so surge current is very big, this is a very big threat to primary power source undoubtedly.Cause busbar voltage to interrupt or fall, make simultaneously between each contact point and produce spark.

For suppressing surge current, method commonly used has:

1. seal in the NTC thermistor at the filter capacitor place of subsystem input, because of it has negative resistance-temperature characteristic, along with the rising resistance value of temperature reduces gradually.Therefore, at the subsystem power initiation initial stage, it becomes big resistance, suppresses overshoot current; Be accompanied by flowing through of electric current afterwards, self-heating (Joule heat), thus the resistance value of reduction oneself is with limit dissipation power.The anti-surge current circuit of thermistor generally is applicable to the subsystem that steady-state current is less.Because the thermal inertia of thermistor, recovering high resistant again needs the time, so for needing the very situation of Quick connecting pipe fitting behind the power cut-off again, do not have metering function sometimes.

2. use fixed resistor to seal in the subsystem input and bring in the formation surge current suppression circuit.But sort circuit power consumption in normal operation is very big, and the energy is very unfavorable for saving.Only be applicable to the subsystem that steady-state current is less.

3. switch elements such as electromagnetic relay in parallel or triode ac switch on fixed resistor.After entering normal operating conditions, power supply, then can limit the power consumption of normal operating conditions with this switch connection.But this practice will cause parts number to increase, and also need the drive circuit of switch element in addition, and this becomes a problem again.

The utility model content

Technology of the present utility model is dealt with problems and is: overcome the deficiencies in the prior art, provide a kind of simple in structure, power consumption is little, need not to increase than multicomponent and suppress to produce when outstanding effect suppresses to start the circuit of instantaneous surge current.

Technical solution of the present utility model is: a kind of circuit that produces instantaneous surge current when suppressing to start comprises field effect transistor VT ₁, capacitor C ₁And resistance R ₁, R ₂, R ₃, capacitor C ₁Be connected in parallel on field effect transistor VT ₁Grid and source electrode between, resistance R ₁, R ₂Be connected in parallel between circuit input end power supply and the ground resistance R after the series connection ₃An end and VT ₁Grid connect the other end and resistance R ₁And R ₂Connect field effect transistor VT ₁Drain electrode be the output of circuit.

Described field effect transistor VT ₁Adopt P channel mosfet pipe.

Described capacitor C ₁And resistance R ₃Pass through formula $U_C=U_i(1-e^{-\frac{t}{R_3{C}_1}})$ Adjust and change capacitor C ₁Charging rate, promptly determine start-up time of subsystem, wherein U _CIt is capacitor C ₁The voltage at two ends, U _iIt is resistance R ₁The voltage at two ends, C ₁It is capacitor C ₁Capacitance, R ₃It is resistance R ₃Resistance value, t is a capacitor C ₁Charging interval.

The utility model compared with prior art beneficial effect is:

(1) the utility model adopts P channel mosfet pipe to replace thermistor, and conducting resistance is very little, and when being used for the bigger subsystem of steady-state current, oneself power consumption is very little;

(2) the utility model need not drive circuit, and circuit is simple, and the device of use is few;

(3) the utility model can be by changing C ₁And R ₃Value change the charging rate of electric capacity, reach the control purpose of start-up time, thereby also can determine time interval of restarting after the subsystem outage;

(4) behind use the utility model, the numerical value of surge current descends significantly, and it is obvious to suppress effect.

Description of drawings

Fig. 1 is an electrical block diagram of the present utility model;

Fig. 2 suppresses front and back contrast oscillogram (curve 1 is not for adopting current waveform of the present utility model, and curve 2 is the current waveform behind employing the utility model) for the utility model surge.

Embodiment

As shown in Figure 1, the utility model comprises field effect transistor VT ₁, capacitor C ₁And resistance R ₁, R ₂, R ₃, capacitor C ₁Be connected in parallel on field effect transistor VT ₁Grid and source electrode between, resistance R ₁, R ₂Be connected in parallel between circuit input end power supply and the ground resistance R after the series connection ₃An end and VT ₁Grid connect the other end and resistance R ₁And R ₂Connect field effect transistor VT ₁Drain electrode be the output of circuit.

Field effect transistor VT ₁Adopt P channel mosfet pipe to replace thermistor, seal in the subsystem input and realize suppressing to power on surge current.MOSFET pipe conducting resistance is very little, has only several ohm of zero points when entering stable state, the conducting electric current I _DCan reach more than the 10A, can be used for the bigger subsystem of steady-state current, and oneself power consumption be also very little.Need not drive circuit, circuit is simple, and the device of use seldom.

After the energising, VT ₁Grid voltage is a capacitor C ₁The voltage at two ends, and capacitor C ₁The voltage U at two ends _CCan pass through formula (2) calculates.

$U_C=U_i(1-e^{-\frac{t}{R_3{C}_1}})---\left(2\right)$

Switch on moment U _C→ 0V.VT ₁End C ₁Through R ₃Current-limiting charge.With capacitor C ₁The rising of both end voltage, field effect transistor VT ₁Conducting resistance descend C ₁(VT when both end voltage rises to 6V～12V ₁Conducting voltage), this moment VT ₁Conducting because its conducting resistance is very little, generally has only several ohm of zero points, has so just avoided at VT ₁The bigger power loss of last generation.Can equivalence be switch closure this moment.

R ₁, R ₂Be divider resistance, guarantee VT ₁The grid threshold voltage in normal range (NR), prevent VT ₁Gate-source voltage too high and damage VT ₁Because VT ₁Required drive current is very little, so R ₁And R ₂Optional big resistance value is pressed in VT as long as can guarantee to divide ₁Grid threshold voltage normal range (NR) in get final product.

R ₃, C ₁Play time-lag action.Pass through formula $U_C=U_i(1-e^{-\frac{t}{R_3{C}_1}}),$ Can be by changing C ₁And R ₃Value change the charging rate of electric capacity, reach the control purpose of start-up time, thereby also can determine time interval of restarting after the subsystem outage, wherein U _CIt is capacitor C ₁The voltage at two ends, U _iIt is resistance R ₁The voltage at two ends, C ₁It is capacitor C ₁Capacitance, R ₃It is resistance R ₃Resistance value, t is a capacitor C ₁Charging interval.

During the subsystem outage, C ₁Pass through resistance R ₂, R ₃Discharge rapidly, VT ₁The very fast decline of conducting voltage, VT ₁Instantaneous closing.

The utility model result of use as shown in Figure 2, can find out used the utility model after, the instantaneous surge current during startup descends obviously.

The unspecified part of the utility model belongs to general knowledge as well known to those skilled in the art.

Claims (3)

1. a circuit that produces instantaneous surge current when suppressing to start is characterized in that: comprise field effect transistor VT ₁, capacitor C ₁And resistance R ₁, R ₂, R ₃, capacitor C ₁Be connected in parallel on field effect transistor VT ₁Grid and source electrode between, resistance R ₁, R ₂Be connected in parallel between circuit input end power supply and the ground resistance R after the series connection ₃An end and VT ₁Grid connect the other end and resistance R ₁And R ₂Connect field effect transistor VT ₁Drain electrode be the output of circuit.

2. a kind of circuit that produces instantaneous surge current when suppressing to start according to claim 1 is characterized in that: described field effect transistor VT ₁Adopt P channel mosfet pipe.

3. a kind of circuit that produces instantaneous surge current when suppressing to start according to claim 1 is characterized in that: described capacitor C ₁And resistance R ₃Pass through formula $U_C=U_i(1-e^{-\frac{t}{R_3{C}_1}})$ Adjust and change capacitor C ₁Charging rate, promptly determine start-up time of subsystem, wherein U _CIt is capacitor C ₁The voltage at two ends, U _iIt is resistance R ₁The voltage at two ends, C ₁It is capacitor C ₁Capacitance, R ₃It is resistance R ₃Resistance value, t is a capacitor C ₁Charging interval.

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