CN201149987Y - Overvoltage protection apparatus - Google Patents

Abstract

The utility model provides an over voltage protecting device aiming at solving the problem of restraining surging voltage and protecting over voltage. The over voltage protecting device comprises a comparing module, a first switch, a second switch and an output switch. The comparing module compares the input voltage and the critical voltage after the operation and the partial pressure, and outputs a controlling signal according to a comparative operating result. The controlling terminal of the first switch is coupled with the comparing module, and is controlled by the controlling signal. The controlling terminal of the second switch is coupled at the drain electrode terminal of the first switch, and is controlled by the output signal at the drain electrode terminal of the first switch. The controlling terminal of the output switch is coupled at the drain electrode terminal of the first second switch, the output switch is controlled by the output signal at the drain electrode terminal of the second switch, and the input voltage is disabled or the input voltage is transmitted to the voltage output terminal. The over voltage protecting device can protect the voltage and restrain the surging voltage.

Description

Overvoltage protection

Technical field

The utility model provides a kind of overvoltage protection, especially provides a kind of use in power-supply adapter (Power Adapter) or palmtop device, has to suppress surging and the circuit arrangement of importing overvoltage protection.

Background technology

Please refer to Fig. 1,, and will use ac power supply the time, all need to utilize power-supply adapter 21 to carry out power source conversion when the electric equipment 20 (for example laptop, LCD etc.) that uses DC power supply.In Fig. 1, power supply changeover device 21 is obtained AC power by ac power plug 22, and converts AC power to DC power supply output, so that electric equipment 20 is powered.In the framework of Fig. 1, problem of ubiquity, promptly when electric equipment 20 is connected (Tum On) or the initial condition of the ac power plug of power-supply adapter 21 22 insertion AC Power supply socket (not shown), very easily cause an excessive surge voltage (Spike), and produce excessive burst current (Inrush Current).Excessive burst current often causes AC Power supply socket, switch to produce spark or disturbs other electrical equipment in using, and then influences the power supply quality.

In addition, if power-supply adapter 21 received AC power are stablized (for example overtension) inadequately, then power-supply adapter 21 can convert superpotential AC power to superpotential DC power supply, and then deliver in the electric equipment 20, so, superpotential DC power supply will cause burning of electric equipment 20.Therefore, in power-supply adapter 21, be badly in need of having the inhibition circuit and the superpotential protective circuit of surge voltage, to solve aforesaid problem.

The utility model content

Suppress surge voltage and the superpotential problem of protection for solving, the utility model provides a kind of overvoltage protection, and it uses in power-supply adapter (Power Adapter), has the surging of inhibition and the superpotential protection of input.

The overvoltage protection of the utility model first embodiment has voltage input end and voltage output end, includes comparison module, first switch, second switch and output switch.Wherein, comparison module is obtained input voltage from voltage input end, and, comparison module comparison operation input voltage and critical voltage, simultaneously, the result exports control signal according to comparison operation.First control end of first switch couples comparison module, and first drain electrode end of first switch couples voltage input end, and first source terminal of first switch is couple to earth terminal, and wherein, first switch is controlled by this control signal.Second control end of second switch couples first drain electrode end, and second source terminal of second switch couples earth terminal, and wherein, second switch is controlled by the output signal of first drain electrode end.The 3rd control end of output switch couples second drain electrode end, the 3rd drain electrode end of output switch couples voltage output end, the 3rd source terminal of output switch couples voltage input end, wherein, the output switch is controlled by the output signal of second drain electrode end, and is sent to voltage output end by input voltage or with input voltage.

In addition, the overvoltage protection of the utility model second embodiment further includes first surge suppressor and second surge suppressor.Wherein, first surge suppressor couples the Input voltage terminal and second control end, comes by this second switch according to surge voltage.Second surge suppressor couples between the 3rd control end and the 3rd source terminal, comes by the output switch according to surge voltage.

In the above-mentioned overvoltage protection, this comparison module can comprise: shunt regulator, couple this voltage input end, and this shunt regulator produces this critical voltage value according to this input voltage; Partial pressure unit couples this voltage input end, receives this input voltage, and produces the input voltage after the dividing potential drop; And comparator, it has non-inverting input, reverse input end and output, and this non-inverting input receives the input voltage after this dividing potential drop, and this reverse input end receives this critical voltage value, and this output is exported this control signal.

In the above-mentioned overvoltage protection, this shunt regulator can comprise Zener diode, input capacitor and input resistor, wherein this this input resistor of Zener diode coupled in series and this input capacitor of coupled in parallel.

In the above-mentioned overvoltage protection; this first surge suppressor can comprise first resistor of coupled in series first capacitor; first end of this first resistor couples this Input voltage terminal; second end of this first resistor couples first drain electrode end of this first switch, second control end of this second switch and first end of this first capacitor jointly, and second end of this first capacitor couples this earth terminal.

In the above-mentioned overvoltage protection; this second surge suppressor can comprise second resistor of coupled in parallel second capacitor; first end of this second capacitor couples this Input voltage terminal, and second end of this second capacitor couples the drain electrode end of this second switch and the 3rd control end of this output switch jointly.

In the above-mentioned overvoltage protection, this first switch can be the N slot field-effect transistor.

In the above-mentioned overvoltage protection, this second switch can be the N slot field-effect transistor.

In the above-mentioned overvoltage protection, this output switch can be the P-channel field-effect transistor (PEFT) transistor.

In the above-mentioned overvoltage protection, this second switch, this output switch and this second surge suppressor can be formed the slow-start circuit of a standard.

To sum up, when the utility model is imported in overvoltage, can control the output switch and end, thereby reach superpotential protection via the judgement of comparison module.Simultaneously, when surge voltage took place, first surge suppressor that the utility model uses can direct into earth terminal with surge voltage, and second surge suppressor can be with the control end and the source terminal short circuit of output switch, make the output of its cut-ff voltage, thereby reach the anti-system of surge voltage.So the utility model can reach the anti-system of superpotential protection and surge voltage.

Description of drawings

Fig. 1 is the function block schematic diagram of conventional power source transducer;

Fig. 2 is the generalized schematic of the utility model voltage protection;

Fig. 3 is the circuit diagram of the voltage protection of the utility model first embodiment;

Fig. 4 is the circuit diagram of the voltage protection of the utility model second embodiment;

Fig. 5 A is the utility model when being operated in normal input voltage, the waveform schematic diagram of output voltage;

Fig. 5 B is the utility model when being operated in input voltage, the waveform schematic diagram of output voltage; And

Fig. 5 C is the utility model when being operated in surge voltage and taking place, the waveform schematic diagram of output voltage.

Wherein, description of reference numerals is as follows:

Tradition:

Electric equipment 20

Power supply changeover device 21

Ac power plug 22

The utility model:

Voltage protection 1,1 '

Voltage input end T1

Voltage output end T2

Input voltage vin

Output voltage V out

Comparison module 10

Shunt regulator 101

Partial pressure unit 102

Comparator 103

Zener diode D1

Input capacitor C1

Input resistor R1

Resistance R 2, R3

The first switch Q1

Second switch Q2

Output switch Q3

Critical voltage Vth

Input voltage V1 after the dividing potential drop

Earth terminal G

Control signal S1

First surge suppressor 12

Second surge suppressor 14

The first capacitor C2

First resistor R 4

The second capacitor C3

Second resistor R 5

Output signal S2, S3

Embodiment

Please refer to Fig. 2, be the generalized schematic of the utility model overvoltage protection.Wherein, overvoltage protection 1 has voltage input end T1 and voltage output end T2, and overvoltage protection 1 is obtained input voltage vin from voltage input end T1, and sends output voltage V out by voltage output end T2.When input voltage vin imported overvoltage protection 1, if the magnitude of voltage of input voltage vin is greater than 1 predefined protection range of overvoltage protection, then overvoltage protection 1 will block too high input voltage vin, and it can't be passed through.In addition, if when excessive surge voltage takes place, overvoltage protection 1 can block input voltage vin equally, and it can't be passed through.

Cooperate Fig. 2, please refer to Fig. 3, Fig. 3 is the circuit diagram of the overvoltage protection of the utility model first embodiment.Overvoltage protection 1 includes comparison module 10, the first switch Q1, second switch Q2 and output switch Q3.Wherein, comparison module 10 is obtained input voltage vin from voltage input end T1, and comparison module 10 comparison operation input voltage vin and critical voltage Vth simultaneously, export control signal S1 according to the comparison operation result again.Simultaneously, first drain electrode end that first control end of the first switch Q1 couples comparison module 10, the first switch Q1 couples voltage input end T1, and first source terminal of the first switch Q1 is couple to an earth terminal G, and wherein, the first switch Q1 is controlled by control signal S1.

Cooperate Fig. 2 again, with reference to figure 3, second control end of second switch Q2 couples first drain electrode end of the first switch Q1, and second source terminal of second switch Q2 couples earth terminal G, and wherein, second switch Q2 is controlled by the output signal S2 of first drain electrode end of the first switch Q1.In addition, the 3rd control end of output switch Q3 couples second drain electrode end of second switch Q2, the 3rd drain electrode end of output switch Q3 couples voltage output end T2, the 3rd source terminal of output switch Q3 couples voltage input end T1, wherein, output switch Q3 is controlled by the output signal S3 of second drain electrode end of second switch Q2, and is sent to voltage output end T2 by input voltage vin or with input voltage vin.

Cooperate Fig. 2 again, with reference to figure 3, the aforesaid first switch Q1 is N slot field-effect transistor (NMOS FET), and second switch Q2 is N slot field-effect transistor (NMOS FET), and output switch Q3 is P-channel field-effect transistor (PEFT) transistor (PMOS FET).

Cooperate Fig. 2 again, with reference to figure 3, comparison module 10 includes shunt regulator 101, partial pressure unit 102 and comparator 103.Wherein, shunt regulator 101 comprises Zener diode D1, input capacitor C1 and input resistor R1, wherein Zener diode D1 coupled in series input resistor R1 and coupled in parallel input capacitor C1.Shunt regulator 101 couples voltage input end T1, produces critical voltage value Vth according to input voltage vin.Simultaneously, partial pressure unit 102 couples voltage input end T1, the input voltage V1 after receiving input voltage vin and producing dividing potential drop.In addition, the non-inverting input (+) of comparator 103 is in order to receive the input voltage V1 after the dividing potential drop, and the reverse input end (-) of comparator 103 then receives critical voltage value Vth, and, the output output control signal S1 of comparator 103.

Cooperate Fig. 2 again; with reference to figure 3; the designer can use the Zener diode D1 of different operating scope to obtain critical voltage value Vth, simultaneously also can be in partial pressure unit 102 resistance value of collocation design resistance R 2, R3, to set needed overvoltage protection scope.When input voltage vin imported overvoltage protection 1, Zener diode D1 punctured along with input voltage vin, and then produced stable critical voltage value Vth output.Simultaneously, the resistance R in the partial pressure unit 102 3 produces the input voltage V1 after the dividing potential drop according to input voltage vin.

When input voltage vin was normal condition, the input voltage V1 after the dividing potential drop did not surpass critical voltage value Vth, promptly is lower than 1 predefined protection range of overvoltage protection.At this moment, comparator 103 can be exported the control signal S1 of electronegative potential " LOW ", to control the first switch Q1 by (OFF).Because the first switch Q1 enters cut-off state, therefore, input voltage vin is delivered to second control end of second switch Q2 by first resistor R 4, with control second switch Q2 conducting (ON).The 3rd control end that the second switch Q2 of conducting will export switch Q3 is directed to earth terminal G, and makes output switch Q3 enter conducting state.At this moment, input voltage vin will be by the output switch Q3 of conducting, and from the voltage input end T1 output of overvoltage protection 1, forms output voltage V out.Please cooperate Fig. 5 A, this figure is the utility model when being operated in normal input voltage vin, the waveform schematic diagram of output voltage V out.Fig. 5 A demonstrates, and output voltage V out is 6V.

In addition, when input voltage vin was too high, the input voltage V1 after the dividing potential drop surpassed critical voltage value Vth, promptly surpassed 1 predefined protection range of voltage protection.At this moment, the control signal S1 of comparator 103 output high potentials " HIGH " is to control the first switch Q1 conducting.The first switch Q1 of conducting is directed to earth terminal G with second control end of second switch Q2, therefore causes second switch Q2 to end.The second switch Q2 that ends allows the 3rd control end of output switch Q3 form suspension joint (Floating) state, ends and make output switch Q3 enter.The output switch Q3 that ends will block too high input voltage vin, makes too high input voltage vin can't pass through voltage protection 1, thereby reaches superpotential protection.Please cooperate Fig. 5 B, this figure is the utility model when being operated in input voltage vin, the waveform schematic diagram of output voltage V out.Fig. 5 B demonstrates, and output voltage V out is through behind the transient time t1, promptly is cut off to be 0V.

Cooperate Fig. 2, please refer to Fig. 4, Fig. 4 is the circuit diagram of the overvoltage protection of the utility model second embodiment.In second embodiment of the invention, illustrate with identical symbol with the first embodiment components identical.Second embodiment is identical with function and the effect reached with the circuit operation principle of first embodiment, and its main difference part is: the overvoltage protection 1 ' of second embodiment has increased by first surge suppressor 12 and second surge suppressor 14.Wherein, first surge suppressor 12 couples second control end of Input voltage terminal T1 and second switch Q2, ends second switch Q2 according to surge voltage (Inrush Voltage).Second surge suppressor 14 couples between the 3rd control end and the 3rd source terminal of output switch Q3, ends output switch Q3 according to surge voltage.

Cooperate Fig. 2 again, with reference to figure 4, first surge suppressor 12 comprises first resistor R 4 of the coupled in series first capacitor C2, wherein first end of first resistor R 4 couples Input voltage terminal T1, second end of first resistor R 4 couples first drain electrode end of the first switch Q1, second control end of second switch Q2 and first end of the first capacitor C2, and second end of this first capacitor C2 couples earth terminal G.In addition, second surge suppressor 14 comprises second resistor R 5 of the coupled in parallel second capacitor C3, first end of the second capacitor C3 couples Input voltage terminal T1, and second end of the second capacitor C3 couples second drain electrode end of second switch Q2 and the 3rd control end of output switch Q3 jointly.

Cooperate Fig. 2 again, please refer to Fig. 4, surge voltage is the AC noise of high frequency, and therefore, according to formula (1), when surge voltage took place, the first capacitor C2 and the second capacitor C3 can form short circuit (capacitive reactance equals 0) because of the surge voltage of high-frequency ac.

$\mathrm{Xc}=-\mathrm{<figure-callout\; id="1"\; label="j"\; filenames="Y20082000125100131.png"\; state="\{\{state\}\}">j</figure-callout>}\frac{1}{\mathrm{\&omega;c}}$ Formula (1)

In formula (1), Xc is the capacitor value of capacitor, and ω is a frequency values, and C is the appearance value of capacitor, and wherein, when the AC noise of high frequency took place, the capacitor value Xc of capacitor approximated 0, so capacitor will form short-circuit condition.

According to aforementioned formula (1), when surge voltage takes place, the first capacitor C2 short circuit at once in first surge suppressor 12, and surge voltage is directed to earth terminal G, at this moment, the first capacitor C2 cross-over connection of short circuit is between second control end and second source terminal of second switch Q2, and Q2 enters cut-off state with the control second switch.The second switch Q2 that ends allows the 3rd control end of output switch Q3 form floating, so that output switch Q3 enters ends.In addition, when surge voltage takes place, the second capacitor C3 short circuit equally at once in second surge suppressor 14, at this moment, the second capacitor C3 cross-over connection of short circuit is between the 3rd control end and the 3rd source terminal of output switch Q3, and Q3 enters cut-off state with control output switch.The output switch Q3 that ends will block input voltage vin, makes input voltage vin can't pass through voltage protection 1, thereby reaches the anti-system of surge voltage.Please refer to Fig. 5 C, this figure is the utility model when being operated in surge voltage and taking place, the waveform schematic diagram of output voltage V out.Fig. 5 C demonstrates, and when surge voltage took place, output voltage V out was cut off at once and is 0V.

With reference to figure 4, wherein second switch Q2, output switch Q3 and second surge suppressor 14 are formed slow-start (Soft-Start) circuit of a standard again.When if burst current takes place, burst current just charges to the slow second capacitor C3 that starts in the circuit, and allows the electric current not so sharply (sharp) of output switch Q3 of flowing through, and then reaches the anti-system of burst current.

In sum, overvoltage protection of the present utility model has the function that suppresses surging and input overvoltage protection, when overvoltage is imported, can control the output switch and end, thereby reach superpotential protection via the judgement of comparison module.Simultaneously, when surge voltage takes place, can use first surge suppressor that surge voltage is directed into earth terminal, use the control end and the source terminal of second surge suppressor short circuit output switch, make the output of its cut-ff voltage, thereby reach the anti-system of surge voltage.

Yet the above only is the detailed description and the diagram of the specific embodiment of one of the utility model the best, and any those skilled in the art are in field of the present utility model, and variation that can contemplate easily or modification all can be encompassed in the scope of the present utility model.

Claims (9)

1. an overvoltage protection is characterized in that, has voltage input end and voltage output end, comprising:

Comparison module is obtained input voltage from this voltage input end, this this input voltage of comparison module comparison operation and critical voltage, and export control signal according to the comparison operation result;

First switch, first control end of this first switch couples this comparison module, and first drain electrode end couples this voltage input end, and first source terminal is couple to earth terminal, and this first switch is controlled by this control signal;

Second switch, second control end of this second switch couples this first drain electrode end, and second source terminal couples this earth terminal, and this second switch is controlled by the output signal of this first drain electrode end;

The output switch, the 3rd control end of this output switch couples this second drain electrode end, the 3rd drain electrode end couples this voltage output end, the 3rd source terminal couples this voltage input end, this output switch is controlled by the output signal of this second drain electrode end, is used for maybe this input voltage being sent to this voltage output end by this input voltage;

First surge suppressor, this first surge suppressor couple this Input voltage terminal and this second control end, and this first surge suppressor comes by this second switch according to surge voltage; And

Second surge suppressor, this second surge suppressor couple between the 3rd control end and the 3rd source terminal, and this second surge suppressor comes by this output switch according to this surge voltage.

2. overvoltage protection as claimed in claim 1 is characterized in that, this comparison module comprises:

Shunt regulator couples this voltage input end, and this shunt regulator produces this critical voltage value according to this input voltage;

Partial pressure unit couples this voltage input end, receives this input voltage, and produces the input voltage after the dividing potential drop; And

Comparator, it has non-inverting input, reverse input end and output, and this non-inverting input receives the input voltage after this dividing potential drop, and this reverse input end receives this critical voltage value, and this output is exported this control signal.

3. overvoltage protection as claimed in claim 2 is characterized in that this shunt regulator comprises Zener diode, input capacitor and input resistor, wherein this this input resistor of Zener diode coupled in series and this input capacitor of coupled in parallel.

4. overvoltage protection as claimed in claim 1; it is characterized in that; this first surge suppressor comprises first resistor of coupled in series first capacitor; first end of this first resistor couples this Input voltage terminal; second end of this first resistor couples first drain electrode end of this first switch, second control end of this second switch and first end of this first capacitor jointly, and second end of this first capacitor couples this earth terminal.

5. overvoltage protection as claimed in claim 1; it is characterized in that; this second surge suppressor comprises second resistor of coupled in parallel second capacitor; first end of this second capacitor couples this Input voltage terminal, and second end of this second capacitor couples the drain electrode end of this second switch and the 3rd control end of this output switch jointly.

6. overvoltage protection as claimed in claim 1 is characterized in that, this first switch is the N slot field-effect transistor.

7. overvoltage protection as claimed in claim 1 is characterized in that, this second switch is the N slot field-effect transistor.

8. overvoltage protection as claimed in claim 1 is characterized in that, this output switch is the P-channel field-effect transistor (PEFT) transistor.

9. overvoltage protection as claimed in claim 1 is characterized in that, this second switch, this output switch and this second surge suppressor are formed the slow-start circuit of a standard.

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