CN205104896U - Overvoltage protection circuit - Google Patents
Overvoltage protection circuit Download PDFInfo
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- CN205104896U CN205104896U CN201520859193.6U CN201520859193U CN205104896U CN 205104896 U CN205104896 U CN 205104896U CN 201520859193 U CN201520859193 U CN 201520859193U CN 205104896 U CN205104896 U CN 205104896U
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- inductance
- descending slope
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Abstract
The utility model provides an overvoltage protection circuit, acquire unit, threshold value settlement unit, judge unit and protected location including load, inductance, switch tube, freewheeling diode, descending slope. Load, inductance and switch tube in proper order the series connection at the circuit output. Freewheeling diode connects between load and inductance, forms the return circuit of discharging between inductance, freewheeling diode and the load, and when the switch tube turn -offed, the inductance discharged through the return circuit of discharging. The descending slope obtains the unit and obtains the descending slope that the switch tube closed the inductive current that has no progeny, and the descending slope is directly proportional with output voltage. The threshold value is compared in the settlement of threshold value settlement unit and electric connection judges the unit. Judge that unit electric connection descending slope acquires unit and threshold value settlement unit, carry out the comparison with descending slope and threshold value relatively, judge the whether excessive pressure of output voltage of circuit according to the comparative result. Protected location electric connection judges unit and switch tube, and when judging that the output voltage excessive pressure is judged to the unit, the switch tube is closed to the protected location.
Description
Technical field
The utility model relates to electronic technology field, and in particular to a kind of overvoltage crowbar.
Background technology
In existing translation circuit, as usually realized overvoltage protection by Direct Sampling output voltage in Buck circuit (Buck conversion circuit).As shown in Figure 1; switching tube is connected with the positive bus-bar of Buck circuit; the source electrode of switching tube connects diode, and one of them input of comparator directly obtains output voltage by divider resistance, and the control exporting switching tube to through logic control after relatively extremely realizes overvoltage protection.In this each circuit, because the source electrode of switching tube connects diode, therefore the V of switching tube
gScurrent potential is not fixed, and switching tube needs to drive floatingly, drives comparatively complicated.
For convenience of driving, the negative busbar of switching tube with Buck circuit is connected, as shown in Figure 2.In the circuit due to output voltage and input voltage not altogether, need, by an auxiliary winding, to realize the sampling of output voltage when switching tube conducting, and then realize overvoltage protection.Increase complexity and cost that auxiliary winding not only increases circuit, and auxiliary winding is a negative voltage during switch conduction, is unfavorable for that the inside of circuit is integrated.
Utility model content
The utility model, in order to overcome the deficiencies in the prior art, provides a kind of overvoltage crowbar.
To achieve these goals, the utility model provides a kind of overvoltage crowbar, comprises load, inductance, switching tube, fly-wheel diode, descending slope acquiring unit, threshold setting unit, identifying unit and protected location.Load, inductance and switching tube are sequentially connected in series at circuit output end.Fly-wheel diode is connected between load and inductance, inductance, forms discharge loop between fly-wheel diode and load, and when switching tube turns off, inductance is discharged by discharge loop.Descending slope acquiring unit obtains the descending slope that switching tube closes inductive current of having no progeny, and descending slope is directly proportional to output voltage.Threshold value assigning unit assigns compare threshold and be electrically connected identifying unit.Identifying unit is electrically connected descending slope acquiring unit and threshold setting unit, the descending slope and compare threshold that characterize circuit output voltage is compared, according to the whether overvoltage of the output voltage of comparative result decision circuitry.Protected location is electrically connected identifying unit and switching tube, when identifying unit judges output voltage overvoltage, and protected location closing switch pipe.
In the utility model one embodiment, descending slope acquiring unit comprises current change quantity sampling unit, timing unit and computing unit, current change quantity sampling unit is electrically connected inductance and timing unit respectively, current change quantity sampling unit obtains inductive current drops to valley current change quantity from peak value, timing unit starts timing in the switching tube shutoff moment, when inductive current drops to valley, timing terminates, obtain fall time, current change quantity and fall time export computing unit to, obtain descending slope afterwards as calculated, computing unit exports descending slope to identifying unit and compares with the descending slope threshold value of setting, when descending slope is greater than descending slope threshold value, output voltage overvoltage.
In the utility model one embodiment, inductive current be critical continuous conduction mode or discontinuous mode time, descending slope acquiring unit comprises zero passage detection unit, time switch, DC source and charging capacitor, zero passage detection unit is electrically connected inductance, obtain inductance when electric current drops to zero point in discharge process, time switch is electrically connected zero passage detection unit, turn off moment time switch at switching tube to close, DC source is charged to charging capacitor, when inductive current drops to zero point, time switch is opened, and capacitor charging terminates;
Threshold setting unit comprises peak current sampling resistor, holding unit and proportional unit, peak current sampling resistor is electrically connected switching tube, and the peak current obtained when switching tube turns off on inductance enters proportional unit and carries out ratio calculating coating-forming voltage threshold value after keeping;
When the capacitance voltage that DC source is formed capacitor charging within inductive current fall time is less than voltage threshold, output voltage overvoltage.
In the utility model one embodiment, when inductive current is critical continuous conduction mode and the peak value of inductive current is constant, or inductive current be discontinuous mode and the peak value of inductive current is constant time, descending slope acquiring unit comprises zero passage detection unit and timing unit, zero passage detection unit is electrically connected inductance, obtain inductance when electric current drops to zero point in discharge process, timing unit is electrically connected zero passage detection unit, turn off moment timing unit at switching tube and start timing, after inductive current drops to zero point, timing terminates, obtain the fall time of inductive current and identifying unit will be exported to fall time, compare with time threshold.
In the utility model one embodiment, zero passage detection unit comprises the detecting voltage unit of current sampling resistor and the detecting current sampling resistor both end voltage of connecting with inductance, and after current sampling resistor both end voltage drops to zero point, detecting voltage element output signal is to timing unit or time switch.
In the utility model one embodiment, zero passage detection unit comprises differential capacitance, differential resistance and negative voltage detecting unit, differential capacitance is connected on the intersection point of switching tube and inductance, differential resistance is connected with differential capacitance and differential resistance ground connection, the negative voltage at negative voltage detecting unit detecting differential capacitance and differential resistance tie point place, negative voltage detecting unit is electrically connected timing unit or time switch, once negative voltage detecting unit detects negative voltage, timing unit or time switch stop timing.
In sum, the overvoltage crowbar that the utility model provides compared with prior art has the following advantages:
Inductance is a kind of energy-storage travelling wave tube, and switching tube closes has no progeny, and inductance descending slope of inductive current in discharge process is directly proportional to the output voltage of circuit.The utility model utilizes this characteristic of inductance, arranges descending slope acquiring unit acquisition inductive current and closes the descending slope of having no progeny at switching tube.Descending slope and compare threshold compare by identifying unit, and judge output voltage whether overvoltage by comparative result, once output voltage overvoltage, protected location closing switch pipe, no longer continues as load supplying, protection output loading.The relation when overvoltage crowbar that the utility model provides utilizes inductive discharge between the descending slope of inductive current and output voltage obtains output voltage indirectly, thus realizes the judgement of output overvoltage.This kind of sample mode, switching tube to drive and also without the need to adopting winding to sample without the need to floating, and not only simple the and parts such as each inductance, inductance sampling unit of circuit structure can integrate with output circuit, substantially reduce the volume of circuit.
For above-mentioned and other objects, features and advantages of the present utility model can be become apparent, preferred embodiment cited below particularly, and coordinate accompanying drawing, be described in detail below.
Accompanying drawing explanation
Fig. 1 and the schematic diagram that Figure 2 shows that existing overvoltage crowbar.
Figure 3 shows that the schematic diagram of the overvoltage crowbar that the utility model embodiment one provides.
Figure 4 shows that the schematic diagram of the overvoltage crowbar that the utility model embodiment two provides.
Figure 5 shows that the schematic diagram of the overvoltage crowbar that another embodiment of the utility model provides.
Figure 6 shows that the schematic diagram of the overvoltage crowbar that the utility model embodiment three provides.
Figure 7 shows that the curent change figure of critical current mode continuous mode.
Figure 8 shows that the curent change figure of discontinous mode.
Embodiment
Embodiment one
Figure 1 shows that existing Buck circuit realizes overvoltage protection by Direct Sampling output voltage, in the circuit due to the V of switching tube
gSdriving voltage and control chip not altogether, therefore need employing to drive floatingly.And in fig. 2, the driving and controlling circuits of switching tube altogether, but exports not altogether, need to realize overvoltage protection by increasing auxiliary winding, this not only considerably increases cost, is also unfavorable for that the inside of circuit is integrated simultaneously.
In view of this, as shown in Figure 3, the utility model provides a kind of overvoltage crowbar to comprise load R, inductance L, switching tube Q, sustained diode, descending slope acquiring unit 1, threshold setting unit 2, identifying unit 3 and protected location 4.Load R, inductance L and switching tube Q three are sequentially connected in series.Sustained diode is connected between load R and inductance L, inductance L, forms discharge loop between sustained diode and load R, and when switching tube Q turns off, inductance L is discharged by discharge loop.Descending slope acquiring unit 1 obtains descending slope K, descending slope K and the output voltage U that switching tube Q closes inductive current of having no progeny
outbe directly proportional.Threshold setting unit 2 sets compare threshold and is electrically connected identifying unit 3.Identifying unit 3 will characterize descending slope K and the compare threshold K of circuit output voltage
refcompare, according to the output voltage U of comparative result decision circuitry
outwhether overvoltage.Protected location 4 is electrically connected identifying unit 3 and switching tube Q, and when identifying unit 3 judges output voltage overvoltage, protected location 4 closing switch pipe Q, no longer continues as load supplying.
In the present embodiment, descending slope acquiring unit 1 comprises current change quantity sampling unit 11, timing unit 12 and computing unit 13, current change quantity sampling unit 11 is electrically connected inductance L and timing unit 12 respectively, current change quantity sampling unit 11 obtains inductive current drops to valley current change quantity from peak value, timing unit 12 starts timing in the switching tube shutoff moment, when inductive current drops to valley, timing terminates, and obtains △ t fall time.Current change quantity △ i and fall time △ t export computing unit 13 to, obtain descending slope K afterwards as calculated, descending slope K is exported to the descending slope threshold k of identifying unit 3 and setting by computing unit 13
refcompare, when descending slope K is greater than descending slope threshold k
reftime, output voltage U
outovervoltage.
In the present embodiment, current change quantity sampling unit 11 comprises current sampling resistor, comparator, memory and the processor of connecting with inductance.Last sampled value stores by memory, and one of them input of comparator is connected with current sampling resistor, and another input is connected with memory, and comparator is by constantly comparing current sample values and last sampled value obtains maximum voltage U
maxwith minimum voltage U
min, after treated device process, obtain current change quantity.In the present embodiment, identifying unit 3 is comparator, and computing unit 13 is divider.
The specific works step of the overvoltage crowbar that the present embodiment provides is:
Step S1, acquisition overvoltage crowbar breaker in middle pipe close the descending slope △ i/ △ t of inductive current of having no progeny, the output voltage U of descending slope △ i/ △ t and circuit
outbe directly proportional, U
out=L △ i/ △ t, L is inductance, and △ i is the current change quantity that switching tube closes that inductive current of having no progeny drops to valley from peak value, and △ t is that inductive current drops to the time of valley from peak value.
In the present embodiment, step S1 comprises:
Step S11, close to have no progeny at switching tube and obtain inductive current to drop to valley current change quantity △ i from peak value.In the present embodiment, adopt current change quantity sampling unit 11 to obtain current change quantity △ i, current change quantity sampling unit 11 comprises current sampling resistor, comparator, memory and the processor of connecting with inductance.When inductive current is in peak value, current sampling resistor has maximum voltage U
max, when inductive current drops to valley, current sampling resistor has minimum voltage U
min.Sampled value on memory storaging current sampling resistor, comparator is more adjacent two sampled values constantly, obtain maximum voltage U
maxwith minimum voltage U
min, maximum voltage U
maxwith minimum voltage U
mintreated device obtains current change quantity △ i=(U after calculating
max-U
min)/R1, R1 is the resistance of current sampling resistor.
Step S12, acquisition inductive current drop to △ t fall time of valley from peak value.For inductance, the immediate current that switching tube turns off is in peak value, and in the present embodiment, timing unit starts timing when switching tube turns off, and obtains minimum voltage U when comparator compares
minand by minimum voltage U
minexport processor to, output signal of processor is to timing unit 12, and timing unit 12 terminates timing and obtains inductive current drops to valley time △ t from peak value.
Step S13, by △ i/ △ t, obtain inductive current descending slope K.
Step S2, by obtain descending slope K and compare threshold K
refcompare, when descending slope K is greater than compare threshold K
reftime, output voltage U
outovervoltage.
Step S3, when output voltage overvoltage, protected location closing switch pipe, no longer continues as load supplying.
Embodiment two
The overvoltage crowbar that the present embodiment provides is applicable to inductive current and is critical continuous conduction mode and peak current is constant or discontinuous mode and the constant circuit of peak current.It is curent change figure under critical continuous conduction mode and discontinuous mode that Fig. 7 and Fig. 8 sets forth inductive current.For critical continuous conduction mode, switching tube turns off when inductive current peak reaches set current peak threshold value, and the moment dropping to zero at inductive current reopens; For discontinuous mode, switching tube turns off when inductive current peak reaches set current peak threshold value, drops to after zero at inductive current, and time delay a period of time reopens.In figures 7 and 8, t0 moment switching tube turns off, and t1 moment inductive current drops to zero, △ i=t1-t0.At critical continuous conduction mode and peak current I
peakconstant or discontinuous mode and peak current I
peakin constant circuit, the electric current on inductance must drop to zero point, in this kind of circuit, and inductive current variable quantity △ i=I
peak-0=I
peak, namely △ i is constant.
According to formula K=△ i/ △ t
Because △ i is constant, the acquisition of descending slope K is converted to and obtains inductive current from peak I
peakdrop to △ t fall time at zero point, fall time, △ t and descending slope K was inversely proportional to, namely with output voltage U
outbe inversely proportional to.Therefore, in the present embodiment, by descending slope K and compare threshold compare be converted to fall time △ t with the comparing of time threshold.Concrete step is:
Step S10, close to have no progeny at switching tube and obtain inductive current to drop to zero △ t fall time from peak value.
Step S20, by △ t and time threshold △ t fall time
refcompare, when △ t is less than △ t
reftime, output voltage U
outovervoltage.
Step S30, when output voltage overvoltage, closing switch pipe, no longer continues as load supplying.
As shown in Figure 4, the utility model provides a kind of overvoltage crowbar to comprise load R, inductance L, switching tube Q, sustained diode, descending slope acquiring unit 1, threshold setting unit 2, identifying unit 3 and protected location 4.Load R, inductance L and switching tube Q three are sequentially connected in series.Sustained diode is connected between load R and inductance L, inductance L, forms discharge loop between sustained diode and load R, and when switching tube Q turns off, inductance L is discharged by discharge loop.Descending slope acquiring unit 1 obtains descending slope K, descending slope K and the output voltage U that switching tube Q closes inductive current of having no progeny
outbe directly proportional.Threshold setting unit 2 sets compare threshold and is electrically connected identifying unit 3.The descending slope K and compare threshold that characterize circuit output voltage compare, according to the output voltage U of comparative result decision circuitry by identifying unit 3
outwhether overvoltage.Protected location 4 is electrically connected identifying unit 3 and switching tube Q, when identifying unit 3 judges output voltage U
outduring overvoltage, protected location 4 closing switch pipe Q, no longer continues as load supplying.
In the present embodiment, descending slope acquiring unit 1 comprises zero passage detection unit 14 and timing unit 12, zero passage detection unit 14 is electrically connected inductance L, obtain inductance L when electric current drops to zero point in discharge process, timing unit 12 is electrically connected zero passage detection unit 14, when switching tube Q turns off, timing unit 12 starts timing, when inductive current drops to zero point, timing terminates, obtain the △ t export △ t fall time to identifying unit 3 fall time of inductive current, identifying unit 3 is by △ t and time threshold △ t fall time
refcompare.
In the present embodiment, zero passage detection unit 14 comprises the current sampling resistor of connecting with inductance L, the detecting voltage unit of detecting current sampling resistor both end voltage, after current sampling resistor both end voltage drops to zero point, detecting voltage element output signal is to timing unit 12.But the structure of the utility model to zero passage detection unit 14 is not limited in any way.
In other embodiment, as shown in Figure 5, zero passage detection unit 14 comprises differential capacitance C2, differential resistance R2 and negative voltage detecting unit T1, differential capacitance C2 is connected on the point of intersection S W point of switching tube Q and inductance L, differential resistance R2 connects with differential capacitance C2 and differential resistance R2 ground connection, negative voltage detecting unit T1 detects the negative voltage at differential capacitance C2 and differential resistance R2 tie point place, and negative voltage detecting unit T1 is electrically connected timing unit 12.
When switching tube Q turns off, timing unit 12 starts timing.Drop to before zero at inductive current, inductive current flows to positive bus-bar end by sustained diode, SW point voltage is the forward conduction voltage drop that positive bus-bar terminal voltage adds sustained diode, and differential capacitance C2 both end voltage equals SW point voltage, and the voltage on differential resistance R2 is zero.When inductive current drops to zero, sustained diode is ended, the resonant tank be made up of the parasitic capacitance of inductance, sustained diode, the parasitic capacitance of switching tube Q produces resonance at SW point place, the moment making SW voltage drop to zero at inductive current starts to vibrate to negative busbar end, differential capacitance C2 produces negative differential electric current, thus makes the point of intersection of differential capacitance C2 and differential resistance R2 produce negative voltage.Namely the point of intersection detecting differential capacitance C2 and differential resistance R2 once negative voltage detecting unit T1 is negative voltage, can assert that inductive current drops to zero, timing unit 12 stops timing, obtain the △ t export △ t fall time to identifying unit 3 fall time of inductive current, identifying unit 3 is by △ t and time threshold △ t fall time
refcompare.
In other embodiment, zero passage detection unit 14 also can be the Intelligent current table of connecting with inductance L, when ammeter detects that inductive current outputs signal to timing unit 12 when being zero.
Embodiment three
As shown in Figure 7 and Figure 8, inductive current be critical continuous conduction mode or discontinuous mode time, inductive current variable quantity △ i equals the peak I of inductive current
peak.The acquisition of descending slope K is converted to and obtains inductive current peak I
peakwith the ratio of △ t fall time.Inductive current peak I
peakwith fall time △ t ratio and output voltage U
outbe directly proportional, therefore, by comparing inductive current peak I
peakthe ratio of △ t can obtain output voltage U with fall time
outwhether overvoltage.Once output voltage U
outovervoltage, then closing switch pipe Q, no longer continues as load supplying.
Accordingly; as shown in Figure 6; the present embodiment additionally provide a kind of inductive current be critical continuous conduction mode or discontinuous mode time overvoltage crowbar, comprise load R, inductance L, switching tube Q, sustained diode, descending slope acquiring unit 1, threshold setting unit 2, identifying unit 3 and protected location 4.Load R, inductance L and switching tube Q three are sequentially connected in series.Sustained diode is connected between load R and inductance L, inductance L, forms discharge loop between sustained diode and load R, and when switching tube Q turns off, inductance L is discharged by discharge loop.Descending slope acquiring unit 1 obtains descending slope K, descending slope K and the output voltage U that switching tube Q closes inductive current of having no progeny
outbe directly proportional.Threshold setting unit 2 sets compare threshold and is electrically connected identifying unit 3.The inductive current descending slope K and compare threshold that characterize circuit output voltage compare, according to the output voltage U of comparative result decision circuitry by identifying unit 3
outwhether overvoltage.Protected location 4 is electrically connected identifying unit 3 and switching tube Q, and when identifying unit 3 judges output voltage overvoltage, protected location 4 closing switch pipe Q, no longer continues as load supplying.
In the present embodiment, descending slope acquiring unit 1 comprises zero passage detection unit 14, time switch S, DC source I1 and charging capacitor C1, zero passage detection unit 14 is electrically connected inductance L, obtain inductance L when electric current drops to zero point in discharge process, time switch S is electrically connected zero passage detection unit 14, turn off moment time switch S at switching tube Q to close, DC source I1 charges to charging capacitor C1; After inductive current drops to zero point, time switch S opens, and electric capacity C1 charges end.
Threshold setting unit 2 comprises peak current sampling resistor R3, holding unit 21 and proportional unit 22, and peak current sampling resistor R3 is electrically connected switching tube Q, obtains the peak I of inductive current at switching tube Q shutdown moment
peak, after keeping, enter proportional unit 22 carry out ratio calculating coating-forming voltage threshold k 1*I
peak, K1 is proportionality constant.Proportional unit 22 can be multiplier.
When DC source I1 is less than voltage threshold K1*I to the capacitance voltage Uc (Uc=I1* △ t/C1) that capacitor charging is formed in fall time in △ t
peaktime, I
peak/ △ t>I1/ (C1*K1).Due at inductive current be critical continuous conduction mode or discontinuous mode time, inductive current variable quantity △ i equals the peak I of inductive current
peak, therefore △ i/ △ t>I1/ (C1*K1).I1, C1 and K1 are fixed value, and this formula identity inductive current descending slope K (△ i/ △ t) is greater than set slope threshold value, output voltage U
outovervoltage.
The overvoltage crowbar that the present embodiment provides by Set scale constant K1 to realize the automatic adjustment of voltage threshold.In actual use, designer is by changing different inductance L or arranging different K1 values to realize the setting of over-voltage protection point, and this arranges and greatly facilitates the design of circuit and integrated.
In other embodiment, when inductive current is continuous mode, now △ t fall time of inductive current equals the turn-off time of switching tube.The acquisition of descending slope is converted to and obtains inductive current from peak I
peakdrop to valley I
valleycurrent change quantity △ i and the ratio of switching tube turn-off time.The output voltage U of this ratio and circuit
outbe directly proportional.Therefore, by comparing the ratio of current change quantity △ i and switching tube turn-off time, output voltage whether overvoltage can be obtained.Once output voltage overvoltage, then closing switch pipe Q, no longer continues as load supplying.For this situation, the basis of the overvoltage crowbar that can provide at the present embodiment is improved, zero passage detection unit 14 is replaced with and inductive current peak I can be detected
peakwith valley I
valleycurrent change quantity sampling unit.When switching tube is closed, time switch S closes, and DC source I1 charges to charging capacitor C1.When inductive current drops to valley I
valleytime, time switch S opens, and terminates the charging of charging capacitor C1.
The voltage U c=I1* △ t/C1 at charging capacitor C1 two ends, when Uc is less than K1* (I
peak-I
valley) time, i.e. (I
peak-I
valley)/△ t>I1/ (C1*K1), because I1, C1 and K1 are fixed value, this formula identity inductive current descending slope K (△ i/ △ t) is greater than set slope threshold value, output voltage U
outovervoltage.
In sum, inductance is a kind of energy-storage travelling wave tube, and switching tube closes has no progeny, and inductance descending slope of inductive current in discharge process is directly proportional to the output voltage of circuit.The utility model utilizes this characteristic of inductance, arranges descending slope acquiring unit acquisition inductance and closes the descending slope of having no progeny at switching tube.Descending slope and compare threshold compare by identifying unit, judge output voltage whether overvoltage, once output voltage overvoltage by comparative result; then closing switch pipe Q; no longer continue as load supplying, make to open a way between output circuit and load, protection output loading.The overvoltage crowbar that the utility model provides utilize inductive discharge time the descending slope of inductive current and output voltage between relation indirectly obtain output voltage, thus realize the judgement of output overvoltage.This kind of sample mode, switching tube to drive and also without the need to adopting winding to sample without the need to floating, and not only simple the and parts such as each inductance, inductance sampling unit of circuit structure can integrate with output circuit, substantially reduce the volume of circuit.
Although the utility model discloses as above by preferred embodiment; but and be not used to limit the utility model; anyly know this those skilled in the art; not departing from spirit and scope of the present utility model; can do a little change and retouching, therefore protection range of the present utility model is when being as the criterion depending on claims scope required for protection.
Claims (6)
1. an overvoltage crowbar, is characterized in that, comprising:
Be sequentially connected in series load in circuit, inductance and switching tube;
Fly-wheel diode, is connected between load and inductance, inductance, forms discharge loop between fly-wheel diode and load, and when switching tube turns off, inductance is discharged by discharge loop;
Descending slope acquiring unit, obtain the descending slope that switching tube closes inductive current of having no progeny, descending slope is directly proportional to output voltage;
Threshold setting unit, sets compare threshold and is electrically connected identifying unit;
Identifying unit, is electrically connected described descending slope acquiring unit and threshold setting unit, will characterize the descending slope of circuit output voltage and compare threshold compares, according to the whether overvoltage of the output voltage of comparative result decision circuitry;
Protected location, is electrically connected identifying unit and switching tube, when identifying unit judges output voltage overvoltage, and protected location closing switch pipe.
2. overvoltage crowbar according to claim 1, it is characterized in that, described descending slope acquiring unit comprises current change quantity sampling unit, timing unit and computing unit, current change quantity sampling unit is electrically connected inductance and timing unit respectively, current change quantity sampling unit obtains inductive current drops to valley current change quantity from peak value, timing unit starts timing in the switching tube shutoff moment, when inductive current drops to valley, timing terminates, obtain fall time, current change quantity and fall time export computing unit to, obtain descending slope afterwards as calculated, computing unit exports descending slope to identifying unit and compares with the descending slope threshold value of setting, when descending slope is greater than descending slope threshold value, output voltage overvoltage.
3. overvoltage crowbar according to claim 1, it is characterized in that, inductive current be critical continuous conduction mode or discontinuous mode time, descending slope acquiring unit comprises zero passage detection unit, time switch, DC source and charging capacitor, zero passage detection unit is electrically connected inductance, obtain inductance when electric current drops to zero point in discharge process, time switch is electrically connected zero passage detection unit, turn off moment time switch at switching tube to close, DC source is charged to charging capacitor, when inductive current drops to zero point, time switch is opened, capacitor charging terminates,
Threshold setting unit comprises peak current sampling resistor, holding unit and proportional unit, peak current sampling resistor is electrically connected switching tube, and the peak current obtained when switching tube turns off on inductance enters proportional unit and carries out ratio calculating coating-forming voltage threshold value after keeping;
When the capacitance voltage that DC source is formed capacitor charging within inductive current fall time is less than voltage threshold, output voltage overvoltage.
4. overvoltage crowbar according to claim 1, it is characterized in that, be critical continuous conduction mode and the peak value of inductive current is constant at inductive current, or inductive current be discontinuous mode and the peak value of inductive current is constant time, descending slope acquiring unit comprises zero passage detection unit and timing unit, zero passage detection unit is electrically connected inductance, obtain inductance when electric current drops to zero point in discharge process, timing unit is electrically connected zero passage detection unit, turn off moment timing unit at switching tube and start timing, after inductive current drops to zero point, timing terminates, obtain the fall time of inductive current and identifying unit will be exported to fall time, compare with time threshold.
5. the overvoltage crowbar according to claim 3 or 4; it is characterized in that; described zero passage detection unit comprises the detecting voltage unit of current sampling resistor and the detecting current sampling resistor both end voltage of connecting with inductance, and after current sampling resistor both end voltage drops to zero point, detecting voltage element output signal is to timing unit or time switch.
6. the overvoltage crowbar according to claim 3 or 4; it is characterized in that; zero passage detection unit comprises differential capacitance, differential resistance and negative voltage detecting unit; differential capacitance is connected on the intersection point of switching tube and inductance; differential resistance is connected with differential capacitance and differential resistance ground connection; the negative voltage at negative voltage detecting unit detecting differential capacitance and differential resistance tie point place; negative voltage detecting unit is electrically connected timing unit or time switch; once negative voltage detecting unit detects negative voltage, timing unit or time switch stop timing.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201520859193.6U CN205104896U (en) | 2015-10-30 | 2015-10-30 | Overvoltage protection circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201520859193.6U CN205104896U (en) | 2015-10-30 | 2015-10-30 | Overvoltage protection circuit |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN205104896U true CN205104896U (en) | 2016-03-23 |
Family
ID=55520652
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201520859193.6U Withdrawn - After Issue CN205104896U (en) | 2015-10-30 | 2015-10-30 | Overvoltage protection circuit |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN205104896U (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105244848A (en) * | 2015-10-30 | 2016-01-13 | 杰华特微电子（杭州）有限公司 | Overvoltage protection method and circuit |
| CN107947123A (en) * | 2017-10-24 | 2018-04-20 | 深圳市必易微电子有限公司 | ACDC protective circuit of switch power source and ACDC switching power units |
-
2015
- 2015-10-30 CN CN201520859193.6U patent/CN205104896U/en not_active Withdrawn - After Issue
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105244848A (en) * | 2015-10-30 | 2016-01-13 | 杰华特微电子（杭州）有限公司 | Overvoltage protection method and circuit |
| CN105244848B (en) * | 2015-10-30 | 2019-02-15 | 杰华特微电子（杭州）有限公司 | Over-voltage protection method and circuit |
| CN107947123A (en) * | 2017-10-24 | 2018-04-20 | 深圳市必易微电子有限公司 | ACDC protective circuit of switch power source and ACDC switching power units |
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