CN104065257A - Hysteretic start-up circuit of power supply control chip - Google Patents
Hysteretic start-up circuit of power supply control chip Download PDFInfo
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Abstract
The invention discloses a hysteretic start-up circuit of a power supply control chip. The circuit is connected with a voltage feedback pin of the power supply control chip. The hysteretic start-up circuit comprises a high level output loop and a low level output loop which are connected with a DC power supply. The high level output loop is used for outputting voltage which is larger than reference voltage to the voltage feedback pin so as to control the turn-off of the power supply control chip when the voltage of the DC power supply is smaller than starting voltage or the voltage of the DC power supply is smaller than turn-off voltage after the power supply control chip is started. The low level output loop is connected with the high level output loop and outputs voltage which is smaller than the reference voltage to the voltage feedback pin so as to control the turn-on of the power supply control chip when the voltage of the DC power supply is larger than the starting voltage. The starting voltage is larger than the turn-off voltage. Through the implementation of the hysteretic start-up circuit, the turn-on and turn-off of the power supply control chip can be effectively controlled, the hysteretic start-up circuit is suitable for a very wide DC voltage range, and the loss is extremely small.
Description
Technical field
The present invention relates to accessory power supply field, more particularly, relate to a kind of hysteresis start-up circuit of power supply control chip.
Background technology
In the larger occasion of some DC voltage change, when DC power supply brownout, system is not worked, and does not now wish secondary power system work yet, because the now work of secondary power system is waste electric energy in vain; When DC power supply change in voltage is more frequent, also do not wish secondary power system startup and shutdown repeatedly again, this can affect the useful life of secondary power system.
In secondary power system, be all if the circuit of UCX84X series is as circuit of reversed excitation, forward converter, push-pull circuit etc. based on power supply control chip.And it is existing in order to realize power supply control chip as the startup of UCX84X series and shutoff, additional control chip more normally, detect the voltage of DC power supply, then by the output of control chip, control power supply control chip as the startup of UCX84X series and shutoff, make starting resistor higher than shutoff voltage, realize hysteresis.
Summary of the invention
The technical problem to be solved in the present invention is, for the above-mentioned of prior art, realize power supply control chip as the startup of UCX84X series and turn-off the defect that needs additional other control chips and voltage detecting circuit, a kind of hysteresis start-up circuit of power supply control chip is provided.
The technical solution adopted for the present invention to solve the technical problems is: the hysteresis start-up circuit of constructing a kind of power supply control chip, be connected with the Voltage Feedback pin of described power supply control chip, comprise the high level output loop and the low level output loop that are all connected with DC power supply; Described high level output loop is for being less than starting resistor or when described DC power supply voltage is less than shutoff voltage after described power supply control chip starts, the voltage that output is greater than reference voltage turn-offs to control described power supply control chip to described Voltage Feedback pin at described DC power supply voltage; Described low level output loop is connected with described high level output loop, and when described DC power supply voltage is greater than described starting resistor, the voltage that output is less than described reference voltage starts to control described power supply control chip to described Voltage Feedback pin; Described starting resistor is greater than described shutoff voltage.
In above-mentioned hysteresis start-up circuit, when the voltage that described Voltage Feedback pin is exported in described low level output loop is less than described reference voltage, corresponding DC power supply voltage is described starting resistor; Described high level output loop is after described power supply control chip starts, and when the voltage of exporting to described Voltage Feedback pin is greater than described reference voltage, corresponding DC power supply voltage is described shutoff voltage.
In above-mentioned hysteresis start-up circuit, described high level output loop comprises the first switching tube, described low level output loop comprises voltage stabilizing didoe and second switch pipe, wherein: the base stage of described the first switching tube is connected with the collector electrode of described second switch pipe, the emitter of described the first switching tube is connected with described Voltage Feedback pin, the collector electrode of described the first switching tube is connected with the negative electrode of described voltage stabilizing didoe, and the anode of described voltage stabilizing didoe is connected with the base stage of described second switch pipe;
At described DC power supply voltage, be less than described starting resistor, or when, described DC power supply voltage rear in described power supply control chip startup is less than described shutoff voltage, described second switch pipe turn-offs, the base voltage of described the first switching tube is provided by described DC power supply, described the first switching tube conducting, institute's voltage stabilizing didoe makes the voltage of exporting to described Voltage Feedback pin be greater than described reference voltage for the emitter-base bandgap grading output voltage of the first switching tube described in clamp, and described power supply control chip turn-offs;
When described DC power supply voltage is greater than described starting resistor, the conducting of described second switch pipe, the collector electrode output low level of described second switch pipe is given the base stage of described the first switching tube, described the first switching tube turn-offs, the emitter-base bandgap grading output voltage of described the first switching tube is that low level voltage is less than described reference voltage so that export to the voltage of described Voltage Feedback pin, and described power supply control chip starts.
In above-mentioned hysteresis start-up circuit, described high level output loop also comprises the first resistance, wherein: one end of described the first resistance is connected with the positive pole of described DC power supply, the other end of described the first resistance is connected with the base stage of described the first switching tube, and the emitter of described the first switching tube is connected with described Voltage Feedback pin.
In above-mentioned hysteresis start-up circuit, described low level output loop also comprises the second resistance, the 3rd resistance and the 4th resistance, wherein: one end of described the second resistance is connected with the positive pole of described DC power supply, the other end of described the second resistance connects the tie point of described the first switching tube and described voltage stabilizing didoe, one end of described the 4th resistance connects the tie point of described voltage stabilizing didoe and described second switch pipe, and the emitter of the other end of described the 4th resistance and described second switch pipe is all connected with the negative pole of described DC power supply.
In above-mentioned hysteresis start-up circuit, when described DC power supply voltage is less than described starting resistor, the voltage ratio of described the 4th resistance in minute hydraulic circuit is
K1＝(Vdc*R3*R4-VZD1*R2*R4-VZD1*R3*R4)/[(R3*R4+R2*R4+R2*R3)*Vdc]；
When described DC power supply voltage is greater than described starting resistor, the voltage ratio of described the 4th resistance in minute hydraulic circuit is
K2＝(Vdc*R4-VZD1*R4)/(R2*Vdc+R4*Vdc)；
Wherein: K1 is less than K2.
In above-mentioned hysteresis start-up circuit, described the first switching tube is NPN type triode.
In above-mentioned hysteresis start-up circuit, described second switch pipe is NPN type triode.
Implement the hysteresis start-up circuit of a kind of power supply control chip of the present invention, there is following beneficial effect: high level output loop DC power supply voltage be less than starting resistor or after power supply control chip starts, DC power supply voltage is while being less than shutoff voltage, the voltage that output is greater than reference voltage turn-offs to control power supply control chip to Voltage Feedback pin; Low level output loop is when DC power supply voltage is greater than starting resistor, the voltage that output is less than reference voltage starts to control power supply control chip to Voltage Feedback pin, starting resistor is greater than shutoff voltage, thereby has effectively realized the hysteresis startup of power supply control chip.
In addition, by utilizing the on-off action of triode and the voltage that voltage stabilizing didoe is controlled power supply control chip Voltage Feedback pin, power supply control chip can be turn-offed, simultaneously by utilizing the emitter of triode Q1 to export, when triode Q1 conducting, the voltage of Voltage Feedback pin is no better than the clamping voltage of voltage stabilizing didoe, (clamping voltage is greater than reference voltage to select suitable voltage stabilizing didoe, but be less than the maximum input of Voltage Feedback pin), power supply control chip is turn-offed, and avoid the too high power supply control chip that causes of voltage of Voltage Feedback pin to damage.When triode Q1 turn-offs, the voltage of Voltage Feedback pin equals zero, and decontrols the shutoff locking to power supply control chip, and when DC power supply voltage is greater than starting resistor, power supply control chip starts.Circuit structure is simple, be applicable to the DC power supply voltage range of non-constant width, and loss is minimum.
Accompanying drawing explanation
Below in conjunction with drawings and Examples, the invention will be further described, in accompanying drawing:
Fig. 1 is the schematic diagram of the hysteresis start-up circuit embodiment of a kind of power supply control chip of the present invention;
Fig. 2 is the circuit diagram of the hysteresis start-up circuit embodiment of a kind of power supply control chip of the present invention;
Fig. 3 is the schematic equivalent circuit that in Fig. 2, DC power supply voltage is less than starting resistor;
Fig. 4 is the schematic equivalent circuit that in Fig. 2, DC power supply voltage is greater than starting resistor.
Embodiment
For technical characterictic of the present invention, object and effect being had more clearly, understand, now contrast accompanying drawing and describe the specific embodiment of the present invention in detail.
As shown in Figure 1, in the schematic diagram of the hysteresis start-up circuit embodiment of a kind of power supply control chip of the present invention, the hysteresis start-up circuit of this power supply control chip U1 is connected with the Voltage Feedback pin VFB of power supply control chip U1, it specifically comprises high level output loop 100 and the low level output loop 200 being all connected with DC power supply Vdc, wherein: high level output loop 100 is connected with low level output loop 200, the voltage that is greater than reference voltage for exporting turn-offs to control power supply control chip U1 to Voltage Feedback pin VFB; Low level output loop 200 is less than the voltage of reference voltage and opens to control power supply control chip U1 to Voltage Feedback pin VFB for exporting.The voltage that above-mentioned reference voltage starts or turn-offs for controlling power supply control chip U1, power cutoff control chip U1 when the voltage of the Voltage Feedback pin VFB of power supply control chip U1 is greater than reference voltage starts power supply control chip U1 when the Voltage Feedback pin VFB of power supply control chip U1 voltage is less than reference voltage.When the voltage that especially, Voltage Feedback pin VFB is exported in low level output loop 200 is less than this reference voltage, corresponding DC power supply voltage is starting resistor V1; After power supply control chip U1 starts, when the voltage that Voltage Feedback pin VFB is exported in high level output loop 100 is greater than this reference voltage, corresponding DC power supply voltage is shutoff voltage V2, wherein: starting resistor V1 is greater than shutoff voltage V2.
DC power supply voltage be less than starting resistor V1 or after power supply control chip U1 starts, DC power supply voltage is while being less than shutoff voltage V2, the voltage that high level output loop 100 is greater than output reference voltage turn-offs to control power supply control chip U1 to Voltage Feedback pin VFB; When DC power supply voltage is greater than starting resistor V1, the voltage that low level output loop 200 is less than output reference voltage starts to control power supply control chip U1 to Voltage Feedback pin VFB, thereby realizes the hysteresis startup of this power supply control chip U1.
Particularly, above-mentioned high level output loop 100 comprises switching tube Q1 (not shown), and low level output loop comprises voltage stabilizing didoe ZD1 and switching tube Q2 (not shown); Wherein: the base stage of switching tube Q1 is connected with the collector electrode of switching tube Q2, the emitter of switching tube Q1 is connected with Voltage Feedback pin VFB, and the base stage of switching tube Q2 is connected with the collector electrode of switching tube Q1 through voltage stabilizing didoe ZD1.When DC power supply voltage is less than starting resistor V1, switching tube Q2 turn-offs, the base voltage of switching tube Q1 is provided by DC power supply, switching tube Q1 conducting, the emitter-base bandgap grading output voltage that now clamping action by voltage stabilizing didoe ZD1 can control switch pipe Q1, thereby the emitter-base bandgap grading output voltage that makes switching tube Q1 exports to the voltage of Voltage Feedback pin VFB, will be greater than reference voltage, power supply control chip U1 turn-offs.When DC power supply voltage is greater than starting resistor V1, switching tube Q2 conducting, the collector electrode output low level of switching tube Q2 is to the base stage of switching tube Q1, switching tube Q1 turn-offs, the emitter-base bandgap grading output voltage of switching tube Q1 is low level voltage, thereby make the voltage of output voltage feedback pin VFB will be less than reference voltage, now power supply control chip U1 starts.
After power supply control chip U1 starts, when DC power supply voltage is less than shutoff voltage V2, switching tube Q2 turn-offs, the base voltage of switching tube Q1 is provided by DC power supply, switching tube Q1 conducting, clamping action by voltage stabilizing didoe ZD1 makes the emitter-base bandgap grading output voltage of switching tube Q1 also will be greater than reference voltage, and power supply control chip U1 turn-offs.Therefore by the variation of DC power supply voltage, carry out the on off state of control switch pipe Q2, and the base stage of switching tube Q1 is connected with the collector electrode of switching tube Q2, its on off state is determined by the on off state of switching tube Q2 again, therefore DC power supply voltage has determined the on off state of switching tube Q2, also determine the voltage of the Voltage Feedback pin VFB of power supply control chip U1, thereby realized startup and the shutoff of power supply control chip U1.In addition, starting resistor V1 is greater than shutoff voltage V2, has realized hysteresis, can effectively control startup and the shutoff of power supply control chip.
As shown in Figure 2, be the circuit diagram of the hysteresis start-up circuit embodiment of a kind of power supply control chip of the present invention, above-mentioned triode Q1 and Q2 are all preferably NPN type triode in the present embodiment, but are not limited to this, can be also metal-oxide-semiconductors etc.As shown in the figure, above-mentioned high level output loop 100 also comprises resistance R 1, and wherein: one end of resistance R 1 is connected with the positive pole of DC power supply Vdc, the other end of resistance R 1 is connected with the base stage of triode Q1, and the emitter of triode Q1 is connected with Voltage Feedback pin VFB.Above-mentioned low level output loop 200 also comprises resistance R 2, resistance R 3 and resistance R 4, wherein: one end of resistance R 2 is connected with the positive pole of DC power supply Vdc, the other end of resistance R 2 is connected with the negative electrode of voltage stabilizing didoe ZD1 with the collector electrode of triode Q1 respectively, the anode of voltage stabilizing didoe ZD1 is connected with the base stage of triode Q2 with one end of resistance R 4 respectively, and the emitter of the other end of resistance R 4 and triode Q2 is all connected with the negative pole of DC power supply Vdc.
Now in conjunction with Fig. 2 to Fig. 4, introduce in detail specific works principle of the present invention as follows: in the present embodiment, take power supply control chip as UCX84X series is example, but be not limited to this.Particularly, its reference voltage is 2.5V, i.e. power cutoff control chip U1 when the voltage of the Voltage Feedback pin VFB of power supply control chip U1 is greater than 2.5V starts power supply control chip U1 when the voltage of the Voltage Feedback pin VFB of power supply control chip U1 is less than 2.5V.When start, it is starting resistor V1 that this hysteresis start-up circuit makes the voltage of Voltage Feedback pin VFB be less than 2.5 o'clock corresponding DC power supply voltage; After power supply control chip U1 starts, when hysteresis start-up circuit makes the voltage of Voltage Feedback pin VFB be greater than 2.5V, corresponding DC power supply voltage is shutoff voltage V2, and wherein, V1 is greater than V2, to realize hysteresis.
When DC power supply voltage is less than starting resistor V1, triode Q1 conducting, not conducting of triode Q2, the clamping voltage that now voltage of Voltage Feedback pin VFB equals voltage stabilizing didoe ZD1 adds the voltage of triode Q2, therefore as long as select suitable voltage stabilizing didoe ZD1 to make the voltage of Voltage Feedback pin VFB be greater than 2.5V, will turn-off this power supply control chip U1.Wherein, resistance R 4 in hysteresis start-up circuit is compared little with resistance R 1, R2 and resistance R 3, to guarantee that the unlikely too high power supply control chip U1 that causes of voltage of Voltage Feedback pin VFB damages, and the ratio of resistance R 3 and resistance R 2 can not be too little, to guarantee when the triode Q1 conducting, voltage stabilizing didoe ZD1 can be breakdown, makes the voltage of Voltage Feedback pin VFB now can be greater than reference voltage 2.5V.
Above-mentioned resistance R 1 can not be too large or too little with the ratio of resistance R 2, to guarantee when triode Q1 or the Q2 conducting, and all can saturation conduction.
When DC power supply voltage is greater than starting resistor V1, now the voltage at resistance R 4 two ends can be greater than the conducting voltage of triode Q2, triode Q2 conducting, because triode Q2 is saturation conduction, is equivalent to short circuit between its collector electrode and emitter, and the collector electrode of triode Q2 is connected with the base stage of triode Q1, therefore the base voltage of triode Q1 is now low level, and triode Q1 turn-offs, and now the voltage of Voltage Feedback pin VFB equals 0, be less than reference voltage 2.5V, power supply control chip U1 starts.
After power supply control chip U1 starts, when DC power supply voltage is less than shutoff voltage V2, triode Q2 turn-offs again, the base stage of triode Q1 is powered through resistance R 1 by DC power supply, triode Q1 conducting, and now the voltage of Voltage Feedback pin VFB is greater than again reference voltage 2.5V, power supply control chip U1 turn-offs
Realize hysteresis.
In above-mentioned, at DC power supply voltage during lower than starting resistor V1, i.e. triode Q1 conducting, triode Q2 turn-off, and as shown in Figure 3, make the now voltage of resistance R 4 is Vx to its equivalent electric circuit, can list following equation:
According to this equation, can draw:
Vx＝(Vdc*R3*R4-VZD1*R2*R4-VZD1*R3*R4)/(R3*R4+R2*R4+R2*R3)
Therefore the voltage ratio of resistance R 4 in minute hydraulic circuit is:
K1＝(Vdc*R3*R4-VZD1*R2*R4-VZD1*R3*R4)/[(R3*R4+R2*R4+R2*R3)*Vdc]；
Wherein: VZD1 is the clamping voltage of voltage stabilizing didoe ZD1.
At DC power supply voltage during higher than starting resistor V1, triode Q1 turn-off, triode Q2 conducting, as shown in Figure 4, make the now voltage of resistance R 4 is Vx ' to its equivalent electric circuit, can list following equation:
According to this equation, can draw:
Vx'＝(Vdc*R4-VZD1*R4)/(R2+R4)；
Therefore the voltage ratio of resistance R 4 in minute hydraulic circuit is:
K2＝(Vdc*R4-VZD1*R4)/(R2*Vdc+R4*Vdc)；
Wherein: K1 is less than K2, be equivalent to triode Q2 and be greater than triode Q2 by the voltage that is conducting to shutoff by the voltage that turn-offs conducting, also be that starting resistor V1 is greater than shutoff voltage V2, thereby realizing hysteresis controls, therefore by selecting starting resistor V1, shutoff voltage V2, and setting and calculated resistance R1, R2, the resistance of R3, R4 and the clamping voltage VZD1 of voltage stabilizing didoe ZD1, can realize the accurate control to power supply control chip hysteresis voltage.
Therefore, implement the hysteresis start-up circuit of a kind of power supply control chip of the present invention, by constructing a circuit being formed by passive device completely, utilize the on-off action of triode and the voltage that voltage stabilizing didoe is controlled power supply control chip Voltage Feedback pin, power supply control chip can be turn-offed, simultaneously by utilizing the emitter of triode Q1 to export, when triode Q1 conducting, the voltage of Voltage Feedback pin is no better than the clamping voltage of voltage stabilizing didoe, (clamping voltage is greater than reference voltage to select suitable voltage stabilizing didoe, but be less than the maximum input of Voltage Feedback pin), power supply control chip is turn-offed, and the too high power supply control chip that causes of the voltage of avoiding Voltage Feedback pin damages.When triode Q1 turn-offs, the voltage of Voltage Feedback pin equals zero, and decontrols the shutoff locking to power supply control chip, and when DC power supply voltage is greater than starting resistor V1, power supply control chip starts.
In addition, under the state of triode Q1 turn-on and turn-off, the ratio of the base bleederresistance R4 of triode Q2 in minute hydraulic circuit is different, and during triode Q1 conducting, dividing potential drop ratio is little, and the needed DC power supply voltage of triode Q2 conducting is higher, during not conducting of triode Q1, dividing potential drop ratio is large, it is lower that triode Q2 turn-offs needed DC power supply voltage, now triode Q2 turn-offs conducting of triode Q1, the voltage of exporting to Voltage Feedback pin is greater than reference voltage, power supply control chip turn-offs, realize hysteresis, also be equivalent to the corresponding DC power supply voltage of triode Q2 turn-on and turn-off different, be that starting resistor V1 is greater than shutoff voltage V2, therefore hysteresis start-up circuit of the present invention is without increasing other control circuit, circuit is simple, practical, reliably, the hysteresis that can realize power supply control chip by simple passive device starts, and can pass through the parameter of Circuit tuning element, accurately control starting resistor and shutoff voltage, thereby effectively control startup and the shutoff of power supply control chip, and be applicable to the direct voltage scope of non-constant width, loss is minimum.
By reference to the accompanying drawings embodiments of the invention are described above; but the present invention is not limited to above-mentioned embodiment; above-mentioned embodiment is only schematic; rather than restrictive; those of ordinary skill in the art is under enlightenment of the present invention; not departing from the scope situation that aim of the present invention and claim protect, also can make a lot of forms, within these all belong to protection of the present invention.
Claims (8)
1. the hysteresis start-up circuit of a power supply control chip, be connected with the Voltage Feedback pin of described power supply control chip (U1), it is characterized in that, comprise the high level output loop (100) and low level output loop (200) that are all connected with DC power supply; Described high level output loop (100) is for being less than starting resistor or when described DC power supply voltage is less than shutoff voltage after described power supply control chip (U1) starts, the voltage that output is greater than reference voltage turn-offs to control described power supply control chip (U1) to described Voltage Feedback pin at described DC power supply voltage; Described low level output loop (200) is connected with described high level output loop (100), and when described DC power supply voltage is greater than described starting resistor, the voltage that output is less than described reference voltage starts to control described power supply control chip (U1) to described Voltage Feedback pin; Described starting resistor is greater than described shutoff voltage.
2. hysteresis start-up circuit according to claim 1, is characterized in that, when the voltage that described Voltage Feedback pin is exported in described low level output loop (200) is less than described reference voltage, corresponding DC power supply voltage is described starting resistor; Described high level output loop (100) is after described power supply control chip (U1) starts, and when the voltage of exporting to described Voltage Feedback pin is greater than described reference voltage, corresponding DC power supply voltage is described shutoff voltage.
3. hysteresis start-up circuit according to claim 2, it is characterized in that, described high level output loop (100) comprises the first switching tube (Q1), described low level output loop (200) comprises voltage stabilizing didoe (ZD1) and second switch pipe (Q2), wherein: the base stage of described the first switching tube (Q1) is connected with the collector electrode of described second switch pipe (Q2), the emitter of described the first switching tube (Q1) is connected with described Voltage Feedback pin, the collector electrode of described the first switching tube (Q1) is connected with the negative electrode of described voltage stabilizing didoe (ZD1), the anode of described voltage stabilizing didoe (ZD1) is connected with the base stage of described second switch pipe (Q2),
At described DC power supply voltage, be less than described starting resistor, or when, described DC power supply voltage rear in described power supply control chip (U1) startup is less than described shutoff voltage, described second switch pipe (Q2) turn-offs, the base voltage of described the first switching tube (Q1) is provided by described DC power supply, described the first switching tube (Q1) conducting, institute's voltage stabilizing didoe (ZD1) makes the voltage of exporting to described Voltage Feedback pin be greater than described reference voltage for the emitter-base bandgap grading output voltage of the first switching tube (Q1) described in clamp, and described power supply control chip (U1) turn-offs;
When described DC power supply voltage is greater than described starting resistor, described second switch pipe (Q2) conducting, the collector electrode output low level of described second switch pipe (Q2) is given the base stage of described the first switching tube (Q1), described the first switching tube (Q1) turn-offs, the emitter-base bandgap grading output voltage of described the first switching tube (Q1) is that low level voltage is less than described reference voltage so that export to the voltage of described Voltage Feedback pin, and described power supply control chip (U1) starts.
4. hysteresis start-up circuit according to claim 3, it is characterized in that, described high level output loop (100) also comprises the first resistance (R1), wherein: one end of described the first resistance (R1) is connected with the positive pole of described DC power supply (Vdc), the other end of described the first resistance (R1) is connected with the base stage of described the first switching tube (Q1).
5. hysteresis start-up circuit according to claim 4, it is characterized in that, described low level output loop (200) also comprises the second resistance (R2), the 3rd resistance (R3) and the 4th resistance (R4), wherein: one end of described the second resistance (R2) is connected with the positive pole of described DC power supply (Vdc), the other end of described the second resistance (R2) connects the tie point of described the first switching tube (Q1) and described voltage stabilizing didoe (ZD1), one end of described the 4th resistance (R4) connects the tie point of described voltage stabilizing didoe (ZD1) and described second switch pipe (Q2), the emitter of the other end of described the 4th resistance (R4) and described second switch pipe (Q2) is all connected with the negative pole of described DC power supply.
6. hysteresis start-up circuit according to claim 5, is characterized in that, when described DC power supply voltage is less than described starting resistor, the voltage ratio of described the 4th resistance (R4) in minute hydraulic circuit is
K1＝(Vdc*R3*R4-VZD1*R2*R4-VZD1*R3*R4)/[(R3*R4+R2*R4+R2*R3)*Vdc]；
When described DC power supply voltage is greater than described starting resistor, the voltage ratio of described the 4th resistance (R4) in minute hydraulic circuit is
K2＝(Vdc*R4-VZD1*R4)/(R2*Vdc+R4*Vdc)；
Wherein: K1 is less than K2.
7. hysteresis start-up circuit according to claim 3, is characterized in that, described the first switching tube (Q1) is NPN type triode.
8. hysteresis start-up circuit according to claim 3, is characterized in that, described second switch pipe (Q2) is NPN type triode.
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| CN201319558Y (en) * | 2008-11-24 | 2009-09-30 | 中兴通讯股份有限公司 | Under-voltage locking circuit |
| JP2010142002A (en) * | 2008-12-10 | 2010-06-24 | Digital Electronics Corp | Power supply start-up circuit and switching power supply device |
| CN101715265A (en) * | 2009-12-14 | 2010-05-26 | 海洋王照明科技股份有限公司 | LED driving power supply control circuit and LED lamp by using same |
| CN101882879A (en) * | 2010-06-30 | 2010-11-10 | 海洋王照明科技股份有限公司 | Circuit converting constant current source to constant voltage source and light using same |
| CN103490604A (en) * | 2013-09-27 | 2014-01-01 | 厦门雅迅网络股份有限公司 | Hysteresis protective circuit of device power source |
| CN103683206A (en) * | 2013-12-18 | 2014-03-26 | 深圳市共进电子股份有限公司 | Input overvoltage and undervoltage protection circuit with high-voltage startup function and input overvoltage and undervoltage protection method |
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| CN104065257B (en) | 2017-03-15 |
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