CN202712830U - Ldo protection circuit - Google Patents
Ldo protection circuit Download PDFInfo
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- CN202712830U CN202712830U CN 201220260455 CN201220260455U CN202712830U CN 202712830 U CN202712830 U CN 202712830U CN 201220260455 CN201220260455 CN 201220260455 CN 201220260455 U CN201220260455 U CN 201220260455U CN 202712830 U CN202712830 U CN 202712830U
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Abstract
The utility model discloses an LDO protection circuit which comprises a discharge circuit used for carry out discharging on an output terminal of an LDO, wherein when voltage of the output terminal of the LDO is larger than that of an input terminal of the LDO, the discharge circuit carries out discharging on the output terminal of the LDO. According to the LDO protection circuit of the utility model, through carrying out discharging on the output terminal of the LDO, when the voltage of the output terminal of the LDO is larger than that of the input terminal of the LDO, that output terminal current in an LDO chip flows back to the input terminal can be effectively inhibited. While ensuring the normal working of the LDO chip, a service life of the LDO chip is prolonged.
Description
Technical field
The utility model relates to a kind of protective circuit, particularly relates to a kind of protective circuit for the protection of the LDO chip.
Background technology
Along with the raising of semiconductor process techniques with the fast development of portable type electronic product, power supply IC(integrated circuit) considerable progress arranged.Power supply IC product mainly comprises the pre-steady device of linear voltage regulator (LDO), Switching Power Supply, AC/DC pressurizer (ac/dc pressurizer) and power factor correction (PFC) etc.And wherein linear voltage regulator is the most frequently used power management chip, because linear voltage regulator is easy to use, volume is little, functional and high reliability, so occupy very large proportion in power management market.
So widely in the power management chip, the LDO chip uses the most extensive at present.The structure of LDO chip is a miniature SOC (system on a chip), and it is according to the interior resistance of the situation of change adjusting self of load resistance, thereby the voltage that guarantees output end of pressure-stabilizing is constant.Usually the LDO chip is by having extremely low conducting resistance, Schottky diode, divider resistance, overcurrent protection, overheat protector, accurate a reference source, differential amplifier, delayer and POK(Power OK; power supply is normal) the MOSFET(mos field effect transistor) etc. the dedicated transistor circuit consist of, and be integrated on the chip.
Because the characteristic of LDO chip itself, there is parasitic diode in the LDO chip, the generation of described parasitic diode is relevant with concrete production technology, NMOS(N type field-effect transistor) require the substrate level to be lower than source electrode, PMOS(P type field-effect transistor) require substrate to be higher than source electrode, in the usually lower situation substrate and source electrode are linked together at tube interior, take N channel enhancement metal-oxide-semiconductor (field-effect transistor) as example, when between the grid source electrode, add a forward voltage, both as Vgs〉0 the time, then just produce one in the insulating barrier between grid and substrate perpendicular to the electric field by grid sensing substrate of semiconductor surface, this electric field energy repels the hole and attracts electronics, thereby repel near the hole of the P type substrate the gate regions, stay irremovable acceptor ion (anion), thereby formation depletion layer, few sub-electronics in the P type substrate attracted to substrate surface simultaneously, so it is larger to work as Vgs, then attract to the electronics of P type substrate surface layer more, when Vgs reaches a certain numerical value, near these electronics surface grid just forms a N-type thin layer, and be connected with two N+ districts in the substrate, thereby between the drain-source utmost point, form the N-type conducting channel, so N-type conducting channel and P type substrate form a PN junction, namely form a PN junction between drain electrode and the source electrode, thereby also just caused producing between the drain-source utmost point parasitic diode.
So when the output end voltage of LDO chip during greater than the input terminal voltage of LDO chip, perhaps during the input short circuit of LDO chip, electric current will be back to by parasitic diode the input of LDO chip from the output of LDO chip, thereby other device in the damage LDO chip, cause the whole system cisco unity malfunction in the LDO chip, when serious, even can cause that fire occurs.
The utility model content
The technical problems to be solved in the utility model is the defective that is back to the LDO chip damage that input causes in order to overcome in the prior art output end current in the LDO chip; a kind of LDO protective circuit is provided; discharge by the output to LDO, thereby suppressed the appearance that output end current in the LDO chip is back to the situation of input.
The utility model solves above-mentioned technical problem by following technical proposals:
The utility model provides a kind of LDO protective circuit, is characterized in that described LDO protective circuit comprises: a discharge loop is used for the output discharge to a LDO;
Wherein when the voltage of the output of described LDO during greater than the voltage of the input of described LDO, described discharge loop is to the output discharge of described LDO.
Preferably, the input of described LDO is by a decoupling capacitor ground connection.Described decoupling capacitor is for the burr of the input power of removing the LDO input and the gimmick commonly used of noise, so no longer at length give unnecessary details herein in the prior art.
Preferably, described discharge loop comprises a switch element, described switch element is serially connected with between the input and output of described LDO, when the voltage of the output of described LDO during greater than the voltage of the input of described LDO, described switch element consists of the galvanic circle between the input of described LDO and output.This moment, described switch element utilized described decoupling capacitor to come ground connection, thereby the electric energy that the LDO output is unnecessary is released into ground.
Preferably, described switch element is a diode, and the output of described LDO is electrically connected with the anode of described diode, and the input of described LDO is connected with the cathodic electricity of described diode.Utilize the switching characteristic of diode, when the voltage of LDO output during greater than the voltage of LDO input, described diode current flow, and when the voltage of LDO output during less than the voltage of LDO input, described diode disconnects, so realize having discharged the LDO output electric energy unnecessary with respect to the LDO input.
Preferably, described decoupling capacitor is electrochemical capacitor.When adopting electrochemical capacitor, thus decoupling capacitor can pcb board (printed circuit board (PCB)) setting away from the LDO some.
Preferably, the output of described LDO is by a filter capacitor ground connection.Described filter capacitor is the gimmick commonly used that is used for the ripple voltage of removal LDO output in the prior art, so no longer at length give unnecessary details herein.
Preferably, described filter capacitor is electrochemical capacitor.In like manner this moment filter capacitor also can pcb board arrange away from the LDO some.
Positive progressive effect of the present utility model is:
LDO protective circuit of the present utility model is discharged by the output to LDO, thereby at the voltage of LDO output during greater than the voltage of LDO input, can effectively suppress the appearance that output end current in the LDO chip is back to the situation of input.Thereby in the normal operation that has guaranteed the LDO chip, prolonged the life-span of LDO chip.
Also utilize in addition the earth terminal in the filter circuit of LDO chip input in the utility model, the electric energy LDO output is unnecessary with respect to the LDO input by switches such as diodes is released into ground.So simple in structure, with low cost and be convenient to realize with respect to special protective circuit.
Description of drawings
Fig. 1 is the structural representation of the first embodiment of LDO protective circuit of the present utility model.
Fig. 2 is the structural representation of the second embodiment of LDO protective circuit of the present utility model.
Embodiment
Provide the utility model preferred embodiment below in conjunction with accompanying drawing, to describe the technical solution of the utility model in detail.
The first embodiment:
The protective circuit of LDO described in the present embodiment discharges by the discharge loop electric energy that the output of LDO is unnecessary with respect to the LDO input; thereby suppress output unnecessary electric energy is released into input by the parasitic diode in the LDO, thereby causes the damage of system in the LDO.
So as shown in Figure 1; the discharge loop 1 of the LDO protective circuit of present embodiment is electrically connected on the output end vo ut of described LDO; and described discharge loop is only at the voltage of described LDO output end vo ut during greater than the voltage on the described LDO input Vin, and the output end vo ut of described LDO is discharged.
So present embodiment can be at the voltage of the output end vo ut of described LDO during greater than the voltage of described LDO input Vin, effectively discharge the electric energy on the described LDO output end vo ut, thereby so that the voltage on the described LDO output end vo ut is all the time less than the voltage on the LDO input Vin, thereby between LDO output end vo ut and LDO input Vin, there is never the situation of current reflux.So protected the safety of LDO work.
The second embodiment:
Although the LDO protective circuit of the first embodiment discharges the situation of having removed current reflux between LDO output end vo ut and the LDO input Vin by the electric energy with LDO output end vo ut; but LDO output end vo ut without stint is discharged; can cause the rapidly decline of the upper voltage of Vout, thereby the electric energy that may cause rear end equipment to obtain is not enough.
So present embodiment, when the voltage of LDO output end vo ut during greater than LDO input Vin voltage, utilize the pressure drop between LDO output end vo ut and the LDO input Vin, by the switching characteristic of a diode D31, only LDO output end vo ut is released into ground with respect to the unnecessary electric energy of LDO input Vin.And also utilize the ground connection of the decoupling capacitor of described LDO input Vin in the present embodiment, just the electric energy of LDO output end vo ut is released into ground by diode.Thereby simplified the structure of protective circuit, and be convenient to realize, but also reduced significantly cost.
Therefore as shown in Figure 2; the protective circuit of LDO described in the present embodiment mainly is made of described diode D31; the input Vin of wherein said LDOU30 is by a decoupling capacitor C336 ground connection; the output end vo ut of described LDOU30 is also by a filter capacitor C334 ground connection; the output end vo ut of described LDOU30 is electrically connected with the anode of described diode D31, and the input Vin of described LDOU30 is connected with the cathodic electricity of described diode D31.
LDOU30 described in the present embodiment is the APL1117-VC chip of Anpec Electronics Corporation.Wherein as shown in Figure 2, the device of other of present embodiment has consisted of the required match circuit of APL1117-VC chip normal operation jointly, so give unnecessary details no longer in detail herein.
In the present embodiment, described decoupling capacitor C336 can limited inhibition input Vin burr and noise, voltage ripple with assurance input Vin is very little, and raising Systems balanth, generally speaking, preferably use the ESR(equivalent series resistance) electric capacity that value is little, this is owing to larger electric current is arranged by described decoupling capacitor C336 during LDO work, and ESR value is understood the operating efficiency that affect chip.When pcb board connects up, require decoupling capacitor and input Vin as far as possible little with the loop of the pin on ground.If so use electrochemical capacitor, just can from LDO away from, meanwhile preferably add the close LDO of an electric capacity in parallel with it.
The output end vo ut of described LDO meets filter capacitor C334 and carries out filtering, thereby guarantees the stable of output voltage, and so that described LDO has good dynamic response.For less output voltage ripple, preferably choose the less electric capacity of ESR simultaneously.When pcb board connects up, require filter capacitor C334 to be close to the Vout pin of described LDO equally, thereby make the output current loop of LDO minimum.Described filter capacitor C334 also can use electrochemical capacitor in addition.
Realize the switch conduction of the input VIn of the output end vo ut of LDO and LDO in the present embodiment with the MMBD4148 diode of fairchild company.Can adopt in addition other switch element to realize the switch conduction of the input VIn of the output end vo ut of LDO and LDO, as long as the switch element that adopts is when the voltage of the output of described LDO during greater than the voltage of the input of described LDO, can so that consist of the galvanic circle between the input of described LDO and the output, just can be used for substituting the diode D31 in the present embodiment.
In the present embodiment when the situations such as system power supply shutoff occur, the voltage of the output end vo ut of described LDO is greater than the voltage of the input VIn of described LDO at this moment, this moment is according to the characteristic of diode D31, described diode D31 conducting, so the filter capacitor C334 of output end vo ut discharge, this moment, electric current flowed to the input Vin of LDO from the output end vo ut of described LDO.Therefore the electric weight that is stored on the filter capacitor C334 discharges by diode D31, and by decoupling capacitor C336, finally releases on the ground.Therefore the electric weight on the filter capacitor C334 of LDO output end vo ut can not pour in down a chimney in LDO, thereby can protect LDO not damage.
So the LDO protective circuit of present embodiment is utilized the earth terminal of the filter capacitor of LDO input Vin, by diode D31 LDO output end vo ut is released into ground with respect to the unnecessary electric energy of LDO input Vin.So when having avoided LDO output end vo ut transition discharged; also effectively suppressed the current reflux between LDO output end vo ut and the LDO input Vin; have more simple structure and with low cost with respect to special protective circuit in addition, be convenient to realize.
Although more than described embodiment of the present utility model, it will be understood by those of skill in the art that these only illustrate, protection range of the present utility model is limited by appended claims.Those skilled in the art can make various changes or modifications to these execution modes under the prerequisite that does not deviate from principle of the present utility model and essence, but these changes and modification all fall into protection range of the present utility model.
Claims (7)
1. a LDO protective circuit is characterized in that, described LDO protective circuit comprises:
One discharge loop is used for when the voltage of the output of a LDO during greater than the voltage of the input of described LDO, and the output of described LDO is discharged.
2. LDO protective circuit as claimed in claim 1 is characterized in that, the input of described LDO is by a decoupling capacitor ground connection.
3. LDO protective circuit as claimed in claim 2; it is characterized in that; described discharge loop comprises a switch element; described switch element is serially connected with between the input and output of described LDO; when the voltage of the output of described LDO during greater than the voltage of the input of described LDO, described switch element consists of the galvanic circle between the input of described LDO and output.
4. LDO protective circuit as claimed in claim 3 is characterized in that, described switch element is a diode, and the output of described LDO is electrically connected with the anode of described diode, and the input of described LDO is connected with the cathodic electricity of described diode.
5. LDO protective circuit as claimed in claim 2 is characterized in that, described decoupling capacitor is electrochemical capacitor.
6. such as each described LDO protective circuit among the claim 1-5, it is characterized in that the output of described LDO is by a filter capacitor ground connection.
7. LDO protective circuit as claimed in claim 6 is characterized in that, described filter capacitor is electrochemical capacitor.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 201220260455 CN202712830U (en) | 2012-06-04 | 2012-06-04 | Ldo protection circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 201220260455 CN202712830U (en) | 2012-06-04 | 2012-06-04 | Ldo protection circuit |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN202712830U true CN202712830U (en) | 2013-01-30 |
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Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN 201220260455 Expired - Fee Related CN202712830U (en) | 2012-06-04 | 2012-06-04 | Ldo protection circuit |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102780213A (en) * | 2012-06-04 | 2012-11-14 | 上海斐讯数据通信技术有限公司 | Protection circuit of LDO (low dropout regulator) |
| CN105700612A (en) * | 2016-01-28 | 2016-06-22 | 上海华虹宏力半导体制造有限公司 | Voltage regulator |
| CN109472969A (en) * | 2018-01-31 | 2019-03-15 | 国网浙江省电力公司湖州供电公司 | A kind of doubling conversion equipment and method based on M-BUS |
-
2012
- 2012-06-04 CN CN 201220260455 patent/CN202712830U/en not_active Expired - Fee Related
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102780213A (en) * | 2012-06-04 | 2012-11-14 | 上海斐讯数据通信技术有限公司 | Protection circuit of LDO (low dropout regulator) |
| CN105700612A (en) * | 2016-01-28 | 2016-06-22 | 上海华虹宏力半导体制造有限公司 | Voltage regulator |
| CN109472969A (en) * | 2018-01-31 | 2019-03-15 | 国网浙江省电力公司湖州供电公司 | A kind of doubling conversion equipment and method based on M-BUS |
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| Date | Code | Title | Description |
|---|---|---|---|
| C14 | Grant of patent or utility model | ||
| GR01 | Patent grant | ||
| CF01 | Termination of patent right due to non-payment of annual fee |
Granted publication date: 20130130 Termination date: 20180604 |
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| CF01 | Termination of patent right due to non-payment of annual fee |