CN201965176U - Two-stage over-current detection device - Google Patents

Abstract

The utility model discloses a two-stage over-current detection device, which is characterized by being composed of a detection resistor, a filter resistor, a voltage-division resistor, bleeder resistor, a filter capacitor, a transient delay capacitor, a diode and an over-voltage detection module. One end of the detection resistor receives the detected current while the other end thereof is grounded; one end of the filter resistor is connected to a current receiving end of the detection resistor while the other end thereof is connected to the over-voltage detection module, the filter resistor and an anode of the diode; one end of the filter capacitor is connected to the over-voltage detection module, the filter resistor and the anode of the diode while the other end thereof is grounded; the anode of the diode is connected with the over-voltage detection module, the filter resistor and the filter capacitor while a cathode thereof is connected with the voltage-division resistor; one end of the voltage-division resistor is connected with the cathode of the diode while the other end thereof is connected to the transient delay capacitor and the bleeder resistor; the transient delay capacitor is connected with the bleeder resistor in parallel, and then, one end of the transient delay capacitor is connected with the voltage-division resistor while the other end thereof is grounded; and the bleeder resistance is much larger than the filter resistance, the voltage-division resistor and the detection resistor. The two-stage over-current detection device can respectively detect dynamic heavy current and static low current.

Description

A kind of two-stage overcurrent detecting device

Affiliated technical field

The utility model relates to a kind of overcurrent detecting device, particularly detects the overcurrent detecting device of immediate current and steady-state current respectively.

Background technology

In the prior art, over-current detection adopts device as shown in Figure 1 usually, comprises the detection resistance R _Sense, filter resistance R1, filter capacitor C1 and overvoltage detection module [01].Detect resistance one termination and receive sensed current I _Sense, other end ground connection.Detect resistance R _SenseWith sensed current I _SenseBe converted to detected voltage V _SenseDetected voltage is formed the first-order filtering network by filter resistance R1 and filter capacitor C1 and is input to the overvoltage detection module; Wherein filter resistance R1 one end is connected to the detection resistance R _SenseThe electric current receiving end, the other end connects overvoltage detection module [01] and filter capacitor C1; Filter capacitor C1 one end is connected to overvoltage detection module [01] and filter resistance R1, other end ground connection.The overvoltage detection module determines by the judgement to voltage whether sensed current exceeds setting value.

In the common working condition of circuit, there is the long-term constant little electric current I of quiescent operation usually _StandbyWill be with the dynamic duty that moment exists big electric current I _Active(as big electric current of circuit start and the periodic big electric current of short-term operation).Because overcurrent detecting device as shown in Figure 1 has only an over-current detection point, so over-current detection value I _pMust be set at and be slightly larger than or equal the dynamic duty electric current I _Active, as shown in Figure 2.In case circuit breaks down, static working current occurs unusual, and its current value increases to and equals the dynamic duty electric current, and then these abnormal conditions can't be detected.

Summary of the invention

The purpose of this utility model is the defective that exists at prior art, has proposed a kind of two-stage overcurrent detecting device.

The utility model is achieved through the following technical solutions (as shown in Figure 3).

Two-stage overcurrent detecting device described in the utility model is by detecting resistance [R _Sense], filter resistance [R1], divider resistance [R2], bleeder resistance [R3], filter capacitor [C1], transient state delay capacitor [C2], diode [D1] and overvoltage detection module [02] form.Detect resistance [R _Sense] termination receipts sensed current [I _Sense], other end ground connection; Filter resistance [R1] end is connected to and detects resistance [R _Sense] the electric current receiving end, the other end is connected to the positive pole of overvoltage detection module [02], filter capacitor [C1] and diode [D1]; Filter capacitor [C1] end is connected to the positive pole of overvoltage detection module [02], filter resistance [R1] and diode [D1], other end ground connection; Positive pole one end of diode [D1] is connected to overvoltage detection module [02], filter resistance [R1] and filter capacitor [C1], and negative pole is connected to divider resistance [R2]; Divider resistance [R2] end is connected to the negative pole of diode [D1], and the other end is connected to transient state delay capacitor [C2] and bleeder resistance [R3]; Transient state delay capacitor [C2] and bleeder resistance [R3] back in parallel one end is connected to divider resistance [R2], other end ground connection; Bleeder resistance [R3] is much larger than filter resistance [R1], divider resistance [R2] and detect resistance [R _Sense].

Two-stage overcurrent detecting device described in the utility model can be operated in two states: big current detecting state of dynamic duty and the little current status of quiescent operation.When transient state delay capacitor [C2] when being recharged, delay capacitor [C2] can equivalence be a lead, and bleeder resistance [R3] is by transient state delay capacitor [C2] short circuit, and the two-stage overcurrent detecting device can equivalence be a circuit as shown in Figure 4, device is operated in dynamically big current detecting state, and the over-current detection value is I _P1The voltage threshold of setting overvoltage detection module [02] is V _Th, diode [D1] forward conduction voltage drop is V _D, can get by Fig. 4:

V _th＝I ₁R ₂+V _D＝(I _p1-I ₁)R _sense-I ₁R ₁ (1)

V _th＝(I _p1-I ₁)R _sense-I ₁R ₁ (2)

By (1), (2) Shi Kede:

$I_{\mathrm{<figure-callout\; id="1"\; label="p"\; filenames="HSA00000386665200041.png"\; state="\{\{state\}\}">p</figure-callout>}1}=\frac{(R_1+R_{\mathrm{sense}})(V_{\mathrm{th}}-V_D)+R_2{V}_{\mathrm{th}}}{R_2{R}_{\mathrm{sense}}}---\left(3\right)$

By (3) formula as can be known, when the threshold value and one timing of diode forward conduction voltage drop of overvoltage detection module, at the over-current detection value I of the big electric current of transient state _P1By filter resistance [R1], divider resistance [R2] and detection resistance [R _Sense] decision.The time that the big electric current of transient state can exist, the time that the big electric current of the big more then transient state of transient state delay capacitor [C2] can exist was long more by transient state delay capacitor [C2] decision.In case transient state delay capacitor [C2] is filled electricity, device changes the static small current detected state over to.

After transient state delay capacitor [C2] is filled electricity, and because bleeder resistance [R3] resistance value is very big, can be similar to and think that divider resistance [R2] is disconnected to the path on ground, the two-stage overcurrent detecting device can equivalence be a circuit as shown in Figure 5, device is operated in the static small current detected state, and the over-current detection value is I _P2Can get by Fig. 5:

$I_{\mathrm{<figure-callout\; id="2"\; label="p"\; filenames="HSA00000386665200041.png"\; state="\{\{state\}\}">p</figure-callout>}2}=\frac{1}{R_{\mathrm{sense}}}\&CenterDot;V_{\mathrm{th}}---\left(4\right)$

By (4) formula as can be known, when the threshold value one of overvoltage detection module regularly, at static small current over-current detection value I _P2By detecting resistance [R _Sense] decision.When sensed current when big electric current transfers little electric current to, bleeder resistance [R3] discharges slowly to transient state delay capacitor [C2], circuit restarts transient state delay capacitor [C2] charging after discharging into to a certain degree, and this moment, device changed dynamically big current detecting state over to.Bleeder resistance [R3] is big more, installs then that to change interval time of dynamic big electric current over to by the static small current detected state long more.

The two-stage overcurrent detecting device that the utility model proposes can detect dynamically big electric current and static small current respectively, and having avoided that quiescent current is excessive but can't detected situation.The over-current detection value of two-stage overcurrent detecting device is set as shown in Figure 6.

Description of drawings

Fig. 1 is conventional overcurrent detecting device synoptic diagram.I wherein _SenseBe sensed current, R _SenseFor detecting resistance, 01 is the overvoltage detection module.

Fig. 2 is that the over-current detection value of conventional overcurrent detecting device is set synoptic diagram.I wherein _StandbyBe static working current, I _ActiveBe moment dynamic duty electric current, I _pBe the over-current detection value.

Fig. 3 is the utility model two-stage overcurrent detecting device synoptic diagram.I wherein _SenseBe sensed current, R _SenseFor detecting resistance, 02 is the overvoltage detection module, and R1 is that filter resistance, R2 are that divider resistance, R3 are that bleeder resistance, C1 are that filter capacitor, C2 are that transient state delay capacitor, D1 are diode.

Equivalent circuit diagram when Fig. 4 the utility model two-stage overcurrent detecting device shown in Figure 3 is operated in dynamically big current detecting state.I wherein _SenseBe sensed current, R _SenseFor detecting resistance, 02 is the overvoltage detection module, and R1 is that filter resistance, R2 are that divider resistance, C1 are that filter capacitor, D1 are diode.

Equivalent circuit diagram when Fig. 5 the utility model two-stage overcurrent detecting device shown in Figure 3 is operated in the static small current detected state.I wherein _SenseBe sensed current, R _SenseFor detecting resistance, 02 is the overvoltage detection module, and R1 is that filter resistance, C1 are filter capacitor.

The over-current detection value of Fig. 6 the utility model two-stage overcurrent detecting device is set synoptic diagram, wherein I _StandbyBe static working current, I _ActiveBe moment dynamic duty electric current, I _P1, I _P2Be the over-current detection value.

Embodiment synoptic diagram, wherein an I of Fig. 7 the utility model two-stage overcurrent detecting device _SenseBe sensed current, R _SenseFor detecting resistance, IC1 is the overvoltage detection module, and R11 is that filter resistance, R12 are that divider resistance, R13 are that bleeder resistance, C11 are that filter capacitor, C12 are that transient state delay capacitor, D11 are diode.

Embodiment

The utility model will be described further by following examples.

Embodiment.

Present embodiment at the circuit start electric current of product be 1.6A, the starting current duration is 25ms, static working current is 0.87A, the static failure electric current is 1.5A.If adopt traditional single-stage overcurrent detecting device, at 1.55A, then product can't start with the design of over-current detection value; If at 1.8A, the static failure electric current can't detect with the design of over-current detection point.

Present embodiment adopts the two-stage overcurrent detecting device that the utility model proposes, and dynamic over-current detection value is set at 3.0A, but the maximum life period of dynamic current is set at 80ms, and static over-current detection value is set at 1.3A.So both guarantee the normal startup of product, and can detect overcurrent condition again.

Present embodiment as shown in Figure 7, this secondary overflow means by overvoltage detection module IC1, filter capacitor C11, transient state delay capacitor C12, detect resistance R _Sense1, filter resistance R11, divider resistance R12, bleeder resistance R13 and diode D11 form.Detect resistance R _SenseOne termination is received sensed current I _Sense, other end ground connection; Filter resistance R11 one end is connected to the detection resistance R _SenseThe electric current receiving end, the other end is connected to the positive pole of overvoltage detection module IC1, filter capacitor C11 and diode D11; Filter capacitor C11 one end is connected to the positive pole of overvoltage detection module IC1, filter resistance R11 and diode D11, other end ground connection; Positive pole one end of diode D11 is connected to overvoltage detection module IC1, filter resistance R11 and filter capacitor C11, and negative pole is connected to divider resistance R12; Divider resistance R12 one end is connected to the negative pole of diode D11, and the other end is connected to transient state delay capacitor C12 and bleeder resistance R13; An end is connected to divider resistance R12 after transient state delay capacitor C12 and the bleeder resistance R13 parallel connection, and the other end is connected to ground.

Wherein, capacitor C 11 is that 470pF, capacitor C 12 are 10uF, resistance R _Sense1Be that 1.3 Ω, resistance R 11 are 100 Ω for 1k Ω, resistance R 12, resistance R 13 is 51k Ω, and the forward conduction voltage drop of diode D11 is 0.7V, and IC1 is LD7535.When circuit just starts, 12 chargings of 12 pairs of capacitor C of resistance R, device is operated in dynamically big current detecting state.As long as starting current does not surpass setting value 3A, then circuit can normally start.After capacitor C 12 is filled electricity, and because the R13 resistance value is very big, can be similar to and thinks that R12 is disconnected to the path on ground, the two-stage overflow means is operated in the static small current detected state.If break down, quiescent current reaches 1.5A, and device also can detect fault.

Claims (1)

1. a two-stage overcurrent detecting device is characterized in that by detecting resistance [R _Sense], filter resistance [R1], divider resistance [R2], bleeder resistance [R3], filter capacitor [C1], transient state delay capacitor [C2], diode [D1] and overvoltage detection module [02] form, and detects resistance [R _Sense] termination receipts sensed current [I _Sense], other end ground connection; Filter resistance [R1] end is connected to and detects resistance [R _Sense] the electric current receiving end, the other end is connected to the positive pole of overvoltage detection module [02], filter capacitor [C1] and diode [D1]; Filter capacitor [C1] end is connected to the positive pole of overvoltage detection module [02], filter resistance [R1] and diode [D1], other end ground connection; Positive pole one end of diode [D1] is connected to overvoltage detection module [02], filter resistance [R1] and filter capacitor [C1], and negative pole is connected to divider resistance [R2]; Divider resistance [R2] end is connected to the negative pole of diode [D1], and the other end is connected to transient state delay capacitor [C2] and bleeder resistance [R3]; Transient state delay capacitor [C2] and bleeder resistance [R3] back in parallel one end is connected to divider resistance [R2], and the other end is connected to ground; Bleeder resistance [R3] is much larger than filter resistance [R1], divider resistance [R2] and detect resistance [R _Sense].

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