High-precision LED current detection circuit

Abstract

The utility model discloses a high-precision LED current detection circuit, which is used for being matched with an LED drive circuit. The high-precision LED current detection circuit comprises a current sampling circuit and a comparison and judgment circuit, the current sampling circuit is connected with the LED driving circuit and is used for collecting the output current of an LED light source of the LED driving circuit, and the comparison judgment circuit is used for judging whether the output current of the LED light source is within a set normal range or not. The detection circuit has the advantages of simple circuit structure, high detection precision and large detection range.

Description

Technical Field

[0001] The utility model relates to the field of LEDs, in particular to a high-precision LED current detection circuit. Background Art

[0002] Most of the lamps used in existing vehicles (such as new energy vehicles and automobiles) are LED lamps; however, due to the complexity and harshness of the vehicle operating environment, the LED drive circuits on vehicles are often subject to various interferences and challenges. In order to confirm whether the LED drive circuit is normal, the vehicle is equipped with an LED current detection circuit that detects whether the output current of the LED light source of the LED drive circuit is normal.

[0003] Cooperate Figure 1 As shown, the existing LED driving circuit generally includes an LED light source ', an operational amplifier OP1', a resistor R1', a MOS tube MN1', a MOS tube MN0', a dimming switch S PWM’ , power tube array'; LED light source' includes at least one LED lamp bead led', the positive electrode of the LED light source' is connected to the driving power supply V LED’ The cathode of the LED light source is connected to the drain of the MOS tube MN0, the gate of the MOS tube MN0 is connected to the output of the operational amplifier OP1, the source of the MOS tube MN0 is connected to the drain of the power tube array and the inverting input of the operational amplifier OP1, the source of the power tube array is grounded, and the gate of the power tube array is connected to the dimming switch S. PWM 'The first end, the dimmer switch S PWM’ The control terminal receives the dimming signal DS PWM’ , dimmer switch S PWM’ The second end of the power tube array 'is connected to the reference current signal Ir' together with the gate of the MOS tube MN1', the source of the MOS tube MN1' is grounded, the drain of the MOS tube MN1' is connected to the first end of the resistor R1' and the in-phase input end of the operational amplifier OP1', and the second end of the resistor R1' is connected to the reference current signal Ir'; the power tube array 'includes 2 n The power tube unit' comprises a power tube MN_i' and a control switch S_i'. The drain of the power tube MN_i' is connected to the drain end of the power tube array'. The gate of the power tube MN_i' is connected to the first end of the control switch S_i'. The second end of the control switch S_i' is connected to the gate end of the power tube array'. The source of the power tube MN_i' is connected to the source end of the power tube array'. The control end of the control switch S_i' is connected to the control signal CS_i'. i' is 0 to 2. n’ integer, n' is a positive integer. Figure 1As shown, the existing current detection circuit includes a MOS tube MNs', a MOS tube MP0', a MOS tube MP1', a resistor R2', a comparator CMPH', a comparator CMPL' and an OR gate U1', the gate of the MOS tube MNs' is connected to the gate end of the power tube array', the source of the MOS tube MNs' is grounded, the drain of the MOS tube MNs' is connected to the gate and drain of the MOS tube MP0' and the gate of the MOS tube MP1', the source of the MOS tube MP0' and the source of the MOS tube MP1' are connected to the control power supply VDD', the drain of the MOS tube MP1' is connected to the first end of the resistor R2', the non-inverting input end of the comparator CMPH' and the inverting input end of the comparator CMPL', the second end of the resistor R2' is grounded, and the inverting input end of the comparator CMPH' is connected to the upper threshold voltage signal V Hth’ The non-inverting input of the comparator CMPL' is connected to the lower threshold voltage signal V Lth’ The output end of the comparator CMPH' and the output end of the comparator CMPL' are connected to two input ends of the OR gate U1' respectively.

[0004] The working principle of the existing LED current detection circuit is as follows: the MOS tube MNs' can mirror the output current of the MOS tube MN1', and the MOS tube MP0', the MOS tube MP1' and the resistor R2' can convert the mirror current signal of the MOS tube MNs' into a corresponding monitoring voltage signal Vs', and the comparator CMPH' and the comparator CMPL' respectively compare the monitoring voltage signal Vs' with the upper threshold voltage signal V Hth’ and the lower threshold voltage signal V Lth’ For comparison, if the voltage of the monitoring voltage signal Vs' is greater than the upper threshold voltage signal V Hth’ The voltage of the monitoring voltage signal Vs' is less than the lower threshold voltage signal V Lth’ The voltage indicates that the output current of the LED light source' exceeds the set normal range. At this time, one of the comparator CMPH' and the comparator CMPL' will output a high-level signal to the OR gate U1', so that the OR gate U1' outputs a high-level signal to the subsequent system, so that the subsequent system knows that the output current of the LED light source' is abnormal.

[0005] The existing LED current detection circuit has the following defects:

[0006] 1. The voltage between the source and drain terminals of the power tube array' is not completely equal to the source-drain voltage of the MOS tube MNs'. In particular, when the current of the reference current signal Ir' changes, the voltage between the source and drain terminals of the power tube array' will change accordingly, which causes a large error in the mirror current of the MOS tube MNs'.

[0007] 2. The MOS tube MNs' and the power tube array' are in parallel relationship. In this way, when the MOS tube MN1' is normal and some or all of the power tubes MN_i' of the power tube array' are aging, the output current of the LED light source' is abnormal, but the mirror current of the MOS tube MNs' is still within the normal range, which will cause the abnormal information to be missed to the subsequent system;

[0008] 3. The output current of the LED light source 'changes accordingly with the number of switches of the control switch S_i' of the power tube array ', which causes the upper threshold voltage signal V Hth’ The voltage and lower threshold voltage signal V Lth’ The voltage needs to be adjusted accordingly according to the number of switches of the control switch S_i' of the power tube array ', which increases the difficulty of design.

[0009] In view of the existence of the above problems, it is necessary to study a high-precision LED current detection circuit to overcome at least one of the above defects. Utility Model Content

[0010] The purpose of the utility model is to provide a high-precision LED current detection circuit to overcome at least one of the defects of the background technology.

[0011] In order to achieve the above purpose, the solution of the utility model is:

[0012] A high-precision LED current detection circuit is used to cooperate with an LED drive circuit; the LED drive circuit includes an LED light source, an operational amplifier OP1, a resistor R1, a MOS tube MN1, a MOS tube MN0, a dimming switch S PWM and a power tube array; the LED light source includes at least one LED lamp bead LED, and the positive electrode of the LED light source is connected to the driving power supply V LED The cathode of the LED light source is connected to the drain of the MOS tube MN0, the gate of the MOS tube MN0 is connected to the output of the operational amplifier OP1, the source of the MOS tube MN0 is connected to the drain of the power tube array and the inverting input of the operational amplifier OP1, the source of the power tube array is grounded, and the gate of the power tube array is connected to the dimming switch S PWM The first end of the dimmer switch S PWM The control end receives the dimming signal DS PWM , dimmer switch S PWM The second end of the power tube array is connected to the reference current signal Ir together with the gate of the MOS tube MN1, the source of the MOS tube MN1 is grounded, the drain of the MOS tube MN1 is connected to the first end of the resistor R1 and the in-phase input end of the operational amplifier OP1, and the second end of the resistor R1 is connected to the reference current signal Ir; the power tube array includes 2 nThe power tube unit includes a power tube MN_i and a control switch S_i. The drain of the power tube MN_i is connected to the drain end of the power tube array. The gate of the power tube MN_i is connected to the first end of the control switch S_i. The second end of the control switch S_i is connected to the gate end of the power tube array. The control end of the control switch S_i is connected to the control signal CS_i, where i is 0 to 2. n An integer, n is a positive integer; the high-precision LED current detection circuit includes a current sampling circuit and a comparison and judgment circuit; the current sampling circuit includes a MOS tube MNs, a MOS tube MNf and an operational amplifier OP2, the non-inverting input terminal of the operational amplifier OP2 is used to be connected to the drain of the MOS tube MN0, the inverting input terminal of the operational amplifier OP2 is connected to the source of the MOS tube MNf and the drain of the MOS tube MNs, the drain of the MOS tube MNf is connected to the input terminal of the comparison and judgment circuit, the gate of the MOS tube MNs is used to be connected to the gate of the MOS tube MN0, and the source of the MOS tube MNs is used to be connected to the source of the MOS tube MN0.

[0013] The comparison and judgment circuit comprises a first current mirror, a second current mirror, a third current mirror, a reference tube array, a comparator CMPH, a comparator CMPL, a MOS tube MNL, a MOS tube MNH and an OR gate U1; the mirrored end of the first current mirror is connected to the input end of the comparison and judgment circuit, the mirrored end of the first current mirror is connected to the in-phase input end of the comparator CMPH, the inverting input end of the comparator CMPL and the drain end of the reference tube array, and the mirrored end of the second current mirror is connected to the lower limit threshold current signal I Lth The mirror end of the second current mirror is connected to the in-phase input end of the comparator CMPL and the drain of the MOS tube MNL, and the mirrored end of the third current mirror is connected to the upper threshold current signal I Hth The mirror end of the third current mirror is connected to the inverting input end of the comparator CMPH and the drain of the MOS tube MNH, the gate of the MOS tube MNL and the gate of the MOS tube MNH are connected to the gate end of the reference tube array, the gate end and the drain end of the reference tube array are short-circuited, and the source end of the reference tube array, the source of the MOS tube MNL and the source of the MOS tube MNH are grounded.

[0014] The reference tube array includes 2 n An identical reference tube unit is provided, the reference tube unit includes a reference tube MNr_i and a reference switch K_i, the drain of the reference tube MNr_i is connected to the drain end of the reference tube array, the gate of the reference tube MNr_i is connected to the first end of the reference switch K_i, the second end of the reference switch K_i is connected to the gate end of the reference tube array, the source of the reference tube MNr_i is connected to the source end of the reference tube array, and the control end of the reference switch K_i is connected to the control signal CS_i.

[0015] The first current mirror includes a MOS tube MP0 and a MOS tube MP1, the gate and drain of the MOS tube MP0 and the gate of the MOS tube MP1 are connected to the mirrored end of the first current mirror, the source of the MOS tube MP0 and the source of the MOS tube MP1 are connected to the control power supply VDD, and the drain of the MOS tube MP1 is connected to the mirror end of the first current mirror.

[0016] The second current mirror includes a MOS tube MP2 and a MOS tube MP3, the gate and drain of the MOS tube MP2 and the gate of the MOS tube MP3 are connected to the mirrored end of the second current mirror, the source of the MOS tube MP2 and the source of the MOS tube MP3 are connected to the control power supply VDD, and the drain of the MOS tube MP3 is connected to the mirror end of the second current mirror.

[0017] The third current mirror includes a MOS tube MP4 and a MOS tube MP5, the gate and drain of the MOS tube MP4 and the gate of the MOS tube MP5 are connected to the mirrored end of the third current mirror, the source of the MOS tube MP4 and the source of the MOS tube MP5 are connected to the control power supply VDD, and the drain of the MOS tube MP5 is connected to the mirror end of the third current mirror.

[0018] After adopting the above scheme, the utility model has the following characteristics:

[0019] 1. The high-precision LED current detection circuit of the utility model includes a current sampling circuit and a comparison and judgment circuit. The current sampling circuit is used to collect the output current of the LED light source, and the comparison and judgment circuit is used to judge whether the output current of the LED light source is within the set normal range;

[0020] 2. The MOS tube MNs of the current sampling circuit of the utility model is used to mirror the output current of the LED light source (i.e., the drain current of the MOS tube MN0) in real time according to a certain mirror ratio, so as to achieve the effect of real-time sampling of the output current of the LED light source; and the MOS tube MNf and the operational amplifier OP2 form a feedback loop, so that the source-drain voltage of the MOS tube MNs is equal to the source-drain voltage of the MOS tube MN0, thereby ensuring the mirroring accuracy when the MOS tube MNs mirrors the output current of the LED light source, that is, the monitoring current signal Is obtained by the MOS tube MNs mirroring the output current of the LED light source can better reflect the output current of the LED light source; in addition, the MOS tube MNs and the power tube array are in series, so that the current abnormality of the power tube array can be directly reflected in the monitoring current signal Is of the MOS tube MNs, thereby solving the problem of underreporting of abnormal information in the existing LED current detection circuit;

[0021] 3. The working principle of the comparison judgment circuit of the utility model is: the first current mirror can mirror the monitoring current signal Is according to a certain mirror ratio to obtain the first mirror current signal I1, and the second current mirror can mirror the lower limit threshold current signal I according to a certain mirror ratio. Lth The third current mirror can mirror the upper threshold current signal I according to a certain mirror ratio. Hth The third mirror current signal I3 is obtained. The first mirror current signal I1 is converted into a monitoring voltage signal Vs through the reference tube array and input into the non-inverting input terminal of the comparator CMPH and the inverting input terminal of the comparator CMPL. The second mirror current signal I2 is converted into a lower threshold voltage signal V through the MOS tube MNL. CL The third mirror current signal I3 is converted into an upper threshold voltage signal V by the MOS tube MNH. CH Input comparator CMPH inverting input terminal; when the output current of the LED light source is normal, the current value of the output current of the LED light source is at the upper threshold current signal I Hth The current value and the lower threshold current signal I Lth The current value is between , at this time the lower threshold voltage signal V CL The voltage value of the monitoring voltage signal Vs is lower than the voltage value of the upper threshold voltage signal V CH The voltage value of the LED light source is higher than the voltage value of the monitoring voltage signal Vs, so that the comparator CMPH and the comparator CMPL both output low-level signals to the OR gate U1, so that the OR gate U1 outputs a low-level signal; when the current value of the output current of the LED light source is lower than the lower threshold current signal I Lth When the current value of the drain current of the MOS tube MNL is equal to the current value of the second mirror current signal I2, the MOS tube MNL should form a current mirror with the reference tube array to make the current value of the drain current of the MOS tube MNL lower than the current value of the second mirror current signal I2. However, since the second current mirror and the MOS tube MNL are in series, in order to make the current value of the drain current of the MOS tube MNL equal to the current value of the second mirror current signal I2, the second current mirror will pull up the lower threshold voltage signal V CL The voltage of the lower threshold voltage signal V CL The voltage value of the LED light source is greater than the voltage value of the monitoring voltage signal Vs, so that the comparator CMPL outputs a high-level signal to the OR gate U1, so that the OR gate U1 outputs a high-level signal; when the current value of the output current of the LED light source is higher than the upper threshold current signal I HthWhen the current value of the MOS tube MNH is 1, the MOS tube MNH should form a current mirror with the reference tube array to make the current value of the drain current of the MOS tube MNH higher than the current value of the third mirror current signal I3. However, since the third current mirror and the MOS tube MNH are in series, in order to make the current value of the drain current of the MOS tube MNH equal to the current value of the third mirror current signal I3, the drain-source voltage of the MOS tube MNH will be greatly reduced, causing the MOS tube MNH to enter the linear region, thereby lowering the upper threshold voltage signal V CH The voltage value makes the lower threshold voltage signal V CH The voltage value of is less than the voltage value of the monitoring voltage signal Vs, so that the comparator CMPH outputs a high level signal to the OR gate U1, so that the OR gate U1 outputs a high level signal;

[0022] The reference tube array of the utility model has the same structure as the power tube array, and the reference switch K_i of the reference tube array and the control switch S_i of the power tube array are controlled by the same control signal CS_i, so that the switch state of the reference tube array is the same as the switch state of the power tube array, so that the lower limit threshold current signal I is not changed. Lth and the upper threshold current signal I Hth In the case of CL and the upper threshold voltage signal V CH It will change in proportion to the switching state of the power tube array, ensuring that the high-precision LED current detection circuit of the utility model can also effectively detect whether the output current of the LED light source is normal, thereby effectively improving the detection range of the utility model and reducing the difficulty of circuit design. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a circuit schematic diagram of an existing LED driving circuit and an LED current detection circuit.

[0024] Figure 2 This is a circuit schematic diagram of the LED drive circuit and the high-precision LED current detection circuit of the utility model. DETAILED DESCRIPTION

[0025] In order to further explain the technical solution of the present utility model, the present utility model is described in detail below through specific embodiments.

[0026] like Figure 2 As shown, the utility model discloses a high-precision LED current detection circuit, which is used to cooperate with an LED driving circuit; the LED driving circuit includes an LED light source, an operational amplifier OP1, a resistor R1, a MOS tube MN1, a MOS tube MN0, a dimming switch S PWMand a power tube array; the LED light source includes at least one LED lamp bead LED, and the positive electrode of the LED light source is connected to the driving power supply V LED The cathode of the LED light source is connected to the drain of the MOS tube MN0, the gate of the MOS tube MN0 is connected to the output of the operational amplifier OP1, the source of the MOS tube MN0 is connected to the drain of the power tube array and the inverting input of the operational amplifier OP1, the source of the power tube array is grounded, and the gate of the power tube array is connected to the dimming switch S PWM The first end of the dimmer switch S PWM The control terminal receives the dimming signal DS PWM , dimmer switch S PWM The second end of the power tube array is connected to the reference current signal Ir together with the gate of the MOS tube MN1, the source of the MOS tube MN1 is grounded, the drain of the MOS tube MN1 is connected to the first end of the resistor R1 and the in-phase input end of the operational amplifier OP1, and the second end of the resistor R1 is connected to the reference current signal Ir; the power tube array includes 2 n The power tube unit includes a power tube MN_i and a control switch S_i. The drain of the power tube MN_i is connected to the drain end of the power tube array. The gate of the power tube MN_i is connected to the first end of the control switch S_i. The second end of the control switch S_i is connected to the gate end of the power tube array. The control end of the control switch S_i is connected to the control signal CS_i, where i is 0 to 2. n An integer, n is a positive integer.

[0027] Cooperate Figure 2 As shown, the high-precision LED current detection circuit of the utility model includes a current sampling circuit and a comparison and judgment circuit. The current sampling circuit is used to collect the output current of the LED light source, and the comparison and judgment circuit is used to judge whether the output current of the LED light source is within a set normal range.

[0028] Cooperate Figure 2 As shown, specifically, the current sampling circuit includes a MOS tube MNs, a MOS tube MNf and an operational amplifier OP2, the non-inverting input terminal of the operational amplifier OP2 is used to be connected to the drain of the MOS tube MN0, the inverting input terminal of the operational amplifier OP2 is connected to the source of the MOS tube MNf and the drain of the MOS tube MNs, the drain of the MOS tube MNf is connected to the input terminal of the comparison judgment circuit, the gate of the MOS tube MNs is used to be connected to the gate of the MOS tube MN0, and the source of the MOS tube MNs is used to be connected to the source of the MOS tube MN0.

[0029] The working principle of the current sampling circuit is as follows: the MOS tube MNs is used to mirror the output current of the LED light source (i.e., the drain current of the MOS tube MN0) in real time according to a certain mirror ratio, so as to achieve the effect of real-time sampling of the output current of the LED light source; and the MOS tube MNf and the operational amplifier OP2 form a feedback loop, so that the source-drain voltage of the MOS tube MNs is equal to the source-drain voltage of the MOS tube MN0, thereby ensuring the mirroring accuracy when the MOS tube MNs mirrors the output current of the LED light source, that is, the monitoring current signal Is obtained by the MOS tube MNs mirroring the output current of the LED light source can better reflect the output current of the LED light source; in addition, the MOS tube MNs and the power tube array are in series relationship, so that the current abnormality of the power tube array can be directly reflected in the monitoring current signal Is of the MOS tube MNs, thereby solving the problem of underreporting of abnormal information in the existing LED current detection circuit.

[0030] Cooperate Figure 2 As shown, the comparison and judgment circuit includes a first current mirror, a second current mirror, a third current mirror, a reference tube array, a comparator CMPH, a comparator CMPL, a MOS tube MNL, a MOS tube MNH and an OR gate U1; the mirrored end of the first current mirror is connected to the input end of the comparison and judgment circuit, the mirrored end of the first current mirror is connected to the non-inverting input end of the comparator CMPH, the inverting input end of the comparator CMPL and the drain end of the reference tube array, and the mirrored end of the second current mirror is connected to the lower limit threshold current signal I Lth The mirror end of the second current mirror is connected to the in-phase input end of the comparator CMPL and the drain of the MOS tube MNL, and the mirrored end of the third current mirror is connected to the upper threshold current signal I Hth The mirror end of the third current mirror is connected to the inverting input end of the comparator CMPH and the drain of the MOS tube MNH, the gate of the MOS tube MNL and the gate of the MOS tube MNH are connected to the gate end of the reference tube array, the gate end and the drain end of the reference tube array are short-circuited, and the source end of the reference tube array, the source of the MOS tube MNL and the source of the MOS tube MNH are grounded.

[0031] Cooperate Figure 2 As shown, the reference tube array includes 2 n An identical reference tube unit is provided, the reference tube unit includes a reference tube MNr_i and a reference switch K_i, the drain of the reference tube MNr_i is connected to the drain end of the reference tube array, the gate of the reference tube MNr_i is connected to the first end of the reference switch K_i, the second end of the reference switch K_i is connected to the gate end of the reference tube array, the source of the reference tube MNr_i is connected to the source end of the reference tube array, and the control end of the reference switch K_i is connected to the control signal CS_i.

[0032] Cooperate Figure 2As shown, the first current mirror includes a MOS tube MP0 and a MOS tube MP1, the gate and drain of the MOS tube MP0 and the gate of the MOS tube MP1 are connected to the mirrored end of the first current mirror, the source of the MOS tube MP0 and the source of the MOS tube MP1 are connected to the control power supply VDD, and the drain of the MOS tube MP1 is connected to the mirror end of the first current mirror.

[0033] Cooperate Figure 2 As shown, the second current mirror includes a MOS tube MP2 and a MOS tube MP3, the gate and drain of the MOS tube MP2 and the gate of the MOS tube MP3 are connected to the mirrored end of the second current mirror, the source of the MOS tube MP2 and the source of the MOS tube MP3 are connected to the control power supply VDD, and the drain of the MOS tube MP3 is connected to the mirror end of the second current mirror.

[0034] Cooperate Figure 2 As shown, the third current mirror includes a MOS tube MP4 and a MOS tube MP5, the gate and drain of the MOS tube MP4 and the gate of the MOS tube MP5 are connected to the mirrored end of the third current mirror, the source of the MOS tube MP4 and the source of the MOS tube MP5 are connected to the control power supply VDD, and the drain of the MOS tube MP5 is connected to the mirror end of the third current mirror.

[0035] The working principle of the comparison and judgment circuit is:

[0036] The first current mirror can mirror the monitoring current signal Is according to a certain mirror ratio to obtain a first mirror current signal I1, and the second current mirror can mirror the lower threshold current signal I according to a certain mirror ratio. Lth The third current mirror can mirror the upper threshold current signal I according to a certain mirror ratio. Hth The third mirror current signal I3 is obtained. The first mirror current signal I1 is converted into a monitoring voltage signal Vs through the reference tube array and input into the non-inverting input terminal of the comparator CMPH and the inverting input terminal of the comparator CMPL. The second mirror current signal I2 is converted into a lower threshold voltage signal V through the MOS tube MNL. CL The third mirror current signal I3 is converted into an upper threshold voltage signal V by the MOS tube MNH. CH Input the inverting input terminal of the comparator CMPH;

[0037] When the output current of the LED light source is normal, the current value of the output current of the LED light source is at the upper threshold current signal I Hth The current value and the lower threshold current signal I Lth The current value is between , at this time the lower threshold voltage signal V CL The voltage value of the monitoring voltage signal Vs is lower than the voltage value of the upper threshold voltage signal VCH The voltage value of is higher than the voltage value of the monitoring voltage signal Vs, so that the comparator CMPH and the comparator CMPL both output low-level signals to the OR gate U1, so that the OR gate U1 outputs a low-level signal;

[0038] When the output current of the LED light source is lower than the lower threshold current signal I Lth When the current value of the drain current of the MOS tube MNL is equal to the current value of the second mirror current signal I2, the MOS tube MNL should form a current mirror with the reference tube array to make the current value of the drain current of the MOS tube MNL lower than the current value of the second mirror current signal I2. However, since the second current mirror and the MOS tube MNL are in series, in order to make the current value of the drain current of the MOS tube MNL equal to the current value of the second mirror current signal I2, the second current mirror will pull up the lower threshold voltage signal V CL The voltage of the lower threshold voltage signal V CL The voltage value of is greater than the voltage value of the monitoring voltage signal Vs, so that the comparator CMPL outputs a high level signal to the OR gate U1, so that the OR gate U1 outputs a high level signal;

[0039] When the output current of the LED light source is higher than the upper threshold current signal I Hth When the current value of the MOS tube MNH is 1, the MOS tube MNH should form a current mirror with the reference tube array to make the current value of the drain current of the MOS tube MNH higher than the current value of the third mirror current signal I3. However, since the third current mirror and the MOS tube MNH are in series, in order to make the current value of the drain current of the MOS tube MNH equal to the current value of the third mirror current signal I3, the drain-source voltage of the MOS tube MNH will be greatly reduced, causing the MOS tube MNH to enter the linear region, thereby lowering the upper threshold voltage signal V CH The voltage value makes the upper threshold voltage signal V CH The voltage value of is less than the voltage value of the monitoring voltage signal Vs, so the comparator CMPH outputs a high level signal to the OR gate U1, so that the OR gate U1 outputs a high level signal.

[0040] The reference tube array of the utility model has the same structure as the power tube array, and the reference switch K_i of the reference tube array and the control switch S_i of the power tube array are controlled by the same control signal CS_i, so that the switch state of the reference tube array is the same as the switch state of the power tube array, so that the lower limit threshold current signal I is not changed. Lth and the upper threshold current signal I Hth In the case of CL and the upper threshold voltage signal V CHIt will change in proportion to the switching state of the power tube array, ensuring that the high-precision LED current detection circuit of the utility model can also effectively detect whether the output current of the LED light source is normal, thereby effectively improving the detection range of the utility model and reducing the difficulty of circuit design.

[0041] The above embodiments and drawings do not limit the product form and style of the present utility model. Any appropriate changes or modifications made by ordinary technicians in the relevant technical field should be deemed to be within the patent scope of the present utility model.

Claims

1. A high-precision LED current detection circuit, which is used to cooperate with the LED drive circuit; The LED driving circuit includes an LED light source, an operational amplifier OP1, a resistor R1, a MOS tube MN1, a MOS tube MN0, a dimming switch S PWM and a power tube array; the LED light source includes at least one LED lamp bead LED, and the positive electrode of the LED light source is connected to the driving power supply V LED The cathode of the LED light source is connected to the drain of the MOS tube MN0, the gate of the MOS tube MN0 is connected to the output of the operational amplifier OP1, the source of the MOS tube MN0 is connected to the drain of the power tube array and the inverting input of the operational amplifier OP1, the source of the power tube array is grounded, and the gate of the power tube array is connected to the dimming switch S PWM The first end of the dimmer switch S PWM The control terminal receives the dimming signal DS PWM , dimmer switch S PWM The second end of the power tube array is connected to the reference current signal Ir together with the gate of the MOS tube MN1, the source of the MOS tube MN1 is grounded, the drain of the MOS tube MN1 is connected to the first end of the resistor R1 and the in-phase input end of the operational amplifier OP1, and the second end of the resistor R1 is connected to the reference current signal Ir; the power tube array includes 2 n The power tube unit includes a power tube MN_i and a control switch S_i. The drain of the power tube MN_i is connected to the drain end of the power tube array. The gate of the power tube MN_i is connected to the first end of the control switch S_i. The second end of the control switch S_i is connected to the gate end of the power tube array. The control end of the control switch S_i is connected to the control signal CS_i, where i is 0 to 2. n An integer, n is a positive integer; it is characterized by: The high-precision LED current detection circuit includes a current sampling circuit and a comparison and judgment circuit; The current sampling circuit includes a MOS transistor MNs, a MOS transistor MNf and an operational amplifier OP2, wherein the in-phase input terminal of the operational amplifier OP2 is used to be connected to the drain of the MOS transistor MN0, the inverting input terminal of the operational amplifier OP2 is connected to the source of the MOS transistor MNf and the drain of the MOS transistor MNs, the drain of the MOS transistor MNf is connected to the input terminal of the comparison judgment circuit, the gate of the MOS transistor MNs is used to be connected to the gate of the MOS transistor MN0, and the source of the MOS transistor MNs is used to be connected to the source of the MOS transistor MN0.

2. The high-precision LED current detection circuit as claimed in claim 1, characterized in that: The comparison and judgment circuit includes a first current mirror, a second current mirror, a third current mirror, a reference tube array, a comparator CMPH, a comparator CMPL, a MOS tube MNL, a MOS tube MNH and an OR gate U1; The mirrored end of the first current mirror is connected to the input end of the comparison judgment circuit, and the mirror end of the first current mirror is connected to the non-inverting input end of the comparator CMPH, the inverting input end of the comparator CMPL and the drain end of the reference tube array. The mirrored end of the second current mirror is connected to the lower threshold current signal I Lth The mirror terminal of the second current mirror is connected to the non-inverting input terminal of the comparator CMPL and the drain of the MOS tube MNL. The mirrored end of the third current mirror is connected to the upper threshold current signal I Hth , the mirror terminal of the third current mirror is connected to the inverting input terminal of the comparator CMPH and the drain of the MOS tube MNH, The gates of MOS tube MNL and MOS tube MNH are connected to the gate end of the reference tube array, the gate end and drain end of the reference tube array are short-circuited, and the source end of the reference tube array, the source of MOS tube MNL and the source of MOS tube MNH are grounded.

3. The high-precision LED current detection circuit as claimed in claim 2, characterized in that: The reference tube array includes 2 n An identical reference tube unit is provided, the reference tube unit includes a reference tube MNr_i and a reference switch K_i, the drain of the reference tube MNr_i is connected to the drain end of the reference tube array, the gate of the reference tube MNr_i is connected to the first end of the reference switch K_i, the second end of the reference switch K_i is connected to the gate end of the reference tube array, the source of the reference tube MNr_i is connected to the source end of the reference tube array, and the control end of the reference switch K_i is connected to the control signal CS_i.

4. The high-precision LED current detection circuit as claimed in claim 2, characterized in that: The first current mirror includes a MOS tube MP0 and a MOS tube MP1, the gate and drain of the MOS tube MP0 and the gate of the MOS tube MP1 are connected to the mirrored end of the first current mirror, the source of the MOS tube MP0 and the source of the MOS tube MP1 are connected to the control power supply VDD, and the drain of the MOS tube MP1 is connected to the mirror end of the first current mirror.

5. The high-precision LED current detection circuit as claimed in claim 2, characterized in that: The second current mirror includes a MOS tube MP2 and a MOS tube MP3, the gate and drain of the MOS tube MP2 and the gate of the MOS tube MP3 are connected to the mirrored end of the second current mirror, the source of the MOS tube MP2 and the source of the MOS tube MP3 are connected to the control power supply VDD, and the drain of the MOS tube MP3 is connected to the mirror end of the second current mirror.

6. The high-precision LED current detection circuit as claimed in claim 2, characterized in that: The third current mirror includes a MOS tube MP4 and a MOS tube MP5, the gate and drain of the MOS tube MP4 and the gate of the MOS tube MP5 are connected to the mirrored end of the third current mirror, the source of the MOS tube MP4 and the source of the MOS tube MP5 are connected to the control power supply VDD, and the drain of the MOS tube MP5 is connected to the mirror end of the third current mirror.

Images