TWI466587B - Light-emitting diode driving circuit and operating method thereof - Google Patents

Description

Light-emitting diode driving circuit and operating method thereof

The invention relates to a driving circuit, and more particularly to a light emitting diode driving circuit and a method of operating the same.

As shown in FIG. 1 , the LED driving circuit 1 currently applied to the backlight module adjusts the size of the _LED current I _LED according to different setting resistors R _SET . First, in the LED driving circuit 1, the set voltage V _{SET can} be obtained through the characteristics of the first set of voltage follower circuits composed of the transistors N0 and N1, the setting resistor R _SET and the amplifier OP1. It is equal to the reference set voltage V _SETREF , and the current mirror I _{REF is} obtained by using a current mirror composed of transistors N1 and N2.

Then, the reference current I _REF can be multiplied by the resistance RT to obtain the reference voltage V _REF , and then passed through the second set of voltage followers composed of the amplifier OP2 , the resistor R _S , the transistor MS and the LED string LED. The circuit obtains a voltage V _S equal to the reference voltage V _REF . Since the LED current I _LED is equal to the voltage V _S divided by the resistance R _S , the corresponding _LED current I _LED can be obtained by setting different setting resistors R _SET .

However, the channel voltage V _{CH of} each channel multiplied by the _LED current I _LED is equal to the power consumption of each channel, that is, the power consumption of each channel is equal to the channel voltage V _CH multiplied by the light-emitting diode Current I _LED . Therefore, under the same _LED current I _LED , the magnitude of the channel voltage V _CH directly reflects the power consumption of the channel. Since the power loss is usually released by thermal energy, it directly causes the surface temperature of the integrated circuit to rise. Especially in the application of multi-channel LED backlight modules, the extra power loss causes the surface temperature rise of the integrated circuit to be more significant.

Since the channel voltage V _CH is equal to the voltage V _S plus the 汲 source voltage V _{DS of the} transistor MS, in order to effectively reduce the power consumption of the channel, the _LED current I _LED can be reduced by increasing the setting resistance R _SET . Further, the value of the voltage V _S (reference voltage V _REF ) is lowered, so that the channel voltage V _CH becomes small. However, if you do not want to sacrifice the size of the _LED current I _LED to reduce the power consumption, it is necessary to increase the area of the transistor MS to effectively reduce the magnitude of the 汲 source voltage V _DS , thereby making the channel voltage V _CH smaller, but increasing The area of the large transistor MS will result in an increase in production costs.

2, assuming that a light emitting diode backlight module CH1 ~ CHn total of n channels, etc., which are channel voltage V _CH V _CH1 ~ V _CHn. Traditionally, there are two main ways to reduce the power loss of each channel:

(1) It is assumed that the positive input terminal of the error amplifier Gm + the received reference voltage value V _FIX is a fixed value. Under different _LED current I _LED settings, the remaining voltages fall on the transistor MS, so In the case where the diode current I _{LED is} small, the power consumption falling on the transistor MS will be more serious.

(2) It is assumed that the positive input terminal of the error amplifier Gm + the received reference voltage value V _FIX slightly changes with the voltage V _S , since the reference voltage value V _FIX is equal to the minimum channel voltage V _{CH, min is} also equal to the voltage V _S plus The 汲 source voltage V _{DS of the} transistor MS and the 汲 source voltage V _DS are fixed values. If the illuminating diode current I _{LED is} smaller, the voltage V _{S is} smaller, so that the reference voltage value V _FIX also slightly changes. However, the improvement in overall power consumption and thermal energy is not significant.

Therefore, the present invention provides a light emitting diode driving circuit and a method of operating the same to solve the above problems encountered in the prior art.

One aspect of the present invention is to provide a light emitting diode driving circuit. In a preferred embodiment, the LED driving circuit is coupled to the LED string and the adjustment resistor. Illuminate The diode driving circuit includes a reference current generating unit, a first resistor, a first transistor, a second resistor, a parameter adjusting unit, and an operational amplifier. The reference current generating unit is coupled to the adjustment resistor and provides a reference current according to the adjustment resistor. The first transistor is coupled to the LED string and the first resistor, respectively. The parameter adjustment unit is coupled to the reference current generation unit, and has a reference voltage node between the reference current generation unit and the parameter adjustment unit to provide a reference voltage. The operational amplifiers are respectively coupled to the parameter adjustment unit, the first resistor, the second resistor, and the first transistor. When a light-emitting diode current exists between the light-emitting diode string, the first transistor, and the first resistor, the reference voltage changes with the light-emitting diode current.

In an embodiment, the parameter adjustment unit is a second transistor.

In an embodiment, the parameter adjustment unit is a third resistor.

In an embodiment, the LED driving circuit further includes an error amplifier for respectively receiving the reference voltage and the channel voltage between the LED string and the first transistor, and generating an error amplification according to the reference voltage and the channel voltage. Signal.

In one embodiment, the first transistor has a first node between the first resistor and the first resistor to provide a first voltage, and the second node is coupled between the parameter adjustment unit and the second resistor to provide a second voltage, the second voltage Equal to the reference voltage minus the parameter adjustment voltage of the parameter adjustment unit, the operational amplifier receives the first voltage and the second voltage, respectively, and outputs the transistor control signal to the first transistor.

In one embodiment, the parameter adjustment voltage of the parameter adjustment unit is equal to the first threshold source voltage of the first transistor.

In an embodiment, the first resistor has a proportional relationship with the second resistor.

In one embodiment, the first size of the first transistor has a proportional relationship with the second size of the second transistor.

In one embodiment, the product of the channel voltage and the LED current is the power consumption of the channel. When the reference voltage changes with the LED current, the channel voltage changes accordingly, resulting in a pass. The power consumption of the channel also changes.

Another aspect of the present invention is to provide a method of operating a light emitting diode driving circuit. In a preferred embodiment, the LED driving circuit is coupled to the LED string and the adjustment resistor, and the LED driving circuit includes a reference current generating unit, a first resistor, a first transistor, and a parameter adjusting unit. , second resistor and operational amplifier. The operating method of the LED driving circuit comprises the following steps: (a) the reference current generating unit provides a reference current according to the adjusting resistor; (b) the reference voltage node between the reference current generating unit and the parameter adjusting unit provides a reference voltage; The operational amplifier receives the first voltage and the second voltage from the first node between the first transistor and the first resistor and the second node between the parameter adjustment unit and the second resistor, and outputs the transistor control signal to the first a transistor; (d) when a light-emitting diode current exists between the light-emitting diode string, the first transistor, and the first resistor, the reference voltage changes with the light-emitting diode current.

Compared with the prior art, the LED driving circuit and the operating method thereof according to the present invention have the following advantages: (1) reducing the power loss and reducing the temperature of the integrated circuit without additionally increasing the area of the integrated circuit. Efficacy to improve the efficiency and life of the integrated circuit; (2) When the set resistance is increased to reduce the LED current, the reference voltage of the error amplifier also decreases, so the power loss can be reduced and the integrated circuit temperature can be reduced. (3) When applied to a multi-channel LED backlight module, the effect of reducing power loss and lowering the integrated circuit temperature will be more significant; (4) It can be applied to various LED driving circuit architectures. For example, AC AC/DC DC plus Current Balance architecture, Boost plus current balance architecture or Buck/Boost plus current balance architecture.

The advantages and spirit of the present invention will be further understood from the following detailed description of the invention.

A preferred embodiment of the present invention is a light emitting diode driving circuit. real In the embodiment, the LED driving circuit of the embodiment is applied to a multi-channel LED backlight module or other LED device for driving and controlling the operation of the LED. In the embodiment, the LED driving circuit adjusts the magnitude of the LED current by changing the setting resistor and reduces the reference voltage of the error amplifier, thereby reducing power loss and lowering the integrated circuit temperature. The efficiency and longevity of the integrated circuit.

Please refer to FIG. 3A. FIG. 3A is a schematic diagram of a light emitting diode driving circuit according to this embodiment. As shown in FIG. 3A, the LED driving circuit 3A is coupled to the LED string LED and the adjustment resistor R _SET . The light emitting diode driving circuit 3A includes a reference current generating unit RCG, a first resistor R _S , a first transistor MS, a second resistor R _T , a parameter adjusting unit RAU, an operational amplifier OP, and an error amplifier GM.

The reference current generating unit RCG is coupled to the adjustment resistor R _SET . The parameter adjustment unit RAU is coupled between the reference current generating unit RCG and the second resistor R _T . The second resistor R _{T is} coupled to the ground. A reference voltage node 33 is provided between the reference current generating unit RCG and the parameter adjusting unit RAU to provide a reference voltage V _REF . The first transistor MS is coupled between the LED string LED and the first resistor R _S . The first resistor R _{S is} coupled to the ground. The LED string LED is coupled to the output voltage V _OUT .

The positive input terminal + of the operational amplifier OP is coupled to the second node 32 between the parameter adjustment unit RAU and the second resistor R _T to receive the second voltage V2. The negative input terminal of the operational amplifier OP is coupled to the first node 31 between the first transistor MS and the first resistor R _S to receive the first voltage V1. The output terminal K of the operational amplifier OP is coupled to the gate of the first transistor MS. The positive input terminal of the error amplifier GM is coupled to the reference voltage V _REF . The negative input terminal of the error amplifier GM is coupled to the channel voltage node 34 between the LED string LED and the first transistor MS to receive the channel voltage V _CH .

The reference current generating unit RCG is coupled to the operating voltage V _DD and provides a reference current I _REF to the parameter adjusting unit RAU according to the adjusting resistor R _SET . In practical applications, the parameter adjustment unit RAU may be a transistor or a resistor. The parameter adjustment unit RAU has a parameter adjustment voltage V _RA , and the parameter adjustment voltage V _{RA is} equal to the first 汲 source voltage V _DS of the first transistor MS, so the second voltage V2 of the second node 32 is equal to the reference voltage V _REF minus Go to the parameter adjustment voltage V _RA .

The first voltage V1 of the first node 31 is equal to the channel voltage V _CH minus the first 汲 source voltage V _DS of the first transistor MS. The negative input terminal and the positive input terminal of the operational amplifier OP receive the first voltage V1 and the second voltage V2, respectively, and output the transistor control signal CTR to the first transistor MS.

The positive input terminal + and the negative input terminal of the error amplifier GM receive the reference voltage V _REF and the channel voltage V _{CH of the} channel voltage node 34, respectively, and generate an error amplification signal Comp according to the reference voltage V _REF and the channel voltage V _CH .

When there is a light-emitting diode current I _LED between the LED array LED, the first transistor MS and the first resistor R _S , the reference voltage V _REF will change with the LED current I _LED . In more detail, the user can reduce the LED current I _LED by increasing the setting resistance R _SET , and the reference voltage V _REF used by the error amplifier GM also decreases, so that the channel voltage V _CH also becomes smaller. Since the power consumption of the channel is equal to the product of the channel voltage V _CH and the LED current I _LED , when the set resistance R _{SET is} increased, the LED current I _LED and the channel voltage V _CH are both reduced, so the channel power consumption is also The utility model can reduce the power loss and reduce the temperature of the integrated circuit without additionally increasing the area of the integrated circuit, so as to improve the use efficiency and the life of the integrated circuit.

Referring to FIG. 3B, FIG. 3B illustrates an embodiment in which the parameter adjustment unit RAU of FIG. 3A is the second transistor MT. As shown in FIG. 3B, the second transistor MT is used as the parameter adjustment unit RAU in FIG. 3A. The source and the drain of the second transistor MT are coupled to the reference current generating unit RCG and the second resistor R _{T , respectively} . The gate of the second transistor MT is coupled to the operating voltage V _DD .

The reference current generating unit RCG includes transistors N0 to N2 and an operational amplifier OP1. The gate of the transistor N1 is coupled to the gate of the transistor N2 to form a current mirror. The positive input terminal of the operational amplifier OP1 is coupled to the reference set voltage V _SETREF , and the negative input terminal thereof is coupled to the node 36 between the transistor N0 and the adjustment resistor R _SET to receive the set voltage V _SET , and the output terminal K1 is coupled. The gate of the transistor N0. The adjustment resistor R _{SET is} coupled between the transistor N0 and the ground. The transistor N0 is coupled to the transistor N1, the adjustment resistor R _SET and the operational amplifier OP1, respectively. The transistor N1 is coupled between the operating voltage V _DD and the transistor N0. The transistor N2 is coupled between the operating voltage V _DD and the second transistor MT. A node 37, to which the gate of the transistor N1 is coupled to the gate of the transistor N2, is coupled to the node 35 between the transistors N1 and N0.

The set current I _SET flows through the transistors N1, N0 and the adjustment resistor R _SET . The reference current I _REF flows through the transistor N2, the second transistor MT, and the second resistor R _T . It is assumed that the set current I _SET flowing through the transistor N1 is converted into a reference current I _{REF by} N times after the current mirror formed by the gate of the transistor N1 and the gate of the transistor N2 are oppositely coupled, that is, flowing through the electricity. The reference current I _REF of the crystal N2 is N times the set current I _SET flowing through the transistor N1, and N is greater than zero.

It is assumed that the proportional relationship between the first resistor R _S and the second resistor R _T is that the second resistor R _T is m times the first resistor R _S , and the first size of the first transistor MS and the second transistor MT are The proportional relationship between the second dimensions is that the first size of the first transistor MS is m times the second size of the second transistor MT, and m is greater than zero, in order to make the second source voltage of the second transistor MT V _{DS2 is} equal to the first 汲 source voltage V _DS of the first transistor MS, and the second drain-source resistance R _DS2 of the second transistor MT needs to be the first drain-source of the first transistor MS The pole resistance R _DS1 is m times, and therefore, the light-emitting diode current I _LED flowing through the light-emitting diode string LED is m times the reference current I _REF flowing through the second transistor MT. The _LED current I _LED obtained by the following formula 1 is determined by the variable adjustment resistor R _SET : I _LED = m * I _REF = m * (N * I _SET ) = m * N * (V _SETREF /R _SET ) (Formula 1)

The second drain-source resistance R _DS2 of the second transistor MT is obtained by the following calculation of Equation 2 as m times the first drain-source resistance R _DS1 of the first transistor MS: V _DS = I _LED *R _DS1

V _DS2 =I _REF *R _DS2

Since V _DS =V _DS2 and I _LED =m*I _REF

Therefore (m*I _REF )*R _DS1 =I _REF *R _DS2

Therefore, R _DS2 =m*R _DS1 (Formula 2) is available.

It should be noted that the reference voltage V _REF of the reference voltage node 33 between the transistor N2 and the second transistor MT is supplied to the error amplifier GM. It is obvious that the reference voltage V _REF is equal to that of the second transistor MT. The sum of the second drain source voltage V _DS2 and the second voltage V2. From the following calculation of Equation 3, the reference voltage V _{REF is} also obtained as a function of the adjustment resistor R _SET : since V _DS2 =I _REF *R _DS2

V2=I _REF *R _T

I _REF =N*I _SET =N*(V _SET /R _SET )

Therefore V _REF =V _DS2 +V2=(I _REF *R _DS2 )+(I _REF *R _T )=N*(V _SET /R _SET )(R _DS2 +R _T )

And V _SET =V _SETREF

Therefore V _REF =N*(V _SETREF /R _SET )(R _DS2 +R _T )=(1/R _SET )*N*V _SETREF *(R _DS2 +R _T ) (Equation 3)

It can be seen from the above that the size of the _LED current I _{LED of the LED} array LED can be rectified by changing the resistance value of the adjustment resistor R _SET , and the transistor N2 and the second transistor MT can also be changed. The magnitude of the reference voltage V _REF between. For example, if the resistance value of the adjustment resistor R _SET is increased, not only the magnitude of the _LED current I _{LED of the LED} string LED but also the magnitude of the reference voltage V _REF can be adjusted.

Since the channel voltage V _CH is equal to the first voltage V1 plus a first drain-source voltage V _DS of the first transistor MS, and the first MS a first transistor drain-source voltage V _DS of the second transistor is equal to the MT The second source voltage V _DS2 , if the offset voltage of the operational amplifier OP is ignored, the first voltage V1 is equal to the second voltage V2, so under the steady state (Steady State) operation, the channel voltage V _CH is equal to the reference voltage V _REF : V _CH =V1+V _DS

V _REF =V2+V _DS2

Assume that the offset voltage of the op amp OP1 is not considered

V1=V2 and V _DS =V _DS2

Therefore V _CH =V _REF (Equation 4)

Since the channel power consumption of each channel is equal to the channel voltage V _CH multiplied by the LED current I _LED . Therefore, under the same _LED current I _LED , the magnitude of each channel voltage V _CH directly reflects the power consumption of the channel of the channel. It can be seen from the above that when the resistance value of the adjustment resistor R _SET is increased, not only the size of the _LED current I _{LED of the LED} string LED can be adjusted, but also the magnitude of the reference voltage V _REF can be lowered. Therefore, as the current of the _LED current I _LED becomes smaller, the channel voltage V _CH also becomes smaller, whereby the channel power consumption can be more effectively reduced.

As shown in FIG. 4, it is assumed that the LED backlight module comprises a total of n LED strings, that is, there are n channels, and the channel voltages thereof are V _CH1 ~ V _{CHn , respectively} . The minimum channel voltage V _CH,min is selected from the n channel voltages V _CH1 to V _CHn of the n channels by the minimum channel voltage selector 30 and output to the negative input terminal of the error amplifier Gm. The negative input terminal of the error amplifier Gm and the positive input terminal + receive the minimum channel voltage V _CH,min and the reference voltage V _REF , respectively, and accordingly generate an error amplification signal Comp.

FIG. 5 illustrates another embodiment of the LED driving circuit of the present invention. The illuminating diode driving circuit 5 of FIG. 5 is different from the illuminating diode driving circuit 3B of FIG. 3B in that the parameter adjusting unit coupled between the transistor N2 and the second resistor R _T is not a transistor. It is the resistance R _M . The parameter adjustment voltage V _RM across the resistor R _M is equal to the reference voltage V _REF minus the second voltage V2, which is also equal to the first threshold source voltage V _DS of the first transistor MS. The operation of the LED driving circuit 5 in FIG. 5 is substantially the same as that of the LED driving circuit 3B in FIG. 3B, and therefore will not be further described herein.

Next, the power consumed by the prior art and the present invention will be compared with a light emitting diode driving circuit having a single channel. Assuming that the resistance R _S is 4 ohms, when the first voltage V1 is 0.4 volts, 0.2 volts, and 0.1 volts, respectively, the illuminating diode current I _LEDs are 100 mA, 50 mA, and 25 mA, respectively.

In the case where the size of the first transistor MS is constant, if the prior art adopts a fixed channel voltage V _CH of 1 volt, when the LED current I _LED is 100 mA, 50 mA, and 25 mA, respectively. The channel consumes power of 100 milliwatts, 50 milliwatts, and 25 milliwatts, respectively. If the prior art uses the first 汲 source voltage V _DS of the fixed first transistor MS to be 0.6 volts, when the illuminating diode current I _LED is 100 mA, 50 mA, and 25 mA, respectively, the channel voltage V _CH is equal to the sum of the first voltage V1 and the first 汲 source voltage V _DS , which are 1 volt, 0.8 volt, and 0.7 volt, respectively, so the channel power consumption is 100 milliwatts, 40 milliwatts, and 17.5 milliwatts, respectively. It can be seen from the above that the methods adopted in the prior art can only slightly reduce the power consumption of the channel.

However, if the LED driving circuit structure of the present invention is adopted, when the user increases the resistance value of the variable adjusting resistor R _SET , the LED current I _LED will become smaller, the first transistor The first 汲 source voltage V _{DS of the} MS also becomes smaller, and the first voltage V1 also becomes smaller. Since the channel voltage V _CH is equal to the sum of the first voltage V1 and the first 汲 source voltage V _DS , the channel voltage V _{The CH} will become smaller, and the channel power consumption is equal to the product of the _LED current I _LED and the channel voltage V _CH , so the channel power consumption will also become smaller. Therefore, when the LED current I _LED is 100 mA, 50 mA, and 25 mA, respectively, the first 汲 source voltage V _DS is 0.6 volts, 0.3 volts, and 0.15 volts, respectively, and the channel voltage V _CH is 1 volt, 0.5 volt and 0.25 volt, the channel power consumption is 100 milliwatts, 25 milliwatts and 6.25 milliwatts, respectively, so the light-emitting diode driving circuit of the invention can significantly reduce the power consumption of the channel.

Please refer to FIG. 6. FIG. 6 is a schematic diagram of a light emitting diode driving circuit having a plurality of channels. As shown in FIG. 6, the LED driving circuit 6 is coupled to the n LED strings LED1 to LEDn and the adjustment resistor R _SET . The LED driving circuit 6 includes n current regulators CR1 to CRn, a minimum channel voltage selector 60, a current setting unit 62, and an error amplifier Gm. One end of the LED string LED1~LEDn is coupled to the output voltage V _OUT , and the other end is coupled to the current regulators CR1~CRn respectively. The current regulators CR1 CR CRn are both coupled to the current setting unit 62 . The error amplifier Gm is coupled to the minimum channel voltage selector 60 and the current setting unit 62.

The light-emitting diode strings LED1 to LEDn and the current regulators CR1 to CRn respectively have n channel voltages V _CH1 to V _CHn corresponding to n channels. The minimum channel voltage selector 60 will receive the n channel voltages V _CH1 ~V _CHn and select the minimum channel voltage V _{CH,min therefrom} . The current regulators CR1 to CRn and the current setting unit 62 each have the same second voltage V2. The error amplifier Gm receives the minimum channel voltage V _CH,min and the reference voltage V _REF from the minimum channel voltage selector 60 and the current setting unit 62, and outputs an error amplification signal Comp according to the minimum channel voltage V _CH,min and the reference voltage V _{REF .} .

7 and FIG. 8 are detailed circuit diagrams of the current regulator CR1 and the current setting unit 62 of FIG. 6, respectively. Since the circuit structure can refer to FIG. 3B, it will not be further described herein.

In summary, the LED driving circuit disclosed in the present invention can be applied to various LED driving circuit architectures, such as AC AC/DC DC plus current balance architecture, Boost plus current balancing. Architecture or Buck/Boost plus current balancing architecture.

Another embodiment of the present invention is a method of operating a light emitting diode driving circuit. In this embodiment, the LED driving circuit operation method is used to operate the LED driving Circuit. The LED driving circuit is coupled to the LED string and the adjustment resistor. The LED driving circuit includes a reference current generating unit, a first resistor, a first transistor, a parameter adjusting unit, a second resistor, and an operational amplifier.

Please refer to FIG. 9. FIG. 9 is a flow chart showing a method for operating the LED driving circuit according to this embodiment. As shown in FIG. 9, in step S10, the reference current generating unit supplies a reference current according to the adjustment resistor. In step S12, a reference voltage is provided by a reference voltage node between the reference current generating unit and the parameter adjusting unit. In step S14, the operational amplifier receives the first voltage and the second voltage from a first node between the first transistor and the first resistor and a second node between the parameter adjustment unit and the second resistor, respectively. In step S16, the operational amplifier generates a transistor control signal to the first transistor according to the first voltage and the second voltage.

The first 汲 source voltage of the first transistor is equal to the parameter adjustment voltage of the parameter adjustment unit, and the first size of the first transistor has a proportional relationship with the second size of the parameter adjustment unit. In fact, the parameter adjustment unit may be a transistor or a resistor, and the parameter adjustment voltage of the parameter adjustment unit may be a source voltage of the transistor or a voltage value across the resistor.

In step S18, the method respectively receives the reference voltage and the channel voltage between the LED string and the first transistor, and generates an error amplification signal according to the reference voltage and the channel voltage. In step S20, when there is a light-emitting diode current between the light-emitting diode string, the first transistor, and the first resistor, the reference voltage changes with the light-emitting diode current. In step S22, when the reference voltage changes with the LED current, the channel voltage changes accordingly, so that the channel power consumption also changes.

It is assumed that the LED driving circuit is coupled to a plurality of LED strings, that is, having a plurality of channels. In step S18, the method may first select the lowest channel voltage from a plurality of channel voltages corresponding to the plurality of channels. And generating an error amplification signal according to the lowest channel voltage and the error amplification reference voltage.

For example, assume that the second resistance is m times the first resistance, and the first transistor One dimension is also m times the second dimension of the parameter adjustment unit, m being greater than zero. The second drain-source resistance of the parameter adjustment unit is m times the first drain-source resistance of the first transistor, and the LED current flowing through the LED string flows through the parameter adjustment unit The reference current is m times.

Compared with the prior art, the LED driving circuit and the operating method thereof according to the present invention have the following advantages: (1) reducing the power loss and reducing the temperature of the integrated circuit without additionally increasing the area of the integrated circuit. Efficacy to improve the efficiency and life of the integrated circuit; (2) When the set resistance is increased to reduce the LED current, the error amplification reference voltage of the error amplifier also decreases, so the power loss can be reduced and the integrated body can be reduced. Circuit temperature; (3) When applied to a multi-channel LED backlight module, the effect of reducing power loss and reducing the temperature of the integrated circuit will be more significant; (4) Applicable to various LED driving circuits Architectures such as AC AC/DC DC plus current balancing architecture, Boost plus current balancing architecture or Buck/Boost plus current balancing architecture.

The features and spirits of the present invention are more apparent from the detailed description of the preferred embodiments. On the contrary, the intention is to cover various modifications and equivalents within the scope of the invention as claimed.

S10~S22‧‧‧ Process steps

1, 3A, 3B, 5, 6‧‧‧Lighting diode driving circuit

I _LED , I _LED1 ~I _{LEDn ‧‧‧Lighting} diode current

LED, LED1~LEDn‧‧‧Light diode string

V _DS , V _DS2 ‧‧‧汲 source voltage

R _SET ‧‧‧Adjusting resistance

I _REF ‧‧‧Reference current

N0, N1, N2, MS, MT‧‧‧ transistors

OP, OP1, OP2‧‧‧Operational Amplifier

C‧‧‧ capacitor

V _SET ‧‧‧Set voltage

V _SETREF ‧‧‧ reference set voltage

R, R _T , R _S , R _M ‧‧‧resistance

V _REF ‧‧‧reference voltage

V _S ‧‧‧ voltage

V _CH , V _CH1 ~V _CHn ‧‧‧ channel voltage

Gm, GM‧‧‧ error amplifier

K, K1, K2‧‧‧ output

+‧‧‧正Input

-‧‧‧negative input

V _FIX ‧‧‧ fixed reference voltage value

V _CH,min ‧‧‧minimum channel voltage

10, 30, 60‧‧‧ minimum channel voltage selector

V _DD ‧‧‧ working voltage

I _SET ‧‧‧Set current

V _OUT ‧‧‧ output voltage

MT‧‧‧second transistor

Comp‧‧‧Error amplification signal

C _out ‧‧‧output capacitor

CR1~CRn‧‧‧ Current Regulator

62‧‧‧ Current setting unit

RCG‧‧‧reference current generation unit

RAU‧‧‧ parameter adjustment unit

31~37‧‧‧ nodes

V1‧‧‧ first voltage

V2‧‧‧second voltage

CTR‧‧‧Crystal control signal

V _RA , V _RM ‧‧‧ parameter adjustment voltage

FIG. 1 is a schematic diagram of a prior art LED driving circuit.

2 is a schematic diagram of an error amplifier in the prior art.

3A is a schematic diagram of a light emitting diode driving circuit according to an embodiment of the present invention.

FIG. 3B is a schematic diagram of a light emitting diode driving circuit according to another embodiment of the present invention.

4 is a schematic diagram of an error amplifier in accordance with an embodiment of the present invention.

FIG. 5 is a schematic diagram of a light emitting diode driving circuit according to another embodiment of the present invention.

FIG. 6 is a schematic diagram of a light emitting diode driving circuit coupled to a plurality of LED strings.

7 and 8 respectively show detailed circuit diagrams of the current regulator and current setting unit of FIG. 6.

FIG. 9 is a flow chart showing a method of operating a light emitting diode driving circuit according to another embodiment of the present invention.

3A‧‧‧Lighting diode drive circuit

R _SET ‧‧‧Adjusting resistance

I _REF ‧‧‧Reference current

I _LED ‧‧‧Lighting diode current

MS‧‧‧O crystal

OP‧‧‧Operational Amplifier

GM‧‧‧Error Amplifier

LED‧‧‧Light diode string

V _OUT ‧‧‧ output voltage

R _T , R _S ‧‧‧ resistance

V _REF ‧‧‧reference voltage

V1‧‧‧ first voltage

V _CH ‧‧‧ channel voltage

V _DS ‧‧‧汲 source voltage

31~34‧‧‧ nodes

K‧‧‧ output

V _DD ‧‧‧ working voltage

+‧‧‧正Input

-‧‧‧negative input

RAU‧‧‧ parameter adjustment unit

RCG‧‧‧reference current generation unit

CTR‧‧‧Crystal control signal

V _RA ‧‧‧ parameter adjustment voltage

Comp‧‧‧Error amplification signal

Claims (14)

A light-emitting diode driving circuit is coupled to a light-emitting diode string and an adjusting resistor. The LED driving circuit includes: a reference current generating unit coupled to the adjusting resistor, and providing a reference according to the adjusting resistor a first resistor; a first transistor coupled to the LED string and the first resistor; a parameter adjustment unit coupled to the reference current generating unit, and the reference current generating unit and the parameter a reference voltage node is provided between the adjustment units to provide a reference voltage; a second resistor; and an operational amplifier coupled to the parameter adjustment unit, the first resistor, the second resistor, and the first transistor, respectively When a light-emitting diode current exists between the light-emitting diode string, the first transistor, and the first resistor, the reference voltage changes with the light-emitting diode current. The illuminating diode driving circuit of claim 1, wherein the parameter adjusting unit is a second transistor. The illuminating diode driving circuit of claim 1, wherein the parameter adjusting unit is a third resistor. The illuminating diode driving circuit of claim 1, further comprising: an error amplifier for respectively receiving the reference voltage and a channel voltage between the illuminating diode string and the first transistor And generating an error amplification signal according to the reference voltage and the channel voltage. The illuminating diode driving circuit of claim 1, wherein the first transistor has a first node between the first resistor and the first resistor to provide a first voltage, the parameter adjusting unit and the first Between the two resistors, a second node is provided to provide a second voltage, the second voltage is equal to the reference voltage minus a parameter adjustment voltage of the parameter adjustment unit, and the operational amplifier receives the first voltage and the second Voltage and output a transistor control signal to the first transistor. The illuminating diode driving circuit of claim 5, wherein the parameter adjusting voltage of the parameter adjusting unit is equal to a first 汲 source voltage of the first transistor. The illuminating diode driving circuit of claim 1, wherein the first resistor and the second resistor have a proportional relationship. The illuminating diode driving circuit of claim 2, wherein a first dimension of one of the first transistors has a proportional relationship with a second dimension of the second transistor. The illuminating diode driving circuit of claim 4, wherein a product of the channel voltage and the LED current is a channel power consumption, and when the reference voltage changes with the illuminating diode current, The voltage of the channel changes accordingly, so that the power consumption of the channel also changes. A method for operating a light-emitting diode driving circuit, the LED driving circuit is coupled to a light-emitting diode string and an adjusting resistor, the LED driving circuit includes a reference current generating unit and a first resistor a first transistor, a parameter adjustment unit, a second resistor, and an operational amplifier, the method comprising the steps of: (a) the reference current generating unit provides a reference current according to the adjusting resistor; and (b) the reference current Providing a reference voltage to a reference voltage node between the generating unit and the parameter adjusting unit; (c) the operational amplifier receives a first voltage and a first node from a first node between the first transistor and the first resistor and a second node between the parameter adjustment unit and the second resistor a voltage, and outputting a transistor control signal to the first transistor; and (d) when a light emitting diode current exists between the LED string, the first transistor, and the first resistor, The reference voltage changes with the LED current. The method of driving a light emitting diode according to claim 10, wherein the parameter adjusting unit is a second transistor. The method of driving a light emitting diode according to claim 10, wherein the parameter adjusting unit is a third resistor. The method for driving a light emitting diode according to claim 10, further comprising the steps of: respectively receiving the reference voltage and a channel voltage between the LED string and the first transistor, and according to the The reference voltage and the channel voltage produce an error amplification signal. The method of driving a light emitting diode according to claim 10, wherein a product of the channel voltage and the LED current is a channel power consumption, and when the reference voltage changes with the LED current, The voltage of the channel changes accordingly, so that the power consumption of the channel also changes.