TWI586215B - A power compensation circuit and an LED lighting system using the power compensation circuit - Google Patents

Description

Power compensation circuit and LED illumination system using the power compensation circuit

The present invention relates to a power compensation circuit; and more particularly to a power compensation circuit for a light emitting diode (LED) driver.

Please refer to FIG. 1 , which is a schematic diagram of a conventional LED illumination system. The conventional LED illumination system includes a power compensation circuit 1000. The power compensation circuit 1000 includes a first resistor pre-R1 and a second resistor pre-R2. The first resistor pre-R1 and the first resistor pre-R2 are connected in series with each other and the voltage at the connection point is pre-V _CS . The first resistor pre-R1 is coupled to the output end of an LED circuit 2000. The voltage across the voltage is pre-V _F , the current flowing through the LED circuit 2000 is a pre-I _LED , and the voltage at the output of the LED circuit 2000 is pre-V _out , and the LED circuit 2000 receives an input current of an input power source 3000. Pre-I _in , the input voltage of the input power source 3000 is pre-V _in , the second resistor pre-R2 is coupled to a resistor pre-R _CS , and a driving chip 4000 is disposed at the output end of the LED circuit 2000 and the Between resistors R _CS .

Wherein the input is equal to the input power 3000 input current pre-I _in the input voltage of the pre-V _in the product, therefore, assuming that the input current pre-I _in a fixed, the input power as the input voltage pre-V _in changes changes, in order to avoid the input power sharp variation, conventional techniques in 4000 outside the driving wafer setting the power compensation circuit 1000 to correct the input current pre-I _in, and more specifically, when When the input voltage is a change _in pre-V _in (for example, becoming large) and the voltage across the pre-V _{F is} fixed, the voltage pre-V _out becomes large (pre-V _out = pre-V _{in -} pre-V _F ) Therefore, the voltage pre-V _CS becomes larger, the current flowing through the power compensation circuit 1000 becomes larger, the power compensation amount increases, the current pre-I _LED becomes smaller, and the input current pre-I _in becomes smaller, according to which under the action of conventional the power compensation circuit 1000, the input voltage value pre-V _in is the input current of the current value of the pre-I _in because there are reasons for compensating and may be presented relationship varies inversely, so that the input The input power of the power supply 3000 does not become large.

However, after the above-mentioned conventional LED illumination system is used for a period of time, the voltage across the pre-V _{F of} the LED circuit 2000 gradually decreases as the temperature increases, which in turn causes the LED illumination system under the prior art to have a A serious defect, because the voltage drop pre-V _F will cause the voltage pre-V _{out to} become larger, the current flowing through the power compensation circuit 1000 becomes larger, the power compensation amount increases, and the voltage pre-V _CS becomes larger. The current pre-I _LED becomes smaller, and the input current pre-I _in becomes smaller, so that the current value of the input current pre-I _in when the voltage value of the input voltage pre-Vi _n does not become large However, it is reduced, resulting in a decrease in the input power of the input power source 3000, resulting in insufficient output brightness.

That is, although the power compensation circuit 1000 may be changed by the input voltage of the pre-V _in the amount of variation of the power compensation, so as to stabilize the input power, however, can not overcome the problems arising due to temperature change of the input power.

In order to solve the above problems of the prior art, an object of the present invention is to provide a power compensation circuit and an LED illumination system using the power compensation circuit, which have the function of adjusting the power compensation amount with temperature.

To achieve the above and other objects, the present invention provides a power compensation circuit, the input end of the power compensation circuit is coupled to an output end of an LED circuit, and the input end of the LED circuit is coupled to an input power source, the power compensation circuit The output end is coupled to a compensation resistor, the power compensation circuit The method is configured to generate a compensation current, and the compensation current flows through the compensation resistor to generate a compensation power, thereby stabilizing the power input to the LED circuit by the compensation power.

The power compensation circuit includes a voltage detecting unit, a temperature change voltage generating unit, an arithmetic unit and an output unit.

The voltage detecting unit receives the voltage of the output end of the LED circuit and adjusts the output of the detected voltage; the temperature-varying voltage generating unit correspondingly generates a temperature-varying voltage according to the detected ambient temperature; the computing unit is respectively coupled Connected to the voltage detecting unit and the temperature-varying voltage generating unit, the computing unit compares the detected voltage and the temperature-varying voltage to output a comparison voltage; and the output unit is coupled to the computing unit to perform the comparison according to the comparison The voltage is used to output the compensation current.

In the above power compensation circuit, the temperature change voltage generating unit includes a voltage generator, the voltage generator generates the temperature change voltage, and the voltage value of the temperature change voltage generated by the voltage generator is proportional to the temperature change voltage Generates the ambient temperature value detected by the unit.

In the above power compensation circuit, the operation unit includes an operational amplifier, and the operational amplifier respectively receives the detection voltage and the temperature change voltage, and amplifies and outputs a voltage difference between the detection voltage and the temperature change voltage. As the comparison voltage.

In the above power compensation circuit, the output unit includes a first voltage control current source and a second voltage control current source, and the first voltage control current source respectively receives the comparison voltage and an internal voltage of the power compensation circuit, The first voltage control current source adjusts the current correspondingly according to the comparison voltage to generate an output current as the compensation current; and the second voltage control current source respectively receives the comparison voltage and the detection voltage, and the second voltage control current The source adjusts the current correspondingly according to the comparison voltage to output a pair of ground currents.

To achieve the above and other objects, the present invention provides an LED lighting system including: an input power source, an LED circuit, a power compensation circuit, a compensation resistor, and a resistor circuit, the input power source having an input power and providing a Input current; the LED circuit is coupled to the output end of the input power source to receive the input current; the power compensation circuit has an input end coupled to the output end of the LED circuit, according to the voltage and the output end of the LED The detected ambient temperature generates a compensation current; the compensation resistor is coupled to the output end of the power compensation circuit to generate a compensation power by flowing the compensation current, and the compensation power is used to stably input the LED The power of the circuit; and the resistor circuit is coupled to the compensation resistor.

In the above LED lighting system, the power compensation circuit includes a voltage detecting unit, a temperature-varying voltage generating unit, an arithmetic unit and an output unit, and the voltage detecting unit receives the voltage of the output end of the LED circuit, and Adjusting the output of the detected voltage; the temperature-varying voltage generating unit correspondingly generates a temperature-varying voltage according to the detected ambient temperature; the computing unit is respectively coupled to the voltage detecting unit and the temperature-varying voltage generating unit, The operation unit compares the detection voltage with the temperature change voltage to output a comparison voltage; and the output unit is coupled to the operation unit to output the compensation current according to the comparison voltage.

In the LED lighting system, the control circuit further includes a control circuit, the control circuit includes an operational amplifier and a switch, the operational amplifier is coupled to the output unit, and the voltage of the output end of the output unit and one of the external reference voltages The voltage difference is amplified to output a control voltage; and the source of the switch is coupled to the input end of the power compensation circuit, and the drain of the switch is coupled to the output end of the power compensation circuit, the switch The gate is coupled to the output of the operational amplifier to control the switch by the control voltage.

In the above LED lighting system, the power compensation circuit, the compensation resistor, and the control circuit are disposed on the same wafer.

Thereby, the present invention utilizes the power compensation circuit and the LED illumination system using the power compensation circuit, which adjusts the compensation current with temperature to stabilize the compensation power (ie, the power compensation amount), thereby stabilizing the input power.

10‧‧‧Input power supply

20‧‧‧LED circuit

21‧‧‧LED

30‧‧‧Power compensation circuit

31‧‧‧Voltage detection unit

32‧‧‧temperature change voltage generating unit

33‧‧‧ arithmetic unit

34‧‧‧Output unit

40‧‧‧Compensation resistance

50‧‧‧Resistor circuit

60‧‧‧Control circuit

100‧‧‧LED lighting system

200‧‧‧ wafer

1000‧‧‧Power compensation circuit

2000‧‧‧LED circuit

3000‧‧‧Input power supply

4000‧‧‧Drive chip

AMP1‧‧‧Operational Amplifier

AMP2‧‧‧Operational Amplifier

I _cmp ‧‧‧compensation current

I _GND ‧‧‧ground current

I _in ‧‧‧Input current

I _LED ‧‧‧current

P _in ‧‧‧Input power

pre-I _in ‧‧‧ input current

pre-I _LED ‧‧‧current

pre-R1‧‧‧first resistance

pre-R2‧‧‧second resistance

pre-R _CS ‧‧‧resistance

pre-V _CS ‧‧‧voltage

pre-V _F ‧‧‧cross pressure

pre-V _in ‧‧‧ input voltage

pre-V _out ‧‧‧voltage

Q1‧‧‧ switch

R _cmp ‧‧‧resistance

R _CS ‧‧‧resistance

VCCS1‧‧‧First Voltage Control Current Source

VCCS2‧‧‧Second voltage controlled current source

V _cmp ‧‧‧compensation voltage

V _CS ‧‧‧ voltage

V _F ‧‧‧cross pressure

V _in ‧‧‧ input voltage

V _out ‧‧‧ voltage

V _{OUT_SEN ‧‧‧Detection} voltage

V _PTAT ‧‧‧temperature change voltage

V _REF ‧‧‧Reference

V _REXT ‧‧‧ voltage

[Fig. 1] is a schematic view of a conventional LED illumination system.

FIG. 2 is a block diagram of a light emitting diode (LED) illumination system according to an embodiment of the present invention.

Fig. 3 is a detailed circuit diagram of the LED lighting system of the embodiment of the present invention.

FIG. 4 is a block diagram of a power compensation circuit according to still another embodiment of the present invention.

Fig. 5 is a detailed circuit diagram of a power compensation circuit according to still another embodiment of the present invention.

In order to fully understand the objects, features and advantages of the present invention, the present invention will be described in detail by the following specific embodiments and the accompanying drawings.

2 and FIG. 3, FIG. 2 is a block diagram of a light-emitting diode (LED) illumination system 100 according to an embodiment of the present invention, and FIG. 3 is a detailed circuit diagram of the LED illumination system of the embodiment of the present invention.

As shown in FIG. 2 and FIG. 3 , the LED illumination system 100 includes an input power source 10 , an LED circuit 20 , a power compensation circuit 30 , a compensation resistor 40 , and a resistor circuit 50 .

In the embodiment, the input power source 10 is a Voltage Controlled Current Source (VCCS) having an input power P _in and an input voltage V _in and providing an input current I _in .

The LED circuit 20 is coupled to the output end of the input power source 10 to receive the input current I _in . The LED circuit 20 includes one or more LEDs 21 to emit light after being energized, and further, a current flowing through the LED circuit 20 . Expressed by I _LED , the voltage across the LED circuit 20 is represented by V _F .

The input end of the power compensation circuit 30 is coupled to the output end of the LED circuit 20 to generate a compensation current I _cmp according to the voltage V _out of the output end of the LED and the detected ambient temperature. The detailed circuit configuration of the circuit 30 will be further described by way of example.

The compensation resistor 40 coupled to the output terminal of the power of the compensation circuit 30, by which to compensate the current flowing through the I _cmp generates a compensation voltage V _cmp.

In this embodiment, the compensation resistor 40 is a resistor R _cmp , and the resistance value of the resistor R _cmp is a fixed value. Therefore, the voltage value of the compensation voltage V _cmp is proportional to the current value of the compensation current I _cmp . Large (decreasing) the compensation voltage V _cmp can be adjusted to decrease (increase) the input current I _in , and further, the input power P _in =V _in *I _in , it can be known that the input current I _in can be adjusted The magnitude of the input power P _in is controlled.

The resistor circuit 50 is coupled to the compensating resistor 40. In the embodiment, the resistor circuit 50 is a resistor R _CS , and the resistance value of the resistor R _cmp is a fixed value, and the current value flowing through the resistor R _CS It is equal to the current I _LED flowing through the LED circuit 20, so that V _REXT = I _LED R _CS can be known.

When the ambient temperature change causes the voltage across the V _{F to} change, the power compensation circuit 30 of the present invention can control the compensation power P _cmp (ie, the power compensation amount) by changing the compensation current I _cmp with the temperature, thereby achieving the compensation power. P _cmp is adjusted with temperature to achieve the effect that the power input to the LED circuit 20 remains constant or stable.

The LED illumination system 100 can include a control circuit 60. The control circuit 60 can include an operational amplifier AMP1 and a switch Q1. The operational amplifier AMP1 is coupled to the power compensation circuit 30 and outputs the output of the power compensation circuit 30. The voltage difference between the voltage and one of the external reference voltages V _REF is amplified to output a control voltage, and the voltage value of the reference voltage V _REF may be equal to V _cmp +V _REXT ; the source of the switch Q1 is coupled to the power An input terminal of the compensation circuit 30, the drain of the switch Q1 is coupled to the output end of the power compensation circuit 30, and the gate of the switch Q1 is coupled to the output end of the operational amplifier AMP1 to be controlled by the control voltage The switch Q1.

Hereinafter, the relationship between the current value of the compensation current I _{cmp and} the current value of the current I _LED is further illustrated by the embodiment shown in FIG. 3, and the relationship is as follows: V _cmp =I _cmp ×R _cmp ... ...(1)

V _REXT =I _LED ×R _CS ......(2)

V _REF =V _cmp +V _REXT ......(3)

By the relationship (1) ~ (3) can be obtained:

It can be known from the relation (4) that the current value of the compensation current I _cmp is inversely related to the current value of the current I _LED . If the compensation current I _cmp becomes larger, the current I _LED becomes smaller, so that the input current is made. I _in becomes smaller, and the input power P _in is stabilized (when V _in becomes larger) or decreased (when V _in does not change).

Therefore, by the above calculation, it can be proved that the control of the compensation current I _cmp can be achieved, and the purpose of adjusting the input power P _in can be achieved.

Furthermore, the power compensation circuit 30, the compensation resistor 40 and the control circuit 60 can be implemented on the same wafer 200 (ie, disposed on the same wafer). Accordingly, the LED illumination system of the present invention does not need to additionally set the power compensation circuit. Outside the wafer, the need to add components outside the wafer is addressed at a lower cost.

4 and FIG. 5, FIG. 4 is a block diagram of a power compensation circuit 30 according to still another embodiment of the present invention, and FIG. 5 is a detailed circuit diagram of the power compensation circuit 30 according to the still further embodiment of the present invention.

The power compensation circuit 30 includes a voltage detecting unit 31, a temperature-varying voltage generating unit 32, an arithmetic unit 33, and an output unit 34.

The voltage detecting unit 31 receives the voltage V _{OUT at} the output end of the LED circuit 20 and adjusts it to a detection voltage V _{OUT — SEN} output. In FIG. 5 , the voltage detecting unit 31 is composed of two resistors and forms a voltage dividing resistor group. And the detection voltage of the voltage V _OUT is lowered to be the output of the detection voltage V _{OUT — SEN} , but it should be noted that the implementation of the circuit of the voltage detection unit 31 is not limited _thereto , and the voltage detection is The "adjustment" of unit 31 is not limited to reducing the voltage value, but also increasing the voltage value, copying the voltage value, or other variations.

The temperature-varying voltage generating unit 32 generates a temperature-varying voltage V _PTAT according to the detected ambient temperature. In FIG. 5 , the temperature-varying voltage generating unit is a PTAT (Proportional To Absolute Temperature) voltage generator. The PTAT voltage generator generates the temperature change voltage V _PTAT .

The voltage value of the temperature-varying voltage V _PTAT generated by the PTAT voltage generator is proportional to the ambient temperature value detected by the temperature-varying voltage generating unit 32, that is, the higher the temperature, the higher the temperature-varying voltage V _PTAT If the temperature is constant, the temperature change voltage V _PTAT does not change.

The computing unit 33 is coupled to the voltage detecting unit 31 and the temperature-varying voltage generating unit 32. The computing unit 33 compares the detecting voltage V _{OUT_SEN} with the temperature-varying voltage V _PTAT to output a comparison voltage. In _FIG. 5, the operation unit 33 is an operational amplifier AMP2, and the operational amplifier AMP2 receives the detection voltage V _{OUT_SEN} and the temperature change voltage V _PTAT , respectively, and the detection voltage V _{OUT — SEN} and the temperature change voltage V _PTAT The voltage difference between them amplifies the output as the comparison voltage.

The output unit 34 is coupled to the operation unit 33 to output a compensation current I _cmp to the output of the power compensation circuit 30 according to the comparison voltage. In FIG. 5, the output unit 34 includes a first voltage control current. The source VCCS1 and a second voltage control current source VCCS2.

The first voltage control current source VCCS1 receives the comparison voltage and the internal voltage VCC of the power compensation circuit, respectively, the first voltage control current source VCCS1 correspondingly adjusts the compensation current I _cmp according to the comparison voltage, and outputs the compensation current I _CMP; and the second voltage controlled current source VCCS2, receives the comparison voltage and the detection voltage _V OUT_SEN, based on the comparison voltage adjustment according to a current corresponding to a pair on I _GND, and outputs the ground current I _GND, such as The embodiment shown in FIG. 5 _realizes the adjustment of the detection voltage V _{OUT — SEN} by the voltage detecting unit 31 and the second voltage control current source VCCS2.

The second voltage control current source VCCS2 is respectively coupled to the output end of the operational amplifier AMP2 and the positive input terminal to form a positive feedback.

With the above configuration, the output current value of the first voltage control current source VCCS1 and the output current value of the second voltage control current source VCCS2 are respectively input to the first voltage control current source VCCS1 and the second voltage control current source VCCS2. The magnitude of the voltage is controlled, and the variation affecting the magnitude of the input voltage includes the voltage value of the voltage V _{OUT and} the voltage value of the temperature change voltage V _PTAT , and therefore, the compensation current I _cmp (ie, the second voltage control current source VCCS2 The magnitude of the output current value) changes as the voltage V _OUT changes and also changes as the ambient temperature changes.

In other words, the LED system 100 using the power compensation circuit 30 can change the power compensation amount according to the change of the input voltage V _in (if V _in increases, V _OUT becomes larger, the compensation current I _cmp increases, and the power compensation amount increases), so as to stabilize the input power P _in, can also be in response to a temperature change to stabilize the input power P _in (when the temperature is increased, the V _PTAT increases, the compensation current I _cmp, decreased power compensation amount), so that the input of the LED circuit 20 The power is stabilized.

Therefore, after the LED system 100 using the power compensation circuit 30 is continuously used for a period of time, the voltage V _{F of} the LED circuit 20 gradually decreases as the temperature increases, so that the voltage V _out becomes larger (which causes the compensation current) I _cmp increases), but the temperature change voltage V _PTAT also becomes larger (which will cause the compensation current I _{cmp to} decrease), so that the compensation current I _cmp can remain stable (or unchanged), so that the current I _LED remains stable ( Or unchanged, the input current I _in remains stable (or unchanged), and the input power P _in of the input power source 10 remains stable (or unchanged), so that the problem of insufficient output brightness can be avoided.

In summary, the present invention provides a power compensation circuit and an LED illumination system using the power compensation circuit, which adjusts the compensation current with temperature to stabilize the compensation power (ie, the power compensation amount), thereby stabilizing the input power.

The invention has been described above in terms of the preferred embodiments, and it should be understood by those skilled in the art that the present invention is not intended to limit the scope of the invention. It should be noted that variations and permutations equivalent to those of the embodiments are intended to be included within the scope of the present invention. Therefore, the scope of protection of the present invention is defined by the scope of the patent application.

30‧‧‧Power compensation circuit

31‧‧‧Voltage detection unit

32‧‧‧temperature change voltage generating unit

33‧‧‧ arithmetic unit

34‧‧‧Output unit

I _cmp ‧‧‧compensation current

V _{OUT_SEN ‧‧‧Detection} voltage

V _PTAT ‧‧‧temperature change voltage

Claims (6)

a power compensation circuit, the input end of the power compensation circuit is coupled to an output end of the LED circuit, the input end of the LED circuit is coupled to an input power source, and the output end of the power compensation circuit is coupled to a compensation resistor, The power compensation circuit is configured to generate a compensation current, the compensation current flows through the compensation resistor to generate a compensation power, and the power of the LED circuit is stably stabilized by the compensation power, the power compensation circuit includes: a voltage detection unit Receiving a voltage of the output end of the LED circuit and adjusting the output of the detected voltage; a temperature-varying voltage generating unit correspondingly generates a temperature-varying voltage according to the detected ambient temperature; and an arithmetic unit coupled to the respective The voltage detecting unit and the temperature-varying voltage generating unit, the computing unit compares the detected voltage and the temperature-varying voltage to output a comparison voltage; and an output unit coupled to the operating unit to be based on the comparison voltage To output the compensation current, the output unit includes a first voltage control current source and a second voltage control current source, the first voltage control power The source respectively receives the comparison voltage and an internal voltage of the power compensation circuit, the first voltage control current source correspondingly adjusts a current according to the comparison voltage to generate an output current as the compensation current; and the second voltage control current source respectively Receiving the comparison voltage and the detection voltage, the second voltage control current source adjusts the current correspondingly according to the comparison voltage to output a pair of ground currents. The power compensation circuit of claim 1, wherein the temperature-varying voltage generating unit comprises a voltage generator, the voltage generator generates the temperature-varying voltage, and the voltage value of the temperature-varying voltage generated by the voltage generator is proportional to The ambient temperature value detected by the temperature-varying voltage generating unit. The power compensation circuit of claim 1, wherein the operation unit comprises an operational amplifier, the operational amplifier respectively receiving the detection voltage and the temperature change voltage, and the voltage between the detection voltage and the temperature change voltage The difference is amplified to output as the comparison voltage. An LED lighting system comprising: an input power source having an input power and providing an input current; an LED circuit coupled to the output end of the input power source to receive the input current; a power compensation circuit having an input end An output end of the LED circuit is coupled to generate a compensation current according to a voltage of the output end of the LED and the detected ambient temperature; a compensation resistor coupled to the output end of the power compensation circuit is configured to The compensation current flows to generate a compensation power for stabilizing the power input to the LED circuit; and a resistor circuit coupled to the compensation resistor, wherein the power compensation circuit comprises: a voltage detection unit Receiving a voltage at an output end of the LED circuit and adjusting the output of the detected voltage; a temperature-varying voltage generating unit correspondingly generates a temperature-varying voltage according to the detected ambient temperature; an arithmetic unit coupled to the voltage detecting unit and the temperature-varying voltage generating unit, wherein the computing unit compares the detecting a voltage and the temperature change voltage to output a comparison voltage; and an output unit coupled to the operation unit to output the compensation current according to the comparison voltage, the output unit comprising a first voltage control current source and a first a voltage control current source, the first voltage control current source respectively receiving the comparison voltage and an internal voltage of the power compensation circuit, the first voltage control current source correspondingly adjusting a current according to the comparison voltage to generate the compensation current And outputting, by the second voltage control current source, the comparison voltage and the detection voltage, respectively, the second voltage control current source correspondingly adjusting the current according to the comparison voltage to output a pair of ground currents. The LED lighting system of claim 4, further comprising a control circuit, the control circuit comprising: an operational amplifier coupled to the output unit and between the voltage of the output of the output unit and one of the external reference voltages The voltage difference is amplified to output a control voltage; and a switch, the source of the switch is coupled to the input end of the power compensation circuit, and the drain of the switch is coupled to the output end of the power compensation circuit, the switch The gate is coupled to the output of the operational amplifier to control the switch by the control voltage. The LED lighting system of claim 5, wherein the power compensation circuit, the compensation resistor, and the control circuit are disposed on the same wafer.