TWI507085B - Power supply device for led and method of supplying power to led - Google Patents

Description

Power supply device for light emitting diode and power supply method thereof

The present invention claims priority to Korean Patent No. 10-2012-0071254 filed on Jun. 29, 2012. This is incorporated herein by reference.

This embodiment relates to a power supply device for a light emitting diode and a power supply method thereof.

Light emitting devices (LEDs) are PN junction elements. The LED is a light emitting semiconductor that converts electrical energy into light energy. The LED emits light by applying a current to the end of a compound semiconductor through a combination of electrons and holes in the PN junction or an active layer.

FIG. 1 is a circuit diagram showing a power supply device for driving an LED according to the related art, and FIG. 2 and FIG. 3 are diagrams showing output curves of related AC voltages.

Referring to FIG. 1, the power supply device converts an alternating current (AC) voltage V _AC into a direct current (DC) voltage through a pulse width modulation (PWM) method, and controls the amount of light according to a pulse width.

The power supply device of FIG. 1 uses an integrated circuit U1 that generates a pulse signal from the primary side circuit and then supplies a boosted signal through a transformer according to a primary side regulation (PSR) method. To the secondary side circuit, thus supplying the LED power connected to the secondary side circuit.

The PSR integrated circuit U1 receives the reference voltage VR from the alternating voltage and outputs a comparison value obtained by comparing the reference voltage VR with the power supply voltage CS of the transistor Q, and outputting it to the transistor Q. The gate level acts as a control signal.

The duty ratio of the control signal is determined based on a comparison value obtained by comparing the reference voltage VR with the power supply voltage CS of the transistor Q.

If the transistor Q is turned on or off according to the control signal to cause current to flow into a gate, the output signal is transmitted to the LED by boosting the transformer connected to the drain.

In this example, regarding the configuration of the peripheral circuit of the integrated circuit U1, the peripheral circuit includes: a plurality of resistors R1 to R14, a plurality of capacitors C1 to C8, and a plurality of diodes D1 to D5, as shown in FIG. Show.

At the same time, the standard AC voltage varies from country to country, ranging from 90V to 240V. Typically, the standard AC voltage for household use is 220V, and the standard voltage in Japan and the Americas is typically 110V.

When the same integrated circuit is applied with a different alternating voltage as described above, the results are shown in Figs. 2 and 3.

FIG 2 shows a line graph of the output when V when _{an AC} voltage is applied AC 220V, and a graph of the output AC voltage V _AC FIG. 3 shows the system when a 110V applied.

2(a) and 3(a) illustrate a transistor reference voltage VR and a power supply voltage CS of the integrated circuit U1. 2(b) and 3(b) illustrate the average voltage V _{LED of the LED} , and FIGS. 2(c) and 3(c) illustrate the average current I _{LED of the LED} .

Referring to FIG. 2 and FIG. 3, if the AC voltage V _{AC is} reduced from 220V to 110V, as shown in FIG. 3, the current flowing through the LED is significantly reduced, thereby reducing the amount of light. .

The embodiment provides a power supply device for a light-emitting diode, which can emit light with uniform light amount without deviation even if different AC input voltages are applied.

According to the embodiment, there is provided a power supply device. The power supply device includes: an input AC voltage; a rectifier module for rectifying the input AC voltage; and a transistor that is turned on or off according to a control signal to output a first current; an integrated circuit module, Receiving a reference voltage according to the rectified input AC voltage, and comparing the reference voltage with the power supply voltage of the transistor to generate a control signal; a voltage compensation module by using an auxiliary voltage of the integrated circuit module to compensate the input AC voltage The amount of deviation to generate the reference voltage; and a transformer to convert the first current to generate a second current.

The integrated circuit module can include: a reference voltage terminal for receiving a reference voltage; an output terminal for outputting a control signal; a power supply terminal for receiving a power supply voltage of the transistor; and an auxiliary terminal Used to receive an auxiliary voltage.

A voltage compensation module can include: a compensation diode inserted between the reference voltage terminal and the auxiliary voltage terminal.

A negative electrode of the compensation diode can be connected to the auxiliary voltage terminal.

The voltage compensation module can further include: a compensation capacitor, and a compensation resistor. The compensation capacitor is inserted between the center node connected to the positive pole of the compensation diode and the ground, and the compensation resistor is connected between the center node and the reference voltage terminal.

The resistance value of the compensation resistor is less than an internal resistance of the reference voltage terminal of the integrated circuit module.

The rectifier module can include: a bridge rectifier.

The power supply device of the patent application may further include: a voltage dividing module for dividing the rectified input AC voltage to generate a reference voltage.

When the input AC voltage drops, the voltage compensation module can reduce a negative voltage of the reference voltage.

The power supply device may further include: an output module for receiving the second current from the transformer and outputting the second current.

The second current can flow to a light emitting diode.

The power supply device may further include: a snubber disposed in a front stage of the transformer.

According to this embodiment, a method of power supply is provided. The method includes: receiving and rectifying an input AC voltage; generating a reference voltage by dividing the rectified input AC voltage; generating a compensation reference voltage according to the rectified input AC voltage deviation amount to compensate the reference voltage; Comparing a reference voltage with a power supply voltage of a transistor to generate a control signal; generating a first current by turning on or off the transistor according to the control signal; and generating a second current by converting the first current .

When the reference voltage is lower than a predetermined range of voltage values, the compensated reference voltage can be generated by applying a negative voltage of an auxiliary voltage.

The magnitude of the auxiliary voltage is determined by the input AC voltage.

The method can include supplying a second current to a light emitting diode.

As explained above, according to the present embodiment, even if different AC voltages are applied, uniform and unbiased light can be emitted. Furthermore, by adding a simple circuit, it can be applied to power supply circuits of different voltages.

Furthermore, the reference voltage is compensated according to the change of the input voltage of the internal auxiliary voltage, so that the reliability of the illuminating device can be improved.

100‧‧‧Power supply unit

110‧‧‧Voltage compensation module

120‧‧‧voltage module

130‧‧‧Transformers

140‧‧‧Output module

A‧‧‧Amp

C1~C9‧‧‧ capacitor

Cc‧‧‧compensation capacitor

CD‧‧‧ output

Co‧‧‧ output capacitor

CS‧‧‧Power supply voltage

CSP‧‧‧ power terminal

D1~D5‧‧‧ diode

Da‧‧‧Rectifier Module

Dc‧‧‧Compensation diode

GND‧‧‧ ground terminal

HV‧‧‧ endpoint

ILED‧‧‧ average current

LED‧‧‧Lighting device

N0‧‧‧ input node

N1‧‧‧ first node

N2‧‧‧ second node

N3‧‧‧ third node

Q‧‧‧Drive transistor

R1~R15‧‧‧resistance

Ra, Rb, Rc, Rd, Re‧‧‧ resistors

Ro‧‧‧ output resistor

t‧‧‧Time

U1‧‧‧ integrated circuit

U1‧‧‧ integrated circuit

V‧‧‧ voltage

V _AC ‧‧‧AC voltage

VCC‧‧‧Auxiliary voltage terminal

Vin‧‧‧AC voltage

VLED‧‧‧ average voltage

VR‧‧‧reference voltage

VRP‧‧‧reference voltage terminal

ZCV‧‧‧ zero crossing voltage terminal

1 is a circuit diagram of a power supply circuit according to the related art.

2 and 3 illustrate the output curve of the power supply device of FIG. 1 according to different input voltages.

FIG. 4 is a circuit diagram showing the power supply circuit according to the embodiment.

FIG. 5 is an exemplary circuit diagram of one of the power supply devices of FIG.

6 and FIG. 7 are graphs showing node voltages of a voltage compensation module and an integrated circuit according to different input voltages.

8 and FIG. 9 are diagrams showing output curves of the power supply device of FIG. 5 according to different input voltages.

Hereinafter, the detailed description will be made with reference to the accompanying drawings, so that the present embodiment can be easily understood by those skilled in the art. However, the present embodiment is not limited to the following description, and various modifications can be made in various forms.

In the following description, when a pre-set portion "includes" a predetermined element, the pre-set portion does not exclude other elements, and further includes other elements unless otherwise stated.

The embodiment provides a light-emitting device that compensates for the deviation of the input voltage by a PWM power supply device having a PSR integrated circuit to uniformly flow current through a light-emitting device.

Hereinafter, according to the present embodiment, a power supply device will be described with reference to FIGS. 4 to 9.

FIG. 4 is a circuit diagram showing the power supply circuit according to the embodiment. FIG. 5 is an exemplary circuit diagram of one of the power supply devices of FIG. 6 and FIG. 7 are graphs showing node voltages of a voltage compensation module and an integrated circuit according to different input voltages. 8 and FIG. 9 show the output curve of the power supply device of FIG. 5 according to different input voltages.

Referring to FIG. 4, a power supply device 100 includes a transformer 130 inserted between an input AC voltage terminal Vin and a light emitting device (LED).

A primary side circuit is disposed on the left side of the transformer 130, and pulse width modulation (PWM) is performed in accordance with the received alternating voltage Vin to generate a first current. The transformer 130 receives the first current to generate a second current, and supplies it to an LED of a secondary side circuit disposed on the right side of the transformer 130.

In this example, the primary side circuit includes: a driving transistor Q for generating a first current; and an integrated circuit U1 for transmitting a control signal to the driving transistor Q.

The integrated circuit U1 generates a control signal having a duty ratio which is determined based on a comparison value obtained by comparing the reference voltage which varies with the input AC voltage Vin with the power supply voltage CS of the driving transistor Q.

The integrated circuit U1 has six terminals, as shown in FIG. 4, but the embodiment is not limited thereto. Although all of the endpoints can be connected to peripheral circuitry, some of the endpoints may not be connected to peripheral circuitry.

The integrated circuit U1 includes a reference voltage terminal VRP, a ground terminal GND, an auxiliary voltage terminal VCC, a zero-crossing voltage terminal ZCV, a power terminal CSP, and an output terminal CD. Among these terminals, the zero-crossing voltage terminal ZCV can be omitted according to the function of the integrated circuit U1.

The primary side circuit includes: a rectifying module Da for receiving, rectifying, and outputting an alternating voltage Vin; a voltage dividing module 120 for dividing and receiving a voltage received from the rectifying module Da To the reference voltage terminal VRP of the integrated circuit U1; the resistors Rc and Rd for receiving the auxiliary coil current from the transformer 130, and being divided and supplied to the auxiliary voltage terminal VCC and the zero-crossing voltage terminal ZCV; and a voltage compensation mode Group 10 is used to compensate the compensation voltage VR of the voltage terminal VRP.

At the same time, the secondary circuit includes an output module 140 for receiving a second current from the transformer 130 and flowing the second current to the LED.

The rectifier module Da rectifies the input AC voltage Vin having a sinusoidal waveform It is a unipolar voltage so that a unipolar voltage is output to an input node n0. Generally, the rectifier module Da can include: a bridge rectifier.

The voltage dividing module 120 can include: at least two resistors Ra and Rb and a plurality of capacitors (not shown) connected in series between the input node n0 and the ground. The rectified input AC voltage Vin is divided by the series resistors Ra and Rb, and is supplied to the reference voltage terminal VRP through a second node n2 interposed between the resistors Ra and Rb.

At the same time, the secondary circuit includes an input module 140 for filtering the output current from the coil of the transformer 130 and outputting the filtered current to the LED. The output module includes: a filter, the filter further comprising: an output capacitor Co and an output resistor Ro.

At the same time, although the voltage supplied from the reference voltage VR to the reference voltage terminal VRP has the same waveform as the rectified input AC voltage Vin (input voltage Vin) and varies with the magnitude of the input voltage Vin, the integrated circuit The reference voltage VR of U1 is still set within a predetermined range.

Therefore, even if the input voltage Vin changes, the amount of change in the reference voltage VR is limited. Conversely, since the input voltage Vin is applied to the input node n0, the current flowing through the driving transistor Q is not limited.

In other words, when the input voltage Vin drops from 220V to 110V, as shown in FIGS. 2 and 3. Although the variation of the reference voltage VR is limited, the power supply voltage CS set according to the current flowing through the transistor Q also drops, so that the current value ILED flowing through the LED also drops significantly.

In order to prevent the above phenomenon, according to the embodiment, the voltage compensation module 110 is additionally provided to limit the connection of the first node n1 and the third node n3. Wherein n1 is connected to the reference voltage terminal VRP, and n3 is connected to the auxiliary voltage terminal VCC.

In detail, the voltage compensation module 110 includes: a compensation diode Dc, a compensation resistor Rc, and a compensation capacitor Cc.

The compensation diode Dc of the voltage compensation module 110 has a negative electrode connected to the third node n3, and a positive electrode connected to the second node n2. The compensation capacitor Cc is connected between the second node n2 and the ground, and the compensation resistor Rc is connected between the first node n1 and the second node n2.

In this example, the resistance of the compensation resistor Rc is higher than the terminal resistance of the reference voltage terminal VRP of the integrated circuit U1 to prevent the current flowing through the reference voltage terminal VRP from flowing out through the compensation resistor Rc.

Referring to FIG. 6 and FIG. 7, in the voltage compensation module 110, the negative electrode of the compensation diode Dc is connected to the third node n3 such that only a negative voltage is selectively supplied from the auxiliary voltage terminal VCC to the second. node.

Therefore, the voltage V2 of the second node n2 has only a negative voltage of the voltage of the third node n3, and the voltage of the auxiliary voltage terminal VCC is proportional to the input voltage Vin. Therefore, the magnitude of the voltage V2 at the second node n2 is proportional to the magnitude of the input voltage Vin.

Therefore, when the input voltage Vin of FIG. 6 is 110 V, and the input supply voltage Vin of FIG. 7 is 220 V, the input voltage Vin is increased by 2 times, the voltage V2 of the second node n2 is a negative value, and The absolute value here is increased by 2 times.

After passing through the compensation capacitor Cc and the compensation resistor Rc, the voltage V2 at the second node n2 is converted to have an alternating current at the first node n1 period. In this example, the voltage V2 of the second node n2 when the input supply voltage is 110V is higher than the voltage V2 of the second node n2 when the input supply voltage is 220V, so when the input supply voltage is 220V, at the first node n1 The voltage V1 has a large amplitude.

Therefore, although the input voltage Vin is increased from 110V to 220V, as shown in FIG. 7, the negative amplitude of the reference voltage VR is also increased, so that the output signal of the comparison value between the power supply voltage CS and the reference voltage VR is available in the integrated circuit U1. The internal maintenance is fixed.

As explained above, regardless of how the input voltage Vin changes, an output signal having a fixed duty ratio can be generated so that the current ILED value flowing through the LED can be fixedly detected regardless of the change of the input voltage Vin, as shown in the figure. 8 and Figure 9 are shown.

Hereinafter, the application of this embodiment will be explained with reference to FIG. 5.

Referring to FIG. 5, a power supply device is modified from the power supply device 100 of FIG. The voltage dividing module 120 can include three resistors: R1, R2, R3, and a buffer circuit, which further includes: R5 R R7 and a capacitor C3 disposed in the front stage of the transformer 130.

The integrated circuit U1 of FIG. 5 further includes: an HV terminal for receiving the input voltage Vin; a filter (RC filter) for filtering the chopping; and a diode D2~D4, As the switching element, it is provided in the front stage of the end point of the integrated circuit U1.

Depending on the circuit design, each component can be sized for a variety of applications. 6 to 9 are graphs showing the power supply device 100 of Fig. 5, each of which has been optimized by simulation.

Although the exemplary embodiments of the present invention have been described, it is understood that the present invention is not limited to the embodiments, and the various modifications or modifications made by those skilled in the art are still included in the following patent applications of the present invention. The spirit and scope of the scope.

100‧‧‧Power supply unit

110‧‧‧Voltage compensation module

120‧‧‧voltage module

130‧‧‧Transformers

140‧‧‧Output module

Cc‧‧‧compensation capacitor

CD‧‧‧ output

Co‧‧‧ output capacitor

CSP‧‧‧ power terminal

Da‧‧‧Rectifier Module

Dc‧‧‧Compensation diode

GND‧‧‧ ground terminal

I _LED ‧‧‧Average current

LED‧‧‧Lighting device

N0‧‧‧ input node

N1‧‧‧ first node

N2‧‧‧ second node

N3‧‧‧ third node

Q‧‧‧Drive transistor

Ra, Rb, Rc, Rd, Re‧‧‧ resistors

Ro‧‧‧ output resistor

U1‧‧‧ integrated circuit

VCC‧‧‧Auxiliary voltage terminal

Vin‧‧‧AC voltage

V _LED ‧‧‧ average voltage

VRP‧‧‧reference voltage terminal

ZCV‧‧‧ zero crossing voltage terminal

Claims (18)

A power supply device includes: an input AC voltage; a rectifying module for rectifying the input AC voltage; and a transistor for starting or turning off a first current according to a control signal; an integrated circuit module, Receiving a reference voltage according to the rectified input AC voltage, and comparing the reference voltage with a power supply voltage of the transistor to generate the control signal; a voltage compensation module, by using the integrated circuit module An auxiliary voltage that compensates for the amount of deviation of the input AC voltage to generate the reference voltage, and a transformer that converts the first current to generate a second current. The power supply device of claim 1, wherein the integrated circuit module comprises: a reference voltage terminal for receiving the reference voltage; an output terminal for outputting the control signal; a power supply voltage for receiving the transistor; and an auxiliary voltage terminal for receiving the auxiliary voltage. The power supply device of claim 2, wherein the voltage compensation module comprises: a compensation diode inserted between the reference voltage terminal and the auxiliary voltage terminal. The power supply device of claim 3, wherein a negative electrode of the compensation diode is connected to the auxiliary voltage terminal. The power supply device of claim 4, wherein the voltage compensation module further comprises: a compensation capacitor inserted between a center node and a ground connected to a positive pole of the compensation diode a compensation resistor connected between the central node and the reference voltage terminal. The power supply device of claim 5, wherein the compensation resistor has a resistance value that is less than an internal resistance of the reference voltage terminal of the integrated circuit module. The power supply device of claim 1, wherein the rectifier module comprises: a bridge rectifier. The power supply device of claim 1, further comprising: a voltage dividing module configured to divide the rectified input AC voltage to generate the reference voltage. The power supply device of claim 7, wherein the voltage compensation module reduces a negative voltage of the reference voltage when the input AC voltage drops. The power supply device of claim 1, further comprising: an output module for receiving the second current from the transformer and outputting the second current. The power supply device of claim 1, wherein the second current flows through a light emitting diode. The power supply device of claim 2, further comprising: a buffer circuit disposed in a front stage of the transformer. A method of supplying power, the method comprising: receiving an input AC voltage and rectifying the input AC voltage; and dividing a rectified input AC voltage to generate a reference voltage; according to the rectified input AC voltage Deviating the amount, generating a compensation reference voltage to compensate the reference voltage; comparing the compensated reference voltage with a power supply voltage of a transistor to generate a control signal; according to the control signal, the transistor is activated or deactivated , generating a first current; The second current is generated by converting the first current. The power supply method of claim 13, wherein when the reference voltage is lower than a predetermined voltage range, the method for generating the compensation reference voltage comprises: applying a negative voltage of an auxiliary voltage. The method of supplying power according to claim 14, wherein the magnitude of the auxiliary voltage is determined according to the input AC voltage. The method of supplying power according to claim 13 further includes: supplying the second current to a light emitting diode. The method of supplying power according to claim 15, wherein when the input AC voltage drops, generating the compensation voltage comprises: reducing a negative voltage of the reference voltage. The method of supplying power according to claim 13, wherein the rectifying the input AC voltage comprises: applying a bridge rectifier.