CN101394699A - Light emitting diode driving device - Google Patents

Abstract

The invention discloses a light emitting diode driving device, comprising: the power factor correction circuit, the bridge type switch circuit, the resonance circuit, the transformer and the feedback circuit. The power factor correction circuit adjusts the output signal according to a feedback signal. The bridge type switching circuit switches the output signal of the power factor correction circuit into a pulse signal. The resonant circuit outputs a sine wave signal to the primary side of the transformer according to the pulse wave signal. The feedback circuit can output a feedback signal to a feedback end of the power factor correction circuit corresponding to the primary side current of the transformer. Therefore, the output current can be adjusted by adjusting the feedback circuit.

Description

LED driver

technical field

The invention relates to a light emitting diode driving device, in particular to a light emitting diode driving device, which is suitable for high power output to drive at least one light emitting diode module.

Background technique

Light emitting diode (LED) is a light-emitting element made of semiconductor materials. At present, it has gradually replaced traditional lighting.

倍；举例来说，当输入电压Vin约为110V(伏特)的交流电压，经桥式整流电路110整流后，产生的一次侧电压V1约为156V的直流电压，脉宽调变(PWM)控制器120通过输出脉宽调变信号Vg控制功率开关Q1的切换，致使变压器130的一次侧电压V1转换至变压器130的二次侧，而产生输出电压Vo，以点亮串接于输出端上的发光二极管LED。以返驰式架构(Flyback Topology)为例，当功率开关Q1导通(on)时，能量储存于变压器130一次侧的激磁电感LP，此时二次侧不导通；而当功率开关Q1截止(off)时，储存于变压器130一次侧的激磁电感LP内的能量释放至二次侧，进而产生输出电压Vo。于此，输出电压Vo为直流(DC)电压。In the design of the LED drive circuit, the primary and secondary side isolation design is generally adopted for safety considerations. Referring to FIG. 1 , the input voltage Vin is rectified by the bridge rectifier circuit 110 to generate a primary side voltage V1. Here, the primary side voltage V1 is approximately the input voltage Vin

times; for example, when the input voltage Vin is about 110V (volts) of AC voltage, after being rectified by the bridge rectifier circuit 110, the generated primary side voltage V1 is about 156V of DC voltage, controlled by pulse width modulation (PWM) The switch 120 controls the switching of the power switch Q1 by outputting a pulse width modulation signal Vg, so that the primary side voltage V1 of the transformer 130 is converted to the secondary side of the transformer 130 to generate an output voltage Vo to light up the Light-emitting diode LED. Taking the flyback topology as an example, when the power switch Q1 is turned on, energy is stored in the magnetizing inductance LP of the primary side of the transformer 130, and the secondary side is not turned on at this time; and when the power switch Q1 is turned off When (off), the energy stored in the magnetizing inductance LP of the primary side of the transformer 130 is released to the secondary side, thereby generating the output voltage Vo. Here, the output voltage Vo is a direct current (DC) voltage.

The current signal I LED flowing through the light emitting diode _LED can pass through the linear voltage regulator TL and the photo coupler (photo coupler) 140 to determine the voltage level of the compensation pin COMP of the PWM controller 120 . The PWM controller 120 adjusts the PWM signal Vg according to the voltage level of the compensation pin COMP, that is, adjusts the duty cycle of the power switch Q1. In other words, the current signal I _LED will be stabilized according to the level voltage (Vref) and the resistance (R _LED ) of the linear regulator TL, that is, I _LED =Vref/R _LED . Therefore, when there are more light-emitting diodes on the output end, the greater the output power, the greater the duty cycle of the PWM signal Vg controlling the power switch Q1; and vice versa.

When applied to high-power output (that is, the output terminal is connected to a large number of light-emitting diodes), in order to meet the current harmonic specifications, a power factor correction circuit (power factor correction circuit) is generally added to the front stage.

correction (PEC) circuit) 150, as shown in Figure 2.

Referring to FIG. 2 , the AC input voltage Vin is rectified by the bridge rectifier circuit 110 and adjusted by the power factor correction circuit 150 to generate a DC primary side voltage V2. For example, if the input voltage Vin is about 110V (AC), the generated primary voltage V2 is about 200V (DC); and if the input voltage Vin is about 220V (AC), the generated primary voltage V2 is about 400V (DC).

There are two sets of feedback paths inside the power factor correction circuit 150 . One is the current feedback path 152 , which is used to make the waveform of the input current Iin follow the waveform of the input voltage Vin and have the same phase as the input voltage Vin, so as to improve the power factor and meet the current harmonic regulation. The other is the voltage feedback path 154 , which adjusts the magnitude of the input current Iin through the feedback of the primary side voltage V2 , thereby stabilizing the primary side voltage V2 .

However, the design of these driving circuits must use linear voltage regulators and optocouplers to isolate the primary and secondary sides. In addition, in the application of high power output (generally greater than 150W), a large-sized transformer must be used, which increases the cost and occupies space, and it is not easy to solve the accompanying heat dissipation problem. In addition, in order to meet the application of high power output, the entire driving circuit must use two independent control ICs (integrated circuits), that is, the PFC controller and the PWM controller. Not only the circuit design is more complicated, but also the cost is relatively expensive.

Contents of the invention

The technical problem to be solved by the present invention is to provide a light-emitting diode driving device, so as to solve the problems of complicated circuit design and high cost in the prior art.

To achieve the above object, the LED driving device disclosed in the present invention includes: a power factor correction (PFC) circuit, a bridge switch circuit, a resonant circuit, a transformer and a feedback circuit. The power factor correction circuit adjusts its output signal according to a feedback signal. The bridge switch circuit is connected to the output end of the power factor correction circuit, which can switch the output signal of the power factor correction circuit into a pulse wave signal. The resonant circuit is connected to the output end of the bridge switch circuit, which can oscillate according to the pulse wave signal to output a sine wave signal. The first end of the primary side of the transformer is connected to the resonant circuit to receive the sine wave signal. The feedback circuit is connected to the second terminal of the primary side of the transformer, and outputs a feedback signal to the feedback terminal of the power factor correction circuit corresponding to the primary side current of the transformer.

The bridge switch circuit may be a half-bridge switch circuit, which includes a pair of switch elements connected in series. The pair of switching elements is connected between the output terminal of the power factor correction circuit and the ground, and the series connection between the two switching elements is connected to the resonant circuit.

Here, the driving control signals of the two switching elements of the half-bridge switching circuit may be a pair of complementary pulse signals, which are respectively input to the control terminals of the two switching elements of the half-bridge switching circuit. Wherein, the pair of complementary control signals may have a 50% duty cycle.

The resonant circuit may include a capacitor-inductor resonant tank.

The feedback circuit may include resistors and rectifying elements. The resistor of the feedback circuit is connected between the second end of the primary side of the transformer and the ground. Wherein, the primary side current of the transformer flows through the resistor to form an AC voltage across the resistor, and the feedback circuit rectifies the AC voltage to generate a feedback signal.

The feedback circuit may further include a filter element to filter the feedback signal and provide the filtered feedback signal to the power factor correction circuit.

The secondary side of the transformer is also coupled to at least one LED module, and the resistance of the resistor in the feedback circuit corresponds to the brightness of the LED module.

In the light-emitting diode driving device according to this case, the primary side current of the transformer is used for feedback control. Therefore, it is not necessary to isolate the primary side and the secondary side of the transformer through a linear voltage regulator and an optocoupler to avoid replacing the output There is no risk of electric shock when light-emitting diodes are used, and the cost can be reduced. In addition, in the LED driving device according to the present application, by adjusting the resistance value of the feedback circuit, for example: adjusting the resistance value of the resistor Rcs, the output current (that is, the secondary side current of the transformer) is adjusted to further control the LED module Compared with the prior art, the control method is relatively simple. Furthermore, the LED driver according to the present application is suitable for high power output (eg >200W). Moreover, in the light-emitting diode driving device according to the present application, only a single controller (ie, a power factor correction circuit) with a feedback function is used, and its control circuit is relatively simple and the overall price is relatively cheap.

Description of drawings

FIG. 1 is a schematic diagram of a light emitting diode driving device in the prior art;

2 is a schematic diagram of another prior art LED driving device;

3 is a schematic diagram of a light emitting diode driving device according to an embodiment of the present invention;

FIG. 4 is a waveform diagram of each signal in FIG. 3; and

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

Among them, reference signs:

110: Bridge rectifier circuit 120: Pulse width modulation (PWM) controller

130: Transformer 140: Optocoupler

150: Power factor correction circuit 152: Current feedback path

154: Voltage feedback path 210: Bridge rectifier circuit

220: Bridge switch circuit 230: Transformer

240: Resonant circuit 250: Power factor correction circuit

252: Current feedback path 254: Voltage feedback path

260: Feedback circuit 280: Signal generator

290: Light-emitting diode module 292: The first light-emitting diode module

294: Second LED module V1: Primary side voltage

Vin: input voltage Q1: power switch

Vg: pulse width modulation signal Vo: output voltage

LP: Transformer primary side excitation inductance NP: Transformer primary side turns

NS: Transformer secondary side turns I _LED : Current signal

TL: Linear Regulator COMP: Compensation pin

Vref: Level voltage R _LED : Resistor

V2: primary side voltage Iin: input current

CS: feedback signal V3: output signal of PFC circuit

Sa: pulse wave signal Sb: sine wave signal

Ipri: primary side current Isec: secondary side current

Q2: Switching element Q3: Switching element

Sc: Control signal Sc’: Control signal

Cr: Capacitance Lr: Inductance

Rcs: Resistance Dcs: Rectification element

Ccs: filter element Vcs: voltage value of the feedback signal

Detailed ways

Please refer to FIG. 3 , which shows a light emitting diode driving device according to an embodiment of the present invention. The LED driving device according to an embodiment of the present invention includes: a bridge switch circuit 220 , a transformer 230 , a resonant circuit 240 , a power factor correction (PFC) circuit 250 and a feedback circuit 260 .

The power factor correction circuit 250 is coupled between the bridge rectifier circuit 210 and the bridge switch circuit 220 . The resonant circuit 240 is coupled between the bridge switch circuit 220 and the first end of the primary side of the transformer 230 . The feedback circuit 260 is coupled between the second end of the primary side of the transformer 230 and the voltage feedback end of the power factor correction circuit 250 .

The input voltage Vin is rectified by the bridge rectifier circuit 210 and then input to the power factor correction circuit 250 . The power factor correction circuit 250 has two sets of feedback paths. The current feedback path 252 is connected to the bridge switch circuit 220 so that the waveform of the input current Iin can follow the waveform of the input voltage Vin and have the same phase as the input voltage Vin. The voltage feedback path 254 receives the feedback signal CS from the feedback circuit 260 , and adjusts the magnitude of the input current Iin according to the feedback signal CS, thereby adjusting the output signal V3 of the power factor correction circuit 250 . In other words, the power factor correction circuit 250 can adjust its output signal V3 according to the feedback signal CS.

The bridge switch circuit 220 can switch the output signal V3 of the power factor correction circuit 250 into the pulse signal Sa. After the pulse signal Sa oscillates through the resonant circuit 240 , a sinusoidal signal Sb is generated at the primary side of the transformer 230 , and the primary side current Ipri of the transformer 230 is also a sinusoidal signal. In other words, the resonant circuit 240 can oscillate according to the pulse signal Sa to output a sine wave signal Sb. The feedback circuit 260 outputs the feedback signal CS corresponding to the primary side current Ipri of the transformer 230 .

Wherein, the bridge switch circuit 220 can be a full bridge switch circuit or a half bridge switch circuit. Taking the half-bridge switching circuit as an example, the bridge switching circuit 220 includes a pair of switching elements Q2 and Q3 connected in series. Here, the switching elements Q2 and Q3 are connected in series between the output terminal of the power factor correction circuit 250 and the ground, and the series connection point between the two switching elements Q2 and Q3 is connected to the input terminal of the resonant circuit 240 .

Here, the operation of the two switching elements Q2, Q3 can be controlled by a pair of control signals Sc, Sc'. The pair of control signals Sc, Sc' is preferably a pair of complementary pulse signals. The pair of complementary control signals Sc, Sc' are respectively input to the control terminals of the switching elements Q2, Q3, so that the two switching elements Q2, Q3 are switched alternately according to the pair of complementary control signals Sc, Sc', so that the power factor correction circuit The output signal V3 of 250 is switched to pulse signal Sa. Here, complementary control signals Sc, Sc' with a duty cycle of 50% can be used.

In addition, a signal generator 280 can be provided in the LED driving device to generate a control signal to drive the bridge switch circuit 220 .

The resonant circuit 240 may include a capacitor Cr and an inductor Lr. One end of the capacitor Cr is connected to the bridge switch circuit 220 , and the other end is connected to the inductor Lr. One end of the inductor Lr opposite to the capacitor Cr is connected to the first end of the primary side of the transformer 230 . In other words, the resonant circuit 240 may include a resonant tank composed of capacitors and inductors.

In one embodiment, the capacitor Cr is connected between the series connection point between the two switching elements Q2, Q3 and the inductor Lr to receive the pulse signal Sa generated by the switching of the switching elements Q2, Q3.

The feedback circuit 260 may include a resistor Rcs and a rectifying element Dcs. The resistor Rcs is coupled between the second end of the primary side of the transformer 230 and the ground. The rectifying element Dcs is coupled between one end of the resistor Rcs opposite to ground and the power factor correction circuit 250 .

The primary side current Ipri of the transformer 230 flows through the resistor Rcs to form an AC voltage across the resistor Rcs, and the AC voltage across the resistor Rcs is rectified by the rectifier Dcs to generate a feedback signal CS.

Here, the feedback circuit 260 may further include a filter element Ccs, so the AC voltage across the resistor Rcs is rectified by the rectifier Dcs and filtered by the filter element Ccs to generate the feedback signal CS to the power factor correction circuit 250 .

Here, the transformer 230 can be a forward type or a flyback type. In addition, different grounds may be used in the circuits on both sides of the transformer 230 .

At least one LED module 290 composed of one or more LEDs can be coupled to the output end of the LED driving device, that is, the secondary side of the transformer 230 . Moreover, the brightness of the LED module 290 can be controlled by adjusting the feedback circuit 260 , that is, adjusting the resistance value of the resistor Rcs. In other words, the resistance of the resistor Rcs corresponds to the brightness of the LED module 290 .

Here, if the resistance value of the resistor Rcs is adjusted, correspondingly, the voltage value Vcs of the feedback signal CS will change with the resistance value of the resistor Rcs. The power factor correction circuit 250 adjusts its output signal V3 according to the feedback signal CS, so its output signal V3 will be changed corresponding to the change of the feedback signal CS, thereby affecting the peak voltage of the pulse signal Sa, and changing the The peak voltage of wave signal Sb. According to the characteristics of the transformer 230 , the secondary side current Isec of the transformer 230 is the primary side current Ipri multiplied by the turns ratio (NP/NS) of the primary side and the secondary side of the transformer 230 . Therefore, changing the primary side current Ipri of the transformer 230 is equivalent to changing the secondary side current Isec of the transformer 230 . For example, if the resistance value of the resistor Rcs is increased, the voltage value Vcs of the feedback signal CS will increase accordingly, causing the voltage value of the output signal V3 of the power factor correction circuit 250 to decrease, thereby causing the primary side current Ipri of the transformer 230 to decrease. , the secondary side current Isec corresponding to the primary side current Ipri will decrease accordingly. Moreover, as the primary side current Ipri of the transformer 230 decreases, the voltage Vcs of the feedback signal CS decreases accordingly, and finally the voltage Vcs of the feedback signal CS stabilizes at a certain value. Here, the resistor Rcs can be a variable resistor, so as to adjust the luminance of light.

In other words, the brightness of the LED module 290 can be adjusted by changing the resistance value of the resistor Rcs of the feedback circuit 260 .

In addition, since the resonant frequency of the resonant circuit 240 is above kHz, human eyes will not perceive flickering of the LED module 290 .

Taking the flyback architecture as an example, the signal waveforms of the pulse signal Sa, the feedback signal CS, the current signal I _LED flowing through the LED module, and the primary side current Ipri and the secondary side current Isec of the transformer 230 are shown in FIG. 4 As shown, FIG. 4 shows the relationship between the various signal signals when the light-emitting diode device driving device according to the present application is in operation. It can be seen from Fig. 4 that corresponding to the pulse signal, a primary side current Ipri is formed on the primary side of the transformer 230, and due to the flyback structure, a secondary side opposite to the primary side current Ipri is formed on the primary side of the transformer 230 The current Isec generates a current signal I _LED corresponding to the secondary side current Isec, and flows through the LED module 290 to drive the LED module 290 . Moreover, when the resistance value of the resistor Rcs is fixed, the feedback signal CS remains stable, so that the output signal V3 of the power factor correction circuit 250 is output stably, so that the bridge switch circuit 220 can provide a pulse signal Sa with a stable peak voltage.

In another embodiment, referring to FIG. 5 , at least one first LED module 292 and at least one second LED module 294 may be coupled to the output end of the LED driving device, ie, the secondary side of the transformer 230 . Moreover, the first LED module 292 and the second LED module 294 are connected in antiparallel, that is, the first LED module 292 and the second LED module 294 are reversely coupled to both ends of the secondary side of the transformer 230 . Here, the transformer 230 provides an output voltage Vo on its secondary side according to the primary side current Ipri to drive the first LED module 292 and the second LED module 294 . The output voltage Vo is an AC sine wave, and the first LED module 292 can be driven in the positive half cycle of the output voltage Vo, and the second LED module 294 can be driven in the negative half cycle. In other words, the transformer 230 alternately drives the first LED module 292 and the second LED module 294 according to the primary side current Ipri. Moreover, the resistance value of the resistor Rcs corresponds to the brightness of the two LED modules (292, 294).

In the light-emitting diode driving device according to this case, since the primary side current of the transformer is used for feedback control, the primary and secondary sides of the transformer are isolated from each other, so the cost of linear voltage regulators and optocoupler components can be saved As well as the overall space volume, the danger of electric shock when replacing the light-emitting diode can also be avoided. In addition, in the LED driving device according to the present application, it is only necessary to adjust the resistance value of the feedback circuit, for example, by adjusting the resistance value of the resistor Rcs, the secondary side current of the transformer can be adjusted, thereby controlling the luminance of the LED module. Compared with the prior art, the control method is relatively simple. Furthermore, the LED driver according to the present application is suitable for high power output (eg >200W). Moreover, in the light-emitting diode driving device according to the present application, only a single controller (ie, a power factor correction circuit) with a feedback function is used, and its control circuit is relatively simple and the overall price is relatively cheap.

Certainly, the present invention also can have other various embodiments, without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and deformations according to the present invention, but these Corresponding changes and deformations should belong to the scope of protection of the appended claims of the present invention.

Claims (14)

1, a kind of light emitting diode drive device is characterized in that, comprising:

One power factor correction circuit is in order to adjust an output signal according to a feedback signal;

One bridge switching circuit connects this power factor correction circuit, switches to a pulse wave signal with this output signal with this power factor correction circuit;

One resonant circuit connects this bridge switching circuit (220), in order to export a string ripple signal according to this pulse wave signal;

One transformer, first end of the primary side of this transformer connects this resonant circuit, to receive this string ripple signal; And

One feedback circuit connects second end of the primary side of this transformer, with output mutually should transformer this feedback signal of primary side current.

2, light emitting diode drive device according to claim 1, it is characterized in that, this bridge switching circuit is half bridge switching circuit, the switch element that comprises pair of series, this is connected between the output and a ground connection of this power factor correction circuit switch element, and this series connection contact to switch element is connected to this resonant circuit.

3, light emitting diode drive device according to claim 2 is characterized in that, this drives with a pair of complementary control signal switch element.

4, light emitting diode drive device according to claim 2 is characterized in that, also comprises: a signal generator connects this control end to switch element, to control this switching to switch element.

5, light emitting diode drive device according to claim 4 is characterized in that, this signal generator produces a pair of complementary control signal to control this to switch element.

6, light emitting diode drive device according to claim 5 is characterized in that, this has 50% responsibility cycle to complementary control signal.

7, light emitting diode drive device according to claim 1 is characterized in that, also comprises: a signal generator connects this bridge switching circuit, to drive this bridge switching circuit.

8, light emitting diode drive device according to claim 1 is characterized in that, this resonant circuit comprises:

One electric capacity, an end of this electric capacity is connected to this bridge switching circuit, to receive this pulse wave signal; And

One inductance is connected between first end of primary side of the other end of this electric capacity and this transformer, to export this string ripple signal.

9, light emitting diode drive device according to claim 1 is characterized in that, this feedback circuit comprises:

One resistance, this resistance are connected between second end and a ground connection of primary side of this transformer, and this primary side current is flowed through this resistance and formed one and exchange cross-pressure on this resistance; And

One rectifier cell carries out rectification with this interchange cross-pressure with this resistance and produces this feedback signal according to this.

10, light emitting diode drive device according to claim 9 is characterized in that, this feedback circuit more comprises a filter element, so that this feedback signal is carried out filtering, offers this power factor correction circuit after the filtering.

11, light emitting diode drive device according to claim 9 is characterized in that, the secondary side of this transformer also couples one first light-emitting diode (LED) module, and the resistance of this resistance is corresponding to the brightness of this first light-emitting diode (LED) module.

12, light emitting diode drive device according to claim 11, it is characterized in that, the secondary side of this transformer also couples one second light-emitting diode (LED) module, this this first light-emitting diode (LED) module of second light-emitting diode (LED) module reverse parallel connection, and the resistance of this resistance is corresponding to the brightness of this second light-emitting diode (LED) module.

13, light emitting diode drive device according to claim 1 is characterized in that, the secondary side of this transformer also couples one first light-emitting diode (LED) module, and this transformer drives this first light-emitting diode (LED) module according to this primary side current.

14, light emitting diode drive device according to claim 1, it is characterized in that, the secondary side of this transformer also couples one second light-emitting diode (LED) module, this this first light-emitting diode (LED) module of second light-emitting diode (LED) module reverse parallel connection, and this transformer is according to this first light-emitting diode (LED) module of this primary side current driven and this second light-emitting diode (LED) module.

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