CN201869417U - LED driving circuit - Google Patents

Abstract

The utility model discloses an LED driving circuit of a switching power supply, which is applied to a circuit system of the switching power supply and comprises a light regulator, an impedance conversion module, a low pass filter and a constant-current control module. The light regulator receives alternating current input, the impedance conversion module is connected with output of the light regulator, realizes impedance conversion of load characteristics of the light regulator and controls output waveforms of the light regulator, the low pass filter is connected with the output of the light regulator and generates light regulating control signals, the constant-current control module is connected between output of the impedance conversion module and input of an LED, and further connected with the low pass filter, and receives the light regulating control signals so as to control output current, and the LED is finally driven by the aid of the constant-current control module. The LED driving circuit can adapt to various existing light regulators and has high performances.

Description

A kind of led drive circuit

Technical field

The utility model relates to LED Driving technique field, particularly relates to a kind of led drive circuit of Switching Power Supply.

Background technology

Switching Power Supply more and more is applied in the various kinds of equipment because volume is little and the high advantage of efficient, is used to the energy output that provides stable.

LED illumination is described as the revolution for the third time that the mankind are thrown light on because of having long, energy-conservation, rich color of life-span, safety, environmental protection characteristic.Under same brightness, LED illumination power consumption only is 1/10 of an ordinary incandescent lamp, and be 80-100 times of incandescent lamp useful life.LED can be widely used in fields such as various indications, demonstration, decoration, backlight, general lighting and urban landscape illumination now.LED belongs to DC driven, has ultralow power consumption, and single tube can reach 0.03～0.06 watt.

And the illumination system layout personnel face the challenge of light modulation to each new light source science and technology.Light modulation is very important in many application, because it can allow the brightness of light meet all-environment demand, and simultaneously can be effectively energy-conservation.Modal light adjusting controller is the phase truncation dimmer, is commonly called the TRIAC dimmer, is to be applied to a large amount of at present incandescent lamp or Halogen lamp LEDs that use.The phase truncation dimmer to be combined application with now light-emitting diode (LED) bulb, just mean demand side to significant design challenge, and the result be also non-fully up to expectations.Trace it to its cause, exactly: traditional TRIAC light adjusting controller is to be used for regulating ohmic load (for example being incandescent lamp or Halogen lamp LED), and led driver solution in the market when making the TRIAC brightness adjustment control, can produce flicker and/or can not realize 100: 1 contrast.

For example following design as shown in Figure 1, adopts passive type (passive) power factor corrector (PFC), that is, whole drive circuit comprises and connecting successively: TRIAC dimmer, passive PFC and Switching Power Supply.Concrete, as Fig. 2 A and Fig. 2 B, be the concrete led drive circuit figure that uses two kinds of passive type power factor correctors, wherein Fig. 2 A is the led drive circuit figure of " inductance compensation formula " power factor corrector, comprises TRIAC dimmer 10, inductance compensation formula PFC12 and Switching Power Supply 14; Fig. 2 B is the led drive circuit figure of " filling out the paddy circuit type " power factor corrector, comprises TRIAC dimmer 10 ', fills out paddy circuit type PFC12 ' and Switching Power Supply 14 '.Though these designs can driving LED, but because the load of dimmer is not a resistive load, when causing AC-input voltage near triac dimmer conduction angle, dimmer is conducting repeatedly, thereby causes LED generation flicker effect and/or can not realize 100: 1 contrast.

Therefore, how to design a kind of led drive circuit that adapts to the Switching Power Supply of existing various dimmers, become one of technical barrier of current urgent need solution.

The utility model content

In view of this, the purpose of this utility model is to provide a kind of led drive circuit, can adapt to existing various dimmer, and have high-performance.

Led drive circuit described in the utility model comprises:

Receive the dimmer of alternating current input;

Be connected with the output of described dimmer and its load characteristic is carried out impedance conversion, controlled the impedance conversion module of its output waveform;

Be connected and produce the low pass filter of dimming control signal with the output of described dimmer;

Be connected in the constant current control module between the input of the output of described impedance conversion module and LED, and described constant current control module also is connected with described low pass filter, receive described dimming control signal, thereby control output current size is also by the final driving LED of described constant current control module.

Wherein, described dimmer is the phase truncation dimmer.

Wherein, described impedance conversion module is for can control the active power factor corrector that its ac input signal is a sinusoidal signal.

Wherein, described dimming control signal is that the simple alternating current input signal of described active power factor corrector is by direct current signal that low pass filter produced.

Wherein, described constant current control module is the Switching Power Supply of former limit control.

In the specific embodiment that described LED drives, described impedance transformer can be an active power factor corrector; And the constant current control module can be the Switching Power Supply of former limit control.This circuit is by connecting the impedance conversion module behind dimmer, make its load be converted into resistive load from the non-resistance load, thereby solved because near conducting repeatedly angle of flow when afterwards dimmer carries out light modulation is imported in interchange, thereby produce the technical problem of flicker, that is, make this led drive circuit can use existing dimmer.In addition, adopt the constant current control module, the Switching Power Supply of particularly former limit control makes its performance height, and cost is low.

Description of drawings

Fig. 1 is the block diagram of existing LED drive scheme;

Fig. 2 A is the led drive circuit figure of concrete application shown in Figure 1 " inductance compensation formula " power factor corrector;

Fig. 2 B is the led drive circuit figure of the concrete application shown in Figure 1 power factor corrector of " filling out the paddy circuit type ";

Fig. 3 is the block diagram of the LED drive scheme of Switching Power Supply of the present utility model;

Fig. 4 is the concrete enforcement circuit diagram of the led drive circuit of Switching Power Supply shown in Figure 3;

Fig. 5 is an active power factor corrector at different dimmer types (preceding cutting/then cut), the input voltage signal under the different angle of flow situations;

Fig. 6 is the led drive circuit angle of flow of the utility model Switching Power Supply and the graph of a relation of LED output current.

Embodiment

For above-mentioned purpose of the present utility model, feature and advantage can be become apparent more, the utility model is described in further detail below in conjunction with the drawings and specific embodiments.

In view of this, the purpose of this utility model is to provide a kind of led drive circuit of Switching Power Supply, can adapt to existing various dimmer, and have high-performance.

The front has been mentioned, the triac dimmer is the light modulation that is applied to traditional illuminating lamp, be that its load need be a resistive, but the drive circuit of the LED of Fig. 1 for example, because the load of dimmer is not a resistive load, when causing AC-input voltage near triac dimmer conduction angle, dimmer is conducting repeatedly, thereby causes LED to produce flicker effect.

Therefore, in order to guarantee the operate as normal of dimmer, at first need impedance conversion is carried out in the load of dimmer.See also Fig. 3, it is structured flowchart of the present utility model, as shown in the figure, led drive circuit of the present utility model comprises: dimmer, impedance conversion module, low pass filter, and constant current control module, wherein, described dimmer receives the alternating current input, and its input is connected with impedance transformer and low pass filter; Described impedance transformer makes the load of dimmer change resistive load into from capacitive character, and its output is connected with the constant current control module; The input of described constant current control module comprises the output of impedance conversion module and the dimming control signal that low pass filter produces, i.e. constant current control module also is connected with the output of described low pass filter.

Like this, this led drive circuit can change the load of described dimmer into resistive load by capacity load, can solve the problem of above-mentioned flicker.In addition, control effectively, make output stable by of the output of constant current control module to entire circuit.

Need to prove that above-mentioned impedance conversion module is when carrying out impedance conversion, under the situation of LED load variations, the resistance characteristic that the conversion of impedance conversion module institute goes out is good more, helps the operate as normal of Triac dimmer more.Adopt the Active Power Factor Correction structure can realize this impedance conversion, see also Fig. 4, it is the specific embodiment of led drive circuit of the present utility model, as shown in the figure, after the capacity load of led drive circuit was transformed to resistive load, the voltage waveform behind rectifier bridge 21 was identical with voltage waveform before the rectifier bridge 21.Impedance conversion module 22 (being active power factor corrector in the present embodiment), LED constant current control module 24 and AC-input voltage are separated, and can control the shape that exchanges input current, make it to equal sinusoidal, as shown in Figure 5, shown that active power factor corrector is at different dimmer types (preceding cutting/then cut), the input voltage signal under the different angle of flow situations.Active power factor corrector comprises: Active Power Factor Correction IC is used for the transformer of power output, power MOS pipe and output rectifying schottky diode.When dimmer 20 was operated in different angle of flow states, the line voltage waveform of entire circuit also was the sinusoidal voltage that is notched.And the APFC booster circuit that application is used always in the active power factor corrector among Fig. 4, the input voltage of APFC is an AC-input voltage, after inserting triac dimmer 20, the input voltage of APFC is the sinusoidal voltage of corner cut, and the voltage waveform behind the rectifier bridge 21 still can well be followed the output voltage waveforms of Triac, can not produce distortion.By such load characteristic conversion, it is about the frequency range of 100Hz that the loading on of rectifier bridge back exchanges the input cycle, is regarded as pure resistive loads, has guaranteed the operate as normal of Triac dimmer 20.Simultaneously, the output voltage of APFC is about the high pressure Bus signal of 400V.Under the situation of different input voltages, this BUS change in voltage is little.Constant current control module 24 (being the Switching Power Supply of former limit control among this embodiment) for the back one-level is equivalent to a changeless input voltage signal.To stablizing the output of entire circuit, also helpful.

Constant current control module 24 of the output termination of impedance conversion module 22.The working method of this module is former sampling edge and control in the present embodiment, the input signal of the constant current output module of described former limit control is the output of Active Power Factor Correction module, and in order to carry out the control signal of LED light modulation, dim signal is the direct current signal that the sinusoidal signal of the corner cut of active power factor corrector is produced by low pass filter 23.Adopt the constant current control module 24 of former sampling edge and control can under the situation that guarantees system's output current precision, significantly reduce the component number of system, reduced cost, also improved simultaneously the reliability of system, it comprises power tube 241, controller 243 and transformer 245.The basic principle of former limit control module constant current output services is:

$\mathrm{Iout}=\mathrm{Ipeak}*\frac{N1}{N2}*\frac{\mathrm{Tons}}{T}$

Wherein, N1/N2 is the turn ratio of transformer 245 former secondary, and Ipeak is the peak current of former limit power tube 241 conductings, and Tons is the time of secondary Schottky diode 246 conductings, and T is the switch periods of controller 243 work.

In the present embodiment, dimmer is phase truncation dimmer (a Triac dimmer).Entire circuit need make the brightness of LED light fixture make corresponding adjustment when the Triac dimmer is operated in the different angles of flow, and for example: the method that reduces LED brightness may be summarized to be two kinds: reduce the DC electric current that LED flows through 1..2. reduce the LED ON time.In an embodiment of the present utility model, carry out low-pass filtering by sinusoidal signal to the Triac corner cut, obtain a d. c. voltage signal DIM corresponding with the dimmer conduction angle.Again by the current sample reference signal in the constant-current controller of the former limit of DIM signal controlling, from the operation principle of former limit controller as can be seen, the output DC stream of constant current control circuit will change with the peak current of power switch pipe.Therefore, reach the output current that reduces constant-current driven module, the brightness of LED is reduced.

See also Fig. 6, be the led drive circuit angle of flow of the utility model Switching Power Supply and the graph of a relation of LED output current, as shown in the figure, the electric current of final LED can access effective adjusting, and can not produce phenomenons such as flicker, make existing dimmer can be applied to the adjusting of LED.

More than to the led drive circuit of a kind of Switching Power Supply provided by the utility model, be described in detail, used specific case herein principle of the present utility model and execution mode are set forth, the explanation of above embodiment just is used for helping to understand method of the present utility model and core concept thereof; Simultaneously, for one of ordinary skill in the art, according to thought of the present utility model, part in specific embodiments and applications all can change.In sum, this description should not be construed as restriction of the present utility model.

Claims (5)

1. a led drive circuit is characterized in that, comprising:

Receive the dimmer of alternating current input;

Be connected with the output of described dimmer and its load characteristic is carried out impedance conversion, controlled the impedance conversion module of its output waveform;

Be connected and produce the low pass filter of dimming control signal with the output of described dimmer;

Be connected in the constant current control module between the input of the output of described impedance conversion module and LED, and described constant current control module also is connected with described low pass filter, receive described dimming control signal, thereby control output current size is also by the final driving LED of described constant current control module.

2. led drive circuit according to claim 1 is characterized in that, described dimmer is the phase truncation dimmer.

3. led drive circuit according to claim 1 is characterized in that, described impedance conversion module is for can control the active power factor corrector that its ac input signal is a sinusoidal signal.

4. led drive circuit according to claim 3 is characterized in that, described dimming control signal is that the simple alternating current input signal of described active power factor corrector is by direct current signal that low pass filter produced.

5. led drive circuit according to claim 1 is characterized in that, described constant current control module is the Switching Power Supply of former limit control.

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