CN104955200A - LED lamp driving circuit - Google Patents

Abstract

The invention discloses an LED lamp driving circuit which relates to the technical field of a driving circuit. The LED lamp driving circuit is provided with a power supply input end and an output circuit and further comprises the components of a rectifying circuit which is connected with the power supply input end, a filtering capacitor which is connected with the DC output end of the rectifying circuit, and a first circuit which is arranged in parallel with the filtering capacitor. The first circuit is obtained through serially connecting a first inductor, a first diode and a switch. The switch is connected with a controller. Furthermore a second circuit which is mounted in parallel with the switch is arranged between two ends of the switch. The second circuit is obtained through serially connecting a second capacitor and a second inductor. The output circuit is in parallel arranged between two ends of the second inductor. The LED lamp driving circuit is beneficial in that: in the circuit structure of the invention, the second capacitor C2 is used for buffering an energy for realizing input of a high-power factor and a stable output current; and the capacitance an output capacitor C3 is not too high; and furthermore in the LED lamp driving circuit, the high-power factor is naturally realized and furthermore no input current checking is required; and the switch can be controlled in a basic voltage mode or a current mode.

Description

A kind of LED lamp drive circuit

[technical field]

The present invention relates to a kind of drive circuit, particularly relate to a kind of LED lamp drive circuit.

[background technology]

LED is irradiative diode, electric current can only single direction conducting (anode A is to negative electrode K), very little lower than electric current time threshold voltage (Vth generally about 2.6 volts) at voltage, when exceeding threshold voltage, electric current rises fast, though though therefore very responsive with voltage control LED current and LED characteristic has variation and temperature and become thus that it is applicable to and determines current drives and make voltage LED characteristic and determine.Voltage loads is determined for driving LED is similar; Stabling current produces light stable.

Drive the input current also needing to consider electrical network demand, waveform as far as possible close to and synchronizing voltage (sine wave) changes power by current amplitude, in order to avoid current spikes or because of electric current and voltage not homophase cause current needs to become large increase power transmission and distribution load and loss.Actual gross power of removing claims power factor (PF), and General Requirements is higher than 0.9.

But when current/voltage is the sine wave of homophase, its input power to be the lowest point be zero sine wave, now as driven without slow weighing apparatus energy part, its power output to be also the lowest point be zero sine wave, and light output also has the flicker in 2*50=100 week.Consider above demand, then to want that cube is little, cost is low be not easy.

Fluorescent lamp is quite general in the past, and it needs ballast to drive with stabling current, and early stage ballast is that a silicon steel sheet inductance is connected with fluorescent tube, and lamp tube ends has tungsten filament connection starter to light to help starting.Nowadays LED improves fast, and efficiency far exceedes fluorescent lamp, and price also reduces makes user demand high.But it is the most convenient fluorescent lamp directly can be changed with LED lamp tube under how or else changing light fixture, and how LED driving easily can be filled in fluorescent tube be a major challenge.

LED and driving need heat radiation, and therefore current LED lamp tube is semi-transparent plastic cement and half radiation aluminium, puts LED therebetween, and driving is placed in this semicircle aluminum pipe, and user may touch fluorescent tube, makes therefore and not easily to get an electric shock, and driving need be isolated.Semi-transparent plastic cement and half radiation aluminium framework as shown in Figure 1, comprise plastic cover 1, LED2, driving 3, semicircle aluminum pipe 4.

The most general isolated driving uses inverse-excitation type to switch power conversion circuit framework, but it cannot reach high power factor and flicker free light output simultaneously; Isolation inverse-excitation type switches power conversion circuit framework as shown in Figure 2.

The simplest LED of low cost product employing adds LED strip on line current stabilization or suitching type step-down (normal shock) circuit after driving and being a rectifier, these belong to non-isolated and therefore adopt overall plastic sebific duct, user can not touch circuit in fluorescent tube, this mode foot gradually advantage, because LED light effect rises, do not need large radiating effect, drive circuit is placed on the one end inside this overall plastic fluorescent tube, and its structure as shown in Figure 3.Linear current stabilization or suitching type step-down (normal shock) circuit also all cannot reach high power factor and flicker free light output simultaneously.Linear current stabilization or suitching type step-down (normal shock) circuit framework are as shown in Figure 4 and Figure 5.

SEPIC can reach high power factor and flicker free light output simultaneously, but person is relatively few to understand this circuit, and current product does not generally use.Non-isolated Sepic switches power conversion circuit framework as shown in Figure 6.Composition graphs 6, when switch S w conducting two electric currents increase simultaneously: the first electric current is from C1 through L1 and Sw, and the second electric current gets back to ground from ground through L2, C2, Sw.When switch S w cut-off, the first electric current from C1 through L1, C2 and diode D to output capacitance C3; Second electric current from ground through L2, diode D to output capacitance C3.Now two electric currents fill output capacitance C3 and energy attenuation simultaneously, and to next circulation, switch S w is conducting again.Some results of study represent, control Sw switching current makes input be similar to input voltage waveform to reach high power factor, but it does not consider that reduce output current glimmers for 100 weeks.

[summary of the invention]

The object of the invention is to the deficiency effectively overcoming above-mentioned technology, provide a kind of input current to reach high power factor and the LED lamp drive circuit of flicker free light output.

Technical scheme of the present invention is achieved in that a kind of LED lamp drive circuit, there is a power input and an output circuit, this LED lamp tube drive circuit comprises the rectification circuit being connected to power input, the filter capacitor be connected with the DC output end of rectification circuit, and the first circuit to be arranged in parallel with filter capacitor, its improvements are: described first circuit is by the first inductance, first diode and switch are composed in series, described switch is connected on a controller, and the two ends of described switch are provided with second circuit with switch in parallel, described second circuit is composed in series by the second electric capacity and the second inductance, the two ends of described second inductance are arranged in parallel above-mentioned output circuit.

In above-mentioned circuit structure, described output circuit comprises output diode and the LED load of series connection, and in parallel an output capacitance in described LED load.

In above-mentioned circuit structure, described output circuit comprises a flyback transformer, the second above-mentioned inductance is the magnetizing inductance of this flyback transformer, and the output of flyback transformer has output diode and the LED load of series connection, in parallel an output capacitance in described LED load.

In above-mentioned circuit structure, be provided with a feeder ear in described LED string, this feeder ear is connected to a current supply line, and the other end of described current supply line is connected on above-mentioned controller, and current supply line is provided with the 3rd diode.

In above-mentioned circuit structure, the numerical values recited of described second capacitor's capacity is 50 times of the current values size of input current, and the capacitance size unit of the second electric capacity is μ F.

In above-mentioned circuit structure, described second electric capacity is electrochemical capacitor.

In above-mentioned circuit structure, the inductance value of described second inductance is at least 1.3 times of the inductance value of the first inductance.

Beneficial effect of the present invention is: in circuit structure of the present invention, and the second electric capacity C2 is except transferring energy also storage power, and therefore capacitance is relatively much bigger, uses electrochemical capacitor in realization; Utilize this second electric capacity C2 can make input high power factor for delaying weighing apparatus energy and have stabilizing output current simultaneously, and output capacitance C3 does not need very large; And in circuit of the present invention, high merit factor is that nature realizes not needing input current prosecution, and fundamental voltage pattern or current-mode switch control rule can.

[accompanying drawing explanation]

Fig. 1 is existing LED lamp tube structural representation;

Fig. 2 is isolation inverse-excitation type switching power conversion circuit Organization Chart;

Fig. 3 is overall plastic sebific duct LED schematic diagram;

Fig. 4 is linear current stabilization circuit Organization Chart;

Fig. 5 is suitching type step-down (normal shock) circuit framework figure;

Fig. 6 is that non-isolated Sepic switches power conversion circuit Organization Chart;

Fig. 7 is the circuit theory diagrams of LED lamp tube drive circuit of the present invention;

Fig. 8, Fig. 9 are respectively the second embodiment of the present invention, the 3rd and implement illustration.

Figure 10 is the specific embodiment figure of LED lamp tube drive circuit of the present invention.

[embodiment]

Below in conjunction with drawings and Examples, the invention will be further described.

With reference to shown in Fig. 7, a kind of LED lamp drive circuit that the present invention discloses, this LED lamp drive circuit has a power input ACin and an output circuit 10, wherein power input Acin is external to the civil power of 200V, specifically in the present embodiment, this LED lamp tube drive circuit comprises the full bridge rectifier 20 being connected to power input, the filter capacitor C1 be connected with the DC output end of rectification circuit 20, and the first circuit 30 to be arranged in parallel with filter capacitor C1, in the present embodiment, first circuit 30 is by the first inductance L 1, first diode D2 and switch S w is composed in series, switch S w is connected on a controller, further, the two ends of described switch S w have been arranged in parallel second circuit 40 with switch S w, second circuit 40 is composed in series by the second electric capacity C2 and the second inductance L 2, the two ends of the second inductance L 2 are arranged in parallel above-mentioned output circuit 10.In the present embodiment, output circuit 10 comprises output diode D and the LED load of series connection, and in parallel an output capacitance C3 in described LED load.

The circuit structure that the present invention is above-mentioned, be similar to Sepic circuit, but its specific implementation circuit parameter and working point greatly different, in known Sepic circuit, the second electric capacity C2 is transferring energy, therefore capacitance is very little, use plastic cement electric capacity in realization, and in circuit structure of the present invention, the second electric capacity C2 is except transferring energy also storage power, therefore capacitance is relatively much bigger, uses electrochemical capacitor in realization.Utilize this second electric capacity C2 can make input high power factor for delaying weighing apparatus energy and have stabilizing output current simultaneously, and output capacitance C3 does not need very large.And in circuit of the present invention, high merit factor is that nature realizes not needing input current prosecution, and fundamental voltage pattern or current-mode switch control rule can.In circuit of the present invention, at least large than the inductance value of the first inductance L 1 more than 1.3 times of second inductance L 2 inductance value, the first inductance L 1, first diode D2, switch S w and the second electric capacity C2 work is made to be made in boost mode, raised by second electric capacity C2 voltage in input peak value, this boost mode does not exist in known Sepic circuit.Utilize the operating voltage of the first inductance L 1 and the second inductance L 2 Proportionality design second electric capacity C2.

Further, we are described in detail circuit working process of the present invention, the alternating current of power input becomes McDonald's voltage at filter capacitor C1 through full bridge rectifier, when switch S w conducting, two electric currents increase simultaneously: the first electric current is from filter capacitor C1 through the first inductance L 1, first diode D2 and switch S w, and the second electric current gets back to ground from ground second inductance L 2, second electric capacity C2, switch S w.When switch S w cut-off, the first electric current is from filtering C1 through the first inductance L 1, first diode D2, the second electric capacity C2 and export diode D to output capacitance C3; Second electric current is from ground second inductance L 2, output diode D to output capacitance C3.Now two electric currents fill output capacitance C3 and energy attenuation simultaneously, and to next circulation, switch S w is conducting again.Wherein, by inductance storage power formula:

$E=\frac{1}{2}{\mathrm{LI}}^2$ And $I=\frac{V}{L}t$ The $E=\frac{1}{2}L{\left(\frac{V}{L}t\right)}^2=\frac{{\left(\mathrm{Vt}\right)}^2}{2L}$

The inductance value of the first inductance L 1 is less than the inductance value of the second inductance L 2 in design, and therefore with similar voltage and time, the first inductance L 1 stores and releases energy larger than the second inductance L 2, and therefore the first inductance L 1 exceedes half in the conversion contribution of energy.

When switch S w conducting, energy is stored into the first inductance L 1 from filter capacitor C1, and the second electric capacity C2 energy trasfer is to the second inductance L 2, and the energy that energy Ratios second inductance L 2 that the first inductance L 1 stores stores is large.

$\frac{{\mathrm{di}}_{L1}}{\mathrm{dt}}=\frac{V_i}{{L:}_1}$ And $\frac{{\mathrm{di}}_{L:2}}{\mathrm{dt}}=\frac{V_{C2}}{L_2}$ Or ${\mathrm{\Δi}}_{L1}=\frac{V_i}{L_1}{t}_{\mathrm{on}}$ And ${\mathrm{\Δi}}_{L2}=\frac{V_{C2}}{L_2}{t}_{\mathrm{on}}$

When switch S w cut-off, the energetic portions that the first inductance L 1 stores is stored into the second electric capacity C2, and part is to exporting.Now the second inductance L 2 voltage equals output voltage, and this voltage adds the voltage that the voltage of the second electric capacity C2 equals input voltage and adds the first inductance L 1, therefore:

V _L1＝V _o+V _C2-V _i

${\mathrm{\Δi}}_{L2}=-\frac{V_o}{L_2}{t}_{f2}$ And ${\mathrm{\Δi}}_{L1}=-\frac{V_o+V_{C2}-V_i}{L_1}{t}_{f1}$

$t_{f2}=\frac{L_2}{V_o}\frac{V_{C2}}{L_2}{t}_{\mathrm{on}}=\frac{V_{C2}}{V_O}{t}_{\mathrm{on}}$ And $t_{f1}=\frac{L_1}{V_o+V_{C2}-V_i}\frac{V_i}{L_1}{t}_{\mathrm{on}}=\frac{V_i}{V_o+V_{C2}-V_i}{t}_{\mathrm{on}}$

Tf1 and tf2 is that the first inductance L 1 and the second inductance L 2 electric current delay the weighing apparatus time, and in the present embodiment, the second electric capacity C2 is large, answers and VC2 can not change with input voltage ripple (because of cost and volume, the capacitance of the second electric capacity C2 is limited and its voltage has some change).Therefore tf2 stablizes, and tf1 is with the change of input voltage ripple, and its difference is kept off by the first diode D2.The switch periods of actual value with switch S w and the ratio of tf1 and tf2.Only when input voltage crest, tf1 is close to tf2 at most, discontinuous at the electric current of most of the time first inductance L 1, the triangular wave at my interval.Therefore stable output and the second electric capacity C2 large time, ton change is little, and input current nature reaches high power factor with input voltage.

As preferred embodiment, with reference to shown in Figure 10, this circuit structure is the distortion of above-mentioned circuit structure, in above-mentioned circuit structure, described LED load is a LED string, a feeder ear is provided with in this LED string, feeder ear is connected to a current supply line, and the other end of described current supply line is connected on above-mentioned controller, current supply line is provided with the 3rd diode D3, the design of this structure, makes controller directly carry out work from power taking LED load, this electric current is more steady, and therefore the work of controller is also more stable.

Described above is the non-isolated circuit of the present invention, further, its relatively isolated circuit is then with reference to shown in Fig. 8, Fig. 9, wherein output circuit comprises a flyback transformer, the second above-mentioned inductance L 2 is the magnetizing inductance of this flyback transformer, the output of flyback transformer has output diode D and the LED load of series connection, and LED load is a LED string, and in parallel an output capacitance C3 on LED string.Here transformer is operated in normal shock and flyback, and the second inductance L 2 can be considered the magnetizing inductance of flyback transformer.As further improvement, LED string arranges a feeder ear, feeder ear is connected to a current supply line, and the other end of described current supply line is connected on above-mentioned controller, current supply line is provided with diode, by this structure, controller is powered, make the work of controller more steady reliable.General transformer is part maximum in the middle of drive circuit, this energy in circuit in fact exceedes half and is stored in the first inductance L 1, and transformer is with positive activation type transmission, therefore transformer can with half as large, and transformer excitation is also utilized as storage and the transferring energy of inverse-excitation type simultaneously.

Described above is only preferred embodiment of the present invention, and above-mentioned specific embodiment is not limitation of the present invention.In technological thought category of the present invention, can occur various distortion and amendment, all those of ordinary skill in the art, according to describing retouching, the amendment made above or equivalent replacing, all belong to the scope that the present invention protects.

Claims (7)

1. a LED lamp drive circuit, there is a power input and an output circuit, this LED lamp tube drive circuit comprises the rectification circuit being connected to power input, the filter capacitor be connected with the DC output end of rectification circuit, and the first circuit to be arranged in parallel with filter capacitor, it is characterized in that: described first circuit is by the first inductance, first diode and switch are composed in series, described switch is connected on a controller, and the two ends of described switch are provided with second circuit with switch in parallel, described second circuit is composed in series by the second electric capacity and the second inductance, the two ends of described second inductance are arranged in parallel above-mentioned output circuit.

2. a kind of LED lamp drive circuit according to claim 1, is characterized in that: described output circuit comprises output diode and the LED load of series connection, and in parallel an output capacitance in described LED load, described LED load is a LED string.

3. a kind of LED lamp drive circuit according to claim 1, it is characterized in that: described output circuit comprises a flyback transformer, the second above-mentioned inductance is the magnetizing inductance of this flyback transformer, the output of flyback transformer has output diode and the LED load of series connection, in parallel an output capacitance in described LED load, described LED load is a LED string.

4. a kind of LED lamp drive circuit according to Claims 2 or 3, it is characterized in that: in described LED string, be provided with a feeder ear, this feeder ear is connected to a current supply line, and the other end of described current supply line is connected on above-mentioned controller, and current supply line is provided with the 3rd diode.

5. a kind of LED lamp drive circuit according to claim 1, is characterized in that: the numerical values recited of described second capacitor's capacity is 50 times of the current values size of input current, and the capacitance size unit of the second electric capacity is μ F.

6. a kind of LED lamp drive circuit according to claim 1 or 5, is characterized in that: described second electric capacity is electrochemical capacitor.

7. a kind of LED lamp drive circuit according to claim 1, is characterized in that: the inductance value of described second inductance is at least 1.3 times of the inductance value of the first inductance.