Utility model content
The purpose of this utility model is the shortcoming overcoming above-mentioned prior art, provide a kind of can by regulating, the operating frequency of variable-resistance resistance value to circuit be modulated, the duty ratio of the switching tube ON time changed in LED drive module, circuit structure are simple, peak current reduces to increase operating frequency, the switching tube loss reduced in LED drive module, working stability, LED light modulating device that cost is low.
To achieve these goals, LED light modulating device of the present utility model has following formation:
This LED light modulating device, its main feature is, described device comprises dim signal generation module, frequency modulation(FM) module and LED drive module; The output of described dim signal generation module is connected with the input of described frequency modulation(FM) module, and the output of described frequency modulation(FM) module is connected with the input of described LED drive module.
Further, described dim signal generation module is adjustable resistance (R).
Further, described frequency modulation(FM) module comprise the first current source (U1), with the first switch (S1), the second current source (U2), with second switch (S2), electric capacity (C) and comparator (COMP); The output of described the first current source (U1) is connected with the first end of described the first switch (S1), the output of described the second current source (U2) is connected with the first end of described second switch (S2), and the input of the first described current source and the input of the second current source are connected with described adjustable resistance (R) respectively; The first end of the second end of described the first switch (S1), the second end of described second switch (S2), described electric capacity (C) is connected and the positive input of described comparator (COMP) is connected, second end of described electric capacity (C) is connected to the ground and connects, and the output of described comparator (COMP) is connected with the input of described LED drive module.
Again further, described the first current source (U1) and the second current source (U2) are controlled current source.
Again further, described the first switch (S1) and second switch (S2) are HF switch.
Further, described LED drive module is the converter working in high frequency switch-mode.
Further, described light modulating device also comprises power module and LED module, and the output of described LED drive module is connected with LED module, and described power module is connected with described LED drive module.
Have employed the LED light modulating device in this utility model, compared with prior art, there is following beneficial effect:
LED light modulating device of the present utility model, by regulating the operating frequency of variable-resistance resistance value to circuit to modulate, changing the duty ratio of LED drive module breaker in middle pipe ON time, finally realizing LED light modulation; LED light modulating device of the present utility model, circuit structure is simple, and peak current reduces to increase operating frequency, and reduce the loss of LED drive module breaker in middle pipe, working stability, cost is low.
Embodiment
In order to more clearly describe technology contents of the present utility model, conduct further description below in conjunction with specific embodiment.
Refer to shown in Fig. 2 to Fig. 5, LED light modulating device of the present utility model is light adjusting circuit based on PFM pattern and implementation.
Refer to shown in Fig. 2, LED light modulating device of the present utility model comprises dim signal generation module, frequency modulation(FM) module and LED drive module; The output of described dim signal generation module is connected with the input of described frequency modulation(FM) module, and the output of described frequency modulation(FM) module is connected with the input of described LED drive module.
logicaloverregulate variable resistor
rthe operating frequency of resistance value to circuit modulate, increase the duty ratio that LED drive module breaker in middle pipe opening time changes switching tube ON time, finally realize LED light modulation.
Wherein, described dim signal generation module is adjustable resistance R.
Refer to shown in Fig. 3, described frequency modulation(FM) module comprise the first current source U1, with the first switch S 1, second current source U2, with second switch S2, electric capacity C and comparator COMP; The output of the first described current source U1 is connected with the first end of the first described switch S 1, the output of the second described current source U2 is connected with the first end of described second switch S2, and the input of the first described current source and the input of the second current source are connected with described adjustable resistance R respectively; The first end of the second end of the first described switch S 1, second end of described second switch S2, described electric capacity C is connected and the positive input of described comparator COMP is connected, second end of described electric capacity C is connected to the ground and connects, and the output of described comparator COMP is connected with the input of described LED drive module.
Wherein, the first described current source U1 and the second current source U2 is controlled current source.The first described switch S 1 and second switch S2 are HF switch.
Adjustable resistance R is for changing the size of the first current source U1 and the second current source U2, and the first switch S 1 closes, and I1 charges to electric capacity C, and the first switch S 1 is opened, and second switch S2 closes, and electric capacity C is discharged by I2.The electric capacity C discharge and recharge time is relevant with the size of I1, I2, is changed the duty ratio of switching tube ON time by the electric capacity C discharge and recharge time controling switching tube opening time increased in LED drive module.
Described LED drive module is the converter working in high frequency switch-mode.Described light modulating device also comprises power module and LED module, and the output of described LED drive module is connected with LED module, and described power module is connected with described LED drive module.
Refer to Fig. 3 and shown in composition graphs 4, for non-isolated LED drive circuit of the present utility model is based on the oscillogram of PFM pattern light modulation, wherein, uncomfortable smooth time without the need to frequency modulation(FM) module work, LED current I
l=I
pK/ 2, I
pKfor inductance peak current.When needing light modulation, frequency modulation module controls LED drive module, uncomfortable smooth time circuit a work period be t1, within the t1 time, electric capacity C charges, and the t1 time terminates, and electric capacity C discharges, by adjustable resistance, I2=I1/N is set, discharge time t2=Nt1, the switching tube that LED drive module controls in LED drive module enters next cycle, I after the time delay t2 time after inductive current is reduced to 0
l=I
pK/ 2 (1+N).
Refer to Fig. 3 and shown in composition graphs 5, for isolation LED drive circuit of the present utility model is based on the oscillogram of PFM pattern light modulation, wherein, first switch S 1 closes, I1 charges to electric capacity C, VC>VREF, the switching tube that LED drive module controls in LED drive module closes, main coil current I
prise, reach peak current, switching tube is opened, and the first switch S 1 is opened, and second switch S2 closes, and electric capacity C is discharged by I2, auxiliary winding electric current I
sstart to reduce (I
sKpeak current for auxiliary winding), when being reduced to 0, the first switch S 1 closes, and second switch S2 opens, and electric capacity C discharges end, and discharge time is that t2, I1 charge again to electric capacity C, and VC>VREF, switching tube is opened again, I
pagain reach peak current, when switching tube turns off, electric capacity C charges end, and the charging interval is t1.
Adjustable resistance R regulates the first current source U1 can obtain I1=I2/N, t1=Nt2, I
lED=I
sK/ 2 (1+N) are not light-modulating mode during N=1.
Have employed the LED light modulating device in this utility model, compared with prior art, there is following beneficial effect:
LED light modulating device of the present utility model, by regulating the operating frequency of variable-resistance resistance value to circuit to modulate, changing the duty ratio of LED drive module breaker in middle pipe ON time, finally realizing LED light modulation; LED light modulating device of the present utility model, circuit structure is simple, and peak current reduces to increase operating frequency, and reduce the loss of LED drive module breaker in middle pipe, working stability, cost is low.
In this description, the utility model is described with reference to its specific embodiment.But, still can make various amendment and conversion obviously and not deviate from spirit and scope of the present utility model.Therefore, specification and accompanying drawing are regarded in an illustrative, rather than a restrictive.