CN203206529U

CN203206529U - A LED driving circuit sampling inductive current in a complete period

Info

Publication number: CN203206529U
Application number: CN201320105231XU
Authority: CN
Inventors: 孙顺根; 于得水; 杨彪
Original assignee: Shanghai Bright Power Semiconductor Co Ltd
Current assignee: Shanghai Bright Power Semiconductor Co Ltd
Priority date: 2013-03-08
Filing date: 2013-03-08
Publication date: 2013-09-18
Anticipated expiration: 2023-03-08

Abstract

The utility model discloses a LED driving circuit sampling inductive current in a complete period. The LED driving circuit comprises a rectifier bridge connected with input AC voltage, and a LED load. Connected with an inductor (L1), a power switch (M1), and a sampling resistor (R4), the LED load is connected with a filtering capacitor (C1) in parallel. The LED driving circuit is characterized in that the according to a current signal passing through the inductor (L1) when the power switch (M1) is turned on or turned off, the LED driving circuit turns off the power switch (M1) with a loop circuit control circuit, that according to the demagnetizing time of the inductor (L1), the LED driving circuit turns on the power switch (M1), that the loop circuit control circuit comprises a sawtooth wave generator, an error amplifier, a comparator, and a integrating capacitor C3, that the current signal of the inductor (L1) passes through the sampling resistor (R4) to be converted into a voltage signal (CS), that the voltage signal (CS) is connected with the input end of the error amplifier, that the output signal of the error amplifier passes through the integrating capacitor C3 to be converted into a DC voltage signal (COMP), that the output end of the error amplifier is connected with the negative input end of the comparator, that the positive input end of the comparator is connected with the sawtooth wave generator, and that the power switch (M1) is turned off when the voltage of the sawtooth wave generator is more than the DC voltage signal (COMP).

Description

A kind of led drive circuit of inductive current complete period sampling

Technical field

The utility model relates to switching mode LED driving power technical field, particularly a kind of led drive circuit of inductive current complete period sampling.

Background technology

Fig. 1 is the rough schematic view of traditional step-down led drive circuit.As shown in Figure 1, alternating current by capacitor C1 filtering, produces power supply through the rectifier bridge rectification, and resistance R 1 and capacitor C2 produce a low-voltage dc voltage starts control chip.Transformer has two windings, comprises a main winding, is connected between power supply and the output LED output capacitance, and an auxiliary winding is connected between diode D2 and the circuit ground.Behind circuit start, sampling resistor R2 samples the current information of main winding with the control output current, auxiliary winding is the control chip power supply, and auxiliary winding also provides the information that detects the output fly-wheel diode current over-zero time and detect output voltage and output current simultaneously.

In above-mentioned traditional voltage-dropping type led drive circuit, there are following two shortcomings:

First, the inductive current sample circuit can only sample the electric current that flows through inductance when power switch pipe is opened, can not detect the electric current that flows through inductance when power tube turn-offs, can not sample really output current, can only realize by the chip internal algorithm, the output current precision is low, and constant-current characteristics is poor, chip internal also will be made compensating circuit, has increased chip cost.

The second, auxiliary winding increases system cost and volume.

The utility model content

In order to overcome the defective that exists in the prior art, the utility model provides a kind of led drive circuit of inductive current complete period sampling to make the output current precision high, permanent good fluidity, improved the overall performance of power supply, the power supply circuits of this led drive circuit need not auxiliary winding simultaneously, can simplify the design of LED driving power, dwindle the volume of LED driving power, reduce the cost of LED driving power.

In order to realize above-mentioned utility model purpose, the utility model discloses a kind of led drive circuit of inductive current complete period sampling, in order to realize that the LED constant current drives, comprise a rectifier bridge that is connected with input ac voltage, one LED load, this LED load and an inductance (L1), a filter capacitor in parallel (C1) after one power switch (M1) and a sampling resistor (R4) connect, it is characterized in that, flow through during according to this power switch (M1) opening and closing current signal of inductance (L1) of this led drive circuit, by a loop control circuit, turn-off this power switch (M1); This led drive circuit is opened this power switch (M1) according to the demagnetization time of this inductance (L1); This loop control circuit comprises: a saw-toothed wave generator, an error amplifier, a comparator and an integrating capacitor C3; The current signal of this inductance (L1) is converted into voltage signal (CS) through this sampling resistor (R4), this voltage signal (CS) is connected with the input of this error amplifier, the output signal of this error amplifier is converted into a direct current voltage signal (COMP) through this integrating capacitor (C3), the output of this error amplifier is connected with the negative input of this comparator, the positive input of this comparator is connected with this saw-toothed wave generator, when this saw-toothed wave generator voltage greater than this d. c. voltage signal (COMP), turn-off this power switch (M1).

Further, this loop control circuit also comprises a logic controller, and the input of this logic controller is connected with this comparator, controls this power switch (M1) according to the output valve of this comparator.

Further, this led drive circuit also comprises power supply circuits, these power supply circuits comprise one for electric diode (D2) and a supplying resistance (R5), when this power switch (M1) turn-offs, by being this led drive circuit power supply for electric diode (D2) and supplying resistance (R5).

Further, when this power switch (M1) turn-offs, sustained diode 1 conducting that is connected with sampling resistor (R4), when this sustained diode 1 conducting, the demagnetization that is connected with this inductance (L1) detects sampling resistor R2 and R3 and samples demagnetization time of this inductance (L1), when the demagnetization time of this inductance (L1) finishes, the demagnetization detection module that is connected with R3 with this demagnetization detection sampling resistor R2 detects the demagnetization end, this demagnetization detection module power ratio control switch (M1) conducting.

Further, this led drive circuit comprises that also a resistor (R1) and capacitor (C2) provide the startup power supply for this LED drives, this resistor (R1) end connects this rectifier bridge, and the other end is connected with this capacitor (C2), the other end ground connection of this capacitor (C2).

The utility model execution mode in terms of existing technologies, the reflected voltage of inductance L 1 is detected to determine the current over-zero time of sustained diode 1, thereby determine the current over-zero time of sustained diode 1, to the full sampling of inductive current to detect the average current of LED load, realize that by closed-loop control high accuracy LED constant current drives, and has improved the output constant current precision of power supply; The reflected voltage of inductance L 1 is by R5 and D2 power supply, and the design of saving auxiliary winding can be simplified the design of LED driving power, dwindles LED driving power volume, reduces LED driving power cost.

Description of drawings

Can describe in detail and appended graphic being further understood by following utility model about advantage of the present utility model and spirit.

Fig. 1 is employed voltage-dropping type LED constant-current drive circuit schematic diagram in the prior art;

Fig. 2 is the led drive circuit schematic diagram of the shown inductive current complete period sampling of the utility model;

Fig. 3 is voltage or the current diagram (voltage signal is with respect to the AGND point voltage) of shown each signaling point of led drive circuit of the utility model.

Embodiment

Describe specific embodiment of the utility model in detail below in conjunction with accompanying drawing.

The purpose of this utility model is to provide a kind of led drive circuit of inductive current complete period sampling, so that the output current precision is high, constant-current characteristics is good, has improved the overall performance of power supply.Power supply circuits need not auxiliary winding simultaneously, can simplify the design of LED driving power, dwindle the volume of LED driving power, reduce the cost of LED driving power.

For solving the problems of the technologies described above, execution mode of the present utility model provides a kind of led drive circuit of inductive current complete period sampling.As shown in Figure 2, this led drive circuit comprises: current sampling resistor R4, be used for sampling inductance L 1 electric current and be converted into voltage signal, inductance L 1 electric current of can both sampling when power switch pipe M1 opens and turn-off is converted into voltage signal, i.e. the sampling of inductive current complete period; This led drive circuit also comprises: demagnetization detection module (202), saw-toothed wave generator module (203), error amplifier module (204), comparator module (205), Logic control module (206), switching power tube M1, integrating condenser C3 and the supply network that is comprised of D2, R5.

This demagnetization detection module (202) input is connected between demagnetization sampling resistor R2 and the R3, output is connected in the first input end of Logic control module (206), for detection of the current over-zero of sustained diode 1, to determine the opening time of power switch pipe M1.

This error amplifier module (204) input is connected in sampling resistor R4 and reference voltage, output is connected in integrating condenser C3, after the voltage that is used for that the electric current of inductance L 1 is changed into amplifies by error amplifier, filter into direct current and carry out loop compensation by integrating condenser C3, obtain the average current information of inductance L 1.

The output of this saw-toothed wave generator module (203) is connected in comparator module (205) positive input, the reverse input end of this comparator module (205) is connected in integrating condenser C3, for the voltage on the comparison integrating condenser C3 and the output voltage of saw-toothed wave generator, to determine the conducting pulse duration of power switch pipe M1.

This supply network is by forming for electric diode D2 and supplying resistance R5, and being used for is capacitor C2 power supply when power switch pipe M1 turn-offs, thereby saves the auxiliary winding of power supply.

Led drive circuit of the present utility model also comprises: resistor R1 and capacitor C2 are used for high tension voltage is changed into direct voltage, for led drive circuit provides the startup power supply; Startup and base modules (201) are used for controlling startup and the shutoff of whole circuit, and produce reference voltage; The demagnetization time sampling network that resistor R2 and resistor R3 form is for the current over-zero time of sampling sustained diode 1.

Specifically describe the course of work according to the led drive circuit of present embodiment below in conjunction with Fig. 2 and Fig. 3:

When power tube M1 opens (301 among Fig. 3), inductance L 1 Current rise, voltage on the sampling resistor R4 (CS) also rises, when power tube M1 turn-offs, inductance L 1 electric current descends, voltage on the sampling resistor R4 also descends, current sample amplifier (204) can be done poor rear the amplification to voltage and reference voltage that R4 is upsampled to, filter into direct voltage (COMP voltage) by capacitor C3, this direct voltage has reacted average current (the being output current) information that flows through inductance L 1, after power tube M1 opens, saw-toothed wave generator (203) can produce the sawtooth waveforms (RAMP) of fixed slope, after sawtooth voltage is above the voltage on the C3 electric capacity, power tube M1 turn-offs (302 among Fig. 3), sustained diode 1 beginning conducting, also begin conducting (power supply beginning) for electric diode D2, demagnetization detects sampling resistor R2 and R3 starts working, the demagnetization time of sampling L1, when the L1 demagnetization finishes (the current over-zero time of sustained diode 1), demagnetization detects (202) and detects demagnetization end (303 among Fig. 3), power ratio control pipe M1 opens, so circulation, system can detect the real average current of LED load, realize that by feedback control loop the LED constant current drives, the output current precision is high, and constant-current characteristics is good, has saved simultaneously the auxiliary winding of circuit supply.

Compared with prior art, present embodiment was sampled to the inductive current complete period, what sample is the actual value of output current, realizes that by feedback control loop the LED constant current drives, and the output current precision is high, constant-current characteristics is good, by D2 and R5 C2 electric capacity is powered when utilizing simultaneously power tube to turn-off, save the design of auxiliary winding, can simplify the design of LED driving power, dwindle LED driving power volume, reduce LED driving power cost.

Described in this specification is preferred embodiment of the present utility model, and above embodiment is only in order to the technical solution of the utility model to be described but not to restriction of the present utility model.All those skilled in the art comply with design of the present utility model by the available technical scheme of logical analysis, reasoning, or a limited experiment, all should be within scope of the present utility model.

Claims

1. An LED drive circuit with full-period sampling of inductance current, used to realize LED constant current drive, comprising a rectifier bridge connected to an input AC voltage, an LED load, and the LED load is connected with an inductor (L1), an A power switch (M1) and a sampling resistor (R4) are connected in parallel with a filter capacitor (C1), characterized in that the LED drive circuit is based on the current flowing through the inductor (L1) when the power switch (M1) is turned on and off signal, through a loop control circuit to turn off the power switch (M1); the LED drive circuit turns on the power switch (M1) according to the demagnetization time of the inductor (L1); the loop control circuit Including: a sawtooth wave generator, an error amplifier, a comparator and an integrating capacitor C3; the current signal of the inductor (L1) is converted into a voltage signal (CS) through the sampling resistor (R4), and the voltage signal (CS) is connected to the input terminal of the error amplifier, the output signal of the error amplifier is converted into a DC voltage signal (COMP) through the integrating capacitor (C3), and the output terminal of the error amplifier is connected to the comparator The negative input terminal of the comparator is connected to the negative input terminal of the comparator, and the positive input terminal of the comparator is connected to the sawtooth wave generator. When the voltage of the sawtooth wave generator is greater than the DC voltage signal (COMP), the power switch ( M1).

2. The LED drive circuit for full cycle sampling of inductor current as claimed in claim 1, wherein said loop control circuit further comprises a logic controller, the input terminal of said logic controller is connected to said comparator connected to control the power switch (M1) according to the output value of the comparator.

3. The LED drive circuit for full-cycle sampling of inductor current according to claim 1, characterized in that, the LED drive circuit further comprises a power supply circuit, and the power supply circuit comprises a power supply diode (D2) and a power supply resistor ( R5), when the power switch (M1) is turned off, it supplies power to the LED driving circuit through the power supply diode (D2) and the power supply resistor (R5).

4. The LED drive circuit for full-cycle sampling of inductor current according to claim 1, characterized in that, when the power switch (M1) is turned off, the freewheeling diode D1 connected to the sampling resistor (R4) is turned on, and when When the freewheeling diode D1 is turned on, the demagnetization detection sampling resistors R2 and R3 connected to the inductor (L1) sample the demagnetization time of the inductor (L1), and when the demagnetization time of the inductor (L1) ends, The demagnetization detection module connected to the demagnetization detection sampling resistors R2 and R3 detects the end of demagnetization, and the demagnetization detection module controls the power switch (M1) to be turned on.

5. The LED drive circuit for full-cycle sampling of inductor current according to claim 1, characterized in that, the LED drive circuit further includes a resistor (R1) and a capacitor (C2) to provide starting power for the LED drive, One end of the resistor (R1) is connected to the rectifier bridge, the other end is connected to the capacitor (C2), and the other end of the capacitor (C2) is grounded.