CN105517272A - Backlighting self-adaption circuit - Google Patents

Abstract

The invention relates to a backlighting self-adaption circuit, in particular to a backlighting self-adaption circuit. The circuit comprises a duty ratio adjustable control circuit and an LED drive circuit. The duty ratio adjustable control circuit is used for achieving adjusting and outputting of a duty ratio by adjusting a PWM signal according to effects on a photoresistance imposed by external light. The LED drive circuit is used for accessing the PWM signal and then achieving dimming of an LED according to the PWM signal. By adjusting the duty ratio via the effects on the photoresistance imposed by the external light and accessing the PWM signal with the variable duty ratio to the LED drive circuit to achieve LED adjustment, the LED backlighting brightness can be automatically adjusted according to brightness of the external ambience light, thereby achieving an energy-saving effect.

Description

A kind of back lighting adaptive circuit

Technical field

The present invention relates to Anesthesia machine technical field, particularly relate to a kind of back lighting adaptive circuit.

Background technology

Along with the development of social electronic technology, the LED scope of application is more and more wider, and the back lighting of anesthesia machine system also generally adopts LED illumination, but existing LED illumination control precision is low, voltage range is little, efficiency is low, and loss is large, and heat dissipation capacity is large, useful life is short, brightness can not regulate along with the light luminance of environment, can not respond energy-saving and emission-reduction, and the society of innovation and development calls.

Summary of the invention

For the defect of above-mentioned existing backlight illuminating system, object of the present invention overcomes above-mentioned shortcoming and defect exactly, provides a kind of back lighting adaptive circuit.

A kind of back lighting adaptive circuit, comprising:

Duty ratio adjustable control circuit and LED drive circuit;

Described duty ratio adjustable control circuit, for realizing the adjustment of duty ratio and export the impact of photo resistance by regulating pwm signal according to extraneous light intensity;

Described LED drive circuit, to realize the light modulation of LED according to the duty ratio of pwm signal for accessing pwm signal.

Preferably, the adjustable control circuit of described duty ratio comprises:

Resistance R1-R2, photo resistance Rp, electric capacity C1-C2, rectifier diode D1-D3, chip U1, wherein, the pin GND of chip U1 respectively with one end of electric capacity C1, one end of electric capacity C2, the first input end of LED drive circuit, second input of LED drive circuit, ground connects, the pin TRI of chip U1 respectively with the negative electrode of rectifier diode D3, the anode of rectifier diode D2, the other end of electric capacity C1, the pin THR of chip U1 connects, and the pin OUT of chip U1 is connected with the 3rd input of LED drive circuit, the pin RES of chip U1 respectively with one end of resistance R1, 5V power supply, the pin VCC of chip U1 connects, the pin DIS of chip U1 respectively with the adjustable side of photo resistance Rp, the anode of rectifier diode D3 connects, and the pin CON of chip U1 is connected with the other end of electric capacity C2, the other end of resistance R1 respectively with one end of resistance R2, one end of photo resistance Rp connects, and the other end of resistance R2 is connected with the anode of rectifier diode D1, the negative electrode of rectifier diode D1 respectively with the other end of photo resistance Rp, the negative electrode of rectifier diode D2 connects.

Preferably, described LED drive circuit comprises:

Chip U2, resistance R3, electric capacity C3-C4, inductance L 1, LED, Schottky diode D4, wherein, the pin VIN of chip U2 respectively with the negative electrode of Schottky diode D4, electric capacity C4 positive pole, one end of resistance R3, power supply VCC connects, the pin CSN of chip U2 respectively with the other end of resistance R3, the anode of LED, the positive pole of electric capacity C3 connects, the pin DIM of chip U2 is the 3rd input of LED drive circuit, the pin GND of chip U2 is the second input of LED drive circuit, the pin SW of chip U2 respectively with the anode of Schottky diode D4, one end of inductance L 1 connects, the other end of inductance L 1 respectively with the negative pole of electric capacity C3, the negative electrode of LED connects, the negative pole of electric capacity C4 is the first input end of LED drive circuit.

Preferably, the average current of described LED is:

$I_{\mathrm{OUT}}=\frac{0.1D}{R3},(0\mathrm{\&delta;D\&delta;}100\%,2.5V<V_{\mathrm{pulse}}<5V);$

$I_{\mathrm{OUT}}=\frac{V_{\mathrm{pulse}}0.1D}{2.5R3},(0\mathrm{\&delta;D\&delta;}100\%,0.5V<V_{\mathrm{pulse}}<2.5V);$

Wherein, D represents the duty ratio of pwm signal, V _pulserepresent the pulse voltage amplitude of pwm signal, R3 represents the resistance of resistance R3.

Preferably, the computing formula of described duty ratio is:

wherein, R1 represents the resistance of resistance R1, R _p', R _{p "}represent the resistance of the photo resistance under different extraneous light intensity respectively.

Preferably, the output frequency computing formula of described pwm signal is:

F=1.4331 (2R1+R _p'+ R _{p "}) C1, wherein, R1 represents the resistance of resistance R1, R _p', R _{p "}represent the resistance of the photo resistance under different extraneous light intensity respectively, C1 represents the value of electric capacity C1.

Back lighting adaptive circuit of the present invention, circuit comprises duty ratio adjustable control circuit and LED drive circuit; Duty ratio adjustable control circuit, for realizing the adjustment of duty ratio and export the impact of photo resistance by regulating pwm signal according to extraneous light intensity; LED drive circuit, to realize the light modulation of LED according to the duty ratio of pwm signal for accessing pwm signal.By extraneous light, the impact of photo resistance is regulated to the duty ratio of pwm signal, realize LED at the pwm signal of LED drive circuit access variable duty ratio and regulate, LED-backlit brightness of illumination, according to the automatic brightness adjustment of external environment light, reaches energy-conservation effect.

Accompanying drawing explanation

Fig. 1 is the frame principle figure of the back lighting adaptive circuit that the embodiment of the present invention provides.

Fig. 2 is the circuit diagram of the back lighting adaptive circuit that the embodiment of the present invention provides.

Embodiment

In order to make object of the present invention, technical scheme and advantage clearly understand, below in conjunction with drawings and Examples, the present invention is further elaborated.Should be appreciated that specific embodiment described herein only in order to explain the present invention, be not intended to limit the present invention.

Fig. 1 shows the frame principle figure of a kind of back lighting adaptive circuit that the embodiment of the present invention provides, and circuit comprises:

Duty ratio adjustable control circuit and LED drive circuit;

Duty ratio adjustable control circuit, for realizing the adjustment of duty ratio and export the impact of photo resistance by regulating pwm signal according to extraneous light intensity;

LED drive circuit, to realize the light modulation of LED according to the duty ratio of pwm signal for accessing pwm signal.

Fig. 2 shows the circuit diagram of a kind of back lighting adaptive circuit that the embodiment of the present invention provides, and details are as follows:

The adjustable control circuit of duty ratio comprises:

Resistance R1-R2, photo resistance Rp, electric capacity C1-C2, rectifier diode D1-D3, chip U1, wherein, the pin GND of chip U1 respectively with one end of electric capacity C1, one end of electric capacity C2, the first input end of LED drive circuit, second input of LED drive circuit, ground connects, the pin TRI of chip U1 respectively with the negative electrode of rectifier diode D3, the anode of rectifier diode D2, the other end of electric capacity C1, the pin THR of chip U1 connects, and the pin OUT of chip U1 is connected with the 3rd input of LED drive circuit, the pin RES of chip U1 respectively with one end of resistance R1, 5V power supply, the pin VCC of chip U1 connects, the pin DIS of chip U1 respectively with the adjustable side of photo resistance Rp, the anode of rectifier diode D3 connects, and the pin CON of chip U1 is connected with the other end of electric capacity C2, the other end of resistance R1 respectively with one end of resistance R2, one end of photo resistance Rp connects, and the other end of resistance R2 is connected with the anode of rectifier diode D1, the negative electrode of rectifier diode D1 respectively with the other end of photo resistance Rp, the negative electrode of rectifier diode D2 connects.

In embodiments of the present invention, chip U1 is LM555 time-base circuit.

Described LED drive circuit comprises:

Chip U2, resistance R3, electric capacity C3-C4, inductance L 1, LED, Schottky diode D4, wherein, the pin VIN of chip U2 respectively with the negative electrode of Schottky diode D4, electric capacity C4 positive pole, one end of resistance R3, power supply VCC connects, the pin CSN of chip U2 respectively with the other end of resistance R3, the anode of LED, the positive pole of electric capacity C3 connects, the pin DIM of chip U2 is the 3rd input of LED drive circuit, the pin GND of chip U2 is the second input of LED drive circuit, the pin SW of chip U2 respectively with the anode of Schottky diode D4, one end of inductance L 1 connects, the other end of inductance L 1 respectively with the negative pole of electric capacity C3, the negative electrode of LED connects, the negative pole of electric capacity C4 is the first input end of LED drive circuit.

In embodiments of the present invention, the self-defined first input end of LED drive circuit, the second input and the 3rd input, be respectively the negative pole of electric capacity C4, the pin GND of chip U2, the pin DIM of chip U2.Wherein, the model of chip U2 is the voltage-dropping type constant-current LED controller that PT4145, PT4115 and inductance L 1, resistance R3 form a free-running continuous inductive current pattern.Resistance R3 is current sampling resistor, and when VIN powers on, the initial current of inductance L 1 and resistance R3 is zero, and LED output current is also zero.At this time, the output of CSN comparator is high, and the conducting of internal power interrupteur SW, the current potential of SW is low.Electric current is by inductance L 1, resistance R3, LED and internal power interrupteur SW flow to ground from VIN, the slope that electric current rises is by VIN, inductance L 1 and LED pressure drop determine, resistance R3 produces a pressure reduction VCSN, as (VIN-VCSN) >115mV, the output step-down of CSN comparator, internal power interrupteur SW turns off, electric current flows through inductance L 1 with another slope, resistance R3, LED and Schottky diode D4, as (VIN-VCSN) <85mV, the conducting again of internal power interrupteur SW, the average current on LED is made to be like this:

$I_{\mathrm{OUT}}=\frac{0.085+0.115}{2R3}=\frac{0.1}{R3}.$

In embodiments of the present invention, adopt PT4145 as LED drive circuit, PT4115 is the step-down constant-current source of a continuous inductive current conduction mode, there is the input voltage 6V-30V of wide region, few peripheral circuit number, adopt the sampling resistor of 1% precision, LED output current controls the precision ± 5%, efficiency is up to 97%, high-power driving can the more LED of load, in addition, inside has open circuit protecting function, load is once open circuit, pin SW is in vacant state, PT4145 will be arranged at safe low-power mode, therefore, during LED load open circuit, LED and PT4145 are safe, normal operating state is entered after load reconnects.In addition, light modulation is realized by pwm signal, the maximum average current of LED is determined by the resistance R3 being connected to pin VIN and pin CSN two ends, LED switch, simulation light modulation and PWM light modulation is carried out by multiplexing pins DIM, pin DIM add variable duty ratio pwm signal can regulation output electric current to realize light modulation, computational methods are as follows:

If pwm signal pulse voltage amplitude is greater than 2.5V, then:

$I_{\mathrm{OUT}}=\frac{0.1D}{R3},(0\mathrm{\&delta;D\&delta;}100\%,2.5V<V_{\mathrm{pulse}}<5V);$

If pwm signal pulse voltage amplitude is less than 2.5V, then:

$I_{\mathrm{OUT}}=\frac{V_{\mathrm{pulse}}0.1D}{2.5R3},(0\mathrm{\&delta;D\&delta;}100\%,0.5V<V_{\mathrm{pulse}}<2.5V);$

Wherein, D represents the duty ratio of pwm signal, V _pulserepresent pwm signal pulse voltage amplitude, R3 represents the resistance of resistance R3.

In embodiments of the present invention, LM555 regulates duty ratio by photo resistance Rp, and realize FR adjustable duty ratio, in addition, the output frequency of LM555 is also adjustable, and computing formula is as follows:

wherein, R1 represents the resistance of resistance R1, R _p', R _{p "}represent the resistance of the photo resistance under different extraneous light intensity, C1 represents the value of electric capacity C1.

Output frequency the F=1.4331 [(R1+R of pwm signal _p')+(R1+R _{p "})] C1=1.4331 (2R1+R _p'+ R _{p "}) C1; Wherein, R1 represents the resistance of resistance R1, R _p', R _{p "}represent the resistance of the photo resistance under different extraneous light intensity, C1 represents the value of electric capacity C1.Therefore, output frequency is also adjustable.

The circuit of above-mentioned all modules is only an embodiment of this module, other circuit can also be taked to realize, be not limited to an above-mentioned embodiment.

Back lighting adaptive circuit of the present invention, circuit comprises duty ratio adjustable control circuit and LED drive circuit; Duty ratio adjustable control circuit, for realizing the adjustment of duty ratio and export the impact of photo resistance by regulating pwm signal according to extraneous light intensity; LED drive circuit, to realize the light modulation of LED according to the duty ratio of pwm signal for accessing pwm signal.By extraneous light, the impact of photo resistance is regulated to the duty ratio of pwm signal, realize LED at the pwm signal of LED drive circuit access variable duty ratio and regulate, LED-backlit brightness of illumination, according to the automatic brightness adjustment of external environment light, reaches energy-conservation effect.

Below know-why of the present invention is described in conjunction with specific embodiments.These describe just in order to explain principle of the present invention, and can not be interpreted as limiting the scope of the invention by any way.Based on explanation herein, those skilled in the art does not need to pay performing creative labour can associate other embodiment of the present invention, and these modes all will fall within protection scope of the present invention.

Claims (6)

1. a back lighting adaptive circuit, is characterized in that, comprising: duty ratio adjustable control circuit and LED drive circuit;

Described duty ratio adjustable control circuit, for realizing the adjustment of duty ratio and export the impact of photo resistance by regulating pwm signal according to extraneous light intensity;

Described LED drive circuit, to realize the light modulation of LED according to the duty ratio of pwm signal for accessing pwm signal.

2. back lighting adaptive circuit as claimed in claim 1, it is characterized in that, described duty ratio adjustable control circuit comprises:

Resistance R1-R2, photo resistance Rp, electric capacity C1-C2, rectifier diode D1-D3, chip U1, wherein, the pin GND of chip U1 respectively with one end of electric capacity C1, one end of electric capacity C2, the first input end of LED drive circuit, second input of LED drive circuit, ground connects, the pin TRI of chip U1 respectively with the negative electrode of rectifier diode D3, the anode of rectifier diode D2, the other end of electric capacity C1, the pin THR of chip U1 connects, and the pin OUT of chip U1 is connected with the 3rd input of LED drive circuit, the pin RES of chip U1 respectively with one end of resistance R1, 5V power supply, the pin VCC of chip U1 connects, the pin DIS of chip U1 respectively with the adjustable side of photo resistance Rp, the anode of rectifier diode D3 connects, and the pin CON of chip U1 is connected with the other end of electric capacity C2, the other end of resistance R1 respectively with one end of resistance R2, one end of photo resistance Rp connects, and the other end of resistance R2 is connected with the anode of rectifier diode D1, the negative electrode of rectifier diode D1 respectively with the other end of photo resistance Rp, the negative electrode of rectifier diode D2 connects.

3. back lighting adaptive circuit as claimed in claim 2, it is characterized in that, described LED drive circuit comprises:

Chip U2, resistance R3, electric capacity C3-C4, inductance L 1, LED, Schottky diode D4, wherein, the pin VIN of chip U2 respectively with the negative electrode of Schottky diode D4, electric capacity C4 positive pole, one end of resistance R3, power supply VCC connects, the pin CSN of chip U2 respectively with the other end of resistance R3, the anode of LED, the positive pole of electric capacity C3 connects, the pin DIM of chip U2 is the 3rd input of LED drive circuit, the pin GND of chip U2 is the second input of LED drive circuit, the pin SW of chip U2 respectively with the anode of Schottky diode D4, one end of inductance L 1 connects, the other end of inductance L 1 respectively with the negative pole of electric capacity C3, the negative electrode of LED connects, the negative pole of electric capacity C4 is the first input end of LED drive circuit.

4. back lighting adaptive circuit as claimed in claim 3, it is characterized in that, the average current of described LED is:

$I_{\mathrm{OUT}}=\frac{0.1D}{R3},(0\mathrm{\&delta;D\&delta;}100\%,2.5V<V_{\mathrm{pulse}}<5V);$

$I_{\mathrm{OUT}}=\frac{V_{\mathrm{pulse}}0.1D}{2.5R3},(0\mathrm{\&delta;D\&delta;}100\%,0.5V<V_{\mathrm{pulse}}<2.5V);$

Wherein, D represents the duty ratio of pwm signal, V _pulserepresent the pulse voltage amplitude of pwm signal, R3 represents the resistance of resistance R3.

5. back lighting adaptive circuit as claimed in claim 4, it is characterized in that, the computing formula of described duty ratio is:

wherein, R1 represents the resistance of resistance R1, R _p', R _{p "}represent the resistance of the photo resistance under different extraneous light intensity respectively.

6. back lighting adaptive circuit as claimed in claim 5, it is characterized in that, the output frequency computing formula of described pwm signal is:

F=1.4331 (2R1+R _p'+ R _{p "}) C1, wherein, R1 represents the resistance of resistance R1, R _p', R _{p "}represent the resistance of the photo resistance under different extraneous light intensity respectively, C1 represents the value of electric capacity C1.