Programmable stroboflash-free LED backlight driving circuit

Abstract

The utility model discloses a programmable stroboflash-free LED backlight drive circuit, which comprises a phase inverter INV1, a phase inverter INV2, a resistor R1, a resistor R2, a capacitor C1, a capacitor C2, an amplifier OP1, an amplifier OP2, a multi-bit decoder, an MOS tube MP1, an MOS tube MP2, an MOS tube MN1 and an LED, the input end of the phase inverter INV1 is connected with a PWM signal, the output end of the phase inverter INV1 is connected with the input end of the phase inverter INV2, and the output end of the phase inverter INV1 is connected with a resistor R11. The programmable stroboflash-free LED backlight driving circuit adopts a full-range linear dimming mode, realizes slow dimming, no stroboflash and programmable setting of driving current, and can freely set the maximum LED driving current according to different application requirements, so that the application is more flexible.

Description

TECHNICAL FIELD

[0001] The utility model relates to LED technical field, especially in a kind of programmable no stroboscopic LED backlight drive circuit. BACKGROUND

[0002] In display unit such as mobile phone, television, display, LED backlight driver needs to be used.Ideal situation, we hope that display brightness has stable linear gradient display effect in dark to bright full range.Traditional PWM dimming technology, in low bright (that is, low gray condition) condition, will due to the current in 10KHz~1MHz range of output current channel PWM adjustment and make stroboscopic phenomenon more obvious.

[0003] Current traditional dimming mode is to add PMOS ( Figure 1 left half side is close to VCC end) or NMOS ( Figure 1 right half side is placed near GND end) in rear stage (LED output stage), and the conduction and turn-off of LED current are realized by controlling the opening and closing of the above PMOS / NMOS through PWM signal, and finally the average current is obtained to determine the brightness of LED. INVENTION CONTENTS

[0004] In order to make up for the deficiency of the prior art, the application provides a programmable no stroboscopic LED backlight drive circuit to solve the problems in the prior art.

[0005] In order to solve the above technical problems, the utility model provides the following technical scheme:

[0006] The programmable stroboscopic-free LED backlight driving circuit comprises an inverter INV1, an inverter INV2, a resistor R1, a resistor R2, a capacitor C1, a capacitor C2, an amplifier OP1, an amplifier OP2, a multi-bit decoder, a MOS transistor MP1, a MOS transistor MP2, a MOS transistor MN1 and an LED, an input end of the inverter INV1 is connected with a PWM signal, an output end of the inverter INV1 is connected with an input end of the inverter INV2, an output end of the inverter INV1 is connected with a resistor R11, the other end of the resistor R11 is connected with a resistor R12 and a capacitor C1, the other end of the resistor R12 is connected with a capacitor C2 and an input end of the amplifier OP1, the other end of the capacitor C1 is grounded, the other end of the capacitor C2 is grounded, an output end of the amplifier OP1 is connected with a capacitor C3 and a non-inverting input end of the amplifier OP2, an output end of the amplifier OP2 is connected with a gate of the MOS transistor MN1, a drain of the MOS transistor MN1 is connected with a drain of the MOS transistor MP1, a gate of the MOS transistor MP1 and a gate of the MOS transistor MP2, a source of the MOS transistor MP1 is connected with a source of the MOS transistor MP2 and a power supply VCC, a drain of the MOS transistor MP2 is connected with the LED lamp, the other end of the LED lamp is grounded, a source of the MOS transistor MN1 is connected with an inverting input end of the amplifier OP2 and a resistor string, the resistor string is composed of a plurality of resistors R1-Rn connected in series, each resistor is connected with a MOS transistor in parallel at both ends, and the gate of each MOS transistor is connected with an output interface of the multi-bit decoder.

[0007] As a further technical scheme of the utility model: the MOS transistor MP1 is a P-MOS transistor.

[0008] As a further technical scheme of the utility model: the MOS transistor MP2 is a P-MOS transistor.

[0009] As a further technical scheme of the utility model: the MOS transistor MN1 is an N-MOS transistor.

[0010] As a further technical scheme of the utility model: the MOS transistor connected in parallel at both ends of the resistor R1-Rn is an N-MOS transistor.

[0011] One or more technical schemes provided in the embodiment of the application have at least the following technical effects or advantages:

[0012] The programmable stroboscopic-free LED backlight driving circuit adopts a full-range linear dimming mode, realizes slow-varying dimming, is free of stroboscopic, and can be programmed to set a driving current, so that the application is more flexible. BRIEF DESCRIPTION OF DRAWINGS

[0013] Figure 1 It is a circuit diagram of prior art.

[0014] Figure 2 This is the overall circuit diagram of this utility model. Detailed Implementation

[0015] The technical solutions in the embodiments of this utility model will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this utility model, and not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model.

[0016] like Figure 1 As shown, a programmable flicker-free LED backlight driving circuit includes inverters INV1 and INV2, resistors R1 and R2, capacitors C1 and C2, amplifiers OP1 and OP2, a multi-bit decoder, MOSFETs MP1, MP2, and MN1, and an LED. The input terminal of inverter INV1 is connected to a PWM signal, and the output terminal of inverter INV1 is connected to the input terminal of inverter INV2. The output terminal of inverter INV1 is connected to resistor R11, the other end of resistor R11 is connected to resistor R12 and capacitor C1, the other end of resistor R12 is connected to capacitor C2 and the input terminal of amplifier OP1, and the other end of capacitor C1 and capacitor C2 are grounded. The output of amplifier OP1 is connected to capacitor C3 and the non-inverting input of amplifier OP2. The output of amplifier OP2 is connected to the gate of MOSFET MN1. The drain of MOSFET MN1 is connected to the drain of MOSFET MP1, the gate of MOSFET MP1, and the gate of MOSFET MP2. The source of MOSFET MP1 is connected to the source of MOSFET MP2 and the power supply VCC. The drain of MOSFET MP2 is connected to an LED, and the other end of the LED is grounded. The source of MOSFET MN1 is connected to the inverting input of amplifier OP2 and a resistor string. The resistor string consists of multiple resistors R1-Rn connected in series, with a MOSFET connected in parallel across each resistor. The gate of each MOSFET is connected to the output interface of a multi-channel decoder. MOSFET MP1 is a P-MOSFET. MOSFET MP2 is a P-MOSFET. MOSFET MN1 is an N-MOSFET. The MOSFET connected in parallel across resistors R1-Rn is an N-MOSFET.

[0017] The working principle is as follows:

[0018] First, the PWM signal is input and filtered into a smooth DC voltage signal after passing through a two-stage RC network. Then, it is regulated and enhanced by a first-stage buffer to obtain the final V. DC This voltage is used as a reference voltage for setting the LED current in subsequent stages.

[0019] The formula for calculating LED current is as follows: Iref = V DCR, I LED = N*Iref, the resistance R in the public show is the final resistance value after programming selection, the resistance value is selected in the following content. N is the mirror ratio of the current mirror, that is, the current amplification multiple, assuming that the Iref current is 1mA, the mirror ratio is 100, then the final output stage LED current is 100mA, the resistance for setting the LED current is programmable, which is a decoder, input n-bit programmable bits, output 2 n Decoding signals are used to set the resistance R, thereby setting the LED current.

[0020] The LED drive can be applied in LED lighting, LED backlight, LED display direct drive three application fields.

[0021] The patent technology is mainly applied to the LED backlight field, which is very sensitive to stroboscopic and directly affects the display effect. The patent technology abandons the traditional end (output stage) PMW direct dimming mode, and solves the root cause of stroboscopic from the physical layer, and improves the display effect.

[0022] The utility model adopts internal programmable way to set the maximum LED current (Imax), instead of using the mode of setting the resistance outside the chip.

[0023] The mode of setting the maximum LED current by external resistance needs to select the corresponding required resistance value for each different requirement, which is a restrictive factor for mass application development and sales;

[0024] The internal programmable design of the chip can internally embed wide range resistors in the chip, and the programmable selection is realized through the internal soft switch of the chip, and the design can be carried out according to the accuracy requirement, more programmable bit positions can be set for high accuracy requirement. Low precision requirement only needs a small amount of bit positions, which is very flexible, and the influence on cost can be ignored. This design no longer needs different users to select and match resistors to set the LED current. In general, this mode can obtain better performance, and the cost can be flexibly controlled according to the actual requirement.

[0025] The design adopts the front-stage dimming mechanism, and abandons the rear-stage (output stage) dimming mode. The output current does not appear 0-Imax mutation (Imax refers to the maximum value of the LED current), but changes between 0-Imax, so the display flicker (stroboscopic) phenomenon does not appear. The display quality and effect can be fundamentally improved and improved.

[0026] The design adopts programmable design, can set arbitrary bit selection bit, suppose setting 3bit (CTRL1, CTRL2, CTRL3) programmable selection bit, can realize 8 kinds of Imax (respectively corresponding: 000, 001, 010, 011, 100, 101, 110, 111). According to application requirement, also can set 2bit, 4bit or other more bit. This kind of soft switch programmable mode can save the common selection different external resistance to realize maximum LED current Imax setting mode, simplify peripheral circuit, reduce BOM cost, application is more flexible.

[0027] It is obvious for those skilled in the art that the present application is not limited to the details of the above exemplary embodiments, and the present application can be implemented in other specific forms without departing from the spirit or essential characteristics of the present application. Therefore, the embodiments should be regarded as exemplary and non-limiting, and the scope of the present application is defined by the appended claims rather than the above description, and all changes falling within the meaning and range of equivalent elements of the claims are intended to be included in the present application.

[0028] In addition, it should be understood that, although the present application is described in terms of embodiments, not every embodiment contains only one independent technical solution, and the description of the present application is only for the sake of clarity, and those skilled in the art should consider the present application as a whole, and the technical solutions in each embodiment have been properly combined to form other embodiments which are easily understood by those skilled in the art.

Claims

1. A programmable flicker-free LED backlight driving circuit, comprising inverter INV1, inverter INV2, resistor R1, resistor R2, capacitor C1, capacitor C2, amplifier OP1, amplifier OP2, multi-bit decoder, MOSFET MP1, MOSFET MP2, MOSFET MN1, and LED, characterized in that: The input terminal of inverter INV1 is connected to a PWM signal, and the output terminal of inverter INV1 is connected to the input terminal of inverter INV2. The output terminal of inverter INV1 is connected to resistor R11, the other end of resistor R11 is connected to resistor R12 and capacitor C1, the other end of resistor R12 is connected to capacitor C2 and the input terminal of amplifier OP1, the other end of capacitor C1 is grounded, the other end of capacitor C2 is grounded, the output terminal of amplifier OP1 is connected to capacitor C3 and the non-inverting input terminal of amplifier OP2, and the output terminal of amplifier OP2 is connected to the gate of MOSFET MN1. The drain of MOSFET MN1 is connected to the drain of MOSFET MP1, the gate of MOSFET MP1, and the gate of MOSFET MP2. The source of MOSFET MP1 is connected to the source of MOSFET MP2 and the power supply VCC. The drain of MOSFET MP2 is connected to an LED, and the other end of the LED is grounded. The source of MOSFET MN1 is connected to the inverting input of amplifier OP2 and a resistor string. The resistor string consists of multiple resistors R1-Rn connected in series, with a MOSFET connected in parallel across each resistor. The gate of each MOSFET is connected to the output interface of a multi-channel decoder.

2. The programmable flicker-free LED backlight driving circuit according to claim 1, characterized in that, The MOS transistor MP1 is a P-MOS transistor.

3. The programmable flicker-free LED backlight driving circuit according to claim 1, characterized in that, The MOS transistor MP2 is a P-MOS transistor.

4. The programmable flicker-free LED backlight driving circuit according to claim 1, characterized in that, The MOS transistor MN1 is an N-MOS transistor.

5. A programmable flicker-free LED backlight driving circuit according to claim 2, characterized in that, The MOS transistor connected in parallel across resistors R1-Rn is an N-MOS transistor.

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