CN216721633U

CN216721633U - LED backlight source driving circuit

Info

Publication number: CN216721633U
Application number: CN202122163890.6U
Authority: CN
Inventors: 张�浩; 黄马虎
Original assignee: Huizhou Goldman Sachs Light Display Technology Co ltd
Current assignee: Huizhou Goldman Sachs Light Display Technology Co ltd
Priority date: 2021-09-08
Filing date: 2021-09-08
Publication date: 2022-06-10
Anticipated expiration: 2031-09-08

Abstract

The utility model relates to the technical field of circuit design, and discloses an LED backlight source driving circuit which comprises a light source, an LED driving module and a voltage reduction conversion module, wherein the LED driving module comprises a first chip, an overvoltage protection unit, an overcurrent protection unit and a short-circuit protection unit; the voltage reduction conversion module comprises a second chip and a voltage reduction unit, the second chip is electrically connected with the light source, and the voltage reduction unit is electrically connected with the second chip; through the setting, can prevent heavy current breakdown in the twinkling of an eye effectively, wherein first chip adjusts luminance pulse signal through outside PWM and controls the output of light source, can adjust the state of light source according to individual comfort, through setting up step-down conversion module, can provide the power supply demand for overall circuit for voltage is more stable, thereby satisfies the long-time steady operation of light source, can not receive the interference fluctuation of voltage.

Description

LED backlight source driving circuit

Technical Field

The utility model relates to the technical field of circuit design, in particular to an LED backlight source driving circuit.

Background

At present, the products are all applied to the traditional technical reference to realize the control of the backlight source. Power is input to the conversion circuit, Power is supplied to the driving module after DC/DC conversion and boosting, the overvoltage circuit, the overcurrent circuit and the voltage stabilizing circuit are triggered simultaneously, then external pulse signals are input to the driving module, the time sequence of the driving module is internally modulated after receiving the signals, and the modulated output provides different currents for the LED lamp set, so that the control of the brightness of the backlight source is realized.

However, most of the above methods control the LED lamp set by resistance-capacitance voltage reduction, but in this case, the instantaneous current passing through the LED lamp set is large, which easily damages the driving module, and further, the LED lamp set at the present stage is greatly affected by the interference fluctuation of the grid voltage, thereby causing unstable working light emission of the LED lamp set.

SUMMERY OF THE UTILITY MODEL

The utility model aims to overcome the defects in the prior art and provide the LED backlight source driving circuit which can prevent the instantaneous current passing through the LED lamp set from being increased, thereby protecting the driving module and ensuring the stable voltage of the LED lamp set without being interfered by the voltage of a power grid.

The purpose of the utility model is realized by the following technical scheme:

an LED backlight driving circuit comprising:

a light source;

the LED driving module comprises a first chip, an overvoltage protection unit, an overcurrent protection unit and a short-circuit protection unit, wherein the first chip is electrically connected with the light source, and the overvoltage protection unit, the overcurrent protection unit and the short-circuit protection unit are respectively electrically connected with the first chip; and

the voltage reduction conversion module comprises a second chip and a voltage reduction unit, the second chip is electrically connected with the light source, and the voltage reduction unit is electrically connected with the second chip.

In one embodiment, the overvoltage protection unit includes a capacitor C523, a capacitor C522, a resistor R536, a resistor R535, and a diode D501, the capacitor C523 is electrically connected to one end of the capacitor C522, the other end of the capacitor C522 is electrically connected to one end of the resistor R536 and one end of the resistor R535, the other end of the resistor R536 is electrically connected to the diode D501, and the other end of the resistor R535 is electrically connected to the diode D501.

In one embodiment, the overvoltage protection unit further includes a resistor R521, a resistor R532 and a resistor R513, the resistor R521 is electrically connected to one end of the resistor R532, the other end of the resistor R532 is electrically connected to one end of the resistor R513, and the other end of the resistor R513 is electrically connected to the first chip.

In one embodiment, the overcurrent protection unit comprises a capacitor C519, a capacitor C509 and a MOS transistor Q501, wherein one end of the capacitor C519 is electrically connected with the MOS transistor Q501, and the other end of the capacitor C519 is electrically connected with the capacitor C509.

In one embodiment, the overcurrent protection unit further includes a resistor R524, a resistor R512, a resistor R515, a resistor R516, a resistor R517, a resistor R518, and a resistor R531, a first end of the resistor R524 is electrically connected to the capacitor C509, a second end of the resistor R524 is electrically connected to one end of the resistor R512 and one end of the resistor R515, respectively, one end of the resistor R512 is electrically connected to the capacitor C509, another end of the resistor R515 is electrically connected to one end of the resistor R516, another end of the resistor R516 is electrically connected to one end of the resistor R517, another end of the resistor R517 is electrically connected to the resistor R518 and the MOS transistor Q501, one end of the resistor R531 is electrically connected to the MOS transistor Q501, and another end of the resistor R531 is electrically connected to the first chip.

In one embodiment, the short-circuit protection unit includes a resistor R523, a resistor R520, and a capacitor C513, where the resistor R523 is electrically connected to one end of the resistor R520, the other end of the resistor R523 is electrically connected to one end of the capacitor C513 and the first chip, the other end of the resistor R520 is grounded, and the other end of the capacitor C513 is grounded.

In one embodiment, the voltage dropping unit includes a resistor R924, a resistor R925, an inductor L901, and a capacitor C917, one end of the resistor R924 is electrically connected to one end of the resistor R925, the other end of the resistor R924 is electrically connected to one end of the inductor L901 and one end of the capacitor C917, respectively, the other end of the inductor L901 is electrically connected to the second chip, and the other end of the capacitor C917 is grounded.

In one embodiment, the voltage reduction unit further includes a capacitor C919, a resistor R929, a resistor R920, and a capacitor C924, one end of the capacitor C919 is electrically connected to one end of the resistor R929, the other end of the capacitor C919 is grounded, the other end of the resistor R929 is electrically connected to one end of the resistor R920, the other end of the resistor R920 is electrically connected to one end of the capacitor C924, and the other end of the capacitor C924 is electrically connected to the second chip.

Compared with the prior art, the utility model has the following advantages and beneficial effects:

the utility model relates to an LED backlight source driving circuit which can effectively prevent instantaneous large current breakdown by arranging a first chip, an overvoltage protection unit, an overcurrent protection unit and a short-circuit protection unit, wherein the first chip controls the output state of a light source through an external PWM dimming pulse signal, the light source effectively protects a dimming output circuit, and a voltage reduction conversion module is arranged to provide power supply requirements for the whole circuit, so that the voltage is more stable, the long-time stable work of the light source is met, and the light source cannot be interfered by voltage fluctuation.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present invention and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained according to the drawings without inventive efforts.

FIG. 1 is a functional block diagram of an LED backlight driver circuit according to an embodiment of the present invention;

fig. 2 is a circuit diagram of an LED driving module according to an embodiment of the utility model;

fig. 3 is a circuit diagram of a buck conversion module according to an embodiment of the utility model.

Detailed Description

To facilitate an understanding of the utility model, the utility model will now be described more fully with reference to the accompanying drawings. Preferred embodiments of the present invention are shown in the drawings. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

It will be understood that when an element is referred to as being "secured to" another element, it can be directly on the other element or intervening elements may also be present. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements may also be present. The terms "vertical," "horizontal," "left," "right," and the like as used herein are for illustrative purposes only and do not represent the only embodiments.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used herein in the description of the utility model is for the purpose of describing particular embodiments only and is not intended to be limiting of the utility model. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

Referring to fig. 1, in an embodiment, an LED backlight driving circuit 10 includes a light source 100, an LED driving module 200, and a step-down conversion module 300, where the light source 100 is an LED lamp module backlight, the LED driving module 200 is used to control an output state, so as to protect a dimming output circuit, and the step-down conversion module 300 is used to provide a stable working voltage for an entire circuit, so as to prevent an interference signal from being mixed into the circuit.

Referring to fig. 1, the LED driving module 200 includes a first chip, an overvoltage protection unit, an overcurrent protection unit, and a short-circuit protection unit, the first chip is electrically connected to the light source, and the overvoltage protection unit, the overcurrent protection unit, and the short-circuit protection unit are respectively electrically connected to the first chip; the voltage-reducing conversion module 300 includes a second chip electrically connected to the light source and a voltage-reducing unit electrically connected to the second chip. It should be noted that the model of first chip is BD9479FV, the model of second chip is EUP3482, through setting up first chip, overvoltage protection unit, overcurrent protection unit and short-circuit protection unit, can prevent the heavy current breakdown in the twinkling of an eye effectively, wherein first chip adjusts luminance the output state that pulse signal controlled the light source through outside PWM, effectual light source protection adjusts luminance output circuit, through setting up step-down conversion module, can provide the power supply demand for whole circuit, make voltage more stable, thereby satisfy the long-time stable work of light source, can not receive the interference fluctuation of voltage.

The specific circuit working principle is as follows: after the DC +24V voltage is input, the output is divided into two paths: the DC-DC boosting voltage of 65V and the DC-DC reducing voltage of 12V are output by the power module after passing through the transformer, and then the 65V voltage is supplied to the LED lamp module for power supply work, so that the LED lamp module can stably work for a long time; the 12V voltage is synchronously output by the EUP3482 through voltage reduction and conversion, can carry current for driving the whole circuit, supplies power to the dimming drive control MCU, and controls and processes the whole circuit, so that the control of the LED lamp backlight circuit is realized. The dimming drive control MCU is the core of the whole circuit, the high-efficiency LED driver is specially used for controlling and processing a large-scale LED array, 16+ paths of output can be controlled, and the built-in DC-DC constant current driver can provide signal processing for the LED lamp module. The independent PWM channel can be used for single-path dimming control, the LED short-circuit protection and overvoltage and overcurrent protection functions are started to operate simultaneously, and the abnormal condition of the circuit is detected at any time. And DC +24V is input into the DC-DC circuit for boosting, and 65V voltage is output after boosting and supplied to the output end of the LED lamp module for power supply work, so that the normal power-on operation of the LED lamp module is ensured. DC +24V is synchronously reduced and transmitted to a REG50 Pin of a BD9479FV through EUP3482, so that each Pin of a driver has reference voltage to work, an LSP Pin is connected with VIN input, and LED short circuit detection is sensed at the first time; the UVOL pin detection voltage is lower than 3V, automatic gain boosting is achieved, and the BD9479FV is prevented from being in unbalanced operation due to insufficient voltage. The SS pin sets soft start time and duration, waits for the whole amplitude process of a PWM signal, increases the voltage of the FB pin when the voltage rises, does not depend on a signal of a PWM dimming duty ratio, controls the output of a built-in differential amplifier by the FB pin, and controls the output of a BS1 pin by detecting the amplitude of the voltage; the DC-DC current detection CS pin has an overcurrent protection function, and when the voltage drop of a switch tube externally connected is higher than 0.4V, the switching operation is forcibly stopped; the OVP is used as an overvoltage short-circuit protection function and is connected with a VBL input circuit for monitoring and detection, the CP end starts to charge when the voltage is higher than 2.25V, and the voltage output is controlled by the OVP when the voltage exceeds 2.5V; when the BD9479FV driver chip is powered on to work, the CP terminal starts to synchronously detect the circuit voltage, when abnormal voltage is detected, the CP pin starts to charge the peripheral capacitor first, the chip stops working when the voltage exceeds 2.5V, the driving voltage gradually decreases, and the FAIL pin outputs a signal. The PWM signal is transmitted to a conversion circuit to modulate the width of a series of pulses, a sine waveform is equivalently output and is transmitted to a PWM pin of a dimming drive control MCU, BD9479FV carries out internal modulation according to a PWM pulse width duty ratio signal, a differential amplifier inside the PWM signal is controlled by a pulse width duty cycle time sequence to carry out comparison, and the PWM signal is transmitted to a peripheral MOS tube and a voltage stabilizing diode by a BS end and an XL end to carry out amplitude limiting output, so that the light and dark switching control of a light source is realized. The current output by the dimming drive control MCU can be controlled by adjusting the duty cycle of the input PWM signal, so that the brightness of the light source lamp module is controlled.

Referring to fig. 2, preferably, the overvoltage protection unit includes a capacitor C523, a capacitor C522, a resistor R536, a resistor R535, and a diode D501, the capacitor C523 is electrically connected to one end of the capacitor C522, another end of the capacitor C522 is electrically connected to one end of the resistor R536 and one end of the resistor R535, another end of the resistor R536 is electrically connected to the diode D501, and another end of the resistor R535 is electrically connected to the diode D501. Still preferably, the overvoltage protection unit further includes a resistor R521, a resistor R532, and a resistor R513, where the resistor R521 is electrically connected to one end of the resistor R532, the other end of the resistor R532 is electrically connected to one end of the resistor R513, and the other end of the resistor R513 is electrically connected to the first chip. The voltage of + DC24 is filtered by a capacitor of the power module, and output VBL1 to the driving output module through a transformer, and then the voltage of VBL1 is coupled by a capacitor C522 and a capacitor C523 and limited by a diode D501, the alternating current high-frequency interference is filtered by a capacitor C506 and released to the ground, and the voltage is subjected to precise voltage division by a resistor, secondary filtering by a capacitor C520, and finally fed back to the 5 pin of the first chip BD9479FV, and compared and detected with the reference voltage of the built-in voltage comparator.

Referring to fig. 2, in an embodiment, the over-current protection unit includes a capacitor C519, a capacitor C509, and a MOS transistor Q501, one end of the capacitor C519 is electrically connected to the MOS transistor Q501, and the other end of the capacitor C519 is electrically connected to the capacitor C509. Specifically, the overcurrent protection unit further includes a resistor R524, a resistor R512, a resistor R515, a resistor R516, a resistor R517, a resistor R518, and a resistor R531, a first end of the resistor R524 is electrically connected to the capacitor C509, a second end of the resistor R524 is electrically connected to one end of the resistor R512 and one end of the resistor R515, one end of the resistor R512 is electrically connected to the capacitor C509, the other end of the resistor R515 is electrically connected to one end of the resistor R516, the other end of the resistor R516 is electrically connected to one end of the resistor R517, the other end of the resistor R517 is electrically connected to the resistor R518 and the MOS transistor Q501, one end of the resistor R531 is electrically connected to the MOS transistor Q501, and the other end of the resistor R531 is electrically connected to the first chip. It should be noted that the VBL1 voltage is coupled through the capacitor C519 and the capacitor C509, and then is provided to the source of the MOS transistor Q501 through a plurality of resistors, where the plurality of resistors are used to prevent the transient current during power-on and power-on from being too high, and directly break down the MOS transistor to damage the circuit to normally operate, the source of the MOS transistor Q501 is provided to the 4-pin CS of the first chip BD9479FV through the secondary protection of the resistor R531, and besides, the capacitor C517 serves as a detection voltage point of the overcurrent protection unit.

Referring to fig. 2, in an embodiment, the short-circuit protection unit includes a resistor R523, a resistor R520, and a capacitor C513, wherein the resistor R523 is electrically connected to one end of the resistor R520, the other end of the resistor R523 is electrically connected to one end of the capacitor C513 and the first chip, the other end of the resistor R520 is grounded, and the other end of the capacitor C513 is grounded. It should be noted that the BSx pin controls the triode to drive the output of the on-load LED lamp module, when the voltage is higher than 9V, the LED detects a short circuit, the LSP pin is in an open state, and 0.3V to 3.0V to LSP pin are input, thereby protecting the circuit.

Referring to fig. 3, in an embodiment, the voltage dropping unit includes a resistor R924, a resistor R925, an inductor L901, and a capacitor C917, one end of the resistor R924 is electrically connected to one end of the resistor R925, the other end of the resistor R924 is electrically connected to one end of the inductor L901 and one end of the capacitor C917, respectively, the other end of the inductor L901 is electrically connected to the second chip, and the other end of the capacitor C917 is grounded. Specifically, the voltage reduction unit further includes a capacitor C919, a resistor R929, a resistor R920 and a capacitor C924, one end of the capacitor C919 is electrically connected to one end of the resistor R929, the other end of the capacitor C919 is grounded, the other end of the resistor R929 is electrically connected to one end of the resistor R920, the other end of the resistor R920 is electrically connected to one end of the capacitor C924, and the other end of the capacitor C924 is electrically connected to the second chip. It should be noted that, DC +24V is transmitted to the second chip EUP3482 to provide voltage for DC-DC voltage reduction, the 24V input IN input end supplies power for work, and is connected to the EN enable end to turn on the chip switch for work, the COMP end is connected to the external RC for voltage compensation, the BS end and the SW output end are connected to the capacitor to drive the switch for operation, the voltage reduction outputs 12V voltage to power the dimming driving MCU, and the FB end is connected to the voltage divider for 12V output to perform built-IN regulation. The second chip EUP3482 regulates the input voltage from 4.5V to 30V down to an output voltage as low as 0.923V and provides a load current of up to 2A. EUP3482 employs current mode control to regulate the output voltage. The output voltage is measured at FB through a resistive voltage divider and amplified by an internal transconductance error amplifier. The voltage at the COMP pin is compared to the switch current (internal measurement) to control the output voltage. The converter uses internal n-channel MOSFET switches to drop the input voltage to a regulated output voltage. Since the high-side MOSFET requires a gate voltage greater than the input voltage, a boost capacitor connected between SW and BS is required to drive the high-side gate. When SW is low, the boost capacitor charges from the internal 5V rail. When the FB pin voltage exceeds 15% of the nominal regulation value of 0.923v, the overvoltage comparator trips, forcing the high side switch to turn off. The second chip EUP3482 employs current mode control to facilitate compensation and fast transient response. The stability and transient response of the system are controlled through the COMP pin. COMP is the output of the internal transconductance error amplifier. The series capacitor-resistor combination sets a pole-zero combination to control the characteristics of the control system.

The above embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the present invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent should be subject to the appended claims.

Claims

1. An LED backlight driving circuit, comprising:

a light source;

the LED driving module comprises a first chip, an overvoltage protection unit, an overcurrent protection unit and a short-circuit protection unit, wherein the first chip is electrically connected with the light source, and the overvoltage protection unit, the overcurrent protection unit and the short-circuit protection unit are respectively electrically connected with the first chip;

2. The LED backlight driving circuit according to claim 1, wherein the overvoltage protection unit comprises a capacitor C523, a capacitor C522, a resistor R536, a resistor R535, and a diode D501, the capacitor C523 is electrically connected to one end of the capacitor C522, the other end of the capacitor C522 is electrically connected to one end of the resistor R536 and one end of the resistor R535, respectively, the other end of the resistor R536 is electrically connected to the diode D501, and the other end of the resistor R535 is electrically connected to the diode D501.

3. The LED backlight driving circuit according to claim 2, wherein the overvoltage protection unit further comprises a resistor R521, a resistor R532 and a resistor R513, the resistor R521 is electrically connected to one end of the resistor R532, the other end of the resistor R532 is electrically connected to one end of the resistor R513, and the other end of the resistor R513 is electrically connected to the first chip.

4. The LED backlight source driving circuit according to claim 1, wherein the over-current protection unit comprises a capacitor C519, a capacitor C509 and a MOS transistor Q501, one end of the capacitor C519 is electrically connected with the MOS transistor Q501, and the other end of the capacitor C519 is electrically connected with the capacitor C509.

5. The LED backlight driving circuit according to claim 4, wherein the over-current protection unit further comprises a resistor R524, a resistor R512, a resistor R515, a resistor R516, a resistor R517, a resistor R518, and a resistor R531, a first end of the resistor R524 is electrically connected to the capacitor C509, a second end of the resistor R524 is electrically connected to one end of the resistor R512 and one end of the resistor R515, respectively, one end of the resistor R512 is electrically connected to the capacitor C509, another end of the resistor R515 is electrically connected to one end of the resistor R516, another end of the resistor R516 is electrically connected to one end of the resistor R517, another end of the resistor R517 is electrically connected to the resistor R518 and the MOS transistor Q501, respectively, one end of the resistor R531 is electrically connected to the MOS transistor Q501, and another end of the resistor R531 is electrically connected to the first chip.

6. The LED backlight driving circuit according to claim 1, wherein the short-circuit protection unit comprises a resistor R523, a resistor R520, and a capacitor C513, wherein the resistor R523 is electrically connected to one end of the resistor R520, the other end of the resistor R523 is electrically connected to one end of the capacitor C513 and the first chip, the other end of the resistor R520 is grounded, and the other end of the capacitor C513 is grounded.

7. The LED backlight source driving circuit according to claim 1, wherein the voltage dropping unit comprises a resistor R924, a resistor R925, an inductor L901 and a capacitor C917, one end of the resistor R924 is electrically connected to one end of the resistor R925, the other end of the resistor R924 is electrically connected to one end of the inductor L901 and one end of the capacitor C917, respectively, the other end of the inductor L901 is electrically connected to the second chip, and the other end of the capacitor C917 is connected to ground.

8. The LED backlight driving circuit according to claim 1, wherein the voltage dropping unit further comprises a capacitor C919, a resistor R929, a resistor R920 and a capacitor C924, one end of the capacitor C919 is electrically connected to one end of the resistor R929, the other end of the capacitor C919 is grounded, the other end of the resistor R929 is electrically connected to one end of the resistor R920, the other end of the resistor R920 is electrically connected to one end of the capacitor C924, and the other end of the capacitor C924 is electrically connected to the second chip.