WO2018223247A1

WO2018223247A1 - Light emitting diode

Info

Publication number: WO2018223247A1
Application number: PCT/CN2017/000383
Authority: WO
Inventors: 吕光辉
Original assignee: 吕光辉
Priority date: 2017-06-09
Filing date: 2017-06-09
Publication date: 2018-12-13

Abstract

A system, for providing a starting voltage to a light emitting diode (LED) unit. The system comprises: a bridge module, for rectifying an AC full-wave waveform from a power source (101) into an AC half-wave waveform; and a step-down circuit module (102) having a metal oxide semiconductor, the step-down circuit module (102) being used for rectifying the AC half-wave waveform into a DC power supply for the LED unit (106). The step-down circuit module (102) corrects a power factor via a power factor correction module (110), and rectifies a full voltage by using a constant current control LED control chip, such that the DC power source (101) can receive the full voltage supplied to the LED unit (106) in a manner corresponding to the starting voltage of the LED unit (106).

Description

Light-emitting diode

Technical field

The present invention relates to an apparatus for a Light-Emitting Diode (LED) driver.

Background technique

A LED driver is a device that adjusts the power to an LED or multiple LEDs. LED drivers can be responsive to the needs of LEDs or LED circuits by providing a fixed amount of power to the LEDs as their electronic characteristics change with temperature.

The LED driver is an independent power supply that has an output corresponding to the electronic characteristics of the LED. The LED driver can provide dimming by means of a pulse width modulation circuit and can have more than one channel for separate control of different LEDs or LED arrays.

The LED power level is fixedly maintained by the LED driver by an increase in temperature and a decrease in electronic characteristics of the LED driver as viewed by the LED or LEDs. Therefore, without a suitable driver or system, the LEDs may overheat or become unstable, thereby performing poorly or failing.

The existing LED driver rectifies an alternating current (AC) full-wave waveform into an AC half-wave waveform through a bridge integrated circuit (IC) before providing the required power to the LED. Typically, the current limiter of an LED is set by a Metal Oxide Semiconductor (MOS) power transistor. However, such a design itself creates two problems, namely power loss and output voltage difference.

The problem of power loss is based on a power supply that uses an AC half-wave waveform. When the starting voltage of the LED is a direct current (DC) power supply, power loss occurs.

Regarding the problem of the output voltage difference, since Vin=Vf+Vds, when Vin increases and the Vf of the LED does not change, Vds will withstand a larger voltage difference power, which will cause the MOS power transistor temperature to increase and eventually burn out. Therefore, this circuit design is only suitable for the use of a single voltage device.

Therefore, it is necessary to improve the power efficiency and full voltage (85Vac to 305Vac) input to overcome the design flaws of current linear LED drivers.

Summary of the invention

An aspect of the invention relates to a system for providing a starting voltage to a light emitting diode unit, the system comprising: a bridge module for rectifying an alternating current full wave waveform from a power source into an alternating current half a waveform circuit module having a metal oxide semiconductor, the step-down circuit module for rectifying the AC half-wave waveform into a DC power supply for the LED unit, wherein the step-down circuit The module uses a power factor adjustment module to perform power factor correction and uses a flow control LED to control the wafer to rectify a full voltage so that the DC power source corresponds to the startup voltage of the LED unit Receiving the full voltage to be supplied to the light emitting diode unit.

Preferably, the bridge module is a bridge circuit.

Preferably, the light emitting diode unit is a light emitting diode driver having an integrated circuit.

Preferably, the light emitting diode unit has a current limit set by a metal oxide semiconductor power transistor

Preferably, the voltage of the system is adjusted to be adjacent to the voltage of the buck circuit module to overcome an input voltage difference.

Preferably, a full range buck output voltage of a constant current illuminating diode between 85 Vac to 305 Vac is used for the luminescent diode unit.

In addition, the system includes an active power factor correction circuit to achieve high power factor values with low total harmonic distortion.

Preferably, the system operates in a continuous power inductor critical mode and a metal oxide transistor operates in a zero power switching mode to reduce switching losses and increase inductor usage.

In addition, the system includes a cycle-by-cycle current limiting protection feature to protect a metal oxide transistor, inductor, and freewheeling diode to improve system reliability.

In addition, the system includes a floating ground wafer to isolate interference and prevent zero voltage and zero crossing effects to protect a metal oxide transistor, freewheeling diode, and the modules in the system.

The features and various combinations included in the system are fully described below in the drawings. It is to be understood that various modifications may be made without departing from the scope of the invention or the advantages of the invention.

DRAWINGS

In order to further clarify aspects of some embodiments of the present invention, a more specific description of the invention will be made by way of the accompanying drawings. These drawings represent only a typical embodiment of the invention and are not intended to limit the scope of the invention. The invention may be described and illustrated in detail with particular reference to the drawings.

Figure 1 shows a flow diagram of a modified circuit design and structure using a DC voltage mode to provide LEDs.

Figure 2 shows a block diagram of a modified circuit design and structure using a DC voltage mode to provide LEDs.

Among them, the reference numerals are as follows:

101 AC power supply

102 step-down voltage circuit module

103 step-down voltage setting module

104 voltage sensing circuit module

105 step-down voltage adjustment module

106 light emitting diode unit

107 LED power setting module

108 power sensing circuit

109 LED power regulator

110 power factor adjustment module

111 light-emitting diode circuit protection module

112 integrated circuit undervoltage protection module

113 wafer thermal regulation protection

114 current sampling protection module

115 overvoltage protection module

116 cycle-by-cycle power limit module

detailed description

The present invention proposes a modified circuit design and structure that uses a DC voltage mode to provide a better power supply for the LED, which better improves power usage efficiency and full voltage (85Vac to 305Vac) input to overcome existing linear LEDs Design flaws in the driver IC. Full voltage means that the incoming voltage is the actual voltage in the bulb, but when a resistor is used, for example, the incoming voltage is reduced and the actual voltage in the bulb is about 12V.

As shown in Figure 1, the full-voltage LED driver rectifies the AC full-wave waveform into an AC half-wave waveform via a bridge IC, and the system can use a step-down voltage circuit module that is implemented by MOS, pole, or electrical fusion. 102, the AC power source 101 is rectified into a DC power source for use as an LED. Preferably, the LED current limit is set by the MOS power transistor or step-down voltage setting module 103 because such a design overcomes the initial design flaws faced by conventional circuits. Regarding the first problem of power loss, since the proposed system has a DC power supply corresponding to the LED unit 106 having a starting voltage using a DC power source, the efficiency of power use can be greatly improved. The power usage improvement can be achieved by using the voltage sensing circuit module 104 to sense the voltage of the circuit; and using the buck voltage regulating module 105 to maintain a regulated voltage while maintaining a fixed output voltage and continuously The difference between the output and the regulated voltage is dissipated as waste heat. Such circuits provide output voltage performance from less than 2V to greater than 100V, switching frequencies as large as 4MHz, and high efficiency operation up to 96%.

Regarding the second problem (ie, overcoming the input voltage difference), since Vin = Vf + Vds, and Vin can be adjusted to a voltage close to Vf at the step-down voltage circuit module 102, Vds will withstand a smaller voltage difference power, Thus the lifetime of the MOS power transistor is increased and can be applied to the use of full voltage devices.

The proposed system for an LED driver is referred to as JF1606, which is a high precision step-down LED constant current control wafer that is a step-down voltage circuit module 102 that includes a power factor adjustment module 110 for power factor adjustment. The LED constant current control chip is suitable for a full range of buck input voltages with fixed current LEDs from 85Vac to 305Vac. The system integrates active power factor correction circuitry to achieve high power factor and low total harmonic distortion. Since the MOS power transistor is in zero power switching mode due to operation in the continuous power inductor critical mode, switching losses are reduced and higher inductor usage is achieved. This improvement in power factor is achieved by adding a power factor correction capacitor to the distribution system. When apparent power (kVA) is greater than work Power (kW), the device must provide this excess reactive current plus the operating current. The power capacitor acts as an inactive current generator.

The constant current controller (stable current, time independent current, fixed current) is a type of DC controller whose strength does not change with time. If the load is fixed, a steady current can be obtained by a fixed voltage source. If the load is variable, a steady current can be obtained by a fixed current supply.

In addition, the system has multiple protection functions to enhance system reliability, including: LED circuit protection module 111 for LED open circuit protection and / or LED short circuit protection; IC under voltage protection module 112 for protection with power supply under voltage IC or wafer; current sampling protection module 114 for protecting current sampling resistors on an open circuit; cycle-by-cycle power limiting module 116 to effectively protect the MOS field effect transistor, and allowing a current regulator or precision Simple configuration of current limit, etc. All protection modes have an automatic restart function. In addition, the system also has a wafer thermal regulation protection 113 for reducing the output current when the drive power source is overheated to improve the reliability of the system.

In addition, the LED module includes: an LED power setting module 107 to determine the power applied by the LED unit 106; a power sensing circuit 108 to sense the power of the LED circuit; and an LED power adjuster 109 to maintain the pair of LED units A stable voltage of 106.

Additional features of the proposed system include:

- Active power factor correction, high power factor, low total harmonic distortion

- up to 95% system efficiency

-±3% LED output current accuracy

- Excellent line voltage regulation and load regulation

- Continuous power inductor critical mode

- Ultra low (30uA) starting voltage

-LED short circuit / open circuit protection

- Current sampling resistor open circuit protection

- Cycle-by-cycle power limit

- Chip power supply undervoltage protection

-Automatic restart function

- Thermal regulation

Applications of the LED unit 106 in the proposed system include:

-LED bulb

-LED tube

-LED street light

- Power for all LED lighting products

The proposed system for an LED driver is referred to as JF1606, and its block diagram is shown in Figure 2, which is an active power factor corrected LED constant current control wafer. The system operates in a continuous power inductor critical mode, thus achieving extremely high power factor, extremely low total harmonic distortion and high efficiency.

The method of using the device as an LED driver includes the following steps.

<1. System startup>

After the system is turned on, the bus voltage is charged to the capacitor of the IC power supply pin (VCC) through the startup resistor. When the VCC voltage rises to the threshold voltage, the internal control circuit of the chip begins to operate and the Vref voltage is quickly pulled up to 1.5V.

Then the device or system begins to output a pulse signal, and the Vref voltage gradually rises from 1.5V, and the peak current of the inductor rises accordingly, thereby achieving a soft start of the output LED current, effectively preventing the output current from overshooting. When the output voltage is established, the VCC voltage is supplied from the output voltage through the diode, thereby reducing power consumption.

<2. Fixed output current control setting>

The device or system then samples the inductor current cycle by cycle and operates in a continuous power inductor critical mode to achieve high precision output current control. The LED output current calculation method is:

Iout=Vref/Rcs

Where Vref is the internal reference reference voltage and Rcs is the current sampling resistance value

<3. Feedback network>

The device or system detects the state of the output voltage through a feedback network. The buck threshold voltage of the feedback network is set at 0.2V and the hysteresis voltage is set to 0.15V. The feedback network pin can also be used to detect Over Voltage Protection (OVP) with a threshold of 1.6V. The ratio of the upper and lower voltage divider resistors of the feedback network can be set to:

Rfbl/(Rfbl+Rfbh)=1.6V/Vovp

Among them, Rfbl is the lower divider resistor of the feedback network, Rfbh is the upper divider resistor of the feedback network, Vovp is the set point of the overvoltage protection, and the divider resistor under the feedback network is recommended to be set at 5KΩ to 10KΩ. about.

<4. Thermal energy adjustment function>

The device or system is then connected to a thermal energy adjustment function. When the driving power supply is overheated, the output current is gradually reduced, thereby controlling and maintaining the output power and temperature at a set value to improve the reliability of the system. The thermal control point inside the wafer is set to 150 degrees Celsius.

<5. Protection function>

The device or system is equipped with multiple built-in protection features to ensure system reliability. When the LED is open, the output voltage gradually rises, and the feedback network pin can detect the output voltage when the power transistor is turned off. When the feedback network rises to the OVP protection threshold, the protection logic is triggered and the switch is stopped. When the LED is short-circuited, since the output voltage is very low, VCC cannot be supplied through the diode, so the VCC voltage will gradually drop until VCC reaches the undervoltage protection threshold. When the system enters protection mode, the VCC voltage begins to drop, and when VCC reaches the undervoltage protection threshold, the system will restart. The system will continue the test and, once the fault is removed, the system will resume normal operation. When the output is shorted or the transformer is saturated, the common source peak voltage value will be higher. When the common source voltage rises to the internal value limit (1V), the switching cycle stops immediately. Such cycle-by-cycle current limiting functions protect power MOS transistors, inductors, and freewheeling diodes.

Typically, all isolated buck lines contain one or several transformers. By adjusting the turns ratio of the transformer, a higher or lower or negative potential output voltage can be obtained. In some isolated buck line configurations, multiple windings can be wound around the transformer to output multiple voltage values. Some converters also use transformers as energy storage devices, but other converters still require separate inductive devices. This type of power conversion mode is a "DC-AC-DC" conversion. However, this can be an expensive way.

The non-isolated power supply is the simplest power switch mode, and its power conversion mode is "DC-DC" conversion. According to the type of voltage conversion, there are three basic types: Boost Chopper (also known as Boost Converter); Buck Chopper (also known as buck) Buck Converter (Buck-Boost Converter); and Buck-Boost Chopper (also known as Buck-Boost Converter). Their structures are very similar, and the input, output, and grounding all meet at one point, using inductors for energy storage. The main difference between them is the way the inductor is connected. If the inductor is placed at the output of the circuit, it is a step-down chopper; when the inductor is placed at the input of the circuit, it is a boost chopper. When the inductor is grounded, it is a buck-boost chopper.

When the pulse duty cycle is extremely short, the efficiency of the switching device is lowered. If a higher voltage conversion is required, then an isolated power supply with a transformer is required.

The full-voltage step-down LED constant current control chip receives the bridge half-wave waveform power, rectifies it into a DC power supply, and after LC filtering, supplies the power to the LED. The LC circuit (also referred to as a resonant circuit, a tank circuit, a tuning circuit) is an inductor (represented by the letter L) and a capacitor (represented by the letter C) connected to each other.

The full-voltage step-down LED constant current control chip is designed for ground landing, which uses a diode connection to control the floating ground of the wafer and the ground of the bridge IC, thereby isolating interference between the two parts and preventing The effect of zero voltage and zero crossing to protect the life of parts such as power MOS transistors and freewheeling diodes.

The invention may be embodied in other specific forms without departing from the essential characteristics. All aspects of the described embodiments are to be considered as illustrative and not limiting. Therefore, the scope of the invention should be defined by the scope of the appended claims rather than the foregoing description. Variations within the meaning and range of the claims are intended to be embraced by the scope of the claims.

Claims

A system for providing a starting voltage to a light emitting diode unit, the system comprising:

a bridge module for rectifying an AC full-wave waveform from a power source into an AC half-wave waveform;

a step-down circuit module having a metal oxide semiconductor, the step-down circuit module for rectifying the AC half-wave waveform into a DC power supply for the LED unit

Wherein, the step-down circuit module rectifies a full voltage by using a power factor adjustment module to perform power factor correction and using a flow control LED to control a full voltage so that the DC power source corresponds to the LED unit The manner of starting the voltage can receive the full voltage to be supplied to the light emitting diode unit.
The system of claim 1 wherein the bridge module is a bridge circuit.
The system of claim 1 wherein the light emitting diode unit is a light emitting diode driver having an integrated circuit.
The system of claim 1 wherein the light emitting diode unit has a current limit set by a metal oxide semiconductor power transistor
The system of claim 1 wherein the voltage of the system is adjusted to be adjacent to a voltage of the buck circuit module to overcome an input voltage difference.
The system of claim 1 wherein a full range buck output voltage of a constant current illuminating diode between 85 Vac and 305 Vac is used for the luminescent diode unit.
The system of claim 1 wherein the power factor adjustment module has an active power factor correction circuit to achieve a high power factor value with low total harmonic distortion.
The system of claim 1 wherein the system operates in a continuous continuous power inductor critical mode and a metal oxide transistor operates in a zero power switching mode to reduce switching losses and increase inductor usage.
The system of claim 1 further comprising a cycle-by-cycle current limiting protection feature to protect a metal oxide transistor, inductor and freewheeling diode to improve the system System reliability.
The system of claim 1 further comprising a floating ground wafer to isolate interference and prevent zero voltage and zero crossing effects to protect a metal oxide transistor, freewheeling diode in the system Polar body and these modules.