ICL8001G thyristor dimming LED driver circuit and application

Abstract: LED lighting has a series of advantages such as high luminous efficiency and energy saving. It has been widely used. Since LED thyristor dimming has a series of advantages such as convenient use, easy implementation and wide range of use, some semiconductor integrated circuit manufacturing companies in the world have introduced LED thyristor dimming control integrated circuits. The working principle and typical application of the newly introduced LED thyristor (TRA IC) dimming control integrated circuit ICL8001G by Infineon are introduced below.

1 LED lighting and LED thyristor (TRAIC) dimming control

It has been more than 30 years since the first LEDs began to enter the market in 1968. With the development of new materials and improvements in LED production processes, LEDs tend to be brighter and full-color. The emergence of blue LEDs on GaN substrates has expanded the field of LED applications.

The principle of LED illumination is the process of converting electrical energy into light. The current is passed through the compound semiconductor. Through the combination of electrons and holes, the excess energy will be released in the form of light to achieve the effect of luminescence. The higher the forward current through the LED, the higher the luminance of the LED. At the same time, the stability of the LED illumination current will affect the illumination stability of the LED. Therefore, in practice, an LED driven constant current source that provides accurate and stable current should be used to power the LED.

The dimming of LEDs can further improve the energy-saving effect of LEDs. The thyristor (TRAIC) dimming of LEDs has a series of advantages such as easy implementation and convenient use. Some large semiconductor integrated circuit manufacturing and manufacturing companies in the world have introduced LEDs. Thyristor (TRAIC) dimming control ICs, such as: LM3445 from National Semiconductor Corporation (NS), NCL30000 from Onsemi, SSL2010T from NXP, and ICL8001G from Infineon Like thyristor (TRAIC) dimming control ICs, PI has also introduced LED thyristor dimming solutions based on PI products, each with its own characteristics. The following describes the working principle, characteristics and typical application circuits of the ICL8001G thyristor (TRAIC) dimming control IC from Infineon.

2 LED thyristor dimming control integrated circuit ICL8001G features

The ICL8001G is a control IC for off-line LED lighting applications that operates in a quasi-resonant mode of operation. It is ideal for LED dimming applications that replace incandescent lighting applications. Precision PWM control ensures reliable phase utilization. The primary side control circuit structure of the dimming control ensures that the circuit power factor PF value is > 98%, which can significantly improve the circuit operation efficiency and make the working efficiency as high as 90%. Compared with other circuit solutions, ICL8001G's LED power supply has a wide operating voltage range (up to 26 V), low power consumption, and complete protection functions. The LED thyristor dimming control circuit composed of ICL8001G has excellent performance and simple circuit.

The ICL8001G is available in an 8-pin PG-DSO-8 package. The outline is shown in Figure 1. The internal working principle of the ICL8001G is shown in Figure 2.

The main technical features of the ICL8001G are as follows:

Figure 1 Pin Diagram (PG - DSO-8 Package) (Top View)

Figure 2 internal working principle block diagram

1) High efficiency and stability over the entire working range; 2) Dimming control applications for thyristor leading or trailing edges; 3) PFC and precision dimming PWM control for the primary side; 4) Constant current precharge control unit circuit for external capacitor of VCC pin; 5) Built-in numerical control soft start control function, foldback control and cycle-by-cycle peak current control; 6) VCC over/under voltage lockout output; 7) Output Adjustable lock mode of operation for overvoltage protection.

(1) ICL8001G pin function

The pin functions of the ICL8001G are shown in Table 1.

Table 1 Pin Functions of the ICL8001G

(2) Introduction to the pin function of ICL8001G

1 ZCV pin: Zero-crossing detection pin, the voltage from the auxiliary winding is added to the pin after a delay of the delay circuit. The pin is connected to the zero-crossing detector circuit through the internal circuit to determine the external power. The on-time of the switch. At the same time, the output overvoltage detection function can be realized by comparing the VZC with the internal preset threshold voltage.

2 VR pin: Voltage detection pin, which is used to detect the AC input rectified output voltage. This detected voltage can set the peak current of the peak current control circuit and complete the APFC and phase-controlled dimming. control function.

3 CS pin: current sense pin, this pin is connected to a current sense resistor for determining the primary side current sense, and used together with the feedback voltage to determine the pulse turn-off time of the PWM control signal generator, and The detection function of the short-circuit winding is realized by detecting the voltage of the voltage VCS during the on-time of the main power switch.

4 GD pin: Gate drive output pin, this pin output signal is used to drive the external power switch MOSFET.

5 HV pin: High voltage input pin, this pin is connected to the external bus voltage and charges the capacitor connected to the VCC pin of the integrated circuit through the external bus voltage.

6 VCC pin: Power supply pin for the integrated circuit, supply voltage range is VV CCoff VVCCOVP.

7 GND pin: Ground pin of the integrated circuit.

(3) Circuit protection of ICL8001G

The ICL8001G has the protection functions shown in Table 2.

Table 2 Protection characteristics

3 Dimmer classification and working principle

(1) Classification of dimmers

Dimmers can be divided into front-cut and post-cut phase dimming according to the implementation. The voltage waveforms of the front-cut and post-cut phase dimming outputs are shown in Figure 3. The front-cut phase dimming is also called controllable. Silicon front-end phase dimming or thyristor dimming. The post-cut phase dimming is also called trailing edge dimming or transistor dimming. The front-cut phase dimming dimming control AC input has a sharper change in the leading edge of the mains, while the trailing edge dimming dimming control AC input mains has a smoother trailing edge change, as can be seen from the waveform shown in Figure 3.

The phased dimmer classification and characteristics are shown in Table 3.

Table 3 Phase Control Dimmer Classification and Features

(2) Working principle of phase-controlled dimmer

As shown in the waveform of Figure 3, by changing the position of the phase control angle of the dimming control, the average value of the output AC power can be changed to achieve the purpose of changing the output power, thereby achieving the purpose of dimming control. However, the AC output voltage waveform of the phase-controlled dimmer has deviated significantly from the sinusoidal waveform, so the power factor is also seriously less than 1, which is also a disadvantage of phase-controlled dimming. In comparison, the waveform distortion of the post-cut phase dimming The waveform distortion of the front-cut phase dimming is smaller.

Figure 3 Voltage waveforms of the front-cut and back-cut phase dimming outputs

(3) Typical application circuit of thyristor dimming

There are many kinds of circuit implementations for thyristor dimming. The typical application circuit of thyristor dimming is shown in Figure 4. In the circuit shown in Figure 4, potentiometer 1 is used to set the internal offset, and potentiometer 2 is used. External control, under the action of potentiometer 1 and potentiometer 2, the resistance varies from 2. 7 Ω to 413 k Ω .

Figure 4 Typical application circuit of thyristor dimming

4 LED thyristor dimmable typical application circuit using ICL8001G

The following describes the characteristics and specific circuit implementation of the evaluation circuit board EVALLED of the LED thyristor dimming typical application circuit using ICL8001G.

(1) Introduction to the circuit

The ICL8001G evaluation board EVAL-LED demonstrates the ICL8001G control IC for LED thyristor dimming. The ICL8001G is a single-stage flyback control IC that operates in a quasi-resonant, primary-side control mode with integrated APFC and phase. Control dimming control function, suitable for LED dimming control applications.

( 2) Evaluation board EVAL-LED of ICL8001G

ICL8001G evaluation board EVAL-LED solder circuit components behind the PCB board diagram top and bottom views are shown in Figure 5 and Figure 6, respectively.

Figure 5 Top view of the EVAL-LED ICL8001G evaluation board

Figure 6 Bottom view of the EVAL-LED ICL8001G evaluation board

(3) Circuit characteristics

The circuit characteristics of the EVAL-LED ICL8001G evaluation board are as follows:

1) In the quasi-resonant mode, it has stable and high working efficiency over the wide AC input mains voltage variation range; 2) It adopts primary side flyback control, with APFC function and phase control dimming control function; The circuit maintains high operating efficiency under phase-controlled dimming control; 4) has constant current charging control function for external capacitor of VCC pin inside ICL8001G; 5) ICL8001G contains numerical control soft start control function; 6) has foldback Compensation and cycle-by-cycle peak current limiting; 7) Overvoltage and undervoltage lockout output control functions on VCC pin; 8) Automatic restart after short circuit protection; 9) Adjustable lockout shutdown mode for output overvoltage protection .

(4) Technical indicators

Table 4 shows the relevant technical specifications of the EVALLEDICL8001G evaluation board. The input voltage in Table 4 indicates the rms value (RMS) of the AC input voltage without phase-controlled dimming. The output voltage indicates the range of variation of the input AC mains input voltage. The range of output DC voltage variation within.

Table 4 circuit performance indicators

(5) Dimming control

Through the phase-controlled dimming control of the thyristor, the DC supply current value of the LED applied to the LED lighting control circuit board can be changed, thereby realizing the dimming control of the LED.

1) Power up the board

There is a start-up unit circuit inside the integrated circuit ICL8001G. This start-up unit circuit can shorten the start-up time of the circuit without reducing the circuit operation efficiency. Under the condition that the external capacitor C 15= 10 μ F of the VCC pin of the ICL8001G, the circuit The startup time is approximately 120m s.

2) EVAL-LED ICL8001G evaluation circuit PCB board diagram

The EVAL-LED ICL8001G evaluation circuit PCB board diagram is shown in Figure 7 and Figure 8, respectively.

Figure 7 EVAL-LED ICL8001G evaluation board PCB top view

Figure 8 EVAL-LED ICL8001G Evaluation Board PCB Bottom View

3) EVAL-LED ICL8001G evaluation circuit schematic.

The circuit diagram of the EVAL-LED ICL8001G evaluation board is shown in Figure 9. The circuit component parameter table is shown in Table 5.

Figure 9 ICL8001G evaluation board circuit schematic

Table 5 Circuit component parameter table

5 Summary

Since lighting thyristor (TR IAC) dimming is easy to use and conforms to people's usage habits, the promotion of thyristor lighting dimming has a good market prospect. Lighting thyristor (TR IAC) dimming in incandescent lighting It has been well applied. However, illuminated thyristor (TR IAC ) dimming in gas discharge lamps and LED lighting dimming applications, thyristor (TR IAC ) dimming in the circuit power factor, dimming flicker and other dimming performance and cost Further efforts are needed to expand the range of applications for thyristor (TR IAC) dimming in gas discharge lamps and LED lighting dimming.