High-Reliability AC-DC LED Lighting Driver Design

Giantec Semiconductor Co., Ltd. recently announced that its controller GT5010, designed for AC-DC LED lighting, chargers, adapters, home appliance power supplies, and auxiliary power applications, has officially entered mass production. Giantec Semiconductor's GT5010 is another main product in the power product line after the two major product lines of EERPOM memory series and smart card series.

GT5010 adopts the latest transformer primary side (PSR) control method and patented full current feedback control technology; drives external high-reliability MOSFET power devices; its constant current and constant voltage characteristics meet the range of less than ±5%; the standby power consumption for mobile phone chargers is less than 30mW; the conversion efficiency fully meets the latest "EPS2.0"; GT5010 adopts SOT23-6 package; can work in the temperature range of -40 to +85 degrees, and has perfect protection features such as over-temperature protection. These features make GT5010 one of the most cost-effective control chips in the best isolated and non-isolated 3W, 5W and 7W high-performance, low-cost MR16, E14, E27 and GU10 LED lighting solutions.

Transformer primary side control

The AC/DC control technology of primary feedback is a new AC/DC control technology developed in the past 10 years. Compared with the traditional structure of secondary feedback optocoupler plus 431, its biggest advantage is that it saves these two chips and a group of components that work with them, thus saving space on the system board, reducing costs and improving system reliability. It has broad application prospects in markets such as LED drivers where cost pressure is high and volume requirements are high.

The GT5010 LED lighting solution is based on this primary feedback method. As shown in Figure 1, this solution eliminates the original secondary feedback optocoupler and voltage regulator 431 and other peripheral devices, making the circuit volume smaller and the production cost more competitive.

Figure 1. Schematic diagram of Juchen GT5010 LED circuit.

Drives external high-reliability MOSFET power devices

In the data sheet of MOSFET, its typical transfer characteristics can usually be found. Note that the two curves of 25℃ and 175℃ have an intersection, which corresponds to the corresponding VGS voltage and ID current value. If the VGS at this intersection is called the turning voltage, it can be seen that: in the lower left part of the curve of the VGS turning voltage, when the VGS voltage is constant, the higher the temperature, the greater the current flowing, and the temperature and current form a positive feedback, that is, the RDS (ON) of the MOSFET is a negative temperature coefficient, and this area can be called the negative temperature coefficient area of ​​RDS (ON).

Figure 2. MOSFET transfer characteristics.

In the upper right part of the curve of the VGS transition voltage, when the VGS voltage is constant, the higher the temperature, the smaller the current flowing, and the temperature and current form a negative feedback, that is, the RDS (ON) of the MOSFET is a positive temperature coefficient, and this area can be called the RDS (ON) positive temperature coefficient area. When the MOSFET is used as a power switch, its VGS is large when it is turned on, so it works in the RDS (ON) negative temperature coefficient area. As a result, as the temperature rises, the current will decrease. It has a self-limiting characteristic. Therefore, it has higher reliability than BJT (RDS (ON) positive temperature coefficient in high temperature environments.

Depending on the power required to drive the LED, this solution can be matched with Juchen brand 1A and 2A MOSFET. This solution can ensure stable operation in the high temperature environment inside the LED lamp body.

± 5% range constant current and constant voltage characteristics

After eliminating these components, in order to achieve high-precision constant current/constant voltage (CC/CV) characteristics, Juchen GT5010 uses new technologies to monitor the real-time changes of load, power supply and temperature as well as the tolerance of components in the same batch, and adopts primary side regulation technology, transformer tolerance compensation, cable compensation and EMI optimization technology. Therefore, GT5010 provides a constant current accuracy of up to ±5%. It can well match the production consistency requirements of LEDs of different materials.

Figure 3. Constant current characteristics of GT5010 at 85~264V input.

Meets the latest "Energy Star 5.0" standard

The solution currently supports 3W, 5W, and 7W LED lighting. It complies with the US Energy Star 5.0 and UL 8750 LED lighting safety standards. After actual measurement, the energy efficiency of the solution reaches 78% under 6.3W LED power consumption. At the same time, after adding appropriate peripheral devices, its PFC value can reach 0.8.

Table 1. 6.3W LED conversion efficiency.

SOT23-6 package

To meet the requirements of LED internal structure, GT5010 adopts SOT23-6 package. In typical application, it reduces 5~8 components compared with similar products. It is very suitable for lighting products with high volume requirements such as MR16 and E14 LED.

Over temperature protection feature

GT5010's built-in over-temperature protection feature will protect the LED from working under extreme conditions.

summary

The LED driver solutions using Juchen GT5010, GT1N60 and GT2N60 have been widely recognized. They have been applied to 3W, 5W and 7W high-performance, low-cost MR16, E14, E27 and GU10 LED lighting. New products based on the latest PFC control technology will be launched soon.