The dimming market for light source products in North America is still mainly focused on thyristor dimming. Due to design and cultural preferences, filament lamps are an important type of lamp. The driver of the filament lamp can only be placed in the lamp holder. Due to volume and space limitations, even using a linear scheme cannot use a large capacity electrolytic capacitor. However, the North American CEC lighting certification standard has requirements for the output strobe index, so an additional chip to remove power frequency ripple is generally required, which makes the design and production of the filament lamp driver more challenging. If the thyristor linear dimming and power frequency ripple removal functions can be integrated into one chip, even with the use of small volume electrolytic capacitors, the problem of limited lamp holder space during the assembly of the driver board can be solved, and the number of components on the filament lamp driver board can be reduced, reducing system costs.
In response to this application requirement, Anbao Electronics has launched the OB5659A, a highly compatible and efficient North American single segment linear thyristor dimming scheme without flicker.
Figure 1 Application diagram of OB5659A system
OB5659A is a North American efficient flickerless single segment linear thyristor dimming scheme, packaged in EASOP8, targeting filament lamp applications and supporting a maximum output current of 50mA; Supports a maximum output current of 80mA for DOB product applications such as bulb lights and down lights.
The OB5659A adopts high-voltage power supply technology, which eliminates the need for power supply capacitors. It is equipped with a built-in Comp capacitor and an integrated power frequency ripple chip, meeting the requirements of North American strobe<25%, PST<1, and SVM<0.4. The system's peripheral components are extremely simple, and only two resistors are needed on the periphery of the chip.
The OB5659A adopts closed-loop constant current control technology, which can ensure constant output current when the input and output voltage changes, thereby ensuring the brightness consistency of the light source.
Figure 2 Output Current of OB5659A System under Different Input Voltages
When the environmental temperature increases, the traditional protection method for drivers is generally chip over temperature protection, so that the driver will not be damaged. At this time, the driver enters a repeated restart state, and the light will continue to flash. The OB5659A provides the function of over temperature and current reduction, which reduces the output current when the chip temperature rises due to an external environmental temperature increase. The system reliability is also guaranteed under continuous driving operation. For different lamp types with different requirements for over temperature protection points, OB5659A can achieve the setting of four over temperature protection points by changing the peripheral circuit of the TH pin of the chip, grounding, suspending, or connecting different resistance values to the TH pin.
OB5659A has been optimized for dimming applications, and the chip detects whether there is an access dimmer on the AC input side during system startup. The type of access dimmer is determined by the category of front edge, rear edge, or intelligent dimmer. When there is no dimmer connected, turning off the maintenance current control circuit can improve the system efficiency by more than 10% compared to traditional linear schemes. In the case of dimmer access, OB5659A automatically performs different maintenance current control for different types of dimmers, thereby achieving excellent dimming compatibility. At the same time, OB5659A uses a digital circuit to detect the dimming phase and generate a dimming current curve, which can meet the dimming curve requirements of North American NEMA SSL6.