Automobile lamp flash control integrated circuit and its application

Photocoupler

The car lamp flash control ASIC 7208 is on the controller of the car light flash device when the car is turning. During normal operation, the front and rear lights and the monitor light flash simultaneously at a frequency of 80 beats/min. Once the lights are damaged, the flashing frequency of the monitor lights is doubled to indicate an alarm. Using the car flash controller made of 7208 can improve driving safety.

The integrated circuit 7208 adopts an eight-line double-in-line plastic package, which has the characteristics of small size, few external components, low power consumption, high precision, and wide power supply voltage range. The flash controller consisting of 7208 is a replacement for the car turning flash controller.

The internal block diagram of the 7208 and the application wiring diagram are shown above. Input detection is a voltage comparator that detects the presence or absence of a supply voltage input and thus controls whether the circuit is functioning properly. The voltage detection section is a high precision claw detector. Its function is to identify the magnitude of the voltage drop across Rs, thereby determining the amplitude of the RC oscillator charge and discharge voltage, and then determining the speed of the oscillation frequency (ie, the flash frequency). The oscillator consists of a comparator and an external RC. Rl is an external feedback resistor, which acts as a stable circuit. The output section can pick up relays with an operating current of less than 180mA.

The Rs size is the key to determining whether the 7208 integrated circuit can work properly. Pay attention to the relationship with the lamp current when selecting the resistance of the sampling resistor Rs, and leave sufficient room. In order to ensure that the .7208 can work reliably in the range of 9~15V power supply voltage, it is necessary to determine Rs by the following method: short circuit the relay contact, at this time the lamp is on and not flashing, and the voltage across the Rs is measured under the power supply voltage of 15v. Drop VRS (VRS=Ig.Rs, where Ig is the lamp current), adjust Rs, make VRS=(1.15～1.20)VTHmax,≈160～180mV. Then Rs is determined.

The outline of the flash controller consisting of 7208 is shown above. The controller has a frame size of 30 x 30 x 40 mm. It uses AT3S molded case. The three lead legs protrude 15mm, where E is the negative pole of the power supply, B is the positive pole of the power supply, and L is the flash control end. It should be adjusted according to the lamp current (3.OA) design. The figure below shows the wiring diagram of the specific electronic flash controller, whose relay contacts can control the flashing or switching of the lamp. Such controllers can also be used in applications such as holiday lights, beacon lights, warning lights, and the like. The power supply voltage is 12V. At this time, Rs selects lOΩ, R, and selects 680Ω.