Explain eight different points of active drive and passive drive matrix in switching power supply design

There are many differences between the active drive and the passive drive matrix in the design of the switching power supply. Below, the author will analyze them one by one, and hope to provide some due help to everyone!

First, the structure is different

The pixels of the passive driving matrix are composed of a cathode and an anode simple substrate, and the intersection of the anode and the cathode can emit light, and the driving IC needs to be externally connected by a connection method such as TCP or COG.

Each pixel of the active drive is equipped with a Low Temperature Poly-Si Thin Film Transistor (LT P-Si TFT) with switching function, and each pixel is equipped with a charge storage capacitor, peripheral drive circuit and display array. The entire system is integrated on the same glass substrate. The same TFT structure as the LCD cannot be used for OLEDs. This is because the LCD is driven by voltage, while the OLED is driven by current. Its brightness is proportional to the amount of current. Therefore, in addition to the address TFT that performs the ON/OFF switching action, the ON impedance that allows sufficient current to pass is lower. Small drive TFT.

Second, the difference in driving methods

The driving method of the passive matrix is ​​multi-channel dynamic driving. This driving method is limited by the number of scanning electrodes, and the duty ratio coefficient is an important parameter of passive driving.

The active matrix driving method is a static driving method. The active matrix OLED has a memory effect and can be driven by 100% load. This driving is not limited by the number of scanning electrodes, and can selectively adjust each pixel independently.

Third, the active matrix can achieve high brightness and high resolution

Due to the duty cycle of the passive matrix, the display disappears quickly when it is not selected. In order to achieve a certain brightness of the display, the brightness of each column during scanning should be the average brightness of the screen multiplied by the number of columns. For example, in the case of 64 columns, the average brightness is 100 cd/m2, and the brightness of one column should be 6400 cd/m2. As the number of columns increases, the brightness of each column must increase accordingly, and accordingly the drive current density must be increased. It can be seen that the passive matrix is ​​difficult to achieve high brightness and high resolution.

The active matrix has no duty cycle problem, and the drive is not limited by the number of scan electrodes, making it easy to achieve high brightness and high resolution.

Fourth, the active matrix can achieve high efficiency and low power consumption

Fifth, the active matrix is ​​easy to achieve colorization

Sixth, the active matrix is ​​easy to improve the integration and miniaturization of the device

Seven, the active matrix is ​​easy to achieve large-area display

Eight, the comparison of process costs

The passive drive is composed of a simple matrix, and the substrate manufacturing process is simple; the active driving low-temperature polysilicon TFT process is complicated, and the equipment investment is huge.

For general OLED devices, the cost of active drives is higher. However, the passive drive requires an external drive circuit. At present, the price of such a circuit chip is still high, and the active matrix built-in drive circuit does not need to be externally connected, and the passive drive of the higher resolution and colorized OLED device is not necessarily required. low cost.