The driving circuit is the key to ensuring the operation of the PMDC Motor. Therefore, in order to ensure the operation of the equipment, the user needs to understand the driving circuit of the equipment in detail, so as to avoid operational errors and affect the performance of the equipment.
The low-power drive circuit of the DC motor can use an H-bridge switch circuit. UA and UB are complementary dual-synthetic or single-synthetic drive signals, TTL level. The withstand voltage of the switching transistor should be greater than 1.5 times Us. Because high-power PNP transistors are expensive and difficult to implement, this circuit is only used in low-power motor drives. When all four power switches use NPN transistors, two need to be resolved. The base and level shift problem of the upper-side transistors (BG1 and BG3), the H-bridge switching circuit uses two transistors to achieve the level shift of the upper-side transistor, but the loss on the resistor R is large, so it only It can be used in small power motor drive.
When the driving power is relatively large, the general bridge arm voltage is also relatively high. For example, directly take the power frequency voltage, single-phase 220V, or three-phase 380V. For safety and reliability, it is hoped that the drive circuit (main circuit) is insulated from the control circuit. , The main circuit must adopt the floating pre-driver. The floating pre-drive circuits are independent of each other and powered by independent power supplies. Due to the photoelectric coupling used in the pre-drive circuit, the control signal is electrically insulated from the respective pre-drive circuit, so the control signal is floating (or not in common) to the main circuit.
The above is the introduction to the drive circuit of the permanent magnet DC motor, according to.