UAA4002 combined with HEF4752V is used for SPWM frequency conversion speed regulation system of three-phase AC motor

The combination of UAA4002 and HEF4752V
is used in AC motor frequency conversion speed regulation systems: Figure 12-33 shows a three-phase transistor full-bridge SPWM
composed of UAA4002 and 8031 ​​microcontrollers and a dedicated three-phase SPWM pulse forming circuit for HEF4752V. Simplified schematic diagram of the inverter system. This system can be used for frequency conversion speed regulation of three-phase power supply and medium frequency motors. In Figure 12-33, the R port of 8031 ​​is set to the position control mode to control the input signals 1 and I required by HEF475ZV. , K. cw. The control program of the entire system is stored in EPROM. The control status and frequency given by the user enter , and are converted into corresponding values ​​by the 8031 ​​CPU through calculation and judgment. The time constant is sent to the 8254 programmable counter, and after being divided by the 8254 count, it provides the four clock inputs required by HF and F4752V. The work completed by the microcontroller here is: starting and stopping the work of HEF475ZV, changing the output pulse phase sequence of HEF4752V, over-current protection, over-voltage protection, display, low-frequency compensation, frequency given, time constant conversion closed-loop adjustment, etc. , and UAA4002 is used to power amplify the pulse output by HEF4752V to complete the optimal base drive of the transistor. The negative power supply is connected from the anode to the ground on the secondary side of the pulse transformer, and the cathode is connected to the UAA4002 pin. Provided by the voltage drop across two diodes in series, this structure eliminates the need for a negative power supply . The above structure determines that the frequency modulation range of the transistor base drive signal is 4 -71. 3Hz (under sinusoidal modulation conditions). And has higher frequency resolution.