Abstract : This paper adopts the PIC16F877 microcontroller and SPWM (Sine Pulse Width Modulation) technology. A new method is proposed to control SPWM using software program based on the intelligent control signal generated by the PIC16F877. A high-efficiency, low-cost, and fully functional small frequency converter is designed. Keywords : Frequency converter; economical; Sine pulse width modulation; PIC16F877 1 Introduction In recent years, asynchronous motor speed control systems have been widely used in many fields. Currently, most small and medium power frequency converters on the market are general-purpose frequency converters. These converters have a wide speed range, high speed control accuracy, and complex functions, thus they are expensive. However, in some specific situations, the speed control requirements are not very high, and general-purpose frequency converters have performance problems, causing unnecessary waste. This paper describes a low-cost, high-efficiency, small-power frequency converter. It introduces the method for generating SPWM signals, the structure of the inverter's main circuit, the specific design of the drive circuit, and the microcontroller-based control implementation. The frequency converter has comprehensive protection functions, including over- and under-voltage protection at the power input, and grounding protection, short-circuit protection, overcurrent protection, and system overheat protection at the power output. It features an LED display interface and a keyboard input interface, capable of displaying output voltage, frequency, and current values. This frequency converter boasts advantages such as small size, reliable operation, ease of operation, and low hardware cost. The hardware block diagram of the frequency converter system is shown in Figure 1. The system consists of a PTC16F877 microcontroller system, a dedicated chip SPWM signal generation circuit, a power drive circuit, a keyboard input and digital display circuit, an analog signal acquisition and conversion circuit, a protection circuit, a rectifier circuit, and an inverter circuit. The PTC16F877 microcontroller system is used to implement its control functions; the SPWM dedicated chip SM2001 generates SPWM signals and is controlled by PTCI61=87.7; the power drive section uses the high-performance intelligent drive chip HCPL-316J and peripheral circuits; and IGBTs are used to form the inverter bridge. [b][align=center]For more details, please click: Research on Economic Frequency Converters[/align][/b]