To control power delivery to the induction cooker, which is transferred to cookware, the authors discuss quasi-resonant and half-bridge topologies with reference designs from STMicroelectronics.
Quasi resonant topology
The quasi resonant induction cooktop system rated at “1.8KW” has been developed using STGWT20IH125DF, a 1,250V, 20A IH series trench gate field-stop IGBT and STM8S003F3, an 8-bit microcontroller.
The ready-to-manufacture reference system is incorporated with comprehensive safety mechanism to handle voltage transients and inconsistent cookware/utensil. The block diagram is shown in Figure 3, while the actual system is shown in Figure 4.
Figure 3: Block diagram of the quasi resonant induction cooktop.
Figure 4: Quasi resonant induction cooktop: A 1.8kW ready-to-manufacture solution.
The half-bridge induction cooktop system evaluation board rated at a much higher “3.5KW” has been developed using STGW40H65DFB – HB series 650V, 40A high speed trench gate field-stop IGBT, the L6491 4A gate driver and STM32F072, a 32-bit MCU.
The system incorporates a comprehensive safety mechanism to handle voltage transients and inconsistent cookware. The block diagram is shown in Figure 5, while the actual system is shown in Figure 6.
Figure 5: Block diagram of the half-bridge resonant induction cooktop.
*Figure 6: Half bridge Induction cooktop. Shown above is a 3,500W evaluation board.
Table 2: Feature comparison between quasi resonant and half bridge resonant induction systems.
Induction cooking is a promising technology for those seeking sustainability in home kitchens, hotels and restaurants, and is clearly a better choice over standard electric or the expense and carbon footprint of installing a gas line.