Power supply no voltage output troubleshooting
The switching power supply part of the induction cooker generally generates two voltages, 18V and 5V, of which 5V supplies power to the main control chip and key display driver chip, and 18V supplies power to the fan and IGBT drive circuit. Because the power consumption of the control circuit of the induction cooker is relatively small, switching power supplies generally use driver chips with on-chip integrated switching tubes. In order to save costs, many power supplies also use non-isolated drivers. The commonly used driver chip models are VIPer12A, etc.
Working principle of induction cooker switching power supply
The parameters of the components used in the peripherals of switching power supplies with different chips and solutions will be slightly different, but their basic working principles are the same. Take VIPer12A as an example, which is a very commonly used model in induction cookers. VIPer12A is a power driver chip launched by STMicroelectronics. The chip integrates a high-voltage power tube and a voltage source is integrated in the drain of the chip switch tube, so the power supply can work without a start-up resistor. The chip is also integrated with over-temperature, over-current, over-voltage and other protection circuits. According to different packages, its maximum output power can reach 13W.
In addition to the internal voltage generating circuit of VIPer12A, its power tube structure is also quite special. The internal switch tube has two sources, and the areas of the two principles are different, and a current sampling resistor is connected between the source with the smaller area and the ground. Since the sampling resistor is connected to the source with a small area, the current flowing through this resistor is not the total current flowing through the switch tube, but a part of it, and the total current can be obtained by proportional calculation. This design not only reduces the loss on the sampling resistor, but also has a certain energy-saving effect, and does not require a current sampling resistor outside the chip, which simplifies the circuit structure and saves costs. This is also a unique aspect of this chip design.
