Application of Vlper12A switching power supply chip in household dishwasher controller

0 Introduction

With the development of electronic technology, the miniaturization, lightness and low cost requirements of home appliance controllers have made the power supply develop in the direction of lightness, thinness and high efficiency. Although the traditional linear power supply technology is now relatively mature, it also has a large number of integrated linear voltage-stabilized power supply modules, and has good stability, small output ripple voltage and reliable use. However, it usually requires a large and bulky power frequency transformer and isolation unit, and the volume and weight of the filter are also large, so its power efficiency is very low, generally only about 45%, which is difficult to meet the requirements of the development of electronic equipment. The switching power supply does not require a heavy power transformer, and has the advantages of small size, light weight, wide input voltage range and high efficiency. At the same time, as the switching power supply becomes increasingly high-frequency, its size is also smaller. Therefore, the application prospects of switching power supplies in home appliances are also broader.

1 Working principle of switching power supply

The switching type voltage-stabilized power supply usually uses power semiconductor devices as switches, and adjusts the output voltage by controlling the duty cycle of the switch. Since the adjustment tube in the switching type voltage-stabilized circuit works in the switching state, the power consumption is small and the circuit efficiency is high. There are many types of switching power supplies. According to the connection method between the adjustment tube and the load, they can be divided into series type and parallel type. The series switch voltage regulator circuit is a step-down circuit, and the parallel switch voltage regulator circuit is a step-up circuit. Its modulation method can be divided into pulse width modulation (PWM), pulse frequency modulation (PFM) and mixed modulation. Among them, PWM is the most popular. This article mainly introduces PWM switching power supplies.

In general, the working principles of various switching power supplies are basically the same. Figure 1 shows the basic structural block diagram of the switching power supply. The working principle of the switching power supply is mainly based on the input voltage and the output voltage change. The duty cycle of the switch is controlled by the feedback circuit to change the width of the control pulse, and the input voltage is converted into a pulse signal, which is then added to the output rectifier filter circuit after being transformed by the pulse transformer. Finally, after smoothing and filtering, a DC output voltage proportional to the output pulse width is generated.


The PWM control process generally adjusts the pulse duty cycle by changing the on-time Ton of the switch tube while keeping the switching period T of the adjustment tube unchanged, so as to achieve the purpose of voltage stabilization. At present, many manufacturers have launched a variety of pulse width modulation switching power supply controller chips. Most of them integrate the switch tube into the chip and contain various protection circuits.

2 VIPER12A intelligent switching power supply chip

VIPer12A is a low-cost single-chip intelligent switching power supply IC that uses the VIPer series as the control element. Its components include a 60 kHz integrated pulse width modulation controller and a high-voltage power MOSFET with a breakdown voltage of 730 V. VIPer12A has an intelligent enhanced adjustment function and a built-in protection control unit. Therefore, the number of components required for its external circuit is only half of that of a discrete circuit. Therefore, it is very consistent with the design requirements of home appliance controllers.

Figure 2 shows the pin arrangement diagram of VIPerl2A. The device has two package forms, SO8 and DIP8. The functions of each pin are as follows:

SOURCE: Source pin, which is the source terminal of the internal MOSFET and the circuit reference ground:

FB: Feedback pin, feedback input, used to expand the 0-1 V feedback control voltage range and limit the drain current peak of the MOSFET;

VDD: Power pin, used to provide power to the control circuit inside the chip, and it is also connected to the drain high-voltage current source. In order to ensure that the power supply is more reliable, its start-up threshold (typical value) should be 14.5 V and should be turned off at 8 V;

DRAIN: Drain pin, which is the drain end of the high-voltage power switch MOS-FET, and can also be used for internal high-voltage current source and charging, with a maximum withstand voltage of 730 V.

3 Application circuit

Figure 3 shows a switching power supply circuit in a washing machine and dishwasher controller using VIPer12A as a control element. The circuit uses a coupled inductor to achieve the conversion of two outputs, and its converter is based on a buck-type BUCK circuit. The circuit works in offline mode and has a wide input voltage range (from 80 to 285V AC voltage), which can provide two outputs of Vout1 of 5 V and Vout2 of 24V. Both outputs use diodes to prevent overvoltage, which are VD04 and VD05 in the figure.


The input part of this circuit includes a resistor RO1, a rectifier diode VD01 and a filter capacitor C01. The resistor is a protective resistor designed to prevent excessive current. The capacitor is a filter element. It can be used to store some energy when the diode is turned on, and then gradually release it. The larger the filter capacitor, the better the filtering effect. However, if the capacitor is too large, the heating of the diode will be more serious. Therefore, all aspects should be considered comprehensively during the design.

The output inductor L is an inductor with two coupled windings wound on the same ferrite core. The correct output voltage can be obtained by using the correct turns ratio and coupling factor. The inductor used in this circuit is 1.5 mH.

The feedback circuit consists of the voltage regulator DZ02, the transistor G01, the diode VD03, the capacitor C04, and the resistors R02 and R03. The startup voltage of VIPer12A is 14.5 V and the shutdown voltage is 8 V. After power is turned on, the circuit first charges C03 to 14.5 V. When the turn-on voltage of Vdd is reached, VIPer12A starts to work and the MOS-FET starts switching. The 5 V and 24 V outputs are obtained through the turns ratio of the transformer. When the 5 V output decreases, the current flowing through VD03 decreases due to the unchanged voltage on the DZ02 voltage regulator, thereby reducing the current entering the feedback pin FB. In fact, the FB pin is very sensitive to current changes, and the resulting feedback voltage also decreases, which in turn causes the circuit to adjust the switch duty cycle and increase it, and finally adjust the output voltage back. The capacitor C02 between FB and S is used to improve the rectification performance and prevent high-frequency interference. C08 and R04 are mainly used for output filtering.

4 Conclusion

After actual application and testing, it has been proved that the circuit has high stability, and the ripple is only 20 mV, and it is very light. At the same time, it meets the electromagnetic interference requirements of international organizations and is a switching power supply with good performance.