Production of ICE385565P single-chip switching power supply-EEWORLD

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As various household appliances are flooding into households, the proportion of standby power in household electricity consumption is also increasing. According to surveys, standby power generally accounts for about one-tenth of the power consumption. If this part of electricity can be saved, 14.3 million tons of CO2 can be reduced to the atmosphere.
Televisions, monitors, computers, etc. all use switching power supplies.
Their standby power reaches 1W, so it is necessary to improve the commonly used switching power supplies and design new switching power supplies with high efficiency and low energy consumption.
In addition, the switching power supply contains a DC conversion circuit. It will generate high-order harmonics in the power supply line, resulting in a low power factor and increased energy consumption of the power supply line. Moreover, the high-order harmonic components in the current may cause the burning of capacitors in the substation and cause the rotor of the hydroelectric generator to vibrate at twice the power frequency and be damaged. Therefore, it is necessary to reduce the high-order harmonics generated by the switching power supply.
The traditional switching power supply structure is shown in the figure below, which connects the power factor correction circuit (PFC, Power Factor Correction) and the DC-DC conversion circuit in series. Therefore, the efficiency is low and it is also quite difficult to reduce the standby power. The structure of the switching power supply of this design is shown in the figure below, which can be called a hybrid parallel mode. By using an excellent DC/DC conversion IC, supplemented by voltage feedback and measures to increase the conduction angle, this switching power supply is within the power range of 70 to 350W. The efficiency is over 90%, the standby power is only 0.1W, and the suppression of high-order harmonics has also reached Class D of the IEC61000-3-2 specification (applicable to LCD TVs, monitors, and computers).

The conversion IC uses Infineon's third-generation highly integrated power integrated circuit, the COOLSETF3 series product ICE385565P. It combines Infineon's COOLMOS power metal oxide semiconductor field effect transistor (MOSFET) and a new pulse width modulation (PWM) control integrated circuit in a single package. The standby power consumption is 1.3 less than other similar products, which is suitable for designing a more cost-effective and efficient power supply system.
The whole machine circuit is shown in the figure below. The AC power supply is rectified by BD1 after passing through the common mode choke Lcm; L1 and C1, C2 form a bamboo filter (the capacity of C1 and C2 is very small, and it is still a pulsating waveform after filtering); PT is used to suppress surge current. The pulsating DC voltage after rectification and filtering is turned on and off by the field effect tube in IC1 through the primary winding of transformer T1 and diode D3. The pulsating DC voltage is output from the secondary winding of T1 through D7. The
DC voltage obtained after filtering by D2 and C3 is turned on and off by the field effect tube through the primary winding of T2. The DC voltage is output from the secondary winding of T2 through D8 and D9.
As a result, the pulsating DC voltage and the DC voltage are added and output. This causes a large ripple in the output waveform, but the ripple disappears after the feedback is added. The 6t coil, inductor L2 and diode D1 are specially designed in the circuit to suppress high-order harmonics.
A π-type filter composed of C10, L3 and C11 is added to the output end of the circuit. When the transformer secondary voltage exceeds the voltage on the filter capacitor, the current waveform flowing through the inductor and the diode becomes a triangular wave. After being averaged by the π-type filter, it is equivalent to expanding the conduction angle, reducing the peak current, and thus suppressing high-order harmonics.

Keywords：ICE385565P Reference address：Production of ICE385565P single-chip switching power supply

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