With the development of the market and widespread environmental concerns, low cost, low standby power consumption and high efficiency power supply IC has been gaining popularity. Reduce system standby power consumption and improve the conversion efficiency of the system direction of development of green power IC. Today's power supply is used widely, but in most cases, the power is in standby mode, although a single power supply power consumption in the standby state is relatively small, but the entire amount add up to a huge market lead to the total power consumption is quite large, accounting for 15% of the total power consumption of the entire power even more. After rapid development in recent years, power IC technology, most of the products currently on the market can meet the requirements of the standby power consumption of 300mW under the Energy Star EPS2.0. Today, ultra-low standby power consumption technology became popular in 30W or less power in standby power consumption can reach a minimum 30mW, the future is expected to be lower.
In the fierce market competition environment, Xi'an core is integrated with technical advantages and strengthens R & D management, and continuously improve high-performance green power chip product line. Based on the existing SW265X series, SW253G and SW2263, the latest SW2273, SW2801 (QR mode) and SW2306 (QR mode) are introduced, and ultra-low standby power-to-high-efficiency, ultra-low standby power consumption green power chips. To meet market demand, the core send targeted introduced a high-performance, low-cost, current mode PWM controller --- SW2604, the peripheral circuit chip simple, flexible system design; standby power consumption is less than 200mW, suitable for adapter, STB power supply, LED lighting and small appliances. This article will focus on the technical characteristics and application design considerations of SW2604.
Reference SW2604 internal circuit block diagram: FIG 1
SW2604 technical characteristics
Reference SW2604 internal circuit block diagram shown in Figure 1. The power controller can operate in typical flyback circuit topology to form a simple an AC / DC converter; wide voltage range of 85 ~ 265V can provide continuous output power of 12W; optimization of circuit design by means of the combination of high and cost bipolar manufacturing process, maximize savings in the overall cost of the product. SW2604 internal circuit shown in Fig. Internal chip enable circuit is designed as a particular current inhalation, amplification itself can be used to complete the startup power switch (switch for amplifying Ib, Ic), thereby significantly reducing the power consumption of the startup resistor. At low output power, Ic will automatically reduce the operating frequency, in order to achieve very low standby power consumption; when the power is turned off the tube, the internal circuit of the power tube reverse bias, the direct use of bipolar transistors of high withstand voltage CB characteristic, a substantial increase in withstand voltage of the power tube of 700V high pressure, which ensures the safety of the power tube; chip also provides a perfect anti-overload, saturation prevention function in real time to prevent overload, saturation of the transformer, output short circuit and other abnormal conditions, improve the reliability of power supply. SW2604 main features are as follows:
A variable operating frequency
SW2604 operating frequency adjustable by an external capacitor CT. Chip internal current source capacitance CT 100μA constant current charging clock rising edge is formed, when the charged voltage to 2.5V, the internal circuit will pull-down current of 1.9mA discharge CT, clock falling edge is formed, to complete one clock cycle. For a bipolar power switching, the storage time need to consider the switching losses, the switching frequency is usually disposed below 70KHz.
B over temperature protection
SW2604 chip integrates accurate over temperature protection. Chip internal temperature reached 140 deg.] C, a thermal protection circuit, the pull-down clock signal, the switching frequency decreases, reducing power consumption. Switching frequency decreases with increasing temperature, until the oscillator is turned off. as shown in picture 2.
FIG 2: SW2604 chip integrates accurate over-temperature protection
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