THX203H switch circuit diagram Daquan (five THX203H switch circuits)

THX203H switch circuit diagram Daquan, THX203H switch circuit diagram 3: The friend's set-top box and color TV were damaged. After I was inspected, I found that the power block THX203H fried, the fuse was blown, the resistance R3 opened, and the remaining elements were removed without damage (at the time, the secondary 3.3V rectifier diode and Each filter capacitor). After replacing THX203H and R3. Do not boot without load. Each voltage output is normal. Then the nine plates are taken. 3.3V voltage is only 3V left and right. The rectifier diode and filter capacitance of the 3.3V side are then replaced. But the fault is still. Maintenance is also in trouble. Direction and check again yesterday. It was found that the R3 resistance of the first change was broken again. Replace the R3 resistor again. No load and load are normal. This maintenance summary is as follows: Due to the 3.3V rectifier diode or filter capacitance, normal 3.3V voltage can be output during no load. But after the load is loaded. The power supply is significantly increased. The primary R3 resistance is caused. It is worth noting to pay attention in future power maintenance. THX203H switch circuit diagram 4: THX203H Output power 12W.THX series power IC adopts patented technology, prevents anti-counterfeiting, which can meet higher green environmental standards, with China's independent intellectual property rights, including more than ten patents worldwide, performance It can be completely replaced by ViPer12A / 22A, Fairchild's FSD200 / 210/311/321/02659, etc. However, no output power consumption can be less than 0.25W, which is more suitable for future new energy standards. THX203H switch circuit Figure 5: In the normal working state, the voltage of the FB will determine the value of the maximum switching current, the higher the voltage, the larger the switch current (limited to peak current limits). The 600UA current source is pulled in the FB pin, and the pull-down electric resistance is about 33 kΩ (approximate equivalent value). In addition, when the FB voltage is less than 1.8V, the oscillating cycle will increase, the switching frequency is lowered, the more the switching frequency will be lower than the switching frequency. External FB capacitors will affect feedback bandwidth, which in turn affect certain external parameters, such as transient characteristics. For the value of the CFB capacitor, the typical application can be selected between 10-100 NF, depending on the frequency characteristics of the feedback loop. Recommended reading: THX203H Chinese information, PDF

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