LCD TV vulnerable integrated circuit - power circuit - circuit diagram - Huaqiang Electronic Network

Industrial Router Crystal 3.2*2.5mm 3225 26M (26.000MHZ) 12PF 10PPM 20PPM 30PPM

MOS power IC full range

One-piece inductor

——STR--W6856, STR-×6759N, TIEA1507
SR-W6856 switching power supply thick film circuit
STR-W6856 is a high-efficiency and high-power thick-film circuit produced by Sanken. It contains a feedback regulator control circuit and a high-power FET. When the load is light (such as standby), the thick MOSFET internal MOSFET The switch tube operates in an intermittent oscillation mode to reduce the power consumption of the power supply, thereby improving power supply efficiency. In addition, the thick film block has overvoltage, overcurrent, and overload protection functions, and is provided with a maximum on-time limiting circuit.
The relevant circuit of STR-W6856 in Xoceco LC-20Y15 LCD TV power supply board is shown in Figure 1. The pin function and measured data are shown in Table 1.



STR-X6759N switching power supply thick film circuit
STR-X6759N is a thick-film circuit for switching power supply introduced by Sanken. It contains an oscillator, error amplifier circuit, voltage regulator control circuit, drive circuit, high-power MOSFET switch tube, etc. It is packaged in a 7-pin vertical package. In Changhong GP02 and other types of LCD TV power supply board, STR-X6759N is used as the main switching power supply circuit, as shown in Figure 2. The pin function and measured voltage are shown in Table 2.
After the second boot, the main board MCU outputs a high level, Q804 saturates and conducts, and the light-emitting diode inside the photoelectric trap IC804 emits light, which causes the equivalent resistance of the phototransistor to become small, Q801 is turned on, and the 22V starting voltage is passed through the Q801 collector. Send to IC8014 foot. After the IC8014 pin receives the startup voltage, it charges the C806, and the voltage of the 4 pin of the IC801 starts to rise. When the voltage of the 4 pin rises to 18.2V, the internal oscillation circuit of the thick film IC801 starts to work and outputs the switching pulse, and the switch is turned on. The power supply enters normal working condition.


TEA1507 second generation green power controller
TEA1507 is a green energy-saving power chip introduced by Philips Semiconductors. Compared with Philips Semiconductors' first-generation green chip, TEA1507's operating mode efficiency has increased by 10%, and it has taken a step forward in energy saving. 3.
The TEA1507 replaces the traditional step-down startup circuit with a chip-scale high-voltage (650V) startup circuit. The drain pin pulls current from the high-voltage power supply and outputs current from the Vcc terminal to quickly charge the external capacitor. When the voltage is higher than 4V, the internal oscillation circuit of the IC starts to work.
The TEA1507 has several operating modes for different output powers to improve efficiency. For high power, only after the transformer is demagnetized (zero current), the next switching cycle is started. At this time, the drain voltage reaches the lowest value to reduce the switching loss. In a very low power state, the voltage controlled oscillator (VCO operating mode) can reduce the frequency down to a minimum of about 6 kHz, and the integrated circuit operates in current mode for better regulation.
The main and sub-switching power supply of Philips 47PF7422 LCD TV adopts TEA1507, the sub-switching power supply generates +12V voltage, and is sent to the main board to supply power to the main board control system after the step-down. The main switching power supply generates +24V voltage, mainly for the backlight driving circuit. As shown in Figure 3. The positive terminal of C907 is about 400V, and the 5th and 4th windings of the switching transformer T907 are applied to the drain of the switching transistor Q901. The other is connected to the 4th and 7th windings of the T907, and the R930 is added to the 8th pin of the TEA1507 (IC904). The starting current source circuit charges the external capacitor C921 of the 1 pin. When the voltage across C921 is higher than 4V, the internal oscillation circuit of IC904 starts to oscillate, and the output pulse from its 6-pin output is applied to the switch through R942, D914, and R963. Tube Q901 gate, control Q901 works in the switch state, so that the switching power supply enters the normal working state. The 8-9 winding of the switching transformer T907 will induce the induced voltage to be rectified by D907, filtered by L915 and C921, and provide the working voltage of the IC904 pin 1 after completion.
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