THX203H is a high-cost current mode PWM controller produced by Tonghua core microelectronics. It is designed for high cost-effective AD / DC converter, providing up to 12W continuous output within the wide voltage range of 85V-265V. Power, peak output power can achieve L8W.
THX203H detection steps
IR refers to a leakage current.
IF is the model of the diode is an ampere number.
VR is the maximum circulation current of the diode.
Vf is a pressure drop, the silicon tube is 0.7V germanium is 0.3V diode detection method and empirical 1 Detection of small power crystal diode discriminant, negative electrode
(A) Observe the symbol mark on the casing.
The symbols typically marked with a diode on the outer casing of the diode, one end with triangular arrows is a positive electrode, and the other end is a negative electrode.
(B) Observe the color point on the outer casing.
On the outer casing of the point contact diode, a polar color point (white or red) is typically labeled.
Generally, one end of the labeled colored point is a positive electrode.
There is also a colored ring on the diode, one end of the colored ring is an negative electrode.
(C) The measurement of the smaller measurement is accurate, the one end of the black table pen is positive, and one end of the red surface pen is negative.
The maximum operating frequency fm is detected.
The crystal diode operates, in addition to visiting outwards from the relevant feature table, commonly used in the practical use of the hair contacts inside the diode to distinguish, if the point contact diode belongs to the high frequency tube, the surface contact diode is mostly a low frequency tube.
In addition, it is also possible to test with a multimeter R1K gear, and generally the forward electrical resistance is less than 1k high-frequency tube.
THX203H troubleshooting method and skills
First check if the fuse FL is blown, and there is a 300V DC voltage at both ends of EC2. If there is an explanation of 300V, the filter circuit is working properly. Whether the switching power supply output terminals 20V, 15V, and 3.3V power group have a weak voltage output, if the power supply has been fixed, that is, the main transform circuit of THX203H is basically normal, and the fault should occur in the feedback network, stable The pressure sample or secondary output portion should focus on the 3.3V power supply of the voltage sample and the sampling voltage circuit composed of IC2 (PC817), IC3 (TL431), and the switching power supply feedback winding, rectifier diode D6 and filter capacitor EC3 The problem can also cause an output voltage, and the output section has a short circuit that will not work properly.
If the output is no voltage and 300V does not immediately disappear immediately after the shutdown, the circuit does not have a registration, and if the start resistor R2 is normal, if R2 is normal, it is necessary to consider whether THX203H itself is damaged. Technology area
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