Fault Analysis:
There are many reasons for this failure, including synchronization circuit, surge protection circuit, pot detection circuit, drive circuit, IGBT high-voltage protection circuit and the PWM signal circuit, the following is the repair method.
(a) Synchronization circuit failure
Check the steps:
①In the case of standby connected to the coil tray, use a multimeter to measure the U1-LM339 8-pin and 9-pin operating voltage, (8-pin 1.75V, 9-pin 1.9V), if the voltage is not normal, please check R18, R1, R4, R239, C214, C209, D213, replace the problematic components, the fault can be eliminated. If the voltage of the above 2 pins is normal, then we measure U1 - LM339 pin 14 voltage is high, the voltage value of 1.23 V. If it is low, it means that U1 has been damaged (here to rule out the failure of the PWM signal circuit).
②If it is high, please use a wire to ground the 9 feet, and then measure the voltage of the 14 feet is low, if it is still high, it means that the U1 - LM339 has been damaged, replaced with the same type and specifications of the U201 - LM339, power on the test machine is normal, the fault is eliminated.
(B), surge protection circuit failure
Fault Analysis:
Surge protection is generally only a few millionths of a second in the power supply of a violent pulse, in order to protect the IGBT is not damaged to protect the circuit will be output a low level so that the IGBT to stop working, when the surge is over the circuit will automatically return to normal.
Check the steps:
①First of all, measure the U2 - LM339 pin 13 is a high level, if it is a high level, that is, the surge protection circuit does not act. If it is low, it means that the surge protection circuit has been acted on (this pin is connected to the output pin of the IGBT high-voltage protection circuit, here is to rule out the failure of the IGBT high-voltage protection circuit analysis). We then measure the U2 11-pin voltage is 3V, 10-pin voltage is lower than the 11-pin voltage (10-pin voltage of 2.51V), if so, it is said that the U2-LM339 has been damaged, replacement of the fault can be eliminated. If U202 6, 7 feet of voltage is not normal, please check R5, C22, R6, D206, D207, C206, C207, C217, R218, R223 is normal, the abnormal component replacement, the fault can be eliminated.
②If the measured voltage of U2 pin 14 is only 0.3V, the voltage of pin 11 is greater than the voltage of pin 10, we then measure the voltage of the main IC pin 1 is low, if so, it means that the main IC has been damaged. Replace the IC with a new one and the problem will be solved.
(C), check the pot circuit failure
Check the steps:
①When there is a pot can not be detected, the first thing we do is to measure the main IC pin 19 whether there is a 5V voltage, if the voltage is 0V, it means that the main IC has been damaged, replace the fault can be eliminated. If the voltage is normal, please measure whether there is 0.8V at pin 2 of U2-LM339, if not, please check it according to the method in step 2. If there is, please check Q202, R42, whether it is normal. Replace the damaged components, the fault can be eliminated. If the above components are not damaged, we have to determine whether it is the problem of the main IC, or U2-LM339. With a wire to the U2 4 feet and 5V power supply, if the measured voltage is low, it means that the main IC is bad, if the measured voltage is still high, it means that the U2 - LM339 has been damaged, to replace the above damaged components, power on the test machine is normal, troubleshooting.
②If in the last step did not short U2 before the measurement of U2 foot 2 is low, then we will measure the U2 foot 4 and 5 feet of the voltage is normal (4 feet of the low level, 5 feet of the voltage of 3V), if the voltage is not normal, it is necessary to power off to check the resistance of R218, R217 is normal, the abnormal component replacement. If the measured voltage is normal, and 2 feet of the output or low level, it is said that U2 has been damaged, replace the same type of LM339, power on the test machine is normal, troubleshooting.
(D), drive circuit failure
Check the steps:
①First, remove the coil disk power measurement of U1 pin 2 is a high level, and then measure the 5 feet and 7 feet of the voltage, these two feet are driving the circuit on the reference voltage of the two comparators, there is a fixed value, (pin 5 1.7V, pin 7 is higher than the 5 feet of the voltage of 0.4V or so) which with the front stage of the pulse signal sent over the oscillation circuit. Oscillator circuit to send over the pulse signal for comparison, the results of the comparison were sent to Q2 and Q1 two transistor base for the drive signal. If the voltage of these two feet is not normal, please check R253, R252, Z203 whether there is a problem, the problem components to replace, try normal, troubleshooting.
② (Note: This step must be removed from the coil disk, otherwise it will cause burning IGBT). If the U1 5, 7 feet of the normal voltage, power off the U1 6 feet and 5V power supply connected to a multimeter to measure the U1 1 feet and 2 feet of the voltage is low, if any one of these two feet for a high level, it is said that the U1 has been damaged, replaced with a new LM339, the fault can be eliminated.
3 If the two feet of the output voltage are normal, and the fault is not ruled out, we have to Q1, Q2, R234, R235, R237, R238, R7, R8, Z1, D212, check the existence of problematic components watchman down, replaced with the same type of components, power on the test machine is normal, the fault can be eliminated.
(E), IGBT high-voltage protection circuit failure
Failure Analysis:
When the C-pole voltage of the IGBT is higher than 1135V, the protection circuit will act. At this time, the IGBT output power will be turned off.
Detection steps:
①First of all, in order to determine whether the failure is caused by the IGBT high-voltage protection circuit, we first measure whether the voltage of U2 pin 14 is high (this pin is connected to the output pin of the surge protection circuit, this is to rule out the failure of the surge protection circuit for analysis). If so, it means that the protection circuit does not operate. If it is low, it means that the protection circuit has acted. We have to measure the U2 pin 8 and 9 of the voltage (8 feet 0.49V, 9 feet 3.85V). If the voltage of these two feet is normal, and the 14-pin output is low, we can determine that the U2-LM339 has been damaged. Replace the fault can be eliminated.
②If the voltage of 4 feet and 5 feet is not normal, we have to check R220, R221, C225, R241, R240, to replace the damaged components. Power on the test machine is normal, troubleshooting.
③If the measured high level of U2 pin 14 is only 0.3V, the voltage of pin 9 is greater than the voltage of pin 8, we then measure the voltage of the main IC pin 1 is low, if so, it means that the main IC has been damaged. Replace the IC with a new one and the problem will be solved.
PWM signal circuit failure
Failure analysis:
If the PWM signal is not output, the IGBT has no drive signal and thus does not work, the pot detection circuit does not detect the correct pulse signal and alarm.
Check the steps:
In the case of standby to measure the main IC voltage of 13 pins, the normal value of 2.25V (RMS), if the voltage value is not normal, please check the R211, R212, R213, EC12, Q202, C208 whether there is a problem, to have problems with the replacement of components. If all the above components are OK, it means the main IC is damaged, please replace it.
Burning water
Failure Analysis:
The main reason for this failure is the current detection circuit, the pot temperature detection circuit problems or the use of pots and pans are not right. The following describes its repair method.
(A), the current detection circuit failure
Check the steps:
①Power on the standby in the case of measuring the main IC 17-pin voltage, the normal value of 0.46V, if the measured voltage is normal, and the fault is not eliminated. Please measure the transformer CT1 is normal, if normal, we can determine is the main IC has been damaged, replace the fault can be eliminated.
②In the previous step if the measured voltage is not normal, we have to D201-D205, D207, R207, R208, R222, C223, C215, VR1, CT1 to check the damaged components for replacement, the fault can be eliminated. If the above components are intact, and the fault still exists, then we can also locate the fault in the main IC, replace the new IC of the same type, power on the test machine is normal, troubleshooting.
3 in this fault, when the transformer CT1 damage, in the case of standby to measure the main IC 16 feet of voltage is not normal to determine whether it is good or bad, so we have to determine its good or bad in order to replace the main IC.
(B), pot temperature detection circuit failure
Failure analysis:
When the pot temperature detection circuit faults Influence the reason for not boiling water, mainly pots and pans temperature detection circuit components in the parameter changes. When the temperature of the water has not yet reached 100 degrees, the main IC detected the temperature has reached 100 degrees, thereby regulating the output of the PWM signal, thus appearing to boil water phenomenon. Please refer to the specific overhaul process - pot temperature circuit overhaul process.
(C), with the wrong pot
Because the induction cooker on different materials pots and pans heating power is different, we just change the United States of America's special pots and pans, the fault can be eliminated.
In addition, in the detection of circuit failure can refer to the attached page of the induction cooker test data in the book of the resistance to ground and pin voltage to determine the fault, the test environment is not connected to the coil disk in the case of measurement.