Knowledge of maintenance of touch switch and key switch in power supply
Release time：2019-05-16 Clicks： Click
What should we pay attention to in the maintenance of power supply when touching switch and key switch? Specific steps and details, we will give you a detailed introduction below.
According to the mechanical performance of on-off position, touch switch and key switch can be divided into self-repetitive switch, non-self-repetitive switch and lock switch. What should we do when the power supply of touch switch and key switch fails? Here we teach you how to repair the power supply of touch switch and key switch.
1. Detecting whether the lightly touched switch and key switch D1D4 of rectifier circuit breaks down or breaks down, whether the capacitance of filter circuit is damaged, whether the balancing resistors R1 and R2 are normal, whether the voltage-reducing resistor R3 is burnt down or if the resistance value increases (test in case of power failure);
2. Detecting whether the absorption circuits D5, R11 and C9 are normal (test under power failure);
3. Under the condition that the above components are normal, we can take off the power supply board of the touch switch and the key switch from the frequency converter and conduct the power-on test separately. When the voltage regulator is slowly adjusted to the rated voltage value of the switching power supply, the squeak of the transformer during starting vibration can be heard. If the sound of starting vibration is not heard, the DC voltage between the positive and negative stages of UC3844 power supply can be detected by a multimeter.
4. Detecting rectifier and filter elements of secondary output winding, focusing on whether the filter capacitor is bulging or damaged, in order to eliminate the possibility of short circuit of secondary circuit;
5. After confirming the normal voltage of UC3844's power supply terminal, the oscilloscope can be used to check whether the six feet of UC3844 have PWM wave output to the trigger end of touch switch and key switch tube (according to the different circuit design, the frequency of PWM wave is generally between 20KHZ100KHZ).
6. If there is no PWM output, replace the timing elements C5, R8, C6 or UC3844. After the removal of the above steps, the switch power supply with light touch and button switch should be able to work normally. In frequency converter, there are many kinds of switching power supply, but the basic principle is the same. For example, every PWM management chip has power supply terminal, timing element RC network, output PWM wave port and so on. As long as we understand their working principle, we can eliminate the fault according to certain methods and steps.