Overhauling method of switching power supply

By authorswitching power supply,Switching Power Supply manufacturer,,AC DC power adapter,Cable,Power Bank,LED Power Supply,China 2017/7/12 16:37:13
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Overhauling method of switching power supply

I. circuit composition

1. if the circuit is mainly composed of self-excited oscillation circuit, voltage regulator circuit, protection circuit, remote control, DC startup and shutdown circuit. Self oscillating circuit is composed of a switch V513, the switch transformer T511 1 and 7, the winding, a capacitor C514, a diode VD517, starting 20, 21, resistance paste paste paste 22.

The 2. voltage stabilizing circuit is composed of two parts: sampling circuit and pulse width adjusting circuit. The sampling circuit is composed of paste 51, paste 52, BP551 and paste 53, etc. the reference circuit is composed of a voltage regulator tube VD561 and a resistor paste 44. The comparison tube is V553. Pulse width adjustment circuit consists of photoelectric roller, VD515, transistor, V511, V512 and bias circuit.

3. protection circuit is mainly composed of over-voltage protection circuit, over-current protection circuit and switch protection circuit of three parts. Overvoltage protection circuit consists of VD518, VD519, R515, paste 23 and V512 and so on. The over-current protection circuit consists of R524, R526, paste 15 and V512.

The protection circuit of the switch tube mainly consists of a damping circuit composed of C516 and paste 25, and a soft starting circuit composed of paste 20, paste 21, R5x and 1511, and paste 24, C517 and so on.

4. remote control DC startup and shutdown "circuit is composed of V576 and VD515 is composed of photoelectric stove.

Two, overhaul methods, first disconnect all the switching power supply, *130v output at the end of 220V / rib w incandescent lamp.

1. the input switch of the power input is composed of rectifier and filter circuit. Can use the multimeter DC voltage file to check whether the voltage of the V513 collector of the switch tube is around 3 rib V, to judge whether the part of the circuit is normal or not. If the voltage is 0V, indicating that this part of the circuit is faulty, it is necessary to overhaul it. The main components of the circuit are fuse F501, current limiting resistor, suspension bridge, filter capacitor, C5 sting and so on.

2. detect intermittent oscillation part of the circuit

Intermittent oscillation is the key part of switching power supply. Whether the switch can enter the switch working state is the key to realize the energy conversion between the primary and secondary of the switch transformer. The operation of the whole intermittent oscillation circuit can be judged by detecting whether the base of the switch tube v513 has a rectangular pulse voltage or not, and the method is as follows.

(1) detecting whether the intermittent oscillator is started or not:

DC voltage detection method. The V513 base voltage of the switch tube is detected by the DC voltage meter of the multimeter. If the moth is between 1 and 0.2V, that is the oscillation of the oscillation circuit.

Voltage detection method of "dB". Test the V513 base or collector with the "6B" voltage in the multimeter dB.

Oscilloscope observation method. Observe whether the V513 base or collector has a rectangular pulse signal by oscilloscope. Note: during the measurement, with the negative form of million table must meet in the 300V voltage of the anode, the filter capacitor C507 anode.

(2) key detection circuit: if the intermittent oscillator does not start vibration, should focus on the following circuit.

Check whether the startup circuit composed of R520, R521 and R522 is open or not.

Check the switch transformer T511, winding winding, paste 19, C514, 15U, paste 24 of the positive feedback circuit, whether there is open circuit or short circuit, especially the capacitor C514.

Check the voltage regulator circuit is faulty, should focus on checking V553, V511, V512, as well as VD515 and VD516.

Check whether the protection circuit is faulty, focus on the VD518V512, and disconnect the protection circuit if necessary.

Detection of the output of 3. switching power supply VD519,

By detecting whether the output voltage is normal or not, judge whether the pulse rectifier circuit is faulty or not. Should focus on detecting rectifier diodes VD551, VD552, VD553, VD554, VD555, filter capacitor C561, C562, C563, C564, C565, and current limiting resistors.

The voltmeter for monitoring the output with 000 detection of 4. voltage stabilizing circuit part, and then slightly adjusted in the sampling circuit of potentiometer, voltage detection output is changing. If the output voltage can rise and fall, that the voltage regulator circuit is basically normal; otherwise there is a fault. Both ljV553 and VD515 should be the focus of inspection, VD56l.

Three, matters needing attention.

1. overhaul switch power supply, first of all should determine the fault is a power failure, not because of load failure caused by power supply is not normal.

2. make sure that the power control terminal of the microprocessor is in the boot state 

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