Switching power supply common breakdown maintenance

Switching power supply common breakdown maintenance

LCD monitor switch power supply is part of the common malfunctions: boot burning insurance tube, boot without output or output voltage high or low, but here is a brief
Introduce the fault maintenance.

Zhejiang netizen: my insurance switch power supply pipe burn out what to do?
Technician: the main examination on 300 v filter capacitor, the diode rectifier bridge and switch tube parts, anti-jamming circuit problem will cause the fuse to burn
Broken, black.It is important to note that because of the switch tube breakdown caused by the fuse is often accompanied by over current detecting damage resistance and power control chip.Negative temperature system
Number of thermistor is also easy to burn with fuse.
Jiangsu netizen: my no output switching power supply, but insurance tube is normal, this is how to return a responsibility?
Technician: this kind of phenomenon that switching power supply does not work, or after work to go into a state protection.First measured power control chip launch if there is a foot
Start voltage, if not start voltage or start voltage is too low, then check the start resistance and start feet whether the leakage of external components, such as power supply control chip normal at this time
, after the examination can quickly find fault.If a start-up voltage, then measuring the output of the control chip in the boot instantly if there is a high and low level of jump, if not jump
Oscillation circuit, control chip bad, periphery components or protection circuit has a problem, can be substitution control chip, first check the peripheral components;If you have jump, general
For switch tube bad or damaged.
Beijing netizen: I have the output voltage of switching power supply, but the output voltage is too high, how to deal with
Technician: in the liquid crystal display, the failure often comes from the voltage sampling and voltage control circuit.We know that the dc output, sampling resistor, error
Sampling amplifier (e.g., TL431), optical coupler and power control chip circuit together form a closed loop, the control of any problems will lead to the output
Voltage rise.

Several kinds of switch power supply topology

Several kinds of switch power supply topology

When we were in the production of switch power supply must know something about the structure of switch power supply, generally speaking of switch power supply structure is refers to the topology of switch power supply
Structure.There’re a lot about switching power supply on the network topology structure of knowledge, for the most part have a plenty of good, but there are still part of the answer and the information
Not enough detail.This article is through online data collecting and organizing relatively, though not the best, but it’s also a summary of switching power supply topology.Want to give
Customers to provide some help.
Dc power converter according to whether the input and output electrical isolation, can be divided into the isolation converter and isolation converter circuit.
Several kinds of switch power supply circuit topology:
Step-down converter (Buck), step-up (Boost) converter, polarity reversal lift pressure (Buck – Boost converter, Cuk converter single straight,
The flyback converter, the push-pull converter, half bridge, full bridge converter.

Several kinds of switch power supply topology

Several kinds of switch power supply topology

When we were in the production of switch power supply must know something about the structure of switch power supply, generally speaking of switch power supply structure is refers to the topology of switch power supply
Structure.There’re a lot about switching power supply on the network topology structure of knowledge, for the most part have a plenty of good, but there are still part of the answer and the information
Not enough detail.This article is through online data collecting and organizing relatively, though not the best, but it’s also a summary of switching power supply topology.Want to give
Customers to provide some help.
Dc power converter according to whether the input and output electrical isolation, can be divided into the isolation converter and isolation converter circuit.
Several kinds of switch power supply circuit topology:
Step-down converter (Buck), step-up (Boost) converter, polarity reversal lift pressure (Buck – Boost converter, Cuk converter single straight,
The flyback converter, the push-pull converter, half bridge, full bridge converter.

Discusses the problems of switch power supply interference

Discusses the problems of switch power supply interference

Switch power supply, both in the domestic and international markets at present, in the digital circuit has been widely used, but due to the switching power supply is always in itself
Working in the condition of high frequency switch, belongs to the strong interference source, so the interference of switch power supply itself directly threatens the normal work of the electronic equipment.Therefore, the antimicrobial
System of the electromagnetic noise of switching power supply itself, at the same time improve the perturbation resistance to electromagnetic interference, to ensure that the electronic equipment can work safely and reliably for a long time, is developed
And design of switch power supply an important subject.Normal use of switching power supply interference
Causes of the interference of the switch power supply which can be generally divided into two categories: one is the internal components of switch power supply interference from within;The second is the
External factors and make the switch power supply interference from outside.

About the switch power supply, internal interference in the first place

Reason: in addition, capacitor, inductor and wire due to work at a high frequency switch power supply, can make the low frequency component characteristics change, the resulting noise.
The internal electromagnetic interference (EMI) caused by the switch power supply is mainly produced by the basic rectifier higher harmonic current and power conversion circuit of peak voltage
Interference.
Basic commutation of the rectifier process is the most common cause of electromagnetic interference EMI.This is because ac power frequency sine wave after rectification is no longer a single frequency
Current, and become always flow component and a series of different frequency harmonic component, harmonic (especially the higher harmonic) along the conducted interference and the radial transmission line
Radiation interference, make the front end current distortion, on the one hand, make the pick up in the front of current waveform distortion on the power cord, on the other hand, through the power line to produce radio frequency (rf) dry
Are the one.The load switch tube is a high frequency transformer or energy storage inductors, at the instant of the switch tube conduction, appeared a lot of transformer inrush current, produce peak noise.
Power conversion circuit is the core of a switching power supply, it is produced with wider and harmonic more abundant.The main components for the pulse interferences
Switch tube switch tube and its radiator and distributed capacitance between the inside of the casing and the power supply wire, when the switch tube through the large, is substantially rectangular wave pulse current
The waveform contains many ingredients;At the same time, shut the power using the storage time of power tube parameters such as switching devices, high-current output stage, switch rectifier diode
Tube of reverse recovery time, can cause instantaneous short circuit, circuit produces large short-circuit current, on the other hand,
High-frequency transformer switching power supply in transformer, used for isolation and pressure, but because of the leakage inductance, will produce electromagnetic induction noise;At the same time, in the high frequency condition
Transformer under layer of the distributed capacitance between the primary side will be higher harmonic noise is passed to the secondary, and transformer distributed capacitance of shell form another high frequency channel, make the change
Transformer produced by electromagnetic field are more likely to form in other lead coupling noise.
The secondary side rectifier diode rectifier diode used in high frequency rectifier, as a result of the reverse recovery time factors, often forward current accumulation in charge plus the reverse voltage
When can’t immediately eliminate (because of the existence of the carrier, and current flows).Once the reverse current recovery when the slope is too large, flows through the coil inductance is pointed
Peak voltage, the leakage inductance of the transformer and other distribution parameters will produce strong under the influence of high frequency interference, the frequency of a few MHz.
Switch power supply, external disturbance
Switch power supply, external disturbance can be “common mode” or “differential mode” mode.Interference type can be from a short duration of peak interference between completely lost electricity
Line change.Changes including voltage, frequency, waveform distortion, continuous noise or noise and transient.Can be transmitted through the power and equipment
Damage or affect their work are mainly electrical transient bursts and surge wave, and interference as long as the power equipment such as electrostatic discharge itself does not produce vibration, output
The phenomenon such as voltage sags, it will be impact caused by the power supply for electric equipment.

LED switching power supply information – really so mysterious

LED switching power supply information – really so mysterious

Recently saw on the Internet there is a saying: LED switching power supply is more special, need to find a professional technician to complete the switch power supply.
Don’t know where such comments come from, but LED switching power supply, there is nothing special about the production process.Access to or biological system
Made of LED power supply all know, LED is nothing special about, if have what characteristics, it is need to constant current limit
And under the condition of full load work for a long time, so would the requirement of efficiency is higher;Other power supply because of the limitation of structure size of height
There are requirements.The following is introduced in detail for everybody but everybody LED switching power supply
LED switching power supply of electronic components: there are three main, LED diode, MOSFET and IGBT.SCR in the input rectifier circuit and switch power supply
Application in soft start circuit is less, GTR drive hard, switching frequency is low, so the two to gradually replaced by the MOSFET and IGBT.
LED switching power supply design parameters: 1, 2, fully digital synchronous rectifier technology control 3, 4, 5 power supply power density, electromagnetic compatibility PFC (
LED drive power factor correction) converter is very important, because of the driving power supply design unreasonable can appear the phenomenon is mainly caused by the following parties
The following phenomena: 1: brightness changes over voltage;2: a noise;3: boot and shut down when shining;4: the temperature is very high;

The LED driver power supply design factors to consider:

1, 2, high efficiency, high power drive mode reasonable, 4, 3, surge protection ability, high reliability to 6, 5 drive power to the LED life
Adapt to life

About LED switching power supply, some details need to be more detailed descriptions of the Francis market analysis as well as technology development department to go to the LED
Close the power supply are introduced.In addition, editors on the Internet to see an essay about the prospect of LED light, one LED light is mentioned
New technology, and of course, this is the market analysis of two years ago.But for now, the LED driver power supply both in domestic and international market one
The competitiveness of the set.