Basic knowledge

The production process of power inverter

Inverter is divided into four parts, each part to do a piece of PCB board. Respectively is the “power board”, “SPWM driver board”, “DC-DC driver board”, “protection board”.
1 power main board:
The power board includes DC-DC push-pull and H bridge inverter two parts.
The machine’s BT voltage of 12V, full power, the working current can reach 55A above, DC-DC boost part of a pair of 190N08, the 247 package of cattle, as long as the heat to do in place, a pair of you can output 600W, you can also use IRFP2907Z, the output power is almost the same price. Main transformer with the EE55 of the magnetic core, in fact, on the 600W, with EE42 is enough, I am in order to facilitate the system, plus the EE55 is there, it used the EE55. on the main transformer winding, the following details. Push-pull part is powered by a symmetrical balance way, this has two advantages, one is can guarantee high current when the second power tube work state of symmetry and ensure a unilateral fever phenomenon can not occur; the second is can reduce the PCB reverse current density of the tin layer stack, of course, can also be greatly reduced because of the interference caused by the unbalanced current. High voltage rectifier fast diode, using the TO220 package RHRP8120, the tube reliability is very good, I used a second-hand tube, only 1 yuan a. High voltage filter capacitor is 470uf/450V, in the case of possible, as much as possible with the capacity of some, to improve the high pressure part of the load characteristics and reduce interference are good.
2 SPWM driver board
As with my 1KW machine, the core part of SPWM uses the TDS2285 chip of Zhang Gong. The chip on the details, you can see my previous post: here unspecified said. U3, U4 composition sequence and dead time circuit, final output used four 250 optocoupler, H bridge of the two works, bootstrap power supply, do is simplified circuit, can not be isolated power supply.
Because BT voltage will vary between the 10-15V, in order to have a reliable driving H-bridge, optocoupler 250 totem pole output stage voltage must to between 12-15, not less than 12V, otherwise it may enable H bridge power tube failures trigger. So, here with a MC34063 (U9), the BT voltage up to 15V (the booster circuit provided by the clock), the experiment proved that this way is very effective.
3.DC-DC driver board
DC-DC boost driver board, the use of a very common line, with a PWM to achieve the output of SG3525, after the two groups of totem output, the experiment, if the use of a pair of 190N08, the totem part can be omitted, directly with the 3525 driver is enough. Because the DC-DC driver board, and my 1000W interface is generic, so there are two groups of output, the machine on the use of a set of. The board has two small button switches, S1, S2, S1 is the boot, S2 is off, you can control the start and shutdown of the inverter.
The driving plate is connected with the J3, the J4 interface and the power plate, wherein, the J3 of the 1P is limited to the input end of the pressure feedback.
4 protection board
I did not do this protection board, there are the following reasons: first, the machine can not protect the machine can work, and this period of time is relatively busy, so the protection board is pulled down; followed by: I announced the power of the motherboard, is amended, the interface also made changes to the protection board, and I use the prototype is not modified PCB board, even made a protective plate, also do not go up. I would like to have a friend if I use my PCB documents to manufacturers proofing, do not forget to give me a set of, sent to me, I can be based on the new power of the main board to draw the protective plate.

The design of switching power supply transformer

Switching power supply transformer is the power transformer, which is added to the switch management. In the use, not only has the function of the ordinary transformer’s voltage transformation, but also has the function of the insulation isolation and power transmission. In the switching power supply and other occasions involving the use of high frequency circuit is widely used. Switching power supply transformer design is very important to the use of the switching power supply, suitable design can make the switch power supply transformer better to control the current, the design method is not reasonable to the use of switching power supply transformer
The main materials of the switching power supply transformer are: insulation materials, wire materials, magnetic materials. Switch power transformer with the switch tube together constitute the self-excited or his excited intermittent oscillator, the DC voltage modulated into a high frequency pulse voltage and finally to energy transfer and conversion. When the switch is switched on, the transformer converts the electric energy into a magnetic field to store it, and when the switch is cut off, it is released. In the forward circuit, when the switch is turned on, the input voltage is supplied directly to the load and the energy stored in the energy storage inductor. When the switch is cut off, the energy transfer is carried out by the energy storage inductor. More simply, the role of the switching power supply transformer is to convert the input DC voltage into the low pressure needed in our use.
In the design of the structure of the switching power supply transformer, we should consider the following points, leakage magnetic must be small so that the leakage inductance of the winding can be reduced. In the structure design to make it easy to winding and lead the way so that the transformer is not only simple and convenient, but also for the maintenance and production of the transformer is very helpful. In the design of a reasonable plan, so that the voltage can have sufficient space and function for cooling. If the design of switching power supply transformer on the full consideration of the above factors, then this design can make the switch power transformer more secure, more durable life.
In the design of switching mode power supply transformer when the material choice is very important, and in the choice of core is switch in power transformer, according to the choice of switching power supply transformer use different materials are also different. For use in the us the most extensive core is iron, manganese, and zinc oxide core used in the power supply input filter is used to high permeability core. Because of the low price of soft ferrite, good adaptation and high frequency performance, it is widely used today.
Switching power supply transformer design has certain requirements, these requirements can make it achieve the best use effect. The first is that the leakage inductance is small, because the voltage spike of the switch is connected with the size of the voltage spike, the circuit condition, the collector circuit configuration and the leakage inductance. Secondly to avoid transient saturation, in instantaneous electrical transformer core serious saturation will produce great surge current, in a very short period of time may cause the switch tube damage, generally in actual use will install soft start circuit to solve the problem. The effect of temperature is also considered in the design.
The detection method is very important in the use of the switching power supply transformer. In the detection, it can be seen whether there is an abnormal phenomenon, and the insulation of the switch power transformer is tested by the test. The above is a small series of switching power supply transformer is a brief introduction, we want to help group.

Dual power supply

Double power supply automatic switch is refers to a controlled by a microprocessor for grid system net power and electric or electric network and power generator start switching device, can make a continuous source of power supply. A series of dual power supply, when the power of a sudden failure or power failure, through the dual power switch, automatically put into standby power, (small load of standby power can also be supplied by the generator,) so that the equipment can still run normally. The most common is the elevator, fire control, monitoring, lighting, etc..
Dual power switch electrical appliance (converting switch) converts one or several load circuit from one source to another. By one (or a few) conversion switch electrical appliances and other necessary electrical components, to monitor the power supply circuit, and one or several load circuit from a power supply automatically converted to another power source. Electric industry is referred to as “dual power automatic conversion switch” or “dual power switch”. The national standard of ATS products is defined as a (or several) switch electrical apparatus and other necessary electrical components for detecting power supply circuit, and one or more load circuit from one power to another power supply, ATS is suitable for the construction field fire and other key load power supply, EPS is suitable for EPS is to solve the emergency lighting, accident lighting, fire facilities and other load power supply equipment as the main goal, to provide an emergency power supply system with independent loop specifications. UPS is mainly for the IT industry equipment to provide electricity, to provide a clean, uninterrupted power supply. Diesel generator power supply mode is suitable for the use of EPS, UPS and ATS in the power supply place with long time standby power supply.

The protection level of switching power supply

IP is internationally used to identify the protection level of the code Ip level by two figures, the first digital representation of dust; second figures from the representation of water, the greater the number of figures, said the leader is better.
Definition of number protection
0 no protection without special protection
1 to prevent the body from more than 50mm to prevent the human body due to accidentally touch the internal parts of the lamp to prevent the diameter greater than 50mm of the object
2 to prevent the object from more than 12mm to prevent the internal parts of the finger to prevent the finger
3 to prevent more than 2.5mm of the whole body to prevent the intrusion of the diameter is greater than the 2.5mm tool, wire or object intrusion
4 more than 1.0mm objects to prevent intrusion prevention diameter greater than 1 of mosquitoes, insects or invasive objects
5 dust can not completely prevent dust intrusion, but the amount of dust will not affect the normal operation of the lamp
6 dust completely prevent dust intrusion
Waterproof grade
Definition of number protection
0 no protection without special protection
1 to prevent the drip of water from the vertical drop
2 tilt 15 degrees when the lamp is still to prevent water intrusion when the lamp is tilted 15 degrees, can still prevent dripping
3 to prevent the injection of water intrusion into the water, or the vertical angle is less than 50 degrees in the direction of the water jet
4 to prevent the splash of water intrusion prevention of the direction of the water intrusion
5 waves of water to prevent intrusion prevention or blowhole rapidly from waves of water intrusion
6 to prevent water intrusion into the water waves lamps in a certain period of time or pressure conditions, to ensure the normal operation of the lamp can be
7 to prevent the intrusion of water into the lamp without a period of water in a certain water pressure, and can ensure the normal operation of the lamp
8 to prevent the impact of the sinking

how switching power supplies work

Switching power supply is the essence of an oscillation circuit, the conversion of electrical energy method is used not only in the power circuit, circuit in other applications are very broad, such as liquid crystal display backlight circuit, the fluorescent lamp. Switching power supply with a transformer with high rate, good stability, small size and other advantages compared. The disadvantage is that the power is relatively small, and the circuit to generate high frequency interference, transformer feedback oscillator circuit, can be bred occurred discipline of pulse current or voltage of the circuit called oscillation circuit, transformer feedback oscillator circuit is the circuitry that satisfied the conditions.

Switching power supply is divided into two forms, which are isolated and non isolated. According to the layout of the distribution of power distribution differences, can be divided into: positive and anti shock type two major categories. Flyback type means that the side of the original side of the transformer is stopped and the transformer can be stored. At the end of the primary side, secondary side conduction, energy is released to the load state of affairs, usual groovy flyback power supply tube, double tube not common. Is the original edge of the transformer in the original side of the side of the original side of the side of the side of the output voltage output to the load, energy through the transformer directly informed. According to the specification can be divided into general forward, including single forward, two transistorforward. Half bridge, bridge circuit belongs to forward circuit.

The forward and flyback circuits have their own characteristics. In the course of the planned circuit, it can be used to reach the optimal price ratio. As often as in small power can choose to use the anti shock. Slightly larger single acceptance is excitation circuit, medium power can accept double positive excitation circuit and half bridge circuit, low voltage acceptance push-pull circuit, and half bridge state of affairs similar. High power output, as usually adopt bridge circuit, low voltage may accept a push-pull circuit.

Flyback power supply because of its simple structure, saves a transformer and large volume of the inductor, and in the middle and small power supply get extensive application. Flyback power supply transformer leakage inductance is a very crucial parameters, due to the energy storage, the necessary transformer of flyback switching power supply, to get full use of the transformer core, usually to open air gap in the magnetic circuit, the target is transformation hysteresis curve of the core of the slope, the transformer to probably suffer large pulse current strike without as core into saturation nonlinear state, air gap in the magnetic circuit in high magnetoresistance state and in the magnetic circuit bred leakage magnetic far outweigh completely closed magnetic circuit.

As far as possible short pulse voltage connection, the input switch to the transformer line output transformer, rectifier to the adjacent line. The pulse current loop is small as small as the input filter capacitor is positive to the transformer to the switch tube to return the capacitor negative. Output unit of transformer output to rectifying tube to output inductance to the output capacitor return circuit transformer x capacitors to although even close to the switch power supply input end, the input line should stop and other circuit parallel, should be avoided. The Y capacitor should be arranged in the chassis grounding terminal or FG connection terminal. A total of inductance to be connected with the transformer to prevent magnetic coupling.

Output capacitor as usually accept two a near rectifier tube and the other should be close to the output terminal, can affect power output ripple index, two small capacitance and results should be better than a large capacity capacitor. Heating device to electrolytic capacitor and maintain a certain interval, in order to extend the service life of the whole machine, electrolytic capacitor is switch power life of the bottle neck, such as transformers, power tube, high power resistance and electrolytic link interval, between electrolysis is also required to set aside space for heat dissipation, conditional capacity allowed to install a fan or increase the exhaust hole.

What is a dc to ac power inverter?

A power inverter is a device that converts DC power (also known as direct current), to standard AC power (alternating current). Inverters are used to operate electrical equipment from the power produced by a car or boat battery or renewable energy sources, like solar panels or wind turbines. DC power is what batteries store, while AC power is what most electrical appliances need to run so an inverter is necessary to convert the power into a usable form. For example, when a cell phone is plugged into a car cigarette lighter to recharge, it supplies DC power; this must be converted to the required AC power by a power inverter to charge the phone.

What is the purpose of an inverter?

An inverter converts direct voltage from batteries or direct bus to alternating voltage, normally 220 Vca with output stabilization and in the form of a 50 Hz sinusoidal wave. This wave is often cleaner that the one obtained from the electrical network. The sinusoidal inverters are used to supply all kinds of load, whereas the “square”, “pseudo sinusoidal” or “modified sinusoidal” wave shape has certain limitations given its effect on inductive or capacitative loads. It is also important to mention that the noise or interference that can cause equipment such as precision instrumentation, telecommunication, etc. to function incorrectly. The main advantage is the price as it is often less than half what a sinusoidal device would cost for similar power.

How to measure a big dc current?Diverter!

To measure a large DC current, such as tens of AMPS, and even greater, hundreds of AMPS, there is no such a large range of current meter for the measurement of current, how to do? It is necessary to use shunt. Is a short piece of conductor, can be all kinds of metal or alloy, connecting terminal; the DC resistance is strictly a good tune; connected in series in the DC circuit, the DC current excessive flow device, both ends of the shunt produced DC millivolt voltage signals, and then in the measurement of the shunt at both ends of the table pointer swing, the reading is the current in a DC circuit values. The so-called triage, a small current to drive indicator, in the small current (MA) and loop current (1a dozens of a) the proportion of smaller, the current table indicating readings of linear better and more accurate. This is the electric circuit of the common products, lightning protection and diversion measures.
The current meter has a variety of different specifications, but the actual meter is standard millivolt meter. For example, a full scale voltage meter for 75mv. So with this voltage meter measurement such as 20A current, you need to give it a 75mV voltage drop of the shunt resistance in the current flowing through the 20A when, also known as 75mV shunt.
Shunt is a to the resistance of the current through the general common 15a and 20a and 35A current meter are the need for a shunt, shunt impedance = header logo full voltage / header full scale current. Such as 20a of the ammeter shunt resistance =75mv/20A=0.00375 Omega, constant impedance according to Ohm’s law U=IR, voltage and current into a proportional, current is linear voltage is linear, so we can use a full 75mV to the voltage of the table shows the current. Therefore, the use of the current meter is actually a voltage meter.

open frame switching power supply

Open Frame (PCB) Type Switching Power Supply (Families: PM, NFM, MPS, MPD, MPT, MPQ, RPS, RPD, RPT, PS, PD, PT, PQ, PPS, PPT, PPQ, ASP, PID, LPS, LPP, EPS, ELP, EPP)

An open frame (PCB) type switching power supply is a power supply designed to be integrated or installed into a system enclosure. Mean Well’s open frame (PCB) type power supplies include on board, general PCB, green PCB, and medical PCB types.

Installation (1)Before commencing any installation or maintenance work, please disconnect your system from the utility. Ensure that it cannot be re‐connected inadvertently! (2)At least 5mm insulation distance on the bottom of the unit should be kept and a Mylar film should be added between the unit and the system. In addition, keep enough insulation distance, 10mm for general type/15mm for medical type, around the unit. (3)Power supplies greater than 120W may require a forced air/fan for cooling. Please refer to specifications to receive a minimum air intensity and air‐flow direction. (4)Allow good ventilation for the unit in use to prevent it from overheating. Also, a 10‐15 cm clearance must be kept when the adjacent device is a heat source. (5)Mounting orientations other than standard orientation or operate under high ambient temperature may increase the internal component temperature and will require a de‐rating in output current. Please refer to the specification sheets to receive the optimum mounting position and information about the de‐rating curve. (6)Recommended wires are shown as below. AWG 18 16 14 12 10 8 Rated Current of Equipment (Amp) 6A 6‐10A 10‐16A 16‐25A 25‐32A 32‐40A Cross‐section of Lead(mm2 ) 0.75 1.00 1.5 2.5 4 6 Note:Current each wire carries should be de‐rated to 80% of the current suggested above when using 5 or more wires connected to the unit. (7)For other information about the products, please refer to for details.

What is atx switching power supply?

ATX is the working power supply of the computer, the role is to convert the AC 220V power supply for internal computer use DC 5V, 12V, 24V power supply.

ATX power supply circuit structure

Each part of the circuit not only the function of mutual cooperation, mutual penetration and the circuit parameters are very strict, slightly improper circuit can not work normally. The circuit can be divided into two parts: part from the power input to the switch transformer T1 before the circuit (including auxiliary power supply of the original circuit), directly linked to the part of the circuit and AC 220V voltage, touch will received an electric shock, known for high voltage circuit; another part of the circuit switch transformer T1, discord AC 220V directly connected, said for the low pressure side of the circuit. Two through C03, C04, C05 high voltage ceramic capacitor circuit, to eliminateelectrostatic interference.

The characteristics of ATX power supply

Compared with the AT power supply, ATX power supply increased by “+3.3V, +5VSB, PS-ON” three output. The “+3.3V” output is mainly used for CPU, and “+5VSB”, “PS-ON” output reflects the characteristics of power ATX. ATX power supply the main features is that it does not use the traditional electric switch to control the power supply is working, but the combination of “the + 5VSB, PS-on” to realize the power of opening and closing, as long as the PS-on signal level change control, can control the power of the opening and closing. “PS-ON” is less than 1V when the voltage of switch, turn off the power greater than 4.5 volts.

The core circuit of ATX power supply

ATX power conversion main circuit and at power supply, but also the “double half bridge it flyback circuit, PWM (pulse width modulation) controller also uses TL494 chip control, but canceled the electric power switch. Due to the cancellation of the electric power switch, so as long as the pick of the power line, in the transform circuit will have +300V DC voltage, and auxiliary power supply TL494 to provide working voltage, to start power ready prepared. Characteristics of ATX power supply is the use of TL494 chip pin 4 of the “death drive control function, when the pin voltage is 5V, TL494 8, 11 feet no output pulse, two switch tube deadline, the power supply is in standby state, the output voltage. When the fourth foot 0V TL494, a trigger pulse supplied to the switchtube, the power supply in normal working condition. One way of the output of the auxiliary power to send TL494, another output by the divider circuit “+ 5VSB” and “PS-on” two signal voltage, all of them is + 5V. Among them, “+ 5VSB output connected to the ATX motherboard” power monitoring unit “, as its working voltage, + 5VSB output can provide the working current of 10mA. “Power monitoring unit of output and the PS-on is connected, in the trigger button switch (non locking switch is not pressed, the PS-on is + 5V. It connects to the voltage comparator U1 the positive input end and U1 negative input voltage is about 4.5V. As the voltage comparator U1 output is + 5V, TL494 sent to the” death drive control foot “, ATX power supply in the standby state. When you press the motherboard power monitor button trigger switch (installed on the panel of the mainframe box), the PS-on variable to a low level, the output of the voltage comparator U1 to 0V, the host ATX power supply is opened. Then press the trigger button switch once on the panel, the “PS-ON” into+5V, then turn off the power. At the same time can also be used to control the program “outputpower monitoring components”, make “PS-ON” into +5V, auto power off. As in the WIN9X platform,issued a shutdown instruction, ATX power off automatically.

Fault analysis of the motherboard does not power

Due to the ATX power supply opening subject to the motherboard power monitoring unit, so when the ATX hosts appear to be not the fault, could not immediately identify fault is the power supply itself or the motherboard “power monitoring unit”, to the maintenance to bring a certain degree of difficulty. Based on the above analysis, we can between the PS-on output and then about a 100 ohm resistor and the PS-on “change to a low level, will be able to start the ATX power supply, which can distinguish the fault position. Also reminds us, if ATX motherboard power monitoring part failure, because of its maintenance is difficult, we can skip the power monitoring unit “, direct control of PS-on voltage, will be able to open or close the host. Of course, the automatic closing functionwithout the host.

Linear switching power supply

Linear power supply is the first alternating current through the transformer to reduce the voltagethrough the rectifier circuit, rectifier, DC pulse can be obtained after filtering, DC voltage with smallripple voltage. In order to achieve high precision DC voltage, must pass through the voltage stabilizing circuit voltage.

Linear power supply compared with switching power supply

The linear power supply voltage feedback circuit is operating in the linear (zoom), switching power supply is used for voltage regulator tube in saturation and cutoff region, namely the switch state.

Linear power supply is generally the output voltage sampling and then sent to the comparing with the reference voltage output voltage amplifier, the voltage amplifier as a voltage regulate transistorinput, is used to control the adjustment of the node voltage varies with the input changes, so as to adjust the output voltage, the switching power supply is adjusted by changing the tube opening and closing the time is to change the duty cycle to change the output voltage!

From its main features: on the linear power supply technology is very mature, low production cost,can achieve very high stability, low ripple, interference and noise itself is relatively small, butbecause of working in the frequency (50Hz), the volume of the transformer is large, efficiency is low(usually with work efficiency is only about 80%) overall volume is larger, more cumbersome andrequires high input voltage range; and is a high-frequency switching power supply working condition, the volume of the transformer is relatively small, relatively light, but compared with thelinear power supply to output ripple, but because of simple structure, low cost, high efficiency(efficiency of switching power supply on the market are up to 90% above) on many occasions has been replaced by the linear power supply, is the future development trend.

Silicon controlled rectifier power supply, linear power supply, switching power supply circuit simplecomparison

On the circuit structure, what is the linear power supply, switching power supply is controllable silicon, depends on the specific situation, the rational use of. The three circuit, with a large number of domestic and international, each have their own characteristics. Silicon controlled rectifier power supply, with its powerful output, so that the linear power supply and switch power supply can not be replaced. Linear power supply with its high precision, excellent performance and has been widely used. Switching power supply, power frequency transformer eliminating the cumbersome and thevolume and weight are reduced, a reduction, is also widely applied in many more stable output voltage, output current.