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 www.meanwell.com for details.
multiplex output power supply
In terms of the power is applied, to the selection of power supply products for the “fool”, that is the choice of power supply voltage as long as the load does not exceed the maximum power, regardless of the system of various load characteristics of how to change, and various power supply voltage is still accurate correct. At this point, the vast majority of multi-channel output power is unsatisfactory. In order to further explain the characteristics of multiplex output power, the block diagram of multi output switch power source is described in Figure 1..
From Figure 1, it can be seen that the real form of closed-loop control is the main circuit Vp, other Vaux2, Vaux1 and other auxiliary circuits are in control of the. From control theory, we know, only VP regardless of the input and output changes (including changes in voltage, load change), under the conditions of the closed-loop feedback control can ensure the accuracy of quite high (generally better than 0.5%), that VP in largely depends only on the reference voltage and sampling rate. For Vaux2, Vaux1, the accuracy of the following aspects mainly depends on:
1) the turn ratio of the T1 main transformer is mainly determined by Np1:Np2 or Np1:Np3
2) the load of the auxiliary circuit.
3) the load of the main circuit.
Note: if the above 3 point set, the impact of the input voltage on the auxiliary circuit has been very limited..
In more than 3 points, as a specific switch power converter, main transformer turns ratio has been set, so the impact auxiliary circuit output voltage accuracy of the largest factors as the main circuit and auxiliary circuit of the load. In the switching power supply products, there are special technical indicators and the power of this feature, that is, the cross load adjustment rate. In order to better relate this problem, the measurement and calculation method of cross load adjustment rate is as follows.
21 power converter multiplex cross load adjustment rate measurement and calculation steps
1) the test gauge and equipment are connected as shown in Figure 2.
2) regulate the power converter input voltage to be measured as the nominal value, closing the switch S1, S2? Sn, adjust the measured power converter output current rating, measuring the output voltage of the j-th road UJ, using the same method measurement other various output voltage.
3) by adjusting the output load current of the various outputs outside of the j path as the minimum, the output voltage of the output voltage of the j is ULj.
4) by type (1) calculate the cross load adjustment rate of J road SIL.
Type: Uj for each other when the current load is minimum, the absolute value of Uj and the ULj output voltage difference;
Uj output current for each of the rated value, the output voltage of J road.
According to the test and the calculation method of the above can cross load adjustment rate and understood as: all other output circuit load step change (100%0%) of the path of output voltage accuracy of the percentage.
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.
“Leakage”, because the power of good quality, good power leakage, leakage power not bad.
“According to the national standard of electromagnetic compatibility (EMC, EMI) and safety requirements. The main content of EMI design is the design of noise filter. The switching power supply filter can effectively suppress noise in the power grid into the equipment (power), equipment(power) can also suppress the noise pollution generated by power grid. There are two kinds ofnoise, is a kind of common mode noise, a differential mode noise. The common mode noise current flowing into the earth, differential mode noise current between lines. In order to suppress the noise pollution must be used to filter circuit, in order to suppress the interference of public needs in two lines of input L, N line respectively and two capacitors to the ground. The capacitor has a great role is separated through, (high noise rejection is generally high frequency signal, understand the main AC signal can be approximated). Such as the ground, this part of the interference signal into the earth, achieve filter function. If missed, if contact is flowed into the human body. That is what we understand by leakage phenomenon. (the voltage of AC, generally up to about 110V). At the same time in the national standard GB4943 (safety of information technology equipment) in theregulations, related to the use of electrical appliances (including power supply) must be grounded.”