1. contact resistance
When the power output is connected to the load, good contact between the two ends of the wiring is very important. Good contact is especially important when the load current is large. The contact resistance of several m Ω to more than 10 m Ω caused by poor contact will cause excessive circuit voltage drop and poor load adjustment rate as well as too long or too thin inappropriate connecting wire. Therefore, the contact points must be cleaned to remove the oxide layer, and the high current contact points should be welded or wound.
2. input fuse
The fuse shall be installed at the input end of each module to prevent the input bus from being short circuited by an input short circuit fault of a module. The general fuse specification shall be 2~3 times of the rated input current. If the module operates within a wide input voltage range, the fuse should use a fast fuse with a fusing time of less than 10ms.
3. input maintaining capacitance
In case of input short-circuit fault of a module or other accidents that cause the instantaneous drop of input bus voltage, the maintenance capacitor installed at the input end of the module can provide the maintenance voltage to the module within a certain period of time. In addition, it can absorb the voltage spikes at the module input. In order to meet the requirements of maintenance time, electrolytic capacitors shall be generally selected. For modules with 300V input and 200W output, the minimum maintenance capacitance shall be 30-50 μ F. For 48V input modules, thousands of μ F. when selecting the capacitor, in addition to considering the pulsating current and voltage, the capacitor with small equivalent series resistance (ESR) shall be selected.
4. input instantaneous overvoltage protection
A transient suppression diode (TVS) or transient absorber (metal oxide varistor) can be installed in front of the electrolytic capacitor to absorb the input transient overvoltage. Transient suppression diode for low input voltage and varistor for high input voltage
5.y capacitor
To reduce common mode noise, it is recommended to install y capacitor. As shown in Figure 4, the Y capacitor connects the module shell and the system protective ground.
6. output voltage fine adjustment range
The user can fine tune the output voltage within about ± 10% of the rated value by connecting an external resistor at the trim terminal. The power of the power module shall be limited to the maximum rated output power. If the output voltage is higher than its nominal value, the output current shall be reduced to the limit of maximum output power. The connection method of external resistance is shown in Figure 5. If the voltage is only increased (or decreased) in one direction, the resistor can be added to the output negative (or output positive) end only at the trim end. The general principle is that if you want to increase the output voltage, you can add a resistance between the trim terminal and the output negative; If you want to lower the output voltage, you can apply a resistance between the trim terminal and the positive output. The trim end can be suspended without fine adjustment.
7. telemetry
The telemetry function can keep the voltage stabilization accuracy at both ends of the load within the range required by the technical specifications. When the distance between the power module and the load is far, the load current is large, and the voltage drop of the connection circuit is large, the remote sensing terminal can directly detect the voltage at both ends of the load to ensure its stable accuracy. Figure 6 is the wiring diagram of the test. The telemetry end shall be connected with shielded twisted pair. In addition, 0.1 can be connected between ± s and ± VO ends close to the module μ Decoupling capacitor around f to prevent noise interference. Compared with the load line, the current on the telemetry terminal line is very small. Please note: the telemetry cable cannot be used to transmit load current, otherwise the power module will be damaged. When the voltage at both ends of the load drops, the signal detected by the telemetry terminal will make the power module produce a response of voltage rise, thus compensating the voltage drop at both ends of the load. The maximum value of the circuit step-down compensation has a certain range. If the circuit step-down exceeds this range, the load adjustment rate will still decrease. As shown in Figure 6, in the power module, a resistor or diode has been connected between the corresponding voltage output terminal and the telemetry terminal to prevent the output voltage from being too high when the telemetry terminal is open circuit.
8. switch control
Switch control refers to "on" and "off" operation of module output voltage. The switch control end is generally called REM end. There are two standard ways to control the switch of the module:
Positive logic: REM terminal is directly connected to -vin and outputs off;
REM terminal is open circuit or connected to high level (greater than 5VDC and less than 40VDC), and output is on.
Negative logic: REM terminal is directly connected with -vin and outputs on; REM terminal is open circuit. Output off.
9. analog line "ground" and digital line "ground"
The analog line ground and the digital line ground are separated, otherwise it may cause some interference problems to the circuit. There is a common grounding point between the two grounds, but they do not share the power supply circuit with each other. In order to prevent some sensitive virtual circuits from being disturbed, designers must carefully analyze each analog "ground" path during board layout to ensure that it is directly connected to the ground. Separate the signal from the power cord.
10. load usage of multi-channel output power supply
The actual use load of the auxiliary circuit (VO2, VO3) of the conventional product must be less than the actual use load of the main circuit (Vo1), otherwise the power supply may work abnormally. If it must be used in this way, please inform our company, which can produce according to your actual use.   
Interactive adjustment of 11 multi-channel output and its application
For multi output power modules, users are more concerned about the impact of different output circuits when the output load changes. For example, when the main output circuit is no-load, the load capacity of the auxiliary output circuit is very low because the load of the main circuit is too light. Because the company's products adopt the concept of integrated magnetic circuit, the interactive regulation between output voltages is greatly improved. The figure below shows the advantages of interactive regulation. In the figure, IO1 is the load current of the main circuit, io2 is the load current of the auxiliary circuit, and VO2 is the output voltage of the auxiliary circuit. It can be seen from the figure that when the load of the main circuit changes from 20% to 100%, the output voltage of the auxiliary circuit is always within ± 4% in the change curve of the output voltage of the auxiliary circuit with the load current of the auxiliary circuit. Even in the worst case, i.e. no-load of main circuit and full load of auxiliary circuit, the output voltage of main circuit and no-load of auxiliary circuit can be guaranteed to be within ± 10% of the nominal voltage. Therefore, under the condition that the accuracy requirements for output voltage stabilization are not too high, the auxiliary output without voltage stabilization can not only meet the power supply conditions, but also has relatively low cost, few devices and high reliability. The company recommends that users first consider the power module with auxiliary output without voltage stabilization.   
12 capacitive load capacity and power output protection
The company suggests that the resistive load of the power module should be greater than 10% of the rated load, so that the module can work stably.   
As a means of power supply coupling and anti-interference, capacitance is essential in modern electronic circuits. Power module of general company
This factor has considerable capacitive load capacity. However, considering the comprehensive protection capability of the power supply, especially the output short-circuit protection,
The capacitive load capacity cannot be too large, otherwise the protection characteristics will deteriorate. Therefore, the total load capacitance shall not exceed
Maximum capacitive load capacity. There are generally four ways of output current protection
Constant current type: when the current protection point is reached, the output current increases slightly with the further increase of the load, and the output voltage decreases continuously. With the further increase of the load, the output voltage decreases continuously.   
Fold back type: when the current protection point is reached, the output current increases with the further increase of the load, the output voltage decreases continuously, and the output current also decreases continuously.   
Cut off type: when the current protection point is reached, the output of the power module is prohibited.
Constant current cut-off mode: when the current protection point is reached, the first is the constant current protection mode. When the output current reaches a certain value, the output of the power module is prohibited.    
In most circuits, constant current type and cut-off type are used more. The ideal protection mode is the constant current cut-off type, in which the constant current type and cut-off type are used more. The ideal protection mode is constant current cut-off protection. Among them, the constant current protection and the fold back protection are self recovery in nature, but the power consumption during output short circuit is large, especially the constant current protection. The cut-off and constant current cut-off self recovery characteristics need an auxiliary reset circuit to complete the self recovery, but the power consumption in case of output short circuit can be adjusted by the cycle of the reset circuit, that is, to adjust the time interval of intermittent startup. Generally, the current protection point is 1.2 times the nominal output current.   
The general output has overvoltage embedded protection.   
13 load transient response
When the output load changes rapidly, the output voltage will rise or fall. The power module is adjusted to restore the original output voltage. There are two important indicators in this response process: overshoot voltage (△ VO) and recovery time (TR). The smaller the overshoot, the shorter the recovery time, and the faster the system response speed. Generally, when the nominal load step changes at 25%, the overshoot of output voltage is 4%vo, and the recovery time is 500 μ S or so.