In the practical application of the power module, we often find that there is no quality problem in the power module itself, but it is caused by the negligence of the equipment personnel, such as the wrong pin connection, the input voltage does not meet the specified value, and the load is too large. Therefore, it is necessary for every practitioner to understand the precautions in the application of the power module:

1. Dispatching of output voltage of power module

For power module products with trim or adj (schedulable) output pins, the output voltage can be scheduled within a certain plan through resistors or potentiometers. The general scheduling plan is ± 10%. For the trim output pin, connect the base of the potentiometer to trim. In the power module with all + s and - s pins, the other ends are connected to + s and - s respectively. If there is no + s or - s, connect both ends to the output positive and negative poles of the corresponding main circuit respectively (+ s is connected to + VIN and - s is connected to - VIN), and then adjust the potentiometer. The resistance value of the potentiometer is generally 5 ~ 10K Ω, which is suitable for comparison. The adj output pins are divided into input side scheduling and output side sections. The output side scheduling is the same as the trim pin scheduling method. The input side dispatcher can only increase the output voltage. At this moment, one end of the potentiometer is connected to the base, and the other end is connected to the ground of the input end.

2. Input protection circuit of power module

General power module products have built-in filters, which can satisfy the request of general power application. It is assumed that a power supply system with a higher request is required, and an input filter network should be added. LC or π network can be selected, but smaller inductance and larger capacitance should be selected as much as possible.

In order to prevent the power module from being damaged by the transient high voltage of the input power supply, it is recommended that the user connect the transient absorption diode at the input terminal and cooperate with the fuse to ensure that the power module is within the safe input voltage plan. In order to reduce common mode noise, y (CY) capacitance can be increased, and several NF high-frequency capacitors are generally selected. R is the fuse, D1 is the protection diode, and D2 is the transient absorption diode (p6ke Series).

3. Remote control on-off circuit of power module

The remote control switch operation of the power module is carried out through the REM terminal. There are two general control methods:

(1) Rem is connected to VIN, remote control is turned off, and vrem is requested to be < 0.4V. Rem is connected to + VIN, the module works and requests vrem > 1V. Rem is suspended and remotely switched off, which is called "suspended shutdown" (- R).

Assuming that the control should be isolated from the input terminal, the optocoupler can be used to transmit the control signal.

(2) Rem is connected to - VIN (refer to ground), remote control is turned off, and VREF is requested to be less than 0.4V. Rem is suspended or connected to + VIN, the module works and requests vrem > 1V.

4. Combination of power modules

(1) Parallel expansion. Paralleling the output terminals of the same power module can enhance the output ability, but the output voltage of the parallel module should be adjusted in comparison to ensure relative current sharing and avoid unnecessary vibration. For modules with large current output, lead resistance can also be carefully planned to achieve current sharing effect. The number of modules connected in parallel in this way should not exceed 2. Together, if there is a defect in the output of one module, all the systems will not work normally. The parallel expansion connection circuit RL is the load.

(2) Redundant hot backup in parallel. The same power module www.zeyun021.com The parallel connection of the output terminal through the diode can enhance the output ability and advance the reliability of the power supply system. In principle, it is assumed that the corresponding output alarm circuit is coordinated, and the module is placed on the detachable bus, so that the module with defects can be replaced in time. There is no quantity constraint for modules connected in parallel in this way. D is generally a Schottky diode.

(3) Series expansion. Connecting the output terminals of the same module in series can multiply the output voltage and increase the power accordingly. The series output terminal must be connected with a diode for protection.