Within industrial equipments, an AC/DC insulated power supply with a large power capacity is installed in order to operate a large load such as a motor. In addition to supplying power to the motor, the same AC/DC power supply is used to supply power to the control circuit board, etc., or a separate discrete AC/DC power supply is used.

When designing a drive system that uses a motor, a large-capacity AC/DC insulated power supply module is used as a power supply for the motor. In this case, power is supplied to the control board from the power supply used by the motor.

The control board in the system from the beginning and the power supply to the I/O board are less troublesome, but what about the power supply to the option board?

In the case of an option board, since it is difficult to obtain additional power from the main power supply, it is necessary to design an AC/DC power supply separately. In this case, since a large capacity power supply is not necessary for the option board, there are times when you want to design with a small discrete component instead of the same module.

As shown in Fig. 1 - (A), in the conventional motor control application, the main AC/DC isolated power supply is prepared to supply the power to the motor and the control board. However, in this configuration, if a problem occurs in the motor related circuit of the drive system, the main AC/DC will shut down and the control circuit of the system that you want to be running until the end will shut down, which may affect the safety of the system. 

To avoid this, the power supply of the control circuit must be disconnected from the main AC/DC and supplied from another AC/DC as shown in Fig. 1 - (B). In this case, an AC/DC power supply module must be prepared separately.

As for the power supply for the control board, it is often low power, and it is inefficient to incorporate a high-power AC/DC module into the system. The same is true for the AC/DC power supply for the option board. In addition, there are problems such as the development schedule is limited for the compact AC/DC design, and the AC/DC design assets for diversion are not available.

We have recently developed a 24V output AC/DC power supply circuit reference board using LT8315 for industrial equipment. This enables the power supply configuration system shown in Fig. 1 - (B).