Overview
Riversdie Design (MaxRefdes8 #) employs H-bridge transformer drivers (MAX256) and LDO (MAX1659), convert 3.3V input to 12V (15V) isolation output power supply (Figure 1). This generic power solution can be used in various different situ isolation power applications, but mainly for industrial sensors, industrial automation, process control, and medical electronics.
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Figure 1. Block diagram of the schematic block of the RiversIde subsystem.
Characteristic
Isolated Power
12V / 15V output voltage
Take a smaller PCB area
Compatible with PMOD (Note) miniaturization design
Application
Industrial sensor
Process control system
automated industry
Medical electronics
Hardware circuit description
The Riverside reference design subsystem is powered by 3.3V DC power supply, the switching frequency of the MAX256 H bridge transformer driver is approximately 475 kHz, which can drive the number of turns ratio of 1: 2.6, such as using HALO (Note) Electronics TGM-H281NF transformer . The secondary side of the transformer is multiplied, converting the AC voltage to DC output. The MAX1659 linear regulator stabilizes the voltage at 12V, Zener diode D3 for protecting linear regulators to ensure that the input voltage is not higher than 16.1V.
The input power can be accessed from the J1 PMOD compatible connector, or the external power supply can also be connected to the EXT3.3V and DGND connector. Simply modify the feedback resistors R2, R3 of the LDO, you can change the output voltage.
The output voltage of the MAX1659 is determined by the following formula:
For example, for applications where 15V output is required, R2 is changed to 187kΩ, and R3 is changed to 16.2kΩ. Some of the cases of the output voltage ripple require it, at this time, a low-pass LC π filter can be added to the front end of the LDO.
The isolation transformer in the design provides 1500VRMS voltage isolation to meet the UL60950 and EN60950 certification requirements, "function" meets the insulation level.
Quick evaluation:
1, need equipment:
Riverside (maxrefdes8 #) board
3.3V 1A power
Digital voltmeter
2, evaluation steps
The Riverside board is fully installed and tested, followed by confirming the operation.
(1) Place the bypass 1-2 position in JU1.
(2) The power supply is connected to the EXT_+ 3.3V connector.
(3) The power supply negative is connected to the DGND connector.
(4) Voltage table piocate connection to + 12V connector.
(5) Voltage meter negative ends to the GND connector.
(6) Turn on the power.
(7) Measure the output voltage with a voltage meter.
Laboratory measurement
Test the 12V and 15V output situations designed for Riverside, and other output voltages can be obtained by adjusting R2 and R3 resistance.
When set to 12V output, the circuit provides maximum 165mA load current. When set to 15V, 60 mA load current can be provided.
In order to improve the load driving capability, the user can improve the voltage of the input power or improve the transformer turns. For more information, please refer to MAX256 data. The power efficiency is commented in Figures 2 and 3.
Figure 2. Efficiency of 12V output voltage.
Figure 3. Efficiency of 15V output voltage. , Reading the full text, the technology area
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