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Twist features

The TWIST board provides a fully integrated fast prototyping platform for anyone wishing to start learning and/or developing in power electronics. Its multiple features are explained in this page.

Board sub-systems Overview#

There are 4 main sub systems inside the SPIN board.

  • The Spin which you can know more about in its repository
  • The Communication Block
  • The Power Block
  • The Measurement Blocks (High and Low Side)
  • The Connectors (High and Low Side)
  • The Feeder Block

These blocks can be seen on the photo of the TWIST below.

twist_board_and_sub_blocks

View of the twist board and its sub-blocks

The Communication Block#

The communication block deploys an unique communication architecture currently under development at LAAS-CNRS. Combining multiple solutions for exchanging information between two power conveters, this block allows the user to deploy a daisy chain and coordinate multiple power converters.

twist_communication_daisy_chain

Three TWIST boards connected in a Communication and Power Daisy Chain

The RJ45 connector deploys 4 different types of communication methods:

  • A slow communication via CAN Bus
  • A fast communication via RS485 and ModBus
  • An ultra-fast analog communication
  • A sync signal

Its schematic is shown in the image below.

RJ45_cable_connection_twist

Schematic of the RJ45 connector used in the communication block

The CAN bus implementation is based on a similar implementation done by LibreSolar in their power converters (a big thanks to Marin Jager).

libre_solar_can_bus_implementation

The schematics of the CAN bus implementation done by LibreSolar

The RS485 communication allows the power converters to exchange data on a much faster pace, typically using it in their inner control loops.

RS485_implementation_twist

The schematics of the RS485 implementation

For a much faster current sharing capabilities, an analog bus sharing bus is also available.

analog_current_sharing_implementation_twist

_Schematic of the analog current control (simulation available here)

This implementation allows the highest current to yielding block to control the bus and provide its current value to the others. This value can then, in turn be used by other blocks to control their own current/voltage.

The Power Block#

Power conversion is the main feature of the twist board. To achieve a re-programmable and flexible power conversion, the twist board uses a special architecture called dual synchronous buck. The circuit below introduces its main components:

twist_power_block_circuit

Circuit diagram of the power block

This architecture has a high voltage and a low voltage side. On the low side, the converter features two channels, which are then connected in parallel on the high side. This high-side connection allows four main conversion functions :

  • Buck mode : Power goes from the low to the high side
  • Boost mode : Power goes from the high to the low side
  • Independent buck-boost mode : Power can go from leg 1 to leg 2 and vice-versa
  • AC mode : Both legs are used together to create a sine wave

Buck mode#

When connected in buck mode, the converter drives power from a high-voltage (up to 100V) source to a low-voltage sink. The image below gives the example of a PV battery charger in buck mode.

twist_board_buck_mode

Twist board in buck mode

The source in the example above is a 40V PV panel which is connected to the high-side. Both legs are driven together, to maximize power transfer and minimize the current ripple. The load in the example is a 12V battery connected to the low-side.

Notice that to operate in DC mode, the converter has a special Neutral to Ground swich (TN_GND) which must be ON to allow the power to flow.

Boost mode#

When connected in boost mode, the converter drives power from a low-voltage (up to 80V) source to a high-voltage sink (up to 100V). The image below gives the example of a PV battery charger in boost mode.

twist_board_boost_mode

Twist board in boost mode

The source in the example above is a 40V PV panel which is connected to the low-side. Both legs are driven together, to maximize power transfer and minimize the current ripple. The load in the example is a 72V battery connected to the high-side.

Notice that to operate in DC mode, the converter has a special Neutral to Ground swich (TN_GND) which must be ON to allow the power to flow.

Independent buck-boost mode#

Imagine you wish to connect two batteries in parallel. When connected in independent buck-boost mode, the converter drives power from a low-voltage (up to 80V) source to another low-voltage sink (up to 80V). The image below gives the example of a battery to battery connection.

twist_board_independent_mode

Twist board in independent buck-boost mode

The battery connected to leg 1 in the example above is 24V and the battery connected to leg 2 is a 12V. Both legs are driven independently, to allow bi-directional power transfer.

Notice that to operate in DC mode, the converter has a special Neutral to Ground swich (TN_GND) which must be ON to allow the power to flow.

AC mode#

Imagine you wish to drive a single phase AC motor. When connected in AC mode, the converter drives power from a high-voltage (up to 100V) source to both low-voltage legs (up to 80Vpk or 56VRMS). The image below gives the example of a battery to battery connection.

twist_board_AC_mode

Twist board in AC mode

The battery connected to leg 1 in the example above is 24V and the battery connected to leg 2 is a 12V. Both legs are driven independently, to allow bi-directional power transfer.

Notice that to operate in AC mode, the special Neutral to Ground swich (TN_GND) must be OFF to allow the neutral to float.

The Measurement Block#

Power control requires accurate measurements. The TWIST board has 6 different measurements which allow full visibility of its power flow:

MeasurementSensor TechnologySensibilitySignal BandwidthComponent reference
Leg 1 Low-side VoltageVoltage divider and isolation amplifier+/- 80V~kHzR + AMC1100 + OPA316
Leg 1 Low-side Current1MHz +/- 20A Isolated Hall effect sensor+/- 10A200kHzACS730 + OPA316
Leg 2 Low-side VoltageVoltage divider and isolation amplifier+/- 80V~kHzR + AMC1100 + OPA316
Leg 2 Low-side Current1MHz +/- 20A Isolated Hall effect sensor+/- 10A200kHzACS730 + OPA316
High-side VoltageVoltage divider and isolation amplifier+120V~kHzR + AMC1311+ OPA316
High-side Current120kHz +/- 20A Isolated Hall effect sensor+/- 20A~kHzACS712 + OPA316
Leg 1 TemperatureThermistor-based temperature sensor-40 to 110°CHz
Leg 2 TemperatureThermistor-based temperature sensor-40 to 110°CHz

All measurements are conditioned and boosted by an operational amplifier that sends the raw signal from the sensor to the Spin board.

The Connectors#

The Feeder Block#