UM0723 datasheet(19/48 Pages) STMICROELECTRONICS

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UM0723

Board description

Doc ID 15870 Rev 4

19/48

Figure 11.

Overcurrent protection

The overcurrent protection can be disabled with software if the W5 jumper is set to the “OCP

OFF” position. This may be necessary and is often useful when the user decides to make

the brake operate by turning on the three low-side switches. In fact, if the motor acts as

a generator, it's necessary to protect the hardware, preventing the bus voltage from

exceeding a safety threshold. In addition to dissipating the motor energy on a brake resistor,

it's possible to short the motor phases, preventing the motor current from flowing through

the bulk capacitors.

Please note that with disabling of the OCP, the demonstration board is not protected against

any overcurrent event.

3.3.6

Current sensing amplifying network

The STEVAL-IHM023V2 motor control demonstration board can be configured to run in

various current reading configuration modes:

●

Three-shunt configuration - suitable for the use of field oriented control (FOC)

●

Single-shunt configuration - suitable for the use of FOC in a single-shunt configuration

●

Single-shunt six-step configuration - suitable for scalar control

Configuration with a shunt resistor, where voltage amplified with an operational amplifier is

sensed, was chosen as the current sensing networks. Single-shunt configuration requires

a single op amp, three-shunt configuration requires three op amps. Just for compatibility

purposes, one of them is common to both basic configurations.

The configuration jumpers W10 and W11 allow the user to set the common op amp to

achieve the compatibility between single-shunt six-step configuration (suitable for scalar

control) and three-shunt or single-shunt FOC current reading configuration.

Three-shunt FOC or single-shunt FOC current reading configuration

The details of the three-shunt current sensing reading configuration are shown in Figure 12.

In this configuration, the alternating signal on the shunt resistor, with positive and negative

–

Shunt

resistor

VREF

COMPARATOR

+5 V

L6390

OPAMP

OP+

CP+

OP–

+3.3 V

R3 (R49, R73, R96)

R1 (R47, R67, R95)

R2 (50, R70, R93)

Smart SD

VCC

–

OPOUT

GND

AM00473

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