User Manual

It is recommended that you drive the load using the sign-magnitude method for H-bridge
applications. This method allows the excess current to recirculate in the motor windings and
reduces current feeding back into the power supply.
If locked-antiphase drive is desired be aware that the power dissipation will increase
especially in the main filter capacitor. This should be monitored carefully by measuring the
temperature of the filter capacitor to make sure it is not getting hot when driving the load. The
PWM frequency should be as high as possible when driving with this method to reduce the
ripple current experienced by the load and the Simple-H.
If regenerative braking of an inductive load such as a motor is desired it can be accomplished
as follows: when slowing or reversing direction supply a low duty cycle drive to the load until
the load has stopped or has reached a low RPM, then apply a brake or coast stop signal to
the unit. The low average applied voltage of the low duty-cycle drive will allow the inductance
of the load to boost the voltage at the battery terminals above the supply voltage and flow
current back into the battery. Unfortunately the current sensors will not read properly during
regeneration so the regeneration current level cannot be measured. Do not attempt
regeneration with a bench power supply only with a battery.
6. Warnings
The following warnings should be heeded when using the Simple-H to avoid failure of the
device:
1. Bench type power supplies do not tolerate regenerative current i.e. current flowing
back into the power supply. Often their voltage will increase until the extra power is
dissipated. If the Simple-H is operated at 24V with a power supply of this type it is
possible to exceed the 28V maximum rating of the device and destroy the power chips.
When using a bench supply it is recommended that you operate at a lower voltage
Adding a battery in parallel with the output of the bench supply will provide a buffer
which can absorb the extra energy and avoid this type of failure.
2. Sensible driving of the load will increase the life of both the electronics and the motor.
Do not repeatedly switch instantly from full forward to full reverse. If possible reduce
the applied load voltage gradually by reducing the PWM duty cycle over the period of a
few milliseconds. This allows the inductive energy in the circuit to dissipate without the
inductive voltage “kick” that often occurs on abrupt interruption of the load current.
When using a bench supply even switching from full speed to full stop may cause an
inductive kick that can damage the device if the operating voltage is close to the upper
limit.
3. Monitor the device temperatures. The power chips will protect themselves against
overloads but repeated operation until the over temperature circuits are activated will
shorten the life of the device. Add a fan to speed the cooling and increase current
capacity.
4. When cooling the device a fan is the recommended method. The heatsink tabs are
electrically connected to the motor outputs so the heatsinks must be isolated from
each other (except in the ganged half-bridge mode). Fan cooling is effective even in
an enclosed box so it may not be necessary to introduce outside air for effective
cooling.