Rev A Jan 2020
Page 5
Chapter 3 Getting Started
3) Switch power ON.
3.3.5 Front Panel Description
Fig. 3.2 Front panel
INPUT
– BNC Connector. Provides connection to the controlling input source. This input allows a -2 V to +10 V signal to drive
the output to its full scale -30 V to +150 V. This gives a gain of 15.
MONITOR
– BNC Connector. Provides connection to a monitoring system (e.g. oscilloscope), in the range -3 V to +15 V.
POWER
– Green LED. Lit when power is applied to the unit.
ERROR
– Red LED. Lit when the power supply voltages are outside their tolerance bands. Under heavy load conditions when
the current demand from the power supply exceeds its specified limit the power supply turns its output off to protect itself from
damage. This results in one of the high voltage supply voltages dropping below their normal levels. This is indicated by the
red ERROR LED.
After a number of seconds the power supply will attempt to switch on its output again. If the overload condition has cleared,
the fault will clear automatically and the amplifier will return to its normal operating mode. If, however, the original load
condition persists, the power supply will shut down again. This can result in cyclic shutdown behaviour.
As the power supply shutdown is caused by the extreme load condition, the fault can be cleared by reducing the load current,
either by reducing the amplitude of the driving waveform or using a lighter load.
OVERLOAD
– Red LED. Lit when that the operating conditions of the output power devices (their semiconductor junction
temperatures) have reached their safe limits and, in order to prevent potential damage to them, the protection circuit has
reduced the maximum output current. The reduction is gradual and changes dynamically as the load current and the junction
temperature of the output devices changes. The OVERLOAD LED reflects this gradual reduction by the intensity of its
illumination. Thus at the onset of current limiting, the LED is lit up dimly and the brightness is increased as the output devices
are nearer their operating limits.
As the OVERLOAD condition is related to the semiconductor junction temperature of output devices, it can also occur under
inadequate cooling conditions, for example if airflow to the fans is blocked, or the ambient temperature is too high.
Note
Although both red LEDs indicate a fault condition and normally turn on under excessive load conditions, the main difference
between the ERROR LED and the OVERLOAD LED is that the former shows that the power supply protection has activated
whilst the latter indicates the same for the amplifier. It is possible, for example, to draw excessive current from the power
supply without excessive dissipation demanded from the output transistors (a typical case being high current drawn at a high
voltage). Similarly, aggressive pulse load conditions or sustained high current demand at low voltages might result in
excessive dissipation on the output transistors without exceeding the maximum current capability of the power supplies.
Neither of these fault conditions results in the output voltage being disabled. The amplifier will operate with a reduced rail
voltage or limited output current and in general this will mean that the output waveform will be clipped or distorted. If the cause
of the problem is removed (for example the amplitude of the input drive signal reduced) the amplifier will return to its normal
operating mode. As the OVERLOAD condition is linked to high temperatures, the recovery might take several seconds, until
the internal temperature had the time to cool down sufficiently.
BPA100 PIEZO AMPLIFIER
POWER
ERROR
OVERLOAD
10:1
