TDA2088

The TDA2088 has the following features including Powered Direct from AC Mains or DC Line;-5V Supply Available for Ancillary Circuitry;Low Supply Current Consumption;Negative Triac Firing Pulses;Guaranteed Minimum 100mA Triac Crive Current;Well-Defined Control Voltage/Phase Angle Relationship;Speed Compensated by Sensing Motor Current;Simple Optimisation of Control Leop Parameters.

The  TDA2088  is  a  bipolar  integrated  circuit  phase controller.  optimised  for  use  in  current  feedback applications. It can also be used in open loop mode. The circuit was primarily designed for motor speed control in applications such as power tools and domestic appliances(foodmixers etc.).The TDA2088 is designed to give a triac pulse that is greater than 100mA for a period of 50 microseconds with standard pulse timing components (47nF. pin 10). Repeated triac gate pulses are given if the triac fails to latch or becomes unlatched due to motor brush bounce.An internal -5V reference circuit is used as the charging voltage for the pulse timing ramp capacitor and as the reference voltage for the speed input potentiometer. This ensures that maximum phase angle can be obtained by adjusting the resistor or capacitor on the pulse timing circuit.without affecting the maximum setting.

The load current is normally sensed in the positive mains half-cycle by means of a low impedance resistor in series with the triac and load-The voltage drop across this resistor is converted back into a low current source by a second resistor and fed into the load current sensing input (pin 1) of the TDA2088. In high load current applications where the power dissipated  in  a  series  sensing  resistor  would  be unacceptable. a current transformer may be utilised.Since the device works with the positive supply common.the triac gate pulses are negative going. This is an advantage when  selecting  a  suitable  triac  since  most  triac manufacturers prefer this drive polarity.Timing functions and triac gate drive pulses are inhibited until there is sufficient supply voltage across the device to guarantee complete gate drive pulses.