How does EBS work?

The Electronic Ballast System (EBS) consists of a power transformer, an SCR module, and a control circuit board mounted on a common base. The main element of the ballast is the power transformer. It scales the input voltage on the primary side to the appropriate lamp voltage on the secondary side.

Power to the lamp is controlled by a technique known as phase-angle modulation. With this method, the SCR module blocks portions of the line input voltage, while allowing other portions to pass. The ratio of passing to blocking determines how much power gets to the lamp. The control circuit measures the actual lamp current, compares it to the setpoint, and drives the SCRs with the proper phase angle.

Closed Loop Lamp Current Control

One of the primary features of the EBS is that it uses feedback to maintain precise control over lamp current. Superior regulation is maintained over variations in temperature, input voltage, and lamp condition. This eliminates a typical problem with magnetic ballasts-that lamp current depends on a high voltage capacitor, the value of which has a ± 20% tolerance.

Electronically Simulated Capacitor

Another feature of the control circuit is that it makes the EBS behave as if there were a capacitor in series with the lamp, even though none is. This is necessary because gas discharge lamps tend to become rectifiers-drawing current in only one direction-unless any DC through the lamp is eliminated. DC through the lamp causes saturation in the power transformer, mercury migration in the lamp, and other related problems. Nicollet's patented circuit measures any DC offset, and independently adjusts the phase angle of each SCR, eliminating any DC in the lamp and transformer. The EBS is therefore able to eliminate the large, unreliable capacitor banks that magnetic ballasts rely upon.

Controlled warmup Mode

When the lamp is first ignited, the EBS drives the lamp current to the specified warmup current. That warmup current is maintained until the lamp reaches the correct operating voltage. At that point, control of lamp current switches from the warmup current to the run current, controlled via the control input. Warmup current is adjustable from less than 100% to more than 300% of the normal lamp run current. Setting the warmup current at the upper end of its range can bring lamps from ignition to full power in as little as ten seconds.

Protection Circuits

The EBS has built-in protection circuits for the safety of the operator and equipment. These circuits shut down the ballast and signal a fault condition if abnormal operation is detected. If the input current is too high, an overcurrent fault is reported. If the lamp fails to start or extinguishes during operation, a lamp out fault is reported. The fault signals are indicated by status indicator lights on the circuit board and also by relay contacts for remote signaling.