During charging, if the charge time exceeds 500 ms, the power supplies will indicate a load fault and trigger the charging supplies to shut down the output current. They then automatically reset themselves after half a second before continuing the charge sequence. This creates a staircase-like charge voltage waveform which continues until the programmed output voltage is reached. See Figure 1.
The load fault condition protects the PSU and the circuit in the event of an external short circuit.
Optimising Charge Performance
To improve charge performance in these applications the ALE Long Charge Adapters (LCA) can be added to the unit. The LCA optimises the output current profile of the power supplies, helping the PSUs charge capacitors in the fastest time possible. They plug into the power supplies remote control interface and modify their output current to minimise charge time.
By using an LCA, the load fault current is defeated and power supplies can continuously deliver their full rated charge current and at the same time, keep the output voltage at less than 50% of rated voltage.
TDK-Lambda’s ALE capacitor charging power supplies rapidly and efficiently charge capacitors in pulsed discharge loads, such as lasers and modulators. These PSUs operate in repetitive circuits of tens or hundreds of charge/discharge cycles per second, reducing the capacitor charge time and the power supply reaching the programmed output voltage within milliseconds.
The power supplies act as a constant current source until the capacitor has reached the programmed voltage, when it then switches to voltage regulation mode.