Over-voltage protection is added to supercapacitor; boosts reliability

Over-voltage protection is added to supercapacitor; boosts reliability

The low power feature enables energy-efficient supercapacitor balancing for products that require low-loss energy power, leakage current regulation and over-voltage protection (OVP), advises the company. The supercapacitors can be used for applications that require balancing, such as automotive, transportation, automation, data centres and power grids.

Supercapacitor cells typically operate at a nominal recommended working voltage, but voltages that exceed the maximum rating for a prolonged period will reduce cell operating life. Supercapacitors have different tolerances in terms of capacitance value, internal resistance, and leakage current but when two or more supercapacitors are connected, either in a series or in parallel, these differences cause an imbalance in cell voltages that must be balanced so that no one cell exceeds its maximum rated voltage.

According to Robert Chao, president and founder of ALD: “The OVP board is the only commercially available balancing scheme that manages both over-voltage and leakage current. The circuit used on the board offers matched precision push–pull voltage/current action, which is ideal for cells with a minimal amount of energy loss.”

The SABMBOVP2XX PCBs enable precision voltage clamp circuits with “extremely high current gains”. This combination is suitable for balancing large supercapacitors that are stacked in a series, from two to hundreds of cells with values of 0.1F to 3,000F and above.

The SABMBOVP family has low output currents at input voltages that are below the threshold voltage when a drastic change in output current balancing is achieved through a sharp and steep change in the output current in response to small, incremental input voltages that are above the threshold voltage and balancing occurs.

The supercapacitors have a high current gain (dl/dV of approximately 3mA/1mV) amplifier, which typically produces more than 1,000,000 times the output increase with very small increments of less than 100mV in input change. By amplifying the output current, the voltage limits are reached quickly and efficiently to safely balance the supercapacitor, explains ALD. For example, a 33mV input voltage change can change the current from 1mA to 100mA.

The SABMBOVP specifically targets cells in which the charging/discharging currents can be up to 1,000A, and charging at a few mA will take too long to reach the supercapacitor’s voltage limits.

The SABMBOVP2XX PCB is populated with one of the company’s ALD9100XXSALI Supercapacitor Auto Balancing (SAB) MOSFETs, which specify the circuit threshold or clamping voltage to balance the circuit with near-zero charge loss. The balancing output current from the SAB MOSFET is amplified to produce (nominally) 1mA of balancing output current at Vin, which is equal to the rated SAB MOSFET threshold.

The PCBs measure just 0.6 x 1.6 inches (15.24 x 40.64mm) and operate in the industrial temperature range of -40 to +85°C.

It is made with RoHS-compliant FR4 material and supplied ready for mounting a single ALD9100XX, eight-lead SOIC.

The company also offers an unpopulated universal PCB for use with ALD9100xx Dual SAB MOSFETs. The boards can be cascaded to form a series-connected chain of boards to balance series-connected supercapacitors. The supercapacitors and PCBs are in stock at Mouser and Digikey.