B1507A Power Device Capacitance Analyzer

Keysight Technologies

B1507A Power Device Capacitance Analyzer

Automatically evaluate all power device capacitance parameters (including Ciss, Coss, Crss, and Rg) under a wide range of operating voltages

Crucial issues facing the power electronics industry

Do you understand the full impact of device capacitance on increasing switching power supply frequencies?

In general, higher switching frequencies allow power electronics circuits to be physically smaller and take up less area. However, as frequency increases the device on-resistance (Ron) becomes less important, and switching loss and driving loss become the dominant factors that determine overall circuit power loss. A power device’s capacitance characteristics (which are nonlinear) are key parameters that help determine both switching and driving losses. Reverse transfer capacitance (Crss) and gate resistance (Rg) determine the switching speed, while the input capacitance (Ciss) determines the gate driving condition. In addition, the output capacitance (Coss) is also a key parameter in determining the switching loss for a resonant converter. Therefore, it has become more important than ever to accurately evaluate these parameters when designing power conversion circuits.

Do you worry about unknowingly using faulty power devices in your products?

As the occurrence of counterfeit and substandard power devices has become more common, the chance of accidentally using one or more of these devices in a power circuit has also increased.

Only checking current-voltage (IV) characteristics such as on-resistance (Ron) is not sufficient to screen out substandard devices. In fact, some devices have been intentionally manufactured with short channel widths to give them low Ron values. However, since capacitance is inversely proportional to channel width, these same devices have large and out-of-spec values for Crss. This means that when used in a circuit, these faulty devices will exhibit high levels of switching loss. For this reason, it is critical to measure device capacitance to prevent the use of defective power devices in your circuits.

The Keysight B1507A meets the challenges of power device capacitance evaluation

With the increasing use of power devices fabricated from emerging new materials such as SiC and GaN, switching power supplies are operating at increasingly higher frequencies. This makes accurate device capacitance characterization more important than ever before. The B1507A Power Device Capacitance Analyzer meets this need, providing a complete solution for the evaluation of power device capacitance (such as input, output, and reverse transfer capacitances). The B1507A can help power device development engineers maximize product value and performance by revealing detailed device characteristics. It can also help power electronic circuit designers maximize their products’ value by helping them to select the optimal power devices for their applications. The B1507A’s intuitive GUI allows you to automatically measure all capacitances under a wide range of operating voltages. In addition, it makes it easy to switch back and forth between leakage tests (to verify the device is not damaged) and capacitance measurements without having to do any recabling.

Measure device junction capacitances accurately and automatically

Measure capacitance at DC biases of up to 3 kV

The drain or collector terminal of a power device is often exposed to high voltages when it is off, which determines the value of its junction capacitances at the moment it turns on. Therefore, understanding how device capacitance changes with applied voltage is very important for power electronics circuit designers. Knowing the true value of device capacitance at a specific voltage and the calculated voltage the device will experience in a circuit allows you to select a power device with the lowest loss.

Measuring capacitance at high voltage biases is not easy. It requires both a good understanding of capacitance measurement theory as well as practical knowledge on how to connect the device and other necessary components (such as DC blocking capacitors and AC blocking resistors) correctly. In addition, since potentially lethal voltages are involved it requires a test setup that prevents the user from touching any high voltage nodes.

The B1507A meets all of these requirements. It can accurately and safely evaluate the junction capacitance voltage dependency of devices at up to 3 kV of DC bias. It can also compensate for the parasitic elements that affect cables and fixturing to produce reliable capacitance measurements.