Wide Band Gap Power Device Evaluation Challenges and Technologies

Transcription

1 Wide Band ap Power evice Evaluation Challenges and Technologies March 2015 Ryo Takeda enior Product Planner Keysight Technologies

2 pplication Requirements from Modern Power Electronics Improved conversion efficiency olume and weight reduction Use in harsh environments ic i Motor drive system Presented by Yaskawa Electric Corp. Page 2

3 Why Use Wide Band ap (WB) emiconductors WB properties Benefits Lower power loss Better conversion efficiency = maller / Lighter cooling system Higher frequency operation maller passive circuit components Higher temperature operation maller / Lighter / ealed cooling system for harsh environment use, (e.g. excavator use) Page 3

4 Expected pplication Map for ic/an ic: uitable for very high power (high current / high voltage) application an: uitable for middle range power application ource ate ource p- n- n+ ubstrate rain ic: ertical ate lan n+ rain Breakdown voltage an ic an Buffer layer ubstrate an: Lateral n- On-resistance Operation speed Page 4

5 Current rating () Expected pplication Map for ic/an ic an On-board power supply utomotive electronics H Communic ation equipment Hybrid / Electric vehicle eneral purpose inverter witching power supply New energy/ istributed P Home appliances Industrial equipment Electrical train Backbone electricity oltage rating () Page 5

6 Critical Evaluation Items for ic/an High Current High current is often used in actual operation in many applications Ron becomes smaller and therefore high current is mandatory for accurate Ron evaluation. Ron is important to calculate conduction loss. High oltage Especially important for ic Basic parameter but one of the most important parameters from reliability perspective Temperature dependency Especially important for ic arious power electronics products are used in harsh environment Capacitance (Ciss, Coss, Crss, Rg, Normally-on device) Especially important for an Critical parameters for switching performance Important to estimate power losses such as output capacitance loss, etc. ate Charge Critical parameter for switching performance and gate drive circuit design Important to estimate switching loss Reliability Long term reliability is one of the main concerns when adopting new/emerging devices Page 6

7 Challenges in ic/an evice Evaluation Lack of tandard olution How many hours have you invested in isolating your test problems? evice manufacturers also suffer the lack of reference measurement equipment evice users have no easy way to make accurate device evaluation High oltage / High Current ccuracy is questionable without having a well thought test circuit and NIT traceable standard Temperature dependency Long cable extension from test equipment to thermostatic chamber results in: 1) current reduction, 2) oscillation, and 3) deteriorated accuracy Capacitance (Ciss, Coss, Crss, Rg & Normally-on) Complicated connections and special techniques result in many measurement problems ate Charge ifficult to construct a test system with good accuracy and safety Intuitive and tandard User Interface nybody should be able to conduct device evaluation without training Page 7

8 High Current / High oltage Many factors to take into account for accurate high power test High Low ppropriate test circuitry Fast pulse to avoid self heating Both voltage & current sources hort, low L and low R cables for high current & fast rise time uarding for low leakage at high voltage test Traceability to international standard tandard solution with NIT traceability is required in all aspects of the power electronics industry. Page 8

9 Issues with Temperature ependency Test using Thermostatic Chamber Time consuming set up / measurement Extremely slow test throughput. Only a few tests performed a day Long cable causes several issues Lowered maximum current eteriorated accuracy High risk of oscillation Thermostatic chamber Measurement equipment lthough the temperature dependent test is important most people don t perform it due to problematic measurement and long test time. Fast and accurate thermal test equipment is necessary across the entire power electronics industry. Page 9

10 Issues ssociated with Capacitance Measurement (1) Measuring Crss? LCR meter High Low Cgd (=Crss) Cgs Ciss = Cgd + Cgs Coss = Cgd + Cds Cds ~ ~ Hc Hp ource Lp Lc Ids +Igd Ids Cds Cgs Igd rain Cgd Igd ate Igd Page 10

11 Issues ssociated with Capacitance Measurement (2) Measuring Ciss with high voltage bias? C Blocking Resistor (e.g. 100kΩ >> ZC short) LCR meter High Low Cgd (=Crss) Cgs Ciss = Cgd + Cgs Cds rain ource shorting cable High LCR meter Low High oltage Bias-T Cgd (=Crss) Cgs C Blocking & C hort Capacitor (>>Cds) Cds Complicated test circuit with manual connection changes make the capacitance test challenging and result in human errors, an industrial solution is required for users of power devices. Page 11

12 Issues with ate Charge Measurement Courtesy of International Rectifier 1. ifficult to prepare a power source at drain that has enough simultaneous current and voltage capacity. Using a capacitor is a solution. However, it has safety issues. 2. ifficult to prepare a constant current source which has small enough current to allow slow gate charge accumulation for accurate sampling. 3. evice is likely to be destroyed by measuring at up to rated current with high voltage bias. esigning a safe and accurate test system is difficult, an industrial solution is required for users of power devices. Page 12

13 Mainframe witches tandard olution Example Keysight B1506 Power evice nalyzer Kelvin connection uarding atasheet format report Low L, R cables Fast pulses High B1506 Low MU technology Critical power device test technologies C switches evice capacitan ce selector Full automation through I, C switches key points atasheet format oftware I/F NIT traceability To cover critical power device test technologies when building test system or test instrument To make the instrument NIT traceable in order to deploy the test system to different locations. Calibration standard must be built first to make it happen. witching matrix that change the test resources connected to UT is necessary to make the automated and reliable test system. For FET capacitance test, the matrix should include C blocking capacitor and C blocking resistor. User interface should be easy enough. One example is to simulate datasheet, which is friendly to device manufacturer and device users. Page 13

14 Mainframe witches 3 Terminal FET Capacitance Measurement Circuit iagrams Ciss C blocking R C blocking R (e.g. 100 kω) Coss Cgd Cgd ~ CMH Necessary for normally-on device Cgs ~ CMH Cds MU LCR meter CML C blocking C (>> Cgd,Cds) MU MU CML LCR meter MU Crss ~ CMH CML Cgd C switches evice capacitan ce selector MU LCR meter MU Page 14

15 Fully utomatic Temperature ependency Test Example key points To bring test resource (i.e. current amplifier in a test fixture) near UT in order to reduce cable inductance and therefore maximize current and reduce the chance of oscillation To use thermal equipment that can be controlled via computer. To avoid condensation in the fixture when cooling UT With Thermostream (-50 C to +220 C) With hot plate (Room temp to +250 C) Page 15

16 Novel Qg Measurement Method Floating MU to control Id Current regulation FET CLK ate drive MU Lout Rout + - Constant Ig UT Constant Ig CLK UT Ultra high current unit ate drive MU High oltage MU key points To separate Qg measurement into two, 1) high voltage low current measurement and 2) low voltage high current measurement To regulate maximum current with another FET To use MU in order to apply precise current to the gate Fast sampling to monitor gate voltage and drain current changes Page 16

17 Reliability Test ystem Concept Choose instrument that has enough voltage or current range for reliability testing Use multiple instruments in order to give stress to multiple devices simultaneously Page 17

18 ummary ic/an brings about new measurement challenges High voltage High current (ccurate Ron) Temperature dependency Capacitances & Rg ate charge standard solution is necessary across the entire power electronics industry Consistent test results in any location every time Everyone should make evaluation without having product training Keysight provides a product that fills the gap Page 18