# US 12,015,394 B2 · Fast turn-on protection of a cascode switch > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,015,394 B2 - Document ID: US12015394B2 - Status: Granted - Kind: B2 - Application number: 18/254,947 - Filed: 2021-12-01 - Published: 2023-10-26 - Granted: 2024-06-18 - Earliest claimed: 2020-12-22 - Assignees: Power Integrations, Inc. - Applicants: Power Integrations, Inc. - Inventors: Rajko Duvnjak - Web page: https://patentgrep.com/patent/US12015394B2 ## CPC - H03K 17/0822: {in field-effect transistor switches} - H03K 2217/94047: Cascode connected switches - Y02B 70/10: Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes - H03K: PULSE TECHNIQUE (measuring pulse characteristics G01R; modulating sinusoidal oscillations with pulses H03C; transmission of digital information H04L; discriminator circuits detecting phase difference between two signals by counting or integrating cycles of oscillation H03D3/04; automatic control, starting, synchronisation or stabilisation of generators of electronic oscillations or pulses where the type of generator is irrelevant or unspecified H03L; coding, decoding or code conversion, in general H03M) - Y02B: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS ## Abstract Fast turn-on protection of a cascode switch is presented herein. A cascode circuit includes a depletion mode field effect transistor and an enhancement mode field effect transistor electrically coupled in cascode. During turn-on, a protection circuit detects an overcurrent fault by observing a plateau of a cascode node voltage. An overcurrent fault may be detected in response to the plateau existing for greater than a threshold time duration. ## Claims ### Claim 1 A power converter comprising: a cascode circuit including a depletion mode field effect transistor and an enhancement mode field effect transistor electrically coupled in cascode, the cascode circuit configured to provide a cascode node voltage; and an overcurrent detection circuit configured to detect a period when the cascode node voltage gradually decreases and to indicate an overcurrent fault when the period exceeds a threshold time duration. ### Claim 2 (depends on 1) The power converter of claim 1, wherein the overcurrent detection circuit comprises a comparator. ### Claim 3 (depends on 1) The power converter of claim 1, wherein the overcurrent detection circuit comprises an AND gate. ### Claim 4 (depends on 1) The power converter of claim 1, wherein the overcurrent detection circuit comprises a controller. ### Claim 5 (depends on 1) The power converter of claim 1, wherein the depletion mode field effect transistor is a gallium nitride (GaN) depletion mode transistor. ### Claim 6 (depends on 1) The power converter of claim 1, wherein the depletion mode field effect transistor is a silicon carbide (SiC) depletion mode transistor. ### Claim 7 (depends on 1) The power converter of claim 1, wherein the enhancement mode field effect transistor is a low voltage field effect transistor. ### Claim 8 A method of detecting overcurrent in a gallium nitride (GaN) cascode circuit comprising: turning on the GaN cascode circuit with a transient step; receiving a cascode node voltage; determining a period when the cascode node voltage gradually decreases; and indicating an overcurrent fault in response to the period existing for greater than a threshold time duration. ### Claim 9 (depends on 8) The method of claim 8, wherein turning on the GaN cascode circuit comprises: providing a gate signal to a low voltage field effect transistor. ### Claim 10 (depends on 9) The method of claim 9, wherein receiving the cascode node voltage comprises: receiving a drain voltage of the low voltage field effect transistor. ### Claim 11 (depends on 10) The method of claim 10, wherein determining the period when the cascode node voltage gradually decreases comprises: comparing the drain voltage of the low voltage field effect transistor with a threshold voltage. ### Claim 12 (depends on 11) The method of claim 11, wherein indicating the overcurrent fault in response to the period existing for greater than the threshold time duration comprises: determining the threshold time duration using a controller. ### Claim 13 A method of rapidly detecting overcurrent in a power converter comprising: turning on a cascode switch with a transient step; receiving a cascode node voltage; determining a period when the cascode node voltage gradually decreases; and indicating an overcurrent fault in response to the period existing for greater than a threshold time duration. ### Claim 14 (depends on 13) The method of claim 13, wherein the cascode switch comprises a depletion mode field effect transistor and an enhancement mode field effect transistor electrically coupled in cascode. ### Claim 15 (depends on 14) The method of claim 14, wherein turning on the cascode switch comprises: providing a gate signal to the enhancement mode field effect transistor. ### Claim 16 (depends on 15) The method of claim 15, wherein receiving the cascode node voltage comprises: receiving a drain voltage of the enhancement mode field effect transistor. ### Claim 17 (depends on 16) The method of claim 16, wherein determining the period when the cascode node voltage gradually decreases comprises: comparing the enhancement mode field effect transistor with a threshold voltage. ### Claim 18 (depends on 17) The method of claim 17, wherein the threshold voltage is between one volt and ten volts. ### Claim 19 (depends on 17) The method of claim 17, wherein indicating the overcurrent fault in response to the period existing for greater than the threshold time duration comprises: determining the threshold time duration using a controller. ### Claim 20 (depends on 19) The method of claim 19, wherein the threshold time duration is between one-hundred nanoseconds and three-hundred nanoseconds.