# US 10,873,270 B2 · Converter apparatus using source-activated discharge circuits > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,873,270 B2 - Document ID: US10873270B2 - Status: Granted - Kind: B2 - Application number: 15/467,711 - Filed: 2017-03-23 - Published: 2018-09-27 - Granted: 2020-12-22 - Earliest claimed: 2017-03-23 - Assignees: Eaton Intelligent Power Limited - Applicants: Eaton Intelligent Power Limited - Inventors: Stan Rex Simms; John David Maurin; Thomas Arthur Farr - Web page: https://patentgrep.com/patent/US10873270B2 ## CPC - H02M 7/06: using discharge tubes without control electrode or semiconductor devices without control electrode - H02J 7/345: {using capacitors as storage or buffering devices} - H02P 29/027: {the fault being an over-current} - H02M 1/322: {Means for rapidly discharging a capacitor of the converter for protecting electrical components or for preventing electrical shock} - H02M: APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF (transformers H01F; dynamo-electric converters H02K47/00; controlling transformers, reactors or choke coils, control or regulation of electric motors, generators or dynamo-electric converters H02P) - H02J: ELECTRIC POWER NETWORKS; CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY - H02P: CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS ## Abstract An apparatus, such as a variable frequency drive (VFD), includes a rectifier, a DC bus coupled to an output of the rectifier and at least one capacitor coupled to the DC bus. The apparatus further includes a normally-conducting switch coupled to the DC bus and configured to discharge the at least one capacitor in a conducting state and a control circuit configured to control the normally-conducting switch responsive to an input to the rectifier. The control circuit may be configured to control the normally-conducting switch responsive to a voltage at the input of the rectifier. The control circuit may include a regulator circuit having an input coupled to the input of the rectifier and a driver circuit coupled to an output of the regulator circuit and configured to drive a control terminal of the normally-conducting switch. ## Claims ### Claim 1 An apparatus comprising: a rectifier; a DC bus coupled to an output of the rectifier; at least one capacitor coupled to the DC bus; at least one n-channel depletion-mode FET and a resistor coupled in series to the DC bus; and a control circuit configured to cause the at least one n-channel depletion-mode FET to transition from a non-conducting state to a conducting state responsive to a decrease in an AC voltage at an input to the rectifier to thereby discharge the at least one capacitor via the at least one n-channel depletion-mode FET and the resistor, the control circuit comprising: a regulator circuit having an input coupled to the input of the rectifier; and an inverting DC-DC converter having an input coupled to the regulator circuit and an output coupled to a control terminal of the at least one n-channel depletion-mode FET. ### Claim 2 (depends on 1) The apparatus of claim 1, comprising a supercascode switch including the at least one n-channel depletion-mode FET. ### Claim 3 (depends on 1) The apparatus of claim 1, wherein the control circuit is further configured to control the at least one n-channel depletion-mode FET responsive to a voltage on the DC bus. ### Claim 4 A motor drive comprising: a rectifier having an input configured to be coupled to an AC power source; a DC bus coupled to an output of the rectifier; an inverter having an input coupled to the DC bus and an output configured to be coupled to a motor; at least one capacitor coupled to the DC bus; and a normally-on or normally-closed switch and a resistor coupled in series to the DC bus; and a control circuit coupled to the input of the rectifier and configured to cause the normally-on or normally-closed switch to transition from a non-conducting state to a conducting state responsive to a decrease in an AC voltage at the input of the rectifier to thereby discharge the at least one capacitor through the normally-on or normally-closed switch and the resistor, the control circuit comprising: a regulator circuit having an input coupled to the input of the rectifier; and a DC-DC converter circuit coupled to an output of the regulator circuit and configured to drive a control terminal of the normally-on or normally-closed switch. ### Claim 5 (depends on 4) The motor drive of claim 4, wherein the control circuit is configured to place the normally-on or normally-closed switch in the non-conducting state responsive to the voltage at the input of the rectifier meeting a predetermined criterion. ### Claim 6 (depends on 4) The motor drive of claim 4, wherein the normally-on or normally-closed switch comprises at least one depletion-mode FET. ### Claim 7 (depends on 6) The motor drive of claim 6, wherein the at least one depletion-mode FET comprises at least one n-channel depletion-mode FET and wherein the DC-DC converter circuit comprises an inverting DC-DC converter circuit having an input coupled to the regulator circuit and an output coupled to a control terminal of the at least one n-channel depletion-mode FET. ### Claim 8 (depends on 6) The motor drive of claim 6, wherein the normally-on or normally-closed switch comprises a normally-on supercascode switch comprising at least one depletion-mode FET. ### Claim 9 (depends on 4) The motor drive of claim 4, wherein the control circuit is further configured to control the normally-on or normally-closed switch responsive to a voltage on the DC bus. ### Claim 10 An apparatus comprising: a normally-on or normally-closed switch and a resistor configured to be coupled in series to a DC bus of a motor drive; and a control circuit configured to cause the normally-on or normally-closed switch to transition from a non-conducting state to a conducting state responsive to a reduction in an AC voltage at an input of a rectifier coupled to the DC bus to thereby discharge at least one capacitor coupled to the DC bus through the normally-on or normally-closed switch and the resistor; the control circuit comprising: a regulator circuit having an input coupled to the input of the rectifier; and a DC-DC converter circuit coupled to an output of the regulator circuit and configured to drive a control terminal of the normally-on or normally-closed switch. ### Claim 11 (depends on 10) The apparatus of claim 10, wherein the control circuit is configured to place the normally-on or normally-closed switch in a non-conducting state responsive to the voltage at the input of the rectifier having a magnitude exceeding a threshold. ### Claim 12 (depends on 10) The apparatus of claim 10, wherein the normally-on or normally-closed switch comprises at least one depletion-mode FET. ### Claim 13 (depends on 12) The apparatus of claim 12, wherein the at least one depletion-mode FET comprises at least one n-channel depletion-mode FET and wherein the DC-DC converter circuit comprises an inverting DC-DC converter. ### Claim 14 (depends on 12) The motor drive of claim 12, wherein the normally-on or normally-closed switch comprises a normally-on supercascode circuit comprising the least one depletion-mode FET.