# US 7,746,043 B2 · Inductor flyback detection using switch gate change characteristic detection > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 7,746,043 B2 - Document ID: US7746043B2 - Status: Granted - Kind: B2 - Application number: 11/967,273 - Filed: 2007-12-31 - Published: 2008-11-06 - Granted: 2010-06-29 - Earliest claimed: 2007-05-02 - Assignees: Cirrus Logic, Inc. - Inventors: John L. Melanson - Web page: https://patentgrep.com/patent/US7746043B2 ## CPC - H02M 1/4225: {using a non-isolated boost converter} - H03M 3/476: {Non-linear conversion systems} - 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 - Y02P 80/10: Efficient use of energy, e.g. using compressed air or pressurized fluid as energy carrier - 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) - H03M: CODING; DECODING; CODE CONVERSION IN GENERAL (using fluidic means F15C4/00; optical analogue/digital converters G02F7/00; coding, decoding or code conversion, specially adapted for particular applications, see the relevant subclasses, e.g. G01D, G01R, G06F, G06T, G09G, G10L, G11B, G11C, H04B, H04L, H04M, H04N; ciphering or deciphering for cryptography or other purposes involving the need for secrecy G09C) - Y02B: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS - Y02P: CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS ## Abstract A method and system monitor gate charge characteristics of one or more field effect transistors in a switching power converter to detect an end of an inductor flyback time interval. The switching power converter includes a switch coupled to an inductor to control current flow in the inductor. When the switch turns OFF, a collapsing magnetic field causes the inductor current to decrease and the inductor voltage to reverse polarity. When the magnetic field completely collapses, the inductor current goes to zero. At the end of the inductor flyback time interval, a voltage is induced across a Miller capacitance of the switch. The voltage can be detected as a transient change in the gate voltage of the switch. A switch gate sensor detects the gate voltage change associated with the end of the inductor flyback time interval and provides a signal indicating an end of the inductor flyback time interval. ## Claims ### Claim 1 An apparatus to detect an end of an inductor flyback time interval of a switching power converter, wherein the switching power converter includes an inductor to couple to an input voltage node and a field effect transistor (FET) switch coupled to the inductor, the apparatus comprising: a switch gate sensor to couple to a gate of the switch, wherein during operation of the switch gate sensor, the switch gate sensor is configured to: detect a charge characteristic on a gate of the switch associated with an end of the inductor flyback time interval; and generate a switch gate sensor signal indicating an end of the inductor flyback time interval. ### Claim 2 (depends on 1) The apparatus of claim 1 wherein the charge characteristic associated with an end of the inductor flyback time interval comprises a gate voltage fluctuation on the gate of the switch. ### Claim 3 (depends on 2) The apparatus of claim 2 wherein the switch gate sensor comprises: a comparator having a first input terminal to couple to the gate of the switch and a second input terminal to couple to a reference voltage, wherein the comparator is configured to generate the switch gate sensor signal when a comparison of the gate voltage to the reference voltage by the comparator indicates the end of the inductor flyback time interval. ### Claim 4 (depends on 3) The apparatus of claim 3 wherein the comparator is configured to generate the switch gate sensor signal when the comparison of the gate voltage to the reference voltage indicates the gate voltage is less than the reference voltage. ### Claim 5 (depends on 1) The apparatus of claim 1 wherein the switch gate sensor is further configured to provide the switch gate sensor signal to a power factor correction and output voltage controller. ### Claim 6 (depends on 1) The apparatus of claim 1 wherein the switching power converter is a member of a group consisting of: switching power supplies, switch mode converters, switch mode transformers, and switching amplifiers. ### Claim 7 (depends on 1) The apparatus of claim 1 further comprising a PFC and output voltage controller coupled to the switch gate sensor to receive the switch gate sensor signal. ### Claim 8 A method to detect an end of an inductor flyback time interval of a switching power converter, wherein the switching power converter includes an inductor to couple to an input voltage node and a field effect transistor (FET) switch coupled to the inductor, the method comprising: detecting a charge characteristic on a gate of the switch associated with an end of the inductor flyback time interval; and generating a switch gate sensor signal indicating an end of the inductor flyback time interval. ### Claim 9 (depends on 8) The method of claim 8 wherein detecting a charge characteristic on a gate of the switch associated with an end of the inductor flyback time interval comprises detecting a gate voltage fluctuation on the gate of the switch. ### Claim 10 (depends on 8) The method of claim 8 wherein generating a switch gate sensor signal indicating an end of the inductor flyback time interval comprises: comparing a gate voltage of the switch to a reference voltage; and generating the switch gate sensor signal indicating the end of the inductor flyback time interval when the comparison of the gate voltage to the reference voltage indicates the end of the inductor flyback time interval. ### Claim 11 (depends on 10) The method of claim 10 wherein generating the switch gate sensor signal further comprises: generating the switch gate sensor signal when the comparison of the gate voltage to the reference voltage indicates the gate voltage is less than the reference voltage. ### Claim 12 (depends on 8) The method of claim 8 further comprising: providing the switch gate sensor signal to a power factor correction and output voltage controller. ### Claim 13 (depends on 8) The method of claim 8 further comprising: maintaining a voltage on the gate of the switch during the inductor flyback time interval that prevents the switch from conducting. ### Claim 14 (depends on 8) The method of claim 8 wherein the switching power converter is a member of a group consisting of: switching power supplies, switch mode converters, switch mode transformers, and switching amplifiers. ### Claim 15 An apparatus to detect an end of an inductor flyback time interval of a switching power converter, wherein the switching power converter includes an inductor to couple to an input voltage node and a field effect transistor (FET) switch coupled to the inductor, the apparatus comprising: means for detecting a charge characteristic on a gate of the switch associated with an end of the inductor flyback time interval; and means, coupled to the means for detecting, for generating a switch gate sensor signal indicating an end of the inductor flyback time interval. ### Claim 16 (depends on 15) The apparatus of claim 15 wherein the charge characteristic associated with an end of the inductor flyback time interval comprises a gate voltage fluctuation on the gate of the switch. ### Claim 17 (depends on 15) The apparatus of claim 15 wherein the means for generating comprises: means for comparing a gate voltage of the switch to a reference voltage; and means, coupled to the means for comparing, for generating the switch gate sensor signal indicating the end of the inductor flyback time interval when the comparison of the gate voltage to the reference voltage indicates the end of the inductor flyback time interval. ### Claim 18 (depends on 17) The apparatus of claim 17 wherein means for generating the switch gate sensor signal further comprises means for generating the switch gate sensor signal when the comparison of the gate voltage to the reference voltage indicates gate voltage is less than the reference voltage. ### Claim 19 (depends on 15) The apparatus of claim 15 further comprising: means, coupled to the means for generating, for providing the switch gate sensor signal to a power factor correction and output voltage controller. ### Claim 20 (depends on 15) The apparatus of claim 15 further comprising: means for maintaining a voltage on the gate of the switch during the inductor flyback time interval that prevents the switch from conducting. ### Claim 21 (depends on 1) The apparatus of claim 1 wherein the end of the inductor flyback time interval occurs when a current in the inductor decreases to zero, wherein the switch gate sensor is further configured to detect the charge characteristic on the gate of the switch associated with the end of the inductor flyback time interval during operation of the switching power converter in discontinuous current conduction mode. ### Claim 22 (depends on 8) The method of claim 8 wherein the end of the inductor flyback time interval occurs when a current in the inductor decreases to zero and detecting a charge characteristic on a gate of the switch associated with an end of the inductor flyback time interval further comprises: detecting the charge characteristic on the gate of the switch associated with the end of the inductor flyback time interval during operation of the switching power converter in discontinuous current conduction mode. ### Claim 23 (depends on 15) The apparatus of claim 15 wherein the end of the inductor flyback time interval occurs when a current in the inductor decreases to zero and the means for detecting the charge characteristic on the gate of the switch associated with the end of the inductor flyback time interval further comprises: means for detecting the charge characteristic on the gate of the switch associated with the end of the inductor flyback time interval during operation of the switching power converter in discontinuous current conduction mode.