# US 12,003,170 B2 · Soft-start circuit for power-up > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,003,170 B2 - Document ID: US12003170B2 - Status: Granted - Kind: B2 - Application number: 17/854,049 - Filed: 2022-06-30 - Published: 2023-09-21 - Granted: 2024-06-04 - Earliest claimed: 2022-03-15 - Assignees: Fremont Micro Devices Corporation - Applicants: Fremont Micro Devices Corporation - Inventors: Jianfeng Liu; Yuquan Huang; Dennis Sinitsky - Web page: https://patentgrep.com/patent/US12003170B2 ## CPC - H02M 1/36: Means for starting or stopping converters - H02M 1/0025: {Arrangements for modifying reference values, feedback values or error values in the control loop of a converter} - H02M 1/32: Means for protecting converters other than automatic disconnection - 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) ## Abstract Disclosed is a soft-start circuit for power-up, which includes a reference value generation circuit, a protection threshold generation circuit and a control circuit. The reference value generation circuit outputs a reference value, which increases slowly, during a start-up process for power-up. The protection threshold generation circuit outputs a protection threshold, which increases slowly, during the start-up process for power-up. The control circuit controls an output voltage to increase slowly along with the reference value based on the reference value, during the start-up process for power-up, and to limit an output current based on the protection threshold to limit the output voltage, during the start-up process for power-up. In this way, even if the output current must operate at the peak current, a smoother current output is realized, and operation at the maximum peak current for a long-time during start-up is not allowed. ## Claims ### Claim 1 A soft-start circuit for power-up, comprising: a reference value generation circuit, which is configured to output a reference value, which increases slowly, during a start-up process for power-up; a protection threshold generation circuit, which is configured to output a protection threshold, which increases slowly, during the start-up process for power-up; a control circuit, which is configured to control an output voltage to increase slowly along with the reference value based on the reference value, during the start-up process for power-up, and to limit an output current based on the protection threshold to limit the output voltage, during the start-up process for power-up. ### Claim 2 (depends on 1) The soft-start circuit for power-up according to claim 1, wherein the soft-start circuit for power-up further comprises a frequency modulation circuit, which is configured to monitor the output voltage, and generate a frequency signal, which is positively related with the output voltage, based on the output voltage, for the soft-start circuit for power-up. ### Claim 3 (depends on 2) The soft-start circuit for power-up according to claim 2, wherein a slow increase rate of the reference value which is outputted by the reference value generation circuit, and/or a slow increase rate of the protection threshold which is outputted by the protection threshold generation circuit, are positively related with the frequency signal which is outputted by the frequency modulation circuit. ### Claim 4 (depends on 2) The soft-start circuit for power-up according to claim 2, wherein the protection threshold generation circuit is specifically configured to control a stepwise increase of the protection threshold based on the frequency signal, which is outputted by the frequency modulation circuit, during the start-up process for power-up; wherein a time step length of the stepwise increase is positively related with the frequency signal which is outputted by the frequency modulation circuit. ### Claim 5 (depends on 2) The soft-start circuit for power-up according to claim 2, wherein the reference value generation circuit is specifically configured to control a stepwise increase of the reference value based on the frequency signal, which is outputted by the frequency modulation circuit, during the start-up process for power-up; wherein a time step length of the stepwise increase is positively related with the frequency signal which is outputted by the frequency modulation circuit. ### Claim 6 (depends on 2) The soft-start circuit for power-up according to claim 2, wherein the soft-start circuit for power-up further comprises a start-up time detection circuit, which is configured to monitor the output voltage during the start-up process for power-up, to time with the frequency signal which is generated by the frequency modulation circuit, to control the control circuit to maintain turning-on when the output voltage increases to a preset value within a first start-up time, and to control the control circuit to turn off when the output voltage fails to increase to the preset value within the first start-up time, to maintain timing and control the control circuit to turn on again when the timing reaches a second start-up time, and to control an output reset of the reference value generation circuit and an output reset of the protection threshold generation circuit through a reset signal, simultaneously; wherein the second start-up time is an integral multiple of the first start-up time. ### Claim 7 (depends on 2) The soft-start circuit for power-up according to claim 2, wherein the frequency modulation circuit comprises a first current source, a second current source, a first diode, a second diode, a voltage controlled current source, a first capacitor and an oscillator; wherein the voltage controlled current source is controlled by a difference between a preset voltage and the output voltage, an anode of the first diode is connected with an output terminal of the first current source and an anode of the second diode; a cathode of the first diode is connected with an output terminal of the second current source and a first end of the first capacitor, a cathode of the second diode is grounded through the voltage controlled current source; a second end of the first capacitor is grounded, and an input terminal of the oscillator is connected with the first end of the first capacitor; wherein the oscillator is configured to generate the frequency signal based on a preset frequency modulation reference voltage and a voltage at the first terminal of the first capacitor. ### Claim 8 (depends on 1) The soft-start circuit for power-up according to claim 1, wherein the soft-start circuit for power-up further comprises a start-up time detection circuit, which is configured to monitor the output voltage during the start-up process for power-up, to time with a frequency signal, to control the control circuit to maintain turning-on when the output voltage increases to a preset value within a first start-up time, and to control the control circuit to turn off when the output voltage fails to increase to the preset value within the first start-up time, to maintain timing and control the control circuit to turn on again when the timing reaches a second start-up time, and to control an output reset of the reference value generation circuit and an output reset of the protection threshold generation circuit through a reset signal, simultaneously; wherein the second start-up time is an integral multiple of the first start-up time. ### Claim 9 (depends on 1) The soft-start circuit for power-up according to claim 1, wherein the reference value and the protection threshold have a linear increase, a stepwise increase, or a curvilinear increase. ### Claim 10 (depends on 1) The soft-start circuit for power-up according to claim 1, wherein the protection threshold comprises one or more protection thresholds, wherein the protection threshold, which has a minimum final-limited output current, has a stepwise increase. ### Claim 11 (depends on 10) The soft-start circuit for power-up according to claim 10, wherein the protection threshold has multiple protection thresholds of both current values and voltage values. ### Claim 12 (depends on 11) The soft-start circuit for power-up according to claim 11, wherein when the protection threshold, which has a minimum final-limited output current, is a current value; the protection threshold, which has a minimum final-limited output current, when comparing with the protection thresholds of the voltage value, has a stepwise increase; wherein a step number of the protection threshold of the voltage value is greater than a step number of the protection threshold of the current value. ### Claim 13 (depends on 1) The soft-start circuit for power-up according to claim 1, wherein the reference value is a voltage value, while the protection threshold is a current value or a voltage value which corresponds to the current value. ### Claim 14 (depends on 13) The soft-start circuit for power-up according to claim 13, wherein the soft-start circuit for power-up comprises a counting segmentation circuit or capacitor charge circuit which is configured to implement a slow increase of the voltage value. ### Claim 15 (depends on 14) The soft-start circuit for power-up according to claim 14, wherein the capacitor charge circuit is specifically configured to output a slowly increased voltage through charge accumulation; or to generate a clock signal by using a frequency signal, and control cyclical charge storage and transfer according to the clock signal, and increase one gradient to its output voltage for each charge transfer. ### Claim 16 (depends on 14) The soft-start circuit for power-up according to claim 14, wherein the counting segmentation circuit is specifically configured to perform a real-time count by using a frequency signal, and control its output voltage to increase one gradient and start a new round of count when each round of count reaches a target value. ### Claim 17 (depends on 13) The soft-start circuit for power-up according to claim 13, wherein the soft-start circuit for power-up comprises the soft-start circuit for power-up comprises a counting segmentation circuit which is configured to implement a slow increase of the current value; or the soft-start circuit for power-up comprises a counting segmentation circuit or capacitor charge circuit which is configured to implement a slow increase of the voltage value, and a current mirror which configured to process an output of the slow increase of the voltage value to generate the slow increase of the current value. ### Claim 18 (depends on 17) The soft-start circuit for power-up according to claim 17, wherein the capacitor charge circuit is specifically configured to output a slowly increased voltage through charge accumulation; or to generate a clock signal by using a frequency signal, and control cyclical charge storage and transfer according to the clock signal, and increase one gradient to its output voltage for each charge transfer. ### Claim 19 (depends on 17) The soft-start circuit for power-up according to claim 17, wherein the counting segmentation circuit is specifically configured to perform a real-time counting by using a frequency signal, and control its output current to increase one gradient and start a new round of count when each round of count reaches a target value.