# US 7,609,042 B2 · Controller for DC-DC converter and method for controlling DC-DC converter > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 7,609,042 B2 - Document ID: US7609042B2 - Status: Granted - Kind: B2 - Application number: 11/390,260 - Filed: 2006-03-28 - Published: 2007-03-29 - Granted: 2009-10-27 - Earliest claimed: 2005-09-29 - Assignees: Fujitsu Microelectronics Limited - Inventors: Masatoshi Kokubun; Katsuyuki Yasukouti; Takashi Matsumoto - Web page: https://patentgrep.com/patent/US7609042B2 ## CPC - H02M 3/1588: {comprising at least one synchronous rectifier element (H02M3/1582, H02M3/1584 take precedence)} - H02M 1/0045: {Converters combining the concepts of switch-mode regulation and linear regulation, e.g. linear pre-regulator to switching converter, linear and switching converter in parallel, same converter or same transistor operating either in linear or switching mode} - 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 - 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) - Y02B: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS ## Abstract A DC-DC converter that suppresses increase in area and obtains high conversion efficiency irrespective of the output current. A controller controls a first output transistor and a second output transistor in a PWM operation mode or a linear operation mode based on output voltage of the DC-DC converter. The controller operates the DC-DC converter as a switching regulator that activates and inactivates the first output transistor and the second output transistor in a complementary manner during the PWM operation mode. The controller operates the DC-DC converter as a linear regulator that inactivates the second output transistor and controls the ON-resistance value of the first output transistor to perform linear operation with the first output transistor during the linear operation mode. ## Claims ### Claim 1 A DC-DC converter for generating output voltage from input voltage, the DC-DC converter comprising: a first output transistor; a second output transistor electrically connected in series to the first output transistor; a choke coil electrically connected to a node between the first output transistor and the second output transistor with at least either one of the first output transistor and the second output transistor being operated to generate the output voltage of the DC-DC converter based on the input voltage; a smoothing capacitor, electrically connected to the choke coil, for smoothing the output voltage of the DC-DC converter; and a controller, electrically connected to the first output transistor and the second output transistor, for controlling the first output transistor and the second output transistor in a first operation mode or a second operation mode based on the output voltage of the DC-DC converter or output current, in which the output current changes in accordance with the output voltage, wherein the controller includes an error amplifier which generates a first error signal based on a differential voltage between the output voltage and a first reference voltage and a second error signal that is complementary to the first error signal, and wherein the controller activates and inactivates the first output transistor and the second output transistor in a complementary manner by a control signal in accordance with the first error signal during the first operation mode, and the controller inactivates the second output transistor and performs linear operation with the first output transistor by the second error signal during the second operation mode. ### Claim 2 (depends on 1) The DC-DC converter according to claim 1, further comprising: a mode control circuit for comparing the output voltage with a second reference voltage and generating a mode control signal, indicating the first operation mode when the output voltage is greater than the second reference voltage and indicating the second operation mode when the output voltage is less than the second reference voltage, wherein the controller controls the first output transistor and the second output transistor in the first operation mode or the second operation mode in accordance with the mode control signal. ### Claim 3 (depends on 2) The DC-DC converter according to claim 2, wherein the controller includes: the error amplifier for comparing the output voltage with the first reference voltage and generating as the first error signal and the second error signal in accordance with the comparison; a triangular wave oscillator for generating a triangular wave signal; a PWM comparator, connected to the error amplifier and the triangular wave oscillator, for comparing the first error signal and the triangular wave signal and generating a control signal in accordance with the comparison; a selection circuit, connected to the mode control circuit, the error amplifier, the PWM comparator, and the first output transistor, for providing, in accordance with the mode control signal, the first output transistor with the control signal during the first operation mode and the first output transistor with the second error signal during the second operation mode; and a signal control circuit, connected to the mode control circuit, the PWM comparator, and the second output transistor, for providing, in accordance with the mode control signal, the second output transistor with the control signal during the first operation mode and generating a signal for inactivating the second output transistor during the second operation mode. ### Claim 4 (depends on 3) The DC-DC converter according to claim 3, wherein at least either one of the triangular wave oscillator and the PWM comparator stops operating during the second operation mode in accordance with the mode control signal. ### Claim 5 A DC-DC converter for generating output voltage from input voltage, the DC-DC converter comprising: a first output transistor; a second output transistor electrically connected in series to the first output transistor; a choke coil electrically connected to a node between the first output transistor and the second output transistor with at least either one of the first output transistor and the second output transistor being operated to generate the output voltage of the DC-DC converter based on the input voltage; a smoothing capacitor, electrically connected to the choke coil, for smoothing the output voltage of the DC-DC converter; and a controller, electrically connected to the first output transistor and the second output transistor, for controlling the first output transistor and the second output transistor in a first operation mode, a second operation mode, or a third operation mode based on the output voltage of the DC-DC converter or output current, in which the output current changes in accordance with the output voltage, wherein the controller activates and inactivates the first output transistor and the second output transistor in a complementary manner during the first operation mode, the controller inactivates the second output transistor and activates and inactivates the first output transistor during the second operation mode, and the controller inactivates the second output transistor and performs linear operation with the first output transistor during the third operation mode, wherein the controller includes an error amplifier which generates a first error signal based on a differential voltage between the output voltage and a first reference voltage and a second error signal that is complementary to the first error signal, and wherein the controller activates and inactivates the first output transistor and the second output transistor in a complementary manner by a control signal in accordance with the first error signal during the first operation mode, the controller inactivates the second output transistor and activates and inactivates the first output transistor by the control signal during the second operation mode, and the controller inactivates the second output transistor and performs linear operation with the first output transistor by the second error signal during the third operation mode. ### Claim 6 (depends on 5) The DC-DC converter according to claim 5, further comprising: a mode control circuit for comparing the output voltage with a third reference voltage and a fourth reference voltage that differ from each other and generating a mode control signal indicating the first operation mode when the output voltage is greater than the third reference voltage and the fourth reference voltage, the second operation mode when the output voltage is less than the third reference voltage but greater than the fourth reference voltage, and the third operation mode when the output voltage is less than the third reference voltage and the fourth reference voltage, wherein the controller controls the first output transistor and the second output transistor in the first operation mode, the second operation mode, or the third operation mode in accordance with the mode control signal. ### Claim 7 (depends on 6) The DC-DC converter according to claim 6, wherein the controller includes: the error amplifier for comparing the output voltage with the first reference voltage and generating as the first error signal and the second error signal in accordance with the comparison; a triangular wave oscillator for generating a triangular wave signal; a PWM comparator, connected to the error amplifier and the triangular wave oscillator, for comparing the first error signal with the triangular wave signal and generating a control signal in accordance with the comparison; a selection circuit, connected to the mode control circuit, the error amplifier, the PWM comparator, and the first output transistor, for providing, in accordance with the mode control signal, the first output transistor with the control signal during the first operation mode and the second operation mode and the first output transistor with the second error signal during the third operation mode; and a signal control circuit, connected to the mode control circuit, the PWM comparator, and the second output transistor, for providing, in accordance with the mode control signal, the second output transistor with the control signal during the first operation mode and generating a signal for inactivating the second output transistor during the second operation mode and the third operation mode. ### Claim 8 (depends on 7) The DC-DC converter according to claim 7, wherein at least either one of the triangular wave oscillator and the PWM comparator stops operating during the third operation mode in accordance with the mode control signal. ### Claim 9 A controller for a DC-DC converter including a first output transistor, a second output transistor electrically connected in series to the first output transistor, a choke coil electrically connected to a node between the first output transistor and the second output transistor with at least either one of the first output transistor and the second output transistor being operated to generate output voltage of the DC-DC converter based on input voltage, and a smoothing capacitor, electrically connected to the choke coil, for smoothing the output voltage of the DC-DC converter, wherein the controller comprising: a circuit for controlling the first output transistor and the second output transistor in a first operation mode or a second operation mode based on the output voltage of the DC-DC converter or output current, in which the output current changes in accordance with the output voltage, wherein the circuit includes an error amplifier which generates a first error signal based on a differential voltage between the output voltage and a first reference voltage and a second error signal that is complementary to the first error signal, the circuit activating and inactivating the first output transistor and the second output transistor in a complementary manner by a control signal in accordance with the first error signal during the first operation mode, and inactivating the second output transistor and performing linear operation with the first output transistor by the second error signal during the second operation mode. ### Claim 10 (depends on 9) The controller according to claim 9, wherein the circuit includes: a mode control circuit for comparing the output voltage with a second reference voltage and generating a mode control signal, indicating the first operation mode when the output voltage is greater than the second reference voltage and indicating the second operation mode when the output voltage is less than the second reference voltage, wherein the controller controls the first output transistor and the second output transistor in the first operation mode or the second operation mode in accordance with the mode control signal. ### Claim 11 (depends on 10) The controller according to claim 10, wherein the circuit includes: the error amplifier for comparing the output voltage with the first reference voltage and generating the first error signal and the second error signal in accordance with the comparison; a triangular wave oscillator for generating a triangular wave signal; a PWM comparator, connected to the error amplifier and the triangular wave oscillator, for comparing the first error signal and the triangular wave signal and generating a control signal in accordance with the comparison; a selection circuit, connected to the mode control circuit, the error amplifier, the PWM comparator, and the first output transistor, for providing, in accordance with the mode control signal, the first output transistor with the control signal during the first operation mode and the first output transistor with the second error signal during the second operation mode; and a signal control circuit, connected to the mode control circuit, the PWM comparator, and the second output transistor, for providing, in accordance with the mode control signal, the second output transistor with the control signal during the first operation mode and generating a signal for inactivating the second output transistor during the second operation mode. ### Claim 12 (depends on 11) The controller according to claim 11, wherein at least either one of the triangular wave oscillator and the PWM comparator stops operating during the second operation mode in accordance with the mode control signal. ### Claim 13 A controller for a DC-DC converter including a first output transistor, a second output transistor electrically connected in series to the first output transistor, a choke coil electrically connected to a node between the first output transistor and the second output transistor with at least either one of the first output transistor and the second output transistor being operated to generate output voltage of the DC-DC converter based on input voltage, a smoothing capacitor, electrically connected to the choke coil, for smoothing the output voltage of the DC-DC converter, wherein the controller comprising: a circuit for controlling the first output transistor and the second output transistor in a first operation mode, a second operation mode, or a third operation mode based on the output voltage of the DC-DC converter or output current, in which the output current changes in accordance with the output voltage, wherein the circuit includes an error amplifier which generates a first error signal based on a differential voltage between the output voltage and a first reference voltage and a second error signal that is complementary to the first error signal, the circuit activating and inactivating the first output transistor and the second output transistor in a complementary manner by a control signal in accordance with the first error signal during the first operation mode, inactivating the second output transistor and activating and inactivating the first output transistor by the control signal during the second operation mode, and inactivating the second output transistor and performing linear operation with the first output transistor by the second error signal during the third operation mode. ### Claim 14 (depends on 13) The controller according to claim 13, wherein the circuit includes: a mode control circuit for comparing the output voltage with a third reference voltage and a fourth reference voltage that differ from each other and generating a mode control signal indicating the first operation mode when the output voltage is greater than the third reference voltage and the fourth reference voltage, the second operation mode when the output voltage is less than the third reference voltage but greater than the fourth reference voltage, and the third operation mode when the output voltage is less than the third reference voltage and the fourth reference voltage, wherein the controller controls the first output transistor and the second output transistor in the first operation mode, the second operation mode, or the third operation mode in accordance with the mode control signal. ### Claim 15 (depends on 14) The controller according to claim 14, wherein the circuit includes: the error amplifier for comparing the output voltage with the first reference voltage and generating the first error signal and the second error signal in accordance with the comparison; a triangular wave oscillator for generating a triangular wave signal; a PWM comparator, connected to the error amplifier and the triangular wave oscillator, for comparing the first error signal with the triangular wave signal and generating the control signal in accordance with the comparison; a selection circuit, connected to the mode control circuit, the error amplifier, the PWM comparator, and the first output transistor, for providing, in accordance with the mode control signal, the first output transistor with the control signal during the first operation mode and the second operation mode and the first output transistor with the second error signal during the third operation mode; and a signal control circuit, connected to the mode control circuit, the PWM comparator, and the second output transistor, for providing, in accordance with the mode control signal, the second output transistor with the control signal during the first operation mode and generating a signal for inactivating the second output transistor during the second operation mode and the third operation mode. ### Claim 16 (depends on 15) The controller according to claim 15, wherein at least either one of the triangular wave oscillator and the PWM comparator stops operating during the third operation mode in accordance with the mode control signal. ### Claim 17 A method for controlling a DC-DC converter for generating output voltage from input voltage, the DC-DC converter including a first output transistor, a second output transistor electrically connected in series to the first output transistor, a choke coil electrically connected to a node between the first output transistor and the second output transistor with at least either one of the first output transistor and the second output transistor being operated to generate the output voltage of the DC-DC converter based on the input voltage, and a smoothing capacitor, electrically connected to the choke coil, for smoothing the output voltage of the DC-DC converter, the method comprising: detecting the output voltage of the DC-DC converter or output current, in which the output current changes in accordance with the output voltage; controlling the first output transistor and the second output transistor in a first operation mode or a second operation mode based on the detected output voltage or the output current; said controlling including: activating and inactivating the first output transistor and the second output transistor in a complementary manner by a control signal in accordance with a first error signal during the first operation mode, wherein the first error signal is generated based on a differential voltage between the output voltage and a first reference voltage; and inactivating the second output transistor and performing linear operation with the first output transistor by a second error signal during the second operation mode, wherein the second error signal is generated complementary to the first error signal. ### Claim 18 (depends on 17) The method according to claim 17, further comprising: comparing the output voltage with a second reference voltage and generating a mode control signal, indicating the first operation mode when the output voltage is greater than the second reference voltage and indicating the second operation mode when the output voltage is less than the second reference voltage, wherein said controlling includes controlling the first output transistor and the second transistor in the first operation mode or the second operation mode in accordance with the mode control signal. ### Claim 19 A method for controlling a DC-DC converter for generating output voltage from input voltage, the DC-DC converter including a first output transistor, a second output transistor electrically connected in series to the first output transistor, a choke coil electrically connected to a node between the first output transistor and the second output transistor with at least either one of the first output transistor and the second output transistor being operated to generate the output voltage of the DC-DC converter based on the input voltage, a smoothing capacitor, electrically connected to the choke coil, for smoothing the output voltage of the DC-DC converter, the method comprising: detecting the output voltage of the DC-DC converter or output current, in which the output current changes in accordance with the output voltage; controlling the first output transistor and the second output transistor in a first operation mode, a second operation mode, or a third operation mode based on the detected output voltage or the output current; said controlling including: activating and inactivating the first output transistor and the second output transistor in a complementary manner by a control signal in accordance with a first error signal during the first operation mode, wherein the first error signal is generated based on a differential voltage between the output voltage and a first reference voltage; inactivating the second output transistor and activating and inactivating the first output transistor by the control signal during the second operation mode; and inactivating the second output transistor and performing linear operation with the first output transistor by a second error signal during the third operation mode, wherein second error signal is generated complementary to the first error signal. ### Claim 20 (depends on 19) The method according to claim 19, further comprising: comparing the output voltage with a third reference voltage and a fourth reference voltage that differ from each other and generating a mode control signal indicating the first operation mode when the output voltage is greater than the third reference voltage and the fourth reference voltage, the second operation mode when the output voltage is less than the third reference voltage but greater than the fourth reference voltage, and the third operation mode when the output voltage is less than the third reference voltage and the fourth reference voltage, wherein said controlling includes controlling the first output transistor and the second output transistor in the first operation mode, the second operation mode, or the third operation mode in accordance with the mode control signal.