Power supply unit and portable apparatus using the same

• US 7,397,151 B2
• Filed: 12/07/2004
• Issued: 07/08/2008
• Est. Priority Date: 12/10/2003
• Status: Active Grant

• Current Assignee: ROHM Co., Ltd.
• Original Assignee: ROHM Co., Ltd.
• Inventors: Ishino, Tsutomu
• Primary Examiner(s): Sherry; Michael J
• Assistant Examiner(s): CAVALLARI, DANIEL J
• Application Number:
  US11/005,953
• Publication Number:
  US 20050189931A1
• Time in Patent Office: 1,309 Days
• Field of Search: 307/150, 323/268, 323/225
• US Class Current: 307/150
• CPC Class Codes: 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
• CPC Class Codes: H02M 3/1584 with a plurality of power processing stages connected in parallel

Abstract

A power supply unit comprises a series regulator and a switching DC-DC converter controlled by a PWM signal and connected in parallel with the series regulator, which are switchably enabled by a mode instruction signal depending on the magnitude of a load current. In switching the series regulator and the DC-DC converter, they are simultaneously enabled for a predetermined overlapping time. Further, in changing the operating condition of the DC-DC converter, the width of the PWM signal is shortened to extend the dead time of the DC-DC converter by a predetermined period, thereby suppressing free oscillations and accompanying overshoots that could take place in the power supply unit during switching.

Claims

1. A power supply unit, comprising

a series regulator for converting an input voltage into a predetermined output voltage in a continuously controlled manner and outputting said output voltage from the output end thereof;

and

a switching DC-DC converter for converting said input voltage into a predetermined output voltage, said switching DC-DC converter connected at the output end thereof in parallel with the output end of said series regulator, wherein

said power supply unit has a mode in which only said series regulator is operated (regulator mode) and a mode in which only said switching DC-DC converter is operated (converter mode), switching from one mode to another in response to a mode instruction signal, wherein

said power supply unit has a predetermined overlapping period in which said series regulator and switching DC-DC converter are simultaneously operated for a predetermined period of time following a switching from one mode to another, wherein

said switching DC-DC converter includes an error amplification circuit for controlling said output voltage in accordance with the difference between a reference voltage and a voltage representing said output voltage, said error amplification circuit having an AC and a DC feedback circuits that are switchable from said AC feedback circuit to said DC feedback circuit during said overlapping period.

2. The power supply unit according to claim 1, wherein said switching DC-DC converter includes:

a first and a second switches connected in series between power sources, said first and second switches adapted to turn on alternately but turn off simultaneously for a dead time;

a smoothing coil and a smoothing capacitor for smoothing the switching voltage appearing at the node of said first and second switches to generate said output voltage; and

a pulse width control circuit for generating, and providing said first and second switches with, a switching control signal based on a PWM signal that is modulated so as to enable generation of said predetermined output voltage; and

wherein

said pulse width control circuit is adapted to shorten the width of said PWM signal based on said mode instruction signal to extend said dead time by a third or a fourth predetermined period when said switching DC-DC converter is enabled from its disabled state or disabled from its enabled state.

3. The power supply unit according to claim 1, wherein said switching DC-DC converter includes:

a first and a second switches connected in series between power sources, said first and second switches adapted to turn on alternately but turn off simultaneously for a dead time;

a smoothing coil and a smoothing capacitor for smoothing the switching voltage appearing at the node of said first and second switches to generate said output voltage; and

a pulse width control circuit for generating, and providing said first and second switches with, a switching control signal based on a PWM signal that is modulated so as to enable generation of said predetermined output voltage; and

wherein

said pulse width control circuit is adapted to shorten said dead time in multiple stages from a predetermined long time to a predetermined short time by regulating the width of said PWM signal when said switching DC-DC converter is enabled from its disabled state, and/or adapted to extend said dead time in multiple stages from a predetermined short time to a

predetermined long time by regulating the width of said PWM signal when said switching DC-DC converter is disabled from its enabled state.

12. A portable apparatus, comprising:

a battery for generating a source voltage;

a power supply unit supplied with said source voltage as an input voltage thereto as defined in claim 1; and

control means for controlling said power supply unit.

4. A power supply unit, comprising:

a series regulator that is enabled by a first enable signal to convert an input voltage into a predetermined output voltage in a continuously controlled manner and outputting said output voltage from the output end thereof;

a switching DC-DC converter that is enabled by a second enable signal to convert said input voltage into a predetermined output voltage through switching of said input voltage, said DC-DC converter connected at the output end thereof in parallel with the output end of said series regulator; and

a switching circuit for selectively switching said first and second enable signals based on a mode instruction signal and for outputting the selected enable signal such that, when switching said first enable signal to said second enable signal, said first and second enable signals overlap each other for a first predetermined period of time, and when switching said second enable signal to a first enable signal, overlap each other for a second predetermined period, wherein

said switching DC-DC converter includes an error amplification circuit for controlling said output voltage in accordance with the difference between a reference voltage and a voltage representing said output voltage, said error amplification circuit having an AC and a DC feedback circuits that are switchable from said AC feedback circuit to said DC feedback circuit during said overlapping period.

5. The power supply unit according to claim 4, wherein said switching DC-DC converter includes:

a first and a second switches connected in series between power sources, said first and second switches adapted to turn on alternately but turn off simultaneously for a dead time;

a smoothing coil and a smoothing capacitor for smoothing the switching voltage appearing at the node of said first and second switches to generate said output voltage; and

a pulse width control circuit for generating, and providing said first and second switches with, a switching control signal based on a PWM signal that is modulated so as to enable generation of said predetermined output voltage, and wherein

said pulse width control circuit is adapted to shorten the width of said PWM signal based on said mode instruction signal to extend said dead time by a third or a fourth predetermined period, when switching DC-DC converter is enabled from its disabled state or disabled from its enabled state.

6. The power supply unit according to claim 4, wherein said switching DC-DC converter includes:

a first and a second switches connected in series between power sources, said first and second switches adapted to turn on alternately but turn off simultaneously for a dead time;

a smoothing coil and a smoothing capacitor for smoothing the switching voltage appearing at the node of said first and second switches to generate said output voltage; and

a pulse width control circuit for generating, and providing said first and second switches with, a switching control signal based on a PWM signal that is modulated so as to enable generation of said predetermined output voltage, and wherein

said pulse width control circuit is adapted to shorten said dead time in multiple stages from a predetermined long time to a predetermined short time by regulating the width of said PWM signal when said switching DC-DC converter is enabled from its disabled state, and/or adapted to extend said dead time in multiple stages from a predetermined short time to a predetermined long time by regulating the width of said PWM signal when said switching DC-DC converter is disabled from its enabled state.

7. A power supply unit, comprising:

a series regulator that is enabled by a first enable signal to convert an input voltage into a predetermined output voltage in a continuously controlled manner and outputting said output voltage from the output end thereof;

a switching DC-DC converter that is enabled by a second enable signal to convert said input voltage into a predetermined output voltage through switching of said input voltage, said DC-DC converter connected at the output end thereof in parallel with the output end of said series regulator; and

a switching circuit for selectively switching said first and second enable signals based on a mode instruction signal and for outputting the selected enable signal such that, when switching said first enable signal to said second enable signal, said first and second enable signals overlap each other for a first predetermined period of time, and when switching said second enable signal to a first enable signal, overlap each other for a second predetermined period, wherein

said first enable signal is formed by a first logic circuit that receives said mode instruction signal and a first counter output issued from a first counter counting clock pulses of a clock supplied from said switching DC-DC converter; and

said second enable signal is formed by a second logic circuit that receives said mode instruction signal and a second counter output issued from a second counter counting clock pulses of said clock.

8. A power supply unit comprising:

a series regulator that is enabled by a first enable signal to convert an input voltage into a predetermined output voltage in a continuously controlled manner and outputting said output voltage from the output end thereof;

a switching DC-DC converter that is enabled by a second enable signal to convert said input voltage into a predetermined output voltage through switching of said input voltage, said DC-DC converter connected at the output end thereof in parallel with the output end of said series regulator; and

a switching circuit for selectively switching said first and second enable signal based on a mode instruction signal, wherein

said switching DC-DC converter includes;

a first and a second switches connected between power sources, said first and second switches adapted to turn on alternately but turn off simultaneously for a dead time;

a smoothing coil and a smoothing capacitor for smoothing the switching voltage appearing at the node of said first and second switches to generate said output voltage; and

a pulse width control circuit for generating, and providing said first and second switches with, a switching control signal based on a PWM signal that is modulated so as to enable generation of said predetermined output voltage, and wherein

said pulse width control circuit is adapted to shorten the width of said PWM signal based on said mode instruction signal to make longer said dead time by a third or a fourth predetermined period when switching DC-DC converter is enabled from its disabled state or disabled from its enabled state, wherein

said first enable signal is formed by a first logic circuit that receives said mode instruction signal and a first counter output issued from a first counter counting clock pulses of a clock supplied from said switching DC-DC converter; and

said second enable signal is formed by a second logic circuit that receives said mode instruction signal and a second counter output issued from a second counter counting clock pulses of said clock.

9. The power supply unit according to claim 8, wherein said pulse width control circuit includes:

an error amplifier for comparing a feedback voltage representing said output voltage with a reference voltage to generate an error signal in accord with the difference between said feedback voltage and reference voltage;

an oscillator for generating a triangular wave signal;

a PWM comparator for comparing said error signal and triangular wave signal to generate a PWM signal;

a predriver for amplifying said PWM signal by cascaded inverters and providing the amplified signal to said first and second switches; and

delay time control means provided in one of said cascaded inverters and operable for said third and fourth predetermined periods, thereby extending said dead time.

10. A power supply unit, comprising:

a series regulator that is enabled by a first enable signal to convert an input voltage into a predetermined output voltage in a continuously controlled manner and outputting said output voltage from the output end thereof;

a switching DC-DC converter that is enabled by a second enable signal to convert said input voltage into a predetermined output voltage through switching of said input voltage, said DC-DC converter connected at the output end thereof in parallel with the output end of said series regulator; and

a switching circuit for selectively switching said first and second enable signals in response to a mode instruction signal;

wherein

said switching DC-DC converter includes;

a first and a second switches connected between power sources, said first and second switches adapted to turn on alternately but turn off simultaneously for a dead time;

a smoothing coil and a smoothing capacitor for smoothing the voltage appearing at the node of said first and second switches to generate said output voltage; and

a pulse width control circuit for generating, and providing said first and second switches with, a switching control signal based on a PWM signal that is modulated so as to enable generation of said predetermined output voltage; and

wherein

said pulse width control circuit is adapted to shorten said dead time in multiple stages from a predetermined long time to a predetermined short time by regulating the width of said PWM signal when said switching DC-DC converter is enabled from its disabled state, and/or adapted to extend said dead time in multiple stages from a predetermined short time to a predetermined long time by regulating the width of said PWM signal when said switching DC-DC converter is disabled from its enabled state, wherein

said first enable signal is formed by a first logic circuit that receives said mode instruction signal and a first counter output issued from a first counter counting clock pulses of a clock supplied from said switching DC-DC converter; and

said second enable signal is formed by a second logic circuit that receives said mode instruction signal and a second counter output issued from a second counter counting clock pulses of said clock.

11. The power supply unit according to claim 10, wherein said pulse width control circuit includes:

an error amplifier for comparing a feedback voltage representing said output voltage with a reference voltage to generate an error signal in accord with the difference between said feedback voltage and reference voltage;

an oscillator for generating a triangular wave signal;

a PWM comparator for comparing said error signal and triangular wave signal to generate a PWM signal;

a predriver for amplifying said PWM signal by cascaded inverters and providing the amplified signal to said first and second switches; and

delay time control means provided in one of said cascaded inverters, for changing said dead time by controlling the delay time of said delay time control means in multiple stages.