Switching power source circuit

• US 20050094420A1
• Filed: 10/26/2004
• Published: 05/05/2005
• Est. Priority Date: 04/26/2002
• Status: Active Grant

• Current Assignee: FDK Corporation (Fujitsu Limited)
• Original Assignee: FDK Corporation (Fujitsu Limited)
• Inventors: Suzuki, Tetsuya, Nakao, Fumiaki, Yamashita, Yasuo, Takehara, Kazuo
• Granted Patent: US 7,072,191 B2
• Time in Patent Office: Days
• US Class Current: 363/21.12
• CPC Class Codes: H02M 1/0032 Control circuits allowing low power mode operation, e.g. in standby mode
• CPC Class Codes: H02M 3/156 with automatic control of output voltage or current, e.g. switching regulators
• CPC Class Codes: H02M 3/33507 with automatic control of the output voltage or current, e.g. flyback converters H02M3/33561, H02M3/33569 take precedence
• CPC Class Codes: 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

Abstract

A switching power supply circuit, which can respond to a rapid and large change in a load quickly and stably and ensure a power supply output having a predetermined voltage, is provided. In the power supply circuit which supplies an input current to a load while switching the input current periodically and controls an output voltage Vo supplied to the load to a predetermined target value by controlling an ON/OFF time ratio (t1/t2) of the switching variably, a control of the ON/OFF time ratio is performed for every one current supply cycle T independently.

Claims

1. A switching power supply circuit which supplies an input current to a load while switching the input current periodically and controls an output voltage supplied to the load to a predetermined target value by controlling an ON/OFF time ratio of the switching,

the switching power supply circuit comprising:

a circuit performing a control of the ON/OFF time ratio for every one current supply cycle independently.

2. The switching power supply circuit according to claim 1, wherein the control of the ON/OFF time ratio is performed based on a control error immediately before each ON period starts.

3. The switching power supply circuit according to claim 1, wherein a control error detected for an OFF period of the switching is integrated, and an ON period after an OFF period is variably set based on an integration result.

4. The switching power supply circuit according to claim 1, comprising a single pulse with-variable-width generator generating a pulse signal for every current supply cycle and variably sets a pulse width of the generated pulse signal by control error information, in order to set an ON period of the switching variably.

5. The switching power supply circuit according to claim 3, wherein the integration is carried out during a period when a control value exceeds the target value, and a time when an integration value reaches a predetermined level is determined as an end timing of an ON period of the switching, whereby the ON period of the switching is variably set in accordance with a control error.

6. The switching power supply circuit according to claim 1, comprising a single pulse generating circuit generating a pulse signal having a constant pulse width by being triggered every time an output voltage as a control value falls below a predetermined reference voltage,

wherein a start timing of an ON period of the switching is controlled by the pulse signal generated by the single pulse generating circuit.

7. The switching power supply circuit according to claim 1, the switching power supply circuit switching the input current flowing through a primary coil of a transformer, and rectifying and smoothing a switching output current appearing at a secondary coil of the transformer by the switching of the input current, thus supplying the rectified and smoothened switching output current to the load.

8. The switching power supply circuit according to claim 7, wherein the transformer is a high frequency transformer.

9. The switching power supply circuit according to claim 1, the switching power supply circuit accumulating the input current supplied at the time of an ON time of the switching in a coil, and rectifying an inertia current of the coil flowing at the time of an OFF time of the switching to charge the rectified inertial current in a capacitor, thus taking out an output voltage from the capacitor.

10. The switching power supply circuit according to claim 9, wherein an ON period of the switching is variably set based on a control error detected for an OFF period of the switching immediately before the ON period thereof and at the time when the output voltage falls below a predetermined reference voltage.

11. The switching power supply circuit according to claim 1, wherein the switching is performed with use of a MOS transistor.

12. The switching power supply circuit according to claim 1, wherein the switching is performed with use of a bipolar transistor.

13. The switching power supply circuit according to claim 1, wherein a part or entire of a control circuit variably setting the ON/OFF time ratio of the switching is integrally formed on a single semiconductor substrate together with active elements performing the switching.

14. A semiconductor circuit device constituting a principal part of a switching power supply circuit comprising a circuit which supplies an input current to a load while switching the input current periodically, and controls an output voltage supplied to the load to a predetermined target value by variably controlling an ON/OFF time ratio of switching, thus performing a control of the ON/OFF time ratio for every one current supply cycle independently, wherein a switching element for switching the input current periodically and at least a part of a control circuit for controlling the ON/OFF time ratio of the switching element for every current supply cycle independently are integrally formed on a single semiconductor substrate.

15. The semiconductor circuit device according to claim 14, wherein a power MOS transistor is formed as the switching element.

16. The semiconductor circuit device according to claim 14, wherein a power bipolar transistor is formed as the switching element.

17. A switching power supply circuit, comprising:

a switching element for switching an input current periodically;

a driving circuit for ON/OFF driving the switching element; and

a circuit for comparing an output voltage supplied to a load with a predetermined target value, and for independently controlling an ON/OFF time ratio of the driving circuit for every one current supply cycle based on a comparison result.