Circuit and method for controlling DC-DC converter
AssigneeFujitsu Limited
InventorHidenobu Ito
Life of this patent
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Abstract
A control circuit for a DC-DC converter that prevents a deficiency from occurring due to sudden interruption in power supply. The control circuit activates and inactivates a main switching output transistor and a synchronous rectification output transistor to convert the input voltage to an output voltage. The output voltage is smoothed by a smoothing capacitor. When the input voltage decreases, the control circuit activates the synchronous rectification output transistor to readily discharge the smoothing capacitor via the synchronous rectification output transistor.
Claims14
A DC-DC converter comprising:
- a main switching transistor for receiving an input voltage;
- a synchronous rectification transistor connected in series to the main switching transistor;
- a choke coil connected to a node between the main switching transistor and the synchronous rectification transistor, with output voltage of the DC-DC converter generated at an output node of the DC-DC converter based on the input voltage by activating the main switching transistor and the synchronous rectification transistor in a complementary manner;
- a smoothing capacitor having a first terminal connected to the choke coil and a second terminal connected to a predetermined voltage, for smoothing the output voltage;
- and
- a control circuit, connected to the main switching transistor and the synchronous rectification transistor, for inactivating the main switching transistor and activating the synchronous rectification transistor when the input voltage decreases below a threshold.
A control circuit for a DC-DC converter including a main switching transistor for receiving an input voltage, a synchronous rectification transistor connected in series to the main switching transistor, a choke coil connected to a node between the main switching transistor and the synchronous rectification transistor, and a smoothing capacitor having a first terminal connected to the choke coil and a second terminal connected to a predetermined voltage,
- wherein the control circuit generates output voltage of the DC-DC converter at an output node of the control circuit based on the input voltage by activating the main switching transistor and the synchronous rectification transistor in a complementary manner, and wherein the control circuit inactivates the main switching transistor and activates the synchronous rectification transistor when the input voltage decreases below a threshold.
A method for controlling a DC-DC converter including a main switching transistor for receiving an input voltage, a synchronous rectification transistor connected in series to the main switching transistor, a choke coil connected to a node between the main switching transistor and the synchronous rectification transistor, and a smoothing capacitor connected to the choke coil, the method comprising:
- generating output voltage of the DC-DC converter at an output node of the DC-DC converter based on the input voltage by activating the main switching transistor and the synchronous rectification transistor in a complementary manner;
- and
- inactivating the main switching transistor and activating the synchronous rectification transistor when the input voltage decreases below a threshold.
Dependencies are inferred from the claim text.