DC/DC converter
AssigneeFujitsu Limited
InventorsMasami Itoyama, Shigeru Honda, Masaharu Kagawa
Life of this patent
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Abstract
A DC/DC converter includes a control unit for outputting a control signal on the basis of a voltage difference between a DC output voltage and a reference voltage; a switching element which is connected to a line of the DC input voltage, and which becomes ON-state or OFF-state in accordance with the control signal; and a minimum ON-state duration setting unit, e.g., a monostable multivibrator, which defines the minimum ON-state duration of the switching element, when a necessary output electric power is low. Preferably, the converter includes a charge-pumping circuit having two diodes and two capacitors, so as to obtain from one capacitor a driving voltage source for driving an N-channel type field-effect transistor as the switching element.
Claims18
A DC/DC converter that converts a DC input voltage to a DC output voltage which is supplied to an electric load, the DC/DC converter comprising:
- a control unit producing a control signal on the basis of a voltage difference between said DC output voltage and a predetermined reference voltage, the control signal being a pulse width modulated control signal with a constant switching frequency;
- a switching element connected in series with a line for supplying said DC input voltage, and adapted to become ON-state or OFF-state in accordance with the pulse width modulation and constant switching frequency of said control signal, so as to obtain said DC output voltage having an output voltage level sufficient for said electric load;
- and
- a minimum ON-state duration setting unit defining a predetermined minimum value of an ON-state duration for which said switching element remains in ON-state and, when said DC output voltage level sufficient for said electric load is low, said minimum ON-state duration setting unit adjusts the control signal produced by the control unit to fix said ON-state duration to a value which corresponds to said predetermined minimum value defined by said minimum ON-state duration setting unit, to thereby control the ON-state and OFF-state of said switching element on the basis of the fixed ON-state duration.
A DC/DC converter that converts a DC input voltage to a DC output voltage and supplies the DC output voltage to an electric load, the DC/DC converter comprising:
- a control unit receiving the DC output voltage and a reference voltage, determining a voltage difference between the DC output voltage and the reference voltage and producing a control signal corresponding to the voltage difference, the control signal being a pulse width modulated control signal with a constant switching frequency;
- a switching element connected to the DC input voltage and selectively switchable to an ON state and an OFF state in accordance with the pulse width modulation and constant switching frequency of the control signal produced by the control unit, the duration in which the switching element is in the ON state being the ON state duration, the switching element being selectively switchable to determine an output voltage level of the DC output voltage to be sufficient for the electric load;
- and
- a minimum ON state duration setting unit determining a minimum value of the ON state duration and, when said DC output voltage level sufficient for said electric load is relatively low, the minimum ON-state duration setting unit adjusts the control signal produced by the control unit to set the ON state duration of the switching element to a value corresponding to the minimum value determined by the minimum 0N state duration setting unit.
A DC/DC converter that converts a DC input voltage to a DC output voltage and supplies the DC output voltage to a load, the DC/DC converter comprising:
- a switching element connected to the DC input voltage and selectively switchable to an ON state and an OFF state, the duration in which the switching element is in the ON state being an ON state duration of the switching element, the switching element being selectively switchable to determine an output voltage level of the DC output voltage to be sufficient for the load;
- a control unit receiving the DC output voltage and a reference voltage, determining a voltage difference between the DC output voltage and the reference voltage and producing a control signal corresponding to the voltage difference, the control signal being a pulse width modulated control signal with a constant switching frequency;
- a minimum ON state duration setting unit determining a minimum value of the ON state duration, wherein
- when the DC output voltage level sufficient for the load is relatively high, the ON state and OFF state of the switching element is controlled in accordance with the pulse width modulation and constant switching frequency of the control signal produced by the control unit, and
- when the DC output voltage level sufficient for the electric load is relatively low, the ON state and OFF state of the switching element is controlled in accordance with the control signal produced by the control unit, where the minimum ON-state duration setting unit adjusts the control signal to set the ON state duration of the switching element to a value corresponding to the minimum value determined by the minimum ON state duration setting unit.
A DC/DC converter that converts a DC input voltage to a DC output voltage and supplies the DC output voltage to a load, the DC/DC converter using both a pulse width modulation control technique and a constant ON-time control technique and comprising:
- a switching element connected to the DC input voltage and selectively switchable to an ON state and an OFF state, the duration in which the switching element is in the ON state being an ON state duration of the switching element, the switching element being selectively switchable to determine an output voltage level of the DC output voltage to be sufficient for the load;
- and
- a mechanism for controlling the switching of the switching element according to the pulse width modulation control technique when the load is relatively high, and for controlling the ON state duration of the switching element according to the constant ON-time control technique when the load is relatively low.
Dependencies are inferred from the claim text.