Apparatus and method for digital control of a power converter current
AssigneeMotorola, Inc.
InventorJohn W. Oglesbee
Life of this patent
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Abstract
A digital control circuit is used for controlling the load current of a power converter circuit (102), and comprises a reference circuit (302), analog comparator circuit (304), control logic circuit (306), and a counter circuit (308). The control logic circuit controls the operation of a power switch (110), and uses counters (314, 316) in conjunction with the analog comparator circuit and reference circuit, to determine when to open and close the power switch. The load current is allowed to vary between a first and second preselected load current levels.
Claims20
A control circuit for digitally controlling a load current level of a power converter circuit, the power converter circuit having a power switch and a means for providing a current sense signal indicative of the load current, the power switch having an open state and a closed state, the control circuit comprising:
- a reference circuit for providing a first reference voltage level corresponding to a first preselected load current level, and for providing a second reference voltage level corresponding to a second preselected load current level, the reference circuit having a digital input for receiving a digital word;
- an analog comparator circuit for comparing the first reference voltage and the second reference voltage with the current sense signal and providing a first digital signal when the load current level is above the first preselected load current level, and a second digital signal when the load current level is below the second preselected load current level;
- a control logic circuit, responsive to the first and second digital signals, for controlling the power switch according to a mode, the mode being selectable to one of a plurality of modes;
- and
- a counter circuit comprising a first counter and a second counter, the first counter and the second counter each operably coupled to the control logic circuit, and each being reversible up/down counters, the counter circuit further comprising a clock signal generator for providing a clock signal to the first counter and the second counter.
A method of controlling a load current of a power converter circuit,
- a) providing a digital word to a reference circuit, the digital word having a value corresponding to a first preselected load current level;
- b) closing a power switch of the power converter circuit at a time t1, allowing current to flow through the power switch;
- c) counting up at a first clock rate, performed by a first counter and beginning at the time t1, the counting beginning at a first counter initial value;
- d) sensing the load current reaching the first preselected load current level at a time t2;
- e) opening the power switch of the power converter such that no current flows through the power switch at the time t2;
- f) counting up at the first clock rate, performed by a second counter and beginning at the time t2, the counting beginning at a second counter initial value;
- g) sensing the load current reaching a second preselected load current level at a time t3, the second preselected load current level lower than the first preselected load current level;
- h) counting down at the first clock rate, performed by the second counter and beginning at the time t3, the second counter reaching the second initial value at a time t4;
- and
- i) counting down, performed by the first counter and beginning at the time t4.
Dependencies are inferred from the claim text.