Method and circuit for reducing losses in DC-DC converters
First Claim
1. A circuit comprising:
- a first switch having first and second transistors being parallel-connected between first and second terminals, the second transistor being larger in size than the first transistor; and
a controller block coupled to the first switch such that;
if a first current to be transferred through the first switch is greater than a predetermined amount the controller block turns on the first switch by;
(i) turning on the first transistor so that a voltage level at the second terminal starts moving towards a predetermined voltage level at the first terminal, and (ii) turning on the second transistor after the voltage level at the second terminal reaches a voltage level substantially equal to the predetermined voltage level, and if the first current is less than the predetermined amount, the controller block turns on the first switch by turning on the first transistor and maintaining the second transistor in the off state so that the first current is transferred only through the first transistor.
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Accused Products
Abstract
In accordance with the present invention, a switching converter includes two transistors Q1 and Q2 parallel-connected between two terminals. Transistor Q1 is optimized to reduce the dynamic loss and transistor Q2 is optimized to reduce the conduction loss. Q1 and Q2 are configured and operated such that the dynamic loss of the converter is dictated substantially by Q1 and the conduction loss of the converter is dictated substantially by Q2. Thus, the tradeoff between these two types of losses present in conventional techniques is eliminated, allowing the dynamic and conduction losses to be independently reduced. Further, the particular configuration and manner of operation of Q1 and Q2 enable reduction of the gate capacitance switching loss when operating under low load current conditions.
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Citations
58 Claims
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1. A circuit comprising:
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a first switch having first and second transistors being parallel-connected between first and second terminals, the second transistor being larger in size than the first transistor; and
a controller block coupled to the first switch such that;
if a first current to be transferred through the first switch is greater than a predetermined amount the controller block turns on the first switch by;
(i) turning on the first transistor so that a voltage level at the second terminal starts moving towards a predetermined voltage level at the first terminal, and (ii) turning on the second transistor after the voltage level at the second terminal reaches a voltage level substantially equal to the predetermined voltage level, andif the first current is less than the predetermined amount, the controller block turns on the first switch by turning on the first transistor and maintaining the second transistor in the off state so that the first current is transferred only through the first transistor. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 22)
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17. A converter circuit comprising:
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a first switch having first and second transistors parallel-connected between first and second terminals, the first transistor being smaller in size than the second transistor; and
a controller block coupled to maintain the first switch in an off-state during a first cycle and to maintain the first switch in an on-state during a second cycle, wherein during a transition from the first cycle to the second cycle;
if a first current to be transferred through the first switch is greater than a predetermined amount the controller block maintains the second transistor in the off state but turns the first transistor on so that a voltage level at the second terminal starts moving towards a predetermined voltage level at the first terminal, and when the voltage level at the second terminal reaches a voltage level substantially equal to the predetermined voltage level the controller block turns on the second transistor, and if the first current is less than the predetermined amount, the controller block turns on the first transistor, and keeps the second transistor off for the duration of the second cycle. - View Dependent Claims (18, 19, 20, 21, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32)
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33. A method of operating a converter circuit having a first switch which includes first and second transistors parallel-connected between first and second terminals, the first transistor being smaller in size than the second transistor, the method comprising:
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turning off the first switch in a first cycle;
turning on the first switch in a second cycle;
during a transition from the first cycle to the second cycle, turning on the first transistor so that a voltage level at the second terminal starts moving towards a predetermined voltage level at the first terminal;
if a first current to be transferred through the first switch is greater than a predetermined amount, turning on the second transistor after the voltage level at the second terminal reaches a voltage level substantially equal to the predetermined voltage level; and
if the first current is less than the predetermined amount, maintaining the second transistor off for the duration of the second cycle. - View Dependent Claims (34, 35, 36, 37, 38, 39, 40)
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41. A circuit comprising:
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a first switch having first and second transistors parallel-connected between first and second terminals, the first terminal being coupled to an input source and the second terminal being coupled to an output load, the second transistor being larger in size than the first transistor;
a second switch having third and fourth transistors parallel-connected between the output load and a reference source; and
a controller block coupled to control the first and second switches such that when the first switch is on the second switch is off and vice versa, wherein the controller block turns on the first switch by;
(i) turning on the first transistor so that a voltage level at the second terminal starts moving towards a predetermined voltage level at the first terminal, and (ii) turning on the second transistor after the voltage level at the second terminal reaches a voltage level substantially equal to the predetermined voltage level. - View Dependent Claims (42, 43, 44, 45, 46)
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47. A converter circuit comprising:
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a first switch having first and second transistors parallel-connected between first and second terminals, the first terminal being coupled to an input source and the second terminal being coupled to an output load, the first transistor being smaller in size than the second transistor;
a second switch having third and fourth transistors parallel-connected between the output load and a reference source; and
a controller block coupled to maintain the first switch in an off-state and the second switch in an on-state during a first cycle and to maintain the first switch in an on-state and the second switch in an off-state during a second cycle, wherein during a transition from the first cycle to the second cycle, the controller block maintains the second transistor in the off state but turns the first transistor on so that a voltage level at the second terminal starts moving towards a predetermined voltage level at the first terminal, and when the voltage level at the second terminal reaches a voltage level substantially equal to the predetermined voltage level the controller block turns on the second transistor. - View Dependent Claims (48, 49, 50)
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51. A method of operating a converter circuit having first and second serially-connected switches, the first switch including first and second transistors parallel-connected between first and second terminals, the first transistor being smaller in size than the second transistor, the method comprising:
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in a first cycle, maintaining the first switch in an off-state and the second switch in an on-state;
in a second cycle, maintaining the first switch in an on-state and the second switch in an off-state;
during a transition from the first cycle to the second cycle;
turning on the first transistor so that a voltage level at the second terminal starts moving towards a predetermined voltage level at the first terminal; and
turning on the second transistor after the voltage level at the second terminal reaches a voltage level substantially equal to the predetermined voltage level. - View Dependent Claims (52, 53, 54, 55)
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56. A circuit comprising:
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a controller block; and
a first switch having first and second parallel-connected transistors coupled to supply a load current to a load under the control of the controller block, the second transistor having a lower on-resistance than the first transistor, wherein;
if the load current is greater than a predetermined amount the controller block turns on the first switch by sequentially turning on the first and second transistors so that the load current is initially supplied to the load only through the first transistor and after a predetermined time period a substantial amount of the load current is supplied to the load through the second transistor, and if the load current is less than the predetermined amount the controller block turns on the first switch by turning on the first transistor and maintaining the second transistor in the off state so that the load current is supplied to the load only through the first transistor. - View Dependent Claims (57, 58)
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Specification