Gate Driver for Depletion-Mode Transistors
First Claim
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1. A deadtime circuit comprising:
- an upper delay block coupled to a PWM signal and a tap of the upper delay block coupled to an upper gate driver;
a lower leading edge (LE) delay block having a plurality of LE delay taps and coupled to an inverted PWM signal line;
a lower LE multiplexer coupled to the plurality of LE delay taps of the lower LE delay block and configured to select one of the plurality of the LE delay taps responsive to a lower LE address for output to a lower LE delay signal line;
a lower trailing edge (TE) delay block having a plurality of delay taps and coupled to the inverted PWM signal line;
a lower TE multiplexer coupled to the plurality of delay taps of the lower TE delay block and configured to select one of the plurality of the TE delay taps responsive to a lower TE address for output to a lower TE delay signal line;
a latch, inputs of the latch coupled to the lower LE delay signal line and the lower TE delay signal line, an output coupled to a lower gate driver; and
a deadtime state machine configured to;
output a lower LE address to the lower LE multiplexer for selecting a LE delay tap,output a lower TE address to the lower TE multiplexer for selecting a LE delay tap,receive an upper gate drive sense signal from output of the upper gate driver,receive a lower gate drive sense signal from output of the lower gate driver,calculate a LE deadtime based on the upper and lower gate drive sense signals, andincrease the LE address if the LE deadtime is greater than a target deadtime, or store the LE address in non-volatile memory (NVM) if the LE deadtime is not greater than the target LE deadtime.
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Abstract
The present disclosure presents a circuit, method, and system for dynamically determining optimal deadtime values in a DC-DC converter power stage while operating the circuit under controlled conditions during a test/trim routine. The determined optimal deadtime values are stored in non-volatile memory. The optimal deadtime values are used as fixed settings during normal PWM operation. On start-up, the optimal, fixed deadtime values are loaded into the deadtime circuits of the driver and used during normal PWM operation of the DC-DC converter power stage circuit.
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Citations
20 Claims
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1. A deadtime circuit comprising:
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an upper delay block coupled to a PWM signal and a tap of the upper delay block coupled to an upper gate driver; a lower leading edge (LE) delay block having a plurality of LE delay taps and coupled to an inverted PWM signal line; a lower LE multiplexer coupled to the plurality of LE delay taps of the lower LE delay block and configured to select one of the plurality of the LE delay taps responsive to a lower LE address for output to a lower LE delay signal line; a lower trailing edge (TE) delay block having a plurality of delay taps and coupled to the inverted PWM signal line; a lower TE multiplexer coupled to the plurality of delay taps of the lower TE delay block and configured to select one of the plurality of the TE delay taps responsive to a lower TE address for output to a lower TE delay signal line; a latch, inputs of the latch coupled to the lower LE delay signal line and the lower TE delay signal line, an output coupled to a lower gate driver; and a deadtime state machine configured to; output a lower LE address to the lower LE multiplexer for selecting a LE delay tap, output a lower TE address to the lower TE multiplexer for selecting a LE delay tap, receive an upper gate drive sense signal from output of the upper gate driver, receive a lower gate drive sense signal from output of the lower gate driver, calculate a LE deadtime based on the upper and lower gate drive sense signals, and increase the LE address if the LE deadtime is greater than a target deadtime, or store the LE address in non-volatile memory (NVM) if the LE deadtime is not greater than the target LE deadtime. - View Dependent Claims (2, 3, 4, 5)
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6. A deadtime adjustment system comprising:
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an upper gate driver coupled to a delayed Pulse Width Modulated (PWM) signal and an upper gate of a DC-DC converter power stage circuit; a first adjustable delay circuit coupled to the PWM signal and configured to output a first delayed PWM signal responsive to a first delay address; a second adjustable delay circuit coupled to the PWM signal and configured to output a second delayed PWM signal responsive to a second delay address; a latch configured to receive the first and second delayed PWM signals and output a lower PWM signal via a lower gate driver to a lower gate of the DC-DC converter power stage circuit; and a deadtime state machine including circuits and logic programmed to; operate in a step mode comprising; applying the first address from a working register to the first adjustable delay circuit, receiving an upper gate drive sense signal derived from the upper gate driver and a lower gate drive sense signal derived from the lower gate driver, measuring a first deadtime using the upper and lower gate drive sense signals, and if the first deadtime is greater than a target first deadtime, increment or decrement the first address in the working register to decrease the first deadtime, and repeat the step mode using the decreased first deadtime, or if the first deadtime is not greater than the target first edge deadtime, store the first address in non-volatile memory (NVM), and exit the step mode; and operate in a test mode comprising; receiving values for working registers including an initial first address, an initial second address, a target first edge deadtime, and a target second edge deadtime, and outputting a fixed first address from NVM to the first addressable delay circuit. - View Dependent Claims (7, 8, 9, 10, 11)
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12. A method for adjusting deadtime in a DC-DC converter power stage circuit, the method comprising:
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placing the DC-DC converter power stage circuit in test mode; loading a delay address to a delay circuit that produces a deadtime output from the deadtime circuit greater than a target deadtime; placing the DC-DC converter power stage circuit in step mode; stepping through delay addresses to progressively reduce the deadtime output of the deadtime circuit until the deadtime output of the deadtime circuit is less than the target deadtime; and placing the DC-DC converter power stage circuit in test mode; storing a deadtime value corresponding to the currently loaded delay address in non-volatile memory of the DC-DC converter power stage circuit. - View Dependent Claims (13, 14, 15, 16)
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17. A system for adjusting deadtime of a DC-DC converter power stage circuit, the method comprising:
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a delay circuit coupled to a PWM signal and a lower gate of the DC-DC converter power stage circuit; means for loading an initial delay address to the delay circuit that corresponds to a maximum deadtime output from the delay circuit while operating in test mode; means for progressively decreasing deadtime output from the delay circuit by stepping through delay addresses loaded to the delay circuit while operating in a step mode; means for determining for each progressive loaded deadtime address if the deadtime output of the delay circuit is less than a target deadtime; non-volatile memory (NVM) for storing a fixed deadtime value corresponding to the delay address loaded for the deadtime output determined to be less than the target deadtime; and means for loading the fixed deadtime value from NVM to the delay circuit for operation in PWM mode. - View Dependent Claims (18, 18, 20)
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Specification