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US 9,337,811 B1Granted
Asymmetric hysteretic controllers
AssigneeMicrochip Technology Incorporated
InventorBryan Kris
Life of this patent
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Abstract
An asymmetric hysteretic controller comprises an analog comparator coupled with a fast slew rate DAC, or a digital comparator coupled with an ADC plus some digital control logic. The comparator, analog or digital, operates as a sequential windowed comparator having high and low limits. The sense parameter is compared to a high or a low limit and when the sense parameter reaches the selected high or low limit, the controlled device is turned off or on, respectively. When the hysteretic controller state comparison reversal occurs: (a) the comparator output may be blanked by the control logic, (b) the comparator polarity may be reversed by the control logic, (c) the control logic may command the other process limit to be selected for comparison with the sense parameter, and (d) then the comparator output may be re-enabled.
Claims25
A method for hysteretic control of a pulse width modulation (PWM) generator, said method comprising the steps of:
- monitoring an output of a PWM generator;
- determining when the output of the PWM generator changes from a low to a high level;
- starting a blanking timer when the output of the PWM generator changes from the low to the high level;
- selecting a high limit value from a high limit register as an input to a digital-to-analog converter (DAC);
- determining when the blanking timer has timed out;
- enabling an output of a comparator when the blanking timer has timed out for indicating a comparison of an output of the DAC representing the high limit value with a process feedback signal;
- determining when the process feedback signal is greater than the DAC output;
- signaling the PWM generator to change its output to the low level when the process feedback signal is greater than the DAC output;
- determining when the output of the PWM generator changes from the high to the low level;
- starting the blanking timer when the output of the PWM generator changes from the high to the low level;
- reversing the output of the comparator;
- selecting a low limit value from a low limit register as the input to the DAC;
- determining when the blanking timer has timed out;
- enabling the output of the comparator when the blanking timer has timed out for indicating a comparison of the output of the DAC representing the low limit value with the process feedback signal;
- determining when the process feedback signal is less than the DAC output;
- signaling the PWM generator to change its output to the high level when the process feedback signal is less than the DAC output;
- and
- returning to the step of monitoring the output of the PWM generator.
15 more elements
A method for hysteretic control of a process, said method comprising the steps of:
- monitoring a process state and a process feedback signal;
- determining whether the process state is on or off;
- wherein if the process state is on further comprising the steps of
- starting a blanking time,
- selecting a high limit value as an input to a digital-to-analog converter (DAC),
- comparing the process feedback signal with an output of the DAC representing the high limit value with an analog comparator after the blanking time ends,
- determining when the process feedback signal is greater than the DAC output with the analog comparator, and
- turning the process state off when the process feedback signal is greater than the DAC output,
- wherein if the process state is off further comprising the steps of
- starting the blank time,
- selecting a low limit value as the input to the digital-to-analog converter (DAC),
- comparing the process feedback signal with the output of the DAC representing the low limit value with the analog comparator after the blanking time ends,
- determining when the process feedback signal is less than the DAC output with the analog comparator,
- turning the process state on when the process feedback signal is less than the DAC output;
- and
- returning to the step of determining whether the process state is on or off.
13 more elements
A method for hysteretic control of a process, said method comprising the steps of:
- monitoring a process state;
- converting a process feedback signal to a digital representation thereof;
- determining whether the process state is on or off;
- wherein if the process state is on further comprising the steps of
- starting a blanking time,
- selecting a high limit digital value as an input to a digital comparator,
- comparing the digital representation of the process feedback signal to the high limit digital value with a digital comparator after the blanking time ends,
- determining when the digital representation of the process feedback signal is greater than the high limit digital value with the digital comparator, and
- turning the process state off when the digital representation of the process feedback signal is greater than the high limit digital value,
- wherein if the process state is off further comprising the steps of
- starting the blanking time,
- selecting a low limit digital value as the input to the digital comparator,
- comparing the digital representation of the process feedback signal with the low limit digital value after the blanking time ends,
- determining when the digital representation of the process feedback signal is less than the low limit digital value,
- turning the digital representation of the process state on when the process feedback signal is less than the low limit digital value;
- and
- returning to the step of determining whether the process state is on or off.
14 more elements
An apparatus for hysteretic control of a pulse width modulation (PWM) generator, comprising:
- a digital-to-analog converter (DAC);
- a digital multiplexer having a first input coupled to a low limit register, a second input coupled to a high limit register, an output coupled to an input of the DAC, and a control input coupled to an output of the PWM generator;
- a comparator having a first input coupled to an output of the DAC and a second input coupled to a sense parameter from an apparatus controlled by the PWM generator;
- a polarity reversing circuit coupled to an output of the comparator;
- pulse stretcher and filter logic having an input coupled to the polarity reversing circuit and an output coupled to a control input of the PWM generator;
- a blanking gate coupled between an output of the polarity reversing circuit and an input of the pulse stretcher and filter logic;
- a blanking timer;
- and
- an edge detector coupled to the output of the PWM generator and an input of the blanking timer, wherein the edge detector generates a pulse when the output of the PWM generator changes from a low level to a high level, or from the high level to the low level, whereby the blanking timer starts a blanking time;
- wherein the comparator compares the sense parameter to the DAC output representative of a high limit value stored in the high limit register and coupled to the DAC input when the output of the PWM generator is high, and the DAC output representative of a low limit value stored in the low limit register and coupled to the DAC input when the output of the PWM generator is low;
- whereby when the sense parameter is greater than the high limit value a signal from the pulse stretcher and filter logic causes the PWM generator output to change from high to low, and when the sense parameter is less than the low limit value the signal from the pulse stretcher and filter logic causes the PWM generator output to change from low to high.
8 more elements
An apparatus for hysteretic control of a process, comprising:
- a digital-to-analog converter (DAC);
- a digital multiplexer having a first input coupled to a low limit register, a second input coupled to a high limit register, an output coupled to an input of the DAC, and a control input coupled to an output state of the process;
- a comparator having a first input coupled to an output of the DAC and a second input coupled to a sense parameter from an apparatus controlled by the process;
- a polarity reversing circuit coupled to an output of the comparator;
- pulse stretcher and filter logic having an input coupled to the polarity reversing circuit and an output adapted to control the process;
- a blanking gate coupled between an output of the polarity reversing circuit and an input of the pulse stretcher and filter logic;
- a blanking timer;
- and
- an edge detector coupled to and monitoring the process output and an input of the blanking timer, wherein the edge detector generates a pulse when the process output state changes from a low level to a high level, or from the high level to the low level, whereby the blanking timer starts a blanking time;
- wherein the comparator compares the sense parameter to the DAC output representative of a high limit value stored in the high limit register and coupled to the DAC input when the output state of the process is high, and the DAC output representative of a low limit value stored in the low limit register and coupled to the DAC input when the output state of the process is low;
- whereby when the sense parameter is greater than the high limit value a signal from the pulse stretcher and filter logic causes the process state to change from high to low, and when the sense parameter is less than the low limit value the signal from the pulse stretcher and filter logic causes the process state to change from low to high.
8 more elements
An apparatus for hysteretic control of a process, comprising:
- an analog-to-digital converter (ADC) having an input coupled to a sense parameter of the process;
- a digital comparator having a first input coupled to an output of the ADC;
- a digital multiplexer having a first input coupled to a low limit register, a second input coupled to a high limit register, an output coupled to a second input of the digital comparator, and a control input coupled to and monitoring the output state of the process;
- a polarity reversing circuit coupled to an output of the digital comparator;
- pulse stretcher and filter logic having an input coupled to the polarity reversing circuit and an output adapted to control the process;
- a blanking gate coupled between an output of the polarity reversing circuit and an input of the pulse stretcher and filter logic;
- a blanking timer;
- and
- an edge detector coupled to and monitoring the process output and an input of the blanking timer, wherein the edge detector generates a pulse when the process output state changes from a low level to a high level, or from the high level to the low level, whereby the blanking timer starts a blanking time;
- wherein the digital comparator compares the ADC output representative of the sense parameter to a high limit value stored in the high limit register and coupled to the ADC input when the output state of the process is high, and a low limit value stored in the low limit register and coupled to the ADC input when the output state of the process is low;
- whereby when the sense parameter is greater than the high limit value a signal from the pulse stretcher and filter logic causes the process state to change from high to low, and when the sense parameter is less than the low limit value the signal from the pulse stretcher and filter logic causes the process state to change from low to high.
8 more elements
Dependencies are inferred from the claim text.