CN1868109A - Total feed forward switching power supply control - Google Patents

Abstract

A power supply comprising a switching converter capable of being controlled by a control signal to provide a desired output from a DC input voltage, an analog to digital converter receiving as analog inputs a gate drive voltage of at least one switch of the switching converter, a temperature related measurement of the switching converter, the DC input voltage and an output current of the switching converter and converting the analog inputs to digital input signals, a digital processor receiving the digital input signals and generating the control signal to drive at least one switch of the switching converter to drive the output of the switching converter to the desired output and a memory storing data relating the digital input signals to the desired output of the switching converter and providing to the digital processor a memory output signal to enable the processor to generate the control signal to drive the at least one switch to provide the desired output from the switching converter.

Description

Fully Feedforward Switching Power Supply Control

Cross References to Related Applications

This application is based on U.S. Provisional Application No. 60/515,325 (IR-2610 Prov II), filed October 29, 2003, entitled "Complete Feedforward Switching Power Supply Control" and filed October 17, 2003, Priority to and benefit of US Provisional Application No. 60/512,349 (IR-2610Prov), entitled "Complete Feedforward Switching Power Supply Control," which is hereby incorporated by reference in its entirety.

Background of the invention

Traditional switching power supplies use feedback that is compared to an internal reference to keep the output within a specified range. In the case of DC, this is ideal since the output is actually controlled to a desired accuracy. But in the case of AC/transients, this is less than ideal due to the finite time required to respond to "input" changes.

In this context, "input" means any one of any factor that can affect the output voltage of a power supply, including:

Input voltage;

power switch drive voltage;

Output current;

power supply temperature;

power frequency.

The input voltage and output current can change very rapidly. Conventional output voltage feedback cannot detect the aforementioned changes in input voltage and output current until the output voltage has been changed. Also, due to hardware limitations and stability specifications, the control system cannot respond immediately to changes in the output voltage.

Ultimately, there is a tradeoff between fast response and absolute stability. Usually, this is sufficient, but in some cases feed-forward elements must be incorporated to obtain the desired performance. An example of this is current mode control with inherent input voltage feed-forward. This is especially useful in applications such as notebook computers that can quickly switch from one input source to another.

Another situation where feedback is not optimal is during high output load transients, such as those encountered in high performance microprocessor power supplies. No satisfactory feed-forward method has been developed to deal with this problem so far, so practical solutions focus on minimizing the time for the power supply to respond to changes in output voltage.

Contents of the invention

If the transfer function of a power supply with respect to its few inputs can be accurately mapped, then the duty cycle of the power supply can be set based on the values of these inputs and precise control of the output voltage can be obtained.

The output of the power supply must be mapped and "memorized" over the entire range of input conditions. This mapping may include memory of discrete operating points, or may depend on a mathematical transfer function of the individual inputs, or a combination of both.

In theory, it is not even necessary to monitor the output voltage, however, there are some potential benefits in doing so, such as fault detection.

While the full feed-forward approach of the present invention is entirely possible for analog circuits, it is quite impractical due to the complexity and cost required. It is therefore an object of the present invention to provide a digital implementation of fully feed-forward control, but the concepts are applicable to analogue circuits.

The objects of the present invention are achieved by providing a power supply comprising: a switching converter capable of being controlled by a control signal to provide a desired output depending on a DC input voltage; an analog-to-digital converter receiving as an analog input the switching converter gate drive voltage of at least one switch of the switching converter, temperature dependent measurements of the switching converter, DC input voltage and output current of the switching converter, and converting said analog input into a digital input signal; a digital processor, receiving the digital input signal, and generating a control signal to drive at least one switch of the switching converter to drive the output of the switching converter to a desired output; and a memory storing digital data relating the digital input signal to the desired output of the switching converter and storing the memory output signal is provided to a digital processor to enable said processor to generate a control signal to drive at least one switch so that a desired output is provided by the switching converter.

The objects of the present invention are also achieved by providing a power supply comprising: a switching converter controllable by a control signal to provide a desired output based on a DC input voltage; a processor receiving at least one input signal, said input The signal includes one or more of the following: a gate drive voltage of at least one switch of the switching converter, a temperature-related measurement of the switching converter, a DC input voltage, and an output current of the switching converter, and the processor generates control signals to drive the switching converter at least one switch of the switch converter to drive the output of the switching converter to a desired output; and an input/output correlator to correlate at least one input signal with the desired output of the switching converter and provide the output signal to the processor so that the processing The converter is capable of generating a control signal to drive at least one switch such that a desired output is provided by the switching converter.

The objects of the present invention are further achieved by a method of controlling the output of a switching converter capable of being controlled by a control signal to provide a desired output in dependence on a DC input voltage, the method comprising: receiving as input a switching converter gate drive voltage of at least one switch of the switching converter, temperature dependent measurements of the switching converter, DC input voltage and output current of the switching converter, and converting an analog input to a digital input signal; performing matching of said input to a switching converter's desired outputting the associated associated operations; and providing information resulting from the associated operations to the processor to enable the processor to generate a control signal to drive at least one switch of the switching converter such that a desired output is provided by the switching converter.

Other features and advantageous effects of the present invention will become apparent from the following detailed description of the present invention with reference to the accompanying drawings.

Brief description of the drawings

The invention will be described in more detail below with reference to the accompanying drawings, in which:

Figure 1 is a block diagram of the circuit of the present invention.

Detailed ways

The benefits of the present technology are obtained through digital control in the form of microcontrollers, microprocessors, DSPs (digital signal processors), logic state machines, or other digital instruments (processors), combined with composite signal circuits for acquiring inputs. actual realization.

Referring now to FIG. 1 , the power converter 10 can be any switching power supply circuit configuration, such as buck, boost, buck/boost, flyback, and the like. The buck converter structure shown includes high-side (HS) and low-side (LS) switches, output inductor L and output capacitor C. The DC bus is represented by a voltage Vin. In theory, this control method is valid for any circuit configuration, but it is most effective when applied to a synchronous rectification configuration (where the output is not a function of the stored inductor value at light loads). The gate drive voltage sensor (GDS) is set to detect the gate drive voltage of the switch. A temperature sensor (TS) can be provided for one or both switches, although for the buck converter shown a single sensor TS on the low side device LS is sufficient to obtain this detection.

A/D converter 20 is provided for all voltage or current inputs. These inputs include input voltage, gate drive voltage, output current, and supply temperature, as shown. The output current can be sensed by resistor Rsense, FET switch R _DSON , inductor impedance, current transformer or any suitable device. Since the operating frequency is controlled by the processor 30, the operating frequency is given and does not need to be measured. A correlator (eg, memory 40 ) coupled to processor 30 stores the power supply output response to the various inputs either directly through a multidimensional look-up table or through a multi-input mathematical function that can model the response. Depending on the accuracy required, this can be a memory storing typical series performance or individual power supply performance during startup calibration, or a memory storing actual historical data of a single power supply during normal operation. It is also desirable, but not necessary, to measure the output voltage to aid in fault detection. This is not shown in the figure. Likewise, output voltage sensing can be used to continuously update the power supply's multi-input transfer function or multidimensional look-up table to compensate for aging effects, or to allow the power supply to "teach itself" or adapt to the appropriate PWM duty cycle or for each An appropriate transfer function for the input. The PWM processor 30 is intelligent enough to process the input based on the stored responses and select the appropriate pulse width modulation (PWM) duty cycle for the switches HS and LS.

It is necessary for the designer to characterize the transfer function of the power supply as a function of its various inputs. This can be done empirically or theoretically, depending on the accuracy required for the assessment. A combination of the above may be desirable since statistically valid sampling of performance may not be practical to achieve during design.

Depending on how the power supply will be used, design-time characterization may be all that is necessary for the power supply's lifetime. If higher accuracy is required, further calibration is required. If run-time calibration is used, design-time accuracy only needs to ensure expected operation at initial power-up.

Runtime calibration may not be necessary for all applications. When performing runtime calibration, it can be done in several ways, for example:

Use external instrumentation, information, and communications to characterize and "program" the power supply at initial power-up while applying a series of input forcing functions;

Characterize itself using the instrumentation and information of the power source while applying a series of input forcing functions;

Use internal instrumentation and information to combine either of the above with ongoing periodic recalibration.

In any case, external means are required to provide the varying forcing function.

The present invention has several beneficial effects, including:

Virtual momentary load and line transient response. The time required to respond is roughly equal to the time to obtain changed input. Unlike traditional feedback control schemes, the duty cycle changes to the new final value as soon as a new input is processed.

Absolute stability. For traditional feedback schemes, proper phase margin needs to be maintained over the available feedback frequency range to avoid reconstruction and thus instability. This requires trimming of the frequency response of the feedback, often slowing down the response of the power supply, as described above. Since there is no "feedback" in conventional detection, conventional stability is a non-concern. New incoming information can be processed without delay.

Simplification of digital power control schemes. Since traditional feedback is not necessary, no computationally intensive digital filtering schemes need to be implemented. This reduces the processing power/speed required for digital control.

While the invention has been described in conjunction with specific embodiments thereof, it is evident to those skilled in the art that many other variations and modifications and uses will be apparent. Accordingly, the invention should not be limited by the specific disclosure herein, but should be limited only by the appended claims.

Claims (35)

1. A power supply, comprising: a switching converter capable of being controlled by a control signal to provide a desired output based on the DC input voltage; an analog-to-digital converter receiving as analog inputs a gate drive voltage of at least one switch of the switching converter, a temperature-dependent measurement of the switching converter, a DC input voltage and an output current of the switching converter, and converting the The analog input is converted into a digital input signal; a digital processor receiving the digital input signal and generating the control signal to drive at least one switch of the switching converter to drive the output of the switching converter to the desired output; and a memory storing digital data relating the digital input signal to a desired output of the switching converter and providing a memory output signal to the digital processor to enable the processor to generate the control signal to drive The at least one switch thereby provides the desired output by the switching converter. 2. The power supply of claim 1, wherein the digital data stored in the memory comprises a multi-dimensional look-up table relating the digital input signal to the memory output signal provided to the The processor is configured to enable the processor to generate the control signal to drive the at least one switch of the switching converter such that the desired output is provided by the switching converter. 3. The power supply of claim 1 , wherein the digital data stored in the memory includes a mathematical function that models the desired output of the switching converter in terms of the digital input signal, the mathematical function providing the memory output signal to the processor in response to the digital input signal, thereby causing the processor to generate the control signal to drive at least one switch of the switching converter from being converted by the switch tor to provide the desired output. 4. The power supply of claim 1, wherein stored in the memory are: digital data comprising a multi-dimensional look-up table relating said digital input signal to said memory output signal to be provided to said processor; and digital data comprising a mathematical function modeling said desired output of said switching converter as a function of said digital input signal, said mathematical function providing said memory output signal to said processing in response to said digital input signal device; Wherein, the processor generates the control signal to drive the at least one switch of the switching converter such that the switching converter is controlled based on one or both of the multidimensional look-up table and the mathematical function Provide the desired output. 5. The power supply of claim 1, wherein the control signal is a PWM signal. 6. The power supply of claim 1, wherein the digital processor periodically receives the digital input signal and periodically provides the control signal to the switching converter. 7. The power supply of claim 1, further comprising a sensor for sensing each of said analog inputs coupled to said switching converter. 8. The power supply of claim 7, further comprising a sensor for detecting the output voltage of the converter. 9. The power supply of claim 8, further comprising an analog to digital converter for converting said output voltage into a digital input signal provided to said processor. 10. A power supply as claimed in claim 9, wherein the output voltage is used to provide fault detection or to compensate for aging effects of the power supply. 11. The power supply of claim 10, wherein the output voltage is used to update the digital data in the memory to compensate for aging effects of the power supply, or to enable the power supply to self-learn properly duty cycle of the PWM or an appropriate transfer function for various inputs. 12. The power supply of claim 1, wherein the processor comprises one of a microcontroller, a microprocessor, or a logic state machine. 13. A power supply comprising: a switching converter capable of being controlled by a control signal to provide a desired output based on the DC input voltage; A processor receiving at least one input signal comprising one or more of the following: a gate drive voltage for at least one switch of the switching converter; temperature dependent measurements of said switching converter; said DC input voltage; and the output current of the switching converter; the processor generates the control signal to drive at least one switch of the switching converter to drive an output of the switching converter to the desired output; and an input/output correlator that correlates the at least one input signal with a desired output of the switching converter and provides an output signal to the processor to enable the processor to generate the control signal to drive the said at least one switch so that said desired output is provided by said switching converter. 14. The power supply of claim 13 , wherein the input/output correlator includes a memory, and the data stored in the memory includes a multidimensional look-up table that correlates the at least one input signal with a memory output signal, the The memory output signal is provided to the processor to enable the processor to generate the control signal to drive the at least one switch of the switching converter such that the switching converter provides the desired output. 15. The power supply of claim 13 , wherein the input/output correlator includes memory, and the data stored in the memory includes modeling the desired output of the switching converter in terms of the at least one input signal A mathematical function for providing a memory output signal to the processor in response to the at least one input signal, thereby causing the processor to generate the control signal to drive at least one switch of the switching converter , so that the desired output is provided by the switching converter. 16. The power supply of claim 13, wherein stored in the input/output correlator is: data comprising a multidimensional look-up table correlating said input signal with said correlator output signal to be provided to said processor; and data comprising a mathematical function modeling the desired output of the switching converter as a function of the input signal, the mathematical function providing the output signal to the processor in response to the input signal; Wherein, the processor generates the control signal to drive at least one switch of the switching converter, so that the switching converter provides the Describe the desired output. 17. The power supply of claim 13, wherein the control signal is a PWM signal. 18. The power supply of claim 13, wherein the processor periodically receives the at least one input signal and periodically provides the control signal to the switching converter. 19. The power supply of claim 13, further comprising a sensor for detecting said at least one input coupled to said switching converter. 20. The power supply of claim 19, further comprising a sensor for detecting the output voltage of the converter. 21. The power supply of claim 20, wherein the output voltage is used to provide fault protection or to compensate for aging effects of the power supply. 22. The power supply of claim 21, wherein the output voltage is used to update the data in the input/output correlator to compensate for aging effects of the power supply, or to enable the power supply to Self-learns the appropriate PWM duty cycle or appropriate transfer function for various inputs. 23. The power supply of claim 13, wherein the processor comprises one of a microcontroller, a microprocessor, a DSP, or a logic state machine. 24. A method of controlling an output of a switching converter, the switching converter being controllable by a control signal to provide a desired output in dependence on a DC input voltage, the method comprising: receiving as input a gate drive voltage of at least one switch of the switching converter, a temperature-dependent measurement of the switching converter, a DC input voltage and an output current of the switching converter, and converting the analog input into digital input signal; performing a correlation operation that correlates the input to a desired output of the switching converter; and Information resulting from the correlation operation is provided to a processor to enable the processor to generate a control signal to drive at least one switch of the switching converter such that the desired output is provided by the switching converter. 25. The method of claim 24, further comprising receiving an input as an analog signal, converting the input to a digital input signal, and providing the digital input signal to the processor. 26. The method of claim 25, wherein said step of correlating said input to a desired output of said switching converter comprises storing digital data comprising a a multidimensional look-up table associated with a memory output signal to be provided to the processor to enable the processor to generate the control signal to drive the at least one switch of the switching converter to be converted by the switch tor to provide the desired output. 27. The method of claim 25, wherein said step of correlating said input to said switching converter's desired output comprises storing said desired output of said switching converter according to said input signal model a mathematical function that provides an output signal to the processor in response to the input signal, thereby causing the processor to generate the control signal to drive the at least one switch of the switching converter , so that the desired output is provided by the switching converter. 28. The method of claim 25, wherein said step of correlating said input to a desired output of said switching converter comprises: storing digital data comprising a multi-dimensional look-up table in memory relating said digital input signal to a memory output signal to be provided to said processor; and storing a mathematical function modeling the desired output of the switching converter as a function of the input signal, the mathematical function providing an output signal to the processor in response to the input signal; wherein the processor generates the control signal to drive the at least one switch of the switching converter such that the switching converter is controlled based on one or both of the mathematical look-up table and the mathematical function Provide the desired output. 29. The method of claim 24, wherein the control signal is a PWM signal. 30. The method of claim 24, further comprising periodically receiving the input signal and periodically providing the control signal to the switching converter. 31. The method of claim 24, further comprising sensing each of said inputs with a sensor coupled to said switching converter. 32. The method of claim 31, further comprising detecting the output voltage of the converter. 33. The method of claim 32, further comprising converting the output voltage to a digital signal provided to the processor. 34. The method of claim 33, further comprising using the output voltage to provide fault protection or to compensate for aging effects of the power supply. 35. The method of claim 34, further comprising using the output voltage in the step of correlating the input to the desired output of the switching converter to perform an aging effect on the power supply compensation, or enable the power supply to self-learn the proper pulse width modulation duty cycle or the proper transfer function for various inputs.