DC-DC converter with communication across an isolation pathway

A power converter comprises a direct current (DC)-DC converter configured to receive an input voltage in a primary domain, a transformer coupled to and driven by the DC-DC converter and supplying an output voltage in a secondary domain, and a transmission path configured to pass a digital feedback signal through an isolation barrier from the secondary domain to the primary domain.

BACKGROUND

Various communications, medical, computing, industrial, and other systems implement isolation barriers to electrically isolate sections of electronic circuitry. An isolator is a device that can transfer a signal between sections of electronic circuitry while maintaining electrical isolation between the sections.

A typical conventional design attains isolation, for example, by connecting to a communication channel through a transformer. The transformer provides isolation both for surge and galvanic isolation. Power can be transmitted on the line through the transformer.

Some circuits and systems have input and output circuitry powered by power supplies that are mutually isolated, for example power supplies with different ground potentials or systems with an isolated DC-DC converter with transformers to derive power for one side of an isolation barrier from power supplied to the other side of the barrier.

SUMMARY

According to an embodiment of a power system, a power converter comprises a direct current (DC)-DC converter configured to receive an input voltage in a primary domain, a transformer coupled to and driven by the DC-DC converter and supplying an output voltage in a secondary domain, and a transmission path configured to pass a digital feedback signal through an isolation barrier from the secondary domain to the primary domain.

DETAILED DESCRIPTION

Referring toFIG. 1, a schematic block diagram illustrates an embodiment of a power converter100with signal isolation. The power converter100comprises a direct current (DC)-DC converter126configured to receive an input voltage in a primary domain136and a transformer134coupled to and driven by the DC-DC converter126that supplies an output voltage in a secondary domain138. The power converter100further comprises a transmission path104that passes a digital feedback signal108through an isolation barrier102from the secondary domain138to the primary domain136.

In some embodiments, the power converter100can comprise a pulse wide modulator (PWM) direct current (DC)-DC converter126that drives a full-bridge transformer134. An oscillator128coupled to the PWM DC-DC converter126generates an oscillator time base for synchronously driving the PWM DC-DC converter126.

A rectifier140can be coupled to the transformer134and a filter144can be coupled to the rectifier to supply a filtered output voltage.

In some implementations, the PWM DC-DC converter126can comprise multiple internal drivers130and multiple external power field effect transistors (FETs)132that drive the transformer134. The rectifier140can be implemented as multiple diodes142or transmission gates coupled to the transformer134. The filter144can be implemented as an inductor L1and a capacitor C1coupled to the rectifier140to supply a filtered output voltage.

In some embodiments, the power converter100can further comprise the rectifier140coupled to the transformer134and a resistor divider146coupled to the rectifier140that produces a feedback voltage VFBin the secondary domain138. A signal conditioner106is coupled to the resistor divider146and receives the feedback voltage VFB, preconditioning the feedback voltage VFBaccording to a modulation function. For example, the signal conditioner106can be a pulse width modulator (PWM) or delta modulator (DM). One or more capacitors122can be\coupled to the signal conditioner106to function as an isolated transmission path104. A signal recovery circuit150can be coupled to the isolated transmission path104in the primary domain136to receive the preconditioned feedback voltage and demodulate the preconditioned feedback voltage, thereby forming a feedback signal for usage in a control loop116.

In the illustrative embodiment, the transmission path104is configured as a differential transmission path with two capacitors122. In various embodiments, the transmission path104can be single-ended or differential.

As depicted inFIG. 1, the transmission path can be considered to comprise a modulator106that receives and modulates a signal such as the feedback voltage VFB, a diode bridge rectifier112, and a full differential alternating current (AC) coupling104that can transmit the modulated signal from the modulator106to the diode bridge rectifier112with capacitive-coupled signal isolation. A D flip-flop152coupled to the diode bridge rectifier112is configured to recover the modulated signal.

In some embodiments, a digital filter118coupled to the rectifier112recovers the modulated signal. A lowpass filter120coupled to the digital filter118restores an analog signal.

FIG. 1shows a general transmission pathway104over an isolation barrier102. The transmission pathway104can be either an analog or digital pathway. A signal VFBis applied to a signal conditioner106and then to a transmission link104including the isolation barrier102. The signal is then passed through a signal recovery block112.

The illustrative circuit100comprises a pulse width (PWM) or delta (DM) modulator106, full differential alternating current (AC) coupling104, and a diode bridge rectifier112, for example implemented as digital flip-flop lowpass filter120. In an analog path, direct current (DC) feedback voltage is modulated and passed through the capacitor122by oversampling and demodulating up to higher frequency, then low pass filtered to restore analog signal.

In an example embodiment, the transmission pathway104can be a feedback pathway, for example a digitized form of feedback that forms a control loop116. A feedback signal is passed through a modulation function, then the transmission pathway104for example passed through one or two capacitors, and through a demodulation of the modulation function. In various implementations, the modulation can be pulse width modulation, delta modulation, frequency modulation, phase modulation, or the like. In a general functional description, an analog input signal can be input to the transmission pathway, digitized, and then passed as a digitized signal through a control loop.

FIG. 1illustrates a power distribution system100that includes a signal isolator. The DC-DC converter126in the power distribution system100has a time base supplied by an oscillator128and includes internal drivers130and power field effect transistors (FETs)132that are shown external to DC-DC converter126but can be internal to the converter in some configurations. As shown, the DC-DC converter126can be a pulse width modulator (PWM) converter. The drivers130and power FETs132drive a transformer134and pass power from the primary side136to the secondary side138through the transformer134to a rectifier140that is depicted as diodes142. In other configurations, the rectifier140can take other forms such as transmission gates or other devices for which a signal is used to drive the gates or devices on a communication pathway that is omitted inFIG. 1.

Following the diodes142is a filter144with an inductor L1and a capacitor C1that passes an output voltage VO. The output voltage VOis applied to a resistor divider146that forms a feedback voltage VFBand is returned on a feedback pathway148by application to a modulator106, for example a pulse width modulator or a delta modulator. The feedback pathway148passes the feedback signal from the secondary side138to the primary side136across the isolation barrier102, illustratively by differentially coupling the signal, although a single-ended embodiment can also be formed. Information, including feedback information, is passed from the modulator106over the differential capacitors122to the primary side136where the modulated signal is demodulated. The demodulation has a low pass filtering functionality and is illustratively implemented in a recovery circuit150that includes diodes in a diode bridge rectifier312, a resistor R3, and a D flip-flop152. The recovered feedback signal can be passed through a lowpass filter120which can be a first-order, second-order, or other suitable lowpass filter. The recovered feedback signal VFB′following the lowpass filter120is applied to an error amplifier (EA)154and passed back to the DC-DC converter126. The feedback voltage VFBis thus returned to the primary side136as recovered feedback signal VFB′and can be passed to the DC-DC converter126either through the error amplifier (EA)154or directly in some implementations, depending on whether the error amplifier154is placed on the primary side136or the secondary side138, or whether functionality is supplied by other circuits in the feedback pathway148. For example, the error function can be supplied via the illustrative digital (D) flip-flop, which is a positive-edge flip-flop that can perform the error function.

In an example operation of error amplifier functionality, the feedback voltage from 0 to a selected value has a linear transformation so that PWM modulator106has a 0 to 100% duty cycle. The frequency does not change as the signal traverses the whole feedback path148and information is contained in the duty cycle. For example, if full scale on the secondary side is 1 volt, then 100% would be 1 volt, 50% would be half volt, and 0% would be zero volts. The transformation and recovery reduces the same voltage at feedback voltage VFBwith some scale factor K that is arbitrarily chosen. For the selected gain or scale factor, the PWM circuitry uses the factor to set a servo value for the output signal to a predetermined fixed value.

FIG. 2is a schematic block diagram illustrating an embodiment of a signal isolator200that enables a general analog transmission isolation method over an isolation barrier202. Referring toFIG. 2in combination withFIG. 1, in some embodiments, the power converter100can include a signal isolator160,200that further comprises a signal conditioner206coupled to a transmission path204in the secondary domain138that receives and preconditions a signal208according to a modulation function and passes the resulting preconditioned signal via the transmission path204. A signal recovery circuit212coupled to the transmission path204in the primary domain136receives the preconditioned signal210via the transmission path204and demodulates the preconditioned signal210, thereby forming a feedback signal VFB′for usage in a control loop116.

The signal isolator160,200can be configured to modulate a direct current (DC) feedback voltage VFBand pass the DC feedback voltage VFBthrough one or more capacitors by oversampling and demodulating to a higher frequency.

The signal conditioner206receives an input signal Vm that is passed through the transmission path204and isolation barrier to the signal recovery circuit212that generates the output signal Vout. In various embodiments, the signal conditioner206can be implemented as a pulse width modulator, a delta modulator, a frequency modulator, a phase modulator, an analog-to-digital converter (ADC), a predriver that performs preconditioning, a simple flip-flop, digital-to-analog converter (DAC), or other device. The signal recovery circuit212acquires an analog input signal, digitize the signal, and pass the digitized signal through a control system116.

The illustrative signal isolator200depicts a general isolation scheme that be used for any kind of transmission, either analog or digital transmission, and forms an isolation barrier by operation of three functional blocks that perform signal conditioning, a transmission path and isolation barrier, and recovery.

The transmission path204can be considered to be a digital transmission path that communicates inherently digital signals. In another perspective, the transmission path204can pass a digital signal in which information is conveyed in an analog format with pulses passed through the path204, for example through a capacitor, in characteristics of the signal such as frequency, phase, modulation index, or other attribute.

In a signal isolator implementation that inserts a sampling function in the pathway, an analog signal is converted to a digital form in which each sample has an associated digital value due to quantization of the original signal through the sampling function. The signal recovery circuit212can perform the sampling function to attain the digital signal by pulse modulation or other suitable type of general sampling conversion.

Other implementations can include a true analog signal, for example a direct current (DC) feedback voltage that is modulated and passes information through the transmission path204, such as a capacitor, by oversampling and modulating up to a higher frequency, then using low pass filtering to recover the analog signal.

Referring toFIGS. 3A,3B,3C, and3D, a set of combined block and circuit diagrams depict several circuits and associated methods for transmitting an analog signal across an isolation boundary. Capacitive isolation generally can be used for passing alternative current (AC) or pulsed signals.

FIG. 3Ais a schematic block diagram illustrating an embodiment of a signal isolator300A that enables a general analog transmission isolation method over an isolation barrier302A. Referring toFIG. 3Ain combination withFIG. 1, in some embodiments, the power converter100can include a signal isolator160,300A that further comprises a signal conditioner configured as an analog to digital converter306A coupled to the transmission path304A in the secondary domain136that receives an input signal and preconditions the input signal according to an analog to digital conversion modulation function for passing a preconditioned signal via the transmission path304A. The transmission path304A can be configured as one or more capacitors CISO. A signal recovery circuit configured as a digital to analog converter312A or flip-flop coupled to the transmission path304A in the primary domain136receives the preconditioned signal via the transmission path304A and demodulates the preconditioned signal, forming a feedback signal VFB′for usage in the control loop116.

FIG. 3Ashows an embodiment with a generalized structure and form for transmitting an analog signal. An isolator circuit300A includes an analog to digital converter (ADC)306A that receives an input voltage VIand converts the voltage signal to digital form for passage over an isolation barrier302A to a digital to analog converter (DAC)312A that converts the signal back to analog form as output voltage VO. Two different symbols are depicted for ground indicating that the ground potential for the primary side and secondary side of the isolation barrier can be different. The analog to digital conversion can take many forms such as a pulse code modulation or other digitization. Conversion can be made from voltage to frequency, voltage to phase, voltage to pulse width, or other suitable parameters.

FIG. 3Bis a schematic block diagram illustrating an embodiment of a signal isolator300B enabling a general analog transmission isolation method over an isolation barrier302B. Referring toFIG. 3Bin combination withFIG. 1, in some embodiments, the power converter100can include a signal isolator160,300B that further comprises a signal conditioner configured as a pulse width modulator306B that can precondition a signal and a differential transmission isolation barrier302B coupled to the pulse width modulator306B that passes a preconditioned signal. A lowpass filter demodulator312B coupled to the differential transmission isolation barrier302B performs error recovery on the passed preconditioned signal.

FIG. 3Bdepicts an embodiment of an isolator circuit300B that comprises a pulse width modulator306B that is configured to precondition a signal and a differential transmission isolation barrier302B coupled to the pulse width modulator306B that is configured to pass a preconditioned signal. A lowpass filter demodulator312B is coupled to the differential transmission isolation barrier302B and is configured to perform error recovery on the passed preconditioned signal.

The isolator circuit300B includes a pathway304B for transmitting an analog signal across an isolation barrier302B wherein a voltage input signal VINis applied to a pulse width (PWM) modulator306B and passed across a capacitively-coupled differential transmission pathway304B to a low pass filter demodulator312B. The isolator circuit300B includes a pulse width modulator (PWM)306B, a differential transmission isolation barrier302B, and a low pass filter (LPF) demodulator312B. The PWM306B is generally used for signal preconditioning. The LPF demodulator312B can be used for error recovery.

Referring toFIG. 3Cin combination withFIG. 1, in some embodiments, the power converter100can include a signal isolator160,300C that further comprises an error amplifier354C coupled to a signal input terminal of the pulse width modulator306B and is configured for comparing the signal to a reference. The isolation circuit500C forms a pathway including preconditioning and error recovery with the error amplifier554C on an input side for comparing an input voltage to a reference voltage, thereby generating an output voltage which is a K-function of the difference.

Referring toFIG. 3Din combination withFIG. 1, in some embodiments, the power converter100can include a signal isolator160,300D that further comprises an error amplifier354D coupled to the lowpass filter modulator306B that regulates the error recovered signal upon reconstruction. The isolation circuit300D forms the pathway with the error function positioned after the signal is reconstructed. The error equation for the implementations shown inFIGS. 3C and 3Dfunction according to the same basic equation. The error function is typically included in the pathway, although some embodiments may omit the function.

Referring toFIG. 4A, a combined block and circuit diagram illustrates an embodiment of a power controller400that includes a bidirectional signal isolator432. The illustrative power controller400comprises a direct current (DC)-DC converter434configured to receive an input voltage VINin a primary domain402, a transformer436coupled to and driven by the DC-DC converter434that supplies an output voltage VOUTin a secondary domain404, and a dual-channel bidirectional isolator432forming a transmission path414,424that passes a signals through an isolation barrier416,426between the primary domain402and the secondary domain404. The dual-channel bidirectional isolator432comprises a digital isolator406and an analog isolator408coupled in parallel between the primary domain402and the secondary domain404configured to transmit data in opposing directions.

The power controller400includes a DC-DC converter434with an isolated path414,424for transmitting varied kinds of signal.

The digital isolator406passes digital data transmission signals from the primary domain402to the secondary domain404. The analog isolator408passes analog information back from the secondary domain404to the primary domain402.

In an illustrative implementation, the digital isolator406can be configured to pass digital information including shut down, power-on-reset, status information, control information, and the like.

In some embodiments, the power controller400can further comprise an error amplifier430coupled to the dual-channel bidirectional isolator432at a primary domain connection or a secondary domain connection. The error amplifier430performs feedback regulation.

The power controller400diagram illustrates a structure and associated technique for transmitting signals across an isolation barrier416,426. The DC-DC converter434in a primary domain402passes power to a transformer436. The transformer436transfers power to a secondary domain404which includes a rectifier438and several discrete components. The rectifier438is a functional block that can perform rectification or signal conditioning in many ways. Signals are passed between the primary domain402and the secondary domain404in two communication pathways. The DC-DC converter434in the primary domain402passes a digital signal to the secondary domain404via a digital isolator406. A feedback signal VFBis returned from the secondary domain404to the DC-DC converter434in the primary domain402over an isolating pathway that includes analog-to-digital conversion (ADC)408. The ADC408can be implemented using a variety of different structures and functional methods. The ADC can be single-ended or differential, and can have capacitive-coupling.

A return communication signal path from the secondary domain404to the primary domain402is also a transmission path incorporating an isolation barrier402. The return transmission path can carry a feedback signal VFBback to the primary domain402and to the DC-DC converter434. The return transmission pathway can include an error amplifier430which is shown on the primary domain402but can otherwise be positioned on the secondary domain404, as shown in dotted lines. For an analog return signal pathway, the feedback signal VFBis used to control the power controller feedback loop. The feedback loop of the DC-DC converter434passes through the transformer436, the rectifier438, a capacitor CO, a resistor divider440, through the analog digital transmission path, and back into the DC-DC converter434. The loop is a regulatory loop for regulating power distribution. The error amplifier430is included to complete the regulation functionality. Error amplifier functionality can be on either the primary domain402or the secondary domain404of the isolation barrier402.

A signal from the DC-DC converter434is passed through the digital isolator406and into the rectifier438to enable synchronous rectification. The digital information pathway through the digital isolator406can carry various other information elements in addition to the rectification signal including shut down, enable, power on reset, or a variety of different types of different status or information data which is desired to be send back and forth between the primary domain402and the secondary domain404.

The forward path is depicted as a DC-DC converter434but other types of paths can be formed. Some implementations can replace the transformer with another type of transmission path and isolation barrier, for example high voltage capacitors. Accordingly, some other type of power path can be implemented and controlled via a feedback loop. One of paths is a feedback path that transmits a digitized form of the feedback and forms a control loop. In various embodiments, the forward path and feedback path can form a servo loop or other type of digital path that can communicate in either direction across the isolation barrier.

The feedback signal is represented as a digital signal passing through a capacitor that is fed back to the DC-DC converter434for controlling power passed through the power isolation barrier from the primary domain402to the secondary domain404.

Referring toFIG. 4B, a block and circuit diagram shows an embodiment of a digital isolator406that can be implemented in the isolator432. The digital isolator406comprises a pre-conditioner410adapted to receive an input signal412and precondition the input signal412using a modulation function and a transmission path414comprising an isolation barrier416coupled to the pre-conditioner410for passing a preconditioned signal. The digital isolator406can further comprise a digital recovery circuit418coupled to the transmission path414.

The transmission path414is illustratively shown as an isolation barrier416formed by a capacitor CISO. The isolation barrier416can be constructed in a variety of forms such as a capacitive isolation barrier, an electrostatic isolation barrier, a transformer isolation barrier, a magnetic isolation barrier, an optical isolation barrier, a thermal isolation barrier, a resistive isolation barrier, a piezoelectric isolation barrier, or others.

The digital isolator406is shown as a digital transmission block with a dashed-line indicating the isolation boundary. One example of a component that can be implemented for passing data or other information across the boundary is a capacitor CISO. Accordingly, the digital isolator406can be configured as one or more capacitors although other embodiments can be any type of barrier transmission path. In various implementations the type of isolation and associated digital isolator can be electrostatic isolation as a capacitor, a magnetic isolation formed as a transformer, a light isolation formed as an optical isolator. Other techniques can also transmit information across the boundary using other effects such as thermal, resistive, or more unusual forms such as piezoelectric and the like. Accordingly, information data signals can be passed, for example as digital information, from the primary domain402to the secondary domain404, and information that can include feedback signals is communicated back from the secondary domain404to the primary domain402, usually as analog signals although some implementations can return digital signals.

Referring toFIG. 4C, a block and circuit diagram shows an embodiment of an analog isolator408that can be implemented in the isolator432. The analog isolator408can comprise an analog-to-digital converter (ADC)420adapted to receive and precondition a feedback signal422and a transmission path424comprising an isolation barrier426coupled to the ADC420for passing a preconditioned signal. The analog isolator408also comprises a digital-to-analog converter (DAC)428coupled to the transmission path424.

The transmission path424is illustratively shown as an isolation barrier426formed by a capacitor CISO. In other embodiments, the isolation barrier426can be a capacitive isolation barrier, an electrostatic isolation barrier, a transformer isolation barrier, a magnetic isolation barrier, an optical isolation barrier, a thermal isolation barrier, a resistive isolation barrier, a piezoelectric isolation barrier, or the like.

In various embodiments, the analog-to-digital converter (ADC)420can be configured to convert, sample, and modulate and analog signal into digital format and pass the digital format signal through a capacitor CISOin the transmission path424. The digital-to-analog converter (DAC)428can be configured to recover the signal to a baseband analog signal.

FIGS. 4B and 4Ccan also show example embodiments of the digital isolator432depicted inFIG. 4A.FIG. 4Billustrates the digital isolator432in a form that receives a digital input signal and passes the digital signal to a driver410or other pre-conditioner. The preconditioned signal passes through an isolation capacitor CISOto a digital recovery block418and then to a digital data output terminal.

FIG. 4Ccan also illustrate an analog signal implementation of the digital isolator406. An analog signal path has an analog signal that is passed through an analog-to-digital converter (ADC) of some type. Many types of components or devices can be implemented to perform the conversion function to convert, sample, and modulate the analog signal into a digital format for passage through a transmission path with an isolation barrier, such as a capacitor. The digital signal passes to a signal recovery device or component such as a digital-to-analog converter (DAC) to return a base-band analog signal.

Referring toFIG. 5, a schematic block and circuit diagram illustrates an embodiment of a power controller500including a signal isolator560that uses capacitors to couple a feedback signal across an isolation barrier502. The illustrative power controller500comprises a power converter526configured to receive an input voltage VIN in a primary domain502, and a transformer534coupled to and driven by the power converter526that supplies an output voltage VOUTin a secondary domain504. An isolated transmission path504couples the primary domain502and the secondary domain504. A modulator506receives the output voltage VOUTand conditions the signal for transmission via the isolated transmission path504. A demodulator512receives the transmitted signal and recovers a feedback signal VFB′for usage in a control loop516.

In various embodiments, the modulator506can be implemented as an analog-to-digital converter; a pulse code modulator, a delta modulator, a voltage to frequency converter, a frequency modulator, a phase modulator, a single-ended analog-to-digital converter (ADC) modulator, a differential ADC modulator, or a capacitively-coupled ADC modulator, or other suitable device.

The modulator506can be constructed as an analog-to-digital converter (ADC) that performs any appropriate modulation such as delta modulation or pulse width modulation to convert a voltage signal to a pulse width signal, frequency modulation to convert the voltage signal to frequency, and a phase modulator to convert the voltage signal to a phase. If the ADC is implemented as a pulse width modulator or delta modulator, the corresponding demodulator512is typically constructed as a low pass filter with frequency modulation constant.

The illustrative transmission path504is implemented as a pair of capacitors with differential capacitor coupling. In other embodiments, the isolated transmission path can be constructed as one or more capacitors such as with single capacitor coupling, or can be constructed using other devices such as transformers, optical isolators, thermal isolating elements, or others.

The illustrative isolation circuit560uses a capacitor, such as a high voltage capacitor, to couple a feedback signal across an isolation barrier. A DC feedback signal is sampled at high frequency or modulated on a secondary side, passed through a coupling capacitor, and demodulated on the primary side.

The illustrative demodulator512is depicted as a digital-to-analog converter (DAC). In other implementations, the demodulator512can be other suitable devices.

A specific example of an isolation circuit560including an ADC modulator206or other modulation scheme such as a pulse code modulator, delta modulator, voltage to frequency conversion modulator, an isolated transmission path504, and a DAC demodulator512can be a class D amplifier that receives and modulates an input signal such as an audio signal, and drives a speaker by passing the signal through a capacitor.

Referring toFIG. 6A, a schematic block diagram shows an example of an embodiment of a pulse width modulator600that can be used in the illustrative power controllers. Modulation can be implemented using techniques other than pulse width modulation and pulse with modulation can be implemented in many other forms. An input voltage VINis applied to a voltage to current converter602and passed to a delta modulator604to product a digital signal DO.FIG. 6Bshows an example implementation of the delta modulator604.FIG. 6Cillustrates an example implementation of the voltage to current converter602.

Referring toFIG. 6B, the illustrative delta modulator602has a self-oscillatory signal loop or hysteretic oscillation loop606and performs simultaneous frequency derivation and pulse width modulation. The delta modulator602uses a dual set of comparators608coupled into the oscillatory signal loop606. The comparator608in the feedback portion of the loop606supplies two clock signals which are switched and passed back to the comparator608in the input portion of the loop. Other embodiments of a delta modulator can include a fixed clock in place of the feedback loop. In another implementation, a clock signal can be driven as an input signal to produce a pulse width modulation output signal.

FIG. 6Cillustrates an embodiment of a voltage to current converter602that can be used in the pulse width modulator600.

Referring toFIG. 7, a schematic block diagram illustrates an embodiment of an isolated power converter that includes a DC-DC converter and optical coupler isolation. The power distribution circuit has an input supply voltage applied into the DC-DC converter, a transformer, a rectifying function include in the integration, and an opto-isolator for crossing the barrier with the information. An error function is formed on the secondary side as a light-emitting diode (LED) stacked on a voltage so the output feedback voltage is compared to an internal reference voltage and the difference of the comparison is represented by the current in the transistor Q1which is labeled a feedback error signal.

In contrast, in the various embodiments shown inFIGS. 1 through 6, the feedback signal is passed through some type of modulation scheme, transmitted on a pathway that includes an isolation barrier, then passed to some type of demodulation. Any suitable type of modulation can be implemented, for example a simple analog-to-digital converter or other simple rectifier. The transmission pathway including an isolation barrier can be any suitable technology, for example one or more capacitors, or other technology. Generally, demodulation can be selected to suitably recover a signal according to the implemented type of modulation.

Modulation can be implemented in a variety of different ways, including but not limited to pulse width modulation (PWM), delta modulation (DM), frequency modulation (FM), phase modulation, and others. Modulation can be used to generate samples in any kind of sample system to produce a serial bit stream with information represented by packets. For example, in classic pulse code modulation, sampling can be implemented to form an eight-bit word so that packets of eight-bit words represent a sample.

In contrast, other embodiment may implement modulation in a form that is not a true sampled data system where the information is carried in a set number of bits like an eight-bit or other size word.

For example, an entire framed serial path can be embedded that transmits information as packets that may be 64-bits long and transmitted at 10 MHz or 100 MHz and used to control the feedback loop. Other information can also be communicated on the serial path, for example data or control information such as temperature issues, control signals for shutdown, or any other information that can be usefully passed.

A simpler implementation of the feedback path can convey in the feedback as a relative variation in feedback voltage end up, whether higher or lower, in a continuous analog approach.

In contrast to a power converter that uses optical techniques for isolation, the illustrative embodiments shown inFIGS. 1 through 6, can enable production of a circuit with the entire path formed in a single integrated circuit or within a single package. For example, isolation barriers formed using capacitors can be integrated into a single integrated circuit chip. In some implementations, the isolation barrier can be formed using magnetic inductors that can be implemented with the entire loop in a single package. Optical isolators cannot easily be integrated into a single package with the DC-DC converter because an optical isolator system includes three disparate components: a light emitting diode (LED), a phototransistor, and an error amplifier or reference, to perform communication with optical isolation alone. The embodiments shown inFIGS. 1 through 6enable production of a realizable circuit in simple packaging and lower cost.

Referring toFIGS. 8A through 8E, a group of flow charts depict aspects of methods that can be implemented individually or in combination in one or more embodiments for controlling power in an electrical system.FIG. 8Ashows a method800comprising receiving802an input voltage in a primary domain, converting804the input voltage from a first direct current (DC) level to a second DC level, and passing806the converted voltage to a load at a secondary domain. The converted voltage is modulated808into a feedback signal and the feedback signal is transmitted810from the secondary domain to the primary domain across an isolation barrier. The feedback signal is demodulated812in the primary domain, controlling814conversion of the input voltage from the first to the second DC level using the demodulated feedback signal.

In various embodiments, passing806the preconditioned signal through the isolation barrier can be implemented by passing the signal through a capacitive isolation barrier, an electrostatic isolation barrier, a transformer isolation barrier, a magnetic isolation barrier, an optical isolation barrier, a thermal isolation barrier, a resistive isolation barrier, a piezoelectric isolation barrier, or other barrier.

In various embodiments, the preconditioned signal can be passed806through a single-ended isolation barrier or a differential isolation barrier.

In some embodiments, the method800can further comprise regulating816the feedback signal by comparison with a reference signal.

Referring toFIG. 8B, controlling power can include a method for transmitting820a signal across the isolation barrier comprising sampling822the converted voltage in the secondary domain whereby the converted voltage is modulated and coupling824the feedback signal across the isolation barrier from the secondary domain to the primary domain through a capacitor. The feedback signal can be demodulated826in the primary domain.

Referring toFIG. 8C, controlling power can include a method for transmitting830a signal across the isolation barrier can further comprise performing832analog to digital conversion of the converted voltage whereby the converted voltage is modulated into the feedback signal. The feedback signal can be lowpass filtered834whereby the feedback signal is demodulated in the primary domain.

Referring toFIG. 8D, controlling power can include a method for transmitting840a signal across the isolation barrier comprising receiving842the converted voltage in the secondary domain as the feedback signal, preconditioning844the feedback signal according to a modulation function, and passing846the preconditioned signal through the isolation barrier. The passed signal can be recovered848according to a demodulation function corresponding to the modulation function, the recovered signal being operative as a feedback signal.

In various embodiments, preconditioning844the feedback signal can comprise converting the feedback signal from an analog signal to a digital signal according to a modulation function such as pulse width modulation, delta modulation, frequency modulation, phase modulation, or other suitable modulation.

Recovering848the passed signal can be implemented according to a bistable multivibrator operation or digital to analog conversion.

Referring toFIG. 8E, controlling power can include a method for transmitting850a signal across the isolation barrier comprising modulating852a direct current (DC) feedback voltage, passing854the modulated DC feedback voltage through a capacitor by oversampling, and demodulating856the passed voltage to an increased frequency, thereby recovering a baseband signal. The demodulated voltage can be lowpass filtered858to restore an analog signal.

Terms “substantially”, “essentially”, or “approximately”, that may be used herein, relate to an industry-accepted tolerance to the corresponding term. Such an industry-accepted tolerance ranges from less than one percent to twenty percent and corresponds to, but is not limited to, component values, integrated circuit process variations, temperature variations, rise and fall times, and/or thermal noise. The term “coupled”, as may be used herein, includes direct coupling and indirect coupling via another component, element, circuit, or module where, for indirect coupling, the intervening component, element, circuit, or module does not modify the information of a signal but may adjust its current level, voltage level, and/or power level. Inferred coupling, for example where one element is coupled to another element by inference, includes direct and indirect coupling between two elements in the same manner as “coupled”.

While the present disclosure describes various embodiments, these embodiments are to be understood as illustrative and do not limit the claim scope. Many variations, modifications, additions and improvements of the described embodiments are possible. For example, those having ordinary skill in the art will readily implement the steps necessary to provide the structures and methods disclosed herein, and will understand that the process parameters, materials, and dimensions are given by way of example only. The parameters, materials, and dimensions can be varied to achieve the desired structure as well as modifications, which are within the scope of the claims. Variations and modifications of the embodiments disclosed herein may also be made while remaining within the scope of the following claims. For example, various aspects or portions of a communication or isolation system are described including several optional implementations for particular portions. Any suitable combination or permutation of the disclosed designs may be implemented.