Patent Description:
In a typical magnetron application, such as a microwave heating application or a plasma light source application, a power supply may be used to convert power provided by a multi-phase power source, such as a three-phase power mains grid power source, to a power suitable for use by the magnetron, and to supply the power to the magnetron. Conventional multi-phase power supplies, however, typically produce a large degree of ripple at the output of the power supply, which may result in a large degree of radio frequency (RF) emissions produced by the magnetron. Further, conventional multi-phase power supplies typically include power factor correction circuits, and accompanying power factor correction electrolytic components, that make the conventional multi-phase power supplies expensive, in both size and cost, and render the conventional power supplies insufficiently reliable for use in some magnetron applications, such as in airborne microwave heating applications.

<CIT> and <CIT> are both concerned with power transfer from a source to a magnetron load. This prior art power supply includes a control module that sends a drive signal to a switched-mode power circuit. In general, the current drawn by the power supply is not linear and so it also includes some form of waveform shaping circuitry, which adjusts the pulse width of signals sent to the switched-mode power circuit so as to suppress instantaneous fluctuations of the input current waveform such that it appears substantially sinusoidal. Prior art circuits specifically for use with three-phase power sources are described in <CIT> and <CIT>. The first document describes a circuit to detect interruption of a single phase of the source. The second describes a conversion circuit that provides direct conversion from a three-phase input to a DC voltage output. The conversion circuit includes an integrated circuit for power factor correction, which ensures input current is in phase and proportional to the AC line voltage. Further prior art is provided by <CIT>, <CIT>, and by <NPL>.

A power supply suitable for providing power to a magnetron, such as a magnetron used on a microwave oven, is described. The power supply is suitable for use in applications in which robustness and high reliability is generally needed or desired, such as in microwave ovens used on aircrafts. The power supply is suitable for use in other applications as well. The dependent claims reciting preferred embodiments.

In an example embodiment, the power supply includes a switched-mode power circuit and a control module that controls operation of the switched-mode power circuit so as to make the power supply appear as a linear resistive load with respect to a power source. The control module may comprise an analog feedback loop circuit or a digital processor, configured to control operation of the switched-mode power circuit. Ensuring that the power supply appears as a linear resistive load with respect to the power source ensures that output of the power supply is at least substantially ripple free and that the power supply achieves a power factor of <NUM> or close to <NUM>.

According to an embodiment, a power supply comprises at least one input to couple the power supply to a power source. The power supply also comprises at least one switched-mode power circuit configured to extract electrical energy from the power source, wherein the electrical energy is to be transferred to a load. The power supply additionally comprises at least one control module coupled between the input and the switched-mode power circuit, wherein the control module is configured to control operation of the switched-mode power circuit to regulate a voltage-to-current ratio at the input of the power supply.

In other embodiments, the power supply comprises any suitable combination of one or more of the following features.

The power source is a three-phase mains power source.

The input comprises respective inputs to couple the power supply to respective phases of the three-phase mains power source.

The switched-mode power circuit comprises respective switched-mode power circuits to extract electrical energy from the respective phases of the three-phase mains power source.

The control module comprises respective control modules configured to control operation of the respective switched-mode power circuits, wherein each of the respective control modules is configured to regulate a voltage-to-current ratio at the corresponding input of the power supply.

The power supply further comprises respective power transformers coupled to outputs of the respective switched-mode power circuits and respective rectifier circuits coupled to outputs of the respective power transformers.

Outputs of the respective rectifier circuits are connected in series to produce a single power supply output to couple the power supply to the load.

The control module is configured to regulate the voltage-to-current ratio at the input of the power supply to make the power supply appear as a linear resistive load to the power source.

The control module includes an error amplifier and a control unit.

The control unit is coupled to the switched-mode power circuit and configured to control operation of the switched-mode power circuit in accordance with a control signal.

The error amplifier is configured to detect a difference between a voltage wave shape and a current wave shape at the input of the power supply, and adjust a level of the control signal in accordance with the detected difference between the voltage wave shape and the current wave shape.

The control unit comprises a voltage controlled oscillator coupled to a field effect transistor driver circuit, wherein a frequency of the voltage controlled oscillator is controlled by the control signal.

The control module includes a digital signal processor configured to generate a control signal to control operation of the switched-mode power circuit based on a sampled voltage wave at the input of the power supply.

The control module is isolated from the switched-mode power circuit and the power supply further comprises an optocoupler to transfer the control signal from the control module to the switched-mode power circuit.

According to another embodiment, a power supply comprises a respective input to couple the power supply to each of three phase outputs of a three-phase power source. The power supply further comprises a respective switched-mode power circuit configured to extract electrical energy from a corresponding phase of the power source. The power supply additionally comprises one or more control modules coupled between the respective power source inputs and the respective switched-mode power circuits. The one or more control modules are configured to control operation of the respective switched-mode power circuits to regulate a voltage-to-current ratio at each of the respective inputs of the power supply.

The one or more control modules comprise a respective error amplifier and a respective control unit for each of the three phases.

Each respective control unit is configured to control operation of the corresponding switched-mode power circuit in accordance with a control signal.

Each respective error amplifier is configured to detect a difference between a voltage wave shape and a current wave shape at the corresponding input of the power supply, and adjust a level of the control signal in accordance with the detected difference between the voltage wave shape and the current wave shape.

Each control unit comprises a voltage controlled oscillator coupled to a field effect transistor driver circuit, wherein the voltage controlled oscillator is configured to control operation of the field effect resistor, wherein a frequency of the voltage controlled oscillator is controlled by the control signal.

The one or more control modules comprise one or more digital signal processors configured to generate control signals to control operation of the respective switched-mode power circuits based on based on respective sampled voltage waves at the respective inputs of the power supply.

The one or more control modules are isolated from the respective switched-mode power circuits.

The power supply further comprises respective optocouplers to transfer control signals from the one or more control modules to the respective switched-mode power circuits.

According to yet another embodiment, a method of regulating a power supply having an input to couple the power supply to a power source and a switched-mode power circuit to extract electrical energy from the power source, wherein the electrical energy is to be provided to a load, comprises obtaining a first signal indicative of a voltage wave shape at the input of the power supply. The method further comprises obtaining a second signal indicative of a current wave shape at the input of the power supply. The method additionally comprises comparing the first signal and the second signal to detect a difference between the first signal and the second signal. The method also comprises controlling, based on the detected difference between the first signal and the second signal, operation of the switched-mode power circuit to regulate a voltage-to-current ratio at the input of the power supply.

Obtaining the first signal comprises obtaining the first single from a rectified voltage signal at the input of the power supply.

Obtaining the second signal comprises sensing a current signal at the input of the power supply using a current sense resistor.

Obtaining the second signal may comprise obtaining the second signal via an adjustable resistor.

The method may further comprise modulating a resistance of the adjustable resistor to adjust amount of energy extracted by the switched-mode power circuit from the power source.

Obtaining the first signal may comprise obtaining the first signal via an adjustable resistor.

Turning first to <FIG> and <FIG>, two conventional power supplies typically used with three-phase (<NUM>-phase) power source applications are illustrated. Referring first to <FIG>, a power supply <NUM> includes three modules <NUM>. Each module <NUM> couples the power supply <NUM> to a power source output corresponding to a particular phase of a three-phase power source. Each module <NUM> includes a power factor correction stage <NUM> and a DC/DC stage <NUM>. Rectified outputs of the modules <NUM> are connected in series to produce a single output of the power supply <NUM>. Each module <NUM> also includes a respective PFC-capacitor <NUM> that temporarily stores energy provided by the PFC stage <NUM> and supplies the stored energy to the DC/DC converter <NUM>.

Referring now to <FIG>, a conventional power supply <NUM> is similar to the power supply <NUM> of <FIG>, except that the power supply <NUM> includes a power factor correction (PFC) stage <NUM> to couple the power supply <NUM> to each phase of a three-phase power source, and a DC/DC stage <NUM>. Similar to the power supply <NUM> of <FIG>, the power supply <NUM> includes a PFC capacitor <NUM> that temporarily stores energy provided by the PFC stage <NUM> and supplies the energy to the DC/DC converter <NUM>.

Conventional power supplies, such as the power supplies illustrated in <FIG>, typically employ PFC electrolytic components, such as PFC capacitors, which may be expensive in terms of both size and cost of the power supply. In addition to being large and expensive, PFC electrolytic components result in reduced reliability of the conventional power supply due at least in part to aging characteristics of the PFC electrolytic components. Additionally, PFC electrolytic components cause high in-rush currents to be supplied to the output of the power supply when a power source is applied to the input of the power supply. Consequently, such conventional power supplies often include by-passing circuits and/or current limiters that may further increase size and cost of the power supply. When a power source is a multi-phase power source, such by-passing circuits are provided for each phase of the multi-phase power supply.

Additionally, such conventional power supplies typically experience a relatively high ripple at the output of the power supply, such as a relatively high ripple in an electrical current at the output of the power supply. Thus, a relatively large filter may be needed to provide a suitable power supply output for loads for which a relatively ripple-free power input may be desired (e.g., a magnetron). Further still, a drop in a voltage level of the power source results in an increase of current provided to a load of the power supply, which may cause instability in the power source, such as in the mains power grid, particularly if the load is large relative to capability of power source.

<FIG> is a set of plots illustrating the effect of a suitably large resistive load provided on each phase of a three-phase power source. In particular, a plot <NUM> represents a periodic voltage wave corresponding to a first phase of the power source, a plot <NUM> represents a periodic voltage wave corresponding to a second phase of the power source, and a plot <NUM> represents a periodic voltage wave corresponding to a third phase of the power source. A plot <NUM>, which represents a sum of absolute voltages of the three phases of the power source, shows a significant ripple present in the sum of absolute voltages of the three phases of the power source. On the other hand, a normalized power level obtained from the three phases of the power source, illustrated by a plot <NUM>, is at least substantially ripple-free.

The ripple-free power level, illustrated by the plot <NUM>, generally results when a suitably large resistive load is provided on each phase of the three-phase power supply. Under this condition, power extracted by the resistive load from each phase of the three phase power supply can be mathematically represented by a sine squared (sin<NUM>) function, with <NUM>° phase shift between the phases. Consequently, a power supply that appears as an at least substantially resistive load with respect to each of the three-phases of a power source ensures that the sum of the power extracted from the three phases of the power source is ripple free, thus ensuring a ripple-free output (e.g., ripple free current or voltage) provided to the load connected to the power supply. Such quasi-resonant power supply can obtain a power factor of <NUM>, or a power factor close to <NUM>, without use of a power factor correction module and power storing electrolytic components often employed in conventional power supplies.

<FIG> is a circuit diagram of a quasi-resonant power supply <NUM>, according to an embodiment of the present disclosure. The power supply <NUM> includes a power module <NUM> coupled to a power source <NUM>. In an embodiment in which the power supply <NUM> operates with a multi-phase power source <NUM>, the power supply <NUM> includes a respective power module <NUM> coupled to each phase of the multi-phase power input power source <NUM>. For example, if the power source <NUM> is a three-phase power source, such as a power mains grid source, the power supply <NUM> includes three power modules <NUM> respectively coupled to the three phase lines of the power source, in an embodiment. Outputs of the power modules <NUM> are arranged in series or in parallel to provide a combined output of the power supply <NUM>, in various embodiments.

With continued reference to <FIG>, the power module <NUM> includes a switched-mode power circuit <NUM>, such as a zero voltage switching (ZVS) converter, coupled to a transformer circuit <NUM>. The switched-mode power circuit <NUM> includes a first switching element <NUM> and a second switching element <NUM>. The first switching element <NUM> and the second switching element <NUM> may be transistors, such as field effect transistors (FET), for example.

The input of the switched-mode power circuit <NUM> is coupled to a control module <NUM> that controls operation of the switched-mode power circuit <NUM>. The control module <NUM> includes a control unit <NUM> which, in turn, includes a voltage controlled oscillator (VCO) <NUM> and a transistor (e.g., FET transistor) driver circuit <NUM>. The VCO <NUM> and the FET transistor driver circuit <NUM> are provided as a single control unit <NUM>, in the illustrated embodiment. In another embodiment, the VCO <NUM> and the FET driver circuit <NUM> are provided as separate control elements in the power module <NUM>. The control module <NUM> also includes a feedback loop circuit <NUM> that controls input signal provided to the control module <NUM>. The feedback loop circuit <NUM> includes an error amplifier <NUM>, which may be an operational amplifier circuit, for example. The error amplifier <NUM> includes an inverting input terminal <NUM>, a non-inverting input terminal <NUM>, and an output terminal <NUM>. A rectifier circuit <NUM> rectifies a voltage signal from the power supply <NUM>. A reference current signal, provided to the inverting input terminal <NUM> of the error amplifier <NUM>, is obtained from the rectified voltage signal of the power source <NUM> via a first diode <NUM>, a second diode <NUM> and a resistor <NUM>. A resistor <NUM> and a capacitor <NUM>, coupled between the inverting terminal <NUM> and the output terminal <NUM> of the error amplifier <NUM>, determine the frequency response and the gain of the error amplifier <NUM>. The feedback loop circuit <NUM> is generally fast-acting. The feedback loop circuit <NUM> is designed to operate with a maximum mains frequency of up to <NUM>, for example, in some embodiments.

In operation, the error amplifier <NUM> compares the reference signal provided to the inverting input of the error amplifier <NUM> to a current sense signal obtained, from a current sensed by a current sense resistor <NUM>, via a resistor <NUM>. The error amplifier <NUM> operates to detect a difference between the power source voltage wave and the power source current shape at the input to the power module <NUM> at various angles of the voltage and current waves supplied by the power source <NUM> to the power module <NUM>, and to adjust a signal at the output of the error amplifier <NUM> in accordance with the detected difference. The signal at the output of the error amplifier <NUM> is provided to the control unit <NUM>. In particular, the signal at the output of the error amplifier <NUM> may control a frequency of the VCO <NUM> of the control unit <NUM>. The FET driver circuit <NUM> is controlled by the frequency of the VCO <NUM> to generate control signals output by the control module <NUM> to control operation of the switched-mode power circuit <NUM>. Control signals from the control module <NUM> may be provided to respective gate terminal of the transistors <NUM> and <NUM> to control respective ON/OFF states of the transistors <NUM> and <NUM> and to thereby adjust amount of power extracted by the switched-circuit circuit <NUM> from the power source <NUM> at any given time. Accordingly, the error amplifier <NUM> dynamically adjusts amount of instant power extracted from the power source at various angles of the voltage and current periodic waveforms of the power source, thereby controlling the voltage-to-current ratio at the input to the power module <NUM>.

Because voltage-to-current ratio at the input to the power module <NUM> is controlled by the feedback loop circuit <NUM>, a drop in power source voltage results in a drop of current extracted from the power source by the power supply <NUM>, thereby maintaining stability of the power source. Further, because the voltage-to-current ratio of the input to the power module <NUM> is controlled, the power supply <NUM> effectively operates as an energy converter by extracting a predefined amount of power from the power source, and providing a converted predefined amount of power to the load, in an embodiment. This characteristic of the power supply <NUM> may be particularly useful in applications with a variable voltage load, such as in a magnetron application in which anode voltage of the magnetron may vary due to RF-load and overall thermal conditions in which the magnetron is operating.

Controlling the voltage-to-current ratio at the input to the power module <NUM> makes the power module <NUM> appear as a linear resistive load with respect to the power source <NUM> and ensures that power extracted from the power source is a sin<NUM> function, as describes above with respect to <FIG>. A linear resistive load with respect to the power source <NUM> results in a power factor of <NUM>, or close to <NUM> (e.g., <NUM>), achieved by the power supply <NUM> even at relatively high power levels (e.g., at <NUM> Watts), in at least some embodiments.

Resistance values of the resistor <NUM> and/or the resistor <NUM> may be adjustable, for example by way of linear resistor modulation or by way of pulse width modulation (PWM). In some embodiments, resistance values of the resistor <NUM> and/or the resistor <NUM> may be dynamically modulated or otherwise adjusted to control the actual average current entering the power module <NUM> and, accordingly, to control the true power level at the output of the power module <NUM>. In an embodiment in which the power supply <NUM> includes multiple modules <NUM> respectively coupled to phase outputs of a multi-phase power source <NUM>, the actual current and the true power level may be simultaneously dynamically adjusted in each of the power modules <NUM>, thereby ensuring at least substantially equal load sharing among the phases of the power source <NUM>. In another embodiment, a multiplier circuit is provided in place of the resistor <NUM> to provide the reference signal to the error amplifier <NUM>. Additionally or alternatively, a multiplier circuit is provided in place of the resistor <NUM> to provide the reference signal to the error amplifier <NUM>, in an embodiment. The multiplier circuit that provides the sense signal and/or the reference signal to the error amplifier <NUM> may be dynamically adjusted during operation of the power module <NUM>.

In an embodiment, the control module <NUM> of the power module <NUM> comprises a signal processing device, such as a digital signal processor, that operates according to a mathematical model of interaction of the phases of a multi-phase power source <NUM>. The signal processing device is used instead of the control unit <NUM> and the feedback loop circuit <NUM> to directly control operation of the switched-mode power circuit <NUM>, in an embodiment. In a multi-phase power source system, operation of the digital signal processors of respective power modules <NUM> may be synchronized with an appropriate phase shift (e.g., <NUM>° in a three-phase system) between the phases of the multi-phase power source to further enhance performance and stability characteristics of the power supply <NUM>. In an embodiment in which power supply <NUM> includes multiple modules <NUM> respectively coupled to phase outputs of a multi-phase power source <NUM>, a respective signal processing device is provided to control operation of the respective the multiple power modules <NUM>. In another embodiment in which the power supply <NUM> includes multiple modules <NUM> respectively coupled to phase outputs of a multi-phase power source <NUM>, a single signal processing device is provided to control operation of the multiple modules <NUM>.

Referring still to <FIG>, in an embodiment, the control module <NUM> is isolated from the switched-mode power circuit <NUM>. The control signals provided by the control module <NUM> to the switched-mode power circuit <NUM> may be coupled to the switched-mode power circuit <NUM> via optocouplers (not shown in <FIG>), or other suitable devices, configured to transfer the control signals from the isolated control module <NUM> to the switched-mode power circuit <NUM>.

Referring briefly to <FIG>, in an embodiment, a power module <NUM> is generally the same as the power module <NUM> of <FIG>, and includes many of the same-numbered elements with the power module <NUM> of <FIG>, except that the power module <NUM> includes a control module <NUM> that is isolated from the switched-mode power circuit <NUM>. The control module <NUM> may comprise the control module <NUM> described with respect to <FIG>, for example. The control module <NUM> includes inputs <NUM>, <NUM> for receiving reference current signal from the power source <NUM> via a transformer <NUM>, and inputs <NUM>, <NUM> for receiving reference voltage signal from the power source <NUM>. The control module <NUM> may compare the reference current signal received via inputs <NUM>, <NUM> and the reference voltage signal received via the inputs <NUM>, <NUM>, and may generate control signals to control operation of the transistors <NUM> and <NUM>, as described with respect to <FIG>. The control signals generated by the control module <NUM> may be provided to outputs <NUM>, <NUM> of the control module, and may then be provided to the transistors <NUM> and <NUM> via optocouplers <NUM>, <NUM>, or via other suitable devices, coupled between the outputs <NUM>, <NUM> and the transistors <NUM> and <NUM>.

Referring back to <FIG>, the power module <NUM> also includes a capacitor <NUM>, a capacitor <NUM> and an inductor <NUM> that limit the maximum power capacity of the power module <NUM>. Additionally, a capacitor <NUM> is provided to limit the ripple across the half bridge circuit of the switching elements <NUM>, <NUM>, in the illustrated embodiment. One or more of the capacitor <NUM>, the capacitor <NUM>, the inductor <NUM> and/or the capacitor <NUM> are omitted from the power module <NUM>, in some embodiments.

With continued reference to <FIG>, because the power supply <NUM> does not include a power factor correction stage and does not store energy in a corresponding PFC capacitor, the voltage level at a primary side <NUM> of the transformer <NUM> in operation does not exceed the peak voltage level of the power source, such as peak voltage of a power mains grid, in an embodiment. A secondary side <NUM> of the transformer <NUM> is coupled to a rectifier circuit, such as a voltage doubler circuit <NUM> in the illustrated embodiment. In another embodiment, the voltage doubler circuit <NUM> is replaced by a full wave rectifier circuit. In an embodiment in which a full wave rectifier circuit is used in place of the voltage doubler circuit <NUM>, a single capacitor, with a relatively smaller capacitance value, is placed at the output of the full wave rectifier, thereby reducing energy loss at the output of the rectifier. Accordingly, a relatively smaller capacitance at the output of the power module <NUM> is subject to the ripple of the switching frequency of the power module <NUM> and/or to harmonics of the frequency of the power supply <NUM>. Further, amount of current flowing through each diode of a full wave rectifier is reduced by <NUM>% relative to the amount of current flowing through each of the diodes D3 and D4 in the voltage doubler <NUM> illustrated in <FIG>. The reduced amount of current flowing through diodes of a full wave rectifier results in a higher reliability of the power module <NUM>, in at least some embodiments.

As described above, in an embodiment, outputs of multiple power modules <NUM> may be connected in series, or in parallel, to produce a single output of the power supply <NUM>, in an embodiment. The turn ratio of the transformer <NUM> of each of the power modules <NUM> may be determined such that output voltage of each of the power modules <NUM> is maintained at <NUM>% of a nominal voltage required at the single output of the power supply <NUM>. Maintaining voltage at <NUM>% of a nominal voltage required or desired at the single output of the power supply <NUM> may increase or maximize efficiency of each power module <NUM>.

<FIG> is a block diagram of a power supply <NUM>, according to an embodiment. The power supply <NUM> includes three power modules <NUM> to respectively couple the power supply <NUM> to each output of a three phase power source, such as a three phase mains power source. In an embodiment, each of the power modules <NUM> is the same as the power module <NUM> of <FIG>. In another embodiment, each of the power modules <NUM> is the same as the power module <NUM> of <FIG>. In an embodiment, respective outputs of the three modules <NUM> are connected in series to produce a single output voltage signal illustrated in <FIG> as Vout <NUM>. In an embodiment, turn ratios of respective transformers of the three power modules <NUM> are such that voltage output signals of the respective converters are at <NUM>% of a nominal voltage required or desired to be maintained at Vout <NUM>. Maintaining voltage output signals of the respective converters are at <NUM>% of the nominal voltage required or desired at Vout <NUM> ensures a relatively high (e.g., a maximum) power converter efficiency in the power supply <NUM>, in at least some embodiments. The voltage signal at Vout <NUM> is supplied to a magnetron anode, in an embodiment.

<FIG> is a flow chart of a method <NUM> of operating a power supply, according to an embodiment. In an embodiment, the method <NUM> is performed in conjunction with the power supply <NUM> of <FIG>. In another embodiment, the method <NUM> is performed with a suitable power supply different from the power supply <NUM> of <FIG>. The power supply comprises an input to couple the power supply to a power source, and a switched-mode power circuit to extract electrical energy from the power source, wherein the electrical energy is to be transferred to a load. At a step <NUM>, a first signal is obtained. The first signal is indicative of a voltage wave shape at the input to the power supply. The first signal is obtained, for example, from a rectified voltage signal provided to the input of the power supply from an output of an alternating current (AC) power source, such as a phase of a mains power source.

At a step <NUM>, a second signal is obtained. The second signal is indicative of a current wave shape at the input of the power supply. The second signal is obtained, for example, by sensing the current via a current sense resistor. At a step <NUM>, the first signal obtained at the step <NUM> is compared with the second signal obtained at the step <NUM> to detect a difference between the first signal and the second signal. The difference between the first signal and the second signal corresponds to an instantaneous difference between the voltage signal and the current signal at the input of the power supply. According to the invention, the first signal and the second signal are compared by an error amplifier. In another non-claimed embodiment, the first signal and the second signal are compared by a digital circuit, such as a digital processor.

At a step <NUM>, operation of the switch-mode power module is controlled based on the difference between the first signal and the second signal detected at the step <NUM>. Operation of the switch-mode power module is controlled to regulate a ratio of the voltage to the current at the input to the power supply. The ratio may be regulated to ensure that the ratio is at least substantially constant, or at least substantially linear, over time. Regulating the voltage-to-current ratio so that the ratio is at least substantially constant, or at least substantially linear, over time, in turn, makes the power supply appear at least substantially resistive to the power source.

Claim 1:
A power supply (<NUM>, <NUM>), comprising:
at least one input for coupling the power supply to an ac power source (<NUM>);
at least one switched-mode power circuit (<NUM>) configured to extract power from the power source (<NUM>), wherein the power is to be transferred to a load;
at least one current sense resistor (<NUM>) for sensing a current signal at the input of the power supply; and
at least one control module (<NUM>, <NUM>), the at least one current sensor (<NUM>) and the at least one control module (<NUM>, <NUM>) are coupled between the at least one input and the at least one switched-mode power circuit (<NUM>), the at least one control module (<NUM>, <NUM>) comprising:
an error amplifier (<NUM>) having an inverting input terminal (<NUM>), a non-inverting input terminal (<NUM>) and an output terminal (<NUM>), wherein the inverting input terminal (<NUM>) is configured for receiving a first signal and a second signal;
a control unit (<NUM>, <NUM>) configured to receive a signal from the output terminal (<NUM>) of the error amplifier (<NUM>) and to generate a control signal, and configured to provide the control signal to the at least one switched-mode power circuit (<NUM>);
wherein
the first signal is a rectified voltage signal of the power source (<NUM>) and the second signal is a signal from the current sense resistor (<NUM>);
the error amplifier (<NUM>) is configured to detect a difference between the first signal and the second signal at various angles of the voltage and current waves supplied by the power source (<NUM>) and to adjust the signal at its output terminal (<NUM>) in accordance with the detected difference;
wherein the control module (<NUM>, <NUM>) is configured to base the control of the switched-mode power circuit (<NUM>) on the detected difference, such that in operation a voltage-to-current ratio at the at least one input of the power supply is regulated to be constant, or linear, over time, such as to mitigate output voltage ripple or output current ripple.