DC-DC converter with regulators having different parameter groups

Abstract

A converter for converting an input voltage into a DC output voltage, the converter having: a regulator for adjusting the DC output voltage toward a desired value, wherein the regulator includes a set of parameters for determining its regulation behavior; the converter includes a measurement module for obtaining at least one characteristic value of at least one characteristic parameter of the converter; and the converter includes at least two replaceable sets of parameters for the regulator, wherein a corresponding set of parameters is activatable in the regulator; wherein the first of the parameter sets has a slower regulation behavior toward the DC output voltage than the second of the parameter sets; and the converter includes a control module for replacing and activating a corresponding set of parameters in the regulator according to at least one of the characteristic parameters.

Description

Technical Field

[0001] As regulations become increasingly stringent, more and more electronic devices incorporate features that optimize the absorption of grid current in terms of its harmonic content. Conventional switching power supply designs typically include a rectifier and a smoothing capacitor. The smoothing capacitor is only charged under load when the instantaneous value of the sinusoidal grid voltage rises above its DC potential. The consequence is a brief current pulse that then charges the capacitor. Fourier analysis of this current variation typically reveals a significant amount of harmonics. Depending on applicable standards, this can make permission or certification difficult or impossible. Background Technology

[0002] As known from DE 10 2010 063 126 A1, charging equipment is required to charge the high-voltage batteries of hybrid vehicles or electric vehicles via, for example, a public power grid. Known charging equipment for vehicle high-voltage batteries mostly consists of a rectifier with a grid filter, a power factor correction circuit, and a potential isolation device. Summary of the Invention

[0004] Within the framework of this invention, a converter according to the invention for converting an input voltage into a DC output voltage is proposed. Preferred or advantageous embodiments of the invention, as well as other categories of invention, are derived from other configurations, the following description, and the accompanying drawings. Preferably, the DC input voltage is nearly constant over time. Preferably, the DC input voltage relates to a direct current voltage generated by rectification and subsequent smoothing of a sinusoidal alternating voltage, such that the voltage is nearly constant over time. Alternatively, the DC input voltage relates to a pulsating DC voltage generated by rectification of a sinusoidal alternating voltage, for example by means of a bridge switch, without subsequent smoothing or with only a small, immediate smoothing.

[0005] The converter includes a regulator for adjusting the DC output voltage toward a desired value. The regulator includes a set of parameters that determine its regulating behavior. The converter includes a measurement module for determining at least one characteristic value of at least one characteristic parameter of the converter.

[0006] The converter includes at least two replaceable parameter sets for the regulator. One corresponding parameter set can be activated in the regulator and is active during operation. The first parameter set has a slower regulation behavior in terms of output voltage compared to the second parameter set. The converter includes a control module for replacing and activating one of the corresponding parameter sets in the regulator. Here, replacement and activation are performed based on at least one of the characteristic parameters or corresponding different characteristic values ​​of the corresponding characteristic parameters.

[0007] Therefore, one can start with a slower parameter set and, when necessary (indicated by characteristic parameters or eigenvalues), switch to a parameter set with faster regulation behavior to prevent excessive rises or falls in the output voltage or to counteract such rises or falls more quickly. Here, transient variations in the power factor are tolerated. The corresponding switching can be implemented quickly and easily. Conventional or established regulation schemes can be retained individually—in the form of corresponding sets of regulation parameters. It is not necessary to create a new, advanced regulation scheme; one only needs to switch between conventional regulation schemes.

[0008] In particular, a hysteresis is set between parameter group switching to prevent continuous back-and-forth switching between faster and slower parameter groups when the eigenvalue is near the limit.

[0009] The eigenvalues ​​are, in particular, the latest values ​​of the respective characteristic parameters in time. Therefore, the latest matching of the regulator in the converter is achieved by responding in real time to the current eigenvalues, so as to respond in particular to the current voltage value of the output voltage, which is an eigenvalue.

[0010] In a preferred embodiment, the characteristic parameters are the DC output voltage and / or time, or time period, and / or the power delivered by the converter or its rate of change over time. Therefore, the selection of the current parameter set can be made to follow or depend on the characteristic parameters that decisively determine the characteristics of the converter, by means of a control module.

[0011] In a preferred variant of this implementation, when the output voltage is outside or deviates from the tolerance range and / or when the rate of change of power per unit time exceeds a limit, a faster parameter set is activated (starting from the currently activated slower parameter set). Rapid adjustment is important precisely when the output voltage deviates from the desired value or the tolerance range of that desired value, in order to bring the output voltage back towards its desired value. Under rapid load or power changes, i.e., when the power change per unit time exceeds a certain limit (e.g., power doubling or halving within 10ms to 50ms), there is a particular risk of output voltage collapse or overshoot. In these cases, rapid output voltage matching is necessary or may become necessary, which can be achieved through faster adjustment.

[0012] In a preferred variant of this implementation, when the output voltage is within or enters the tolerance range and / or when the rate of change of power per unit time does not exceed or falls below a limit value and / or when a time interval ends after the activation of a faster parameter group, a slower parameter group is activated (starting from the currently activated faster parameter group). Based on the above, overshoot or collapse of the output voltage is no longer expected when the voltage is near the desired voltage or when the power changes only slowly, thus achieving or striving for slower regulation while improving the power factor. This is mainly achieved by limiting the duration of faster regulation (and consequently, a worse power factor), thereby maintaining a high time-averaged power factor and adhering to defined standard limits under all operating conditions.

[0013] In a preferred embodiment, the regulator has an internal sub-regulator for the current value of the current absorbed by the converter and an external sub-regulator for the voltage value of the DC output voltage. Specifically, only the parameter set of the external sub-regulator can be changed.

[0014] Therefore, the regulator has an outer regulating ring (with an outer sub-regulator) and an inner regulating ring (with an inner sub-regulator) contained within the outer regulating ring.

[0015] The replaceable parameter set is either the parameter set of an external sub-regulator or an external control loop. This implementation corresponds to a widely popular regulator structure used in DC-DC converters. Therefore, the present invention is suitable for this widely popular converter scheme.

[0016] Therefore, the present invention is particularly effective at the most critical point for the output voltage of a DC-DC converter, namely, at current regulation, in that voltage regulation is achieved by means of a set of parameters that meet the current requirements.

[0017] In a preferred embodiment, the converter includes a memory for a set of parameters. Therefore, the set of parameters can be quickly retrieved when necessary and is immediately available in the regulator.

[0018] In a preferred variant of this implementation, the memory includes a lookup table for parameter sets. Here, each feature value, such as each current value, or (in the case of multiple feature parameters) each combination of feature values, is assigned a corresponding parameter set. Therefore, after retrieving the corresponding feature value(s), the assigned parameter set must simply be retrieved quickly and easily from the lookup table and provided to the regulator or activated there. This ensures particularly fast and simple replacement of parameter sets in the converter.

[0019] In a preferred embodiment, the converter is a boost converter. Boost converters, in particular, are affected by the problem of fluctuating output voltage, thus the present invention can be used particularly effectively here. The converter is especially a CCM (Continuous Current Mode) converter or a DCM (Discontinuous Current Mode) converter. In another preferred embodiment, the converter is constructed as a PFC circuit. The goal of a PFC circuit (Power Factor Correction) is to optimize harmonics—the spectrum of which is evaluated by the power factor—so that it contains only a small number of harmonics besides the fundamental frequency (the current at 50 Hz). Therefore, the power factor describes the ratio of absorbed active power to apparent power. These converter types are popular converters, thus the present invention offers advantages in a wide range of technical environments.

[0020] In a preferred embodiment, the regulator is a digital regulator. A digital regulator, in its current sense, outputs its regulation result only at a defined moment, so that the regulation result can be applied to or incorporated into the converter. During the time interval until the next relevant moment, no change is made in the converter by the regulator intervention. Such digital regulators are widely used in converters, thus this invention offers advantages to most converters.

[0021] In a preferred variant of this implementation, the activated parameter set remains unchanged within the regulator during the regulator's digital adjustment cycle. During the corresponding adjustment cycle, the regulator performs determined internal calculations based on the input values ​​to subsequently provide its adjustment result at its output. This ensures that no parameter changes occur within the regulator during its internal processing, which could lead to unpredictable adjustment results, and thus avoids this. Consequently, the regulation and the converter become more stable.

[0022] This invention is based on the following understanding, observation, or consideration, and also includes the following embodiments. Here, these embodiments are also referred to herein in a simplified form as "this invention." These embodiments may also include a portion or combination of the embodiments mentioned above, or corresponding to them, and / or, if necessary, include embodiments not mentioned to date.

[0023] This invention is based on the understanding that the power factor thus describes the ratio of absorbed active power to apparent power. To optimize this ratio, the absorbed grid current is first regulated in PFC. The output voltage plays only a subordinate role and may only be regulated with small dynamics due to the regulation technique. Therefore, by principle, power supply units with PFC functionality typically have poor transient behavior, meaning that load surges at the output can only be poorly regulated and react with strong voltage drop and overshoot. If the poor transient behavior of the PFC stage is unacceptable for the application, then in many cases, for example, it can be considered to have a second power supply stage switching between PFC and the appliance with higher regulation dynamics.

[0024] In modern audio amplifiers, the power supply is implemented in two stages, for example, consisting of a power accelerator (PFC) and a main power supply, which is often implemented unregulated for cost and efficiency reasons. Alternatively, it may be implemented in a single stage using a single-stage PFC.

[0025] If power is now being jerked across the amplifier, this causes a voltage drop across the output capacitor of the main power supply. While the main power supply can keep the voltage drop small through its own regulation (as long as it generally exists), it still draws high current from the intermediate circuit capacitor in a jerking manner. Due to the inherently low voltage regulation dynamics of the PFC, it can only react slowly to new load conditions. Inevitably, a strong voltage drop occurs in the intermediate circuit.

[0026] Depending on the main power supply topology, this can also cause problems until the output voltage collapses. The latter is particularly problematic when the main power supply topology is unregulated. The main power supply topology transmits intermediate loop voltage to the output voltage side with only a fixed transfer factor and therefore also transmits load collapse of the intermediate loop voltage.

[0027] Another challenge in dynamically loaded PFC stages is that when the intermediate loop voltage collapses below the instantaneous grid voltage, the PFC boost diode begins to conduct, and therefore the current drawn by the device can no longer be controlled by the PFC. On the one hand, it can no longer be guaranteed that the boost diode operates at a safe operating point, and on the other hand, the harmonic spectrum is undefined.

[0028] The following are the technical considerations for adjusting the aforementioned situation: PFC typically consists of two regulation loops. The internal current regulation loop regulates the absorbed current and makes it follow the mains voltage. This regulation requires high dynamics and is essentially responsible for the harmonic spectrum of the current absorbed by the device. The external second regulation loop—voltage regulation—regulates the intermediate loop voltage (in the case of a classic two-stage boost PFC) or the output voltage (in the case of a single-stage PFC). It must be considered here that the external regulation loop, voltage regulation, must have much lower dynamics than the internal current regulation loop.

[0029] If the voltage regulation is designed with excessive dynamism, it attempts to regulate the 100Hz frequency inherent in the intermediate circuit (in the case of a 50Hz grid operation), which adversely affects the harmonic spectrum. Here, the third harmonic of the harmonic spectrum is significantly increased.

[0030] Therefore, the basic idea of ​​this invention is as follows: If the voltage across the intermediate circuit capacitor is within certain limits, slow regulation is used to adjust the intermediate circuit voltage. This ensures an optimal power factor for low and medium loads. If a load jump now occurs, the voltage across the output capacitor and therefore also across the intermediate circuit capacitor will collapse sharply.

[0031] Once the intermediate loop voltage drops below a certain limit, the regulation algorithm switches to a faster set of parameters, which provides rapid counter-effects and counteracts or even prevents further collapse. This avoids a situation where the PFC voltage collapses to such an extent that the PFC diode becomes conductive and the current it draws becomes uncontrolled for one or more grid half-waves.

[0032] If the voltage in the intermediate circuit exceeds the upper limit again, the regulation is switched back to the initial set of regulation parameters. Alternatively, this switching can occur in a controlled manner based on power or approximately in time.

[0033] The method described has no significant impact on the measured harmonic spectrum below the standard limits. The harmonic spectrum is obtained by measuring the current absorbed by the circuit over a certain time period—according to applicable standards, but typically a few seconds—and decomposing it into its components using Fourier analysis. Depending on the frequency of intervention, slight, usually non-critical, increases in the measured values ​​occur in higher-frequency harmonics. It is impossible to operate continuously with these varied adjustment parameters because, as mentioned above regarding considerations of adjustment techniques, a strong increase in the third harmonic may occur. The main focus of this method is to prevent / reduce voltage drop across the intermediate-loop capacitor and, in extreme cases, to prevent bypass caused by the PFC turning on the boost diode.

[0034] This invention is based on the understanding that the principle of dynamically adjusting parameter changes can be applied not only to audio amplifiers but also to many other applications. When an appliance operating through a power supply with PFC functionality exhibits high dynamism, this invention can always improve the stability of its internal operating voltage. Because electronic devices are now mostly controlled by digital control units, in many cases, a suitable signal regarding the accumulated power of the appliance is available, which is appropriately coupled to the regulation of the PFC stage.

[0035] According to the present invention, improvements are made, particularly in the transient behavior of a dynamically loaded PFC circuit in an audio amplifier, by adjusting parameters that depend on the intermediate loop voltage. Attached Figure Description

[0036] Further features, effects, and advantages of the invention will become apparent from the following description of preferred embodiments and the accompanying drawings. Here, schematic schematic diagrams illustrate: Figure 1 The converter according to the present invention. Detailed Implementation

[0037] Figure 1 The converter 2 is shown in the form of a CCM average current mode boost converter.

[0038] Converter 2 is used to convert the DC input voltage UE into a DC output voltage UA. Converter 2 includes an inductor 4 and a capacitor 6, which are interconnected in a power-guiding path 8.

[0039] Converter 2 includes a regulator 12 for adjusting the current voltage value of the output voltage UA toward a desired value UAS. Regulator 12 includes a parameter group 14a that currently determines its regulating behavior. Therefore, parameter group 14a is currently active in regulator 12.

[0040] Furthermore, converter 2 includes a measurement module 16 for determining at least one characteristic value K of at least one characteristic parameter 18 of converter 2. In this example, characteristic parameter 18 is the output voltage UA, and characteristic value K is the current voltage value UAI (the actual value of UA). Therefore, measurement module 16 is a voltage measuring device. Alternatively or additionally, in other embodiments, characteristic parameter 18 is the power P delivered by the converter (indicated by the arrow) or time ta, during which parameter group 14 is active. Measurement module 16 is accordingly configured as a power measuring device or a time measuring device (not shown).

[0041] The converter 2 contains a total of multiple parameter groups 14a-c for the regulator 12. Parameter group 14b or 14c can also be activated in the regulator 12. The corresponding activated parameter group 14a, 14b, or 14c then determines the current regulation behavior. The two corresponding other parameter groups are not activated. Therefore, the (activated) parameter group 14 can be replaced in the regulator 12.

[0042] Therefore, in this example, parameter group 14a is activated first. Thus, regulator 12 operates based on parameter group 14a. Parameter groups 14b and 14c currently have no effect on the regulating behavior.

[0043] Converter 2 includes a control module 20. This control module is used not only to replace but also to activate a corresponding parameter group from parameter groups 14a to c in regulator 12. Control module 20 performs replacement and activation based on at least one of the characteristic parameters 18, where, in this example, there is only one unique characteristic parameter 18 as the output voltage UA. In this example, its characteristic value K is the current value (voltage value UAI) of characteristic parameter 18 (UA). In an alternative example, a second characteristic parameter 18 exists in the form of power P. The corresponding additional characteristic value K is the current power value of power P or the power change per unit time. Therefore, in converter 2, there are two different characteristic values ​​K, which are provided to control module 20 and used by the control module to select parameter groups 14a to c.

[0044] Regulator 12 has an internal sub-regulator 22 (part of an internal regulating loop) and an external sub-regulator 24 (part of an external regulating loop). The internal regulating loop or sub-regulator 22 adjusts the current value Ia to the desired value IS. Finally, the external regulating loop or sub-regulator 24 adjusts the DC output voltage UA to its desired value UAS based on its current voltage value (actual value UAI). Here, only the parameter set 14a-c of the external sub-regulator 24 is replaceable. Therefore, the internal sub-regulator 22 operates with a fixed parameter set.

[0045] The converter 2 has a memory 26 for parameter groups 14a-c, wherein the memory 26 contains a lookup table for parameter groups 14a-c or is implemented as such a lookup table. Therefore, in this example, the characteristic value K in the form of voltage value UAI is compared with the corresponding value range 28a-c, and if the value K is within the corresponding value range 28a-c, the relevant parameter group 14a, 14b, or 14c is activated and used for the regulation of the regulator 12.

[0046] In this example, regulator 12 is a digital regulator. Therefore, the characteristic value K and the DC output voltage UA are controlled by the analog-to-digital converter (A / D-Umsetzer) 30. The current regulation result is output as the current regulation result of PWM stage 32 in the form of duty cycle PWM for pulse width modulation (i.e., the value of PWM[n]), using the values ​​UA[n] and K[n] of the current scan, as well as the corresponding values ​​(not further shown) stored in regulator 12 from the previous scan intervals [n-1] and [n-2]. Here, the duty cycle PWM[n-1] and PWM[n-2] output at the previous scan times [n-1] and [n-2] are also considered in regulator 12. The duty cycle PWM operates via switch 34 in converter 2, as is generally known in common converters, and therefore will not be elaborated further here.

[0047] The time interval between the output of duty cycle PWM[n] and the corresponding input values ​​UA[n] and K[n] is called the adjustment period Z. Figure 1 The arrows symbolically indicate this. During the duration of the regulation period Z, the corresponding parameter group 14a, b, or c remains active in the regulator 12, meaning the entire regulation algorithm is performed according to one of parameter groups 14a to c. After the end of the regulation period Z and before the start of a new regulation period Z, that is, before the analysis and processing of the output voltage UA and characteristic parameter K in the regulator 12 begins, another parameter group from parameter groups 14a-c may be activated only if necessary—according to the decision of the control unit 20.

Claims

1. A converter (2) for converting an input voltage (UE) into a DC output voltage (UA), said converter having a regulator (12) for regulating the DC output voltage (UA) towards a desired value (UAS), wherein The regulator (12) includes a set of parameters (14a-c) that determine its regulatory behavior. Its features are, The converter (2) includes a measurement module (16) for obtaining at least one characteristic value (K) of at least one characteristic parameter (18) of the converter (2), and The converter (2) includes at least two replaceable parameter sets (14a-c) for the regulator (2), wherein a corresponding parameter set of the parameter sets (14a-c) can be activated in the regulator (2). The first parameter in the parameter set (14a-c) has a slower regulation behavior in terms of the DC output voltage (UA) compared to the second parameter in the parameter set (14a-c). The converter (2) includes a control module (20) for replacing and activating a corresponding parameter group in the parameter group (14a-c) according to at least one of the characteristic parameters (18) in the regulator (2). The regulator (2) has an internal sub-regulator (22) for the current value (Ia) and an external sub-regulator (24) for the voltage value (UAI) of the DC output voltage (UA), and the parameter group (14a-c) of the external sub-regulator (22) is replaceable. Specifically, once the intermediate loop voltage of the converter drops below a predetermined limit, it switches to the faster second parameter group. The internal sub-regulator (22) operates with a fixed set of parameters. The regulator (12) is a digital regulator (12). The activated parameter group (14a-c) remains unchanged in the regulator (2) during the adjustment period (Z) of the digital value of the regulator (2).

2. The converter (2) according to claim 1, characterized in that The characteristic parameter (18) is the output voltage (UA) and / or time (ta) and / or power (P) delivered through the converter (2).

3. The converter (2) according to claim 2, characterized in that The faster parameter set (14a-c) is activated when the output voltage (UA) is outside the tolerance range and / or when the rate of change of the power (P) per unit time exceeds a limit value.

4. The converter (2) according to claim 2 or 3, characterized in that When the output voltage (UA) is within the tolerance range and / or when the rate of change of the power (P) per unit time is below a limit value and / or when a slower parameter group (14a-c) is activated at the end of a time interval (ta) after the faster parameter group is activated.

5. The converter (2) according to any one of the preceding claims, characterized in that Memory (26) for the parameter group (14a-c).

6. The converter (2) according to claim 5, characterized in that The memory (26) contains lookup tables for the parameter sets (14a-c).

7. The converter (2) according to any one of the preceding claims, characterized in that The converter (2) is a boost converter.

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