TWI399018B - Current ripple cancelling circuit - Google Patents

Description

Current chopping cancellation circuit

The invention is a current chopping elimination technology, which discloses a current chopping elimination method and circuit suitable for a switching power converter, which is capable of achieving current chopping at the input or output of a conventional switched power converter. Eliminate the purpose of power electronics technology.

Switched power converters are widely used in computer communication, automation, and industrial products due to their high efficiency, high density, small size, and light weight. However, since the switching power converter adopts an active switching or an on/off control strategy, there is a high frequency current ripple. In practical applications, it derives many problems such as electromagnetic interference (EMI), affecting output voltage quality, transient response control, reducing conversion efficiency, and filter element lifetime. In the past, the easiest way to improve high-frequency current chopping is to increase the switching frequency or increase the value of the filter inductor or capacitor to reduce its effects. However, increasing the switching frequency will reduce the conversion efficiency and increase the filter inductance or capacitance, which is likely to cause excessive volume and is not conducive to the converter power density [1-2].

At present, the existing chopping elimination technology can be roughly divided into passive and active. The passive chopper cancellation circuit is mainly a filter circuit composed of passive components such as inductors and capacitors, and does not need any additional control signals. The coupled inductor (Coupling Inductor) method [3-7] and the Ripple Filter [8-11] discussed in the literature are passive chopper cancellation techniques. Coupling inductors are often used in non-isolated Cuk converters. The main concept is to use a shared magnetic component to form a coupled inductor, and then adjust the inductor value and its coupling coefficient to achieve output and input zero chopping current. Unfortunately, this method is not suitable for basic converters such as buck, boost and buck-boost, which only contain a single inductor, and the effect of chopping elimination is achieved by adjusting the coupling coefficient, which requires precision process technology and is therefore difficult to achieve. Zero current chopping is eliminated. In addition, the leakage inductance energy generated by the coupled inductor winding must also be properly resolved to avoid affecting converter efficiency. Another type of current ripple filter (Current Ripple Filter) is composed of a coupled inductor and a filter capacitor. This method can be applied to a converter with only a single inductor, but the effect is still susceptible to the inductive coupling coefficient.

Compared with the above passive cancellation technology, the active chopper cancellation circuit is composed of a passive component and an active power switch, so an external driving signal is needed to control the auxiliary circuit. The active chopper cancellation circuit mentioned in the literature, the most common is the parallel converter of interleaving control [12-14]. Although the interleaved control switching strategy has the advantages of reducing converter current ripple and reaching load sharing, there are some limitations in this method. In addition to the complexity and cost of the control loop, this method is not suitable for current chopping cancellation of a single converter. In addition, the chopping effect of the interleaved control is limited by the duty cycle of the switch. When the duty cycle leaves the design operating point, the current ripple generated by the converter cannot be completely eliminated.

【references】

[1] SS Ang, Power Switching Converters. Marcel Dekker, Inc. 1995.

[2] RW Erickson and D. Maksimovics, Fundamentals of Power Electronics. Kluwer Academic Publisher, Inc. 2001.

[3] AF Witulski, "Introduction to Modeling of Transformers and Coupled Inductors," IEEE Transactions on Power Electronics , Vol. 10, No. 3, pp. 349357, May 1995.

[4] R. Martinelli and C. Ashley, "Coupled Inductor Boost Converter with Input and Output Ripple Cancellation," IEEE Applied Power Electronics Conference , pp. 567-572, 1991.

[5] J. Wang, WG Dunford, and K. Mauch, "Analysis of a Ripple-Free Input-Current Boost Converter with Discontinuous Conduction Characteristics," IEEE Transactions on Power Electronics , Vol. 12, No. 4, pp. 684 -694, July 1997.

[6] S. Cuk, "A New Zero-Ripple Switching DC-to-DC Converter and Integrated Magnetics," IEEE Transactions on Magnetics , Vol. 19, No. 2, pp. 57-75, Mar. 1983.

[7] J. Wang, WG Dunford, and K. Mauch, “Design of Zero-Current-Switching Fixed Frequency Boost and Buck Converters with Coupled Inductors,” IEEE Power Electronics Specialists Conference , pp. 273-279, 1995.

[8] DC Hamill and PT Krein, "A'Zero'Ripple Technique Applicable To Any DC Converter," IEEE Power Electronics Specialists Conference , pp. 1165-1171, 1999.

[9] DS Lymar, TC Neugebauer, and DJ Perreault, "Coupled -Magnetic Filters with Adaptive Inductance Cancellation," IEEE Power Electronics Specialists Conference , pp. 590-600, 2005.

[10] JW Kolar, H. Sree, N. Mohan, and FC Zach, "Novel Aspects of an Application of 'Zero'-Ripple Techniques to Basic Converter Topologies," IEEE Power Electronics Specialists Conference , pp. 796-803, 1997 .

[11] MJ Schutten, RL Steiqerwald, and JA Sabate, "Ripple Current Cancellation Circuit," IEE E Applied Power Electronics Conference , pp. 464-470, 2003.

[12] BR Linand CL Huang, “Interleaved ZVS Converter with Ripple-Current Cancellation,” IEEE Transactions on Industrial Electronics , Vol. 55, No. 4, pp. 1576-1585, April 2008.

[13] S. Chandrasekaran and LU Gokdere, "Integrated Magnetics for Interleaved DC-DC Boost Converter for Fuel Cell Powered Vehicles," IEEE Power Electronics Specialists Conference , pp. 356-361, 2004.

[14] TF Wu, JR Tsai, YM Chen, and ZH Tsai, "Integrated Circuits of a PFC Controller for Interleaved Critical-Mode Boost Converters," IEEE Applied Power Electronics Conference , pp. 1347-1350, 2007.

Therefore, the object of the present invention is to provide a Current Ripple Cancelling Circuit for eliminating the disadvantages of the above existing methods, which can be used for eliminating high frequency current ripple at the input or output of the switching power converter. So that it reaches zero input or zero output current chopping.

Another object of the present invention is to provide a current chopping cancellation circuit which does not require any external active power switch, and thus does not increase the cost of the active switch and its driving circuit.

A further object of the present invention is to provide a current chopping cancellation circuit that does not require additional control and feedback circuitry and therefore does not affect the stability of the original switched power converter. In addition, the current ripple cancellation effect of this circuit is not limited by the output voltage or input voltage specifications set by the original switching converter and the switching duty cycle, so it can be widely used.

A further object of the present invention is to provide a current chopping cancellation circuit which is different from a parallel converter which is conventionally used for interleaving control. The invention can be applied to a single converter and can be used as a conventional switching converter. The use of a smaller energy storage inductor reduces the converter power loss caused by copper losses and ripples.

According to the above object of the present invention, a current chopping cancellation circuit is proposed, comprising at least a high frequency transformer, a chopper cancellation inductor and two DC blocking capacitors. Wherein, the high frequency transformer is matched with the blocking capacitor and the chopper eliminating inductor to provide a high frequency chopping current, and the charging and discharging waveform and the slope of the high frequency chopping current are opposite to the inductance current of the original switching power converter. The resulting current observed by the converter at the input or output has zero chopping characteristics. Among them, the DC blocking capacitor is used to block the DC component from entering the current chopping elimination circuit, so that the circuit only contains the AC chopping component, so it does not cause excessive energy loss, and does not need to be additionally applied with active power switch control. The ground reaches the current chopping elimination effect.

In the following, the specific embodiments and the accompanying drawings are explained in detail, and it is easier to understand the technical contents, characteristics and effects of the invention.

Please refer to the first figure, which is the current chopper elimination circuit of the invention. The circuit consists of a high frequency transformer (103), a chopping cancellation inductor (102) and two DC blocking capacitors (104, 105). The primary side and the secondary side of the high-frequency transformer are respectively connected in series with the DC blocking capacitor and respectively connected to the converter inductor (101) through which the current chopping is to be eliminated, and the chopper eliminating inductor can be respectively The current chopper cancellation circuit of the present invention is formed by being connected in series between the primary side or secondary side capacitor of the high frequency transformer and the end of the high frequency transformer.

Please refer to the second figure, which shows the original converter inductor current i _L , the chopping elimination inductor current i _Lf and the compensated synthesized zero chopping current waveform i _{l in the} above first figure. When the inductance L of the original switching power converter is a constant constant voltage, the current i _L rises linearly; at this time, the primary side of the high-frequency transformer is a positive voltage, and the chopper eliminates the inductance after being mapped by the high-frequency transformer. The voltage across L _f becomes a negative voltage, so the current i _Lf decreases linearly. According to the working principle of the above circuit, when the voltage across the inductor L is negative, the current i _L decreases linearly; at this time, the primary side of the high-frequency transformer is a negative voltage, and the chopper eliminates the inductance L after being converted by the high-frequency transformer. _The voltage across _f becomes a positive voltage, so the current i _Lf rises linearly to compensate for i _L . As shown in the second figure, when the rising slope of the current i _L and the falling slope of the current i _Lf are opposite each other, the chopping eliminating inductor current i _Lf can completely compensate the current chopping of the original converter inductor current i _L , The compensated resultant current i ₁ will be a pure DC current with zero chopping. According to the above principle, the present invention proposes a current chopping cancellation circuit suitable for a switching power converter.

For convenience of further explanation, the secondary side blocking capacitor of the current chopper cancellation circuit of the present invention is equivalent to the high frequency transformer turns ratio (Turn Ratio) to the primary side to become an equivalent capacitance C _f , which can be expressed as follows:

At the same time, Ikehoff's voltage and current law can list equations (2) to (4):

Wherein V ₁ and V ₂ are the input terminal voltage and the output terminal voltage in the first figure, respectively, and v _cf is the terminal voltage of the equivalent capacitance C _f .

From equations (2) to (3), the current change rate after compensation by the circuit of the present invention can be obtained as follows: Assume that the rate of change of current after synthesis is zero, that is, when there is no current chopping, Then we can further derive the following equation (7): nL _f = L (7)

Substituting equation (7) into equation (8),

According to the above derivation, the current chopping elimination circuit of the present invention can design the chopping elimination inductance value and the high frequency transformer turns ratio to achieve the zero chopping current effect according to the formula (7), and the terminal voltage of the equivalent DC blocking capacitor C _f . The value is determined by equation (10).

Therefore, the current chopper cancellation circuit invented by the present invention can be applied to a buck converter, a boost type (Boost), a Sepic type, a Zeta type, a Cuk type, etc., as shown in the third figure. As shown in the seventh figure, a switched power converter with zero input or zero output current chopping is formed.

According to the foregoing theory, the present invention implements and measures an embodiment of a Cuk-type DC power converter with zero input current chopping. The basic specifications of the circuit are input 36V _dc , output 24V _dc , switching frequency 20kHz and rated power 150W. The input inductance of the implementation circuit and the voltage measurement waveform of the chopper cancellation inductor are as shown in the eighth figure. Referring to the eighth figure, it can be seen that the inductor input voltage across the voltage v _{L1 is} opposite to the ripple cancellation inductor voltage across the voltage v _Lr1 , so that the chopping elimination inductor chopping can be used to compensate the input terminal inductor current chopping. . For the relevant current waveform in this circuit example, please refer to the ninth figure. When the converter switch is turned on, the input terminal inductor current i _L1 is positive slope rising, and the chopping elimination inductor current i _Lr1 is negative slope decreasing; when the converter switch is turned off When the input terminal inductor current i _L1 is negatively decreasing, the chopping elimination inductor current i _Lr1 is positive slope rising, so the chopping elimination inductor chopping can be used to compensate the input terminal inductor current chopping, so that the synthesized input current涟The wave Δ i _{s is} almost zero. Therefore, the above measured waveform can prove that the current chopping elimination circuit of the present invention does have a good chopping elimination effect. Of course, we can also apply to the converter shown in Figure 7 to obtain zero input and zero output current chopping effect.

According to the foregoing theory, the present embodiment is further described by taking a single-phase AC power converter with zero output current chopping as an embodiment. When the switching frequency is much higher than the AC frequency of the converter input or output, the AC voltage can be regarded as DC voltage in a switching cycle. Therefore, please refer to the tenth figure. The basic specifications of the circuit are 200Vdc input and 110V output. _Rms / 60Hz, switching frequency 20kHz and rated power 400W. When the circuit is operated, the power switch is controlled by Sinusoidal Pulse Width Modulation (SPWM). The measured waveforms of the output AC voltage v _o , the output current i _o , the output inductor current i _{Lo ,} and the chopping elimination inductor current i _Lf of the real circuit are as shown in FIG. 11 and FIG. 12 , respectively. Please refer to the eleventh and twelfth figures. Even if there is current chopping on the output inductor, the output current after chopper-eliminating inductor current compensation can still reach zero chopping. This means that after the chopper cancellation circuit is added, the converter can use a smaller filter inductor value to reduce the wirewound resistance, while the output zero current chopping characteristic still exists. In addition, the converter embodiment can prove that the chopping cancellation characteristic of the circuit is based on the theory and the switching duty cycle, frequency and input of the original power converter under the condition that the switching duty cycle is continuously varying sinusoidal pulse width modulation. The output voltage specification does not matter.

According to the measured results of the above two embodiments, it can be known that after the switching power converter is added to the current chopper cancellation circuit of the present invention, the current at the input or output can reach zero chopping. Therefore, this creative invention has the following four contributions:

1. This current chopping cancellation circuit can be used to eliminate the current chopping at the input or output of the switching power converter, which is characterized in that it does not need to additionally increase the active switch and its driving circuit.

2. This current chopping cancellation circuit is independent of the switching duty cycle, switching frequency, input voltage, and output voltage specifications of the original power converter.

3. This current chopping cancellation circuit is simple and easy to modular, making it easy to integrate into a switching power converter.

4. This current chopping cancellation circuit extends its application to isolated DC power converters, as well as three-phase AC/DC or DC AC power converters.

In summary, the current chopping cancellation technology provided by the present invention is applied to a switching power converter, so that the input or output of the converter becomes zero chopping current, effectively improving the lack of the aforementioned prior art, so that The industrial value, in turn, achieves the purpose of developing the invention.

The above-mentioned embodiments are merely illustrative of the technical idea and features of the present invention, and the purpose thereof is to enable those skilled in the art to understand the contents of the present invention and implement it according to the invention, and the patent of the creation cannot be limited thereto. The scope, that is, the equivalent changes and modifications made by the general disclosure of the invention, should be covered by the scope of the invention.

101‧‧‧Transducer inductance

102‧‧‧ ripple elimination inductor

103‧‧‧High frequency transformer

104‧‧‧Primary DC blocking capacitor

105‧‧‧secondary DC blocking capacitor

First figure: shows the circuit architecture diagram of the present invention.

The second figure shows the converter inductor current i _L , the chopping elimination inductor current i _Lf and the compensated synthesized zero chopping current waveform i _{1 in the} first figure.

Fig. 3 is a circuit diagram showing the circuit of a buck switching power converter having a zero output current chopper after the current chopper cancellation circuit of the present invention is added.

Fig. 4 is a circuit diagram showing the circuit of a Boost switching power converter with zero input current after the current chopper cancellation circuit of the present invention is added.

Fig. 5 is a circuit diagram showing the circuit of a switched-type power converter with a zero input current chopping Sepic type after the current chopper cancellation circuit of the present invention is added.

Fig. 6 is a circuit diagram showing the circuit diagram of a zero-output current chopping Zeta switching power converter after the current chopper cancellation circuit of the present invention is added.

Figure 7 is a circuit diagram showing the chopper-type switching power converter with zero input and zero output current after the current chopper cancellation circuit of the present invention is added.

Figure 8: This example shows the implementation of the zero-input chopper Cuk-type switching power converter. The measured input voltage of the converter is measured across the voltage v _L1 and the ripple-eliminating inductor cross-voltage v _Lr1 measured waveform.

The ninth picture shows that the case is implemented as a zero-input chopper Cuk-type switching power converter. The converter input inductor current i _L1 , the chopping elimination inductor current i _Lr1 and the combined input current chopping Δ i are measured. _s measured waveform.

Fig. 10 is a circuit diagram showing the circuit of a single-phase AC power converter with zero output current chopping after the current chopper cancellation circuit of the present invention is added.

Figure 11: This shows the single-phase AC power converter with zero output current chopping. The measured output voltage v _o , output current i _o , output inductor current i _Lo , chopping elimination inductor current i _Lf measured waveform.

Twelfth figure: This shows the single-phase AC power converter that implements zero output current chopping. The measured output voltage v _o , the output current i _o measured waveform and the output inductor current i _Lo , the chopping elimination inductor The current i _{Lf is a} measured waveform enlarged view.

101. . . Converter inductance

102. . . Chopper elimination inductance

103. . . High frequency transformer

104. . . Primary side DC blocking capacitor

105. . . Secondary side DC blocking capacitor

Claims (8)

A current chopper cancellation circuit applicable to a switched power converter, characterized in that a circuit comprising a high frequency transformer, a chopper cancellation inductor and two DC blocking capacitors is combined with a switched power conversion The switching of the active power switch of the device forms a switched power converter with zero input or zero output current chopping, wherein: the high frequency transformer operates according to the active power switch of the switched power converter to Eliminating an AC square wave voltage generated on the inductor; the DC blocking capacitors are electrically connected to the primary side and the secondary side of the high frequency transformer, respectively, for blocking the DC component from entering the current ripple cancellation circuit, so that the circuit only includes AC chopping component, so it does not cause excessive energy loss; the chopper eliminating inductor is electrically connected between the primary side or secondary side capacitor of the high frequency transformer and the end point of the high frequency transformer, and uses the high frequency transformer The reverse AC square wave voltage is generated, which in turn generates an appropriate ripple to cancel the inductor current. A zero-input or zero-output current chopping switching power converter as described in claim 1, wherein the basic zero-output current chopping-switching power converter includes a buck switching power conversion Device. A zero-input or zero-output current chopping switching power converter as described in claim 1, wherein the basic zero-input current chopping-switching power converter includes a boost-type switching power conversion Device. A switched input power converter of zero input or zero output current chopping as described in claim 1 wherein the basic zero input current chopping switching power converter comprises a Sepic type switching power converter. A switched input power converter of zero input or zero output current chopping as described in claim 1 wherein the basic zero output current chopping switching power converter comprises a Zeta switched power converter. A zero-input or zero-output current chopping switching power converter as described in claim 1, wherein the basic zero-input and zero-output current chopping-switching power converter includes a Cuk-type switching power converter . A switching power converter with zero input or zero output current chopping as described in claim 1, wherein the basic zero output current chopping switching power converter comprises a single phase or three phase direct AC switching power converter. A zero-input or zero-output current chopping switching power converter as described in claim 1, wherein the basic zero-input current chopping-switching power converter includes a single-phase or three-phase AC-DC switching power conversion Device.