E-type resonant inverter circuit supporting wide load range constant current output

Abstract

The invention provides an E-type resonant inverter circuit supporting wide load range constant current output, and belongs to the technical field of circuits and systems. The circuit comprises an input unit, an output unit and a load network, the input unit comprises a DC power supply voltage Vin, a resonant inductor Lin, a resonant capacitor Cin and a switching tube S, the output unit comprises a filter inductor L1, a filter capacitor C1 and a filter capacitor C2, and the load network is a load resistor RL; a network formed by an inductor, a capacitor and a switch tube of the input unit is equivalent to a constant-output alternating current voltage source; capacitors, inductors and capacitors of the output unit form a voltage and current conversion unit, and an input end alternating current voltage source is converted into an alternating current source, so that the alternating current source is equivalent to an alternating current source with constant current output. Constant current output is achieved without control of an external feedback circuit, the circuit structure is simple, optimization and compromise of indexes in multiple aspects such as soft switching and load change insensitivity can be supported at the same time, and wide application prospects are achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of circuits and systems, and in particular relates to a topological design of a class E resonant inverter circuit supporting constant current output over a wide load range. Background Art

[0002] With the development of consumer electronics, people's demand for small-sized, high-performance electronic devices continues to increase. Inverters are converters that convert DC power (batteries, storage batteries) into constant-frequency, constant-voltage or frequency-modulated, voltage-regulated AC power. They are widely used in wireless power transmission, gate drivers, battery chargers, and other places. In order to reduce the size of electronic equipment, it is necessary to miniaturize the power converter, and Class E converters have important appeal in these applications. Compared with the traditional totem pole structure, the Class E inverter uses a single switch and is adaptable to zero-voltage switching, so the number of electronic components can be reduced. At the same time, the resonant circuit of the Class E switch topology can achieve higher-frequency working conditions, thereby reducing the size of passive components to achieve miniaturization. Therefore, the inverter circuit based on the Class E topology is of great significance to the miniaturization of power supplies and electronic devices.

[0003] The classic class E inverter is a milestone in switching high-frequency amplifiers. It uses a choke inductor at the input and a series resonant circuit at the output to achieve zero voltage switching at the moment of switch on. However, these switching conditions are very sensitive to changes in load resistance. Deviation from the switching conditions will lead to reduced power conversion efficiency and changes in output power. In practical applications, it is necessary to maintain the stability of power conversion efficiency and output voltage or current. At present, the academic community has proposed a class E inverter that is independent of the load, has a constant output voltage, and maintains high-efficiency operation, which has attracted people's attention in the application of wireless power transmission. In the application of actual charging mode, achieving constant output current is also an important part, but it is difficult to achieve a current source with constant current output based on a pure class E topology. The existing constant current output inverter has a complex structure and can only achieve constant current output under a small range of load changes. There is little mention of an inverter that has a simple structure and is insensitive to load changes and achieves constant current output in a wide load range. Therefore, it is of great significance to study a class E resonant inverter circuit with a simple structure and constant current output over a wide load range. Summary of the invention

[0004] In view of the problems existing in the above-mentioned prior art, the present invention proposes a class E resonant inverter circuit that supports constant current output in a wide load range, realizes the constant current output function in the load range of 0.5 ohms to 80 ohms, and has a simple circuit structure. The power device always maintains soft switching operation throughout the whole process, which is suitable for inverter circuit applications such as high-efficiency and miniaturized wireless charging.

[0005] The technical solution of the present invention is as follows:

[0006] A class E resonant inverter circuit supporting constant current output over a wide load range, characterized in that it comprises an input unit, an output unit and a load network, wherein the input unit comprises a DC power supply voltage V in , resonant inductor L in , resonant capacitor C in and switch tube S, the output unit includes filter inductor L1, filter capacitors C1 and C2, and the load network is load resistor R L In the input unit, the DC power supply voltage V in The positive electrode and the resonant inductor L in The negative electrode is connected to one end of the switch tube S connected in parallel with it, and the resonant inductor L in The other end of the switch tube S is connected to the other end of the resonant capacitor C in In the output unit, one end of the filter inductor L1 is connected to the resonant capacitor C in , resonant inductor L in The other end is connected to the switch tube S, and the other end is connected in parallel to one end of the filter capacitor C1 and in series to one end of the filter capacitor C2. The other end of the filter capacitor C2 is connected in series with the load resistor R L , load resistance R L The other end of the filter capacitor C1 and the DC power supply voltage V in negative connection.

[0007] Furthermore, an equivalent circuit analysis is performed using a frequency domain analysis method. The network composed of the resonant inductor, resonant capacitor and switch tube of the input unit is equivalent to an AC voltage source with a constant output. The filter capacitor, filter inductor and filter capacitor of the output unit form a voltage-current conversion unit, which converts the input AC voltage source into an AC current source, making it equivalent to an AC current source with a constant current output. Combined with the small signal current gain of the equivalent circuit, the operating frequency f of the switch tube at which the output current of the circuit remains constant as the load changes is found, and the conditions are met:

[0008] Furthermore, the output unit filters out the harmonic components in the equivalent voltage source, and the output current is a standard sinusoidal waveform.

[0009] Furthermore, the switch tube S in the input unit is driven by a square wave signal.

[0010] The technical effects of the present invention are as follows:

[0011] (1) Through the integrated design of input unit, output unit and load network, an inverter circuit with constant current output in a wide load range is realized, and constant current output is achieved without the control of external feedback circuit.

[0012] (2) The circuit structure of the present invention is simple and can simultaneously support the optimization and compromise of multiple indicators such as soft switching and load change insensitivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is the circuit principle diagram of the present invention;

[0014] Figure 2 is an equivalent circuit diagram of the circuit input unit of the present invention;

[0015] Figure 3 An equivalent circuit diagram common to the input and output circuits of the circuit of the present invention;

[0016] Figure 4 It is the frequency domain small signal characteristic of the constant current output of the circuit of the present invention under different load conditions. DETAILED DESCRIPTION

[0017] The present invention will be further clearly and completely described below through specific embodiments in conjunction with the accompanying drawings.

[0018] The class E resonant inverter circuit supporting constant current output over a wide load range proposed by the present invention provides a constant output current and zero voltage switching of the switch over a wide load range. Figure 1 As shown, it includes an input unit, an output unit and a load network. The input unit includes a DC power supply voltage V in , resonant inductor L in , resonant capacitor C in and switch tube S, the output unit includes filter inductor L1, filter capacitors C1 and C2, and the load network is load resistor R L In the input unit, the DC power supply voltage V in The positive electrode and the resonant inductor L in The negative electrode is connected to one end of the switch tube S connected in parallel with it, and the resonant inductor L in The other end of the switch tube S is connected to the other end of the resonant capacitor C in In the output unit, one end of the filter inductor L1 is connected to the resonant capacitor C in , resonant inductor L in The other end is connected to the switch S, and the other end is connected in parallel to one end of the filter capacitor C1 and in series to one end of the filter capacitor C2. The other end of the filter capacitor C2 is connected in series with the load resistor R L , load resistance R L The other end of the filter capacitor C1 and the DC power supply voltage V in negative connection.

[0019] Using the equivalent circuit method Figure 1 The E-class resonant inverter circuit is analyzed and designed. Figure 2 for Figure 1 The equivalent circuit diagram of the circuit input unit, in which the network composed of the inductor-capacitor-switch tube at the input end can be equivalent to an AC voltage source with a constant output; Figure 3 for Figure 1 The final equivalent circuit diagram of the entire inverter circuit, where Figure 1 The voltage-current conversion unit composed of capacitor-inductor-capacitor of the output unit can convert the input AC voltage source into an AC current source, making it equivalent to an AC current source with a constant current output; combined with the small signal current gain of the equivalent circuit, the operating frequency f of the switching tube at which the output current of the circuit remains constant as the load changes can be found.

[0020] The input unit is analyzed using the frequency domain analysis method. The switch tube S is driven by a square wave signal with a duty cycle of D. The input unit can in Converted into a half-sinusoidal AC voltage V at both ends of the switch tube DS . Resonant inductor L in and capacitor C in In parallel with the switch tube, according to Kirchhoff's voltage law, when the switch tube S is turned off, the voltage V DS The expression for (drain-source voltage) is as follows:

[0021]

[0022] In the formula, ω=2πf, f is the operating frequency of the switch tube S, that is, the frequency of the square wave input to the switch tube S, which is also the operating frequency of the entire circuit and the frequency of the sine wave output of the entire circuit. t is the time, at which the voltage V across the drain and source of the switch tube S is DS is a half-sinusoidal AC voltage, and when the switch tube S is turned on, the voltage across the drain and source V DS is 0; therefore, during the period of the switch tube S being turned off and on, a half-sinusoidal AC voltage can be obtained across the drain and source of the switch tube S.

[0023] The output unit is analyzed using the frequency domain analysis method. The LCC network of the output unit has two functions: one is to convert the equivalent voltage source of the input unit into a constant current source through the output unit, and the other is to effectively filter out the harmonic components in the equivalent voltage source, so that the output current is a standard sinusoidal waveform.

[0024] Function 1: By designing the parameters of the specific operating frequency f, the output unit components L1, C1 and C2, the independence of the load can be ensured, that is, when the load value changes, the circuit can still maintain a constant current output. Figure 2 ; To ensure the output current amplitude and load resistance R L independent of the output current to maintain constant current and to facilitate the conversion of the voltage source into a current source, V DSFundamental voltage V DS_1 With the output current I out The relationship between them is derived as follows:

[0025]

[0026] In the formula, ω=2πf, and the operating frequency f of the circuit is selected to satisfy the condition That is I out Relative to R L The point where the derivative of is zero. This allows the equivalent voltage source to be converted into a constant current source that is independent of load changes, such as Figure 3 .

[0027] Function 2: The design of the LCC network of the output unit selectively extracts the fundamental frequency component from the output waveform and effectively suppresses high-order harmonics. This design makes the circuit output current waveform close to a sine wave.

[0028] By adjusting the different parameters of the topology, different load variations R can be obtained at different operating frequencies f. L Based on the above analysis, the present invention provides a set of design parameters to illustrate its technical effect; the input voltage is 10V, and the constant current output current is 0.6A in the range of load resistance of 0.5Ω to 80Ω. The circuit component parameters are as follows:

[0029] Switch tube S operating frequency: f = 6.78MHz;

[0030] Inductance: L in =200nH; L1 = 560nH;

[0031] Capacitance: C in =6nF; C1=1nF; C2=100pF;

[0032] like Figure 4 As shown, the current gain does not change with the load at f = 6.78MHz, that is, in a wide load resistance R from 0.5Ω to 80Ω L In addition, the current gain at 13.56MHz is 24dB lower than that at 6.78MHz, which also shows that the circuit design reduces the second harmonic frequency.

[0033] Although the present invention has been disclosed as above with preferred implementation parameters, it is not intended to limit the present invention. Any technician familiar with the art can use the above disclosed methods and technical contents to make many possible changes and modifications to the technical solution of the present invention without departing from the scope of the technical solution of the present invention, or modify it into an equivalent embodiment of equivalent changes. Therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention still falls within the scope of protection of the technical solution of the present invention.

Claims

1. A class E resonant inverter circuit supporting constant current output over a wide load range, characterized in that: It includes an input unit, an output unit and a load network. The input unit includes a DC power supply voltage V in , resonant inductor L in , resonant capacitor C in and switch tube S, the output unit includes filter inductor L1, filter capacitors C1 and C2, and the load network is load resistor R L ; In the input unit, the DC power supply voltage V in The positive electrode and the resonant inductor L in The negative electrode is connected to one end of the switch tube S connected in parallel with it, and the resonant inductor L in The other end of the switch tube S is connected to the other end of the resonant capacitor C in In the output unit, one end of the filter inductor L1 is connected to the resonant capacitor C in , resonant inductor L in The other end is connected to the switch tube S, and the other end is connected in parallel to one end of the filter capacitor C1 and in series to one end of the filter capacitor C2. The other end of the filter capacitor C2 is connected in series with the load resistor R L , load resistance R L The other end of the filter capacitor C1 and the DC power supply voltage V in negative connection.

2. The class E resonant inverter circuit supporting constant current output over a wide load range as claimed in claim 1, characterized in that: The equivalent circuit analysis is performed using the frequency domain analysis method. The network composed of the resonant inductor, resonant capacitor and switch tube of the input unit is equivalent to an AC voltage source with a constant output. The filter capacitor, filter inductor and filter capacitor of the output unit form a voltage-current conversion unit, which converts the input AC voltage source into an AC current source, making it equivalent to an AC current source with a constant current output. Combined with the small signal current gain of the equivalent circuit, the operating frequency f of the switch tube at which the output current of the circuit remains constant with the load change is found to meet the conditions:

3. The class E resonant inverter circuit supporting constant current output over a wide load range as claimed in claim 2, characterized in that: The output unit filters out the harmonic components in the equivalent voltage source, and the output current is a standard sinusoidal waveform.

4. The class E resonant inverter circuit supporting constant current output over a wide load range as claimed in claim 2, characterized in that: The switch tube S in the input unit is driven by a square wave signal.

5. The class E resonant inverter circuit supporting constant current output over a wide load range as claimed in claim 2, characterized in that: Design circuit component parameters: Given input voltage V in =10V; switch tube S operating frequency f = 6.78MHz; resonant inductor L in =200nH; filter inductor L1 = 560nH; resonant capacitor C in =6nF; filter capacitor C1 = 1nF; filter capacitor C2 = 100pF; load R L The resistance range is 0.5Ω~80Ω, and the circuit achieves a constant current output current of 0.6A.

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