Series resonant inverter

Abstract

The utility model discloses a series resonant inverter, which comprises a direct-current filter capacitor Cd, an Nmos circuit, an inductor L, a resistor R and a capacitor C, the Nmos circuit comprises a first Nmos transistor, a second Nmos transistor, a third Nmos transistor and a fourth Nmos transistor; the first Nmos transistor, the second Nmos transistor, the third Nmos transistor and the fourth Nmos transistor are respectively provided with a power switch S1, a power switch S2, a power switch S3 and a power switch S4. One end of the first Nmos transistor is connected with the fourth Nmos transistor, and the other end of the first Nmos transistor is connected with the second Nmos transistor; the other end of the second Nmos transistor is connected with a third Nmos transistor, and the other end of the third Nmos transistor is connected with a fourth Nmos transistor; the inductor L, the resistor R and the capacitor C are connected in series, and a path formed by the connection is connected with the Nmos circuit in parallel. According to the utility model, through the arrangement of the plurality of Nmos transistors and the power switch, the switching loss is relatively small in a proper working mode, so that the power supply can stably work at a relatively high working frequency.

Description

Technical Field

[0001] The utility model relates to the field of resonant converters, and in particular to a series resonant inverter. Background Art

[0002] Energy conversion technology occupies an important position in power electronics technology. The conversion efficiency of the switching converter has a huge impact on whether the converter can be widely used, and the resonant conversion technology plays a vital role in improving the efficiency of the converter and reducing the switching loss. For example, in soft switching technology, the use of circuit resonance can greatly reduce the switching loss and improve the transmission efficiency of the converter circuit; in the wireless power transmission system, the introduction of the resonance link greatly increases the efficiency of short-distance power transmission, which brings great vitality to the promotion and application of wireless power transmission equipment. In addition, the emergence of resonant converters has laid a solid foundation for the high frequency and low noise of energy processing equipment. Its development has promoted the miniaturization of AC and DC energy equipment and greatly improved its reliability. Energy conversion equipment is widely used in home appliances, aviation, instruments, national defense, etc.

[0003] Resonant converter technology is widely used in inverter circuits, especially in the field of high-frequency inverter circuit technology. The series resonant inverter is also called the voltage resonant inverter. The output voltage of the series resonant inverter is approximately a square wave. Since the circuit operates near the resonant frequency, the oscillation circuit has the minimum impedance to the fundamental wave, so the load current is close to a sine wave; at the same time, in order to avoid direct conduction between the upper and lower bridge arms of the inverter, the commutation must follow the principle of shutting down before opening, and sufficient dead time must be left between shutting down and opening. However, there is still no more reasonable circuit structure for the current series resonant inverter. Utility Model Content

[0004] In view of this, the utility model provides a series resonant inverter to solve the above problems.

[0005] In order to solve the above technical problems, the utility model provides a series resonant inverter, comprising:

[0006] DC filter capacitor Cd, Nmos circuit, inductor L, resistor R and capacitor C;

[0007] The Nmos circuit includes a first Nmos transistor, a second Nmos transistor, a third Nmos transistor and a fourth Nmos transistor; the first Nmos transistor, the second Nmos transistor, the third Nmos transistor and the fourth Nmos transistor respectively correspond to power switches S1, S2, S3 and S4;

[0008] One end of the first Nmos transistor is connected to the fourth Nmos transistor, and the other end is connected to the second Nmos transistor; the other end of the second Nmos transistor is connected to the third Nmos transistor, and the other end of the third Nmos transistor is connected to the fourth Nmos transistor;

[0009] The inductor L, the resistor R and the capacitor C are connected in series, and a path formed by the connection is connected in parallel with the Nmos circuit.

[0010] As an optional manner, the first Nmos transistor, the second Nmos transistor, the third Nmos transistor and the fourth Nmos transistor are respectively provided with a first freewheeling diode, a second freewheeling diode, a third freewheeling diode and a fourth freewheeling diode.

[0011] As an optional manner, the Nmos transistor in the Nmos circuit is an enhancement type N-channel MOS tube.

[0012] The beneficial effects of the utility model are:

[0013] The parallel resonant inverter of the utility model can achieve low switching loss under a proper working mode by setting a plurality of Nmos transistors and power switches, and thus can work stably under a higher working frequency. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 A schematic diagram of the structure of a series resonant inverter circuit provided by an embodiment of the utility model;

[0015] Figure 2 A schematic diagram of the working waveform of the series resonant inverter circuit provided by the embodiment of the utility model;

[0016] Figure 3 A schematic diagram of the working principle of the series resonant inverter circuit provided by an embodiment of the utility model in a first state;

[0017] Figure 4 A schematic diagram of the working principle of the series resonant inverter circuit provided by an embodiment of the utility model in the second state;

[0018] Figure 5 A schematic diagram of the working principle of the series resonant inverter circuit provided by an embodiment of the utility model in the third state;

[0019] Figure 6 A schematic diagram of the working principle of the series resonant inverter circuit provided by an embodiment of the utility model in the fourth state; DETAILED DESCRIPTION

[0020] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention is further described in detail below in conjunction with specific implementation methods.

[0021] Example

[0022] See also Figure 1 , Figure 1 A schematic diagram of the structure of a series resonant inverter circuit is provided for the present embodiment, including: a DC filter capacitor Cd, an Nmos circuit, an inductor L, a resistor R and a capacitor C; the Nmos circuit includes a first Nmos transistor, a second Nmos transistor, a third Nmos transistor and a fourth Nmos transistor; the first Nmos transistor, the second Nmos transistor, the third Nmos transistor and the fourth Nmos transistor respectively correspond to power switches S1, S2, S3 and S4; one end of the first Nmos transistor is connected to the fourth Nmos transistor, and the other end is connected to the second Nmos transistor; the other end of the second Nmos transistor is connected to the third Nmos transistor, and the other end of the third Nmos transistor is connected to the fourth Nmos transistor; the inductor L, the resistor R and the capacitor C are connected in series, and the path formed by the connection is connected in parallel with the Nmos circuit. Figure 2 : is the working waveform of this embodiment, where UH is the load voltage and IH is the load current.

[0023] Through the above circuit, in an optional scenario, this embodiment describes four working states of the above circuit in time linearity:

[0024] See also Figure 3 ,exist Figure 3 In the state described, S1 and S3 are turned on, S2 and S4 are turned off, the voltage of C1 and C3 is zero, the voltage of C2 and C4 is the DC bridge voltage Ud, and the freewheeling diodes D1, D2, D3, and D4 are all in the cut-off state. Among them, C1, C2, C3, and C4 are the absorption capacitors of the power switch devices S1, S2, S3, and S4 (including the junction capacitance of the switch devices, with equal capacitance values). D1, D2, D3, and D4 are the anti-parallel fast recovery diodes of the power switch devices; Cr is the resonant capacitor, Lr and Rr are the equivalent inductance and resistance of the inductor and the heated workpiece; L0 is the equivalent lumped inductance of the DC line and the stray inductance of the device; Cd is the DC filter capacitor.

[0025] See also Figure 4At t0, the pulses of S1 and S3 are turned off. S1 and S3 are quickly turned off under the conditions of very small load current and zero voltage. At the same time, capacitors C1 and C3 are charged, and capacitors C2 and C4 begin to discharge to maintain the continuous flow of load current. During this period of time, the load current continues to maintain the same direction. Due to the charging and discharging of the absorption capacitor, the terminal voltage of the switching devices S1 and S3 starts to rise from zero, and the terminal voltage of S2 and S4 starts to drop from Ud. At t1, the voltages of the absorption capacitors C1, C2, C3, and C4 are all Ud / 2, and the load terminal voltage is zero. At t2, capacitors C1 and C3 are charged to Ud, and capacitors C2 and C4 are discharged to zero. In the following short period of time, the energy stored in the stray inductance L0 continues to charge C1 and C3 to make their voltage slightly higher than the DC power supply voltage Ud, and then the oscillation decays to a stable value Ud. Since the current is very small when the switching device is turned off, the energy stored in the stray inductance is also very small, so the voltage of capacitors C1 and C3 does not increase much.

[0026] See also Figure 5 At time t2, since the load current has not yet commutated, the load current will continue to flow through diodes D2 and D4. Although the trigger pulses of S2 and S4 arrive at time t3, since the load current has not yet commutated, no current will flow through the switch devices S2 and S4.

[0027] See also Figure 6 At time t4, the load current starts to commutate, diodes D2 and D4 are cut off, and S2 and S4 start to flow the load current. Since the commutation occurs between the fast recovery diode and the switch device in the same bridge arm, the diode has no reverse recovery problem, and since the voltage across the switch devices S2 and S4 is zero at this time, it can be obtained that S2 and S4 are zero voltage commutation (ZVS) and zero current commutation (ZCS).

[0028] Based on the above, the series resonant inverter described in this embodiment has very small switching loss and retains a suitable dead time under an appropriate working mode, so it can operate at a higher operating frequency and be applied in semiconductor high-frequency induction heating power supplies.

[0029] The above are only preferred embodiments of the present invention. It should be noted that the above preferred embodiments should not be regarded as limiting the present invention. The protection scope of the present invention should be based on the scope defined by the claims. For ordinary technicians in this technical field, several improvements and modifications can be made without departing from the spirit and scope of the present invention, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A series resonant inverter, characterized in that: include: DC filter capacitor Cd, Nmos circuit, inductor L, resistor R and capacitor C; The Nmos circuit includes a first Nmos transistor, a second Nmos transistor, a third Nmos transistor and a fourth Nmos transistor; the first Nmos transistor, the second Nmos transistor, the third Nmos transistor and the fourth Nmos transistor respectively correspond to power switches S1, S2, S3 and S4; One end of the first Nmos transistor is connected to the fourth Nmos transistor, and the other end is connected to the second Nmos transistor; the other end of the second Nmos transistor is connected to the third Nmos transistor, and the other end of the third Nmos transistor is connected to the fourth Nmos transistor; The inductor L, the resistor R and the capacitor C are connected in series, and a path formed by the connection is connected in parallel with the Nmos circuit.

2. A series resonant inverter according to claim 1, characterized in that: The first Nmos transistor, the second Nmos transistor, the third Nmos transistor and the fourth Nmos transistor are respectively provided with a first freewheeling diode, a second freewheeling diode, a third freewheeling diode and a fourth freewheeling diode.

3. A series resonant inverter according to claim 1, characterized in that: The Nmos transistor in the Nmos circuit is an enhancement type N-channel MOS transistor.

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