A main circuit structure of a synchronous induction heating power supply

Abstract

The present invention provides a main circuit structure of a synchronous induction heating power supply, characterized in that the negative end of the DC voltage supply circuit is connected to the cathodes of N diodes, and the anodes of the N diodes are respectively connected to the DC shunts of the N induction heating units; a group of diodes is connected between the negative ends of the inverter bridges of every two induction heating units in the N induction heating units. The present invention connects a diode in series at the rear end of the shunt of each unit, and uses the diode to prevent the current from reversing, ensuring that the accurate DC current can be collected through the shunt; the present invention connects two positive and negative parallel diodes in series between the negative ends of every two inverter bridges to prevent the DC currents of the two inverter bridges from shunting each other, providing a circulating loop for the induced current, so that the induced current will not flow through the shunt, ensuring that the accurate DC current can be collected through the shunt.

Description

Technical Field

[0001] The invention relates to a main circuit structure of a synchronous induction heating power supply. Background Art

[0002] The commonly used synchronous induction heating power supply with multiple unit output adopts the common DC bus mode, and there is no special treatment for the circuit between multiple inverter units. When multiple induction coils are close to each other, the magnetic fields in the induction coils will couple with each other, and the units with weaker magnetic fields in the induction coils are easily coupled to the induced current by the units with stronger magnetic fields. The induced current is fed back to the DC bus through the internal loop including the medium-frequency transformer and the inverter bridge reverse rectification, and forms an induced loop on the DC bus. This induced loop will flow through the shunt of the induced unit. The power P acquisition is calculated by the DC voltage U and the DC current I collected on the shunt, P = U × I. If there is an induced current in the current signal on the shunt, and the current direction is opposite to the actual output current direction of this unit, then it will cause a current cancellation effect, the detected DC current I will become smaller, and the calculated power value P will also become smaller, resulting in inaccurate power calculation. The system cannot collect the actual output power of each unit, and it is impossible to perform power control.

[0003] like Figure 1 As shown, taking the main circuit structure of a synchronous induction heating power supply including two induction coils and multiple unit outputs as an example, in the main circuit of the conventional structure, the magnetic field coupling of the induction coils COIL1 and COIL2 generates an induced current in the primary and inverter circuits of the transformer, and the induced current flows through the shunt RB2 in the forward direction and flows through the shunt RB1 in the reverse direction, resulting in an increase in the DC current collected on the shunt RB2 and a decrease in the DC current collected on the shunt RB1, resulting in inaccurate power calculation when calculating the output power of each unit. Summary of the invention

[0004] The purpose of the present invention is to prevent the mutual coupling of magnetic fields in a plurality of induction coils resulting in inaccurate power collection of each unit, and to ensure that the power collected by each unit is the actual output power of the unit.

[0005] In order to achieve the above-mentioned object, the technical solution of the present invention is to provide a synchronous induction heating power supply main circuit structure, including a DC voltage supply circuit and N induction heating units, N≥2, each induction heating unit includes a DC shunt, an inverter bridge, an isolation transformer and an induction coil, the AC current output by the inverter bridge flows through the primary winding of the isolation transformer, the induced current output by the secondary winding of the isolation transformer flows through the induction coil, the DC shunt is connected to the negative end of the inverter bridge, and is characterized in that it also includes N diodes 1 and N-1 diode groups consisting of two reverse-parallel diodes 2;

[0006] The positive terminals of the N inverter bridges are connected to the positive terminal of the DC voltage supply circuit;

[0007] The negative end of the DC voltage supply circuit is connected to the cathodes of the N diodes 1, and the anodes of the N diodes 1 are respectively connected to the DC shunts of the N induction heating units;

[0008] A diode group is connected between the negative terminals of the inverter bridges of every two induction heating units in the N induction heating units.

[0009] Preferably, the diode 1 is a high current fast diode.

[0010] Preferably, a filter capacitor is connected across the positive terminal and the negative terminal of each inverter bridge.

[0011] Preferably, the DC voltage supply circuit includes an AC power interface, which is connected to a circuit breaker, which is connected to a three-phase rectifier bridge, and the three-phase rectifier bridge outputs a DC voltage; the positive end of the DC voltage is connected to the positive end of N inverter bridges after passing through a buffer contactor and a smoothing reactor; and a charging buffer circuit is connected in parallel at both ends of the contactor.

[0012] Preferably, the charging buffer circuit comprises a buffer resistor and a resettable fuse connected in series.

[0013] Compared with the prior art, the present invention has the following advantages:

[0014] 1) The present invention connects a diode in series at the rear end of the shunt of each unit, and uses the diode to prevent the current from reversing, thereby ensuring that accurate DC current can be collected through the shunt;

[0015] 2) The present invention connects two diodes connected in parallel in series between the negative ends of each of the two inverter bridges to prevent the DC currents of the two inverter bridges from being shunted from each other, providing a circulating loop for the induced current so that the induced current does not flow through the shunt, thereby ensuring that accurate DC current can be collected through the shunt; BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a schematic diagram of the main circuit structure of a conventional synchronous induction heating power supply;

[0017] Figure 2 A schematic diagram of the main circuit structure of a synchronous induction heating power supply disclosed in an embodiment;

[0018] Figure 3 for Figure 2 Schematic diagram of the induced current return flow direction. DETAILED DESCRIPTION

[0019] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0020] The main circuit structure of a synchronous induction heating power supply provided by the present invention is used for the main circuit design of a synchronous multi-output induction heating power supply, and is applied to induction heating applications where multiple induction coils are close to each other and there is magnetic field coupling between them. For example: heat treatment applications with multi-unit zone heating, crystal growth industry with double coil heating, online heating of bars with multi-temperature zone control requirements, etc.

[0021] This embodiment takes the main circuit structure of a synchronous induction heating power supply including two induction coils COIL1 and COIL2 as an example to further illustrate the present invention.

[0022] like Figure 2 As shown, a main circuit structure of a synchronous induction heating power supply disclosed in this embodiment is shown. The three-phase 380VAC power supply enters the circuit breaker KP1 through the three-phase power supply interfaces L1, L2, and L3, and is then connected to the three-phase rectifier bridge BD1. After being rectified by the three-phase rectifier bridge BD1, a DC voltage is output. The positive end of the DC voltage passes through the buffer contactor K1 and the smoothing reactor L1, and then is connected to the positive terminals of the inverter bridge Bridge1 and the inverter bridge Bridge2. The buffer resistor R1 and the self-recovery fuse FR1 are connected in series and connected to both ends of the contactor K1 to form a charging buffer circuit. The function of the buffer circuit is to eliminate the current impact on the input circuit and the rectifier bridge when power is turned on, and to reduce the impact and interference on the power grid.

[0023] A capacitor C3 is connected across the positive end of the DC voltage and the negative end of the DC voltage. The negative end of the DC voltage is connected to the cathodes of the diode D2 and the diode D1. The anode of the diode D1 is connected to the negative end of the inverter bridge Bridge1 via the DC shunt RB1. The anode of the diode D2 is connected to the negative end of the inverter bridge Bridge2 via the DC shunt RB2. The induced current will be cut off by the diodes D1 and D2, so the induced current will not flow through the DC shunt RB1 and the DC shunt RB2. The DC shunt RB1 and the DC shunt RB2 are used to detect the DC current of the inverter bridge Bridge1 and the inverter bridge Bridge2, respectively.

[0024] A filter capacitor C1 is connected between the positive terminal and the negative terminal of the inverter bridge Bridge1. The inverter bridge Bridge1 is a full-bridge inverter bridge composed of four IGBTs. The diode D1 uses a large current fast diode to prevent the current on the DC shunt RB1 from reversing. The inverter bridge Bridge1 inverts and outputs an AC current, which flows through the primary winding of the medium frequency isolation transformer TRAN1 after passing through the DC isolation capacitor group CP1. The secondary winding of the medium frequency isolation transformer TRAN1 senses the current and flows through the resonant capacitor group CP3, and then passes through the induction coil COIL1 to form a resonant circuit.

[0025] A filter capacitor C2 is connected between the positive terminal and the negative terminal of the inverter bridge Bridge2. Bridge2 is a full-bridge inverter bridge composed of four IGBTs. Diode D2 uses a high-current fast diode to prevent the current on the DC shunt RB2 from reversing. The inverter bridge Bridge2 inverts and outputs an AC current, which flows through the primary winding of the medium-frequency isolation transformer TRAN2 through the DC isolation capacitor group CP2. The secondary winding of the medium-frequency isolation transformer TRAN2 senses the current and flows through the resonant capacitor group CP4, and then through the induction coil COIL2 to form a resonant circuit.

[0026] Two reverse parallel diodes D3 are connected in series between the negative terminals of the inverter bridge Bridge1 and the inverter bridge Bridge2, so that the induced current forms a circulation directly through the diode D3 without passing through the DC shunt RB1 and the DC shunt RB2. Another function of the diode D3 is to ensure that the power output DC current loops of the inverter bridge Bridge1 and the inverter bridge Bridge2 do not affect each other. The DC current of the inverter bridge Bridge1 flows through the DC shunt RB1 and the diode D1 back to the negative terminal of the three-phase rectifier bridge BD1. If it is to go through the diode D3, the DC shunt RB2, and the diode D2 to return to the negative terminal of the three-phase rectifier bridge BD1, it needs to flow through two diodes. Since the voltage drop of the two diodes of diode D3 and diode D2 is twice that of the diode D1, the DC current of the inverter bridge Bridge1 will not flow through the diode D3, the DC shunt RB2, and the diode D2, but will only flow through the DC shunt RB1 and the diode D1. Similarly, the DC current of the inverter bridge Bridge2 will not flow through the diode D3, the DC shunt RB1, and the diode D1, but will only flow through the DC shunt RB2 and the diode D2.

Claims

1. A main circuit structure of a synchronous induction heating power supply, comprising a DC voltage supply circuit and N induction heating units, N ≥ 2, each induction heating unit comprising a DC shunt, an inverter bridge, an isolation transformer and an induction coil, the AC current output by the inverter bridge flows through the primary winding of the isolation transformer, the induced current output by the secondary winding of the isolation transformer flows through the induction coil, the DC shunt is connected to the negative terminal of the inverter bridge, and is characterized in that: It also includes N diodes 1 and N-1 diode groups consisting of two reverse-parallel diodes 2, wherein the diodes 1 are large current fast diodes; The positive terminals of the N inverter bridges are connected to the positive terminal of the DC voltage supply circuit; The negative end of the DC voltage supply circuit is connected to the cathodes of the N diodes 1, and the anodes of the N diodes 1 are respectively connected to the DC shunts of the N induction heating units; A diode group is connected between the negative terminals of the inverter bridges of every two induction heating units in the N induction heating units; A filter capacitor is connected across the positive terminal and the negative terminal of each inverter bridge.

2. A synchronous induction heating power supply main circuit structure as claimed in claim 1, characterized in that: The DC voltage supply circuit includes an AC power interface, which is connected to a circuit breaker, which is connected to a three-phase rectifier bridge, and the three-phase rectifier bridge outputs a DC voltage; the positive end of the DC voltage is connected to the positive ends of N inverter bridges after passing through a buffer contactor and a smoothing reactor; and a charging buffer circuit is connected in parallel at both ends of the contactor.

3. A synchronous induction heating power supply main circuit structure as claimed in claim 2, characterized in that: The charging buffer circuit comprises a buffer resistor and a resettable fuse connected in series.

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