Planar transformer isolation type flyback circuit for driving IGBT (Insulated Gate Bipolar Translator)

Abstract

The utility model discloses a planar transformer isolation type flyback circuit used for driving an IGBT. The planar transformer isolation type flyback circuit comprises an input filter circuit, a control chip circuit and a planar transformer circuit. The planar transformer circuit comprises a transformer T1, a diode D1, capacitors C5 and C6, resistors R8, R9, R10, R11, R12, R13, R14 and R15 and an MOS tube Q1, a pin 2 of the transformer T1 is connected to a negative electrode of the diode D1, a positive electrode of the diode D1 is connected to the resistors R8, R9, R10, R11, R12, R13, R14 and R15 which are connected in parallel through the capacitors C5 and C6 which are connected in parallel, a drain electrode of the MOS tube Q1 is connected between the diode D1 and the transformer T1, and a grid electrode and a source electrode of the MOS tube Q1 are connected to the control chip circuit. According to the utility model, the voltage of the auxiliary winding is fed back to stabilize the voltage, the winding of the secondary side is the isolation winding, and components of the primary side and the auxiliary winding are difficult to influence when the components are damaged at the end of the isolation winding; and a planar transformer is used, so that the manufacturing error in the aspect of manual work is reduced.

Description

Technical Field

[0001] The utility model relates to the technical field of IGBT driving power supply, in particular to a planar transformer isolated flyback circuit for driving IGBT. Background Art

[0002] IGBT plays a huge role in new energy vehicles. Whether it is the motor on the car or the air pump and oil pump on the bus, IGBT is needed. To drive the IGBT, an isolated driver is needed, and the isolated driver requires an isolated power supply, so that the peripheral equipment or the IGBT will not be damaged when the IGBT is damaged or externally damaged. The current isolated power supplies are basically flyback power supplies, so there is a new demand for the transformer in the flyback power supply. At present, the vast majority of flyback power supplies on the market are still using traditional transformers. The traditional transformer is composed of a magnetic core, a winding and a skeleton. This type of transformer is not as good as a planar transformer in terms of power density and cost. Therefore, a good planar transformer can greatly reduce the cost of the product and have a greater power output in a smaller volume. Utility Model Content

[0003] The utility model aims to provide a planar transformer isolated flyback circuit for driving IGBT.

[0004] To achieve the above object, the utility model provides the following technical solution: a planar transformer isolated flyback circuit for driving an IGBT, comprising:

[0005] An input filter circuit is used to obtain the voltage, filter it and output it to the control chip circuit;

[0006] A control chip circuit is used to obtain a voltage, perform voltage stabilization control, and then output it to a planar transformer circuit; and

[0007] Planar transformer circuit, used to obtain voltage, transform it and output it to IGBT;

[0008] The planar transformer circuit includes a transformer T1, a diode D1, capacitors C5, C6, resistors R8, R9, R10, R11, R12, R13, R14, R15 and a MOS tube Q1. Pin 2 of the transformer T1 is connected to the cathode of the diode D1, and the anode of the diode D1 is connected to the parallel resistors R8, R9, R10, R11, R12, R13, R14, R15 through the parallel capacitors C5 and C6. The drain of the MOS tube Q1 is connected between the diode D1 and the transformer T1, and the gate and source of the MOS tube Q1 are connected to the control chip circuit.

[0009] Furthermore, the input filter circuit includes capacitors C8, C9, C10, C11, C7, C1, and a magnetic bead U2. The capacitors C7, C11, C10, C8, and C8 are connected in parallel in sequence and connected to the capacitor C1 through the magnetic bead U2. A control chip circuit is connected between the magnetic bead U2 and the capacitor C1.

[0010] Furthermore, the control chip circuit includes a chip U1, capacitors C2, C3, C16, C17, resistors R1, R2, R3, R6, R7, R28, and a diode D6. The VCC pin of the chip U1 is connected to the capacitor C2, the DR pin of the chip U1 is connected to the resistor R3 through the parallel resistors R1, R2 and the diode D6, the resistor R3 is connected to the MOS tube Q1 after being connected in parallel with the capacitor C3, the FA / SYNC / SD pins of the chip U1 are connected to the series resistors R6 and R7 in sequence, and the COMP pin of the chip U1 is connected to the parallel resistor R28, capacitors C16 and C17.

[0011] Furthermore, it also includes an auxiliary winding output feedback circuit for shaping, filtering and dividing the voltage entering the chip U1, and the auxiliary winding output feedback circuit includes resistors R18, R19, R20, R36, R23, R24, R25, R26, R27, capacitors C12, C13, C14, C15, C22, diodes D2, D3, and light-emitting diode LED1. The resistors R26 and R27 are connected in parallel and then connected to the capacitor C15. The resistors R23, R24, and R25 are connected in series in sequence. One end of the resistor R23, R24 and R25 is connected in series with the chip U1 in parallel, and the other end of the resistor R23, R24 and R25 is connected in series with the resistor R36, the light-emitting diode LED1, the resistor R20, the capacitor C22, C13, C12, C14, the resistor R18 and R19 connected in series and in parallel with each other. One end of the resistor R19 is connected to the pin 4 of the transformer T1, the diode D2 is connected to the pin 3 of the transformer T1 through one end of the resistor R18, and the diode D3 is connected between the resistor R19 and the capacitor C14.

[0012] Furthermore, it also includes a secondary winding output circuit for isolating the secondary side and the primary side of the transformer, and the secondary winding output circuit includes resistors R34, R33, R35, R37, diodes D4, D5, capacitors C19, C20, C21, C23 and light-emitting diode LED2. The cathode of the diode D4 is connected to pin 6 of the transformer T1, the cathode of the diode D5 is connected to pin 5 of the transformer T1, the positive electrodes of the diodes D4 and D5 are connected to the capacitors C19, C20, C21, C23 and the resistor R35 in parallel, one end of the resistor R34 is connected between the diode D5 and the transformer T1, one end of the resistor R33 is connected between the diode D4 and the transformer T1, and the other end of the resistor R33 is connected to the other end of the resistor R34 and then connected to one end of the capacitor C19, the other end of the capacitor C19 is connected to one end of R37, and the other end of the resistor R37 is connected to the light-emitting diode LED2.

[0013] Furthermore, the model of the chip U1 is LM3481.

[0014] It can be seen from the above technical solution that the utility model has the following beneficial effects:

[0015] The planar transformer isolated flyback circuit used to drive the IGBT uses the voltage of the auxiliary winding to feedback a stable voltage, and the secondary winding is an isolated winding. Damaged components at the isolation winding end are unlikely to affect the components on the primary side and the auxiliary winding. A planar transformer is used, and the copper wire of the traditional transformer is replaced by the copper of the PCB board. The skeleton of the traditional transformer is removed, which can reduce the cost of the skeleton. In addition, the spacing between PCB layers is strictly controlled, which reduces the manual production error compared to the traditional hand-wound transformer. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is the overall diagram of the utility model;

[0017] Figure 2 This is the circuit diagram of the input filter circuit and control chip of the utility model;

[0018] Figure 3 This is a planar transformer circuit and an auxiliary winding output feedback circuit diagram of the utility model;

[0019] Figure 4 This is the secondary winding output circuit diagram of the utility model;

[0020] Figure 5 This is the winding diagram of each layer of the planar transformer of the utility model. DETAILED DESCRIPTION

[0021] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments in the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0022] See also Figure 1-5 The utility model provides a planar transformer isolated flyback circuit for driving IGBT, including an input filter circuit, a control chip circuit, a planar transformer circuit, an auxiliary winding output feedback circuit and a secondary winding output circuit. The input filter circuit includes capacitors C8, C9, C10, C11, C7, C1, and a magnetic bead U2. The capacitors C7, C11, C10, C8, and C8 are connected in parallel in sequence and connected to capacitor C1 through a magnetic bead U2. The control chip circuit is connected between the magnetic bead U2 and the capacitor C1. C8 is a 100uF aluminum electrolytic capacitor, capacitors C9, C10, and C11 are 10uF capacitors, capacitor C7 is a 100nF chip ceramic capacitor, and capacitor C1 is a 100uF capacitor. The input filter circuit obtains a 9-32V voltage, filters it, and outputs it to the control chip circuit.

[0023] The control chip circuit includes chip U1, capacitors C2, C3, C16, C17, resistors R1, R2, R3, R6, R7, R28, and diode D6. The model of chip U1 is LM3481. The VCC pin of the chip U1 is connected to capacitor C2. The DR pin of the chip U1 is connected to resistor R3 through parallel resistors R1, R2 and diode D6. The resistor R3 is connected to the gate of MOS tube Q1 after being connected in parallel with capacitor C3. The FA / SYNC / SD pins of the chip U1 are connected to series resistors R6 and R7 in turn. The COMP pin of the chip U1 is connected to parallel resistor R28, capacitors C16 and C17. The control chip circuit obtains the voltage input by the input filter circuit, performs voltage stabilization control, and then outputs it to the planar transformer circuit;

[0024] VCC is the input voltage of 9-32V. After passing through capacitors C8, C9, C10, C11, and C7, it enters the LM3481 chip through the LC filter formed by the chip U2 magnetic beads and capacitor C1 to power the chip. The VCC pin of the LM3481 chip is the output pin after its internal voltage regulation, and capacitor C2 performs filtering. The DR pin of chip U1 is its MOS drive pin, which is input to the gate of MOS tube Q1 through the drive resistor, while resistor R3 and pole tube D6 can enable MOS tube Q1 to be quickly turned off, and capacitor C3 can reduce the Miller platform of MOS tube Q1. The FA / SYNC / SD pin is the chip control frequency selection pin. The current 141.2kR formed by the series connection of resistors R6 and R7 can enable the chip U1 to output a square wave of about 109kHz for control. The COMP pin is the loop compensation pin of the chip U1. By changing the resistor R28, capacitors C16 and C17, the adjustment of the internal PID of the chip U1 can be changed. UVLO is the undervoltage protection pin. If the pin voltage is less than 1.25V, the chip will be shut down.

[0025] The planar transformer circuit includes a transformer T1, a diode D1, capacitors C5, C6, resistors R8, R9, R10, R11, R12, R13, R14, R15 and a MOS tube Q1. The 2nd pin of the transformer T1 is connected to the cathode of the diode D1, and the anode of the diode D1 is connected to the parallel resistors R8, R9, R10, R11, R12, R13, R14, R15 through the parallel capacitors C5 and C6. The drain of the MOS tube Q1 is connected between the diode D1 and the transformer T1, and the gate and source of the MOS tube Q1 are connected to the control chip circuit. The planar transformer circuit obtains the voltage input by the control chip circuit, converts it and outputs it to the IGBT.

[0026] Pin 1 of the transformer is the same-name terminal. The input voltage enters from the same-name terminal and comes out from the opposite-name terminal of pin 2 to the MOS tube Q1. The chip U1 controls the MOS tube Q1 through PWM to control the time when the voltage passes, thus forming a voltage regulation function. The diode D1, capacitors C5-C6 and resistors R8, R9, R10, R11, R12, R13, R14, and R15 form an RCD absorption circuit. This circuit is used to suppress the peak voltage of the primary winding of the planar transformer, because one winding of the transformer can be regarded as an inductor. The inductor has the characteristic that the current does not change suddenly but the voltage can change suddenly. Therefore, the inductor will store energy at this end, resulting in a peak voltage when the switch is turned off. If the voltage is too large, it will damage the MOS tube Q1. Therefore, adding the RCD absorption circuit can protect the MOS tube Q1 to a certain extent.

[0027] The auxiliary winding output feedback circuit includes resistors R18, R19, R20, R36, R23, R24, R25, R26, R27, capacitors C12, C13, C14, C15, C22, diodes D2, D3, and a light-emitting diode LED1. The resistors R26 and R27 are connected in parallel and connected to the capacitor C15. One end of the resistors R23, R24, and R25 that are connected in series in sequence is connected to the chip U1 in parallel with the capacitor C15. The other end of the resistors R23, R24, and R25 that are connected in series in sequence is connected to the resistor R36, the light-emitting diode LED1, the resistor R20, the capacitor C22, C13, C12, C14, the resistor R18, and R19 that are connected in series and in parallel in sequence. One end of the resistor R19 is connected to pin 4 of the transformer T1. The diode D2 is connected to pin 3 of the transformer T1 through one end of the resistor R18. The diode D3 is connected between the resistor R19 and the capacitor C14. After being shaped and filtered by capacitors C12, C13, C14, C15, and C22, and divided by resistors R20, R36, R23, R24, R25, R26, and R27, the voltage enters the FB pin of chip U1. Chip U1 can control the auxiliary winding output feedback circuit to stabilize at +15V voltage by controlling the duty cycle of pwm. The calculation method is Vout = 1.25*((R23+R24+R25) / R25). The auxiliary winding output feedback circuit shapes, filters, and divides the voltage entering chip U1.

[0028] The secondary winding output circuit includes resistors R34, R33, R35, R37, diodes D4, D5, capacitors C19, C20, C21, C23 and light-emitting diode LED2, the cathode of the diode D4 is connected to pin 6 of the transformer T1, the cathode of the diode D5 is connected to pin 5 of the transformer T1, the anodes of the diodes D4 and D5 are connected to capacitors C19, C20, C21, C23 and capacitor R35 in parallel, one end of the resistor R34 is connected between D5 and the transformer T1, one end of the resistor R33 is connected between the diode D4 and the transformer T1, and the other end of the resistor R33 is connected to the other end of the resistor R34 and then connected to one end of the capacitor C19, the other end of the capacitor C19 is connected to one end of the resistor R37, and the other end of the resistor R37 is connected to the light-emitting diode LED2. The secondary winding output circuit is the isolated output circuit of the entire circuit, which can isolate the secondary side of the transformer from the primary side. Theoretically, if the sudden voltage on the secondary side is not sensed back to the primary side by the transformer, the probability of damaging the primary side components is very low. The secondary winding output circuit can output 24V voltage through the transformer.

[0029] In the present invention, the planar transformer has lower cost, higher power density, smaller leakage inductance and higher efficiency compared to the traditional transformer. To design the planar transformer of the present invention, it is necessary to first confirm the basic parameters in the circuit, such as the minimum input voltage V in (min)∶=9V、output voltage V0∶=24V、on-state voltage drop V F ∶=0.7V、Maximum duty cycle D∶=0.5、Efficiency η∶=0.75、Switching frequency f sw ∶=150kHz、output power P0∶=20W.

[0030] The turns ratio is calculated by the above parameters. The calculation formula is as follows:

[0031]

[0032] Then calculate the inductance of the primary side, the calculation formula is as follows:

[0033]

[0034] Choose a core EI22. From the manual, you can see that the maximum output power of the core is 20W and its cross-sectional area is 79mm. 2 , the maximum magnetic flux density is 0.25T, then the peak current of the primary side and the corresponding winding turns ratio can be calculated (because the flyback power supply is in the worst state when the input voltage is the minimum, so the minimum input voltage is used as the calculation of the primary side peak current):

[0035] The EI22 core is tentatively selected. The standard output power of the core is 20W and the cross-sectional area Ae is 79mm. 2

[0036] Primary peak current

[0037] Maximum magnetic flux density: B m ∶=0.25T

[0038] Core cross-sectional area: A e ∶=79mm 2

[0039] Number of turns of primary winding: Take 2 turns

[0040] Secondary winding turns: Take 4 turns

[0041] Confirm the number of turns of the primary winding again: N p1 ∶=4·N=1.457Take 2 turns

[0042] Auxiliary winding turns: Take 2.5 turns

[0043] Confirm the number of turns of the secondary winding again: N s1 ∶=4.002 take 4 turns

[0044] Of course, when making a transformer, you also need to know the corresponding copper wire size:

[0045] Primary circuit: I PRMS ∶=2.3A

[0046] Secondary current: I SRMS ∶=1.2A

[0047] For every 1A / mm2 line:

[0048] Original edge diameter: Take a 2mm diameter copper wire

[0049] Secondary wire diameter: Take a 1.25mm diameter copper wire

[0050] The width of the original edge printed line is 2mm;

[0051] Secondary side printed line width 1.25mm;

[0052] In the case of a 1-ounce copper layer on a circuit board, a current of about 1A can be carried per 1mm2, so according to the above formula, it can be calculated that the primary winding wire needs to be 2mm thick and the secondary winding wire needs to be 1.25mm thick.

[0053] Next, open AD or the corresponding PCB production tool, and make a planar transformer according to the size of the magnetic core. It should be noted that a certain spacing is required between the winding wires of the planar transformer. In this utility model, a spacing of 0.3 is sufficient. In the above two 4-layer PCB stacks, the sandwich winding method is used, such as Figure 5 As shown, the first layer is half of the primary winding (2 turns), the second layer is half of the secondary winding (4 turns), the third layer is half of the secondary winding (4 turns), the fourth layer is half of the auxiliary winding (2.5 turns), the fifth layer is half of the auxiliary winding (2.5 turns), the sixth layer is half of the secondary winding in parallel (4 turns), the seventh layer is half of the secondary winding in parallel (4 turns), and the eighth layer is half of the primary winding (2 turns). Note that the secondary winding is connected in parallel, so that the wire thickness is larger under the same number of turns, so the current that can pass through is also increased.

[0054] The planar transformer isolated flyback circuit uses the voltage of the auxiliary winding to feedback a stable voltage, and the secondary winding is an isolated winding. Damaged components at the isolation winding end are unlikely to affect the components on the primary side and the auxiliary winding. A planar transformer is used, and the copper of the PCB board replaces the copper wire of the traditional transformer, removing the skeleton of the traditional transformer. This can reduce the cost of the skeleton, and the spacing between PCB layers is strictly controlled, which is very different from the hand-wound traditional transformer. It has a huge advantage in quality control. After all, the PCB is made from more sophisticated instruments, and its winding error comes more from the design error of the engineer, which reduces the manual production error.

[0055] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A planar transformer isolated flyback circuit for driving an IGBT, characterized in that: include: An input filter circuit is used to obtain the voltage, filter it and output it to the control chip circuit; A control chip circuit is used to obtain a voltage, perform voltage stabilization control, and then output it to a planar transformer circuit; as well as Planar transformer circuit, used to obtain voltage, transform it and output it to IGBT; The planar transformer circuit includes a transformer T1, a diode D1, capacitors C5, C6, resistors R8, R9, R10, R11, R12, R13, R14, R15 and a MOS tube Q1. Pin 2 of the transformer T1 is connected to the cathode of the diode D1, and the anode of the diode D1 is connected to the parallel resistors R8, R9, R10, R11, R12, R13, R14, R15 through the parallel capacitors C5 and C6. The drain of the MOS tube Q1 is connected between the diode D1 and the transformer T1, and the gate and source of the MOS tube Q1 are connected to the control chip circuit.

2. The planar transformer isolated flyback circuit for driving an IGBT according to claim 1, characterized in that: The input filter circuit includes capacitors C8, C9, C10, C11, C7, C1, and a magnetic bead U2. The capacitors C7, C11, C10, C8, and C8 are sequentially connected in parallel and connected to the capacitor C1 through the magnetic bead U2. A control chip circuit is connected between the magnetic bead U2 and the capacitor C1.

3. The planar transformer isolated flyback circuit for driving an IGBT according to claim 2, characterized in that: The control chip circuit includes a chip U1, capacitors C2, C3, C16, C17, resistors R1, R2, R3, R6, R7, R28, and a diode D6. The VCC pin of the chip U1 is connected to the capacitor C2, the DR pin of the chip U1 is connected to the resistor R3 through the parallel resistors R1, R2 and the diode D6, the resistor R3 is connected to the MOS tube Q1 after being connected in parallel with the capacitor C3, the FA / SYNC / SD pins of the chip U1 are connected to the series resistors R6 and R7 in sequence, and the COMP pin of the chip U1 is connected to the parallel resistor R28, capacitors C16 and C17.

4. The planar transformer isolated flyback circuit for driving an IGBT according to claim 3, characterized in that: The auxiliary winding output feedback circuit is also included for shaping, filtering and dividing the voltage entering the chip U1. The auxiliary winding output feedback circuit includes resistors R18, R19, R20, R36, R23, R24, R25, R26, R27, capacitors C12, C13, C14, C15, C22, diodes D2, D3, and light-emitting diode LED1. The resistors R26 and R27 are connected in parallel and then connected to the capacitor C15. The resistors R23, R24, and R25 are connected in series in sequence. One end is connected to the chip U1 in parallel with the capacitor C15, and the other end of the resistors R23, R24, and R25 are connected in series in sequence. The resistor R36, the light-emitting diode LED1, the resistor R20, the capacitors C22, C13, C12, C14, the resistors R18, and R19 are connected in series and in parallel in sequence. One end of the resistor R19 is connected to pin 4 of the transformer T1, the diode D2 is connected to pin 3 of the transformer T1 through one end of the resistor R18, and the diode D3 is connected between the resistor R19 and the capacitor C14.

5. The planar transformer isolated flyback circuit for driving an IGBT according to claim 4, characterized in that: The invention also includes a secondary winding output circuit for isolating the secondary side and the primary side of the transformer, wherein the secondary winding output circuit includes resistors R34, R33, R35, R37, diodes D4, D5, capacitors C19, C20, C21, C23 and a light emitting diode LED2, wherein the cathode of the diode D4 is connected to the 6th pin of the transformer T1, the cathode of the diode D5 is connected to the 5th pin of the transformer T1, the anodes of the diodes D4 and D5 are connected to the capacitors C19, C20, C21, C23 and the resistor R35 in parallel after being connected, one end of the resistor R34 is connected between the diode D5 and the transformer T1, one end of the resistor R33 is connected between the diode D4 and the transformer T1, and the other end of the resistor R33 is connected to the other end of the resistor R34 and then connected to one end of the capacitor C19, the other end of the capacitor C19 is connected to one end of the resistor R37, and the other end of the resistor R37 is connected to the light emitting diode LED2.

6. The planar transformer isolated flyback circuit for driving an IGBT according to claim 3, characterized in that: The model of the chip U1 is LM3481.

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