An ultra-wide input voltage flyback circuit with MOSFET series voltage divider

Abstract

This invention discloses an ultra-wide input voltage flyback circuit with MOSFET series voltage division, comprising a rectifier and filter circuit disposed between the L and N lines, a transformer primary winding connected in series across the rectifier and filter circuit, an upper MOSFET circuit, and an integrated power supply chip with a built-in lower MOSFET. The transformer secondary winding is connected to the output rectifier and filter circuit. With this structure, the voltage across MOSFET Q1 and the management IC with the built-in MOSFET when the switching circuit is off is determined by the parasitic capacitance of MOSFET Q1, the voltage divider capacitor C1 of the upper MOSFET, and the voltage divider ceramic capacitor C2 of the lower MOSFET. MOSFET Q1 is selected based on the parasitic capacitance of the integrated power supply chip with the built-in lower MOSFET, and the capacitance values ​​of the voltage divider capacitors C1 and C2 are adjusted. This invention solves the problem of the scarcity and high cost of integrated high-voltage MOSFET power supply chips when the input voltage is high by using a voltage division method with upper and lower MOSFETs.

Description

Technical Field

[0001] This utility model relates to an ultra-wide input voltage flyback circuit with MOSFET series voltage division, and more particularly to an ultra-wide input voltage flyback circuit with MOSFET series voltage division that is low in cost, has a wide selection range, and whose withstand voltage can be adjusted within a certain range. Background Technology

[0002] With the advancement of technology, the electrification and intelligentization of human society are accelerating, especially with the development of smart homes and electric vehicles. This has led to a continuous increase in the demand for switching power supplies, resulting in the replacement of many low-power linear transformers by switching power supply modules. While there is a wide selection of switching power supply control ICs for standard input voltages, the input voltage increases significantly, particularly in three-phase power or photovoltaic auxiliary power supplies, far exceeding the common 240Vac or 277Vac systems. Most power supply ICs with built-in MOSFETs cannot meet the requirements, and using power supply ICs with discrete MOSFETs also faces the problem of high-voltage discrete MOSFETs. Therefore, low-power ultra-wide voltage input modules have always been relatively expensive, and the number of manufacturers capable of designing and producing them is far fewer than that of conventional power supply modules. Utility Model Content

[0003] The technical problem to be solved by this utility model is to provide an ultra-wide input voltage flyback circuit with MOSFET series voltage division, which has the characteristics of low cost, wide selection range, and adjustable withstand voltage within a certain range.

[0004] To solve the above-mentioned technical problems, the technical solution of this utility model is as follows: an ultra-wide input voltage flyback circuit with MOS transistor series voltage division, the innovation of which is: the ultra-wide input voltage flyback circuit with MOS transistor series voltage division includes a rectifier and filter circuit disposed between the L line and the N line, a transformer primary winding, an upper MOS transistor circuit, and an integrated power supply chip with a built-in lower MOS transistor disposed in series at both ends of the rectifier and filter circuit, and the transformer secondary winding is connected to the output rectifier and filter circuit.

[0005] Preferably, the rectifier-filter circuit includes a rectifier circuit composed of four diodes and a filter circuit composed of capacitors and inductors, and the rectifier-filter circuit is provided with a ground terminal.

[0006] Preferably, an RCD snubber circuit is connected in parallel on the primary winding of the transformer. The RCD snubber circuit includes a resistor R3 and a capacitor C3 connected in parallel, a resistor R4 connected in series with the parallel resistor R3 and capacitor C3, and a diode D1 connected in series with the resistor R4.

[0007] Preferably, the upper MOS transistor circuit includes a MOS transistor Q1 and an upper driving circuit connected to the MOS transistor Q1. The upper driving circuit includes a resistor R1 connected to the rectifier filter circuit and a resistor R5 connected in series with the resistor R1. The resistor R5 is connected to the gate of the MOS transistor Q1, the drain of the MOS transistor Q1 is connected to the primary winding of the transformer, and the source of the MOS transistor Q1 is connected to the integrated power supply chip of the built-in lower MOS transistor.

[0008] Preferably, an upper MOSFET voltage divider capacitor C1 is provided between the drain and source of the MOSFET Q1.

[0009] Preferably, a Zener diode ZD2 is disposed between the source and gate of the MOSFET Q1, and the Zener voltage of the Zener diode ZD2 is less than the maximum withstand voltage Vgs of the MOSFET Q1.

[0010] Preferably, the gate of the MOS transistor Q1 is connected to the ground terminal through the resistor R5 and the lower transistor voltage regulator circuit. The lower transistor voltage regulator circuit includes a lower transistor voltage divider ceramic capacitor C2 disposed between the resistor R5 and the ground terminal, a resistor R2 connected in parallel across the lower transistor voltage divider ceramic capacitor C2 and connected in series with each other, and a Zener diode ZD1.

[0011] Preferably, the integrated power supply chip with built-in lower MOSFET is the Lishengmei LIC3901C.

[0012] Preferably, the transformer is provided with a primary secondary winding, which forms a circuit with a diode D2 and a capacitor EC3 connected in series, and the capacitor EC3 is grounded.

[0013] Preferably, the output rectifier filter circuit includes a diode D3 and a capacitor EC4 connected in series, with the capacitor EC4 grounded.

[0014] The advantages of this invention are as follows: By adopting the above structure, when the switching circuit is turned off, the voltage across MOSFET Q1 and the power management IC containing the built-in MOSFET is determined by the parasitic capacitance of MOSFET Q1, the voltage divider capacitor C1 of the upper MOSFET, and the voltage divider ceramic capacitor C2 of the lower MOSFET. MOSFET Q1 is selected based on the parasitic capacitance of the integrated power chip with the built-in lower MOSFET, and the capacitance values ​​of the voltage divider capacitor C1 of the upper MOSFET and the voltage divider ceramic capacitor C2 of the lower MOSFET are adjusted. This invention solves the problem of the scarcity and high cost of integrated high-voltage MOSFET power chips when the input voltage is high by using the voltage divider method of the upper and lower MOSFETs. Attached Figure Description

[0015] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0016] Figure 1This is a block diagram of an ultra-wide input voltage flyback circuit with MOSFET series voltage divider according to this utility model.

[0017] Figure 2 This is a breakdown voltage diagram of MOSFET Q1 (upper MOSFET) and lower MOSFET in an ultra-wide input voltage flyback circuit with series voltage division of MOSFETs according to this utility model.

[0018] In the diagram: 1-rectifier and filter circuit, 2-transformer primary winding, 3-integrated power supply chip with built-in lower MOSFET, 4-transformer secondary winding, 5-output rectifier and filter circuit, 6-RCD absorption circuit, 7-upper MOSFET circuit, 8-ZD2 Zener diode, 9-lower MOSFET voltage regulator circuit, 10-primary secondary winding. Detailed Implementation

[0019] This invention relates to an ultra-wide input voltage flyback circuit with MOSFET series voltage divider, comprising a rectifier and filter circuit 1 located between the L and N lines, a transformer primary winding 2 connected in series across the rectifier and filter circuit 1, an upper MOSFET circuit 7, and an integrated power supply chip 3 with a built-in lower MOSFET. The transformer secondary winding 4 is connected to the output rectifier and filter circuit 5. With this structure, the voltage across the MOSFET Q1 and the management IC with the built-in MOSFET when the switching circuit is off is determined by the parasitic capacitance of MOSFET Q1, the upper MOSFET voltage divider capacitor C1, and the lower MOSFET voltage divider ceramic capacitor C2. MOSFET Q1 is selected based on the parasitic capacitance of the integrated power supply chip 3 with the built-in lower MOSFET, and the capacitance values ​​of the upper MOSFET voltage divider capacitor C1 and the lower MOSFET voltage divider ceramic capacitor C2 are adjusted. This invention solves the problem of the scarcity and high cost of integrated high-voltage MOSFET power supply chips when the input voltage is high by using a voltage divider method with upper and lower MOSFETs.

[0020] The principle behind this invention lies in the fact that, for series circuits, the voltage across a series device is primarily determined by its impedance. When MOSFETs are connected in series, the withstand voltage across the upper and lower transistors is mainly determined by the impedances of the MOSFET's drain and source, including the resistance at cutoff and the junction capacitance. Furthermore, the capacitance and resistance are in parallel. For static or low-frequency circuits, the resistance and capacitance of the MOSFET at cutoff are close to infinity. For MOSFETs operating in a fast-switching state, the capacitance is significantly less than the resistance. Therefore, in high-frequency circuit applications, when the MOSFET is cutoff, the capacitance dominates, and the transient voltage division can be achieved by adjusting the capacitance between the drain and source of the MOSFET.

[0021] The aforementioned rectifier-filter circuit 1 includes a rectifier circuit composed of four diodes and a filter circuit composed of capacitors and inductors. The rectifier-filter circuit 1 is provided with a ground terminal, and the filter circuit is a π-type filter circuit composed of a high-voltage electrolytic capacitor and a power inductor.

[0022] An RCD snubber circuit 6 is connected in parallel on the primary winding 2 of the transformer. The RCD snubber circuit 6 includes a resistor R3 and a capacitor C3 connected in parallel, a resistor R4 connected in series with the parallel resistor R3 and capacitor C3, and a diode D1 connected in series with the resistor R4.

[0023] In this invention, the upper MOSFET circuit 7 includes a MOSFET Q1 and an upper driving circuit connected to the MOSFET Q1. The upper driving circuit includes a resistor R1 connected to the rectifier filter circuit and a resistor R5 connected in series with the resistor R1. The resistor R5 is connected to the gate of the MOSFET Q1. The drain of the MOSFET Q1 is connected to the primary winding of the transformer, and the source of the MOSFET Q1 is connected to the integrated power supply chip with a built-in lower MOSFET. An upper MOSFET voltage divider capacitor C1 is provided between the drain and source of the MOSFET Q1. A Zener diode ZD28 is provided between the source and gate of the MOSFET Q1. The Zener voltage of the Zener diode ZD28 is less than the maximum withstand voltage Vgs of the MOSFET Q1.

[0024] The gate of the aforementioned MOSFET Q1 is connected to ground via resistor R5 and the lower-side voltage regulator circuit 9. The lower-side voltage regulator circuit 9 includes a lower-side voltage divider ceramic capacitor C2 disposed between resistor R5 and ground, a resistor R2 connected in series across the lower-side voltage divider ceramic capacitor C2, and a Zener diode ZD1. The lower-side voltage regulator circuit 9 in this invention can also be composed of a Zener diode or a resistor and a transistor to absorb voltage spikes generated when the switching circuit is turned off.

[0025] In this invention, the integrated power chip 3 with a built-in lower-side MOSFET is the Lishengmei LIC3901C, which will not be described in detail here. The integrated power chip 3 with a built-in lower-side MOSFET includes the necessary external resistors and capacitors. Depending on the input conditions and output requirements, the integrated power chip 3 with a built-in lower-side MOSFET can select either an SSR (Secondary Feedback) or PSR (Primary Feedback) power management scheme. The aforementioned transformer has a primary-side secondary winding 10. The primary-side secondary winding 10, together with a series-connected diode D2 and capacitor EC3, forms a circuit, with capacitor EC3 grounded. The transformer is an EE type or other commonly used frame, and consists of a magnetic core, insulated wire, and insulating tape. The output rectifier and filter circuit 5 includes a series-connected diode D3 and capacitor EC4, with capacitor EC4 grounded.

[0026] In this invention, the MOSFET Q1 is selected based on the input voltage and output power, taking into account both performance and cost. Its drive resistor circuit is designed based on the input voltage and the voltage rating of the surface-mount resistor; the series resistor's voltage rating must be greater than the maximum input voltage. The upper MOSFET voltage divider capacitor C1 is a through-hole or surface-mount ceramic capacitor, and its voltage rating must be greater than that of the MOSFET Q1. The lower MOSFET voltage divider ceramic capacitor C2 is a through-hole or surface-mount ceramic capacitor, and its voltage rating must be greater than that of the lower MOSFET in the integrated power chip 3 that houses the lower MOSFET.

[0027] The working principle of this utility model is as follows: When the circuit input terminal is powered on, the integrated power chip with built-in lower MOSFET obtains the starting current through the high voltage start-up circuit of the built-in MOSFET drain. Under the internal PWM drive, the built-in MOSFET will enter the conducting state. At this time, the pull-up resistors R1 and R5 will charge the gate of MOSFET Q1 (upper MOSFET). When the turn-on threshold is reached, MOSFET Q1 will turn on, and the flyback circuit will enter the primary-side conducting state.

[0028] Zener diode ZD2 acts as a clamp to the gate and source voltages of MOSFET Q1, preventing the voltage from exceeding the drain-source withstand voltage of MOSFET Q1 and causing damage. When the conduction state ends, the integrated power chip with the built-in lower MOSFET will first turn off the built-in MOSFET. At this time, the upper MOSFET drive path formed by resistors R1 and R5 will be cut off, and MOSFET Q1 will turn off accordingly. The flyback circuit then enters the primary-side turn-off state.

[0029] At the moment of turn-off, the voltage reflected from the transformer secondary to the primary, combined with the primary bus voltage and the voltage spike generated by the leakage inductance, is applied to the series circuit formed by MOSFET Q1 and the built-in MOSFET in the integrated power chip. At this moment, the voltage across MOSFET Q1 and the built-in MOSFET of the integrated power chip is determined by the equivalent capacitance impedance distribution of MOSFET Q1 and the built-in MOSFET, with the connection point between the source and drain of MOSFET Q1 as a reference point. The withstand voltage is inversely proportional to the equivalent capacitance impedance value. Considering the consistency of mass-produced devices, to ensure that the withstand voltage of the built-in MOSFET in the integrated power chip does not exceed the limit, a voltage regulator circuit is set for the built-in MOSFET. When the withstand voltage of the built-in MOSFET exceeds the threshold of the voltage regulator circuit, the voltage regulator circuit will conduct, clamping the voltage within a safe range.

[0030] The above description is for illustrative purposes and not for limitation. Many embodiments and applications beyond the provided examples will be apparent to those skilled in the art upon reading the above description. Therefore, the scope of this invention should not be determined by reference to the above description, but rather by reference to the appended claims and the full scope of their equivalents. For purposes of completeness, all articles and references, including patent applications and publications, are incorporated herein by reference. The omission of any aspect of the subject matter disclosed herein in the preceding claims is not intended as a waiver of that subject matter, nor should it be construed as an indication that the inventors have not considered it part of the disclosed inventive subject matter.

Claims

1. A MOSFET series voltage divider ultra-wide input voltage flyback circuit, characterized in that: The ultra-wide input voltage flyback circuit with MOSFET series voltage division includes a rectifier and filter circuit located between the L and N lines, a transformer primary winding connected in series at both ends of the rectifier and filter circuit, an upper MOSFET circuit, an integrated power supply chip with a built-in lower MOSFET, and the transformer secondary winding connected to the output rectifier and filter circuit.

2. The ultra-wide input voltage flyback circuit with MOS transistor series voltage divider as described in claim 1, characterized in that: The rectifier and filter circuit includes a rectifier circuit composed of four diodes and a filter circuit composed of capacitors and inductors, and a ground terminal is provided on the rectifier and filter circuit.

3. The ultra-wide input voltage flyback circuit with MOS transistor series voltage divider as described in claim 1, characterized in that: An RCD snubber circuit is connected in parallel on the primary winding of the transformer. The RCD snubber circuit includes a resistor R3 and a capacitor C3 connected in parallel, a resistor R4 connected in series with the parallel resistor R3 and capacitor C3, and a diode D1 connected in series with the resistor R4.

4. The ultra-wide input voltage flyback circuit with MOSFET series voltage divider as described in claim 1, characterized in that: The upper MOS transistor circuit includes a MOS transistor Q1 and an upper driving circuit connected to the MOS transistor Q1. The upper driving circuit includes a resistor R1 connected to the rectifier filter circuit and a resistor R5 connected in series with the resistor R1. The resistor R5 is connected to the gate of the MOS transistor Q1. The drain of the MOS transistor Q1 is connected to the primary winding of the transformer. The source of the MOS transistor Q1 is connected to the integrated power chip of the built-in lower MOS transistor.

5. The ultra-wide input voltage flyback circuit with MOS transistor series voltage divider as described in claim 4, characterized in that: A voltage divider capacitor C1 is provided between the drain and source of the MOS transistor Q1.

6. The ultra-wide input voltage flyback circuit with MOS transistor series voltage divider as described in claim 4, characterized in that: A Zener diode ZD2 is disposed between the source and gate of the MOSFET Q1. The Zener voltage of the Zener diode ZD2 is less than the maximum withstand voltage Vgs of the MOSFET Q1.

7. The ultra-wide input voltage flyback circuit with MOSFET series voltage divider as described in claim 4, characterized in that: The gate of the MOS transistor Q1 is connected to the ground terminal through the resistor R5 and the lower transistor voltage regulator circuit. The lower transistor voltage regulator circuit includes a lower transistor voltage divider ceramic capacitor C2 disposed between the resistor R5 and the ground terminal, a resistor R2 connected in series across the lower transistor voltage divider ceramic capacitor C2, and a Zener diode ZD1.

8. The ultra-wide input voltage flyback circuit with MOSFET series voltage divider as described in claim 1, characterized in that: The integrated power supply chip with built-in lower MOSFET is the Lishengmei LIC3901C.

9. The ultra-wide input voltage flyback circuit with MOSFET series voltage divider as described in claim 1, characterized in that: The transformer is provided with a primary secondary winding, which forms a circuit with diode D2 and capacitor EC3 connected in series, and capacitor EC3 is grounded.

10. The ultra-wide input voltage flyback circuit with MOS transistor series voltage divider as described in claim 1, characterized in that: The output rectifier and filter circuit includes a diode D3 and a capacitor EC4 connected in series, with the capacitor EC4 grounded.

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