LLC secondary series output high voltage circuit

Abstract

The utility model discloses a LLC secondary series output high voltage's circuit, LLC resonant conversion circuit is connected with high voltage group transformer and low voltage group transformer's primary respectively, the secondary connection high voltage group LLC secondary output circuit of high voltage group transformer, the secondary connection low voltage group LLC secondary output circuit of low voltage group transformer, high voltage group LLC secondary output circuit connects high voltage group synchronous rectifier circuit, low voltage group LLC secondary output circuit connects low voltage group synchronous rectifier circuit, the negative pole of high voltage group LLC secondary output circuit with the positive pole of low voltage group LLC secondary output circuit is connected, the positive pole of high voltage group LLC secondary output circuit low voltage group LLC secondary output circuit's negative pole is connected with the positive pole and the negative pole of series output circuit respectively. Compared with primary use two separate LLC circuit, the utility model discloses can reduce the use of LLC chip and MOS pipe, and the circuit structure is simplified.

Description

Technical Field

[0001] This utility model relates to the field of LLC circuit technology, specifically to a circuit in which the secondary winding of an LLC circuit outputs a high voltage in series. Background Technology

[0002] When using an LLC scheme to output DC power, a synchronous rectification scheme is required when the output voltage exceeds 65V and a large current is needed. However, existing synchronous rectification ICs, when detecting the synchronous rectification MOS Vds voltage, have a maximum pin withstand voltage of 200V. When the output voltage exceeds 65V, the synchronous rectification MOS Vds voltage will exceed 200V. Therefore, there is no directly usable chip; the only option is to use two separate LLC circuits in the primary winding. Each LLC circuit includes an LLC chip, a MOS transistor, and a transformer to achieve the high voltage output. This circuit design has room for optimization. While achieving the same function, the number of LLC chips and MOS transistors can be reduced, further simplifying the circuit and saving manufacturing costs and wiring space. Utility Model Content

[0003] The purpose of this invention is to address the above-mentioned problems by providing a circuit that outputs high voltage via a series connection of LLC secondary windings. This circuit not only achieves high voltage output but also reduces the use of LLC chips and MOSFETs compared to using two separate LLC circuits in the primary winding, thus simplifying the circuit and saving manufacturing costs and wiring space.

[0004] This utility model is achieved through the following technical solution: A circuit for high-voltage output from an LLC secondary winding, comprising an LLC resonant converter circuit, characterized in that: the LLC resonant converter circuit is driven by an LLC control drive circuit with an LLC control chip; the LLC resonant converter circuit is connected to the primary windings of a high-voltage group transformer and a low-voltage group transformer respectively; the secondary winding of the high-voltage group transformer is connected to the secondary output circuit of the high-voltage group LLC winding; the secondary winding of the low-voltage group transformer is connected to the secondary output circuit of the low-voltage group LLC winding; the secondary output circuit of the high-voltage group LLC winding is connected to a high-voltage group synchronous rectifier circuit; and the secondary output circuit of the low-voltage group LLC winding is connected to a low-voltage group synchronous rectifier circuit. The negative terminal of the secondary output circuit of the low-voltage group LLC is connected to the positive terminal of the secondary output circuit of the low-voltage group LLC, and the negative terminal of the secondary output circuit of the low-voltage group LLC is grounded; the grounding pin of the rectifier chip of the high-voltage group synchronous rectifier circuit is connected to the positive terminal of the secondary output circuit of the low-voltage group LLC, the operating voltage input pin of the rectifier chip of the high-voltage group synchronous rectifier circuit is connected to the operating voltage power supply circuit of the synchronous rectifier circuit, and the grounding pin of the rectifier chip of the low-voltage group synchronous rectifier circuit is grounded; the positive terminal of the secondary output circuit of the high-voltage group LLC and the negative terminal of the secondary output circuit of the low-voltage group LLC are respectively connected to the positive and negative terminals of the series output circuit.

[0005] Furthermore, the LLC chip driven by the LLC control drive circuit is model UCC256403.

[0006] Furthermore, the high-voltage transformer and the low-voltage transformer have the same turns ratio and the same number of turns in the primary coil, and the output voltages of the high-voltage LLC secondary output circuit and the low-voltage LLC secondary output circuit are equal.

[0007] Furthermore, the rectifier chip model of the high-voltage group synchronous rectifier circuit and the low-voltage group synchronous rectifier circuit is UCC24624.

[0008] Furthermore, the series output circuit is provided with a feedback circuit connected to the LLC control drive circuit.

[0009] The beneficial effects of this utility model are as follows: The LLC secondary series output high voltage circuit of this utility model adopts one LLC resonant converter circuit to drive two transformers. The secondary windings of these two transformers are respectively equipped with synchronous rectifier chips for rectification, and the negative terminal of one transformer is connected to the positive terminal of the other transformer. The high voltage output is generated through the series output circuit. Compared with the primary winding using two separate LLC circuits, the use of LLC chips and MOSFETs can be reduced, simplifying the circuit structure and thus saving manufacturing costs and wiring space. Attached Figure Description

[0010] Figure 1 This is a schematic diagram of the principle of this utility model.

[0011] Figure 2 This is the circuit schematic diagram of this utility model.

[0012] Figure 3 This is a circuit diagram of one embodiment of the present invention.

[0013] In the diagram, 1 is the LLC resonant converter circuit, 2 is the high-voltage transformer, 3 is the low-voltage transformer, 4 is the high-voltage LLC secondary output circuit, 5 is the low-voltage LLC secondary output circuit, 6 is the high-voltage synchronous rectifier circuit, 7 is the low-voltage synchronous rectifier circuit, 8 is the synchronous rectifier circuit operating voltage power supply circuit, and 9 is the series output circuit. Detailed Implementation

[0014] The present invention will be further illustrated below with reference to specific examples and accompanying drawings.

[0015] like Figures 1-3As shown, a circuit for high-voltage output from the secondary winding of an LLC converter is described. The mains input circuit is connected to a bridge rectifier circuit via an EMC filter circuit. The bridge rectifier circuit is then connected to a PFC power conversion circuit, which is controlled by a PFC control drive circuit. The PFC control drive circuit is equipped with a PFC power control chip U1. The output of the PFC power conversion circuit is connected to an LLC resonant converter circuit 1, which is driven by an LLC control drive circuit with an LLC control chip U2. The LLC chip driven by the LLC control drive circuit is model UCC256403. The LLC resonant converter circuit 1 is connected to the primary windings of the high-voltage transformer 2 (T1) and the low-voltage transformer 3 (T2), respectively. The secondary winding of the high-voltage transformer 2 (T1) is connected to the high-voltage LLC secondary output circuit 4, and the secondary winding of the low-voltage transformer 3 (T2) is connected to the low-voltage LLC secondary output circuit 5. The primary and secondary windings of the high-voltage transformer 2 (T1) and the low-voltage transformer 3 (T2) have the same turns ratio and the same number of turns in the primary windings, respectively. Therefore, the output voltages of the high-voltage LLC secondary output circuit and the low-voltage LLC secondary output circuit are approximately equal, for example, both are 48V. The high-voltage LLC secondary output circuit 4 is connected to the high-voltage synchronous rectifier circuit 6, and the low-voltage LLC secondary output circuit 5 is connected to the low-voltage synchronous rectifier circuit 7. The rectifier chips U4 and U5 in both the high-voltage group synchronous rectifier circuit 6 and the low-voltage group synchronous rectifier circuit 7 are model UCC24624, with a voltage difference of 12V between their VDD and PGND pins. The synchronous rectifier circuit's operating voltage power supply circuit 8, based on the 48V output of the low-voltage group LLC secondary output circuit 5, generates a 60V voltage using the secondary winding of the low-voltage group transformer 3 (T2). This 60V voltage is applied to the VDD pin of the high-voltage group synchronous rectifier circuit 6, while the PGND pin of the high-voltage group synchronous rectifier circuit 6 is connected to the positive terminal (+48V) of the low-voltage group LLC secondary output circuit, thus maintaining a 12V voltage difference between the VDD and PGND pins. The ground pin (PGND) of the rectifier chip U5 in the low-voltage group synchronous rectifier circuit is grounded, and the VDD pin is connected to the +12V generated by other circuits. In this case, the pins of the rectifier chips U4 and U5 in the high-voltage synchronous rectifier circuit 6 and the low-voltage synchronous rectifier circuit 7 will not exceed 200V.

[0016] The negative terminal of the high-voltage LLC secondary output circuit 4 is connected to the positive terminal of the low-voltage LLC secondary output circuit 5. The positive terminal of the high-voltage LLC secondary output circuit 4 and the negative terminal of the low-voltage LLC secondary output circuit 5 are respectively connected to the positive and negative terminals of the series output circuit 9. Therefore, the voltage between the positive and negative terminals of the series output circuit 9 is equal to the sum of the output voltages of the high-voltage LLC secondary output circuit 4 and the low-voltage LLC secondary output circuit 5, reaching 96V. However, the output voltage of either the high-voltage LLC secondary output circuit 4 or the low-voltage LLC secondary output circuit 5 is 48V, which is less than 65V. Even under conditions of high current generation, the pins of the rectifier chips U4 and U5 in the high-voltage synchronous rectifier circuit 6 and the low-voltage synchronous rectifier circuit 7 will not exceed 200V.

[0017] A feedback circuit is provided between the positive and negative terminals of the series output circuit 9, which is connected to the LLC control drive circuit. The feedback circuit includes an optocoupler PC3.

[0018] The above embodiments are merely preferred embodiments of the present utility model and are only used to explain the present utility model, not to limit the present utility model. Any changes, substitutions, combinations, simplifications, modifications, etc., made by those skilled in the art without departing from the spirit and principle of the present utility model shall be considered equivalent substitutions and shall be included within the protection scope of the present utility model.

Claims

1. A circuit for outputting a high voltage via a series secondary winding of an LLC converter, comprising an LLC resonant converter circuit, characterized in that: The LLC resonant converter circuit is driven by an LLC control drive circuit with an LLC control chip. The LLC resonant converter circuit is connected to the primary windings of both the high-voltage and low-voltage transformers. The secondary winding of the high-voltage transformer is connected to the secondary output circuit of the high-voltage LLC converter, and the secondary winding of the low-voltage transformer is connected to the secondary output circuit of the low-voltage LLC converter. The secondary output circuit of the high-voltage LLC converter is connected to the high-voltage synchronous rectifier circuit, and the secondary output circuit of the low-voltage LLC converter is connected to the low-voltage synchronous rectifier circuit. The negative terminal of the output circuit is connected to the positive terminal of the secondary output circuit of the low-voltage group LLC; the grounding pin of the rectifier chip of the high-voltage group synchronous rectifier circuit is connected to the positive terminal of the secondary output circuit of the low-voltage group LLC; the operating voltage input pin of the rectifier chip of the high-voltage group synchronous rectifier circuit is connected to the operating voltage power supply circuit of the synchronous rectifier circuit; the grounding pin of the rectifier chip of the low-voltage group synchronous rectifier circuit is grounded; the positive terminal of the secondary output circuit of the high-voltage group LLC and the negative terminal of the secondary output circuit of the low-voltage group LLC are respectively connected to the positive and negative terminals of the series output circuit.

2. The circuit for high voltage output from the secondary winding of an LLC capacitor according to claim 1, characterized in that: The LLC chip driven by the LLC control drive circuit is model UCC256403.

3. The circuit for high voltage output from the secondary winding of an LLC capacitor according to claim 1, characterized in that: The high-voltage transformer and the low-voltage transformer have the same turns ratio and the same number of primary coil turns.

4. The circuit for high voltage output from the secondary winding of an LLC capacitor according to claim 1, characterized in that: The rectifier chip model of the high-voltage group synchronous rectifier circuit and the low-voltage group synchronous rectifier circuit is UCC24624.

5. The circuit for high voltage output from the secondary winding of an LLC capacitor according to claim 1, characterized in that: The series output circuit is provided with a feedback circuit that is connected to the LLC control drive circuit.

Images