CN109560706B

CN109560706B - PSR current control system under LLC framework

Info

Publication number: CN109560706B
Application number: CN201710892388.4A
Authority: CN
Inventors: 杨森泰
Original assignee: Yujing Energy Technology Co ltd
Current assignee: Yujing Energy Technology Co ltd
Priority date: 2017-09-27
Filing date: 2017-09-27
Publication date: 2020-08-25
Anticipated expiration: 2037-09-27
Also published as: CN109560706A

Abstract

The invention discloses a PSR current control system under an LLC framework, which comprises a voltage polarity conversion circuit, a current signal sampling circuit, a current crossing detection circuit, a zero current detection circuit and a current integration circuit, wherein the voltage polarity conversion circuit acquires a voltage signal from the primary side of an LLC transformer and outputs a positive voltage signal, then the current integration circuit respectively acquires a current input signal output by the current signal sampling circuit, a zero current point output by the current crossing detection circuit and a zero current state output by the zero current detection circuit, the lowest current level of the current input signal is increased to zero current according to the zero current point and the zero current state, a current integration waveform is generated and integrated to generate an output current, and the LLC transformer directly acquires the output current for controlling the state of the secondary side output from the primary side.

Description

PSR current control system under LLC framework

Technical Field

The present invention relates to a PSR current control system under an LLC architecture, and more particularly, to a PSR current control system under an LLC architecture, which obtains a transformer current signal at a primary side and calculates an output current to achieve stable control.

Background

In recent years, the market for consumer electronics and LED driving circuits has grown, so that the power converter needs to be more power-saving and smaller. LLC architectures have been used extensively in high efficiency voltage conversion systems, such as power supplies for PCs, servers, lighting or network power supplies, etc. Conventional LLC control uses conventional secondary-side regulation feedback to achieve constant-voltage and constant-current control through a set of optocouplers and comparators (Error Amp comparators) on the secondary side. In the secondary side circuit, the primary purpose is to conduct the signal of the secondary side to the primary side, and the feedback circuit can adjust the duty cycle of the pulse signal by the signal, so that when the output load varies, the power supply can still provide stable current and voltage for the output load, and along with the variation of the load, the operating frequency of the LLC can show negative correlation change, and the transformer current can be operated in three different modes, that is: when the operating frequency is lower than the resonance frequency, the transformer current operating mode enters a discontinuous mode (DCM); when the operation frequency is equal to the resonance frequency, the transformer current operation mode enters a critical mode; and, when the operating frequency is higher than the resonant frequency, the transformer current operating mode may enter a continuous mode (CCM). The current control method needs to increase the number of parts, PCB space and cost on the secondary side, and the detection circuit on the secondary side will generate power loss and affect the standby power consumption. Therefore, many manufacturers are moving towards PSR (Pr average-Si de Regu l at i on, primary side regulation).

The PSR can achieve constant current and constant voltage control by controlling the output load condition of the primary side without a feedback control circuit on the secondary side. The control method is to control the duty cycle of the pulse signal to stabilize the output load condition by detecting the voltage signal on the auxiliary winding of the primary side transformer.

The most common architecture for PSR control is F-lback (fly-back control), but F-lback must operate in critical mode, or discontinuous mode, and once the continuous mode (COM) is entered, the PSR control of F-lback will be out of control. But LLC architectures utilize varying frequency to vary the gain of the output. There is no way to limit in which mode the operation of the LLC is.

In view of the above disadvantages, the present inventors have studied improvements on the above disadvantages, and have finally made the present invention.

Disclosure of Invention

The primary objective of the present invention is to provide a PSR current control system under LLC architecture, which obtains the transformer current signal at the primary side, calculates the output current, and achieves stable control.

To achieve the above objects and effects, the present invention comprises the following technical means:

a voltage polarity conversion circuit, electrically connected to a primary side of a default LLC transformer, for converting a negative voltage in a voltage signal to a positive voltage and outputting a positive voltage signal;

a current signal sampling circuit electrically connected to the voltage polarity converting circuit for receiving the positive voltage signal to obtain a current input signal;

a current cross detection circuit, electrically connected to the voltage polarity conversion circuit, for receiving the positive voltage signal and calculating a zero current point;

a zero current detection circuit electrically connected to the primary side of the LLC transformer for detecting a zero current state; and the number of the first and second groups,

a current integrating circuit, which is electrically connected to the current signal sampling circuit, the current crossover detecting circuit and the zero current detecting circuit, respectively, and receives the current input signal, the zero current point and the zero current state, and according to the zero current point and the zero current state, the lowest current level of the current input signal is raised to the zero current, and a current integrating waveform is generated and integrated to generate an output current;

therefore, the voltage polarity conversion circuit obtains the voltage signal from the primary side of the LLC transformer and outputs a positive voltage signal, then the current integration circuit obtains the current input signal output by the current signal sampling circuit, the zero current point output by the current crossing detection circuit and the zero current state output by the zero current detection circuit respectively, the lowest current level of the current input signal is increased to the zero current according to the zero current point and the zero current state, a current integration waveform is generated and an output current is generated after integration, and the LLC transformer directly obtains the output current for controlling the state of the secondary side output from the primary side.

According to the above structure, the zero current detection circuit is electrically connected to a zero potential node preset by the LLC transformer.

According to the above structure, the current integration circuit is electrically connected to a default LED driving circuit.

In order to more particularly appreciate the above objects, features and advantages of the present invention, reference is made to the following description taken in conjunction with the accompanying drawings in which:

drawings

FIG. 1 is a block diagram of a circuit configuration according to a preferred embodiment of the present invention.

Fig. 2 is a block diagram of a part of the circuit structure in fig. 1.

Fig. 3 is a waveform diagram showing the operation of the present invention in the continuous mode.

Fig. 4 is an exploded view of the waveform of fig. 3.

Fig. 5 is a waveform diagram illustrating the operation of the present invention in the discontinuous mode.

Fig. 6 is a waveform diagram illustrating the operation of the present invention in the critical mode.

Detailed Description

Referring to fig. 1 and fig. 2, it can be seen that the structure of the present invention mainly includes:

a voltage polarity converting circuit 2, electrically connected to a primary side of a default LLC transformer 1, for converting a negative voltage in a voltage signal into a positive voltage and outputting a positive voltage signal;

a current signal sampling circuit 3 electrically connected to the voltage polarity converting circuit 2 for receiving the positive voltage signal to obtain a current input signal;

a current cross detection circuit 4 electrically connected to the voltage polarity conversion circuit 2 for receiving the positive voltage signal and calculating a zero current point;

a zero current detection circuit 5 electrically connected to the primary side of the LLC transformer 1 for detecting a zero current state, i.e. electrically connected to a zero potential node ZCD preset in the LLC transformer; and the number of the first and second groups,

a current integration circuit 6, electrically connected to the current signal sampling circuit 3, the current crossover detection circuit 4 and the zero current detection circuit 5, respectively, for receiving the current input signal, the zero current point and the zero current state, and according to the zero current point and the zero current state, raising the lowest current level of the current input signal to the zero current point, generating a current integration waveform and integrating the current integration waveform to generate an output current, and transmitting the output current to a default LED driving circuit 7;

therefore, the voltage polarity converting circuit 2 obtains a voltage signal from the primary side of the LLC transformer 1 and outputs a positive voltage signal, and then the current integrating circuit 6 obtains a current input signal output by the current signal sampling circuit 3, a zero current point output by the current crossover detecting circuit 4, and a zero current state output by the zero current detecting circuit 5, respectively, according to the zero current point and the zero current state, the lowest current level of the current input signal is raised to a zero current, a current integrating waveform is generated and integrated to generate an output current, so that the LLC transformer 1 directly obtains the output current for controlling the secondary side output state from the primary side, and controls the LED driving circuit 7.

Referring to fig. 3 to 6, the control waveform of the control signal a is divided into a positive period S1 and a negative period S2 according to the positive and negative half cycles, the sampled current ISH corresponds to the control signal a, and the actual current waveform i r is a current waveform diagram displayed as an oscilloscope; the excitation current iM is generated when the LLC transformer 1 acts and is used for calculating and obtaining an output current IOUT; the stable excitation current iM is temporarily cut off in a stable output state when the LLC transformer 1 switches over the control signal A; and ID1 and ID2, and the result obtained by the final calculation, when the present invention starts to operate:

time points t0-t 1: the sampling current ISH is a negative voltage, and therefore, the voltage polarity conversion circuit 2 converts the negative voltage back to a positive voltage;

time points t1-t 2: obtaining a sampling current SH converted into a positive voltage;

time points t2-t 4: when the zero current output is detected by the zero current detection point ZCD of the zero current detection circuit 5, the sampling current ish is fixed at the current value at the time of the zero current output;

time points t3-t 4: the current crossover detection circuit 4 senses the cycle transition of the control signal a, and the cycle transition is from low potential to high potential, at this time, the output current iout is in a positive voltage state;

time points t4-t 5: meanwhile, the output current enters a negative period S2 from the positive period S1, and the voltage polarity conversion circuit 2 converts the sampling current of the negative voltage into a positive voltage;

time points t6-t 0: at this time, the current integration circuit 6 integrates the current integration waveform at time t0-t6 to generate an output current IOUT, that is, the current integration circuit 6 integrates the resonant current ID1 of the positive half cycle S1 and the resonant current ID2 of the negative half cycle S2, so that the LLC transformer 1 directly obtains the output current for controlling the state of the secondary output at the primary side; after a complete cycle of the control signal A, the following operations are repeated from time t0 to time t 6.

The above-described operations are similar to those of fig. 5 and 6 in terms of the waveform decomposition operation, and are different in the operation mode.

In summary, the PSR current control system under the LLC architecture of the present invention is a novel and progressive invention, and the application of the invention patent is legally proposed; however, the above description is only for the purpose of illustrating the preferred embodiments of the present invention, and it is intended that the present invention cover all the modifications, alterations, changes, and equivalents of the embodiments of the invention which fall within the scope of the claims of the present invention.

Claims

1. A PSR current control system under an LLC framework is characterized in that: the method comprises the following steps:

and the current integrating circuit is respectively electrically connected with the current signal sampling circuit, the current cross detection circuit and the zero current detection circuit, receives the current input signal, the zero current point and the zero current state, and raises the lowest current level of the current input signal to the zero current according to the zero current point and the zero current state to generate a current integrating waveform and generate an output current after integration, so that the LLC transformer directly obtains the output current for controlling the state of the secondary side output at the primary side.

2. The PSR current control system under the LLC architecture of claim 1, wherein: the zero current detection circuit is electrically connected to a zero potential node preset by the LLC transformer.

3. The PSR current control system under the LLC architecture of claim 1, wherein said current integration circuit is electrically connected to a default LED driver circuit.