Full voltage range LLC resonant converter and control method thereof

Abstract

The invention relates to a full voltage rang LLC resonant converter and control method thereof, belonging to the LLC resonant power conversion technical field. The technical scheme includes that: a current type primary ring current sampler acquires a primary ring current signal of LLC resonant conversion circuit, the primary ring current signal is transmitted into a primary ring energy counter connected with the LLC resonant conversion circuit through rectification of a rectifier, when bus voltage changes in the range from Vmax to 5%Vmax, the bus transient voltage value immediately counted by the primary ring energy counter is corresponding to LLC resonant main loop residual energy value, and stable energy waveform Vo is output; and when LLC resonant primary ring residual energy value is reduced to the preset energy value, an energy comparator outputs a control signal to control an electronic switch corresponding to the LLC resonant conversion circuit to close, so that the electronic switch corresponding to the next half working period of LLC resonant conversion circuit is in zero voltage state when the electronic switch is put into operation. The invention realizes full voltage working range of LLC resonant converter, the reliability thereof is fundamentally ensured, so that LLC resonant converter can be designed into solid state converter and the entire life of converter is equal to that of semi-permanent device. The invention can be widely applied to the industries such as electromobile non contact type charging station, electromagnetic induction heating, switch power supply and the like.

Description

[0001] Technical field: [0002] The invention relates to a full voltage range LLC resonant converter and a control method, belonging to the technical field of LLC resonant power conversion. Background technique: [0003] LLC resonant power conversion technology is widely used in non-contact charging stations for electric vehicles, electromagnetic induction heating, switching power supplies and non-contact energy transmission and other industries. The solution to the reliability of the existing LLC resonant converter is to use phase-locked loop control technology; the LLC resonant converter has the advantages of high efficiency, low electromagnetic interference, and simple line control, such as figure 1 As shown, the resonant current signal is sampled by the transformer and sent to the phase-locked loop circuit, and the phase is compared with the phase-locked loop output signal in the phase-locked loop to generate a phase error voltage. After smoothing and filtering, the osc...

AI Technical Summary

Problems solved by technology

However, the core problem of this technology is that the phase error voltage generated by the phase-locked loop must pass through the smoothing filter network. Therefore, it takes 5-10 cycles to complete the action to prevent the LLC resonant converter from entering the hard switching state; Changes and dynamic and random load changes cannot achieve immediate response, and the reliability problem has not been completely resolved

[0004] In 2004, the American IR company launched the IR2159 series LLC resonant converter control chip in the field of energy-saving lamps, but its core reliability problem has not been fundamentally resolved; the reason is that the 2159 series still uses the phase-locked loop control method, through The integral circuit completes the adjustment of the lower limit frequency of the oscillator. As a result, it cannot achieve real-time control of each turn-on pulse of the LLC resonant power converter, resulting in low reliability and cannot enter large-scale industrial production.

[0005] The technical solution disclosed in Chinese invention patent 200680010615.6 is: the current of the main loop exceeds the preset maximum value, the current of the main loop exceeds the predetermined time of the control system, and after the current of the main loop has crossed zero (the resonant capacitor picks up the voltage signal), turn off the on-pulse to ensure The second half cycle is zero current and zero voltage turn-on; the problem with this control method is: once the current crosses zero, the zero-voltage and zero-current turn-on and turn-off conditions of S1 or S2 have been lost; the reason is that the LLC resonance main The remaining resonance energy of the ring is not enough to make the in-phase current continue to the energy required for the reverse conduction of the electronic switch corresponding to the second half of the on-pulse period, and the natural zero-voltage and zero-current states will not appear

Moreover, the discrete type of the main loop parameters and the uncertain factors of the load will lead to the incomplete control theory of turning off the on-pulse based on the timing device and detecting the zero-crossing current of the main loop.

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