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PFC+LLC Composite controller.


For high power density, high power output fast charge needs, Sillij launched a high-performance PFC+LLC combination controller SY5055, which sealed the front BOOST PFC and the rear LLC controller, making the peripheral circuit more concise, saving costs and also conducive to improving the power density of the entire power solution.


Characteristic advantage

Built-in high voltage starting

Low standby power consumption (<100mW)

Very low design cost and minimal BOM

Compact package: SOP16


High PF(>0.95), low THD(<5%)

Built-in loop compensation

Built-in valley bottom detection turned on

Built-in X capacitor discharge


Fast dynamic response

Built-in half-bridge drive


PFC BO/BI, output undervoltage/overvoltage protection, sampling resistance short-circuit protection, etc

LLC BO/BI, output overvoltage/overload/capacitive/overtemperature/adaptive dead-time protection, etc

Architectural advantage

Typical application circuit diagram

The SY5055 has more protection features and better power-on timing. The BOOST PFC part uses average current control to better achieve high PF and low THD. Under full load condition, PF>0.95 and THD<5% can be achieved by SY5055. The LLC part realizes fast dynamic response and simple loop compensation parameter design through specific current mode control.

1. High PF, low THD

BOOST PFC control block diagram

The SY5055 BOOST PFC uses average current control and is mainly composed of an external voltage loop, a current waveform generating module and an internal current loop. The external voltage loop adjusts the BOOST output voltage to the design value, which realizes the built-in BOOST loop parameters and simplifies the peripheral circuit. The current waveform generator module detects the input AC voltage through the LNS pin to generate sinusoidal current reference signal in the same phase as the current loop, realizing the functions of high PF and low THD.

Ac input voltage and input current waveform

2. Fast dynamic response

LLC current control block diagram

The SY5055 LLC section uses specific current mode control for fast dynamic response. The current feedback signal proportional to the output power is obtained through the ISEN pin, and the signal is compared with the COMP voltage compensation signal to control the switching state of the upper and lower tubes in each switching cycle, so as to control the output power, so as to achieve fast dynamic response when the output power changes. The LLC load dynamic response waveform is as follows:

Load dynamic response

3. High efficiency, low EMI

The SY5055 PFC circuit uses bottom detection to reduce on-turn losses and achieve better EMI performance, while enabling the system to operate in different operating modes depending on the size of the output load. When the load is heavy, PFC works in the CrM mode, gradually enters the DCM mode as the load drops, and enters the Burst mode under very low load, so that PFC can obtain higher efficiency under different loads.

PFC power curve

The SY5055 LLC circuit also adjusts different operating modes depending on the load. When the load is heavy, it works in CCM mode; when the load is light, it enters DCM mode, and the control DCM frequency is higher than 25kHz; when the load continues to decrease, it enters Burst mode, and the control Burst frequency is less than 1kHz. Based on this working mode, the LLC conversion efficiency is improved, and the light load noise is greatly reduced.

LLC power curve

In addition, the SY5055 has a built-in high-voltage start to reduce standby power consumption, integrated X-capacitor discharge to meet safety requirements, and a built-in LLC half-bridge drive to simplify peripheral circuitry. It includes PFC level BO/BI, UVP/OVP, HV OVP, LLC level BO/BI, output OVP, OLP, capacitive protection, adaptive dead time, OTP and other protection functions.

Application scenario

The SY5055 is particularly suitable for medium power applications ranging from 100 to 300W, such as PC integrated power supplies, electric vehicle chargers, large-size TVS, and outdoor lighting.

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