UCC256302 LLC Resonant Controller - TI High Voltage Startup Technology

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"TI-UCC256302是一款由德州仪器（Texas Instruments，简称TI）推出的 LLC谐振控制器，专为实现低待机功率设计。该芯片具有集成高压启动功能，能够消除对外部偏置电源的需求，同时提供了优秀的瞬态响应。UCC256302采用了混合磁滞控制（Hybrid Hysteretic Control，HHC），保证了卓越的瞬态性能和简单的补偿设计。此外，其优化的低功耗特性有助于实现75毫瓦的待机功率设计，符合CoC Tier II标准。" TI的UCC256302 LLC谐振控制器主要特点包括： 1. 集成高压启动：这一特性使得UCC256302在没有外部偏置电源的情况下也能正常工作，简化了系统设计并降低了成本。 2. 混合磁滞控制：HHC提供了一流的瞬态响应，确保系统在负载变化时能快速稳定，同时简化了补偿网络的设计，使得系统调整更为容易。 3. 低功耗特性：通过高级的间歇模式（Burst Mode）和光耦低功耗操作，UCC256302有助于满足严格的待机功率要求，适用于能源效率高的应用。 4. 快速退出间歇模式：在系统需要快速恢复全功率运行时，UCC256302能够迅速从间歇模式切换到正常工作模式。 5. 改进的电容区域避免方案：这个功能有助于防止在特定工作条件下发生不稳定或振荡，提高了系统的稳定性。 6. 自适应死区时间：自动调整死区时间以优化开关性能，减少损耗，提高效率。 7. 内置高侧栅极驱动器：具备0.6A和1.2A的驱动能力，可以驱动大电流MOSFET，支持高效能转换。 8. 软启动功能：采用无硬开关的软启动技术，降低了启动过程中的电磁干扰（EMI）和应力。 9. 完善的保护功能：包括过温保护、输出过电压保护、输入过压和欠压保护，为系统提供了多重安全防护。这款芯片适用于需要低待机功率和高效能的电源转换系统，如服务器、数据中心、通信设备和家用电器等。通过其独特的特性和功能，UCC256302能够帮助设计者实现更节能、更可靠的产品。

Temperature (qC)

- V

HOH

(mV)

-50 -25 0 25 50 75 100 125 150

100

150

200

250

300

D002

VCC = 13 V

VCC = 15 V

VCC = 25 V

Temperature (qC)

CCStartSel

f (V)

-50 -25 0 25 50 75 100 125 150

25.95

26.05

26.1

26.15

D002

VCC = 13 V

VCC = 15 V

VCC = 25 V

Temperature (qC)

RVCC

-V

LOH

(mV)

-50 -25 0 25 50 75 100 125 150

100

150

200

250

300

D002

VCC = 13 V

VCC = 15 V

VCC = 25 V

Temperature (qC)

HOL

- V

(mV)

-50 -25 0 25 50 75 100 125 150

D002

VCC = 13 V

VCC = 15 V

VCC = 25 V

Temperature (qC)

HB-HSUVLOFall

(V)

-50 -25 0 25 50 75 100 125 150

7.23

7.24

7.25

7.26

7.27

7.28

7.29

D002

VCC = 13 V

VCC = 15 V

VCC = 25 V

Temperature (qC)

LOL

(mV)

-50 -25 0 25 50 75 100 125 150

D002

VCC = 13 V

VCC = 15 V

VCC = 25 V

UCC256302

www.ti.com

SLUSD69 –NOVEMBER 2017

Product Folder Links: UCC256302

Typical Characteristics (continued)

Figure 19. I

HB-HSUVLOFall

vs Temperature Figure 20. V

LOL

vs Temperature

Figure 21. V

RVCC-VLOH

vs Temperature Figure 22. V

HOL

- V

vs Temperature

Figure 23. V

- V

HOH

vs Temperature Figure 24. V

CCStartself

vs Temperature

UCC256302

www.ti.com

SLUSD69 –NOVEMBER 2017

Product Folder Links: UCC256302

6 Detailed Description

6.1 Overview

The high level of integration of UCC256302 enables significant reduction in the list of materials and solution size

without compromising functionality. UCC256302 achieves extremely low standby power using burst mode. The

device's novel control scheme offers excellent transient performance and simplified compensation.

Many consumer and industrial applications with mid-high power consumption, including large screen televisions,

AC-DC adapters, server power supplies, and LED drivers, employ PFC + LLC power supplies because they offer

improved efficiency, and small size, compared with a PFC + Flyback topology. A disadvantage of the PFC + LLC

power supply system is that it naturally offers poor light load efficiency and high no-load power because the LLC

stage requires a minimum amount of circulating current to maintain regulation. To meet light load efficiency and

no load power requirement it is therefore necessary to use an auxiliary flyback converter that runs continuously

and allows the main PFC + LLC power system to be shut down when the system enters low power or standby

mode. UCC256302 LLC controller is designed to make a LLC power supply system with advanced control

algorithm and high efficient burst mode. UCC256302 contains a number of novel features that enable it to offer

excellent light load efficiency and no load power. This will allow customers to design power systems that meet

150-mW no-load power target without needing an auxiliary flyback converter. UCC256302 includes a high-

voltage startup JFET to initially charge the VCC capacitor to provide the energy needed to start the PFC and LLC

power system. Once running, power for the PFC and LLC controllers is derived from a bias winding on the LLC

transformer.

UCC256302 uses a novel control algorithm, Hybrid Hysteretic Control (HHC), to achieve regulation. In this

control algorithm, the switching frequency is defined by the resonant capacitor voltage, which carries accurate

input current information. Therefore, the control effort controls the input current directly. This enables excellent

load and line transient response, and high efficient burst mode. In addition, comparing with traditional Direct

Frequency Control (DFC), HHC changes the system to a first order system. Therefore, the compensation design

is much easier and can achieve higher loop bandwidth.

UCC256302 includes robust algorithms for avoiding ZCS operation region. When near ZCS operation is

detected, UCC256302 over-rides the feedback signal and ramps up the switching frequency until operation is

restored. After which the switching frequency is ramped back down at a rate determined by the soft-start

capacitor until control has been handed back to the voltage control loop.

UCC256302 monitors the half-bridge switched node to determine the required dead-time in the gate signals for

the outgoing and incoming power switches. In this way the dead-time is automatically adjusted to provide

optimum efficiency and security of operation. UCC256302includes an algorithm for adaptive dead-time that

makes its operation inherently robust compared with alternative parts.

UCC256302

SLUSD69 –NOVEMBER 2017

www.ti.com

Product Folder Links: UCC256302

Overview (continued)

UCC256302 includes high and low-side drivers that can directly drive LLC power stage delivering up to 1-kW

peak/500-W continuous power. This allows complete and fully featured power systems to be realized with

minimum component count.

An integrated high voltage JFET allows the power system to be regulating its output voltage within one second of

the mains voltage appearing at the input of the PFC stage. UCC256302 provides start-up power for both the LLC

and PFC stages. Once operating, the JFET is switched OFF to limit power dissipation in the package and reduce

standby power consumption.

At low output power levels UCC256302 automatically transitions into light-load burst mode. The LLC equivalent

load current level during the burst on period is a programmable value. The space period between bursts is

terminated by the secondary voltage regulator loop based on the FB pin voltage. During burst mode, the

resonant capacitor voltage is monitored so that the first and last burst pulse widths are fully optimized for best

efficiency. This method allows UCC256302 to achieve higher light-load efficiency and reduced no-load power

compared with alternative parts.

In addition, UCC256302 enables the opto-coupler to operate at a low power mode, which can save up to 20 mW

at standby mode comparing with conventional solution.

Additional protection features of UCC256302 include three-level over current protection, output over voltage

protection, input voltage OVP and UVP, gate driver UVLO protection, and over temperature protection.

The key features of UCC256302 can be summarized as follows:

• Integrated high voltage start up and high voltage gate driver

• Hybrid Hysteretic Control helps achieve best in class load and line transient response

• Optimized light load burst mode enables 150-mW standby power design

• Improved capacitive region operation prevention scheme

• Adaptive dead time

• Wide operating frequency range (35 kHz ~ 1 MHz)

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