TI-UCC2891：高效脉宽调制控制器，简化电源设计
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更新于2024-06-30
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TI-UCC2891是一款高性能脉宽调制控制器，它专为简化不同主动钳/重置开关功率拓扑的实现而设计。这款设备具备一系列关键特性：
1. **低输出抖动**：UCC2891具有出色的控制精度，能提供稳定的输出波形，减少噪声干扰，这对于需要高稳定性的应用如服务器电源、数据通信等至关重要。
2. **软启动和辅助功能**：它支持软启动，有助于保护主电路在上电时避免冲击，同时具有可编程的辅助驱动器，提供死区时间（AUX与MAIN开关间的延迟），确保切换过程的协同工作。
3. **峰值电流模式控制**：采用周期性电流限制技术，能够在每个周期内精确控制电流，确保转换效率和系统安全。
4. **集成110V输入启动稳压器**：针对UCC2891/3型号，内置的稳压器便于系统在各种输入电压下稳定工作。
5. **驱动能力**：拥有两个可作为sink（负载）和source（源）的真驱动输出，能够满足多种负载需求。
6. **线电压检测**：内置准确的过电压（OV）和欠电压（UV）阈值检测，可以保护电路免受电压异常影响。
7. **可编程斜坡补偿**：允许用户根据具体应用调整控制斜率，优化转换效率。
8. **高频率同步振荡器**：1.0-MHz的可同步振荡器提供了快速的开关速度，适用于高效率和低电磁干扰的应用。
9. **最大 duty cycle 设置**：可编程的最大占空比设置，为用户提供灵活的性能调整空间。
10. **广泛应用领域**：UCC2891适用于功率范围广泛的场合，包括150W到700W的开关模式电源（SMPS）、高效低EMI/RFI的离线或直流/直流转换器，以及48V电信、数据中心电源以及高功率适配器、LCD电视和PDP电视等。
UCC2891是一款高度灵活且性能卓越的PWM控制器，适合于对效率、稳定性和易用性有较高要求的电力转换系统设计，广泛应用于服务器、电信、数据通信和家用电器等领域。其丰富的功能和易于集成的特点，简化了设计师在不同功率级和拓扑中的应用开发工作。
SLUS542F − OCTOBER 2003 − REVISED JULY 2009
8
www.ti.com
DETAILED PIN DESCRIPTIONS
RDEL (pin 1)
This pin is internally connected to an approximately 2.5-V DC source. A resistor (R
DEL
) to GND (pin 6) sets the
turn-on delay for both gate drive signals of the UCC2981 family of controllers. The delay time is identical for both
switching transitions, between OUT (pin 13) is turning off and AUX (pin 14) is turning on as well as when AUX
(pin 14) is turning off and OUT (pin 13) is turning on. The delay time is defined as:
t
DEL1
+ t
DEL2
+ 11.1 10
*12
R
DEL
) 15 10
*9
seconds
For proper selection of the delay time refer to the various references describing the design of active clamp power
converters.
RTON (pin 2)
This pin is internally connected to an approximately 2.5-V DC source. A resistor (R
ON
) to GND (pin 6) sets the
charge current of the internal timing capacitor. The RTON pin, in conjunction with the RTOFF pin (pin 3) are used
to set the operating frequency and maximum operating duty cycle of the UCC2891 family.
RTOFF (pin3)
This pin is internally connected to an approximately 2.5-V DC source. A resistor (R
OFF
) to GND (pin 6) sets the
discharge current of the internal timing capacitor. The RTON and RTOFF pins are used to set the switching
period (T
SW
) and maximum operating duty cycle (D
MAX
) according to the following equations:
t
ON
+ 36.1 10
*12
R
ON
* t
DEL1
seconds
t
OFF
+ 15 10
*12
R
OFF
) t
DEL1
) 170 10
*9
seconds
T
SW
+ t
ON
) t
OFF
D
MAX
+
t
ON
T
SW
VREF (pin 4)
The controller’s internal, 5-V bias rail is connected to this pin. The internal bias regulator requires a good quality
ceramic bypass capacitor (C
VREF
) to GND (pin 6) for noise filtering and to provide compensation to the regulator
circuitry. The recommended C
VREF
value is 0.22-µF. The minimum bypass capacitor value is 0.022-µF limited
by stability considerations of the bias regulator, while the maximum is approximately 22-µF. Also, capacitor
value on VDD should be minimum 10 times greater than that on VREF.
The VREF pin is internally current limited and can supply approximately 5-mA to external circuits. The 5-V bias
is only available when the undervoltage lock out (UVLO) circuit enables the operation of UCC289x controllers.
For the detailed functional description of the undervoltage lock out (UVLO) circuit refer to the Functional
Description section of this datasheet.
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