有源嵌位pwm控制器lm5025原理及应用（Principle and application of active position locked PWM controller lm5025）.doc

有源嵌位pwm控制器lm5025原理及应用（Principle and application of active position locked PWM controller lm5025） Key words: active clamp, PWM controller, voltage mode Abstract:A, unique, PWM, controller, LM5025, designed, for, Active, is, Clamp Introduced, in, this, paper., LM5025, have, additional, features, include:, UVLO, soft, start, Oscillator, UP/DOWN, sync, capability, and, thermal, shutdown., Typical, circuit, application Is, recommended.Keywords:Active, Clamp, PWM, Controller, Voltage, Mode I. Introduction The LM5025 is an active clamp dedicated PWM converter whose internal drive can drive either a P channel or a N channel clamp switch. Compared with the conventional winding or RDC clamping technique, the active clamp technique has the characteristics of high efficiency and high power density. The LM5025 has two control outputs: the main power drive (OUT_A) output and the active clamp driver (OUT_B) output. The active clamp output can set the overlap time (P channel switching tube) or dead time (N channel switching tube). The two driver outputs have good driving performance, which can drive the MOS tube and also drive the bipolar transistor. LM5025 oscillator frequency up to 1MHz, PWM and current sampling transmission delay time is less than 100ns. The LM5025 has a high voltage start regulator that allows the power to have a wide input range of 13V to 90V. LM5025 also features input undervoltage lockout, soft start, oscillator synchronization, and thermal protection. Two, pin function The pin arrangement of the LM5025 is shown in figure 1. The functions of each pin are as follows: VIN: start the regulator input. RAMP: ramp signal setting end. The VIN pin is externally connected with RC to set the slope of the slope. The inner discharge MOS tube is controlled by an internal clock or a volt second product clamp comparator to control the on-off of the MOS tube. CS1: pulse to pulse current limiting sampling terminal. When the CS1 terminal voltage is higher than 0.25V, it enter