基于LM5032的高电压双路交错电流模式控制器

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基于LM5032的高电压双路交错电流模式控制器

　　1 Features

　　Two Independent PWM Current Mode Controllers

　　Integrated High-Voltage Startup Regulator

　　Compound 2.5-A Main Output Gate Drivers

　　Single Resistor Oscillator Setting to 2 MHz

　　Synchronizable Oscillator

　　Programmable Maximum Duty Cycle

　　Maximum Duty Cycle Fold-Back at High-Line Voltage

　　Adjustable Timer for Hiccup Mode Current Limiting

　　Integrated Slope Compensation

　　Adjustable Line Undervoltage Lockout

　　Independently Adjustable Soft-Start (Each Regulator)

　　Direct Interface with Opto-Coupler Transistor

　　Thermal Shutdown

　　TSSOP 16-Pin Package

　　2 Applications

　　Telecommunication Power Converters

　　Industrial Power Converters

　　42-V Automotive Systems

　　3 Description

　　The LM5032 dual current mode PWM controller contains all the features needed to control either two independent forward dc/dc converters or a single high current converter comprised of two interleaved power stages. The two controller channels operate 180° out of phase thereby reducing input ripple current. The LM5032 includes a startup regulator that operates over a wide input range up to 100 V and compound (bipolar + CMOS) gate drivers that provide a robust 2.5-A peak sink current. The adjustable maximum PWM duty cycle reduce stress on the primary side MOSFET switches. Additional features include programmable line undervoltage lockout, cycle-by-cycle current limit, hiccup mode fault operation with adjustable response time, PWM slope compensation, soft-start, and a 2-MHz capable oscillator with synchronization capability.

　　The LM5032 contains all the features necessary to implement two independently regulated current mode dc/dc converters, or a single high current converter comprised of two parallel interleaved channels using the Forward converter topology. The two controllers operate 180° out of phase from a common oscillator, thereby reducing input ripple current. Each regulator channel contains a complete PWM controller, current sense input, soft-start circuit, and gate driver output. Common to both channels are the startup and VCC regulator, line under-voltage lockout, 2 MHz capable oscillator, maximum duty cycle control, and the hiccup mode fault protection circuit.

　　The gate driver outputs (OUT1, OUT2) are designed to drive N-channel MOSFETs. Their compound configuration reduces the turn-off-time, thereby reducing switching losses. Additional features include thermal shutdown, slope compensation, and the oscillator synchronization capability.

The LM5032 contains a line under-voltage lockout circuit (UVLO) designed to enable the VCC regulator and output drivers when the system voltage (VPWR) exceeds the desired level (see Figure 14). VPWR is the voltage normally applied to the transformer primary, and usually connected to the VIN pin (see the schematic on Page 1). The threshold at the UVLO comparator is 1.25V. An external resistor divider connected from VPWR to ground provides 1.25V at the UVLO pin when VPWR is increased to the desired turn-on threshold. When VPWR is below the threshold the VCC regulator and output drivers are disabled, and the internal 20 µA current source is off. When VPWR reaches the threshold, the comparator output switches low to enable the internal circuits and the 20 µA current source. The 20 µA flows into the external divider’s junction, raising the voltage at UVLO, thereby providing hysteresis. Internally the voltage at UVLO also drives the Maximum Duty Cycle Limiter circuit (described below), which may influence the values chosen for the UVLO pin resistors. At maximum VPWR, the voltage at UVLO should not exceed 6V. Refer to the Applications Information section for a procedure to calculate the resistors values.

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　　The LM5032 controller can be shutdown by forcing the UVLO pin below 1.25V with an external switch. When the UVLO pin is low, the outputs and the VCC regulator are disabled, and the LM5032 enters a low power mode. If VCC pin is not powered from an external source, the current into VIN drops to a nominal 500 µA. If the VCC pin is powered from an external source, the current into VIN is nominally 50 µA, and the current into the VCC pin is approximately 4.3 mA. To disable one regulator without affecting the other, see the description of the Soft-start section.