Texas Instruments UCC3580EVM, Руководство пользователя

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SLUU085 – November 2001
5 UCC3580EVM
1 Introduction
This user’s guide describes the UCC3580EVM flyback converter evaluation board for comparing an
active-clamp configuration with a hard-switched configuration. The UCC3580EVM is originally configured as
an active-clamp flyback converter. Instructions and parts list are included in order to reconfigure the
UCC3580EVM as a hard-switched flyback converter. Both configurations use the UCC3580 PWM controller.
The active clamp configuration operates noticeably more efficiently than the hard switched configuration. Most
of the efficiency differences will be seen in the primary-side components.
2 Features
D
Provides auxiliary-switch activation complementary to main-power switch drive
D
Programmable dead time (turnon delay) between activation of each switch
D
Voltage mode control with feedforward operation
D
Programmable limits for both transformer volt-second product and PWM duty cycle
D
High-current gate driver for both main and auxiliary outputs
D
Multiple protection features with latched shutdown and soft restart
D
Low supply current (160-
µ
A startup, 2.5-mA operation)
3 Description
3.1 Operating Guidelines
WARNING:
DANGER: HIGH VOLTAGE! This evaluation board is intended for professional use
only. It has exposed high voltages. Do not operate this board without proper
isolation and high-voltage/high-current safety practices.
Refer to the recommended test setup, as shown in Figure 1, and the test points in Table 1. Connect the
UCC3580EVM, configured for either active clamp operation or hard-switched operation, as shown in Figure 1.
Close the ac line switch and verify that the UCC3580EVM is operating correctly (12 V should be measured by
the hand-held DVM on the converter output). Using the appropriate oscilloscope probes, observe the main
transistor drain source voltage (TP14 to TP13) and the cathode to anode voltage of the output rectifier (TP6 to
TP8). The active clamp implementation will have crisp, clamped voltages and no overshoot on the output
rectifier. Converter dynamics can be observed [1] using TP3, 4 and 5.
Other test points are included to observe voltages and currents that are of interest for a specific application.
Table 1 describes the intended purpose of the test points that are installed in the board and how they should
be used.