Method and apparatus providing a multi-function terminal for a power supply controller
DC CAFCFirst Claim
1. A power supply controller circuit, comprising:
- a current input circuit coupled to receive a current representative of an input voltage applied to a power supply, the current input circuit to generate a maximum duty cycle adjustment signal in response thereto; and
a control circuit to generate a switching waveform, the control circuit coupled to receive the maximum duty cycle adjustment signal, the control circuit to limit the duty cycle of the switching waveform to a maximum value in response to the maximum duty cycle adjustment signal, the switching waveform to regulate the power supply output.
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Abstract
A power supply controller having a multi-function terminal. In one embodiment, a power supply controller for switched mode power supply includes a drain terminal, a source terminal, a control terminal and a multi-function terminal. The multi-function terminal may be configured in a plurality of ways providing any one or some of a plurality of functions including on/off control, external current limit adjustments, under-voltage detection, over-voltage detection and maximum duty cycle adjustment. The operation of the multi-function terminal varies depending on whether a positive or negative current flows through the multi-function terminal. A short-circuit to ground from the multi-function terminal enables the power supply controller. A short-circuit to a supply voltage from the multi-function terminal disables the power supply controller. The current limit of an internal power switch of the power supply controller may be adjusted by externally setting a negative current from the multi-function terminal. The multi-function terminal may also be coupled to the input DC line voltage of the power supply through a resistance to detect an under-voltage condition, an over-voltage condition and/or adjust the maximum duty cycle of power supply controller. Synchronization of the oscillator of the power supply controller may also be realized by switching the multi-function terminal to power or ground at the desired times.
112 Citations
12 Claims
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1. A power supply controller circuit, comprising:
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a current input circuit coupled to receive a current representative of an input voltage applied to a power supply, the current input circuit to generate a maximum duty cycle adjustment signal in response thereto; and
a control circuit to generate a switching waveform, the control circuit coupled to receive the maximum duty cycle adjustment signal, the control circuit to limit the duty cycle of the switching waveform to a maximum value in response to the maximum duty cycle adjustment signal, the switching waveform to regulate the power supply output. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A method for controlling a power supply, comprising:
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receiving a first current representative of an input voltage to the power supply through a first terminal of a power supply controller;
switching a second current flowing through a primary winding with a switching waveform having a duty cycle;
adjusting the duty cycle of the switching waveform in response to the first current. - View Dependent Claims (9, 10, 11, 12)
generating a positive current sense signal in response to the first current;
generating a first voltage in response to the positive current sense signal;
comparing the first voltage with a switching sawtooth waveform; and
resetting a latch to limit the maximum duty cycle of the switching waveform in response to comparing the first voltage with the switching sawtooth waveform.
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12. The method of claim 8 wherein receiving the first current representative of the input voltage to the power supply comprises coupling a resistance between the first terminal and an input of the primary winding.
Specification