Shaping a current sense signal by using a controlled slew rate
First Claim
1. A circuit comprising:
- an amplifier having a controlled maximum slew rate, connected for receiving a current sense signal including a meaningful portion proportional to a current in a switched power device and a current spike portion and for generating an output, the maximum slew rate of said amplifier being set so as to attenuate the current spike portion without attenuating the meaningful portion of the current sense signal; and
a switching regulator controller connected to receive the output of said amplifier and to control the switched power device.
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Accused Products
Abstract
A method and circuit for reducing the leading edge spike in a current sense signal. The current sense signal is a measure of the current through a switched power device controlled by a switching regulator controller. The slew rate of the current sense signal is limited to prevent the slew rate from exceeding a predetermined maximum. The limited slew rate signal is provided to the switching regulator controller. A transconductance amplifier may be used to limit the slew rate of the current sense signal. A capacitor at the output of the transconductance amplifier contributes to controlling the maximum slew rate of the amplifier. The capacitor is charged by the current output of the amplifier to provide a voltage signal for use in place of the original current sense signal. A switch may be provided for selecting between the slew rate limited current sense signal and the original current sense signal. A time delay may be used to control the switch so that the slew rate limiting is replaced by the original current sense signal after a first predetermined time portion of each “on cycle” of the switched power device.
54 Citations
17 Claims
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1. A circuit comprising:
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an amplifier having a controlled maximum slew rate, connected for receiving a current sense signal including a meaningful portion proportional to a current in a switched power device and a current spike portion and for generating an output, the maximum slew rate of said amplifier being set so as to attenuate the current spike portion without attenuating the meaningful portion of the current sense signal; and
a switching regulator controller connected to receive the output of said amplifier and to control the switched power device. - View Dependent Claims (2, 3, 4, 5)
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6. A method of current sensing comprising:
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controlling a switched power device with a switching regulator controller;
producing a sense signal proportional to the current in the switched power device;
applying a maximum slew rate limit to the sense signal to produce a slew rate limited sense signal having a slew rate that is prevented from exceeding the maximum slew rate limit; and
providing the slew rate limited sense signal to the switching regulator controller. - View Dependent Claims (7)
measuring a predetermined time delay following switching on the switched power device;
switching off the slew rate limited sense signal to the switching regulator controller after the predetermined time delay and providing instead the sense signal to the switching regulator controller.
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8. A circuit comprising:
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a gain stage connected to receive a current sense signal having a voltage proportional to a current in a switched power device, said gain stage generating an output current proportional to the voltage of the current sense signal unless a maximum output current is reached;
a capacitor coupled to said gain stage so as to be charged by the output current, said capacitor charging at a maximum slew rate when the output of said gain stare is the maximum output current; and
a switching regulator controller having an input connected to said capacitor and an output for controlling the switched power device. - View Dependent Claims (9, 10, 11, 12)
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13. A circuit comprising:
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means for receiving a current sense signal having a slew rate;
active components, coupled to said receiving means, for producing a modified current sense signal, said active components being arranged to set the modified current sense signal at a predetermined maximum slew rate whenever the slew rate of the current sense signal exceeds the predetermined maximum slew rate, so as, to produce the modified current sense signal; and
a switching regulator controller connected to receive the modified current sense signal and having an output for controlling a switched power device. - View Dependent Claims (14, 15, 16, 17)
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Specification