Programmable current-sensing circuit providing continuous temperature compensation for DC-DC converter

A power supply comprising:

• a buck mode pulse width modulator (PWM) DC-DC converter circuit having an input, a high side output and a low side output;
• a high side switch coupled between a first voltage supply terminal and common output node, and being operative to control current flow therethrough in response to said high side output;
• a low side switch coupled between said common output node and to a second voltage supply terminal, and being operative to control current flow therethrough in response to said low side output;
• a sense amplifier unit having a first input, a second input and an output, said second input coupled to said second voltage supply terminal;
• a current feedback resistor electrically coupled between said common output node and said first input of said sense amplifier;
• a variable impedance component electrically connected to said output of said sense amplifier unit and to said first input of said sense amplifier, said variable impedance component configured to vary in impedance in response to said output of said sense amplifier unit;
• a sample and hold circuit coupled to said variable impedance component, and being operative to sample and hold current flowing through said variable impedance component as a sensed current;
• and
• a sensed current correction circuit, coupled between said sample and hold circuit and said buck mode PWM DC-DC converter, and being operative to supply, to said input of said buck mode PWM DC-DC converter, a correction current having a prescribed temperature-compensating relationship to said sensed current as sampled and held by said sample and hold circuit.

A method of controlling the operation of a DC-DC converter, said DC-DC converter being coupled to a supply voltage, and being operative to generate a regulated output voltage derived from said supply voltage, said DC-DC converter including

• a pulse width modulation generator, which generates a PWM switching signal that switchably controls operation of a switching circuit containing first and second electronic power switching devices coupled between respective first and second power supply terminals, a common node thereof being coupled through an inductor element to an output voltage terminal, and
• a controller for controlling the operation of said PWM generator, said controller including a sense amplifier unit having a first input coupled to said first power supply terminal, a second input and an output, a current feedback resistor coupled between said common output node and said second input of said sense amplifier unit, a variable impedance coupled to said output of said sense amplifier unit, said variable impedance configured to vary in impedance in response to said output of said sense amplifier unit, and a sample and hold circuit coupled to said variable impedance, and being operative to sample and hold current flowing through said variable impedance as a sensed current,
• said method comprising the steps of:
• (a) generating a correction current having a prescribed temperature-compensating relationship to said sensed current as sampled and held by said sample and hold circuit;
• and
• (b) coupling said correction current to said controller, so that said controller controls the operation of said PWM generator in accordance with said correction current.