Self-oscillating switched mode converter with valley detection
AssigneeNXP B.V.
InventorsCheng Zhang, Wilhelmus H. M. Langeslag
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Abstract
An energy converter is disclosed in which self oscillation mode operation is improved by a closed loop feedback control. The feedback control utilises the voltage error from the voltage valley in the drain voltage (Vdrain) of the converter switch (1), to determine an error (E(n)) in the time domain. Control circuitry (61, 62, 63) is used to minimise this time-domain error (E(n)) to optimise the control of the switch mode converter.
Claims29
An energy converter comprising
- a switch having a gate and a source and a drain connected to a switch node,
- an inductor connected between a voltage terminal and the drain and having an associated inductor current, the drain having an associated drain voltage,
- a driver for providing a drive signal to the gate, and
- a controller for controlling the driver,
- the switch being operable by the controller to conduct current between the drain and source during each of a plurality of primary strokes,
- the controller comprising
- reference-fixing means for determining a moment Tref which precedes a moment when the drain voltage next has a local minimum by a constant time interval ΔF,
- the controller being adapted to switch on the switch to commence the (n)th primary stroke at the end of an interval ΔT(n), which interval starts at the moment Tref, and determining means for determining ΔT(n+1) in dependence on ΔT(n) and the drain voltage at the start of (n)th primary stroke.
A method of controlling a switched-mode energy converter comprising
- a switch having a gate and a source and a drain connected to a switch node,
- an inductor connected between a voltage terminal and the drain and having an associated inductor current,
- the drain having an associated drain voltage,
- a driver for providing a drive signal to the gate,
- and a controller for controlling the driver,
- the switch being operable by the controller to conduct current between the drain and source during each of a plurality of primary strokes,
- the method comprising the steps of
- (a) determining a moment Tref which precedes a moment when the drain voltage next has a local minimum by a constant time interval ΔF,
- (b) switching on the switch to commence the (n)th primary stroke at the end of an interval ΔT(n), which interval starts at the moment Tref;
- and
- (c) determining ΔT(n+1) in dependence on ΔT(n) and the drain voltage at the start of the n(th) primary stroke.
A method as claimed in 23, including the steps of detecting a peak in the ringing of the drain voltage corresponding to a start of the ringing of the drain voltage by
- (i) converting the drain voltage into a resonant current across a capacitor and
- (ii) comparing the current with a reference signal, and
- starting a voltage-to-time conversion at the start of the ringing of the drain voltage.
Dependencies are inferred from the claim text.