Generating bias voltage in a voltage converter
AssigneeSwitch Power, Inc.
InventorsAnatoly Shteynberg, Dmitry Goder
Life of this patent
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Abstract
For use with a power converter, a bias voltage generator samples a fraction of the input voltage Vin using a bias switch coupled to a tap on the power converter transformer input winding. The bias switch is driven from the same control circuit that drives the converter switch, and the fraction of Vin sampled by the bias switch is coupled to a low pass filter to generate the bias voltage Vbias. Vbias≈(Vin)·(Kf)·(Kdc), where Kf is the fractional location of the transformer tap, and Kdc is duty cycle of the power converter switch. Vbias enjoys automatic compensation against variation in Vin because the power converter will automatically compensate Kdc to correct for Vin variation. The resultant bias voltage generator requires no additional transformer winding.
Claims22
For use with a voltage converter outputting a desired magnitude of output voltage Vout over variation in output current and having a transformer with a transformer primary winding coupled between a source of Vin and a converter switch, and having a control circuit driving the converter switch with a duty cycle Kdc, a bias voltage generator to provide a bias voltage Vbias of desired magnitude, the bias voltage generator comprising:
- a bias switch having an input lead coupled to said Vin through at least a fraction Kf of said primary winding, having a drive lead coupled to respond to an output of said control circuit, and having an output lead, wherein said fraction Kf is provided without adding a further winding to said transformer.
A voltage converter outputting a desired magnitude of output voltage Vout over variation in output current, comprising:
- a transformer having a primary winding having a first end coupleable to a source of Vin, and having a second end;
- a converter switch having an output lead coupled to said second end of said transformer primary winding, and having an input lead;
- a control circuit coupled to drive said input lead of said converter switch with a duty cycle Kdc;
- a bias voltage generator to provide a bias voltage Vbias, the bias voltage generator comprising a bias switch having an input lead coupled to receive a fraction Kf of said Vin, having a drive lead coupled to respond to an output of said control circuit, and having an output lead, wherein said fraction Kf is provided without adding a further winding to said transformer;
- wherein said Vbias is present at said output lead.
For use with a voltage converter outputting a desired magnitude of output voltage Vout over variation in output current and having a transformer with a primary winding coupled between a source of Vin and a converter switch, and having a control circuit driving the converter switch with a duty cycle Kdc, a method of generating a bias voltage Vbias in which changes in Vin are at least partially compensated for:
- sampling at least a fraction Kf of said Vin, said sampling being accomplished without adding a further winding to said transformer;
- wherein the sampled said fraction of Vin provides said Vbias.
Dependencies are inferred from the claim text.