Synchronous switching regulator which employs switch voltage-drop for current sensing
AssigneeLinear Technology Corporation
InventorsMilton E. Wilcox, Christopher B. Umminger
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Abstract
Synchronous switching regulator circuits with voltage-drop sensing circuitry are presented in which the current sensing element typically in series with a load is eliminated, resulting in reduced dissipative losses and less costly manufacture. Voltage drops are measured across the regulator's synchronous switching element, and, in some cases, also across the regulator's main switching element. Measured voltage drops are used to derive a current analog signal indicative of the amount of current being supplied by the regulator. The current signal is then compared with a threshold value to determine whether the regulator's duty cycle should be varied.
Claims30
A synchronous switching regulator circuit for supplying current at a regulated voltage to a load, said regulator circuit comprising:
- an input terminal for coupling to a source of input supply voltage;
- an output terminal for coupling to said load;
- control circuitry for regulating the duty cycle of said regulator circuit;
- output circuitry coupled to said input terminal, to said output terminal, and to said control circuitry, said output circuitry comprising an inductor, a main switching element that causes current in said inductor to increase, and a synchronous switching element that conducts said inductor current when said main switching element is non-conductive;
- and
- voltage-drop sensing circuitry coupled to said synchronous switching element and to said control circuitry for providing current information to said control circuitry when said synchronous switching element is conductive.
A method of regulating current supplied to a load by a synchronous switching regulator, said regulator comprising control circuitry for controlling the regulator's duty cycle, output circuitry coupled to said control circuitry and to said load, said output circuitry comprising an inductor, a main switching element that causes current in said inductor to increase, a synchronous switching element that conducts said inductor current when said main switching element is non-conductive, and voltage-drop sensing circuitry coupled to said synchronous switching element and to said control circuitry, said method comprising the steps of:
- sensing the voltage drop across said synchronous switching element when said synchronous switching element is conductive;
- deriving current information from said sensing;
- and
- varying said duty cycle in response to said current information.
A method of protecting a synchronous switching regulator from damage when a fault occurs, said regulator providing current to a load and comprising control circuitry for controlling the regulator's duty cycle, output circuitry coupled to said control circuitry and to said load, said output circuitry comprising an inductor, a main switching element that causes current in said inductor to increase, a synchronous switching element that conducts said inductor current when said main switching element is non-conductive, and voltage-drop sensing circuitry coupled to said synchronous switching element and to said control circuitry, said method comprising the steps of:
- sensing the voltage drop across said synchronous switching element when said synchronous switching element is conductive;
- deriving a signal from said sensing indicative of an amount of current being supplied by said regulator;
- and
- reducing the duty cycle of said regulator if said signal exceeds a threshold.
Dependencies are inferred from the claim text.