| 摘要 |
In a switching regulator power supply, the primary winding of a switching transformer is coupled to a source of input voltage and to a power switch. Secondary supply voltages for a load circuit such as a television receiver are obtained from a secondary winding of the transformer. A regulator control circuit develops a pulse width modulated signal that is used to control the duty-cycle of the power switch for regulating the supply voltages. A disabling circuit is coupled to the regulator control circuit and is responsive to a low bias voltage at a disabling control terminal to change the duty cycle of the power switch in a manner that disables the normal transfer of energy to the load circuit. A disabling input terminal is coupled to an input terminal of a comparator and to the disabling control terminal. The comparator output is coupled to a disabling switch having an output coupled to the disabling control terminal. A first signal generator is responsive to a first condition requiring the disabling of the power supply and develops at the disabling input terminal a first bias voltage that is low enough to, in turn, bias low the disabling control terminal to initiate the disabling of the power supply. A second signal generator is responsive to a second condition requiring the disabling of the power supply and develops a second bias voltage that is higher than the first bias voltage and is high enough to activate the comparator. When the comparator is activated, the disabling switch turns on to bias low the disabling control terminal to initiate the disabling of the power supply. |
