Constant-voltage switching power supply provided with overvoltage output protecting circuit, and electronic apparatus provided with overvoltage protecting circuit
AssigneeSeiko Epson Corporation
InventorSeiji Takamatsu
Life of this patent
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Abstract
An overvoltage output protector is electrically connected to a constant-voltage switching power supply which includes a switching transistor converting a DC voltage obtained by smoothing an AC voltage supplied from an AC power source into a cyclic pulse signal. In the overvoltage output protector, an overvoltage monitor whether a potential of the cyclic pulse signal is a predetermined value or more. A deactivator turns off the switching transistor in a case where the overvoltage monitor judges that the potential of the cyclic pulse signal is the predetermined value or more.
Claims10
A constant-voltage switching power supply, comprising:
- a smoother, which converts an AC voltage supplied from an AC power source into a first DC voltage;
- a switching transistor, which converts the first DC voltage into a first cyclic pulse signal;
- a transformer, which voltage-transforms the first cyclic pulse signal to obtain a second cyclic pulse signal, the transformer comprising a first primary coil to which the first cyclic pulse signal is applied, a second primary coil at which a third cyclic pulse signal corresponding to the first cyclic pulse signal is induced;
- an overvoltage monitor, which monitors a potential of the third cyclic pulse signal to judge whether a potential of the first cyclic pulse signal is a predetermined value or more, the overvoltage monitor comprising a Zener diode through which a backward current flows in a case where the potential of the third cyclic pulse signal reaches a Zener voltage of the Zener diode;
- and
- a deactivator, which turns off the switching transistor when the backward current flows through the Zener diode;
- wherein:
- the overvoltage monitor comprises a transistor having a grounded base, an emitter to which the Zener diode is electrically connected, and a collector which is electrically connected to the deactivator;
- and
- the deactivator turns off the switching transistor when the backward current turns on the transistor.
An electronic apparatus, connected to a constant-voltage DC power supply provided with a first controller which is externally controlled to vary a DC output voltage to be supplied, the electronic apparatus comprising:
- an overvoltage detector, which detects whether a power voltage of the electronic apparatus which is generated from a rated output voltage in the constant-voltage DC power supply is a predetermined value or more, the overvoltage detector comprising a Zener diode;
- and
- a second controller, which controls the first controller to vary the DC output voltage of the constant-voltage DC power supply in a case where the overvoltage detector detects that the power voltage is the predetermined value or more,
- wherein the overvoltage detector deactivates the second controller when the power voltage reaches a Zener voltage of the Zener diode and maintains a deactivated state of the second controller even when the power voltage decreases lower than the Zener voltage of the Zener diode afler the second controller is once deactivated.
An overvoltage protector, provided within an electronic apparatus and connected to a constant-voltage DC power supply provided with a first controller which is externally controlled to vary a DC output voltage to be supplied, the overvoltage output protector comprising:
- an overvoltage detector, which detects whether a power voltage of the electronic apparatus which is generated from a rated output voltage in the constant-voltage DC power supply is a predetermined value or more, the overvoltage detector comprising a Zener diode;
- and
- a second controller, which controls the first controller to vary the DC output voltage of the constant-voltage DC power supply in a case where the overvoltage detector detects that the power voltage is the predetermined value or more,
- wherein the overvoltage detector deactivates the second controller when the power voltage reaches a Zener voltage of the Zener diode and maintains a deactivated state of the second controller even when the power voltage decreases lower than the Zener voltage of the Zener diode afler the second controller is once deactivated.
Dependencies are inferred from the claim text.