Switching regulator with voltage step up or pass in standby mode and with voltage step up/step down in normal operation mode
In a standby mode, a voltage step up DC/DC converter 5 supplies a power output voltage equal to or higher than a second set voltage which is lower than a first set voltage in a normal operating mode to a microcomputer (load) 1 with current supply performance which is smaller than in the normal operating mode. On the other hand, in the normal operating mode, a voltage step up/step down DC/DC converter 4 supplies the first set voltage in the normal operating mode to the microcomputer 1.
1. A switching regulator comprising:
an input terminal connected to a supply voltage source;
an output terminal connected to a load operable in a normal operating mode and a standby mode;
a voltage step up/step down DC/DC converter for converting a power input voltage from said supply voltage source to a first set voltage corresponding to the normal operating mode, thereby generating a power output voltage at an output node of the voltage step up/step down DC/DC converter;
a voltage step up DC/DC converter for converting the power input voltage from said supply voltage source to a second set voltage corresponding to the standby mode, when a power output voltage of the step up DC/DC converter is equal to or lower than the second set voltage which is lower than the first set voltage, and for allowing the power input voltage from the supply voltage source to pass without any conversion to the second set voltage when the power output voltage exceeds the second set voltage, thereby generating the power output voltage of the step up DC/DC converter at an output node of the step up DC/DC converter; and
a mode switching switch for connecting said output terminal and the output node of said voltage step up/step down DC/DC converter in the normal operating mode, and connecting said output terminal and the output node of said voltage step up DC/DC converter in the standby mode.
2. The switching regulator according to claim 1 , wherein said voltage step up DC/DC converter uses the power input voltage from said supply voltage source as a supply voltage of said voltage step up DC/DC converter.
3. The switching regulator according to claim 1 , wherein said voltage step up DC/DC converter comprises:
a detection circuit for detecting the power output voltage of said voltage step up DC/DC converter and generating a detected voltage;
a chopping wave generation circuit for generating a chopping wave signal;
a comparator for comparing the detected voltage and the chopping wave signal, and generating a comparison result signal;
a switching element for performing a switching operation according to the comparison result signal;
a coil for receiving the power input voltage from said supply voltage source at one end and the other end being driven by the switching operation of said switching element;
a diode connected to the other end of said coil; and
an output node to which an output voltage of said coil is applied via said diode, wherein
in the standby mode, the output voltage of said coil driven by the switching operation of said switching element is rectified by said diode and the rectified voltage is generated at said output node as the power output voltage of said voltage step up DC/DC converter, when the power output voltage of said voltage step up DC/DC converter is equal to or lower than the second set voltage, and
the switching operation of said switching element is stopped and the power input voltage from said supply voltage source having passed through said coil and said diode is generated at said output node as the power output voltage of said voltage step up DC/DC converter, when the power output voltage of said voltage step up DC/DC converter exceeds the second set voltage.
4. The switching regulator according to claim 2 , wherein said voltage step up DC/DC converter comprises:
a detection circuit for detecting the power output voltage of said voltage step up DC/DC converter and generating a detected voltage;
a chopping wave generation circuit for generating a chopping wave signal;
a comparator for comparing said detected voltage and said chopping wave signal, and generating a comparison result signal;
a switching element for performing a switching operation according to said comparison result signal;
a coil for receiving the power input voltage from said supply voltage source at one end and the other end being driven by the switching operation of said switching element;
a diode connected to the other end of said coil; and
an output node to which an output voltage of said coil is applied via said diode, wherein
in the standby mode, the output voltage of said coil driven by the switching operation of said switching element is rectified by said diode and the rectified voltage is generated at said output node as the power output voltage of said voltage step up DC/DC converter, when the power output voltage of said voltage step up DC/DC converter is equal to or lower than the second set voltage, and
the switching operation of said switching element is stopped and the power input voltage from said supply voltage source having passed through said coil and said diode is generated at said output node as the power output voltage of said voltage step up DC/DC converter, when the power output voltage of said voltage step up DC/DC converter exceeds the second set voltage.
5. The switching regulator according to claim 3 , wherein said voltage step up DC/DC converter further comprises an AND circuit for stopping said switching element in an OFF state in the normal operating mode.
6. The switching regulator according to claim 4 , wherein said voltage step up DC/DC converter further comprises an AND circuit for stopping said switching element in an OFF state in the normal operating mode.