Switching power supply circuitry
View Patent ↗An output voltage VC obtained by boosting an input voltage VIN by means of a charge pump control circuit 3 of a charge pump 102 is supplied as a power supply voltage to a control circuit 4 of a step-up converter. It is thus possible to eliminate the need for a conventional self-bias method, eliminate switching from startup oscillation to main oscillation of the conventional self-bias method upon startup, and overcome problems caused by the switching of oscillation states, thereby achieving switching power supply circuitry starting in a reliable and stable manner.
1. A switching power supply circuit, comprising:
a step-up converter for boosting a DC input voltage to obtain a first boosted voltage and supplying the first boosted voltage to a load;
a charge pump for boosting the DC input voltage without using a voltage based on the first boosted voltage to obtain a second boosted voltage; and
a control circuit supplied with power at the second boosted voltage from the charge pump, the control circuit for controlling the step-up converter.
2. The switching power supply circuit according to claim 1 , wherein the step-up converter comprises a switch element for performing switching to generate the first boosted voltage.
3. The switching power supply circuit according to claim 2 , wherein the control circuit is for controlling a switching operation of the switch element.
4. The switching power supply circuit according to claim 2 , wherein the control circuit controls a switching operation of the switch element of the step-up converter when the second boosted voltage from the charge pump is equal to or higher than a predetermined operation start voltage.
5. The switching power supply circuit according to claim 1 , wherein the charge pump comprises:
an oscillation circuit for generating driving pulses of a predetermined frequency;
a plurality of second switch elements for performing switching in response to the driving pulses; and
a jumping capacitor for being charged or discharged by switching of the second switch elements.
6. The switching power supply circuit according to claim 5 , wherein the oscillation circuit is a ring oscillation circuit including inverters of multiple stages connected like a ring.
7. The switching power supply circuit according to claim 5 , wherein the charge pump comprises a stabilizing circuit for stabilizing the second boosted voltage.
8. The switching power supply circuit according to claim 7 , wherein the stabilizing circuit is a series regulator.
9. The switching power supply circuit according to claim 3 , wherein the control circuit comprises:
an error amplifier for comparing the first boosted voltage of the step-up converter with a target value and for generating an error signal; and
a PWM circuit for generating a driving pulse for controlling the switching operation of the switching element of the step-up converter in response to the error signal, so that
when the first boosted voltage of the step-up converter is equal to or higher than a predetermined value, at least one of the error amplifier and the PWM circuit is supplied with power from the first boosted voltage of the step-up converter, not from the second boosted voltage of the charge pump.
10. The switching power supply circuit according to claim 1 , wherein when the first boosted voltage of the step-up converter is equal to or higher than a predetermined value, the control circuit is for being supplied with power from the first boosted voltage of the step-up converter, not from the second boosted voltage of the charge pump.
11. The switching power supply circuit according to claim 1 , wherein the charge pump is for stopping operation when the first boosted voltage of the step-up converter is equal to or higher than a predetermined value.
12. The switching power supply circuit according to claim 1 , further comprising:
a DC-to-DC converter for obtaining an output voltage from the DC input voltage; and
a second control circuit is for being supplied with power at the second boosted voltage from the charge pump and for controlling the DC-to-DC converter when the second boosted voltage from the charge pump reaches a predetermined operation start voltage.