Switching power converter employing pulse frequency modulation control
View Patent ↗A method for controlling a switching power converter provides an efficient algorithm for controlling the output voltage across loads that are relatively light with small transients. When the output voltage is at or below a predetermined first magnitude, a determination is made of the charge required for one or more pulses to increase the output voltage to a predetermined second magnitude which is greater than a target output voltage. Corrective action is taken to raise the output voltage to the second magnitude and the system takes no further corrective action until output voltage is determined to be at or below the first magnitude. The method is useful with synchronous or non-synchronous power converters of buck, boost, buck/boost or other topologies. The method further provides a simple means for determining the amount of charge removed from a battery.
1. A method for regulating an output voltage applied to a load at an output terminal of a power converter to maintain the output voltage within a range of voltages above and below a target voltage, the power converter including an output capacitor coupled between the output terminal and a ground reference, the method comprising:
sensing a magnitude of the output voltage;
comparing the magnitude of the output voltage to a first predetermined voltage value and if the output voltage is equal to or less than the first predetermined value determining a characteristic of a conduction control signal required to cause the output voltage to attain a second predetermined voltage value which is greater than the target voltage; and
providing a conduction control signal having the characteristic to the power converter.
2. The method according to claim 1 , wherein providing the conduction control signal comprises providing the conduction control signal to one switch in the power converter.
3. The method according to claim 2 , wherein determining a characteristic of a conduction control signal comprises calculating a length of one conduction control signal for application within a switching cycle.
4. The method according to claim 2 , wherein determining a characteristic of a conduction control signal comprises calculating a length of a plurality of conduction control signals for application within a switching cycle.
5. The method according to claim 2 , wherein the power converter includes an input terminal for connection to a source of electrical potential, and further wherein providing the conduction control signal comprises:
storing a characteristic of a plurality of conduction control signals for corresponding magnitude values of electrical potentials; and
sensing a magnitude of the electrical potential at the input terminal and providing, based on a comparison of the sensed potential to the stored magnitude values, the conduction control signal corresponding to the sensed magnitude of voltage at the input terminal.
6. The method according to claim 1 , wherein the power converter includes first and second switches, and further wherein determining a characteristic of a conduction control signal comprises:
determining a length of a conduction control signal to be applied to the first and second switches as a function of a value of an input voltage to the power converter.
7. The method of claim 6 , wherein determining a length of the conduction control signals comprises:
calculating the length of the signals as a function of stored model circuit parameters of circuit elements in the power converter.
8. The method of claim 6 , wherein determining a length of the conduction control signals comprises:
calculating the length of the signals as a function of estimated circuit parameters of circuit elements in the power converter.
9. The method according to claim 1 , wherein the power converter, includes an input terminal for connection to a source of electrical potential and further wherein determining a characteristic of the conduction control signal comprises:
sensing a magnitude of a voltage at the input terminal; and
calculating a length of the conduction control signal as a function of the magnitude of the voltage at the input terminal.
10. The method according to claim 9 , wherein calculating a length of a conduction control signal comprises:
storing parameters of one or more circuit elements in the power converter; and
calculating the length of the conduction control signal as a function of the stored circuit parameters.
11. The method according to claim 9 , wherein calculating a length of a conduction control signal comprises:
storing estimated parameters of circuit elements in the power converter; and
calculating the length of the conduction control signal as a function of the stored estimated circuit parameters.
12. The method according to claim 9 , wherein calculating a length of a conduction control signal as a function of the magnitude of the voltage at the input terminal comprises:
utilizing in the calculation of the length of the conduction control signal for a to be performed voltage correction an operational result from a prior-correction event.
13. The method according to claim 12 , further comprising:
storing operational results from a plurality of correction events; and
calculating the length of the conduction control signal for a to be performed voltage correction as a function of the operational results of the plurality of correction events.
14. The method according to claim 12 , further comprising:
determining from the operational result from a prior correction event a magnitude of a term for a calculation algorithm used to calculate a length of the conduction control signal.
15. The method according to claim 14 , wherein the term is a function of an inductive and a capacitive characteristic of circuitry in the power converter.