Voltage buck-boost switching regulator
A stable, high-speed, high-efficiency constant voltage is provided without a complicated, large-scale, high-cost phase compensation circuit over a wide range of operating conditions. This voltage buck-boost switching regulator consists of a pair of voltage reducing transistors, a pair of voltage boosting transistors, inductance coil, output capacitor and controller. The controller has the following parts for performing PWM control of constant voltage for voltage reducing transistors and voltage boosting transistors: an output voltage feedback circuit, an inductor current sense circuit, a variable sawtooth wave signal generator, switching controllers, and a voltage boosting driver.
1. A voltage buck-boost switching regulator comprising:
a first switching circuit for voltage reducing connected between a voltage input terminal and one terminal of an inductance element;
a second switching circuit for voltage boosting connected between another terminal of said inductance element and the voltage output terminal;
an error amplifier that compares the output voltage obtained at a voltage output terminal or the output divided voltage obtained by a resistive voltage divider with a prescribed reference voltage, and amplifies the difference between them at a prescribed amplification rate to generate an error voltage;
a current sense circuit that detects an inductance current flowing in said inductance element and generates a current sense signal corresponding to said inductance current;
a variable sawtooth wave generator that generates a first variable sawtooth wave signal having a first top peak level and a first bottom peak level corresponding to said error voltage and a first slope corresponding to said output voltage, and a second variable sawtooth wave signal having a second top peak level and a second bottom peak level corresponding to said error voltage and a second slope corresponding to the input voltage input at said voltage input terminal;
a first switching controller that compares the voltage level of said current sense signal and the voltage level of said first variable sawtooth wave signal, and controls said first switching circuit corresponding to their magnitude relationship; and
a second switching controller that compares the voltage level of said current sense signal and the voltage level of said second variable sawtooth wave signal, and controls said second switching circuit corresponding to their magnitude relationship.
2. The voltage buck-boost switching regulator described in claim 1 comprising a phase compensation circuit for adjusting the frequency transfer function of the constant-voltage feedback loop with respect to said output voltage.
3. The voltage buck-boost switching regulator described in claim 2 wherein said phase compensation circuit comprises an integrator.
4. The voltage buck-boost switching regulator described in claim 3 wherein said phase compensation circuit comprises a resistor and a capacitor.
5. The voltage buck-boost switching regulator described in claim 4 wherein said phase compensation circuit is connected between the output terminal of said error amplifier and the reference voltage terminal.
6. The voltage buck-boost switching regulator described in claim 5 wherein said variable sawtooth wave generator comprises:
an oscillator that generates a clock signal at a constant frequency;
a first reference sawtooth wave generator that generates a first reference sawtooth wave signal synchronized with said clock signal and having a first slope proportional to said output voltage;
a second reference sawtooth wave generator that generates a second reference sawtooth wave signal synchronized with said clock signal and having a second slope proportional to said input voltage;
a first arithmetic and logic unit circuit that performs a first arithmetic and logic operation for said error voltage and said first reference sawtooth wave signal to generate said first variable sawtooth wave signal; and
a second arithmetic and logic unit circuit that performs a second arithmetic and logic operation for said error voltage, said input voltage, said output voltage, and said second reference sawtooth wave signal to generate the second variable sawtooth wave signal.
7. The voltage buck-boost switching regulator described in claim 6 wherein said first arithmetic and logic unit circuit has a first subtracter that subtracts said first reference sawtooth wave signal from said error voltage to generate a first difference signal representing the difference between them, and it outputs said first difference signal as said first variable sawtooth wave signal.
8. The voltage buck-boost switching regulator described in claim 7 wherein said second arithmetic and logic unit circuit has a first adder that adds said input voltage and said output voltage to generate a first sum signal representing their sum, a multiplier that multiplies a prescribed constant to said first sum signal to generate a product signal representing their product, and a second adder that adds said second difference signal and said second reference sawtooth wave signal to generate a second sum signal representing their sum, and said second sum signal is output as said second variable sawtooth wave signal.
9. The voltage buck-boost switching regulator described in claim 8 wherein said constant has a value obtained by dividing the period of said clock with the inductance of said inductance element.
10. The voltage buck-boost switching regulator described in claim 6 wherein said first and second arithmetic and logic unit circuits are analog arithmetic and logic unit circuits.
11. The voltage buck-boost switching regulator described in claim 1 wherein the slope of said first variable sawtooth wave signal is negative, and the slope of said second variable sawtooth wave signal is positive.
12. The voltage buck-boost switching regulator described in claim 1 wherein the first bottom peak level of said first variable sawtooth wave signal is equal or approximately equal to the second top peak level of said second variable sawtooth wave signal.
13. The voltage buck-boost switching regulator described in claim 1 wherein said current sense circuit is connected to said voltage input terminal, said voltage output terminal and the two terminals of said inductance element.
14. The voltage buck-boost switching regulator described in claim 1 wherein said current sense signal has a voltage level proportional to the instantaneous value of said inductance current.
15. The voltage buck-boost switching regulator described in claim 1 wherein:
said first switching circuit has a first switching element connected between said reference voltage terminal and one terminal of said inductance element, and a second switching element connected between said voltage input terminal and said one end of said inductance element; and
said first switching controller performs a switching operation of said first switching circuit in said first switching circuit when the voltage level of said current sense signal crosses the voltage level of said first variable sawtooth wave signal; during the former period, from the start of each switching cycle to the time when the voltage level of said current sense signal crosses the voltage level of said first variable sawtooth wave signal, said first switching element is turned off; during the latter period, from the time when the voltage level of said current sense signal crosses the voltage level of said first variable sawtooth wave signal to end of said switching cycle, said first switching element is turned on, and said second switching element is turned off.
16. The voltage buck-boost switching regulator described in claim 1 wherein:
said second switching circuit has a third switching element connected between said reference voltage terminal and said other terminal of said inductance element and a fourth switching element connected between said voltage output terminal and said other terminal of said inductance element; and
said second switching controller performs a switching operation for said second switching circuit when the voltage level of said current sense signal crosses the voltage level of said second variable sawtooth wave signal; during a former period, from the start of each switching cycle to the time when the voltage level of said current sense signal crosses the voltage level of said second variable sawtooth wave signal, said third switching element is turned off and said fourth switching element is turned on; and, during a latter period, from the time when the voltage level of said current sense signal crosses the voltage level of said second variable sawtooth wave signal to end of said switching cycle, said third switching element is turned on and said fourth switching element is turned off.