High efficiency voltage regulator with auto power-save mode
A DC-to-DC converter comprises an error amplifier, a comparator, a PWM controller, a power switch unit, and a control signal monitoring circuit. The PWM controller receives a comparison signal from the comparator and generates a digital control signal that controls the power switch unit such that the DC-to-DC converter supplies a regulated voltage onto a load. The control signal monitoring circuit monitors the digital control signal and detects either a heavy load or a light load condition based on characteristics of the digital control signal. Under the light load condition, the monitoring circuit generates a first enabling signal such that the DC-to-DC controller operates in a power-save mode. Under the heavy load condition, the monitoring circuit generates a second enabling signal such that the DC-to-DC controller operates in a normal operation mode. The DC-to-DC converter consumes substantially less power in the power-save mode than in the normal operation mode.
1. A DC-to-DC converter, comprising:
a power switch unit;
an amplifier that compares a feedback voltage to a reference voltage and outputs an error signal;
a comparator that compares the error signal to a ramp signal and outputs a comparison signal;
a PWM controller that receives the comparison signal and outputs a digital control signal, wherein the digital control signal is used to control the power switch unit such that the DC-to-DC converter supplies a regulated voltage onto a load; and
a control signal monitoring circuit that monitors the digital control signal, wherein the control signal monitoring circuit detects a light load condition and in response outputs a first enabling signal such that the DC-to-DC converter operates in a power-save mode.
2. The DC-to-DC converter of claim 1 , wherein the control signal monitoring circuit detects a heavy load condition and in response outputs a second enabling signal such that the DC-to-DC converter operates in a normal operation mode.
3. The DC-to-DC converter of claim 2 , wherein the DC-to-DC converter consumes less power in the power-save mode than in the normal operation mode.
4. The DC-to-DC converter of claim 2 , wherein the comparator has a substantially smaller power consumption in the power-save mode than in the normal operation mode.
5. The DC-to-DC converter of claim 2 , wherein the power switch unit comprises a switch and a current amplifier, and wherein the current amplifier has a substantially smaller power consumption in the power save mode than in the normal operation mode.
6. The DC-to-DC converter of claim 1 , wherein the control signal monitoring circuit comprises:
a timer that monitors the digital control signal and outputs a digital value when the digital control signal remains unchanged for a predetermined time period; and
a sequential logic element that outputs the first enabling signal in response to the digital value.
7. The DC-to-DC converter of claim 6 , wherein the sequential logic element outputs the second enabling signal when the digital control signal changes from a digital low to a digital high.
8. The DC-to-DC converter of claim 6 , wherein the sequential logic element is taken from the group consisting of: a flip-flop circuit, and an SR latch circuit.
9. The DC-to-DC converter of claim 1 , wherein the DC-to-DC converter further comprises a synchronous rectifier.
10. A method, comprising:
(a) monitoring a digital control signal generated by a PWM controller of a DC-to-DC converter, wherein the DC-to-DC converter supplies a regulated voltage onto a load;
(b) detecting that the DC-to-DC converter is operating in a light load condition based on characteristics of the digital control signal; and
(c) in response to the detecting in (b), outputting a first enabling signal such that the DC-to-DC converter operates in a power-save mode.
11. The method of claim 10 , wherein the light load condition is detected in (b) by determining that the digital control signal remains unchanged for a predetermined time period.
12. The method of claim 10 , further comprising:
(d) detecting that the DC-to-DC converter is operating in a heavy load condition based on the characteristics of the digital control signal; and
(e) in response to the detecting in (d), outputting a second enabling signal such that the DC-to-DC converter operates in a normal operation mode.
13. The method of claim 12 , wherein the heavy load condition is detected in (d) by determining that the digital control signal changes from a digital low to a digital high.
14. The method of claim 12 , wherein the DC-to-DC converter consumes less power in the power-save mode than in the normal operation mode.
15. The method of claim 12 , wherein the DC-to-DC converter comprises a synchronous rectifier.
16. A DC-to-DC converter comprising:
a power switch unit;
a controller that outputs a digital control signal such that the power switch unit supplies a regulated voltage onto a load; and
means for monitoring the digital control signal, wherein the means detects a light load condition based on characteristics of the digital control signal and in response outputs a first enabling signal such that the DC-to-DC converter operates in a power-save mode.
17. The DC-to-DC converter of claim 16 , wherein the light load condition is detected by determining that the digital control signal remains unchanged for a predetermined time period.
18. The DC-to-DC converter of claim 15 , wherein the means also detects a heavy load condition based on the characteristics of the digital control signal and in response outputs a second enabling signal such that the DC-to-DC converter operates in a normal operation mode.
19. The DC-to-DC converter of claim 18 , wherein the heavy load condition is detected by determining that the digital control signal changes from a digital low to a digital high.
20. The DC-to-DC converter of claim 18 , wherein the DC-to-DC converter consumes less power in the power-save mode than in the normal operation mode.
21. The DC-to-DC converter of claim 16 , wherein the DC-to-DC converter comprises a synchronous rectifier.