Adaptive zero current sense apparatus and method for a switching regulator

• US 20100052629A1
• Filed: 11/03/2009
• Published: 03/04/2010
• Est. Priority Date: 04/04/2007
• Status: Active Grant

• Current Assignee: Chien-Ping Lu, Kwan-Jen Chu, Nien-Hui Kung, Tzu-Huan Chiu
• Original Assignee: Chien-Ping Lu, Kwan-Jen Chu, Nien-Hui Kung, Tzu-Huan Chiu
• Inventors: Lu, Chien-Ping, Kung, Nien-Hui, Chiu, Tzu-Huan, Chu, Kwan-Jen
• Granted Patent: US 7,940,596 B2
• Time in Patent Office: Days
• US Class Current: 323/239
• CPC Class Codes: H02M 1/0009 Devices or circuits for detecting current in a converter
• CPC Class Codes: H02M 3/1588 comprising at least one synchronous rectifier element H02M3/1582, H02M3/1584 take precedence
• CPC Class Codes: Y02B 70/10 Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

Abstract

A switching regulator includes a low-side switch having a body diode. During the low-side switch is on, a zero-current sense circuit monitors the inductor current of the switching regulator and triggers a signal to turn off the low-side switch when the inductor current falls down to a zero-current threshold, to prevent reverse inductor current from the output terminal of the switching regulator. A body-diode turn-on time controller monitors the turn-on time of the body diode and adjusts the zero-current threshold according thereto, and the turn-on time of the body diode can be reduced to an optimal interval subsequently. The self-adjustable zero-current threshold is adaptive according to the application conditions, such as the inductor size, input voltage and output voltage of the switching regulator.

Claims

1. An adaptive zero-current sense method for a switching regulator including a low-side switch connected to a phase node and switched to control an inductor current, the low-side switch having a body diode, the method comprising the steps of:

A. monitoring the inductor current during the low-side switch is on;

B. triggering a first signal to turn off the low-side switch if the inductor current falls down to a zero-current threshold during the low-side switch is on;

C. monitoring a turn-on time of the body diode after the low-side switch is turned off in response to the first signal;

D. determining a second signal to adjust the zero-current threshold according to the turn-on time of the body diode; and

E. adjusting the zero-current threshold if the turn-on time of the body diode is shorter than a given value.

2. The adaptive zero-current sense method of claim 1, wherein the step A comprises the step of comparing a voltage on the phase node with a reference voltage by a comparator.

3. The adaptive zero-current sense method of claim 2, further comprising the step of turning off the first signal when the voltage on the phase node rises up across the reference voltage.

4. The adaptive zero-current sense method of claim 2, wherein the step C comprises the step of determining the turn-on time of the body diode by using the first signal and the voltage on the phase node.

5. The adaptive zero-current sense method of claim 2, wherein the step E comprises the steps of providing an offset voltage to the input of the comparator which receives the voltage on the phase node or the reference voltage.