Power Supply IC Control for High Power Factor Switching
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Solution Overview
Problem
Existing power supply circuits face challenges in maintaining a high power factor while reducing switching loss, as turning on a transistor after a predetermined time period since the inductor current reaches zero can lead to negative inductor currents and deteriorated power factor.
Innovation Solution
An integrated circuit is designed to control the switching of a transistor in a power supply circuit, utilizing a first command value to turn on the transistor for a first time period based on a voltage difference, and then correcting this value to output a second command value for a longer second time period, thereby adjusting the transistor's on-time to prevent negative inductor currents and maintain a high power factor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the transistor is turned on after a predetermined time period has elapsed since the inductor current has reached zero, then switching loss decreases, but the power factor deteriorates due to negative inductor current
Solution Approach 1:
The patent dynamically adjusts the turn-on timing parameter based on the actual inductor current waveform characteristics. By changing the timing parameter adaptively rather than using a fixed predetermined time period, the system achieves both reduced switching loss and prevention of negative inductor current, resolving the technical contradiction.
Solution Approach 2:
The control circuit monitors the inductor current in real-time and uses this feedback information to determine the optimal turn-on timing. The feedback mechanism allows the system to adjust the switching timing based on actual current conditions, preventing negative current while minimizing switching loss.
2Object-generated harmful factors
If the transistor is turned on immediately when the inductor current reaches zero, then the power factor is maintained, but switching loss increases
Solution Approach 1:
Instead of using a fixed timing parameter, the system dynamically adjusts the turn-on timing parameter based on monitored inductor current characteristics. This parameter adaptation allows the system to optimize both power factor and switching loss simultaneously.
Solution Approach 2:
The patent transitions from a static, fixed timing approach to a dynamic timing approach where the turn-on moment is continuously adjusted based on real-time inductor current conditions. This dynamic adjustment enables the system to achieve both low switching loss and high power factor.
3Object-generated harmful factors
If the transistor on-time is extended to prevent negative inductor current, then power factor improves, but the control complexity increases
Solution Approach 1:
The control circuit uses the inductor current waveform itself as the basis for determining turn-on timing, eliminating the need for external complex control mechanisms. The system serves itself by using its own operational characteristics (current waveform) to optimize its control parameters.
Solution Approach 2:
The control circuit incorporates feedback from the inductor current measurement to automatically adjust the turn-on timing. This feedback mechanism simplifies the control approach by using direct current monitoring rather than complex predictive algorithms or external control signals.
Data Source
AI summary
An integrated circuit including: a first command value output circuit outputting a first command value to turn on a transistor for a first time period; an on signal output circuit outputting an on signal to turn on the transistor, in response to an inductor current decreasing to or below a predetermined value after turning-off of the transistor; a delay circuit delaying the on signal by a predetermined time period; a correction circuit generating a second command value to turn on the transistor for a second time period; a driver circuit turning on and off the transistor respectively based on the delayed on-signal and the second command value; and a second estimation circuit estimating the rectified voltage. The correction circuit corrects the first command value based on the first voltage, the estimated rectified voltage, and the predetermined time period.