Negative injection for power factor correction circuit performance enhancements
地域：
CA
CA Moorpark
摘要
A negative injection circuit is coupled to a power factor correction (PFC) controller of a power supply system and includes a downshifter configured to downshift a ground signal to generate a negative voltage signal, a variable impedance coupled between the downshifter and the PFC controller, and configured to inject a negative injection voltage into a voltage sampling input of the PFC controller, the variable impedance including a first current limiting resistor and a second current limiting resistor coupled in series with one another and between the downshifter and the voltage sampling input of the PFC controller, and a bypass switch configured to selectively short across the second current limiting resistor in response a range selection signal.
說(shuō)明書(shū)
This application claims priority to, and the benefit of, U.S. Provisional Application No. 63/078,031 (“NEGATIVE INJECTION FOR MULTIPLIER PERFORMANCE ENHANCEMENTS”), filed on Sep. 14, 2020, the entire content of which is incorporated herein by reference.
Aspects of the present invention are related to power supply systems for light sources.
In current LED lighting applications, LED drivers are generally required to provide a PFC (power factor correction) function, that is, to make an input current in phase with a full-wave-rectified line input voltage. The PFC circuits are often designed for a particular line input voltage range. Some universal input voltage LED drivers use a circuit that selects between two reference signal gain levels for low-line and high-line input voltage operation. However, it may be difficult to meet industry standard requirements for total harmonic distortion (THD) and power factor (PF) across all input voltages and load conditions.
The above information disclosed in this Background section is only for enhancement of understanding of the invention, and therefore it may contain information that does not form the prior art that is already known to a person of ordinary skill in the art.
權(quán)利要求
What is claimed is:1. A negative injection circuit coupled to a power factor correction (PFC) controller of a power supply system, the negative injection circuit comprising:a downshifter configured to downshift a ground signal to generate a negative voltage signal; and a variable impedance coupled between the downshifter and the PFC controller, and configured to inject a negative injection voltage into a voltage sampling input of the PFC controller, the variable impedance comprising:a first current limiting resistor and a second current limiting resistor coupled in series with one another and between the downshifter and the voltage sampling input of the PFC controller; and a bypass switch configured to selectively short across the second current limiting resistor in response a range selection signal. 2. The negative injection circuit of claim 1 , wherein the voltage sampling input of the PFC controller is configured to sample a rectified signal of a rectifier of the power supply system, andwherein the downshifter and the variable impedance are together configured to shift the sampled rectified signal downward by an amount of the negative injection voltage. 3. The negative injection circuit of claim 1 , wherein the negative injection voltage has a value of ?0.5 V to ?1.0 V when the bypass switch is deactivated, and a value of ?0.25 V to ?0.5 V when the bypass switch is activated. 4. The negative injection circuit of claim 1 , wherein the downshifter is configured to receive the ground signal from bias windings of the power supply system. 5. The negative injection circuit of claim 4 , wherein the downshifter is coupled to a negative terminal of a primary binding of the bias windings, andwherein the bias windings are configured to derive power from an output of a converter of the power supply system. 6. The negative injection circuit of claim 1 , wherein the ground signal is a pulsed signal, andwherein the downshifter is further configured to rectify and filter the pulsed signal to generate a negative voltage that is a DC signal. 7. The negative injection circuit of claim 1 , wherein the downshifter comprises:a diode configured to rectify the ground signal, and having an anode configured to receive the ground signal and a cathode coupled to the first current limiting resistor; and a capacitor coupled in parallel to the diode and configured to filter the ground signal. 8. The negative injection circuit of claim 1 , wherein the bypass switch is coupled in parallel with the second current limiting resistor. 9. The negative injection circuit of claim 1 , wherein the bypass switch comprises:a first transistor coupled in parallel with the second current limiting resistor and having a gate resistively coupled to a ranging circuit, the first transistor being configured selectively turn on and off in response to the range selection signal from the ranging circuit; and a second transistor coupled between the first transistor and the downshifter and having a gate resistively coupled to a bias supply of the ranging circuit, the second transistor being configured to selectively apply the negative voltage signal from the downshifter to the gate of the first transistor in response to the range selection signal from the ranging circuit. 10. The negative injection circuit of claim 9 , wherein the first and second transistors are n-type metal-oxide-semiconductor (NMOS) field effect transistors (FETs). 11. The negative injection circuit of claim 9 , wherein the ranging circuit is configured to determine an AC input voltage of the power supply system as being within a first range or a second range, and to generate the range selection signal according to the determination. 12. The negative injection circuit of claim 11 , wherein the first range is 100 VAC to 120 VAC, and the second range is 240 VAC to 277 VAC,wherein when the AC input voltage is within the first range, the range selection signal has a first value, and when the AC input voltage is within the second range, the range selection signal has a second value, and wherein the bypass switch is configured to deactivate in response to the range selection signal having the first value, and to activate to short across the second current limiting resistor in response to the range selection signal having the second value. 13. The negative injection circuit of claim 1 , wherein a ratio of resistances of the first and second current limiting resistor is 1:1 to 2:1. 14. A power supply system comprising:a power factor correction (PFC) controller configured to reduce a total harmonic distortion and increase a power factor of the power supply system, and having a voltage sampling input configured to sample a rectified signal of a rectifier of the power supply system, and a negative injection circuit coupled to the PFC controller and comprising:a downshifter configured to downshift a ground signal to generate a negative voltage signal; and a variable impedance coupled between the downshifter and the PFC controller, and configured to inject a negative injection voltage into the voltage sampling input of the PFC controller, the variable impedance comprising:a first current limiting resistor and a second current limiting resistor coupled in series with one another and between the downshifter and the voltage sampling input of the PFC controller; and a bypass switch configured to selectively short across the second current limiting resistor in response a range selection signal. 15. The power supply system of claim 14 , further comprising:The rectifier configured to rectify an AC input signal to generate the rectified signal. 16. The power supply system of claim 14 , wherein the downshifter and the variable impedance are together configured to shift the sampled rectified signal downward by an amount of the negative injection voltage. 17. The power supply system of claim 14 , further comprising:a converter coupled to the PFC controller; and bias windings are configured to derive power from an output of the converter of the power supply system, and having a primary winding and a secondary winding, wherein the downshifter is configured to receive the ground signal from a negative terminal of the primary winding. 18. The power supply system of claim 14 , wherein the ground signal is a pulsed signal, andwherein the downshifter is further configured to rectify and filter the pulsed signal to generate a negative voltage that is a DC signal. 19. The power supply system of claim 14 , wherein the downshifter comprises:a diode configured to rectify the ground signal, and having an anode configured to receive the ground signal and a cathode coupled to the first current limiting resistor; and a capacitor coupled in parallel to the diode and configured to filter the ground signal. 20. The power supply system of claim 14 , further comprising:a ranging circuit configured to determine an AC input voltage of the power supply system as being within a first range or a second range, and to generate the range selection signal according to the determination, wherein the first range is 100 VAC to 120 VAC, and the second range is 240 VAC to 277 VAC, wherein when the AC input voltage is within the first range, the range selection signal has a first value, and when the AC input voltage is within the second range, the range selection signal has a second value, and wherein the bypass switch is configured to deactivate in response to the range selection signal having the first value, and to activate to short across the second current limiting resistor in response to the range selection signal having the second value.
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