Power converter and an LED lighting circuit comprising the same

Patent metadata

Field	Value
Publication number	US-10141842-B2
Application number	US-201615741636-A
Country	US
Kind code	B2
Filing date	Jun 29, 2016
Priority date	Jul 3, 2015
Publication date	Nov 27, 2018
Grant date	Nov 27, 2018

Abstract

The invention provides a power converter comprising: an input for receiving input power with a variable nominal mains level, wherein said variable nominal mains level falls within at least 90V to 240V; a main power switch (Q1) driven by the input power, and a control circuit (Q2, Q3) for controlling a control current of the main power switch (Q1), wherein the control circuit in (Q2, Q3) is adapted to sense the level of the input power and draw current from a control terminal of the power switch (Q1) according to the level, and said control circuit is adapted to operate in linear region and increase the drawn current along with the increase of the level throughout the variable nominal mains level of the input power, wherein the control circuit comprises: a Darlington bridge with a first transistor (Q2) and a second transistor (Q3), the first transistor (Q2) with a base terminal connected to a circuit position indicative of the voltage amplitude of the input power, the second transistor (Q3) with a base terminal connected to an emitter terminal of the first transistor (Q2) and a collector terminal connected to the control terminal of the main power switch (Q1) and a collector terminal of the first transistor (Q2); and a resistor network (R3, R7) coupled to the emitter of the second transistor (Q3) for regulating the amplification of the second transistor (Q3) and keep the second transistor (Q3) working at linear region throughout the variable nominal mains level of the input power.

First claim

The invention claimed is:

1. A ring choke power converter comprising
an input for receiving an input power with a nominal mains level, wherein said nominal mains level is variable and falls within at least 90V to 240V;
a main power switch driven by the input power, wherein the main power switch is a main power bipolar transistor; and
a control circuit for controlling a control current of the main power switch;
wherein the control circuit is adapted to sense the level of the input power and draw current from a control terminal of the power switch according to the level, and said control circuit is adapted to operate in a linear region and increase the drawn current along with the increase of the level throughout said variable nominal mains level of the input power, wherein the control circuit comprises:
a Darlington bridge with a first transistor and a second transistor, the first transistor with a base terminal connected to a circuit position indicative of the voltage amplitude of the input power, the second transistor with a base terminal connected to an emitter terminal of the first transistor and a collector terminal connected to the control terminal of the main power switch and a collector terminal of the first transistor; and
a resistor network coupled to the emitter of the second transistor for regulating the amplification of the second transistor and keeping the second transistor working in the linear region throughout the variable nominal mains level of the input power.

2. The ring choke power converter as claimed in claim 1 , wherein the resistor network comprises a first resistor connected to the emitter of the second transistor.

3. The ring choke power converter as claimed in claim 2 , wherein the switch set further comprises:
an impedance tuning circuit, adapted to tuning the impedance of the resistor network according to an amplitude of the input power.

4. The ring choke power converter as claimed in claim 2 , wherein the power converter is a self-oscillation type converter, and the power converter comprising:
a main inductor, for storing energy from the input power and releasing energy during the switching of the main power switch; and
an auxiliary inductor, magnetically coupled to the main inductor and connected to the control terminal of the main power switch, adapted for controlling the main power switch.

5. The ring choke power converter as claimed in claim 4 , wherein the auxiliary inductor is adapted to increase inductor current provided toward the control terminal of the main power switch along with the increase of the input power throughout said variable nominal mains level range of the input power, and
the difference current between the inductor current and the drawn current which eventually reaches the control terminal of the main power switch is substantially the same or slightly decreases as the input power increases throughout the variable nominal mains level range.

6. The ring choke power converter as claimed in claim 4 , wherein said circuit position is on a buffering capacitor that is charged by said auxiliary inductor.

7. The ring choke power converter as claimed in claim 4 , wherein said control terminal of the switch set is coupled to the auxiliary inductor via a forward diode.

8. The ring choke power converter as claimed in claim 1 , wherein said first transistor is adapted to operate in saturation region throughout the said variable nominal mains level of the input power.

9. The ring choke power converter as claimed in claim 1 , wherein the power converter further comprises a second resistor connected between the emitter of the main power bipolar transistor and ground, wherein said second resistor is adapted to increase the collector voltage of the second transistor such that the collector-base voltage of the second transistor is forwardly biased away from saturation region and
the base of the first transistor is decoupled from the second resistor.

10. The ring choke power converter as claimed in claim 9 , wherein an impedance tuning circuit is adapted to decrease the impedance of the resistor and increase the amplification of the second switch when the voltage amplitude of the input power is above a threshold, and said variable nominal mains level falls within at least 90V to 305V.

11. A light emitting diode (LED) lighting circuit, comprising a LED and a ring choke power converter as claimed in claim 1 for powering said LED.

Assignees

• Philips Lighting Holding Bv

Inventors

• Zhang Xianhui
• Li Ken K
• Chen Zhi Quan
• Liu Junhu
• Li Ace

Classifications

• H02M3/3385 Primary

  with automatic control of output voltage or current (H02M3/33561 takes precedence) · CPC title

• H05B45/3725

  Switched mode power supply [SMPS] · CPC title

• H05B45/39

  Circuits containing inverter bridges · CPC title

• H05B47/10

  Controlling the light source · CPC title

• H05B33/0815

  Electricity · mapped topic