LIGHT-EMITTING DIODE DRIVING APPARATUS AND SEMICONDUCTOR DEVICE

• US 20150077009A1
• Filed: 11/24/2014
• Published: 03/19/2015
• Est. Priority Date: 05/28/2012
• Status: Active Grant

• Current Assignee: Panasonic Semiconductor Solutions Co., Ltd. (Winbond Electronics Corporation)
• Original Assignee: Panasonic Intellectual Property Management Co., Ltd. (Panasonic Holdings Corporation)
• Inventors: KUNIMATSU, Takashi
• Granted Patent: US 9,131,563 B2
• Time in Patent Office: Days
• US Class Current: 315/224
• CPC Class Codes: H02M 1/4291 by using a Buck converter to switch the input current
• CPC Class Codes: H05B 45/375 using buck topology
• CPC Class Codes: H05B 45/385 using flyback topology
• 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

Provided is a light-emitting diode driving apparatus including: a rectifying circuit; a switching element; a choke coil; an output current sensing circuit; an LED light source; a rectifier diode; a control circuit; a feedback sensing circuit; an input voltage sensing circuit; and a conduction time counting circuit, wherein the feedback sensing circuit outputs a feedback dummy current to the output current sensing circuit, the conduction time counting circuit adjusts the feedback dummy current, the feedback sensing circuit outputs to the control circuit a control signal which controls switching of the switching element in response to a signal based on an error between an output feedback signal and a feedback dummy signal generated by the feedback dummy current.

Claims

1. A light-emitting diode driving apparatus comprising:

a rectifying circuit which rectifies an AC voltage input from an AC power source, to output a DC voltage;

a switching element having an input terminal connected to a high side of the rectifying circuit, which turns on and off the DC voltage;

a choke coil having one end connected to an output terminal of the switching element;

an output current sensing circuit connected between the output terminal of the switching element and the one end of the choke coil, for sensing a current through the choke coil;

an LED light source which includes one or more light-emitting diodes each having an anode terminal connected to another end of the choke coil and a cathode terminal connected to a low side of the rectifying circuit;

a rectifier diode having an anode terminal connected to the low side of the rectifying circuit and a cathode terminal connected to the output terminal of the switching element, the rectifier diode supplying the LED light source with counter electromotive force developed in the choke coil;

a control circuit which outputs a drive signal that controls on and off operation of the switching element, based on an operation reference voltage which is a voltage at a same potential as a node between the output terminal of the switching element and the cathode terminal of the rectifier diode;

a feedback sensing circuit connected to the output current sensing circuit, for receiving an output feedback signal output from the output current sensing circuit;

an input voltage sensing circuit which senses input voltage information rectified by the rectifying circuit; and

a conduction time counting circuit which counts a switching grant period signal output from the input voltage sensing circuit, wherein

the feedback sensing circuit outputs a feedback dummy current to the output current sensing circuit,

the conduction time counting circuit adjusts the feedback dummy current to be output from the feedback sensing circuit, depending on the counted switching grant period signal, and

the feedback sensing circuit outputs to the control circuit a control signal which controls switching of the switching element in response to a signal based on an error between the output feedback signal and a feedback dummy signal generated from the feedback dummy current.

2. The light-emitting diode driving apparatus according to claim 1, further comprising

a phase control dimmer between the AC power source and the rectifying circuit, which controls an alternating conduction angle to control a phase of a voltage to be output to the rectifying circuit.

3. The light-emitting diode driving apparatus according to claim 1, wherein

the output current sensing circuit includes:

a first resistor connected to the output terminal of the switching element and the one end of the choke coil;

a second resistor connected to the one end of the choke coil and a feedback sensing terminal of the feedback sensing circuit through which the feedback dummy current is output; and

a capacitor connected between the output terminal of the switching element and the feedback sensing terminal of the feedback sensing circuit, wherein

the output feedback signal is a first potential difference existing across the first resistor due to the current through the choke coil,

the feedback dummy signal is a second potential difference existing across the second resistor due to the feedback dummy current,

the feedback sensing circuit includes;

an adjustable current source which supplies the feedback dummy current;

an error amplifier which compares a voltage generated between the feedback sensing terminal and an operation reference terminal of the control circuit, due to a voltage difference between the first potential difference and the second potential difference, with a reference voltage; and

a control signal converter which generates the control signal that controls the switching of the switching element, based on an output signal from the error amplifier, and

if the voltage generated between the feedback sensing terminal and the operation reference terminal of the control circuit due to the voltage difference between the first potential difference and the second potential difference is higher than the reference voltage of the error amplifier, the control circuit provides control to substantially increase energy output to the LED light source in response to the control signal from the control signal converter, and

if the voltage generated between the feedback sensing terminal and the operation reference terminal of the control circuit due to the voltage difference between the first potential difference and the second potential difference is lower than the reference voltage of the error amplifier, the control circuit provides control to substantially decrease the energy output to the LED light source in response to the control signal from the control signal converter.

4. The light-emitting diode driving apparatus according to claim 3, wherein

the reference voltage of the error amplifier is substantially equal to the operation reference voltage of the control circuit.

5. The light-emitting diode driving apparatus according to claim 1, wherein

the input voltage sensing circuit includes a sample-and-hold circuit which samples the input voltage information as a sampling signal in an off-period in the on and off operation of the switching element, and holds the sampling signal during an on-period in the on and off operation of the switching element.

6. The light-emitting diode driving apparatus according to claim 1, wherein

the input voltage sensing circuit includes a sample-and-hold circuit which samples the input voltage information as a sampling signal in a preset sampling period which is after the switching element is turned off in the on and off operation, and holds the sampling signal after the preset sampling period.

7. The light-emitting diode driving apparatus according to claim 5, wherein

the input voltage sensing circuit further includes:

a comparator which outputs to the control circuit and the conduction time counting circuit the switching grant period signal which grants the switching of the switching element if the sampling signal is at or above a first reference level which is preset, and prohibits the switching of the switching element if the sampling signal is below a hysteresis value of the first reference level; and

a peak current sensed value converter which outputs to the control circuit a signal which

changes, if the sampling signal is at or above the first reference level which is preset, a sensed value of a peak current through the switching element at a preset rate in response to a level of the sampling signal, and

holds the sensed value of the peak current to a preset upper limit, when the sensed value of the peak current reaches the preset upper limit.

8. The light-emitting diode driving apparatus according to claim 1, wherein

the conduction time counting circuit:

includes a charging and discharging circuit;

charges the charging and discharging circuit if the switching grant period signal from the input voltage sensing circuit is a grant signal, and adjusts the feedback dummy current to be output from the feedback sensing circuit depending on a charged voltage level; and

discharges the charging and discharging circuit if the switching grant period signal is a prohibit signal, and sets the feedback dummy current to be output from the feedback sensing circuit to a zero level.

9. The light-emitting diode driving apparatus according to claim 1, wherein

the conduction time counting circuit includes an oscillator circuit having a preset frequency, and a counter, and operates the oscillator circuit to apply periodic clock signals to the counter if the switching grant period signal from the input voltage sensing circuit is a grant signal,

the counter adjusts the feedback dummy current to be output from the feedback sensing circuit, depending on the number of periodic clock signals applied to the counter, and

the conduction time counting circuit stops the oscillator circuit, resets the counter, and sets the feedback dummy current to be output from the feedback sensing circuit to a zero level if the switching grant period signal is a prohibit signal.

10. The light-emitting diode driving apparatus according to claim 8, wherein

the conduction time counting circuit further includes a clamping circuit,

the clamping circuit holds the feedback dummy current from the feedback sensing circuit to a preset lower limit if a period where the switching grant period signal from the input voltage sensing circuit is the grant signal is less than or equal to a threshold indicating a first preset time, and

holds the feedback dummy current from the feedback sensing circuit to a preset upper limit if the period where the switching grant period signal from the input voltage sensing circuit is the grant signal is greater than or equal to a threshold indicating a second preset time.

11. The light-emitting diode driving apparatus according to claim 10, wherein

the threshold, set by the clamping circuit, indicating the second preset time is less than or equal to 7 ms.

12. The light-emitting diode driving apparatus according to claim 1, wherein

the feedback dummy current adjusted by counting the period, in a certain input half-cycle, where the switching grant period signal output from the input voltage sensing circuit is a grant signal, is applied as the feedback dummy current to be output from the feedback sensing circuit, when the switching grant period signal is output in a next input half-cycle, and a value of the feedback dummy current is held during the next input half-cycle.

13. The light-emitting diode driving apparatus according to claim 3, wherein

the control circuit controls a switching frequency of the switching element, using the control signal from the control signal converter of the feedback sensing circuit.

14. The light-emitting diode driving apparatus according to claim 3, wherein

the control circuit controls an on-time of the switching element which operates at a certain frequency, using the control signal from the control signal converter of the feedback sensing circuit.

15. The light-emitting diode driving apparatus according to claim 3, wherein

the control circuit controls a sensed value of a peak current through the switching element which operates at a certain frequency, using the control signal from the control signal converter of the feedback sensing circuit.

16. The light-emitting diode driving apparatus according to claim 13, wherein

the input voltage sensing circuit outputs to the control circuit a signal which controls a sensed value of a peak current through the switching element, based on the input voltage information rectified by the rectifying circuit, and

the control circuit controls a sensed value of a peak current through the switching element so that an input current generated due to the switching of the switching element is substantially proportional to the input voltage information rectified by the rectifying circuit.

17. The light-emitting diode driving apparatus according to claim 13, wherein

the input voltage sensing circuit outputs to the control circuit a signal which controls an on-time of the switching element, based on the input voltage information rectified by the rectifying circuit, and

the control circuit controls a sensed value of a peak current through the switching element so that an input current generated due to the switching of the switching element is substantially proportional to the input voltage information rectified by the rectifying circuit.

18. The light-emitting diode driving apparatus according to claim 1, wherein

the input voltage sensing circuit outputs to the control circuit a signal which sets a sensed value of a peak current through the switching element to a desired value smaller than a preset upper limit during a certain time period after a grant signal, which is the switching grant period signal, is output, the certain time period being preset.

19. The light-emitting diode driving apparatus according to claim 1, wherein

the input voltage sensing circuit outputs to the control circuit a signal which sets a switching frequency of the switching element to a desired value smaller than a preset upper limit during a certain time period after a grant signal, which is the switching grant period signal, is output, the certain time period being preset.

20. The light-emitting diode driving apparatus according to claim 18, wherein

the control circuit includes:

a constant current source having one end connected to the high side of the rectifying circuit; and

a regulator connected to another end of the constant current source, which outputs an activation signal if an output voltage of the constant current source is greater than or equal to a predetermined value, and outputs a deactivation signal if the output voltage of the constant current source is less than the predetermined value, and

during a period in which the regulator outputs the activation signal, the conduction time counting circuit fixes the feedback dummy current to be output from the feedback sensing circuit to the preset upper limit if a period where the switching grant period signal is the grant signal is greater than or equal to a threshold indicating a third preset time.

22. A semiconductor device for use in the light-emitting diode driving apparatus according to claim 1, the semiconductor device comprising

at least the switching element, the control circuit, the feedback sensing circuit, the input voltage sensing circuit, and the conduction time counting circuit formed on a same semiconductor substrate or incorporated in a same package.

23. The light-emitting diode driving apparatus according to claim 1, further comprising

a base connected to one of the AC power source and a DC power source, the base having a cylindrical shape, wherein

an input of the rectifying circuit is connected to the base, and

the rectifying circuit, the LED light source which includes the one or more light-emitting diodes, the choke coil, and the rectifier diode which supplies the LED light source with the counter electromotive force developed in the choke coil are integrated within a housing.

24. A light-emitting diode driving apparatus comprising:

the semiconductor device according to claim 22; and

a base connected to one of the AC power source and a DC power source, the base having a cylindrical shape, wherein

the rectifying circuit, the LED light source which includes the one or more light-emitting diodes, the choke coil, the rectifier diode which supplies the LED light source with the counter electromotive force developed in the choke coil, and the semiconductor device are integrated within a housing, and

an input of the rectifying circuit is connected to the base.

21. A light-emitting diode driving apparatus comprising:

a rectifying circuit which rectifies an AC voltage input from an AC power source, to output a DC voltage;

a load which includes an LED light source which includes one or more light-emitting diodes;

an energy conversion circuit coupled to a high side of the rectifying circuit and the load;

a switching element having an input terminal connected to a primary side of the energy conversion circuit and an output terminal connected to a low side of the rectifying circuit, the switching element turning on and off the DC voltage;

a control circuit which outputs a drive signal that controls on and off operation of the switching element, based on an operation reference voltage which is a voltage on the low side of the rectifying circuit;

an output current sensing circuit connected to the load and a low side of a secondary side of the energy conversion circuit, for sensing a current through the load;

a feedback sensing circuit connected to the output current sensing circuit, for receiving an output feedback signal output from the output current sensing circuit;

an input voltage sensing circuit which senses input voltage information rectified by the rectifying circuit;

a conduction time counting circuit which counts a switching grant period signal output from the input voltage sensing circuit; and

a phase control dimmer between the AC power source and the rectifying circuit, which controls an alternating conduction angle to control a phase of a voltage to be output to the rectifying circuit, wherein

the feedback sensing circuit outputs a feedback dummy current to the output current sensing circuit,

the conduction time counting circuit adjusts the feedback dummy current to be output from the feedback sensing circuit, depending on the counted switching grant period signal, and

the feedback sensing circuit outputs to the control circuit a control signal which controls switching of the switching element in response to a signal based on an error between the output feedback signal and a feedback dummy signal generated from the feedback dummy current.