Switch control circuit, switch controlling method, and power supply device using the switch control circuit

• US 8,873,206 B2
• Filed: 01/03/2012
• Issued: 10/28/2014
• Est. Priority Date: 01/26/2011
• Status: Active Grant

• Current Assignee: Semiconductor Components Industries LLC (ON Semiconductor Corporation)
• Original Assignee: Fairchild Korea Semiconductor Limited (ON Semiconductor Corporation)
• Inventors: Lee, Young-Je, Cho, Gye-Hyun, Hong, Seung-Woo, Lee, Jae-yong
• Primary Examiner(s): Leja, Ronald W
• Application Number:
  US13/342,404
• Publication Number:
  US 20120188670A1
• Time in Patent Office: 1,029 Days
• Field of Search: 361/18
• US Class Current: 361/18
• CPC Class Codes: H02H 3/24 responsive to undervoltage or no-voltage H02H3/207 takes precedence
• CPC Class Codes: H05B 45/3725 Switched mode power supply [SMPS]
• CPC Class Codes: H05B 45/375 using buck topology
• CPC Class Codes: H05B 45/50 responsive to malfunctions or undesirable behaviour of LEDs; responsive to LED life; Protective circuits
• CPC Class Codes: Y02B 20/30 Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]

Abstract

Embodiments of the present invention relate to a switch control circuit, a switch control method, and a power supply device using the same.

Embodiments generate a reference signal according to a full-wave rectification voltage and control a switching operation of a power switch according to a comparing result of a sense voltage corresponding to a current flowing to the power switch and the reference voltage. Embodiments determine whether a line is opened between a first output terminal and a second output terminal of the power supply device using the sense voltage. When the line is opened, Embodiments turn off the protection switch.

Claims

1. A power supply device comprising:

a DC-link wire connected between a full-wave rectification voltage and a first output terminal and having a protection switch formed therein;

an inductor charging power using the full-wave rectification voltage and supplying the power to a load connected between the first output terminal and a second output terminal;

a power switch connected to the inductor and controlling power supplied to the load; and

a switch control circuit generating a reference signal according to the full-wave rectification signal, controlling a switching operation of the power switch according to a result of comparison between a sense voltage corresponding to a current flowing to the power switch and the reference voltage, determining whether an open line between the first output terminal and the second output terminal using the sense voltage, and turning off the protection switch when the line open is generated.

2. The power supply device of claim 1, wherein the switch control circuit determines whether a line is opened according to the result of the comparison between a sense voltage at a turn-off time point of the power switch and a predetermined open reference voltage.

3. The power supply device of claim 2, wherein the switch control circuit determines that the line is opened when a period during which the sense voltage is lower than the open reference voltage is maintained longer than a predetermined open determination period.

4. The power supply device of claim 3, wherein the switch control circuit turns off the protection switch for a predetermined open protection period after the open determination period, and starts the next open protection period when the sense voltage is lower than the open reference voltage during the next open determination period after expiration of the open protection period.

5. The power supply device of claim 3, wherein the switch control circuit terminates the open line protection operation when the AC input to the power supply device is blocked due to a plug-out after the open determination period.

6. The power supply device of claim 1, wherein the switch control circuit comprises an open protection operator that determines whether a line is opened using the sense voltage for every switching cycle of the power switch and turns off the protection switch when the line-open is determined.

7. The power supply device of claim 6, wherein the open protection operator comprises:

a comparator generating an open comparison signal according to a comparison result between the sense voltage and a predetermined open reference voltage;

a D-flipflop synchronized by an inverse gate control signal that is an inverse signal of a gate control signal controlling the switching operation of the power switch to generate a comparison output voltage according to the open comparison signal;

a counter counting a clock signal that determines a switching frequency of the power switch to generate a protection start signal when a open determination period is passed and generating a protection expiring signal when the open protection period is passed;

a first login gate generating a counter reset signal by performing a logic operation on a under-voltage lockout signal that is generated when the comparison output voltage, the protection expiring signal, and the power voltage are lower than a predetermined normal level;

a second logic gate generating a protection reset signal by performing a logic operation on the protection expiring signal and the under-voltage lockout signal to control termination of the open line protection operation;

an SR latch generating an open protection signal controlling the start of the open ling protection operation by being synchronized by the protection start signal and controlling termination of the open line protection operation by being synchronized by the protection reset signal; and

a high voltage device controller controlling the switching operation of the protection switch according to the open protection signal.

8. The power supply device of claim 6, wherein the open protection operator comprises:

a comparator generating an open comparison signal according to a comparison result between the sense voltage and a predetermined open reference voltage;

a D-flipflop synchronized by an inverse gate control signal that is an inverse signal of the gate control signal that controls the switching operation of the power switch to generate a comparison output voltage according to the open comparison signal;

a counter counting a clock signal that determines a switching frequency of the power switch to generate a protection start signal when the open determination period is passed;

a first logic gate generating the counter reset signal by performing a logic operation on a under-voltage lockout signal that is generated when the comparison output voltage and the power voltage are lower than a predetermined normal level;

an SR latch generating an open protection signal controlling the start of the open ling protection operation by being synchronized by the protection start signal an controlling termination of the open ling protection operation by being synchronized by the low-voltage blocking signal; and

a high voltage device controller controlling the switching operation of the protection switch according to the open protection signal.

9. A switch control circuit controlling operation of a protection switch connected between a full-wave rectification voltage rectified from an AC input and a first output terminal and controlling a switching operation of a power switch that controls power supplied to a load connected between the first output terminal and a second output terminal through an inductor charged with power by the full-wave rectification voltage, the switch control circuit comprising:

a reference signal generator generating a reference signal according to the full-wave rectification voltage;

a PWM controller controlling the switching operation of the power switch according to a comparison result between a sense voltage corresponding to a current flowing to the power switch with the reference signal; and

an open protection operator determining whether a line between the first output terminal and the second output terminal is opened using the sense voltage and turning off the protection switch when the line open occurs.

10. The switch control circuit of claim 9, wherein the open protection operator compares a sense voltage of the turn-off time of the power switch with a predetermined open reference voltage, and determines the line is opened when a period during which the sense voltage is lower than open reference voltage is maintained longer than a predetermined open determination period.

11. The switch control circuit of claim 10, wherein the open protection operator turns off the protection switch during a predetermined open protection period after the open determination period, and starts the next open protection period when the sense voltage is lower than the open reference voltage during the next open determination period after the open protection period is terminated.

12. The switch control circuit of claim 11, wherein the open protection operator terminates the open line protection operation when the AC input to a power supply device including the switch control circuit is blocked due to a plug-out after then open determination period.

13. The switch control circuit of claim 10, wherein the open protection operator comprises:

a comparator generating an open comparison signal according to a comparison result between the sense voltage and a predetermined open reference voltage;

a D-flipflop synchronized by an inverse gate control signal that is an inverse signal of a gate control signal that controls the switching operation of the power switch to generate a comparison output voltage according to the open comparison signal;

a counter counting a clock signal that determines a switching frequency of the power switch to generate a protection start signal when the open determination period is passed and generating a protection expiring signal when the open protection period is passed;

a first logic gate performing a logic operation on a under-voltage lockout signal that is generated when the comparison output voltage, the protection expiring signal, and a power voltage for operation of the switch control circuit are lower than a predetermined normal level to generate the counter reset signal;

a second logic gate performing a logic operation on the protection expiring signal and the under-voltage lockout signal to generate a protection reset signal for control of termination of the open line protection operation;

an SR latch generating an open protection signal controlling the start of the open line protection operation by being synchronized by the protection start signal and controlling termination of the open line protection operation by being synchronized by the protection reset signal; and

a high voltage device controller controlling the switching operation of the protection switch according to the open protection signal.

14. The switch control circuit of claim 10, wherein the open protection operator comprises:

a comparator generating an open comparison signal according to a comparison result between the sense voltage and a predetermined open reference voltage;

a D-flipflop synchronized by an inverse gate control signal that is an inverse signal of the gate control signal that controls the switching operation of the power switch to generate a comparison output voltage according to the open comparison signal;

a counter counting a clock signal that determines a switching frequency of the power switch to generate a protection start signal when the open determination period is passed;

a third logic gate performing a logic operation on a under-voltage lockout signal that is generated when the comparison output voltage and a power voltage for operation of the switch control circuit are lower than a predetermined normal level to generate the counter reset signal;

an SR latch generating an open protection signal controlling the start of the open ling protection operation by being synchronized by the protection start signal an controlling termination of the open ling protection operation by being synchronized by the low-voltage blocking signal; and

a high voltage device controller controlling the switching operation of the protection switch according to the open protection signal.

15. A switch control method for controlling a switching operation of a power switch that controls an operation of a protection switch connected between a full-wave rectification voltage rectified from an AC input and a first output terminal and controls a switching operation of a power switch that controls power supplied to a load connected between the first output terminal and a second output terminal through an inductor charged with power by the full-wave rectification voltage, the switch control method comprising:

generating a reference signal according to the full-wave rectification voltage;

controlling the switching operation of the power switch according to the comparison result between a sense voltage corresponding to a current flowing to the power switch with the reference signal; and

determining whether a line between the first output terminal and the second output terminal is opened using the sense voltage, and turning off the protection switch controlling the open protection operation when the line open occurs.

16. The switch control method of claim 15, wherein the controlling of the open protection operation comprises:

comparing a sense voltage at a turn-off time of the power switch and a predetermined open reference voltage; and

determining the line is opened when a period during which the sense voltage is lower than the open reference voltage is maintained longer than a predetermined open determination period.

17. The switch control method of claim 16, wherein the controlling of the open protection operation further comprises:

turning off the protection switch during a predetermined open protection period after the open determination period; and

starting the next open protection period when the sense voltage is lower than the open reference voltage during the next open determination period after the open protection period.

18. The switch control method of claim 17, wherein the controlling of the open protection operation further comprises:

counting a clock signal that determines a switching frequency of the power switch to generate a protection start signal when the open determination period is passed and generating a protection expiring signal when the open protection period is passed;

resetting the counting result of the clock signal according to a logic operation result of a under-voltage lockout signal that is generated when the protection expiring signal and a power voltage for switching control operation of the power switch are lower than a predetermined normal level as a result of the comparison between the sense voltage and the open reference voltage; and

controlling termination of the open line protection operation by performing a logic operation on the protection expiring signal and the low-voltage blocking signal.

19. The switch control method of claim 16, wherein the controlling of the open protection operation further comprises terminating the open line protection operation when a plug-out occurs and thus the AC input to a power supply device including the switch control circuit is blocked after then open determination period.

20. The switch control method of claim 19, wherein the controlling of the open protection operation further comprises:

generating a protection start signal when an open determination period is passed by counting a clock signal that determines the switching frequency of the power switch;

resetting the counting result of the clock signal according to the comparison result between the sense voltage and the open reference voltage and the result of the logic operation performed on a under-voltage lockout signal that is generated when the protection expiring signal and a power voltage for switching control operation of the power switch are lower than a predetermined normal level; and

controlling the start of the open ling protection operation by being synchronized by the protection start signal and controlling termination of the open line protection operation by being synchronized by the low-voltage blocking signal.