Power converter, power conversion method and lighting apparatus

1. A power converter, comprising:

a first capacitor;

a flyback conversion module, coupled with the first capacitor and configured to receive a first control voltage (V 1 ) across the first capacitor and to supply a particular voltage or current to a load;

a soft start module, coupled with the first capacitor and configured to charge the first capacitor during a startup stage, to increase the first control voltage (V 1 ) to an expected voltage value (V e ) at an end of the startup stage, wherein the soft start module comprises:

a current source, coupled with the first capacitor and configured to provide a charging current to the first capacitor, wherein the charging current is a substantially constant current denoted as Is, which is calculated by: Is=C1*Ve/Ts, wherein Ts represents a time duration of the startup stage, C1 represents a capacitance of the first capacitor, Ve represents the expect voltage value of the first control voltage (V1), and

a charge time control module, coupled between the current source and the first capacitor, and configured to disconnect the current source from the first capacitor at the end of the startup stage; and

a feedback control module, coupled with the flyback conversion module at a first node and with the load at a second node and configured to control the flyback conversion module to output a substantially constant voltage or current after the startup stage, wherein the first node is different from the second node, the load having a first side and a second side, wherein the load is electrically coupled to the flyback conversion module at the first side and the load is electrically coupled to the feedback control module at the second side;

wherein the expected voltage value (V e ) is a value of the first control voltage (V 1 ) when the flyback conversion module outputs the substantially constant voltage or current after the startup stage.

2. The power converter according to claim 1 , wherein the current source comprises:

a first resistor having a first terminal and a second terminal;

a first semiconductor device coupled in series with the first resistor between an auxiliary source and the first capacitor, wherein the first semiconductor device is coupled to the second terminal of the first resistor; and

a voltage stabilizer coupled between the first terminal of the first resistor and a control terminal of the first semiconductor device.

3. The power converter according to claim 2 , wherein the first semiconductor device comprises a bipolar junction transistor, a metal-oxide-semiconductor field-effect transistor or a combination thereof.

4. The power converter according to claim 2 , wherein the voltage stabilizer comprises at least one of a zener diode, a transient voltage suppressor and an adjustable shunt regulator.

5. The power converter according to claim 1 , wherein the charge time control module comprises a controllable switch coupled between the current source and the first capacitor and configured to be switched off at the end of the startup stage.

6. The power converter according to claim 1 , wherein the flyback conversion module comprises:

a flyback convertor comprising a controllable switch; and

a control circuit, coupled between the first capacitor and a control terminal of the controllable switch, and configured to receive the first control voltage (V 1 ) and output a control signal to the controllable switch.

7. The power converter according to claim 1 , further comprising a rectifier, coupled between the flyback conversion module and a power source.

8. A power converter, comprising:

a first capacitor;

a flyback conversion module, coupled with the first capacitor and configured to receive a first control voltage (V 1 ) across the first capacitor;

a soft start module, coupled with the first capacitor and configured to charge the first capacitor during a startup stage, to increase the first control voltage (V 1 ) to an expected voltage value (V e ) at an end of the startup stage, wherein the soft start module comprises:

a current source, coupled with the first capacitor and configured to provide a charging current to the first capacitor; and

a charge time control module, coupled between the current source and the first capacitor, and configured to disconnect the current source from the first capacitor at the end of the startup stage; and

a feedback control module, coupled with the flyback conversion module and configured to control the flyback conversion module to output a substantially constant voltage or current after the startup stage;

wherein the expected voltage value (V e ) is a value of the first control voltage (V 1 ) when the flyback conversion module outputs the substantially constant voltage or current after the startup stage;

wherein the charge time control module comprises a second semiconductor device coupled between the current source and the first capacitor and configured to be cut off at the end of the startup stage.

9. The power converter according to claim 8 , wherein the second semiconductor device comprises at least one of a bipolar junction transistor and a metal-oxide-semiconductor field-effect transistor.

10. The power converter according to claim 8 , wherein the charge time control module further comprises a second capacitor, coupled to an auxiliary source and configured to provide a second control voltage (V2) to control the second semiconductor device;

wherein the auxiliary source is configured to charge the second capacitor to increase the second control voltage (V2) to a threshold value to cut off the second semiconductor device at the end of the startup stage.

11. A power conversion method, comprising:

controlling a flyback conversion module to convert energy by a first voltage across a first capacitor and to supply a particular voltage or current to a load, wherein the controlling the flyback conversion module comprises:

charging the first capacitor during a startup stage to increase the first control voltage to an expected voltage value at an end of the startup stage, wherein charging the first capacitor during the startup stage comprises:

providing a charging current to the first capacitor, wherein the charging current is a substantially constant current denoted as Is, which is calculated by: Is=C1*Ve/Ts, wherein Ts represents a time duration of the startup stage, C1 represents a capacitance of the first capacitor, Ve represents the expect voltage value of the first control voltage (V1), and

disconnecting the current source from the first capacitor at the end of the startup stage, and

controlling the flyback conversion module to output a substantially constant voltage or current after the startup stage,

wherein the expected voltage value is a value of the first control voltage when the flyback conversion module outputs a substantially constant voltage or current after the startup stage, and

wherein a feedback control module is coupled with the flyback conversion module at a first node and with the load at a second node and is configured to control the flyback conversion module to output a substantially constant voltage or current after the startup stage, the first node being different from the second node, the load having a first side and a second side, wherein the load is electrically coupled to the flyback conversion module at the first side and the load is electrically coupled to the feedback control module at the second side.

12. The method according to claim 11 , wherein the charging of the first capacitor comprises:

providing a charging current to the first capacitor by a current source; and

disconnecting the current source from the first capacitor at the end of the startup stage.

13. A lighting apparatus, comprising:

a light-emitting diode (LED); and

a power converter, coupled to the LED and configured to convert energy from a power source and transport the converted energy to the LED, the power converter comprising:

a first capacitor,

a flyback conversion module, coupled with the first capacitor and configured to receive a first control voltage (V 1 ) across the first capacitor and to supply a particular voltage or current to a load,

a soft start module, coupled with the first capacitor and configured to charge the first capacitor during a startup stage, to increase the first control voltage (V 1 ) to an expected voltage value (V e ) at an end of the startup stage, wherein the soft start module comprises:

a current source, coupled with the first capacitor and configured to provide a charging current to the first capacitor, wherein the charging current is a substantially constant current denoted as Is, which is calculated by: Is=C1*Ve/Ts, wherein Ts represents a time duration of the startup stage, C1 represents a capacitance of the first capacitor, Ve represents the expect voltage value of the first control voltage (V1), and

a charge time control module, coupled between the current source and the first capacitor, and configured to disconnect the current source from the first capacitor at the end of the startup stage, and

a feedback control module, coupled with the flyback conversion module at a first node and with the load at a second node and configured to control the flyback conversion module to output a substantially constant voltage or current after the startup stage, wherein the first node is different from the second node, the load having a first side and a second side, wherein the load is electrically coupled to the flyback conversion module at the first side and the load is electrically coupled to the feedback control module at the second side,

wherein the expected voltage value (V e ) is a value of the first control voltage (V 1 ) when the flyback conversion module outputs the substantially constant voltage or current after the startup stage.