Power conversion device, slow soft-startup circuit, and power conversion chip

Patent metadata

Field	Value
Publication number	US-10498254-B2
Application number	US-201715632321-A
Country	US
Kind code	B2
Filing date	Jun 24, 2017
Priority date	Apr 21, 2017
Publication date	Dec 3, 2019
Grant date	Dec 3, 2019

Abstract

The invention provides a power conversion device, including: a voltage conversion stage, including a primary side for receiving a rectified voltage and a secondary side for generating a rectified voltage according to the rectified voltage, wherein the primary side includes a primary side switch; a switch control circuit having a startup status and a normal operation status, the switch control circuit being configured to operably provide a control signal to a control terminal of the primary side switch; a startup circuit, providing a current to the control terminal when the switch control circuit is in the startup status, to at least partially conduct the primary side switch; and a slow soft-startup circuit, wherein when the switch control circuit is in the startup status and the output voltage does not reach a predetermined voltage in a first predetermined time period, the slow soft-startup circuit reduces a total current quantity supplied to the control terminal in a second predetermined time period which is after the first predetermined time period.

First claim

What is claimed is:

1. A power conversion device, comprising:
a voltage conversion stage, including a transformer having a primary side for receiving a rectified voltage and a secondary side for generating an output voltage according to the rectified voltage, the primary side including a primary side switch which is controlled by a control signal to control a primary side current through the primary side;
a switch control circuit, having a startup status and a normal operation status, the switch control circuit providing the control signal to a control terminal of the primary side switch when the switch control circuit is in the normal operation status, for controlling a current conduction status of the primary side switch;
a startup circuit, configured to operably provide a current to the control terminal of the primary side switch when the switch control circuit is in the startup status, to at least partially conduct the primary side switch; and
a slow soft-startup circuit, configured to operably adjust the control signal when the switch control circuit is in the startup status, wherein when the output voltage does not reach a predetermined level in a first predetermined time period, the slow soft-startup circuit reduces a total current quantity supplied to the control terminal in a second predetermined time period, which is another time period after the first predetermined time period.

2. The power conversion device of claim 1 , wherein the slow soft-startup circuit stops reducing the total current quantity supplied to the control terminal in a third predetermined time period, which is another time period after the second predetermined time period.

3. The power conversion device of claim 1 , wherein when the switch control circuit is in the startup status, the startup circuit adjusts the control signal to have a voltage waveform including repeated peaks and valleys, and wherein the slow soft-startup circuit reduces the total current quantity supplied to the control terminal in the second predetermined time period by one or more of following steps:
the slow soft-startup circuit prolonging a time period from the valley to the peak in the second predetermined time period;
the slow soft-startup circuit reducing a frequency of reaching the peak in the second predetermined time period; and/or
the slow soft-startup circuit prolonging a duration of the voltage waveform staying at the valley.

4. The power conversion device of claim 1 , wherein the slow soft-startup circuit includes:
at least one current discharge circuit, coupled between the control terminal of the primary side switch and ground; and
a control unit, configured to operably control a current conduction status of the current discharge circuit, wherein when the switch control circuit is in the startup status and the output voltage does not reach the predetermined level in the first predetermined time period, the control signal has a voltage waveform including repeated peaks and valleys, and the control unit conducts the at least one current discharge circuit to prolong a time period from the valley to the peak in the second predetermined time period.

5. The power conversion device of claim 4 , wherein each current discharge circuit includes a current switch and a current source connected in series, the series circuit of the current switch and the current source being coupled between the control terminal of the primary side switch and ground, wherein when the current switch is conducted, the control terminal of the primary side switch is conducted to the ground through the current source, to reduce the total current quantity supplied to the control signal in the second predetermined time period.

6. The power conversion device of claim 4 , wherein the slow soft-startup circuit includes a plurality of current discharge circuits, wherein when the switch control circuit is in the startup status and the output voltage does not reach the predetermined level in the first predetermined time period, the control unit gradually increases a number of the current discharge circuits which are conducted in the second predetermined time period, to reduce the total current quantity supplied to the control signal in the second predetermined time period.

7. The power conversion device of claim 6 , wherein when the control unit conducts the current discharge circuits till an end of the second predetermined time period, the control unit stops conducting the current discharge circuits, so as to determine whether the output voltage reaches the predetermined level in the third predetermined time period, wherein the third predetermined time period is another time period after the second predetermined time period.

8. The power conversion device of claim 1 , wherein when the output voltage reaches the predetermined level, a power-on reset signal is generated to switch the switch control circuit from the startup status to the normal operation status.

9. The power conversion device of claim 8 , wherein the slow soft-startup circuit stops adjusting the control signal according to the power-on reset signal.

10. The power conversion device of claim 1 , wherein when the switch control circuit is in the startup status, the startup circuit adjusts the control signal to have a voltage waveform including repeated peaks and valleys, wherein the startup circuit includes:
a resistor, coupled between the rectified voltage and the control terminal of the primary side switch;
a grounding switch, coupled between the control terminal of the primary side switch and ground; and
a pulse generator, configured to alternately generate a plurality of pulses for turning the grounding switch on and off.

11. The power conversion device of claim 10 , wherein the slow soft-startup circuit is coupled between the pulse generator and ground, and is configured to prolong a time length of at least one of the pulses, wherein when the switch control circuit is in the startup status and the slow soft-startup circuit receives the pulse, the slow soft-startup circuit prolongs a conduction time period of the grounding switch, so as to prolong a duration of the voltage waveform staying at the valley.

12. The power conversion device of claim 1 , further comprising a power supply circuit, which is coupled to the control terminal of the primary side switch, for supplying power to the startup circuit and the slow soft-startup circuit.

13. A slow soft-startup circuit, for controlling a voltage conversion circuit which includes a transformer having a primary side for receiving a rectified voltage and a secondary side for generating an output voltage according to the rectified voltage, the primary side including a primary side switch, wherein the voltage conversion circuit further includes a switch control circuit and a startup circuit, the switch control circuit having a startup status and a normal operation status, the switch control circuit in the startup status providing a control signal to the control terminal of the primary side switch to at least partially conduct the primary side switch, the slow soft-startup circuit comprising:
at least one current discharge circuit, coupled between the control terminal of the primary side switch and ground; and
a control unit, configured to operably control a current conduction status of the current discharge circuit, wherein when the switch control circuit is in the startup status and the output voltage does not reach a predetermined level in a first predetermined time period, the control unit conducts the at least one current discharge circuit in a second predetermined time period after the first predetermined time period, to reduc

Assignees

• Richtek Technology Corp

Inventors

• Ho Jyun-Che
• Chen Isaac Y
• Lee Yi-Wei

Classifications

• G05F1/40 Primary

  using discharge tubes or semiconductor devices as final control devices · CPC title

• H02M3/335

  using semiconductor devices only · CPC title

• H02M3/33507

  with automatic control of the output voltage or current, e.g. flyback converters (H02M3/33561, H02M3/33569 take precedence) · CPC title

• H02M1/36

  Means for starting or stopping converters · CPC title

• H02M3/156

  with automatic control of output voltage or current, e.g. switching regulators · CPC title