Switched-mode power supply, power supply circuit thereof, and power supply method

Patent metadata

Field	Value
Publication number	US-12101025-B2
Application number	US-202217978912-A
Country	US
Kind code	B2
Filing date	Nov 1, 2022
Priority date	Nov 1, 2021
Publication date	Sep 24, 2024
Grant date	Sep 24, 2024

Abstract

A switched-mode power supply includes a first switch transistor. A drain of the first switch transistor receives an input voltage on a direct current input bus of the switched-mode power supply, and a source is connected to a reference ground. The power supply circuit includes a junction field-effect transistor (JFET), where a drain of the JFET receives the input voltage, a gate is connected to the reference ground, and a source outputs a supply voltage or a supply current. During each switch cycle, the first switch transistor is controlled to be turned off or a drain voltage is controlled to be greater than or equal to a first threshold voltage when the first switch transistor is turned on, such that the supply voltage or the supply current satisfies a drive voltage of the first switch transistor and an operating voltage of a to-be-powered circuit of the switched-mode power supply.

First claim

What is claimed is:

1. A power supply circuit of a switched-mode power supply, wherein the switched-mode power supply comprises a first switch transistor, wherein a drain of the first switch transistor receives an input voltage on a direct current input bus of the switched-mode power supply, and a source of the first switch transistor is connected to a reference ground; and the power supply circuit comprises:
a junction field-effect transistor (JFET), wherein a drain of the JFET receives the input voltage, a gate of the JFET is connected to the reference ground, and a source of the JFET outputs a supply voltage or a supply current; and
during each switch cycle, a drain voltage is controlled to be greater than or equal to a first threshold voltage when the first switch transistor is turned on, such that the supply voltage or the supply current satisfies a drive voltage of the first switch transistor and an operating voltage of a to-be-powered circuit.

2. The power supply circuit according to claim 1 , wherein the JFET is turned on.

3. The power supply circuit according to claim 1 , further comprising:
a first voltage generation unit, wherein an input terminal of the first voltage generation unit is connected to the JFET to output a first voltage, and the first voltage is used as the drive voltage of the first switch transistor to control the drain voltage to be greater than or equal to the first threshold voltage when the first switch transistor is turned on; and
a second voltage generation unit, wherein an input terminal of the second voltage generation unit is connected to the source of the JFET or the first voltage generation unit to output a second voltage, and the second voltage is used as the operating voltage of the to-be-powered circuit;
wherein if the drain voltage is equal to the first threshold voltage when the first switch transistor is turned on, the first voltage reaches a voltage not less than a minimum voltage capable of driving the first switch transistor or the second voltage reaches a voltage not less than a minimum operating voltage, wherein the to-be-powered circuit operates properly at the minimum operating voltage.

4. The power supply circuit according to claim 3 , wherein the first voltage generation unit comprises a gate-source capacitor of the first switch transistor; and
a gate of the first switch transistor is connected to the source of the JFET, and the gate-source capacitor receives the supply current to generate the first voltage.

5. The power supply circuit according to claim 3 , wherein the first voltage generation unit comprises:
a step-down circuit, wherein an input terminal of the step-down circuit is connected to the source of the JFET, and an output terminal of the step-down circuit is connected to a gate of the first switch transistor, and wherein a first voltage drop is generated between the source of the JFET and the gate of the first switch transistor when the first switch transistor is turned on; and
a gate-source capacitor of the first switch transistor, wherein the gate-source capacitor receives the supply current to generate the first voltage.

6. The power supply circuit according to claim 5 , wherein the input terminal of the second voltage generation unit is connected to the output terminal of the step-down circuit.

7. The power supply circuit according to claim 3 , wherein the first voltage generation unit comprises:
an input voltage detection and control unit configured to receive the input voltage to obtain an input voltage feedback signal, and output a first error voltage based on the input voltage feedback signal and a first reference voltage; and
an adjustment unit configured to receive the supply voltage and the first error voltage to output the first voltage.

8. The power supply circuit according to claim 7 , wherein the adjustment unit comprises an adder, and the adder performs an addition operation on the supply voltage and the first error voltage to output the first voltage.

9. The power supply circuit according to claim 7 , wherein the second voltage is used as the operating voltage of the first voltage generation unit.

10. A switched-mode power supply, comprising the power supply circuit according to claim 1 , the first switch transistor, a switch control circuit, and a drive circuit, wherein
the drain of the first switch transistor receives the input voltage on the direct current input bus of the switched-mode power supply;
the switch control circuit samples from the switched-mode power supply to obtain an inductor current sampling signal, receives an output voltage feedback signal characterizing an information about an output voltage of the switched-mode power supply, and obtains a switch control signal based on the inductor current sampling signal and the output voltage feedback signal;
the drive circuit receives the switch control signal, the state of the first switch transistor is controlled by the switch control signal; and
a first voltage generated by the power supply circuit is used as the drive voltage of the first switch transistor, and a second voltage generated by the power supply circuit is used as the operating voltage of the switch control circuit.

11. The switched-mode power supply according to claim 10 , wherein the switch control circuit comprises:
an inductor current detection unit configured to sample from the switched-mode power supply and obtain a current flowing through the first switch transistor when the first switch transistor is turned on to output the inductor current sampling signal;
an output voltage detection and holding unit configured to receive, when the first switch transistor is turned off, the output voltage feedback signal characterizing the output voltage of the switched-mode power supply to output an output voltage sampling signal; and
a logic control unit configured to receive the inductor current sampling signal and the output voltage sampling signal to generate the switch control signal.

12. The switched-mode power supply according to claim 11 further comprising a current detection circuit, wherein the current detection circuit comprises:
a first sampling resistor, wherein a first terminal of the first sampling resistor is connected to the source of the first switch transistor, and a second terminal of the first sampling resistor is connected to the reference ground, wherein the first terminal of the first sampling resistor is used as an output terminal of the current detection circuit to output the inductor current sampling signal.

13. The switched-mode power supply according to claim 11 further comprising a current detection circuit, wherein the current detection circuit comprises:
a second switch transistor, wherein a gate of the second switch transistor is connected to a gate of the first switch transistor, and a drain of the second switch transistor is connected to the drain of the first switch transistor; and
a second sampling resistor, wherein a first terminal of the second sampling resistor is connected to a source of the second switch transistor, and a second terminal of the second sampling resistor is connected to the source of the first switch transistor and connected to the reference ground, wherein the first terminal of the second sampling resistor is used as an output terminal of the current detection circuit to output the inductor current sampling signal.

14. The switched-mode power supply according to claim 10 , further comprising:
an output voltage transmission circuit configured to receive the output voltage of the switched-mode power supply to output the output voltage feedback signal.

Assignees

• Joulwatt Tech Co Ltd

Inventors

• Long Hao

Classifications

• H02M1/0006

  Arrangements for supplying an adequate voltage to the control circuit of converters · CPC title

• H02M3/1582

  Buck-boost converters (H02M3/1584 takes precedence) · CPC title

• H02M1/0045

  Converters combining the concepts of switch-mode regulation and linear regulation, e.g. linear pre-regulator to switching converter, linear and switching converter in parallel, same converter or same transistor operating either in linear or switching mode · CPC title

• H02M1/0054

  Transistor switching losses (periodically suspending operation of switching converter in low power mode H02M1/0035) · CPC title

• H02M1/0009

  Devices or circuits for detecting current in a converter · CPC title