Switching power supply

Patent metadata

Field	Value
Publication number	US-10693362-B2
Application number	US-201816226260-A
Country	US
Kind code	B2
Filing date	Dec 19, 2018
Priority date	Dec 25, 2017
Publication date	Jun 23, 2020
Grant date	Jun 23, 2020

Abstract

A switching power supply includes an insulated transformer, a full-bridge circuit which converts input DC power into AC power and outputs the AC power to a primary-side coil, an output circuit which converts AC power input from secondary-side coils into DC power and outputs the DC power, and a control circuit which controls the full-bridge circuit by using a phase shift method based on voltage output by the output circuit. When a measured value of the amount of phase shift determined from at least one of the voltage and current output by the output circuit is smaller than a theoretical value of the amount of phase shift corresponding to the switching power supply operating in a continuous current mode, the control circuit prolongs dead time used in the full-bridge circuit in accordance with the difference between the measured value and the theoretical value.

First claim

What is claimed is:

1. A switching power supply comprising: an insulated transformer including a primary-side coil and a secondary side coil; a full-bridge circuit that converts input DC power into AC power and outputs the AC power to the primary-side coil; an output circuit that converts AC power input from the secondary-side coil into an output DC power and outputs the output DC power; and a control circuit that controls the full-bridge circuit by using a phase shift method based on voltage output by the output circuit, wherein when the switching power supply is determined to be in a discontinuous current mode when a measured value of an amount of phase shift determined from at least one of the voltage and current output by the output circuit is smaller than a theoretical value of the amount of phase shift corresponding to the switching power supply operating in a continuous current mode, the control circuit prolongs dead time used in the full-bridge circuit in accordance with a difference between the measured value and the theoretical value.

2. The switching power supply according to claim 1 , wherein the control circuit calculates the theoretical value of the amount of phase shift based on input voltage input to the full-bridge circuit and output voltage output by the output circuit.

3. The switching power supply according to claim 2 , wherein the control circuit calculates the theoretical value of the amount of phase shift based also on an oscillation cycle in accordance with which the full-bridge circuit is controlled in addition to the input voltage and the output voltage.

4. The switching power supply according to claim 3 , wherein the theoretical value of the amount of phase shift is calculated by the following expression:

T
ON

=

V
OUT

+

K
1

V
IN

×

(

N
S

N
P

+

K
2

)

×
T

where V OUT represents the output voltage, V IN represents the input voltage, T represents the oscillation cycle, N P represents a turn count of the primary-side coil, and N S represents a turn count of the secondary-side coil with K1 and K2 being predetermined parameters.

5. The switching power supply according to claim 2 , wherein the control circuit calculates the input voltage from input current input to the full-bridge circuit, output current output by the output circuit, the output voltage, and conversion efficiency.

Assignees

• Fdk Corp

Inventors

• Hamada Kenji
• Sato Tadashi
• Fukui Norio

Classifications

• H02M3/01

  Resonant DC/DC converters · CPC title

• H02M3/33573

  Full-bridge at primary side of an isolation transformer · CPC title

• H02M3/3376 Primary

  with automatic control of output voltage or current · CPC title

• H02M1/083 Primary

  for the ignition at the zero crossing of the voltage or the current · CPC title

• Y02B70/10

  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 · CPC title