Power supply control unit and isolation type switching power supply device

Patent metadata

Field	Value
Publication number	US-10491127-B2
Application number	US-201715704256-A
Country	US
Kind code	B2
Filing date	Sep 14, 2017
Priority date	Sep 16, 2016
Publication date	Nov 26, 2019
Grant date	Nov 26, 2019

Abstract

The power supply control unit includes an on trigger signal generating unit arranged to generate an on trigger signal for turning on the switching element on the basis of a feedback signal of flyback voltage, a first timer arranged to measure a predetermined minimum OFF time, a second timer arranged to measure time based on an ON time, a minimum OFF time setting unit arranged to compare the predetermined minimum OFF time measured by the first timer with the time measured by the second timer so as to set a longer time as a minimum OFF time, and an on timing determining unit arranged to determine timing for turning on the switching element on the basis of the set minimum OFF time and the on trigger signal.

First claim

What is claimed is:

1. A power supply control unit used for an isolation type flyback switching power supply device including a transformer having a primary winding and a secondary winding, and a switching element, one terminal of the primary winding being connected to an application terminal of an input voltage, while the other terminal of the primary winding being connected to the switching element, the power supply control unit comprising:
an on trigger signal generating unit arranged to generate an on trigger signal for turning on the switching element on the basis of a feedback signal of a flyback voltage;
a first timer arranged to measure a predetermined minimum OFF time;
a second timer arranged to measure time based on ON time;
a minimum OFF time setting unit arranged to compare the predetermined minimum OFF time measured by the first timer with the time measured by the second timer so as to set a longer time as a minimum OFF time; and
an on timing determining unit arranged to determine timing for turning on the switching element on the basis of the set minimum OFF time and the on trigger signal.

2. The power supply control unit according to claim 1 , wherein the second timer measures time that is a predetermined ratio of the ON time.

3. The power supply control unit according to claim 1 , further comprising:
a duty information obtaining unit arranged to obtain duty information on the basis of a PWM signal corresponding to PWM drive of the switching element;
a third timer arranged to measure ON time on the basis of the obtained duty information; and
an off timing determining unit arranged to determine timing for turning off the switching element on the basis of the ON time measured by the third timer, wherein
the second timer measures time on the basis of the duty information.

4. The power supply control unit according to claim 1 , wherein the minimum OFF time setting unit is an AND circuit.

5. The power supply control unit according to claim 1 , wherein the on timing determining unit is an AND circuit.

6. An isolation type switching power supply device comprising:
the power supply control unit according to claim 1 ;
a switching element; and
a transformer.

7. The power supply control unit according to claim 2 , wherein the predetermined ratio is 20% to 80%.

8. The power supply control unit according to claim 3 , wherein
the duty information obtaining unit is a low pass filter to which the PWM signal is input, and
the duty information is obtained as output voltage of the low pass filter.

9. The power supply control unit according to claim 7 , wherein the predetermined ratio is 50%.

10. The power supply control unit according to claim 8 , wherein
each of the second timer and the third timer includes a capacitor, a constant current circuit arranged to charge the capacitor, and a comparator to which voltage of the capacitor and reference voltage are input,
output voltage of the low pass filter is the reference voltage of the third timer, and
voltage that is a predetermined ratio of the output voltage of the low pass filter is the reference voltage of the second timer.

11. A power supply control unit used for an isolation type flyback switching power supply device including a transformer having a primary winding and a secondary winding, and a switching element, one terminal of the primary winding being connected to an application terminal of an input voltage, while the other terminal of the primary winding being connected to the switching element, the power supply control unit comprising:
an ON time setting unit arranged to set an ON time on the basis of switching duty of the switching element;
an on trigger signal generating unit arranged to generate an on trigger signal for turning on the switching element on the basis of a feedback signal of flyback voltage;
a first timer arranged to measure a predetermined minimum OFF time;
a second timer arranged to measure time based on the ON time set by the ON time setting unit;
a minimum OFF time setting unit arranged to compare the predetermined minimum OFF time measured by the first timer with the time measured by the second timer so as to set a longer time as a minimum OFF time; and
an on timing determining unit arranged to determine timing for turning on the switching element on the basis of the set minimum OFF time and the on trigger signal.

12. An isolation type switching power supply device comprising:
the power supply control unit according to claim 11 ;
a switching element; and
a transformer.

13. A power supply control unit used for an isolation type flyback switching power supply device including a transformer having a primary winding and a secondary winding, and a switching element, one terminal of the primary winding being connected to an application terminal of an input voltage, while the other terminal of the primary winding being connected to the switching element, the power supply control unit comprising:
an OCP unit (overcurrent protection unit) arranged to detect overcurrent of primary side current;
an off control unit arranged to turn off the switching element when the overcurrent is detected;
a first timer arranged to measure a predetermined minimum OFF time at timing delayed from turning off by the off control unit;
an on trigger signal generating unit arranged to generate an on trigger signal for turning on the switching element on the basis of a feedback signal of flyback voltage; and
an on timing determining unit arranged to determine timing for turning on the switching element on the basis of the measured minimum OFF time and the on trigger signal.

14. The power supply control unit according to claim 13 , further comprising:
a second timer arranged to start measurement of time that is a predetermined ratio of ON time at the same timing as the first timer; and
a minimum OFF time setting unit arranged to compare the predetermined minimum OFF time measured by the first timer with the time measured by the second timer so as to set a longer time as a minimum OFF time, wherein
the on timing determining unit determines timing for turning on the switching element on the basis of the set minimum OFF time and the on trigger signal.

15. The power supply control unit according to claim 13 , wherein the on timing determining unit is an AND circuit.

16. The power supply control unit according to claim 13 , further comprising:
a third timer arranged to measure ON time;
a first latch circuit to which output of the third timer is input;
an OR circuit to which output of the OCP unit and output of the third timer are input; and
a second latch circuit to which output of the OR circuit is input, wherein
the off control unit includes the OR circuit and the second latch circuit,
a second PWM signal output from the second latch circuit is input to a driver arranged to drive the switching element,
a first PWM signal output from the first latch circuit is input to the first timer, and
output of the on timing determining unit is input to the first latch circuit and to the second latch circuit.

17. An isolation type switching power supply device comprising:
the power supply control unit according to claim 13 ;
a switching element; and
a transformer.

18. The power supply control unit according to claim 14 , wherein the predetermined ratio is 20% to 80%.

19. The power supply control unit according to claim 14 , wherein the minimum OFF time setting unit is an AND circuit.

20. The power supply control unit acc

Assignees

• Rohm Co Ltd

Inventors

• Hara Hideo
• Akamatsu Yohei

Classifications

• H02M3/3385

  with automatic control of output voltage or current (H02M3/33561 takes precedence) · CPC title

• H02M3/335

  using semiconductor devices only · CPC title

• H02M3/33523 Primary

  with galvanic isolation between input and output of both the power stage and the feedback loop · CPC title

• H02M1/32

  Means for protecting converters other than automatic disconnection · CPC title

• H02M3/1563

  without using an external clock (H02M3/158 takes precedence) · CPC title