Insulated DC power supply and a method of controlling same

Patent metadata

Field	Value
Publication number	US-9602010-B2
Application number	US-201514964448-A
Country	US
Kind code	B2
Filing date	Dec 9, 2015
Priority date	Dec 15, 2014
Publication date	Mar 21, 2017
Grant date	Mar 21, 2017

Abstract

An insulated DC power supply includes a voltage transformer, a switching device and a primary-side regulating circuit. The voltage transformer includes primary and secondary windings and an auxiliary winding. The switching device causes current to flow intermittently through the primary winding. The primary-side regulating circuit receives a voltage proportional to a current flowing through the primary winding of the transformer, and a voltage proportional to a voltage induced in the auxiliary winding of the transformer to generate and output a drive pulse for turning on or off the switching device. The primary-side regulating circuit includes an ON/OFF signal generator circuit and first and second timer circuits. The switching device is turned off upon expiration of the first timer circuit, and the ON/OFF signal generator circuit does not generate a signal for turn-on of the switching device when the second timer circuit expires.

First claim

What is claimed is:

1. An insulated DC power supply comprising:
a voltage transformer comprising a primary winding, a secondary winding, and an auxiliary winding;
a switching device causing current to flow intermittently through the primary winding of the transformer; and
a primary-side regulating circuit receiving a voltage proportional to a current flowing through the primary winding of the transformer, and a voltage proportional to a voltage induced in the auxiliary winding of the transformer to generate and output a drive pulse for turning on or off the switching device, the primary-side regulating circuit comprising:
a voltage detector circuit giving ON-timings for the switching device with reference to a voltage across the primary winding of the transformer, the voltage induced in the auxiliary winding, or the voltage proportional to the voltage induced in the auxiliary winding;
a current detector circuit giving OFF-timings for the switching device with reference to the voltage proportional to the current flowing through the primary winding of the transformer;
an ON/OFF signal generator circuit generating signals for turning on or off the switching device with reference to signals from the current detector circuit and the voltage detector circuit;
a first timer circuit starting up in synchronization with the ON timing of the switching device, starting to measure the ON time of the switching device, and then expiring upon lapse of a predetermined primary side maximum ON time; and
a second timer circuit starting up upon expiration of the first timer circuit, starting time measurement, and then expiring upon lapse of a predetermined maximum demagnetization time, wherein

the switching device is turned off upon expiration of the first timer circuit, and the ON/OFF signal generator circuit does not generate a signal for turn-on of the switching device when the second timer circuit expires.

2. The insulated DC power supply of claim 1 , further comprising a demagnetization period detector detecting a demagnetization period of the transformer, wherein the second timer circuit executes time measurement only during the demagnetization period detected by the demagnetization period detector.

3. The insulated DC power supply of claim 1 , wherein the current detector circuit receives a voltage resulting from current-to-voltage conversion in a resistor connected in series with the switching device.

4. The insulated DC power supply of claim 1 , wherein the voltage detector circuit receives a voltage from a voltage divider that divides the voltage induced in the auxiliary winding of the transformer.

5. The insulated DC power supply of claim 4 , further comprising an input-voltage-level detector circuit detecting the potential of the input voltage of the primary winding of the transformer, wherein the first timer circuit measures a time inversely proportional to the input voltage.

6. The insulated DC power supply of claim 4 , further comprising an induced-voltage-level detector circuit detecting the potential of the voltage from the voltage divider, wherein the second timer circuit measures a time inversely proportional to the induced voltage.

7. The insulated DC power supply of claim 4 , wherein the current detector circuit is a voltage comparator circuit that compares the voltage resulting from current-to-voltage conversion in the resistor connected in series with the switching device with the voltage proportional to the voltage from the voltage divider, and outputs a signal indicating OFF-timings for the switching device.

8. A method of controlling an insulated DC power supply comprising:
a voltage transformer comprising a primary winding, a secondary winding, and an auxiliary winding;
a switching device causing current to flow intermittently through the primary winding of the transformer; and
a primary-side regulating circuit receiving a voltage proportional to a current flowing through the primary winding of the transformer, and a voltage proportional to a voltage induced in the auxiliary winding of the transformer to generate and output a drive pulse for turning on or off the switching device, the method comprising:
monitoring the voltage induced in the auxiliary winding of the transformer or the voltage proportional to the voltage induced in the auxiliary winding, and the voltage proportional to the current flowing through the primary winding of the transformer,
starting a first time-measurement in synchronization with each ON-timing of the switching device,
starting the next ON operation of the switching device when the current detector circuit detects that the current flowing through the primary winding of the transformer reaches a predetermined current value before expiration of a predetermined primary side maximum ON time,
turning off the switching device and starting a second time-measurement upon expiration of the primary side maximum ON time before the current detector circuit detects that the current flowing through the primary winding of the transformer reaches the predetermined current value, and
preventing generation of an ON signal for the switching device after expiration of a predetermined maximum demagnetization time.

Assignees

• Arima Satoshi
• Nakata Kenji
• Sato Takeshi
• Mitsumi Electric Co Ltd

Inventors

• Arima Satoshi
• Nakata Kenji
• Sato Takeshi

Classifications

• H02M3/33507 Primary

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

• H02M2001/0009

  Electricity · mapped topic

• H02M1/0009

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

• H02H7/1213

  for DC-DC converters · CPC title