Semiconductor device for switching power supply and AC-DC convertor

Patent metadata

Field	Value
Publication number	US-10720847-B2
Application number	US-201916591573-A
Country	US
Kind code	B2
Filing date	Oct 2, 2019
Priority date	Oct 4, 2018
Publication date	Jul 21, 2020
Grant date	Jul 21, 2020

Abstract

A semiconductor device for a switching power supply includes first and second external terminals, ON and OFF timing generation circuits, and a drive pulse generation circuit. To the first and second external terminals, a feedback voltage and a voltage induced in an auxiliary winding are input, respectively. The ON and OFF timing generation circuits respectively generate timing signals turning on and off a switching element based on the voltages. The drive pulse generation circuit generates a pulse signal based on these signals. The ON timing generation circuit includes: a bottom detection circuit detecting a lowest point of the voltage of the second external terminal; and a timer circuit, and operates in a PWM mode and a quasi-resonant mode in response to a timing of an output of the timer circuit being before a timing of an output of the bottom detection circuit and the reverse case, respectively.

First claim

What is claimed is:

1. A semiconductor device for a switching power supply, the semiconductor device generating a drive signal for ON/OFF control of a switching element connected in series to one terminal of a primary-side winding of a transformer for voltage conversion including an auxiliary winding, comprising:
a first external terminal to which a feedback voltage corresponding to a voltage output from a secondary side of the transformer is input;
a second external terminal to which a voltage induced in the auxiliary winding or a voltage obtained by dividing the induced voltage is input;
an ON timing generation circuit that generates a timing signal that turns on the switching element, based on the voltage of the first external terminal and the voltage of the second external terminal;
an OFF timing generation circuit that generates a timing signal that turns off the switching element, based on the voltage of the first external terminal and a voltage proportional to a current that flows in the switching element; and
a drive pulse generation circuit that generates a pulse signal as an origin of the drive signal, based on the signal output from the ON timing generation circuit and the signal output from the OFF timing generation circuit, wherein
the ON timing generation circuit includes:
a bottom detection circuit that detects a lowest point of the voltage of the second external terminal; and
a first timer circuit that measures a predetermined time, and

the ON timing generation circuit,
in response to a change timing of an output of the first timer circuit being before a change timing of an output of the bottom detection circuit, controls the drive pulse generation circuit such that after the measurement by the first timer circuit, the pulse signal rises at an output timing of the first timer circuit, thereby operating in a pulse width modulation mode, and
in response to the change timing of the output of the bottom detection circuit being before the change timing of the output of the first timer circuit, controls the drive pulse generation circuit such that the pulse signal rises at an output timing of the bottom detection circuit, thereby operating in a quasi-resonant mode.

2. The semiconductor device according to claim 1 , wherein the predetermined time measured by the first timer circuit is set according to the voltage of the first external terminal so as to be long in response to the voltage of the first external terminal being low and to be short in response to the voltage of the first external terminal being high.

3. The semiconductor device according to claim 2 , wherein
the ON timing generation circuit includes:
a second timer circuit; and
a voltage comparator circuit that compares the voltage of the second external terminal with a preset voltage,

in response to (i) the change timing of the output of the bottom detection circuit being before the change timing of the output of the first timer circuit, and (ii-a) the voltage of the second external terminal being attenuated to the preset voltage or lower or (ii-b) the voltage of the second external terminal not exceeding the preset voltage, the second timer circuit starts measurement (iii-a) when the voltage comparator circuit last detects decrease of the voltage of the second external terminal to the preset voltage or lower after the voltage of the second external terminal rises or (iii-b) when the switching element is turned off, and
the ON timing generation circuit controls the drive pulse generation circuit such that the pulse signal rises at an output timing due to a timeout of the second timer circuit.

4. The semiconductor device according to claim 2 , wherein
the ON timing generation circuit includes a second timer circuit,
the second timer circuit starts measurement after the switching element is turned off, and is reset and restarts the measurement at the change timing of the output of the bottom detection circuit, and
the ON timing generation circuit controls the drive pulse generation circuit such that the pulse signal rises when the second timer circuit finishes the measurement as a timeout of the bottom detection circuit.

5. The semiconductor device according to claim 1 , wherein
the ON timing generation circuit includes a logic circuit that determines which is earlier, the change timing of the output of the bottom detection circuit or the output timing due to a timeout of the first timer circuit, and
the ON timing generation circuit includes a terminal to which a signal that invalidates a result: of the determination by the logic circuit can be input from outside, the result indicating that the output timing due to the timeout of the first timer circuit is earlier.

6. An AC-DC convertor comprising:
the semiconductor device according to claim 1 ;
the transformer that includes the auxiliary winding and in which a voltage obtained by rectifying an alternating current voltage is applied to the primary-side winding; and
the switching element connected to the primary-side winding, wherein
the AC-DC convertor controls the switching element by using the semiconductor device.

Assignees

• Matsuda Hiroki
• Arima Satoshi
• Murata Yukio
• Mitsumi Electric Co Ltd

Inventors

• Matsuda Hiroki
• Arima Satoshi
• Murata Yukio

Classifications

• 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

• H02M1/0058

  by employing soft switching techniques, i.e. commutation of transistors when applied voltage is zero or when current flow is zero (using an auxiliary actively switched resonant commutation circuit connected to an intermediate DC voltage or between two push-pull branches of an inverter bridge H02M7/4811; in resonant inverters H02M7/4815; in inverters operating from a resonant DC source H02M7/4826) · CPC title

• H02M3/33523

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

• H02M7/217

  using semiconductor devices only · CPC title

• H02M3/28 Primary

  using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate AC · CPC title