Level shift circuit and switching power source apparatus

• US 9,350,352 B2
• Filed: 11/15/2010
• Issued: 05/24/2016
• Est. Priority Date: 11/19/2009
• Status: Active Grant

• Current Assignee: Sanken Electric Company Limited
• Original Assignee: Sanken Electric Company Limited
• Inventors: Koike, Kengo
• Primary Examiner(s): Lam, Tuan T
• Application Number:
  US12/946,247
• Publication Number:
  US 20110115542A1
• Time in Patent Office: 2,017 Days
• Field of Search: None
• US Class Current: 1/1
• CPC Class Codes: H03K 19/017509 Interface arrangements
• CPC Class Codes: H03K 19/0185 using field effect transistors only
• CPC Class Codes: H03K 19/018507 Interface arrangements
• CPC Class Codes: H03K 19/018514 with at least one differential stage H03K19/018528 and H03K19/018542 take precedence
• CPC Class Codes: H03K 19/018521 of complementary type, e.g. CMOS

Abstract

A level shift circuit includes a first resistor connected to a level shift power source, a first transistor having a drain connected to a second end of the first resistor and a source to the ground, a second resistor connected to the level shift power source, a second transistor having a drain connected to a second end of the second resistor and a source to the ground, a pulse generator controlling ON/OFF of the first and second transistors according to an input signal, a control part generating a set signal if the first transistor is ON, a reset signal if the second transistor is ON, and no signal if there is no voltage difference between a voltage at the drain of the first transistor and a voltage at the drain of the second transistor, and a flip-flop providing an output signal according to the set and reset signals.

Claims

1. A level shift circuit comprising:

a first resistor having a first end being connected to a level shift power source;

a first n-type MOSFET having a drain connected to a second end of the first resistor and a source connected to the ground;

a second resistor having a first end connected to the level shift power source, the first and second resistors having the same resistance value;

a second n-type MOSFET having a drain connected to a second end of the second resistor and a source connected to the ground;

a pulse generator configured to control ON/OFF of the first and second n-type MOSFETs according to an input signal;

a control part configured to generate a set signal as the first n-type MOSFET is ON, a reset signal as the second n-type MOSFET is ON, and no signal as there is no voltage difference between a voltage at the drain of the first n-type MOSFET and a voltage at the drain of the second n-type MOSFET; and

a flip-flop configured to provide an output signal according to the set and reset signals generated by the control part, the output signal being a level-shifted signal of the input signal, wherein

the control part includes;

a fifth resistor having a first end connected to the level shift power source;

a third n-type MOSFET having a drain connected to a second end of the fifth resistor and a set terminal of the flip-flop, a source connected to the drain of the first n-type MOSFET, and a gate connected to the drain of the second-type MOSFET;

a sixth resistor having a first end connected to the level shift power source, the fifth and sixth resistors having the same resistance value; and

a fourth n-type MOSFET having a drain connected to a second end of the sixth resistor and a reset terminal of the flip-flop, a source connected to the drain of the second n-type MOSFET, and a gate connected to the drain of the first n-type MOSFET.

2. The level shift circuit of claim 1, further comprising:

a seventh resistor connected between the source of the first n-type MOSFET and the ground; and

an eighth resistor connected between the source of the second n-type MOSFET and the ground.

3. A switching power source apparatus having a high-side switching element and a low-side switching element comprising the level shift circuit of claim 1 for controlling the high-side switching element.

4. A level shift circuit comprising:

a first resistor having a first end being connected to a level shift power source;

a first n-type MOSFET having a drain connected to a second end of the first resistor and a source connected to the ground;

a second resistor having a first end connected to the level shift power source, the first and second resistors having the same resistance value;

a second n-type MOSFET having a drain connected to a second end of the second resistor and a source connected to the ground;

a pulse generator configured to control ON/OFF of the first and second n-type MOSFETs according to an input signal;

a control part configured to generate a set signal as the first n-type MOSFET is ON, a reset signal as the second n-type MOSFET is ON, and no signal as there is no voltage difference between a voltage at the drain of the first n-type MOSFET and a voltage at the drain of the second n-type MOSFET; and

a flip-flop configured to provide an output signal according to the set and reset signals generated by the control part, the output signal being a level-shifted signal of the input signal, wherein

a first amplifier arranged between the control part and the flip-flop, the first amplifier being configured to amplify the set signal of the control part so that the set signal is detected by the flip-flop; and

a second amplifier arranged between the control part and the flip-flop and configured to amplify the reset signal generated of the control part so that the reset signal is detected by the flip-flop.

5. The level shift circuit of claim 4, wherein:

the first amplifier includes a first p-type MOSFET and a third resistor that are connected in series between the level shift power source and a level shift reference voltage point having a predetermined voltage difference with respect to the level shift power source;

the second amplifier includes a second p-type MOSFET and a fourth resistor that are connected in series between the level shift power source and the level shift reference voltage;

the first p-type MOSFET turns on and off according to the set signal generated by the control part; and

the second p-type MOSFET turns on and off according to the reset signal generated by the control part.

6. The level shift circuit of claim 4, wherein the control part includes:

a fifth resistor having a first end connected to the level shift power source;

a third n-type MOSFET having a drain connected to a second end of the fifth resistor and a set terminal of the flip-flop, a source connected to the drain of the first n-type MOSFET, and a gate connected to the drain of the second n-type MOSFET;

a sixth resistor having a first end connected to the level shift power source, the fifth and sixth resistors having the same resistance value; and

a fourth n-type MOSFET having a drain connected to a second end of the sixth resistor and a reset terminal of the flip-flop, a source connected to the drain of the second n-type MOSFET, and a gate connected to the drain of the first n-type MOSFET.

7. The level shift circuit of claim 5, wherein the control part includes:

a fifth resistor having a first end connected to the level shift power source;

a third n-type MOSFET having a drain connected to a second end of the fifth resistor and a set terminal of the flip-flop, a source connected to the drain of the first n-type MOSFET, and a gate connected to the drain of the second n-type MOSFET;

a sixth resistor having a first end connected to the level shift power source, the fifth and sixth resistors having the same resistance value; and

a fourth n-type MOSFET having a drain connected to a second end of the sixth resistor and a reset terminal of the flip-flop, a source connected to the drain of the second n-type MOSFET, and a gate connected to the drain of the first n-type MOSFET.