Reverse level shift circuit and power semiconductor device

• US 6,498,738 B1
• Filed: 04/09/2002
• Issued: 12/24/2002
• Est. Priority Date: 07/12/2001
• Status: Expired due to Term

• Current Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Original Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Inventors: Tanaka, Yoshikazu, Orita, Shoichi
• Primary Examiner(s): Vu, Bao Q.
• Application Number:
  US10/118,252
• Publication Number:
  US 20030012040A1
• Time in Patent Office: 259 Days
• Field of Search: 363/73, 363/74
• US Class Current: 363/73
• CPC Class Codes: H03K 17/18 Modifications for indicating state of switch
• CPC Class Codes: H03K 19/018521 of complementary type, e.g. CMOS
• CPC Class Codes: H03K 2217/0063 High side switches, i.e. the higher potential [DC] or life wire [AC] being directly connected to the switch and not via the load

Abstract

A reverse level shift circuit that is low in cost and excellent in reliability is provided by employing no Pch-DMOS transistor and forming it together with a level shift circuit on one semiconductor substrate. An input voltage signal (VIN) on high side is converted to a current signal by a voltage-current conversion circuit (CV1) and a current source (CS1). Using a Nch-DMOS transistor (ND1) of common gate construction as a high breakdown voltage resistance, the current signal is then transferred to low side, on which the current signal is converted to a voltage signal by a current source (CS2) and a current-voltage conversion circuit (CV2). Thereby, the signal change of the signal (VIN) using potential (HGND) as a reference potential can be outputted as a signal change of signal (VOUT) that uses potential (GND) as a reference potential.

Claims

1. A reverse level shift circuit that converts an input voltage signal using a first potential as a reference potential to an output voltage signal using a second potential lower than said first potential, as a reference potential, and then outputs said output voltage signal,

said reverse level shift circuit comprising:

a voltage-current conversion part operating based on said first potential, which converts said input voltage signal to a current signal corresponding to a value of said input voltage signal, then outputs said current signal;

a Nch-MOS transistor having a source to which said second potential is applied via a load, a drain responsive to the current signal from said voltage-current conversion part, and a gate to which a fixed potential is applied; and

a current-voltage conversion part operating based on said second potential, which converts current from said source of said Nch-MOS transistor to a voltage signal corresponding to a value of said current, and then outputs said voltage signal as said output voltage signal.

2. The reverse level shift circuit according to claim 1 further comprising:

a first current source operating based on said first potential, which outputs current corresponding to said current signal from said voltage-current conversion part, to said drain of said Nch-MOS transistor; and

a second current source operating based on said second potential, which contains said load and outputs a current signal corresponding to said current from said source of said Nch-MOS transistor, to said current-voltage conversion part.

3. The reverse level shift circuit according to claim 2 wherein

said voltage-current conversion part contains a first resistance to which said input voltage signal is applied to generate said current signal;

said first current source contains a first current mirror circuit that receives said current signal from said voltage-current conversion part and outputs current corresponding to said current signal;

said second current source contains a second current mirror circuit serving as said load, which receives said current from said source of said Nch-MOS transistor and outputs a current signal corresponding to said current; and

said current-voltage conversion part contains a second resistance that receives said current signal from said second current source to cause a voltage drop for generating said output voltage signal.

4. The reverse level shift circuit according to claim 3 wherein

said voltage-current conversion part further contains

an operational amplifier having a negative input terminal and a positive input terminal to which said input voltage signal is applied, and

a first transistor having (a) a first current electrode, (b) a second current electrode connected in common to said negative input terminal of said operational amplifier and one terminal of said first resistance, and (c) a control electrode to which output of said operational amplifier is applied,

said first potential is applied to the other terminal of said first resistance;

in said current-voltage conversion part, a third potential higher than said second potential by a fixed value is applied to one terminal of said second resistance;

said first current mirror circuit comprises

a second transistor having (d) a first current electrode connected to said first current electrode of said first transistor, (e) a second current electrode to which a fourth potential higher than said first potential by a fixed value, and (f) a control electrode connected to said first current electrode, and

a third transistor having (g) a first current electrode connected to said drain of said Nch-MOS transistor, (h) a second current electrode to which said fourth potential is applied, and (i) a control electrode connected to said control electrode of said second transistor; and

said second current mirror circuit comprises

a fourth transistor having (j) a first current electrode connected to said source of said Nch-MOS transistor, (k) a second current electrode to which said second potential is applied, and (l) a control electrode connected to said first current electrode, and

a fifth transistor having (m) a first current electrode connected to the other terminal of said second resistance, (n) a second current electrode to which said second potential is applied, and (o) a control electrode connected to said control electrode of said fourth transistor.

5. The reverse level shift circuit according to claim 3 wherein

said second current source further contains a third current mirror circuit operating based on a third potential that is higher than said second potential by a fixed value, said third current mirror circuit receiving a current signal from said second current mirror circuit and outputting a current signal corresponding to said current signal, to one terminal of said second resistance of said current-voltage conversion part;

and

said second potential is applied to the other terminal of said second resistance.

6. The reverse level shift circuit according to claim 5 wherein

said voltage-current conversion part further contains

an operational amplifier having a negative input terminal and a positive input terminal to which said input voltage signal is applied, and

a first transistor having (a) a first current electrode, (b) a second current electrode connected in common to said negative input terminal of said operational amplifier and one terminal of said first resistance, and (c) a control electrode to which output of said operational amplifier is applied,

said first potential is applied to the other terminal of said first resistance;

said first current mirror circuit comprises

a second transistor having (d) a first current electrode connected to said first current electrode of said first transistor, (e) a second current electrode to which a fourth potential higher than said first potential by a fixed value, and (f) a control electrode connected to said first current electrode, and

a third transistor having (g) a first current electrode connected to said drain of said Nch-MOS transistor, (h) a second current electrode to which said fourth potential is applied, and (i) a control electrode connected to said control electrode of said second transistor;

said second current mirror circuit comprises

a fourth transistor having (j) a first current electrode connected to said source of said Nch-MOS transistor, (k) a second current electrode to which said second potential is applied, and (l) a control electrode connected to said first current electrode, and

a fifth transistor having (m) a first current electrode, (n) a second current electrode to which said second potential is applied, and (o) a control electrode connected to said control electrode of said fourth transistor;

said third current mirror circuit comprises

a sixth transistor having (p) a first current electrode connected to said first current electrode of said fifth transistor, (q) a second current electrode to which said third potential is applied, and (r) a control electrode connected to said first current electrode, and

a seventh transistor having (s) a first current electrode, (t) a second current electrode to which said third potential is applied, and (u) a control electrode connected to said control electrode of said sixth transistor; and

in said current-voltage conversion part, said first current electrode of said seventh transistor is connected one terminal of said second resistance, and said second potential is applied to the other terminal of said second resistance.

7. The reverse level shift circuit according to claim 1 wherein

said input voltage signal is PWM signal,

said reverse level shift circuit further comprising:

an integrating circuit that integrates said voltage signal outputted from said current-voltage conversion part and outputs the result as said output voltage signal.

8. The reverse level shift circuit according to claim 1 further comprising:

a signal output part that based on said input voltage signal, generates and outputs other output voltage signal using said first potential as a reference potential.

9. The reverse level shift circuit according to claim 8 wherein

said signal output part contains an RS flip-flop that receives at its set input terminal said input voltage signal and outputs said other output voltage signal.

10. The reverse level shift circuit according to claim 1 further comprising:

a control part that stops operation of said Nch-MOS transistor in accordance with a change in said output voltage signal from said current-voltage conversion part.

11. The reverse level shift circuit according to claim 10

said control part containing:

an RS flip-flop that receives at its set input terminal said output voltage signal from said current-voltage conversion part; and

a switch that applies said second potential to said gate of said Nch-MOS transistor when output of said RS flip-flop is activated.

12. A power semiconductor device comprising:

a reverse level shift circuit according to claim 1;

switching elements on a high-voltage side and a low-voltage side connected in series; and

a stop signal output circuit that receives said output voltage signal of said reverse level shift circuit and outputs a stop signal to stop operation of said switching element of high-voltage side,

an output voltage of said switching element on said high-voltage side being used as said input voltage signal applied to said reverse level shift circuit.