Drive circuit for insulated gate type FETs

• US 6,429,635 B2
• Filed: 03/08/2001
• Issued: 08/06/2002
• Est. Priority Date: 03/10/2000
• Status: Expired due to Fees

• Current Assignee: ROHM Co., Ltd.
• Original Assignee: ROHM Co., Ltd.
• Inventors: Okubo, Toshiro
• Primary Examiner(s): VU, BAO Q
• Application Number:
  US09/801,412
• Publication Number:
  US 20010020841A1
• Time in Patent Office: 516 Days
• Field of Search: 323/271, 323/268, 323/282, 323/284, 323/273, 323/274
• US Class Current: 323/282
• CPC Class Codes: H02M 3/07 using capacitors charged and discharged alternately by semiconductor devices with control electrode , e.g. charge pumps
• CPC Class Codes: H03K 17/04123 in field-effect transistor switches
• CPC Class Codes: H03K 2217/0036 Means reducing energy consumption

Abstract

A drive circuit for driving an FET includes a charge pump circuit which comprises multi-stage switching elements, condensers, and inversion buffers, and operates in response to the oscillatory output of an oscillator circuit; and a comparison means for comparing the output voltage of the charge pump circuit with a preset reference voltage to thereby control the oscillation of the oscillator circuit. The charge pump circuit is thus operated intermittently so as to provide a sufficiently large gate voltage to the MOSFET in a stable manner, thereby maintaining a constant output-load characteristic.

Claims

1. A drive circuit for use with an insulated gate type FET, comprising:

an oscillator circuit providing an oscillatory output;

a charge pump circuit for boosting up a voltage input thereto in response to said oscillatory output of said oscillator circuit; and

comparison means for comparing the output voltage of said charge pump circuit with a preset reference voltage and for outputting the result of the comparison;

wherein said charge pump circuit includes;

at least one charge pump unit, concatenated if more than one charge pump unit exist, each charge pump unit having

a switch turned on/off by said oscillatory output of said oscillator circuit and

a condenser connected between said switch and said oscillator circuit; and

a charge pump unit in the output stage of the drive circuit having

a switch turned on/off by said oscillatory output of said oscillator circuit and

a condenser connected between said switch and a source of predetermined electrical potential; and

wherein said charge pump unit in the output stage of the drive circuit is further concatenated with said at least one charge pump unit;

wherein said charge pump circuit supplies said output voltage thereof to the gate of the FET; and

wherein said comparison means controls stopping/starting of the oscillation of said oscillator circuit in accordance with the comparison.

2. The drive circuit according to claim 1, wherein said comparison means has a voltage divider for generating a divided voltage from said output voltage and a comparator for comparing said divided voltage with said preset reference voltage.

3. The drive circuit according to claim 1, wherein the phase of the output voltage of said oscillator is chosen such that said switch of said charge pump unit in said output stage is turned off when said oscillator circuit is stopped, so that said condenser of said charge pump unit in said output stage is quickly charged when said oscillation is resumed subsequently.

4. The drive circuit according to claim 1, wherein said switch is a P-channel MOSFET and the gate of said switch is driven by the output of an inversion buffer circuit.

5. The drive circuit according to claim 1, wherein said charge pump circuit with said charge pump unit in the output stage includes three charge pump units.

6. A driver circuit for use with an insulated gate type FET, comprising:

an oscillator circuit providing an oscillatory output;

a charge pump circuit for boosting up a voltage input thereto in response to said oscillatory output of said oscillator circuit; and

a comparator coupled to said oscillator circuit for comparing the output voltage of said charge pump circuit with a preset reference voltage and for outputting the result of the comparison;

wherein said charge pump circuit includes;

at least one charge pump unit, concatenated if more than one charge pump unit exist, each charge pump unit having

a switch turned on/off by said oscillatory output of said oscillator circuit and

a condenser connected between said switch and said oscillator circuit; and

a charge pump unit in the output stage of the drive circuit having

a switch turned on/off by said oscillatory output of said oscillator circuit and

a condenser connected between said switch and a source of predetermined electrical potential; and

wherein said charge pump unit in the output stage of the drive circuit is further concatenated with said at least one charge pump unit;

wherein said charge pump circuit supplies said output voltage thereof to the gate of the FET; and

wherein said comparator controls stopping/starting of the oscillation of said oscillator circuit.

7. The drive circuit according to claim 6, further comprising a voltage divider coupled to said comparator for generating a divided voltage from said output voltage.

8. The drive circuit according to claim 7, wherein the comparator compares said divided voltage with said preset reference voltage.

9. The drive circuit according to claim 6, wherein the phase of the output voltage of said oscillator is chosen such that said switch of said charge pump unit in said output stage is turned off when said oscillator circuit is stopped, so that said condenser of said charge pump unit in said output stage is quickly charged when said oscillation is resumed subsequently.

10. The drive circuit according to claim 6, wherein said switch is a P-channel MOSFET and the gate of said switch is driven by the output of an inversion buffer circuit.

11. The drive circuit according to claim 6, wherein said charge pump circuit with said charge pump unit in the output stage includes three charge pump units.

12. A method for providing power to an insulated gate FET, comprising the steps of:

providing an oscillatory output;

generating an output voltage by boosting up an input voltage in response to said oscillatory output;

supplying the output voltage to the gate of the FET;

comparing the output voltage with a preset reference voltage; and

controlling the stopping/starting of said oscillatory output in accordance with the comparison of the output voltage with the preset reference voltage.

13. The method of claim 12, further comprising the step of generating a divided voltage from said output voltage.

14. The method of claim 13, further comprising the step of comparing said divided voltage to said preset reference voltage.

15. The method of claim 14, further comprising the step of controlling the stopping/starting of said oscillatory output in accordance with the comparison of said divided voltage with said preset reference voltage.