Control of a pass switch by a current source

Patent metadata

Field	Value
Publication number	US-2019131963-A1
Application number	US-201715802258-A
Country	US
Kind code	A1
Filing date	Nov 2, 2017
Priority date	Nov 2, 2017
Publication date	May 2, 2019
Grant date	—

Abstract

In some examples, a controller is configured to control a power switch electrically connected in series with a winding. In some examples, the controller is also configured to control a pass switch electrically connected between an output node of the winding and a bus out node. In some examples, the controller includes a current source configured to selectively drive a charging current from an intermediate node between the power switch and the winding to a control terminal of the pass switch to turn on the pass switch.

First claim

1 : A controller configured to:
control a power switch electrically connected in series between a winding and a voltage rail; and control a pass switch electrically connected between an output node of the winding and a bus out node, wherein the controller comprises a current source configured to selectively drive a charging current from an intermediate node between the power switch and the winding to a control terminal of the pass switch to turn on the pass switch.

2 : The controller of claim 1 , further comprising clamping circuitry configured to allow an electrical current to flow from the control terminal to the output node when a voltage level of the control terminal exceeds a voltage level of the output node by at least a threshold level.

3 : The controller of claim 2 , wherein the clamping circuitry comprises:
a Zener diode configured to allow electrical current to flow from the control terminal to the output node when a voltage level of the control terminal exceeds the voltage level of the output node by at least the threshold level; and a diode electrically connected in series with the Zener diode, wherein the diode is configured to allow electrical current to flow from the control terminal to the output node.

4 : The controller of claim 2 ,
wherein the controller is configured to control the pass switch by at least controlling an n-type metal-oxide-semiconductor field-effect transistor (NMOSFET) including a drain terminal electrically connected to the output node and a source terminal electrically connected to the bus out node, wherein the control terminal is a gate terminal of the NMOSFET, and wherein the clamping circuitry is configured to allow the electrical current to flow by at least allowing the electrical current to flow from the control terminal to the drain terminal when the voltage level of the control terminal exceeds a voltage level of the drain terminal by at least the threshold level.

5 : The controller of claim 1 , wherein the voltage rail comprises an external low-side voltage rail, the controller further comprising:
an internal low-side voltage rail connected to the external low-side voltage rail; and discharge circuitry configured to: receive a control signal; and selectively allow electrical current to flow from the control terminal to the internal low-side voltage rail to turn off the pass switch based on the control signal.

6 : The controller of claim 5 , wherein the control signal is a second control signal, and wherein the discharge circuitry comprises:
a first discharge switch configured to: receive the first control signal; and selectively allow electrical current to flow from the control terminal to the internal low-side voltage rail based on the first control signal; a Zener diode electrically connected in series with the first discharge switch, wherein the Zener diode is configured to allow electrical current to flow from the control terminal to the internal low-side voltage rail when the first discharge switch is closed and a voltage level of the control terminal exceeds a voltage level of the internal low-side voltage rail by at least a threshold level; and a second discharge switch configured to:
receive a second control signal; and
selectively allow electrical current to flow from the control terminal to the internal low-side voltage rail to turn off the pass switch based on the second control signal.

7 : The controller of claim 1 , further comprising a diode electrically connected in series with the current source, wherein the diode is configured to allow electrical current to flow from the intermediate node to the control terminal.

8 : The controller of claim 1 ,
wherein the pass switch is a first pass switch, wherein the control terminal of the first pass switch is a first control terminal, wherein the controller is further configured to control a second pass switch electrically connected in series with the first pass switch, and wherein the current source is configured to selectively drive the charging current from the intermediate node to a second control terminal of the second pass switch to turn on the second pass switch.

9 : The controller of claim 8 , wherein the clamping circuitry is configured to allow electrical current to flow from the first control terminal and the second control terminal to the output node when a voltage level of the first control terminal and the second control terminal exceeds a voltage level of the output node by at least a threshold level.

10 : The controller of claim 9 , wherein the clamping circuitry comprises:
at least two Zener diodes configured to allow electrical current to flow from the first control terminal and the second control terminal to the output node when the voltage level of the first control terminal and the second control terminal exceeds the voltage level of the output node by at least the threshold level; and a diode electrically connected in series with the at least two Zener diodes, wherein the diode is configured to allow electrical current to flow from the first control terminal and the second control terminal to the output node.

11 : A method comprising:
controlling, by a controller, a power switch electrically connected in series between with a winding and a voltage rail; and controlling, by the controller, a pass switch electrically connected between an output node of the winding and a bus out node, wherein controlling the pass switch comprises selectively driving, by a current source of the controller, a charging current from an intermediate node between the power switch and the winding to a control terminal of the pass switch to turn on the pass switch.

12 : The method of claim 11 , further comprising allowing, by a Zener diode, electrical current to flow from the control terminal to the output node when a voltage level of the control terminal exceeds a voltage level of the output node by at least a threshold level.

13 : The method of claim 11 , wherein the voltage rail comprises a low-side voltage rail, the method further comprising:
receiving a first control signal at a first discharge switch; allowing electrical current to flow from the control terminal to the low-side voltage rail through the first discharge switch and a Zener diode based on the first control signal and when a voltage level of the control terminal exceeds a voltage level of the low-side voltage rail by at least a threshold level; receiving a second control signal at a second discharge switch; and allowing electrical current to flow from the control terminal to the low-side voltage rail through the second discharge switch to turn off the pass switch based on the second control signal.

14 : The method of claim 11 ,
wherein the pass switch is a first pass switch, wherein the control terminal of the first pass switch is a first control terminal, wherein the method further comprises controlling a second pass switch electrically connected in series with the first pass switch, and wherein selectively driving the charging current comprises selectively driving the charging current from the intermediate node to a second control terminal of the second pass switch to turn on the second pass switch.

15 : A system comprising:
primary-side circuitry including:
a primary-side switch;
a primary-side winding of a transformer, and
a primary-side controller configured to control the primary-side switch; and
secondary-side circuitry including:
a secondary-side switch;
a secondary-side winding of the transformer magnetically coupled to the primary side and electrically connected in ser

Assignees

• Infineon Technologies Austria Ag
• Infineon Technologies Americas Corp

Inventors

• Gong Xiaowu
• Malinin Andrey

Classifications

• H03K17/04106 Primary

  in field-effect transistor switches (H03K17/0412, H03K17/0416 take precedence) · CPC title

• H03K17/0424

  by the use of a transformer · CPC title

• H03K2217/0054

  Gating switches, e.g. pass gates · CPC title