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Switched current source circuit and method

A technology of switching current sources and switching circuits, which is applied to circuits, electrical components, and adjusting electrical variables, etc., and can solve problems such as limiting the pre-charging speed of circuits

Active Publication Date: 2017-04-12
NXP BV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Furthermore, the small value of the reference current Iref limits the precharging speed of the circuit, i.e. the time required to recharge the charge storage used after the discharge phase

Method used

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  • Switched current source circuit and method

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Embodiment Construction

[0057] The present invention provides a switched current source in which a reference voltage value used in driving the gate of an output transistor is sampled and stored. The reference voltage is derived using a reference current source feeding the sense transistor. The current sense transistor is turned off when the output transistor is turned off so that no power is consumed by the reference current source. Thus, a larger reference current Iref can be used for a short time.

[0058] EP2354882 discloses a kind of as Figure 4 The shown implementation of a fast current switch based on a simple switched capacitor circuit. exist Figure 4 In the pre-charging stage shown in (a), the gate of the output transistor Mout is short-circuited to its source through the switch S2, and the buffer capacitor Cbuf is charged to the reference voltage Vref through the switch S0. The current through Mout is zero.

[0059] exist Figure 4 In the discharge phase shown in (b), switches S0 and...

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Abstract

A switched current source in which the reference voltage value used when driving the gate of the output transistor is sampled and stored. The reference voltage is derived using a reference current source feeding the current sense transistor. The current sense transistor is turned off when the output transistor is turned off so that no power is consumed by the reference current source. Then, a larger reference current Iref can be used for a short time.

Description

technical field [0001] The present invention relates to switched current source circuits, ie circuits that provide the required current at an output and can be switched on or off. Background technique [0002] An important aspect of switching circuits such as Class D amplifiers and switch mode power supplies is Electromagnetic Compatibility (EMC). [0003] One of several measures that can be taken in a switch design to improve EMC performance is to slow down the transition speed of the output voltage node. This is commonly referred to as "slope control". A well-known method to obtain a constant slope at the output when a power MOSFET is turned on is to exploit the feedback Miller effect of the parasitic gate-drain capacitance Cgd of the power MOSFET. [0004] figure 1 An example of a power MOSFET utilizing slope control when the transistor is turned on is shown. The gate-drain capacitance Cgd and the diode are part of the transistor equivalent circuit. [0005] exist f...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H02M3/157
CPCG05F3/262H03K17/04206H03F3/2173G05F3/02H03F3/00
Inventor 马克·伯克豪特
Owner NXP BV