Charge Pump Circuit Reducing Rise Time for High-Frequency RF Signals
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Solution Overview
Problem
Conventional charge pump circuits in optical disk reproducing devices experience distortion and difficulty in maintaining a 50% duty ratio for high-frequency analog RF signals, leading to jitter in the digital RF signal waveform due to long rise times and switching delays in the current mirror circuit.
Innovation Solution
A charge pump circuit with a current mirror configuration using P-channel MOS transistors and switching elements, including a dummy current path and additional switching elements to reduce distortion by ensuring continuous current flow and immediate switching states, thereby reducing the rise time of output currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a conventional charge pump circuit is used with high-frequency analog RF signals, then the circuit structure is simple, but the rise time of output current becomes long causing distortion and difficulty in maintaining 50% duty ratio
Solution Approach 1:
The charge pump circuit is segmented into two independent current sources (first current source for charging, second current source for discharging) instead of using a single current source with a current mirror. This segmentation allows each current source to be optimized independently for fast switching and minimal distortion, resolving the contradiction between fast rise time and circuit complexity.
Solution Approach 2:
The circuit uses dynamic switching elements (switching circuit) that respond rapidly to comparator output changes, enabling the current sources to switch between charging and discharging modes instantaneously. This dynamic response eliminates the long rise time and distortion problems while maintaining a relatively simple overall circuit structure.
2Manufacturing precision
If the charge pump circuit uses a current mirror configuration, then the circuit design is straightforward, but switching delays occur making it difficult to maintain equal charging and discharging current values
Solution Approach 1:
The current mirror configuration is segmented into separate first and second current sources, each independently controlled by the switching circuit. This eliminates the switching delays inherent in current mirror configurations while ensuring that charging and discharging current values remain equal through symmetric circuit design and matched current source characteristics.
Solution Approach 2:
The switching circuit monitors the comparator output and rapidly switches between connecting the first current source (for charging) and the second current source (for discharging). This feedback mechanism ensures that current values remain equal and switching delays are minimized by immediately responding to changes in the digital RF signal level.
3Productivity
If high-frequency analog RF signals are input to the SLC circuit, then the signal processing capability is improved, but jitter occurs in the digital RF signal waveform due to distortion
Solution Approach 1:
By segmenting the charge pump into separate first and second current sources with independent switching control, the circuit achieves fast response to high-frequency input signals without distortion. This maintains equal charging and discharging current values, preventing duty ratio deviation and eliminating jitter in the digital RF signal waveform while preserving high-frequency signal processing capability.
Solution Approach 2:
The dynamic switching circuit responds instantaneously to high-frequency comparator output changes, enabling the charge pump to accurately track and process high-frequency analog RF signals. This dynamic response ensures equal current values are maintained during rapid switching, preventing waveform distortion and jitter while maintaining high signal processing capability.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively maintains a 50% duty ratio for the digital RF signal and reduces jitter in the waveform, ensuring accurate signal processing even with high-frequency analog RF inputs.
Implementation Method 1
a first transistor; a second transistor forming a current mirror circuit with the first transistor
Implementation Method 2
a switching circuit controlling itself so as to connect the first current source to the first transistor... when the input signal is of a first level, and connect the second current source to the first transistor... when the input signal is of a second level
Implementation Method 3
a capacitor 103... Such charging and discharging of the capacitor 103 adjust the level of the mean voltage of the analog RF signal
Data Source
AI summary
The invention provides a charge pump circuit which reduces rise time of an output current even when an input signal is of high frequency. PMOS1 and PMOS2 have gates connected to each other, and the gate of the PMOS1 is connected to the drain thereof. A supply potential (Vdd) is applied to the sources of the PMOS1 and the PMOS2, and the PMOS1 and the PMOS2 form a current mirror circuit. First and second switching elements and a first constant-current source are connected to the drain of the PMOS2. A connection point (a node) of the first switching element and the second switching element is connected to an output terminal. The drain of the PMOS1 is connected to the first constant-current source through a third switching element, and connected to a second constant-current source through a fourth switching element.