Voltage Compensation Circuit for LDO Regulator Recovery
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Solution Overview
Problem
Conventional low-dropout (LDO) regulators experience slow recovery from voltage drops due to high current peaks, leading to critical malfunctions in memory devices, as they require large power transistors and compensation capacitance, resulting in increased area, cost, and power consumption.
Innovation Solution
A high-speed circuit portion with parallel stages acting as current drivers, enabled by comparators with threshold voltages, reduces voltage drops by adding extra current branches at the output terminal, independent of power supply and output voltage, without using feedback networks, allowing for faster recovery and reduced power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If conventional LDO regulators use negative feedback networks to stabilize output voltage, then voltage stability is improved, but recovery speed from voltage drops deteriorates
Solution Approach 1:
The patent divides the regulator into two independent parts: a conventional LDO regulator for stable voltage regulation and a high-speed compensation circuit for fast recovery. The compensation circuit includes multiple parallel stages with different threshold voltages that can be independently activated based on the voltage drop severity, allowing fast response without affecting the stability of the main regulator.
Solution Approach 2:
The compensation circuit is pre-configured with multiple stages having different threshold voltages (Vth1, Vth2, ..., Vthn) so that when a voltage drop occurs, the appropriate stage is already ready to activate immediately. This preliminary preparation of multiple response levels enables instant counter-action without waiting for feedback loop response.
2Power
If large power transistors are used to feed current peaks, then current supply capability is improved, but device area and power consumption increase
Solution Approach 1:
The patent uses dynamically controllable current mirrors in the compensation circuit stages. Each stage includes transistors whose current transmission ratio can be adjusted by controlling the gate voltage of the master transistor. This dynamic control allows the circuit to provide high current only when needed (during voltage drop recovery) while consuming minimal current during normal operation, eliminating the need for continuously large transistors.
Solution Approach 2:
The compensation circuit operates periodically or event-driven rather than continuously. The stages are activated only when voltage drops are detected (periodically or on-demand), and remain inactive during normal operation. This periodic/event-based operation allows smaller transistors to be used since they don't need to continuously handle peak currents.
3Speed
If compensation capacitance is increased to improve voltage recovery, then recovery speed is improved, but circuit complexity and die size increase
Solution Approach 1:
The patent changes the control parameter from capacitance value to threshold voltage levels. Instead of increasing compensation capacitance (which would increase die size and complexity), the invention uses multiple stages with different threshold voltages (Vth1 < Vth2 < ... < Vthn) to provide staged current compensation. This parameter change achieves fast recovery through voltage-level control rather than capacitance scaling, reducing circuit complexity.
Solution Approach 2:
The compensation circuit stages automatically activate based on the output voltage level without requiring external control signals. When the output voltage drops below a stage's threshold voltage, that stage's comparator automatically triggers the current mirror to provide compensation current. This self-service mechanism eliminates the need for complex external control logic, reducing overall circuit complexity.
4Measurement precision
If feedback networks are used for voltage regulation, then voltage precision is improved, but response time to current peaks deteriorates
Solution Approach 1:
The patent introduces a compensation circuit as an intermediary between the load and the main LDO regulator. This intermediary circuit provides immediate current compensation during voltage drops before the main regulator's feedback loop responds. The compensation circuit acts as a buffer that bridges the gap between fast current changes and the slower feedback response, allowing both precision regulation and fast response to coexist.
Data Source
AI summary
A method of recovering a voltage drop at an output terminal of a voltage compensation circuit connected to a load including a variable load current according to a condition of the load. A circuit portion for a regulator having an output terminal connected to a load including a variable load current may be provided. The circuit portion may include a plurality of stages connected in parallel to said output terminal. Each of said stages may be configured as a current driver having an output connected to the output terminal of said regulator. The circuit portion may include a comparator in each of said stages configured for receiving from a first input a reference voltage value and a predetermined threshold voltage from an other input. Each of said stages may receive a corresponding different threshold voltage value on said other input. The threshold voltage values may be correlated to the variable load current. At least a group of said stages may be sequentially enabled by each corresponding comparator to drive an extra current on said output terminal according to the amount of load current required by the load.